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This work reports the utilization of lignin, a renewable and biomass-based material, as an effective modifying agent for thermally stable and hydrophobic membranes based on crosslinked polybenzoxazine (CRPBz) to significantly enhance their permeation fluxes in pervaporation dehydration tests. Lignin could involve in the crosslinking reaction of polybenzoxazine so as to be chemically embedded in the polymer networks. In addition to the inherent hydrophilicity of lignin, lignin could release the hydrophilic groups (phenol and tertiary amine) of crosslinked polybenzoxazine with formation of hydrogen bonding with crosslinked polybenzoxazine, consequently to significantly enhance the hydrophilicity and water permeation fluxes of the studied membranes. With feeding a 70 wt% tetrahydrofuran aqueous solution at 25 °C, lignin modification increases the permeation flux of the CRPBz based membrane from 237 g m−2 h−1 to 490 g m−2 h−1 and separation factor from 11,920 to 19,440. Lignin modification significantly enhances the water permeation flux of the membrane without scarifying separation ability. A 3.4-folds of pervaporation separation index (PSI, the product of permeation flux and separation factor) has been demonstrated with the lignin modification. Similar performance has also been recorded on the tests on a 70 wt% isopropanol aqueous solution. The effect of lignin has been attributed to increase the membrane hydrophilicity for facilitating water permeation. The results demonstrate the wide application scopes of the lignin-modified CRPBz based membranes in pervaporation dehydration based on their high stability and hydrophilicity.

One critical issue for the application of high-temperature polymer electrolyte membranes (HT-PEMs) is to obtain good balance between their proton conductivities and mechanical strength. In this work, a novel strategy has been developed to achieve the balance by increasing the number of functional groups in the grafting site of the side chain of polysulfone (PSU). 2,4,6-tri(dimethylaminomethyl)-phenol (TDAP) with three tertiary amine groups was grafted on PSU (TDAP-PSU) to achieve higher phosphoric acid (PA) uptake at a lower grafting degree. Moreover, the bundle of amine groups in one grafting site reduces the volume swelling compared to the single tertiary amine group grafted PSU membrane (DMA-PSU). Thereby, the TDAP-PSU membrane with 75% grafting degree achieves comparable PA uptake with the DMA-PSU membrane with 99% grafting degree, whereas the mechanical strength of former membrane after PA doping is 2.2 times higher than that of the later one after PA doping. Moreover, single cells based on the TDAP-PSU membrane reach the peak power density of 453 mW cm−2 and excellent stability without external humidification. Overall, increasing the number of active groups in the grafting site of the polymer side chain is a promising strategy to deal with the trade-off between the proton conductivity and membrane dimensional stability of HT-PEMs.

A series-connected tetracation cross-linker, DB, was synthesized successfully from 1,4-diazabicyclo[2.2.2]octane (DABCO) and dibromomethane. Which had two terminal tertiary amine groups and reacted with the bromomethylated poly(aromatic ether sulfone) (BPAES) based on 9,9-bis(4-hydroxyphenyl)fluorene and the other copolycondensation monomers giving a series of series-connected hexacations cross-linked anion exchange membranes, QPAES-DBs, for acid recovery by diffusion dialysis (DD). When applied in mostly reported simulated solution mixture of HCl and FeCl2, QPAES-DB50 shows the best DD performances with separation factor of H+ to Fe2+ ( S H + / Fe 2 + ) value of 127 and dialysis coefficient of hydrogen ion ( U H + ) value of 18.92 × 10−3 m/h, which are much higher than that of the commercial membrane TWDDA1 ( U H + = 9.18 ×10−3 m/h, S H + / Fe 2 + = 38.08). The phenomena are possibly resulted from the strengthened DONNAN effect provided by the crosslinking network containing series-connected hexacation segments at a certain crosslink density. In addition, the application in DD of QPAES-DB50 was extended to the multi-metals ions chlorides system of Mn2+/Ni2+/Cu2+/Cd2+/Cr3+. The separation factors of H+ to Ni2+, Mn2+, Cr3+, Cu2+ and Cd2+ reach up to 137.48, 119.90, 54.59, 32.84 and 16.19 separately. Evidently, QPAES-DB50 exhibits excellent DD performances and great potential of acid recovery.

Troger's base (TB) polymers have received increasing interest for different potential applications in the field of membrane techniques. In this study, a TB polymer was used for the first time to prepare ultrafiltration (UF) membrane and its antifouling property was enhanced through membrane quaternization process. The pure water flux of TB UF membrane prepared from NMP solution was 448 L m−2 h−1 with a high rejection for solute (97% for bovine serum albumin (BSA) and 90% for humica acid). The high permeability of TB UF membrane was related to its high overall porosity, while the high separation property was attributed to its small average pore size on the surface as evidenced by SEM observations. Due to the presence of tertiary amine groups, the TB membrane was further functionalized by the quaternization with methyl iodide. Surprisingly, the antifouling property of quaternized TB (QTB)membrane was improved when using BSA as a model foulant when compared to the TB membrane. The flux recovery ratio of QTB membrane was enhanced from 55% to 91% when the quaternization degree was 10%. This may be attributed to the enhanced hydrophilicity of membrane surface after the quaternization of tertiary amino groups. More importantly,QTB membrane showed higher pure water flux, BSA solution flux and flux recovery ratio than the commercial PAN, PES, PSf and PVDF membranes through a three-cycle of membrane fouling test. Moreover, the effect of polymer concentration in the casting solution, type of solvent and coagulation bath temperature on the UF membrane morphology and ultrafiltration performance were investigated.

