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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.


Representation of the formation of intermolecular hydrogen bonding networks between CS chains after treatment with NaOH and water.
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fig02: Representation of the formation of intermolecular hydrogen bonding networks between CS chains after treatment with NaOH and water.

Mentions: The chemical composition was confirmed by ATR-IR spectroscopy. The spectra showed characteristic CS peaks at 1013 cm−1 (C−N stretch), 1584 cm−1 (N−H bending), and 3400–3800 cm−1 (O−H stretching). Bands at 1150 cm−1 (−SO2 stretch), 1242 cm−1 (C−O−C linkage), and 2967 cm−1 (aliphatic C−H stretch) denote the presence of PSf. The two traces in Figure 1 show similar spectral banding patterns except for the O−H stretching region. Figure 1 a depicts sharp O−H peaks due to intramolecular hydrogen bonding between the OH and NH2 groups of CS, whereas Figure 1 b shows a broad peak for O−H stretching due to intermolecular hydrogen bonding.26 Washing the membrane with a sodium hydroxide solution removes the trapped acetic acid, causing intermolecular hydrogen bonding between the active hydroxy and amino groups of CS and the hydroxy groups of PVA (Figure 2), leading to the stability of the membranes. Therefore, membranes washed with NaOH are more stable than unwashed membranes.


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)

Representation of the formation of intermolecular hydrogen bonding networks between CS chains after treatment with NaOH and water.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig02: Representation of the formation of intermolecular hydrogen bonding networks between CS chains after treatment with NaOH and water.
Mentions: The chemical composition was confirmed by ATR-IR spectroscopy. The spectra showed characteristic CS peaks at 1013 cm−1 (C−N stretch), 1584 cm−1 (N−H bending), and 3400–3800 cm−1 (O−H stretching). Bands at 1150 cm−1 (−SO2 stretch), 1242 cm−1 (C−O−C linkage), and 2967 cm−1 (aliphatic C−H stretch) denote the presence of PSf. The two traces in Figure 1 show similar spectral banding patterns except for the O−H stretching region. Figure 1 a depicts sharp O−H peaks due to intramolecular hydrogen bonding between the OH and NH2 groups of CS, whereas Figure 1 b shows a broad peak for O−H stretching due to intermolecular hydrogen bonding.26 Washing the membrane with a sodium hydroxide solution removes the trapped acetic acid, causing intermolecular hydrogen bonding between the active hydroxy and amino groups of CS and the hydroxy groups of PVA (Figure 2), leading to the stability of the membranes. Therefore, membranes washed with NaOH are more stable than unwashed membranes.

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.