Catalytic ozonation of refractory O-isopropyl-N-ethylthionocarbamate collector with coexisted kaolinite in sulfide flotation wastewaters

Abstract

Clay minerals, acting as effective ozonation catalysts, are always coexisted with detrimental flotation reagents in sulfide flotation wastewaters. In this study, the catalytic ozonation of refractory O-isopropyl-N-ethylthionocarbamate (IPETC) collector was investigated with coexisted kaolinite (Kaol). The removal of IPETC, mineralization and the decrease of electrical energy consumption were enhanced by catalytic ozonation with Kaol relative to sole ozonation. The IPETC removal increased at higher initial pH and larger Kaol dosage, suggesting a beneficial role of coexisted Kaol in the IPETC removal in alkaline medium. The hydroxyl radicals (•OH) scavenging experiments confirmed •OHs as the main reactive species responsible for IPETC removal by catalytic ozonation. The Rct characterization revealed the yields of more •OH radicals at larger Kaol dosage. The presence of Kaol reduced equilibrium ozone concentrations in pure water, showing the positive roles of Kaol in the catalytic ozone decomposition and ozone mass transfer. The changes of byproducts adsorbed on Kaol indicated that surface oxidation reactions by active species might also contribute to IPETC removal and its mineralization. The mechanisms of IPETC removal were proposed by catalytic ozonation with Kaol.