| 1. |
- Sauer, Christopher, 1993
(författare)
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Green Aromatics: Catalytic Valorisation of bio-derived 2,5-dimethylfuran over Zeolites and Zeotypes
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis discusses the use of biomass as a potentially green feedstock for the chemical industry in the urgent shift away from fossil resources. I elaborate on reasons why we cannot afford to burn virgin biomass for energy production, among them a variety of ecosystem services that forests and other lands provide. In addition, the utilisation of biomass should be focused on products that sequester and lock away carbon for more extended periods, e.g. timber, materials and chemicals. In particular, biomass can be used as an alternative "carbon neutral" feedstock for the chemical industry, where we can preserve the already existing chemical complexity in the bio-based molecules. One example is the upgrading of furans to benzene, toluene and xylene (BTX) aromatics with the help of zeolite catalysis. These aromatics are important commodity chemicals, where the shift to a bio-based resource could make use of already existing knowledge, catalyst and production infrastructure. However, research is necessary to understand these new feedstock molecules and their interaction with the catalysts and to enable the design of applicable catalysts. In order to study the interaction of the furans, in particular 2,5-dimethylfuran (2,5-dmf), I describe and discuss the development of an analytical methodology that utilises infrared spectroscopy and mass spectrometry for the on-line identification and quantification of product molecules during catalytic reactions. This on-line analysis method is then applied to the catalytic conversion of 2,5-dmf to aromatics over a range of zeolite and zeotype catalysts. In-depth studies with ammonia as a probe molecule of the catalytic active acid sites, as well as temperature programmed experiments with ammonia and 2,5-dmf give insights into product distribution, selectivity changes and deactivation of the catalyst. For example, olefins and aromatics are initially preferred products, while with increasing time on stream, the isomerisation of 2,5-dmf becomes dominant. The incorporation of Ga into the zeotype framework, resulting in a Ga-Silicate, shows how targeted catalyst design can increase overall aromatics production. This catalyst is also suitable for selective isomerisation of 2,5-dmf to 2,4-dimethylfuran, which has a rare substitution pattern. Finally, itwas found that the most valuable of BTX, p -xylene, can be produced more selectively when 2,5-dmf is pre-adsorbed onto zeolite ZSM-5 and then released during a temperature programmed product desorption.
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| 2. |
- Guo, Y. D., et al.
(författare)
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Identification of highly oxygenated organic molecules and their role in aerosol formation in the reaction of limonene with nitrate radical
- 2022
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 22:17, s. 11323-11346
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Tidskriftsartikel (refereegranskat)abstract
- Nighttime NO3-initiated oxidation of biogenic volatile organic compounds (BVOCs) such as monoterpenes is important for the atmospheric formation and growth of secondary organic aerosol (SOA), which has significant impact on climate, air quality, and human health. In such SOA formation and growth, highly oxygenated organic molecules (HOM) may be crucial, but their formation pathways and role in aerosol formation have yet to be clarified. Among monoterpenes, limonene is of particular interest for its high emission globally and high SOA yield. In this work, HOM formation in the reaction of limonene with nitrate radical (NO3) was investigated in the SAPHIR chamber (Simulation of Atmospheric PHotochemistry In a large Reaction chamber). About 280 HOM products were identified, grouped into 19 monomer families, 11 dimer families, and 3 trimer families. Both closed-shell products and open-shell peroxy radicals (RO2 center dot) 2 were observed, and many of them have not been reported previously. Monomers and dimers accounted for 47% and 47% of HOM concentrations, respectively, with trimers making up the remaining 6 %. In the most abundant monomer families, C10H15-17NO6-14, carbonyl products outnumbered hydroxyl products, indicating the importance of RO2 center dot termination by unimolecular dissociation. Both RO2 center dot autoxidation and alkoxy-peroxy pathways were found to be important processes leading to HOM. Time-dependent concentration profiles of monomer products containing nitrogen showed mainly second-generation formation patterns. Dimers were likely formed via the accretion reaction of two monomer RO2 center dot , and HOM-trimers via the accretion reaction between monomer RO2 center dot and dimer RO2 center dot. Trimers are suggested to play an important role in new particle formation (NPF) observed in our experiment. A HOM yield of 1.5%(+1.7%)(-0.7%) was estimated considering only first-generation products. SOA mass growth could be reasonably explained by HOM condensation on particles assuming irreversible uptake of ultra-low volatility organic compounds (ULVOCs), extremely low volatility organic compounds (ELVOCs), and low volatility organic compounds (LVOCs). This work provides evidence for the important role of HOM formed via the limonene +NO3 reaction in NPF and growth of SOA particles.
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| 3. |
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| 4. |
- Armanious, Antonius, 1981, et al.
(författare)
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Determination of Nanosized Adsorbate Mass in Solution Using Mechanical Resonators: Elimination of the So Far Inseparable Liquid Contribution
- 2021
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 125:41, s. 22733-22746
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Tidskriftsartikel (refereegranskat)abstract
- Assumption-free mass quantification of nanofilms, nanoparticles, and (supra)molecular adsorbates in a liquid environment remains a key challenge in many branches of science. Mechanical resonators can uniquely determine the mass of essentially any adsorbate; yet, when operating in a liquid environment, the liquid dynamically coupled to the adsorbate contributes significantly to the measured response, which complicates data interpretation and impairs quantitative adsorbate mass determination. Employing the Navier-Stokes equation for liquid velocity in contact with an oscillating surface, we show that the liquid contribution for rigid systems can be eliminated by measuring the response in solutions with identical kinematic viscosity but different densities. Guided by this insight, we used the quartz crystal microbalance (QCM), one of the most widely employed mechanical resonators, to experimentally demonstrate that the kinematic-viscosity matching can be utilized to quantify the dry mass of rigid and in many cases also nonrigid adsorbate systems, including, e.g., rigid nanoparticles, tethered biological nanoparticles (lipid vesicles), as well as highly hydrated polymeric films. For all the adsorbates, the dry mass determined using the kinematic-viscosity matching was within the uncertainty limits of the corresponding mass determined using complementary methods, i.e., QCM in air, scanning electron microscopy, surface plasmon resonance, and theoretical estimations. The same approach applied to the simultaneously measured energy dissipation made it possible to quantify the mechanical properties of the adsorbate and its attachment to the surface, as demonstrated by, for example, probing the hydrodynamic stabilization induced by nanoparticle crowding. In addition to a unique means to quantify the liquid contribution to the measured response of mechanical resonators, we also envision that the kinematic-viscosity-matching approach will open up applications beyond mass determination, including a new means to investigate orientation, spatial distribution, and binding strength of adsorbates without the need for complementary techniques.
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| 5. |
- Brownwood, B., et al.
(författare)
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Gas-Particle Partitioning and SOA Yields of Organonitrate Products from NO3-Initiated Oxidation of Isoprene under Varied Chemical Regimes
- 2021
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Ingår i: Acs Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 5:4, s. 785-800
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Tidskriftsartikel (refereegranskat)abstract
- Alkyl nitrate (AN) and secondary organic aerosol (SOA) from the reaction of nitrate radicals (NO3) with isoprene were observed in the Simulation of Atmospheric PHotochemistry In a large Reaction (SAPHIR) chamber during the NO(3)Isop campaign in August 2018. Based on 15 day-long experiments under various reaction conditions, we conclude that the reaction has a nominally unity molar AN yield (observed range 90 +/- 40%) and an SOA mass yield of OA + organic nitrate aerosol of 13-15% (with similar to 50 mu g m(-3) inorganic seed aerosol and 2-5 mu g m-3 total organic aerosol). Isoprene (5-25 ppb) and oxidant (typically similar to 100 ppb O-3 and 5-25 ppb NO2) concentrations and aerosol composition (inorganic and organic coating) were varied while remaining close to ambient conditions, producing similar AN and SOA yields under all regimes. We observe the formation of dinitrates upon oxidation of the second double bond only once the isoprene precursor is fully consumed. We determine the bulk partitioning coefficient for ANs (K-p similar to 10(-3) m(3) mu g(-1)), indicating an average volatility corresponding to a C-5 hydroxy hydroperoxy nitrate.
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| 6. |
- Carlsson, P. T. M., et al.
