ABSTRACT The suppression of internal phosphorus (P) release from sediments represents a critical step in eutrophication control. In this study, waste biomass‐derived biochar was modified with metal chlorides (Fe, Mg, and Zn) as a potential remediation material, aligning with a “waste‐to‐remediation” strategy. Material characterization confirmed the successful incorporation of metal (hydr)oxide phases (e.g., Fe 3 O 4 , MgO, and ZnOHCl) and distinct property tailoring: ZnCl 2 modification increased the specific surface area of sawdust biochar by 37‐fold to 255.85 m 2 /g, whereas FeCl 3 and MgCl 2 imparting strongly acidic and alkaline surface properties, respectively. Batch adsorption experiments indicated that two Mg‐modified biochars exhibited the highest phosphate removal efficiency (96.8%, 23.6 mg/g and 96.7%, 19.4 mg/g), with kinetics and isotherm data well described by pseudo‐second‐order and Langmuir models, suggesting chemisorption‐dominated monolayer adsorption. The adsorption mechanisms were metal‐specific, involving precipitation (e.g., formation of Mg 2 (OH)PO 4 and Zn 3 (PO 4 ) 2 ) and surface complexation. In a pilot‐scale sediment‐water simulation, Fe‐modified sawdust biochar significantly inhibited endogenous P release at the sediment‐water interface and upper water and sustaining low P levels through the formation of stable iron‐phosphate complexes under an induced oxidative microenvironment. These findings offer a systematic framework for designing targeted biochar‐based materials for sustainable management of internal P loading in aquatic systems.
Xinyu et al. (Sun,) studied this question.