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 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 to 500 mg L− 1 favors the Cr6+ reduction by reducing the reaction time from 108 to 48 h and improving the current production from 3.9 to 6.2 mA m− 2, respectively. Nevertheless, at pH 4, the efficacy of Cr6+ reduction and electricity generation from MFC is decreased from 63 to 18% and 4.4 to 1.1 mA m− 2, respectively, by increasing the Cu2+ concentration from 50 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 9.6 mg L− 1 for CC, 0.2 mg L− 1 for CF, and 51.3 mg L− 1 for Pt cathodes. The reduction of Cr6+ (initial concentration of 100 mg L− 1) at pH 4 in 120 h is 44.7 mg L− 1 for CC, 32.1 mg L− 1 for CF, and 70.9 mg L− 1 for Pt cathodes. Maximum power densities of 1659, 1509, and 1284 mW m− 2 were achieved when CF, CC, and Pt, respectively were employed as cathodes in the MFC.

Improved defluoridation and energy production using dimethyl sulfoxide modified carbon cloth as bioanode in microbial desalination cell

“…5 a), signifying the presence of electric double-layer capacitive characteristics and the non-availability of considerable redox mediators, whereas a single peak was evident in the case of CC DMSO [ 58 ]. The higher area under the CV curve and peak current of CC DMSO could be owing to an increase in the available electroactive sites that enhance the charge transfer capability [ 59 , 60 ]. This implies that coating DMSO onto CC increases the number of available attachment sites for microbes and the electrochemically active surface area, which is an important requisite for a high-performance anode in MDC [ 39 ].…”

Research progress on using biological cathodes in microbial fuel cells for the treatment of wastewater containing heavy metals

“…When both Cu(II) and Cr(VI) were present in the cathode, the pH of the solution had a significant effect on the reduction of the two heavy metals. At pH > 4, Cu(II) and Cr(VI) could be reduced simultaneously, and the reduction efficiency and power density of Cr(VI) decreased from 63 to 18% and from 4.4 to 1.1 mA/m 2 , respectively, with an increase in the concentration of Cu(II) from 50 to 500 mg/L ( Gangadharan and Nambi, 2020 ). As abovementioned, the cathode pH of the MFC increased as the reaction proceeded, and numerous heavy metals produced various types of precipitates following the cathode reduction, which reduced the cathode activity.…”

Cu(II) and Cr(VI) Removal in Tandem with Electricity Generation via Dual-Chamber Microbial Fuel Cells

“…Cu, Cr, and O were the main elements attached to the cathode (Table 1). The electrochemical reduction of Cu(II) and Cr(VI) was the most important process at the cathode [12,32,33]. Zhou et al discovered that Cu(II) was reduced to elemental copper in two steps rather than directly gaining two electrons.…”

“…However, catholyte pH had a significant effect on the reduction of heavy metals when Cu(II) and Cr(VI) were present in the cathode. At pH > 4, Cu(II) and Cr(VI) were reduced simultaneously, and the reduction efficiency of Cr(VI) and power density decreased from 63% to 18% and 4.4 to 1.1 mA/m 2 , respectively, when the Cu(II) concentration increased from 50 to 500 mg/L [12]. After 240 h, the reduction efficiencies as electron acceptors were 67.9% and 75.4%, respectively, with a maximum power density of 970.2 mW/m 2 [13].…”