Fabrication of an antifouling GO-TiO2/PES ultrafiltration membrane

PES ultrafiltration membrane is widely used in various fields due to its high-filtration efficiency. However, due to its hydrophobicity, PES ultrafiltration membrane has poor antifouling performance, this reduced service life and increased industrial cost. Blending is a common method in ultrafiltration membrane hydrophilic modification. Adding a small amount of inorganic nanoparticles into the polymer membrane can improve the properties of the polymer membrane. However, nanoparticles are not uniformly dispersed in polymer membrane, which hindering the modification ability of nanoparticles to ultrafiltration membrane. In this paper, GO-TiO₂ materials were prepared by hydrothermal method, and GO-TiO₂/PES blended ultrafiltration membranes were fabricated by nonsolvent induced phase separation (NIPs). The experimental results show that GO-TiO₂ disperse uniformly in GO-TiO₂/PES ultrafiltration membrane, which greatly improved the antifouling performance of the membrane. When the addition amount of GO-TiO₂ is 0.6%, the water flux of membrane reaches 194.5 (L m⁻² h⁻¹), and the rejection rate of BSA reaches 89.4%. After three pollutions-cycles, the flux recovery rate of the membrane is 90.2%.     

Fabrication of a poly(N‐vinyl‐2‐pyrrolidone) modified macroporous polypropylene membrane via one‐pot reversible‐addition fragmentation chain‐transfer polymerization and click chemistry

In this study, a macroporous polypropylene membrane (MPPM) was grafted with hydrophilic poly(N‐vinyl‐2‐pyrrolidone) (PNVP) based on a one‐pot reversible‐addition fragmentation chain transfer (RAFT) polymerization and click chemistry. First, we prepared the clickable membrane by bromination and following S_N2 nucleophilic substitution reaction; then, click chemistry and RAFT polymerization were performed in one‐pot to graft PNVP to the MPPM surface. The surface characterizations, including attenuated total reflectance/Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and field‐emission scanning electron microscopy, illustrated that PNVP was really grafted onto the MPPM surface. The permeation and antifouling characteristics of the MPPMs were measured by the filtration of a bovine serum albumin dispersion; this showed that in contrast to the nascent membrane, the grafted membrane efficiently obstructed protein molecules because of the compactly grafted polymer chains. The hydrophilicity and antifouling properties of MPPM were greatly ameliorated after modification. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42649.     

Surface modification of UHMWPE/fabric composite membrane via self‐polymerized polydopamine followed by mPEG‐NH2 immobilization

In this work, a novel approach to improve the antifouling properties of membrane surfaces was developed. First, a polydopamine layer was attached onto the surface of an ultrahigh molecular weight polyethylene/fabric composite microporous membrane based on dopamine self‐polymerization and adhesive behavior. Then, methoxy polyethylene glycol amine was covalently bonded with the polydopamine layer via a Schiff base reaction. The physicochemical properties of the modified composite membrane surface were investigated, and the results indicated this modification could effectively enhance the membrane surface hydrophilicity. Furthermore, the protein fouling resistance of both dopamine‐coated and methoxy polyethylene glycol amine immobilized composite membranes was evaluated. It was found that a dopamine coating cannot obviously enhance the membrane antifouling properties due to its strong bioadhesion behavior. However, the antifouling properties of the composite membranes were significantly improved after being immobilized with a methoxy polyethylene glycol amine layer. Consequently, a layer‐by‐layer modified composite membrane with excellent antifouling property was obtained. The pure water flux and flux recovery ratio of the resultant membrane were 764 L m^?2 h^?1 and 83%, respectively. The aim of this paper was to provide an effective approach to optimizing the separation efficiency and antifouling performance of the ultrahigh molecular weight polyethylene/fabric composite membrane. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46428.     

Preparation and characterization of antifouling and antibacterial polysulfone ultrafiltration membranes incorporated with a silver–polydopamine nanohybrid

A silver–polydopamine (Ag–PDA) nanohybird was used to produce polysulfone (PSf) ultrafiltration membranes with excellent antifouling and antibacterial properties. First, the catechol functional groups of polydopamine (PDA) helped with the in situ immobilization of silver (Ag) nanoparticles (<10 nm) on the PDA sphere surface; this led to the formation of the Ag–PDA nanohybrid. Then, Ag–PDA/PSf hybrid membranes were prepared via the phase‐inversion method, and the influence of Ag–PDA loading on the hybrid membrane properties was systematically investigated. When the content of Ag–PDA was 0.5 wt %, the hybrid membrane achieved optimal separation performance, including a dramatically increased pure water flux and a well‐maintained bovine serum albumin rejection. Furthermore, the Ag–PDA/PSf hybrid membranes presented a significantly enhanced protein‐fouling resistance and a good antibacterial activity. These improvements were attributed to the unique structure and properties of the Ag–PDA nanohybrid because of the synergistic effect of the hydrophilic PDA substrate and well‐distributed Ag nanoparticles. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46430.     

