Hybrid Ultrafiltration Membranes Research Articles

Polyethersulfone ultrafiltration membrane incorporated with ferric-based metal-organic framework for textile wastewater treatment

• Incorporation of Fe-MOF nanoparticles improved dye rejection of polymeric membrane. • The optimum loading of Fe-MOF for the MMM fabrication is 6 wt%. • The developed MMM is promising for the treatment of textile wastewater. The wastewater discharged from dye-manufacturing industries can pose severe problems to the ecosystem and the use of conventional ultrafiltration (UF) polymeric membrane is still not capable of removing dyes from the wastewater. In this work, hybrid flat sheet mixed matrix membranes were fabricated by blending polyethersulfone (PES) with different weight percentage of ferric-based metal–organic framework (Fe-MOF), aiming to overcome the drawback of PES membrane. Findings revealed that the Fe-MOF/PES membranes attained excellent rejections (>98.5%) for cationic and anionic dyes with its optimum permeation flux as high as 165.68 L/m 2 h, comparable to other reported UF membranes. Moreover, the fouling study conducted using real textile wastewater revealed the potential of the hybrid membrane for reducing the levels of total suspended solid (100% rejection) and chemical oxygen demand (>92%) while exhibiting high flux recovery rate (>90%). These results suggested that the Fe-MOF/PES hybrid UF membrane has great potential for efficient industrial wastewater treatment.

Hybrid ultrafiltration membranes based on PES and MOFs @ carbon quantum dots for improving anti-fouling performance

Metal organic frameworks (MOFs) have raised considerable interest because of their favorable impacts on the performance of water treatment membranes. Herein, the novel nanocomposite based on both nanoporous MOFs and hydrophilic carbon quantum dots (CQDs) was exploited as a novel dopant for the fabrication of PES ultrafiltration (UF) membranes. CQDs were synthesized via pyrolysis of citric acid, and UiO-66-NH2@CQDs were synthesized via the condensation reactions of CQDs and UiO-66-NH2 using EDC and NHS as the condensating agents. The properties of resulting membranes on the porosity, membrane morphology, hydrophilicity, permeability and anti-fouling performance were adequately investigated. The membranes incorporated with UiO-66-NH2@CQDs exhibited significantly improved water flux (up to 358.5 Lm−2h−1), which was ~1.82 times that of pristine PES membrane. Additionally, the BSA rejections rates for the hybrid membranes were all maintained above 95.0%. Furthermore, the hybrid membranes exhibited enhanced anti-fouling performance and the highest flux recovery ratio (FRR) of the hybrid membrane with 0.5% UiO-66-NH2@CQDs reached 77.6%. The membranes incorporated with UiO-66-NH2@CQDs exhibited better permeability and anti-fouling performance than those incorporated with CQDs or UiO-66-NH2. This work reveals that the novel hydrophilic nanofillers combining CQDs and MOFs exhibit great potential for application in water treatment membranes.

Polyethersulfone hybrid ultrafiltration membranes fabricated with polydopamine modified ZnFe2O4 nanocomposites: Applications in humic acid removal and oil/water emulsion separation