(författare)
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Comparison of isoprene chemical mechanisms under atmospheric night-time conditions in chamber experiments: evidence of hydroperoxy aldehydes and epoxy products from NO3 oxidation
- 2023
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 23:5, s. 3147-3180
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Tidskriftsartikel (refereegranskat)abstract
- The gas-phase reaction of isoprene with the nitrate radical (NO3) was investigated in experiments in the outdoor SAPHIR chamber under atmospherically relevant conditions specifically with respect to the chemical lifetime and fate of nitrato-organic peroxy radicals (RO2). Observations of organic products were compared to concentrations expected from different chemical mechanisms: (1) the Master Chemical Mechanism, which simplifies the NO3 isoprene chemistry by only considering one RO2 isomer; (2) the chemical mechanism derived from experiments in the Caltech chamber, which considers different RO2 isomers; and (3) the FZJ-NO3 isoprene mechanism derived from quantum chemical calculations, which in addition to the Caltech mechanism includes equilibrium reactions of RO(2 )isomers, unimolecular reactions of nitrate RO(2 )radicals and epoxidation reactions of nitrate alkoxy radicals. Measurements using mass spectrometer instruments give evidence that the new reactions pathways predicted by quantum chemical calculations play a role in the NO3 oxidation of isoprene. Hydroperoxy aldehyde (HPALD) species, which are specific to unimolecular reactions of nitrate RO2, were detected even in the presence of an OH scavenger, excluding the possibility that concurrent oxidation by hydroxyl radicals (OH) is responsible for their formation. In addition, ion signals at masses that can be attributed to epoxy compounds, which are specific to the epoxidation reaction of nitrate alkoxy radicals, were detected. Measurements of methyl vinyl ketone (MVK) and methacrolein (MACR) concentrations confirm that the decomposition of nitrate alkoxy radicals implemented in the Caltech mechanism cannot compete with the ring-closure reactions predicted by quantum chemical calculations. The validity of the FZJ-NO3 isoprene mechanism is further supported by a good agreement between measured and simulated hydroxyl radical (OH) reactivity. Nevertheless, the FZJ-NO3 isoprene mechanism needs further investigations with respect to the absolute importance of unimolecular reactions of nitrate RO2 and epoxidation reactions of nitrate alkoxy radicals. Absolute concentrations of specific organic nitrates such as nitrate hydroperoxides would be required to experimentally determine product yields and branching ratios of reactions but could not be measured in the chamber experiments due to the lack of calibration standards for these compounds. The temporal evolution of mass traces attributed to product species such as nitrate hydroperoxides, nitrate carbonyl and nitrate alcohols as well as hydroperoxy aldehydes observed by the mass spectrometer instruments demonstrates that further oxidation by the nitrate radical and ozone at atmospheric concentrations is small on the timescale of one night (12 h) for typical oxidant concentrations. However, oxidation by hydroxyl radicals present at night and potentially also produced from the decomposition of nitrate alkoxy radicals can contribute to their nocturnal chemical loss.
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| 7. |
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| 8. |
- Salvador, Christian Mark, 1989, et al.
(författare)
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Ambient nitro-aromatic compounds - biomass burning versus secondary formation in rural China
- 2021
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 21:3, s. 1389-1406
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Tidskriftsartikel (refereegranskat)abstract
- Nitro-aromatic compounds (NACs) were measured hourly at a rural site in China during wintertime to monitor the changes due to local and regional impacts of biomass burning (BB). Concurrent and continuous measurements of the concentrations of 16 NACs in the gas and particle phases were performed with a time-of-flight chemical ionization mass spectrometer (CIMS) equipped with a Filter Inlet for Gases and AEROsols (FIGAERO) unit using iodide as the reagent ion. NACs accounted for <2 % of the mass concentration of organic matter (OM) and total particulate matter (PM), but the total particle mass concentrations of these compounds can reach as high as 1000 ng m(-3) (299 ng m(-3) avg), suggesting that they may contribute significantly to the radiative forcing effects of atmospheric particles. Levels of gas-phase NACs were highest during the daytime (15:00-16:00 local time, LT), with a smaller night-time peak around 20:00LT. Box-model simulations showed that this occurred because the rate of NAC production from gas-phase sources exceeded the rate of loss, which occurred mainly via the OH reaction and to a lesser degree via photolysis. Data gathered during extended periods with high contributions from primary BB sources (resulting in 40 %-60 % increases in NAC concentrations) were used to characterize individual NACs with respect to gas-particle partitioning and the contributions of regional secondary processes (i.e. photochemical smog). On days without extensive BB, secondary formation was the dominant source of NACs, and NAC levels correlated strongly with the ambient ozone concentration. Analyses of individual NACs in the regionally aged plumes sampled on these days allowed precursors such as phenol and catechol to be linked to their NAC derivatives (i.e. nitrophenol and nitrocatechol). Correlation analysis using the high time resolution data and box-model simulation results constrained the relationships between these compounds and demonstrated the contribution of secondary formation processes. Furthermore, 13 of 16 NACS were classified according to primary or secondary formation process. Primary emission was the dominant source (accounting for 60 %-70 % of the measured concentrations) of 5 of the 16 studied NACs, but secondary formation was also a significant source. Photochemical smog thus has important effects on brown carbon levels even during wintertime periods dominated by primary air pollution in rural China.
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| 9. |
- Voliotis, A., et al.
(författare)
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Chamber investigation of the formation and transformation of secondary organic aerosol in mixtures of biogenic and anthropogenic volatile organic compounds
- 2022
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 22:21, s. 14147-14175
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Tidskriftsartikel (refereegranskat)abstract
- A comprehensive chamber investigation of photochemical secondary organic aerosol (SOA) formation and transformation in mixtures of anthropogenic (o-cresol) and biogenic (alpha-pinene and isoprene) volatile organic compound (VOC) precursors in the presence of NOx and inorganic seed particles was conducted. To enable direct comparison across systems, the initial concentration (hence reactivity) of the systems towards the dominant OH oxidant was adjusted. Comparing experiments conducted in single-precursor systems at various initial reactivity levels (referenced to a nominal base case VOC concentration, e.g. halving the initial concentration for a 1/2 initial reactivity experiment) as well as their binary and ternary mixtures, we show that the molecular interactions from the mixing of the precursors can be investigated and discuss challenges in their interpretation. The observed average SOA particle mass yields (the organic particle mass produced for a mass of VOC consumed) in descending order were found for the following systems: alpha-pinene (32 +/- 7 %), alpha-pinene-o-cresol (28 +/- 9 %), alpha-pinene at 1/2 initial reactivity (21 +/- 5 %), alpha-pinene-isoprene (16 +/- 1 %), alpha-pinene at 1/3 initial reactivity (15 +/- 4 %), o-cresol (13 +/- 3 %), alpha-pinene-o-cresol-isoprene (11 +/- 4 %), o-cresol at 1/2 initial reactivity (11 +/- 3 %), o-cresol-isoprene (6 +/- 2 %), and isoprene (0 +/- 0 %). We find a clear suppression of the SOA mass yield from alpha-pinene when it is mixed with isoprene, whilst no suppression or enhancement of SOA particle yield from o-cresol was found when it was similarly mixed with isoprene. The alpha-pinene-o-cresol system yield appeared to be increased compared to that calculated based on the additivity, whilst in the alpha-pinene-o-cresol-isoprene system the measured and predicted yields were comparable. However, in mixtures in which more than one precursor contributes to the SOA particle mass it is unclear whether changes in the SOA formation potential are attributable to physical or chemical interactions, since the reference basis for the comparison is complex. Online and offline chemical composition as well as SOA particle volatility, water uptake, and "phase" behaviour measurements that were used to interpret the SOA formation and behaviour are introduced and detailed elsewhere.
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| 10. |
- Wang, Xuan, et al.
(författare)
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Effects of Anthropogenic Chlorine on PM2.5 and Ozone Air Quality in China
- 2020
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 54:16, s. 9908-9916
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Tidskriftsartikel (refereegranskat)abstract
- China has large anthropogenic chlorine emissions from agricultural fires, residential biofuel, waste incineration, coal combustion, and industrial processes. Here we quantify the effects of chlorine on fine particulate matter (PM2.5) and ozone air quality across China by using the GEOS-Chem chemical transport model with comprehensive anthropogenic emissions and detailed representation of gas-phase and heterogeneous chlorine chemistry. Comparison of the model to observed ClNO2, HCl, and particulate Cl- concentrations shows that reactive chlorine in China is mainly anthropogenic, unlike in other continental regions where it is mostly of marine origin. The model is successful in reproducing observed concentrations and their distributions, lending confidence in the anthropogenic chlorine emission estimates and the resulting chemistry. We find that anthropogenic chlorine emissions increase total inorganic PM2.5 by as much as 3.2 μg m-3 on an annual mean basis through the formation of ammonium chloride, partly compensated by a decrease of nitrate because ClNO2 formation competes with N2O5 hydrolysis. Annual mean MDA8 surface ozone increases by up to 1.9 ppb, mainly from ClNO2 chemistry, while reactivities of volatile organic compounds increase (by up to 48% for ethane). We find that a sufficient representation of chlorine chemistry in air quality models can be obtained from consideration of HCl/Cl- thermodynamics and ClNO2 chemistry, because other more complicated aspects of chlorine chemistry have a relatively minor effect.
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| 11. |
- Wu, R. R., et al.
(författare)
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Molecular composition and volatility of multi-generation products formed from isoprene oxidation by nitrate radical
- 2021
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 21:13, s. 10799-10824
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Tidskriftsartikel (refereegranskat)abstract
- Isoprene oxidation by nitrate radical (NO3) is a potentially important source of secondary organic aerosol (SOA). It is suggested that the second or later-generation products are the more substantial contributors to SOA. However, there are few studies investigating the multi-generation chemistry of isoprene-NO3 reaction, and information about the volatility of different isoprene nitrates, which is essential to evaluate their potential to form SOA and determine their atmospheric fate, is rare. In this work, we studied the reaction between isoprene and NO3 in the SAPHIR chamber (Julich) under near-atmospheric conditions. Various oxidation products were measured by a high-resolution time-offlight chemical ionization mass spectrometer using Br as the reagent ion. Most of the products detected are organic nitrates, and they are grouped into monomers (C-4 and C-5 products) and dimers (C-10 products) with 1-3 nitrate groups according to their chemical composition. Most of the observed products match expected termination products observed in previous studies, but some compounds such as monomers and dimers with three nitrogen atoms were rarely reported in the literature as gas-phase products from isoprene oxidation by NO3. Possible formation mechanisms for these compounds are proposed. The multi-generation chemistry of isoprene and NO3 is characterized by taking advantage of the time behavior of different products. In addition, the vapor pressures of diverse isoprene nitrates are calculated by different parametrization methods. An estimation of the vapor pressure is also derived from their condensation behavior. According to our results, isoprene monomers belong to intermediate-volatility or semi-volatile organic compounds and thus have little effect on SOA formation. In contrast, the dimers are expected to have low or extremely low volatility, indicating that they are potentially substantial contributors to SOA. However, the monomers constitute 80% of the total explained signals on average, while the dimers contribute less than 2 %, suggesting that the contribution of isoprene NO3 oxidation to SOA by condensation should be low under atmospheric conditions. We expect a SOA mass yield of about 5% from the wall-loss- and dilution-corrected mass concentrations, assuming that all of the isoprene dimers in the low- or extremely low-volatility organic compound (LVOC or ELVOC) range will condense completely.
