New modified combination mathematical models including the pores blocking models and the cake layer models were developed to describe the continuous cross-flow microfiltration in an airlift external loop slurry reacto...New modified combination mathematical models including the pores blocking models and the cake layer models were developed to describe the continuous cross-flow microfiltration in an airlift external loop slurry reactor. The pores blocking models were created based on the standard blocking law and the intermediate blocking law, and then the cake layer models were developed based on the hydrodynamic theory in which the calculation method of porosity of cake layer was newly corrected. The Air-Water-FCC equilibrium catalysts cold model experiment was used to verify the relevant models.Results showed that the calculated values fitted well with experimental data with a relative error of less than 10%.展开更多
A cross-flow microfiltration process had been developed to separate alumina fine particles from the suspension using a stainless steel membrane tube with a pore size of 10 μm. The influence of cross-flow velocity and...A cross-flow microfiltration process had been developed to separate alumina fine particles from the suspension using a stainless steel membrane tube with a pore size of 10 μm. The influence of cross-flow velocity and trans-membrane pressure on the permeate flux and the solid holdup in permeate had been investigated. It was found that both the permeate flux and the solid holdup in permeate decreased with time. Moreover, the permeate flux increased with an increasing transmembrane pressure but the influence of cross-flow velocity on the permeate flux was quite complex. Both the permeate flux and the solid holdup in permeate in long term filtration had been studied. The operation of cross-flow microfiltration could be carried out stably for 10 hours with the permeate flux values ranging from 520.5 to 936 L/(m^2·h) at rs=1%, while it could continue in 10 hours with the permeate flux values ranging from 226 to 432 L/(m^2·h) at rs=5%. The solid holdup in permeate had been less than 10 mg/L during the whole operating cycle.展开更多
Experimental investigation of the microfiltration （MF） using a revolving cross-flow membrane filter was performed under the condition of constant pressure difference, and different flat membranes made of polyvinylid...Experimental investigation of the microfiltration （MF） using a revolving cross-flow membrane filter was performed under the condition of constant pressure difference, and different flat membranes made of polyvinylidene fluoride （PVDF, 0.1 μm）, cellulose acetate （CA, 0.22 μm）, sulfonated polyethersulfone （SPES, 0.22 μm） and polyamide （PA, 0.45 μm）, respectively, were used in filtration experiments. The dependence of the filtrate mass of the cross-flow MF on time was measured on-line. The experimental results showed that the effect of the cross-flow on high viscosity medium was more significant than that on the low viscosity one.展开更多
Filtration is a prevalent treatment modality in the domain of wastewater management.Depending on the materials and properties of the filtration media,filtration can be classified into four main categories:microfiltrat...Filtration is a prevalent treatment modality in the domain of wastewater management.Depending on the materials and properties of the filtration media,filtration can be classified into four main categories:microfiltration,ultrafiltration,nanofiltration,and reverse osmosis.The present study focuses on the preparation of a novel porous CaCO_(3)microfiltration membrane,which is based on the microbial-induced calcium carbonate precipitation(MICP)biomineralization process.Initially,CaCO_(3) crystal particles with urease activity are prepared by controlling the MICP mineralization process.Secondary microbial mineralization is used to cement the loose calcium carbonate particles,forming a continuous porous solid CaCO_(3)membrane with certain mechanical strength.Filtration tests on bacterial cells,extracellular proteins,and polysaccharides show that the MICP-driven porous CaCO_(3) membrane effectively removes Escherichia coli,Brachybacterium sp.,and activated sludge,with removal rates of 99.998%,99.983%,and 99.996%,respectively.Compared to conventional filter paper,this porous CaCO_(3) membrane demonstrates superior capability in removing extracellular polymers(EPS).Furthermore,the CaCO_(3) microfiltration membrane prepared using the MICP process also exhibits ideal pore space,non-blocking characteristics,and high permeability.展开更多
A novel thermally induced graft polymerization technique was used to modify a polyvinylidene fluoride （PVDF） hollow fibre microfiltration membrane. An artificial neural network （ANN） was applied to optimize the pr...A novel thermally induced graft polymerization technique was used to modify a polyvinylidene fluoride （PVDF） hollow fibre microfiltration membrane. An artificial neural network （ANN） was applied to optimize the prepared condition of the membrane. The optimized dosing of acrylic acid （AA）, acrylamide （AM）, N, N＇- methylenebisacrylamide （NMBA） and potassium persulphate （KSP） designed by ANN was that AA was 40.63 ml/L; AM acted as 6.25 g/L; NMBA was 1.72 g/L and KSP was 1.5 g/L, respectively. The thermal stability of the PVDF modified hollow fibre membrane （PVDF-PAA） was investigated by thermogravimetric （TG） and differential scanning calorimetry （DSC） analysis. The polycrystallinity of the PVDF-PAA membrane was evaluated by X-ray diffraction （XRD） analysis. The complex formation of the modified membrane was ascertained by Fourier transform infrared spectroscopy （FTIR）. The morphology of the PVDF-PAA membrane was studied by environmental scanning electron microscopy （ESEM）. The surface compositions of the membrane were analyzed by X-ray photoelectron spectroscopy （XPS）. The adsorption capacity of Cu^2＋ ion on the PVDF-PAA hollow fibre membrane was also investigated.展开更多
Surface charge characteristics of a membrane can be determined by the streaming potential. In order to obtain more accurate streaming potential value during the measurement, four measurement operation modes were inves...Surface charge characteristics of a membrane can be determined by the streaming potential. In order to obtain more accurate streaming potential value during the measurement, four measurement operation modes were investigated in this study, and among the four modes, the steady mode with pressure stepped downward was considered the best one. Experimental results showed that the effects of compaction on the streaming potential measurement for a microfiltration membrane was more obvious than that for a ultrafiltration membrane. Both feed pH and presoaking could affect the measurement of streaming potential.展开更多
