High-capacity recovery of Cs+ ions by facilely synthesized layered vanadyl oxalatophosphates with the clear insight into remediation mechanism

Radiocesium remediation is of great significance for the sustainable development of nuclear energy and ecological protection. It is very challenging for the effective recovery of 137Cs from aqueous solutions due to its strong radioactivity, solubility and mobility. Herein, the efficient recovery of Cs+ ions has been achieved by three layered vanadyl oxalatophosphates, namely (NH4)2[(VO)2(HPO4)2C2O4]·5 H2O (NVPC), Na2[(VO)2(HPO4)2C2O4]·2 H2O (SVPC), and K2.5[(VO)2(HPO4)1.5(PO4)0.5(C2O4)]·4.5 H2O (KVPC). NVPC exhibits the ultra-fast kinetics (within 5 min) and high adsorption capacity for Cs+ (qmCs = 471.58 mg/g). It also holds broad pH durability and excellent radiation stability. Impressively, the entry of Cs+ can be directly visualized by the single-crystal structural analysis, and thus the underlying mechanism of Cs+ capture by NVPC from aqueous solutions has been illuminated at the molecular level. This is a pioneering work in the removal of radioactive ions by metal oxalatophosphate materials which highlights the great potential of metal oxalatophosphates for radionuclide remediation.