Effect of coating and surface modification on water and organic solvent nanofiltration using ceramic hollow fiber membrane

Nanofiltration ceramic hollow fiber membranes were developed to simplify the manufacturing process and improve water and organic solvent permeation performance. The alumina hollow fiber support was prepared by a phase-inversion/sintering method, and a gamma-Al2O3 sol was coated thereon as a selective layer. Polyvinyl alcohol and ethanol were used as the drying control chemical additive in the coating solution, so that a coating layer could be formed without defects in only one coating step. The coating layer thickness could be adjusted to 0.6-2 mu m depending on the coating drawing speed. A sintering temperature of 350 degrees C was selected to provide both reasonable water permeability (6.91 LMH/bar) and rejection (a molecular weight cutoff of 1000 Da or less) and to form a stable gamma-Al2O3 phase. In the case of a membrane that was surface-modified with (3-chloropropyl)-trimethoxysilane, the permeability of toluene and hexane was 2.3 and 4.3 LMH/bar, respectively. The newly developed ceramic membrane showed excellent permeability and separation properties, as well as potential effectiveness for organic solvent nanofiltration applications.