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Electropolishing is a common method for decreasing surface roughness and removing surface irregularities. In this paper the electropolishing of nickel and cobalt are successfully demonstrated in a deep eutectic solvent, comprising a 2: 1 molar mixture of ethylene glycol (EG) and choline chloride. Voltammetric and electrochemical impedance studies were used to characterise the polishing mechanism and show that film formation occurs prior to polishing. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterise the morphology before and after polishing and 3D optical microscopy was used in-situ to observe film formation during polishing. This study shows that the impact of film formation and subsequently mass transport factor are responsible for electropolishing of both metals in the choline chloride-based ionic liquid.

Although the World Health Organization (WHO) recommends a limit of 1.5 mg l−1 fluoride ions in drinking water, this is not satisfied in many parts of the world. When this limit is exceeded, the electrochemically switched ion-exchange (ESIX) technique (mainly based on conductive polymers) has been identified as a promising method for removing the excess fluoride ions. The present study aimed to develop an efficient method based on the ESIX technique by using poly(aniline-co-o-aminophenol) copolymer to extract fluoride ions. Electrochemical quartz crystal microbalance (EQCM) and acoustic admittance data were utilized to assay the synthetic efficiency of copolymer deposition, and to evaluate the dependence of the defluoridation process on the proportions of the monomers in the copolymer matrix and on film thickness. The resulting films were characterised by Fourier transform infrared spectroscopy (FTIR) and scanning electrochemical microscopy (SEM) techniques. For optimized co-monomer ratio in the feedstock, poly(aniline-co-o-aminophenol) at an applied potential of 0.30 V showed excellent performance for fluoride removal from water at pH 6.6, to the extent of 20 (mg F−) (g polymer)−1. Comparison of the performance of ESIX using poly(aniline-co-o-aminophenol) with that of other techniques and materials reveal that it has significant potential for water defluoridation.

Alternating anodic and cathodic current pulses have been applied to a metal powder on an electrode surface to fuse the particles together. It is shown that homogeneous films can be electroformed with different morphologies depending on the size of the powder and the experimental conditions.

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