Complete separation of Cu(II), Co(II) and Li(I) using self-driven MFCs–MECs with stainless steel mesh cathodes under continuous flow conditions

Abstract

Complete separation of Cu(II), Co(II) and Li(I) each other from aqueous mixtures is one critical step for recycling spent lithium ion batteries, and generally consumes large amount of energy and chemicals. Previous tests have primarily examined fed-batch operated self-driven microbial fuel cells (MFCs)–microbial electrolysis cells (MECs) for Cu(II) and Co(II) recovery. Mixed Cu(0) and Co(0) however, were simultaneously deposited on the MEC cathodes and Co(II) in effluents was much above water quality standard in addition to the lack of considering Li(I) species in actual wastewaters and necessarily optimizing inexpensive stainless steel (SS) as MEC cathodes for system performance. Various mesh size SS was thus explored in self-driven MFCs–MECs with different influent metal concentrations and hydraulic retention times (HRTs) under continuous flow conditions for complete separation of Cu(II), Co(II) and Li(I) each other. Mesh #60 achieved the best and complete separation of Cu(II), Co(II) and Li(I) each other with an influent metal concentration of 10mgL−1 Cu(II), 10mgL−1 Co(II) and 3mgL−1 Li(I) at an HRT of 9h. These results demonstrate mesh size of SS as MEC cathodes, HRT and influent metal concentration were critical for complete separation of Cu(II), Co(II) and Li(I) each other in self-driven MFCs–MECs under continuous flow conditions.