title: Selective reduction of Cr(VI) in chromium, copper and arsenic (CCA) mixed waste streams using UV/TiO2 photocatalysis.
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.
authors: Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA.
authors: Shan
authors: S
authors: Zheng
authors: Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA. wjian001@fiu.edu.
authors: Wenjun
authors: W
authors: Jiang
authors: Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA. mrash008@fiu.edu.
authors: Mamun
authors: M
authors: Rashid
authors: Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA. cai@fiu.edu.
authors: Yong
authors: Y
authors: Cai
authors: Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH 45221-0012, USA. dionysios.d.dionysiou@uc.edu.
authors: Dionysios D
authors: DD
authors: Dionysiou
authors: Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA. osheak@fiu.edu.
authors: Kevin E
authors: KE
authors: O'Shea
mesh_terms: D001149:Arsenates / Q000737:chemistry*; D001151:Arsenic / Q000737:chemistry; D002384:Catalysis; D002857:Chromium / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D004785:Environmental Pollutants / Q000737:chemistry*; D052918:Environmental Restoration and Remediation; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays; D014866:Waste Products
chemical_list: D001149:Arsenates; D004785:Environmental Pollutants; D014866:Waste Products; D002857:Chromium; C009495:titanium dioxide; C074702:chromium hexavalent ion; C040890:chromated copper arsenate; D003300:Copper; D014025:Titanium; D001151:Arsenic
references: Environ Sci Technol. 2014 Jul 15;48(14):8078-85
references: 24901955
references: Waste Manag. 2003;23(6):537-46
references: 12909094
references: Environ Sci Technol. 2007 Aug 1;41(15):5471-7
references: 17822119
references: Water Res. 2011 Mar;45(6):2207-12
references: 21303713
references: J Photochem Photobiol A Chem. 2010 Feb 5;210(1):61-68
references: 20473340
references: Water Res. 2014 Apr 15;53:12-25
references: 24486715
references: J Hazard Mater. 2012 Nov 30;241-242:395-403
references: 23092612
references: Comp Biochem Physiol C. 1989;93(1):121-5
references: 2567222
references: J Hazard Mater. 2009 Sep 30;169(1-3):136-45
references: 19362776
references: Environ Sci Technol. 2006 Feb 1;40(3):988-93
references: 16509347
references: Chemosphere. 2006 Apr;63(2):254-60
references: 16169572
references: Toxicol Sci. 2002 May;67(1):32-7
references: 11961213
references: Bull Environ Contam Toxicol. 1997 Jan;58(1):22-9
references: 8952921
references: J Hazard Mater. 2008 Oct 30;158(2-3):384-91
references: 18375058