Biochar-based materials for the adsorption of phosphorus: a review

Phosphorus pollution is a major driving force of aquatic eutrophication, and its nonrenewable nature further highlights the necessity for efficient removal and recovery strategies. Biochar-based materials have attracted considerable attention for phosphorus adsorption due to their low cost and environmental friendliness. This review summarizes recent advances in biochar-based adsorbents, with emphasis on the effects of metal modification on adsorption performance. Key removal mechanisms, including electrostatic attraction, ligand exchange, surface complexation, and precipitation, are discussed. The application of metal-modified biochar in real wastewater treatment and phosphorus recovery is also evaluated, particularly the potential of phosphorus-loaded biochar as a slow-release fertilizer. In addition, phosphorus release behavior, environmental risks, and emerging machine learning approaches for material optimization are reviewed, and future research directions are proposed.