a membrane separation process using a highly fluorinated polymer membrane that selectively permeates water of an aqueous ionic liquid solution to provide dry ionic liquid . preferably the polymer is a polymer that includes polymerized perfluoro - 2 , 2 - dimethyl - 1 , 3 - dioxole . the process is also capable of removing small molecular compounds such as organic solvents that can be present in the solution . this membrane separation process is suitable for drying the aqueous ionic liquid byproduct from precipitating solutions of biomass dissolved in ionic liquid , and is thus instrumental to providing usable lignocellulosic products for energy consumption and other industrial uses in an environmentally benign manner .