The weak base of tertiary amine groups was introduced into poly (2, 6-dimethyl-1, 4-phenylene oxide) (PPO) anion exchange membranes (AEMs) by Cu(I)-catalyzed “click chemistry” in order to fabricate proton blockage membranes for sulfonic acid concentration in electrodialysis (ED). The degree of functionalization has been confirmed quantitatively by 1H NMR spectroscopy. Fourier transform infrared spectroscopy (FTIR) was also used to confirm the functional groups in the membranes matrix. The prepared proton blockage membrane with tertiary ammonium groups showed lesser swelling and water uptake ratios than the typical AEMs with strong organic base of quaternary ammonium groups. It is believed that the strong organic base of quaternary ammonium has a stronger hydration effect on water than that of tertiary amine groups. Interestingly, the concentration limitation of membranes with tertiary amine groups was higher than that of the membrane with quaternary ammonium groups, indicative of the proton blocking capabilities of the AEMs as a result of the weak base introduced into the matrix. Moreover, it was found that the concentration limitation of tertiary amine based AEMs was also influenced by the weight-based ion exchange capacities (IECw), essentially the water uptake and swelling ratios of the membranes. The highest concentration limitation of AEMs with tertiary ammonium groups for H+ was 3.02 mmol/L with IECw value of 1.67 mmol/g, which is slightly higher than the 3.00 mol/L reported for the commercial AEM (Neosepta ACM). Therefore, AEMs containing weak base groups are potential candidates for proton blockage membrane for acid recovery applications by ED process.

Due to the predominance of CO2 as a new trigger with source abundance, non-toxicity, good reversibility and no byproduct accumulation compared to other triggers, CO2-responsive membranes recently attract wide interest in stimuli-switchable separation. Here we report on the development of CO2-responsive nanoporous membranes with poly(2-dimethylaminoethyl methacrylate)-block-polystyrene (PDMAEMA-b-PS) block polymer (BCP) under the instruction of selective swelling-induced pore generation strategy, where hydrophilic chains of PDMAEMA can be enriched on the membrane surface and pore walls in the swelling process. The tertiary amine of PDMAEMA can be reversibly switched in conformation and charge property under the stimulation of CO2/N2. The CO2-responsive behavior of PDMAEMA enriched on the surface and pore walls has further enabled as-prepared membranes to feature the tunable pore size by introducing and removing CO2 gas. As a result, the PDMAEMA-b-PS nanoporous membranes exhibit excellent regulation in separation performances in terms of the permeance and rejection to varied proteins under the stimulation of CO2/N2. This work represents a simple and reliable way for making CO2-responsive membranes.

A polydopamine mediated amphiphilic molecular grafting approach was designed by combining hydrophilic and hydrophobic segments into the same moiety for creating amphiphilic surfaces with enhanced antifouling properties. Polydopamine (PDA) coating was performed on microporous polysulfone (PSF) membranes to form an active mediating layer. After that N,N-dimethyl ethylenediamine (DMEDA) was grafted on the PDA layer via Michael addition reaction and the tertiary amine functionality of DMEDA was reacted with 1-Iodo-1H,1H,2H, 2H-perfluorodecane to obtain amphiphilic molecular functionalization. All modification steps were confirmed by characterizations using X-ray photoelectron spectroscopy, scanning electron microscopy, capillary flow porometry, and surface wetting using a dynamic contact angle method. The antifouling study by protein adsorption shows that the hydrophilic-hydrophobic molecular layers in proximity effectively prevent nonspecific protein adsorption compared to the virgin PSF membrane. The antifouling property was further evaluated by real-time cyclic filtration with a 5 mg ml−1 bovine serum albumin (BSA) solution. The final modified amphiphilic surface has shown reduced irreversible protein bounded properties on and inside the membrane surfaces along with high flux recovery. Furthermore, the oil-in-water emulsion filtration shows excellent oil rejection at a high flux rate with nearly complete flux recovery. These findings indicate a promising and smart membrane surface modification technique that can be readily tailored for water filtration and separation applications.

A self-assembly strategy has been developed for the synthesis of anion-exchange membranes (AEMs) with high alkaline stability. Cardo poly(aryl ether sulfone ketone)s with pendent tertiary amine groups were grafted with alkyl siloxane to form a polymer with cation quaternary ammonium groups. This polymer produced a zwitterionic polymer via partially hydrolysis of the alkyl siloxane in weak basic medium. The flexible and transparent zwitterionic polymer membranes possessing a Si-O-Si cross-linked network were prepared via the sol-gel polycondensation reaction and a self-assembly process. The homogeneous and continuous Si-O-Si cross-linked network inhibited membrane swelling and improved the mechanical properties and thermochemical stability. The membrane showed alkaline stability in 1 M NaOH aqueous solution at 60 °C for 600 h and solvent resistance in polar aprotic solvents (DMAc, NMP, and DMSO) at 60 °C for 30 days.

Ionic complexing induced phase inversion in an aqueous polyacrylic acid (PAA) coagulation bath was studied for fabricating highly permeable and selective nanofiltration (NF) membranes. To obtain membranes using classical liquid-liquid phase inversion, poly (arylene ether sulfone) with tertiary amine groups (PES-TA)/N, N-dimethylformamide/tetrahydrofuran was used as the polymer dope solution. The polycationic character of PES-TA allows ionic complexation with the carboxylic acid groups of PAA. The complexing reaction at the interface of the two liquids was shown to affect the rate of phase inversion, the morphology of membranes in the phase inversion process, and enhance membrane performance. At optimized conditions, the pure water flux of the PES-TA-PAA NF membrane was 26.1 L m−2 h−1, 2.6 times greater than unmodified PES-TA membrane (10.7 L m–2 h–1). The rejection of salts and dyes of PES-TA-PAA membrane improved compared with PES-TA membrane and the rejection to MgCl2, MgSO4 and Na2SO4 were measured above 93%. The PES-TA-PAA NF membrane was shown to have stable performance in the pH range from 1 to 9 and maintain stable NF performance 100 h of filtration.

