Efficient degradation of organic dyes by BiAgxOy

A novel, simple and efficient approach for degrading organic dye, based on BiAgxOy (bismuth silver oxide, BSO), is reported for the first time. The oxidative powder BSO was prepared by simple coprecipitation of NaBiO3 center dot 2H(2)O and AgNO3. The technique was evaluated for the decolorization and oxidative decomposition of Rhodamine B (RhB). The results demonstrated that mixing BSO with an aqueous solution of RhB (20 mg/L) resulted in rapid decolorization (pseudo-first-order kinetic constant k = 0.5594 min(-1)) and formation of several small molecular weight products. Significant reduction in TOC (32% TOC removal in 10 min) also occurred via mineralization of RhB to CO2/CO32-. The reaction proceeds at ambient temperature and pressure, and requires no external energy sources or light. An advantage of the technique is that BSO can be used to degrade sequential additions of dye without significant fouling or loss of activity. The characterization of BSO and its corrosion products by XRD, FTIR, TEM, EDX and XPS revealed that Ag species were reduced to metallic silver and NaBiO3 center dot 2H(2)O was transformed into the Bi2O2CO3 during the reaction process. Singlet oxygen (O-1(2)) was identified as the major reactive species generated by BSO for the degradation of RhB and several other dyes. This novel approach could be used as a highly efficient and green technology for organic dye degradation. (C) 2011 Elsevier B.V. All rights reserved.