Effect of Anions and Related Organic Compounds on the Kinetics of Thiocyanate Oxidation in a Solar-induced Oxidative System

Abstract

The effect of anions (hydrocarbonates, chlorides, sulfates) and organic compounds (xanthates) on the kinetics of thiocyanate oxidation in a photoinduced iron-persulfate system was studied using natural sunlight as a radiation source. It was found that the introduction of anions into the solution inhibits the degradation of thiocyanates. Hydrocarbonates have the maximum effect, so at a HCO–3 concentration of 1 mM, the processing time required for the complete destruction of thiocyanates increased from 6 to 15.7 minutes. At high concentrations of bicarbonates (≥5 mM), the oxidation efficiency of thiocyanates does not exceed 52 %. The adding of butyl xanthate into the solution has no significant effect on the photochemical oxidation of thiocyanates. In real water matrices (tap water and circulating water of the tailing dump of a gold mining plant), oxidative processes are significantly slowed down. In tap water, this effect is mainly due to the influence of hydrocarbonates, and in waste water, it is due to the multicomponent nature of the water matrix. The efficiency of wastewater treatment from thiocyanates was 100 %, for COD – 82 %, for dissolved organic carbon – 65 %. No cyanides were found after the treatment