Grafting polyacrylic acid brushes onto zirconia membranes: Fouling reduction and easy-cleaning properties

Highly protein-resistant and easily cleaned ceramic membranes were prepared by grafting PAA brushes onto ZrO2 membranes via chemical graft polymerization. The pure water flux decreased with increases in the thickness of PAA coating on the ZrO2 membrane surface. The water flux of the PAA-g-ZrO2 membranes was highly dependent on the solution pH, and increased at lower solution pH. In addition, the initial flux when filtering a bovine serum albumin (BSA) solution using the PAA-grafted membranes was higher than the pure water flux. The antifouling performance of the PAA-g-ZrO2 membranes was assessed via the filtration of a BSA solution. All of the PAA-g-ZrO2 membranes showed a higher initial rejection and a lower reduction in flux for the BSA solution compared with ZrO2 membranes. The fouled BSA could be easily eluted from the PAA-g-ZrO2 membrane surface using cleaning with pure water, and the flux recovery was approximately 70% (the flux recovery of the ZrO2 membrane was only 17% or so). The densely packed brush-shaped structure of the PAA chains was considered to be responsible for reducing the protein adsorption on the membrane surface.