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

Abstract

BACKGROUND This work studied the treatment of and metal recovery from a synthetic acid mine drainage (AMD) containing 500 mg L−1 copper (Cu2+) and iron (Fe+3), and 50 mg L−1 nickel (Ni2+) and tin (Sn2+) 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 Fe3+ was reduced to Fe2+ in about 24 h and Cu2+ was electrodeposited onto the cathodic surface, a Cu electrode, obtaining pure Cu0. 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 Fe2+, Ni2+ and Sn2+ 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 Cu0 while generating electricity at the same time using a BES. The cell voltage required for the metal electrodeposition of Fe2+, Ni2+ and Sn2+ 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

Modelling of a bioelectrochemical system for metal‐polluted wastewater treatment and sequential metal recovery

“…The present subsection summarizes the description of the benchscale BES experimental device, the operating mode, and the working conditions used by León -Fernandez et al 18 to obtain the experimental data that will be used as a starting point for mathematical modelling.…”

“…To ensure anaerobic conditions, both reservoirs were purged with nitrogen gas at the beginning of each batch cycle. Additional details about the experimental procedure are as follows: sampling, along with chemical and electrochemical analyses, are available in León-Fernández et al 18 The experimental data obtained were discussed in that work, and they are plotted in the present work (Figs 2, 4, and 5) together with the results of the model fittings.…”

“…Figure 1 shows a conceptual description of the BES for the sequential recovery of metals according to the results reported by León-Fernández et al 18 This work showed that only biological mechanisms were considered for acetate utilization in the anode chamber. The Faradaic efficiencies attained at the anode (less than 20%) showed that only a fraction of the organic substrate was oxidized via exoelectrogenic mechanisms, and the rest of the substrate could be used by different mechanisms, such as methanogenesis or denitrification.…”

“…12 The present work uses data sets from a previously published work by the same authors. 18 In that work, the sequential cathodic removal of four metals (Cu 2+ , Fe 3+ , Ni 2+ , and Sn 2+ ) from simulated metal-polluted industrial wastewater was studied by using a BES, first working as an MFC and then as an MEC. They found that, operating as an MFC, all the Fe 3+ was reduced to Fe 2+ in approximately 24 h, and then, almost all the Cu 2+ was deposited as Cu 0 on the cathodic surface after 4 days.…”

“…The second stage was the BES operating as an MEC, which allowed the simultaneous removal of the Fe 2+ , Ni 2+ , and Sn 2+ remaining in solution by fixing the cathode potential. The present work begins with the experimental results reported by León-Fernández et al 18 In this context, the aim of the present work is to develop a simplified mathematical model able to describe the performance of a BES for the sequential recovery of dissolved metals contained in simulated industrial wastewater (Fe, Cu, Sn, and Ni), first working as an MFC and then as an MEC, and to simulate its performance under different operating conditions. The main novelty points of the present work are as follows.…”