Green synthesis of low silica PHI molecular sieve micron rods assisted by β-cyclodextrin and their enhanced Cs+ adsorption performance

Abstract

Radioactive wastewater containing ¹³⁷Cs poses a serious threat to the environment and human health. However, traditional treatment methods exhibit low efficiency and are prone to secondary pollution. This study synthesized micron-scale PHI-typed molecular sieves with high ¹³⁷Cs⁺ adsorption capacity using an environmentally friendly hydrothermal method and β-cyclodextrin as a crystallization assistant. Structure and morphology of the products were characterized using PXRD, IR, TG, XPS, and SEM- techniques, while adsorption experiments conducted to evaluate their ¹³⁷Cs⁺ adsorption performance. The results demonstrated that rod-shaped PHI-typed molecular sieves were prepared with layered structures, exhibiting particle sizes ranging from 14 ∼ 20μm and a low Si/Al molar ratio of 2.25. Adsorption experiments results showed that the prepared molecular sieve exhibited Cs⁺ adsorption behavior consistent with quasi-second-order kinetics and the Langmuir isothermal model, with a maximum adsorption capacity of 415.79 mg/g and stability maintained within the temperature range of 298∼338 K. In a competitive system containing K⁺, Na⁺, Mg²⁺, and Sr²⁺ (each at 100 mg/L), the Cs⁺ removal efficiency remained above 70%, while also demonstrating adsorption capacity for Sr²⁺ of 31.96 mg/g. This work contributes to advancing sustainable green synthesis methodologies for PHI molecular sieves materials with high efficiency in removing radioactive Cs⁺, demonstrating significant application potential in the field of nuclear wastewater treatment.