Electrochemically Controlled Ion Separation Performances of Electrodeposited Nickel Hexacyanoferrate Thin Films in Alkaline Earth Metal Solution

Abstract

Nickel hexacyanoferrate(NiHCF)thin films were synthesized on platinum substrates by cathodic deposition and the film-electrode systems were investigated as electrochemically controlled ion separation(ECIS)materials for the selective separation of alkaline earth ions in aqueous nitrate solutions.In 0.1 mol.L~(-1)Mg(NO_3)_2,Ca(NO_3)_2,Sr(NO_3)_2 and Ba(NO_3)_2 solutions,cyclic voltammetry (CV)was used to reversibly intercalate and deintercalate alkaline earth cations from the matrix and to investigate the electroactivity,electrochemical behavior and the loading mechanism of NiHCF film electrodes.CV and electrochemical quartz crystal microbalance(EQCM)were used to investigate the ion selectivity of the films in 0.1 mol.L~(-1)[Mg(NO_3)_2+Ba(NO_3)_2]mixture solution.The chemical composition and elemental valence of NiHCF films in reduced and oxidized form were also characterized by X-ray photoelectron spectroscopy(XPS).Experimental results show that the cathodically deposited NiHCF film electrodes have reversible electrochemical behavior in alkaline earth metal solution and display a high Ba~(2+)selectivity in Mg~(2+)/Ba~(2+)mixtures.The alkaline earth metal ions can be separated effectively by ECIS processes.