This study explored the impact of eco-friendly polydopamine (PDA) coated ZnFe2O4 nanocomposites (PDA@ZnFe2O4 NCs) as nanofillers to fabricate a new class of polyethersulfone (PES) hybrid ultrafiltration (UF) membranes for wastewater treatment applications. The hybrid UF membrane was prepared by incorporating PDA@ZnFe2O4 NCs into PES via the non-solvent induced phase separation (NIPS) process. The PDA@ZnFe2O4 NC was characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Additionally, the morphology and performance of the prepared hybrid membranes were characterized by SEM, contact angle, surface charge, and thermogravimetric analysis (TGA). The incorporation of PDA@ZnFe2O4 NC into the PES membrane affects the porosity, mean pore radius, hydrophilicity, and thermal stability of the developed hybrid membranes. The pure water flux of the PES hybrid membrane with 4 wt% PDA@ZnFe2O4 reached ∼687 L/m2 h, which is about 188% higher than that of the pristine PES membrane. The performance of the PES/ PDA@ZnFe2O4ultrafiltration hybrid membrane was also investigated using humic acid (HA) foulant and oil/water emulsion individually. Compared to the pristine PES and PES/ZnFe2O4 membranes, the developed hybrid membranes showed enhanced permeability and HA foulant removal. HA's removal efficiency has improved from ∼65% in the pristine PES membrane to ∼94% in the 4 wt% PDA@ZnFe2O4 hybrid membrane. The abundant functional groups on the PDA@ZnFe2O4 NC surface also enhanced the separation of the oil/water emulsion (96%). In both the HA and oil/water emulsion separation tests, the flux recovery ratio (FRR) and reversible fouling ratio (Rr) were also significantly improved, suggesting that the PES/PDA@ZnFe2O4 membrane was a very promising candidate for HA removal and treatment of oily wastewater.

Sodium Alginate Modified Hydroxyapatite Nanotubes as a Novel Ecofriendly Additive for Preparation of Polyethersulfone Hybrid Ultrafiltration Membranes

Background:: Hydrophilic nanomaterials have been extensively exploited their applications in the field of hybrid water treatment membranes. However, some of the modification process to nanomaterials may be complicated, and the nonselective pores caused by the poor compatibility between nanoparticles and the polymer matrix impair the rejection efficiency for ultrafiltration application. Thus, it is highly desirable to develop a kind of effective nano dopant with favorable compatibility by a facile way for the preparation of ultrafiltration membranes. Objective:: The aim of this study was to fabricate a novel environmentally friendly and low-cost nano additive with good compatibility for the preparation of ultrafiltration membranes. Methods:: Hydroxyapatite nanotubes were prepared via a biomimetic process, and then SA was coated on the surface of hydroxyapatite nanotubes. Subsequently, a series of hybrid ultrafiltration membranes were fabricated with different amounts of modified HANTs and polyethersulfone (PES). Results:: Exhaustive characterizations were conducted for the membranes, including hydrophilicity, porosity, mean pore size, morphologies and UF performance test. The highest water flux of the hybrid membranes displayed 1.9 times that of the original PES membrane. Meanwhile, the hybrid membrane with 0.2% hydroxyapatite nanotubes obtained elevated antifouling ability, achieving a flux recovery ratio of 85.6%. Conclusion:: The facile coating of SA endowed the nanotubes improved hydrophilicity and meanwhile enhanced the compatibility between PES and HANTs. This work provides a facile way in the construction of green nanofillers and promising results in the preparation of hybrid UF membranes.

Fabrication of novel polyethersulfone (PES) hybrid ultrafiltration membranes with superior permeability and antifouling properties using environmentally friendly sulfonated functionalized polydopamine nanofillers

Developing hybrid ultrafiltration (UF) membranes with high permeability and low fouling tendency is important for a wide range of wastewater treatment applications. Herein, we report the synthesis of novel environmental-friendly sulfonated functionalized polydopamine (SPDA) nanocomposite as a nanofiller for UF membranes. Firstly, mussel-inspired PDA nanoparticles (NPs) were synthesized based on oxidation and self-polymerization of dopamine monomer. PDANPsweresubsequentlysulfonatedwith3-mercapto-1-propanesulfonicacid(athiolwith –SO3H group)throughMichael's addition reaction to produce the SPDA nanofiller. Fourier transform infrared spectroscopy and zeta potential measurements verified the functionalization of the PDA. Hybrid UF membranes were then fabricated via the non-solvent-induced phase separation process (NIPS), using polyethersulfone (PES) as a matrix and SPDA nanofiller at different loading levels (0–4 wt%). The water contact angle values showed an increase in the hydrophilicity of the fabricated UF membranes. The water permeability and antifouling capability of the hybrid UF membranes were dependent on the nanofiller's loading quantity. At 1 bar feed pressure, the pure water flux of the 2 percent SPDA nanofiller membrane was 2.7 times higher than that of the pristine membrane. Foulant solutions have been used to determine the antifouling efficiency of the hybrid membranes using sodium alginate (SA), humic acid (HA) and bovine serum albumin (BSA). The antifouling properties of the PES membranes have been significantly improved by incorporating the SPDA nanofillers in accordance with the foulant rejection and flow recovery ratios. The results indicated that SPDA nanofillers have great potential to improve the permeability and antifouling properties of PES membranes.Capsule: High-flux and antifouling PES hybrid membranes fabricated using environmentally-friendly sulfonated functionalized polydopamine nanofillers.

