Performance of solvent resistant nanofiltration membranes for purification of residual solvent in the pharmaceutical industry: experiments and simulation

This study explores the possibility of developing a sustainable extraction method for use in pharmaceutical production, based on purification with membrane processes. Two types of commercial polymeric organic solvent nanofiltration membranes (StarMem122 and DuraMem150) were selected and tested for their abilities to recover the solvent from a pharmaceutical/solvent mixture (5, 10, 50 mg L−1). Five different pharmaceutical compounds have been selected in this work, namely: Imatinib mesylate, Riluzole, Donepezil HCl, Atenolol and Alprazolam. Solvents tested in the experiment were those used in the manufacturing process, i.e., methanol, ethanol, iso-propanol and ethyl acetate. An acceptable performance (rejection over 90%) was obtained for DuraMem150 in all tested pharmaceutical and solvent mixtures except for iso-propanol. No flux was observed for iso-propanol over the DuraMem150 due to its high viscosity. No separation was observed by using StarMem122 for Imatinib mesylate in iso-propanol (over 80%). Commercially available solvent resistant nanofiltration (SRNF) membranes (StarMem™122 and DuraMem™150) show promising performances as alternative tools to traditional separation units such as distillation columns for the recovery of solvents. Furthermore, to evaluate the potential of SRNF as a substitution for traditional solvent recovery, a model was developed for nanofiltration membrane units and implemented in a common process simulation software (Aspen Plus). These models were based on the pore flow mechanism and describe a single membrane module. A membrane module is not available in Aspen Plus and in its Model Library. In this study, this shortcoming was overcome through implementation of the NF membrane module within the Aspen Custom Modeler link to Aspen Plus. The model has been tested for two model solutes (Disperse orange 3 and Disperse red 19) since the pharmaceutical physical properties are not included in the Aspen Properties Database. The results presented here confirm the value of the Aspen Custom Modeler as a simulation tool for the use of NF as a novel and sustainable tool in pharmaceutical manufacturing.