Antifouling Ultrafiltration Membranes Research Articles

Antifouling poly(vinylidene fluoride) ultrafiltration membranes containing amphiphilic comb polymer additive

AbstractAn amphiphilic comb polymer consisting of poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) [P(VDF‐co‐CTFE)] main chains and poly(oxyethylene methacrylate) (POEM) side chains was synthesized using direct initiation of the chlorine atoms in CTFE units through atom transfer radical polymerization, as confirmed by 1H NMR and FTIR spectroscopy. The P(VDF‐co‐CTFE)‐g‐POEM comb polymer was introduced as an additive to prepare poly(vinylidene fluoride) antifouling ultrafiltration membranes. As the contents of comb polymer increased, the mechanical properties of membranes slightly decreased due to the decreased crystallinity of the membranes, as revealed by universal testing machine and X‐ray diffraction. However, water contact angle measurement and X‐ray photoelectron spectroscopy showed that the hydrophilic POEM segments spontaneously segregated on the membrane surfaces. As a result, the antifouling property of the membranes containing P(VDF‐co‐CTFE)‐g‐POEM comb polymer was considerably improved with a slight change of water flux. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 183–189, 2010

Preparation of antifouling ultrafiltration membranes with poly(ethylene glycol)- graft-polyacrylonitrile copolymers

Preparation of antifouling ultrafiltration membranes by self-organization with amphiphilic materials is a simple and effective method. A series of amphiphilic poly(ethylene glycol)- graft-polyacrylonitrile (PEG- g-PAN) copolymers with various molecular weights of PEGs were synthesized by water-phase precipitation copolymerization using ceric(IV) ammonium nitrate as an initiator. PEG- g-PAN ultrafiltration membranes were fabricated by phase inversion in a wet process. Scanning electron microscopy (SEM) revealed that PEG- g-PAN membranes have the typical asymmetric structure. X-ray photoelectron spectroscopy (XPS) analysis confirmed the enrichment of PEG segments on PEG- g-PAN membrane surfaces. The surface segregation enhances the hydrophilic property and antifouling ability of PEG- g-PAN membranes. All prepared PEG- g-PAN ultrafiltration membranes have lower BSA adsorption, higher flux for protein solution, higher flux recovery ratio, and lower membrane fouling during protein ultrafiltration in comparison with the control PAN membrane. The excellent antifouling property endows PEG- g-PAN membranes with potential applications in protein separation and purification.

Modification of polyethersulfone ultrafiltration membranes with phosphorylcholine copolymer can remarkably improve the antifouling and permeation properties

The synthesized phosphorylcholine copolymer composed of 2-methacryloyloxyethylphosphorylcholine (MPC) and n-butyl methacrylate (BMA), blended with polyethersulfone (PES), was used to fabricate antifouling ultrafiltration membranes. Water contact angle measurements confirmed that the hydrophilicity of the MPC-modified PES membranes was enhanced to certain extent. X-ray photoelectron spectroscopy (XPS) analysis verified the substantial enrichment of MPC at the surface of the MPC-modified PES membranes. The adsorption experiments indicated that the adsorption amounts of bovine serum albumin (BSA) on the MPC-modified PES membranes were dramatically decreased in comparison with the control PES membrane. Ultrafiltration experiments were carried out to investigate the effect of MPC modification on the antifouling and permeation properties of the PES membranes, it was found that the rejection ratio of BSA was decreased, the flux recovery ratio was remarkably increased, and the degree of irreversible fouling decreased from 0.46 to 0.09. In addition, the MPC-modified PES membranes could run several cycles without substantial flux loss.

