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It is urgent to develop functional nanocarriers for targeted drug therapy of cancer. This work developed a smart drug controlled release system based on the dendritic mesoporous silica nanoparticle (DMSN) for dual gatekeepers drug delivery. The DMSN-Cys grafted with disulfide bonds appeared as spheres of uniform size with a porous structure, which enabled a drug loading efficiency of 68.32%. Since the protonated amino groups of chitosan were responsive to pH and the disulfide bonds were sensitive to glutathione, the modified 5-Fu@DMSN-Cys/CS can be used for pH/GSH responsive drug delivery. Release behaviors showed excellent drug controlled release effects. Good biocompatibility and pronounced cytotoxicity of 5-Fu@DMSN-Cys/CS were confirmed by cytotoxicity test. Noted specially, the microcosmic adsorption interaction between drug molecules and DMSN-Cys has been evaluated through molecular dynamic simulation. Electrostatic potential and adsorption simulation confirmed that the driving force of 5-Fu adsorption was originated from electrostatic force and hydrogen bonding interaction between the nanocarriers and 5-Fu molecules. These results indicated that 5-Fu@DMSN-Cys/CS could be potential carriers for anticancer drug delivery. [ABSTRACT FROM AUTHOR]

High concentrations of fluoride in drinking water can lead to fluorosis of teeth and bones and other serious diseases, while nanofiltration is an attractive technique for fluoride removal. Interfacial temperature can determine the monomer diffusion rate in interfacial polymerization (IP) process, thereby tuning the structure of membrane such as thickness, pore size and surface charge. Herein, a fully‐aromatic polyamide nanofiltration membrane with desirable separation performance was customized by interface temperature. The resulting membrane exhibits a flux of 6 L m−2 h−1 bar−1 and the molecular weight cut‐off is 211 Da, most importantly, a 90.3% F− rejection to underground water, indicating that the membrane has application potential in underground water treatment. This work helps to better understand the effects of interface temperature on the IP process and provides a new strategy to address the drinking water problem. [ABSTRACT FROM AUTHOR]

A trade‐off behavior is noteworthy between protein rejection and pure water flux (PWF) for ultrafiltration membranes; it is recommendable to increase flux without reducing selectivity. The poly (meta‐phenylene isophthalamide) (PMIA) ultrafiltration membrane was modified via incorporating 1,3,5‐benzene tricarboxylic chloride (TMC) to optimize the performance for the first time. Molecular dynamics (MD) simulation was applied to probe the mechanism of the effects of the concentrations of cosolvent LiCl and addition TMC on the dissolving process. It was turned out that a suitable concentration of TMC in the dope solution markedly enhanced the PWF (from 276.22 to 566.20 m−2 h−1 bar−1) with an increasing bovine serum albumin rejection (from 92.05% to 94.64%). Besides, the optimized membrane also possesses excellent anti‐fouling and mechanical performance. These improvements can be due to the crosslinking between PMIA and TMC and enlarged average pore diameter. This work broadens the application of PMIA and TMC in ultrafiltration and provides a novel methodology for PMIA modification. [ABSTRACT FROM AUTHOR]

Atomic layer deposition (ALD) has been a promising technique in fabricating membranes and tuning their properties with a precision at the atomic level. Fabrication of zeolitic imidazolate framework (ZIF) membranes using the ligand‐induced permselectivation (LIPS) method starts with the formation of an oxide in a mesoporous substrate by ALD and is followed by the transformation of this oxide to ZIF using imidazolate vapor treatment. The objective of the ALD step is to block the mesopores with a thin deposit, that is, one with small penetration depth and small thickness on the top surface of the substrate. Unlike typical ALD on nonporous substrates, where all available sites react per ALD cycle, thin deposit formation in a mesoporous substrate requires that only a small fraction of the available deposition sites (i.e., close to the substrate surface) is subjected to ALD. Consequently, reactant dosing and duration of pulses are important process variables which, together with diffusion and reaction kinetics determine the deposit structure. Quantitative understanding of the interplay of these variables and phenomena can enable the rational design of ALD within mesoporous substrates. Here, we extend our earlier modeling effort considering the coexistence of ALD both inside the pores and on the external surface of the substrate. Finite‐volume based models were developed and validated to simulate the two distinct modes of deposition cycle by cycle. The total mass uptake of the substrate with ALD cycles can be predicted using the combined surface deposition and pore reaction–diffusion models as affirmed by in situ quartz crystal microbalance experimental data. The ALD reactor model combined with the deposition model can accurately capture the number of ALD cycles needed to block the pores of the substrate. Based on the model, we designed a modified ALD process and examined the performance of the corresponding LIPS membranes. The present modeling work provides a new understanding of the deposit formation via ALD within mesoporous substrates for a variety of membrane applications. [ABSTRACT FROM AUTHOR]

