Improving anti-fouling properties of alumina tubular microfiltration membranes through the use of hydrophilic silica nanoparticles for oil/water separation

ABSTRACTIn this study, hydrophilic silica nanoparticles (Si NPs) were used to modify α-alumina tubular membranes to improve their performance in terms of flux, oil rejection, and anti-fouling properties. Our work focuses on enhancing membrane performance, particularly for difficult applications such as produced water treatment. The prepared membranes were applied for oil-in-water emulsion treatment. After coating hydrophilic Si NPs, the oil contact angle improved from 133.8° to 171.4°. To prevent Si NPs from leaching off the surface of α-alumina tubular membranes, polyvinyl alcohol was used to coat the membranes as a pre-treatment step before Si NP modification. After coating the membrane with Si NPs, the roughness of the membrane surface decreased, likely leading to less fouling. After coating Si NPs, Total Organic Carbon rejection increased from 93.1% for pristine α-alumina tubular membranes to 97.7% for silica-modified membranes because of hydrophilic improvements of the modified membranes. The Si NP coating improved the anti-fouling property of membranes with the flux recovery ratio increasing from 71.3% for pristine α-alumina tubular membranes to 85.9% for silica-modified membranes. Scanning Electron Microscopy, Energy-dispersive X-ray spectroscopy, oil contact angle, and Atomic Force Microscopy characterization tests were done. The tests showed successful Si NPs impregnation and altered wettability.KEYWORDS: Oil/Water emulsionmembrane filtrationdip coatinghydrophilicitysilica modification AcknowledgmentsWe want to thank Dr. Imran Shaik for his assistance in measuring the oil contact angles.Disclosure statementNo potential conflict of interest was reported by the author(s).Statement of noveltyThe membrane development technique combines a novel pre-treatment method (using Polyvinyl alcohol) and a silica grafting technique to produce stable fumed silica coatings on membranes. After incorporating the hydrophilic Si NPs, the oil contact angle (OCA) improved from 133.8° to 171.4°. In addition, the surface roughness and associated containment traps on the membrane surface decreased, likely leading to less fouling. Total Organic Carbon (TOC) rejection increased from 93.1% for pristine α-alumina tubular membranes to 97.7% for silica-modified membranes because of hydrophilic improvements of the modified membranes. The Si NP coating improved the anti-fouling properties of membranes as evidenced by the flux recovery ratio increasing from 71.3% for pristine α-alumina tubular membranes to 85.9% for silica-modified membranes. To the best of our knowledge, there are no literature sources reporting the separation of oil and water using α-alumina membranes modified with fumed silica in a continuous cross-flow process.Additional informationFundingThe work was supported by the National Science Foundation under Grant No. OIA-1946093.