Fabrication of a hybrid ultrafiltration membrane based on MoS2 modified with dopamine and polyethyleneimine.

The hydrophobicity of ultrafiltration membranes is the main cause of membrane fouling and reduced permeability, so it is necessary to improve the hydrophilicity and anti-fouling performance of ultrafiltration membrane materials. MoS2 nanoparticles that were modified with polydopamine (PDA) and polyethyleneimine (PEI), named MoS2-PDA-PEI, were added to fabricate a polyethersulfone ultrafiltration membrane (PES/MoS2-PDA-PEI) for the first time. The effects of modified MoS2 nanoparticles on membrane performance were clarified. The results indicated that the permeability, rejection, and anti-fouling capability of the hybrid PES/MoS2-PDA-PEI membrane have been improved compared with the pristine PES membrane. When the content of MoS2-PDA-PEI nanoparticles in the membrane is 0.5%, the pure water flux of the hybrid membrane reaches 364.03 L m−2 h−1, and the rejection rate of bovine serum albumin (BSA) and humic acid (HA) is 96.5% and 93.2% respectively. The flux recovery rate of HA reached 97.06%. As expected, the addition of MoS2-PDA-PEI nanoparticles promotes the formation of the porous structure and improves the hydrophilicity of the membrane, thereby improving its antifouling performance.

Combined strategy of blending and surface modification as an effective route to prepare antifouling ultrafiltration membranes

Ultrafiltration (UF) membranes blended with hydrophilic nanomaterials usually exhibit preferable overall performance including the membrane permeability and antifouling capability. However, the improvement in antifouling performance may be not outstanding due to the small amount of nanomaterial distributed near the membrane surface and the limited improvement in membrane hydrophilicity. Notably, excess addition of nanomaterials may lead to the decline in membrane permeability. In order to solve the above problem, we integrated the strategy of blending and surface modification to construct novel hybrid UF membranes. Novel nanohybrid was prepared via tannic acid (TA) coating on hydroxyapatite nanotubes (HANTs) and the subsequent grafting of zwitterionic polyethylenimine (ZPEI). The prepared nanohybrid (HANTs@TA-ZPEI) was incorporated with the polysulfone containing tertiary amine groups to fabricate hybrid membranes via the solution blending and the subsequent immersion-precipitation phase inversion process. Then the matrix was modified with zwitterions via the reaction of tertiary amine group with 1, 3-propane sultone. UF tests were conducted using the bovine serum albumin (BSA) and humic acid (HA) as the representative foulants. Results showed that both the permeability and the antifouling performance of the membranes achieved favorable promotion. Thereinto, the water flux of M-B0.4-Z membrane (pre blended with 0.4 wt% HANTs@TA-ZPEI in the casting solution and post-surface modified) exhibited 2.6 times that of the pristine membrane and the flux recovery ratio (FRR) for BSA and HA attained 93.4% and 96.1%, respectively. By the combination of blending and surface modification, both the membrane permeability and fouling resistant properties could attain remarkable promotion, which exerted the advantages of two methods and made up the deficiency of single blending method.