Drawing self-cleaning technology into polymer membranes offers an extensive solution to overcome the membrane fouling obstacle. Herein, the GO-ZnO-Ag nano-hybrid particles with photocatalytic activity prepared via the microwave hydrothermal method were immobilized in poly(m-phenylene isophthalamide) (PMIA) membranes. Not only was the thorny issue in catalyst recovery avoided, but also the satisfactory photocatalytic self-cleaning performance of the polymer membrane was awarded. GO and noble metal silver nanoparticles (AgNPs) acted as a conductive electron transfer carrier and an electron host, respectively, which hindered the recombination rate of excited electrons and holes on ZnO under UV light. The UV-driven PMIA membrane photodegradation rates of MB and Cr(VI) were up to 97.2% and 94.3%, respectively, at 150 min on photodegradation kinetics. Also, MB was completely degraded at 180 min. For MB and Cr(VI) mix solutions, their degradation efficiencies were 78.1% and 71%, respectively. The BSA rejection rate of the modified polymer membrane was 93.8%, and the water flux was 408.8 (L·m−2·h−1). Permeability was maintained at a high level after repeated use. Therefore, the newly designed PMIA/GO-ZnO-Ag series membranes could expand the application of polymers in wastewater disposal industry. [ABSTRACT FROM AUTHOR]

ZnO deposition in porous γ‐Al2O3 via atomic layer deposition (ALD) is the critical first step for the fabrication of zeolitic imidazolate framework membranes using the ligand‐induced perm‐selectivation process (Science, 361 (2018), 1008–1011). A detailed computational fluid dynamics (CFD) model of the ALD reactor is developed using a finite‐volume‐based code and validated. It accounts for the transport processes within the feeding system and reaction chamber. The simulated precursor spatiotemporal profiles assuming no ALD reaction were used as boundary conditions in modeling diethylzinc reaction/diffusion in porous γ‐Al2O3, the predictions of which agreed with experimental electron microscopy measurements. Further simulations confirmed that the present deposition flux is much less than the upper limit of flux, below which the decoupling of reactor/substrate is an accurate assumption. The modeling approach demonstrated here allows for the design of ALD processes for thin‐film membrane formation including the synthesis of metal–organic framework membranes. [ABSTRACT FROM AUTHOR]

Imidazolate-based ZIF-8 catalysts M@ZIF-8 (M = Au NR, Au@Ag NR, or Au@PtAg NRT; NR = nanorod, NRT = nanorattle), were assembled. Au NRs acted as the core for the epitaxial growth of the Ag shell, and oxidative etching of Au@Ag NRs led to Au@PtAg NRTs with K2PtCl4 aqueous solution. All metal nanorods (MNRs) and metal nanorattles (MNRTs) were well dispersed and fully encapsulated in ZIF-8. Au@PtAg NRTs encapsulated in ZIF-8 could lead to enhanced stability and selectivity for catalytic applications, combining the advantages of ZIF-8 (tailorable porosity) with the high surface area and improved optical sensitivity of rod-shaped NRTs. The catalyst Au@PtAg@ZIF-8 exhibited efficient catalytic activity and CO selectivity for the gas-phase photoreduction of CO2 with H2O. [ABSTRACT FROM AUTHOR]

Transient simulation of filtration in hollow‐fiber membranes with nonuniform permeability distribution was conducted. The diversity of permeability distributions caused different initial flux and transmembrane pressure distributions. Manipulating the permeability distribution enables a hollow‐fiber membrane to achieve its maximum volumetric flow rate. During solid‐liquid separation, the inter‐adjustment between flux and cake distributions improved their uniformities simultaneously. The reciprocal of the volumetric flow rate of the membranes all increased linearly with water production. Severely nonuniform permeability distribution caused low water production. The numerical results could be applicable to account for the non‐ideal performance of industrial hollow‐fiber membrane modules. Despite its great significance, membrane engineering receives less attention than the membrane materials. Herein, the focus is on evaluating the time‐dependent filtration process in hollow‐fiber membranes (HFM) with various kinds of nonuniform permeability distributions. New understanding of fluid flow and fouling behavior in the HFM system is proposed. [ABSTRACT FROM AUTHOR]

ABSTRACT: In a previous study, we proved that tailoring the polyamide backbone stiffness is an effective way to fabricate high‐performance polyamide nanofiltration (NF) membranes. However, in the previous study, we mainly focused on the flat membrane and did not consider its chlorine tolerance. In this study, by regulating the aqueous‐phase compositions in the interfacial polymerization process, chlorine tolerance on NF hollow‐fiber membranes was endowed while the membrane performance stayed high. The experimental results show that when the ratio of Piperazine (PIP)–bisphenol F (BPF)/2,2′‐bis(1‐hydroxyl‐1‐trifluoromethyl‐2,2,2‐triflutoethyl)‐4,4′‐methylene dianiline (BHTTM) was 5:1:4, the NF membrane possessed a permeate flux of 21.0 L m−2 h−1 bar−1 and an Na2SO4 rejection up to 90.0%. X‐ray photoelectron spectroscopy analysis also confirmed that the polymerization degree of the PIP–BPF–BHTTM NF membrane was the highest. Moreover, the NF membrane could tolerate active chlorine to over 10,000 ppm h Cl. After the active chlorine treatment, the permeate flux increased over 30.0 L m−2 h−1 bar−1, and the Na2SO4 rejection was about 90.0%. Although the PIP–BHTTM NF membrane also possessed good chlorine tolerance, its permeate flux (after active chlorine treatment) was only 60% of that of the PIP–BPF–BHTTM NF membrane. Therefore, the PIP–BPF–BHTTM NF membrane possessed a combination of high flux and high chlorine tolerance and showed good potential in water treatment in rigorous environments. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46482. [ABSTRACT FROM AUTHOR]

