Rapid recovery of cesium from geothermal water by zinc ferrocyanide composite membrane with exfoliated α-ZrP as enhancer

Zinc ferrocyanide (ZnFC) composites exhibit high selectivity for cesium, but conventional bulk forms suffer from slow mass transfer. In this work, ZnFC was anchored onto exfoliated α-phosphazene ( E -ZrP) nanosheets via an in-situ growth method to construct ZnFC@ E -ZrP composites, which were further fabricated into ZnFC@E-ZrP/PSf adsorption membranes. The two-dimensional E-ZrP support inhibited ZnFC agglomeration and enhanced Cs + mass transfer through shortened diffusion paths and a surface P–OH-induced electronegative field. Experimental results indicated that ZnFC@ E -ZrP exhibited Cs + adsorption properties significantly surpassing that of the α-ZrP support, along with good acid-base stability and recyclability. The corresponding membrane combined rapid transport from E -ZrP with precise capture from ZnFC, achieving adsorption equilibrium within 5 min in filtration and maintaining >98% Cs + recovery from geothermal brine under high ionic competition. The strategy demonstrated in this work enables the design of efficient materials for rapid cesium separation.