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Journal of Environmental Sciences 2019年第9期31卷 144-151页

作者： Kai Zhao Jingqiu Sun Chengzhi Hu Jiuhui Qu State Key Laboratory of Environmental Aquatic Chemistry Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China University of Chinese Academy of Sciences Beijing 100049 China

Coupling coagulation and applied electric field is an efficient method to regulate cake layer porosity and hydrophilicity for alleviating ultrafiltration membrane(UF) fouling. However,the Al/Fe flocs aggregation behavior are induced from electric field and determine the cake layer structure, which has not been studied comparatively yet. Herein, the anti-fouling performance in an efficient electro-coagulation membrane reactor(ECMR, in which UF membrane modules are placed between electrodes) was investigated with Al/Fe anode and various electrochemical parameters from the viewpoint of regulating flocs aggregation.Both the cake layers formed from Al and Fe flocs under an electric field were more porous and hydrophilic in comparison with that formed without electric fields, resulting in an enhanced water flux under higher electric field strength. Comparing with Fe flocs, Al flocs had a faster growth rate and larger size, facilitating membrane pore block resistant, which was more pronounced in a higher current density. Furthermore, the cake layer formed from Al flocs was more porous than that formed from Fe flocs. Therefore, the anti-fouling performance of ECMR with Al anode was superior to that of ECMR with Fe anode. When the electric field strength increased from 0 to 10 V/cm, the normalized specific flux was improved from 71.2% to 89.4% for ECMR(Al) and from 48.1% to 70.1% for ECMR(Fe) at 30 min.

关键词： Electrocoagulation Ultrafiltration membrane fouling Electric field Cake layer

Conductive and stable polyphenylene/CNT composite membrane for electrically enhanced membrane fouling mitigation

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Frontiers of Environmental Science & Engineering 2024年第1期18卷 35-47页

作者： Huijuan Xie Haiguang Zhang Xu Wang Gaoliang Wei Shuo Chen Xie Quan Key Laboratory of Industrial Ecology and Environmental Engineering(Ministry of Education) School of Environmental Science and TechnologyDalian University of TechnologyDalian 116024China

Nanocarbon-based conductive membranes, especially carbon nanotube (CNT)-based membranes, have tremendous potential for wastewater treatment and water purification because of their excellent water permeability and selectivity, as well as their electrochemically enhanced performance (e.g., improved antifouling ability). However, it remains challenging to prepare CNT membranes with high structural stability and high electrical conductivity. In this study, a highly electroconductive and structurally stable polyphenylene/CNT (PP/CNT) composite membrane was prepared by electropolymerizing biphenyl on a CNT hollow fiber membrane. The PP/CNT membrane showed 3.4 and 5.0 times higher electrical conductivity than pure CNT and poly(vinyl alcohol)/CNT (PVA/CNT) membranes, respectively. The structural stability of the membrane was superior to that of the pure CNT membrane and comparable to that of the PVA/CNT membrane. The membrane fouling was significantly alleviated under an electrical assistance of −2.0 V, with a flux loss of only 11.7% after 5 h filtration of humic acid, which is significantly lower than those of PP/CNT membranes without electro-assistance (56.8%) and commercial polyvinylidene fluoride (PVDF) membranes (64.1%). Additionally, the rejection of negatively charged pollutants (humic acid and sodium alginate) was improved by the enhanced electrostatic repulsion. After four consecutive filtration-cleaning cycle tests, the flux recovery rate after backwashing reached 97.2%, which was much higher than those of electricity-free PP/CNT membranes (67.0%) and commercial PVDF membranes (61.1%). This study offers insights into the preparation of stable conductive membranes for membrane fouling control in potential water treatment applications.

关键词： Polyphenylene CNTs membrane Electro-assistance membrane fouling mitigation

Experimental investigation on degradation mechanism of membrane electrode assembly at different humidity under automotive protocol

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Chinese Journal of Chemical Engineering 2023年第4期56卷 70-79页

作者： Jiajun Wang Wenbin Yang Jiangtao Geng Zhigang Shao Wei Song Fuel Cell System and Engineering Laboratory Key Laboratory of Fuel Cells and Hybrid Power SourcesDalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023China University of Chinese Academy of Sciences Beijing 100039China

