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Torkaman, Pariya

University of British Columbia

Artisanal gold mining significantly contributes to mercury pollution, resulting in severe environmental and health problems, especially for workers and local communities. The annual release of over 2000 tonnes of mercury by artisanal miners is the largest source of artificial mercury pollution. The author offers unconventional and innovative processes for gold leaching to eliminate the use of mercury in artisanal mining activities. A sample from the La Maria deposit, mined by Colombian artisanal miners, was used in all tests to compare the results. Lab tests on the sample with 48.87ppm Au, ground 80% below 0.13mm, showed that amalgamation only extracted less than 20% of the gold, while cyanidation with 1g/L of CN⁻ for 24h recovered 84% of the gold. One alternative process studied was using a liquid (effluent) from a local cassava plant, common in many artisanal mining areas in Latin America, Africa, and Asia. The liquid contains hydrogen cyanide, generated from the hydrolysis of cyanogenic glycosides in the cassava plant. The study tested two varieties of cassava that produce a liquid with 267 and 600 mg/L of free cyanide. The gold content extracted from ore in 24h was 50.9% and 82.4%, respectively. Another method was using Dimethyl sulfoxide (DMSO), a water-free reagent, as a gold-leaching lixiviant, providing over 95% of gold extraction in 24 hours. Additionally, the author studied a modification of the classical Merrill-Crowe process, zinc cementation, which aimed to simplify the gold extraction process by eliminating filtration and vacuum by using bags filled with zinc (or aluminum) in the pulp agitation process. Over 99% of gold was precipitated on the zinc shavings in two hours when the agitation was reduced to avoid aeration. Chloride application was also studied, with results showing 100% gold extraction in 8h at 50°C. All the alternative strategies herein investigated involve knowledge and investment and must be adapted to site-specific conditions. The ideal conditions to eliminate mercury include transforming the polluting processing centers into small, responsible companies. While technology is essential in this process, a broader approach is required to minimize the negative impact of artisanal mining activities on the environment and local communities.

Text

2023-05-04

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/84568

Mining Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/