Firstly, preparation of porous polyvinyl alcohol (PVA) spheres were investigated in detail by phase inversion method using N,N-dimethylacetamide (DMAc) and polyvinylpyrrolidone (PVP) as pore-forming additives. The morphology and pore structure of PVA spheres were characterized by SEM and BET measurements. It was found that the addition of DMAc and PVP increased the pore volume and the surface pore size of PVA sphere respectively. The maximum surface area of the porous PVA sphere reached 220 m2/g. Secondly; the synthesis of photoactive TiO2 NPs (anatase type) at the low temperature was developed by controlling the aging process of the TiO2 precursors. The crystallinity and photoactivity of TiO2 NPs increased with the aging time. Finally, TiO2 NPs/PVA composite spheres were prepared by immersing PVA sphere into TiO2 precursor solution. Their structures were characterized by XRD pattern, TEM and TGA measurement. It was found that TiO2 NPs were successfully immobilized into PVA spheres. The photodegradation of methyl orange (MO) under UV light by TiO2/PVA spheres showed a good photocatalytic efficiency. Moreover, TiO2/PVA spheres can be easily regenerated by the repeated immersion process. Overall, the porous TiO2/PVA sphere displays a good photoactive property and an advantage of easier recovery, which facilitates its application in large-scale wastewater treatment. [ABSTRACT FROM AUTHOR]

A novel three‐dimensional CFD model has been developed on the basis of fluid flow in the shell and lumen sides, and permeation and fouling behavior in the porous membrane zone. The simulated 25‐min dead‐end outside‐in filtration process showed that the energy consumed by the inlet manifold decreases during the constant pressure filtration. The velocity and pressure distributions in the module change with time. Flux distribution both in the axial and radial directions becomes increasingly more uniform, so does the cake distribution. Flux distribution and cake distribution inter‐adjust each other in different modes. A correlation equation has been developed to describe the relationship between the volumetric flow rate and accumulated water production. The correlation equation with simple experiment enables the dynamic evolution of energy consumed by shell inlet manifold to be presented, which can be the criterion of how well the shell inlet manifold or module has been designed. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2655–2669, 2018 [ABSTRACT FROM AUTHOR]

The blend polyethersulfone (PES)/cellulose acetate (CA) flat‐sheet microporous membranes were prepared by reverse thermally induced phase separation (RTIPS) process. The effects of CA content and coagulation bath temperature on membrane structures and properties were investigated in terms of membrane morphology, water contact angle, permeation performance, and mechanical properties. The cloud point results indicated that the cloud point decreased with the increasing content of CA. When the coagulation bath temperature was lower than the cloud point, the membrane formation process underwent nonsolvent induced phase separation (NIPS) process and dense skin layer and finger‐like structure were formed in membranes. These membranes had lower pure water flux and poor mechanical properties. But when the coagulation bath temperature was higher than the cloud point, the membrane formation process underwent RTIPS process. The porous top surface as well as porous cross‐section of the membranes were formed. Therefore, high pure water flux and good mechanical properties were obtained. The contact angles results indicated that the hydrophilicity of the prepared membranes improved obviously with the addition of CA. When the content of CA was 0.5 wt% and the membrane formation temperature was 323K, the PES/CA microporous membrane which was prepared via the RTIPS process displayed a optimal permeability of the pure water flux of 816 L m−2 h−1 and the BSA rejection rate of 49.5%, which showed an increase of 48.9% and 23.6% than that of pure PES membrane, respectively. Moreover, the mechanical strengths of the membranes obtained by RTIPS process were better than those membranes prepared by NIPS process. POLYM. ENG. SCI., 58:180–191, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

A new metal–organic framework (MOF), [Zn(ATA)(bpd)]∝ (1Zn) (ATA: 2‐aminoterephthalic acid; bpd: 1,4‐bis(4‐pyridyl)‐2,3‐diaza‐1,3‐butadiene), exhibiting a three‐dimensional extended porous structure was successfully assembled in a MeOH–H2O solvent system. Under various controlled conditions, 1Zn was obtained in a variety of morphologies such as microspheres, microblocks, microsheets, microplates and microrods. The catalytic performance of the 1Zn microsized MOF was evaluated, and a possible catalytic mechanism was proposed. The flexibility of this MOF assembly strategy for shape control will certainly enhance new potential applications of micro−/nano−MOFs. [ABSTRACT FROM AUTHOR]

The hydrophilic modification of poly (vinylidene fluoride) (PVDF) membrane with poly (ethylene glycol) dimethacrylate (PEGDMA) through grafting reaction for antifouling was reported. The influence of PEGDMA content, reaction temperature and time, on the structure, morphology, antifouling, and hydrophilicity of PVDF-g-PEGDMA membrane has been investigated. The PEGDMA monomers that were grafted on the surface of PVDF microfiltration membrane were confirmed by Attenuation total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS), and morphology study conducted by SEM revealed the changes before and after modification. The protein adsorption, filtration performance, water content, and dynamic contact angle were used to characterize the antifouling and hydrophilicity of the modified PVDF membranes. Compared with the pristine PVDF membrane, the bovine serum albumin (BSA) adsorption on the PVDF-g-PEGDMA membrane decreased about 80%, and the water contact angle of the membrane dropped to 0°. Besides, the experimental results revealed no significant differences between the membrane samples with respect to pore size. [ABSTRACT FROM PUBLISHER]