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| 12. |
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| 13. |
- Nilsson, Robin, 1993
(författare)
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Interactions Between Water and Cellulose Esters
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biopolymers, which are produced from natural sources, are gaining interest as a potential replacement for fossil-based polymers. As such, they are already widely used in several industries, including the food, healthcare, and personal care industries. To harness the full potential of biopolymers as materials in new products designed for specific tasks, an ability to accurately predict their properties and how these properties change in different environments, is desirable. Hansen Solubility Parameters (HSP) combine dispersive, polar, and hydrogen bonding energies to understand interactions between molecules. This thesis explores the potential use of HSP as predictors of glass transition temperatures (Tg) and water interactions. It also focuses on elucidating the effect of an increased side-chain length of cellulose esters on their thermal properties, structural properties, and water interactions, together with how these properties are affected by the absorption of water. The cellulose esters studied here were cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. The HSP showed that the dispersive energy dominates the total cohesive energy, followed by the hydrogen bonding and then the polar energy. Counter-intuitively, the Tg decreased with an increased total cohesive energy. The HSP explained this phenomenon, namely, that the increased length of the substituents screened the short-range hydrogen bonds. A similar effect was observed for water solubility and penetration into the cellulose esters, which decreased with increasing side-chain lengths despite the approximately constant hydrogen bonding energies. This indicates the importance of focusing on each of the different interaction parameters instead of only the total HSP.
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| 14. |
- Sauer, Christopher, 1993
(författare)
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Green aromatics for a bio-based economy - Valorization of biomass derived model compounds over zeolites studied by online analysis
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the strive towards sustainable chemical production, its carbon-based products can no longer be produced from fossil resources but need to be manufactured from a renewable feedstock. Simple aromatic building blocks like benzene, toluene and xylenes (BTX) can be obtained by catalytic valorization of biomass derived platform molecules such as furans provided efficient catalysts can be formulated. To evaluate catalysts for the conversion of furans to BTX and study the involved catalytic reactions, advanced analytical methods are needed. The observation of dynamic responses in catalytic activity and selectivity necessitates time-resolved analysis of rather complex hydrocarbon (HC) streams. In this work, an online analysis method combining Fourier transform infrared spectroscopy and ion molecule reaction mass spectrometry has been developed for the direct monitoring of the effluent stream during conversion of furans over zeolite catalysts. The sampling frequency is shown to be at least 4 per minute, which is considerably higher compared to that of separation-based methods operating on time scales of several minutes. A wide range of HCs and other smaller molecules is identified and individual species quantified simultaneously. The carbon balance of around 90% shows that the vast majority of the complex HC stream is indeed analysed. The developed online analysis has been applied to catalytic step-response experiments, where different zeolites were exposed to concentration steps of 2,5-dimethylfuran at steady temperatures. It is found that the HC stream consists of a range of olefins and aromatics, including BTX. Most interestingly, 2,5-dimethylfuran is isomerized to 2,4-dimethylfuran as well as 2- and 3-methyl-2-cyclopenten-1-one. The formation of BTX is linked to the availability of olefins, which is supported by temperature programmed desorption experiments. Furthermore, to build understanding of the catalytic mechanisms, surface species were characterised in situ by use of diffuse reflectance infrared Fourier transform spectroscopy. It is clear that upon adsorption, 2,5-dimethylfuran interacts with the zeolite structure and undergoes transforming reactions to olefins and aromatics upon temperature increase, but further studies are necessary to comprehend how the rather low selectivity towards BTX can be increased by catalyst design.
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| 15. |
- Nilsson, Robin, 1993
(författare)
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An Investigation of Mixed Cellulose Esters and Acyclic Polyacetates: Effects of Side-Chain Lengths and Degrees of Ring-Opening
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bio-based polymers produced from natural sources are gaining an increased interest as potential replacement for today’s conventional fossil-based plastic polymers. Their use is already wide in many large-scale industrial areas such as healthcare, personal care, and food. To widen the potential of biopolymers in new applications such as plastics, their properties need to be tuned by modification to handle factors like relative humidity, which is especially important for gas barriers in food packaging. This thesis explores the effect of two structural variations of cellulose esters, one where the average side-chain length is increased, going from cellulose acetate to cellulose acetate propionate and then cellulose acetate butyrate, and another where the polymer backbone of cellulose acetate is ring-opened. These two modifications affect the glass transition temperature, an important structural factor. The effect of the average side-chain length is explored to a greater extent where they are studied for impact on mechanical properties, water content, water sorption at different RH, the kinetics of water sorption at different RH, mechanical properties at different RH and oxygen permeation at different RH. The focus is on how water interacts with the different esters with regard to the average side-chain length and how water affects their properties. An increase of average sidechain length and the ring-opening were shown to decrease the glass transition temperature. Together with the water sorption and Hansen solubility parameter, it was concluded that longer average side-chain length screens out hydrogen bonding between the polymers. The studies on the average side-chain length and water sorption indicated that water entering the cellulose acetate creates clusters. These formed water clusters create cavities in the polymer which makes the polymer hold more water than before introducing of the water clusters. Oxygen permeation studies on prewetted films prove that these cavities created by water clustering are still present after drying the material at 0% RH and thus resulted in a higher oxygen permeation compared to films that had not been exposed to higher than 50% RH.
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| 16. |
- Swensson, Beatrice, 1992
(författare)
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Dissolution of cellulose in aqueous hydroxide base solvents
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As we move towards a circular bioeconomy, new and advanced materials based on cellulose are constantly developed. Unlike most plastics or metals, cellulose cannot be melted, and therefore dissolution is an important tool for processing of cellulose but also for analytical purposes. There is, however, both a knowledge gap in understanding the mechanisms behind dissolution as well as a continued search for new and improved solvents. Aqueous solutions of hydroxide bases are a group of solvents with considerable variation in both dissolution capacity and stability of cellulose solutions, and their properties need to be improved to be useful solvents. Despite this, they are interesting because they have the potential to be cheap and non-toxic, depending on the base of choice. Therefore, the purpose of this thesis has been to further understand the interactions governing cellulose dissolution and properties in aqueous solutions of hydroxide bases, so that in the future, new and improved solvents can be designed. In order to achieve this, cellulose dissolution at low temperatures in aqueous solutions of NaOH and selected quaternary ammonium hydroxide bases has been investigated. The effect of combining NaOH with a quaternary ammonium hydroxide was also investigated, along with the influence of the commonly used additive urea. Results based on light scattering measurements revealed that dissolution in NaOH(aq) is poor, with relatively large aggregates present already at very dilute concentrations and a fraction of undissolved cellulose always present. Upon comparing NaOH to more hydrophobic quaternary ammonium hydroxides, it was observed that the dissolution capacity of the bases increased with increasing hydrophobicity of the cation, alongside their ability to act as hydrogen bond acceptors. Rheology measurements showed that compared to pure NaOH(aq) or pure tetramethylammonium hydroxide (TMAH)(aq), combining NaOH with TMAH improved the stability of the solutions over time and against increasing temperature. It was therefore proved that combining bases can have a similar effect as an additive, but the results were highly dependent on the base pair employed and indicated that both bases need to be able to dissolve cellulose on their own, within the same temperature interval and be miscible with each other in order to improve solution properties.
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| 17. |
- Angelin, Eva Mariasole, et al.
(författare)
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The multi-analytical in situ analysis of cadmium-based pigments in plastics
- 2020
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Ingår i: Microchemical Journal. - : Elsevier BV. - 0026-265X. ; 157
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Tidskriftsartikel (refereegranskat)abstract
- © 2020 Elsevier B.V. Colorants are present in trace concentration in objects made of plastic and their identification is a methodological and analytical challenge. In conservation, the identification of colorants may allow a better understanding of colorant degradation (such as color change and fading) and provide information about the historical development, production and processing of plastics. Although micro-destructive analytical protocols are well established for the analysis of colorants, in cultural heritage, where in situ methodologies are preferred and, in some cases, mandatory, new approaches are greatly needed. In this work, an in situ multi-analytical approach is used to specifically study inorganic cadmium-based pigments that were commonly used for coloring plastics during the 20th c. First introduced as vivid artists’ pigments, cadmium-based additives were used for coloring plastics because of their exceptional performance properties. Eighteen colored polymethyl methacrylate (PMMA) samples, produced in the second half of the 20th c. by the company Plásticos do Sado (Portugal), were studied with a combination of optical microscopy, colorimetry, UV–Vis-NIR diffuse reflectance, laser-induced photoluminescence, vibrational (µ-Raman) and elemental (µ-EDXRF) spectroscopies. On the basis of complementary data, the chemical composition of most of the coloring agents employed in the acrylic samples were identified without any micro-sampling.
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| 18. |
- Cen, Peng, et al.