Pebax–polydopamine microsphere mixed‐matrix membranes for efficient CO2 separation

Novel facilitated‐transport mixed‐matrix membrane (MMM) were prepared through the incorporation of polydopamine (PDA) microspheres into a poly(amide‐b‐ethylene oxide) (Pebax MH 1657) matrix to separate CO₂–CH₄ gas mixtures. The Pebax–PDA microsphere MMMs were characterized by Fourier transform infrared spectroscopy, scanning electron microcopy, X‐ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. The PDA microspheres acted as an adhesive filler and generated strong interfacial interactions with the polymer matrix; this generated a polymer chain rigidification region near the polymer–filler interface. Polymer chain rigidification usually results in a larger resistance to the transport of gas with a larger molecular diameter and a higher CO₂–CH₄ selectivity. In addition, the surface of PDA microspheres contained larger numbers of amine, imine, and catechol groups; these were beneficial to the improvement of the CO₂ separation performance. Compared with the pristine Pebax membrane, the MMM with a 5 wt % PDA microsphere loading displayed a higher gas permeability and selectivity; their CO₂ permeability and CO₂–CH₄ selectivity were increased by 61 and 60%, respectively, and surpassed the 2008 Robeson upper bound line. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44564.     

High-flux PVDF/PVP nanocomposite ultrafiltration membrane incorporated with graphene oxide nanoribbones with improved antifouling properties

A novel polyvinylidene fluoride (PVDF) nanocomposite membrane containing graphene oxide nanoribbones (GONRs) as a new nanofiller and polyvinylpyrrolidone (PVP) as pore former agent was prepared via phase inversion method. GONRs were prepared by oxidative unzipping of multi-walled carbon nanotubes (MWCNTs) via chemical approach. Chemical vapor deposition method was used to synthesis MWCNTs. The effects of adding GONRs and PVP into the casting solution on morphology, hydrophilicity and pure water flux (PWF) of the prepared nanocomposite membranes were explored. Antifouling experiments were also performed. It was found that compared to the neat PVDF membrane, PWF of the PVDF/PVP, PVDF/(0.5GONRs) and PVDF/(0.5GONRs)/PVP membranes were improved 80%, 44.9%, and 241.6%, respectively. The obtained results showed that GONRs and PVP exhibit synergistic effects in controlling the membrane properties. This work shows that GONRs can be suitable as nanofiller for preparation of high performance PVDF ultrafiltration membranes with improved antifouling properties.     

Preparation and characterization of a poly(vinyl alcohol)/tetraethoxysilane ultrafiltration membrane by a sol–gel method

Using poly(vinyl alcohol) (PVA) with highly hydrophilic properties as membrane material and poly(ethylene glycol) (PEG) as an additive, we prepared PVA/tetraethoxysilane (TEOS) ultrafiltration (UF) membranes with good antifouling properties by a sol–gel method. The PVA/TEOS UF membranes were characterized by X‐ray diffraction patterns, Fourier transform infrared spectroscopy, scanning electron microscopy, and static contact angle of measurement of water. The hybridization of TEOS to PVA for preparing the PVA/TEOS UF membranes achieved the required permeation performance and good antifouling behaviors. The morphology and permeation performance of the PVA/TEOS membranes varied with the different TEOS loadings and PEG contents. The pure water fluxes (J_W) increased and the rejections (Rs) decreased with increasing TEOS loading and PEG content. The PVA/TEOS UF membrane with a PVA/TEOS/PEG/H₂O composition mass ratio of 10/3/4/83 in the dope solution had a J_W of 66.5 L m^?2 h^?1 and an R of 60.3% when we filtered it with 300 ppm of bovine serum albumin aqueous solution at an operational pressure difference of 0.1 MPa. In addition, the filtration and backwashing experiment proved that the PVA/TEOS membranes possessed good long‐term antifouling abilities. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4066–4074, 2013     

Development of antifouling polyamide thin‐film composite membranes modified with amino‐cyclodextrins and diethylamino‐cyclodextrins for water treatment

The fouling behavior of polyamide thin‐film composite (TFC) membranes modified with amino‐ and diethylamino‐cyclodextrins (CDs) through an in situ interfacial polymerization process is reported. Modified polyamide TFC membranes exhibited improved hydrophilicity, water permeability, and fouling resistance as compared to the unmodified TFC membranes, while restricting the passage of NaCl salt (98.46 ± 0.5%). The increase in hydrophilicity was attributed to the secondary and tertiary hydroxyl groups of the CDs, which were not aminated. The membranes modified with amino‐CDs had increased surface roughness while the membranes modified with diethylamino‐CDs had smoother surfaces. However, despite the surface roughness of the membranes modified with amino‐CDs, low fouling was observed due to the highly hydrophilic surfaces, which superseded the roughness. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40109.     