A new metal-organic framework (MOF), {Zn(oba)(3-bpdh)0.5}∝⋅2 H2O (1 Zn; oba=4,4'-oxybis(benzoic acid), 3-bpdh=N,N'-bis(1-pyridine-3-yl-ethylidene)hydrazine), was successfully assembled in a solvothermal system. The Zn2+ ion center located in a five-coordinate environment combined with oba to produce a layer-like structure, which is again linked with 3-bpdh to yield a 3D channel framework. MOF 1 Zn microcrystals with different morphologies were synthesized through coordination modulation and solvent-dependent methods. The effects of the concentration of the modulator, the reaction temperature, and the volume ratio of mixed solvents have been investigated. Furthermore, the catalytic performance in Knoevenagel condensation was studied for different morphologies of 1 Zn microcrystals; this revealed that the MOF microcrystals exhibited excellent and morphology-dependent catalytic properties. [ABSTRACT FROM AUTHOR]

Herein, electrospinnability of perfluorosulfonic acid (PFSA)–polyvinylidene fluoride (PVDF) blends with different ratios of PVDF were investigated in detail. A well-formed nanofiber structure can be obtained only when the minimum ratio of PVDF in the blend reaches 9%. The reason was explained by the change in the properties, such as viscosity, conductivity, and surface tension, and interconnected aggregates in the blend solutions as revealed by dynamic light scattering (DLS) and the viscoelasticity behavior. After this, the property and morphology of the PFSA–PVDF nanofibers were investigated. SEM images showed that the average diameter of the nanofibers ranged from 75 to 170 nm. Small-angle X-ray scattering (SAXS) and DSC results showed that the microstructure of PFSA and the crystallization of PVDF in the nanofiber interfered with each other, which was attributed to the interaction between the backbone of PFSA and PVDF. CA and IEC revealed that the nanofibers were highly hydrophobic. Finally, the PFSA–PVDF nanofiber membranes were evaluated as a catalyst in the esterification reaction and as a separator in Li-ion battery. It was found that PFSA/PVDF nanofiber membrane with high PFSA ratio showed higher capacity and more stable cycle performance after 100 cycles as compared to the PVDF nanofiber, which could be used as a separator in Li-ion battery. [ABSTRACT FROM AUTHOR]

ABSTRACT Cellulose triacetate (CTA) forward-osmosis (FO) membranes were prepared via the phase inversion method. The influence of thickness on the performance and morphology of CTA FO membranes was discussed in detail. When the thickness of the membrane was 50.0 ± 0.5 μm (CTA4), the prototype CTA membranes displayed a water flux of 20.2 L m−2 h−1 and a reverse salt transport of 14.6 g m−2 h−1 using 1 mol/L NaCl as the draw solution and deionized water as the feed solution during the FO process at 25 °C. In addition, the high-performance CTA4 FO membranes have been used to process spent electroless nickel plating baths where the water flux could reach 13 L m−2 h−1 and NiSO4·6H2O crystals occurred in the feed solution of the spent electroless nickel plating baths. The recovery rates of NiSO4·6H2O and water from the spent electroless nickel plating baths were 44.54% and 53.53%, respectively. This study focused on improving membrane design for the FO process and finding a new method of waste liquor or wastewater treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45049. [ABSTRACT FROM AUTHOR]

