| 1711. |
- Simões Dos Reis, Glaydson
(författare)
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Adsorption of rare earth elements on a magnetic geopolymer derived from rice husk: studies in batch, column, and application in real phosphogypsum leachate sample
- 2024
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Ingår i: Environmental Science and Pollution Research. - 0944-1344 .- 1614-7499. ; 31, s. 10417–10429-
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Tidskriftsartikel (refereegranskat)abstract
- There is a growing need to develop new strategies for rare earth element (REE) recovery from secondary resources. Herein, a novel approach to utilize biogenic silica (from rice husk) and metakaolin was employed to fabricate magnetic geopolymer (MGP) by incorporating metallic iron. The fabricated MGP adsorbent material was used to uptake Ce3+, La3+, and Nd3+ from synthetic solutions and real phosphogypsum leachate in batch and column modes. The MGP offers a negatively charged surface at pH above 2.7, and the uptake of REEs rises from pH 3 to 6. The kinetic study validated that the kinetics was much faster for Nd3+, followed by La3+ and Ce3+. A thermodynamic investigation validated the exothermic nature of the adsorption process for all selected REEs. The desorption experiment using 2 mol L−1 H2SO4 as the eluent demonstrated approximately 100% desorption of REEs from the adsorbent. After six adsorption–desorption cycles, the MGP maintained a high adsorption performance up to cycle five before suffering a significant decrease in performance in cycle six. The effectiveness of MGP was also assessed for its applicability in recovering numerous REEs (La3+, Ce3+, Pr3+, Sm3+, and Nd3+) from real leachate from phosphogypsum wastes, and the highest recovery was achieved for Nd3+ (95.03%) followed by Ce3+ (86.33%). The operation was also feasible in the column presenting suitable values of the length of the mass transfer zone. The findings of this investigation indicate that MGP adsorbent prepared via a simple route has the potential for the recovery of REEs from synthetic and real samples in both batch and continuous operations modes.
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| 1712. |
- Simões Dos Reis, Glaydson
(författare)
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Composite of methyl polysiloxane and avocado biochar as adsorbent for removal of ciprofloxacin from waters
- 2022
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Ingår i: Environmental Science and Pollution Research. - : Springer Science and Business Media LLC. - 0944-1344 .- 1614-7499. ; 29, s. 74823-74840
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Tidskriftsartikel (refereegranskat)abstract
- Two carbon composite materials were prepared by mixing avocado biochar and methyl polysiloxane (MK). Firstly, MK was dissolved in ethanol, and then the biochar was added at different times. In sample 1 (R-1), the time of adding biochar was immediately after dissolving MK in ethanol, and in sample 2 (R-2), after 48 h of MK dissolved in ethanol. The samples were characterized by nitrogen adsorption/desorption measurements obtaining specific surface areas (S-BET) of 115 m(2) g(-1) (R-1) and 580 m(2) g(-1) (R-2). The adsorbents were further characterized using scanning electron microscopy, FTIR and Raman spectroscopy, adsorption of vapors of n-heptane and water, thermal analysis, Bohem titration, pHpzc, and C H N elemental analysis. R-1 and R-2 adsorbents were employed as adsorbents to remove the antibiotic ciprofloxacin from the waters. The t(1/2) and t(0.95) based on the interpolation of Avrami fractional-order were 20.52 and 246.4 min (R-1) and 14.00 and 157.6 min (R-2), respectively. Maximum adsorption capacities (Q(max)) based on the Liu isotherm were 10.77 (R-1) and 63.80 mg g(-1) (R-2) for ciprofloxacin. The thermodynamic studies showed a spontaneous and exothermic process for both samples, and the value of Delta H degrees is compatible with physical adsorption.
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| 1713. |
- Simongini, Camilla, et al.
