Ultrathin TiO2 microfiltration membranes supported on a holey intermediate layer to raise filtration performance

Abstract

Ultrathin TiO2 microfiltration membranes with thicknesses in the range of 1−7 μm were prepared by coating TiO2 suspensions on purposely designed holey Al2O3 substrates. The effects of the TiO2 top layer thickness on surface roughness, pore size distribution, and thereby on water flux, steady permeate and retention performance of the overall membrane were systematically investigated. The ultrathin TiO2 membrane layer with a thickness of ∼3 μm, surface roughness of ∼109 nm and an average pore size of 87 nm shows the best overall performance. Its pure water flux (2214 Lm−2 h-1 bar-1) at 100 kPa and normalized permeate flux (59 %) after 50-min filtration in a feed solution of 70-nm polystyrene nanospheres (2 ppm) are much higher than those of the control TiO2 membrane (696 Lm−2 h-1 bar-1 and 27 %). The disruptively improved pure water flux and normalized steady permeate flux, without significantly sacrificing the retention performance, are correlated to the unique membrane structural features. © 2020 Elsevier Ltd