ABSTRACT The interforce between the magnetic composite forward osmosis (FO) membranes and the magnetic draw solution was proposed to reduce the internal concentration polarization (ICP) of FO process, and realized the synergetic permeability improvement of resultant FO membranes. The key factor was the successful fabrication of the Fe3O4 magnetic nanoparticles (MNPs) with small-size and narrow distribution via co-precipitation method. The cellulose triacetate (CTA) magnetic composite FO membranes were fabricated using Fe3O4 as additive via in situ interfacial polymerization, and named CTA-Fe3O4. Dynamic light scattering (DLS) and zeta results showed that the coated sodium oleate on the MNPs explained their reducing aggregation and the stability of various pHs. The MNPs' surface segregation during demixing process resulted in the improvement of hydrophilicity, Fe content and roughness of resultant CTA-Fe3O4 composite FO membranes. Furthermore, the in situ interfacial polymerization resulted in the formation of the polyamide selective layer, and the CTA-Fe3O4 membrane's N content was 11.02% to 11.12%. The permeability properties (FO and pressure retarded osmosis modules) were characterized using 1.0 M NaCl and 100 mg/L Fe3O4 as draw solutions, respectively. The results indicated that the higher concentration of MNPs supplied more interforce and better FO permeability properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44852. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride (PVDF)/polyvinyl alcohol (PVA) ultrafiltration (UF) membranes were prepared via a phase inversion method employing the modification of carboxylated multiwalled carbon nanotubes (MWCNTs-COOH). Various contents of MWCNTs-COOHs (0.00-0.15 wt%, weight of casting solution) were added into PVDF/PVA/dimethyl sulfoxide systems for the fabrication of the plate UF membrane. Fourier transform infrared spectroscopy spectra identified the successful introduction of carboxyl through the CO peak at 1730 cm−1. Scanning electron microscopy images exhibited the external surface and the asymmetric morphology with the appearance of a sponge-like inner structure. Atomic force microscopy analysis determined the roughness values and rougher topography. The hydrophilicity of the composite membrane containing 0.09 wt% of MWCNTs-COOHs improved the most. This sample has the highest pure water flux, approximately doubled (126.6 L·m−2·h−1) compared to the PVDF/PVA membrane (68.6 L·m−2·h−1), an enhanced bovine serum albumin flux recovery rate, showing an increase of 17%, and the best fouling resistance ability. Meanwhile, the porosity and dynamic contactangle also indicate the enhancement of membrane hydrophilicity. Dextran (DEX) 600k rejection reached 91.0%. Break strength, elongation at break, and Young's modulus also had improvements of 60%, 215.5%, and 56.7%, respectively, when the MWCNTs-COOH content was 0.12 wt%. POLYM. ENG. SCI., 56:955-967, 2016. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Using 316L stainless steel powder (SSP) with a nominal particle size of 25 μm, porous stainless steel hollow fibers (SSHFs) have been prepared via dry-wet spinning of a particle-loaded casting solution based on non-solvent induced phase inversion, followed by temperature programming sintering. The morphology and performances were characterized by the maximum/mean pore size, SEM, porosity, density, shrinkage, pure water flux and mechanical strength. Subsequently, SSHFs were modified by adding TiO, ZrO and SiO nano-particles for the first time. The morphology of SSHFs relied on not only the SSP contents, but also the contents of TiO, ZrO and SiO nano-particles. The corresponding results demonstrated that SSHFs with TiO nano-particles possessed excellent properties, especially for mechanical strength having a more than 100 % increase and a maximum pore size of 4.5 μm. What's more, nano-particles also reduced the defects of SSHFs' structure, which could be observed from SEM images. [ABSTRACT FROM AUTHOR]

The porous Polyvinylidene fluoride (PVDF) nanofibers were prepared by leaching method using polyethylene oxide (PEO) as porogen for the first time. The influences of the molecular weight (MW) and concentration of PEO, and the leaching solution on the morphology and the surface area of the porous PVDF nanofiber were systematically investigated. Polyethylene glycol 6000 (PEG6000) showed a better pore-forming effect. Optimized preparation parameters were obtained. With the ratio of PEG6000/PVDF reaching 1:1, the surface area of the resulting porous PVDF nanofiber was about three times higher than that of the pure PVDF nanofiber. Moreover, NaClO solution as leaching solution showed a very limited influence on the surface area of porous PVDF nanofiber. Afterwards, Ag NPs coated PVDF (Ag/PVDF) nanofiber was prepared by physical adsorption of Ag ions and in-situ reduction reaction using sodium borohydride as reductant. The photoactivity of Ag/PVDF nanofiber was evaluated by the photodegradation of methyl orange (MO) under visible light irradiation. Ag/PVDF nanofiber showed a better photoactivity than PVDF-Ag nanofiber prepared by the ex-situ blending method. [ABSTRACT FROM AUTHOR]

The surface modification of poly (vinylidene fluoride) (PVDF) membrane was performed via a two-step polymerization reactions. Poly (acrylic acid) (PAAc) was first grafted onto the membrane surface for the preparation of PVDF-g-PAAc membrane, and then poly (ethylene glycol) 200 (PEG 200) was immobilized on the membrane surface by the esterification reaction for the fabrication of PVDF-g-PEGA membrane. Attenuated total reflectance (ATR) FTIR, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and protein adsorption, water flux, water content and dynamic contact angle were conducted to characterize the structures and performance of the resultant PVDF membranes. The experimental results showed that the adsorption of bovine serum albumin (BSA) on the PVDF-g-PEGA membrane decreased about 80% when the grafting ratio reached to 15 wt%, compared with the pristine PVDF membrane. Moreover, the water contact angle of the membrane dropped to 60.5°, while the membrane pore sizes remained little changed. [ABSTRACT FROM AUTHOR]

ABSTRACT A novel nanofiltration (NF) membrane was prepared with cyclen and trimesoyl chloride by interfacial polymerization on a poly(ether sulfone) ultrafiltration membrane with a molecular weight cutoff of 50,000 Da. The effects of the reaction time, monomer concentration, and heat-treatment temperature are discussed. The physicochemical properties and morphology of the prepared NF membrane were characterized by Fourier transform infrared spectroscopy-attenuated total reflectance, scanning electron microscopy, energy-dispersive spectrometry, and atomic force microscopy. The NF performances were evaluated with solutions of Na2SO4, MgSO4, Mg(NO3)2, and NaCl. The salt-rejection order of the prepared NF membrane was as follows: Na2SO4 > MgSO4 > Mg(NO3)2 > NaCl. The resulting rejection of Na2SO4 and PEG600 (polyethylene glycol with the average molecular weight of 600) were more than 90%, whereas that of NaCl was approximately 10%. After the addition of silica sol in the aqueous phase (silica sol concentration = 0.1% w/v), the salt rejection of the membrane changed slightly. However, the water flux was from 24.2 L·m−2·h−1 (25°C, 0.6 MPa) up to 38.9 L·m−2·h−1 (25°C, 0.6 MPa), and the resulting membrane exhibited excellent hydrophilicity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42345. [ABSTRACT FROM AUTHOR]

