Membrane fouling is a critical problem in membrane filtration processes for water purification. Electrocatalytic membrane reactor (ECMR) was an effective method to avoid membrane fouling and improve ...water quality. This study focuses on the preparation and characterization of a novel functionalized nano-TiO2 loading electrocatalytic membrane for oily wastewater treatment. A TiO2/carbon membrane used in the reactor is prepared by coating TiO2 as an electrocatalyst via a sol–gel process on a conductive microporous carbon membrane. In order to immobilize TiO2 on the carbon membrane, the carbon membrane is first pretreated with HNO3 to generate the oxygen-containing functional groups on its surface. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS) analyses are used to evaluate the morphology and microstructure of the membranes. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements are employed to illustrate the eletrochemical activity of the TiO2/carbon membrane. The membrane performance is investigated by treating oily wastewater. The oil removal rate increases with a decrease in the liquid hourly space velocity (LHSV) through the ECMR. The COD removal rate was 100% with a LHSV of 7.2 h–1 and 87.4% with a LHSV of 21.6 h–1 during the treatment of 200 mg/L oily water. It suggests that the synergistic effect of electrocatalytic oxidation and membrane separation in the ECMR plays a key role.
Phenol, as a representative organic pollutant in aquatic environments, has posed a serious threat to humans and ecosystem. In this work, a novel integration system combined coal-based carbon membrane ...with sulfate radicals-based advanced oxidation processes (SR-AOPs) was designed for degradation of phenol. The integrated system achieved 100% removal efficiency under the optimal condition (peroxydisulfate dosage is 0.2 g/L, at alkaline condition with 2 mL/min flow velocity). The quenching experiments revealed that the efficient removal of phenol by the integrated system were attributed to the co-existence of radical and nonradical mechanisms. This study proposes a green and efficient technique for the removal of phenol.
•Coal-based carbon membrane coupled with SR-AOPs was successfully designed.•Nitrogen from coal improved the catalytic performance of carbon membrane on PDS.•Both SO4·- and ·OH could generated and act as oxidizing agents of phenol.•Co-existence of radical and nonradical mechanisms could efficiently remove phenol.
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•An electroactive NiHCF/CTCM composite membrane was fabricated successfully.•Adjusting aperture can shorten ion transport path and accelerate mass transfer.•NiHCF/CTCM exhibited an ...ultrahigh removal efficiency (over 99.99%).•NiHCF/CTCM showed an excellent selectivity to Cs+ ions by affinity of NiHCF.
Radioactive cesium (137Cs) ions exhibit high-energy gamma radiation and long half-life. When they enter water body, serious environmental problems and damage to the human body are always generated. Herein, an electroactive composite membrane was facilely prepared by uniformly deposition of nickel hexacyanoferrate (NiHCF) nanoparticles on the surface and inner wall of coal-based tubular carbon membrane (CTCM) for rapid and selective separation of Cs+ from wastewater. This NiHCF incorporated CTCM tube exhibited an extremely high removal rate (over 99.99%) over a long period. Meanwhile, it also demonstrated extreme Cs+ selectivities even in the solutions with high coexisting ion concentrations (e.g., Cs+:Na+ = 1:99, Cs+:K+ = 1:99). The rapid and selective Cs+ uptake/release should be attributed to the better dispersion of NiHCF nanoparticles with high selectivity to Cs+ in the CTCM tube, which reduced the mass transfer distance, increased fluid turbulence and accelerated mass transfer rate. It is expected that such a NiHCF incorporated CTCM tube could be a promising alternative of conventional materials for the separating of radioactive Cs+ ions.
•Microfiltration carbon membranes were fabricated for oily wastewater treatment.•Air oxidation was developed to improve the separation performance of carbon membranes.•The effects of oxidation ...temperature and holding time were investigated.•The optimum permeation flux and oil rejection could achieve to 554.5 kg m−2 h−1 and 99.0%, respectively.•The anti-fouling ability is improved by two-fold after modification.