The oily wastewater generated from pretreatment unit of electrocoating industry contains oils, phosphate, organic solvents, and surfactants. In order to improve the removal efficiencies of phosphate and oils, to mitig...The oily wastewater generated from pretreatment unit of electrocoating industry contains oils, phosphate, organic solvents, and surfactants. In order to improve the removal efficiencies of phosphate and oils, to mitigate the membrane fouling, coagulation for ceramic membrane microfiltration of oily wastewater was performed. The results of filtration tests show that the membrane fouling decreased and the permeate flux and quality increased with coagulation as pretreatment. At the coagulant Ca （OH）2 dosage of 900 mg/L, the removal efficiency of phosphate was increased from 46.4% without coagulation to 99.6%; the removal of COD and oils were 97.0% and 99.8%, respectively. And the permeate flux was about 70% greater than that when Ca（OH）2 was not used. The permeate obtained from coagulation and microfiltration can be reused as make-up water, and the recommended operation conditions for pilot and industrial application are transmembrane pressure of 0.10 MPa and cross-flow velocity of 5 m/s. The comparison results show that 0.2 μm ZrO2 microfilter with coagulation could be used to perform the filtration rather than conventional ultrafilter, with very substantial gain in flux and removal efficiency of phosphate.展开更多
To understand the adsorption behavior of endocrine disrupting chemicals（EDCs） is important for enhancing the treatment performance and preventing potential secondary pollution caused by EDCs desorption in a microfil...To understand the adsorption behavior of endocrine disrupting chemicals（EDCs） is important for enhancing the treatment performance and preventing potential secondary pollution caused by EDCs desorption in a microfiltration system. The dynamic adsorption of four representative EDCs, namely estriol（E3）, 17β-estradiol（E2）, 17α-ethynylestradiol（EE2）, and 4-nonylphenol（4-NP） in a microfiltration system was investigated using the Thomas＇ model.The product of the equilibrium constant and the total adsorption capacity of the membrane,Ka, for E3, E2, EE2, and 4-NP were 4.91, 9.78, 15.6, and 826, respectively, strongly correlating with the compound octanol–water partition coefficient（KOW）. Adsorption appeared to be enhanced when organic fouling formed on the surface of membrane, indicating the role of an additional adsorption column for EDCs acted by a fouling layer in microfiltration. Results of a comparison between the Ka values for clean membrane and fouled membrane illustrated that the significant contribution made by fouling layers may be attributed to the foulant layer＇s hydrophobicity（in the case of calcium humate layer） and thickness（in the case of calcium alginate layer）. This study provided a novel perspective to quantitatively analyze the dynamic adsorption behavior of trace pollutants in membrane process.展开更多
Precluding the excessive lipoproteins from plasma rapidly and effectively is highly needed for biomedical detection and reducing plasma product scrap in blood donation stations.The current centrifugation procedure is ...Precluding the excessive lipoproteins from plasma rapidly and effectively is highly needed for biomedical detection and reducing plasma product scrap in blood donation stations.The current centrifugation procedure is high-cost and time-consuming.Herein,we fabricated an anionic microfiltration polyethersulfone(PES)membrane modified by interface swelling and implanting of acrylic acid(AA)for screening out large particle lipoprotein chylomicron(CM)and adsorbing cationic very low-density lipoproteins(VLDL).To improve the separation efficiency,a two-stage filtration through carboxylated polyethersulfone microfiltration membranes with the mean pore size of 0.45 and 0.22μm respectively were conducted.Attenuated total reflection Fourier transform infrared technique(ATR-FTIR),water contact angle(WCA),Zeta potential and scanning electron microscope(SEM)were employed to characterize the modified membrane.To test the effectiveness of this membrane,plasma flux and concentration variation of plasma components were examined to study the purification effectiveness.Furthermore,the hemocompatibility of modified membranes was tested to confirm its practicability on bloodcontacting materials.The carboxylated polyethersulfone microfiltration membrane shows its promising potential application to purify chylous plasma.展开更多
Surface charge characteristics of a membrane can be determined by the streaming potential. In order to obtain more accurate streaming potential value during the measurement, four measurement operation modes were inves...Surface charge characteristics of a membrane can be determined by the streaming potential. In order to obtain more accurate streaming potential value during the measurement, four measurement operation modes were investigated in this study, and among the four modes, the steady mode with pressure stepped downward was con- sidered the best one. Experimental results showed that the effects of compaction on the streaming potential meas- urement for a microfiltration membrane was more obvious than that for a ultrafiltration membrane. Both feed pH and presoaking could affect the measurement of streaming potential.展开更多
In the microalgae harvesting process,which includes a step for dewatering the algal suspension,directly reusing extracted water in situ would decrease the freshwater footprint of cultivation systems.Among various alga...In the microalgae harvesting process,which includes a step for dewatering the algal suspension,directly reusing extracted water in situ would decrease the freshwater footprint of cultivation systems.Among various algae harvesting techniques,membrane-based filtration has shown numerous advantages.This study evaluated the reuse of permeate streams derived from Scenedesmus obliquus(S.obliquus)biomass filtration under bench-scale and pilot-scale conditions.In particular,this study identified a series of challenges and mechanisms that influence the water reuse potential and the robustness of the membrane harvesting system.In a preliminary phase of this investigation,the health status of the initial biomass was found to have important implications for the harvesting performance and quality of the permeate stream to be reused;healthy biomass ensured better dewatering performance(i.e.,higher water fluxes)and higher quality of the permeate water streams.A series of bench-scale filtration experiments with different combinations of cross-flow velocity and pressure values were performed to identify the operative conditions that would maximize water productivity.The selected conditions,2.4 m·s^(-1)and 1.4 bar(1 bar=105 Pa),respectively,were then applied to drive pilot-scale microfiltration tests to reuse the collected permeate as a new cultivation medium for S.obliquus growth in a pilot-scale photobioreactor.The investigation revealed key differences between the behavior of the membrane systems at the two scales(bench and pilot).It indicated the potential for beneficial reuse of the permeate stream as the pilot-scale experiments ensured high harvesting performance and growth rates of biomass in permeate water that were highly similar to those recorded in the ideal cultivation medium.Finally,different nutrient reintegration protocols were investigated,revealing that both macro-and micro-nutrient levels are critical for the success of the reuse approach.展开更多