(författare)
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Metal extraction from a deep eutectic solvent, an insight into activities
- 2020
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 22:19, s. 11012-11024
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Tidskriftsartikel (refereegranskat)abstract
- The solvent extraction of gold, palladium, technetium, indium and rhenium from both mixtures of a deep eutectic solvent with aqueous salt solutions and of two different aqueous salt solutions has been performed. Initially using gold and then the other metals the solvent extraction results were interpreted using an activity coefficient/function equation (specific ion interaction theory). The most important presented result is the addition of a new term to the specific ion interaction theory equation. Using the new model it will be possible to make predictions of the behaviour of a solvent extraction system where one of the liquid phases is a mixture of aqueous salts and the deep eutectic solvent.
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| 19. |
- Grommet, Angela Beth, 1991, et al.
(författare)
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Molecular Photoswitching in Confined Spaces
- 2020
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Ingår i: Accounts of Chemical Research. - : American Chemical Society (ACS). - 0001-4842 .- 1520-4898. ; 53:11, s. 2600-2610
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Forskningsöversikt (refereegranskat)
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| 20. |
- Hertzog, Manuel, 1989, et al.
(författare)
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Enhancing Vibrational Light-Matter Coupling Strength beyond the Molecular Concentration Limit Using Plasmonic Arrays
- 2021
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 21:3, s. 1320-1326
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Tidskriftsartikel (refereegranskat)abstract
- Vibrational strong coupling is emerging as a promising tool to modify molecular properties by making use of hybrid light-matter states known as polaritons. Fabry-Perot cavities filled with organic molecules are typically used, and the molecular concentration limits the maximum reachable coupling strength. Developing methods to increase the coupling strength beyond the molecular concentration limit are highly desirable. In this Letter, we investigate the effect of adding a gold nanorod array into a cavity containing pure organic molecules using FT-IR microscopy and numerical modeling. Incorporation of the plasmonic nanorod array that acts as artificial molecules leads to an order of magnitude increase in the total coupling strength for the cavity with matching resonant frequency filled with organic molecules. Additionally, we observe a significant narrowing of the plasmon line width inside the cavity. We anticipate that these results will be a step forward in exploring vibropolaritonic chemistry and may be used in plasmon based biosensors.
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| 21. |
- Kajan, Ivan, et al.
(författare)
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Effect of diluent on the extraction of europium(iii) and americium(iii) with N,N,N ',N '-tetraoctyl diglycolamide (TODGA)
- 2021
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 11:58, s. 36707-36718
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Tidskriftsartikel (refereegranskat)abstract
- Solvent extraction of Eu3+ and Am(3+)via N,N,N ',N'-tetraoctyl diglycolamide (TODGA) dissolved in different molecular diluents was studied. The diluent types used in this work were primary and secondary alcohols, secondary ketones and alkanes. Effects of concentration of extracting agent, temperature, diluent type and its carbon chain length on the extractions were determined. Distribution ratios of Eu3+ and Am3+ showed high dependence on the diluent type as well as the carbon chain length within the same type of diluent. The highest distribution ratios for both Eu3+ and Am3+ as well as the separation factors of Eu3+ over Am3+ were observed in the alkane diluents. Unexpectedly high distribution ratios for Eu3+ and Am3+ were observed in polar diluents with 5 carbon atoms in the chain, clearly standing out against the general trends. It was found that Eu3+ and Am3+ extraction via TODGA is enthalpy driven in all the studied diluents and that extraction is more exothermic in alkane diluents. Analysis of the stoichiometry of the extracted complexes shows that the average ligand number of TODGA molecules in the extracted complex is lower for Am3+ compared to Eu3+ except for with alkane diluents.
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| 22. |
- Kaur, Amanpreet, et al.
(författare)
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Chemoselective bicyclobutane-based mass spectrometric detection of biological thiols uncovers human and bacterial metabolites
- 2023
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Ingår i: Chemical Science. - : Royal Society of Chemistry. - 2041-6520 .- 2041-6539. ; 14:20, s. 5291-5301
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Tidskriftsartikel (refereegranskat)abstract
- Sulfur is an essential element of life. Thiol-containing metabolites in all organisms are involved in the regulation of diverse biological processes. Especially, the microbiome produces bioactive metabolites or biological intermediates of this compound class. The analysis of thiol-containing metabolites is challenging due to the lack of specific tools, making these compounds difficult to investigate selectively. We have now developed a new methodology comprising bicyclobutane for chemoselective and irreversible capturing of this metabolite class. We utilized this new chemical biology tool immobilized onto magnetic beads for the investigation of human plasma, fecal samples, and bacterial cultures. Our mass spectrometric investigation detected a broad range of human, dietary and bacterial thiol-containing metabolites and we even captured the reactive sulfur species cysteine persulfide in both fecal and bacterial samples. The described comprehensive methodology represents a new mass spectrometric strategy for the discovery of bioactive thiol-containing metabolites in humans and the microbiome.
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| 23. |
- Lin, Weifeng, et al.
(författare)
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Identification of nutritional biomarkers through highly sensitive and chemoselective metabolomics
- 2023
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Ingår i: Food Chemistry. - : Elsevier. - 0308-8146 .- 1873-7072. ; 425
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Tidskriftsartikel (refereegranskat)abstract
- The importance of a healthy diet for humans is known for decades. The elucidation of key molecules responsible for the beneficial and adverse dietary effects is slowly developing as the tools are missing. Carbonyl-containing metabolites are a common bioproducts through conversion of diet by the microbiome. In here, we have utilized our recently developed mass spectrometric methodology based on chemoselective conjugation of carbonyl-metabolites. The method has been applied for urine sample analysis from a dietary (poly)phenol intervention study (N = 78 individuals) for the first time. We have identified a series of carbonyl-metabolites of dietary origin and the chemical structure was validated for 30 metabolites. Our sensitive analysis led to the discovery of four unknown dietary markers with high sensitivity and selectivity (AUC > 0.91). Our chemical metabolomics method has been successfully applied for large-scale analysis and provides the basis for targeted metabolomics to identify unknown nutritional and disease-related biomarkers.
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| 24. |
- Lyseid Authen, Thea, 1993, et al.
(författare)
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Batch flowsheet test for a GANEX-type process: the CHALMEX FS-13 process
- 2022
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Ingår i: Solvent Extraction and Ion Exchange. - : Informa UK Limited. - 0736-6299 .- 1532-2262. ; 40:3, s. 189-202
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Tidskriftsartikel (refereegranskat)abstract
- The Chalmers grouped actinide extraction (CHALMEX) process is focused on the co-separation of actinides from all other elements in spent nuclear fuel solution, with the ultimate purpose of transmuting the actinides into shorter-lived and less radiotoxic elements. Based on solvent extraction equilibrium distribution data of actinides and fission products, a preliminary flowsheet was developed and tested in batch mode. The flowsheet consists of one extraction step with the CHALMEX FS-13 solvent (25 mM CyMe4-BTBP in 30% v/v TBP and 70% v/v FS-13), using hydrophilic masking agents (20 mM bimet and 0.2 M mannitol) in the aqueous phase for the complexation of troublesome fission products. Two nitric acid scrub steps (0.5 M HNO3) were efficient in removing co-extracted acid, all molybdenum and the majority of silver. Two stripping stages (0.5 M glycolic acid at pH 4) were efficient in recovery of the actinides from the organic phase. The need for a solvent clean-up stage for the removal of nickel, cadmium, iron and the remaining silver from the organic phase was demonstrated. Based on the distribution data, it was calculated that a 99.9% recovery of americium is possible using only 3 ideal extraction stages, 3 ideal scrubbing stages and 2 ideal stripping stages.
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| 25. |
- Orzan, Eliott, 1995, et al.
(författare)
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Elucidation of cellulose phosphorylation with phytic acid
- 2024
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Ingår i: Industrial Crops and Products. - 0926-6690. ; 218
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Tidskriftsartikel (refereegranskat)abstract
- The worldwide ban on the use of halogenated flame retardants has accelerated the development of non-toxic alternatives from natural feedstock, such as phytic acid. The fire suppressing mechanisms which acidic phosphates impart on cellulosic materials rivals most solutions yet promotes cellulose hydrolysis and degradation. Current attempts to prevent degradation that results from the acid hydrolysis and to improve flame retardancy rely on the use of catalysts without evaluating the effect of curing temperature on cellulose phosphorylation. In this study, the fundamental condensation reaction between cellulose and phytic acid reveals how varying curing temperature affects the phosphorylation and degradation of cellulosic structures. Curing a low concentration of phytic acid on cellulose at 160 °C was shown to promote the phosphorylation of cellulose over the formation of oligo-phosphates. The addition of phytic acid and rise in curing temperature degraded non-crystalline moieties and improved thermo-oxidative stability credit to the char layer formation of the phosphorylated cellulose structure. Increased phosphorus content expectedly led to improved thermal stability, yet cross-linking of phytic acid to cellulose overcame the need for increased phytic acid concentrations. This work thus provides the basis for the application of heat-curing phytic acid at low concentrations to target cellulose fire-retardancy using a chemical catalyst-free and solvent-free approach.
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| 26. |
- Sjöblom, Magnus, et al.
