Development of the optimal wastewater treatment technologies refining of precious metals

The most widespread method in gold production is cyanide leaching of ore concentrates. Most of gold ore deposits in the Russian Federation are located in the Far North and Far East with their climate zone characterized by a positive water balance. In this regard, there arises a need to solve the problem of wastewater treatment. The process of cyanide removal is well known and proven in an industrial scale. The presence of nonferrous metal sulfides and iron in ore concentrates leads to an increased consumption of cyanides caused by thiocyanate production. As a result, gold mining companies have to solve the problem of neutralization of discharged water both in terms of cyanide and thiocyanates. The problem is currently particularly burning at Russia’s operations as requirements for cyanide and thiocyanate contents in treated effl uents are virtually commensurate. This present paper summarizes the results of research in the field of treatment of wastewater containing, along with cyanides, a signifi cant amount of thiocyanates. Our studies have shown high effi ciency of the process of wastewater oxidation by ozone. It has been shown that the ozone oxidation process runs at high rate and is accompanied by cyanide regeneration. This saves more than fifty percent on the cost of ozone production, the latter being a major economic limiting factor for the application of this technology. The ozonation technology ensures the absence of secondary contamination by reagents and treated effl uent intermediates. The developed method provides the compliance with the legislation requirements on the content of cyanides and thiocyanates in wastewater. Lower cost of the process resulted from the lack of reagents, and hence, cost of their purchase and delivery to gold mining operations, and a potential for cyanide regeneration make a proposed method very attractive.