| 1. |
- Albán Reyes, Diana Carolina, et al.
(författare)
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Activation of dissolving cellulose pulp at low water content
- 2015
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Ingår i: 4th EPNOE International Polysaccharide Conference.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Mercerisation of cellulose by alkali treatment is the first step in modifying natural cellulose fibres into many commercial cellulosic materials. During treatment, the fiber transforms into a reactive and highly swollen material called alkali cellulose (Na-Cell). In case NaOH is washed out of the cellulose structure, Na-Cell turn into Cellulose II upon drying (Langan et al. 2001). The aim of the present study was to gain a better understanding of the mercerisation of dissolving cellulose pulp at low water content. This has been done by spraying NaOH onto milled cellulose in a kneader, then washing the cellulose to neutrality to stop the reaction. After drying the transformation degree to cellulose II was analysed. The experiments include variation of temperature (30-60°C), reaction time (5 and 25 min), [NaOH] (45-55%), and NaOH:Cellulose molar ratio (0.8- 1.8). A combination of NIR Raman imaging and multivariate data analysis have been used to study the transformation degree. To the authors’ knowledge, this is the first time the influence of NaOH: Cellulose molar ratio on the mercerisation process has been studied in a single model together with temperature, reaction time and [NaOH]. Our results indicate that increased NaOH: Cellulose molar ratio has a significant positive influence on transformation degree of dissolving cellulose pulp at low water content.
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| 2. |
- Albán Reyes, Diana Carolina, et al.
(författare)
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Activation of dissolving celluloses pulp for viscose and cellulose ether production
- 2016
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Ingår i: The 7th workshop on cellulose, regenerated cellulose and cellulose derivatives. - Umeå ; Karlstad : Umeå university ; Karlstad university. ; , s. 29-30
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Mercerisation of cellulose by alkali treatment is the most common procedure used to activate natural cellulose fibres into many commercial cellulosic materials. During mercerisation, the NaOH solution enters the cellulose fibres, transforming them into a swollen and a highly reactive material called alkali cellulose (Na-Cell). In case NaOH is completely washed out of the cellulose structure, Na-Cell turns into Cellulose II upon drying.Traditionally the cellulose is mercerised by suspending it in a 15-20 % NaOH solution. The result is a high (15-25 mol/mol) NaOH: Anhydroglucose molar ratio (r) and mercerisation in these conditions have been extensively studied. However, in modern production of cellulose ethers, the mercerisation conditions are often very different. The main reason is that any excess of water and OH--ions used during the mercerisation can later react with different chemicals in the process, thus forming unwanted by-products e.g. methanol. One way to avoid this kind of side reaction is by using low-water-content mercerisation conditions, i.e. low (r) = 0.8-1.8 mol/mol and high NaOH concentration (45-55% w/w). The traditional mercerisation is a suspension process while the cellulose during the latter process, i.e low-water-content mercerisation conditions, remains quite “dry”. Thus, although the chemical reaction principles of activation of cellulose for both viscose and cellulose ethers processes are the same, the activation conditions used are often very different. Therefore, the different dependencies of process parameters as well as any similarities between the processes are interesting.The presentation summarises the findings presented in two papers which described the influence of the different parameters on the mercerisation/activation of softwood Sulphite dissolving pulp in viscose production conditions (Albán Reyes et al. 2016) and cellulose derivatives production conditions (Albán Reyes et al.) respectively. In the individual studies this has been done by analysing the degree of transformation (DoT) of dissolving pulp to Na-cellulose (or more correctly cellulose II after washing and upon drying) as a function of simultaneous variation of [NaOH], temperature, and reaction time varied using design of experiment. Also the (r) was varied for samples mercerised at dry conditions. A combination of Raman imaging and multivariate data analysis have been used to study the DoT to Cellulose II.It was found that the mercerisation under the different conditions was dependent on different parameters. For traditional mercerisation, on the one hand, the temperature was shown to be important for the DoT and showed negative correlation with the data, while [NaOH] showed a positive correlation. On the other hand, at low-water-content mercerisation conditions the (r) was overall most important while the temperature showed no statistical importance in a Partial least squares analysis. Traditional mercerisation gave much higher DoT than the low-water-content mercerisation. Thus, the data for low-water-content mercerisation was further examined at the different (r). The same chemistry is always expected and the different influences of the parameters seen is understood and discussed in terms of the different physical reaction mechanisms.
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| 3. |
- Albán Reyes, Diana Carolina, et al.
(författare)
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Is there a diffusion of alkali in the activation of dissolving cellulose pulp at low NAOH stoichiometric excess?
- 2019
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Ingår i: Cellulose. - : Springer. - 0969-0239 .- 1572-882X. ; 26:2, s. 1297-1308
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Tidskriftsartikel (refereegranskat)abstract
- We conducted a quantitative study, following the degree of activation (i.e. the transformation to alkali cellulose, denoted as DoA) over time for dissolving cellulose pulp treated with different [NaOH] at low NaOH/anhydroglucose unit stoichiometric ratio (denoted as (r) ≤ 2.6). Our quantitative approach was based on Raman spectroscopy data, evaluated by partial least squares regression modelling. The results show strong influence of the (r) on DoA (increasing from DoA= 45% at (r) = 0.8, to DoA = 85% at (r) = 2.6), and its complex dependence on [NaOH]. At (r) = 0.8 the highest DoA (DoA ≳ 60%) was found at 30% [NaOH], while at (r) =1.3 it was found at 20% [NaOH] (DoA ≳ 80%). Although activation of cellulose happens in minutes at the studied temperature (30 °C), it was found that the reaction may be slow when a low (r) is used. A gradual increase of the DoA from ≈ 30% to ≈ 70% in time was seen when samples were activated with 30% [NaOH] at (r) = 0.8. At the same (r), a similar increase of DoA from ≈ 30 % to ≈ 60 % was also observed when 40% [NaOH] was used. Slow diffusion of NaOH through poorly swollen cellulose fibres is proposed as an explanation for this phenomenon. Lastly, solid-state CP/MAS NMR measurements suggest that at a fixed temperature, the Na-Cell allomorph mostly depends on [NaOH]. However, in the transition area between Na-Cell I and Na-Cell II, its influence might be affected by (r).
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| 4. |
- Albán Reyes, Diana Carolina, et al.
(författare)
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The influence of different parameters on the mercerisation of cellulose for viscose production
- 2016
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Ingår i: Cellulose. - : Springer Netherlands. - 0969-0239 .- 1572-882X. ; 23:2, s. 1061-1072
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Tidskriftsartikel (refereegranskat)abstract
- A quantitative analysis of degree of transformation from a softwood sulphite dissolving pulp to alkalised material and the yield of this transformation as a function of the simultaneous variation of the NaOH concentration, denoted [NaOH], reaction time and temperature was performed. Samples were analysed with Raman spectroscopy in combination with multivariate data analysis and these results were confirmed by X-ray diffraction. Gravimetry was used to measure the yield. The resulting data were related to the processing conditions in a Partial Least Square regression model, which made it possible to explore the relevance of the three studied variables on the responses. The detailed predictions for the interactive effects of the measured parameters made it possible to determine optimal conditions for both yield and degree of transformation in viscose manufacturing. The yield was positively correlated to the temperature from room temperature up to 45 A degrees C, after which the relation was negative. Temperature was found to be important for the degree of transformation and yield. The time to reach a certain degree of transformation (i.e. mercerisation) depended on both temperature and [NaOH]. At low temperatures and high [NaOH], mercerisation was instantaneous. It was concluded that the size of fibre particles (mesh range 0.25-1 mm) had no influence on degree of transformation in viscose processing conditions, apparently due to the quick reaction with the excess of NaOH.
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| 5. |
- Albán Reyes, Diana Carolina, et al.
(författare)
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Variation of the alkalisation conditions during the synthesis of a cellulose ether
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We show the effect of simultaneous variation of i) the NaOH/AGU (anhydroglucose unit) stoichiometric ratio (r), ii) added [NaOH], and iii) mercerization time, on the degree of cellulose substitution (DS), and by-product formation including proportions of insoluble particles and unreacted chemicals, in the synthesis of carboxymethylcellulose (CMC), under conditions resembling those often used for production of non-ionic cellulose ethers and without the use of alcohols. The DS was found to increase when (r) was increased (range 1.0-1.3) and added [NaOH] was decreased (range 50-30%). However, such changes also favoured the formation of unwanted by-products. Decreased (r) and increased [NaOH] resulted in increased the quantities of insoluble particles and unreacted chemicals. In the CMC samples, DS of 0.18-0.7 was obtained. The measured solubility (46%-86%) was lower than expected for a given DS. This, along with a deviation of the substituent distribution from the statistical calculations, indicated a high heterogeneity in the samples. The substitution at hydroxyl positions within the AGU shows the order of < ≈ , and that substitution increases with (r). The relative importance of substitution at increases with an increased [NaOH].
