Here we describe the electrolytic deposition of Zn, Sn and Zn/Sn alloys from a solution of the metal chloride salts separately in urea and ethylene glycol/choline chloride based ionic liquids. We show that the deposition kinetics and thermodynamics differ from the aqueous processes and that qualitatively different phases, compositions and morphologies are obtained for the metal coatings in the different ionic liquid systems. We have quantified the electrochemical stripping responses using cyclic voltammetry together with compositional analysis using SEM/EDAX and X-ray diffraction. The differences in electrochemical responses are rationalised in terms of the speciation of both Zn and Sn chlorides in the ionic liquids that have been identified using FAB mass spectrometry. Also we demonstrate that composite metal coatings, e.g. containing Al2O3 particles, can be obtained from these liquid systems by virtue of the stable liquid suspensions. This novel feature of these liquids is a function of their relatively high viscosity.

A eutectic formed between choline chloride and urea is shown to be a good solvent for the dissolution of a range of metal oxides. It is demonstrated that this ambient temperature ionic liquid can be applied to the processing of electric arc furnace dust. Zinc and lead can be selectively removed and subsequently electrowon from the liquid. This leaves the insoluble iron and aluminosilicates, which can be recycled through the electric arc furnace.

ChemPhysChemVolume 7, Issue 4 p. 803-806 Communication Design of Improved Deep Eutectic Solvents Using Hole Theory Andrew P. Abbott Prof., Andrew P. Abbott Prof. [email protected] Chemistry Department, University of Leicester, Leicester, LE1 7RH, United Kingdom, Fax: (+44) 116-252-3789Search for more papers by this authorGlen Capper Dr., Glen Capper Dr. Chemistry Department, University of Leicester, Leicester, LE1 7RH, United Kingdom, Fax: (+44) 116-252-3789Search for more papers by this authorStephen Gray, Stephen Gray Chemistry Department, University of Leicester, Leicester, LE1 7RH, United Kingdom, Fax: (+44) 116-252-3789Search for more papers by this author Andrew P. Abbott Prof., Andrew P. Abbott Prof. [email protected] Chemistry Department, University of Leicester, Leicester, LE1 7RH, United Kingdom, Fax: (+44) 116-252-3789Search for more papers by this authorGlen Capper Dr., Glen Capper Dr. Chemistry Department, University of Leicester, Leicester, LE1 7RH, United Kingdom, Fax: (+44) 116-252-3789Search for more papers by this authorStephen Gray, Stephen Gray Chemistry Department, University of Leicester, Leicester, LE1 7RH, United Kingdom, Fax: (+44) 116-252-3789Search for more papers by this author First published: 04 April 2006 https://doi.org/10.1002/cphc.200500489Citations: 347Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract Extraordinary solvents: The authors design deep eutectic solvents (DESs) based on small cations and fluorinated hydrogen-bond donors (see figure). These DESs display properties of decreased viscosity and increased conductivity with differences up to four orders of magnitude compared to ionic liquids. Citing Literature Volume7, Issue4April 10, 2006Pages 803-806 RelatedInformation

The solubility of 17 commonly available metal oxides in the elemental mass series Ti through Zn have been determined in three ionic liquids based on choline chloride. The hydrogen bond donors used were urea, malonic acid, and ethylene glycol. The results obtained are compared with aqueous solutions of HCl and NaCl. Some correlation is observed between the solubility in the deep eutectic solvents and that in aqueous solutions but some significant exceptions offer an opportunity for novel solvato-metallurgical processes.

We demonstrate the first practical alternative to the use of phosphoric and sulphuric acid mixtures for the electropolishing of stainless steel. In this paper, efficient electropolishing of type 316 stainless steel is demonstrated in an ionic liquid composed of ethylene glycol (HOCH2CH2OH) and choline chloride (HOC2H4N(CH3)3+Cl−). Linear sweep voltammetry, chronoamperometry, scanning electron microscopy, atomic force microscopy and AC impedance methods were used to investigate the steel dissolution mechanism and the results are compared to polishing done in aqueous acidic solutions. It is shown that the quality of the polish is related to the breakdown of the oxide film and preliminary data suggest that the polishing process may be controlled by the diffusion of chloride ions. The dissolution is different from that found in aqueous acid solutions, and oxide breakdown is shown to be slower, which can lead to pitting at low current densities.

We have studied the anodic dissolution (electropolishing) of various stainless steel alloys in an ionic liquid comprising a 2 : 1 stoichiometric mix of ethylene glycol (EG) and choline chloride. We have used a combination of electrochemical and spectroscopic methods together with in situ liquid probe microscopy. We discuss the role and influence of the surface oxide passivation layer, characterized here by X-ray photoelectron spectroscopy (XPS) and linear sweep voltammetry, on the polishing process. We address the question of dealloying during the polish in order to contribute to our understanding of the viability of the ionic liquid as a replacement industrial electropolishing medium; the current commercial process uses a corrosive mixture of phosphoric and sulfuric acids. Also, we present data from ex situ and in situ liquid AFM studies giving both a qualitative and quantitative insight into the nature and scale of morphological changes at the steel surface during the polishing process.

