PVDF/palygorskite composite ultrafiltration membranes: Effects of nanoclay 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.