Fluorographite modified PVDF membranes for seawater desalination via direct contact membrane distillation

Membranes with high hydrophobicity are essential for membrane distillation of seawater desalination. A facile surface modification method has been developed to obtain hydrophobic PVDF membranes by depositing fluorographite particles on the membrane surface. The surface hydrophobicity increases with an increase in the number of fluorographite particles on the membrane surface. After the fluorographite modification, the resultant membranes exhibit good wetting resistance and better performance sustainability in direct contact membrane distillation (DCMD) tests using a highly concentrated (10 wt%) sodium chloride solution. The modified PVDF membrane can last about 200 h while the pristine PVDF membrane can only sustain about 70 h. A variety of techniques including field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were applied to examine the effects of the fluorographite modification on surface chemistry and morphology of the derived membranes. This work may provide a facile and useful approach for the hydrophobic modification of MD membranes for seawater desalination.