Improving efficiency and circularity of selective metals recovery from acid mine drainage

The mining sector in Europe is considered one of the main pillars of the economy. However, the mining activities generate a large volume of acid mine drainage containing dissolved metals, some of them with economic impact. In addition, the increasing global water scarcity makes it imperative to evaluate industrial wastewater as an alternative source for water reclamation. A treatment system based on reverse osmosis for metals concentration and water reclamation, followed by chemical precipitation for selective metals recovery, and electrodialysis with bipolar membranes for NaOH recovery and reuse is suggested in this work. The main objective is to improve the efficiency and circularity of precipitation processes by overcoming some of its main limitations, namely metal ions concentration and reagent consumption. The treatment system yielded promising results as 97 % of the water was recovered as reclaimed water, targeted metals (Al, Zn, Cu, Mn, Mg, and Ca) were selectively recovered at rates greater than 60 %, and up to 58 % of NaOH was recovered, potentially reusable in the precipitation process.