A nonwoven supported mixed matrix membrane for CH4/N2 separation

Efficiently enriching low-concentration CH4 is pivotal for enhancing the utilization of unconventional energy sources and mitigating greenhouse gas emissions.This study focuses on modifying the overall performance of CH_(4)/N_(2)separation membranes.A novel mixed matrix membrane(MMM)with a reinforced substrate structure was developed through a straightforward dip-coating technique.This MMM incorporates a polytetrafluoroethylene(PTFE)porous membrane as the supporting framework,while a composite of block polymer(styrene-butadiene-styrene)and metal-organic framework(Ni-MOF-74)forms the selective separation layer.Comprehensive characterization of Ni-MOF-74 and the fabricatedmembranes was conducted using X-rays diffraction,scanning electron microscope,Brunauer-Emmett-Teller analysis,and gas permeance tests.The findings indicate a robust integration of the PTFE porous support with the membrane layer,enhancing the mechanical stability of theMMM.Under optimal conditions,the mechanical strength of the PM20 membrane(containing 20%Ni-MOF-74)was observed to be 37.7 MPa,representing remarkable increase compared to the non-reinforcedMMM.Additionally,thePM20membrane exhibited an impressive CH4 permeation rate of 92 barrer(1 barrer﹦3.35×10^(-16)mol·m·m^(-2)·s^(-1)·Pa^(-1))alongside a CH_(4)/N_(2)selectivity of 4.18.These results underscore the MMM's substantial performance and its promising potential in methane enrichment applications.

4-Pyrazolecarboxylic Acid-based MOF-5 Analogs Framework with High Adsorption and Separation of Light Hydrocarbons

One porous framework [Zn4（μ4-O）（μ4-4-pca）3]·2（DEF）·2（H2O）（1, 4-H2Pca = 4-pyrazolecarboxylic acid, DEF = N,N-diethylformamide） with MOF-5 type topology has been synthesized solvothermally. Significantly, this compound exhibits high capacity of C2 hydrocarbons. C2H2 capacity could compare with the highest value of the reported MOFs, far exceeding that of MOF-5, as well as the high selectivity adsorption of C2s over C1.

Rare Earth Separation with 1-Hexyl-4-Ethyloctyl Isopropylphosphonic Acid Extractant

A new extractant 1 hexyl 4 ethyloctyl isopropylphosphonic acid (HHEOIPP or HA) in heptane was employed to extract rare earths from hydrochloric acid medium. The dependence of extraction distribution ratio on equilibrium aqueous pH and the concentration of extractant were investigated. On the basis of slope analysis, it was proposed that two different kinds of extracted species were formed. For rare earth elements (La～Ho) the extracted species was LnA 3(HA) 3 and for heavy rare earth elements (Er～Lu) the species was LnClA 2(HA) 3. The steric hindrance plays an important role in forming the species. The extraction constants and separation factors of the adjacent rare earths were calculated too. Compared with HDEHP and HEH/EHP, HHEOIPP is a valuable extractant with high separation selectivity. The “tetrad effect” between K ex and atomic number was observed.

CH4/N2 separation on methane molecules grade diameter channel molecular sieves with a CHA-type structure

Samples of methane molecules grade diameter channel CHA-type molecular sieves(Chabazite-K, SAPO-34 and SSZ-13) were investigated using the adsorption separation of CH4/N2 mixtures. The isotherms recorded for CH4 and N2 follow a typical type-Ι behavior, which were fitted well with the Sips model(R2>0.999) and the selectivity was calculated using IAST theory. The results reveal that Chabazite-K has the highest selectivity(SCH4/N= 5.5).2 SSZ-13 has the largest capacity, which can adsorb up to a maximum of 30.957 cm3·g-1(STP) of CH4, due to it having the largest pore volume and surface area, but the lowest selectivity(SCH4/N2= 2.5). From the breakthrough test, we can conclude that SSZ-13 may be a suitable candidate for the recovery of CH4 from low concentration methane(CH4<20%) based on its larger pore volume and higher CH4 capacity. Chabazite-K is more suited to the separation of high concentration methane(CH4>50%) due to its higher selectivity.

