Stable zeolitic imidazolate framework-8 supported onto graphene oxide hybrid ultrafiltration membranes with improved fouling resistance and water flux

Abstract

ZIF-8@GO composites were successfully synthesized through the in-situ growth method and were subsequently employed as fillers in low amounts of 0.1–0.5 wt% in the preparation of polyethersulfone (PES) ultrafiltration (UF) membranes via phase inversion. The use of trimethylamine (TEA) was critical in controlling the ZIF-8 nanoparticle sizes at ca. 30–50 nm with uniform distribution on the GO sheets. The composition and physico-chemical properties of the composites were characterized using Brunauer, Emmett, and Teller (BET), powder X-ray diffraction (pXRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The incorporation of ZIF-8@GO composite improved the surface roughness and resulted in increased hydrophilicity of the PES membranes. Remarkably, the water permeation increased from ~28 (PES) to ~71 (Mh) L m−2h−1 at 100 kPa in the ZIF-8@GO composite membranes. The resultant UF composite membranes exhibited improved fouling resistance with ~90% water flux recovery at high composite loading with the recovery maintained for at least six cycles. The nanocomposites membranes rejected above 80% of Congo red dye through size exclusion mechanism. No other solute rejection mechanisms were observed for the lower molecular weight dyes resulting in their passage through the membranes (>80%) for both negatively and positively charged dyes.