Induction of titanium reduction using pyrrole and polypyrrole in the ionic liquid ethyl-methyl-imidazolium bis(trifluoromethanesulphonyl)amide

Abstract

The electrowinning of titanium currently involves high temperature processing and quite extreme condition. As part of a project investigating the use of ionic liquids to refine titanium, we have investigated the use of a polymeric nucleating agent to assist the electro-deposition of the metal. Initial attempts focussed on polypyrrole coatings on the working electrode. These were unsuccessful due to the low conductivity of the conducting polymer in the IL at the reductive potentials required to deposit the titanium. However, it was found that pyrrole was a very successful additive able to induce deposition of titanium species from a TiCl 4 containing ionic liquid electrolyte ([emim][Ntf 2]). Well characterised titanium containing polypyrrole co-deposits have been achieved, when pyrrole was introduced, however bulk metallic titanium was not observed. The presence of titanium species in these deposits was confirmed by XPS. It is thought that the growing pyrrole oligomers form nucleation sites either in situ at the electrode–liquid interface or as a thin film on the electrode allowing co-precipitation of reduced Ti species from solution.