Electrochemically switched ion separation (ESIX) is an ecologically benign and economic way via reversible electrochemical modulation of the matrix charge density.Ion adsorption and desorption can be easily controlled by regulating redox states of the ion exchange thin films prepared on conductive substrates to achieve ion separation and/or regenerate the ion exchange films.Since electricity is the main driving force for ion separation,the secondary pollution from the chemical regeneration of the rinse water in traditional ion exchange technology is eliminated.Thus,ESIX receives more and more attentions and becomes a hot topic in ion separation field due to its potential to replace the traditional ion exchange method.Nickel hexacyanoferrate (NiHCF) film was synthesized on porous three-dimensional carbon felt (PTCF) substrate by repetitious batch chemical depositions,and the NiHCF/PTCF electrode was used as electrochemically switched ion exchange (ESIX) electrode in a packed bed for continuous separation for cesium ions.The morphologies of the prepared electrodes were characterized by scanning electron microscopy and the effects of solution concentration on the ion-exchange capacity of the electrodes were investigated by cyclic voltammetry technique.Cycling stability and long-term storage stability of NiHCF/PTCF electrodes were also studied.The NiHCF/PTCF electrodes with excellent ion-exchange ability were used to assemble a diaphragm-isolated ESIX reactor for cesium separation.Continuous separation of cesium and regeneration of NiHCF/PTCF electrode based on the diaphragm-isolated reactor were performed in a laboratory-scale two-electrode system.A series of experiments were performed to evaluate the continuous separation of cesium based on an electrochemically switched ion exchange (ESIX) process using a diaphragm-isolated reactor with two identical nickel hexacyanoferrate/porous three-dimensional carbon felt (NiHCF/PTCF) electrodes as working electrodes.The effects of applied potential,initial concentrations and pH values of the simulation solutions on the adsorption of cesium ion were investigated.The adsorption rate of cesium ion in the ESIX process was fitted by a pseudo-first-order reaction model.The experiments revealed that the introduction of applied potential on the electrodes greatly enhanced the adsorption/desorption rate of Cs+ and increased the separation efficiency.H3O+ was found to play a dual role of electrolyte and competitor,and the adsorption rate constant showed a curve diversification with an increase in pH value.Also,it was found that the electrochemically switched adsorption process of Cs+ by NiHCF/PTCF electrodes proceeded in two main steps,i.e.,an ESIX step with a fast adsorption rate and an ion diffusion step with a slow diffusion rate.Meanwhile,the NiHCF/PTCF film electrode showed adsorption selectivity for Cs+ in preference to Na+.These results also show that the NiHCF/PTFC composite electrodes in a diaphragm-isolated reactor developed in this work are excellent candidates for practical alkaline cation separation devices.