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Additive approach provides a simple, yet very effective way of improving the performance of polyamide (PA) thin film composite (TFC) membranes. However, the correlation between physical and chemical properties of a wide range of additives and the final membrane properties is still barely understood. In this work, a variety of additives were systematically used to prepare RO membranes to provide fundamental mechanistic understanding of membrane performance improvement by additives. The membranes were characterized in detail by FTIR, XPS, SEM, AFM, water contact angle, zeta potential, QCM etc. The separation performance of the TFC membrane was measured with 2000 ppm NaCl solution at 1.5 MPa and 25 °C. The results show that by adding DMSO, formamide, acetamide into the aqueous solution, or cyclohexanone into the organic phase, approximately 2 times higher water flux was achieved without significantly decreasing salt rejection. Both aqueous and organic phase additives bring out better MPD diffusion and higher crosslinking density. However, their effect on the kinetic of interfacial polymerization are different. The aqueous phase additives promotes the formation of a thinner and smoother PA selective layer with less film mass, while the organic phase additives sustain the solubility of PA oligomers so that the film mass increases and greater film mass correlates with improved membrane flux.

Silicon anodes have attracted much attention owing to their high theoretical capacity. Nonetheless, an inevitable and enormous volumetric expansion of silicon in the lithiated state restrained the development of the silicon anode for lithium-ion batteries. Fortunately, the utilization of the high-performance binder is a promising and effective way to overcome such obstacles. Herein, a polymer of intrinsic microporosity (PIM) is applied as the binder for the silicon anode, which is composed of a rigid polymer backbone, an intrinsic porous structure, and active carboxyl groups (PIM-COOH). Compared to the traditional binder, both the long-term stability and rate performance of the electrode using PIM-COOH as the binder are significantly improved. The mechanism responsible for the enhanced performance is investigated. The PIM-COOH binder provides stronger adhesion toward the current collector than the conventional binders. The unique rigid polymer backbone and porous structure of the PIM-COOH binder enable a good capability to withstand the volume change and external stress generated by the Si anode. The porous structure of the PIM-COOH binder enhances lithium-ion transportation compared to the SA binder, which improves rate performance of the silicon anode. This work provides a unique insight into design, synthesis, and utilization of the binders for lithium-ion batteries.

Metal–organic framework (MOF) membranes exhibit enormous potential for molecular mixtures’ sieving with high permeance, as well as high selectivity. Current MOF composite membranes suffer from unduly thick MOF layer and poor adhesion to the porous support. By a simple multiple seeded growth method, the ultrathin (less than 200 nm) and defect-free MOF layer is prepared on a ZIF-8 in-situ embedded PSf substrate. On the one hand, the nano-sized ZIF-8 crystals embedded on substrate surface act as anchors linking the ZIF-8 layer with the substrate. On the other hand, these ZIF-8 crystals also act as seeds to promote the formation of the ZIF-8 layer and reduce the crystallization time, leading to a thin and continuous ZIF-8 layer. The obtained ultrathin ZIF-8 membrane shows superior gas molecular sieving performance, with a high gas permeance of 24.5 × 10−7 mol/m2/s/Pa for H2 and selectivity of 4.5, 23.2, and 31.5 for H2/CO2, H2/N2, and H2/CH4, respectively. In addition, neither the permeance or the selectivity shows a noticeable change after 3% elongation, which indicates high mechanical integrity of the MOF layer on the ZIF-8 in-situ embedded PSf substrate. We believe that the utilization of MOF in-situ embedded polymer substrate offers a universal and simple strategy strengthening and thinning the MOF layer of its composite membranes.

The traditional methods to introduce multi-functional groups onto the surface of membrane require unpleasant reaction conditions and complex procedures. Motivated by the need of an economical purification method in the downstream processing of therapic proteins, we develop a simple approach to fabricate mixed mode membrane adsorbers. Nanofibrous membrane support was fabricated by electrospinning a blend of poly(styrene-co-maleic anhydride) (SMA) with polyvinylidene fluoride (PVDF). Mixed mode ligands were then immobilized on the membrane through the conversion of anhydride moieties by aminolysis with functional amines, n-butylamine (BAE), n-octylamine(OAE), N-methyl- d -glumine(NMG). The obtained mixed-mode membrane adsorbers, PVDFS-g-BAE, PVDFS-g-OAE, and PVDFS-g-NMG, which contain hydrophobic interaction/ion exchange, reverse phase interaction/ion exchange, and hydrophilic interaction/ion exchange interactions respectively, were used for protein separation. The success of modification was supported by FTIR and XPS, indirectly confirmed by WCA measurements. Static protein binding property was measured with several model proteins. The PVDFS-g-BAE membrane showed a capacity of 120 mg/mL for IgG and fair selectivity over BSA or Lym; The PVDFS-g-OAE membrane showed a capacity of 140 mg/mL for ɑ-CTP and high selectivity over CYT-C. In addition, the nanofibrous membrane has large total pore area, high porosity, and good mechanical property, which is sufficient for the demands of practical use.