A cake layer is formed by coagulation aggregates under certain transmembrane pressure in the coagulation-microfiltration （MF） process. The characteristics of humic acid aggregates coagulated by different iron-based ...A cake layer is formed by coagulation aggregates under certain transmembrane pressure in the coagulation-microfiltration （MF） process. The characteristics of humic acid aggregates coagulated by different iron-based coagulants, such as charge, size, fractal dimension and compressibility, have an effect on the cake layer structure. At the optimum iron dose of 0.6 to 0.8 mmol/L for ferric chloride （FC） and polymer ferric sulfate （PFS） pre-coagulation, at the point of charge neutralization for near zero zeta potential, the aggregate particles produced possess the greatest size and highest fractal dimension, which contributes to the cake layer being most loose with high porosity and low compressibility. Thus the membrane filterability is better. At a low or high iron dose of FC and PFS, a high negative or positive zeta potential with high charge repulsion results in so many small aggregate particles and low fractal dimension that the cake layer is compact with low porosity and high compressibility. Therefore the membrane fouling is accelerated and MF permeability becomes worse. The variation of cake layer structure as measured by scanning electric microscopy corresponds with the fact that the smaller the coagulation flocs size and fractal dimension are, the lower the porosity and the tighter the cake layer conformation. This also explains the MF membrane flux variation visually and accurately.展开更多
Membrane microfiltration fermentation (MMF) with cell recycling was successfully applied to the production of glucose oxidase (GOD). A plate microfiltration module was found suitable for such purpose. By feeding whole...Membrane microfiltration fermentation (MMF) with cell recycling was successfully applied to the production of glucose oxidase (GOD). A plate microfiltration module was found suitable for such purpose. By feeding whole medium in MMF, the productivity of GOD was much higher than that by feeding glucose alone. With increasing dilution rate the enzyme productivity increased and average enzyme activity decreased. The enzyme productivity of MMF under D = 0.12h-1 and 0.20h-1 were 3871 and 3945U·h-1 respectively, which was about 3 times as that of batch fermentation (BF) and the average enzyme activity was still as high as STU·mL-1 under D = 0.12h-1. The relative efficiency of MMF applied to low yield strain was higher than that applied to high yield strain.展开更多
Because the natural organic matters (NOMs) and proteins are the principal foulants of microfiltration membranes in drinking water, the primary aim of this paper is to obtain a better understanding of the interactions ...Because the natural organic matters (NOMs) and proteins are the principal foulants of microfiltration membranes in drinking water, the primary aim of this paper is to obtain a better understanding of the interactions between those foulants and the microfiltration membrane from a novel view of coagulation. Based on reviewed literature and our own analysis, the authors consider that the behaviors of NOMs in the fouling of microfiltration membrane are like a form of crystal growth, and we recognize that the extent of the membrane hydrophobicity plays an essential role in NOMs fouling. However, proteins’ fouling is more affected by intermolecular interaction. Additionally, the effect of membrane surface chemistry is not as essential as it is in the situation of NOMs.展开更多
Microfiltration membrane technology has been widely used in various industries for solid-liquid separation. However, pore clogging remains a persistent challenge. This study employs (CFD) and discrete element method (...Microfiltration membrane technology has been widely used in various industries for solid-liquid separation. However, pore clogging remains a persistent challenge. This study employs (CFD) and discrete element method (DEM) models to enhance our understanding of microfiltration membrane clogging. The models were validated by comparing them to experimental data, demonstrating reasonable consistency. Subsequently, a parametric study was conducted on a cross-flow model, exploring the influence of key parameters on clogging. Findings show that clogging is a complex phenomenon affected by various factors. The mean inlet velocity and transmembrane flux were found to directly impact clogging, while the confinement ratio and cosine of the membrane pore entrance angle had an inverse relationship with it. Two clog types were identified: internal (inside the pore) and external (arching at the pore entrance), with the confinement ratio determining the type. This study introduced a dimensionless number as a quantitative clogging indicator based on transmembrane flux, Reynolds number, filtration time, entrance angle cosine, and confinement ratio. While this hypothesis held true in simulations, future studies should explore variations in clogging indicators, and improved modeling of clogging characteristics. Calibration between numerical and physical times and consideration of particle volume fraction will enhance understanding.展开更多
