A Critical Appraisal of Remediation Techniques for Heavy Metal–Contaminated Soils: Geotechnical and Geoenvironmental Perspectives

The rapid growth of global populations and infrastructure has had a profound impact on the environment, resulting in extensive soil contamination by heavy metals (HMs). Heavy metal contamination (HMC) in soils poses significant risks to human health, ecosystems, and infrastructure stability. Due to the limited availability of uncontaminated land, the use of contaminated soils for construction has become unavoidable. Various remediation techniques exist to improve the soil quality, but their efficacy and suitability in different types of soils need discussion for future planning and adoption. Hence, this review article aims to present a comprehensive review of the geotechnical and geoenvironmental aspects of HMs in soils and corresponding remediation methods. A comprehensive search was conducted using multiple databases following the PRISMA protocol, which resulted in the review of approximately 180 relevant research articles. The findings reveal that the effectiveness of remediation techniques mainly depends on soil properties. For instance, soil flushing and washing are better suited for coarse-grained soils, whereas electrokinetic remediation is more effective in low-permeability, clay-rich soils. Additionally, microbial adaptability to the contaminated soil environment is a key factor in bioremediation. Soil pH is another critical parameter that significantly influences the mobility of HM ions, thereby directly impacting the effectiveness of their removal during remediation processes. Furthermore, the results indicate that HMs alter soil structure, affecting physicochemical properties by reducing the diffuse double layer thickness and promoting particle flocculation. These changes lead to higher permeability and modifications to strength parameters. Further, a regression analysis of liquid and plastic limits is also performed to identify general trends in the impact of HMs on various soil types. Evaluating geotechnical parameters in contaminated and remediated soils is essential before any construction activity, as remediation techniques can significantly alter the engineering behavior of soils. This review provides critical insights to help academicians and professionals not only understand these changes but also make informed decisions regarding site suitability and the reuse of remediated soils under real field conditions. Future research should focus on hybrid, eco-friendly strategies that enhance geotechnical properties and ensure site-specific, sustainable restoration with minimal secondary impacts.