Solar energy conversion on g-C3N4 photocatalyst:Light harvesting,charge separation,and surface kinetics

Photocatalysis. which utilizes solar energy to trigger chemical reactions, is one of the most desirable solar-energy-conversion approaches. Graphitic carbon nitride （g-C3N4）. as an attractive metal-free photocatalyst, has drawn worldwide research interest in the area of solar energy conversion due to its easy synthesis, earth-abundant nature, physicochemical stability and visible-light-responsive properties. Over the past ten years, g-C3N4 based photocatalysts have experienced intensive exploration, and great progress has been achieved. However, the solar conversion efficiency is still far from industrial applications due to the wide bandgap, severe charge recombination, and lack of surface active sites. Many strategies have been proposed to enhance the light absorption, reduce the recombination of charge carriers and accelerate the surface kinetics. This work makes a crucial review about the main contributions of various strategies to the light harvesting, charge separation and surface kinetics of g-C3N4 photocatalyst. Furthermore, the evaluation measurements for the enhanced light harvesting, reduced charge recombination and accelerated surface kinetics will be discussed. In addition, this review proposes future trends to enhance the photocatalytic performance of g-C3N4 photocatalyst for the solar energy conversion.

In situ fabrication of CdMoO4/g-C3N4 composites with improved charge separation and photocatalytic activity under visible light irradiation

To further improve the charge separation and photocatalytic activities of g-C3N4 and CdMoO4 under visible light irradiation,CdMoO4/g-C3N4 composites were rationally synthesized by a facile precipitation-calcination procedure.The crystal phases,morphologies,chemical compositions,textural structures,and optical properties of the as-prepared composites were characterized by the corresponding analytical techniques.The photocatalytic activities toward degradation of rhodamine B solution were evaluated under visible light irradiation.The results revealed that integrating CdMoO4 with g-C3N4 could remarkably improve the charge separation and photocatalytic activity,compared with those of pristine g-C3N4 and CdMoO4.This would be because the CdMoO4/g-C3N4 composites could facilitate the transfer and separation of the photoexcited electron-hole pairs,which was confirmed by electrochemical impedance spectroscopy,transient photocurrent responses,and photoluminescence measurements.Moreover,active species trapping experiments demonstrated that holes(h+)and superoxide radicals(?O2?)were the main active species during the photocatalytic reaction.A possible photocatalytic mechanism was proposed on the basis of the energy band structures determined by Mott-Schottky tests.This work would provide further insights into the rational fabrication of composites for organic contaminant removal.

MORPHOLOGIES AND GAS SEPARATION PROPERTIES OF MELT-SPUN ASYMMETRIC POLY(4-METHYL-1-PENTENE)HOLLOW FIBER MEMBRANES

Poly(4-methyl-1-pentene) (PMP) hollow fiber membranes were prepared by the melt-spun and cold-stretch(MSCS) method. Scanning electronic microscopy (SEM) was used to characterize the section and surface structures of themembranes with special asymmetric structure. The preliminary results of gas permeation measurements indicated that the resultant hollow fiber membranes have the potential ability for oxygen/nitrogen separation.

Synthesis of a PEBAX-1074/ZnO nanocomposite membrane with improved CO_2 separation performance

In this investigation, polymeric nanocomposite membranes（PNMs） were prepared via incorporating zinc oxide（ZnO） into poly（ether-block-amide）(PEBAX-1074) polymer matrix with different loadings. The neat membrane and nanocomposite membranes were prepared via solution casting and solution blending methods, respectively. The fabricated membranes were characterized by field emission scanning electron microscopy（FESEM） to survey cross-sectional morphologies and thermal gravimetric analysis（TGA）to study thermal stability. Fourier transform infrared（FT-IR） and X-ray diffraction（XRD） analyses were also employed to identify variations of the chemical bonds and crystal structure of the membranes, respectively. Permeation of pure gases, CO, CHand Nthrough the prepared neat and nanocomposite membranes was studied at pressures of 3–18 bar and temperature of 25 °C. The obtained results showed that the fabricated nanocomposite membranes exhibit better separation performance compared to the neat PEBAX membrane in terms of both permeability and selectivity. As an example, at temperature of 25 °C and pressure of 3 bar, COpermeability, ideal CO/CHand CO/Nselectivity values for the neat PEBAX membrane are 110.67 Barrer, 11.09 and 50.08, respectively, while those values are 152.27 Barrer,13.52 and 62.15 for PEBAX/ZnO nanocomposite membrane containing 8 wt% ZnO.