In order to improve the antibacterial efficiency and spectrum of cellulose acetate reverse osmosis membrane (CA–RO), both quaternary ammonium and bromoacetyl groups were introduced into cellulose diacetate under mild conditions forming CA–RO with bi-antibacterial groups for seawater desalination. Bromoacetyl bromide and a series of tertiary amine were chosen as the modification agents respectively. The characterization results showed that both two antibacterial groups were successfully introduced with a certain density. The obtaining membrane had a less hydrophilic but more electronegative surface as well as improved mechanical property. The flux values increased firstly and decreased subsequently after twice modifications while the salt rejection rose. The membrane modified with N,N-dimethyloctylamine (DMOA) had the optimal comprehensive performance of flux and salt rejection. The antibacterial testing results indicated that the resulting RO membranes showed high antibacterial efficiency and broad-spectrum. Their bactericidal rates against gram-negative Escherichia coli (E. coli) and gram-positive Staphylococcus aureus (S. aureus) were more than 99.9%.

By blending the modified laponite (OHec) and polyacrylonitrile (PAN), we prepared polyacrylonitrile nanofiber membranes (PAN@OHec) using the electrospinning technique. Then, the amidoxime modification was carried on using the hydroxylamine hydrochloride, yielding NH2 contained amidoximated polyacrylonitrile nanofiber membranes (AO-PAN@OHec). Amino acids were grafted onto AO-PAN@OHec by a hydrothermal method to prepare materials with a good hemocompatibility. The morphology, structure, wettability, and chargeability of the modified Lys-PAN@OHec nanofiber membranes were characterized by Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), Energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), WCA and Solid zeta potential measurements. We investigated the anti-protein contamination ability of the modified PAN nanofiber membranes. Hemocompatibility of the modified PAN nanofiber membranes were evaluated by the adhesion property of the platelet and erythrocyte. As a result, the hydrophilicity of the modified PAN nanofiber membranes were significantly improved. The protein adsorption was decreased. Besides, the modified membranes were proved to suppress the adhesion of platelet and erythrocyte compared with original PAN membranes.

It remains a major challenge to prepare membranes with minimal protein adsorption for bio-related applications. In this work, modified polyvinylidene difluoride (PVDF) membranes having ultralow protein adsorption were prepared by grafting zwitterionic and PEGylated cross-linked polymers onto the membrane surface. The PVDF membrane was first treated with alkaline and tethered with cross-linked polyethylene glycol diacrylate (CPEGDA) via ATRP. By reacting the abundant alkene group at the periphery of CPEGDA with cystine or monomethyl PEG thiol (MPEG-SH, Mn = 200, 600, 2000) by thio-ene reaction, the membrane surface was tethered with high density protein repellent groups. The PVDF-g-CLPEG2000 membrane shows the best performance and its bovine serum albumin (BSA) and bovine serum fibrinogen (BFG) adsorptions can be lowered to only 1/50 and 1/40 that of the original PVDF membrane, respectively. Similar fouling tendencies were observed in the dynamic filtration process. This work addresses the significance of cross-linked grafting on altering membrane surface properties.

The synergized optimization of water flux and salt rejection by blending with inorganic fillers has been achieved for the polyamide (PA) thin film nanocomposite (TFN) membrane. However, it is difficult to characterize its mass transport properties due to the very thin and heterogeneous PA film. In this work, we select cellulose triacetate (CTA) as the base to prepare hybrid films and their transport properties were studied according to solution-diffusion theory. A series of inorganic fillers, such as reduced graphene oxide (RGO), zeolites, ZIF-8, SiO2 and graphene oxide (GO) were incorporated. The SEM and EDX results indicate a less than 1 wt% filler content for a uniform dispersion. The blending of inorganic fillers leads to enhanced glass transition temperature (Tg) and density, little effect on the water transport property but dramatically decreased salt permeability values, which are nearly ten-fold of that of the CTA film. The blending of GO can densify and hydrophilize CTA simultaneously, which is most promising for a desalination application. The increased water uptake should contribute to its increased water permeability, while the decreased free volume size and FFV value and various interactions between the ions (Na+, Cl-) and GO sheets account for salt permeability decrease.

Hydrophobic charge-induction chromatography (HCIC) has emerged as an efficient method for antibody purification, but traditional packed-bed chromatography continues to suffer from high pressure drop and low transport efficiency. A versatile surface modification method is proposed to prepare HCIC membrane adsorbers. We first modified a commercial regenerated cellulose (RC) membrane by the cationic ring-opening polymerization (CROP) of diethylene glycol diglycidyl ether (DEGDE), producing the RC-g-PDEGDE membrane, which was then modified by the ring-opening reaction of an epoxy group with a sulfydryl group in four mercaptoheterocyclic ligands. Bovine serum albumin (BSA) and human immunoglobulin G (IgG) were used as model contaminant and antibody, respectively. The highest ligand density achieved is 370 mmol/L, and the static and dynamic adsorption capacities of IgG reached 195 and 65 mg/mL, respectively. The high dynamic capacity and IgG recovery (96%) are believed to benefit from the branched structure of ...

