Electrochemical response and effect evaluation of high belite sulphoaluminate cement combined with red mud-fly ash on solidification of Cu2+-contaminated kaolin

Abstract

In this paper, the solidification of Cu2+-contaminated kaolin by high belite sulphoaluminate cement (HBSC) combined with red mud (RM) and fly ash (FA) was investigated. The effects of solidification/stabilization (S/S) and its electrochemical responses were experimentally explored by mixing RM and FA as the main raw materials with small amounts of low-energy HBSC and quicklime serving as solidifiers of heavy metal contaminated soil. The solidification mechanism of the solidifier on Cu2+ and its solidification effect were then systematically investigated by analyzing the unconfined compressive strength (UCS) of the solidified body, toxic leaching, permeation characteristics, and surfaces morphologies. The study of the electrochemical response of the solidified body during the solidifying and remediation process allowed the development of an evaluation method for repairing the effect of Cu2+-contaminated kaolin based on electrochemical impedance spectroscopy (EIS). The results showed that the strength, impermeability, and leaching toxicity of solid waste co-HBSC solidifying of contaminated soil met industrial requirements. The incorporation of low energy consumption HBSC generated a mass ratio of RM to FA of 8:2 with the best solidification effect. Heavy metals can be absorbed by chemical precipitation, displacement reactions, and encapsulation by hydration gels. In addition, the electrochemical impedance characteristics of the solidified bodies were found consistent with the conventional evaluation of the solidification effect. In sum, HBSC synergistic solid waste solidifier looks very promising for use in the S/S remediation of Cu2+-contaminated soil.

Keywords

• Cu2+-contaminated soil
• Solidifying agent
• Unconfined compressive strength
• Electrochemical impedance spectroscopy
• Life cycle assessment