AgBF_4/[emim][BF_4] supported ionic liquid membrane for carbon monoxide/nitrogen separation

In this paper,AgBF_4/[emim][BF_4] supported ionic liquid membranes(SILMs) were prepared successfully for CO/N_2 separation using nitrogen pressure immobilization procedures.The incorporation of AgBF_4 could decrease membrane weight loss,improve the pressure-resistant ability,and keep the critical pressure(0.45 MPa) of the SILMs.The high viscosity and undissolved Ag BF_4 solids in membrane liquid would disturb gas molecular transport through membrane and give rise to the gas transport resistance.Therefore,the gas permeability decreased remarkably with increasing AgBF_4 carrier content in the membrane.When the molar ratio of AgBF_4 to [emim][BF_4] increased from 0:1 to 0.3:1,the CO/N_2 selectivity of the SILMs showed a great increase from ～1 to ～9 at 20 °C and 0.4 MPa,suggesting that AgBF_4 was an effective carrier for CO facilitated transport.The permeabilities of N_2 and CO increased at higher transmembrane pressure,indicating that molecular transport would dominate the transport process at high pressure.The temperature-dependent gas permeability followed the Arrhenius equation.Moreover,the differences between the activation energies of CO and N_2 became larger after introducing AgBF_4,resulting in more obvious decrease in the CO/N_2 selectivity at higher operating temperature.

CO2/CH4 separation using inside coated thin film composite hollow fiber membranes prepared by interfacial polymerization

Carbon dioxide(CO_2) is greenhouse gas which originates primarily as a main combustion product of biogas and landfill gas. To separate this gas, an inside coated thin film composite(TFC) hollow fiber membrane was developed by interfacial polymerization between 1,3–cyclohexanebis–methylamine(CHMA) and trimesoyl chloride(TMC). ATR-FTIR, SEM and AFM were used to characterize the active thin layer formed inside the PSf hollow fiber. The separation behavior of the CHMA-TMC/PSf membrane was scrutinized by studying various effects like feed gas pressure and temperature. Furthermore, the influence of CHMA concentration and TMC concentration on membrane morphology and performance were investigated. As a result, it was found that mutually the CHMA concentration and TMC concentration play key roles in determining membrane morphology and performance. Moreover, the CHMA-TMC/PSf composite membrane showed good CO_2/CH_4 separation performance. For CO_2/CH_4 mixture gas(30/70 by volume) test, the membrane(PD1 prepared by CHMA 1.0% and TMC 0.5%) showed a CO_2 permeance of 25 GPU and the best CO_2/CH_4 selectivity of 28 at stage cut of 0.1. The high CO_2/CH_4 separation performance of CHMA-TMC/PSf thin film composite membrane was mostly accredited to the thin film thickness and the properties of binary amino groups.

Spontaneous separation of Pb from PbSO_(4)-coprecipitated jarosite using freeze-thaw cycling with thiourea

To separate Pb from PbSO_(4)-coprecipitated jarosite,a novel thiourea-induced freeze-thaw cycling(T-FTC)process was investigated.Results show that distributed PbSO_(4)particles are pressed and aggregated around the jarosite particles by T-FTC.Under the freezing-concentration effect of T-FTC,the reaction between PbSO_(4)and thiourea is also promoted,forming lead thiourea sulfate(Pb-tu).As the cycles of T-FTC increase,PbSO_(4)around jarosite disappears for the reaction of forming Pb-tu.After 12 cycles of T-FTC,a spontaneous separation is observed between Pb-tu and jarosite,i.e.,Pb-tu is separated into the upper layer while jarosite-rich phases remain in the lower layer.Due to this spontaneous separation,leaching toxicity of the jarosite coprecipitates is reduced by 73.7%.These results suggest that T-FTC process can achieve the separation of Pb from PbSO_(4)-coprecipitated jarosite and is a promising approach for removing and recovering metals from iron-rich jarosite residues.

Density functional calculations of efficient H_2 separation from impurity gases(H_2,N_2,H_2O,CO,Cl_2, and CH_4)via bilayer g-C_3N_4 membrane

Membrane technology has been used for H_2 purification. In this paper, the systematic density functional simulations are conducted to study the separation of H_2 from the impurity gases(H_2, N_2, H_2 O, CO, Cl_2, and CH_4) by the bilayer porous graphitic carbon nitride(g-C_3 N_4) membrane. Theoretically, the bilayer g-C3 N4 membrane with a diameter of about3.25 A? should be a perfect candidate for H_2 purification from these mixed gases, which is verified by the high selectivity(S) for H_2 over other kinds of gases(3.43 × 1028 for H_2/N2; 1.40 × 1028 for H_262/H_2 O; 1.60 × 10 for H_2/CO; 4.30 × 10^(14) for H_2/Cl_2; 2.50 × 10^(55) for H_2/CH_4), and the permeance(P) of H_2(13 mol/m^2·s·Pa) across the bilayer g-C_3 N_4 membrane at 300 K, which should be of great potential in energy and environmental research. Our studies highlight a new approach towards the final goal of high P and high S molecular-sieving membranes used in simple structural engineering.

