A novel pathway for the high energy efficiency production of metal from metal oxide via electrolysis in ionic liquids at low temperature was investigated. Metals such as Cu, Zn, and Pb are normally produced by the application of very high temperatures. The main goal is to eliminate the use of carbon and high temperature application in the reduction of metal oxides to metals. Experimental results for electrochemical extraction of Zn from ZnO using Urea ((NH2)2CO) and Choline chloride (HOC2H4N(CH3)3+Cl-) or (ChCl) in a molar ratio 2:1, constant voltage at 85°C is discussed. Solubility of ZnO in solution was measured using FTIR and ICP. Electrolysis experiments were conducted using EG&G potentiostat/galvanostat with three electrode cell systems. The deposits were characterized using XRD and SEM. The results showed that pure zinc metal was deposited on the cathode. Successful extraction of zinc metal from zinc oxide dissolved in Urea/ChCl (2:1) was accomplished. This technology will advance the metal oxide reduction process by reducing the energy consumption and also eliminating the production of CO2 which makes this an environmentally benign technology for metal extraction.


Ionic liquids (ILs) are organic salts that are liquids over a wide temperature range, including room temperature. They are considered as new generation solvents, which are capable of replacing volatile organic compounds that are traditionally used as industrial solvents. The important properties of ionic liquids include wide electrochemical window, high ionic conductivity, almost non-volatile, non-flammable, corrosion resistance to plastics and carbon steels, high thermal stability, wide temperature range for liquid phase, and high solvating capability. These properties offer significant advantages in the design and performance of metal extraction processes [1]. The wide electrochemical window (~ 4 V) of ionic liquids also enables the possibility of extracting reactive metals or alloys which would be very difficult in aqueous solvents. Chloroaluminate ionic liquids such as 1-butylpyridinium chloride (BuPyCl-AlCl3) and 1-ethyl-3-methylimidazolium chloride (EMIC-AlCl3) systems have been successfully used as the electrolytes for metal electro-deposition [2–5]. The thermo-physical properties of chloride based (C2mimCl, C4mimCl, C6mimCl) and fluoride based ionic liquids (CnmimPF6, CnmimBF4) were investigated [6, 7].

A comprehensive review was made on extraction of metals and alloys using ionic liquids [1]. Several investigations have been carried out on extraction of metals from its chlorides using low temperature ionic liquids. To use chlorides as the starting material adds an additional step when considering an industrial operation wherein the metal oxides need to be converted to chlorides, only then it can be dissolved in an ionic liquid. Metal oxides are not readily dissolved in ionic liquids.

This content is only available via PDF.
You can access this article if you purchase or spend a download.