PAN/PAMAM blend nanofiber mats with different ratios were prepared by electrospinning process for the first time. Their structures were characterized by SEM, N adsorption/desorption and contact angle. It was found that PAN/PAMAM nanofiber with ratio of 12:3 has the highest surface area. The adsorption of methyl orange on blend nanofiber was investigated. With the ratio of PAMAM increasing in blend nanofiber, the adsorption capacity increased not very much. Overall the PAN/PAMAM nanofiber with ratio of 12:3 has the best property, its maximum adsorption capacity was found to be 120 mg/g although its surface area was only about 9.97 m/g. It still maintained an efficient adsorption capacity even at 5th experiment, indicating an effective adsorbent for dye removal. The adsorption isotherm and adsorption kinetics were further investigated. The Freundlich isotherm provided the best fit for dye adsorption and the dynamical data fitted well with the second-order kinetic model. The possible mechanism was discussed. [ABSTRACT FROM AUTHOR]

The batch mode of vacuum membrane distillation–crystallization (VMDC) process was carried out in the ammonium salt solutions. Vacuum membrane distillation (VMD) was used to permeate water to a desired concentration and the crystallizer was applied for the precipitation of crystals. The influence of concentration time on the permeate flux was investigated and the transfer resistances were estimated. Membrane fouling resistance increased gradually when the solution was concentrated up to the critical point of supersaturation factor. Beyond this critical point, the NH4Cl system revealed an irreversible membrane fouling, whereas the (NH4)2SO4system revealed a reversible membrane fouling. By analyzing the transfer resistances, the determining concentration in the VMD process could be obtained, which would provide a way of avoiding membrane fouling problem. The permeated total nitrogen (TN) increased significantly from 4.7 to 59.8 mg/L with the NH4Cl solution. However, low level permeated TN (TN < 3 mg/L) with (NH4)2SO4solution was maintained during the whole concentration process. The NH4Cl crystals with dendritic structure and (NH4)2SO4crystals of lamellar form were obtained by the crystallizer with the production of 125.7 and 58.4 kg/m3, respectively. [ABSTRACT FROM PUBLISHER]

A series of hyperbranched polyesters (HBPEs) using trimethylolpropane (TMP) as a core were synthesized via an esterification reaction, and the molecular weights of these HBPEs were 1600, 2260, 3370, and 5170 g/mol, respectively. Then, these HBPEs were added into dope solutions to prepare PSf hollow fiber membranes via a wet-spinning method. When the HBPE molecule weight increased from 1600 to 5170 g/mol, the initial viscosities of the PSf-HBPE-PEG400-DMAc dope solutions increased, and the shear-thinning phenomenon of these dope solutions became increasingly obvious. When these dope solutions were immersed into the deionized water, the demixing rate increased with an increase in the HBPE molecule weight at first and then decreased; this results in the increase of membrane porosity and the coexistence of finger-like and sponge-like structures. With the addition of HBPE, the start pure water contact angle and the mean effective pore size of the membranes decreased, and the Jw increased. For the mechanical properties of the membranes, the breaking strength and the elongation of the membranes also increased. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this present study, the facile approaches of coagulants and in situ free radical polymerization method for modulating configurations and performances of polyvinylidene fluoride (PVDF) membranes are investigated. Configuration images show that the supramolecular aggregates of PVDF-P(PEGMA-r-MMA) caused by in situ polymerization act as "template" of the tuned configurations of the resultant PVDF membranes. During delay demixing process (ethanol coagulant), the confine of the aggregates resulted in shift of the cauliflower nanograins to the stripe-type nanograins. On the other hand, for the membranes prepared from the instantaneous demixing process in water coagulant, the aggregates contributed to the formation of the confined finger-like structures and the globule agglomerates that constructed the whole thickness of the membrane bulk. Furthermore, those narrow distribution supramolecular aggregates and variation coagulants (water and ethanol) also yield the tuned performances. The membranes' improved mechanical properties and limited hydrophilicity improvement are attributed to the strong interconnection between the aggregates. Because of the fore-forming of the P(PEGMA-r-MMA) aggregates with narrow distribution, all PVDF membranes prepared from the two coagulants possess enlarged flux, narrow distributionmean effective pore size (µ), andmolecular weight cut-off. The delay demixing process contributes to the narrower µ andmolecular weight cut-off, as well increased flux. [ABSTRACT FROM AUTHOR]