An air oxidation strategy was developed for the first time to modify the microstructure and separation performance of microfiltration carbon membranes (MFCMs) for oily wastewater treatment. The structure and property of MFCMs were characterized by the techniques of Fourier transform infrared spectroscopy, scanning electron microscope, pore size distribution, porosity, X-ray diffraction, nitrogen adsorption and water contact angle. The results have shown that the oxidation can effectively modulate the porous structure, surface property and separation performance of MFCMs by varying air oxidation temperature and holding time. The optimal separation performance was respectively achieved to 554.5 kg m−2 h−1 for water permeation flux and 99.0% for oil rejection when MFCMs were oxidized at 80 °C for 30 min. Meanwhile, the anti-fouling ability of MFCMs was substantially improved by two-fold for the flux recovery ratio after oxidation modification. In brief, the work has been proved that the air oxidation is one of the most promising strategies for tailoring MFCMs to efficiently remove the emulsified oil from wastewater.
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A series of alicyclic polyimide/graphene oxide(PI/GO) nanocomposites were successfully prepared by in situ polymerization of 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene(6FAPB) and ...1,2,3,4-cyclobutanetetracarboxylic dianhydride(CBDA) as well as GO, followed by thermal imidization. The effect of GO on the thermal stability, optical properties, mechanical properties, water absorption and water surface contact angle of the PI-based nanocomposites was investigated. The uniform dispersion of GO in PI matrix was proved, and the pure PI and PI/GO nanocomposite films were amorphous.
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•A series of alicyclic polyimide/graphene oxide(PI/GO) nanocomposites based on 6FAPB and CBDA were successfully prepared.•Without any treatment, GO could be formed a good dispersion in the alicyclic PI matrix.•The PI/GO nanocomposites exhibited the improvement of mechanical properties, thermal stability and so on.•To prepare the light colored and transparent PI/GO nanocomposite films, the thickness of film and GO loadings must be controlled strictly.
A series of alicyclic polyimide/graphene oxide(PI/GO) nanocomposites were successfully prepared by in situ polymerization of 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene(6FAPB) and 1,2,3,4-cyclobutanetetracarboxylic dianhydride(CBDA) as well as GO, followed by thermal imidization. The effect of GO on the thermal stability, optical properties, mechanical properties, water absorption and water surface contact angle of the PI-based nanocomposites was investigated. The optical properties of the pure alicyclic PI and corresponding PI-based nanocomposite films showed that the addition of GO reduced the transparency of PI films in the range of 200–800nm obviously. With the increase of GO loading, the mechanical and thermal properties of alicyclic PI-based nanocomposites were enhanced. For the PI-1.0%GO nanocomposite films, the tensile strength was increased from 96MPa (pure PI) to 109MPa, and the Young’s modulus was improved from 2.41GPa (pure PI) to 3.83GPa. The 10wt% decomposition temperature for PI-1.0%GO nanocomposite films was increased from 464 (pure PI) to 481°C, while the glass transition temperature (Tg) of PI/GO was slightly increased. In addition, the water surface contact angle of PI/GO enhanced from 71° to 82.5°, and the water uptake of PI/GO decreased from 2.58% to 1.48% with increasing the GO loadings. The uniform dispersion of GO in PI matrix was proved, and the pure PI and PI/GO nanocomposite films were amorphous.
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•A novel BPEI-CQD/PPy/PSS membrane was successfully synthesised and used for the removal of Cu2+.•Sorption-diffusion model was proposed for the ESIP system.•3D BPEI-CQD/PPy/PSS ...membrane exhibited excellent permselectivity for Cu2+.•The current efficiency of the ESIP system reached 39.9%.
The continuous separation of dilute Cu2+ from wastewater was performed by using a branched poly(ethylenimine) (BPEI)-functionalized carbon quantum dots (BPEI-CQD)/polypyrrole (PPy)/ polystyrenesulfonate (PSS) membrane in an electrochemically switched ion permselective (ESIP) process. The membrane with a high selectivity for Cu2+ separation was prepared by pressure filtering BPEI-CQD/PPy/PSS solution through a polytetrafluoroethylene (PTFE) membrane. In this ESIP system, the directional uptake/release of Cu2+ was realized by modulating the redox state of the membrane coupling with an external electric field. The effects of the operating parameters on the flux of Cu2+ and membrane permselectivity were investigated. The BPEI-CQD/PPy/PSS composite electrode showed excellent permselectivity for Cu2+ with a flux of 0.108mg·cm−2·h−1, a current efficiency of 39.9% and an excellent cycling stability. The Cu2+ concentration in the solution was reduced from 30 to 0.82ppm with a removal efficiency of 97.2%. Furthermore, the effects of BPEI-CQD content and the membrane thickness on the separation properties of the membrane from a mixed nitrate solution containing Cu2+, Ni2+ and Cd2+ were investigated. It is expected to understand the sorption-diffusion mechanism of such a membrane and provide more information on the design of it for a practical metal ion separation process.
