Search

[Display omitted] • Cys-MoS 2 was introduced into Pebax to prepare MMMs for CO 2 /N 2 separation. • The vacancies, defects and amine groups synergically improved CO 2 permeation properties of MMMs. • MMMs exhibited a CO 2 permeability of 297 Barrer with a CO 2 /N 2 selectivity of 120. The incorporation of lamellar materials into polymer matrix can improve the gas separation performance of mixed matrix membranes (MMMs), which have great potential in chemical separation process. However, few intrinsic selectivity sites on MoS 2 sheets suppress further employment in the membrane separation. In this work, the vacancies and defects-containing MoS 2 sheets were prepared by high temperature oxidation and hydrothermal reaction in NaOH solution, and then L-cysteine-functionalized MoS 2 (Cys-MoS 2) was synthesized by a thiol-click chemistry reaction between S vacancies and thiol groups as confirmed by transmission electron microscope (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N 2 absorption. After blending with polyether-block-amide (Pebax), the as-prepared MMMs showed outstanding mechanical properties as a result of the homogeneous dispersion of Cys-MoS 2 and hydrogen bonding between two phases as evidenced by attenuated total reflectance-FTIR, scanning electron microscope (SEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The highest permeability of 297 Barrer accompanied with a CO 2 /N 2 selectivity of 120 was obtained for MMMs loaded with 1.5 wt% Cys-MoS 2 , which were enhanced by 206.2 % and 124.7 % over the pristine Pebax membrane, respectively. Meanwhile, this value was superior to that of the previously reported Pebax-based MMMs, transcending 2019 upper bound. The enhanced gas separation performance is due to the improved CO 2 adsorption selectivity by the vacancies and defects of Cys-MoS 2 , while the amine groups carrier enhanced CO 2 reactivity selectivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • The SPEEK/NaY mixed matrix membranes were prepared for CO 2 /N 2 separation. • The string-like nanochannels for facilitating CO 2 transport in MMMs were formed. • NaY zeolite was uniformly dispersed in SPEEK matrix due to good compatibility between two phases. • Improved CO 2 permeability and CO 2 /N 2 selectivity of MMM were simultaneously obtained due to selective surface flow effect. Mixed-matrix membranes (MMMs) have aroused great attention for CO 2 capture due to high gas separation properties and good processability. However, besides high cost, poor interfacial compatibility and inorganic particles aggregation in MMMs hinder their further development. Herein, we chose microporous sodium zeolite-Y (NaY) as a filler, which was added into sulfonated poly (ether ether ketone) (SPEEK) to engineer the MMMs for CO 2 /N 2 separation. We deeply studied the influence of NaY incorporation on microstructure and separation properties of the membrane. It is obvious that NaY particles were evenly distributed in the SPEEK matrix due to strong interfacial interaction by hydrogen bonding, which was verified by ATR-FTIR and SEM results, and the string-like nanochannels were formed from the SAXS observation. MMM incorporated with 20 wt% NaY exhibited the separation properties (CO 2 permeability of 765 Barrer; CO 2 /N 2 selectivity of 63) at 1 bar under the pure gas conditions, which were superior to the pristine SPEEK membrane as well as the MMMs incorporated with other zeolites, transcending the 2008 Robeson's upper bound. The enhancement in separation properties is due to the fact that CO 2 molecules preferentially pass through the string-like nanochannels faster than N 2 molecules under elevated relative humidity owing to selective surface flow effect. Moreover, an increase in total water of MMMs loaded with NaY also contributed to enhanced CO 2 permeability, while improved CO 2 /N 2 selectivity resulted from high bound water. More importantly, stability studies reveal that the MMM (with 20 wt% NaY loading) held outstanding CO 2 separation properties for over 360 h, demonstrating outstanding stability under a gas mixture testing condition. [ABSTRACT FROM AUTHOR]