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| 6. |
- Bünder, Anne, et al.
(författare)
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CELLULOSE SYNTHASE INTERACTING 1 is required for wood mechanics and leaf morphology in aspen
- 2020
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Ingår i: The Plant Journal. - : John Wiley & Sons. - 0960-7412 .- 1365-313X. ; 103:5, s. 1858-1868
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose microfibrils synthesized by CELLULOSE SYNTHASE COMPLEXES (CSCs) are the main load‐bearing polymers in wood. CELLULOSE SYNTHASE INTERACTING1 (CSI1) connects CSCs with cortical microtubules, which align with cellulose microfibrils. Mechanical properties of wood are dependent on cellulose microfibril alignment and structure in the cell walls, but the molecular mechanism(s) defining these features is unknown. Herein, we investigated the role of CSI1 in hybrid aspen (Populus tremula × Populus tremuloides ) by characterizing transgenic lines with significantly reduced CSI1 transcript abundance. Reduction in leaves (50–80%) caused leaf twisting and misshaped pavement cells, while reduction (70–90%) in developing xylem led to impaired mechanical wood properties evident as a decrease in the elastic modulus and rupture. X‐ray diffraction measurements indicate that microfibril angle was not impacted by the altered CSI1 abundance in developing wood fibres. Instead, the augmented wood phenotype of the transgenic trees was associated with a reduced cellulose degree of polymerization. These findings establish a function for CSI1 in wood mechanics and in defining leaf cell shape. Furthermore, the results imply that the microfibril angle in wood is defined by CSI1 independent mechanism(s).
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| 7. |
- Chambi, Diego, et al.
(författare)
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Production of Exopolysaccharides by Cultivation of Halotolerant Bacillus atrophaeus BU4 in Glucose- and Xylose-Based Synthetic Media and in Hydrolysates of Quinoa Stalks
- 2022
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Ingår i: Fermentation. - : MDPI AG. - 2311-5637. ; 8:2
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Tidskriftsartikel (refereegranskat)abstract
- A halotolerant, exopolysaccharide-producing bacterium isolated from the Salar de Uyuni salt flat in Bolivia was identified as Bacillus atrophaeus using next-generation sequencing. Comparisons indicate that the genome most likely (p-value: 0.0024) belongs to a subspecies previously not represented in the database. The growth of the bacterial strain and its ability to produce exopolysaccharides (EPS) in synthetic media with glucose or xylose as carbon sources, and in hydrolysates of quinoa stalks, was investigated. The strain grew well in all synthetic media, but the growth in glucose was better than that in xylose. Sugar consumption was better when initial concentrations were low. The growth was good in enzymatically produced cellulosic hydrolysates but was inhibited in hemicellulosic hydrolysates produced using hydrothermal pretreatment. The EPS yields were up to 0.064 g/g on initial glucose and 0.047 g/g on initial xylose, and was higher in media with relatively low sugar concentrations. The EPS was isolated and purified by a sequential procedure including centrifugation, cold ethanol precipitation, trichloroacetic acid treatment, dialysis, and freeze-drying. Glucose and mannose were the main sugars identified in hydrolyzed EPS. The EPS was characterized by size-exclusion chromatography, Fourier-transform infrared (FTIR) spectroscopy, heteronuclear single-quantum coherence nuclear magnetic resonance (HSQC NMR) spectroscopy, scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis. No major differences were elucidated between EPS resulting from cultivations in glucose- or-xylose-based synthetic media, while some divergences with regard to molecular-weight averages and FTIR and HSQC NMR spectra were detected for EPS from hydrolysate-based media.
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| 8. |
- Escamez, Sacha, 1987-, et al.
(författare)
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Fluorescence Lifetime Imaging as an in Situ and Label-Free Readout for the Chemical Composition of Lignin
- 2021
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society. - 2168-0485. ; 9:51
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Tidskriftsartikel (refereegranskat)abstract
- Naturally fluorescent polymeric molecules such as collagen, resilin, cutin, suberin, or lignin can serve as renewable sources of bioproducts. Theoretical physics predicts that the fluorescence lifetime of these polymers is related to their chemical composition. We verified this prediction for lignin, a major structural element in plant cell walls that form woody biomass. Lignin is composed of different phenylpropanoid units, and its composition affects its properties, biological functions, and the utilization of wood biomass. We carried out fluorescence lifetime imaging microscopy (FLIM) measurements of wood cell wall lignin in a population of 90 hybrid aspen trees genetically engineered to display differences in cell wall chemistry and structure. We also measured the wood cell wall composition by classical analytical methods in these trees. Using statistical modeling and machine learning algorithms, we identified parameters of fluorescence lifetime that predict the content of S-type and G-type lignin units, the two main types of units in the lignin of angiosperm (flowering) plants. In a first step toward tailoring lignin biosynthesis toward improvement of woody biomass feedstocks, we show how FLIM can reveal the dynamics of lignin biosynthesis in two different biological contexts, including in vivo while lignin is being synthesized in the walls of living cells. © 2021 The Authors.
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| 9. |
- Essalhi, Mohamed, et al.
(författare)
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Gamma-irradiated janus electrospun nanofiber membranes for desalination and nuclear wastewater treatment
- 2024
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Ingår i: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 700
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Tidskriftsartikel (refereegranskat)abstract
- This study presents the fabrication of double-layer electrospun nanofibrous membranes (DL-ENMs) using polyvinylidene fluoride (PVDF) and polyether sulfone (PES) based polymers with different degrees of hydrophilicity (PES, sulfonated PES, and PES with hydroxyl terminals). A comparative analysis was carried out with single-layer electrospun nanofiber membranes (SL-ENM) with a total thickness of about 375 μm. Using feed solutions, including sodium chloride, sodium nitrate, and simulated nuclear wastewater (SNWW), the performance of DL-ENMs was evaluated for desalination and radionuclide decontamination by direct contact membrane distillation (DCMD) and air gap membrane distillation (AGMD) techniques. The results showed that DL-ENMs, especially those incorporating a sulfonated PES-based hydrophilic layer, exhibited superior permeate fluxes, reaching values of 72.72 kg/m2h and 73.27 kg/m2h in the DCMD using aqueous feed solutions of NaCl and NaNO3, respectively, and 70.80 kg/m2h and 41.96 kg/m2h using aqueous feed solutions of SNWW in DCMD and AGMD, respectively. Both SL-ENMs and DL-ENMs exhibited high rejection efficiencies and decontamination factors for the feed solutions (>99.9%). In addition, the prepared ENMs were exposed to gamma radiation to evaluate their applicability in real-life applications. The result of irradiation revealed the negative impact of gamma radiation on the fluorine content of PVDF which could be a critical point in using PVDF as a hydrophobic material for decontaminating nuclear wastewater by membrane distillation.
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| 10. |
- Essalhi, Mohamed, et al.
(författare)
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Gamma-irradiated janus electrospun nanofiber membranes for desalination and nuclear wastewater treatment
- 2024
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Ingår i: Journal of Membrane Science. - : Elsevier B.V.. - 0376-7388 .- 1873-3123. ; 700
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Tidskriftsartikel (refereegranskat)abstract
- This study presents the fabrication of double-layer electrospun nanofibrous membranes (DL-ENMs) using polyvinylidene fluoride (PVDF) and polyether sulfone (PES) based polymers with different degrees of hydrophilicity (PES, sulfonated PES, and PES with hydroxyl terminals). A comparative analysis was carried out with single-layer electrospun nanofiber membranes (SL-ENM) with a total thickness of about 375 μm. Using feed solutions, including sodium chloride, sodium nitrate, and simulated nuclear wastewater (SNWW), the performance of DL-ENMs was evaluated for desalination and radionuclide decontamination by direct contact membrane distillation (DCMD) and air gap membrane distillation (AGMD) techniques. The results showed that DL-ENMs, especially those incorporating a sulfonated PES-based hydrophilic layer, exhibited superior permeate fluxes, reaching values of 72.72 kg/m2.h and 73.27 kg/m2.h in the DCMD using aqueous feed solutions of NaCl and NaNO3, respectively, and 70.80 kg/m2.h and 41.96 kg/m2.h using aqueous feed solutions of SNWW in DCMD and AGMD, respectively. Both SL-ENMs and DL-ENMs exhibited high rejection efficiencies and decontamination factors for the feed solutions (>99.9%). In addition, the prepared ENMs were exposed to gamma radiation to evaluate their applicability in real-life applications. The result of irradiation revealed the negative impact of gamma radiation on the fluorine content of PVDF which could be a critical point in using PVDF as a hydrophobic material for decontaminating nuclear wastewater by membrane distillation.
