Strategies for reducing the environmental impact of reprocessing mercury-contaminated tailings in the artisanal and small-scale gold mining sector: insights from Tapajos River Basin,Brazil |
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| Authors: | Rodolfo N Sousa Marcello M Veiga Bern Klein Kevin Telmer Aaron J Gunson Ludovic Bernaudat |
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| Institution: | 1. Mining & Petroleum Engineering Department, University of São Paulo, Brazil;2. Research Center for Responsible Mining, University of Sao Paulo, Brazil;3. Institute of Mining Engineering, University of British Columbia, Canada;1. International Institute for Water and Environmental Engineering (2iE), Department of Water and Sanitary Engineering, Laboratory of Water, Decontamination, Ecosystem and Health (LEDES), 01 PO Box 594, 01 Ouagadougou, Burkina Faso;2. Swiss Federal Institute of Aquatic Science and Technology (EAWAG), Department of Water Resources and Drinking Water, Postfach 611, 8600 Dübendorf, Switzerland;3. International Institute for Water and Environmental Engineering (2iE), Department of Civil and Hydraulic Engineering, Laboratory of Water Resources and Hydrology (LEAH), 01 PO Box 594, 01 Ouagadougou, Burkina Faso;1. Department of Mining Engineering, Colorado School of Mines, Golden, CO, United States;2. Facultad de Minas, Universidad Nacional de Colombia, Medellin, Colombia;3. Norman B. Keevil Institute of Mining, University of British Columbia, Vancouver, Abbreviation: |
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| Abstract: | Worldwide, the environmental impacts of artisanal and small-scale gold mining (ASGM) are extensive. Annual losses from mercury, which is used to amalgamate gold, are in the range of 1000 tonnes, and at advanced sites, there is the additional threat of cyanide contamination.Recent developments in The Brazilian Amazon, an area populated by 200,000 small-scale gold miners, have the potential to reduce these impacts considerably. In the locality of Garimpo Ouro Roxo, miners are presently using amalgamation and cyanidation in vat-leaching. Each cycle typically recovers 50% of the gold and lasts 20 days (per tank), consuming around 3300 kg NaCN/month. A new process has been developed and implemented in a pilot plant in this area, involving gravity concentration followed by cyanidation in a ball mill. Concentrate leaching is conducted with a PVC capsule filled with activated carbon inserted in the cyanide solution in the mill. The cycle takes less than 24 h and recovers up to 98% of the gold in the concentrate. The main advantages of wide adoption of this method, apart from a reduced gold recovery cycle and improved recovery, include possible phase out of amalgamation altogether, and marked reductions in cyanide consumption (from current 22,000 kg–980 kg annually). |
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