A green method to prepare asymmetric positively charged poly(arylene ether sulfone) nanofiltration (NF) membranes was explored by grafting water-soluble poly (ethylene imine) (PEI) onto a poly (arylene ether sulfone) membrane containing tertiary amine groups (PES-TA) and cross-linking with poly(ethylene glycol) diglycidyl ether (PEGDGE). The modifications were shown to increase the positive charge and decrease the pore size of the PES-TA substrate. The optimized NF membrane displayed a pure water flux of 15.5 L m−2 h−1. Membrane rejection NaCl, MgCl2, and methyl violet (MV) (at a constant pressure of 4 bar) were measured to be 46.2%, 94.9%, and 99.8%, respectively. Moreover, the membrane maintained excellent chlorine resistance during 100 h of exposure to chlorine. Thus, the membrane shows potential for water desalination and purification applications.

We report a strategy in improving the diffusion dialysis efficiency of anion exchange membranes (AEMs) by implementing a multi-amine oligomer bridge in the membrane matrix. The multi-amine oligomer, poly-dimethyl aminoethyl methacrylate (PD) was prepared via free radical polymerization, followed by partial quaternization with methyl iodide. The remaining tertiary amine groups were designed to react with benzyl bromide groups in the polymer brominated poly(2,6-dimethyl-1,4-phenylene oxide (BPPO) matrix, thus creating an intermolecular connection. The intermolecular connection serves as crosslinks and also helps to regulate the interconnectivity of the hydrophilic regions. By tuning the molecular weight and the remaining tertiary amine groups within PD, series of AEMs were fabricated. These membranes show potential in recovering waste acid via diffusion dialysis. For example, membrane M-5 shows an extraordinarily high separation factor ( S H/Fe ) of ∼2074 along with acceptable proton dialysis coefficient ( U H =0.0098 m/h). The S H/Fe is much higher than that of the conventional quaternized poly(2,6-dimethyl-1,4-phenylene oxide) (QPPO) membrane without oligomer cross-linker ( U H = 0.0080–0.0132 m/h , S H/Fe =5–60). The improvement in diffusion dialysis efficiency could be attributed to the improved interconnectivity of the hydrophilic regions, which stems from the incorporation of inter-chain ionic bridge.

Two types of phenolphthalein-based copolymers, random and block cardo poly(aryl ether sulfone)s with pendant tertiary amine groups were synthesized via copolycondensation. Both of the copolymers were grafted with (3-bromopropyl) trimethylammonium bromide to prepare anion exchange membranes with bis-quaternary ammonium groups for hydroxide ion conductivity measurements. The block anion exchange membrane QBPES-60 with an ion exchange capacity (IEC) of 1.93 mmol g−1 exhibited higher ionic conductivity (40.5 mS cm−1) in water at 60 °C than the random copolymer QRPES-60 (30.0 mS cm−1) under the same conditions. Small-angle X-ray scattering and transmission electron microscopy suggested the membrane constructed from the block polymer exhibited a more obvious phase-separated structure and formed ion clusters which would be responsible for the high conductivity. Moreover, the block anion exchange membrane with bis-quaternary ammonium groups showed better alkaline stability than the random membrane where degradation could be recognized by 1H NMR spectra as well as ion conductivities. In conclusion, integrating the block hydrophilic bis-quaternary ammonium ion groups along with the long aliphatic side chains, and the hydrophobic copolymer backbone, this synthetic strategy is promising to prepare AEMs with high conductivity and good alkaline stability.

Two hyperbranched polymers, hyperbranched polyglycidol (HPG) and 2, 3-Dihydroxypropyl-hyperbranched polyethylenimine (Diol-HPEI), were synthesized and studied as polychelatogens for boron reclamation via a hybrid ultrafiltration process, with the objectives of evaluating the key factors for polymer–boron chelation and improving boron rejection efficiency. Their chemical structures were unveiled by FTIR and XPS analyses whilst molecular weights were carefully tailored in order to be fully retained by a commercial ultrafiltration (UF) membrane. The chelation capacity of the two polymers was compared under different operating conditions i.e., chelating temperature, polymer loading and pH. It appears that Diol-HPEI prominently outperforms HPG because the tertiary amine group may be more competent than the ether group in terms of their protonation capability. Eventually, a rejection of 66–91% was achieved with a Diol-HPEI polymer loading of 100 g per g boron in the pH range of 6.9–9.0. Besides, the effects of interfering ions, i.e., Na+, Mg2+, Cl− and SO 4 2 - on polymer–boron interactions were examined in the Diol-HPEI/boron solution at the neutral condition. Results reveal that divalent cations may exert more negative influence on boron rejection owing to the competition between them and boron to form complexes with chelating polymers. These findings may provide useful insights in design of efficient boron-chelating polymers.