[Display omitted] • ZIF-8-d-MK hybrid with the interlayer spaces was developed by coordinating ZIF-8 particles to amorphous MK sheets. • PVAm/ZIF-8-d-MK MMCMs for CO 2 /N 2 separation were successfully fabricated. • The interlayer spaces of ZIF-8-d-MK in the MMCMs function as CO 2 transport pathways. • The ZIF-8-d-MK hybrid was homogenously dispersed in PVAm matrix due to amorphous structure of MK sheets. Mixed-matrix composite membranes (MMCMs) have great potential in chemical separation process due to high performance, but the dispersibility of the filler is an enormous challenge we face. In this study, a ZIF-8-decorated metakaolin (ZIF-8-d-MK) hybrid was prepared by the AlO 4 tetrahedron oxygens in amorphous MK coordinating with the zinc ions of ZIF-8. MMCMs by coating polysulfone (PSf) ultrafiltration membranes with a mixture of hybrid and polyvinylamine (PVAm) were obtained, which can efficiently separate CO 2 from N 2. SEM and TEM results indicated that ZIF-8 particles were present between the amorphous MK sheets, and the coordination between the two phases was validated by FTIR. ZIF-8-d-MK, with a partially amorphous structure, exhibited homogeneous distribution in the PVAm matrix, as verified by SEM and XRD, and ZIF-8-d-MK had a strong interaction with the polymer matrix as certified by attenuated total reflectance-FTIR. A highest CO 2 permeance of 169 GPU with CO 2 /N 2 selectivity of 86.7 were acquired for MMCMs, loaded with 3 wt% ZIF-8-d-MK under pure gas conditions, which were much higher than those of MMCMs loaded with MK, ZIF-8, or a mixture of MK and ZIF-8. The improved values were primarily ascribed to the well-dispersed ZIF-8-d-MK serving as CO 2 transport pathways because of its molecular sieving effect for CO 2 /N 2. Importantly, under mixed gas feed conditions, the stability measurement demonstrated that the MMCMs adding 3 wt% ZIF-8-d-MK did long-term operation for over 360 h, and maintained great CO 2 separation performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel core–shell ZIF-8@NENP-NH 2 was engineered to prepare high-performance MMCMs for CO 2 separation. • The surface chemistry environment and molecular sieving pore in the short-range order facilitate CO 2 permeation. • Thus, a CO 2 permeance of as high as 301 GPU with a CO 2 /N 2 selectivity of 91 was observed. Mixed matrix composite membranes (MMCMs) for CO 2 capture have great potential in carbon neutral goal. However, simultaneous enhancement in permeance and selectivity is very difficult, since mismatching pore and chemical structures of filler with polymer matrix are the stumbling block. Herein, novel core–shell MOFs@COFs hybrids were prepared by growing hierarchical pore covalent organic frameworks (COFs, nitrogen-enriched nanoporous polytriazine (NENP)) on the surface of metal organic framework (MOFs, zeolite imidazolate framework-8 (ZIF-8)), where ethylenediamine were impregnated into NENP pore to adjust the chemistry environment of the shell. Subsequently, a porous polysulfone (PSf) membrane-supported MMCMs were developed by a coating method using a mixed dispersion of ZIF-8@NENP-NH 2 and polyvinylamine (PVAm), which was used to efficiently separate CO 2 from N 2. The rough COFs layer (NENP-NH 2) was closely wrapped on the smooth surface of ZIF-8 as identified by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and N 2 adsorption. Even-distributed ZIF-8@NENP-NH 2 had well miscibility with the PVAm matrix from hydrogen bonding as evidenced by SEM, attenuated total reflectance-FTIR and differential scanning calorimetry. The CO 2 permeance as high as 301 GPU accompanied with a selectivity of 91 was obtained for MMCMs loaded with 7 wt% ZIF-8@NENP-NH 2 , which were enhanced by 296.1% and 89.6%, respectively, when compared with the pristine PVAm membrane, transcending 2019 upper bound. We assume that the surface chemistry environment in hierarchical pore of the shell and molecular sieving pore in the core in the short-range order facilitate CO 2 permeation. Furthermore, this membrane maintained an average CO 2 permeance of 369 GPU and a CO 2 /N 2 selectivity of 97.3 for over 360 h using CO 2 /N 2 mixed gas as feed gas. [ABSTRACT FROM AUTHOR]

Radioactive iodide (I − ) and cesium (Cs + ) ions were first simultaneously separated using electrochemically switched ion exchange (ESIX) method based on polypyrrole (PPy) and nickle hexacyanoferrate (NiHCF) films, which were chemically deposited on two porous three-dimensional carbon felts (PTCF), respectively. It was found that applied potential significantly facilitated the adsorption efficiency and the lower pH value was beneficial to the separation process. The maximum adsorption capacity of both ions approached above 95.3 mg/g. The adsorption ratios of I − ion kept above 88% at pH value ranged from 1.89 to 9.36. The ultimate I − and Cs + ion desorption rates were proximately 87% and 90%, respectively. Such