For years, cyanide heap leaching is the traditional method adopted to recover metal ores. This low-cost practice helped gold mines to extract gold deposits profitably. Cyanide is adopted in 90% of gold extracted worldwide. Of the 1.1 million tons of hydrogen cyanide (HCN) produced annually, only 6% is converted into sodium cyanide for use in the mining industry.
Because this chemical compound has, on occasions, caused environmental problems through mishandling or spills, mines have increasingly come under stricter regulations by governments and condemnation by environmental groups.
Cyanide is highly toxic and can result in substantial environmental impacts and public health risks if released into the environment. Cyanide spills have resulted in major fish kills, contaminated drinking water supplies and harmed agricultural lands.
In 2000, a tailings dam ruptured at a mine operated by Aural S.A. in Romania, spilt 3.5 million cubic metres of cyanide-contaminated waste into the Tisz and Danube Rivers killing fish and poisoning water supplies as far as 400 kilometres down the river in Hungary and Yugoslavia. In 2014, 500,000 gallons of cyanide solution used in heap-leach gold mining spilled from a retaining pond at the Proyecto Magistral mine in Mexico after heavy rain.
Industry claims cyanide is relatively safe because even if it spills, it breaks down rapidly in surface water. But, the compounds that cyanide breaks down into can be harmful. Cyanide spills into ground water can persist for long periods of time and can contaminate drinking water aquifers.
With so much inherent danger of using cyanide in gold mining, isn’t it time for the industry to search for sustainable alternatives?
Clean Mining, part of the Clean Earth Technologies Group, is one of the first companies in the world to develop an effective and commercially viable solution to get rid of toxic chemicals in gold ore processing. Mining companies can also do away with tailings by using a de-watering process in conjunction with Clean Earth Technologies’ solutions to generate dry tailings.