The performance of Cu2+ as dissolved cathodic electron-shuttle mediator for Cr6+ reduction in the microbial fuel cell

Abstract

The study investigates the performance of Cu2+ as dissolved cathodic electron-shuttle mediator (dcESM) for simultaneous Cr6+ reduction and electricity generation in a microbial fuel cell (MFC) at pH 2 and 4 conditions. The dcESM behavior of Cu2+ on carbon cloth (CC) catalyzes the reduction of Cr6+ into Cr3+ at pH 2 by undergoing redox reactions. However, at pH 4, a simultaneous reduction of Cu2+ and Cr6+ was observed. Cyclic voltammetry (CV) studies were performed at pH 2 and 4 to probe the dcESM behavior of Cu2+ for Cr6+ reduction on CC electrode. Also, at pH 2, increasing the concentration of Cu2+ from 50 mg L− 1 to 500 mg L− 1 favors the Cr6+ reduction by reducing the reaction time from 108 h to 48 h and improving the current production from 3.94 mA m− 2 to 6.24 mA m− 2, respectively. Nevertheless, at pH 4, the efficacy of Cr6+ reduction and electricity generation from MFC is decreased from 62.91–18.21% and 4.42 mA m− 2 to 1.10 mA m− 2, respectively, by increasing the Cu2+ concentration from 50 mg L− 1 to 500 mg L− 1. Furthermore, the performance of dcESM behavior of Cu2+ was explored on carbon felt (CF) and platinum (Pt) electrodes, and compare the results with CC. In MFC, at pH 2, with an initial concentration of 100 mg L− 1, the reduction of Cr6+ in 60 h is 9.63 mg L− 1 for CC, 0.17 mg L− 1 for CF, and 51.32 mg L− 1 for Pt cathodes. The reduction of Cr6+ (initial concentration of 100 mg L− 1) at pH 4 in 120 h is 44.72 mg L− 1 for CC, 32.13 mg L− 1 for CF, and 70.85 mg L− 1 for Pt cathodes. Maximum power densities of 1659 mW m− 2, 1509 mW/m− 2, and 1284 mW/m− 2 were achieved when CF, CC, and Pt, respectively were employed as cathodes in the MFC.

Enhanced photocatalytic removal of nitric oxide over Ag-decorated ZnSn(OH)6 microcubes

“…The metal decoration is one of the best ways to signi cantly enhance the photocatalytic performance for NO x gas removal through the surface plasmon resonance (SPR) effect [23,24]. Also, Ag is well-known as a good combination with other semiconductors [25] to reduce their bandgap and increase photocatalytic e ciency.…”