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| 11. |
- Essalhi, Mohamed, et al.
(författare)
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Improvement of nanostructured electrospun membranes for desalination by membrane distillation technology
- 2021
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Ingår i: Desalination. - : Elsevier. - 0011-9164 .- 1873-4464. ; 510
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Tidskriftsartikel (refereegranskat)abstract
- A systematic study is carried out to determine the optimum electrospinning preparation condition to prepare an adequate electrospun nanofibrous membrane (ENM) for direct contact membrane distillation (DCMD). A structural properties investigation of ENM was carried out because of the significant impact of its architectural structure, nanofiber diameter, inter-fiber space and ENM thickness, on DCMD performance. The morphology, hydrophobicity, mechanical properties, crystallinity and DCMD desalination were investigated. A long-term DCMD experiment (100h) was carried out using 30 g/L NaCl aqueous solution, both in the feed and permeate side of the optimum ENM membrane to evaluate its potential to produce drinkable water in case of lack of distilled water, for instance in a remote area, emergency situation, and/or portable system. In this case, drinkable water could be produced after 28 h with a permeate flux of 57.5 kg/m2.h and a salt rejection factor greater than 99.9%. Another long-term DCMD experiment (65 h) was conducted using 30 g/L NaCl aquesous solution as feed but at a higher temperature and distilled water as permeate to evaluate the desalination stability, wettability and scaling of the optimum ENM. A permeate flux of 58.5 kg/m2.h was obtained with a salt rejection factor greater than 99.9%.
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| 12. |
- Fall, Andreas, et al.
(författare)
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Colloidal Stability of Aqueous Nanofibrillated Cellulose Dispersions
- 2011
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 27:18, s. 11332-11338
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanofibrils constitute an attractive raw material for carbon-neutral, biodegradable, nanostructured materials. Aqueous suspensions of these nanofibrils are stabilized by electrostatic repulsion arising from deprotonated carboxyl groups at the fibril surface. In the present work, a new model is developed for predicting colloidal stability by considering deprotonation and electrostatic screening. This model predicts the fibril-fibril interaction potential at a given pH in a given ionic strength environment. Experiments support the model predictions that aggregation is induced by decreasing the pH, thus reducing the surface charge, or by increasing the salt concentration. It is shown that the primary mechanism for aggregation upon the addition of salt is the surface charge reduction through specific interactions of counterions with the deprotonated carboxyl groups, and the screening effect of the salt is of secondary importance.
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| 13. |
- Forsberg, Diana Carolina Reyes, et al.
(författare)
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On the importance of variation of alkalisation conditions on cellulose ether synthesis
- 2022
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Ingår i: Cellulose Chemistry and Technology. - : Publishing House of the Romanian Academy. - 0576-9787. ; 56:3-4, s. 227-238
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Tidskriftsartikel (refereegranskat)abstract
- With a multivariate approach, we investigate and correlate the effect of mercerization conditions on the properties of a cellulose ether. We have chosen to work with carboxymethylcellulose (CMC) for analytical reasons. As expected, the DS was found to increase when the NaOH/AGU (anhydroglucose unit) stoichiometric ratio (r) was increased (range 1.0–1.3) and [NaOH] was decreased (range 50-30%). However, such changes also favoured the formation of unwanted side products. Decreased (r) and increased [NaOH] resulted in increased heterogeneity, and thus the quantities of insoluble particles and unreacted chemicals also increased. As another result, the prediction between mercerisation and synthesis weakens. Consequently, a DS of 0.18–0.7 was obtained; the measured solubility was much lower than expected. A non-statistical distribution of substituents was further found. Interestingly, the relative importance of substitution at increases with an increased [NaOH].
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| 14. |
- Jablonski, Piotr, et al.
(författare)
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Scalable and sustainable processing of intracellular polyhydroxyalkanoates with biobased solvents
- 2023
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 11:51, s. 17990-18000
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Tidskriftsartikel (refereegranskat)abstract
- The replacement of fossil-based plastics with biobased and biodegradable alternatives has become an important research challenge in recent years, aiming to eliminate the negative environmental impact of persistent plastics in nature. In this report, design of experiments was successfully exploited to develop an efficient and sustainable method for extracting intracellular PHA from Photobacterium ganghwense C2.2 using dihydrolevoglucosenone (Cyrene) and ethanol as biobased solvents obtainable from sustainable sources. The extraction conditions were studied and optimized against the yield and molecular weight. The temperature range for the extraction was scouted by using differential scanning calorimetry, while size exclusion chromatography coupled to refractive index and multiangle light scattering detectors was used to assess the molecular weights of the extracted polymers. The examined ranges in the model were, respectively, 1.6–8.4% (w/v) of lyophilized cells content per 10 mL of solvent, 3–17 min extraction time, and temperatures from 116 to 144 °C. Time and temperature strongly affected the extraction yields and molecular weights of the obtained polymers while the concentration of bacterial biomass only effected the molecular weight. Several quadratic and interaction coefficients were significant in the well-fit partial least-squares regression models (R2 > 0.8, Q2 > 0.6) indicating that nonlinear effects and interacting parameter contributed to the optimization targets. The optimized extraction should be performed at 130 °C for 15 min with 2% loading of bacterial biomass. The predicted yield and molecular weight of the polymer matched the values obtained from the real experiment under the optimized conditions. The method setup provided similar yield and higher molecular weight in much shorter time compared to overnight Soxhlet extraction with CHCl3. The clean 1H nuclear magnetic resonance spectra of polymers extracted from bacteria indicate that high purity materials can be obtained using an optimized extraction scheme. Additionally, the Cyrene solvent could be recycled at least five times and still performed the extraction equally well as the fresh solvent. Finally, the current method demonstrated a high potential for scalability using a HP4750 stirred filtration cell. Three different filtration conditions were tested, achieving up to 97.4% recovery at 80 °C using a 0.3 μm glass fiber membrane, with a flux of 312.5 LMH.
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| 15. |
- Jilal, I, et al.
(författare)
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New benzyloxyethyl cellulose (BEC) crosslinked EDTA : synthesis, characterization and application for supramolecular self-assembling nanoencapsulation of Pb (II)
- 2019
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Ingår i: Materials today: Proceedings. - : Elsevier. - 2214-7853. ; , s. 909-919
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Konferensbidrag (refereegranskat)abstract
- Cellulosic derivatives-modification by Ethylenediaminetetraacetic acid dianhydride (EDTAD) leads to an advanced state of the crosslinking degree, which often limits the adsorbent-metal ion interactions at the superficial level. Moreover, the specific area decreases by increasing crosslinking degree, resulting in a degradation of the adsorptive properties of the materials. In the present work, a new synthesis strategy of crosslinkedcellulose derivative with Ethylenediaminetetraacetic acid (EDTA) was proposed. The preparation of the adsorbent was based on the hydrophobation of hydroxyethyl cellulose (HEC) by partial benzylation (DS similar to 1). This helped to obtain a new cellulose derivative (Benzyloxyethyl cellulose (BEC)) soluble in the majority of the usual solvents, and the EDTA grafting reaction was performed under homogeneous conditions to ensure homogenous distribution of the chelating sites. The resulting BEC-EDTA material was then characterized by FT-IR, SEM and TGA. Thus, the Pb (II)-adsorption behavior on the bio-adsorbent was studied at the supramolecular level and the study of changes in adsorbent morphology before and after modification was performed based on SEM images and EDX spectra. Effect of Pb (II) on BEC-EDTA morphology was investigated as well. However, a self-assembly of BEC-EDTA as nanometric rods in the presence of Pb (II) ions was a strong indication of the Pb (II) nano-encapsulation in a stable polymer network. (c) 2019 Elsevier Ltd. All rights reserved.
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| 16. |
- Jilal, Issam, et al.
