Scalable in-situ activated mineral intergrowths as multi-metal adsorbents for deep phosphorus immobilization and recovery

Phosphorus pollution and the growing scarcity of phosphorus resources necessitate advanced materials capable of both efficient phosphorus removal and subsequent recovery. In this study, natural mineral intergrowths of mixed-phase palygorskite clay, in which carbonates are intergrown with clay minerals, were engineered to develop a high-performance adsorbent (WPAC700) via one-step thermal activation. This activation strategy generates in-situ multi-metallic sites by converting native carbonates and inert mineral surfaces into highly dispersed active metal centers comprising Ca, Mg, Al, and Fe. The clay matrix imposed a confinement effect that inhibits particle coalescence, thereby yielding a high density of accessible multi-metal sites. WPAC700 demonstrated exceptional phosphorus uptake kinetics, with a rate of 6.372 mg·g −1 ·min −1 at an initial phosphate concentration ≤ 10 mg·L −1 , achieving over 99.9% removal within 10 min and an adsorption capacity of 61.4 mg·g −1 . In real water matrices, including Yellow River water and seawater, residual phosphorus concentrations were consistently reduced to below 0.2 mg·L −1 , substantially outperforming commercial activated carbons. Site energy distribution analysis quantified the dominance of high-energy binding sites responsible for rapid sequestration. Mechanistic investigations revealed a synergistic interplay among Ca-dominated precipitation, Al/Fe-mediated ligand exchange, and pore filling. Notably, the phosphorus-laden material can be directly repurposed as a slow-release fertilizer, which promoted plant growth without phytotoxicity and reduced phosphorus leaching from soil. This work establishes a closed-loop paradigm that integrates deep water purification with phosphorus recovery, offering a transformative strategy for converting natural mineral architectures into advanced environmental materials.