| ECIS (Electrochemically Controlled Ion Separation, ECIS) is a separationtechnology as an alternative to conventional ion exchange for removing metalions from wastewater. In ECIS, which combines ion exchange andelectrochemistry, ion uptake and elution can be controlled directly bymodulating the potential of an ion exchange film that has been electrochemicallydeposited onto an electrode. Because the main driving force is the electrodepotential in the ECIS process, chemical regeneration of the ion exchangesubstrate is not necessary. Eliminating secondary waste created by chemicalregenerants makes this new ion exchange technology more environmentallybenign.Firstly, the electroactive nickel hexacyanoferrate(NiHCF) thin films wereprepared on graphite substrates by cathodic deposition and capillary chemicaldeposition, respectively. In 1M KNO3 solution, potential cycling in the range0～1000mV vs SCE was used to reversibly intercalate and deintercalate K+ fromthe matrix and to compare the electroactivity, ion-exchange capacity,regenerability and cycle life of NiHCF films. In 1M (KNO3+CsNO3) mixturesolution, cyclic voltammetry (CV) was used to investigate the ion selectivity ofthe films. The results show that the NiHCF thin films formed on graphitesubstrates are suitable for electrochemically controlled ion-separation (ECIS)process, that the films display a high Cs+ selectivity and the regeneration speed of cathodically deposited film is higher than that of chemically deposited filmbut the cycle life or stability is contrary.The electroactive NiHCF thin films were synthesized on the multirowgraphite substrates which were composed of 27 graphite cores (the surface areais 85.67cm2) by a cathodical deposition. The composition and morphology ofthe NiHCF thin films were investigated using EDS and SEM. Cyclicvoltammetry was used to study the electrochemical behavior of NiHCF in 1MNaNO3 solutions. And Cyclic Voltammetry(CV), Chronocoulometry andElectrochemical impedance spectra(EIS) were used to study the surfaceproperties of NiHCF films and determine the diffusion coefficient of Na+ andCs+. Chronocoulometry was performed to determine the active surface area(9.88cm2), the active volume (1.21×10-4cm3), and the concentrations(6.64×10-3mol/cm3) of oxidized and reduced centers of the NiHCF filmelectrode. The concentrations (6.64×10-3mol/cm3) of oxidized and reducedcenters is equal to Kahlert etc. The active surface area is smaller than thetheoretical surface area of working electrode 85.67cm2. The ECIS is anelectrochemical reversible process controlling by the diffusion process. Withcyclic voltammetry the diffusion coefficients of Na+ (6.4556×10-8cm2s-1) andCs+(2.1×10-8cm2 s-1) were determined. These datas are close to the diffusioncoefficient of K+ (1.49×10-9cm2 s-1) which comes from Kahlert etc.Experimental results show that the NiHCF films formed on the multirowgraphite substrates which were composed of 27 graphite cores also have goodECIS performance. It has been demonstrated that the NiHCF thin films have thehigh regeneration ability. And the electrochemical stability is better than NiHCFfilms prepared on two-dimensional graphite substrates.Finally, this paper presents the effects of conditions (initial cesiumconcentration, potential, state of film, regeneration and flow rates) on ECISsystem using nickel hexacyanoferrate films deposited on multirow graphite electrodes with Ion Chromatography(IC). Experimental results show that thediffusion process is the controlling step, and NiHCF film electrode will have ahigher remove rate in the bigger initial cesium concentration. The regenerationprocess did not greatly affect the ECIS performance. It can accelerate the rate ofuptake and elution process with potential. And the oxidized NiHCF films aremore suitable for ECIS. It has a good performance at a flow rate of 5mL/min.
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