Humidity can affect the attenuation of MEA(membrane electrode assembly), however, the relationship between humidity and MEA decays is complex and ambiguous in realistic application. Herein, we design a simulating automotive protocol, performed on five single fuel cells under RH(relative humidity) 100%,RH 80%, RH 64%, and RH 40%, RH 10%, respectively, to study the relationship of MEA decays and humidity and suggest optimized humidity range to extend the durability. With the electrochemical impedance spectroscopy, cyclic voltammetry, X-ray fluorescence, X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, the four degradation mechanisms about catalyst layer, including Pt dissolution, Pt coarsening, carbon corrosion and ionomer degradation, are observed. Pt coarsening and carbon corrosion are accelerated by higher water content at high humidity. Ionomer degradation and Pt dissolution are enhanced in low humidity. With the linear sweep voltammetry, ion chromatography,nuclear magnetic resonance, tensile test and scan electron microscope, chemical and mechanical degradation in proton exchange membrane are all observed in these five fuels. Chemical degradation, characterized by membrane thinning and more fluoride loss, occurred markedly in RH 10%. Mechanical degradation, characterized by the non-uniformity thickness and bad mechanical properties, is more pronounced in RH 100%, RH 80%, RH 64%. These two degradations are in a moderate level in RH 40%. The research suggests that the RH range from 64% to 40% is conductive to mitigate the degradation of MEAs operated in automotive applications.

关键词： Fuel cell Simulating automotive protocol Relative humidity Degradation membrane

Frost prediction based on a 3D CFD model of heat and mass transfer in a counter-cross-flow parallel-plate liquid-to-air membrane energy exchanger

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Building Simulation 2023年第11期16卷 2063-2076页

作者： Mohammad Alipour Shotlou Nader Pourmahmoud Mechanical Engineering Department Urmia UniversityUrmiaIran

The frosting is a critical phenomenon in building systems because it decreases the performance of exchangers and damages them.In this article,heat and mass transfer in a specified liquid-to-air membrane energy exchanger(LAMEE)and their effects on condensation and frost formation are simulated numerically using the 3D computational fluid dynamics(CFD)technique.The CFD model has been validated with experimental results for different design parameters,and the agreement is within±2%.The developed CFD model provides the distribution of temperature and humidity ratio and MgCh concentration along the LAMEE.In the present study,effects of exchanger structure on producing viscosity and heat and mass transfer are studied.The selected LAMEE is a counter cross structure,therefore vortices appear in the inlet and outlet solution channel,and their influence can be seen on heat transfer in these parts.In addition,the diffusion of heat and mass transfer are studied on distributions of temperature and humidity ratio.Results show that the permeable membrane and moisture transfer make more regular temperature distribution along airflow direction in energy exchangers.This study provides an extended vision of heat and mass transfer.A 3-dimensional CFD model is developed to predict frost formation based on obtained temperature and humidity ratio.The CFD model is validated with an experimental study by calculating the frost limit.The developed model distinguishes condensed and frosted areas,and a new parameter is defined for this purpose namely as the frosted humidity ratio.Results show that frost and condensation distributions depend significantly on temperature and humidity ratio distributions.Adjusting temperature and humidity ratio to avoid air vapor to reach to saturation conditions is the better way to combat frosting.

关键词： frost CFD simulation moisture transfer membrane HVAC LAMEE

Electro-conductive crosslinked polyaniline/carbon nanotube nanofiltration membrane for electro-enhanced removal of bisphenol A

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Frontiers of Environmental Science & Engineering 2023年第5期17卷 81-92页

作者： Haiguang Zhang Lei Du Jiajian Xing Gaoliang Wei Xie Quan Key Laboratory of Industrial Ecology and Environmental Engineering(Ministry of Education) School of Environmental Science and TechnologyDalian University of TechnologyDalian 116024China