(författare)
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MICROPLASTICS IDENTIFICATION IN LANDFILL LEACHATES BY DIFFERENT SPECTROSCOPIC TECHNIQUES
- 2022
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Ingår i: Detritus. - : Eurowaste SRL. - 2611-4135. ; 18, s. 58-69
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Tidskriftsartikel (refereegranskat)abstract
- Discovered more than 40 years ago, microplastics have become a major environmental issue. With increasing global plastic production, microplastics are of growing concern. Landfills have been pinpointed as primary sources of microplastics to surface waters and they have, in fact, been identified and quantified as such. Due to their small size, different polymers and interfering non-plastic materials, microplastics are difficult to analyse in a complex matrix such as leachate. To elucidate the impact of pre-treatment on the performance of the most common microspectroscopical analytical methods employed, i.e., FT-IR and Raman, we re-examined previously pre-treated and analysed leachate samples. Additionally, we subjected duplicates of previously analysed samples to different concentrations of H2O2 with varied reaction times to digest and remove non-plastic organic matter. The pre-treated samples were subjected density separation and (re-)analysed by means of FT-IR and Raman microspectroscopy. Larger particles were also analysed by near-infrared (NIR) hyperspectral imaging. We found the concentration of H2O2 to impact the possibility of identifying and quantifying PET particles, with Raman scattering microspectroscopy enabling more particles to be counted than with FT-IR. This is likely due to the increased detectable particle size range, from around 50 μm for FT-IR to 1 μm for Raman scattering microspectroscopy. Optimized H2O2 concentration with subsequent density separation enabled to clearly identify numerous PE particles, but also PP, PS, and PET particles and carbon compounds with Raman scattering microspectroscopy. Hyperspectral imaging performed well for particles larger than 30 μm.
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| 1714. |
- Skoglundh, Magnus, 1965
(författare)
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New Materials in Environmental Catalysis
- 1995
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents new approaches to the control of emissions within the field of environmental catalysis. Three catalytic systems; bimetallic catalysts, perovskites and promoted catalysts have been prepared and evaluated for complete oxidation of volatile organic compounds and for simultaneous conversion of CO, hydrocarbons and nitrogen oxides. The activities for complete oxidation of CO and hydrocarbons over coimpregnated Pd-Pt catalysts did not vary linearly with the Pd:Pt-ratio. This non-linear variation strongly implies that bimetallic Pd-Pt clusters are formed in such catalysts. Maxima in activity for oxidation of xylene and CO were reached over Pd0.8Pt0.2/Al2O3. The activity increased with increasing total noble metal content, decreasing reactant concentration and increasing oxygen concentration. Catalysts with supports of .gamma.-Al2O3, hydrothermally treated (814 °C, 100% steam) prior to impregnation with noble metal complexes, exhibited higher activity for oxidation of xylene than those having thermally (550 °C, air) treated supports. Using a technique with repeated impregnations and subsequent calcinations at 900 °C, a barrier layer, which acted as a precursor or support for perovskite formation, was created on alumina when impregnated with La3+, Sr2+, Cu2+ and Ru3+. A perovskite phase of the nominal composition La1-xSrxAl1-2yCuyRuyO3 was formed in increasing amount with increasing content of Sr and Ru in the stock solutions used. The presence of Sr and Ru seemed to retard formation of La2CuO4 and promote formation of the perovskite phase. Cu was well dispersed over the entire support while Ru was found only in the grains of the perovskite phase. The perovskite phase seemed to take an active part in the simultaneous conversion of NO, CO and C3H6. Promoting complex metal oxides based on Cu or Co, having the overall metal composition La0.45Sr0.15Ce0.35Zr0.05M1.0 (M=Cu or Co), with small amounts of Pt-Rh, yielded high activity for the simultaneous conversion of CO, C3H6 and NO. Addition of 4.4 micromol Pt-Rh to La0.45Sr0.15Ce0.35Zr0.05Co/Al2O3 yielded a three-way activity quite similar to that obtained over a commercial three-way catalyst containing more than four times as much Pt-Rh. Pd/Al2O3 exhibited three-way activity in a narrow interval around the stoichiometric balance between oxidizing and reducing gases. Addition of La or Co to Pd broadened this interval under net reducing conditions. The conversions of CO and C3H6 started at about 100 °C lower temperatures over Pd/Co/La/Bl2O3 compared with Pd/La/Al2O3. The conversion of NO under transient conditions was markedly increased over Co-promoted Pd compared with unpromoted Pd.