separation was suggested to proceed in two main steps: an ESIX step in which electrochemical oxidation of PPy and electrochemical reduction of NiHCF occurred rapidly (the fast step), and an IX step which was controlled by the gradients of ion concentrations between films and bulk solution (the slow step). The separation factors ( α Cl I = 90 and α Na Cs = 458.8 ) showed high selectivity for I − (PPy film) and Cs + (NiHCF film) ions over Cl − and Na + ions, respectively. And five consecutive adsorption–desorption experiments indicated that the NiHCF/PTCF and PPy/PTCF electrodes can be effectively regenerated and are stable. It is expected that the developed method can be taken as a promising technology for actual wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • MMCMs for a spice 2-phenylethanol separation were developed by incorporating β-CD-MOFs into PDMS matrix. • The β-CD-MOFs enhanced 2-phenylethanol pervaporation performance by hydrogen bonds and hydrophobic interaction. • MMCMs had distinctive molecular discrimination for 2-phenylethanol over a spice maltol. • The permeation total flux of as-prepared MMCMs were 1186 g m−2 h−1 with a separation factor of 21.3. Natural 2-phenylethanol (2-PE) is a spice with the rose-like fragrance and non-toxicity to human, whose classical separation technique from the plants has faced great challenge owing to high energy consumption, chemical engineering safety and environmental pollution issue. Herein, the mixed matrix composite membranes (MMCMs) for 2-PE pervaporation separation from aqueous solution were engineered by incorporating beta-cyclodextrin metal organic frameworks (β-CD-MOFs) with a large amount of hydroxyl groups and hydrophobic cavities into the polydimethylsiloxane (PDMS) matrix. The as-prepared MMCMs exhibited excellent 2-PE pervaporation separation performance with the permeation total flux, separation factor, and pervaporation separation index of 1186 g m−2 h−1, 21.3 and 24076 g m−2 h−1, respectively, which increased by 25.8 %, 129.0 % and 208.6 % compared with that of the pristine one, outperforming MMCMs embedding with other fillers, when 2-PE concentration in aqueous solution is 6000 ppm. This can be explained by the fact that the hydrogen bonding and hydrophobic interaction between β-CD-MOFs and 2-PE improves 2-PE dissolution in the membrane, thus enhancing the 2-PE solubility selectivity in MMCMs. Thus, MMCMs had specific recognition for 2-PE over a spice maltol, whose 2-PE flux and the 2-PE/water separation factor only reduced by 15.0 % and 37.6 % respectively, when maltol concentration increased to 2000 ppm in 6000 ppm of 2-PE aqueous solution. Besides, resultant MMCMs showed long-term stability for over 140 h with the average permeation total flux of 1317 g m−2 h−1 and the separation factor of 21.8. [ABSTRACT FROM AUTHOR]

In recent years, zeolitic imidazolate framework-8 (ZIF-8) has received tremendous attention due to its hydrophobic inner channels and good compatibility with the polymer as an inorganic filler for preparation of the mixed matrix membrane (MMM). In this study, ZIF-8 particles were synthesized and incorporated into Ploy (ether block amide) matrix (PEBA-2533) to fabricate a MMM for the enhancement of phenol permselective pervaporation. The structure and morphology of ZIF-8 particle and the obtained MMMs were characterized by XRD, SEM, FTIR, contact angle and BET. It is found that the hydrophobicity of the membrane was enhanced by the incorporation of hydrophobic ZIF-8, and the obtained MMM withstand the extreme operation conditions of pervaporation. The effects of particle loading amount, feed concentration and temperature on the separation performance of ZIF-8 incorporated MMMs were investigated in details. Compared with the pure PEBA-2533 membrane, the permeate flux of ZIF-8 incorporated PEBA-2533 MMM with a 10 wt% loading amount was significantly increased from 846 g m −2 h −1 to 1310 g m −2 h −1 , while the separation factor increased from 39 to 53 at 70 °C with 8000 ppm feed phenol concentration. The enhancement of the pervaporation performance could be mainly attributed to the preferential highly permeable regions of the bimodal membrane structure for phenol molecules, which was consisted of ZIF-8 particles. Finally, both of the excellent overall membrane pervaporation performance and the long-term revealed that such a ZIF-8 incorporated MMM has a great potential in separation and recovery of phenol from its aqueous solution for a practical process. [ABSTRACT FROM AUTHOR]