Regeneration, Recovery and Removal of Ionic Liquids

Much attention has been paid to ionic liquids related environmental aspects, like toxicity, (eco)toxicity and biodegradability. However, the main efforts are still concentrated on the synthesis of new ionic liquids, the measurement of their properties and the quest for new application fields, while the technical aspects regarding the extent of the ionic liquid lifetime have been neglected. Nevertheless, some experiences have already been reported in the study areas of regeneration, recovery and removal of ionic liquids, for both commercial and potential applications; and in this review it is intended to present them in a useful way. Based on the waste hierarchy, contained in European and other countries regulations, and classifying the experiences according to the separation mechanism used, it was possible to cover the whole spectrum of alternatives known up to now. Last but not least, strategic approaches for the regeneration and recovery of ionic liquids were developed and presented, as a contribution to produce authentic “green” ionic liquids. Insofar, an encouraging pathway is waiting to be explored, and it will be possible to take advantage of a variety of opportunities for further research and development in the areas covered by this review.