Enhancing forward osmosis (FO) performance of polyethersulfone/polyamide (PES/PA) thin-film composite membrane via the incorporation of GQDs@UiO-66-NH2 particles

In this study, first, the UiO-66-NH2 metal-organic frameworks (MOFs) were modified with graphene quantum dots (GQDs) to facilitate the water attraction on MOF surface as well as improve their compatibility/affinity with the polyamide layer matrix of forward osmosis (FO) membranes. Next, to fabricate a new type of thin-film nanocomposite (TFN) membranes, the synthesized GQDs@UiO-66-NH2 composites are incorporated into the polyamide (PA) selective layer of FO membranes during the interfacial polymerization reaction of m-phenylenediamine (MPD) and trimesoyl chloride (TMC). The influence of the prepared fillers on the chemical structure, morphology, surface roughness and hydrophilicity of the PA active layer was investigated by FT-IR spectroscopy, powder x-ray diffraction (XRD) patterns, water contact angle (CA) goniometer, field emission scanning electron microscopy (FE-SEM) imaging, energy-dispersive X-ray analysis (EDS) and atomic force microscope (AFM) analysis. Addition of the GQDs@MOF particles altered the water flux and selectivity of the FO membranes, so that, the J(w) for the TFN-0.25 (containing 250 ppm of fillers) in the FO mode was obtained 59.3 LMH using 1 M NaCl as a draw solution and deionized water as feed solution; which was around 102 % greater than with the TFC membrane. At the same time, the selectivity was about 1.5 times those of the control membrane without GQDs@MOF particles, which is one of the most critical goals in membrane designing.