The antibacterial alkyl bromide groups were introduced into cellulose diacetate (CDA) through the esterification between highly active bromoacetyl bromide and hydroxyl groups under mild conditions and the modified cellulose acetate reverse osmosis membrane (Br-CA-RO) was obtained subsequently after phase inversion process. The results of FTIR and 1H-NMR indicated the existence of alkyl bromide groups in the modified CDA powder. The optical density method was used to confirm its antibacterial ability. The chemical structure and morphology characterization demonstrated that the anchoring of bromoacetyl groups as antibacterial part brought out minimal alteration on membrane chemical structure and its asymmetric structure, but the regularity and density of membranes increased with the degree of esterification. The property testing results showed that the whole physical performance was enhanced with the thermal stability getting slightly worse. Both the flux and salt rejection of Br-CA-RO increased after modification and the latter was close to that of cellulose triacetate RO membrane. The dynamic contact antibacterial testing implied that Br-CA-RO showed much higher antibacterial ability than unmodified RO membranes, and its relative bactericidal rates against E. coli (gram negative) and S. aureus (gram positive) were higher than 73.0% and 93.5%, respectively. This method offers a new approach for antibacterial and functional modification of CA-RO membranes.

Ideal adsorbents are featured by both high adsorption capacity and high adsorption rate. Current adsorptive membranes enjoy good mass transfer performance but have limited sorption capacity. Microporous organic polymer has superiorities of small pore size and high surface area which is conductive to high adsorption capacity, but usually suffers from high mass transfer resistance. In this work, the polymer of intrinsic microporosity PIM-1 was fabricated into microfiber membranes by electrospinning for carbendazim and phenol adsorption. The PIM-1 and its electrospun membranes were characterized by 1H NMR, GPC, ATR-FTIR, FESEM, TG and BET measurements. The electrospun PIM-1 membrane was demonstrated to have hierarchical porous structure with high surface area. The equilibrium adsorption capacity for carbendazim and phenol was 0.084 mmol/g and 0.804 mmol/g, respectively. The adsorption isotherm fits well with Langmuir model and the adsorption kinetic can be described by film diffusion and chemical reaction model. The membrane can retain 95% of its initial capacity after cycling 10 times. Both the sorption capacity and kinetic coefficients are high when comparing with other sorbents for either carbendazim or phenol, demonstrating that the electrospun PIM-1 is a good adsorbent.

A novel procedure to fabricate quaternized cellulose triacetate reverse osmosis (QCTA-RO) membranes via the etherification procedure between partially hydrolyzed CTA-RO membrane and 3-chloro-2-hydroxypropyl-trimethyl ammonium chloride (CHPTAC) in alkaline solutions (pH = 9–11) for different reaction time (1, 2, 3 and 4 h) was proposed. The structure and performances of the obtained QCTA-RO membranes were characterized and their antibacterial performances against E. coli and S. aureus were evaluated through colony counting method. The results showed that quaternary amine group was successfully grafted on the surface of membrane via covalently bond without significant damage to morphology, mechanical performance and thermal stability. The permeation flux values increased with prolonging modification time to 3 h, while the salt rejection decreased slightly but remained above 92%. QCTA-RO membranes displayed good antibacterial activity against Gram-negative E. coli and Gram-positive S. aureus and their bactericidal rates were 78.7–89.0% and 64.7–76.6% respectively at the optimized modification time of 2–3 h.

The deployment of fossil resources such as petroleum, coal and natural gas to produce fuels and chemicals has resulted in excessive carbon dioxide (CO2) emissions and serious environmental issues. The implementation of CO2 utilization as a raw material for synthesis of fuels and chemicals has potential to reduce CO2 emissions and close the carbon cycle. Cyclic carbonates, materials used as building blocks for polymers or green solvents in batteries, can be synthesized from CO2 and alkylene oxides. Although a variety of catalysts have been synthesized to activate CO2 and alkylene oxides for transformation into cyclic carbonates, either the catalytic efficiency is low or the catalyst cost is high. In the present work, we report a hierarchical porous metallized poly-melamine-formaldehyde (PMF) polymer catalyst that has a 100-fold monomer cost reduction and six- to several hundred-fold activity enhancement compared to the state-of-the-art catalysts for propylene carbonate synthesis from epoxide and CO2 under the same reaction conditions. The hierarchically interconnected macro-, meso- and micro-pore structures in PMF that are formed via one-step high internal phase emulsion polymerization facilitate mass transport and accessibility to active sites. The high density of aminal groups and triazine rings in PMF provides multiple sites for CO2 adsorption and the subsequent reaction with epoxide. The unprecedented low-cost and high-efficiency of metallized PMF as well as the simplicity in its synthesis exhibit great potential in the synthesis of cyclic carbonates for the chemical and plastics industries.