Porous stainless steel hollow fiber has been widely used due to its high mechanical strength, excellent thermal conductivity and good sealing properties compared with other porous supports. We successfully prepared porous stainless steel hollow fibers using polyacrylonitrile (PAN) as polymer via dry-wet spinning followed by sintering through temperature programming method. The PAN concentration had an obvious impact on the structure and property of porous stainless steel hollow fiber even if it would be burned off during sintering. The results showed that the morphology could be tuned by adjusting the concentration of PAN. With increasing PAN concentration in casting solution for spinning, the viscosity was increased dramatically, resulting in much compact structures with high pure water flux (higher than 3×10 L·m·h·Pa). A more dense structure could be obtained by adding additive polyvinylpyrrolidone (PVP) as viscosity enhancer. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride (PVDF) flat-sheet membranes were prepared via a non-solvent-induced phase separation (NIPS) method at 60°C using a hydrophilic surfactant OP-10 (octylphenol polyoxyethylene ether) solely (Blank) or with a second additive [H2O or lithium chloride (LiCl)] as pore-forming agents. The influence of OP-10 concentration on the surface tension, viscosity, and precipitation rate of PVDF/(H2O, LiCl, or Blank) systems were investigated, and the ultrafiltration and mechanical properties of the resultant membranes were measured. It was found that an increased demixing rate during the coagulation process was the reason for the change in membrane morphology and properties. An obviously improved flux and slightly decreased mechanical properties and rejection were found in membranes prepared using a high concentration of OP-10 and the second component as additives. SEM pictures revealed an increased porous structure on the resultant membrane surface. A hypothesis was proposed to explain these phenomena; the reoriented surfactant molecules at the interface facilitated the water diffusion channels, which finally became the porous structure on the membrane surface. The weakened mechanical properties were due to the macrovoid structure in its membrane cross-section, which developed from the micelle structure in the casting solution. This hypothesis was further confirmed in a PVDF/OP-10/polyethylene glycol (PEG) system. Aconsistent conclusion was obtained. [ABSTRACT FROM AUTHOR]

Polytetrafluoroethylene (PTFE) flat-sheet membrane with the mean pore size of 0.1 μm was used to treat the high concentration (NH4)2SO4 and NH4Cl solutions by vacuum membrane distillation (VMD). The permeate flux was varied in the range 8-48 L h−1 m−2 and was dependent on the operating conditions. The effects of permeate pressures and feed parameters in terms of pH values, feed temperature, flow rate and feed concentration on both the permeate fluxes and the permeate concentrations of total nitrogen (TN) were investigated. Experiment results showed the feed temperature has the most significant effect on the permeate flux. The feed pH value was observed to be the most dominant factor on permeate concentration of TN. Ammonium was rejected with low feed pH value, high feed temperature and low permeate pressure. When the feed pH value was 3, the permeate concentration of TN was kept in the range of 1-3 mg/L and the ammonia nitrogen rejection rate is 99.95%, despite that the feed concentration was increased. [ABSTRACT FROM AUTHOR]

ABSTRACT Poly(vinylidene fluoride) (PVDF) membranes were prepared with various residence times using water-ethanol (50 : 50, mass ratio) and pure ethanol coagulants as first coagulant, respectively. The physical properties of PVDF solution after free radical polymerization were investigated by dynamic light scattering (DLS), scanning electron microscopy (SEM), viscosity, precipitation kinetics, and surface tension. Resultant PVDF membranes were characterized by SEM, contact angle, mechanical properties, and filtration properties. The results showed that the longer residence time in the first coagulant contributed to the filtration properties improvement. Contact angles of the top-surfaces and bottom-surfaces of membranes decreased as residence time increasing in the first coagulant, and the top-surface showed better hydrophilicity than that of the bottom-surface. The pore size distributions of PVDF membranes showed that the dominating demixing process of the casting solution in water-ethanol coagulant was 5 s, and in that of ethanol was 10-15 s. Additionally, the short-time delay demixing process in water-ethanol first coagulant resulted in a thin dense layer near the top surface, and the longer time delay demixing process in that of ethanol contributed to the shift of the inter-globules to the cellular morphology in the case of the residence time increasing. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39987. [ABSTRACT FROM AUTHOR]

Hydrophobic polydimethylsiloxane — polytetrafluoroethylene (PDMS-PTFE) flat-sheet membranes for pervaporation (PV) of chloroform from aqueous solution were successfully fabricated by solution casting method. The structures and the performance of the membranes was characterized by X-ray diffraction (XRD), scanning electron microscope combined with energy dispersive X-ray spectroscopy (SEM-EDXS), Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA) and the tests of contact angle and mechanical properties. The adding of PTFE particles (<4 μm) in the PDMS matrix enhanced the crystallinity, hydrophobicity, mechanical strength and thermal stability of the membranes. The examinations showed that the PTFE filled PDMS membranes exhibited striking advantages in flux and separation factor as compared with unfilled PDMS membranes. All the filled PDMS membranes with different PTFE content showed excellent PV properties for the separation of chloroform from water. When the content of the PTFE additive in PDMS composite membrane was 30 wt%, membrane performance was the best at feed temperature 50 °C and permeate-side vacuum 0.101MPa. For the 30% PTFE-PDMS membrane, with the increase of the feed temperature from 30 to 60 °C, the total, water and chloroform fluxes as well as the separation factor increased, the apparent activation energy (ΔEa) of total, chloroform and water were 21.08, 66.65 and 11.49 KJ/mol, respectively, with an increase of chloroform concentration in the feed from 50 to 950 ppm, total, water and chloroform fluxes increased but the separation factor decreased. [ABSTRACT FROM AUTHOR]

