A Systematic Review on Modification Technology of Agricultural and Forestry Waste Biochar: From Raw Material Characteristics to Heavy Metal Adsorption Mechanisms

Abstract With the increasingly serious problem of heavy metal pollution, it is particularly urgent to find economically efficient and sustainable technologies for heavy metal pollution treatment. Biochar, as an environmentally friendly material with low cost, a wide range of raw materials, large specific surface area, rich pore structure, and excellent adsorption performance, attracts much attention in the field of heavy metal ion adsorption in recent years. This paper systematically reviews the research progress on biochar modification using agricultural and forestry biomass waste as feedstock while elucidating the intrinsic mechanisms by which physical activation, chemical loading, and microbial synergism enhance adsorption capacity through comparative analysis. This paper also elucidates the mechanisms governing functional group distribution and pore structure regulation on biochar surfaces that influence heavy metal adsorption characteristics, thereby enhancing the mechanistic understanding of heavy metal removal processes. Additionally, this paper prospects future directions in the resource‐oriented biochar production from agricultural and forestry waste, aiming to establish a synergistic theoretical‐practical paradigm that integrates biomass valorization with precision‐heavy metal remediation.