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Preparation and Characterization of Chitosan Thin Films on Mixed-Matrix Membranes for Complete Removal of Chromium.

Nayak V, Jyothi MS, Balakrishna RG, Padaki M, Ismail AF - ChemistryOpen (2015)

Bottom Line: Structure property elucidation was carried out by X-ray diffraction, microscopy, spectroscopy, contact angle measurement, and water uptake studies.The increase in hydrophilicity followed the order: PSf < PSf/TiO2 < PSf/TiO2/CS membranes.The observations reveal 100 % reduction of Cr(VI) to Cr(III) through electrons and protons donated from OH and NH2 groups of the CS layer; the reduced Cr(III) species are adsorbed onto the CS layer via complexation to give chromium-free water.

View Article: PubMed Central - PubMed

Affiliation: Center for Nano and Material Sciences, Jain University Ramanagaram, Bangalore, 562112, India.

ABSTRACT
Herein we present a new approach for the complete removal of Cr(VI) species, through reduction of Cr(VI) to Cr(III), followed by adsorption of Cr(III). Reduction of chromium from water is an important challenge, as Cr(IV) is one of the most toxic substances emitted from industrial processes. Chitosan (CS) thin films were developed on plain polysulfone (PSf) and PSf/TiO2 membrane substrates by a temperature-induced technique using polyvinyl alcohol as a binder. Structure property elucidation was carried out by X-ray diffraction, microscopy, spectroscopy, contact angle measurement, and water uptake studies. The increase in hydrophilicity followed the order: PSf < PSf/TiO2 < PSf/TiO2/CS membranes. Use of this thin-film composite membrane for chromium removal was investigated with regards to the effects of light and pH. The observations reveal 100 % reduction of Cr(VI) to Cr(III) through electrons and protons donated from OH and NH2 groups of the CS layer; the reduced Cr(III) species are adsorbed onto the CS layer via complexation to give chromium-free water.

No MeSH data available.


UV/Vis spectra for CrIII adsorbed onto the membrane surface a) after and b) before CrIII adsorption.
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fig09: UV/Vis spectra for CrIII adsorbed onto the membrane surface a) after and b) before CrIII adsorption.

Mentions: In this study the medium was maintained at pH 4 by the addition of formic acid to facilitate the formation of HCrO4− and Cr2O72− ions and reduction by the electron-donor groups present in the CS layer. As soon as the CrVI solution comes into contact with the CS layer, the reduction starts, which can be confirmed from Figure 8. The reduced CrIII is present in Cr+3, Cr(OH)2+, and Cr(OH)+2 forms,39 which are adsorbed onto the CS surface by complexation; this is supported by the change in membrane color from yellow to pale green, which is typical for CrIII complexes.40 The presence of Cr+3 can also be substantiated by the peak observed at λmax=580 nm41 in the UV/Vis spectra of the used membrane (Figure 9).


Preparation and Characterization of Chitosan Thin Films on Mixed-Matrix Membranes for Complete Removal of Chromium.

Nayak V, Jyothi MS, Balakrishna RG, Padaki M, Ismail AF - ChemistryOpen (2015)

UV/Vis spectra for CrIII adsorbed onto the membrane surface a) after and b) before CrIII adsorption.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4522177&req=5

fig09: UV/Vis spectra for CrIII adsorbed onto the membrane surface a) after and b) before CrIII adsorption.
Mentions: In this study the medium was maintained at pH 4 by the addition of formic acid to facilitate the formation of HCrO4− and Cr2O72− ions and reduction by the electron-donor groups present in the CS layer. As soon as the CrVI solution comes into contact with the CS layer, the reduction starts, which can be confirmed from Figure 8. The reduced CrIII is present in Cr+3, Cr(OH)2+, and Cr(OH)+2 forms,39 which are adsorbed onto the CS surface by complexation; this is supported by the change in membrane color from yellow to pale green, which is typical for CrIII complexes.40 The presence of Cr+3 can also be substantiated by the peak observed at λmax=580 nm41 in the UV/Vis spectra of the used membrane (Figure 9).

Bottom Line: Structure property elucidation was carried out by X-ray diffraction, microscopy, spectroscopy, contact angle measurement, and water uptake studies.The increase in hydrophilicity followed the order: PSf < PSf/TiO2 < PSf/TiO2/CS membranes.The observations reveal 100 % reduction of Cr(VI) to Cr(III) through electrons and protons donated from OH and NH2 groups of the CS layer; the reduced Cr(III) species are adsorbed onto the CS layer via complexation to give chromium-free water.

View Article: PubMed Central - PubMed

Affiliation: Center for Nano and Material Sciences, Jain University Ramanagaram, Bangalore, 562112, India.

ABSTRACT
Herein we present a new approach for the complete removal of Cr(VI) species, through reduction of Cr(VI) to Cr(III), followed by adsorption of Cr(III). Reduction of chromium from water is an important challenge, as Cr(IV) is one of the most toxic substances emitted from industrial processes. Chitosan (CS) thin films were developed on plain polysulfone (PSf) and PSf/TiO2 membrane substrates by a temperature-induced technique using polyvinyl alcohol as a binder. Structure property elucidation was carried out by X-ray diffraction, microscopy, spectroscopy, contact angle measurement, and water uptake studies. The increase in hydrophilicity followed the order: PSf < PSf/TiO2 < PSf/TiO2/CS membranes. Use of this thin-film composite membrane for chromium removal was investigated with regards to the effects of light and pH. The observations reveal 100 % reduction of Cr(VI) to Cr(III) through electrons and protons donated from OH and NH2 groups of the CS layer; the reduced Cr(III) species are adsorbed onto the CS layer via complexation to give chromium-free water.

No MeSH data available.