Rejection modeling of ceramic membranes in organic solvent nanofiltration

In this work, a transport model based on equations for aqueous nanofiltration has been adapted to describe the rejection of ceramic membranes for nanofiltration in organic solvents. Required membrane parameter were taken from permporometry measurements of the respective membrane. The calculated results were validated by rejection measurements with different membranes of MWCOs between 350 and 1200 g/mol. By selecting an appropriate standard deviation of the pore size, rejection curves measured with polystyrenes in THF were successfully described using the model without any fitting parameters. Differences between the calculated and the experimental rejections were smaller than 0.7% for the membrane with the smallest pore size. The use of the model for a real life solute system has been checked with different specialty chemicals and indicates a good transferability. Variations of process parameters as temperature, pressure and feed velocity were in excellent accordance with the experimental observations. However, to reflect the incomplete rejection of membranes with a high amount of defect pores (detectable by the permporometry measurement), the model has to be extended as well as for the applicability to different solvents.