Fouling resistant, high flux, charge tunable hybrid ultrafiltration membranes using polymer chains grafted graphene oxide for NOM removal

The unprecedented performance of fouling resistant, high flux and high rejection hybrid ultrafiltration polysulfone membranes with charge tunable channels using functionalized polymer chains grafted graphene oxide (SPK-g-GO) nanosheets for natural organic matter removal from aqueous feed is herein reported. The novel SPK-g-GO nanosheets were first prepared by esterification reaction at 55 °C using hydroxylated sulfonated poly(ether ether ketone) and graphene oxide. Then, polysulfone blend hybrid membranes with charge tunable channels were produced via the non-solvent induced phase separation method and optimized by varying the SPK-g-GO concentration from 1 to 8 wt.% in the casting solution. The membranes were characterized using scanning electron microscopy, Raman spectroscopy, atomic force microscopy, surface zeta potential and contact angle measurements. The surface texture and hydrophilicity of the membranes were altered due to the incorporation of SPK-g-GO. The hybrid membrane’s water flux was highly dependent on the amount of SPK-g-GO incorporated within the membrane matrix. The maximum water flux (485.7 L m−2 h−1), obtained using the membrane with 4 wt.% SPK-g-GO, was almost 270% higher than that of the membrane without SPK-g-GO (181.1 L m−2 h−1). The fouling resistance and natural organic matter retention capabilities of the membranes were examined via UF tests of synthetic natural organic matter solution at 1 bar feed pressure and neutral pH. The hybrid membrane with 4 wt.% SPK-g-GO loading exhibited remarkable improvement over the pristine one, rejecting more than 86% of the and recovering ~90% of its initial water flux after washing with a stable retention rate during a long-term filtration test.

Stable zeolitic imidazolate framework-8 supported onto graphene oxide hybrid ultrafiltration membranes with improved fouling resistance and water flux

ZIF-8@GO composites were successfully synthesized through the in-situ growth method and were subsequently employed as fillers in low amounts of 0.1–0.5 wt% in the preparation of polyethersulfone (PES) ultrafiltration (UF) membranes via phase inversion. The use of trimethylamine (TEA) was critical in controlling the ZIF-8 nanoparticle sizes at ca. 30–50 nm with uniform distribution on the GO sheets. The composition and physico-chemical properties of the composites were characterized using Brunauer, Emmett, and Teller (BET), powder X-ray diffraction (pXRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The incorporation of ZIF-8@GO composite improved the surface roughness and resulted in increased hydrophilicity of the PES membranes. Remarkably, the water permeation increased from ~28 (PES) to ~71 (Mh) L m−2h−1 at 100 kPa in the ZIF-8@GO composite membranes. The resultant UF composite membranes exhibited improved fouling resistance with ~90% water flux recovery at high composite loading with the recovery maintained for at least six cycles. The nanocomposites membranes rejected above 80% of Congo red dye through size exclusion mechanism. No other solute rejection mechanisms were observed for the lower molecular weight dyes resulting in their passage through the membranes (>80%) for both negatively and positively charged dyes.

Photo-Fenton assisted self-cleaning hybrid ultrafiltration membranes with high-efficient flux recovery for wastewater remediation

Membrane fouling problems severely hindered the integrated development of membrane technology. Currently, construction of a fouling-resistance membrane was an everlasting and ubiquitous research focus. In this study, β-FeOOH nanorods were anchored onto commercial polysulfone (PSF) ultrafiltration (UF) membranes surface via in-situ mineralization to fabricate an anti-fouling UF membrane for organic and dyes wastewater treatment. The ion-dipole interaction and π-cation interaction between Fe3+ and PSF chains guaranteed β-FeOOH nanorods attaching onto the surface without an intermediate layer. A satisfying flux recovery ratio (93.6% and 94.3%) and a low irreversible fouling ratio (6.4% and 5.9%) for bovine albumin (BSA) and sodium alginate (SA) solutions, respectively, were acquired on account of the photo-Fenton catalytic property and hydrophilicity of nanorods without sacrificing the permeation flux sharply. Importantly, the resultant membrane exhibited a desirable separation performance for various dyes solutions, with high permeation flux (53.6–100.0 L·m−2·h−1·bar−1) and appropriate rejection rates (60.9–92.6%). This work not only improved the anti-organic fouling performance extensively, but also provided a novel insight to decorate the conventional UF membrane surface straightforward without an intermediate layer.