(författare)
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Enzyme-Assisted CO2 Absorption in Aqueous Amino Acid Ionic Liquid Amine Blends
- 2020
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society. - 2168-0485. ; 8:36, s. 13672-13682
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Tidskriftsartikel (refereegranskat)abstract
- The influence of carbonic anhydrase (CA) on the CO2 absorption rate and CO2 load in aqueous blends of the amino acid ionic liquid pentaethylenehexamine prolinate (PEHAp) and methyl diethanolamine (MDEA) was investigated and compared to aqueous monoethanolamine (MEA) solutions. The aim was to identify blends with good enzyme compatibility, several fold higher absorption rates than MDEA and superior desorption potential compared to MEA. The blend of 5% PEHAp and 20% MDEA gave a solvent with approximately five-fold higher initial absorption rate than MDEA and a two-fold higher regeneration compared to MEA. Experiments in a small pilot absorption rig resulted in a mass transfer coefficient (KGa) of 0.48, 4.6, and 15 mol (m3 s mol fraction)−1 for 25% MDEA, 5% PEHAp, 20% MDEA, and 25% MEA, respectively. CA could maintain approximately 70% of its initial activity after 2 h incubation in PEHAp MDEA blends. Integration of CA with amine-based absorption resulted in a 31.7% increase in mass of absorbed CO2 compared to the respective non-enzymatic reaction at the optimal solvent: CA ratio and CA load. Combining novel blends and CA can offer a good compromise between capital and operating costs for conventional amine scrubbers, which could outperform MEA-based systems.
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| 27. |
- Zhang, Xin, 1990-
(författare)
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Tailoring Fluorescent Probes for Organelle-Specific Imaging and Sensing
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Exploring and visualizing biological and pathological processes in living cells are useful for both fundamental research and applications. An understanding on the molecular level for these processes with focus on tracking biomarkers, collecting information about their surroundings, and uncovering essential molecular pathways and functions in live cells are of vital interest for cell biological study and clinical diagnosis application. Fluorescent imaging technologies have become essential tools in cell biology studies, providing dynamic information about the localization and quantity of the analytes in living systems that we can not see by our naked eyes. Since the discovery of organic fluorescent dyes, unremitting efforts have been made to visualize the behaviors of specific targets by using these fluorophores as labels. Today, a variety of probes and nanoprobes have been developed for specific targeting and sensing. However, the current probes and nanoprobes still show some inherent deficiencies, such as poor specificity, strong photobleaching, high toxicity, low signal-to-noise ratio, poor cell membrane penetration, etc. To conquer these limitations, this thesis will focus on developing fluorescent platforms for bioimaging and biosensing with improved sensitivity, selectivity, specificity, and stability.A red-emitting fluorescent probe is first proposed that not only tracks the dynamic changes in real-time, during migration and fusion of lipid droplets but also monitors starvation-induced lipophagy (Paper I). In addition to organic fluorophores, hybrid fluorescent silica nanoparticles (SiNPs) are very promising for bioimaging/sensing owing to the advantages of low toxicity, high biocompatibility, multifunctionality, hydrophilicity and accessible surface functionality. Nonetheless, to apply SiNPs for such purposes, it is mandatory to address common problems of poor cell penetration and lack of specificity. Therefore, in this thesis, an efficient membrane-penetration SiNP is tailored with the intention to enable subcellular imaging/sensing. The proposed SiNPs are characterized by rapid cellular uptake (˂ 30 min) and specific subcellular targeting capabilities with surface modification. Finally, real-time tracking of dynamic changes in mitochondria and lysosomes during autophagy process is successfully performed (Paper II). Through the rational design of new functionalities on the established SiNPs, mitochondria- and lysosome-specific pH nanoprobes are further tailored for real-time monitoring of pH variations under various stimuli (Paper III and IV). Another ratiometric nanoprobe is developed for quantitative indication of lysosomal adenosine 5'-triphosphate (ATP) levels in living cells. The nanoprobe enables a deeper understanding of the interplay between energy metabolism and autophagy (Paper V).In conclusion, throughout the studies in this thesis, the fabrication and utilization of fluorescent molecular probes and SiNP-based nanoprobes for cellular probing have been investigated and analyzed. The strategies and the fabricated SiNPs can facilitate our deeper understanding of cellular pathological processes and provide basic knowledge for the development of other functional materials for life science applications.
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| 28. |
- Hultmark, Sandra, 1994, et al.
(författare)
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Vitrification of octonary perylene mixtures with ultralow fragility
- 2021
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 7:29
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Tidskriftsartikel (refereegranskat)abstract
- Strong glass formers with a low fragility are highly sought-after because of the technological importance of vitrification. In the case of organic molecules and polymers, the lowest fragility values have been reported for single-component materials. Here, we establish that mixing of organic molecules can result in a marked reduction in fragility. Individual bay-substituted perylene derivatives display a high fragility of more than 70. Instead, slowly cooled perylene mixtures with more than three components undergo a liquid-liquid transition and turn into a strong glass former. Octonary perylene mixtures display a fragility of 13 +/- 2, which not only is a record low value for organic molecules but also lies below values reported for the strongest known inorganic glass formers. Our work opens an avenue for the design of ultrastrong organic glass formers, which can be anticipated to find use in pharmaceutical science and organic electronics.
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| 29. |
- Meng, X. X. Y., et al.
(författare)
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Humidity-Dependent Phase State of Gasoline Vehicle Emission-Related Aerosols
- 2021
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Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 55:2, s. 832-841
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Tidskriftsartikel (refereegranskat)abstract
- The phase states of primarily emitted and secondarily formed aerosols from gasoline vehicle exhausts were investigated by quantifying the particle rebound fraction (f). The rebound behaviors of gasoline vehicle emission-related aerosols varied with engines, fuel types, and photochemical aging time, showing distinguished differences from biogenic secondary organic aerosols. The nonliquid-to-liquid phase transition of primary aerosols emitted from port fuel injection (PFI) and gasoline direct injection (GDI) vehicles started at a relative humidity (RH) = 50 and 60%, and liquefaction was accomplished at 60 and 70%, respectively. The RH at which f declined to 0.5 decreased from 70 to 65% for the PFI case with 92# fuel, corresponding to the photochemical aging time from 0.37 to 4.62 days. For the GDI case, such RH enhanced from 60 to 65%. Our results can be used to imply the phase state of traffic-related aerosols and further understand their roles in urban atmospheric chemistry. Taking Beijing, China, as an example, traffic-related aerosols were mainly nonliquid during winter with the majority ambient RH below 50%, whereas they were mostly liquid during the morning rush hour of summer, and traffic-related secondary aerosols fluctuated between nonliquid and liquid during the daytime and tended to be liquid at night with increased ambient RH.
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| 30. |
- Peng, X., et al.
(författare)
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Photodissociation of particulate nitrate as a source of daytime tropospheric Cl2
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Chlorine atoms (Cl) are highly reactive and can strongly influence the abundances of climate and air quality-relevant trace gases. Despite extensive research on molecular chlorine (Cl2), a Cl precursor, in the polar atmosphere, its sources in other regions are still poorly understood. Here we report the daytime Cl2 concentrations of up to 1 ppbv observed in a coastal area of Hong Kong, revealing a large daytime source of Cl2 (2.7 pptv s−1 at noon). Field and laboratory experiments indicate that photodissociation of particulate nitrate by sunlight under acidic conditions (pH < 3.0) can activate chloride and account for the observed daytime Cl2 production. The high Cl2 concentrations significantly increased atmospheric oxidation. Given the ubiquitous existence of chloride, nitrate, and acidic aerosols, we propose that nitrate photolysis is a significant daytime chlorine source globally. This so far unaccounted for source of chlorine can have substantial impacts on atmospheric chemistry. © 2022, The Author(s).
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| 31. |
- Tsiligiannis, Epameinondas, et al.
(författare)
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A Four Carbon Organonitrate as a Significant Product of Secondary Isoprene Chemistry
- 2022
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 49:11
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Tidskriftsartikel (refereegranskat)abstract
- Oxidation of isoprene by nitrate radicals (NO3) or by hydroxyl radicals (OH) under high NOx conditions forms a substantial amount of organonitrates (ONs). ONs impact NOx concentrations and consequently ozone formation while also contributing to secondary organic aerosol. Here we show that the ONs with the chemical formula C4H7NO5 are a significant fraction of isoprene-derived ONs, based on chamber experiments and ambient measurements from different sites around the globe. From chamber experiments we found that C4H7NO5 isomers contribute 5%-17% of all measured ONs formed during nighttime and constitute more than 40% of the measured ONs after further daytime oxidation. In ambient measurements C4H7NO5 isomers usually dominate both nighttime and daytime, implying a long residence time compared to C-5 ONs which are removed more rapidly. We propose potential nighttime sources and secondary formation pathways, and test them using a box model with an updated isoprene oxidation scheme.
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| 32. |
- Wang, Y. J., et al.
(författare)
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Comparative Study of Particulate Organosulfates in Contrasting Atmospheric Environments: Field Evidence for the Significant Influence of Anthropogenic Sulfate and NOx
- 2020
-
Ingår i: Environmental Science & Technology Letters. - : American Chemical Society (ACS). - 2328-8930. ; 7:11, s. 787-794
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Tidskriftsartikel (refereegranskat)abstract
- Organosulfates (OSs) are an important group of secondary organic aerosols, but the key influential factors of their formation in polluted atmospheres are not well understood. In this study, we monitored particulate OSs (carboxy OSs, hydroxyacetone sulfate, and isoprene- and monoterpene-derived OSs) at an urban site and a regional site in Beijing and examined their compositions and formation pathways under contrasting atmospheric conditions. The quantified OSs were most abundant in the summer at the regional site due to higher biogenic emissions and favorable formation conditions (higher aerosol acidity and humidity), followed by urban summer and winter conditions. Larger fractions of inorganic sulfate were converted to organosulfur when sulfate was less abundant. This implies that OSs would play more important roles in aerosol properties as the decline of sulfate. Monoterpene-derived nitrooxy-OSs were enhanced via NO3 oxidation in the summer under high-NOx conditions at night, while the day-night variations in the winter were not as obvious. Among isoprene-OSs, IEPOX (isoprene epoxydiols)-OS formation was clearly suppressed under high-NOx conditions, while other isoprene-OSs that are favored under high-NOx conditions showed increasing formation with NOx. The results highlight that isoprene-OS formation pathways in polluted atmospheres could be different from the IEPOX-dominated regions reported for the low-NOx environments in the literature.
