Cobalt/peroxymonosulfate and related oxidizing reagents for water treatment.

摘要

This dissertation explores the fundamentals of a novel advanced oxidation technology, the cobalt/peroxymonosulfate (CoII/KHSO5) reagent, for the treatment of persistent and hazardous substances in water. CoII/KHSO5 is based on the chemistry of the Fenton Reagent and proceeds via the generation of sulfate radicals, which similarly to hydroxyl radicals, readily attack and degrade organic and microbial contamination in water. Very few studies have exploited the reactivity of sulfate radicals for environmental applications. Compared to the extensively investigated hydroxyl radicals, sulfate radicals are not fully understood. Following this approach, the coupling of nine transition metals with hydrogen peroxide (H2O 2), potassium peroxymonosulfate (KHSO5) and persulfate (K 2S2O8) was also explored. The objective was again the generation of inorganic radicals and the efficient degradation of organic contaminants in water. The determination of reactive metal-oxidant couples and the identification of the transient species formed by such interactions significantly contribute to the better understanding of oxidation-reduction phenomena and provide new tools for decontamination of specialty wastewater. Additional use of germicidal ultraviolet (UV) radiation led to the development of several other novel systems. All the reagents explored here can be classified in the following three general categories of advanced oxidation processes: (1) M/Ox: Fe(II)/H2O2, Fe(III)/H 2O2, Co(II)/KHSO5, Ag(I)/K2S2 O8; (2) UV/Ox: UV/H2O2, UV/KHSO5, UV/K2S2O8; (3) UV/M/O x: UV/Fe(II)/H2O2, UV/Fe(III)/H2O 2, UV/Co(II)/KHSO5, UV/Ag(I)/K2S2O 8.; Many of these technologies, never tested before, demonstrated several operational advantages against established ones. Those were due to the high oxidizing strength of the sulfate radicals formed, the high photosensitivity of the peroxides used and the pure catalytic activity of cobalt both homogeneously and heterogeneously. This study is also one of the very few dealing with intermediates formed via sulfate radical attack on phenolic compounds. It is also the first that explores the sulfate radical mechanism of oxidation, when sulfate radicals are generated via the CoII/KHSO 5 reagent and provides strong evidence on the interaction of chloride ions with sulfate radicals leading to the formation of free available chlorine in water. It also includes the very first documented heterogeneous activation of peroxymonosulfate using Co3O4. Previous investigations on the metal activation of peroxymonosulfate are limited to homogeneous systems.