Harvesting Corrosion Energy for Self-Powered Gravity-Driven Membrane Filtration and Fouling Regulation

Decentralized water treatment requires low-cost technologies that can remove dissolved metal ions while maintaining stable water production without external energy input. Here, we developed a soil-mediated corrosion-current hydrogel filtration system (SCHFs) that integrates a conductive adsorptive hydrogel membrane with a soil-based corrosion-energy-harvesting unit. Natural soil served as the solid electrolyte, while discarded Al and carbon cloth enabled direct harvesting of corrosion energy for conductive-membrane regulation during gravity-driven filtration. In 60-day continuous river water filtration, the SCHFs permeate concentrations of Cu2+ and Mn2+ approaching the detection limit under the tested conditions. In addition, SCHFs also accelerated NH4+-N stabilization and reduced the final permeate concentration to 0.2 mg L–1. Moreover, a thicker but more porous surface cake layer was formed during SCHF operation, limiting pore blockage and reducing the 60-day flux decline. Microbial community analysis further indicated that SCHFs reshaped the membrane biofilm and enriched taxa associated with nitrogen transformation. Soil and electrode analyses suggested that Al released from the sacrificial electrode was partly immobilized as aluminum-containing silicate minerals, suggesting a low secondary environmental risk under controlled Al input. These results suggest that coupling soil-mediated microcurrent in SCHFs regulate interfacial transport and fouling-layer architecture, thereby improving dissolved-metal retention and long-term hydraulic stability.