A novel precursor, 3,3′,4,4′-oxydiphthalic dianhydride-4,4′-oxydianiline (ODPA–ODA) type polyetherimide (PEI), was synthesized and used to prepare carbon membranes by preoxidation and heat treatment. ...The thermal stability of the ODPA–ODA type PEI was evaluated by thermogravimetric analysis. The surface properties, elemental composition, microstructure, morphology and gas separation performance of the as-made carbon membranes were examined by the Fourier transform infrared spectroscopy, elemental analysis, X-ray diffraction, scanning electron microscopy and gas permeation techniques. The effects of the preoxidation temperature and zeolite incorporation on the microstructure and gas separation performance of carbon membranes were investigated. The results have shown that ODPA–ODA type PEI is a good precursor for producing carbon membranes. The preoxidation of the ODPA–ODA type PEI is essential to make defect-free carbon membranes, which also helps to improve the thermal stability and porosity during pyrolysis by forming crosslinking structure in precursor. The carbon membranes made after preoxidation at 480°C and heat treatment at 650°C have an oxygen permeability of 131.5 Barrer and an ideal O2/N2 selectivity of 9.7. The incorporation of ZSM-5 into the carbon membranes further helps to improve the separation performance of the carbon/zeolite membranes for H2/N2 gas mixture.
•ODPA–ODA type polyetherimide was developed to prepare carbon membranes.•The effect of preoxidation temperatures on membranes was discussed.•The gas separation data of the carbon membranes surpass Robeson׳s upper bound.•The incorporation of zeolite ZSM-5 into carbon membranes improves the H2/N2 selectivity.
We developed and tested an unmanned aerial vehicle-based gas sampling system (UGSS) for collecting gases and atmospheric particulate matter (PM). The system applies an alternative way of collecting ...both vertical and horizontal transects of trace gases in order to analyze them in the laboratory. To identify the best position of the UGSS intake port, aerodynamic flow simulations and experimental verifications of propeller airflow were conducted with an unmanned aerial vehicle (UAV) in hover mode. The UGSS will automatically replace the original gas in the system with gas from a target location to avoid the original gas being stored in the air bags. Experimental results show that the UGSS needs 5 s to replace the system’s own original gas using its pump. CO2 and PM2.5/10 above the corn field are used as the test species to validate the accuracy of the CO2 gas and PM concentrations collected by UGSS. Deming regression analyses showed good agreement between the measurements from the UGSS and the ground sampling station (y = 1.027x – 11.239, Pearson’s correlation coefficient of 0.98 for CO2; y = 0.992x + 0.704, Pearson’s correlation coefficient of 0.99 for PM).The UGSS provides a measuring method that actively collects gases and PM for manual analyses in the laboratory.
Ordered mesoporous silica/carbon composite membranes with a high CO2 permeability and selectivity were designed and prepared by incorporating SBA-15 or MCM-48 particles into polymeric precursors ...followed by heat treatment. The as-made composite membranes were characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and N2 adsorption, of which the gas separation performance in terms of gas permeability and selectivity were evaluated using the single gas (CO2, N2, CH4) and gas mixtures (CO2/N2 and CO2/CH4, 50/50mol.%). In comparison to the pure carbon membranes and microporous zeolite/C composite membranes, the as-made mesoporous silica/C composite membranes, and the MCM-48/C composite membrane in particular, exhibit an outstanding CO2 gas permeability and selectivity for the separation of CO2/CH4 and CO2/N2 gas pairs owing to the smaller gas diffusive resistance through the membrane and additional gas permeation channels created by the incorporation of mesoporous silicas in carbon membrane matrix. The channel shape and dimension of mesoporous silicas are key parameters for governing the gas permeability of the as-made composite membranes. The gas separation mechanism and the functions of porous materials incorporated inside the composite membranes are addressed.
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