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| 1715. |
- Strömberg, Dan, 1959, et al.
(författare)
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Non-relativistic and relativistic calculations on some Zn, Cd and Hg complexes
- 1989
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Ingår i: Chemical Physics. - 0301-0104. ; 133:2, s. 207-219
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Tidskriftsartikel (refereegranskat)abstract
- A number of species containing Hg, Cd and Zn have been studied at the CI level using non-relativistic and relativistic techniques. Effective core potentials were used for Hg and Cd, while an all-electron description was used for Zn. Spectroscopic constants have been calculated for the positive hydride ions and the dichlorides of the three metals. The agreement with experiment was good in all cases. Calculations have also been carried out on Hg (OH)2, HgO and ZnO. The Hg (OH)2 molecule is predicted to be covalently bound by two σ bonds formed between a metal sp hybrid with small but significant 5d contribution and the OH. The binding energy of Hg(OH)2 is significant although smaller than the binding energy of HgCl2 by 20 kcal/mol. The near UV spectra of HgCl2 and Hg(OH)2 are calculated to be quite similar except for excitations involving the O---H bond. The calculated dissociation energies of HgO and ZnO are severely underestimated.
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| 1716. |
- Strömberg, Dan, 1959, et al.
(författare)
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Relativistic calculations on some mercury sulphide molecules
- 1991
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Ingår i: Water Air and Soil Poll. - 0049-6979. ; 56:1, s. 681-695
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Tidskriftsartikel (refereegranskat)abstract
- Relativistic quantum calculations at the CASSCF- and CCI-levels were performed on the Hg(SH)2, HgSH and HgS molecules. The relativistic effects were taken into account by a relativistic effective core potential method. Dissociation energies and optimal geometries were calculated for these three molecules, which are plausible atmospheric Hg compounds. The Hg(SH)2 and HgSH molecules (in the gaseous phase) have never been studied before, neither experimentally nor theoretically, i.e. the existence of these molecules are uncertain. The theoretical dissociation energies, De's, of Hg(SH)2 and HgSH (at the CCI-level) were 59 kcal·mol–1 and 3 kcal·mol–1, respectively, indicating that Hg(SH)2 could be stable in the atmosphere but probably not HgSH. The theoretical De of HgS differs very much from the experimental one, but the reason for this is not clear. The Hg-S distances for Hg(SH)2, HgSH and HgS were found to be 2.38, 2.63 and 2.30 Å, respectively. The Hg-S-H angle in Hg(SH)2 was optimized to 93°. The excitation energies of Hg(SH)2, Hg(SH)2(H2O)4 and (HSHg)2S were calculated in order to see whether these species can absorb photons with wavelengths longer than 290 nm (the sunlight limit) and subsequently be photolyzed. The Hg(SH)2(H2O)4 complex is intended as a model for Hg(SH)2(aq). Photoreduction of Hg-sulfide species in sea water, yielding Hg0, could be an important source of Hg in the atmosphere. Excitation energies lower than the sunlight limit (4.3 eV290 nm) were found for Hg(SH)2 and Hg(SH)2(H2O)4, although the lowest spin and dipole allowed excitations probably lie slightly (0.2 to 0.3 eV) above this limit. Therefore a photodecomposition of Hg(SH)2(g) and Hg(SH)2(aq) by sunlight seems likely to occur.
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| 1717. |
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| 1718. |
- Svensson, Britt-Marie, et al.
