Temporal evolution of the selectivity-permeability relationship during porous membrane filtration of protein solutions

• Membrane selectivity and permeability were affected by its pore structure.
• The removal mechanisms of BSA varied for different structured membranes.
• The tradeoff between permeability and selectivity was achieved by adjusting pH.
• Intermolecular interactions strongly affected BSA removal by porous membranes.

Currently, there is no clear understanding on the effects of membrane properties on temporal evolution of membrane selectivity-permeability relationships during microfiltration or ultrafiltration-based water treatment. In this study, porous polyvinylidene fluoride (PVDF) membrane, polyvinyl chloride membrane, and glass-fiber membrane with distinctive physical and chemical properties were employed to filter bovine serum albumin (BSA) at different pH, coupled with model simulation approaches. Both the experimental results and model prediction showed that, due to the existence of different filtration mechanisms, selectivity of the PVDF membrane and the PVC membrane increase with decreasing permeability, whereas an opposite trend was observed for the glass-fiber membrane. Also, pH strongly affected permeability by changing the zeta potentials of the solutes and the membrane surfaces. Moreover, membrane selectivity was less significantly affected by pH for the polymeric membranes than for the glass-fiber membrane. Practically, high selectivity and permeability may be simultaneously achieved during water treatment by: (1) selection of membranes with suitable pore structure (such as control of solute diameter >1/5 pore diameter); (2) control of feed water condition (such as pH) to suppress intermolecular interactions or solute-membrane interactions, further influence the deposition/adsorption of solute on membrane.