A comparative study on the degradation of ethyl xanthate collector by O3, UV254nm, UV185+254nm, O3/UV254nm and O3/UV185+254nm processes

To separate sulfide minerals from ores, xanthates are widely used as flotation collectors in global mining industry. However, nearly half of xanthates dosed into flotation circuits are discharged into flotation effluents. Residual xanthates and byproducts must be removed because of their toxicity to animals and detrimental effects on mineral flotation. In this work, the degradation of ethyl xanthate (EX) collector by O 3 , UV 254nm , UV 185+254nm , O 3 /UV 254nm and O 3 /UV 185+254nm was compared. The TOC and SO 4 2− concentrations were measured to study the mineralization of EX. The generation of CS 2 and H 2 S byproducts was investigated in both aqueous and gaseous phases. The degradation rate and mineralization extent of EX had the order O 3 /UV 185+254nm >O 3 /UV 254nm >UV 185+254nm >UV 254nm >sole O 3 . The EX removal by O 3 /UV 185+254nm reached 99.13 % within 15 min with the half-life of 2.29 min. The higher solution pH promoted the EX degradation for the O 3 /UV 185+254nm and sole O 3 . After 90 min, 1.72 % of total sulfur in EX had emitted into gas for the O 3 /UV 185+254nm , slightly higher than that (0.49 %) for sole O 3 . The solid phase extraction and gas chromatography‒mass spectrometry (SPE/GC–MS) and UV–vis spectroscopic analysis revealed that 13 organic byproducts were generated from EX collector and most of them could be further decomposed by O 3 /UV 185+254nm . Because the O 3 /UV 254nm and UV 185+254nm photolysis were included, the O 3 /UV 185+254nm was the most efficient process in the removal and mineralization of xanthate collectors among five processes.