In this research,the treatability of solids from sanitary landfill leachate by microfiltration membrane was investigated and the fouling of the membrane was carefully studied.Continuous microfiltration process was car...In this research,the treatability of solids from sanitary landfill leachate by microfiltration membrane was investigated and the fouling of the membrane was carefully studied.Continuous microfiltration process was carried out for 21 h in experimental system involved coagulation with Moringa oleifera followed by filtration using submerged hollow fibre microfiltration membrane (MFM).Coagulation with M.Oleifera,air diffusers and back flush technique were used for preventing or alleviating fouling of the membrane.The hollow fibre MFM showed high removals of 98%,91% and 99% for turbidity,colour and total suspended solids respectively.It was obtained at the beginning of the filtration.However,quality of the filtrate rapidly declined during the filtration process.Fouling was found to proceed according to the classical cake filtration model.Coagulation with M.Oleifera as well as the back-flush technique could not fully restore the deterioration occurred to the membrane.展开更多
Chemical cleaning has been reported as the best method to restore ceramic filters flow rate by removing fouling agents. Even though there are several chemicals that can be used as cleaning agents, sodium hydroxide (Na...Chemical cleaning has been reported as the best method to restore ceramic filters flow rate by removing fouling agents. Even though there are several chemicals that can be used as cleaning agents, sodium hydroxide (NaOH) has been widely used as a cleaning agent. Literature reports that main factors of this cleaning are sodium hydroxide concentration, treatment temperature and contact time. However, the most significant factors have not been determined nor the interactions between them. The aim of this study was to determine the most significant parameter and the interactions between sodium hydroxide concentration, treatment temperature and contact time. This was done using Box-Behnken experimental design. The results, based on ANOVA analyses, showed that temperature is the most significant factor and that interaction between sodium hydroxide concentration and treatment temperature is the most significant interaction.展开更多
In this work, we study the coupled cross-flow and in-line vortex-induced vibration （VIV） of a fixedly mounted flexible pipe, which is free to move in cross-flow （ Y- ） and in-line （ X- ） direction in a fluid flo...In this work, we study the coupled cross-flow and in-line vortex-induced vibration （VIV） of a fixedly mounted flexible pipe, which is free to move in cross-flow （ Y- ） and in-line （ X- ） direction in a fluid flow where the mass and natural frequencies are precisely the same in both X- and Y-direction. The fluid speed varies from low to high with the corresponding vortex shedding frequency varying from below the first natural frequency to above the second natural frequency of the flexible pipe. Particular emphasis was placed on the investigation of the relationship between in-line and cross-flow vibration. The experimental results analyzed by using these measurements exhibits several valuable features.展开更多
It has been recently shown that Sub Boundary layer Vortex Generator(SBVG,abbreviated as VG hereafter)can suppress the Cross-Flow(CF),and therefore,can eliminate corner separation and increase aerodynamic loading when ...It has been recently shown that Sub Boundary layer Vortex Generator(SBVG,abbreviated as VG hereafter)can suppress the Cross-Flow(CF),and therefore,can eliminate corner separation and increase aerodynamic loading when installed on the end wall inside middle-load compressor passages.However,when VGs are applied in high-load compressors,it is difficult to achieve ideal results.This is because the definition of the VG attack angle in the presence of CF in existing research is confusing,and the stronger CF in high-load compressors worsens the problem and results in an improper design and optimization range of VG attack angle.Therefore,this paper clarifies the definition of the VG attack angle in the presence of CF and reveals the CF controlling mechanism of VG on a flat plate.The differences in the flow phenomena around a VG both with and without CF are also studied.The numerical results show that a larger height or attack angle of the VG generates a greater CF suppression effect.However,the cross velocity increases when surmounting the primary vortex induced by the VG,except that this enhanced CF is less conspicuous for larger VG heights.Compared to the cases without CF,the VG suffers an additional loss because of the stronger separation and primary vortex loss caused by the CF.展开更多
Vibration in heat exchangers is one of the main problems that the industry has faced over last few decades. Vibration phenomenon in heat exchangers is of major concern for designers and process engineers since it can ...Vibration in heat exchangers is one of the main problems that the industry has faced over last few decades. Vibration phenomenon in heat exchangers is of major concern for designers and process engineers since it can lead to the tube damage, tube leakage, baffle damage, tube collision damage, fatigue, creep etc. In the present study, vibration response is analyzed on single tube located in the centre of the tube bundle having parallel triangular arrangement （60-） with P/D ratio of 1.44. The experiment is performed for two different flow conditions. This kind of experiment has not been reported in the literature. Under the first condition, the tube vibration response is analyzed when there is no internal flow in the tube and under the second condition, the response is analyzed when the internal tube flow is maintained at a constant value of 0.1 rn/s. The free stream shell side velocity ranges from 0.8 rn/s to 1.3 m/s, the reduced gap velocity varies from 1,80 to 2.66 and the Reynolds number varies from 44500 to 66000. It is observed that the internal tube flow results in larger vibration amplitudes for the tube than that without internal tube flow. It is also established that over the current range of shell side flow velocity, the turbulence is the dominant excitation mechanism for producing vibration in the tube since the amplitude varies directly with the increase in the shell side velocity. Damping has no significant effect on the vibration behavior of the tube for the current velocity range.展开更多
基金financially supported by the National Key Research & Development Program of China (2016YFB0301600)
文摘New modified combination mathematical models including the pores blocking models and the cake layer models were developed to describe the continuous cross-flow microfiltration in an airlift external loop slurry reactor. The pores blocking models were created based on the standard blocking law and the intermediate blocking law, and then the cake layer models were developed based on the hydrodynamic theory in which the calculation method of porosity of cake layer was newly corrected. The Air-Water-FCC equilibrium catalysts cold model experiment was used to verify the relevant models.Results showed that the calculated values fitted well with experimental data with a relative error of less than 10%.
