Search

Facile fabrication of the ultra-high-performance adsorbent can effectively ameliorate the Cr(VI)-pollution elimination in sewage control. Herein, a simple synthesis strategy is proposed to tap a versatile chelating resin poly(pyrogallol-tetraethylene pentamine) (PPTA) with respect to Cr(VI) removal from solution. Multiple changing factors which affect the adsorption behavior of PPTA are explored sequentially, such as initial pH, adsorbate concentration, adsorbent dosage, temperature, foreign ions etc. The microstructure and functional mechanism of synthetic adsorbent are investigated systematically by means of various characterizations including TEM, EDS, FT-IR, XPS, etc. Consequently, as-prepared PPTA-3 microsphere by the reactant ratio of 1: 1 represents a brilliant synergistic adsorption and reduction result for Cr(VI) by the drastic electrostatic interaction of -NH3+ and -OH2+ groups, including satisfactory removal efficiency which closes to 100 % in low concentration, favorable specificity for the influence from coexistent ions (Mo(VI), Mn(VII), Cl-, Cr(III), etc), and passable recyclability. Following the surpassingly fitting with Langmuir isotherm model, its maximum capacity reaches 714.29 mg g-1 at 30 °C. The removal performance is essentially in agreement with the pseudo-second-order kinetics, simultaneously, suffers the rate-limiting impact depending on intra-particle diffusion process. In brief, this newly developed chelating resin presents an effective means with regard to the Cr(VI)-wastewater treatment or other uses in the future.

High proton conductivity and sufficient stability of the polybenzimidazole membrane are important for the application of high-temperature proton exchange membrane fuel cells (HT-PEMFCs). A series of composite membranes based on crosslinked mPBI (cPBI) with cerium 2,4,6-triphosphono-1,3,5-triazine (CeTPT) were resoundingly fabricated. Novel cPBI networks with tetrafunctional N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) were synthesized. It is noteworthy that a new high-temperature proton conductor CeTPT was added. CeTPT contained three phosphonic acid groups, which offered good proton conductivity at moderate-to-low humidity and had good thermal stability. Tetrafunctional crosslinker TGDDM had multiple functional groups. With a relatively low crosslinking degree (CLD), the mechanical properties, dimensional stability, and oxidative resistance of the membranes were efficiently improved. The low CLD and good physicochemical stability also allowed high doping levels of CeTPT (up to 50%) and consequently high proton conductivity. At 180 °C and 50% RH, the proton conductivity of cPBI-5-CeTPT-50 and cPBI-10-CeTPT-50 was 0.072 and 0.068 S cm–¹, respectively. The cPBI-CeTPT membranes showed good methanol resistance and membrane selectivity, and thus the membranes were suitable for direct methanol fuel cells.

Zirconium (1,3,5,2λ5,4λ5,6λ5-triazatriphosphinine-2,2,4,4,6,6-hexyl) hexa(phosphate) (ZrTHPA) is synthesized by chelation combination (1,3,5,2λ5,4λ5,6λ5-triazatriphosphinine-2,2,4,4,6,6-hexyl) hexa(phosphonic acid) (THPA) with zirconium ion in a certain ratio. The THPA is synthesized by hexachlorocyclotriphosphazene with P(OEt)3, and hydrolyzed in HCl. Their structure is characterized by nuclear magnetic resonance (NMR) and infrared spectroscopy (IR), and hydrogen bonding and chelation interactions between Zr4+ and phosphonic acid are detected. X-ray diffraction and scanning electron microscopy (SEM) show that ZrTHPA has a layered structure. Thermogravimetry-differential thermal analysis (TG-DTA) shows that ZrTHPA has good thermal stability. ZrTHPA also has good oxidative stability and hydrolysis resistance. The ion exchange capacity of ZrTHPA (1:2) is 2.21 meq g−1. At 180 °C, the proton conductivity of ZrTHPA (1:2) at 100%, 50%, and 0 relative humidity is 0.128 S cm−1, 0.069 S cm−1, and 0.038 S cm−1, respectively. ZrTHPA can be used as solid acid catalyst or proton conductor which is doped into proton exchange membranes.

To use a minimized cross-linking agent to best improve the performance of a membrane, chloromethylated poly(2,5-benzimidazole) (CMABPBI) is designed to achieve self-covalent cross-linking. Poly(2,5...

