Bioelectrochemical recovery of silver from wastewater with sustainable power generation and its reuse for biofouling mitigation

Abstract

Precious metals recovery and wastewater treatment using the microbial fuel cell (MFC) is an attractive approach for a sustainable environment. Silver recovery from wastewater and its valorization in the form of silver nanoflakes (AgNFs) brings back waste material to production stream and helps in transition from linear to circular economy. In the present study, bioelectrochemical performance of MFC fed with silver laden artificial wastewater (MFC-Ag) was compared with MFC fed with potassium ferricyanide (MFC-FC) and MFC fed with phosphate buffer as catholyte (MFC-blank). High silver removal (83 ± 0.7%) and recovery (67.8 ± 1%) efficiencies were achieved from MFC-Ag after 72 h operation. The maximum power density (3006 mW/m3) and current density (34100 mA/m3) of MFC-Ag were found to be significantly higher than the MFC-FC and MFC-blank. High chemical oxygen demand (COD) removal efficiency of MFC-Ag (82.7 ± 1.5%) compared with MFC-FC (76 ± 2) highlighted the suitability of silver laden wastewater as a cost effective catholyte. The high coulombic efficiency (8.73 ± 0.9%) and low solution resistance (24.38 Ω) for MFC-Ag also indicate the potential of silver laden wastewater for large scale applications. Analytical characterizations of electrochemically recovered silver revealed the pure (99%) and crystalline AgNFs with a mean diameter of 18 ± 1.2 nm on the cathode surface. Furthermore, a significant anti-biofouling activity of recovered AgNFs indicate the valorization of waste by current study with potential applications in several industrial and environmental processes. Our method has diverse potential to scale up the MFC technology for industrial waste management as a closed loop process with minimum facilities and higher sustainability.