Solvent transport in organic solvent nanofiltration membranes

Solvent transport in organic solvent nanofiltration membranes has been studied in a lab-scale cross-flow nanofiltration rig over extended periods using the common solvents methanol, toluene, ethyl acetate and their mixtures. The organic solvent nanofiltration membranes STARMEM™ 122 (W.R. Grace and Co.) and MPF50 (Koch Membrane Systems) were investigated. It was found that it took a few days to obtain stable solvent flux using STARMEM™ 122, and that the solvent flux in this membrane showed good repeatability between different sample discs. MPF50 did not provide reproducible results, therefore, no modelling/data analysis was performed for this membrane. Our experimental data shows that both solution-diffusion and pore-flow models can be used to predict permeation of solvent mixtures, using only the permeabilities of the pure solvents to obtain input parameters to each model. The solution-diffusion model gave more accurate predictions. Our conclusion is that for the solvents studied, it is possible for reasonable predictions of solvent mixture flux to be made over the whole concentration range, based on the data for pure solvents.