On average, only 0.00001% of the ore being extracted is refined into gold. The remaining 99.9999% is waste, much of which is highly toxic. Low-quality gold ore is often mixed with sodium cyanide to dissolve gold. Cyanide is a highly poisonous chemical substance that destroys ecosystems if left uncontained.
Mining has been identified as one of the human activities that can have a negative impact on the quality of the environment. As a process that eliminates soil and vegetation and produces burials under waste disposal sites, mining destroys natural ecosystems. The biooxidation of sulfide contained in refractory gold ores improves the release of gold particles from the sulfide matrix, making gold susceptible to dissolution using leaching agents such as cyanide. To develop an efficient bioremediation approach for gold mine waste, a better understanding of bacterial interactions with metals in this environment is required.
Mercury, a liquid metal, is used in artisanal and small-scale gold mining to extract gold from rocks and sediments. This award-winning gold processing technology from Clean Mining, part of Clean Earth Technologies, creates a new benchmark for gold mining companies and operators. The ore collected from gold mines is dissolved using a non-toxic reagent before the gold is recovered from the ore using polymer. As demand for gold remains high, gold mining must be carried out in a way that does not harm the environment.
The gold is first dissolved using cyanide in the extraction stage and then the dissolved gold is recovered from the cyanide solution by cement with zinc or adsorption on activated carbon. Gold mining alters the landscape, the water table, geological stability and surrounding ecosystems because large quantities of ore have to be extracted to obtain small quantities of gold. Heap leaching is used for low-quality minerals and involves the extraction of crushed oxide gold ore stacked on plastic-coated pads with leaching solvents such as acids or cyanide to dissolve the gold that is collected at the bottom of the pad. The high demand for gold and fluctuating gold prices have made it necessary to process lower quality minerals, waste landfill materials and scrap waste.
Another source of environmental pollution from gold mines are chemicals used in gold processing. Although some HM are required for the normal functioning of life processes, high concentrations of these metals, such as those found in today's mining environments, can be toxic to bacteria that are responsible for the biogeochemical cycle of nutrients, which is therefore beneficial to human health. Clear advantages of bioleaching gold compared to traditional physicochemical methods have been described. These characteristics of gold mines cause complex tensions for the bacteria that inhabit these environments and lead to the selection of different resistant bacterial species.
The use of bacteria in gold mining, known as biomining, has received considerable attention due to the potential roles played by these bacteria in recovering gold from gold-containing minerals. Since gold is a precious metal found in small quantities, gold mining operations tend to cover large areas and can therefore cause environmental damage over a geographically wide area.