Acid mine drainage treatment and sequential metal recovery by means of bioelectrochemical technology

BACKGROUND This work studied the treatment of and metal recovery from a synthetic acid mine drainage (AMD) containing 500 mg L −1 copper (Cu 2+ ) and iron (Fe +3 ), and 50 mg L −1 nickel (Ni 2+ ) and tin (Sn 2+ ) by using a bioelectrochemical system (BES). The presence of electroactive bacteria improved the performance of such reactor configuration, by contrast with systems with abiotic anodes. RESULTS Operating as a microbial fuel cell (MFC), all of the Fe 3+ was reduced to Fe 2+ in about 24 h and Cu 2+ was electrodeposited onto the cathodic surface, a Cu electrode, obtaining pure Cu 0 . Almost all of the Cu in the catholyte was recovered after four days. The maximum current density and power attained in this stage were 0.136 mA cm −2 and 0.0134 mW cm −2 , respectively. Subsequent operation as a microbial electrolysis cell (MEC) allowed simultaneous recovery of the Fe 2+ , Ni 2+ and Sn 2+ by fixing the cathode potential at −0.7 V versus Ag/AgCl. The electrode material in this stage was titanium. The tin was completely deposited onto the cathodic surface after one day of electrolysis. After three days, 77% and 60% of Ni and Fe, respectively, was recovered. CONCLUSION It was possible to recover Cu 0 while generating electricity at the same time using a BES. The cell voltage required for the metal electrodeposition of Fe 2+ , Ni 2+ and Sn 2+ was low in the case of the BES because of the contribution of the electroactive bacteria. Sequential metal deposition is possible by adjusting the operating parameters of the BES reactors. © 2021 Society of Chemical Industry