Morphological control and cross-flow filtration of microfiltration membranes prepared via a sacrificial-layer approach

The main parameters in controlling the polysulfone (PSf) membrane morphology via a co-casting sacrificial approach were investigated. PEI/NMP and PSf/PVPK90/NMP were used as the coating and supporting solutions, respectively. The effect of PSf concentration, PVP concentration, PEI layer thickness and the coagulation bath temperature were studied. Scanning Electron Microscopy, pore size, porosity, pure water permeability and cross-flow filtration of suspension were utilized to characterize the membranes. Increase in PSf concentration efficiently avoided the concave defects in top surface with the penalty of significantly low permeability, small pore size and compact matrix structure. On increasing the PVP concentration from 0 wt.% to 10 wt.%, the membrane surface transformed from with a dense skin to a more open one. Further increase of PVP concentration to 20 wt.% led to a decline in the surface porosity. At higher coagulant temperature and thicker PEI coating, PSf membranes showed higher permeability and larger pore size. In cross-flow filtration of CaCO3 suspensions, very high rejection rates were found for particles of 5.7 μm; a stable membrane permeability of 3000–6000 l m−2 h−1 bar−1 was obtained.