Treatment of jewelry manufacturing effluent containing cyanide using ozone-based photochemical advanced oxidation processes

Abstract

This article considers Advanced Oxidation Processes involving O-3, O-3/UV, O-3/H2O2/UV, and H2O2/UV to destroy cyanide in jewelry manufacturing wastewaters. All experiments were performed in a semibatch reactor. The results showed that total cyanide can be reduced with different reaction rates, and the decrease of total cyanide can be described by pseudo-first-order kinetics. The reaction was performed under different pH values and H2O2 dosages to find the optimal conditions for the oxidation processes. The ozonation process destroyed total cyanide faster at a pH = 12, whereas ozonation combined with H2O2 and/or UV destroyed cyanide faster at a pH =10. The total cyanide destruction rate in the UV/H2O2 (700 mg/L) treatment was the highest among all studied processes, with removal efficiencies of 99% for CN-, 99% for COD and 99% for TOC.