High-Flux, Antifouling Hydrophilized Ultrafiltration Membranes with Tunable Charge Density Combining Sulfonated Poly(ether sulfone) and Aminated Graphene Oxide Nanohybrid.

In this work, a new protocol was developed for creating charge-tuned, hydrophilic hybrid ultrafiltration (UF) membranes with high flux, rejection rate, and fouling resistance. The membranes were fabricated using a combination of sulfonated poly(ether sulfone) (SPES) and aminated graphene (GO-SiO2-NH2) nanohybrid via the non-solvent-induced phase separation (NIPS) method. The GO-SiO2-NH2 nanohybrid was first synthesized using GO nanosheets and 3-aminopropyl triethoxysilane (APTES) through the covalent condensation reaction at 80 °C and was thoroughly characterized. Then, 2-8 wt% of the nanohybrid was incorporated into the matrix of SPES for the fabrication of the hybrid membranes. The resulting membranes were characterized using an electrokinetic analyzer, a contact angle goniometer, and Raman, field emission scanning electron microscopy-energy-dispersive X-ray spectrometry (FESEM-EDX), and atomic force microscopy experiments. The porosity, charge density, and surface morphology were altered, and the hybrid membranes became more hydrophilic after the incorporation of the nanohybrid. The pure water flux of the hybrid membranes systematically increased with the loading amount of the nanohybrid. The pure water flux of the hybrid membrane containing 6 wt% GO-SiO2-NH2 nanohybrid at a 2 bar feed pressure was 537 L m-2 h-1, about 3-fold that of pristine membrane (186 L m-2 h-1). The fouling resistance of the hybrid membranes was evaluated and confirmed using several representative foulants, including bovine serum albumin, humic acid, sodium alginate, and a synthetic solution of natural organic matter (NOM). The fabricated membranes were capable of removing more than 97% of NOM, without a compromise of their rejection rate.

Fabrication of graphene oxide incorporated polyethersulfone hybrid ultrafiltration membranes for humic acid removal

In this study, hybrid polyethersulfone membranes incorporated with graphene oxide were synthesized by a non-solvent induced phase separation approach. The influence of graphene oxide content on the membrane efficiency and fouling durability was elucidated, with emphasis on water flux, natural organic matter (NOM) rejection using humic acid as a model for NOM, and flux reduction due to fouling. The results revealed that the water flux increased with increasing GO content. It is worth noting that the MGO-5 membrane exhibits the highest Jw value (340 L m−2 h−1) among all the fabricated membrane, while the greatest JHA (193.78 L m−2 h−1) value was obtained for MGO-3 membrane. NOM rejection was improved significantly by the incorporation of GO. The best rejection value of HA solution using the membranes was observed for MGO-3 at pH 7. The presence of GO also improved the membrane reusability and antifouling capabilities, due to the enhancement of the hydrophilicity of the GO-membrane surface.

Optimized anti-biofouling performance of bactericides/cellulose nanocrystals composites modified PVDF ultrafiltration membrane for micro-polluted source water purification.

