Preparation and characterization of novel modified PVDF-HFP/GO/ODS composite hollow fiber membrane for Caspian Sea water desalination

In this Study, a novel modified PVDF-HFP/GO/ODS hollow fiber membrane fabricated by dry/wet jet spinning. The dope solution containing 12 wt% polymer, and different amounts of graphene oxide (GO) nanosheets (0, 1, 3 and 5%) were prepared in NMP as a solvent. Then the composite membranes were silanized using ODS in acidic condition. Various techniques such as SEM, AFM, FTIR, LEP, contact angle (CA) and tensile measurement tests were used to investigate the effects of modifications on the structure, surface chemistry, and performance of the membranes. The modified membrane exhibits a permeation flux of 34.1 +/- 1.1 kg m(-2) h(-1). Furthermore, the contact angle and LEP were increased from 115 degrees +/- 1.5 and 112 +/- 4.5 kPa for PVDF-HFP membrane to 162 degrees +/- 1.7 and 181 +/- 5.3 kPa for modified PVDF-HFP/GO/ODS membrane, respectively. The incorporation of GO in the membrane matrix induces the hierarchy roughness on the membrane surface and provides reactive hydroxyl sites for further chemical modification. Desalination of Caspian Sea water (CSW) was conducted using prepared membranes through direct contact membrane distillation (DCMD). Results showed that salt precipitation and permeation flux reduction partially occurred after 10 days for modified membranes. Finally, the membranes recovered by chemical cleaning in HCI solution (pH = 5).