Carnauba Wax/Halloysite Nanotube with Improved Anti-Wetting and Permeability of Hydrophobic PVDF Membrane via DCMD

The hydrophobic membranes have been widely explored to meet the membrane characteristics for the membrane distillation (MD) process. Inorganic metal oxide nanoparticles have been used to improve the membrane hydrophobicity, but limited studies have used nano clay particles. This study introduces halloysite nanotube (HNT) as an alternative material to synthesis a hydrophobic poly(vinylidene fluoride) (PVDF)-HNT membrane. The PVDF membranes were fabricated using functionalized HNTs (e.g., carnauba wax and 1H,1H,2H,2H-perfluorooctyl-trichlorosilane (FOTS)). The results were determined by Fourier transform infrared-attenuated total reflection, scanning electron microscope, goniometer and porometer to determine the desired hydrophobic membrane for direct contact membrane distillation (DCMD). The addition of FOTS-HNT (f(s)-HNT) and carnauba wax-HNT (f(w)-HNT) in the PVDF membrane enhanced the water contact angle (CA) to 127 degrees and 137 degrees, respectively. The presence of f(w)-HNT in the PVDF membrane exhibited higher liquid entry pressure (LEP) (2.64 bar) compared to f(s)-HNT in the membrane matrix (1.44 bar). The PVDF/f(w)-HNT membrane (Pf(w)-HNT) obtained the highest flux of 7.24 L/m(2)h with 99.9% salt removal. A stable permeability in the Pf(w)-HNT membrane was obtained throughout 16 h of DCMD. The incorporation of f(w)-HNT in the PVDF membrane had improved the anti-wetting properties and the membrane performance with the anti-fouling effect.

Automated summary

The study introduces the use of halloysite nanotubes (HNT) to synthesize a hydrophobic poly(vinylidene fluoride) (PVDF) membrane, which has shown enhanced water contact angle and liquid entry pressure. The PVDF membrane with functionalized HNTs exhibited improved membrane performance, anti-wetting properties, and anti-fouling effect in direct contact membrane distillation (DCMD) process.