Review of recent advances in the design, synthesis, and modification of biochar for remediation of heavy metal pollution in water

Abstract Heavy metal contamination of water has long been a serious environmental issue. Biochar and biochar‐based composites are emerging as effective and sustainable solutions for heavy metal removal due to their strong adsorption abilities and environmentally friendly nature. This review focuses on the latest developments in designing, producing, and modifying biochar for heavy metal remediation. It discusses key factors like biomass selection, pyrolysis conditions, and activation processes that influence biochar properties. Methods for preparing magnetic biochar, including pre‐pyrolysis treatment, co‐pyrolysis, and post‐pyrolysis modification, are explained. The review highlights the importance of biochar properties that impact their functionality in heavy metal adsorption. The latest progress in different modification methods, physical, chemical, and biological, are also discussed. Additionally, it discusses the primary characterization techniques used for biochar characterization and performance evaluations. The review also examines in‐depth how biochar is functioning in removing specific heavy metals like cadmium, chromium, lead, and nickel. It explains adsorption kinetics, mechanisms, and modelling, and explores ways to regenerate and reuse biochar. The potential of machine learning (ML) to optimize biochar applications in wastewater treatment is discussed. Finally, the review considers life cycle assessment (LCA) and techno‐economic assessment (TEA) to evaluate the sustainability and cost‐effectiveness of biochar use. The paper concludes by identifying knowledge gaps and suggesting future research directions to further improve biochar technologies for wastewater treatment.