Leaching gold with cassava: An option to eliminate mercury use in artisanal gold mining

Mercury pollution from artisanal gold mining causes severe environmental and health problems, especially to operators and people living around the processing facilities. Over 2000 tonnes/a of mercury is released to the environment by the artisanal miners which is the largest man-made source of mercury pollution. Here we present a novel method using a local plant, cassava, common in many artisanal mining areas in Latin America, Africa, and Asia, to dissolve gold from ores. In our experiments, we used a liquid by-product of cassava flour manufacturing, “manipueira” to leach gold from the gold ore. It contains hydrogen cyanide, generating from the hydrolysis of cyanogenic glycosides in the cassava plant. The results were very promising to replace the use of mercury, as approximately 50% of the gold content was extracted from the ore in 24 h.