Iron-based materials for immobilization of heavy metals in contaminated soils: A critical review

Soil contamination by heavy metals (HMs) has resulted in harmful environmental effects and hazards to human health. In response, there has been significant interest in using iron-based materials for in situ immobilization of soil HMs due to their high adsorption capacity, reactivity, environmental friendliness, cost-effectiveness, and ease of control. This review paper examines recent types of iron-based materials, synthesis methods, and their mechanisms of action in reducing the bioavailability of HMs in soil, including surface adsorption, electrostatic attraction, ion exchange, surface complexation, redox reactions, and co-precipitation. It also discusses the potential for iron-based materials to simultaneously stabilize multiple metals and summarizes the long-term stability of immobilized HMs. Additionally, it explores the effects of pH, temperature, reaction time, coexisting components, organic matter, and dissolved oxygen on the immobilization of HMs by iron-based materials. In conclusion, this paper provides a comprehensive overview of iron-based materials, their synthesis methods, reaction mechanisms, synchronous stabilization of polymetals, influencing factors on immobilized HMs, and their long-term stability in the environment. Finally, it outlines future prospects for the development of soil HMs immobilization using iron-based materials.