文摘A cross-flow microfiltration process had been developed to separate alumina fine particles from the suspension using a stainless steel membrane tube with a pore size of 10 μm. The influence of cross-flow velocity and trans-membrane pressure on the permeate flux and the solid holdup in permeate had been investigated. It was found that both the permeate flux and the solid holdup in permeate decreased with time. Moreover, the permeate flux increased with an increasing transmembrane pressure but the influence of cross-flow velocity on the permeate flux was quite complex. Both the permeate flux and the solid holdup in permeate in long term filtration had been studied. The operation of cross-flow microfiltration could be carried out stably for 10 hours with the permeate flux values ranging from 520.5 to 936 L/(m^2·h) at rs=1%, while it could continue in 10 hours with the permeate flux values ranging from 226 to 432 L/(m^2·h) at rs=5%. The solid holdup in permeate had been less than 10 mg/L during the whole operating cycle.
基金Supported by the State Key Development Program for Basic Research of China(2003CB615705)
文摘Experimental investigation of the microfiltration （MF） using a revolving cross-flow membrane filter was performed under the condition of constant pressure difference, and different flat membranes made of polyvinylidene fluoride （PVDF, 0.1 μm）, cellulose acetate （CA, 0.22 μm）, sulfonated polyethersulfone （SPES, 0.22 μm） and polyamide （PA, 0.45 μm）, respectively, were used in filtration experiments. The dependence of the filtrate mass of the cross-flow MF on time was measured on-line. The experimental results showed that the effect of the cross-flow on high viscosity medium was more significant than that on the low viscosity one.
基金Jiangsu Province Key Project of Research and Development Plan(No.BE2020676)Nantong Science and Technology Project(No.MS22021006)。
文摘Filtration is a prevalent treatment modality in the domain of wastewater management.Depending on the materials and properties of the filtration media,filtration can be classified into four main categories:microfiltration,ultrafiltration,nanofiltration,and reverse osmosis.The present study focuses on the preparation of a novel porous CaCO_(3)microfiltration membrane,which is based on the microbial-induced calcium carbonate precipitation(MICP)biomineralization process.Initially,CaCO_(3) crystal particles with urease activity are prepared by controlling the MICP mineralization process.Secondary microbial mineralization is used to cement the loose calcium carbonate particles,forming a continuous porous solid CaCO_(3)membrane with certain mechanical strength.Filtration tests on bacterial cells,extracellular proteins,and polysaccharides show that the MICP-driven porous CaCO_(3) membrane effectively removes Escherichia coli,Brachybacterium sp.,and activated sludge,with removal rates of 99.998%,99.983%,and 99.996%,respectively.Compared to conventional filter paper,this porous CaCO_(3) membrane demonstrates superior capability in removing extracellular polymers(EPS).Furthermore,the CaCO_(3) microfiltration membrane prepared using the MICP process also exhibits ideal pore space,non-blocking characteristics,and high permeability.
文摘A novel thermally induced graft polymerization technique was used to modify a polyvinylidene fluoride （PVDF） hollow fibre microfiltration membrane. An artificial neural network （ANN） was applied to optimize the prepared condition of the membrane. The optimized dosing of acrylic acid （AA）, acrylamide （AM）, N, N＇- methylenebisacrylamide （NMBA） and potassium persulphate （KSP） designed by ANN was that AA was 40.63 ml/L; AM acted as 6.25 g/L; NMBA was 1.72 g/L and KSP was 1.5 g/L, respectively. The thermal stability of the PVDF modified hollow fibre membrane （PVDF-PAA） was investigated by thermogravimetric （TG） and differential scanning calorimetry （DSC） analysis. The polycrystallinity of the PVDF-PAA membrane was evaluated by X-ray diffraction （XRD） analysis. The complex formation of the modified membrane was ascertained by Fourier transform infrared spectroscopy （FTIR）. The morphology of the PVDF-PAA membrane was studied by environmental scanning electron microscopy （ESEM）. The surface compositions of the membrane were analyzed by X-ray photoelectron spectroscopy （XPS）. The adsorption capacity of Cu^2＋ ion on the PVDF-PAA hollow fibre membrane was also investigated.
