Cobalt recovery via a waste-derived hybrid electrode material in a flow-through electrosorption system

Abstract

A novel metal‑carbon composite was synthesized by pyrolyzing a mixture of industrial waste (red mud) and biomass (lignin) under a CO2 atmosphere, and is introduced as a new electrode platform for a flow-through electrosorption system targeting cobalt (Co2+) recovery. The composite exhibited superior electrical conductivity and abundant adsorption active sites, attributed to the synergistic interaction between the carbon framework derived from lignin and the metal oxide active sites provided by red mud. This structural synergy significantly enhanced the electrosorption capacity toward cobalt ions when utilized as a cathodic electrode, leading to high recovery efficiency even under low energy operational conditions. Furthermore, electrochemical analyses together with surface characterizations verified that the catalyst exhibited strong interactions with Co2+ species and sustained both high recovery stability and robust electrode surface regeneration throughout repeated electrosorption and electrodesorption cycling. Overall, this study highlights a sustainable recovery approach for high-value metals by integrating an eco-friendly catalyst produced from waste materials with electrochemical purification technology, establishing a key platform for future advances in metal resource circulation and recycling.