Chapter 6. Catalytic oxidation of organic pollutants in aqueous solution using sulfate radicals

Abstract

Advanced oxidation processes (AOPs) have significantly contributed to destruction of a wide variety of pollutants in air, soil and water, by applying reactive radicals to attack the bonds of C–C, C–H, C–N, C–S, or C–P in organic contaminants. Hydroxyl radicals are the most popular species, which are readily available in many AOPs, especially in the Fenton reaction. As a promising alternative, sulfate radicals were discovered over half a century ago, and have been demonstrated to be flexible to a wide pH range with a higher redox potential, and be almost non-selective to all organics, compared to hydroxyl radicals. This chapter provides a comprehensive survey in the discovery, activation and generation, and evolution of sulfate radicals from both persulfate (PS) and peroxymonosulfate (PMS). Particular interests are focused on the catalysts in homogeneous and heterogeneous oxidation processes, along with a basic introduction to photo and heat generations. It is expected that this chapter can provide a historical view in the development of AOPs using sulfate radicals. The chemistry of PS and PMS is introduced. The detailed developments of activation approaches are presented and the associated applications in decomposition of various organic pollutants are summarized. Research advances in heterogeneous catalysis with PMS activation might be able to inspire and encourage readers to further pave the avenue to wide applications of sulfate radicals. At the end of this chapter, some key issues that require further research endeavour are highlighted.