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| 33. |
- Zhou, L. Y., et al.
(författare)
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Emissions and Secondary Formation of Air Pollutants from Modern Heavy-Duty Trucks in Real-World Traffic-Chemical Characteristics Using On-Line Mass Spectrometry
- 2021
-
Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 55:21, s. 14515-14525
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Tidskriftsartikel (refereegranskat)abstract
- Complying with stricter emissions standards, a new generation of heavy-duty trucks (HDTs) has gradually increased its market share and now accounts for a large percentage of on-road mileage. The potential to improve air quality depends on an actual reduction in both emissions and subsequent formation of secondary pollutants. In this study, the emissions in real-world traffic from Euro VI-compliant HDTs were compared to those from older classes, represented by Euro V, using high-resolution time-of-flight chemical ionization mass spectrometry. Gas-phase primary emissions of several hundred species were observed for 70 HDTs. Furthermore, the particle phase and secondary pollutant formation (gas and particle phase) were evaluated for a number of HDTs. The reduction in primary emission factors (EFs) was evident (similar to 90%) and in line with a reduction of 28-97% for the typical regulated pollutants. Secondary production of most gas- and particle-phase compounds, for example, nitric acid, organic acids, and carbonyls, after photochemical aging in an oxidation flow reactor exceeded the primary emissions (EFAged/EFFresh ratio >= 2). Byproducts from urea-selective catalytic reduction systems had both primary and secondary sources. A non-negative matrix factorization analysis highlighted the issue of vehicle maintenance as a remaining concern. However, the adoption of Euro VI has a significant positive effect on emissions in real-world traffic and should be considered in, for example, urban air quality assessments.
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| 34. |
- Eswaran, Muthusankar, 1988, et al.
(författare)
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A flexible multifunctional electrode based on conducting PANI/Pd composite for non-enzymatic glucose sensor and direct alcohol fuel cell applications
- 2023
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 345
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we fabricated a flexible, multifunctional polyimide (PI)/Au-polyaniline (PAN)/Pd nanocomposite electrode with excellent electrochemical properties. Structural geometry, morphological views, and functional group analyses indicated that the physicochemical and electrochemical performance of the electrode is based on the strong and synergistic metal-polymer interaction between the conducting PAN and Pd, which ensured high conductivity, rapid response, and high electron transfer rate through more electroactive spots available in the nanocomposite. Here, we demonstrated that the fabricated PI/Au-PAN/Pd electrodes can be successfully used for biomedical sensing of glucose, as well as for energy conversion application, using the oxidation of alcohols such as methanol and ethanol in fuel cells. The electrochemical analysis shows that the flexible sensor (PI/Au-PAN/Pd) has ultra-high sensitivity of 2140 μA/μM.cm2 with a low detection limit of 0.3 μM for glucose. Also, the interference analysis, reproducibility, and stability studies reveal its excellent capability for glucose sensing. Furthermore, the electrode also demonstrates prominent electrocatalytic behavior to the electrooxidation of methanol and ethanol in an alkaline medium with a current density of 3 mA/cm2 and 0.96 mA/cm2 along with good cyclic stability. Thus, this efficient flexible electrocatalyst with good stability, practicability, and reproducibility claims its potential applications in flexible/wearable healthcare diagnostics systems as well as in alternative energy conversion devices.
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| 35. |
- Ismail, Norafiqah, et al.
(författare)
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Investigating the potential of membranes formed by the vapor induced phase separation process
- 2020
-
Ingår i: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 597
-
Forskningsöversikt (refereegranskat)abstract
- About 100 years ago, Zsigmondy and Bachmann invented a new method to induce phase inversion, the so-called vapor induced phase separation (VIPS). Since then many researchers have demonstrated this method in membrane fabrication. Here we present a review on membrane fabrication via VIPS to provide insights into membrane formation parameters in order to achieve desired properties for different applications. The key factors upon membrane preparation including solution parameters (i.e. polymer type and concentration, type of solvent, and additives) as well as operating parameters (i.e. exposure time, relative humidity, dissolution temperature, and vapor temperature) are comprehensively discussed. Furthermore, the design of a fouling-resistance membrane by the VIPS process has recently gained attention and is elaborated in details. The applications of the produced membranes via VIPS in water and wastewater treatment, gas separations, electrochemical applications (i.e. secondary batteries and supercapacitors) as well as in medical and biological applications are summarized and an outlook for future investigation is presented.
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| 36. |
- Klement, W. J. Niels, et al.
(författare)
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Selective Analysis of Redox Processes at the Electrode Interface with Time-Resolved Raman Spectroscopy
- 2023
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 39:30, s. 10383-10394
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemistry and electrochemical reactions are increasinglyimportant in the transition to a sustainable chemical industry. Theelectron transfer that drives such reactions takes place within nanometersof the electrode surface, and follow-up chemical reactions take placewithin the diffusion layer. Hence, understanding electrochemical reactionsrequires time-, potential-, and spatially resolved analysis. The confocalnature of Raman spectroscopy provides high spatial resolution, inaddition to detailed information on molecular structure. The intrinsicweakness of nonresonant Raman scattering, however, is not sensitiveenough for relatively minor changes to the solution resulting fromreactions at the electrode interface. Indeed, the limit of detectionis typically well above the concentrations used in electrochemicalstudies. Here, we show that surface-enhanced Raman scattering (SERS)and resonance Raman (rR) spectroscopy allow for spatially and time-resolvedanalysis of solution composition at (<1-2 nm) and near (within5 & mu;m) the electrode surface, respectively, in a selective mannerfor species present at low (<1 mM) concentrations. We show changesin concentration of species at the electrode surface, without theneed for labels, specific adsorption, or resonance enhancement, usinga SERS-active gold electrode prepared readily by electrochemical surfaceroughening. A combination of smooth and roughened gold electrodesis used to distinguish between surface and resonance enhancement usingthe well-known redox couples ferrocene and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonicacid) (ABTS). We discuss the impact of specific adsorption on thespectral analysis with the ruthenium(II) polypyridyl complex, [Ru(bpy)(3)](2+). The dual function of the electrode (surfaceenhancement and electron transfer) in the analysis of solution processesis demonstrated with the reversible oxidation of TMA (4,N,N-trimethylaniline), where transient soluble species are identifiedin real time, with rapid spectral acquisition, making use of localizedenhancement. We anticipate that this approach will find use in elucidatingelectro(catalytic) reactions at electrode interfaces.
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| 37. |
- Murphy, Colin, 1983, et al.
(författare)
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Plasmonic Temperature-Programmed Desorption
- 2021
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 21:1, s. 353-359
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Tidskriftsartikel (refereegranskat)abstract
- Temperature-programmed desorption (TPD) allows for the determination of the bonding strength and coverage of molecular mono- or multilayers on a surface and is widely used in surface science. In its traditional form using a mass spectrometric readout, this information is derived indirectly by analysis of resulting desorption peaks. This is problematic because the mass spectrometer signal not only originates from the sample surface but also potentially from other surfaces in the measurement chamber. As a complementary alternative, we introduce plasmonic TPD, which directly measures the surface coverage of molecular species adsorbed on metal nanoparticles at ultrahigh vacuum conditions. Using the examples of methanol and benzene on Au nanoparticle surfaces, the method can resolve all relevant features in the submonolayer and multilayer regimes. Furthermore, it enables the study of two types of nanoparticles simultaneously, which is challenging in a traditional TPD experiment, as we demonstrate specifically for Au and Ag.
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| 38. |
- Ranjbari, Elias, et al.
(författare)
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Direct Measurement of Total Vesicular Catecholamine Content with Electrochemical Microwell Arrays
- 2020
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 92:16, s. 11325-11331
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Tidskriftsartikel (refereegranskat)abstract
- We have designed and fabricated a microwell array chip (MWAC) to trap and detect the entire content of individual vesicles after disruption of the vesicular membrane by an applied electrical potential. To understand the mechanism of vesicle impact electrochemical cytometry (VIEC) in microwells, we simulated the rupture of the vesicles and subsequent diffusion of entrapped analytes. Two possibilities were tested: (i) the vesicle opens toward the electrode, and (ii) the vesicle opens away from the electrode. These two possibilities were simulated in the different microwells with varied depth and width. Experimental VIEC measurements of the number of molecules for each vesicle in the MWAC were compared to VIEC on a gold microdisk electrode as a control, and the quantified catecholamines between these two techniques was the same. We observed a prespike foot in a significant number of events (similar to 20%) and argue this supports the hypothesis that the vesicles rupture toward the electrode surface with a more complex mechanism including the formation of a stable pore intermediate. This study not only confirms that in standard VIEC experiments the whole content of the vesicle is oxidized and quantified at the surface of the microdisk electrode but actively verifies that the adsorbed vesicle on the surface of the electrode forms a pore in the vicinity of the electrode rather than away from it. The fabricated MWAC promotes our ability to quantify the content of vesicles accurately, which is fundamentally important in bioanalysis of the vesicles.
