Investigating the effects of polypropylene-TiO2 loading on the performance of polysulfone/polyetherimide ultrafiltration membranes for azo dye removal: Experimental and molecular dynamics simulation

This research paper delves into developing and analyzing advanced composite ultrafiltration (UF) membranes specifically tailored for water treatment and dye removal applications. The composite UF membranes were designed using a combination of polysulfone (PSF), polyetherimide (PEI), and polypropylene-80 wt% TiO2 (PPTiO2) to create the active layer, while a flat polyamide (PA) serves as the support material and is prepared via the spin/spray-coating method. Three different PPTiO2 contents were considered, including 5 wt% (M05), 10 wt% (M10), and 15 wt% (M15). The properties of these membranes were characterized using a range of techniques, including Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (NMR), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDX), Atomic Force Microscopy (AFM), contact angle measurements, mechanical testing and zeta potential. Performance evaluation involved filtering Reactive Red 120 (RR120) and Direct Blue 6 (DB6) solutions through the prepared composite membranes at 5 bar and demonstrates that the optimized membrane M15 exhibited remarkable water permeability of 82.13 L.m−2.h−1 bar−1 and maximum dye rejections of 92.82 % and 97.07 % for DB6 and RR120 respectively. Furthermore, molecular dynamics (MD) simulations were conducted to analyze the thermal and structural properties of the membranes. The simulations reveal that increasing the content of PPTiO2 reduced membrane pore size, consequently limiting dye mobility and diffusion. This study is the first-of-its-kind to explore the effect of PPTiO2 content on the membrane (PSF/PEI) properties; the optimized composite UF membrane showcases exceptional water permeability and dye rejection performance, making it a promising candidate for water treatment and dye removal applications.