Deep insight into green remediation and hazard-free disposal of electrolytic manganese residue-based cementitious material

Abstract

This work presents an innovative approach to developing a low-carbon and hazard-free cementitious material (EGC) by activating ground granulated blast-furnace slag (GGBS) with electrolytic manganese residue (EMR), which has an excellent heavy metal solidified capacity. Herein, the multi-step leaching was creatively conducted to investigate the solidified morphology of heavy metals in hazardous EMR. CO2 emission per unit strength factor was calculated to quantitatively analyze the low-carbon degree. The results show that the added hazardous EMR rich in sulfate and the dilution effect caused by the decrease in GGBS lessen the final setting time and fluidity. Low-temperature calcination (200 °C) alters the dissolution rate of ettringite and AFm-like phases by changing the sulfate crystal. Excessive acidic EMR consumes more calcium hydroxide and lowers the pH of the EGC system, resulting in weakened GGBS activity. The formation of jouravskite, thaumasite, and henritermierite are AFm-like hydrated lamellated structures, which provides evidence for the immobilization of Mn2+ in EMR. Vast Mn2+ are embedded in the main interlayer of [Ca2Al(OH)6]+ by substituting Al to form AFm-like phase. The lowest 60d unit compressive strength carbon emission of the EGC system containing 20 % calcinated EMR is 0.78 kg∙MPa−1∙m−3, meaning the substitution barrier is better addressed by adding calcined EMR. This work provides an innovative solution for high value-added and hazard-free utilization for EMR and carbon reduction in the cement industry.