基金the National Natural Science Foundation of China （No.29976031）, the Collaboration Project Foundation of Tianjin University and Nankal University, and the Key Project Foundation of Tianjin （No.0331810112）.
文摘Surface charge characteristics of a membrane can be determined by the streaming potential. In order to obtain more accurate streaming potential value during the measurement, four measurement operation modes were investigated in this study, and among the four modes, the steady mode with pressure stepped downward was considered the best one. Experimental results showed that the effects of compaction on the streaming potential measurement for a microfiltration membrane was more obvious than that for a ultrafiltration membrane. Both feed pH and presoaking could affect the measurement of streaming potential.
文摘The oily wastewater generated from pretreatment unit of electrocoating industry contains oils, phosphate, organic solvents, and surfactants. In order to improve the removal efficiencies of phosphate and oils, to mitigate the membrane fouling, coagulation for ceramic membrane microfiltration of oily wastewater was performed. The results of filtration tests show that the membrane fouling decreased and the permeate flux and quality increased with coagulation as pretreatment. At the coagulant Ca （OH）2 dosage of 900 mg/L, the removal efficiency of phosphate was increased from 46.4% without coagulation to 99.6%; the removal of COD and oils were 97.0% and 99.8%, respectively. And the permeate flux was about 70% greater than that when Ca（OH）2 was not used. The permeate obtained from coagulation and microfiltration can be reused as make-up water, and the recommended operation conditions for pilot and industrial application are transmembrane pressure of 0.10 MPa and cross-flow velocity of 5 m/s. The comparison results show that 0.2 μm ZrO2 microfilter with coagulation could be used to perform the filtration rather than conventional ultrafilter, with very substantial gain in flux and removal efficiency of phosphate.
基金supported by the National Natural Science Foundation of China(No.51678336)the KWEF-AIT Research Grant,the President Fund for Science and Education Fusion of UCAS(No.Y552022Y00)the special fund of SKLECE,Chinese Academy of Sciences(No.KF2016-19)
文摘To understand the adsorption behavior of endocrine disrupting chemicals（EDCs） is important for enhancing the treatment performance and preventing potential secondary pollution caused by EDCs desorption in a microfiltration system. The dynamic adsorption of four representative EDCs, namely estriol（E3）, 17β-estradiol（E2）, 17α-ethynylestradiol（EE2）, and 4-nonylphenol（4-NP） in a microfiltration system was investigated using the Thomas＇ model.The product of the equilibrium constant and the total adsorption capacity of the membrane,Ka, for E3, E2, EE2, and 4-NP were 4.91, 9.78, 15.6, and 826, respectively, strongly correlating with the compound octanol–water partition coefficient（KOW）. Adsorption appeared to be enhanced when organic fouling formed on the surface of membrane, indicating the role of an additional adsorption column for EDCs acted by a fouling layer in microfiltration. Results of a comparison between the Ka values for clean membrane and fouled membrane illustrated that the significant contribution made by fouling layers may be attributed to the foulant layer＇s hydrophobicity（in the case of calcium humate layer） and thickness（in the case of calcium alginate layer）. This study provided a novel perspective to quantitatively analyze the dynamic adsorption behavior of trace pollutants in membrane process.
基金financially supported by Natural Science Foundation of Ningbo City(2018A610026)Zhejiang Provincial Natural Science Foundation of China for Distinguished Young Scholars(LR20E030002)+1 种基金Ten thousand plan-high level talents special support plan of Zhejiang province,China(ZJWR0108020)Youth Innovation Promotion Association of Chinese Academy of Science(2014258)。
文摘Precluding the excessive lipoproteins from plasma rapidly and effectively is highly needed for biomedical detection and reducing plasma product scrap in blood donation stations.The current centrifugation procedure is high-cost and time-consuming.Herein,we fabricated an anionic microfiltration polyethersulfone(PES)membrane modified by interface swelling and implanting of acrylic acid(AA)for screening out large particle lipoprotein chylomicron(CM)and adsorbing cationic very low-density lipoproteins(VLDL).To improve the separation efficiency,a two-stage filtration through carboxylated polyethersulfone microfiltration membranes with the mean pore size of 0.45 and 0.22μm respectively were conducted.Attenuated total reflection Fourier transform infrared technique(ATR-FTIR),water contact angle(WCA),Zeta potential and scanning electron microscope(SEM)were employed to characterize the modified membrane.To test the effectiveness of this membrane,plasma flux and concentration variation of plasma components were examined to study the purification effectiveness.Furthermore,the hemocompatibility of modified membranes was tested to confirm its practicability on bloodcontacting materials.The carboxylated polyethersulfone microfiltration membrane shows its promising potential application to purify chylous plasma.
基金Supported by the National Natural Science Foundation of China (No.29976031), the Collaboration Project Foundation of Tian-jin University and Nankai University, and the Key Project Foundation of Tianjin (No.0331810112).
文摘Surface charge characteristics of a membrane can be determined by the streaming potential. In order to obtain more accurate streaming potential value during the measurement, four measurement operation modes were investigated in this study, and among the four modes, the steady mode with pressure stepped downward was con- sidered the best one. Experimental results showed that the effects of compaction on the streaming potential meas- urement for a microfiltration membrane was more obvious than that for a ultrafiltration membrane. Both feed pH and presoaking could affect the measurement of streaming potential.