Anion exchange membrane (AEM) is useful for the removal of salts via electrodialysis (ED) process. AEM is also used for the recovery of acid from an aqueous feed containing acid and metal ion through diffusion dialysis (DD). However, for the selective separation of monovalent and divalent ions, special type of AEM is required. Herein, we report the preparation of poly(acrylonitrile-co-n-butyl acrylate-co-polydimethylamino ethyl methacrylate) (PAN-co-PnBA-co-PDMA) terpolymer-based crosslinked AEMs for the separation of monovalent ion from bivalent ion via ED process and recovery of hydrochloric acid (HCl) from aqueous feed of HCl and FeCl2 through DD. The slowing down the movement of bivalent anion under electrical potential, and hindering the diffusion of metal ion are the key factors for the optimization of the membranes. The tuning the polarity of the microenvironment of quaternized nitrogen (from DMA moieties) of the terpolymer by changing the length of alkyl chain gave membranes with different monovalent to bivalent anions selectivity, and separation factor for acid recovery. AEM-TP-C1, AEM-TP-C4 and AEM-TP-C10 membranes were prepared by quaternizing the DMA moieties (C1 to C10 denote length of alkyl) of the terpolymer followed by crosslinking. The AEM-TP-C10 membrane exhibited best selectivity (4.76) during desalination of sodium chloride and sodium sulfate mixture (0.01 M, 0.01 M) via ED process. Best performance in terms of acid recovery was obtained with AEM-TP-C4 membrane with dialysis coefficient of 0.031 m/h and separation factor of 38 during acid recovery. The length of alkyl and the hydrophobicity of the environment of the quaternized nitrogen is a governing factor for deciding the performance of the AEMs. This work provides an insight to design crosslinked AEMs for selective separation and acid recovery. The tertiary amine presence in the terpolymer may be quaternized with varieties of halide compounds to further correlate the structure of quaternized amine and property of the AEMs.

High permselectivity of cation exchange membrane for H+ and divalent metallic ions is essential for waste acid recovery by electrodialysis. Basic tertiary amine and imidazole groups were introduced into sulfonated poly (ether ether ketone) (SPEEK) membrane via a facile and controllable reaction, named as TA-x and IM-x (x was the basic group content), to construct acid-base pairs and reduce the swelling degree of membranes. 1H NMR confirmed the chemical structure of the as-obtained materials and protonation of tertiary amine and imidazole groups. As expected, all TA-x and IM-x membranes showed lower Fe2+ fluxes than pristine SPEEK membrane during electrodialysis because of their lower swelling degree and the electrostatic repulsion of protonated tertiary amine and imidazole groups. Remarkably, their H+ fluxes were kept similar to that of pristine SPEEK membrane. Therefore, the H+/Fe2+ permselectivity of membrane was improved considerably. Among them, IM-30 membrane showed the highest H+/Fe2+ permselectivity of 65.4, which was over three times that of pristine SPEEK membrane (19.1). Therefore, the introduction of basic groups into cation exchange membrane could reduce the swelling degree of membrane and improve the permselectivity between H+ and divalent metallic ions.

This work focused on modification of polyamide based thin-film composite membrane via a novel strategy combining surface tertiary amination and zwitterionic functionalization for improved separation and anti-dye-deposition properties. Surface tertiary amination was conducted through grafting polyethyleneimine (PEI) onto the surface of base membrane at the sites of carboxylic groups activated by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide. Zwitterionic functionalization was implemented through in situ ring-open reaction between tertiary amine groups of grafted PEI molecules and 1, 4-butanesultone. It was found that grafting of PEI could enhance CaCl2/NaCl rejection ratio from 0.36 to 3.05 through reversal of surface charge at a sacrifice of pure water permeation coefficient from 9.7 to 8.6 l/m2 h bar. The following incorporation of zwitterions under desired condition could resume pure water permeation coefficient to a higher value of 12.6 l/m2 h bar and further enhance CaCl2/NaCl rejection ratio to 3.11. Furthermore, proper surface tertiary amination and zwitterionic functionalization could even significantly improve membrane resistance to deposition by both cationic and anionic dyes. Membrane's water permeation coefficients to aqueous Congo red, Victoria blue B and methylene blue solutions under steady state were enhanced by 72.5, 78.8 and 53.2%, respectively, and relative flux decline ratios were lowered by 80.5, 80.3 and 79.0%.

A novel stimuli-responsive and anti fouling poly(vinylidene fluoride) (PVDF) membrane is proposed by incorporating amphiphilic copolymer, poly(vinylidene fluoride)-graft-Poly(2-N-morpholino)ethyl methacrylate (PVDF-g-PMEMA) as modifier due to presence of tertiary amine and heterocyclic oxygen (oxa-group). The prepared membrane exhibits dual responsive properties, i.e. pH responsive and temperature responsive behaviour as well as antifouling characteristics. The mechanism of the pH-responsive performance is originated from the pH-responsive swelling and shrinking of PMEMA chains embedded in the membrane and Temperature-responsive performance is attributed to the Temperature-responsive extended and collapsed state of PMEMA chains at around LCST. The antifouling property is induced owing to presence of hydrophilic PMEMA chains in the membrane. As a result, the permeability of the novel PVDF membrane was increased from 0.29 L / m 2 hkPa (plain membrane) to 0.77 L / m 2 hkPa (modified membrane) with addition of amphiphilic copolymer from 0 wt % to 3 wt %. The maximum o/w emulsion rejection percentage of about 97% was obtained through blended membrane. Thus the proposed membrane in this research work offers an approach for the treatment of oily wastewater.