(författare)
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New quaternized cellulose based on hydroxyethyl cellulose (HEC) grafted EDTA : Synthesis, characterization and application for Pb (II) and Cu (II) removal
- 2018
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Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 180, s. 156-167
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, new quaternized cellulose derivative based on Ethylenediaminetetraacetic acid (EDTA) and hydroxyethyl cellulose (HEC) is successfully prepared in homogeneous medium. The resulted product is characterized using spectroscopy techniques (FTIR, 1H NMR and 13C NMR). At the supramolecular level, the x-ray patterns show that a high hydrogen bond density occurs by grafting EDTA on the HEC fibers. The new adsorbent (HEC-EDTA) shows a high adsorption capacity of heavy metals (Pb (II) and Cu (II)) from aqueous metals solutions. The adsorption of the both metal ions follows the pseudo-second-order kinetic model, while the adsorption isotherms are well described by the Langmuir model. The qm values are determined for Pb (II) and Cu (II), respectively. For each metal, the equilibrium adsorption time is found to be 30 min. Moreover, the HEC-EDTA adsorption capacity is strongly dependent on the pH value; and the adsorption is favorable for pH values between 4 and 6. Moreover, the results show a high affinity toward Cu (II) than Pb (II).
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| 17. |
- Jilal, Issam, et al.
(författare)
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Unconventional synthesis, characterization and theoretical study (HF and DFT computations) of new cellulosic copper complex : benzyloxyethyl cellulose copper (CuBEC)
- 2018
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Ingår i: Cellulose. - : Springer. - 0969-0239 .- 1572-882X. ; 25:8, s. 4375-4388
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Tidskriftsartikel (refereegranskat)abstract
- The partial hydrophobization of hydroxyl ethyl cellulose (HEC), by incorporating benzyl entities, was successfully performed. So, cavities with binding sites enable to encapsulate the copper ion (Cu(II)) by coordination interaction result from. The resulting product (BEC, DS ae 1) thus contained two types of chelating sites: 2,2'-oxydiethanol and 2,2'-(ethane-1,2-diylbis (oxy))diethanol. The complex formed upon reaction with Cu(II) (labeled CuBEC) was studied using UV-Vis spectroscopy, and the results indicate strong ligand-metal charge transfer transitions of O -> Cu. The chemical structures of HEC, BEC and CuBEC were characterized by FTIR and NMR (H-1, H-1 DOSY, C-13 DEPT-135 and C-13) and UV-Vis spectroscopy was investigated. Furthermore, the crystalline order and the thermal stability were studied based on XRD patterns and thermogravimetric analysis, respectively. The structural results indicated that the copper ion has been encapsulated in square planar geometry formed by the two oxygen atoms of free hydroxyethyl (unbenzylated), the oxygen of the osidic bond and that of the hydroxyl of C-3 of adjacent anhydroglucose unit. A theoretical study was conducted using Hartree-Fock and density functional theory computations; the experimental results were in good agreement with the Theoretical ones. [GRAPHICS]
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| 18. |
- Jogunola, Olatunde, et al.
(författare)
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Ionic liquid mediated technology for synthesis of cellulose acetates using different co-solvents
- 2016
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Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 135, s. 341-348
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Tidskriftsartikel (refereegranskat)abstract
- In this work, cellulose acetate was synthesized under homogeneous conditions. Cellulose was first dispersed in acetone, acetonitrile, 1,5-diazabicyclo(4.3.0)non-5-ene (DBN) or dimethyl sulphoxide (DMSO) and the resulting suspension was dissolved in an ionic liquid, 1,5-diazabicyclo(4.3.0)non-5-enium acetate [HDBN][OAc] at 70 °C for 0.5 h. It was possible to dissolve more than 12 wt% cellulose with a degree of polymerization in the range of 1000–1100. The dissolved cellulose was derivatized with acetic anhydride (Ac2O) to yield acetylated cellulose. As expected, the use of the co-solvents improved the acetylation process significantly. In fact, cellulose acetates with different properties could be obtained in half an hour, thus facilitating rapid processing. When DBN was used as the dispersing agent (the precursor of the ionic liquid), the problems associated with recycling of the ionic liquid were significantly reduced. In fact, additional [HDBN][OAc] was obtained from the interaction of the DBN and the by-product, acetic acid (from Ac2O). However, the cellulose acetate obtained in this manner had the lowest DS. Consequently, the native cellulose and acetylated celluloses were characterized by means of 1H- and 13C-NMR, FT-IR, GPC/SEC and by titration. The cellulose acetates produced were soluble in organic solvents such as acetone, chloroform, dichloromethane and DMSO which is essential for their further processing. It was demonstrated that the ionic liquid can be recovered from the system by distillation and re-used in consecutive acetylation batches.
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| 19. |
- Junka, Karoliina, et al.
(författare)
-
Multilayers of cellulose derivatives and chitosan on nanofibrillated cellulose
- 2014
-
Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 108, s. 34-40
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to study the effect of solution conditions and polysaccharide structure on their Layer-by-Layer (LbL) deposition on nanofibrillated cellulose (NFC). Multilayer build-up of cellulose derivatives and chitosan on NFC model surfaces was studied using Quartz Crystal Microbalance with Dissipation (QCM-D) and Colloidal Probe Microscopy (CPM). The type of cationic polysaccharide was found to significantly affect the multilayer build-up and surface interactions. Cationic cellulose derivative quaternized hydroxyethyl cellulose ethoxylate (HECE) formed highly water-swollen layers with carboxymethyl cellulose (CMC), and the build-up was markedly influenced by both the ionic strength and pH. The ionic strength did not significantly influence the multilayer build-up of chitosan–CMC system, and adsorbed chitosan layers decreased the viscoelasticity of the system. Based on the results, it was also confirmed that electrostatic interaction is not the only driving force in case of the build-up of polysaccharide multilayers on nanofibrillated cellulose.
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| 20. |
- Khokarale, Santosh G., et al.
(författare)
-
Poly (Vinylidene Difluoride) Polymer in 1-Ethyl-3-methylimidazolium Acetate and Acetic Acid Containing Solvents: Tunable and Recoverable Solvent Media to Induce Crystalline Phase Transition and Porosity
- 2022
-
Ingår i: Sustainable Chemistry. - : MDPI. - 2673-4079. ; 3:4, s. 455-474
-
Tidskriftsartikel (refereegranskat)abstract
- In this report, 1-ethyl-3-methylimidazolium acetate, [EMIM][AcO] ionic liquid (IL) and acetic acid (AA) comprised solvents were used for the thermal treatment of poly (vinylidene difluoride), PVDF. Here, besides the various combinations of IL and AA in solvents, the pure IL and AA were also applied as a solvent upon thermal treatments. The samples obtained after the treatment were analysed for structural and crystalline phase changes, porosity, and molecular weight distribution with various analytical techniques. The Kamlet-Taft parameters measurement of the IL and AA containing solvents with different solvatochromic dyes was also performed to examine their solvent properties and correlate with the properties of the treated PVDF materials. The treatment of PVDF with pure IL results in the formation of highly carbonaceous material due to extensive dehydroflurination (DHF) as well as possibly successive cross-linking in the polymer chains. Upon IL and AA combined solvent treatment, the neat PVDF which composed of both α- and β crystalline phases was transformed to porous and β-phase rich material whereas in case of pure AA the non-porous and pure α-phase polymeric entity was obtained. A combined mixture of IL and AA resulted in a limited the DHF process and subsequent cross-linking in the polymer chains of PVDF allowed the formation of a porous material. It was observed that the porosity of the thermally treated materials was steadily decreasing with increase in the amount of AA in solvents composition and solvent with an AA:IL mole ratio of 2:1 resulted in a PVDF material with the highest porosity amongst the applied solvents. A recovery method for the IL and AA combined solvent after the thermal treatment of PVDF was also established. Hence, with varying the type of solvents in terms of composition, the highly carbonaceous materials as well as materials with different porosities as well as crystalline phases can be obtained. Most importantly here, we introduced new IL and AA containing recoverable solvents for the synthesis of porous PVDF material with the electroactive β-phase.
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| 21. |
- Lützenkirchen, J, et al.