A fast and facile protocol is reported aiming at improving the antifouling property and hemocompatibility of poly(vinylidene fluoride) (PVDF) membranes by tethering PEG hydrogel and zwitterion immobilization. The coated PEG hydrogel was first prepared by interfacial polymerization and tethered on an alkali treated PVDF membrane (PVDFA) surface via a simultaneous thio-ene and thiol-epoxy reaction. Then, the thiol groups of cysteine reacted with the epoxy groups in PEG hydrogel to fabricate the PVDFA-g-Cys membrane. The membrane fabrication was complete within less than 20 min and was conducted in mild conditions. The successful preparation of PVDFA-g-Cys membrane was confirmed by ATR-FTIR and XPS. Raman spectroscopy showed that the hydrogels covalently bonded to the PVDF membrane surface. The membrane retained its mechanical strength after modification. The SEM measurements suggested that the membrane became denser after hydrogel coating, meanwhile, the EDX test verified that the functional species uniformly distributed in the membrane matrix. Water contact angle (WCA), protein adsorption and protein filtration tests showed significant improvements in hydrophilicity and antifouling properties for the modified membrane. The negativity of the membrane surface measured by the streaming potential method provides a basis for protein resistance and hemocompatibility. Moreover, the suppressed platelet adhesion and prolonged plasma coagulant time show that the PVDFA-g-Cys membrane has ultralow thrombotic potential and better hemocompatibility. The reported surface modification method combing thio-ene and thio-epoxy chemistry not only facilitates fabrication of hemocompatible PVDF membrane but also provide an universal chemical platform for multifunctionalization of porous membranes.

Sinomenine is a natural alkaloid with important biological activities (e.g. anti-cancer, anti-inflammatory, and anti-allergic). However, the unstability and short half-life absolutely limited its application to foods. Microencapsulation technology can offer a way to solve these issues. In this study, polylactic acid microcapsules loading sinomenine hydrochloride were fabricated by phase inversion emulsification-drying in liquid technique. The results showed that microcapsules had nice spherical shape, uniform particle size, and free flowing. The encapsulation efficiency was 89.2% and drug loading was 8.9% under the optimal conditions. In vitro release assays demonstrated that release of sinomenine from microcapsules was sustained and slow. Moreover, it was found that the sinomenine release fitted Fickian diffusion mechanism. The results of cytotoxicity study showed that sinomenine-loaded microcapsules were biocompatible. Sinomenine-loaded microcapsules could inhibit the growth of MDA-MB-231 cells using methyl thiazolyl tetrazolium assay. In summary, polylactide microcapsules exhibit excellent properties for sinomenine that can be used in drug or food industry.

Antifouling PVDF membranes were prepared by grafting hyperbranched polyols on the membrane surface via a three-step modification method. The membrane was first prepared by alkaline treatment to introduce alkenyl groups, then chemically immobilizing hyperbranched poly(ethyleneimine) (HPEI) on membrane surface through Michael reaction followed by ring opening reaction of the glycidol with amine groups. Chemical compositions, surface morphology and physicochemical properties of the original and modified membranes were characterized via attenuated total refection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), water contact angle (WCA) and zeta potential measurements. The antifouling property of the modified membrane was assessed by the static bovine serum albumin (BSA) and lysozyme (LZM) adsorption as well as cross-flow filtration of BSA aqueous solution. The results explicate that surface modification using hyperbranched polymers can alter membrane chemistry and morphology significantly. In contrast to the original PVDF membrane, the modified membrane shows superhydrophilic property and relatively high capability to resist nonspecific protein adsorption. Three HPEIs were used for modification and the obtained PVDFA-g-PG 60,000 membrane has a static BSA protein adsorption of 45 μg/cm 2 and shows the highest protein resistance. However, the PVDF-g-PG membrane is positively charged due to the unreacted amine groups. As a result, the PVDF-g-PG membranes also show high flux decline during the filtration of BSA aqueous solution due to the electrostatic interaction. In spite of that, the PVDF-g-PG membranes still maintain high flux recovery ratio and good washing properties.

The development of efficient adsorbents with high sorption capacity remains as a challenge for the removal of micropollutants occurred globally in water resources. In this work, poly (amic acid) (PAA) electrospun nanofiber membranes grafted with hyperbranched polyols were synthesized and used for boron removal. The PAA nanofiber was reacted with hyperbranched polyethylenimine (HPEI) and further with glycidol to introduce the vicinal hydroxyl groups. The chemical composition and surface characteristics of the obtained PAA-g-PG membranes were evaluated by FESEM, FTIR, XPS and water contact angles (WCA) measurements. The boron adsorption thermodynamics and kinetics were investigated systematically. The results showed that the PAA nanofiber spun from concentration of 15% had uniform morphology and narrow diameter distribution. The PAA-g-PG nanofiber membrane had a maximum boron uptake of 5.68 mmol/g and could adsorb 0.82 mmol/g boron from a 5 mg/L solution in 15 min. Both the high surface area of nanofibers and the hyperbranched structure should contribute to the high boron uptake and high adsorption rate. The nanofiber membrane obeyed the Langmuir adsorption model and the pseudo-first-order kinetic model. The regeneration efficiency of the nanofiber membrane remained 93.9% after 10 cycled uses, indicating good regenerability of the membrane.

