Polyamide Nanofiltration Membranes with Enhanced Desalination and Antifouling Performance Enabled by Surface Grafting Polyquaternium-7

Abstract

Polyamide nanofiltration (NF) membranes with enhanced desalination and fouling resistance were fabricated via grafting N,N-dimethyl-N-2-propenyl-2-propene-1-ammonium chloride-2-propenamide (polyquaternium-7, PQ7), which consists of dimethyl diallyl ammonium chloride and acrylamide monomers. Compared to the control polyamide NF membrane, the PQ7grafting membrane exhibited higher hydrophilicity, rougher membrane surface, and stronger positive charge. The surface grafting process had no distinct influence on membrane thickness. After modification, the water flux of the resulting membrane improved from 47.8 to 79.6 L m −2 h −1 under 5 bar, showing a significant improvement in permeability. Meanwhile, the rejection to divalent ions was elevated to a superior level due to the introduction of the positively charged quaternary ammonium groups from PQ7. Furthermore, the antifouling evaluation indicated that the modified polyamide NF membrane owed superior flux recovery capacity and fouling resistance to both sodium alginate solution and bovine serum albumin. Owing to the low cost of the surface modifier and facile grafting process, this strategy has wide application potential in fabricating superior NF membranes used for water softening.

Nanofiltration Membranes with Crumpled Polyamide Films: A Critical Review on Mechanisms, Performances, and Environmental Applications

“…Post-treatment is an important step in improving the stability and performance of NF membranes. Because the polyamide layer may have different thermal expansion and contraction coefficients compared with the substrate, a heating post-treatment may lead to delamination and buckling of the polyamide layer at the micro/nanoscale and result in a rough morphology. , Additionally, surface coating and grafting sometimes cause a rough morphology by adding an additional layer or changing the properties of polyamide layers. − Patterning methods can also be used in the post-treatment of the polyamide layer. Because of the thin thickness of the polyamide layer, − the dimension of the pattern is generally tens of nanometers, and previous studies generally used a nanoimprinting method. ,,, After the nanoimprinting of commercial NF membranes, their antifouling performances are significantly improved (see the section “Critical Analysis of Fouling Propensities of Crumpled NF Membranes”).…”

Ionic liquid‐induced deep grafting of polyelectrolyte to reform polyamide layer for antifouling nanofiltration membrane

“…ATR‐FTIR spectrum is employed to prove the occurrence of polymerization and the formation of the PA layer. As evident in Figure 2A, all of the membranes exhibit the characteristic peaks of PIP/TMC‐based semi aromatic PA at 1630 cm −1 , which can be assigned to the tertiary amide group 24 . After post‐treatment with IL‐EtOH, the signal intensity of the tertiary amide group becomes weaker, and the peak shape broadens.…”

“…As evident in Figure 2A, all of the membranes exhibit the characteristic peaks of PIP/TMC-based semi aromatic PA at 1630 cm À1 , which can be assigned to the tertiary amide group. 24 After post-treatment with IL-EtOH, the signal intensity of the tertiary amide group becomes weaker, and the peak shape broadens. Besides that, there is no obvious difference in ATR-FTIR spectra between IP and IP-PEI/IL membranes due to the similar chemical structure.…”

“…[21][22][23] The chemicals containing amine are used to react with them to further control the membrane surface properties, which is essential for the fabrication of NF membranes with precise sieving and strong fouling resistance. [24][25][26] These secondary reactions have commonly been conducted in an aqueous phase, during which hydrolysis of acyl chloride groups also simultaneously occurs with an inevitable impairment to the grafting efficiency and controllability. 27 Such problem can be solved by executing the grafting in organic solvents.…”

Thin-Film Composite Nanofiltration Membrane Modified by Fulvic Acid to Enhance Permeability and Antifouling Performance

“…At present, a typical conventional NF membrane is a thin-film composite (TFC) configuration comprised of a poriferous supporting substrate and a thinnish polyamide (PA) separation layer. , Generally, the PA separation layer is manufactured by the interfacial polymerization (IP) process of acyl chlorides and amines, which mainly controls the rejection capacity and permeability of the NF membrane. − Meanwhile, the porous supporting substrate used for affording a suitable surface and mechanical strength for the generation of the PA layer is a dense asymmetric membrane prepared via the phase inversion method . Recently, the poly­( m -phenylene isophthalamide) (PMIA) substrate has obtained much attention because of its various excellent properties.…”