Recycling Concept for Aluminum Electrodeposition from the Ionic Liquid System EMIM[Tf2N]-AlCl3

In the last years, the ionic liquid system formed by specific mixtures of 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide (EMIM[Tf2N]) and AlCl3 proved to be a very suitable electrolyte for the electrodeposition of aluminum. In order to establish an industrial electrodeposition process based on this novel electrolyte system, the suitability of melt crystallization for purification and recycling of these electrolytes has been studied. It exists a composition range in the ternary system where the compound EMIM[AlCl4] can be crystallized in a high purity. The layer melt crystallization technique is successfully applied to the binary system EMIMCl-AlCl3 and to the real ternary electrolytes. Hydrolysis is proposed for treatment of the residue. In aqueous solutions, the membrane process nanofiltration is applied for concentration and recovery of the ionic components. An integral recycling concept is presented.