Tris(hydroxymethyl)aminomethane polyamide thin‐film‐composite antifouling reverse osmosis membrane

For the applications of reverse osmosis (RO) process, membrane fouling caused by organic molecule adsorption is still a serious problem which significantly decreases membrane lifespan and increases operation costs. In this present article, we report the thin film composite (TFC) RO membrane functionalized with tris(hydroxymethyl)aminomethane (THAM) using one‐step method for improved antifouling property. The results of surface characterization indicated that THAM was successfully grafted onto the active layer of membrane by covalent linkage. Mult‐hydroxyl‐layer was generated and remained steadily on TFC membrane surface after modification. The contact angle decreased from 75.9 ± 3.0° to 46.9 ± 2.3°, which showed a distinct improvement of membrane surface hydrophilicity after modification. The grafted THAM improved water flux by 28.3%, while salt rejection was almost unchanged in membrane property tests. The modified membranes presented preferable antifouling property to foulants of bovine serum albumin, sodium alginate, and dodecyl trimethyl ammonium bromide than that of pristine membranes during dynamic fouling experiments. The method in this study provided an effective way to improve antifouling property of the polyamide thin‐film‐composite RO membrane. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45891.     

Thin film composite sodium alginate membranes for dehydration of acetic acid and isobutanol

Dehydration of widely used organic solvents such as acetic acid (AA) and isobutanol (IB) is challenging tasks, which form close boiling mixtures with water. Sodium alginate (SA) thin film composite membranes were prepared and crosslinked with 2,4‐toluene diisocyanate (TDI) and glutaraldehyde for dehydration of IB and AA/water mixtures through pervaporation (PV). The crosslinked and uncrosslinked SA composite membranes were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy, and universal testing machine for intermolecular interactions, crystalline nature, thermal stability, surface morphology, and tensile strength, respectively. At a feed composition of 98 wt % IB and 95 wt % AA aqueous solutions, the TDI crosslinked SA composite membrane exhibited separation factors of 3229 and 708 with reasonable fluxes of 0.021 and 0.012 kg m^?2 h^?1, respectively. The results obtained in the study for IB and AA systems were compared with other SA membranes reported in the literature. The membranes appeared to have potential for commercial PV ability to dehydrate the solvents up to desirable purity levels (>99%) and feasibility of preparing them in a composite form which would enable scale‐up into modular configurations. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40018.     

The preparation of SPEEK/phosphate salts membranes and application for CO2/CH4 separation

SPEEK/phosphate salts membranes were prepared and utilized for CO₂/CH₄ separation. SPEEK with abundant –SO₃H groups and EO groups on polymer chains would be beneficial for CO₂ transport. The doped phosphate salts (NaH₂PO₄, Na₂HPO₄ and Na₃PO₄) with different acid‐base properties increased the water content in the membrane, and water was expected to increase both the solubility and diffusivity of CO₂ in the membrane. All membranes were characterized by FTIR, TGA, and XRD. The CO₂ permeability and CO₂/CH₄ selectivity of SPEEK/Na₃PO₄ membranes were higher than that of SPEEK/NaH₂PO₄ and SPEEK/Na₂HPO₄ membranes. Compared to the pure SPEEK membrane, the CO₂ permeability and CO₂/CH₄ selectivity of SPEEK/Na₃PO₄?10 membrane were increased by 144% and 65%, respectively. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43399.     

Recovery of metals and complexant in wastewater by shear induced dissociation coupling with ultrafiltration

Heavy metals (Pb (II), Hg (II), and Cd (II)) in ore dressing wastewater (ODW) were selectively separated by shear-induced dissociation coupling with ultrafiltration (SID-UF) using polyacrylic acid sodium (PAAS) as complexant. Metals (Pb (II), Hg (II), and Cd (II)) were complexed with PAAS and rejected by ultrafiltration membrane at first. The effects of pH and P/M (mass ratio of polymer to metal ions) on the rejection were investigated and the suitable pH and P/M were obtained, at which the rejection arrived at almost 100%. For the recovery of metals and polymer complexant from the retained, the shear stabilities of PAA-metal (PAA-M) complexes were studied, and the critical shear rates of PAA-Pb, PAA-Hg, and PAA-Cd complexes at pH 7.0 were 2.72 × 10,⁵ 2.42 × 10⁵ and 2.01 × 10⁵ s⁻¹, respectively. According to the difference of the critical shear rates of the PAA-M complexes, SID-UF was used to recover Pb (II), Hg (II), Cd (II) and PAAS. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48854.     