Carbon capture and storage (CCS) is the process of capturing carbon dioxide (CO2) produced from the combustion of fossil fuels. CO2 is a major contributor to global warming and should be removed after combustion. The objective of this research is to design a CO2 capture membrane consisting of tertiary-amine-stabilized gold nanoparticles (Au NPs), graphene oxide (GO), and polyelectrolytes. A high CO2 capture ability is most important for designing a CO2 capture membrane that can maintain a high gas permeance. Multilayer films were fabricated using an automatic spray-assisted layer-by-layer (LbL) machine. The polar affinity of polyelectrolytes assisted the CO2 capture of tertiary amines. The randomly oriented and loosely stacked GO layers not only helped align the Au NPs in the polyelectrolyte matrix, but also helped maintain the permeance of N2. Thus, we successfully fabricated a CO2 adsorptive multilayer nanocoating with a maximum CO2/N2 selectivity of 48.48 while maintaining the N2 permeance at 1204.25 GPU.

Anion exchange membrane fuel cells (AEMFCs) have become one of the most promising energy-conversion devices due to the potential of adopting non-noble metal catalysts and faster oxygen reduction reaction kinetics in an alkaline operating environment. Here, a series of anion exchange membranes with high ionic-conductivity and low swelling ratio were prepared from imidazolium-functionalized crosslinked cardo poly(arylene ether sulfone)s for AEMFCs. Two oligomers, tertiary amine-containing poly(arylene ether sulfone) (PES-DA) and bromomethyl-containing poly(arylene ether sulfone) (BPES), are synthesized and then mixed at −40 °C. They are spontaneously inter-crosslinked at room temperature to form dense anion exchange membranes (AEMs), in which the tertiary amine groups of PES-DA rapidly react with the bromomethyl groups of BPES to form the crosslinked bonds. This avoids the use of crosslinking agents and the expense of functional groups. The resulting membranes show a high hydroxide conductivity up to 82.4 mS cm−1 at 80 °C and a slight swelling low to traditional AEMs due to its crosslinked network structure. An open circuit voltage (OCV) of 0.82 V and a maximum power density of 92.1 mW cm−2 are achieved in a H2/O2 single cell. The as-prepared membranes have a great potential for the application in AEMFCs.

4-diethylamino-2-butanol (DEAB), as a novel tertiary amine, shows a promising potential for CO2 capture. In this study, the mass transfer performance of CO2 absorption into aqueous DEAB solution in a non-wetted and partially-wetted mode of hollow fiber membrane contactor (HFMC) was theoretically investigated in comparison with that of monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA) and 2-amino-2-methyl-1-propanol (AMP). A 2D mathematical model based on finite element method (FEM) was established to solve the steady-state continuity equations for the shell, tube and membrane sides simultaneously. The influences of the operating parameters on the CO2 absorption flux in HFMC including liquid and gas velocity and CO2 partial pressure were comprehensively investigated. The numerical results show that the CO2 absorption flux can increase with the increasing liquid velocity and CO2 partial pressure, and slightly increases with the increasing gas velocity. Moreover, the CO2 absorption performance of aqueous DEAB solution was further compared with different amine solutions, which reveals that the CO2 absorption flux of DEAB is higher than those of DEA, MDEA and AMP, and is also comparable to MEA. The analysis on the mass transfer resistance indicates that the proportion of the membrane mass transfer resistance increased rapidly from 13.7% to 75.3% as membrane wetting ratio increased from 0% to 20%. Instead of the liquid phase, the mass transfer in wetted membrane phase becomes the rate-controlling step ultimately. The increase in the membrane wetting leads to the significant decrease in CO2 absorption performance with 49.4% and 80.5% decrease in CO2 absorption flux and the overall mass transfer coefficient at membrane wetting ratio of 5% and 50%, respectively. Based on the analysis on enhancement factor, it demonstrates that the chemical reaction between CO2 and DEAB for the non-wetted mode generally occurs in the intermediate fast-instantaneous regime and gradually transfers to the instantaneous regime with membrane wetting.

A novel bisphenol monomer bearing a cyclic tertiary amine was prepared in good yields by the acid-catalyzed reaction of N-methyl-4-piperidone and phenol. Tertiary amine poly(aryl ether sulfone) (TAPES) with high molecular weights of up to 95.3 kg mmol−1 and good thermal stability was synthesized by nucleophilic substitution of the bisphenol monomer with 4,4′-dichlorodiphenyl sulfone. The spatial separation between the cyclic tertiary amine groups and the hydroxyl ortho-position improves the stability of the intermediate and was the key to the polymerization. The anion exchange membranes (AEMs) QPES or DQPES are obtained by quaternization of TAPES with methyl iodide or (3-bromopropyl)trimethylammonium bromide, respectively. DQPES (ion exchange capacity = 3.12 mmol g−1) shows a higher ion conductivity of 59.8 mS cm−1 and reasonable dimensional stability in water at 80 °C. DQPES membrane revealed that the high conductivity might be due to its phase-separated structure in small-angle X-ray scattering test. The alkaline stability of QPES and the methoxy-capped QPES was compared, end-capping was found to improve the stability of piperidinium cations. This method offers a versatile platform for cost-effective synthesis of piperidinium-based AEMs with poly (aryl ether) backbones, and may provide a strategy to improve alkaline stability.

We report an effective and simplified procedure for the synthesis of cross-linked alkaline anion-exchange membranes (AEMs). A new monomer containing two tertiary amine groups on 4,4'-dihydroxydiphenyl ether (DABPE) is used in nucleophilic aromatic substitution step-growth copolymerization with 4,4'-difluorobenzophenone, 2,2',6,6'-tetramethyl-4,4'-biphenol to obtain the corresponding poly(arylene ether ketone) copolymers containing tertiary amine groups. After partial quaternization, the residual tertiary amine groups of the polymer react with p-xylylene dichloride to produce a cross-linked membrane, which is followed by anion exchange with hydroxide ions. The resulting cross-linked membranes exhibit high hydroxide ion conductivity (above 10(-2) S cm(-1) at room temperature), good mechanical properties, and reduced water uptake relative to the linear uncross-linked membrane. This facile synthetic approach enables the preparation of cross-linked materials with the potential to meet the demands of hydrogen-powered fuel cells as well as direct methanol fuel cells. (c) 2012 Elsevier B.V. All rights reserved.

