CONCEPTUAL METHODS FOR RECOVERING METAL RESOURCES FROM PASSIVE TREATMENT SYSTEMS

Recovering mineral resources retained in passive systems for treating acid drainage may be a way for mining companies to achieve sustainability goals. While the development of metallurgical methods for Fe oxide recovery from passive systems is underway, no parallel research effort has apparently been undertaken for the recovery of precious metals, sulfides, or carbonates from sulfate reducing bioreactors (SRBRs), another effective passive treatment technique. The examination of conceptual beneficiation, pyrometallurgical, and hydrometallurgical processes that might be used in resource recovery is a logical first step in this effort. Resource recovery process challenges include dealing with the abundance of organic matter in the SRBR substrate media and the dispersed and probably microscopic character of the metal precipitates. Screening, wet classification, and roasting of the SRBR media appear to be common threads for recovering the four elements considered in the paper: copper, gold, silver, and uranium. As the SRBR technology matures further, research could help close the loop in a process that is now considered to be solely treatment.