The covalently functionalized cellulose nanocrystal (CNC) composites were synthesized by bonding common bactericides, such as dodecyl dimethyl benzyl ammonium chloride (DDBAC), ZnO and graphene oxide (GO) nanosheets, onto the CNC's surface. Then, the DDBAC/CNC, ZnO/CNC and GO/CNC nanocomposites modified polyvinylidene fluoride (PVDF) ultrafiltration membranes were fabricated by a simple one-step non-solvent induced phase separation (NIPS) process. The resultant hybrid membranes possessed porous and rough surfaces with more finger-like macropores that even extended through the entire cross-section. The hydrophilicity, permeability, antibacterial and antifouling performance and mechanism of the hybrid ultrafiltration membranes were evaluated and compared in detail, aiming at screening a superior hybrid membrane for practical application in micro-polluted source water purification. Among these newly-developed hybrid membranes, GO/CNC/PVDF exhibited an enhanced perm-selectivity with a water flux of 230 L/(m2 h bar) and humic acid rejection of 92%, the improved antibacterial activity (bacteriostasis rate of 93%) and antifouling performance (flux recovery rate (FRR) of >90%) being due to the optimized pore structure, higher surface roughness, incremental hydrophilicity and electronegativity. A lower biofouling level after three weeks' filtration of the actual micro-polluted source water further demonstrated that embedding the hydrophilic and antibacterial GO/CNC nanocomposite into the polymer matrix is an effective strategy to improve membrane anti-biofouling ability.

Preparation and application of zinc oxide/poly(m‐phenylene isophthalamide) hybrid ultrafiltration membranes

ABSTRACTA small molecular‐weight cut‐off (MWCO) of 6000 Da poly(m‐phenylene isophthalamide) (PMIA) embedded zinc oxide (ZnO) hybrid ultrafiltration (UF) membrane was synthesized via nonsolvent‐induced phase separation (NIPS). Tests of field emission scanning electron microscope (FE‐SEM), energy dispersive X‐ray spectroscopy (EDX), atomic force microscopy (AFM), thermal gravimetric analyzer (TGA), Fourier transform infrared (FTIR), capillary flow porometer (CPF), mechanical test, and pure water flux (PWF) for characterization of membranes were carried out. The EDX, FTIR, and TGA indicated the presence of ZnO in the polymer matrix. The hybrid membranes showed enhanced pore density, PWF by the presence of the particles. The contact angle and water flux of modified membrane with 0.03 wt % of nano‐ZnO were 47.7° and 52.58 L·m−2·h−1compared to 71.6° and 36.27 L·m−2·h−1respectively; Compared with the hydrophobic membrane, the PMIA membrane, with hydrophilicity, is supposed to exhibit good antifouling properties. Furthermore, the thermal stability and mechanical properties of the modified membranes were increased. Finally, the hybrid membrane was used in treating papermaking white wastewater and exhibited good separation and high water flux. The great properties of the ultrafiltration PMIA membranes indicate their potential for excellent performance in industrial applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2019,136, 47583.

Fabrication of hybrid ultrafiltration membranes with improved water separation properties by incorporating environmentally friendly taurine modified hydroxyapatite nanotubes

In this work, hydroxyapatite nanotubes (HANTs) were explored as a novel environment-friendly additive for the fabrication of ultrafiltration (UF) membranes. Hydrophilic modification was conducted to the prepared HANTs, which includes the polydopamine (PDA) coating and the following grafting of taurine (TA), a kind of amino acid with -SO3H group. Subsequently, the modified HANTs (HANTs-DA-TA) were mixed with polyethersulfone (PES) to fabricate nanocomposite UF membranes. The prepared membranes were fully characterized, including the porosity, hydrophilicity, membrane morphology, and practical UF capability. The fabricated PES/HANTs-DA-TA membranes exhibited remarkably elevated water flux (up to 439 L m−2 h−1), which was ~2.6 times that of PES membrane (169 L m−2 h−1), whereas the rejection of PES/HANTs-DA-TA membranes was still kept at a high state. The improved flux mainly benefited from the more porous membrane structure, declined skin layer thickness, and the enhanced hydrophilicity. Meanwhile, the PES/HANTs-DA-TA membranes exhibited increased antifouling capability and the highest flux recovery ratio (FRR) reached 77.9% due to the improved surface hydrophilicity. Furthermore, the short rod-like nano hydroxyapatite (HA) was prepared and functionalized the same way as the HANTs-DA-TA. It was found that compared to rod-like HA, the tubular nano HA was more efficient in facilitating the membrane permeation due to the superiority of nanotubular structure. This work reveals that as a novel green additive, the HANTs have great application potential in fabricating water treatment membranes and can be employed for further studies.

