Potassium ion exchange and crown ether-loaded modified zeolites for efficient and selective adsorption of thallium(I) from aqueous solution: synergistic effect and mechanisms

Thallium (Tl) is a highly toxic rare element. The selective and efficient removal of Tl(I) from water is critical for water safety, yet remains a significant challenge. Herein, a series of highly effective adsorbents with coordination/ion-exchange sites have been developed for Tl(I) removal through composite modification of zeolites via potassium ion exchange and crown ether loading. Within 1 min, 99.42 % of Tl(I) could be removed by 18C6@K-4 a, and the maximum adsorption capacity derived from the sips isotherm model reached 1199.01 mg·g −1 . The adsorption process of Tl(I) was determined to be spontaneous and exothermic based on thermodynamic studies. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations were employed to elucidate the adsorption mechanism and propose optimized adsorption configurations. Both control experiments and computational results consistently demonstrated that the enhanced performance can be attributed to the synergistic effect between exchangeable K + and crown ether complexation, wherein 18-crown-6 captures Tl + through coordination, while K + /Tl + cation exchange contributes to the selectivity and rapid adsorption kinetics. This study offers a straightforward strategy for modifying thallium adsorption materials, which operates under mild conditions, generates no hazardous waste, and leads to significantly improved Tl(I) adsorption performance along with high reusability of the material