Comparison of alkyl xanthates degradation in aqueous solution by the O3 and UV/O3 processes: Efficiency, mineralization and ozone utilization

The removal of four alkyl xanthates (ethyl, isopropyl, n-butyl and n-amyl) by the O-3 and UV/O-3 processes was investigated in a semi-batch, bubble column reactor. Each alkyl xanthate was almost completely decomposed within 10 min by both the O-3 and UV/O-3 processes, confirmed by UV-vis spectroscopic analysis. However, the mineralization of xanthates was less effective compared to simple decomposition of xanthate molecules. The removal of COD in 40 min was just 50.9-61.2% by O-3 oxidation of four alkyl xanthates, but the removal increased to 66.2-81.2% by the UV/O-3 process. Additionally, the ozone utilization ratio increased by 15-30% by adding UV radiation in the O-3 process. The sulfur mineralization ratio of CSS- groups of xanthates in 40 min reached approximately 45% and 55% in the O-3 and UV/O-3 processes, respectively, revealing the effective mineralization of sulfur byproducts such as CS2, COS and S2-. The enhancement mechanism of xanthate mineralization and ozone utilization was discussed for the UV/O-3 system. In a weak acid solution, direct oxidation with O-3 was predominant for O-3 process. In contrast, O-3 could be readily decomposed by UV radiation to form reactive radicals in the UV/O-3 process, thus enhancing xanthate mineralization and ozone utilization. Compared to the O-3 process, the UV/O-3 process was more effective in mineralization of xanthates and reduced O-3 consumption. (C) 2015 Elsevier Ltd. All rights reserved.