Self-sustained recovery of silver with stainless-steel based Cobalt/Molybdenum/Manganese polycrystalline catalytic electrode in bio-electroreduction microbial fuel cell (BEMFC).

In this study, a novel bio-electroreduction microbial fuel cell (BEMFC) assisted by stainless-steel based Cobalt/Molybdenum/Manganese (Co/Mo/Mn-SS) polycrystalline catalytic electrode was used to achieve high recovery to silver. The exoelectrogens (Shewanella sp. etc.) using organic wastewater (the inflow was controlled at 1.2 L d) as nutrient matrix in the anode chamber generated electrons, while silver ions were simultaneously electroreduced and electrodeposited on the surface of the catalytic electrode as electron acceptors. Silver nanoplates could be observed directly. The products of electroreduction on the cathode were analyzed by Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffractometer (XRD), and the results of electrochemical characterization confirmed the existence of silver in the products. In the operation, the silver ions were in-situ recovered and enriched from the initial concentration of 20-300 mg L to almost complete recovery (8-18 h), with the maximum power density of 1008.2 mW m and 5.5 A m current density. The recovery efficiency of silver in the BEMFC using the Co/Mo/Mn-SS electrode was up to 9.60 kg mh, and the energy efficiency was 27.8 kg kWh. Under the continuous flow operation mode, the BEMFC still achieved 90.2% recovery efficiency of the silver.