Electrochemical Recovery of Iron from Sulfuric Acid Leachates of Coal Ash

Abstract

Coal ash represents a major industrial by-product containing significant amounts of iron, yet its recovery is hindered by the inert aluminosilicate matrix. In this study, a two-step approach was developed for selective extraction and electrochemical recovery of iron. Coal ash was first treated with concentrated sulfuric acid at elevated temperature, producing a leachate enriched in Fe²⁺ ions. The effects of Fe²⁺ concentration (0.1-0.5 mol/L), current density (1250-5000 A/m²), and electrolysis time (1-6 h) on recovery efficiency, current efficiency, and energy consumption were systematically investigated. Under optimal conditions (0.30 mol/L Fe2+, 2500 A/m2, 4 h), iron recovery reached 89% with a current efficiency of 65%, while energy consumption was as low as 1.8 Wh/L. XRD and SEM analyses confirmed that optimized parameters favor the formation of metallic Fe with minor magnetite content. These results demonstrate the feasibility of integrating acid leaching and electrolysis into a practical route for coal ash valorization and selective iron recovery.