Electroactive nickel hexacyanoferrate (NiHCF) thin films were synthesized by cathodic deposition and investigated as electrochemically switched ion exchange (ESIX) materials for the separation of Y3+ from aqueous solutions. In 0.1 mol·L-1 Y(NO3)3 solution, cyclic voltammetry (CV) combined with electrochemical quartz crystal microbalance (EQCM) technique was used to investigate the electroactivity, reversibility of the film electrodes and the mechanism of ion exchange. The electrochemical behavior of NiHCF film electrodes was also compared with that in Sr(NO3)2 solutions. The ion selectivity of the film was investigated in 0.1 mol·L-1 solutions containing [Y(NO3)3 + Sr(NO3)2]. The elementary composition of NiHCF films in reduced and oxidized forms were also characterized by X-ray photoelectron spectroscopy (XPS). Experimental results show that the electroactive NiHCF films have reversible electrochemical behavior in aqueous solutions containing Y3+ and Sr2+, respectively. The NiHCF film electrodes displayed a high Y3+ selectivity in Y3+/Sr2+ binary mixtures and the Y3+ ions could be separated effectively from aqueous solutions by ESIX processes.
The PANI/NiHCF nanocomposite particles were synthesized on the CNTs-modified Pt substrate by one-step co-polymerization using cyclic voltammetry. Electrochemical quartz crystal microbalance (EQCM) technique was adopted to investigate the polymerization process of the nanocomposite particles and the mechanism of ion exchange in aqueous solution containing Cd2+. The morphology and structure of the as-prepared composite particles were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), and Fourier transform infrared spectroscopy (FT-IR). Combined with cyclic voltammetry (CV) and energy dispersive spectroscopy (EDS), the electrochemical behavior and the mechanism of ion exchange were also investigated in electrolytes of Cd2+. Experimental results indicated that the cubic nanocomposite particles of PANI/NiHCF were formed and distributed uniformly on the CNTs substrate. The particles exhibited good electroactivity and reversible electrochemical behavior in aqueous solution containing Cd2+, and the Cd2+ ions could be separated from aqueous solutions by ESIX processes.
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