(författare)
-
Adsorption of Al13–Keggin clusters to sapphire c-plane single crystals : Kinetic observations by streaming current measurements
- 2010
-
Ingår i: Applied Surface Science. - : Elsevier B V. - 0169-4332 .- 1873-5584. ; 256:17, s. 5406-5411
-
Tidskriftsartikel (refereegranskat)abstract
- We have carried out streaming current measurements of sapphire c-plane single crystals in contact with the solutions containing the Al13–-Keggin ions at different pH values. We followed the evolution of the zeta-potential as a function of time and pH. The Keggin ions were synthesised and characterised by ESI-MS in two different laboratories, and the results showed that nearly 100% of Al was in the form of Al13 cluster. The streaming current measurements were carried out to investigate whether Al13 clusters would (i) be adsorbed to the surface and (ii) remain stable. Close to the isoelectric point of the sapphire c-plane (around pH 4) it was found that the Al13 ions were adsorbed and stable in the systems for an extended period. After some time the conductivity of the solution strongly increased and the zeta-potential declined, indicating that the clusters were destroyed (certainly in solution, as indicated by the conductivity reading, but potentially also at the surface). ESI-MS measurements at various dilution factors or decreased pH also showed disintegration of the clusters resulting in a multitude of smaller Al species, in agreement with the conductivity measurements during the streaming current measurements. Additions at higher pH showed clear adsorption of the clusters but resulted in stability over the complete observation period as inferred from the conductivity measurements.
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| 22. |
- Miranda, Diego A., et al.
(författare)
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Production and characterization of poly(3-hydroxybutyrate) from Halomonas boliviensis LC1 cultivated in hydrolysates of quinoa stalks
- 2023
-
Ingår i: Fermentation. - : MDPI. - 2311-5637. ; 9:6
-
Tidskriftsartikel (refereegranskat)abstract
- The global production of fossil-based plastics has reached critical levels, and their substitution with bio-based polymers is an urgent requirement. Poly(3-hydroxybutyrate) (PHB) is a biopolymer that can be produced via microbial cultivation, but efficient microorganisms and low-cost substrates are required. Halomonas boliviensis LC1, a moderately halophilic bacterium, is an effective PHB producer, and hydrolysates of the residual stalks of quinoa (Chenopodium quinoa Willd.) can be considered a cheap source of sugars for microbial fermentation processes in quinoa-producing countries. In this study, H. boliviensis LC1 was adapted to a cellulosic hydrolysate of quinoa stalks obtained via acid-catalyzed hydrothermal pretreatment and enzymatic saccharification. The adapted strain was cultivated in hydrolysates and synthetic media, each of them with two different initial concentrations of glucose. Cell growth, glucose consumption, and PHB formation during cultivation were assessed. The cultivation results showed an initial lag in microbial growth and glucose consumption in the quinoa hydrolysates compared to cultivation in synthetic medium, but after 33 h, the values were comparable for all media. Cultivation in hydrolysates with an initial glucose concentration of 15 g/L resulted in a higher glucose consumption rate (0.15 g/(L h) vs. 0.14 g/(L h)) and volumetric productivity of PHB (14.02 mg/(L h) vs. 10.89 mg/(L h)) than cultivation in hydrolysates with 20 g/L as the initial glucose concentration. During most of the cultivation time, the PHB yield on initial glucose was higher for cultivation in synthetic medium than in hydrolysates. The produced PHBs were characterized using advanced analytical techniques, such as high-performance size-exclusion chromatography (HPSEC), Fourier transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). HPSEC revealed that the molecular weight of PHB produced in the cellulosic hydrolysate was lower than that of PHB produced in synthetic medium. TGA showed higher thermal stability for PHB produced in synthetic medium than for that produced in the hydrolysate. The results of the other characterization techniques displayed comparable features for both PHB samples. The presented results show the feasibility of producing PHB from quinoa stalks with H. boliviensis.
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| 23. |
- Raut, Dilip G., et al.
(författare)
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A morpholinium ionic liquid for cellulose dissolution
- 2015
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 130, s. 18-25
-
Tidskriftsartikel (refereegranskat)abstract
- A series of substituted morpholinium ionic salts and allyl ammonium acetates were prepared. Amongst those, N-allyl-N-methylmorpholinium acetate ([AMMorp][OAc]) was found to dissolve cellulose readily without any pre-processing of native cellulose. At 120 degrees C, [AMMorp][OAc] could dissolve 30 wt%, 28 wt% and 25 wt% of cellulose with degree of polymerization (DPn) - 789, 1644 and 2082 respectively, in 20 min. Importantly, SEC analysis indicated that no discernible changes occurred in terms of the degree of polymerization of the different celluloses after regeneration. Furthermore, when comparing the cellulose dissolution capability of these newly synthesized ionic liquids, it is evident that the combination of all three constituents - the morpholinium cation, the existence of an allyl group and choosing the acetate anion are essential for efficient cellulose dissolution. The structure and morphology of the regenerated cellulosic materials were characterized by SEM, XRD, TGA, CP/MAS C-13 NMR and FTIR, respectively.
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| 24. |
- Reyes, Diana Carolina Alban, et al.
(författare)
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Alkalization of dissolving cellulose pulp with highly concentrated caustic at low NaOH stoichiometric excess
- 2017
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 165, s. 213-220
-
Tidskriftsartikel (refereegranskat)abstract
- We present a quantitative study, using Raman spectroscopy combined with multivariate data analysis, to determine the degree of activation of softwood sulphite dissolving cellulose pulp by aqueous sodium hydroxide. We have chosen industrially relevant conditions, including low stoichiometric ratio of NaOH/Anhydroglucose Unit (AGU) <2 and highly concentrated caustic (>= 45% w/w [NaOH]). A design of experiments is used to investigate the effects of simultaneous variation of a set of key parameters on the degree of activation (i.e. transformation to alkali cellulose, denoted as DoA): (a) the NaOH/AGU stoichiometric ratio, denoted (r); (b) the concentration of NaOH, denoted [NaOH]; (c) temperature, denoted (T); and (d) reaction time, denoted (t). Solid-state C-13 CP/MAS NMR spectroscopy was applied to investigate the reproducibility of the experiments and to select the range for (t). According to the model, (r) is found to have a statistically significant effect on DoA (increasing from DoA= 6-30% at the lowest (r)=0.8, to DoA= 48-87% at the highest (r)=1.8), together with [NaOH]. The influence of [NaOH] depends strongly on (r). The other studied variables are found to be insignificant in the model and has a complicated influence on the activation. In particular, (T) is found to be unimportant in the studied range (30-60 degrees C), but increasing (t) from 5 to 25 min shows a positive influence on DoA, depending on both (r) and [NaOH]. A mercerisation mechanism that is controlled by diffusion is proposed to explain these phenomena.
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| 25. |
- Reyes Forsberg, Diana Carolina, 1984-
(författare)
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Experimental study of alkalinisation of cellulose in industrial relevant conditions
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mercerisation of cellulose pulp with a solution of NaOH is the first step of manufacturing cellulose-based value-added products, e.g. viscose fibres and cellulose ethers. During this process, cellulose transforms into a swollen crystalline structure, alkali cellulose (Na-Cell). This increases the reactivity of the cellulose and makes it more accessible for reagents to penetrate and react with the hydroxyl groups. The mercerisation conditions are known to affect the degree of alkalinisation of cellulose as well as the final products. The main objective of this thesis is to investigate how the alkalinisation of softwood sulphite dissolving cellulose pulp is influenced by the co-variation of process variables in the mercerisation in industrial relevant conditions, for both viscose and cellulose ether production. This objective was achieved by quantitative analysis of the effect of simultaneous variation of a set of key parameters on the degree of alkalinisation (i.e. degree of activation, DoA) of the chosen dissolving pulp. Quantitative measurements were performed using Raman spectroscopy data, evaluated by partial least squares (PLS) regression. For mercerisation at viscose production conditions, the effect of studied variables on mass yield was also considered. In the case of mercerisation at ether processing conditions, formation of alkali cellulose at a fixed temperature was included. The knowledge obtained on mercerisation under ether processing conditions was then applied for preparation of the ionic cellulose ether carboxymethylcellulose (CMC). The overall results show that temperature has a strong effect on DoA and mass yield for mercerised samples under steeping conditions. Measured DoA decreases as the temperature increases from 20 to 70 °C. Mass yield correlates positively with the temperature up to 45-50 °C in the PLS model, after which the relation is negative. The [NaOH] and reaction time show a complex dependence of other variables. At mercerisation conditions for cellulose ether production, the NaOH/AGU stoichiometric ratio, denoted as (r), shows to be very important for DoA, with a positive correlation. At these mercerisation conditions, temperature shows no effect on DoA. The influence of the [NaOH] (which also refers to the concentration of water) shows a complex dependence on (r). As (r) increases and [NaOH] decreases, the measured DoA increases. Prolonged mercerisation time shows no significance in the modelled DoA. However, a gradual increase of the DoA over time was seen when mercerisation was performed with 30% and 40% [NaOH] at (r) = 0.8, suggesting a slow diffusion of NaOH and Na-Cell formation. 13C CP-MAS NMR measurements of samples produced at room temperature show that formation of the Na-Cell allomorph is mainly determined by the [NaOH]. However, in the transition area between Na-Cell I and Na-Cell II, (r) also seems to be of importance. An increase of DS in the produced CMC samples also shows to be consistent at such conditions with the increase in the measured DoA and with increased (r) and decreased [NaOH]. However, these conditions also favour the formation of by-products. In the synthesised CMC samples, a DS of up to 0.7 was achieved. Measured solubility was lower than expected for any given DS. This, along with the non-statistical distribution of monomer units in the polymer chains, indicates high heterogeneity in the synthesised samples. The distribution of substituents within the AGU shows attachment to hydroxyl oxygens in the order O3 < O2 ≈ O6. The relative importance of the substitution at O3 indicates an increase at this position when [NaOH] increases.The models presented in this thesis will hopefully serve as a basis for predicting the effects of the studied variables on the DoA, as well as on the mass yield of cellulose pulp when mercerisation conditions are adjusted. Moreover, it is believed that the presented studies can give a better understanding of mercerisation at cellulose ether conditions, hence enabling further development of this process step.
