Abstract
Mixed-matrix membranes (MMMs) were developed by impregnating organofunctionalized nanoadditives within fouling-susceptible polysulfone matrix following the non-solvent induced phase separation (NIPS) method. The facile functionalization of nanoparticles of anatase TiO2 (nano-TiO2) by using two different organoligands, viz. Tiron and chromotropic acid, was carried out to obtain organofunctionalized nanoadditives, FT-nano-TiO2 and FC-nano-TiO2, respectively. The structural features of nanoadditives were evaluated by X-ray diffraction, X-ray photoelectron spectroscopy, Raman and Fourier transform infrared spectroscopy, which established that Tiron leads to the blending of chelating and bridging bidentate geometries for FT-nano-TiO2, whereas chromotropic acid produces bridging bidentate as well as monodentate geometries for FC-nano-TiO2. The surface chemistry of the studied membranes, polysulfone (Psf): FT-nano-TiO2 UF and Psf: FC-nano-TiO2 UF, was profoundly influenced by the benign distributions of the nanoadditives enriched with distinctly charged sites (), as evidenced by superior morphology, improved topography, enhanced surface hydrophilicity and altered electrokinetic features. The membranes exhibited enhanced solvent throughputs, viz. 3500–4000 and 3400–4300 LMD at 1 bar of transmembrane pressure, without significant compromise in their rejection attributes. The flux recovery ratios and fouling resistive behaviours of MMMs towards bovine serum albumin indicated that the nanoadditives could impart stable and appreciable antifouling activity, potentially aiding in a sustainable ultrafiltration performance.
Highlights
The daunting task and challenge of providing adequate and safe drinking water becomes complicated by progressive contamination of accessible freshwater resources with newer contaminants owing to population growth, industrialization and, more importantly, climate change and energy demand
The X-ray diffraction (XRD) pattern depicted in figure 2a reveals the presence of a strong diffraction peak at 25.3° (FWHM: 0.6561), indexed to (101) plane diffraction and a few successive peaks with lower intensities at 37.8°, 48.1°, 54.2°, 55.2°, 62.6°, 68.9°, 70.1° and 75.1°, which are indexed to the (004), (200), (105), (211), (204), (116), (220) and (215) plane diffractions, respectively, and can be attributed to the anatase phase of FT-nano-TiO2
In the XRD pattern shown in figure 2b, an intense diffraction peak appears at 25.3° (FWHM: 0.7071) followed by a few peaks of lower intensities appearing at 37.9°, 48.1°, 54.3°, 55.1°, 62.6°, 68.8°, 70.3° and 75.2° that are indexed to the (101) and (004), (200), (105), (211), (204), (116), (220) and (215) plane diffractions, respectively, and can be attributed to the anatase phase of FC-nano-TiO2 [40]
Summary
The daunting task and challenge of providing adequate and safe drinking water becomes complicated by progressive contamination of accessible freshwater resources with newer contaminants owing to population growth, industrialization and, more importantly, climate change and energy demand. Membrane-based water treatment technologies outweigh all other conventional and competitive methods in terms of energy footprint, no chemical regenerants necessary, requirement of less space, possibility of continuous operation, environmental friendliness, scalability and product water quality This involves application of pressure-driven membranes, e.g. ultrafiltration (UF), nanofiltration and reverse osmosis or a combination thereof based on the nature of industrial effluents in context. The polymeric UF membranes made of polysulfone (Psf), polyethersulfone (PES) and polyvinylidene fluoride (PVDF) undergo persistent deterioration of permeability and selectivity by fouling, which is an impact of a prolonged exposure to influent raw water streams [1,2,3] These polymeric membranes are widely used in filtration industries owing to their good mechanical, thermal and chemical stabilities as well as amendable morphologies. We attempted to obtain superior physico-chemical features of the membrane matrix through impregnating the surface-tailored nano-TiO2 above and beyond the pristine nanoparticles. The variations in the UF performance and antifouling activity of the membranes were addressed to justify our approach towards superior industrial applications
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