Solvent resistant nanofiltration for acetonitrile based feeds: A membrane screening

A range of commercially available and lab-made membranes was screened for use in feeds containing acetonitrile (ACN). ACN was selected as it is one of the most widely used solvents in pharmaceutical industry and surprisingly absent in earlier studies on solvent resistant nanofiltration (SRNF). The selected membranes ranged from the tight nanofiltration range to the lower end ultrafiltration range, prepared from different membrane chemistries and with different membrane preparation methods. Multiple dyes were tested as probe molecules to study the retention behavior of the membranes in ACN. Gel content measurements were conducted on the membranes and interaction parameters with ACN, the dyes and the membranes were calculated to link physico-chemical properties to separation performances. ACN was found to be a very appropriate solvent for SRNF applications, as most membranes reached high fluxes and retentions, comparable to those obtained in most other solvents. As most membrane polymers did not dissolve in ACN, membrane crosslinking is not even strictly necessary to ensure stability of the membranes when applied in these feeds. This study thus showed that for ACN-based solutions, many different types of SRNF membranes can potentially be selected to achieve the aimed separations.