Nanofiltration(NF)has attracted increasing attention for wastewater treatment and potable water purification.However,the high-efficiency removal of micropollutants by NF membranes is a critical challenge.Owing to the adsorption and subsequent diffusion,some weakly charged or uncharged micropollutants,such as bisphenol A(BPA),can pass through NF membranes,resulting in low removal rates.Herein,an effective strategy is proposed to enhance the BPA removal efficiency of a crosslinked polyaniline/carbon nanotube NF membrane by coupling the membrane with electro-assistance.The membrane exhibited a 31.9%removal rate for 5 mg/L BPA with a permeance of 6.8 L/(m2·h·bar),while the removal rate was significantly improved to 98.1%after applying a voltage of 2.0 V to the membrane.Furthermore,when BPA coexisted with humic acid,the membrane maintained 94%removal of total organic carbon and nearly 100%removal of BPA at 2.0 V over the entire filtration period.Compared to continuous voltage applied to the membrane,an intermittent voltage(2.0 V for 0.5 h with an interval of 3.5 h)could achieve comparable BPA removal efficiency,because of the combined effect of membrane adsorption and subsequent electrochemical oxidation.Density functional theory calculations and BPA oxidation process analyses suggested that BPA was adsorbed by two main interactions:π–πand hydrogen-bond interactions.The adsorbed BPA was further electro-degraded into small organic acids or mineralized to CO_(2) and H2O.This work demonstrates that NF membranes coupled with electro-assistance are feasible for improving the removal of weakly charged or uncharged micropollutants.

关键词： Nanofiltration membrane Electro-assistance Adsorption Bisphenol A

Axisymmetric wetting of a liquid droplet on a stretched elastic membrane

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Applied Mathematics and Mechanics(English Edition) 2023年第6期44卷 997-1006页

作者： C.Q.RU Department of Mechanical Engineering University of AlbertaEdmontonAB T6G 2G8Canada

Wetting of a liquid droplet on another liquid substrate is governed by the well-known Neumann equations.The present work aims to develop an explicit modified version of the Neumann equations for axisymmetric wetting of a liquid droplet on a highly stretched elastic membrane of non-zero bending rigidity.An explicit modified form of the Neumann equations is derived to determine the two contact angles,which is reduced to Young's equation for a liquid droplet on a rigid membrane or to the Neumann equations for a liquid droplet on another liquid substrate.Further implications of the modified Neumann equations are examined by comparison with some previous results reported in the recent literature,particularly considering the ranges of material and geometrical parameters of the liquid droplet-membrane system which have not been recently addressed in the literature.

关键词： Neumann equation Young's equation liquid droplet membrane pretension

Numerical Study on the Linear and Nonlinear Behavior of A Fluid-Filled Piezoelectric membrane Under Gravity Waves

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China Ocean Engineering 2023年第5期37卷 768-780页

作者： LIU Chun-rong YANG Wen-yu School of Civil Engineering and Architecture Xiamen University of TechnologyXiamen 361024China

This study integrated piezoelectric layers in a flexible membrane to form a piezoelectric membrane.A fluid-filled piezoelectric membrane,which can be used as breakwater and wave energy converter simultaneously,was presented.The mathematical models to describe the interactions of the waves with the piezoelectric membrane were given.The dimensionless parameters to control the behavior of the piezoelectric membrane were obtained.The mixed EulerianLagrangian method was employed to simulate the mathematical models.The simulation code was verified.Based on the simulation results,the effects of dimensionless elastic modulus of the membrane E^(*),tension of the membrane T_(0)^(*)and the resistance of the load R^(*)on the behavior of the piezoelectric membrane were discussed.As E^(*)is small(E^(*)0.0001),the response of the piezoelectric membrane can be considered as linear.For linear response,the minimum transmission coefficient and maximum output electric power of the piezoelectric membrane can be achieved simultaneously by adjusting T_(0)^(*)and R^(*).For larger E^(*),nonlinear behavior of the piezoelectric membrane is observed.At some larger values of E^(*),working frequency of piezoelectric elements can reach eight times the wave frequency.In these cases,higher output electric power can be achieved for smaller strain of the membrane.

关键词： wave energy breakwater piezoelectric membrane nonlinear

Silk nanofibril as nanobinder for preparing COF nanosheet-based proton exchange membrane

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Green Energy & Environment 2023年第3期8卷 915-926页

作者： Ping Li Ningxin Zhang Xuan Li Shaokun Tang School of Chemical Engineering&Technology Tianjin UniversityTianjinChina Collaborative Innovation Center of Chemical Science and Engineering(Tianjin) Tianjin UniversityTianjinChina

