JWSS - Journal of Water and Soil Science

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Malehmir Chegini M, Golchin A, Babaakbari M. Heavy metals, Mineral clays, Oxygen-containing functional groups, Adsorption mechanisms, Synergism.. jwss 2026; 30 (2) :177-202
URL: http://jstnar.iut.ac.ir/article-1-4535-en.html

Biochar, a stable, economical, and environmentally friendly carbonaceous material, has garnered significant attention in the development of advanced adsorbents for the immobilization and removal of environmental pollutants from water and soil. This interest stems from its oxygen-containing functional groups, aromatic structure, notable porosity, high specific surface area, and suitable cation exchange capacity. However, the performance limitations of pristine biochar in pollutant removal underscore the necessity for its modification and engineering. In this regard, the production of biochar composites through the combination with minerals and iron-containing compounds has emerged as an effective strategy to enhance structural and chemical properties, as well as surface reactivity. This review paper examines the primary methods for synthesizing biochar composites, including post-pyrolysis modification and direct mixing with mineral phases. Synergistic and direct loading methods are introduced as novel approaches. Furthermore, the influence of biomass type, pyrolysis conditions, modifier type, and synthesis pathway on the final physicochemical characteristics of the composites is analyzed. Additionally, the governing mechanisms underlying the performance of these materials in immobilizing and removing heavy metals are discussed, encompassing adsorption, precipitation, complexation, ligand exchange, redox reactions, electron transfer, electrostatic interactions, and ion exchange. Study results indicate that the synergy between biochar and mineral/iron-bearing phases can significantly enhance the efficiency of immobilizing pollutants, including both anionic and cationic heavy metals. This review emphasizes the importance of targeted design of biochar composites based on a precise understanding of the relationship between synthesis methods and functional properties. Future challenges and prospects concerning the application of biochar-mineral composites in environmental remediation and the promising commercialization of this technology are also addressed.