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Environmental context. As a low-cost adsorption material with good biocompatibility and high adsorption efficiency, biochar is widely used to treat contaminants in water and soil environments. However, due to its low adsorption capacity and narrow adsorption range, it is necessary to modify biochar to improve its adsorption performance. This review describes the three major biochar modification methods and reviews their adsorption effects on different contaminants, then makes recommendations and suggestions for future development of biochar.