Two-dimensional covalent organic framework nanosheets(CONs)with ultrathin thickness and porous crystalline nature show substantial potential as novel membrane materials.However,bringing CONs materials into flexible membrane form is a monumental challenge due to the limitation of weak interactions among CONs.Herein,one-dimensional silk nanofibrils(SNFs)from silkworm cocoon are designed as the nanobinder to link sulfonated CON(SCON)into robust SCON-based membrane through vacuum-filtration method.Ultrathin and large lateral-sized SCONs are synthesized via bottom-up interface-confined synthesis approach.Benefiting from high length-diameter ratio of SNF and rich functional groups in both SNF and SCON,two-dimensional(2D)SCONs are effectively connected together by physical entanglement and strong H-bond interactions.The resultant SCON/SNF membrane displays dense structure,high mechanical integrity and good stability.Importantly,the rigid porous nanochannels of SCON,high-concentration-SO3H groups insides the pores and H-bonds at SCON-SNF interfaces impart SCON/SNF membrane high-rate proton transfer pathways.Consequently,a superior proton conductivity of 365 mS cm^(-1)is achieved at 80C and 100%RH by SCON/SNF membrane.This work offers a promising approach for connecting 2D CON materials into flexible membrane as high-performance solid electrolyte for hydrogen fuel cell and may be applied in membrane-related other fields.

关键词： Covalent organic framework nanosheet Silk nanofibril membrane Proton conductivity Fuel cell

Tuning d-spacing of graphene oxide nanofiltration membrane for effective dye/salt separation

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Rare Metals 2023年第2期42卷 418-429页

作者： Chao Xing Chang-Yu Liu Chao Lai Shan-Qing Zhang Center for Clean Environment and Energy School of Environment and ScienceGold Coast CampusGriffith UniversitySouthportQLD4222Australia School of Chemistry and Materials Science Jiangsu Normal UniversityXuzhou221116China School of Biotechnology and Health Sciences Wuyi UniversityJiangmen529020China

The interlayer spacing(i.e.,d-spacing)plays a crucial role in determining the selectivity and permeability of nanofiltration membranes.A high-throughput directional filtration can be achieved by designing and controlling the d-spacing.In this study,the d-spacing of a graphene oxide(GO)membrane was tuned and fixed to the desired value(approximately 0.79 nm)using a solution of polyethyleneimine(PEI)and GO at a PEI/GO mass ratio of15:1.The resultant PEI/GO was deposited on a polyacrylonitrile(PAN)substrate to form a robust composite nanofiltration membrane(a PEI/GO@PAN membrane).The as-prepared membrane exhibited an ultrahigh flux of117.8 L·m^(-2)·h^(-1),and the rejection values for Direct Red80(DR80)and Na_(2)SO_(4)reached 99.7%andmembrane exhibited an excellent filtration performance,and had a longer lifespan and excellent reusability because of its reinforced nature.This work suggested that tuning the d-spacing with PEI would be an effective strategy to achieve the anticipated functions of nanofiltration membranes.

关键词： Separation Nanofiltration Graphene oxide membrane d-spacing

Non-equilibrium thermodynamic analysis of coupled heat and moisture transfer across a membrane

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Chinese Journal of Chemical Engineering 2022年第4期35卷 497-506页

作者： Zhijie Shen Jingchun Min Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Engineering MechanicsTsinghua UniversityBeijing 100084China

Non-equilibrium thermodynamics theory is used to analyze the transmembrane heat and moisture transfer process,which can be observed in a membrane-type total heat exchanger(THX).A theoretical model is developed to simulate the coupled heat and mass transfer across a membrane,total coupling equations and the expressions for the four characteristic parameters including the heat transfer coefficient,molardriven heat transfer coefficient,thermal-driven mass transfer coefficient,and mass transfer coefficient are derived and provided,with the Onsager’s reciprocal relation being confirmed to verify the rationality of the model.Calculations are conducted to investigate the effects of the membrane property and air state on the coupling transport process.The results show that the four characteristic parameters directly affect the transmembrane heat and mass fluxes:the heat and mass transfer coefficients are both positive,meaning that the temperature difference has a positive contribution to the heat transfer and the humidity ratio difference has a positive contribution to the mass transfer.The molar-driven heat transfer and thermal-driven mass transfer coefficients are both negative,implying that the humidity ratio difference acts to reduce the heat transfer and the temperature difference works to diminish the mass transfer.The mass transfer affects the heat transfer by 1%–2%while the heat transfer influences the mass transfer by7%–14%.The entropy generation caused by the temperature difference-induced heat transfer is much larger than that by the humidity difference-induced mass transfer.

关键词： membrane Non-equilibrium thermodynamics Heat transfer Mass transfer Coupling effect