Restoration of heavy metal-contaminated soil and water through biosorbents: A review of current understanding and future challenges

Heavy metal pollution in soil and water is a potential threat to human health as it renders food quality substandard. Different biosorbents such as microbial and agricultural biomass have been exploited for heavy metal immobilization in soil and sorptive removal in waters. Biosorption is an effective and sustainable method for heavy metal removal in soil and water, but the inherent challenges are to find cheap, selective, robust, and cost-effective bioadsorbents. Microbial and agricultural biomass and their modified forms such as nanocomposites and carbonaceous materials (viz., biochar, nanobiochar, biocarbon), might be useful for sequestration of heavy metals in soil via adsorption, ion exchange, complexation, precipitation, and enzymatic transformation mechanisms. In this review, potential biosorbents and their metal removal capacity in soil and water are discussed. The microbial adsorbents and modified composites of agricultural biomasses show improved performance, stability, reusability, and effectively immobilize heavy metals from soil and water. In the future, researchers may consider the modified composites, encapsulated biosorbents for soil and water remediation.