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| 26. |
- Sundman, Ola, et al.
(författare)
-
A multitechnique study of the interactions between H+, Na+, Ca2+ and Cu2+, and two types of softwood Kraft fibre materials
- 2008
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 328:2, s. 248-56
-
Tidskriftsartikel (refereegranskat)abstract
- Aiming for a better understanding of the interactions between water suspended cellulose fibres and metal ions, this study was focused on characterising the interactions between Ca2+, Cu2+ and two different fibre materials—a fully bleached softwood Kraft pulp, and a chemically modified fully bleached softwood Kraft fibre material. The study was conducted as a function of pH (2–7), and both in the absence and presence of an excess of Na+ ions, 0–100 mM Na(Cl). For both fibre materials, adsorption data collected in the absence of Na+ were fully explained by the unspecific Donnan ion-exchange model. However, in an excess of Na(Cl), data clearly indicated that higher amounts of divalent metal ions adsorbed, than predicted by the Donnan model. Therefore, to model these data, specific metal ion–fibre surface complexes were assumed to form, in addition to the Donnan ion-exchange. A neutral surface species involving two surface carboxylate groups and one metal ion was, for both metal ions, found to yield a good description of data at all ionic strengths. In the case of Cu2+, the existence of this complex was corroborated by Cu K-edge EXAFS data, suggesting that copper ions interacts directly with carboxyl groups present int the fibres. EXAFS data also indicate that one Cu2+ interacts with two carboxyls.Graphical abstractIn combination with unspecific Donnan interactions, specific interactions between divalent metal ions (Ca2+ and Cu2+) and cellulose fibre carboxylic groups were evidenced from both macroscopic adsorption data and spectroscopic measurements.
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| 27. |
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| 28. |
- Sundman, Ola, et al.
(författare)
-
Acid/base and metal adsorption properties of CMC-type softwood Kraft pulps of different charge
- 2006
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 21:3, s. 372-381
-
Tidskriftsartikel (refereegranskat)abstract
- Pulp materials ranging in charge from zero to 280 mmol/g were synthesised and characterised with respect to ion exchange properties. Both the Constant Capacitance and the Basic Stern Models were found applicable to simulate the acid/base properties. For all materials, the Donnan distribution model gave a good description for the metal binding properties.
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| 29. |
- Sundman, Ola
(författare)
-
Adsorption of four non-ionic cellulose derivatives on cellulose model surfaces
- 2014
-
Ingår i: Cellulose. - : Springer Netherlands. - 0969-0239 .- 1572-882X. ; 21:1, s. 115-124
-
Tidskriftsartikel (refereegranskat)abstract
- The adsorption of four commercial non-ionic cellulose derivatives onto two different model surfaces of cellulose fibres has been studied with surface plasmon reflectance. The model surfaces of cellulose were ultrathin films of either nano fibrillated cellulose or regenerated cellulose on Au(s). Partial least squares models were used in the analysis of the data and it was found that the type of cellulose model surface seems to be most important for both the total adsorption and the initial adsorption rate of the studied cellulose derivatives. It is believed that this can be explained by morphological differences between the surfaces, and it was found that the properties of the cellulose derivatives that affect the adsorption of the two types of cellulose surface differ. For adsorption onto a NFC-based model surface, the type of cellulose derivative and the polydispersity index (PDI) of the cellulose derivative seem to be the two most important variables for the observed adsorption of these cellulose derivatives. For the regenerated cellulose surface the three most important variables are the M (n) of the cellulose derivatives, the DS (NMR) of the methyl celluloses, and PDI of the cellulose derivatives. Thus the adsorption of cellulose derivatives on the NFC-based cellulose model surface is strongly affected by the type of substituent, while the same cannot be said for a surface regenerated from N-methylmorpholine-N-oxide. Additionally, the DS (NMR) of methyl celluloses affects their adsorption differently on the investigated cellulose model surfaces.
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| 30. |
- Sundman, Ola, et al.
(författare)
-
Alternative models for describing the acid/base properties of bleached softwood fibres
- 2005
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 20:4, s. 378-382
-
Tidskriftsartikel (refereegranskat)abstract
- To evaluate the capacity of different thermodynamic models to mimic the build-up of charge on fully bleached softwood fibres as a function of -log[H+] and ionic strength (0.01-0.6 M NaCl), the model of an Ideal Monoprotic Acid, the Constant Capacitance Model (CCM), the Basic Stern Model (BSM), and the Diffuse Layer Model (DLM) were compared. The Ideal Monoprotic Acid, IMA, model consistently yielded a too steep increase in the build up of charge with -log[H+] and thereby indicated the need for applying a surface potential model. The "best" of these, with respect to describing the experimental data, was found to be the Constant Capacitance Model, which utilises an individual equilibrium constant and an individual capacitance value at each ionic strength modelled. However, the Basic Stern Model, which uses only two variables over the entire ionic strength interval, was found to describe data almost as well. Therefore, in modelling applications where a variation in the salt concentration is significant, the Basic Stern Model must be judged as being superior to the Constant Capacitance Model. As for the IMA model, the Diffuse Layer Model, finally, was found to yield a too steep increase in the fibre charge with rising -log[H]. Nevertheless, it was found to model the variation of the apparent acidity with ionic strength, relatively well.
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| 31. |
- Sundman, Ola, 1979-
(författare)
-
Cation adsorption properties of substituted kraft fibres : an experimental and thermodynamic modelling study
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Acid/base and metal ion adsorption properties have been investigated for a range of chemically modified bleached Kraft fibre materials (pulps). The studies were performed via potentiometric titrations, Flame Atomic Absorbtion (and Emission) Spectroscopy, Inductively Coupled Plasma Optical Emission Spectroscopy and Extended X-ray Absorbtion Fine Structure measurements. As a result of a chemical modification procedure, the total concentration of acidic carboxylate groups in the fibre materials ranged between 43 and 590 μmol/g. The preferable surface potential model for modelling the ionic strength dependent acid/base properties of fibre materials with low charge densities, i.e. unmodified fully bleached Kraft fibre materials, was found to be the Basic Stern Model. For fibre materials with high total charge, ≳100 μmol/g, this model resulted in poor fits to data, and for such materials a number of Constant Capacitance Models, one at each ionic strength, must be recommended. With respect to metal ion adsorption, the results have indicated that the unspecific Donnan theory could correctly model the simultaneous adsorption of several metal ions, i.e. K+, Na+, Mg2+, Ca2+ and Cu2+, provided that the salt concentration in the fibre suspension is low. In suspensions of high salt concentration it was, however, found that this very same model strongly underestimated the adsorption of Ca2+ and Cu2+. Here, the Donnan model had to be complemented by specific ion exchange equilibria. These results were corroborated by spectroscopic evidence of specific interactions between Cu2+-ions and fibres. The spectroscopic indication of a complex formed between two fibre surface carboxylate groups and one Cu2+-ion, agree with the specific ion exchange model. It was therefore concluded that specific metal ionfibre interactions cannot be neglected, especially at high salt concentrations. The interactions occurring between the polycation GaO4Al12(OH)24(H2O)127+ and fibre materials were studied by both adsorption and spectroscopic measurements. These indicate that GaO4Al12(OH)24(H2O)127+ is surprisingly stable in fibre suspensions and that intact GaO4Al12(OH)24(H2O)127+- ions are strongly adsorbed onto the fibres. Also for this ion, specific interactions has to be considered, since the strong adsorption registered was too strong to be explained by Donnan equilibria. In the thesis, the stochiometric composition and an equilibrium constant characterising these interactions is presented.
