Recovery of platinum-group metals using a microbial fuel cell

Abstract

The aim of this study is to develop a recovery system of platinum group metals (PGMs), such as palladium, platinum, and rhodium from wastewaters that contain [PdCl4], [PtCl6] or [RhCl6-n(H2O)6] ions. A built-in electromotive force from a microbial fuel cell (MFC) was utilized for recovering the PGMs from its cathode chamber under the biofilm-coated anode. After 40 hours of reaction, the obtained Pd, Pt and Rh recovery efficiencies from MFC cathodes with an initial concentration of 200 ppm were 99.2%, 99.5%, and 98.7%, respectively. The highest maximum power density of 7.03 W/m2 with a fill factor of 0.638 was achieved at 1000 ppm Pd2+ catholyte concentration under the experimental range. Using an initial catholyte concentration of 500 ppm for comparison, the maximum power density that was achieved was 4.22 W/m2 for [PdCl4], 5.04 W/m2 for [PtCl6], and 2.44 W/m2 for [RhCl6-n (H2O)6], respectively. Finally, the electrical energy generation rate was obtained from discharging curves and remaining concentration data in the order of Pd-MFC (39.2 Wh/kg) > Rh-MFC (35.1 Wh/kg) > Pt-MFC (17.2 Wh/kg). The metals recovered on the electrode surface were found to be pure based on the SEM micrographs and EDS analysis. *Correspondence to: platinum group metal recovery, built-in electromotive force, microbial fuel cell, biofilm-coated anode, electrical energy generation, wastewater treatment