A composite membrane composed of hyperbranched poly(amidoamine) (HYPAM) and polysulfone (PSf) was successfully prepared to enable the removal of heavy metal ions from contaminated aqueous media. HYPAM was prepared by a one-pot reaction followed by modification with palmitoyl chloride, which included a long aliphatic chain that improved the compatibility with the hydrophobic PSf. The dendritic chelating agent HYPAM was incorporated into PSf via a phase inversion process to produce a HYPAM/PSf membrane. The resulting membrane was characterized by thermogravimetric analysis, X-ray photoelectron spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, and field-emission scanning electron microscopy. The binding capacity of the HYPAM/PSf membrane toward heavy metal ions [Cd(II)] was investigated by inductively coupled plasma atomic emission spectroscopy. The efficiency of Cd(II) removal was 51% and resulted from metal ion complexation by a tertiary amine of HYPAM, and primary amine and amide groups grafted onto the PSf membrane surface. Moreover, the water permeability and the bovine serum albumin (BSA) retention of the HYPAM/PSf composite membrane were as high as 18 L m−2 h−1 at 1 bar and 85%, respectively. Under acidic conditions, the composite membrane recovered 86% of the Cd(II) ions. The findings of the present study highlight the potential for using HYPAM/PSf composite membranes as effective recyclable materials for the removal of heavy metal ions in the context of water treatment.

The goal of the present work is the development of nanofiltration membranes by the phase inversion technique using a newly developed polymer, cardo poly(arylene ether sulfone) with pendant tertiary amine groups (PES-TA). The obtained membranes were characterised in terms of their water flux, salt and basic dye rejections, the cross-sectional and surface morphologies, surface charge characteristic, and chlorine tolerance. A typical membrane (M-40) exhibited moderate rejection to salts (36.6% to NaCl, 63.3% to MgCl(2) and 70.2% to FeCl(3)), but high rejection to basic dyes (>98%). Zeta potential measurements indicated that the PES-TA membranes were positively charged below pH 10.7. The M-40 membrane showed excellent chlorine tolerance. After exposure to an aqueous NaOCl solution (active chlorine concentration >= 1000 ppm) for 20 days, the rejection of membrane was not changed. In addition, the obtained membrane showed efficient separation of basic dyes in the presence of NaCl salt. (C) 2011 Elsevier B.V. All rights reserved.

Production of bioethanol from lignocellulosic biomass requires pretreatment of the biomass in order to improve the susceptibility of the cellulose to enzymatic hydrolysis to glucose. When dilute acid is used to perform this process, the hemicellulose is also hydrolyzed to its component sugars while simultaneously releasing acetyl groups attached to the hemicellulose backbone. Other compounds from the lignin and sugar degradation products are also produced that inhibit subsequent bioconversion of the solubilized sugars to the desired products. In this work we focused on removal of acetic acid from a dilute sulphuric acid pretreated corn stover hydrolysate. Acetic acid has been extracted into an organic phase at pH values below its pKa. The organic phase diluent consisted of octanol. Alamine 336, a tertiary amine and Aliquat 336 a quaternary amine were used as the aliphatic amine extractants. Our results indicate more than 60% removal of acetic acid using Alamine 336. Extraction rates were much slower for Aliquat 336 probably due to the higher viscosity of the Aliquat 336/octanol phase. The presence of sulphate anions, as a result of dilute sulphuric acid pretreatment, results in the co-extraction of bisulphate anion. Bisulphate anion is preferentially extracted at pH values below its pKa. Consequently the pH of the hydrolysate increases from between 1 and 2 to above 4.0 during extraction. In addition, extraction of low molecular weight lignins and phenolics is also observed. Thus the membrane extraction process developed here may be used not only for removal of acetic acid but also to adjust the pH of the hydrolysate to values that are more compatible for fermentation and to remove other inhibitory compounds.

Microporous polypropylene (PP) hollow fiber (PPHF) membranes with surface-grafted block copolymer brushes of poly(ethylene glycol) monomethacrylate (PEGMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) (PPHF- g -(PPEGMA- b -PDMAEMA)) were prepared via consecutive surface-initiated atom transfer radical polymerization (ATRP). The effective pore size of the surface modified PPHF membranes could be adjusted by controlling the graft chain length, or the ATRP time. Quaternization of the tertiary amine groups of the PDMAEMA block with 1-bromododecane gave rise to a high concentration of quaternary amine salt (QAS) on the PPHF membrane surface. The antibacterial effect of the quaternized PPHF- g -(PPEGMA- b -PDMAEMA) membrane was assayed with Escherichia coli ( E. coli , a Gram-negative bacterium) and Staphylococcus aureus ( S. aureus , a Gram-positive bacterium) cultures. In addition to bactericidal properties, the functionalized membrane surface also exhibited anti-fouling effect for bacteria due to the hydrophilic nature of the P(PEGMA) block on the PPHF- g -(PPEGMA- b -PDMAEMA) membrane. The permanence of antibacterial effect of the functionalized PPHF membrane was also demonstrated in repeated applications of the quaternized PPHF- g -(P(PEGMA)- b -PDMAEMA) membrane.