The exploration of novel O/W filters having not only high permeation and rejection but also durable performance is a key driver of membrane material research. In this study, a glass fiber membrane (GF) was grafted with hyperbranched polyethyleneimine (HPEI) via a two-step process and used for O/W separation. The silanol group in the GF was reacted with epichlorohydrin followed by the reaction with the amine groups in the HPEI molecules. The obtained GF-g-HPEI membranes were characterized by FTIR, XPS, SEM and WCA measurements. The O/W separation performance was evaluated by dead-end filtration of a series of oil dispersion and emulsions. ATR-FTIR and XPS measurements indicated that HPEI was grafted on GF membrane surface successfully. The engineered GF membranes exhibit superwetting properties, outstanding permeability (1000 L/m2h at 10 cm gravity pressure) and quantitative oil rejection (≧99.6%) for emulsified and dispersed oil. In addition, the modified membrane showed excellent thermal and chemical stability, compared with polymer-based membranes. All the above characteristics render the modified GF membrane cheap, effective and durable filters for O/W emulsion separation.

A series of charge-modified polyacrylonitrile (PAN) membranes with different surface charge properties and densities have been obtained via first grafting with hyperbranched polyethylenimine (PEI) and then ring-opening with 1,4-butane sultone. The obtained PAN-gr-PEI membranes and PAN-gr-PEIS membranes have hyperbranched polycation and hyperbranched zwitterions tethered on the surface, respectively. They were characterized in detail by FT-IR, AFM, XPS, SEM, WCA, and zeta-potential measurements. Bovine serum albumin (BSA) and lysozyme (Lys) were chosen as model proteins in order to evaluate the separation performance of the modified membranes via dead-end ultrafiltration. The membranes grafted with PEI of different densities have different surface chemical compositions but very similar surface charge properties. PAN and PAN-gr-PEI membranes are highly negatively charged and moderately positively charged. PAN-gr-PEIS membranes show typical amphoteric characteristics. The UF performance is highly dependent o...

In this work, a novel mixed matrix membrane (MMM) was fabricated by Non-solvent induced phase inversion of the blend of polysulfone (PSF) with a boron selective resin (BSR) and used for boron removal. The membrane surface chemical composition was characterized by ATR-FTIR and XPS. The membrane morphology was observed by FESEM, AFM and BET measurements. The effects of BSR content on boron adsorption properties were studied in detail. Addition of BSR leads to rougher and more hydrophilic membrane surface and higher permeation flux. The boron uptake increases obviously with the BSR content and has the maximum over 2.0 mmol/g. The membrane shows S-type isotherm and the adsorption kinetics can be well described by the pseudo-first-order model. Compared with the polymeric resin, the PSF/BSR membrane shows similar boron uptake but much higher adsorption rate. With a membrane of 1.76 cm2, a boron removal efficiency as high as 97.6% can be obtained for 10 mL of 5 mg/L boron solution in the flow-through experiment at flux rate of 25 L/m2·h. It is concluded that the MMM can combine the advantage of the resin on high uptake and that of the membrane on convective transport.

A new approach to improving the compaction resistance and polyamide skin layer adhesion onto the substrate in thin film composite (TFC) membranes was developed. It was based on in situ polymerization of p-phenylene terephthamide (PPTA) in a polysulfone (PSf) solution prior to membrane casting via the phase inversion process, thereby forming a PPTA-embedded PSf substrate. The TFC membrane was prepared by interfacial polymerization on such (PPTA/PSf) substrates. The crystal structure of the PPTA polymerized in the PSf/NMP solution was investigated by XRD and TEM. The immobilization of PPTA in the PSf substrate was confirmed by FTIR and XPS. The surface properties of the PPTA/PSf substrates were characterized by FESEM, AFM and WCA measurements. Incorporating PPTA into the substrates resulted in more open porous structures and a thinner dense layer, as well as a rougher and more hydrophilic surface. Both the compaction resistance of the TFC membrane and the polyamide skin layer adhesion onto the substrates were improved by the presence of PPTA. The TFC membranes exhibited a typical nanofiltration performance with salt rejections in the order of Na2SO4 > MgSO4 > MgCl2 > NaCl.

As a common CO2 separation membrane material, polyethylene glycol (PEG) with ether oxygen groups shows high dissolution selectivity to CO2. However, high molecular weight PEG has strong crystallinity, resulting in low gas flux, while the low molecular weight PEG has poor mechanical properties. Block copolymers containing PEG segments can address this challenge but are difficult to synthesize. In this work, a series of polyether sulfone (PES) comb-like copolymer with PEG side chains were prepared by the polycondensation followed by the thiol-ene click chemistry. By manipulating the density and length of PEG side chains (Mn = 550, 1000, 2000) to adjust the fine structure of the micro-phase separation, the gas separation performance of the PES-g-PEG membrane was optimized. The PES-g-PEG polymers have two glass transition temperatures (Tg), which are attributed to the PES main chain and PEG side chains. The Tg-PEG and Tg-PES difference (ΔTg) is highly correlated with the PEG side chain density and can be used to interpret the phase separation degree. The copolymer membrane with shorter PEG side chains achieved higher chain density and more developed micro-phase separation, which was facilitated by thermal annealing. As a result, PES A-g-PEG550 membrane shows the best gas separation performance with the CO2 permeability of 26.8 Barrer and the CO2/N2 selectivity of 27.6. The permeability variation with the microstructure of PES-g-PEG mostly relies on the side chain density rather than volume fraction or side chain molecular weight. We believe this study of the gas separation performance of the comb-like copolymer material is meaningful for the further application of membrane technology in CO2 capture and separation.

