Advancements in Anode Slime Treatment: Effects of pH, Temperature, and Concentration of ClO−/OH− on Selenium Dissolution from Decopperized Anode Slimes

Selenium has been classified as a strategic element as it is required for the technology and energy industry. It is not found in abundance in the Earth’s crust, which is why about 90% of selenium is obtained from the treatment of anode slimes, which are a by-product of copper mining. In recent years, several hydrometallurgical treatments have been investigated; as a result, this article presents an alternative proposal using an alkaline-oxidizing medium (ClO−/OH−). The Taguchi method was used to design an experiment to evaluate the changes in the conditions and interactions found in previous studies with regard to the ClO− concentration, temperature, and pH. The best combination of conditions was a ClO− concentration between 0.53 and 0.68 M, pH between 11.0 and 11.5, and temperature of 55 °C, with which selenium dissolution values between 91.8 and 94.2% were achieved. According to the SEM/EDS analysis, it is evident that an increase in temperature allowed an increase in the selenium reaction, and the selenium was not trapped in the AgCl layer formed by the same selenium dissolution reaction; the slowness of the selenium dissolution mainly depends on the low availability of sodium hypochlorite over time.