Evaluation of acid mine drainage (AMD) from tailings and their valorization by copper recovery

Abstract

Recent investigations have found that the mining industry generates approximately 10 billion tons of tailings per year, tending towards doubling this amount by 2035. For this reason, a systematic method is needed to study acid mine drainage (AMD) potential, as well as determining the dissolution of potentially toxic elements (PTEs). Furthermore, the possible recovery of base or precious metals could transform the tailings into value-added materials. In the present investigation, the potential for the generation of acid mine drainage in a sample of mine tailings was evaluated, as well as an analysis of the dissolution of PTEs through a sequential extraction of appropriate chemical solutions with increasing strength of reactivity to identify base or precious metals that can be recovered through a metallurgical process consisting of leaching, solvent extraction and electrolysis, operating at moderate pressure and temperature. The results of this research showed that these tailings contain approximately 3.7% of pyrite occluded in silicates and therefore are not a high risk for generating acid drainage and PTEs dissolution. On the other hand, a process for obtaining metallic copper was proposed, which resulted in a leaching liquor with 1226 ppm using 0.21 M H2SO4 and a pulp density of 300 g/L. Solvent extraction in a single stage allowed the leach liquor to be concentrated at 9200 mg Cu/L, recovering the majority of the copper in metallic form by electrolysis.