(författare)
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Leachability testing of metallic wastes
- 2005
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Ingår i: Waste Management & Research. - 1096-3669 .- 0734-242X. ; 23:5, s. 457-467
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Tidskriftsartikel (refereegranskat)abstract
- The performance of two tests, a batch test and a percolation test for the characterization of waste as suggested in the EU council decision 2003/33/EC was investigated. The tests were carried out on two solid waste streams from a metal recycling industry. The concentrations of heavy metals Such as Cu, Zn and Pb were more than one order of magnitude lower than the proposed limit values. Generally, batch test values were equal or higher than percolation test values. With the proposed test procedures both materials could be considered as non-dangerous wastes. The test performance was also investigated using a leachant with higher ionic strength instead of demineralized water as prescribed. The results clearly show a significant increase in the concentration of some heavy metals. Total concentrations of phenolic compounds and polychlorinated biphenyls were less than 1 p.p.m. and 2 p.p.b., respectively. The precision of the batch and the percolation tests were on average 48 and 35%, respectively.
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| 1719. |
- Szabo, Drew, 1990-, et al.
(författare)
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Online and Offline Prioritization of Chemicals of Interest in Suspect Screening and Non-targeted Screening with High-Resolution Mass Spectrometry
- 2024
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Ingår i: Analytical Chemistry. - 0003-2700 .- 1520-6882. ; 96:9, s. 3707-3716
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Forskningsöversikt (refereegranskat)abstract
- Recent advances in high-resolution mass spectrometry (HRMS) have enabled the detection of thousands of chemicals from a single sample, while computational methods have improved the identification and quantification of these chemicals in the absence of reference standards typically required in targeted analysis. However, to determine the presence of chemicals of interest that may pose an overall impact on ecological and human health, prioritization strategies must be used to effectively and efficiently highlight chemicals for further investigation. Prioritization can be based on a chemical's physicochemical properties, structure, exposure, and toxicity, in addition to its regulatory status. This Perspective aims to provide a framework for the strategies used for chemical prioritization that can be implemented to facilitate high-quality research and communication of results. These strategies are categorized as either online or offline prioritization techniques. Online prioritization techniques trigger the isolation and fragmentation of ions from the low-energy mass spectra in real time, with user-defined parameters. Offline prioritization techniques, in contrast, highlight chemicals of interest after the data has been acquired; detected features can be filtered and ranked based on the relative abundance or the predicted structure, toxicity, and concentration imputed from the tandem mass spectrum (MS2). Here we provide an overview of these prioritization techniques and how they have been successfully implemented and reported in the literature to find chemicals of elevated risk to human and ecological environments. A complete list of software and tools is available from https://nontargetedanalysis.org/.
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| 1720. |
- Sörengård, Mattias, et al.
(författare)
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Simultaneous analysis of neutral and ionizable per- and polyfluoroalkyl substances in air
- 2021
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 280
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Tidskriftsartikel (refereegranskat)abstract
- A new method is preliminarily validated for the simultaneous analysis of ionic and neutral per- and polyfluomalkyl substances (PFASs) in both particulate and gaseous phases in air using a nanosampler-20 air sampler (NS20) composed of quartz fiber filters (QFFs), polyurethane foam (PUF) and artificial activated charcoal (GAIAC (TM)). Perfluoroalkane sulfonamido ethanols (FOSEs) mainly remained in PUF, whereas the other neutral analytes were mainly found in GAIAC. Satisfactory recoveries were obtained for FOSEs, fluorotelomer alcohols (FTOHs), fluomtelomer iodides (FTIs), ranging fron 70%-120%, moderate recoveries were achieved for perfluorinated iodine alkanes (FIAs) and diiodofluoroalkanes (FDIAs), ranging from 50%-70%, while poor recoveries were found for perfluoroalkane sulfonamides (FOSAs). Breakthrough experiments revealed that almost all the target analytes were well trapped in GAIAC (TM), including the very volatile 4:2 FTOH. Applying to real sampling, our results showed that 6:2 and 8:2 FTOH were the most abundant species, with levels detected at 190 pg/m(3) and 160 pg/m(3). To the best of our knowledge, FDIAs were detected in ambient air for the first time at an average level of 8.3 pg/m(3). Overall, the profiles observed from the real air samples reflected current industrial transition from longer chain to shorter chain in PFAS production. Our results revealed that the current method is promising for a more comprehensive understanding on the fates of PFASs in air.
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