Decomposition of Cyanide from Gold Leaching Tailingsby Using Sodium Metabisulphite and Hydrogen Peroxide

Abstract

Cyanidation is widely used by most gold mine worldwide and will remain prevail in years (or decades) to come, while cyanide is hazardous, toxic pollutants whose presence in wastewater and tailings can seriously affect human and its environment; hence, it is necessary to control these contaminants. The purpose of this study was to examine the effects through the investigation of changes in pH, concentration, and contact time, and the optimal conditions were obtained. It has been proven that the decomposition of cyanide in solution and tailings increased as the alkalinity in the presence of 0.5 g/L Na2S2O5. An increase in H2O2 (30%) concentration (from 1 to 4 mL/L) increased the decomposition in solution, while the effect on removing cyanide was better when pH was 9 than 8 and 10 in tailings. The cyanide in tailings decreased in the first 4 h and increased after 4 h. The effective and economic conditions for maximum decomposition of cyanide from leach tailings are first treated in 0.5 g/L Na2S2O5 at pH 10 for 3 hours and then 2 mL/L H2O2 (30%) is added to the tailings at pH 9 for 4 hours through comparative study. The findings provide the basis to optimize the decomposition of cyanide from gold leaching tailings in mining or backfilling by using the synergetic effect of Na2S2O5 and H2O2.

Impacts of cyanide in gold mining and cyanide removal methodologies in liquid waste from gold processing

“…The reaction of formation of this complex, called dicyanoaurate, occurs in the presence of oxygen in an aqueous solution, as described in the equation below. This process requires excess cyanide dosage to increase gold recovery (Ciminelli and Gomes, 2002;Hou et al, 2020).…”

“…A currently applied variation of the Inco Process is the use of sodium metabisulfite (Na 2 S 2 O 5 ), which provides the sulfur dioxide necessary for cyanide oxidation to occur (Botz, 2001;Hou et al, 2020).…”

Photocatalytic Gold Recovery from Industrial Gold Plating Effluent by ZnO Nanoparticles: Optimum Condition and Possible Applications

“…Currently, various methodologies have been implemented to recover gold concurrently with the conversion of cyanide species into a more stable form. These techniques include chemical oxidation, solvent extraction, , and adsorption. − Another promising process that offers the dual benefits of gold recovery and mitigation of cyanide toxicity is the photocatalytic process . This process is distinguished by its straightforward operation, cost-effectiveness, wide applicability, and environmental friendliness. − The photocatalytic process involves a multistep chemical reaction facilitated by the presence of appropriately irradiated light.…”

Application of Response Surface Methodology (RSM) for Simultaneous Optimization of Kinetic Parameters Affecting Gold Leaching in Thiosulfate Based Media: A Statistical Approach

“…For more than a century, cyanide solution has been predominantly used as the lixiviant agent to extract gold from its ores [3]. However, the use of cyanide is associated with an environmental impact ascribed to its virulent and lethal e ects on humans, terrestrial animals, and aquatic organisms [4,5]. Moreover, gold complexation with cyanide is characterized by slow reaction kinetics and consumes large quantities of reagents in the presence of refractory sul dic and carbonaceous ores as well as copper-rich gold ores; leading to an increase in the leaching process cost thereof [6].…”