PMWCNT/PVDF ultrafiltration membranes with enhanced antifouling properties intensified by electric field for efficient blood purification

Hybrid ultrafiltration membranes of poly(vinylidene fluoride) (PVDF) and poly(ethylene glycol)-multi-walled carbon nanotubes (PMWCNTs) have been prepared via phase inversion method. Compared with pristine PVDF membranes, PMWCNT/PVDF hybrid membranes showed a significant higher water flux (384 L m−2 h−1), more stable rejection rate of bovine serum albumin (BSA) and better antifouling properties because of better hydrophilicity. Besides, the antifouling properties of PMWCNT/PVDF hybrid membranes can be further reduced applying a weak electric field (direct current, about 2 V cm−1). More important, PMWCNTs/PVDF membrane exhibited the lowest hemolysis ratio of 0.4% ever reported, which has improved the hemocompatibility and safety of blood. Moreover, after the introduction of weak electric field, the adhesion of red blood cells is minimized. This study shows that the novel PMWCNT/PVDF hybrid membranes have excellent antifouling ability and hemocompatibility which opens up a new field for the application of PVDF membranes.

Development of a high‐performance polysulfone hybrid ultrafiltration membrane using hydrophilic polymer‐functionalized mesoporous SBA − 15 as filler

ABSTRACTA novel polysulfone hybrid ultrafiltration membrane was developed by blending hydrophilic poly[poly(ethylene glycol) methyl ether methacrylate] [P(PEGMA)] grafted mesoporous SBA‐15 [SBA‐g‐P(PEGMA)] as filler. The hydrophilic SBA‐g‐P(PEGMA) fillers were synthesized via surface‐initiated atom transfer radical polymerization. The effects of the SBA‐g‐P(PEGMA) fillers on the prepared hybrid membranes were systematically investigated. Compared with pristine SBA‐15 fillers, SBA‐g‐P(PEGMA) fillers contributed to higher hydrophilicity and a more developed pore structure in the hybrid membranes. Specifically, SBA‐15 grafted with a moderate P(PEGMA) molecular weight could better preserve the valid open‐ended filler pore structure in the membrane matrix, thus facilitating membrane permeability. The pure water flux of the as‐prepared polysulfone (PSF)/SBA‐g‐P(PEGMA) membrane was three times that of the PSF/SBA‐15 membrane (271.7 L m−2 h−1 vs. 88.2 L m−2 h−1) with similar membrane selectivity. Moreover, the PSF/SBA‐g‐P(PEGMA) membranes showed improved antifouling property. This work paves the way for developing high‐performance hybrid membranes by blending of hydrophilic polymer‐functionalized mesoporous fillers in the future. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47353.

Efficient removal of nickel(II) from high salinity wastewater by a novel PAA/ZIF-8/PVDF hybrid ultrafiltration membrane

Enhanced removal of trace toxic metals (ppm level) from high-salinity wastewater is crucial to ensure water safety but still a challenging task. In this study, we fabricated a new hybrid ultrafiltration membrane (PAA/ZIF-8/PVDF) by immobilizing zeolitic imidazolate framework-8 (ZIF-8) particles onto the surface of trimesoyl chloride (TMC)-modified polyvinylidene fluoride (PVDF) membrane under protection of polyacrylic acid (PAA) layer. The resultant PAA/ZIF-8/PVDF membrane exhibited relatively high water flux of 460 L·m−2 h−1 and outstanding nickel ion (Ni(II)) capacity (219.09 mg/g) from a synthetic high-salinity ([Na+] = 15000 mg/L) wastewater. X-ray photoelectron spectroscopic studies revealed that preferable Ni(II) uptake was mainly attributed to the specific interaction between Ni(II) and hydroxyl groups on ZIF-8 frameworks and carboxyl groups in PAA layer as well. Compared to PAA, ZIF-8 could selectively bind Ni(II) with negligible effect exerted by concentrated sodium ion. The filtration study showed that the 12.56-cm2 membrane could effectively treat 5.76 L high-salinity wastewater ([Ni(II)0 = 2 mg/L, [Na+]0 = 15000 mg/L) to conspicuously reduce Ni(II) below the maximum contaminant level of China, 0.1 mg/L. Moreover, the hybrid membrane could be regenerated by HCl-NaCl solution (pH = 5.5) for repeated use under direct current electric field. Generally speaking, the newly developed ZIF-8 hybrid ultrafiltration membrane showed a very promising potential in enhanced removal of toxic metals from high-salinity wastewater treatment.