Tip-induced directional charge separation on one-dimensional BiVO4 nanocones for asymmetric light absorption

One dimensional(1D)semiconductor is a class of extensively attractive materials for many emerging solar energy conversion technologies.However,it is still of shortage to assess the impact of 1D structural symmetry on spatial charge separation and understand its underlying mechanism.Here we take controllably-synthesized 1D BiVO_(4)nanocones and nanorods as prototypes to study the influence of 1D symmetry on charge separation.It is found that the asymmetric BiVO_(4)nanocones enable more effective charge separation compared with the symmetric nanorods.The unexpected spatial charge separation on the nanocones is mainly ascribed to uneven light absorption induced diffusion-controllable charge separation due to symmetry breaking of 1D nanostructure,as evidenced by spatial and temporal resolved spectroscopy.Moreover,the promotion effect of charge separation on the nanocones was quantitatively evaluated to be over 20 times higher than that in BiVO_(4)nanorods.This work gives the first demonstration of the influence of 1D structural symmetry on the charge separation behavior,providing new insights to design and fabricate semiconductor materials for efficient solar energy conversion.

Extraction Separation of Scandium，Iron and Lutetium with Isopropyl Phosphonic Acid Mono（1－hexyl－4－ethyl）OctylEster

The extraction and stripping of scandium from its sulfate solutions by isopropyl phosphonic acid mono (1-hexyl-4-ethyl) octyl ester (PT-2, HL) diluted with n-hexane are reported. A high efficiency of separation between scandium, iron and lutetium can be achieved by controlling aqueous acidity. Different mechanisms of Sc3+ with PT-2 in various acid range have been proposed.At lower aqueous acidity, it is a cation exchange reaction, while at higher acidity. a solvation reaction was ascertained. Its IR and NMR spectra have been discussed. The effect of temperature on extraction of Sc3+ was observed and thermodynamic functions were calculated.

Separation and identification of cis and trans isomers of 2-butene-1,4-diol and lafutidine by HPLC and LC-MS

The cis and trans isomers separation of 2-butene-1,4-diol and lafutidine were studied by HPLC on two kinds of chiral columns: (S,S)-Whelk-O 1 and ChiraSpher. The isomers of 2-butene-1,4-diol can be separated on both chiral columns while the isomers of lafutidine can only be resolved on ChiraSpher column. The influence of different type and amount of mobile phase modifier on the isomers separation was extensively studied. The resolution of cis and trans isomers of 2-butene-1,4-diol was 2.61on (S,S)-Whelk-O 1 column with hexane-ethanol (97:3, v/v) as the mobile phase. The resolution of lafutidine was 1.89 on ChiraSpher column with hexane-ethanol-THF-diethylamine (92:3:5:0.1, v/v/v/v) as the mobile phase. LC-MS methods were developed to identify the isomer peaks.

Octa-<i>O</i>-Methoxy Resorcin [4] Arene Amberlite XAD-4 Polymeric Chelating Resin for Solid Phase Extraction, Preconcentration, Separation and Trace Determination of Ni(II), Cu(II), Zn(II) and Cd(II) Ions

Synthetic resin, Amberlite XAD-4 was linked covalently with the third generation supramolecule, octa-O-methoxy resorcin [4] arene through -N=N-group to form chelating resin, which has been characterized and effectively used for the separation and preconcentration of metal ions such as Ni(II), Cu(II), Zn(II) and Cd(II). Critical parameters such as pH, flow rate, sorption capacity, breakthrough studies, distribution coefficient, preconcentration factor, concentration of eluting agents responsible for quantitative extraction of metal ions were optimized. The synthesized resin showed good binding affinity towards Ni(II), Cu(II), Zn(II) and Cd(II) under selective pH conditions. Good breakthrough capacity and fast exchange kinetics of the resin lead to effective separation of metal ions from their binary and ternary mixture by column method on the basis of pH and eluting agents. The resin could be reused for about 8 -10 cycles. The proposed method having the analytical data with the relative standard deviation (RSD) 2% and with recoveries of analytes higher than 98%, reflects upon the reproducibility and reliability of the method which has been successfully applied in the separation and determination of Ni(II), Cu(II), Zn(II) and Cd(II) ions in synthetic, natural and ground water samples.

