Water flux reduction in microfiltration membranes: a pore network study

Abstract

Flow of the contaminated water through membrane causes fouling and leads to change membrane transport properties. Understanding how membrane hydraulic properties change during the operation is critical for evaluating the performance of membrane and helps to improve their design. In this study, a 3D pore network model is developed to simulate the removal of dextran contaminant molecule from water. Initially, a well‐connected network of differently‐sized pores was utilized to represent the microscopic structure of the porous membrane. Advanced FIB‐SEM (Scanning Electron Microscopy combined with Focused Ion Beam) analysis was used to obtain the operating pores sizes. The required input transport parameters for modeling were obtained by performing dynamic experiments on adsorption of dextran within the pore structures of a polysulfone membrane. The results showed a change of pore structure and a decrease of flux over time due to the adsorption of contaminants at pore surfaces. The simulated flux changes demonstrated a good agreement with the experimental data showing that such a model can be used to study the effect of various parameters during the separation process. Specifically, our results showed an increase in the applied pressure, due to an increase of the driving force, leads to a rise of the flux passing through the membrane. Decreasing of the membrane thickness and an increase of the pore size, due to reduction in resistance to flux, leads to an increase of flux over time. Furthermore, contaminant molecular size affects the thickness of the generated adsorbed layer. Observations showed that, with an increase in the size of contaminant molecule, the flux decreased.