Removal of Toxic Thallium from Polluted Waters by Surface Electrostatics and Inner Pores of Prussian Blue Metal-Organic Frameworks

Abstract

Thallium (Tl) is a technology-critical element known for its high toxicity due to its non-biodegradable nature and bio-accumulative potential. Removing Tl contamination from polluted water remains a significant challenge. This study invents a stable nanomaterial, the Prussian Blue metal-organic framework (PB-MOF), characterized by a porous, cube-shaped structure with low isoelectric points. This structure contributes to a high surface area and specificity, enabling efficient capture of monovalent Tl(I) ions across various water matrices. The PB-MOF exhibits pH-dependent Tl(I) sorption, achieving a maximum sorption capacity of over 380 mg/g at pH 8–9. The sorption process follows pseudo-second-order kinetics and the Temkin isotherm model, driven by electrostatic attraction on the outer layers (e.g., negative surface charges interacting with cationic Tl(I)) and the cage-like inner pores that match the size of Tl(I) ions. Furthermore, the PB-MOF demonstrates high selectivity and efficiency for removing Tl(I) and its associated toxicity in different water matrices at environmentally relevant concentrations, with minimal matrix interference. This study highlights PB-MOF as an environmentally friendly material with exceptional specificity, efficiency, and practicality for recovering Tl(I) pollution in a wide range of environmental applications.

Keywords: Thallium (Tl), technology-critical element, Prussian Blue metal-organic framework (PB-MOF), pH-dependent sorption, environmental remediation