Hydrophobic Al₂O₃ Membrane for Sucrose Concentration via Vacuum Membrane Distillation System

Abstract

Hydrophobic Al 2 O 3 membranes were prepared by grafting C 6 F 13 C 2 H 4 Si(OC 2 H 5 ) 3 molecules, and then applied to a vacuum membrane distillation (VMD) system for concentration of sucrose solution as a model solution of fruit juice. The e ects of sucrose concentration and solution temperature on the VMD performance were discussed. By exposing the surface side of the tube membrane to an aqueous solution of 10 wt% sucrose at 60°C and applying vacuum at the inner side of the Al 2 O 3 tube to a pressure of 0.5 kPa, permeation ux of over 7 kg m 2 h 1 was attained through the hydrophobic Al 2 O 3 membrane with asymmetric structure. A mathematical model based on Knudsen and Knudsen-viscous models revealed that the permeance of the asymmetric membrane depends on that of the substrate layer, due to its thickness of 1.47 mm.