Dynamic and microstructural analysis of zeolite-stabilized heavy metal contaminated clayey sand

Abstract

Heavy metal contamination in soil poses significant environmental and geotechnical challenges, requiring effective stabilization to limit contaminant mobility, enhance soil stability, and reduce deformation. This study investigates the dynamic response and microstructural changes in heavy metal-contaminated clayey sand, emphasizing the effects of clay type (kaolin and bentonite) and zeolite stabilization at varying contents (5%, 10%, and 15%). Laboratory tests, including cyclic triaxial, bender element, adsorption, sedimentation, pH measurements, Atterberg limits, and SEM analyses, were performed. Results reveal that contamination significantly reduces liquefaction resistance, with kaolin-based mixtures more susceptible than bentonite-based ones due to differences in plasticity, specific surface area, and swelling capacity. Zeolite stabilization, especially at 10% content, improves resistance by strengthening the soil structure and mitigating pore pressure under cyclic loading. Contamination affects shear modulus and damping ratio differently for kaolin and bentonite mixtures, with zeolite amplifying these impacts at higher contents through enhanced particle dispersion. Heavy metal adsorption increases with bentonite and zeolite addition, with bentonite exhibiting 180% greater lead adsorption than kaolin. Optimal adsorption performance is achieved with 10% zeolite. Microstructural analysis indicates contamination disrupts hydrogen bonding of kaolin, induces flocculation in bentonite, and has minimal effect on the stable structure of zeolite. These findings highlight the importance of clay type, zeolite content, and soil composition in mitigating contamination effects, providing insights into effective soil stabilization strategies.