A novel functionalized ionic liquid [DOC4mim][DEHG] for impurity removal of aluminum in rare earth leaching solution

The separation of rare earth (RE) and aluminum (Al) has always been a practical challenge. In this article, a novel functionalized ionic liquid 1-butyl-3-(3,3-dimethyl-2-oxobutyl)-imidazol-3-ium bis(2-ethylhexyl)glycinate ([DOC4mim][DEHG]) with high selectivity was developed for the impurity removal of Al from ion-adsorbed type RE ores leaching solution. In the sulfuric acid system, the ionic liquid extracted Al through an ion association mechanism. Salting out agent of Na2SO4 could change the stoichiometric number of extraction equilibrium. For the actual RE leaching solution, the inhibitory effect exhibited by Na2SO4 prevented more RE elements from being removed together with Al. Under the optimized extraction conditions, the removal rate of Al was more than 95%, also the recovery rate of RE was more than 96%. Compared with saponified industrial extractant naphthenic acid, it revealed better interface phenomenon and higher RE recovery performance. NaOH solution with low concentration could be used to strip and regenerate RE-loaded [DOC4mim][DEHG] at the same time. In five cycles, the extraction system maintained good reproducibility. There was no acid consumption in the separation process. This work provides a new insight into the efficient and sustainable removal of Al impurity from actual RE leaching solution.