Response Surface Methodological (RSM) Approach for Optimizing Free Cyanide Destruction from Gold Cyanidation Waste in Artisanal and Small-Scale Gold Mining using Sulfur Dioxide and Air Process

Artisanal and small-scale gold mining (ASGM) in Indonesia has transitioned from using mercury to cyanidation, but the treatment of cyanide waste remains unaddressed, posing environmental and health risks. This research aimed to optimize the destruction of free cyanide in gold processing waste using the sulfur dioxide and air processes catalyzed by copper, employing a response surface methodology (RSM). The cyanide waste destruction process was conducted in laboratory-scale aeration system reactors with fixed variables: an initial pH of 9.48±0.065, maintained at pH 8, dissolved oxygen levels of 4.21±0.73 mg/L, and a temperature of 28.82±0.89°C. Independent variables of the process were determined to be an SO₂/CN⁻ weight ratio of 10, a copper (II) catalyst concentration of 50 mg/L, and a processing time of 4 hours. These parameters effectively reduced free cyanide from 200 mg/L to less than 0.5 mg/L, meeting the strict environmental standards set by the Indonesian Government. This method utilizes readily available materials and equipment, aligning with the knowledge level of ASGM operators and supported by local resources. The findings contribute to addressing the environmental and health risks associated with cyanide waste in the ASGM sector in Indonesia.