Improvement of antifouling performance of poly(l‐lactic acid) membranes through incorporating polyaniline nanoparticles

Poly(l ‐lactic acid) (PLLA) composite membranes were fabricated by nonsolvent induced phase separation method using polyaniline (PANI) as an additive. Membrane structure was characterized by attenuated total reflectance Fourier transform‐infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, porosity, and pore size analysis. Membrane performance was assessed by goniometer, pure water flux, molecular weight cut‐off, static adsorption and dynamic filtration. The incorporation of PANI significantly improved the hydrophilicity and permeability of PLLA composite membrane, and eventually enhanced the antifouling performance of composite membrane compared with pure PLLA membrane. It was demonstrated that PLLA composite membrane with 1 wt % PANI had better separation and antifouling performance compared with other composite membranes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44452.     

Thin film composite forward osmosis membranes with poly(2‐hydroxyethyl methacrylate) grafted nano‐TiO2 as additive in substrate

The poly(2‐hydroxyethyl methacrylate) grafted titanium dioxide nanoparticles were synthesized and added to the substrate of flat‐sheet thin film composite forward osmosis (TFC‐FO) membranes. The hydrophilicity of substrate was improved, which was advantageous to enhance the water flux of TFC‐FO membranes. The membranes containing a 3 wt % TiO₂‐PHEMA in the substrate exhibited a finger‐like structure combined with sponge‐like structure, while those with lower or without TiO₂‐PHEMA content showed fully finger‐like structures. As for FO performance, the TFC‐FO membranes with 3 wt % TiO₂‐PHEMA content achieved the highest water flux of 42.8 LMH and 24.2 LMH against the DI water using 2M NaCl as the draw solution tested under the active layer against draw solution (AL‐DS) mode and active layer against feed solution (AL‐FS) mode, respectively. It was proven that the hydrophilic property of membrane substrates was a strong factor influencing the water flux in FO tests. Furthermore, the structural parameter was remarkably decreased with an increase of TiO₂‐PHEMA content in membrane substrate, indicating the reducing of internal concentration polarization. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43719.     

Enhanced the antifouling and antibacterial performance of PVC/ZnO-CMC nanoparticles ultrafiltration membrane

Inorganic nanoparticles (NPs) have been employed in modification for polyvinyl chloride (PVC) membrane intrinsic hydrophobicity. Carboxymethyl chitosan (CMC), a natural organic matter, was used to relieve the agglomeration of zinc oxide (ZnO) NPs in the membrane matrix. In this paper, ZnO-CMC NPs were successfully prepared via co-precipitation approach, blended with PVC membranes, and the effect of ZnO-CMC NPs for the membrane properties was studied. The SEM and EDX confirmed excellent dispersion of ZnO-CMC NPs on the membrane surface. The enhanced hydrophilicity, porosity and inter-connected finger-like strcture of modified membranes confirmed by water contact angle and SEM. In addition, pure water flux of PVC/ZnO-CMC composite membrane was 107.36 L m⁻² h⁻¹ (PVC/ZnO-CMC (0.25 wt%)), which was higher than that of neat PVC membrane (83.11 L m⁻² h⁻¹). Importantly, the modified membranes exhibits lower static BSA adsorbtion because of the improved hydrophilicity, and a higher flux recovery rate (>90%) after three sequential filtration cycles. The antibacterial behavior of PVC/ZnO-CMC membrane was tested simply using Escherichia coli, and the results indicated that all composite membranes possess excellent antibacterial properties. Our work presents PVC/ZnO-CMC NPs composite membrane a promising future in wastewater treatment and antibacterial application.     

