Characterization of red mud and fly ash based for co-curing of Cu2+-contaminated soil

Abstract

Currently, solid waste accumulates significantly, including red mud (RM) and fly ash (FA). Meanwhile, traditional cement-based curing agents pose challenges due to their high energy consumption and substantial pollution during the remediation of heavy metal-contaminated soil. In light of the need for resource utilization of solid waste and demands for energy conservation and emission reduction, this study investigates the stabilization/solidification of Cu2+-contaminated loess using a novel curing agent. This agent comprises low-energy, environmentally friendly high-belite sulfoaluminate cement (HBSAC) and quicklime (CaO) mixed with RM and FA. The study evaluates the samples across various metrics, including mechanical properties, permeability, pH, conductivity, leached ion concentration, and microstructure, to systematically investigate the curing effect and mechanism of the new curing agent on contaminated soil. It conducts an assessment related to the economics and carbon emissions of the solidified body. The results show that the optimal ratio for the curing agent consists of RM and FA, CaO, and HBSAC at 20%, 5%, and 7%, respectively, with a water-to-solid ratio of 0.38 and a mass ratio of RM to FA at 13:2. This new curing agent not only possesses superior properties but also offers excellent economic benefits and reduces carbon emissions. It holds significant potential for applications in the remediation of Cu2+-contaminated soils.