Preparation of superhydrophobic nanofiltration membrane by embedding multiwalled carbon nanotube and polydimethylsiloxane in pores of microfiltration membrane

• Superhydrophobic NF membrane was prepared by coating MWCNT/PDMS on PVDF membrane.
• SDS and Triton X-100 surfactants were used for homogenous dispersing of MWCNT.
• Pure water flux was reduced by increasing concentration of PDMS.
• AFM images revealed that the MWCNTs inserted membrane possesses rougher surface.
• The prepared membranes showed high flux recovery ratio and antifouling properties.

In this study, a novel superhydrophobic nanofiltration membrane was fabricated by deposition of multiwalled carbon nanotubes (MWCNTs) on the surface of polyvinylidene fluoride (PVDF) microfiltration membrane followed by polydimethylsiloxane (PDMS) coating. Superhydrophobicity property of the membrane surface diminishes interaction between the feed water solution and membrane surface. This causes a reduction in the fouling tendency and self-cleaning characteristic. The influences of two surfactants of Triton X-100 and SDS as dispersing agents of MWCNTs, and concentration of PDMS coating solution on the membranes permeation flux, morphology and antibiofouling performance were investigated. The membrane structure and characteristic were analyzed using AFM, SEM, contact angle and salt rejection measurements. The pure water flux of the prepared membrane with Triton X-100 was high compared to the SDS dispersed MWCNTs due to low dispersing capability of SDS surfactant and pore blocking of the membrane with agglomerated MWCNTs. The pure water flux was reduced by increasing the concentration of PDMS. SEM images showed that at low concentration of PDMS, MWCNTs are almost vertically oriented on the surface of NF membranes and reasonably coated with PDMS layer. The salt retention sequence was in the range of R (Na2SO4) > R (MgSO4) > R (NaCl). Static adsorption and fouling resistances elucidated using whey as a foulant. The results revealed that the flux recovery ratio for membrane coated with 5 wt.% PDMS was 82%. This shows that the fabricated superhydrophobic NF membrane possesses superior antibiofouling property.

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