New insight into the bioinspired sub-10 nm Sn(HPO4)2 confinement for efficient heavy metal remediation in wastewater

[Display omitted] Heavy metal pollution poses a severe threat to the water environment. Engineering sub-10 nm active functional materials is an important approach to address the problems, and nanocomposites, developed in recent years by pore confinement always present weaken diffusion and low utilization of nanoparticles. In this study, we successfully prepared the polydopamine confined high-density sub-10 nm Sn(HPO4)2 coating for toxic lead(II) removal and its unique external coating structure and superior active sub-10 nm size achieved remarkable performances for heavy metal remediation. The hybrid sub-10 nm coating exhibits an extended acidic environment application (pH = 2.0–7.0) as well as significant selectivity with a superior Kd values (9.4 × 104 mL/g, which is 450 times greater than that of commercial sulfonated polystyrene. Ultrafast filtrations by vacuum further validate its superior sequestration (near to 100%) to Pb and Cd ions at different concentrations (10–100 mg/L) for 2 mins. The real column application further demonstrates the remarkable capacity of 11800 kg/kg sorbents, the trace effluents with three orders (∼103) reduction to below 1 ppb (> 99.9% Pb removal) and efficient stability for several cycles. The effective performances are mainly driven by the PDA motivated external nanoparticles arrangement and strong inner-sphere complexation by small size of Sn(HPO4)2. These results set a new benchmark for removing toxic metals and the proposed approach (engineering sub-10 nm coating design) is unique for heavy metal removal.