Investigating the aerated VUV/PS process simultaneously generating hydroxyl and sulfate radicals for the oxidation of cyanide in aqueous solution and industrial wastewater

The present study was designed to investigate the cyanide oxidation by the aerated VUV/S2O82- (VUV/PS) advanced process. The effect of persulfate concentration, cyanide concentration, aeration and nitrogen gas blowing in the batch experiments and of hydraulic retention time and presence of radical scavengers in the continuous-flow experiments were investigated. It was found that cyanide oxidation in the aerated VUV/PS process followed a pseudo-first order reaction kinetic. Complete destruction of 50 mg/L cyanide was achieved in the aerated VUV/PS batch process in the presence of 200 mg/L persulfate within the reaction time of 10 min. The scavenging tests indicated that both hydroxyl and sulfate radicals were simultaneously generated in the aerated VUV/PS process contributed in the cyanide oxidation. It was also found that the aeration could enhance performance of the process in oxidation of cyanide due to the generation of ozone. The presence of water anions considerably decreased the cyanide removal efficiency in the aerated VUV/PS process and carbonate had the highest interference. Carbonate, ammonium, and nitrate were the main by-products of cyanide oxidation in the aerated VUV/PS process showing that cyanide was completely oxidized to much less noxious compounds. The complete oxidation of 50 mg/L cyanide in the continuous-flow aerated VUV/PS process at a hydraulic retention time of 20 min indicates the potential of its field-scale application. A real industrial wastewater sample containing high concentration of cyanide, Cr(VI) and organic content was also efficiently treated in the aerated VUV/PS process. Therefore, it is concluded that the aerated VUV/PS process is a promising process for complete destruction of cyanide in industrial wastewater.