Disclosed herein are processes in which precipitation permits removal of metal halides (e.g. AlCl3) from ionic liquids. After precipitation, the precipitated metal halides can be physically separated from the bulk ionic liquid. More effective precipitation can be achieved through cooling or the combination of cooling and the provision of metal halide seed crystals. The ionic liquids can be regenerated ionic liquid catalysts, which contain excess metal halides after regeneration. Upon removal of the excess metal halides, they can be reused in processes using ionic liquid catalysts, such as alkylation processes.