Enhanced Ligand-Assisted pH Swing Process for Highly Concentrated Mn Recovery and CO2 Storage Using Steelmaking Slag

Abstract

Manganese (Mn), vital for industrial processes such as steelmaking, faces supply concerns due to declining natural reserves. Electric arc furnace (EAF) slag, a steelmaking byproduct rich in Mn and calcium (Ca), offers a sustainable alternative source for Mn while enabling CO2 storage through carbon mineralization. This study explores a ligand-assisted pH-swing process to enhance Mn recovery and CaCO3 precipitation. Chelating agents, such as NTA, EDTA, and DTPA, were employed to modulate metal solubility and selectivity of Mn during precipitation. The influence of ligand binding strength on metal–ligand complexation, competing with hydroxide and carbonate formation, was systematically examined. EDTA showed overall better performance, achieving 91.3 wt % Mn concentration in precipitates and enabling CO2 storage of 138.4 kg of CO2/t slag. These findings highlight the effectiveness of tailored ligand chemistry in optimizing resource recovery from industrial waste, contributing to both the critical metal supply and CO2 mitigation.