Atomic layer deposition of Al2O3 on porous polypropylene hollow fibers for enhanced membrane performances

Porous polypropylene hollow fiber (PPHF) membranes are widely used in gas and liquid purification. However, the strong hydrophobicity of polypropylene has limited its applications in water treatments. Herein, the atomic layer deposition (ALD) of Al2O3 has been firstly demonstrated as a simple and effective method to upgrade the performances of PPHF membranes in multiple aspects. Al2O3 is distributed via ALD along the cross section of the PPHF membranes, with decreasing concentration from the outer surface to the inner surface. Interestingly, the hollow fibers become much more ductile after deposition as their elongation at break is increased more than six times after deposition with 100 cycles. The membranes show simultaneously enhanced water permeance and retention after deposition with moderate ALD cycles. After 50 ALD cycles a 17% increase in water permeance and one-fold increase in BSA rejection are observed. Moreover, the PPHF membranes exhibit improved fouling-resistance after ALD deposition of Al2O3.124