Separation of gibberellin A4 from A4 and A7 mixture by selective complex

Gibberellin A4 is effectively separated from mixture of gibberellin A4 and its analogue gibberellin A7, in the form of its crystalline complex with N,N,N＇,N＇-tetramethylethylenediamine. After removing the tetramethylethylenediamine from the crystal by dilute HCI, gibberellin A4 is obtained a purity of 98.1% and a yield of 72.7%.

Efficient separation of C_(4) olefins using tantalum pentafluor oxide anion-pillared hybrid microporous material

With the increasing demand for synthetic rubber,the purification of 1,3-butadiene(C_(4)H_(6))is of great industrial significance.Herein,the successful removal of n-butene(n-C_(4)H_(8))and iso-butene(iso-C_(4)H_(8))from 1,3-butadiene(C_(4)H_(6))was realized by synthesizing a novel TaOF_(5)^(2-) anion-pillared ultramicroporous material TaOFFIVE-3-Ni(also referred to as ZU-96,TaOFFIVE=TaOF_(5)^(2-),3=pyrazine).Single-component adsorption isotherms show that TaOFFIVE-3-Ni can achieve the exclusion of n-C_(4)H_(8) and iso-C_(4)H_(8) in the low pressure region(0–30 kPa),and uptake C_(4)H_(6) with a high capacity of 92.78 cm^(3)·cm^(-3)(298 K and 100 kPa).The uptake ratio of C_(4)H_(6)/iso-C_(4)H_(8) on TaOFFIVE-3-Ni was 20.83(298 K and 100 kPa),which was the highest among the state-of-the-art adsorbents reported so far.With the rotation of anion and pyrazine ring,the pore size changes continuously,which makes smaller-size C_(4)H_(6) enter the channel while larger-size n-C_(4)H_(8) and iso-C_(4)H_(8) are completely blocked.The excellent breakthrough performance of TaOFFIVE-3-Ni shows great potential in industrial separation of C4 olefins.The specific adsorption binding sites within ZU-96 was further revealed through the modeling calculation.

Separation of potassium from sodium in alkaline solution by solvent extraction with 4-tert-butyl-2-(α-methylbenzyl)phenol

This work investigated the separation of potassium from sodium in alkaline solution using substituted phenol-based extractants.Superior potassium extraction was achieved with 4-tert-butyl-2-(α-methylbenzyl)phenol(t-BAMBP)than 4-sec-butyl-2-(α-methylbenzyl)phenol(BAMBP).The optimum conditions for the extraction were 1 mol/L t-BAMBP,3:1 volumetric phase ratio(O/A),and two extraction stages.After cross-current extraction,the extraction ratio of potassium reached 90.8%.After scrubbing with deionised water at phase ratio of 4:1 and scrubbing stage of 4,a sodium scrubbing efficiency of 88.2%was obtained.After stripping using 1 mol/L H_(2)SO_(4) at phase ratio of 3:1,the stripping efficiency of potassium reached 94.2%.The potassium/sodium(K/Na)concentration ratio increased 14.3 times from 0.15 in the feed solution to 2.3 in the stripping solution.The efficient separation of potassium from sodium in alkaline solution was achieved via solvent extraction with t-BAMBP.

Effects of Terpinen-4-ol on Four Metabolic Enzymes and Polyphenol Oxidase (PPO) in Mythimna separta Walker

To study insecticidal mechanism of terpinen-4-ol, a main insecticidal composition in the essential oil of Sabina vulgaris, the 5th instar larvae of Mythimna separta, were investigated with terpinen-4-ol by topical application. The activities of phosphatase, glutathione S-transferase （GSTs）, cytochrome P450 （P450）, and polyphenol oxidase （PPO） of tested insects were determined in all poisoning stages, including exciting stage, convulsing stage, paralysis stage, and recover stage. The result showed that the activities of both acid phosphatase （ACP） and alkaline phosphatase （AKP） in treated insects were induced by terpinen-4-ol, but ACP was inhibited in paralysis stage. The activities of GSTs were inhibited in exciting stage, convulsing stage, and paralysis stage, but gradually recovered in recover stage. O-demethylase activity of cytochrome P450 was inhibited by terpinen-4-ol, and the inhibition rate in all poisoning stages were 26.27, 46.03, 80.24, and 90.22%, respectively. PPO activities were strongly inhibited by terpinen-4-ol both in vitro and in vivo. In conclusion, the activities of P450, GSTs, and PPO could have relation with toxicity of terpinen-4-ol against larvae of the Mythimna separta, but recover stage of the poisoning insects might be related to GSTs induced. As a new insecticide or synergist, terpinen- 4-ol has a potential value in field of insecticide resistance management.