Surface modification of polyvinylidene fluoride membranes with ZIF-8 nanoparticles layer using interfacial method for BSA separation and dye removal

In this research, porous polyvinylidene fluoride (PVDF) membranes were prepared by the phase inversion method and coated with ultra-thin zeolitic imidazolate framework-8 (ZIF-8) layer using interfacial synthesis to fabricate an inorganic-organic nanofiltration membrane with good antifouling properties. The ZIF-8 layer was created by interfacial reaction of Zn²⁺ aqueous solution and 2-methylimidazole/n-hexane solution by two steps immersion of the PVDF support in these solutions with different contact times (1, 2, 3, 5 and 8 h). The coated ZIF-8 layer on the surface of membranes was characterized with SEM, EDX, ATR-FTIR and XRD analyses. Effect of the ZIF-8 on membrane hydrophilicity was studied by the water contact angle analysis. Also, water flux, BSA protein solution flux and dye rejection were investigated using a dead-end membrane cell test. The results showed that the membranes flux was significantly increased by modifying the membrane surface by ZIF-8 due to hydrophilicity improvement and formation of special water-pass channels in ZIF-8 layer. With increasing reaction time of interfacial synthesis, the flux decreased due to the increased thickness of the deposited layer. Three types of dyes (Rhodamine B, Reactive Green 19 and Direct Black 38) were applied for rejection test and the fabricated membranes indicated high capability in the dyes solution removal (74%, 82% and 98%, respectively). The ZIF-8 coated membranes presented appropriate antifouling properties.