Measurement of membrane pore interconnectivity

Several studies have suggested that the rate and extent of membrane fouling can be strongly affected by the interconnectivity of the membrane pore structure. For example, membranes with highly interconnected pores should allow fluid to flow around and under any pore blockage on the membrane surface, significantly reducing the effect of this blockage on the filtrate flux. It has not, however, been possible to quantify these effects due to the absence of any experimental technique for measuring the pore connectivity. We have developed a new technique for evaluating the pore connectivity from data for the hydraulic permeability and/or solute diffusion coefficient in the directions normal to and parallel to the membrane surface. Experiments were performed by blocking different regions of the upper and lower surfaces of the membrane to change the relative contributions of the normal and transverse flows. Data were analyzed using a theoretical model for two-dimensional flow or transport in the porous membrane. Studies performed with polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) membranes showed distinct differences in the extent of pore connectivity, consistent with the different formation methods and underlying pore morphologies for these membranes.