Annually, 1.1 million metric tons of hydrogen cyanide are produced, with approximately 6% used to produce cyanide reagents for gold and silver processing.
Cyanide usage is popular because it easily combines with many metals especially gold. In gold mining, a sodium cyanide solution is generally used to leach gold from ore. There are two types of leaching:
- Heap Leaching. In the open, cyanide solution is sprayed over huge heaps of crushed ore spread atop giant collection pads. The cyanide dissolves the gold from the ore into the solution as it trickles to the heap. The pad collects the now metal-impregnated solution which is stripped of gold and resprayed on the heap until the ore is depleted.
- Vat or tank leaching. The ore is mixed with cyanide solution in large tanks. Although the chances of spills are lower because the leaching process is more controlled, the resulting waste, known as tailings, is stored behind large dams which can and do fail.
Keeping tailing dams safe is the most challenging task in the mining industry. On average, three of the world’s 3,500 tailings dams fail every year. When tailings dams leak or break, the result is substantial environmental impacts and public health risks.
Cyanide is highly toxic and when released into the environment, there are fish kills, contaminated drinking water and harmed agricultural lands. To resolve this dilemma for the gold mining industry, cyanide usage should be stopped.
Technology innovator Clean Mining, part of the Clean Earth Technologies group, is taking the solution one step further by eliminating the need for tailings dams altogether.
Clean Mining’s cyanide and mercury-free gold processing offers a clean, green and cost-effective retreatment option for tailings and an alternative to conventional tailings storage. It uses a benign reagent made from low-cost, plant-based organics that has proven to be as effective and much safer for people and the environment.
Used in conjunction with a de-watering system, the process produces dry tailings that are safer and easier to store. Better still, the reagent itself can be recovered after processing and reused.