Tannic acid/Fe^(3+)interlayer for preparation of high-permeability polyetherimide organic solvent nanofiltration membranes for organic solvent separation

Organic solvent nanofiltration(OSN)membranes have a great application prospect in organic solvent separation,but the development of OSN membranes is mainly restricted by trade-off between permeability and rejection rate.In this work,a TA/Fe^(3+)polymer was introduced into polyetherimide(PEI)ultrafiltration membranes crosslinked with hexamethylene diamine as the intermediate layer,and OSN membranes with high separation performance and solvent permeability were obtained through interfacial polymerization and solvent activation.The interlayer with high surface hydrophilicity and a fixed pore structure controlled the adsorption/diffusion of the amine monomer during interfacial polymerization,forming a smooth(average surface roughness<5.5 nm),ultra-thin(separation layer thickness reduced from 150 to 16 nm)and dense surface structure polyamide(PA)layer.The PA-Fe^(3+)_3-HDA/PEI membrane retained more than 94%of methyl blue(BS)in 0.1 g·L^(-1)BS ethanol solution at 0.6 MPa,and the ethanol permeation reached 28.56 L^(-1)·m^(-2)·h^(-1).The average flux recovery ratio(FRR)of PA-Fe^(3+)_(3)-HDA/PEI membrane was found to be 84%,which has better fouling resistance than PA-HDA/PEI membrane,and it was found to have better stability performance through different solvent immersion experiments and continuous operation in 0.1 g·L^(-1)BS ethanol solution.Compared with thin-film composite nanofiltration membranes,the PA-Fe^(3+)_(3)-HDA/PEI membrane can be manufactured from an economical and environment-friendly method and overcomes the trade-off between permeability and rejection rate,showing great application potential in organic solvent separation systems.

Efficient and selective recovery of Gd(Ⅲ)via polyethyleneimine modification of lanthanum-based metal-organic frameworks

With the development of the economy and the increasing demand for environmental protection,the efficient and selective recovery of Gd(Ⅲ)from actual wastewater is of critical importance.In this work,lanthanum-based metal-organic framework(LaBDC)materials were prepared by a hydrothermal method,and then polyethyleneimine(PEI)and LaBDC were combined by an impregnation method to form a novel LaBDC@xPEI composite.The prepared materials were characterized using Fourier transfo rm infrared spectroscopy(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDX),B runauer-Emmett-Teller(BET),thermogravimetric analysis(TGA)and X-ray photoelectron spectroscopy(XPS).Experiments show that LaBDC@50%PEI has the highest adsorption capacity(181.77 mg/g)among lanthanum-based MOFs with different PEI loadings at pH=5.5,which is about 5.1 times that of bare LaBDC.The adsorption isotherm analysis shows that LaBDC@50%PEI follows the Langmuir model.In addition,the adsorption kinetics of LaBDC@50%PEI follows a pseudo-second-order kinetic model,indicating that the adsorption process is chemical adsorption.It is worth noting that LaBDC@50%PEI maintains good adsorption performance and stability after three recycling tests,and exhibits excellent selectivity in cation interference experiments.Overall,the LaBDC@50%PEI composites possess good stability and hold great promises in rapid recovery of Gd(Ⅲ)from practical aqueous environments.

Ultrathin organic solvent nanofiltration membrane with polydopamine-HKUST-1 interlayer for organic solvent separation

Polydopamine(PDA)and metal-organic skeleton HKUST-1 were co-deposited on the base membrane of hexamethylenediamine(HDA)-crosslinked polyetherimide(PEI)ultrafiltration membrane as the interlayer,and high-throughput organic solvent nanofiltration membrane(OSN)was prepared by interfacial polymerization and solvent activation reaction.The polyamide(PA)layer surface roughness from 28.4 nm in PA/PEI to 78.3 nm in PA/PDA-HKUST-10.6/PEI membrane,reduced the thickness of the separation layer from 79 to 14 nm,and significantly improved the hydrophilic,thermal and mechanical properties.The flux of the PA/PDA-HKUST-10.6/PEI membrane in a 0.1 g/L Congo Red(CR)ethanol solution at 0.6 MPa test pressure reached 21.8 L/(m^(2)·hr)and the rejection of CR was 92.8%.Solvent adsorption test,N,N-dimethylformamide(DMF)immersion experiment,and long-term operation test in ethanol showed that the membranes had high solvent tolerance.The solvent flux test demonstrated that,under the test pressure of 0.6 MPa,the flux of different solvents ranked as follows:methanol(56.9 L/(m^(2)·hr))>DMF(39.6 L/(m^(2)·hr))>ethanol(31.2 L/(m^(2)·hr))>IPA(4.5 L/(m^(2)·hr))>N-hexane(1.9 L/(m^(2)·hr)).The ability of the membranes to retain dyes in IPA/water dyes solution was also evaluated.The flux of the membrane was 30.4 L/(m^(2)·hr)and the rejection of CR was 91.6%when the IPA concentration reached 50%.This OSN membrane-making strategy is economical,environment-friendly and efficient,and has a great application prospect in organic solvent separation systems.