Construction of Zeolite-Type Metal Sulfide "Ion Sieve" Into Electrospun Membranes for Ultrafast and Selective ¹³⁷Cs⁺ Sequestration.

Abstract

Selective ¹³⁷Cs⁺ sequestration is challenging due to its high solubility, environmental mobility, and the influence of excessive competitive ions. Herein, we demonstrate an effective strategy for Cs⁺ separation by constructing zeolite-type metal sulfide as "cesium ion sieve" (CIS), obtaining GaGeS-1 with "ion-sieving effect". Its structure features a zeolite-type metal sulfide framework with sodalite (SOD) topology based on supertetrahedral T2 clusters. GaGeS-1 with radiation resistance possesses a maximum Cs⁺ adsorption capacity of 332.52 mg/g and ultrafast adsorption kinetics with removal rate (R^Cs) of 97.06% within 1.5 min. It achieves highly selective Cs⁺ capture under excessive competing ions, even for actual industrial ¹³⁷Cs⁺-liquid-waste (R^Cs > 90%). Single crystal structure analysis and density functional theory calculation reveal that "ion-sieving" originates from strong Cs⁺···S^2- interaction, flexible-robust framework, and optimal Cs⁺ coordination in SOD cage. Furthermore, GaGeS-1 is integrated with gelatin to fabricate GaGeS-1/Gel nanofibrous electrospun membranes for a multi-stage filtration system, enabling efficient, continuous, and recyclable treatment of mixed Na/Cs wastewater (3.58 L/m², R^Cs = 99.39%) and Cs⁺-contaminated river water (2.63 L/m², R^Cs = 99.23%). This study pioneers an efficient "CIS" by developing zeolite-type metal sulfide, and provides a universal assembly method toward practical application, opening new insight into radiocesium remediation and advanced nuclear waste management.