Robust removal of thallium(I) from water with nano-MnO₂ implanted zwitterionic porous hydrogel

The uncontrolled disposal of Tl(I) waste comes at a significant economic and environmental cost because of the acute toxicity and high mobility. To resolve the aggregation problem for most reported MnO₂ based adsorbent materials which significantly affected the adsorption efficiency, porous zwitterionic ammonium propyl sulfonate (zw) polyacrylamide hydrogel (PAAm) has been fabricated to disperse nano-MnO₂ as a support. The developed nano-MnO₂@PAAm-zw exhibited a specific surface area of 5.06 m²/g and a pore diameter of 23.8 nm. particularly amenable to removal of Tl(I) for environmental remediation. The factors, including adsorbent MnO₂ incorporation, feeding amount, adsorption time, pH of the solution, Tl(I) initial concentration and existence of competing cations that governing the adsorption performances were fully elucidated. The maximal removal capacity Q_e reaches up to 336.5 mg (Tl) g^-1(MnO₂) with 99.92 % elimination efficiency and a low residue of 4.5 μg L^-1. The materials exhibit an astonishing robustness against nature matrix and high concentration of cations with adsorption capacity being 928.6-41.43 times larger than various competing counterparts for lab-made and mineral samples, representing the state-of-the-art level of adsorbents. The adsorbent can be regenerated at least five times retaining 86.0 % of original efficiency. A novel concerted mechanistic pathway of retention mainly associated with re-dox reaction is possible. These features offer great potentials for selective and deep elimination of total thallium in water samples.