In this work, we employed an environmentally friendly approach based on plasma enhanced chemical vapour deposition (PECVD) to modify titania nanotubes (TNTs), aiming to obtain better dispersion of nanofillers in polyamide (PA) layer of thin film nanocomposite (TFN) reverse osmosis membrane. Owing to the hydrophilic nature of TNTs, dispersing it homogenously in organic solvent during interfacial polymerization process is difficult to achieve. Therefore, the TNTs are mildly modified by PECVD technique in order to ameliorate its stability in organic solvent. Our results showed that depositing thin layer of methyl methacrylate (MMA) on the TNTs surface could enhance its dispersion quality in organic solvent and further improve the properties of PA layer by enhancing membrane water flux by 16% without compromising NaCl rejection. More importantly, the developed TFN membrane showed excellent fouling resistance by recording flux recovery rate of 85.77% compared to 57.94% shown by the control membrane. Its antibacterial property was also obviously better than that of control membrane. Overall, the developed TFN membrane demonstrated good performance stability with respect to NaCl rejection and water permeability and the trace amount of nanofillers detected in the water sample (in the level of μg/L) did not negatively influence the membrane filtration performance.

The polymeric gutter layers of current thin film composite membranes (TFCMs) suffer from high gas diffusion resistance and fast performance deterioration. We designed a TFC membrane consisting of an ultrathin 2-D MOF nanosheets gutter layer and an ultrathin selective microporous polymer top layer via interfacial polymerization for H2 separation. The 2-D MOF nanosheets gutter layer was shown to be thin and highly permeable with extremely low resistance for gas transport, thereby maximizing the gas permeance of the resulting composite membranes. The resulting TFCMs exhibited outstanding H2 permeance (8.2 × 10−7 mol m−2 s−1 Pa−1) with an ideal H2/CO2 selectivity of 12.3–12.6. In addition, the TFCMs showed excellent long-term stability due to the rigidity and integrity of the 2-D MOF nanosheets. This study is expected to provide a new approach to design high performance TFCMs for H2 separation.

A series of stimuli-responsive reverse (RO) membranes were prepared by tethering three stimuli-responsive polymers, poly (sulfobetaine methacrylate) (PSBMA), poly (4-(2-Sulfoethyl)-1-(4-vinyl-benzyl) pyridinium betain) (PSVBP) and poly (N-isopropylacrylamide) (PNIPAM) onto the surface of a commercial thin-film (TFC) RO membrane via surface-initiated graft polymerization. The membrane surface was characterized by ATR-FTIR, XPS, zeta potential, water contact angle (WCA), FESEM and AFM. Membrane characterization indicates successful grafting of these polymers, with more negatively-charged, smoother and more hydrophilic surfaces as a result. Long-term fouling-rinsing cycled experiments were conducted to evaluate fouling resistance and cleaning efficiency. With CaCO 3 as the foulant, the modified membranes showed better fouling resistance in the whole testing as long as 320 h; with BSA as the foulant, they only showed better antifouling performance in short term. However, the modified membranes showed much higher cleaning efficiency in both cases, with the PA-g-PSVBP membrane as the best one.

A new strategy to synthesize hierarchical, porous titania/carbon (TiO2/C) hybrid microspheres via solvothermal reaction in N,N'-dimethyl formamide (DMF) has been developed. In situ formed polystyrene (PS) colloids have been used as templating agent and carbon source, through which TiO2/PS microspheres with a diameter of ca. 1 μm are built by packed TiO2 nanoparticles of tens of nanometers. The TiO2/PS microspheres are converted to TiO2/C microspheres with different amounts of carbon under controlled calcination condition. The mechanism investigation unveils that the introduction of concentrated HCl creates surface tension between PS and DMF, leading to the formation of PS colloids in solution. The solvothermal treatment further promotes the formation of PS colloids and integration of the titania nanoparticles within the PS colloids. The morphology, crystallinity, nature and content of carbon, UV-Vis absorption, carbon doping, pore size distribution, pore volume, and BET surface area of the TiO2 microspheres with different amounts of carbon have been measured. The applications of the TiO2/C hybrid microspheres as photo catalyst for water splitting and lithium-ion battery anode have been demonstrated. Superior photo catalytic activity for hydrogen conversion under both full spectrum and visible light illumination compared to commercial P25 has been observed for the TiO2/C microspheres with 2 wt% of carbon. Besides, the TiO2/C microspheres with 8 wt% of carbon as lithium-ion battery anode showed a much higher capacity than the bare TiO2 microsphere anode. The origin for the enhanced performance as photo catalyst and lithium-ion battery anode is discussed.

