Investigating the effect of various foulants on the performance of intrinsically superhydrophobic polyvinylidene fluoride membranes for direct contact membrane distillation

Abstract

Conventional water-induced polyvinylidene fluoride (PVDF) hydrophobic membranes for membrane distillation (MD) are highly prone to fouling and wetting by the different foulant constituents present in seawater. This research study was aimed at investigating the effect of various foulants on the performance of intrinsically superhydrophobic PVDF (Super H-PVDF) membrane fabricated by ethanol induced phase inversion. The fouling resistance of three types of PVDF membranes including superhydrophobic PVDF, conventional water-induced PVDF (Conv-PVDF), and commercial PVDF (Com-PVDF) membrane were compared. The effects of organic, inorganic, and bio-foulants were investigated using synthetic and raw seawater in direct contact membrane distillation (DCMD) system. Different membrane characterization tools such as scanning electron microscopy (SEM), atomic force microscope (AFM) and energy-dispersive X-ray (EDX) spectroscopy were used. Results showed that the rate of membrane fouling was insignificant in the Super H-PVDF membrane when compared to both Conv-PVDF and Com-PVDF membranes. Despite the thick layer of silica which was observed on the surface of the Super H-PVDF membrane, higher water flux was reported. The permeate quality remained high, reporting 99.9% rejection with the presence of four foulants when compared to both Conv-PVDF (94–98%) and Com-PVDF (93–97%) membranes. The unique property of intrinsically Super H-PVDF owing to its interconnected fibrous structure along with 80% porosity has resulted in anti-wetting and anti-fouling capacity. The outcomes of this research study demonstrate a great potential for membrane fouling reduction in the field of seawater desalination using MD systems.