Heavy metal pollution has been strictly regulated in the last years. However, illegal activities still endanger several areas and their population around the world, creating a problem which cannot be easily prevented. For instance, very high levels of metals such as cadmium, mercury and copper have been detected in rivers close to illegal mining sites. Remediation through the use of sorbents is often proposed due to its simplicity, high efficiency and apparent low cost, even though the processes for sorbent disposal is always a concern. It would be beneficial to use residual materials whose disposal is already planned and/or required, such as sulfide-based mineral residues from mining activities, which need to be safely disposed. These minerals can behave as efficient sorbents of metals, as demonstrated here using a pyrite-based tailing, obtained from a large-scale cyanidation process in the Peruvian Andes. Using copper as a test metal, tailings are used as sorbents in batch and continuous adsorption modes, finding a maximum removal capacity of 0.46 and 0.72 mg Cu / g tailing, respectively. Tailings are found to have faster adsorption kinetics than minerals before processing. In spite of the ability of tailings to remove copper, minerals release metals during the process and, indeed, the adsorption of copper is surpassed by a release of 0.49 mg Pb / g tailing. Thus, our results suggest that tailings can be very efficient in removing metals from water, but a complete view of the process should be considered. Experiments of neutralizing acid mine water with tailings are also explored. It is proposed that, providing that a tailing is proven to be advantageous, this strategy can be applied in case of the need of large amounts of sorbents, or for the treatment of industrial wastewaters of severe toxicity.

Use of sulfide-based tailings from mining processes for effective copper removal from contaminated water

256th National Meeting (2018)

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