Template-free synthesis of TiO2 architectures with controlled morphology evolution has been developed through solvothermal reaction in 1,4-dioxane. By simply varying the molar ratio of the concentrated HCl over Titanium isopropoxide (TTIP) from 0 to 5.0, series of morphologies including nanoparticle-built microspheres, nanoparticle-built microspheres decorated with nanorods, nanorod cauliflowers, and nanorod dendrites have been obtained. The influence of several key factors on the morphology control of TiO2 has been systematically investigated. These parameters include the mass (molar) ratio of HCl/TTIP, solvothermal reaction temperature and time, acid species (concentrated nitric acid), and solvent type (tetrahydrofuran and 1,3-dioxane). The mechanism for the formation of the TiO2 architectures with controlled morphology evolution has been discussed. The application of the TiO2 architectures as water splitting photocatalyst and lithium–ion battery anode has been demonstrated. And the corresponding structure–property correlation has been discussed.

Efficient polymeric adsorbents, including complexing membranes, attract increasing attention due to the global occurrence of micropollutants in water resources. Grafting polyhydroxy polymers onto a microporous membrane surface to prepare a complexing membrane for flow-through boron removal is also an emerging method. However, it remains a great challenge to develop efficient sorbents with both high capacity and high adsorption rate. In this work, hyperbranched polyols are grafted onto a polyacrylonitrile (PAN) membrane surface to prepare complexing membranes with high capacity and high adsorption rate, which utilize the structural characteristics of hyperbranched molecules to optimize the three-dimensional distribution of the chelating ligands. First, the PAN membrane was grafted with three hyperbranched polyethyleneimine (HPEI) macromolecules through a water mediated hydrolysis and amidation reaction in an autoclave followed by a ring opening reaction with glycidol. ATR-FTIR, XPS, FESEM and WCA methods were used to characterize the modified membranes. The results demonstrated that HPEI was successfully anchored onto the membrane surface and reacted with glycidol. Large quantities of hydroxyl groups were enriched on the surface of the membranes leading to rougher and superhydrophilic surfaces. The study on boron adsorption shows that the complexing membrane can absorb 3.2 mmol g−1 within only 4 min, which is superior to other reported sorbents. The adsorption isotherm can be described by the Langmuir model and the kinetic adsorption data fit very well with the pseudo-first-order expression. In addition, the boron adsorption can be completely regenerated for ten cycles of use by 15 min acid leaching without obvious degradation. The rapid boron removal and high regeneration are believed to benefit from the hyperbranched scaffold thanks to the high density and good accessibility of the ligands.

Simple methods for dual functional modification of membrane surfaces have been rarely reported but are highly desirable for the fabrication of antifouling and antibacterial membranes. In this work, we exploit a multicomponent reaction, Ugi-4CR (Ugi four-component reaction), to prepare novel antifouling and antibacterial reverse osmosis (RO) membranes. With the aid of the high number of residual carboxyl groups on a commercial polyamide RO membrane as the anchor and methyl isocyanoacetate as a component, a hydrophilic macromolecular component, methoxy poly(ethylene glycol) aldehyde (MPEG-CHO), and an amino-terminated antibacterial component, tris(2-aminoethyl)amine (TAEA) or sulfamethoxazole (SMZ), were grafted onto the surface in a single step via the Ugi-4CR. The surfaces of the original and modified membranes were characterized by ATR-FTIR, XPS, TG, WCA, FESEM and AFM measurements. The antifouling performance was evaluated by cross-flow filtration of protein and inorganic salt solution. The antibacterial performance was assessed by the shake flask method. The results show that the Ugi-4CR was successfully conducted on the RO membrane surface and that MPEG-CHO and the antibacterial agents were successfully grafted. The surface roughness decreased and surface the hydrophilicity improved upon modification. After 48 h fouling experiments, the obtained PA-g-PEG/TAEA and PA-g-PEG/SMZ membranes showed obviously lower flux attenuation ratios and higher flux recovery ratios than the original membrane in both cases when fouled by protein or inorganic salt. In addition, the bacterial concentrations in the suspensions shook with the modified membranes were much lower than that of the original membrane. As for the PA-g-PEG/SMZ membrane, hardly any bacterial growth was seen, even after 24 h culture. In contrast to current multi-step grafting processes, this work reports a “one pot” procedure with two functional groups grafted simultaneously under very mild conditions without the use of any catalyst.

The relationship between desalting membrane and its water/salt transport properties remain largely unknown. This is especially true for polyamide thin film nanocomposite (TFN) membranes which have shown excellent desalination performance and attracted booming attention in recent years. Considering cellulose triacetate (CTA) can be made into dense membranes whose transport properties can be measured based on the solution-diffusion theory, we systematically study the water/salt transport property of the CTA nanocomposite membranes blended with reduced graphene oxide (rGO) of varying reduction degrees, with multilayer graphene oxide (MGO) and single layer graphene oxide (SGO) as control samples. The nanocomposite membranes show enhanced membrane density and glass transition temperature (Tg) due to the interaction of the polar group in GO/rGO with CTA chains. The GO (rGO) frustrates the polymer chain packing and decreases crystallinity of CTA membrane. The adding of rGO increases the water permeability by increasing its diffusivity due to the decreased crystallinity and additional channel from (r)GO, but decreases the salt permeability by decreasing its diffusivity due to membrane densification and the interactions of ions with GO/rGO. The water permeability and diffusivity of the nanocomposites increase when its water sorption decreases, which is against the trend of pure polymers, presumably due to the fact that water sorption is not a good reflection of the free volume in this heterogeneous membrane. Meanwhile, the GO/rGO blending slightly increases water sorption without changing the salt sorption because the newly-introduced polar groups in GO/rGO traps water and suppress its solvation capacity for salt. Both the water permeability and the water/salt selectivity increase with the reduction degree due to the decreased water transport resistance.