Preparation of composite‐imprinted alumina membrane for effective separation of p‐hydroxybenzonic acid from its isomer using Box–Behnken design–based statistical modeling

Highly selective composite imprinted membrane for p‐hydroxybenzonic acid (p‐HB) was prepared by using semicovalent imprinting technique. A thermally reversible covalent bond was used to link p‐HB molecule to a functional alkoxysilane monomer to generate covalently bound imprint precursor. This precursor was incorporated into a cross‐linked functional silica sol with the tetraethoxysilane as cross‐linker via a typical acid‐catalyzed, sol‐gel synthesis. Then, the SCIM was prepared through dipping and grafting on the upper side and inner pores of the Al₂O₃ microporous membrane and then removing of the template molecule after thermal treatment. Compared with composite imprinted membrane via noncovalent imprinting approach as well as the black Al₂O₃ microporous membrane, the SCIM exhibited higher membrane flux and selective rebinding of p‐HB as well as showing excellent permeability for p‐HB. Response surface methodology was used to investigate the best combination of separation conditions in the dynamic separation process. The optimal conditions for the separation of p‐HB from salicylic acid were as follows: the p‐HB concentration of 5 mg L^?1, the temperature of 10°C, and the flow rate of 1 mL min^?1. Under these conditions, the experimental selective separation factor was 32.75 ± 0.91%, which was close to the predicted selectivity coefficient value. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40621.     

Vacuum membrane distillation simulation of desalination using polypropylene hydrophobic microporous membrane

Numerical simulation is an effective method to get the optimal operating parameters in the chemical engineering process. In this work, the transport mechanism of vacuum membrane distillation (VMD) process was simulated and predicted by mathematical model, which was established based on the convective heat transfer coefficient, and 0.5M aqueous NaCl solution was concentrated with isotactic polypropylene (iPP) hydrophobic microporous membrane prepared via thermally induced phase separation (TIPS) in the VMD process. The as‐presented mathematical model simulated the effects of different operating parameters on the VMD performances for aqueous NaCl solution, such as feed temperature, feed flow rate, absolute pressure of membrane permeate side, temperature coefficient, membrane thickness, and porosity. A comparison between experimental data and simulated data was also considered to verify the proposed mathematical model. Additionally, the salt rejection of aqueous NaCl solution production water in VMD was higher than 99.9%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41632.     

Enhancing antifouling performance of poly(l‐lactide) membranes by TiO2 nanoparticles

Poly(l ‐lactide) (PLLA)/TiO₂ composite membranes were fabricated by immersion precipitation method. The resulting membranes were characterized using various methods including XRD, ATR‐FTIR, TGA, DSC, SEM, goniometer, and molecular weight cut‐off. The antifouling performance of the membrane was investigated through the filtration experiments of the oil/water emulsion. XRD, SEM, and ATR‐FTIR results indicated that TiO₂ was successfully introduced into the membrane, while DSC and TGA indicated the enhancement of thermal stability of membrane. The improvement of membrane hydrophilicity was confirmed by goniometer. In addition, the pore size and porosity on the membrane surface varied obviously with increasing the TiO₂ loading. It was concluded that PLLA/TiO₂ composite membranes had better antifouling and recycling performance compared with the pure PLLA membrane. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43542.     

Fabrication of a pilot scale module of thin film composite hollow fiber membrane for osmotic pressure‐driven processes

Polyamide thin film composite hollow fiber membranes have advantages in their unique structure compared to flat sheet membranes. This study examined interfacial polymerization methods for fabricating pilot scale hollow fiber membranes (membrane area: 1.2 m², number of hollow fiber strands: 1200). For use in osmotic pressure‐driven processes, a one‐pot hydrophilic interfacial polymerization procedure was developed simultaneously to modify the surface property and synthesize polyamide thin film. With the procedure, a pilot scale module has a water flux of 13 LMH using a draw solution of 0.6M NaCl and a feed solution of distilled water through the design of the module configuration. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46110.     

Separation of oil/water emulsions using nano MgO anchored hybrid ultrafiltration membranes for environmental abatement

This work focuses on utilizing the dual role of sulfonated polyphenyl sulfone (SPPSU) as both an anchoring agent and an interlayer modifying agent in the preparation of nano MgO/SPPSU/PPSU membranes for oil removal from water. These asymmetric membranes were prepared using the phase inversion technique. The dispersed nano MgO was observed in the membrane matrix as seen by scanning electron microscope and energy dispersive X‐ray analysis. The reduction in contact angle value establishes the increases in hydrophilicity. An increase in SPPSU (wt %) loosens the nano MgO/SPPSU/PPSU membrane packing as exhibited by the increase of d‐spacing by X‐ray diffraction analysis. The antifouling properties were tested using humic acid, as a model foulant. Further, in castor oil/water emulsion separation, it was found that the membrane with 25 wt % anchored moiety SPPSU/nano MgO produced a greater flux recovery ratio of 94.9% (±0.3) without compromising the oil rejection of 99% (±0.4) and better oleophobic surfaces for oil. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42848.