A novel kind of zwitterionic polymer, tertiary amine-modified PES (TA-PES), bearing cationic tertiary amine groups and anionic sulfonic groups, was synthesized in this study. The as-synthesized TA-PES was employed to fabricate ultrafiltration membranes by phase inversion in a wet process using pure water or sodium chloride aqueous solution as coagulation bath. It was found that the as-fabricated ultrafiltration membranes exhibited distinct ion-strength-dependent flux due to the inherent zwitterionic characteristics of TA-PES. The permeation flux of TA-PES membranes can be varied dramatically by simply changing the ionic content in coagulation bath. Furthermore, TA-PES membranes displayed superior anti-protein-fouling property and desirable ultrafiltration performance.

Determining membrane sorption selectivity by conventional methods is usually fairly time-consuming and can even become a rather difficult task for membrane materials with low sorption levels. In this case, the amount of the species absorbed by the membrane is indeed so low that large amounts of membrane materials are usually required to determine the composition of the sorbed mixture by a common desorption method with several associated drawbacks (e.g. experimental uncertainty, long sorption and desorption times). The paper describes how performing desorption experiments directly in a 1H NMR tube can overcome all the former limitations. The sorption selectivity of new poly(urethane-imide) membranes containing increasing contents in tertiary amine groups was determined for the azeotropic mixture ethanol (20 wt%)/ethyl-tert-butyl ether ETBE. Membrane selectivity values given by this method were very close to those obtained by the most common former method, with the advantages of being both very simple and much quicker to implement.

Microporous carbon membranes were prepared on an α-alumina support by a pyrolysis of cationic tertiary amine/anionic polymer composites. The precursor solutions contain a thermosetting resorcinol/formaldehyde (RF) polymer and a cationic tertiary amine. Three types of cationic tertiary amines with different chain lengths were used, such as tetramethlammonium bromide (TMAB), tetrapropylammonium bromide (TPAB) and cetyltrimethylammonium bromide (CTAB). A porous structure was produced by a decomposition of the amine and the resulting pores assisted the further gasification of the RF polymer at high temperature. The carbon/alumina membranes have thin and continuous carbon top layers with a thickness of 1 μm. Gas permeation tests were performed using single gases of CO 2 , O 2 , N 2 , CF 4 , n -C 4 H 10 and i -C 4 H 10 , as well as binary mixtures of CH 4 / n -C 4 H 10 and N 2 /CF 4 at different temperatures between 23 and 150 °C. The carbon membrane prepared using TMAB showed separation factors higher than 650 for the CH 4 / n -C 4 H 10 mixtures and higher than 8100 for the N 2 /CF 4 mixture. From the permeation of pure gases with different molecular sizes, the pore sizes of the carbon membrane prepared using TMAB, TPAB and CTAB are estimated to be 4.0, 5.0 and larger than 5.5 A, respectively, indicating that the micropore size of the carbon membranes is controllable by using different amines.

To intensify mass transfer and simplify the separation processes in recovering and concentrating organic acids from their fermentation broths, an in situ coupling separation process of electro-electrodialysis with back-extraction has been developed. In this new process an oil-in-water disperse system comprised by extractant phase and stripping phase flew in the cathode chamber concurrently. The two steps, including back-extraction and concentration, happen at the same time in one module. The experimental studies on the process were carried out, with a mixed solvent of a kind of tertiary amine with long aliphatic chains and n-octanol as the extractant, and citric acid as the solute. The salt aqueous solution of mono-sodium citrate was used as the stripping phase. The influence of the current density, phase ratio of the extractant phase to the stripping phase, salt concentration of the stripping phase and initial concentration of receptor was investigated. The experimental results showed that the new process integrated the EED process with the back-extraction process in one module successfully, which made the separation process simple and the equipment cost less. The current efficiency of 103.5% and the specific energy consumption of 2.48 kW h/kg were reached. Meanwhile the voltage was not higher than 24 V. Compared with a normal EED process, it is a process with the advantages of higher mass transfer performance and slightly lower energy consumption.

A steady-state model is presented for a hollow fibre liquid membrane extractor which describes the mass transfer performance as a function of phase flows, geometry and system physical properties. The model is compared with the experimental results for Cr(VI) extraction with a tertiary amine carrier. Shell side mass transfer correlations, developed primarily for gas–liquid membrane contactors, are also incorporated into the model and compared. This model is subsequently used to optimise both operating and design parameters for maximum mass flux in hollow fibre liquid membranes.

Cadmium has been extracted as a chloride complex through a flat-sheet-supported liquid membrane (SLM), using the tertiary amine Alamine 304-1 (mainly trilaurylamine or TLA) in kerosine. The typical permeability of the membrane was 1.1×10 −6 m s −1 . The rate limiting step is diffusion through the membrane. The cadmium loading of the extractant at the feed–membrane interface is high. Trilaurylammonium chloride crystallizes at the surface of the membrane above 0.2 M TLA. This salt blocks the pores and lowers the extraction rate up to a factor of 3. Apart from this blocking effect, the permeability through the membrane is described well with the presented model, using physically realistic parameter values. When the precipitation can be minimized, the system has good potentials for the extraction of cadmium chloride complexes.

