Effect of membrane pore morphology on microfiltration organic fouling: PTFE/PVDF blend membranes compared with PVDF membranes

Abstract

This study provides an insight into the effect of membrane pore morphology on microfiltration organic fouling, by comparing the fouling behaviors of a series of polytetrafluoroethylene/polyvinylidene fluoride (PTFE/PVDF) blend membranes with those of PVDF membranes at varied hydrophobicity and pore size levels. Unlike the PVDF membrane pore morphology which resembled particulate bed, the PTFE/PVDF blend membrane morphology was characterized as fibrous network with thread-like pore walls and interconnected pore channels of high structural complexity. Fouling evolution rate and irreversibility of these membranes were assessed using batch filtration tests, with a membrane bioreactor supernatant employed as the foulant. Fouling of the PVDF membranes deteriorated significantly with increasing hydrophobicity and decreasing pore size. By comparison, all the blend membranes showed moderate fouling, much less sensitive to hydrophobicity and pore size. It was demonstrated that hydrophobicity and pore size pertain to hydrophobic adsorption and size exclusion respectively, which are fundamental membrane–foulant interactions for promoting fouling. Pore morphology may affect fouling by influencing these interactions. For the case of the blend membranes, it was inferred that the thread-like pore walls with limited adsorption area discouraged hydrophobic adsorption, while the high structural complexity encouraged size exclusion on the other hand.