Interfacial assembly of PBAs/ZIF-8 composites for ultrahigh-capacity and selective thallium capture with exceptional alkaline tolerance.

Abstract

Effective Tl+ elimination under extreme alkaline pH remains challenging, as alkali triggers decomposition of Prussian blue analogs (PBAs), lowering adsorption efficiency and generating secondary pollutants. Furthermore, conventional PBAs nanocrystals (<100 nm) require costly high-speed centrifugation for separation. Herein, we address both bottlenecks simultaneously by a controlled interfacial assembly of a ZIF-8 protective shell onto a micron-sized KMgFC core. The optimized KMgFC@ZIF8-Ⅱ achieves a maximum Tl+ adsorption capacity of 629.03 mg/g and a removal efficiency of 97.78%, significantly surpassing most reported adsorbents, with over 90% removal within 10 min. The micron-sized particles enable convenient separation by simple filtration, while the ZIF-8 shell confers stable Tl+ removal across pH 2-12, a tolerance unattainable by bare PBAs, through a complementary protection mechanism. In actual industrial leachate and in the presence of competing ions, the material reduces residual Tl+ to below 5 μg/L with a distribution coefficient Kd > 104 mL/g. Mechanistic studies confirm a near-equimolar K+/Tl+ ion-exchange pathway. This work offers a promising stabilization strategy for structurally vulnerable adsorbents and a viable candidate for deep Tl+ removal from hazardous wastewater.