To prepare new high temperature organic-inorganic proton conductor for applications in proton exchange membrane fuel cells (PEMFC), 2,4,6-triphosphono-1,3,5-triazine (TPT) was synthesized and reacted with three different types of metal ions (Ce, Zr and Fe) in varied molar ratios. In each TPT molecule, three phosphonic acid groups were introduced into the triazine ring to obtain an organic compound with high content of proton conducting groups, which was then reacted with metal ions to ensure the insolubility in water aiming to avoid leaking during PEMFC operation. CeTPT(1:2) exhibited good thermal stability up to 200 °C and showed crystalline phase. MTPT exhibited high ion exchange capacity (IEC, 1.53–2.12 meq. g−1). CeTPT(1:2) exhibited highest proton conductivity among all samples, which reached 0.116, 0.070 and 0.034 S cm−1 at 100% relative humidity (RH), 50% RH and anhydrous conditions at 180 °C, respectively. The corresponding activation energy for proton conduction was 14.5, 16.0 and 21.5 kJ mol−1 at 100% RH, 50% RH and anhydrous conditions, respectively. The mechanism for proton conduction was proposed according to the activation energy. The proton conductor can find promising applications in fuel cells, corrosion inhibition and water desalination due to its good thermal stability and high IEC.

Few work focuses on the 7Li+ enrichment materials even though each Li isotope plays an important role in the nuclear industry. In this work, we present an efficient composite membrane for 7Li+ enrichment. The composite membrane was prepared using nonsolvent-induced phase separation (NIPS) method, obtained by casting the polymer polyvinyl alcohol (PVA) grafted formoxylbenzo-15-crown-5 (FB15C5) (PVA-g-FB15C5) in DMSO solution on non-woven fabrics (NWF). The composite membrane exhibited a large amount of sponge-like structure with the average pore diameter of 0.36 µm. The dynamic liquid–solid extraction results clearly indicated that the distribution coefficient (Kd) increased dramatically from 136 to 175 mL g−1 with an increase of crown ether immobilization amount from 0.76 to 2.13 mmol g−1, and the equilibrium separation factor (α) also increased significantly from 1.013 ± 0.002 to 1.065 ± 0.002, which is much higher than that obtained using FB15C5 by the liquid–liquid extraction (1.022 ± 0.002) and non-porous PVA-g-FB15C5 film via liquid–solid static extraction (1.046 ± 0.002). More importantly, 7Li+ concentrated on the composite membrane as a result of the enhanced electron density of the crown ether after grafted onto PVA. In a word, the functional composite membrane exhibits an attractive application potential in the development of green and highly efficient membrane chromatography for lithium isotope adsorptive separation.

Membrane coupling with electrochemical processes has proven to be an effective way for wastewater treatment. However, it still suffering from high energy consumption and low operational stability. Three different forms nanosheet-MoO3 were prepared by hydrothermal synthesis method via adjusting various additives to ammonium heptamolibdate. MoO3 loaded porous Ti membranes was employed as anode to constitute fixed-bed electrocatalytic reactor (FBER) for synthetic dye wastewater treatment to overcome the drawback of three different forms. The electrochemical properties of MoO3/Ti membranes were investigated, results showed that the MoO3/Ti membranes with hexadecyltrimethylammonium bromide (CTAB) additive exhibited the best electrochemical performance. Meanwhile, three MoO3/Ti membranes were used to constitute FBER for 100 mg l−1 MO wastewater treatment, the MO and COD removal rate of MoO3/Ti without additive, MoO3/Ti with CrCl3 additive and MoO3/Ti with CTAB additive were 78.6% and 65.3%, 83.2% and 72.9%, 90.3% and 81.6%, respectively. Furthermore, the energy consumption of MoO3/Ti with CTAB additive was only 0.76 kWh·kg−1·COD. After 3 repeated stabilities experiment of 12 h MO wastewater treatment, the removal rate of MO and COD remained above 97.2% and 88.6%. In sum, the FBER exhibits a great potential in the dye wastewater treatment with high efficiency and excellent stability.

