Degradation of sodium n-butyl xanthate by vacuum UV-ozone (VUV/O3) in comparison with ozone and VUV photolysis

Sodium n-butyl xanthate (SBX) is widely used as a collector in the flotation of sulfide minerals. Residual SBX and its byproducts in the flotation effluents may cause environmental pollution. The degradation of SBX by a vacuum UV-ozone (VUV/O-3) in comparison with ozone and VUV photolysis was studied. The effects of the pH and ozone dosage were investigated. The SBX was almost completely degraded within 5 min by both the O-3 and VUV/O-3 processes, whereas the removal of COD became less efficient compared to SBX removal. The COD removal and sulfur mineralization ratio in the VUV/O-3 increased by 30.4-41.6% and 16.2-23.3%, respectively, compared to the ozonation. The large ozone dosage enhanced the mineralization of SBX, but resulted in low ozone consumption ratio. However, the ozone consumption ratio increased by 17.3-45.1% while involving VUV irradiation in the ozonation. The concentrations of formed sulfur byproducts (CS2 and SO42-) were measured. The rapid conversion of CS2 to SO42- ions was observed, showing the effective mineralization of sulfur byproducts in the O-3 and VUV/O-3 processes. The enhancements of the SBX mineralization and ozone consumption ratio by involving VUV radiation with ozone were discussed, and the decomposition pathway of SBX was proposed. (C) 2016 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.