Selective electrochemical removal of cesium ion based on nickel hexacyanoferrate/reduced graphene oxide hybrids

A co-precipitation strategy is developed to prepare the reduced graphene oxides (RGOs) supported nickel hexacyanoferrate (NiHCF) nanoparticles. The NiHCF nanoparticles were uniformly deposited on RGOs with a size distribution of 60 nm. The NiHCF/RGO hybrids exhibit a reversible current response to alkali ion, and the ion exchange can be controlled by the applied potentials. As an electrochemical-switched ion exchange (ESIX), NiHCF/RGO hybrids show a high selectivity toward Cs+ ion in the presence of K+ ion. Their Cs+ uptake capacity (Qe) can reach up to be 320 mg g−1 with a Cs+ distribution coefficient (Kd) of 625 L g−1 in 1 mol L−1 KCl solution. The Cs removal performance of NiHCF/RGO hybrids is superior to that of the pure NiHCFs (Qe 235 mg g−1, 376 L g−1), comparative to or better than those of state-of-the-art metal HCF sorbents or ESIXs reported recently. In addition, NiHCF/RGO hybrids show a high cycling stability with 92% ion-exchange capability after 160 cycles of Cs+ separation.