Improving Separation Performance of PVDF Ultrafiltration Membranes by Blending with Cellulose Acetate

Membrane technology is a clean technology for various separation processes, in which additional waste products are not produced. Poly(vinylidene fluoride) (PVDF) is one of the synthetic polymers widely used as commercial ultrafiltration membranes. Unfortunately, this polymer is hydrophobic and consequently, it has low flux in the aqueous system and creates fouling phenomena on the surface of the membrane. Therefore, the objective of this work is to improve the hydrophilicity of PVDF membranes by preparing blend membranes using cellulose acetate. Cellulose Acetate (CA) with varied concentrations ranging between 1 and 10 wt.% were added to poly(vinylidene fluoride) and those blend membranes were prepared via the phase inversion method. The effects of CA on various membrane characteristics such as hydrophilicity, membrane porosity, antifouling properties, and separation performances were investigated using Methylene Blue (MB) as a dye. It was found that the PVDF-CA membranes were more hydrophilic compared to the pristine PVDF membrane, revealed by the decrease of water contact angle from 72.93˚ to 56.43˚ along with CA addition. The water flux increased with CA concentration; its value reached 132.95 L/m2 h for blend membranes with 5% CA. Moreover, this composition also exhibited the optimum MB rejection of 90.24%. Furthermore, the improvement of hydrophilicity increased the antifouling properties, indicated by the increase of Flux Recovery Ratio (FRR) from 45-96%, the decrease of irreversible fouling from 60-3%, and the improvement of reversible fouling from 10-55%.