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| 39. |
- Wiorek, Alexander
(författare)
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Solving Analytical Challenges with Thin Layer Electrochemistry
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The decentralization of chemical sensing to attain environmental-related information is today highly desirable to increase the knowledge on biological or geological events as well as effluents. The current state of the field moves toward submersible probes; chemical sensors implemented into submersible devices for quantifying analytes over extended times. However, many sensors are still not robust enough for such applications. Additionally, the detections of most analytes require reagent addition and other steps before analysis (i.e., pre-treatments). For such analyses to be implemented in decentralized measurements, it would be beneficial to find reagentless approaches to modify samples and avoid waste associated with the reagent addition. This thesis aimed to develop such strategies using different solid materials capable of imposing ion-transfer events (actuators) under electrochemical control, to achieve measuring the analytes in the same sample using chemical sensors. Both actuators and sensors were jointly employed in thin layer (or near thin layer) samples, inside newly designed 3D-printed cells. This allowed for small sample volumes (ca 100 µm thicknesses) down to 0.5 µL to be analyzed, and resulted in fast, non-diffusion limited measurements that facilitated the sensor-actuator concepts. First, acidification of thin layer samples using polyaniline (PANI) was investigated. By electrochemical oxidation of PANI, its molecular structure changed resulting in hydrogen ions (acid) being delivered to the thin layer sample within two minutes or less, shifting its pH from ca 8 down to 2–3. By combining PANI and pH-sensors, reliable detection of alkalinity in real and artificial water samples could be achieved for a period of two weeks and possibly more. Also, by combining the PANI-based acidification with planar optodes capable of measuring pH or CO2 with high spatial resolution, buffer capacity or dissolved inorganic carbon (DIC) gradients could be resolved in a 2D domain with sub-mm resolution. PANI-based acidification was tested for sensing several environmental samples, including freshwater plants, brackish water, seawater, and soil, presenting great versatility in analytical performance. Second, a concept of selective deionization of thin layer samples was developed. The importance of such a concept is related to the selectivity of ion-based measurements, where ions such as Li+ or NH4+ are difficult to detect in real samples because of interfering ions increasing their limit of detection (LOD). Non-faradic processes were explored to remove such interferents by using carbon nanotubes (CNTs) for modulating the ion transfer with the sample. To facilitate selective deionization to only remove one ion species, the CNTs were covered with ultra-thin ion-selective membranes (ISMs; ca 200 nm thick). The tandem of CNTs-ISM was found to be capable of selectively removing multiple different cations, proven with the monitoring from both potentiometric sensors and optodes additionally implemented into the thin layer sample. Overall, the CNTs-ISM tandem shows great promise for lowering the LOD of chemical sensors in complex matrixes such as biological or environmental samples, which could aid to decentralized measurements in the future.
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| 40. |
- Oudbashi, Omid, 1978, et al.
(författare)
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Lead isotope analysis of Bronze Age copper alloy objects from Deh Dumen graveyard, southwestern Iran
- 2023
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Ingår i: Archaeological and Anthropological Sciences. - : Springer Science and Business Media LLC. - 1866-9557 .- 1866-9565. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- This research presents the lead isotopic composition of ten objects made of copper-tin alloy or arsenical copper that was recovered at the Bronze Age cemetery at Deh Dumen (southwestern Iran). Grave goods associated with different cultures in eastern Iran, Susa, or Luristan were identified at the site, and lead isotopic analyses were conducted to identify the copper sources used for the production of copper alloy objects found in multiple tombs. Comparison with data for ore sources shows that some of the objects have a signature that is compatible with that of the Iranian sources located in the Urumieh-Dokhtar and the Sanandaj-Sirjan. It also shows that three objects are compatible with the signature of objects found in the Gujarat and ore sources in the Aravalli-Delhi Belt deposits (Rajasthan and Gujarat) in India, demonstrating long-distance exchange between southwestern Iran and the Indus valley.
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| 41. |
- Shaner, Sebastian W., et al.
(författare)
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Skin stimulation and recording: Moving towards metal-free electrodes
- 2022
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Ingår i: Biosensors and Bioelectronics: X. - : Elsevier Ltd. - 2590-1370. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- When one thinks about electrodes, especially ones meant for humans, one typically thinks of some kind of metal. Whether on the skin or in the brain, metal electrodes are characteristically expensive, stiff, non-efficient in electron-ion transduction, and prone to toxic metal ion by-products during stimulation. In order to circumvent these disadvantages, electrically-conductive laser-induced graphene (LIG) and mixed electron-ion conducting polymer (poly(3, 4‐ethylenedioxythiophene) polystyrene sulfonate – PEDOT:PSS) was leveraged to create a metal-free electrode combination that allows for an economical, soft, and organic electrode for applications on human skin. Compared to clinical-standard silver – silver chloride (Ag/AgCl) skin electrodes, the metal-free hydrogel electrodes show notable improvement in electrochemical stability and prolonged stable potentials during long-term DC stimulation (0.5–24 h). Recording and stimulation performance on human participants rivals that of Ag/AgCl, thus fortifying the notion that they are an appropriate progression to their noble metal counterparts.
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| 42. |
- Wang, Aiyong, 1989, et al.
(författare)
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Insight into hydrothermal aging effect on Pd sites over Pd/LTA and Pd/SSZ-13 as PNA and CO oxidation monolith catalysts
- 2020
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Ingår i: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 278
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Tidskriftsartikel (refereegranskat)abstract
- In this study, Pd/LTA and Pd/SSZ-13 were prepared and then hydrothermally aged at the temperature of 750, 800, 850, and 900 °C. Multiple Pd species, including isolated Pd ions (Pd2+ and [Pd(OH)]+) and 1∼2 nm PdOx nanoparticles, were presented in two fresh samples. The Pd/LTA sample showed remarkable hydrothermal stability, but the Pd/SSZ-13 sample experienced severe damage after aging at 900 °C. The destruction of the aged Pd/SSZ-13 sample led to the migration and sintering of PdOx nanoparticles, which formed bulk PdOx particles on the surface of the zeolite crystallite. A large number of PdOx nanoparticles were retained after aging of the Pd/LTA sample. Pd/LTA contained a higher concentration of Pd2+ sites, while Pd/SSZ-13 had more [Pd(OH)]+ sites. It is found that the improvement of NO adsorption ability with CO addition onto Pd2+ was more significant than onto [Pd(OH)]+.
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| 43. |
- Khataee, Amirreza, et al.
(författare)
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Poly(arylene alkylene)s functionalized with perfluorosulfonic acid groups as proton exchange membranes for vanadium redox flow batteries
- 2023
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Ingår i: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 671
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Tidskriftsartikel (refereegranskat)abstract
- With the aim to develop vanadium redox flow battery (VRFB) membranes beyond state of the art, we have in the present work functionalized poly(p-terphenylene)s with highly acidic perfluorosulfonic groups and investigated their performance as proton exchange membranes (PEMs). Consequently, two poly(p-terphenylene alkylene)s tethered with perfluoroalkylsulfonic acid and perfluorophenylsulfonic acid, respectively, were synthesized through superacid-mediated polyhydroxyalkylations and cast into PEMs. Compared with Nafion 212, the PEM carrying perfluorophenylsulfonic acid groups (PTPF-Phenyl-SA) was found to exhibit higher ionic conductivity and eight times lower vanadium (IV) permeation rate. The latter explains the longer self-discharge duration of the VRFB based on the PTPF-Phenyl-SA. In addition, the VRFB assembled with the PTPF-Phenyl-SA PEM exhibited a high average coulombic efficiency of 99.6% for over 100 cycles with a capacity fade of 0.24% per cycle, which was 50% lower than when Nafion 212 was used. More importantly, excellent capacity retention was achieved through electrochemical rate performance experiments at different current densities.
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| 44. |
- Wärnheim, Alexander, et al.
(författare)
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Depth-Resolved FTIR-ATR Imaging Studies of Coating Degradation during Accelerated and Natural Weathering─Influence of Biobased Reactive Diluents in Polyester Melamine Coil Coating
- 2022
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 7:27, s. 23842-
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Tidskriftsartikel (refereegranskat)abstract
- Improved methods to assess the degradation of coil coatings to approximate lifetime have been an area of academic and industrial interest for decades. This work aims to elucidate the differences in the degradation behavior of two coil coating systems: one standard commercial formulation and one formulation with a significant addition of biorenewable reactive diluents. Depth-resolved degradation behavior of samples exposed to accelerated and natural field weathering is assessed. Focal plane array attenuated total reflection-Fourier transform infrared spectroscopy was used to acquire high-resolution chemical data from a sloping cross section. The results agreed with conventional photoacoustic spectroscopy. Degradation profiles for the two coatings were significantly different, with the biobased samples showing a more durable behavior. This study provides a method for detailed assessment of coating degradation, giving a good estimation of its durability. This is both a way to compare the performance of coating systems and to improve the understanding of the impact of exposure conditions, paving the way for the development of more sustainable coil coatings.
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| 45. |
- Ali, Sajid, et al.