The influence of sulfonated hyperbranched polyethersulfone-modified halloysite nanotubes on the compatibility and water separation performance of polyethersulfone hybrid ultrafiltration membranes

Sulfonated hyperbranched polyethersulfone (SHBPES)-modified halloysite nanotubes (HNTs), HNT-SHBPES, were synthesized and mixed with polyethersulfone (PES) to prepare hybrid ultrafiltration (UF) membranes via the phase inversion method. Pure PES and PES hybrid membranes mixed with SHBPES and HNTs were also prepared. The HNT-SHBPES showed good compatibility with the PES membrane matrix, and a series of PES/HNT-SHBPES hybrid membranes offered improved porosity, surface mean pore size, hydrophilicity, permeability, and anti-fouling properties. These were mainly attributed to the synergistic effects of hydrophilic -SO3H of SHBPES, porous HNTs, and the tiny interspace between HNT-SHBPES and PES matrix. When 8% HNT-SHBPES was doped into PES casting solution (MHS–8), its pure water flux reached 351.6 L/m2 h—this was nearly 2.2 times that of the pure PES membrane (M–0); its rejection rate remained high primarily due to the occurrence of delayed phase separation in the solidification process and the good compatibility between HNT-SHBPES and PES matrix. This resulted in a relatively dense, uniform, and defect-free surface. Additionally, bovine serum albumin (BSA) and humic acid (HA) were chosen as model contaminants to evaluate the anti-fouling properties of all prepared membranes. After multi-cycles UF experiments, MHS–8 retained a higher flux recovery rate and rejection rate than the other membranes confirming its excellent anti-fouling properties and stable overall performance. This work offers a new possibility for hyperbranched polymer-modified nanomaterials to enhance their compatibility with membrane matrix and improve membrane separation performance.

Hydrophilic hollow zeolitic imidazolate framework-8 modified ultrafiltration membranes with significantly enhanced water separation properties

Metal-organic frameworks (MOFs) are being intensively investigated for the design of advanced composite membranes, primarily due to their favorable polymer affinity, and highly tunable porous structure and surface properties. However, the development of engineered MOF-based ultrafiltration (UF) membranes for water treatment remains in its infancy. In the present study, hydrophilic hollow zeolitic imidazolate framework-8 (hZIF-8) was meticulously synthesized via surface functionalization-assisted etching approach by using tannic acid (TA), and then incorporated into polysulfone (PSf) casting solution to fabricate novel hybrid UF membranes via phase inversion method. The resultant hZIF-8 not only possessed a highly hydrophilic surface derived from the coated TA but also yielded a unique hollow structure without destroying the intrinsic frameworks. Thanks to the well-tailored surface property and nanostructure of hZIF-8, the obtained PSf/hZIF hybrid UF membranes showed highly improved water permeation (597 L m−2 h−1), which was 2.8 times that of the pristine PSf membrane (210 L m−2 h−1), while well maintaining the rejection property. What's more, the incorporation of hZIF-8 rendered the membrane with enhanced resistance to fouling. These results indicated the great application potential of such MOF/polymer hybrid UF membranes in wastewater treatment and separation in many industrial fields.