Synthesis and Characterization of a Thin-Film Composite Nanofiltration Membrane Based on Polyamide-Cellulose Acetate: Application for Water Purification

Abstract

Membrane separation has been widely used for various applications including microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) processes in the fields of biomedicine, food, and water purification. In this work, a facile synthesis of new polyamide thin-film composite nanofiltration membranes (NF-TFC) for water purification was described. The polyamide thin film was deposed over a synthetic cellulose acetate (CA) support by interfacial polymerization method. 1,3 cyclohexane bis (methylamine) (CHMA) and trimesoyl chloride (TMC) were used as monomers. The membranes were characterized using Scanning Electron Microscopy (SEM), Fourier Transform Infrared spectroscopy (FT-IR), water uptake, porosity, contact angle, water permeability and rejection towards specific salt and dye molecules. The effect of the variation of the CHMA concentration (0.2–2 wt.%) on the morphology, porosity, water permeation and rejection properties of the prepared membranes was studied. SEM results displayed the growth of the membrane thickness when the CHMA concentration increased from 0.2 to 2 wt.%. The strong adhesion between the cellulose acetate substrate and the polyamide layer explained by the formation of the polyamide film in the substrate surface and inside the pores. The water permeability varied from 36.02 to 17.09 L h−1 m−2 bar−1. The salt rejection of Na2SO4 and NaCl increased from 9 to 68% and from 38.41% to 89.4%, respectively, when the CHMA concentration was changed from 0.2 to 2 wt.%. The prepared membranes were further applied successfully for the removal of malachite green and congo red. The results indicated that the maximum rejection reached 89% and 85% for malachite green and congo red, respectively.