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| 32. |
- Sundman, Ola, et al.
(författare)
-
Comparison between specific surface complexation and Donnan ion-exchange models for describing the adsorption of cations on kraft fibres : literature evidence and EXAFS study of Cu(II) binding
- 2010
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 25:2, s. 178-184
-
Tidskriftsartikel (refereegranskat)abstract
- A compilation of the applied experimental conditions when studying metal ion adsorption onto kraft fibres, and the resulting conclusion, revealed that the ionic strength conditions used during the experiments were an important dividing factor. At low ionic strengths, the conclusion has regularly been that the Donnan ion-exchange model could correctly predict the adsorption while, at higher ionic strengths, it has often been concluded that the formation of specific metal-ion fibre complexes must be assumed. To study this apparent influence from the presence of monovalent sodium ions, Cu K-edge EXAFS spectra of Cu2+ ions adsorbed to kraft fibres were collected in media of "0" to 100 mM NaCl. Combined with previous data, these measurements confirmed that at very low ionic strength, the importance of specific interactions between the chemically modified cellulose fibres and the Cu(II) ions significantly decreased. For a detailed description of the adsorption phenomenon, both types of interactions must be considered simultaneously. For most technical and engineering applications, however, the Donnan model can be used at low ionic strength conditions, i.e. I ≤ 10 mM. At higher ionic strengths, though, the inclusion of specific complexes in the model is necessary for correctly describing the adsorption of di- and trivalent cations with strong complex forming properties.
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| 33. |
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| 34. |
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| 35. |
- Sundman, Ola, 1979-, et al.
(författare)
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Homogenous benzylation of cellulose : impact of different methods on product properties
- 2015
-
Ingår i: Cellulose Chemistry and Technology. - 0576-9787. ; 49:9-10, s. 745-755
-
Tidskriftsartikel (refereegranskat)abstract
- This paper offers an evaluation of different methods for synthesizing benzyl cellulose and of how they affect characteristics such as solubility, degree of substitution, thermal stability and molecular weight of the products. Benzyl celluloses with degrees of substitution between 0.1 and 2.5 were synthesised from microcrystalline cellulose in (1) aqueous NaOH/Urea and (2) dimethyl sulfoxide/tert-butyl ammonium fluoride (DMSO/TBAF) systems in order to evaluate the different properties of the benzyl celluloses of low degree of substitution. In contrast to previous findings in the literature, both systems yielded soluble benzyl celluloses at degrees of substitution <0.5. Also in contrast to the literature, the low degree of substitution benzyl celluloses from both systems showed similar thermal properties. The filtration of the benzyl celluloses in DMSO/TBAF solutions before precipitation gave significantly higher solubility of the products and increased their thermal stability. The molecular weights of the benzyl celluloses of low degree of substitution (0.4 < DS < 1.25) were similar between the systems and differed in the range of one order of magnitude from the molecular weights of the higher degree of substitution benzyl celluloses. 13C-NMR data indicated differences in the substitution pattern between the two systems.
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| 36. |
- Sundman, Ola, et al.
(författare)
-
Interactions between GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+) and cellulosic materials
- 2012
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 374:1, s. 250-257
-
Tidskriftsartikel (refereegranskat)abstract
- The adsorption qualities of GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+), a polycation with ε-Keggin structure, and its stability in contact with anionic cellulosic materials, was investigated under different concentration and ionic strength conditions. The cellulosic materials employed were two different fully bleached fibre materials, carboxyl methyl cellulose (CMC), and a spin-coated cellulose model surface. As analytical techniques, pH-measurements, potentiometric titrations, ICP-OES, QCM-D, equilibrium calculations and Extended X-ray Absorption Fine Structure (EXAFS) were used. The adsorption is substantial and the addition of GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+) to a fibre suspension results in a rapid decrease in pH, followed by a small and slow increase in pH. This behaviour can be explained as due to a rapid and strong (log β>2) equilibrium adsorption of intact GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+) ions, followed by a slow, and minor, 3-8%, decomposition into different monomers. Alternative layer by layer adsorption of this ion, and CMC, on a spin-coated cellulose model surface constitutes further evidence for the strong interactions between the anionic cellulose materials and GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+). It is shown that the adsorption observed could not be described as due to an unspecific Donnan adsorption behaviour, neither of GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+) nor Ga and Al monomers, and specific surface complex formation is therefore discussed and applied. The (≡COO)(7)GaO(4)Al(12)(OH)(24)(H(2)O)(12) species found to explain the pH- and metal adsorption data should be considered strictly as a stoichiometric entity.
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| 37. |
- Sundman, Ola, et al.
(författare)
-
Layer-by-Layer Adsorption of Two Cellulose-Based Polyelectrolytes on Cellulose Fibers. Dependence of pH and Ionic Strength on the Resulting Charge Density as Measured by Polyelectrolyte Titration
- 2013
-
Ingår i: BioResources. - : North Carolina State University. - 1930-2126. ; 8:4, s. 4827-4836
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Tidskriftsartikel (refereegranskat)abstract
- The charge density of a bleached Kraft hardwood pulp, subjected to layer-by-layer adsorption of the oppositely charged cellulose derivative polyelectrolytes hydroxyethylcellulose ethoxylate, quaternised (HECE), and carboxymethyl cellulose (CMC), was studied by polyelectrolyte titration as a function of pH and ionic strength. The experimental design included a simultaneous variation of the experimental parameters, and the trends were evaluated with the help of partial least squares regression. As expected from the literature, the data indicate that both pH and ionic strength influence the charge of cationic fibers. It is also obvious that CMC as an outermost layer is more sensitive to changes in pH than the deprotonation of COOH groups suggests. High ionic strength seems to be beneficial for the adsorption of HECE, while the pH dependence seems much more complicated. The non-linear pH dependence indicates that, in addition to electrostatic interactions, entropy factors and hydrogen bonding between OH groups on both the substrates and ligands are responsible for the adsorption, which is in agreement with literature on the subject.
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| 38. |
- Sundman, Ola, et al.
(författare)
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On the origin of the spectroscopic signals of cellulose II-type in sulphite dissolving pulp
- 2016
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 31:1, s. 54-60
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Tidskriftsartikel (refereegranskat)abstract
- Sulphite dissolving pulp was fractionated and the differences in the spectroscopic signals between the fines and bulk cellulose were investigated. Raman spectroscopy and CP/MAS 13C NMR were used as spectroscopic techniques while fines content and particle size was investigated using Pulpeye®. Also the molecular weight distribution was analysed with size exclusion chromatography and the carbohydrate composition was investigated using ion chromatography. The spectral data were investigated with the use of multivariate data analysis and both Raman spectroscopy and NMR measurements indicated a higher content of a cellulose II type material in the small particles than in the bulk cellulose. The molecular weight distribution measure-ments showed a higher content of low molecular weight material in the fines fractions, and this was concluded from the ion chromatography data to probably originate from both hemicelluloses and low molecular weight cellulose. As a conclusion it was hypothesised that regeneration of hemicellulose and low molecular weight cellulose, as a result of process parameters, occurred on the fines in particular.
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| 39. |
- Sundman, Ola, et al.
(författare)
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Potentiometric titrations of five synthetic tetraacids as models for indigenous C80 tetraacids
- 2010
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 26:3, s. 1619-29
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Tidskriftsartikel (refereegranskat)abstract
- The acid/base properties, critical micelle concentrations (cmcs), and pH-dependent solubility of five synthetic tetraacids have been studied at several ionic strengths (20-600 mM NaCl) and in the pH range of 1.5-11 using high precision potentiometric titrations, tensiometer measurements, and UV spectroscopy, respectively. The molecular weight of the tetraacids ranged between 478 and 983 g/mol. The potentiometric titration data was evaluated in terms of thermodynamic equilibrium models, developed in the light of relevant solubility data, Langmuir monolayer compressions and cmc of the different tetraacids. The results indicate that for two of the tetraacids, called BP5 and BP7, two chemical forms fully dominate the speciation of the monomers; the insoluble fully protonated form, and the soluble fully deprotonated form. The partly protonated species, only play a very minor role in the speciation of these tetraacids. For the other tetraacids the results are more complicated; for the smallest tetraacid, called BP1, all species seem to play important roles, and for the most hydrophobic, BP10, the formation of micelles and aggregates severely complicates the evaluation of the speciation. For the tetraacid BP3 one of the partly deprotonated forms seems to be important, thus confirming the structure to properties relationship. In spite of the complicated micelle formation chemistry, and although not actually measured, the acid/base properties for the monomers of BP10 were interpreted by means of surface charge densities of the micellar aggregates. The modeling indicates an increase of the aggregation number of the micelle upon acidification, a result of formation of mixed micelles incorporating the fully protonated and deprotonated species. An intrinsic pK(a) of 5.4 for BP5 was used to model the monomer pK(a) of BP10, and corresponded well with a monolayer acidity constant pK(s)(a) of 5.5 obtained from surface collapse pressures of Langmuir monolayers as a function of pH.