The solubility of a range of metal oxides in a eutectic mixture of urea/choline chloride is quantified, and it is shown that the dissolved metals can be reclaimed from a mixed metal oxide matrix using electrodeposition.

Efficient electropolishing of stainless steel is demonstrated in an ionic liquid produced from ethylene glycol and choline chloride (HOC2H4N(CH3) Cl-+(3)-). It is shown that the metal dissolves without prior passivation and no gassing is observed at the anode surface. No dealloying of the substrate is observed and no changes in the polish quality are observed as the ionic liquid ages.

Deep Eutectic Solvents (DES) can be formed between a variety of quaternary ammonium salts and carboxylic acids. The physical properties are significantly affected by the structure of the carboxylic acid but the phase behavior of the mixtures can be simply modeled by taking account of the mole fraction of carboxylic acid in the mixture. The physical properties such as viscosity, conductivity, and surface tension of these DES are similar to ambient temperature ionic liquids and insight into the cause of these properties is gained using hole-theory. It is shown that the conductivity and viscosity of these liquids is controlled by ion mobility and the availability of voids of suitable dimensions, and this is consistent with the fluidity of other ionic liquids and molten salts. The DES are also shown to be good solvents for metal oxides, which could have potential application for metal extraction.

The synthesis of ionic liquids based upon functionalized quaternary ammonium salts and metal salts of zinc, tin, or iron is demonstrated. The freezing point of these ionic liquids was studied as a function of the quaternary ammonium cation. The complex anions were identified and quantified using mass spectrometry and potentiometry. It is shown that the primary zinc anion is Zn2Cl5- with Zn3Cl7- becoming more abundant in more Lewis basic solutions. Similar results were observed for ionic liquids containing SnCl2. The surface tension was also measured and was used to explain the high viscosity of the ionic liquids in terms of the large ion:hole size ratio and the small probability of finding a hole of suitable dimensions adjacent to a given ion to permit movement. The phase behavior of a variety of quaternary ammonium halides/ZnCl2 mixtures is characterized and it is shown that the depression of freezing point is related to the increase in size of the component ions.

A dark green, viscous liquid can be formed by mixing choline chloride with chromium(III) chloride hexahydrate and the physical properties are characteristic of an ionic liquid. The eutectic composition is found to be 1:2 choline chloride/chromium chloride. The viscosity and conductivity are measured as a function of temperature and composition and explained in terms of the ion size and liquid void volume. The electrochemical response of the ionic liquid is also characterised and it is shown that chromium can be electrodeposited efficiently to yield a crack-free deposit. This approach could circumvent the use of chromic acid for chromium electroplating, which would be a major environmental benefit. This method of using hydrated metal salts to form ionic liquids is shown to be valid for a variety of other salt mixtures with choline chloride.

SUMMARY The efficient electrodeposition of chromium from an ionic liquid formed between choline chloride and CrClr6H20 is demonstrated. The addition of lithium chloride is found to allow the deposition of black chromium films that afford excellent corrosion resistance. The deposits formed are crack-free and made up of nanocrystalline material.

Ionic liquids can be formed between ZnCl2 and a range of substituted quaternary ammonium salts. These ionic liquids are easy to prepare and are insensitive to water and air. They have conductivities comparable to other ionic liquids and as such they are suitable for electrochemical applications. The deposition of zinc is investigated and it is shown that the film formed on an electrode surface following the electroreduction of the melt is non-porous and produces an extremely effective corrosion resistant coating with very high current efficiency. The characteristics of a battery based on a zinc ionic liquid are also demonstrated. Other metals such as chromium are also shown to form ionic liquids with choline chloride and a generic method for depositing metals is demonstrated.

Eutectic mixtures of urea and a range of quaternary ammonium salts are liquid at ambient temperatures and have interesting solvent properties.

Eutectic mixtures of urea and a range of quaternary ammonium salts are liquid at ambient temperatures and have interesting solvent properties.

Eutectic mixtures of urea and a range of quaternary ammonium salts are liquid at ambient temperatures and have interesting solvent properties.

Synthetically important Diels-Alder reactions occur in high yield in novel Lewis acidic ambient temperature ionic liquids composed of choline chloride-MCl2 (1:2) (M = Zn or Sn), The liquids are not moisture-sensitive and after separation of the products they can be reused with no noticeable drop in activity.

This work shows that novel ambient temperature ionic liquids can be produced from substituted quaternary ammonium salts and some metal salts. The ionic liquids are sufficiently, conducting to allow electrochemical investigations to be carried out, Data on the electrochemical reduction of the metal ions is presented together with information on the deposit morphology of Zn, and Zn Sn and Zn,Co alloys, The loir cost and low, toxicity of the ionic liquids makes possible their use for large-scale metal finishing applications.