The electrospinning of sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) and its blend with polyether sulfone (PES) were investigated and the blend nanofibers were applied as a catalyst in esterification. Attempts to electrospin pure SPPESK resulted in electrospraying rather than electrospinning. However, a blend polymer solution of SPPESK and PES resulted in smooth electrospinning when SPPESK content was lower than 9 wt%. The geometrical properties such as fiber diameter and distribution, surface chemical properties such as inter-molecular interaction and crystalline, mechanical properties were investigated by SEM, FTIR, XRD, etc. The catalytic activities of SPPESK-PES nanofibers were measured by esterification of ethanol with acetic acid. A pseudo-homogeneous model was established to describe the kinetics of esterification with nanofiber as a catalyst. The results showed that the SPPESK-PES blend nanofiber had a high specific surface area (46.7-58.9 m/g), good mechanical properties, good catalytic properties (ethanol conversion up to 80 % when reacted 8 h), and good forward rate constants (10.0 × 10-14.6 × 10 L/(mol∙min)). [ABSTRACT FROM AUTHOR]

The effects of nucleating agents on the morphology and performance of poly(vinylidene fluoride) (PVDF) microporous membranes via thermally induced phase separation were investigated. The nucleating agents studied were dicyclohexyl benzene amide (TMB-5), 2,2-methylene bis(4,6-tertiary butyl phenol) sodium phosphate (TMP-1), and 1,3 : 2,4-di- p-methylbenzylidene sorbitol (DM-LO). Light transmittance experiments and differential scanning calorimetry (DSC) were performed to obtain phase diagrams of PVDF/tributyl citrate/di(2-ethylhexyl) phthalate/nucleating agent doped solutions. The morphology and performance of the prepared PVDF microporous membranes were characterized with scanning electron microscopy and microfiltration experiments. The results show that the thermodynamics of liquid-liquid phase separation were not affected by the addition of the nucleating agents, but solid-liquid phase separation was influenced. The system with 0.3 wt % TMB-5 had the fastest crystallization rate and a better nucleation ability. The PVDF microporous membranes had a partly closed, lacy bicontinuous structure with TMP-1 and DM-LO, whereas the membrane with 0.3 wt % TMB-5 had an interconnected bicontinuous structure. The pore size distribution became narrower with the addition of nucleating agent. With 0.3 wt % TMB-5, the membrane had the minimum mean pore size (0.095 μm), a porosity of 80.3%, and a pure water flux of 270 L·m−2·h−1; these values were higher than those of the pure PVDF membrane. The performances of the membranes decreased with additions of TMB-5 of greater than 0.3 wt %. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

A novel composite nanofiltration (NF) membrane was prepared by interfacial polymerization of 2,2′-bis(1-hydroxyl-1-trifluoromethyl-2,2,2-trifluoroethyl)-4,4′-methylenedianiline (BHTTM) and trimesoyl chloride (TMC) on polyethersulfone (PES) supporting membrane. Different preparation conditions and NF membrane performances were discussed. The membrane structures of composite NF membranes were characterized by attenuated total reflectance infrared (ATR-IR), scanning electron microscope (SEM), and atomic force microscopy (AFM). The results showed that the NF membrane prepared under the optimum condition exhibited Na2SO4rejection of 85.3% and the water flux of 10.1 l.m−2.h−1. The NF membrane was treated by 5000 ppm chlorine solution for 1 h. The salt rejection and water flux of the treated membrane reached to 94.5% and 94.8 l.m−2.h−1. The rejection of two NF membranes for inorganic electrolyte solutions decreased in the order of Na2SO4, MgSO4, MgCl2, and NaCl, which were typical characteristics of negatively charged membranes. [ABSTRACT FROM PUBLISHER]

Poly(vinylidene fluoride) (PVDF) membranes possessing interconnected bicontinuous structures with superior mechanical properties and improved hydrophilicity were obtained from PVDF/ N, N-dimethylacetamide (DMAc)/Tween 80/water systems via non-solvent induced phase separation (NIPS) with 60 °C and ambient temperature casting solution. Tween 80/HO mixtures were adopted as dopant; water/ethanol (50:50, mass ratio) and ethanol were chosen as coagulants. The effects of process parameters in terms of variations in dopant contents, casting solution temperatures, and coagulant compositions on the phase inversion process and performance of the resultant membranes were investigated. During the demixing process, water diffused from the interior of Tween 80 reverse micelles, resulting in an accelerated precipitation rate and surface segregation process of the polar head groups of Tween 80. The high temperature of the casting solution contributed to enhancing the diffusion rate of liquid-liquid demixing on crystallization. The coagulant compositions changed the liquid-liquid and solid-liquid demixing dynamics of the casting solutions. Ethanol coagulant contributed to crystallization of PVDF/DMAc/Tween 80/water systems prior to liquid-liquid demixing. This delayed demixing process favored the formation of porous foliage-type top structures with fibril or lath bicontinuous fine structure of membrane bulk, increasing flux, and significant hydrophilicity improvement. Casting solutions in water/ethanol coagulant exhibited a less delayed demixing process with both liquid-liquid demixing and crystallization, resulting in formation of fine structure in the form of strings or stripes and limited hydrophilicity improvement. The predominant typical α- and β-type crystallinity in PVDF was attributed to the existence of dopants, the high temperature of the casting solution, and water/ethanol coagulant. This was consistent with the superior mechanical properties of the corresponding PVDF membrane. The newly developed hydrophilic PVDF membranes with superior mechanical properties and low-fouling of bovine serum albumin (BSA) are anticipated to be suitable not only for wastewater treatment, but also for bioseparation. [ABSTRACT FROM AUTHOR]