Kinetic Analysis of Heterogeneous Photocatalysis: Role of Hydroxyl Radicals

Abstract This article provides the current research activities that concentrate on the role of hydroxyl radicals in heterogeneous photocatalysis by transition metal oxides for different nanostructures. We devote most attention to Al-based Fe2O3 nanostructures that have been synthesized using chemical methods. The visible light photocatalytic activity of nanocrystalline pure and Al-based Fe2O3 photocatalysts for degradation of Salicylic acid, 4-Cholorphenol, and Acid orange 7 (Azo dye) is reported. The catalytic activity and selectivity for organic species are remarkably influenced by the size of the different photocatalyst. Utilization of various structures, advanced oxidation processes, heterojunction between Al-based Fe2O3 and TiO2, and application of solar energy for heterogeneous photocatalysis of water impurities were discussed. Extent of complete mineralization of such compounds by measuring COD and TOC was discussed. We conclude this review with personal perspectives on the directions towards which future research on this new class of nanostructured materials for photocatalysis might be directed. Keywords: Hydroxyl radicalsAl-based Fe2O3 Advanced oxidation processesEnvironment ACKNOWLEDGMENTS The authors are very thankful to the Defense Research and Development Organization (DRDO), New Delhi, for the financial support through its project No. "ERIP/ER/0503504/M/01/1007." The authors also thank the UGC-DSA-I, DST-PURSE, and DST-FIST-II programs for financial support.

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