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In this study, membranes from chitosan with different molecular weights (175-230 kDa) and degree of deacetylation (92%-98%) were prepared and dehydration of a ethanol-water azeotropic mixture by pervaporation on membranes in the swollen and dry initial state was investigated. The influence of chitosan characteristics and the effect of the initial membrane state on separation properties are discussed. The structure of the obtained membranes changed during the drying process and affected the membrane transport parameters and time to membrane stabilisation. The impact of chitosan characteristics on the transport parameters depended on the initial membrane state. The chitosan molecular weight influenced ethanol transport, whereas the chitosan degree of deacetylation affected water transport. In addition, chitosan with the lowest molecular weight improved the separation properties of the membranes. [ABSTRACT FROM AUTHOR]

Membranes were prepared using three chitosans with different molecular weights and degrees of deacetylation. The influence of chitosan features on membrane physicochemical properties, i.e. degree of swelling, contact angle and tensile strength, as well as membrane separation properties in ethanol dehydration by the vapour permeation process are discussed. The conducted experiments showed that an increase in the chitosan molecular weight led to an increase in the membrane surface contact angle concomitant with a decrease in the material selectivity coefficient. On the other hand, an increase in the chitosan degree of deacetylation caused a reduction in ethanol and improved the water permeate flux. There was greater selectivity in the test process for membranes prepared from chitosan with the lowest molecular weight. [ABSTRACT FROM AUTHOR]

Alginate membranes filled with different metal oxide particles were prepared and the influence of the presence of different amounts of Fe3O4, ZnO, and Ag2O particles on ethanol and water permeation was discussed. Ethanol and water vapour permeation rates were determined using the measuring cell method, and the mass transport coefficients were evaluated. It was found that the highest transport parameters were obtained for membranes with the highest metal oxide content. Furthermore, the highest flux, equal 8.49 kg·m−2·h−1, was obtained for the alginate membrane filled with 15 wt% of silver oxide particles, while the greatest selectivity coefficients were noted for membranes containing magnetite. In this case, for the alginate membrane with 15 wt% of magnetite content, the selectivity coefficient reached the best value of 108.15. [ABSTRACT FROM AUTHOR]

Chitosan-based membranes filled with different metal oxide particles were prepared and their performance in ethanol dehydration process depending on the type of oxide and loading was discussed. For membrane preparation three oxides: TiO2, Cr2O3 or Fe3O4 were selected. From experimental data suitable ethanol and water transport coefficients were evaluated. As shown in the results, applied fillers in different ways affect the separation properties. Presence of TiO2 significantly affects the normalized total flux, increasing its value. On the other hand, addition of Fe3O4 influences most of all the separation factor, which is the among all investigated membranes. For membranes containing chromium(III) oxide as a filler, improvement in the separation properties is observed only in the case when the Cr2O3 content equals to 5 wt%. Above this concentration significant deterioration of separation properties is observed. The best performance has mixed-matrix membranes (MMMs) with magnetite, where the values of PSI are equal to 16.3 and 296.8 kg/m−2 h µm for pristine and 15 wt% filler content, respectively. [ABSTRACT FROM AUTHOR]

Various metal-oxide nanoparticles and chitosan were blended to form new adsorbents (M-Oxide-CTS) for removing boron from aqueous solutions in a batch system. The maximum boron adsorption capacity (q= 7.8 mg/g) was reached at pH = 4 within 5 min. Calculations based on Langmuir, Freundlich, and Dubinin–Radushkevich models showed the heterogeneous and physical nature of boron adsorption on M-Oxide-CTS. Modeling of the thermodynamic date indicated the nonspontaneous and exothermic process. The pseudo-second-order model adequately described the boron adsorption on M-Oxide-CTS. Desorption by means of alkaline solution at pH = 12 was carried out successfully. [ABSTRACT FROM AUTHOR]

This paper presents a study of novel hybrid membranes consisting of sodium alginate as a polymer matrix and magnetite and two cross-linking agents, that is, orthophosphoric acid and Ca+2 ions. Ethanol/water separation parameters were determined using the vapour permeation process. The permeate parameters were estimated on the basis of weight loss of the measuring cell over time using an analytical balance. The results have shown the influence of magnetite particles content in the alginate matrix and the effect of cross-linking agents on ethanol/water separation properties. Comparing permeation coefficients of both types of discussed membranes more advantageous separation properties for the membranes cross-linked with orthophosphoric acid were observed. The best ideal selectivity (55.54) was recorded for membranes with iron oxide content between 5 and 10 w/w%. For Ca+2 ions cross-linked membranes, the highest ideal selectivity coefficient can be obtained at 15–20 w/w% magnetite content (32.18). [ABSTRACT FROM AUTHOR]

This paper presents a study of novel hybrid membranes consisting of sodium alginate as a polymer matrix and magnetite and two cross-linking agents, that is, orthophosphoric acid and Ca+2 ions. Ethanol/water separation parameters were determined using the vapour permeation process. The permeate parameters were estimated on the basis of weight loss of the measuring cell over time using an analytical balance. The results have shown the influence of magnetite particles content in the alginate matrix and the effect of cross-linking agents on ethanol/water separation properties. Comparing permeation coefficients of both types of discussed membranes more advantageous separation properties for the membranes cross-linked with orthophosphoric acid were observed. The best ideal selectivity (55.54) was recorded for membranes with iron oxide content between 5 and 10 w/w%. For Ca+2 ions cross-linked membranes, the highest ideal selectivity coefficient can be obtained at 15-20 w/w% magnetite content (32.18). [ABSTRACT FROM AUTHOR]