基金supported by the Politecnico di Torino and the CleanWaterCenter@PoliTo(58_DIM20TIRALB,58_DIM22TIRALB,and 01_TRIN_CI_CWC).
文摘In the microalgae harvesting process,which includes a step for dewatering the algal suspension,directly reusing extracted water in situ would decrease the freshwater footprint of cultivation systems.Among various algae harvesting techniques,membrane-based filtration has shown numerous advantages.This study evaluated the reuse of permeate streams derived from Scenedesmus obliquus(S.obliquus)biomass filtration under bench-scale and pilot-scale conditions.In particular,this study identified a series of challenges and mechanisms that influence the water reuse potential and the robustness of the membrane harvesting system.In a preliminary phase of this investigation,the health status of the initial biomass was found to have important implications for the harvesting performance and quality of the permeate stream to be reused;healthy biomass ensured better dewatering performance(i.e.,higher water fluxes)and higher quality of the permeate water streams.A series of bench-scale filtration experiments with different combinations of cross-flow velocity and pressure values were performed to identify the operative conditions that would maximize water productivity.The selected conditions,2.4 m·s^(-1)and 1.4 bar(1 bar=105 Pa),respectively,were then applied to drive pilot-scale microfiltration tests to reuse the collected permeate as a new cultivation medium for S.obliquus growth in a pilot-scale photobioreactor.The investigation revealed key differences between the behavior of the membrane systems at the two scales(bench and pilot).It indicated the potential for beneficial reuse of the permeate stream as the pilot-scale experiments ensured high harvesting performance and growth rates of biomass in permeate water that were highly similar to those recorded in the ideal cultivation medium.Finally,different nutrient reintegration protocols were investigated,revealing that both macro-and micro-nutrient levels are critical for the success of the reuse approach.
基金supported by the National Natural Science Foundation of China (No.50978014)the Fundamental Research Funds for the Central Universities (No.2011JBM077)
文摘A cake layer is formed by coagulation aggregates under certain transmembrane pressure in the coagulation-microfiltration （MF） process. The characteristics of humic acid aggregates coagulated by different iron-based coagulants, such as charge, size, fractal dimension and compressibility, have an effect on the cake layer structure. At the optimum iron dose of 0.6 to 0.8 mmol/L for ferric chloride （FC） and polymer ferric sulfate （PFS） pre-coagulation, at the point of charge neutralization for near zero zeta potential, the aggregate particles produced possess the greatest size and highest fractal dimension, which contributes to the cake layer being most loose with high porosity and low compressibility. Thus the membrane filterability is better. At a low or high iron dose of FC and PFS, a high negative or positive zeta potential with high charge repulsion results in so many small aggregate particles and low fractal dimension that the cake layer is compact with low porosity and high compressibility. Therefore the membrane fouling is accelerated and MF permeability becomes worse. The variation of cake layer structure as measured by scanning electric microscopy corresponds with the fact that the smaller the coagulation flocs size and fractal dimension are, the lower the porosity and the tighter the cake layer conformation. This also explains the MF membrane flux variation visually and accurately.
基金Supported by the National Natural Science Foundation of China(No.39170020).
文摘Membrane microfiltration fermentation (MMF) with cell recycling was successfully applied to the production of glucose oxidase (GOD). A plate microfiltration module was found suitable for such purpose. By feeding whole medium in MMF, the productivity of GOD was much higher than that by feeding glucose alone. With increasing dilution rate the enzyme productivity increased and average enzyme activity decreased. The enzyme productivity of MMF under D = 0.12h-1 and 0.20h-1 were 3871 and 3945U·h-1 respectively, which was about 3 times as that of batch fermentation (BF) and the average enzyme activity was still as high as STU·mL-1 under D = 0.12h-1. The relative efficiency of MMF applied to low yield strain was higher than that applied to high yield strain.
文摘Because the natural organic matters (NOMs) and proteins are the principal foulants of microfiltration membranes in drinking water, the primary aim of this paper is to obtain a better understanding of the interactions between those foulants and the microfiltration membrane from a novel view of coagulation. Based on reviewed literature and our own analysis, the authors consider that the behaviors of NOMs in the fouling of microfiltration membrane are like a form of crystal growth, and we recognize that the extent of the membrane hydrophobicity plays an essential role in NOMs fouling. However, proteins’ fouling is more affected by intermolecular interaction. Additionally, the effect of membrane surface chemistry is not as essential as it is in the situation of NOMs.
文摘Microfiltration membrane technology has been widely used in various industries for solid-liquid separation. However, pore clogging remains a persistent challenge. This study employs (CFD) and discrete element method (DEM) models to enhance our understanding of microfiltration membrane clogging. The models were validated by comparing them to experimental data, demonstrating reasonable consistency. Subsequently, a parametric study was conducted on a cross-flow model, exploring the influence of key parameters on clogging. Findings show that clogging is a complex phenomenon affected by various factors. The mean inlet velocity and transmembrane flux were found to directly impact clogging, while the confinement ratio and cosine of the membrane pore entrance angle had an inverse relationship with it. Two clog types were identified: internal (inside the pore) and external (arching at the pore entrance), with the confinement ratio determining the type. This study introduced a dimensionless number as a quantitative clogging indicator based on transmembrane flux, Reynolds number, filtration time, entrance angle cosine, and confinement ratio. While this hypothesis held true in simulations, future studies should explore variations in clogging indicators, and improved modeling of clogging characteristics. Calibration between numerical and physical times and consideration of particle volume fraction will enhance understanding.
