Study on ultrasonic enhanced ozone oxidation of cyanide-containing wastewater

Gold smelting wastewater contains cyanide ions and copper ions, which may cause potential risks to the environment. In this study, a new ultrasonic enhanced ozone (US/O3) oxidation method was developed for the comprehensive treatment of cyanide-containing wastewater, destruction of cyanide and further recovery of copper. The cyanide removal rate and copper recovery rate reached 99.96 % and 99.3 % under the optimum conditions of ozone flow rate of 80 L/h, temperature of 25 °C, reaction time of 15 min and ultrasonic power density of 80 W/L, respectively. The dried sediment was characterized by XRD, SEM and particle size analysis, the results showed that the dry sediment was Cu slag. The experimental results were in accordance with the pseudofirst-order kinetic model with apparent rate constants of 0.1662 L/(mg·min) and 0.2056 L/(mg·min) for ozone oxidation and ultrasonic enhanced ozone (US/O3) oxidation, respectively. The mechanism of ultrasonic enhanced ozone was studied by FT-Raman, FT-IR, EPR and Gas chromatography. Ultrasonic enhanced ozone (US/O3) oxidation process for treatment of cyanide containing wastewater is characterized by rapid and complete decomposition of cyanide in wastewater and efficient recovery of valuable element copper.