Abstract
In this work, a facile preparation method was proposed to reduce natural organics fouling of hydrophobic membrane via UV grafting polymerization with methacrylic acid (MAAc) and methyl acrylamide (MAAm) as hydrophilic monomers, followed by multihydrogen bond self-assembly. The resulting poly(vinylidene fluoride)-membranes were characterized with respect to monomer ratio, chemical structure and morphology, surface potential, and water contact angle, as well as water flux and organic foulants ultrafiltration property. The results indicated that the optimal membrane modified with a poly(MAAc-co-MAAm) polymer gel layer derived from a 1:1 monomer ratio exhibited superior hydrophilicity and excellent gel layer stability, even after ultrasonic treatment or soaking in acid or alkaline aqueous solution. The initial water contact angle of modified membranes was only 36.6° ± 2.9, and dropped to 0° within 13 s. Moreover, flux recovery rates (FRR) of modified membranes tested by bovine serum albumin (BSA), humic acid (HA), and sodium alginate (SA) solution, respectively, were all above 90% after one-cycle filtration (2 h), significantly higher than that of the pure membrane (70–76%). The total fouling rates (Rt) of the pure membrane for three foulants were as high as 47.8–56.2%, while the Rt values for modified membranes were less than 30.8%. Where Rt of BSA dynamic filtration was merely 10.7%. The membrane designed through grafting a thin-layer hydrophilic hydrogel possessed a robust antifouling property and stability, which offers new insights for applications in pure water treatment or protein purification.
Highlights
Membrane separation technology shows great potential in sewage treatment for its easy operation, energy saving, and environmental friendliness [1,2,3]
The results indicated that the optimal membrane modified with a poly(MAAc-co-methyl acrylamide (MAAm)) polymer gel layer derived from a 1:1 monomer ratio exhibited superior hydrophilicity and excellent gel layer stability, even after ultrasonic treatment or soaking in acid or alkaline aqueous solution
The characteristic peak at 1168 cm−1 was ascribed to C-F stretching modes of Poly(vinylidene fluoride) (PVDF) [33], the peak strength of the modified membranes decreased compared with that of the pure membrane (M0)
Summary
Membrane separation technology shows great potential in sewage treatment for its easy operation, energy saving, and environmental friendliness [1,2,3]. The FRR of the membrane maintained at 99% after four-cycle filtration test, while the Rt was 30% at pH 7.0 It showed long superior stability after ultrasonic 30 min and 7 days pure water filtration tests, which indicated that the gel layer grafted onto membrane surfaces through covalent bonds and its cross-linking structure based on supramolecular self-assembly played key points. The PNAGA hydrogel layer showed relatively high swelling degree for the good hydrophilicity of the double-amide on the side chains, decreasing the pore size and porosity, and reducing water flux dramatically. An antifouling PVDF UF membrane with favorable hydrophilicity and stability was designed and prepared via a facile as well as green process, which was expected to provide new thoughts for designing novel fouling resistant membranes used in the fields of food processing, protein concentration, and drinking water treatment
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