Effects of PVDF/SiO2 hybrid ultrafiltration membranes by sol–gel method for the concentration of fennel oil in herbal water extract

Abstract

In this paper, organic–inorganic polyvinylidene fluoride (PVDF)/silica (SiO₂) hybrid membranes were prepared via phase inversion by a tetraethoxysilane (TEOS) sol–gel process and were used to concentrate fennel oil in herbal water extract. Such characteristics of the hybrid membranes as crystal structure, mechanical properties, thermal stability, morphology, hydrophilicity, and permeation performance were investigated thoroughly. The analytical results showed that the interaction existed between SiO₂ nanoparticles and PVDF polymers, and that the thermal and mechanical properties of the hybrid membranes were improved by the introduction of SiO₂. Besides, the crystalline structure of PVDF changed from β phase to α phase when TEOS content surpassed 20%. Furthermore, the experimental data indicated that hydrophilicity, permeation, rejection, porosity and mean pore size of the hybrid membranes also increased with ascending TEOS contents, but higher TEOS contents had negative effect on those properties. Finally, the concentration process of fennel oil in herbal water extract through the hybrid membranes was conducted and it proved that the separation performance was effectively improved.