Preparation An Properties Of NiHCF Thin Films For Electrochemically Switched Ion Exchange

ESIX (Electrochemically Switched Ion Exchange) is a separation technology as an alternative to conventional ion exchange for removing metal ions from wastewater. In ESIX, which combines ion exchange and electrochemistry, direct oxidation and reduction of an electroactive film attached to an electrode surface is used to load and unload the film with alkali metal cations and enable the film to obtain the regeneration. Because the main driving force is the electrode potential in the ESIX process, chemical regeneration of the ion exchange substrate is not necessary. Secondary waste created by chemical regenerants is eliminated. So it makes this new ion exchangetechnology more environmentally benign.In this paper, thin films of cathodically deposited nickel hexacyanoferrate (NiHCF) on different substrates are investigated as electrochemically switched ion exchange (ESIX) materials for the selective separation of alkali cations in aqueous nitrate solutions. The films have been generated on platinum, aluminum and graphite substrates. In 1M KNO₃ solution cyclic voltammetry (CV) is used to reversibly intercalate and deintercalate K⁺ from the matrix and to investigate the electroactivity, ion-exchange capacity and the regeneration capability of NiHCF films. In 1M (KNO₃+CsNO₃) mixture solution CV is used to investigate the ion selectivity of the films. The effect of synthetic condition on electrochemical performance of the films and the relationship between the composition and the electrochemical behavior of the NiHCF films are also studied using CV and the energy dispersive X-ray spectroscopy (EDS). Experimental results show that different electrolytic solutions can prepare different NiHCF films which are dominated by either"soluble" or "insoluble" structure and the electroactive NiHCF films can be successfully deposited onto Pt, Al and graphite substrates. The NiHCF films formed on graphite and Al substrates also have good ESIX performance.In this paper the electroactive NiHCF thin films are synthesized as electrochemically switched ion-exchange both on the Graphite and platinum by a chemical deposition. Cyclic voltammetry is used to study the effects of different combination of source reagent and substrate material on the electrochemical behavior in 1M KNO3 solutions. Experiment results show that cyclic voltammetry curve of NiHCF thin films of Fe3+-rich group condition is double peak, while cyclic voltammetry of NiHCF thin films of Ni2+-rich group condition is single peak and the current of Ni2+-rich group is greater than Fe3+-rich group . We investigate ion selectivity of NiHCF and the electrochemical behavior in 1M (KNO3+CsNO3) solution by cyclic voltammetry and found that the film show high cation affinity for Cs+ in nitrate mixture solution only containing little Cs+. In addition ithas been demonstrated that NiHCF thin films prepared by chemical deposition have the high electrochemical stability and regeneration ability.The electroactive NiHCF thin films deposited cathodically on Pt and Al substrates were analyzed. Cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) are determined in 1M (KNO3+CsNO3) and 1M (NaNO3+CsNO3) mixture solutions. The ion selectivity (Cs+/K+ and Cs+/Na+) of NiHCF thin film is investigated based on the change characteristic of CV and EIS curves. Experimental results show that EIS combining CV curves can be used to analyze the ion selectivity of thin films rightly.