Synthesis of cyclic carbonates via cycloaddition of CO2 to epoxides is an important strategy for CO2 valorization. However, efficient and easy-to-handle catalytic system for this type of reaction at mild conditions is still rare. In this work, we present a polyimide-based catalytic membrane with hierarchical pore structure for flow through synthesis of cyclic carbonates at mild conditions. The membrane was fabricated by incorporating a porous and metallized poly-melamine-formaldehyde (Zn@PMF) into phase inversed polyimide (PI) matrix. Upon in-situ crosslinking with tris(2-aminoethyl)amine, the solvent-resistant PI membrane can not only facilitate the CO2 adsorption and immobilize the catalysts, but also promote mixing by flow-through operations. As a result, the nanocomposite membrane exhibited an excellent catalytic performance with a maximum TOF value of 3362 h−1 at ambient conditions. This catalytic activity is not only higher than the Zn@PMF particle but also is the highest among reported catalysts under the similar reaction conditions. Its high catalytic performance was also confirmed in CO2 cycloaddition in a synthetic flue gas stream.

Crosslinked poly(ionic liquid) (PIL) and poly(ionic liquid)-ionic liquid (PIL-IL) based membranes with tunable micromolecular structure have been synthesized in a simple way to optimize their CO2 capture performance. Amino-terminated PILs of two molecular weights (MW) were synthesized via the Debus-Radziszewski multicomponent reaction and then reacted with two commercial glycidyl ether crosslinkers, (polyoxyethylene bis(glycidyl ether) and trimethylolpropane triglycidyl ether). The effects of the PIL MW, crosslinker type and content, and IL content on CO2/N2 permeation-separation performance were systematically investigated. For the neat PIL membranes, both the utilization of ether-containing crosslinker and an increase in the crosslinker content increased the CO2 solubility and diffusivity, with the best PILs membrane exhibiting an excellent CO2 permeability of 170 Barrer and a CO2/N2 permselectivity of 36. For the PIL-IL membranes, an increase in the IL content increased the CO2 solubility and diffusivity, but also resulted in a decrease in the diffusivity selectivity. The best permeation-selectivity performance belongs to a PIL-IL membrane that showed a CO2 permeability of 2070 Barrer and a CO2/N2 permselectivity of 24.6. Among all the PIL-IL membranes reported in literature, this PIL-IL membrane demonstrated the highest permeability and also a cost-effective permselectivity, with its separation performance approaching the 2008 Robeson upper bound.

A novel positive-charged polyamine-based cyclophosphazene nanofiltration membrane (NF) was prepared via interfacial polymerization between branched polyethyleneimine (PEI) and hexachlorocyclotriphosphazene (HCCP). The composite membranes were characterized using ATR-FTIR, XPS, SEM, AFM, water contact angle, and zeta potential analysis. The membrane with optimal performance was prepared by interfacial reaction with 5 wt% PEI (Mn = 600 g/mol) in aqueous phase, 1 wt% HCCP in organic phase, 5 min dwell time, and 15 min curing time at 100 °C. The resultant membrane has a 97% rejection to MgCl2 and a water permeation of 55 L/m2 h when testing at 1.5 MPa and 25 °C with a 1000 ppm salt solution. The results for filtrating various dyes showed that the PEI/HCCP membrane could remove small organic compounds and contaminants. Antibacterial assay results indicated that the membrane had a nearly 100% bacterial inhibitate rate against both Gram-negative E. coli and Gram-positive S. aureus. In addition, all bacteria in a concentrated suspension (107 CFU/mL) could be completely eliminated within 20 min contacting with the PEI/HCCP membrane. Finally, a 140 h cross-flow testing indicates an excellent membrane performance stability.

A new facile scalable method has been developed to synthesize silicon oxycarbide (SiOC)/carbon nanohybrids using difunctional dental methacrylate monomers as solvent and carbon source and the silane coupling agent as the precursor for SiOC. The content (from 100% to 40% by mass) and structure (ratio of disordered carbon over ordered carbon) of the free carbon matrix have been systematically tuned by varying the mass ratio of methacryloxypropyltrimethoxysilane (MPTMS) over the total mass of the resin monomers from 0.0 to 6.0. Compared to the bare carbon anode, the introduction of MPTMS significantly improves the electrochemical performance as a lithium-ion battery anode. The initial and cycled discharge/charge capacities of the SiOC/C nanohybrid anodes reach maximum with the MPTMS ratio of 0.50, which displays very good rate performance as well. Detailed structures and electrochemical performance as lithium-ion battery anodes have been systematically investigated. The structure-property correlation and corresponding mechanism have been discussed.