Highly selective capture of cesium using an electrochemically renewable molybdenum-based crystalline adsorbent

Abstract

The development of highly efficient adsorbents for the capture of 133Cs and the removal of radioactive isotope 137Cs from complex aqueous solutions is crucial for the chemical production and environmental remediation. Herein, Mo-based crystalline adsorbent with sub-nanometer (5.76 Å) channels was successfully prepared and used in electrochemically controlled Cs+ separation process. Crystalline structures of MoIC (HNO3) before and after adsorption of Cs+ were clearly elucidated using powder X-ray diffractometer (PXRD). A more environmentally friendly electrochemical method was employed to achieve easy release and recapture of Cs+. Adsorption comparison experiments revealed that our material clearly outperforms the reported adsorbents for the removal or recovery of trace amount of Cs+ (< 10 mg L−1). Furthermore, MoIC (HNO3) also exhibited excellent selectivity for low concentration of Cs+ over highly excess of competitive cations, such as Mg2+, Ca2+ and K+, which are commonly distributed in brines. The maximum separation factors of Cs+/Mg2+, Cs+/Ca2+ and Cs+/K+ are 1.2 × 105, 1.3 × 104 and 66, respectively. The remarkable selectivity can be attributed to the outstanding ion-sieving ability of sub-nanometer channels based on the differences in ionic radius and hydration energy of these cations. A real brine was introduced to further prove that one complete cycle of electrochemical adsorption and desorption can dramatically reduce the competing ions concentrations up to 980 times. We anticipate that our findings may give the prospect of opening up new path for the efficient separation of Cs+ from brines using molybdenum-based adsorbent via electrochemically controlled process as a green and sustainable way.