Review of modified biochar for removing humic acid from water: analysis of structure-activity relationship

Abstract Humic acid (HA), as an important part of natural organic matter (NOM), is a precursor of disinfection byproducts. HA affects the migration and transformation of inorganic substances such as metal ions, causing direct harm to the ecological environment and human health. Therefore, HA removal is an important aspect of geochemical research. In this review, research on the application of biochar and modified biochar, which exhibit excellent removal capability, in the treatment of HA-like NOM in water is summarized. The different mechanisms of HA removal via biochar are discussed by analyzing the structure-activity relationship of biochar in the removal of NOM in water under various influencing conditions. The performance and mechanism of adsorption, Fenton, photocatalysis, and electrochemical oxidation methods are analyzed, and their advantages and disadvantages are compared. Finally, the application potential and development direction of multifunctional biochar materials for the removal of NOM, including HA, from water are reviewed. This review provides theoretical and technical support for the removal of HA-like NOM in water using biochar materials and provides a novel direction for its application in actual water bodies. Graphical Abstract