PVDF/palygorskite composite ultrafiltration membranes with enhanced abrasion resistance and flux

The anti-wearing property is important to the lifetime of membranes especially when they are used in heavy-duty water treatment, where the content of suspended solid is often high. Abrasion-resistant membranes are expected to have prolonged lifetimes and reduce considerably the maintenance cost of water treatment plants. In this research, palygorskite (PGS), a natural abundant nano rod-like clay material with hydrophilic properties and excellent mechanical strength, was used as the reinforcement filler in poly(vinylidene fluoride) (PVDF) ultrafiltration membranes to improve the anti-wearing property. The prepared membranes were subjected to a series of characterisations to investigate membrane structure, surface hydrophilicity, filtration performance and mechanical strength. A simple, quantitative methodology was also proposed to assess the abrasion resistance of the membranes, aiming to establish a feasible and reliable testing protocol in the laboratory. It is found that the PGS readily improves tensile strength, Young's modulus and the abrasion resistance to SiC particles, whilst the permeability of the membranes increases without sacrificing selectivity. Particularly, the addition of 10% PGS leads to a drastic increase in abrasion resistance, with the abrasion rate reduced to 1/170 of the unreinforced membrane, which could be attributed to the transition of abrasion from a ductile manner to a brittle manner. Moreover, the 10% PGS reinforced membrane shows increased permeation flux from 106.1 L/m2h to 282.5 L/m2h, and the dextran molecular weight cut-off (MWCO) was maintained at a level of 150-200 kDa.