Chitosan membranes filled with different amount of ferroferric oxides and cross-linked by two different agents, i.e. sulfuric acid or glutaraldehyde, were prepared and the influence of iron oxide and cross-linking agents on ethanol and water permeation has been discussed. Ethanol and water vapors permeation rates were determined using the measuring cell method and mass transport coefficients were evaluated. It was found that permeation of water for both types of chitosan membranes after addition of magnetite gradually increased. Furthermore, the difference between ethanol/water permeation coefficients was larger for glutaraldehyde cross-linked membranes (CHGA) than for sulfuric acid cross-linked membranes (CHSA). [ABSTRACT FROM PUBLISHER]

The effect of oxygen conditioning on the performance of polyaniline (PANI) membranes is presented and discussed. The presence of the conditioning effect in such kind of polymer matrix was confirmed by measuring a variation in spin concentration using electron paramagnetic resonance (EPR) spectroscopy. The observed decrease in spin concentration indicates the presence of the dissolved oxygen incompletely removed from PANI matrix. After the prolonged contact between oxygen and PANI membrane, a pronounced decrease in membrane’s selectivity was observed, which may be explained by the firm and permanent interaction between oxygen molecules and nitrogen paramagnetic centers of PANI and could be considered as a kind of PANI irreversible doping process. [ABSTRACT FROM PUBLISHER]

Pervaporative separation properties of crosslinked chitosan and alginate membrane on ethanol-water mixture at room temperature was studied. The influence of crosslinking agents on the separation properties were discussed. Selected crosslinking agents were affected differently on used polymer matrices. The better separation properties were obtained for membranes crosslinked by phosphoric (V) acid. The highest pervaporation separation index (309.6 kg/m2·h) and separation factor (52.6) were obtained for phosphoric (V) acid crosslinked alginate membranes, however, the greatest total flux (12.4 kg/m2·h) obtained for phosphoric acid crosslinked chitosan membranes. [ABSTRACT FROM AUTHOR]

A vapour permeation of water and ethanol through homogenous chitosan and alginate membranes was investigated. The influence of the polymer matrix and crosslinking agents, and measurement protocol on the transport properties were discussed. The conducted experiments showed the greater separation factor, better stability and resistant to solvents for chemically crosslinked membranes. On the other hand, stronger association of the matrix, than the physical, caused decrease of vapour fluxes. [ABSTRACT FROM AUTHOR]

The aim of this work was to a study various adsorption processes of methyl violet (model compound of aniline dye) on chitin and chitin deacetylation products. Two types of adsorption processes - batch and continuous - were tested. Results illustrated that raw chitin is an effective adsorbent for methyl violet and the adsorption activity of chitin deacetylation products strongly decrease with increasing degree of deacetylation (DDA). The continuous process is more effective then batch process. [ABSTRACT FROM AUTHOR]

Boron is an essential element for plants and living organisms; however, it can be harmful if its concentration in the environment is too high. In this paper, lanthanum(III) ions were introduced to the structure of chitosan via an encapsulation technique and the obtained hydrogel (La-CTS) was used for the elimination of the excess of B(III) from modelling solutions. The reaction between boric acid and hydroxyl groups bound to the lanthanum coordinated by chitosan active centres was the preponderant mechanism of the bio-adsorption removal process. The results demonstrated that La-CTS removed boric acid from the aqueous solution more efficiently than either lanthanum hydroxide or native chitosan hydrogel, respectively. When the initial boron concentration was 100 mg/dm3, the maximum adsorption capacity of 11.1 ± 0.3 mg/g was achieved at pH 5 and the adsorption time of 24 h. The successful introduction of La(III) ions to the chitosan backbone was confirmed by Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy, Fourier-Transform Infrared Spectroscopy, X-Ray Diffraction, X-ray Photoelectron Spectroscopy, and Inductively Coupled Plasma Optical Emission Spectroscopy. Due to its high-performance boron adsorption-desorption cycle and convenient form, La-CTS seems to be a promising bio-adsorbent for water treatment. [ABSTRACT FROM AUTHOR]

In this study, a chitosan hydrogel supported with ceria (labelled Ce-CTS) was prepared by an encapsulation technique and used for the efficient removal of excess B(III) from aqueous solutions. The functionalisation of chitosan with Ce(IV) and the improvement in the adsorptive behaviour of the hydrogel were determined by SEM-EDS, FTIR, XRD, and inductively coupled plasma optical emission spectrometer (ICP-OES) analyses and discussed. The results demonstrate that Ce-CTS removes boric acid from aqueous solutions more efficiently than either cerium dioxide hydrate or raw chitosan beads, the precursors of the Ce-CTS biosorbent. The maximum adsorption capacity of 13.5 ± 0.9 mg/g was achieved at pH 7 after 24 h. The equilibrium data of boron adsorption on Ce-CTS fitted the Freundlich isotherm model, while the kinetic data followed the Elovich pseudo-second-order model, which indicated that the process was non-homogeneous. The dominant mechanism of removal was the reaction between boric acid molecules and hydroxyl groups bound to the ceria chelated by chitosan active centres. Due to its high efficiency in removing boron, good regeneration capacity and convenient form, Ce-CTS may be considered a promising biosorbent in water purification. [ABSTRACT FROM AUTHOR]