PVDF/palygorskite composite ultrafiltration membranes: Effects of nano-clay particles on membrane structure and properties

Palygorskite (PGS) was incorporated into a polyvinylidene fluoride (PVDF) matrix and PVDF/PGS nanocomposite UF membranes were prepared successfully via a combination of non-solvent-induced phase separation (NIPS) and thermally-induced phase separation (TIPS) processes. The influence of the size of the PGS particles (PGS-L, 450 nm and PGS-S, 302 nm) on the membrane pore structure, morphology, mechanical strength, filtration performance and antifouling property were investigated. The results showed that the PVDF/PGS-S composite membranes had higher porosity and lower overall membrane thickness and skin layer thickness. This directly resulted in better PWF , BSA flux, BSA rejection and FRR for the membranes loaded with PGS-S, when compared with the characteristics of PVDF/PGS-L membranes. Thus, the physical structures are dominant factors in determining the separation performance of PVDF/PGS composite membranes. However, the surface roughness and thermal stability of PVDF/PGS-L membranes were greater than those of PVDF/PGS-S membranes and their surface was also more hydrophilic . Moreover, they exhibited higher mechanical strength owing to stronger binding forces and lower porosity. Thus, the composite properties of PVDF/PGS UF membranes could be adjusted by controlling the scale of the inorganic filler .