Degradation of ethyl xanthate in flotation residues by hydrogen peroxide

The degradation behavior of ethyl xanthate (EX) salt was the most widely used collector in sulfide mineral flotation and emission of flotation tailings with residual EX was harmful to environment. In this work, hydrogen peroxide (H2O2) was investigated by UV-visible spectroscopy (UV/Vis) at different pH values from 3 to 12. For pH value from 5 to 12, EX was oxidized into ethyl per xanthate (EPX) by H2O2. Then EPX was further oxidized into thiosulfate (TS) salt rather than ethyl thiocarbonate (ETC) and this step was the reaction-limited step. Then depending on pH values, TS was degraded into sulphate and carbonate salts (pH > 7) or elemental sulfur (pH < 7). The kinetics data show that the degradation rate of EX increases with increasing the H2O2 concentration and is independent on the pH values. Without H2O2, EX is hydrolyzed to carbon disulfide fast at pH value < 3.0, but the reaction of hydrolysis is undetectable at pH value > 3.0 during test time.