High-flux PVDF membrane incorporated with β-cyclodextrin modified halloysite nanotubes for dye rejection and Cu (II) removal from water

The application of polyvinylidene fluoride (PVDF) membrane is impeded by its intrinsic hydrophobic property. In this work, a series of novel membranes were fabricated by blending different contents of -cyclodextrin modified halloysite nanotubes (-CD-HNTs) into the casting solution. Elemental mapping images confirmed the good dispersion of -CD-HNTs in the PVDF membrane matrix. The microstructure of membrane was improved as revealed by the morphological characterizations. Besides, the permeation and separation performances of all membranes were extensively studied. The results demonstrated that as-prepared blend membranes exhibited better hydrophilicity, which included lower contact angle and higher water flux than pristine PVDF membrane. In the separation experiments, the dye rejection for the blend membranes was not declined (85%-90%), even though the pore size of membranes was increased with the addition of -CD-HNT nanoparticles. More importantly, because of the chelation reaction between -CD-HNTs and heavy metal, the removal ratio of Cu (II) for 3wt.% content of blend membrane could reach 20.9%, compared with unmodified membrane of 4.2%. After 3 filtration cycles, blend membranes showed superior antifouling property. Overall, this method demonstrated very promising characteristics for removing different scales of pollutants using membrane technology.