Mechanism of K+, Cs+Ion Exchange in Nickel Ferrocyanide: A Density Functional Theory Study

Abstract Since the accident at the Fukushima nuclear power plant, the removal of radioactive cesium ions ( 137 Cs + ) from wastewater has become an important topic. Nickel ferrocyanide (Ni-FeCN) is known to adsorb 137 Cs + preferentially from radioactive waste solutions. However, the mechanism underlying the selectivity of Ni-FeCN is not clearly understood. In the present study, the ion selectivity of Ni-FeCN was investigated by means of density functional theory (DFT) calculations to determine why Ni-FeCN selectively adsorbs Cs + . Models of the interactions of Cs + and K + with Ni-FeCN were examined via DFT calculations, which revealed that the hydration energy of Cs + plays an important role in its selective adsorption by Ni-FeCN. The electronic states of Cs + /K + in Ni-FeCN are discussed based on the theoretical results.