Hindawi Publishing Corporation International Journal of Photoenergy Volume 2013, Article ID 943256, 7 pages http://dx.doi.org/10.1155/2013/943256 Research Article Photocatalytic Mineralization of Organic Acids over Visible-Light-Driven Au/BiVO 4 Photocatalyst Kanlaya Pingmuang, 1 Natda Wetchakun, 2,3 Wiyong Kangwansupamonkon, 4 Kontad Ounnunkad, 1,5 Burapat Inceesungvorn, 1,5 and Sukon Phanichphant 2 1 Nanoscience Research Laboratory and Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Tailand 2 Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Tailand 3 Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Tailand 4 National Nanotechnology Center, Tailand Science Park, Paholyothin Road, Klong 1, Klong Luang, Phathumthani 12120, Tailand 5 NANOTEC Center of Excellence, Chiang Mai University, Chiang Mai 50200, Tailand Correspondence should be addressed to Sukon Phanichphant; sphanichphant@yahoo.com Received 31 October 2012; Revised 3 May 2013; Accepted 7 May 2013 Academic Editor: Vincenzo Augugliaro Copyright © 2013 Kanlaya Pingmuang et al. Tis 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. Au/BiVO 4 visible-light-driven photocatalysts were synthesized by coprecipitation method in the presence of sodium dodecyl benzene sulfonate (SDBS) as a dispersant. Physical characterization of the obtained materials was carried out by X-ray difraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), UV-Vis difuse refectance spectroscopy (DRS) and Brunauer, and Emmett and Teller (BET) specifc surface area measurement. Photocatalytic performances of the as- prepared Au/BiVO 4 have also been evaluated via mineralizations of oxalic acid and malonic acid under visible light irradiation. XRD and SEM results indicated that Au/BiVO 4 photocatalysts were of almost spherical particles with scheelite-monoclinic phase. Photocatalytic results showed that all Au/BiVO 4 samples exhibited higher oxalic acid mineralization rate than that of pure BiVO 4 , probably due to a decrease of BiVO 4 band gap energy and the presence of surface plasmon absorption upon loading BiVO 4 with Au as evidenced from UV-Vis DRS results. Te nominal Au loading amount of 0.25 mol% provided the highest pseudo-frst-order rate constant of 0.0487 min −1 and 0.0082 min −1 for degradations of oxalic acid (C 2 ) and malonic acid (C 3 ), respectively. By considering structures of the two acids, lower pseudo-frst-order rate constantly obtained in the case of malonic acid degradation was likely due to an increased complexity of the degradation mechanism of the longer chain acid. 1. Introduction In the past few years, interest has been paid to research on water remediation with the application of an ideal “green” technology known as semiconductor photocatalysis. It has been widely accepted that this process successfully combines the principle of heterogeneous catalysis with a utilization of solar energy. By using this photocatalytic process, degrada- tion of a wide range of organic pollutants into harmless car- bon dioxide and water is made possible. Titanium dioxide, a well-known UV-light-active photocatalyst, has demonstrated an outstanding photocatalytic performance on degradation of various organic compounds [1–3]. However, with its wide band gap energy of 3.2 eV, the application of TiO 2 is limited to UV light region which accounts for only 4% of the whole solar energy [4]. Terefore, extensive research has currently been devoted to the development of visible-light-driven catalyst in order to efectively utilize the vast majority of the solar energy [4–6]. Bismuth vanadate (BiVO 4 ) has long been recognized for its ferroelasticity [7] and its application as a nontoxic and bright yellow pigment [8]. It has also been used as a gas sensing semiconductor, solid-state electrolyte, and cathode material in solid oxide fuel cells, and has recently been proved to be an active visible-light-responsive photo- catalyst for water splitting [9] and organic pollutant decom- position [10, 11]. Since BiVO 4 is stable and neutral in water