In-situ enrichment and removal of Cu(II) and Cd(II) from low-strength wastewater by a novel microbial metals enrichment and recovery cell (MMERC)

Removal of Copper (Cu) and Cadmium (Cd) at low concentrations is attracting more attention due to the cumulative toxicity and difficulty in the removal process. In this study, a novel microbial metals enrichment and recovery cell (MMERC) is proposed for efficient and cost-effective recovery of Cu(11) and Cd(II) at low concentrations. The superiority of the proposed system is that the metal ions are in-situ separated from wastewater and enriched in the cathodic chamber driven by self-generated electricity, as well as recovered simultaneously taking advantage of the produced caustic. In the operation, Cu(II) and Cd(II) in the contaminated wastewater decrease from initial concentrations of 5 mg L-1 to less than 0.2 mg L-1, and these separated metals are highly enriched in the catholyte and removed simultaneously with 99.0% for Cu(II) and 96.5% for Cd(II). The system shows great separation and enrichment performance with increased metals concentrations to 20 mg L-1. A 20cycle operation demonstrates long-term stability, as the removals remained above 95%, and the deposited hydroxides have no significant effects on the cathode. The energy balance analysis further demonstrates the great promise of the MMERC system in energy-efficient treatment of metal contaminated wastewater.