Phosphorus recovery from wastewater by enhanced microbial electrolysis cell: Cathode modification and circulation operation.

Abstract

Facing the issue of phosphorus (P) resource scarcity, microbial electrolysis cells (MECs) have garnered widespread attention from researchers due to their ability to recover P in the form of struvite without the need for external alkali addition. This study focuses on enhancing P recovery efficiency through modifying stainless steel mesh (SSM) cathodes with nickel-cobalt-tin (Ni-Co-Sn) composite materials and the circulation of catholyte in MECs. Results demonstrated that under optimal electrodeposition parameters (current density: 0.3 A/dm², duration: 1800 s, temperature: 50 °C, and Ni:Co:Sn molar ion ratio of 2:1:0.5), the Ni-Co-Sn-SSM cathode system significantly reduced the charge transfer resistance of the original SSM, achieved a solution pH of 8.85 within 12 h, and exhibited exceptional P recovery efficiency of 87.5 %. In cyclic operation mode with controlled conditions, the P recovery efficiency reached 96.4 % within 8 h and attained near-complete recovery (99.9 %) after 12 h. The Ni-Co-Sn-SSM cathode enhances P recovery by maximizing hydrogen adsorption and desorption, increasing OH^- generation, improving hydrogen evolution catalytic activity, and expanding the specific surface area to boost active sites and catholyte pH. Cathode modification and catholyte circulation significantly enhance P recovery, offering a sustainable solution for efficient P resource recycling.