Correlation between membrane fouling and the ratio of particle to pattern size

Abstract

Membrane fouling remains as one of the critical problems which drastically reduce filtration performance of membrane in water and wastewater treatment. Among various studies attempted to solve this problem, patterned membrane has proven the positive effects on membrane fouling. However, the ratio of particle size to pattern size in view point of fouling still remains unclear. In this study, we prepared new nano- and micro-scale patterned membranes and investigated the correlation between membrane fouling and the ratio of particle to pattern size. Through SEM and AFM imaging, it was confirmed that successful transfer of nano- and micro-scale features with size of 110 nm and 2 µm respectively was made onto the surface of PES UF membrane via hot-embossing NIL method. Although all the membranes have similar pore size, which is approximately 10 nm, regardless of existence of pattern or pattern size, patterned membrane showed 10 – 30 % higher water permeability than flat membrane due to increased effective surface area of patterned surface. Finally, the effect of particle to pattern ratio on membrane fouling in patterned membrane system was investigated through conducting ultrafiltration of various sized colloidal latex particles. The new parameter, the ratio of particle size to pattern size (Rp), was defined to accurately describe anti-fouling performance of patterned membrane. Also, the extent of membrane fouling was plotted against Rp value and it was found that the range of optimal Rp value was located around 5 when using particles with size from 0.1 to 6 µm. This range of optimal Rp value is expected to provide a useful guide line when selecting effective pattern size to remove specific sizes of foulants in future research or industrial application.