African Oxygen, part of The Linde Group, is using ozone for the cyanide destruction process at gold mines. Ozone is generated on site, by using ozone generators and using oxygen. The ozone was injected using a specially developed contacting system to ensure that optimal reaction efficiency took place before the water was pumped into the tailings dam. Cyanide oxidation occurs quickly, with free ?cyanide being reduced by more than 85%. The ozone consumption during the trial was about 2 g of ozone for every gram of cyanide.
The need for cyanide destruction has ?increased over the years due to the growing demand for sustainable solutions to neutralize destructive cyanide in tailings dams as more mining companies voluntarily subscribe to the United Nation’s International Cyanide Management Code (ICMC). The fundamental aim of the code is to manage the use of cyanide throughout the gold beneficiation process, which limits the release of solutions containing cyanide into the environment from spillages and tailings disposal. Although compliance with the code is voluntary, it has been implemented by the world’s major gold producers.
The advantages of using the ozone-based process for cyanide destruction should, however, be a huge driver for mines when considering a cyanide destruction process. ?The advantages associated with using this system include the fact that no adjustment to the tailings stream is required when installing ozone equipment and the reaction is rapid, complete, irreversible and by-product free.