Microscale parallel-structured, cross-flow filtration system for evaluation and optimization of the filtration performance of hollow-fiber membranes

Hollow-fiber (HF) membranes are an ideal format for various separations applications due to the high amounts of surface area available in compact module configurations. However, there is an ongoing need in the development of new HF membrane processes to evaluate the effects of operating parameters on the overall filtration performance. To this end, we present the development of a ‘next-generation’ microscale HF cross-flow filtration system that uses a multi-channel peristaltic pump and an array of miniaturized feed reservoirs to run multiple filtration experiments at once. The combination of requiring small feed volumes (∼100 mL) and short HF membrane segments (∼10 cm) for each filtration module is ideal for conducting a thorough exploration of the ‘design space’ for a given separation process. In this study, commercial polyvinylidenefluoride (PVDF) ultrafiltration HF membranes were used in a total of 84 separate filtration experiments to evaluate the effects of run time, solution conditions, solute type, and a polydopamine-based antifouling surface modification strategy. It is asserted that the membrane filtration performance and the fouling propensity strongly depend on the solution composition, and the membrane rejection depends significantly on the buffers and model foulants that are filtered. The modification of the PVDF membrane was first verified via attenuated total reflection and contact angle characterization, then the filtration performance of the modified membranes was evaluated in terms of hydraulic permeability and solute rejection performance. It was found that the dopamine concentration, oxidizer concentration and reaction time were all significant factors affecting the separation performance and surface properties of the membrane. Overall, this study demonstrates the usefulness of the presented microscalefiltration system in studying different aspects of HF membranes as it facilitates parallel experiments which use minimal amounts of material.