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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.


Water uptake of a) CS, b) PSf/TiO2/CS, c) PSf/CS, d) PSf/TiO2, and e) PSf membranes at various pH levels; error bars represent the SD.
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fig07: Water uptake of a) CS, b) PSf/TiO2/CS, c) PSf/CS, d) PSf/TiO2, and e) PSf membranes at various pH levels; error bars represent the SD.

Mentions: To study water uptake, prepared PSf/TiO2/CS and PSf/CS membranes were dipped into water for 24 h at pH 4, 7, and 9. Figure 7 clearly indicates CS to have the highest affinity for water, with the PSf showing the lowest. Furthermore, the water uptake capacity decreases with increased pH. The CS membrane shows a higher absorption of water at acidic pH due to protonation of the amino groups present in the backbone of CS; this leads to chain relaxation, resulting in efficient solvent diffusion, and this phenomenon is not observed at basic or neutral pH. Incorporation of TiO2 NPs further increases the hydrophilicity of the membrane. This is evident in Figure 7, in that PSf/TiO2 and PSf/TiO2/CS membranes have a greater capacity for water absorption than PSf and PSf/CS membranes, respectively. This results from the addition of TiO2 NPs to the PSf polymer solution; owing to the high affinity of TiO2 for water, it attracts more water during the diffusion process, and hence more water penetrates, creating larger and more numerous pores in the PSf membrane. The membrane can now absorb more water due to the increased number of pores, thus increasing its water uptake capacity.


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)

Water uptake of a) CS, b) PSf/TiO2/CS, c) PSf/CS, d) PSf/TiO2, and e) PSf membranes at various pH levels; error bars represent the SD.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig07: Water uptake of a) CS, b) PSf/TiO2/CS, c) PSf/CS, d) PSf/TiO2, and e) PSf membranes at various pH levels; error bars represent the SD.
Mentions: To study water uptake, prepared PSf/TiO2/CS and PSf/CS membranes were dipped into water for 24 h at pH 4, 7, and 9. Figure 7 clearly indicates CS to have the highest affinity for water, with the PSf showing the lowest. Furthermore, the water uptake capacity decreases with increased pH. The CS membrane shows a higher absorption of water at acidic pH due to protonation of the amino groups present in the backbone of CS; this leads to chain relaxation, resulting in efficient solvent diffusion, and this phenomenon is not observed at basic or neutral pH. Incorporation of TiO2 NPs further increases the hydrophilicity of the membrane. This is evident in Figure 7, in that PSf/TiO2 and PSf/TiO2/CS membranes have a greater capacity for water absorption than PSf and PSf/CS membranes, respectively. This results from the addition of TiO2 NPs to the PSf polymer solution; owing to the high affinity of TiO2 for water, it attracts more water during the diffusion process, and hence more water penetrates, creating larger and more numerous pores in the PSf membrane. The membrane can now absorb more water due to the increased number of pores, thus increasing its water uptake capacity.

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.