A unique one-pot polymer synthesis and membrane formation technique was developed to fabricate polysulfone-graft-4′-aminobenzo-15-crown-5-ether (PSf-g-AB15C5) membranes for lithium isotope adsorptive separation. This is, the reaction system and the preparation of casting solution were integrated into one step without separation and purification of the product. Herein, PSf-g-AB15C5 was prepared by the grafting reaction of AB15C5 and chloromethylated polysulfone (CMPSf). The viscosity of reaction solution was controlled by the grafting time. The reaction solution with a certain viscosity or at a certain grafting time as a casting solution was in-situ cast to porous membranes through non-solvent induced phase separation (NIPS). Results showed that the resultant membrane structures changed gradually from macrovoids to sponge-like with the viscosity increase of the reaction solution, which is attributed to the grafting and self-crosslinking of PSf-g-AB15C5 polymers. This endows the membranes can be formed even at a very low polymer solution concentration of 10%. Interestingly, the sponge-like crosslinked networks displayed a strong mechanical strength at the range of 2.12–3.72 MPa. Moreover, all membranes showed high porosity. Especially, the membrane with the reaction time of 20 h exhibited a remarkable porosity of 85.2%. These porous membranes promoted the effective adsorption between Li+ ions and crown ether groups and led to a high distribution coefficient. A remarkable equilibrium separation factor of 6Li+/7Li+ up to 1.055 was obtained from the membrane containing 0.521 mmol g−1 of the immobilization crown ether, which is much higher than the acceptable industrial scale separation factor of 1.03. Due to the higher affinity of 6Li+ to crown ether than 7Li+, 6Li+ and 7Li+ were enriched in the membrane phase and the solution phase, respectively. Therefore, the membrane shows a great potential in the development of green and highly efficient membrane chromatography for lithium isotope adsorptive separation applications.

Polysulfone-graft-monoazabenzo-15-crown-5 ether (PSf-g-BN15C5) was synthesized via nucleophilic substitution reaction and used to prepare PSf-g-BN15C5/non-woven fabrics (NWF) composite membrane for lithium isotopes adsorptive separation by non-induced phase separation (NIPS). The influences of polymer concentration, additive and coagulation bath temperature on membrane properties were systematically explored. A solid–liquid dynamic extraction method was employed to investigate the lithium isotopes separation of the composite membrane. Results showed that the PSf-g-BN15C5/NWF composite membrane with a sponge-like pore structure, the porosity of 69% and the pure water flux of 1433 L/m2/h were obtained under the conditions: PSf-g-BN15C5 polymer concentration of 14 wt%, DMF as solvent and water as a non-solvent in coagulation bath at 60 °C. Moreover, it was found that the lithium isotopes equilibrium separation factor obtained from the membrane with immobilization amount (IA) of 0.81 mmol/g was up to 1.052 ± 0.002, which was much higher than that obtained from the traditional liquid–liquid extraction system of H2O-LiI/BN15C5-CHCl3 (1.007 ± 0.002) and the solid–liquid static extraction using PSf-g-BN15C5 polymer (1.014 ± 0.002) as extractant. In brief, the composite membrane has a great potential application in the development of a green-friendly adsorptive separation method for lithium isotopes.

Branched polybenzimidazole (PBI) derivatives with large free volume and deformation rate exhibit unexpected properties in high temperature proton exchange membranes (HTPEMs) applications. However, the weak chain entanglement of branched structure implies poor membrane-forming property. To effectively improve the comprehensive performance of HTPEMs, a branched tqPBI polymer is prepared by direct polymerization of mPBI polymers with tetra-acids (TCAQ), and crosslinked interpenetrating networks are constructed by thermal crosslinking with brominated polyimide (dBPEI) crosslinker. The networks can completely wrap the synthesized cerium pentaphosphonic acid (CePMP) by ionic and hydrogen bonds to achieve high doping levels of proton conductors. Meanwhile, the good mechanical property, chemical stability, and dimensional stability of tqPBI-dBPEI/CePMP membranes are acceptable. The permeability coefficient of tqPBI-dBPEI/CePMP membranes is 1–2 orders of magnitude lower for gas (H2 & O2) and liquid (methanol) phase fuel than Nafion membrane. At 180 °C, the proton conductivity of tqPBI-dBPEI(8)/CePMP(40) is 0.143–0.048 S/cm from 100% RH to anhydrous conditions. More importantly, after the proton-conducting durability test for 96 h, the conductivity of tqPBI-dBPEI(8)/CePMP(40) decayed by 1.9% at 100% and 1.0% at anhydrous conditions. The results demonstrate the effectiveness of crosslinking and doping strategy in the branched membrane, which is suitable for HTPEMS applications.

A film material, polyvinyl alcohol-graft-benzo-15-crown-5 ether (PVA-g-B15C5) for lithium isotope separation by liquid–solid extraction was prepared from polyvinyl alcohol (PVA) and 4′-formoxylbenzo-15-crown-5 ether (FB15C5). The effect of immobilization amount of crown ether on film, the counter anion of lithium salt, extraction solvent and temperature on separation factor were explored in detail. The maximum separation factor 1.060 ± 0.002 was obtained by an isopropanol-LiI/PVA-g-B15C5 film system at 20 °C. The heavy isotope, 7Li was enriched in the film phase owning to a stronger bonding environments from the synergistic effect of B15C5 and hydrophilic PVA as well as the linking groups.

