Research Enhancing Acidic Mine Wastewater Purification: Innovations in Red Mud–Loess

Abstract

This study investigates the adsorption of cadmium (Cd) by red mud–loess mixed materials and assesses the influence of quartz sand content on permeability. Shear tests are conducted using various pore solutions to analyze shear strength parameters. The research validates solidification methods for cadmium-contaminated soils and utilizes SEM-EDS, FTIR, and XRD analysis to elucidate remediation mechanisms. The findings suggest that the quartz sand content crucially affects the permeability of fine-grained red mud–loess mixtures. The optimal proportion of quartz sand is over 80%, significantly enhancing permeability, reaching a coefficient of 6.7 × 10−4 cm/s. Insufficient quartz sand content of less than 80% fails to meet the barrier permeability standards, leading to a reduced service life of the engineered barrier. Adsorption tests were conducted using various pore solutions, including distilled water, acidic solutions, and solutions containing Cd, to evaluate the adsorption capacity and shear characteristics of the red mud–loess mixture. Additionally, the study examines the behavior of Cd-loaded red mud–loess mixtures in various pore solutions, revealing strain-hardening trends and alterations in cohesiveness and internal friction angle with increasing Cd concentrations. The analysis of cement–red mud–loess-solidified soil demonstrates enhancements in soil structure and strength over time, attributed to the formation of crystalline structures and mineral formations induced by the curing agent. These findings provide valuable insights into the remediation of cadmium-contaminated soils.