Exploitation of mineable oil sands in Canada has thus far produced over 50 km 2 of tailings in ponds where the fine solids remain suspended for years, even decades. These ponds represent a major liability and environmental burden for operating companies, with their dewatering critical to their remediation. In this work, we used the chemistry of the tailing pond constituents to design an ionic liquid (IL) for dewatering the mature fine tailings (MFT), taking advantage of the ability to introduce unique and different functionalities into each ion of the IL. We chose a class of protic ILs whose ions will interact with the solids while rejecting water. As an example, octylammonium oleate can be used to remove more than 70% of the water from MFT. The nature of the ILs makes their use amenable to a variety of large-scale separation techniques allowing engineering versatility in the design of the final process.