Photocatalytic degradation of 2,4,6-tribromophenol on Fe2O3 or FeOOH doped ZnIn2S4 heterostructure: Insight into degradation mechanism

Taking advantage of the powerful photo-oxidation of iron (hydr)oxides and the outstanding reducing power of ZnIn2S4, Fe2O3 or FeOOH doped ZnIn2S4 showed excellent photocatalytic activity in debromination of 2,4,6-tribromophenol (2,4,6-TBP). Though the FeOOH has great adsorption capacity, the Fe2O3-doped ZnIn2S4 was found more active than FeOOH-doped ZnIn2S4 in mineralization of 2,4,6-tribromophenol. The addition of Fe2O3 or FeOOH narrowed the band gap of ZnIn2S4. The degradation followed pseudo-first-order kinetics and the calculated overall photocatalytic degradation constants (K-r) of ZnIn2S4, FeOOH-ZnIn2S4 and Fe2O3-ZnIn2S4 were 0.0499 min(-1), 0.0599 min(-1) and 0.0861 min(-1) under visible light illumination, and 0.35 min(-1), 1.52 min(-1) and 1.59 min(-1) under UV irradiation, respectively. After 2.0 h photocatalytic reaction on Fe2O3-ZnIn2S4 and FeOOH-ZnIn2S4, the released Br- concentration was 26.3 mgl(-1) and 23.8 mgl(-1) corresponding 88% and 80% debromination, which was 1.41 and 1.28 times higher than the debromination by ZnIn2S4, respectively. The tentative photocatalytic degradation pathways on Fe2O3-ZnIn2S4 and FeOOH-ZnIn2S4 were proposed based on the detected intermediates. (C) 2013 Elsevier B.V. All rights reserved.