Four types of salts of tri-n-octylamine (TOA salts) were prepared by equilibrating xylene solutions of TOA and aqueous solutions of nitric, hydrochloric, sulfuric, and citric acids. A comparison was made for the transport of citric acid from aqueous solutions through a supported liquid membrane using these TOA salts and pure TOA as mobile carriers. The strip phase was either deionized water or sodium carbonate solution. Experiments were performed as a function of total TOA concentration and different loadings of TOA salts in the membrane phase. In contrast to the use of pure TOA, it was generally shown that the amount of citric acid transported increased for all TOA salts in long-term tests (over 8 h). Under the conditions studied, such an enhancement decreased in the order for TOA salts: citrate > nitrate > sulfate > chloride, regardless of the strip phases employed.

Co(II) and Fe(III) transport through a supported liquid membrane consisting of a microporous nitrocellulose film (Synpor) immobilizing a tri-n-octylamine (TOA) as a carrier and n-decane as a liquid membrane matrix, has been investigated. Membrane transport was evaluated by measuring the 60 Co- and 59 Fe-radioactivity in the strip solution. The conductivity of the extracted compounds through the membrane was also measured. A maximum in the curve of Co(II) flux vs. TOA concentration was found. This maximum in flux was shown to occur at the same (e.g. 1.8 M ) TOA concentration as the main maximum in the conductivity. It was shown that this phenomenon can be connected with a changing from the common transport mechanism to so-called “jumping” membrane transport which previously theoretically has been predicted by Cussler [J. Membrane Sci., 43 (1989) 149]. Such membrane transport is realized in a relatively narrow interval of the carrier (TOA) concentration and may be more effective than the common facilitated diffusion mechanism. To obtain the described effect one needs to hold such a supported liquid membrane under transfer conditions during a certain period of time, in order for the membrane medium in the “jumping” region to become self-organized and self-fitted for the membrane transport process.

Functional groups, i.e. tertiary amine and carboxyl groups, were introduced into polyurethane membranes in order to investigate the effects of these groups on the vapor and gas permeability of the membranes. It was observed that, when the contents of the functional groups increased, the crystallinity, density and glass transition temperature of the membranes increased, whereas the vapor and gas permeability of the membranes decreased. The oxygen/nitrogen separation coefficient increased with increasing functional group content in the membrane, and was strongly dependent on the functional group.

The pervaporation of ethanol-water mixtures was examined on cationic/anionic interpenetrating polymer network (IPN) membranes. The cationic polyurethane prepared by quaternizing the tertiary amine from N-methyldiethanolamine and the anionic acrylic copolymer from acrylic acid were used as the cationic and anionic component. The permselectivity of the membrane was investigated with variations in the IPN composition and the ion concentration in the membrane. The separation factor increased as the content of the anionic component in the membrane increased. The ion content in the membrane was also found to be an important factor for the optimum permseparation of water. Better performance was achieved by using PEG-based polyurethane as the cationic component of the IPN membrane. Moreover, the highest selectivity was observed for the IPN membrane with 10 wt.% of PEG-based polyurethane. This result could be explained by high swelling restriction due to the increase in physical crosslinking between networks.

This is the second paper describing the coupled transport of uranium ions through liquid membranes. The membranes consist of a microporous polymeric support with an organic solution of a tertiary amine complexing agent held within the pores by capillary forces. p]Both the composition of the organic solution and the structure of the microporous support have a marked effect on uranium flux. With increasing concentration of the agent in an inert diluent, both the amount of uranium that can be extracted into the membrane and the viscosity of the organic solution increase. These opposing effects result in a maximum flux at about 30 vol.% agent in the diluent. The size of the pores in the support also affects the flux; it appears that interaction with the pore walls in membranes with small pores hinders diffusion. p]Two types of interfacial effects have also been observed. The first of these is concentration polarization in the aqueous solution adjacent to the membrane surface. This effect can be reduced by increased stirring. Second, the transmembrane flux of uranium can be limited by the rate of formation (or dissociation) of the uranium complex at the membrane—solution interfaces.

This paper describes the parameters controlling the coupled transport of uranium anions through liquid membranes. The membranes consist of a microporous polymeric support with a liquid, tertiary amine complexing agent held within the pores by capillary forces. When this liquid membrane is interposed between two aqueous solutions of unequal ion concentrations, the complexing agent can pick up the anion on one side of the membrane and carry it across the membrane by diffusion in the form of a neutral complex. Ions of opposite charge may be carried in the same direction, or ions of like charge may be carried in the opposite direction. We refer to these two modes of transport as “co-transport” and “counter-transport”, respectively. In the coupled transport of uranium, both co-transport and counter-transport can occur. p]The coupling of the flows of two ions permits one of the ions to be pumped against its concentration gradient. We have demonstrated “uphill diffusion” of uranium against substantial concentration gradients, and at significant rates. A number of factors affect uranium flux, principally the concentrations of uranium and the coupled ion in the aqueous solutions. The base strength of the tertiary amine is also an important parameter.

A nitrate-specific anion-exchange membrane was obtained by suitable amination of bromomethylated polysulfone blended with polysulfone. The presence of a tertiary amine is required. In transport from aqueous solutions containing a 7-fold excess of chloride ions over nitrate ions, nitrate flux is larger than chloride flux by a factor of two as a result of membrane selectivity.

Four kinds of cationic membranes were prepared by quaternary amination of haloacetalized poly(vinyl alcohol) membrane with triethylamine, tri-n-propylamine, tri-n-butylamine and N,N - dimethyl-n-dodecylamine. Membrane potentials and permeabilities for the sodium salts mentioned below were analyzed based on the Teorell-Meyer-Sievers (TMS) theory. The observed order of the permeabilities, namely NaI > NaClO 4 > NaNO 3 > NaBr > NaCl, is explained by the differences in affinities of the respective anions for the water-swollen membranes.