Depth filter membranes retain particles in water in the filter media to avoid the formation of filter cakes (particle layers on membrane surfaces), which cause a large increase in the filter resistance. Filter membranes of conventional synthetic polymers have problems at disposal after their uses. Recently biodegradable polyesters have received increased attention as materials for sustainable technologies because they are degradable in natural environments and composting processes. Membranes of biodegradable polyesters can degrade in the composting machines. In this study we developed microfiltration membranes of two biodegradable polyesters, poly(ε-caprolactone) (PCL) and poly(L-lactic acid) (PLLA). The porous structures of the membranes were formed via the thermally induced phase separation process [1,2]. The membranes prepared from the polymer blend of PCL and PLLA at the ratio of 4:1 showed the characteristics of the depth filters in the filtration of a suspension of 6-μm particles (yeast cells). Depth filter membranes of biodegradable polyesters will be environmentally-friendly prefilters for drinking water supply systems.

REFERENCES [1] Tanaka, T. and Lloyd, D.R., J. Membr. Sci., 238, 65-73 (2004). [2] Lloyd, D. R., Kim, S. S., Kinzer, K. E., J. Membr. Sci., 64, 1-11 (1991).