Studies on Cr (VI) removal by constructed wetland integrated microbial fuel cell: Effect of electrodes

Heavy metal contamination significantly threatens human health and the environment, even at low concentrations. Among these metals, hexavalent chromium (Cr (VI)), primarily originating from mining activities, stands out as a significant concern. The Constructed Wetland-Microbial Fuel Cell (CW-MFC) represents an engineered solution inspired by natural wetlands. This study presents a novel approach to utilizing cementgraphite (CG) electrodes in CW-MFC to reduce Cr (VI). In this study, Cr (VI) spiked synthetic wastewater (25 mg/L to 100 mg/L) was treated using CG-CW-MFC (Cement-Graphite) and G-CW-MFC (Graphite) systems, at a constant hydraulic retention time of 48 hours. The results indicated that both CG-CW-MFC and G-CW-MFC exhibited a removal efficiency of 99% for Cr (VI). COD removal rates for CG-CW-MFC and G-CW-MFC ranged from 89% to 94% and 82.5 -91.35%, respectively. Meanwhile, CG-CW-MFC showed stable voltage generation at 100 mg/L of Cr (VI) (Average voltage 191.45 mV), while G-CW-MFC showed a steep reduction in voltage generation with an average voltage of 1.48 mV. Thus, the study concludes that, in contrast to the G-CW-MFC electrode, the CG electrode can generate voltage under highly hazardous conditions because of the porous structure of CG. The findings of this study highlight the potential of CG electrodes in CW-MFC systems designed to remediate wastewater contaminated with Cr (VI).