文摘In this research,the treatability of solids from sanitary landfill leachate by microfiltration membrane was investigated and the fouling of the membrane was carefully studied.Continuous microfiltration process was carried out for 21 h in experimental system involved coagulation with Moringa oleifera followed by filtration using submerged hollow fibre microfiltration membrane (MFM).Coagulation with M.Oleifera,air diffusers and back flush technique were used for preventing or alleviating fouling of the membrane.The hollow fibre MFM showed high removals of 98%,91% and 99% for turbidity,colour and total suspended solids respectively.It was obtained at the beginning of the filtration.However,quality of the filtrate rapidly declined during the filtration process.Fouling was found to proceed according to the classical cake filtration model.Coagulation with M.Oleifera as well as the back-flush technique could not fully restore the deterioration occurred to the membrane.
文摘Chemical cleaning has been reported as the best method to restore ceramic filters flow rate by removing fouling agents. Even though there are several chemicals that can be used as cleaning agents, sodium hydroxide (NaOH) has been widely used as a cleaning agent. Literature reports that main factors of this cleaning are sodium hydroxide concentration, treatment temperature and contact time. However, the most significant factors have not been determined nor the interactions between them. The aim of this study was to determine the most significant parameter and the interactions between sodium hydroxide concentration, treatment temperature and contact time. This was done using Box-Behnken experimental design. The results, based on ANOVA analyses, showed that temperature is the most significant factor and that interaction between sodium hydroxide concentration and treatment temperature is the most significant interaction.
基金This project was financially supported by the High Technology Research and Developmant Programof China (GrantNo.2006AA09Z356) the National Natural Science Foundation of China (Grant No.503795)
文摘In this work, we study the coupled cross-flow and in-line vortex-induced vibration （VIV） of a fixedly mounted flexible pipe, which is free to move in cross-flow （ Y- ） and in-line （ X- ） direction in a fluid flow where the mass and natural frequencies are precisely the same in both X- and Y-direction. The fluid speed varies from low to high with the corresponding vortex shedding frequency varying from below the first natural frequency to above the second natural frequency of the flexible pipe. Particular emphasis was placed on the investigation of the relationship between in-line and cross-flow vibration. The experimental results analyzed by using these measurements exhibits several valuable features.
基金sponsored by the National Natural Science Foundation of China(Nos.51976010,52006011)National Major Science and Technology Projects of China(Nos.2017Ⅱ-0006-0020,2017-Ⅱ-0001-0013,J2019-Ⅱ-0003-0023)Beijing Institute of Technology Research Fund Program for Young Scholars,China。
文摘It has been recently shown that Sub Boundary layer Vortex Generator(SBVG,abbreviated as VG hereafter)can suppress the Cross-Flow(CF),and therefore,can eliminate corner separation and increase aerodynamic loading when installed on the end wall inside middle-load compressor passages.However,when VGs are applied in high-load compressors,it is difficult to achieve ideal results.This is because the definition of the VG attack angle in the presence of CF in existing research is confusing,and the stronger CF in high-load compressors worsens the problem and results in an improper design and optimization range of VG attack angle.Therefore,this paper clarifies the definition of the VG attack angle in the presence of CF and reveals the CF controlling mechanism of VG on a flat plate.The differences in the flow phenomena around a VG both with and without CF are also studied.The numerical results show that a larger height or attack angle of the VG generates a greater CF suppression effect.However,the cross velocity increases when surmounting the primary vortex induced by the VG,except that this enhanced CF is less conspicuous for larger VG heights.Compared to the cases without CF,the VG suffers an additional loss because of the stronger separation and primary vortex loss caused by the CF.
基金the financial and technical support of University of Engineering and Technology, Taxila for carrying out the research
文摘Vibration in heat exchangers is one of the main problems that the industry has faced over last few decades. Vibration phenomenon in heat exchangers is of major concern for designers and process engineers since it can lead to the tube damage, tube leakage, baffle damage, tube collision damage, fatigue, creep etc. In the present study, vibration response is analyzed on single tube located in the centre of the tube bundle having parallel triangular arrangement （60-） with P/D ratio of 1.44. The experiment is performed for two different flow conditions. This kind of experiment has not been reported in the literature. Under the first condition, the tube vibration response is analyzed when there is no internal flow in the tube and under the second condition, the response is analyzed when the internal tube flow is maintained at a constant value of 0.1 rn/s. The free stream shell side velocity ranges from 0.8 rn/s to 1.3 m/s, the reduced gap velocity varies from 1,80 to 2.66 and the Reynolds number varies from 44500 to 66000. It is observed that the internal tube flow results in larger vibration amplitudes for the tube than that without internal tube flow. It is also established that over the current range of shell side flow velocity, the turbulence is the dominant excitation mechanism for producing vibration in the tube since the amplitude varies directly with the increase in the shell side velocity. Damping has no significant effect on the vibration behavior of the tube for the current velocity range.
