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Mining wastes bio/weathering, pollution control and monitoring

Final Report Summary - MINPOLLCONTROL (Mining wastes bio/weathering, pollution control and monitoring)

Mining in the State of Minas Gerais (Brazil) is one of the activities with the strongest impact on the environment: heavy metals (Zn, Cd and Pb) and metalloid (As) pollute surface water, sediments and irrigated agricultural soils. This is a major drawback of this economical important activity. This project focused on pollution of zinc mining activities in this Brazilian region. The project started by an advanced training and knowledge transfer program through the organization a Summer-school that was held in Belo Horizonte (MG, Brazil) in September 2010.

The research aspect of the project mainly consisted in describing metallurgical sludge mineralogy and weathering in the surrounding of zinc refinery plants. Sludges, dusts, residues and other wastes originating from non-ferrous metallic industries pose a serious environmental threat, if not disposed properly. Disposal of these wastes is expensive and remediation is a necessary step to be implemented to control the adverse environmental effects if disposal is done improperly. Since the past couple of decades, the world’s high-grade metal reserves have been depleted considerably, but the demand for metals in day-to-day life in this electronic era is growing rapidly. The depletion of the high-grade ores urges the mineral industry to look for alternative resources for metal extraction. Sludges, dusts, and other wastes generated in the metallurgical industries are interesting options as they still contain significant amounts of valuable base and heavy metals, sometimes even precious metals like gold and silver and also rare earth elements, depending on the nature of the mining site and composition of the primary ores used. This study overviews various hydrometallurgical and bio-hydrometallurgical leaching processes for the extraction of metals from these wastes. Different recycling processes and strategies of metals recovery (solvent extraction, electrowinning, (bio)sorption and (microbial) precipitation) from the wastes generated by various ferrous and non-ferrous metallic industries were overviewed. Future prospects of using these metal bearing wastes as secondary resources for metal extraction for commercial beneficiaries were proposed.

Finally a final dissemination meeting synthesised and disseminated the findings of the project by the organisation of an international Workshop - Symposium dedicated to Mining Activities, Refineries, Pollution Control and Remediation Strategies was organized in Pirapora (MG, Brazil) in August 2014.