Next-generation electrochemically switched ion exchange with engineered copper hexacyanoferrate sorbents for efficient cesium recovery from aqueous solutions

Abstract

Nuclear energy, despite being carbon-free, produces hazardous waste like 137Cs, requiring efficient removal and secure storage to minimize environmental and health risks. To address this challenge, electrochemically switched ion exchangers (ESIX) have emerged as a breakthrough technology for the efficient and highly selective removal of hazardous radioactive cesium from wastewater while minimizing secondary waste generation. We present a state-of-the-art ESIX system using copper hexacyanoferrate sorbents, optimized via citric acid–tuned coprecipitation (0.25–0.75 M) and drop-cast onto carbon cloth, enabling efficient and selective cesium removal from aqueous solutions. The ESIX performances of CuHCF-0, CuHCF-0.25, CuHCF-0.5, and CuHCF-0.75 were systematically analyzed across various matrices, with CuHCF-0.5 exhibiting the highest cesium (Cs+) sorption capacity of 278 mg/g and achieving 40 % removal within 3 h, demonstrating its superior ion-exchange efficiency. Extended operation under an electrochemical bias of −1/+1.3 V achieved above 90 % adsorption–desorption efficiency over 21 cycles. CuHCF-0.5 operated in ESIX modality, demonstrated highly selective Cs+ adsorption, with Cs+ ions occupying interstitial lattice spaces, typically replacing Na+-occupied sites. X-ray diffraction and X-ray photoelectron spectroscopy provide mechanistic insights into the Cs+ interaction with CuHCF-0.5. The sorbent exhibits efficient regeneration using 1 mM NaCl, maintaining stable performance over twenty-one cycles, highlighting its strong potential for cesium-remediation in contaminated wastewater.