Crown ethers containing polymer membranes are considered as one of the most promising candidates for selective separation of Li+. Herein, a novel dibenzo- 14-crown-4 ether-based polyimide (Poly(DAB14C4-6FDA)) was synthesized by condensation polymerization between di(aminobenzo)-14-crown-4 (DAB14C4) and 4,4′-(hexafluoro-isopropylidene) diphthalic anhydride (6FDA). The resultant polyimide with a high molecular weight (63 kDa) was employed to fabricate microporous membranes by non-solvent induced phase separation using N,N-Dimethylformamide (DMF) as a solvent and water as coagulation bath. The pure-water permeance of the PI membrane (porosity of 80.5%) reached 580 L/m2 h (LMH) bar−1. Simultaneously, this membrane displayed excellent Li+ adsorption capacity (34.05 mg g−1) owing to the high crown ether content of 1.36 mmol g−1. The Li+ adsorption kinetics followed a pseudo-second-order adsorption equation and the adsorption isotherm data fitted a Langmuir model, indicating monolayer chemical adsorption. The selective separation factors of Li+ to Na+, K+, Mg2+, and Ca2+ were 45.6, 48.3, 23.5, and 41.2, respectively. Adsorption energy results obtained from density functional theory (DFT) calculations were consistent with the experimental results. The membrane also exhibited good adsorption repeatability and stability. The high performance of this novel membrane is ascribed to the sieving and chelating effects of the unique crown ether, and its porous structure.

An insoluble sulfonated polyphosphazene (SPOP) with high degree of sulfonation is synthesized and used as the proton conductor in polybenzimidazole (PBI) high-temperature proton exchange membrane. Polyfunctional triglycidyl isocyanurate (TGIC) is used as covalent cross-linking agent to obtain a high proton conductivity at low cross-linking degrees. The composite membrane is characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD). SPOP has good compatibility with mPBI-TGIC, leading to uniform dispersion in the obtained membranes with neither phase separation nor agglomeration. As a highly efficient cross-linking agent, TGIC not only makes the composite membrane have good mechanical properties, thermal stability, anti-swelling and anti-oxidation properties at low cross-linking degrees, but also leads to high doping amount of SPOP, thus making the composite the membrane have a high proton conductivity. The conductivity of mPBI-TGIC(5%)/SPOP(50%) at 100% RH, 50% RH and 0 RH is 0.143, 0.076 and 0.044 S cm−1 at 180 °C, respectively. In addition, the composite membranes has good methanol resistance and selectivity, so the composite membrane can be applied in the direct methanol fuel cell.

Adsorptive membrane-based chromatography can provide the high separation efficiency common to column chromatography but at a lower working pressure. Herein, a novel membrane chromatography system for lithium isotope adsorptive separation is reported. It uses polysulfone-graft-4′-aminobenzo-15-crown-5-ether (PSf-g-AB15C5) porous membranes (0.52 mmol/g of immobilization crown ether, average pore size of 62.7 nm, porosity of 80.4%) as a stationary phase packed in a chromatography column (O 25 × 100 mm). Furthermore, a four-stage tandem membrane chromatography system was designed to enhance lithium isotope separation performance. The partial eluate from the former column was used as the feed solution for the next stage. Results show that the flow rate of the eluent could reach 18 mL/h owing to the lower internal diffusion resistance of membranes. Meanwhile, adsorption isotherms and adsorption kinetics show that Li+ adsorption was an exothermic and spontaneous process. The surface diffusion, multilayer adsorption and ion–pore electrostatic interaction between Li+ and the crown ether groups on the membranes played a key role in the separation of 7Li+ and 6Li+ by membrane chromatography. The separation factor obtained from the single-stage membrane chromatography was up to 1.0232. The abundances of 7Li+ and 6Li+ gradually increased with an increase in the elution stages. The relative abundances of 7Li+ and 6Li+ obtained from the four-stage tandem membrane chromatography increased by 0.26% (from 92.40 to 92.66%) and 0.2% (from 7.60 to 7.80%), respectively. In conclusion, our current research opens a new avenue for the simultaneous enrichment of 7Li+ and 6Li+ during lithium isotope adsorptive separation.