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| 40. |
- Sundman, Ola, et al.
(författare)
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Study of the aqueous chemical interactions between a synthetic tetra-acid and divalent cations as a model for the formation of metal naphthenate deposits
- 2010
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Ingår i: Energy & Fuels. - : American Chemical Society. - 0887-0624 .- 1520-5029. ; 24:11, s. 6054-6060
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Tidskriftsartikel (refereegranskat)abstract
- The previously presented synthetic tetra-acid model compound BP10 was used to investigate the chemistry behind the formation of metal naphthenate deposits. The interactions between BP10 and the cations Ba2+, Ca2+, H+, Mg2+, and Sr2+ were investigated using potentiometric titrations, metal ion depletion by inductively coupled plasma−atomic emission spectrometry (ICP−AES), pH measurements, and elemental analysis of precipitates, in 20−600 mM NaCl ionic medium. The interactions of BP10 with the monovalent Na+ are discussed on the basis of a previous study. The data given indicate that Ca2+ shows the strongest affinity toward BP10 and Ba2+, and Sr2+ form approximately equally stable solid phases with BP10, while Mg2+ is less tightly bound to the tetra-acid. H+ interacts more strongly than the Me2+ ions, and Na+ shows a rather small affinity for BP10. No soluble complexes could be detected, and all products in the chemical reactions are therefore believed to be solid materials. We suggest that BP10 show the following preference of cations: H+ Ca2+ > Ba2+ ≈ Sr2+ > Mg2+ Na+. This order could be due to the hydration state and size of the cations. In comparison to typical concentrations found of each in saline water, it is proposed that the dominance of Ca2+ in naphthenate deposits is dependent upon both availability and selectivity.
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| 41. |
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| 42. |
- Yahia, Mohamed, et al.
(författare)
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Effect of incorporating different ZIF-8 crystal sizes in the polymer of intrinsic microporosity, PIM-1, for CO2/CH4 separation
- 2021
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier. - 1387-1811 .- 1873-3093. ; 312
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Tidskriftsartikel (refereegranskat)abstract
- Effective and economical carbon dioxide-methane separation (CO2/CH4) is highly desirable in several industries such as sweetening natural gases and renewable natural gas (RNG) from biogas and landfills. Among the different separation technologies, membrane separation has been shown to have lower cost of production and lower CH4 losses. In this study, Zeolitic Imidazole Frameworks (ZIF-8) crystals with sizes varying from 45 nm to 450 nm were synthesized and incorporated in the polymer of intrinsic microporosity, PIM-1, to form mixed matrix membranes (MMMs). The structure, morphology, and physicochemical properties of the MMMs were characterized by 1H NMR, FTIR, XRD, TGA, and SEM. ZIF-8 crystal size was controlled using the concentration of sodium formate. The influence of the ZIF-8 crystal size on MMMs was studied by sorption, gas permeability, and aging of the membranes. The MMMs with ZIF-8 crystals of 120 nm particle diameter yielded the greatest improvement in gas transport properties; the CO2/CH4 selectivity-CO2 permeability was 11.4 and 9700 Barrer compared to PIM-1 with 6.4 and 9300 Barrer respectively. The former is near the Robeson 2008 upper bound, while PIM-1 is on the 1991 upper bound. After 40 days of aging, selectivity increased and permeability decreased; the changes were parallel to the Robeson upper bounds indicating increased polymer packing and diffusivity selectivity.
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| 43. |
- Yahia, Mohamed, et al.
(författare)
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Replacing benzyl chloride with a lignin-degradation product in cellulose etherification decreases the melting point
- 2023
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Ingår i: BioResources. - : North Carolina State University. - 1930-2126. ; 18:1, s. 161-174
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Tidskriftsartikel (refereegranskat)abstract
- A cellulose ether that is easier to melt than benzyl cellulose was produced from the lignin degradation product veratryl alcohol. Veratryl chloride and bromide were synthesized from the alcohol, and these two chemicals were used to react with Avicel® cellulose to form the novel cellulose ether veratryl cellulose (VC). Spectroscopic characterisation techniques (1H NMR, FTIR) indicated the successful conversion of Avicel® cellulose to the cellulose ether VC, by both routes, at a degree of substitution of 1.4 to 1.6. Melting measurements of the VC samples showed a gradual softening from approximately 110 °C; the VC was melted below 200 °C. XRD analysis confirmed that the chemical treatments affect the degree of crystallinity. Size exclusion chromatography results showed that the products differ remarkably in molecular weight. The VC synthesized with veratryl chloride degraded almost twice as much as when veratryl bromide were used. The cellulose ethers were soluble in DMSO, DMAc, and CHCl3.
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| 44. |
- Zannagui, C., et al.
(författare)
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Design, Characterization and Investigation of Heavy Metal Ions Removal by New Cellulose-Ether Based adsorbent
- 2020
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Ingår i: Moroccan Journal of Chemistry. - : UNIV MOHAMMED PREMIER OUJDA. - 2351-812X. ; 8:1, s. 332-346
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Tidskriftsartikel (refereegranskat)abstract
- The present investigation deals with the elaboration in homogenous conditions of new cross-linked, hydroxyl cellulose (HEC) based material. Further, its application as a new eco-friendly low-cost efficient adsorbent of hazardous metal ions from an aquatic environment is treated. In this respect, the functionalization of HEC has been carried out using EDTA as a cross-linking agent exploiting its high capacity to chelate heavy metal ions in aqueous solutions. The proposed structure of the new crosslinked material (HECD) was investigated using structural analyses (FTIR-ATR vibrational spectroscopy and CP/MAS 13C NMR Spectroscopy). Also, the thermal and crystalline behaviours of unmodified and modified HEC were studied using thermogravimetric (TG and DTG) and DRX patterns. In addition, SEM images were recorded to demonstrate the changes expected at the morphological and textural level. Furthermore, the adsorption capacity of Pb (II), Cu (II), Cd (II) and Zn (II) ions from aqueous solutions by HECD was investigated using batch technique and optimized according to metal concentration, pH, contact time, ionic selectivity and regenerability. Thus, to examine the mechanism of adsorption, the experimental data is fitted to kinetic, isothermal, and thermodynamic modelling.
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| 45. |
- Zannagui, Chahid, et al.
(författare)
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Homogeneous succinylation of cellulose acetate : design, characterization and adsorption study of Pb(II), Cu(II), Cd(II) and Zn(II) ions
- 2021
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Ingår i: E3S Web of Conferences. - : EDP Sciences.
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Konferensbidrag (refereegranskat)abstract
- In this study, the removal of Pb(II), Cu(II), Cd(II), and Zn(II) ions from aqueous solutions was investigated using succinic anhydride modified cellulose monoacetate. In the first part, the cellulose acetate was successfully succinylated in a homogenous medium of DMF using 4-dimethylaminopyridine (DMAP) as a catalyst. The obtained material (AcS) was analyzed by FTIR and CP/MAS 13C NMR Spectroscopy, thermogravimetry analysis and DRX patterns. The titration method was used to determinate the degree of hydroxyl group substituted by carboxyl group (DS) and was found to be 1.36. In the second part, the Bach technique was used to study the effects of pH, contact time, concentration of metals, ionic selectivity and regeneration. Maximum sorption capacities of AcS for Pb(II), Cu(II), Cd(II), and Zn(II) were 241.81, 133.76, 156.61 and 73,58 mg.g-1, respectively. The Langmuir isotherm and the pseudo second order kinetic models provided best fit to the experimental data of metal ion sorption. The nature of the adsorption process was exothermic and spontaneous in nature with negative values of ΔG° and ΔH°. Regeneration of the modified cellulose acetate was accomplished using nitric solution and showed high stability and good recyclability.
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