The application of the modified PVDF ultrafiltration membranes in further purification of Ginkgo biloba extraction

By using KMnO4 and KOH as oxidant and strong base to facilitate the HF-elimination from polyvinylidene fluoride (PVDF) chain, and polyvinyl pyrrolidone (PVP) aqueous solution as a coating media, the hydrophilic PVDF–PVP ultrafiltration membrane was achieved. The modified membrane was used to further purify the flavonoids from the Ginkgo biloba extraction (GBE) crude product by ultrafiltration, taking advantage of the hydrogen-bond effects between flavonoids and PVP function. Experiments showed that the flux of GBE solution was greatly improved and the flavonoids content in the final product could be purified to 34.8 wt.% from 21.3 wt.% in the GBE crude product, and the mass transfer of flavonoids decreased with increasing pH value of GBE solution. The flux of GBE solution increased linearly at low pressure and approached a steady state at high pressure because of the concentration polarization.