Graphene Oxide@4-(2-Aminoethyl)Benzo-12-Crown-4 Grafted- PVDF/Polyamide nanocomposite for water treatment

Abstract

Separation techniques based on membrane technology are crucial due to high efficiency, good durability, and mechanical stability. The separation process can be enhanced by improving the separation efficiency for heavy metals and hydrocarbons and the surface wettability of membranes. Herein, the dopamine crown ether was first synthesized. ¹H NMR, ¹³C NMR, and ¹⁵N NMR spectra confirmed the formation of dopamine crown ether. This compound was then grafted on the graphene oxide via nucleophilic addition where amine interacted with the epoxy of the graphene. This was achieved by covalent bonding of GO with dopamine crown ether moieties through a chemical grafting reaction. The obtained modified graphene (GO@12-C-4) was then embedded into the polyamide via interfacial polymerization onto the polyvinylidene fluoride (PVDF) membrane support. The polyamide layer (PAm) with nanocomposite of graphene oxide@12-Crown-4 (GO@12-C-4) adjusted the surface of the membrane. The influence of the PAm and GO@12-C-4 on the structure, and morphology of the GO@12-C-4-g- PAm/PVDF membrane was investigated. Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction results indicate the successful preparation. Scanning Electron Microscopy (SEM) was used to evaluate the membrane surface morphology. When it was used in water treatment, the prepared membrane was very stable under an operating pressure of 300 kPa with 23.8 L.m^-2h⁻¹ flux. The membrane showed a rejection of about 99 % for hydrocarbons (pentane, toluene, hexadecane, and isooctane), and over 90 % for the tested heavy metals (lead, cobalt, and strontium). It showed also a good rejection of salts. The results indicated the comparable performance of the reported new membrane compared with those reported in the literature. This study provides new insights into surface transformation to advance PVDF membranes’ flux and separation properties in water purification.