الفهرس 
Literature ReviewOnly 14 pages are availabe for public view
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Abstract
Nanofiltration is extensively used for desalination and water reuse of brackish water, agricultural drainage water, and industrial water recycling. The present study aims at investigating the effects of incorporating silica nanoparticles (NPs) on the morphological and mechanical characteristics of polyamide (PA) coated polyvinylidene fluoride (PVDF) hollow fiber membranes (HFMs) to design tailored membranes for specific applications. Further microwave (MW) irradiation was conducted as a post-treatment intervention for fabricated and loaded PVDF HFMs. Tetraethyl orthosilicate (TEOS) was included as a version of silica loading inside the dope.
Morphological properties studied included scanning electron microscopy (SEM) and atomic force microscopy (AFM) in addition to mechanical properties (break stress, break strain, and Young’s modulus). Additional surface properties, such as membrane porosity, contact angle, and zeta potential have been assessed as well.
Results revealed dimensional stability of the fabricated unloaded and silica NPs incorporated thin-film PVDF HFMs with marked changes in the surface roughness average (Ra) ranging from 28.5 nm to 73 nm. Assessment of relevant mechanical properties indicated a minor to moderate effect on mechanical properties ranging from 38 to 99 MPa for modulus, 30 to 97 MPa for break strain, and 1.85 to 3.29 MPa for break stress. Interestingly, incorporation of silica NPs as well as MW post-treatment decreased the contact angle, 89° to 33.6°, consequently increasing HFMs hydrophilicity. Finally, porosity investigations manifested moderate changes in mean pore diameter with minor changes in membrane total porosity. As far as zeta potential is considered, results indicated increasing surface potential positivity with varying degrees according to pH and silica NPs concentration. On the other hand, the MW post-treatment showed a marked decrease in zeta potential for as spun, coated and silica NPs loaded coated MW post-treated samples.
Finally, empirical correlations for predicting zeta potential in terms of pH and NPs concentration have been developed. These developed correlations have been validated using selected comparable values from published relevant publications. In general, the obtained results allow precise control of membrane characteristics by smart combination of silica NPs loading and MW exposure, allowing improvement extent and efficiency of membrane separation with minimum fouling potential.
Keywords: PVDF, silica nanoparticles, TEOS, Polyamide coating, hollow fiber membranes, thin-film nanocomposites, microwave post-treatment, zeta potential