Scalable structural reconstitution of natural clay into an active silicate with synergistic active sites for Pb(II) sequestration across trace to high concentrations

The simultaneous realization of high adsorption efficiency, low cost, and scalable fabrication in a single adsorbent remains a significant challenge for the remediation of heavy metals-contaminated water. Here we propose a thermal-induced structural reorganization strategy to convert naturally abundant low-grade attapulgite clay into a porous silicate composite (denoted HJSiCa1.75). The composite exhibits a high uptake capacity (139.39 mg·g −1 ) and removal efficiency over 99.5% across a broad concentration range (10 mg·L −1 -200 mg·L −1 ). In real water matrices (lake water, river water, and tap water), HJSiCa1.75 outperforms commercial activated carbon 2–3 times at equivalent dosages, maintaining a removal efficiency above 99%. Site-energy distribution (SED) analysis reveals that the overall average site density of HJSiCa1.75 (0.012 g·mol/(g·kJ)) exceeds that of GHJ (0.007) and AC-CN (0.004). Thermodynamics analysis revealed that adsorption is spontaneous (ΔG° < 0) and endothermic (ΔH° = +11.95 kJ·mol −1 ). Phytotoxicity tests using aquatic plants indicate substantially reduced toxicity in treated water, as evidenced by seed germination rates and root growth comparable to those observed in clean tap water, thereby suggesting improved ecological compatibility. Pelletization and column adsorption experiments confirm the structural integrity and operational stability of the adsorbent. Mechanistic investigation identifies a synergistic interplay of electrostatic attraction, ion exchange, surface complexation, and in-situ mineralization. Collectively, this work provides a rational structural engineering route to designing high-performance heavy-metal scavengers and facilitates the value-added utilization of natural clay for scalable water purification.