Anti-fouling properties of poly(acrylic acid) grafted ultrafiltration membranes - experimental and theoretical study

Grafting of ultrafiltration membranes with polyelectrolyte chains is considered as an anti-fouling treatment. In this research, grafting of poly(acrylic acid) chains to the surface of polypropylene ultrafiltration membrane was obtained by a Fenton-type reaction. Due to the surface modification treatment, we observe a decrease of susceptibility to particulate fouling of the modified membranes. The improvement of membrane properties is observed as a decrease of silica deposited on the surface of membranes in a given time of ultrafiltration process. This effect is exceptionally visible at high pH of filtered suspension. The experimental results have been supported by the numerical modeling of dynamics of polyelectrolyte chain anchored to the membrane surface. This model (based on coarse grained molecular dynamics) allowed us to obtain the dependence of the repulsive force between the membrane and particle on their distance. Considering the value of this force, together with the classical DLVO interactions (van der Waals force, electric double layer force) we were able to predict the stability of suspension in the vicinity of the membrane surface and thus the susceptibility of membrane to fouling.