A novel polymer polysulfone (PSF)-graft-4′-aminobenzo-15-crown-5-ether (AB15C5) (PSF-g-AB15C5) for lithium isotope separation was prepared from PSF and AB15C5 as starting materials via nucleophilic substitution reaction. The chemical structure and properties of PSF-g-AB15C5 polymers were characterized by FT-IR, 1H NMR, XPS, and TGA. The polymers obtained were used for lithium isotope separation by solid–liquid extraction. The effects of the immobilization amount of crown ether grafting on PSF, the type of counteranion of lithium salt, and the kind of solvent on the single stage separation factor were explored. Results showed that the single stage separation factor was only 1.002 ± 0.002 for AB15C5 in the traditional liquid–liquid extraction system of H2O–LiCl/CHCl3–AB15C5, whereas the single stage separation factor increased from 1.003 ± 0.001 to 1.015 ± 0.002 with the increase of the immobilization amount of crown ether from 0.23 to 0.79 mmol g–1 on PSF-g-AB15C5 polymers in the solid–liquid extraction sy...

An antibacterial and environmentally friendly chitosan (CS) /polyvinyl alcohol (PVA) blend membrane for air filtration was prepared via nonsolvent induced phase separation (NIPS) method. The chemical structure, thermal behavior, morphology, mechanical property and surface charge of the resultant CS/PVA membranes were characterized. Results showed that CS and PVA were miscible due to the intermolecular hydrogen bond between them. The blend membrane obtained from over 20 wt.% CS concentration exhibited a gradient interconnected porous structure without skin layer. The air filtration efficiency and pressure drop obtained from CS/PVA membrane with 30 wt.% CS concentration and the thickness of 37 μm under a face velocity of 5.3 cm s−1 were 95.59% and 633.5 Pa, respectively. The performance of air filtration obtained is mainly attributed to the direct interception of membrane surface. Further, the antibacterial rate of the blend membrane was up to 94.8% for E. coli and 91.3% for S. aureus.

Polysulfone (PSf)-grafted graphene oxide (GO) nanosheets (GO-g-PSf) were synthesized via a nucleophilic substitution reaction between hydroxyl groups of GO and chloromethyl groups of chloromethylated polysulfone (CMPSf). GO-g-PSf dispersion in N-methyl pyrrolidone (NMP) was employed to fabricate GO-g-PSf composite membranes for dye separation by a vacuum filtration self-assembly method using polyamide (PA) composite membranes as the supports. The chemical structure and morphology of GO-g-PSf nanosheets were characterized by XRD, FTIR, Raman, XPS and TEM analyses. The morphology and filtration performance of membranes with various GO and GO-g-PSf depositions were investigated. The GO-g-PSf composite membrane with a deposition rate of 31.8 μg cm−2 exhibited a much higher pure water flux (88.0 L m−2 h−1 (LMH)) than pure GO composite membrane (12.8 LMH) at 2 bar owing to the enlarged interlayer spacing between the GO-g-PSf nanosheets. Simultaneously, the rejection rate of the GO-g-PSf composite membrane reached 90.3% for acid black 1 (AB), 99.5% for Congo red (CR) and 99.8% for methyl blue (MB) dyes under a cross-flow process at 2 bar. Moreover, the water permeance of the GO-g-PSf composite membrane remained at 25.9 LMH bar−1 after 60 h of operation for CR separation. Notably, the GO-g-PSf composite membrane also exhibited improved structural stability after 2 h of ultrasonic irradiation due to the physical entanglement of PSf chains. This study provides a simple approach to enhancing the permeability and structural stability of GO-based membranes used for dye separation.

An environmentally-friendly halloysite nanotubes@chitosan/polyvinyl alcohol/non-woven fabric (HNTs@CS/PVA/NWF) hybrid membrane with a uniform hierarchical porous structure for air filtration was prepared using a developed dip coating method combined with nonsolvent induced phase separation (NIPS) and the surface deposition of HNTs. Additionally, a TiO2/H2O2 photocatalysis approach was developed to improve the hydrophilicity of the polyester NWF. It was found that the porous CS/PVA blend was embedded into the NWF to frame a reinforced composite membrane with an intact polymer membrane. The results showed that the structure and properties of the resultant membranes were closely related to the thickness of the casting solution and the presence of HNTs. The filtration efficiency (FE) and pressure drop (PD) of the resultant membranes under a face velocity of 5.3 cm s−1 were 96.8% and 143.9 Pa, respectively. The filtration performance was mainly attributed to the direct interception on the membrane surface as well as the strong interactions and diffusion adsorption caused by the CS/PVA matrix and HNTs, respectively. Furthermore, the antibacterial rate of the resultant membranes reached to 99.6% for E. coli and 99.1% for S. aureus due to the synergistic effects of the CS component and the sensitized TiO2 nanoparticles.