Chemical treatment of gold tailings for the degradation of sodium cyanide

Abstract

Objective: This study aimed to evaluate the chemical treatment of gold tailings for the degradation of sodium cyanide using sodium hypochlorite, hydrogen peroxide, and pH control. Methods: An experimental investigation was conducted using gold tailings from the Vicus SAC mining operations. Eleven tests were carried out under a 2^3 factorial design with 8 experimental tests and 3 central tests. The variables evaluated were pH, sodium hypochlorite (NaClO), and hydrogen peroxide (Hwith a 95% confidence level and a 5% error margin. The tests were performed with 250 mL samples agitated for 25 minutes. Cyanide degradation was then analyzed using a YSI 9300 photometer. Results: Sodium hypochlorite and pH proved to be the most influential factors in the degradation of sodium cyanide, achieving a maximum degradation of 97,65% under conditions of 0,17 g/L of NaClO, 0,05 g/L of Hand a pH of 10. The interactions between NaClO/pH and Hwere significant, while Halone did not have a significant effect. However, the treated water did not meet international standards, as it registered 0,73 ppm of residual cyanide, exceeding the limits set by the WHO, the EU, and local environmental regulations. Conclusions: Sodium hypochlorite and pH are key factors in the efficient degradation of sodium cyanide in gold tailings. However, adjustments to treatment parameters are necessary to comply with international water quality standards.