Effects of Organic and Inorganic Passivators on the Immobilization of Cadmium in Contaminated Soils: A Review

Cadmium (Cd) pollution poses a major threat to all life forms in the environment due to its harmful effects. Cd is very reactive at low concentrations and can easily transfer in the food chain. Immobilization using chemical amendments has garnered much attention in recent times as superior to instead of conventional and physical methods. Use of organic (biochar) and inorganic (zeolite, kaolinite, sepiolite, bentonite, and CaCO3) and chemical fertilizer (SSP, TSP, and DAP) is eco-friendly and cost effective; thus, it is an effective substitute for the remediation of Cd-contaminated environments. These immobilizing agents have the ability to reduce the translocation of Cd from polluted soils to plants and leaching to ground water. These amendments have various Cd immobilization mechanisms such as adsorption, complexation, and precipitation capacities. This review also discusses the sources of Cd and describes its mobility factors in contaminated soil. In addition, further research directions are also highlighted in this review to ensure safe and sustainable use of these immobilizing materials for the remediation of Cd in contaminated soil.