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Molecules 2015, 20(2), 2622-2635; doi:10.3390/molecules20022622

Selective Reduction of Cr(VI) in Chromium, Copper and Arsenic (CCA) Mixed Waste Streams Using UV/TiO2 Photocatalysis

1
Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
2
Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH 45221-0012, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Pierre Pichat
Received: 15 December 2014 / Revised: 8 January 2015 / Accepted: 22 January 2015 / Published: 3 February 2015
(This article belongs to the Special Issue Photocatalysis)
View Full-Text   |   Download PDF [1476 KB, uploaded 3 February 2015]   |  

Abstract

The highly toxic Cr(VI) is a critical component in the Chromated Copper Arsenate (CCA) formulations extensively employed as wood preservatives. Remediation of CCA mixed waste and discarded treated wood products is a significant challenge. We demonstrate that UV/TiO2 photocatalysis effectively reduces Cr(VI) to less toxic Cr(III) in the presence of arsenate, As(V), and copper, Cu(II). The rapid conversion of Cr(VI) to Cr(III) during UV/TiO2 photocatalysis occurs over a range of concentrations, solution pH and at different Cr:As:Cu ratios. The reduction follows pseudo-first order kinetics and increases with decreasing solution pH. Saturation of the reaction solution with argon during UV/TiO2 photocatalysis had no significant effect on the Cr(VI) reduction demonstrating the reduction of Cr(VI) is independent of dissolved oxygen. Reduction of Cu(II) and As(V) does not occur under the photocatalytic conditions employed herein and the presence of these two in the tertiary mixtures had a minimal effect on Cr(VI) reduction. The Cr(VI) reduction was however, significantly enhanced by the addition of formic acid, which can act as a hole scavenger and enhance the reduction processes initiated by the conduction band electron. Our results demonstrate UV/TiO2 photocatalysis effectively reduces Cr(VI) in mixed waste streams under a variety of conditions. View Full-Text
Keywords: TiO2 photocatalysis; CCA; chromium(VI); remediation; reduction TiO2 photocatalysis; CCA; chromium(VI); remediation; reduction
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Zheng, S.; Jiang, W.; Rashid, M.; Cai, Y.; Dionysiou, D.D.; O'Shea, K.E. Selective Reduction of Cr(VI) in Chromium, Copper and Arsenic (CCA) Mixed Waste Streams Using UV/TiO2 Photocatalysis. Molecules 2015, 20, 2622-2635.

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