Cost-effective copper removal by electrosorption powered by microbial fuel cells

Electrochemical and microbial community responses of electrochemically active biofilms to copper ions in bioelectrochemical systems

Heavy metals play an important role in the conductivity of solution, power generation and activity of microorganisms in bioelectrochemical systems (BESs). However, effect of heavy metal on the process of exoelectrogenesis metabolism and extracellular electron transfer of electrochemically active biofilms (EABs) was poorly understood. Herein, we investigated the impact of Cu²⁺ at gradually increasing concentration on the morphological and electrochemical performance and bacterial communities of anodic biofilms in mixed-culture BESs. The voltage output decreased continuously and dropped to zero at 10 mg L^-1, which was attributed to the toxic inhibition that cased anodic biofilm damage and decreased secretion of outer membrane cytochromes. When stopping the introduction of Cu²⁺ to anodic chamber, the maximum voltage production recovered 75.1% of the voltage produced from BES and coulombic efficiency was higher but acetate removal rate was lower than that before Cu²⁺ addition, demonstrating the recovery capability of EABs was higher compared to nonelectroactive bacteria. Moreover, SEM-EDS and XPS suggested that most of Cu²⁺ was adsorbed by the anode electrode and reduced by EABs on anode. Compared to the open-circuit BES, the flow of electrons through a circuit could improve the reduction of copper. Community analysis showed a decrease in Geobacter accompanied by an increase in Stenotrophomonas in response to Cu²⁺ shock in anodic chamber.

Removal of copper from water using a thermally regenerative electrodeposition battery

A thermally regenerative ammonia battery (TRAB) recently developed for electricity generation using waste heat was adapted and used here as a treatment process for solutions containing high concentrations of copper ions. Copper removal reached a maximum of 77% at an initial copper concentration (C_i) of 0.05M, with a maximum power density (P) of 31Wm^-2-electrode area. Lowering the initial copper concentration decreased the percentage of copper removal from 51% (C_i=0.01M, P=13Wm^-2) to 2% (C_i=0.002M, P=2Wm^-2). Although the final solution may require additional treatment, the adapted TRAB process removed much of the copper while producing electrical power that could be used in later treatment stages. These results show that the adapted TRAB can be a promising technology for removing copper ions and producing electricity by using waste heat as a highly available and free source of energy at many industrial sites.