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Treatment of dye wastewater nanofiltration concentrates containing high anion levels by a pH-sensitive nano-sized Fe(III)@silica microgel

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Abstract

Herein, Fe(III) ions showed a pH-sensitive dual function on the surface of an L-cysteine-modified nano-sized silica microgel (Cys-Fe(III)@mSiO2). The total color and COD degradation efficiencies of Cys-Fe(III)@mSiO2 are higher than 95% and 83%, respectively, for high salt level nanofiltration concentrates without other post-treatment methods. In the first stage, Fe(III) ions act as an enhanced Fenton-like degradation catalyst on the surface of Cys-Fe(III)@mSiO2 for the treatment of actual nanofiltration concentrates in dye wastewater under acidic conditions (pH < 5.5). Then, the pH value of the nanofiltration concentrates increases (pH > 7.5) upon the simple addition of Ca(OH)2, and the same Fe(III) ions act as an excellent coagulant component for the nanofiltration concentrates with the aid of the silica microgel in the second stage. Characterization via transmission electron microscopy (TEM), X-ray diffraction (XRD), infrared (FTIR) spectroscopy, and related techniques demonstrates that the Fe(III)/Fe(II) redox cycle in Cys-Fe(III)@mSiO2 is accelerated with the addition of L-cysteine; this increases the Fe(II) concentration and enhances the generation rate of hydroxyl radicals (˙OH). Additionally, the apparent rate constant of Cys-Fe(III)@mSiO2 is almost 5 times higher than that of Fe(III) Fenton-like degradation systems.

Graphical abstract: Treatment of dye wastewater nanofiltration concentrates containing high anion levels by a pH-sensitive nano-sized Fe(iii)@silica microgel

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Publication details

The article was received on 15 Jul 2017, accepted on 25 Oct 2017 and first published on 30 Oct 2017


Article type: Paper
DOI: 10.1039/C7NJ02575K
Citation: New J. Chem., 2017, Advance Article
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    Treatment of dye wastewater nanofiltration concentrates containing high anion levels by a pH-sensitive nano-sized Fe(III)@silica microgel

    C. Zheng, D. Lian, S. Chang, C. Ma, M. Du and X. Sun, New J. Chem., 2017, Advance Article , DOI: 10.1039/C7NJ02575K

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