Performance of Pb(II) reduction on different cathodes of microbial electrolysis cell driven by Cr(VI)-reduced microbial fuel cell

Abstract

A self-driven electrochemical system contains microbial fuel cell and microbial electrolysis cell is developed to reduce Cr(VI) and Pb(II) without external energy input, and the performance of coupling system is in connection with cathode materials, initial concentration of metal ions, and anions. Pb(II) reduction is similar to all materials, while nickel foam electrode shows the optimal Cr(VI) reduction rate (1.72 g m−3 h−1) and achieves the maximum output power (702.86 mW m−2), following by stainless steel mesh electrode (1.47 g m−3 h−1 and 477.84 mW m−2) and carbon cloth electrode (1.32 g m−3 h−1 and 420.65 mW m−2). Besides, Cr(VI) (from 1.69 g m−3 h−1 to 1.73 g m−3 h−1) and Pb(II) (from 4.09 g m−3 h−1 to 4.16 g m−3 h−1) reduction rates for nickel foam electrodes are increased with initial Pb(II) concentration (except 300 mg L−1). The self-driven system using nickel foam electrode and PbCl2 catholyte achieves a 0.402 g m−3 h−1 increase in Cr(VI) reduction rate, a 0.447 g m−3 h−1 increase in Pb(II) reduction rate, a 3.33% increase in Pb-yield, and a 15.85% increase in system efficiency comparing to catholyte with (CH3COO)2Pb. These results confirm that a self-driven system can be used to reduce Cr(VI) and Pb(II) simultaneously, providing a promising approach for exploiting the power generation from microbial fuel cells in-situ.