Anti-fouling ultrafiltration membrane prepared from polysulfone-graft-methyl acrylate copolymers by UV-induced grafting method

Membrane fouling is one of the most important challenges faced in membrane ultrafiltration operations. The copolymers of polysulfone-graft-methyl acrylate were synthesized by homogeneous photo-initiated graft copolymerization. The variables affecting the degree of grafting, such as the time of UV (Ultraviolet-visible) irradiation and the concentrations of the methyl acrylate and photoinitiator, were investigated. The graft copolymer membranes were prepared by the phase inversion method. The chemical and morphological changes were characterized by attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FT-IR), scanning electron microscopy, and water contact angles measurements. Results revealed that methyl acrylate groups were present on the membranes and the graft degree of methyl acrylate had remarkable effect on the performance of membranes. Pure water contact angle on the membrane surface decreases with the increase of methyl acrylate graft degree, which indicated that the hydrophilicity of graft copolymer membranes was improved. The permeation fluxes of pure water and bovine serum albumin solution were measured to evaluate the antifouling property of graft copolymer membranes, the results of which have shown an enhancement of antifouling property for graft copolymer membranes.

A facile method for synthesis of pegylated polyethersulfone and its application in fabrication of antifouling ultrafiltration membrane

Pegylated polyethersulfone (PES) was readily synthesized via a reaction of chlorosulfonated PES with oligomeric poly(ethylene glycol) (PEG). The pegylated PES materials were then utilized as a hydrophilic modifier for fabrication of PES ultrafiltration membranes. It was found that the surface hydrophilicity of the modified PES ultrafiltration membranes was remarkably enhanced with an increase of pegylated PES content. Liquid porosimetry and protein rejection experiments were jointly carried out to probe the membrane pore size and to further elucidate the permeation and antifouling properties of the membranes. The modified membranes showed superior resistance to bovine serum albumin (BSA) adsorption compared to the unmodified counterparts. Furthermore, ultrafiltration experiments revealed that both pegylated PES and sulfonated PES could enhance the permeation properties of PES membranes, but the pegylated PES reduced BSA fouling in a wider pH range and endowed membranes with better permeation properties. The improved antifouling property rendered the modified membranes longer operation lifespan. After three cycles of BSA solution (1.0 mg/mL) ultrafiltration and simple hydraulic cleaning, the water fluxes of the 2.16 g pegylated PES-modified membranes were still higher than 130 L/(m 2 h).

Antifouling ultrafiltration membrane composed of polyethersulfone and sulfobetaine copolymer

A new random copolymer was synthesized by reacting hydrophilic N, N-dimethyl- N-methacryloxyethyl- N-(3-sulfopropyl) (DMMSA) with hydrophobic butyl methacrylate (BMA) through a conventional radical polymerization. The as-prepared sulfobetaine copolymer (DMMSA–BMA) was blended with polyethersulfone (PES) to fabricate antifouling ultrafiltration membrane for BSA separation. The X-ray photoelectron spectroscopy analysis of blend membranes revealed concentration of sulfobetaine groups at the membrane surfaces that endowed the membrane with higher hydrophilicity and better antifouling property. For the membrane with 8.0 wt% DMMSA–BMA copolymer concentration (No. 5), irreversible fouling has been considerably reduced and the flux recovery rate of the blend membrane reached as high as 82.8%. Furthermore, the blend membrane could effectively resist BSA fouling in a wide pH range from 4.0 to 8.0.

Hydrophilic modification of poly(ether sulfone) ultrafiltration membrane surface by self-assembly of TiO 2 nanoparticles

Membrane fouling is one of the major obstacles for reaching the ultimate goal, which realizes high flux over a prolonged period of ultrafiltration (UF) operation. In this paper, TiO 2 nanoparticles of a quantum size (40 nm or less) in anatase crystal structure were prepared from the controlled hydrolysis of titanium tetraisopropoxide and characterized by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). The hydrophilic modification of poly(ether sulfone) UF membrane was performed by self-assembly of the hydroxyl group of TiO 2 nanoparticle surface and the sulfone group and ether bond in poly(ether sulfone) structure through coordination and hydrogen bond interaction, which was ascertained by X-ray photoelectron spectroscopy (XPS). The morphology and hydrophilicity were characterized by scanning electron microscopy (SEM) and contact angle test, respectively. The composite UF membrane was also characterized in terms of separation behavior for polyethylene glycol-5000 solute. The experimental results show that the composite UF membrane has good separation performance and offers a strong potential for possible use as a new type of anti-fouling UF membrane.