Influence of blending zwitterionic functionalized titanium nanotubes on flux and anti-fouling performance of polyamide nanofiltration membranes

Organic-inorganic hybrid membranes represent an efficient approach to construct membranes with both improved membrane flux and solute selectivity. Zwitterions bearing equimolar number of anions and cations in one monomer unit exhibit excellent anti-fouling characteristics. Based on the exceptional separation performance of hybrid membrane and fouling resistance feature of zwitterions, a novel nanofiltration membrane was fabricated by incorporating zwitterionic functionalized titanium nanotubes (z-TNTs) into polyamide (PA) layer. The special tubular structure of z-TNTs can provide more and shorter internal channels to shorten flow lanes for water molecules. The zwitterionic functionalization on the titanium nanotubes surface improved not only the interfacial compatibility between nano-materials and polymer matrix but also the antifouling performance of membranes. The water flux of membrane prepared with z-TNTs was up to 220 L m(-2) h(-1) MPa-1 while the Na2SO4 rejection remained above 90%. The as-prepared z-TNTs/PA membrane exhibited improved anti-fouling property against protein with a notably reduced flux decline ratio.