(författare)
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Dual centrifugation as a novel and efficient method for the preparation of lipodisks
- 2024
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Ingår i: International Journal of Pharmaceutics. - : Elsevier. - 0378-5173 .- 1873-3476. ; 653
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Tidskriftsartikel (refereegranskat)abstract
- Polyethylene glycol (PEG)-stabilized lipodisks have emerged as innovatiive, promising nanocarriers for several classes of drugs. Prior research underscores the important role of lipid composition and preparation method in determining the lipodisk size, uniformity, and drug loading capacity. In this study, we investigate dual centrifugation (DC) as a novel technique for the production of PEG-stabilized lipodisks. Moreover, we explore the potential use of DC for the encapsulation of two model drugs, curcumin and doxorubicin, within the disks. Our results show that by a considerate choice of experimental conditions, DC can be used as a fast and straightforward means to produce small and homogenous lipodisks with a hydrodynamic diameter of 20-30 nm. Noteworthy, the technique works well for the production of both cholesterol-free and cholesterol-containing disks and does not require pre-mixing of the lipids in organic solvent. Furthermore, our investigations confirm the efficacy of DC in formulating curcumin and doxorubicin within these lipodisks. For doxorubicin, careful control and optimization of the experimental conditions resulted in formulations displaying an encouraging encapsulation efficiency of 84 % and a favourable drug-to-lipid ratio of 0.13 in the disks.
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| 46. |
- Andersson, Erika, et al.
(författare)
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Generation and properties of organic colloids extracted by water from the organic horizon of a boreal forest soil
- 2023
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Ingår i: Geoderma. - : Elsevier BV. - 0016-7061. ; 432
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Tidskriftsartikel (refereegranskat)abstract
- Organic colloids are an important part of dissolved organic matter (DOM) yet many of their properties remain elusive. The main aims of this study were to assess how the colloidal properties of DOM extracted with water from an organic boreal soil horizon varied with the extraction protocol, and thereby provide insight into the nature of the DOM colloids and develop a mechanistic understanding of how the colloids were generated from the parent soil aggregates. This was accomplished by systematic variations of extraction temperature (4 °C–100 °C), time, mechanical agitation, and pH, together with a combination of chemical analyses, and light and X-ray scattering. Our results agreed with the previous identification of two main colloidal DOM species, one fractal cluster and a second, smaller colloidal DOM species described as chains or coils. Fractal clusters completely dominated the colloidal DOM in extracts from our soil at room temperature and below. Colloidal coils only existed in DOM extracted above room temperature, and their amount increased significantly between 50 °C–100 °C. Moreover, the temperature variation indicated that the fractal clusters partly dissolved into colloidal coils at elevated temperatures. Mechanical agitation at 4 °C significantly increased the amount of DOM extracted, increasing the concentrations of both fractal clusters and low-molecular weight organic compounds. While the clusters were extracted from agitated and non-agitated soil suspensions, the low molecular weight organics were mainly released by agitation. Based on the experimental observations, we propose a conceptual model where parent soil aggregates contain the fractal clusters in mobile and occluded forms, and that the occluded clusters co-exist with occluded low molecular weight organics. These occluded forms may be released by mechanical forces, increasing pH and temperature. At higher temperatures, the soil aggregates and the fractal clusters start to break up, and subsequently individual colloidal coils, presumably carbohydrates, disperse in the water phase. The model explains the origin and properties of the fractal clusters that completely dominate the colloidal DOM extracted from our soil at room temperature and below.
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| 47. |
- Andersson, John, 1993, et al.
(författare)
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Pore performance: artificial nanoscale constructs that mimic the biomolecular transport of the nuclear pore complex
- 2022
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Ingår i: Nanoscale Advances. - : Royal Society of Chemistry (RSC). - 2516-0230. ; 4:23, s. 4925-4937
-
Forskningsöversikt (refereegranskat)abstract
- The nuclear pore complex is a nanoscale assembly that achieves shuttle-cargo transport of biomolecules: a certain cargo molecule can only pass the barrier if it is attached to a shuttle molecule. In this review we summarize the most important efforts aiming to reproduce this feature in artificial settings. This can be achieved by solid state nanopores that have been functionalized with the most important proteins found in the biological system. Alternatively, the nanopores are chemically modified with synthetic polymers. However, only a few studies have demonstrated a shuttle-cargo transport mechanism and due to cargo leakage, the selectivity is not comparable to that of the biological system. Other recent approaches are based on DNA origami, though biomolecule transport has not yet been studied with these. The highest selectivity has been achieved with macroscopic gels, but they are yet to be scaled down to nano-dimensions. It is concluded that although several interesting studies exist, we are still far from achieving selective and efficient artificial shuttle-cargo transport of biomolecules. Besides being of fundamental interest, such a system could be potentially useful in bioanalytical devices.
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| 48. |
- Badetti, Elena, et al.
(författare)
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Novel multimethod approach for the determination of the colloidal stability of nanomaterials in complex environmental mixtures using a global stability index: TiO2 as case study
- 2021
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 801
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Tidskriftsartikel (refereegranskat)abstract
- A systematic study on the colloidal behavior of uncoated and polyvinylpyrrolidone (PVP) coated TiO2 engineered nanomaterials (ENMs) in simulated aqueous media is herein reported, in which conditions representative for natural waters (pH, presence of divalent electrolytes (i.e. Ca2+/Mg2+ and SO42−), of natural organic matter (NOM) and of suspended particulate matter (SPM)) were systematically varied. The colloidal stability of the different dispersions was investigated by means of Dynamic and Electrophoretic Light Scattering (DLS and ELS) and Centrifugal Separation Analysis (CSA), and a global stability index based on these three techniques was developed. The index allows to quantitatively classify the nano-based dispersions according to their colloidal stability affected by the different parameters studied. This multimethod approach clearly identifies inorganic SPM followed by divalent electrolytes as the main natural components destabilizing TiO2 ENMs upon entering in simulated natural waters, while it highlights a moderate stabilization induced by NOM, depending mainly on pH. Moreover, the PVP coating was found to attenuate the influence of these parameters on the colloidal stability. The obtained results show how the global stability index developed is influenced by the complexity of the system, suggesting the importance of combining the information gathered from all the techniques employed to better elucidate the fate and behavior of ENMs in natural surface waters.
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| 49. |
- Bilesan, Mohammad Reza, et al.
(författare)
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Efficient separation of precious metals from computer waste printed circuit boards by hydrocyclone and dilution-gravity methods
- 2021
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Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526. ; 286
-
Tidskriftsartikel (refereegranskat)abstract
- To fulfill the different aspects of green chemistry and to achieve full use of the secondary resources (waste printed circuit boards (WPCB)), the necessity of developing green methods for recovery of precious metals (Au, Pd, and Ag) is highly demanded. In this study, a novel environment-friendly physical separation approach; the combination of crushing, grinding, sieving as pretreatment steps alongside hydrocyclone and the dilution-gravity method (DGM) as the main final steps; is proposed. Inductively coupled plasma-mass spectrometry (ICP-MS), atomic absorption spectroscopy (AAS), and energy-dispersive X-ray spectroscopy (EDS) characterization methods were utilized to understand the effects of different separation steps applied in this research. The size and shape of grinded materials and the ones produced after hydrocyclone and DGM were evaluated using scanning electron microscopy. The results showed that the sieving step separated the highest gold fraction in the finer classification (<75 μm) while placed the copper (70 wt.%) into the coarser contents. The overflow to underflow outlet diameter ratio and inlet pressure was evaluated to determine the separation efficiency of a hydrocyclone effect of parameters. In the best-case scenario at 3 bar hydrocyclone operation pressure where the overflow to underflow outlet diameter (Do/Du) was 6.5, the highest metal fraction (87 wt.%) was achieved in the sink of the DGM. In this case, the total separation efficiency of gold, palladium, silver, and copper was 75%, 78%, 64%, 72%, respectively. Thus, this study demonstrates the feasibility of utilizing the sieving as mentioned above classification pretreatment steps followed by hydrocyclone and DGM methods as promising approaches for recovering precious metals from WPCBs that contain annually almost 50 million tons of e-waste.
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| 50. |
- Burks, Raychelle Marie, 1975, et al.
(författare)
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Clarifying the complex chemistry of cobalt(II) thiocyanate-based tests for cocaine using single-crystal X-ray diffraction and spectroscopic techniques
- 2024
-
Ingår i: Journal of Forensic Sciences. - 0022-1198 .- 1556-4029. ; 69:1, s. 291-300
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Tidskriftsartikel (refereegranskat)abstract
- Cobalt(II) thiocyanate-based tests are routinely used to screen cocaine products, with the formation of a blue species interpreted as a positive response. An array of other organic bases has been identified as false positives – including well-documented cocaine product adulterant lidocaine and its salt. False positives prompt continued test development, though improvements are hindered by unresolved product structures and reaction pathways. Toward greater clarity, cobalt(II) thiocyanate reactions with cocaine hydrochloride, along with lidocaine and its salt, were investigated using multiple analytical techniques. Reactions involving cocaine hydrochloride yielded glassy, amorphous blue material while reactions of lidocaine hydrochloride monohydrate produced larger, needle-like crystals whose structure was determined via single-crystal X-ray diffraction to be an ion pair (Hlidocaine+)2([Co(SCN)4]2−)·H2O. While the blue precipitate isolated from reactions involving cocaine hydrochloride was unsuitable for crystallographic structure determination, comparative ultraviolet–visible, attenuated total reflectance infrared, and Raman spectroscopic analysis – along with elemental analysis – supports that this solid is comprised of a comparable ion pair (Hcocaine+)2[Co(SCN)4]2−. Pink crystals isolated from lidocaine reaction vessels were identified as coordination compounds cis-[CoL2(SCN)2] and trans-[CoL2(SCN)2] where L = lidocaine, while pink crystals from both cocaine hydrochloride and lidocaine hydrochloride monohydrate reaction vessels were the coordination polymer trans-[Co(H2O)2(SCN)2]·H2O. The results presented herein enable reaction optimization to favor a desired product, whether ion pair or coordination species.
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