MPTES-modified halloysite nanotube supported Prussian blue for rapid and selective Tl(I) removal from high-salinity wastewater.

Conventional adsorbents suffer severe performance loss in high-salinity media due to ion competition and electric double-layer compression, limiting trace Tl(I) removal. In this study, a Prussian blue composite supported on MPTES-modified halloysite nanotubes (MAHNTs/PB) was developed. At a low dosage of 0.2 g/L, MAHNTs/PB showed fast adsorption kinetics and reached equilibrium within 5 min. The composite achieved a high adsorption capacity of 795.8 mg/g and maintained Tl(I) removal efficiencies of 97.1-99.5% over a salinity range of 0-10 g/L. It also describes broad pH adaptability over pH 1-11 and resists interference from competing ions at concentrations 10 to 100 times higher. Molecular dynamics simulations revealed interfacial Tl+ enrichment, reduced apparent diffusion coefficient from 2.95 × 10-5 to 1.76 × 10-5 cm2 s-1 following interfacial accumulation, and site-dependent spatial associations with O-, N-, and S-containing regions. DFT calculations gave adsorption energies of -3.996, -6.002, and -4.618 eV for Tl+ at the HNT-O, PB-N, and sulfur-containing S sites, respectively, supporting the cooperative contribution of PB-mediated ion exchange, thiol interfacial interactions, and auxiliary hydroxyl interactions. In real wastewater, 1 g/L MAHNTs/PB reduced Tl(I) from 1.86 mg/L to 0.13 μg/L and maintained >99.8% Tl(I) removal after 10 adsorption-desorption cycles. The composite also maintains good stability, with limited component release, has low risk of secondary contamination. In fixed-bed tests, a MAHNTs/PB-packed column treated 1724 bed volumes before reaching the 0.1 μg/L breakthrough point and 6551 bed volumes before reaching 5 μg/L. This work suggests MAHNTs/PB is a promising adsorbent for the selective removal of Tl(I) from high-salinity industrial wastewater.