Ionic liquid and water separation by membrane distillation

An environmentally-friendly method to pretreat biomass prior to conversion to liquid fuel is deconstruction by ionic liquids (ILs). Typically, water is added as an anti-solvent to the IL and biomass mixture and is also used to rinse the biomass. Separation of the resulting water and IL mixtures is required prior to recycling the IL. Direct contact membrane distillation, a low temperature and ambient pressure process, was used to separate water from 1-ethyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium formate, two ILs commonly used for biomass pretreatment. IL concentrations ten times those of the original feed (5-50% by mass) were achieved, with greater concentrations possible. Using direct contact membrane distillation for ionic liquid-solvent separation has not previously been reported in the literature. The effect of the ILs on the hydrophobicity of the polytetrafluoroethylene and polyvinylidene fluoride membranes used was also investigated. (C) 2015 Elsevier B.V. All rights reserved.