Flow-Induced Clogging in Microfiltration Membranes: Numerical Modeling and Parametric Study

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.

Preparation and Characterization of the Modified Polyvinylidene Fluoride (PVDF) Hollow Fibre Microfiltration Membrane

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.

Modeling of Continuous Cross-flow Microfiltration Process in an Airlift External-loop Slurry Reactor

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%.

Treatment of phosphate-containing oily wastewater by coagulation and microfiltration

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.

Purifying chylous plasma by precluding triglyceride via carboxylated polyethersulfone microfiltration membrane

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.

Study on Separation of Water and Alumina Fine Particles by Cross-Flow Microfiltration

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.

Removal of endocrine disrupting chemicals from water through urethane functionalization of microfiltration membranes via electron beam irradiation

Polyethersulphone(PES)membranes modified with urethane functional groups were prepared through an interfacial reaction using electron beam irradiation.The removal of eight endocrine disrupting chemicals(EDCs)was studied using both pristine and functionalized PES membranes.The prepared membranes underwent characterization using several techniques,including attenuated total reflectance-Fourier transform infrared(ATR-FTIR)spectroscopy,scanning electron microscopy,contact angle analysis,and measurements of pure water flux.Furthermore,dynamic adsorption experiments were conducted to evaluate the adsorption mechanism of the prepared membrane toward the eight EDCs.The urethane functionalized membranes were hydrophilic(52°contact angle)and maintained a high permeate flux(26000 L/h m2 bar)throughout the filtration process.Dynamic adsorption results demonstrated that the introduction of urethane functional groups on the membranes significantly enhanced the removal efficiency of 17β-estradiol,estriol,bisphenol A,estrone,ethinylestradiol,and equilin.The adsorption loading of 17β-estradiol on the functionalized PES membrane was 6.7±0.7 mg/m^(2),exhibiting a 5-fold increase compared to the unmodified PES membrane.The membranes were successfully regenerated and reused for three adsorption cycles without experiencing any loss of adsorption capacity.

Polyaniline-poly(vinylidene fluoride) blend microfiltration membrane and its spontaneous gold recovery application

Structural regular polyaniline was synthesized via a modified-chemical oxidative polymerization reaction. Highly hydrophilic polyaniline(PANi) and polyaniline-poly(vinylidene fluoride) blend(PANi-PVDF) membranes were prepared by solution casting and phase inversion techniques. Both of the mechanical and filtration properties of the membranes depend on the polymer composition and doping level of the blends. The elasticity of the membrane is greatly improved upon introducing poly(vinylidene fluoride) into the blend. The water permeability of the blend membranes is further enhanced when the membranes are doped with hydrochloric acid. The PANi-PVDF blend membranes are capable of recovering metallic gold from the acid/halide leaching streams spontaneous and sustainably, and are promising candidates for wastewater treatments in electronic industries.

Roles of membrane and organic fouling layers on the removal of endocrine disrupting chemicals in microfiltration

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.

Bisphenol A removal from synthetic municipal wastewater by a bioreactor coupled with either a forward osmotic membrane or a microfiltration membrane unit

Forward osmotic membrane bioreactor is an emerging technology that combines the advantages of forward osmosis and conventional membrane bioreactor. In this paper, bisphenol A removal by using a forward osmotic membrane bioreactor and a conventional mem- brane bioreactor that shared one biologic reactor was studied. The total removal rate of bisphenol A by the conventional membrane bioreactor and forward osmotic membrane bioreactor was as high as 93.9% and 98%, respectively. Biodegradation plays a dominant role in the total removal of bisphenol A in both processes. In comparison of membrane rejection, the forward osmosis membrane can remove approximately 70% bisphenol A from the feed, much higher than that of the microfiltration membrane （below 10%）. Forward osmosis membrane bioreactor should be operated with its BPA loading rate under 0.08 mg. g-1. d-1 to guarantee the effluent bisphenol A concentration less thanlO μg·L-1.

反渗透预处理及膜清洗方法

基于预处理和膜清洗对于反渗透RO(reverseosmosis)长期稳定运行的重要性 ,介绍了常规预处理方法及其改进、膜法预处理等预处理方法 ,以及各种新型的物理、化学膜清洗方法 .

Fulvic acid degradation using nanoparticle TiO_2 in a submerged membrane photocatalysis reactor

The degradation of fulvic acid（FA） by nanoparticle TiO2 in a submerged membrane photocatalysis（SMPC） reactor was studied. In this reactor, photocatalytic oxidation and membrane separation co-occured. The continuous air supplier provided O2 for the photocatalytical reaction and mixed the solution through an airflow controller. The particle TiO2 could automatically settle due to gravity without particle agglomeration so it could be easily separated by microfiltration（MF） membrane. It was efficient to maintain high flux of membranes. The effects of operational parameters on the photocatalytic oxidation rate of FA were investigated. Results indicated that photocatalyst at 0.5 g/L and airflow at 0.06 m^3/h were the optimum condition for the removal of fulvic acid, the removal efficiency was higher in acid media than that in alkaline media. The effects of different filtration duration on permeate flux rate of MF with P25 powder and with nanoparticle TiO2 were compared. Experimental results indicated that the permeate flux rate of MF was improved and the membrane fouling phenomenon was reduced with the addition of nanoparticle TiO2 catalyst compared with conventional P25 powder. Therefore, this submerged membrane photocatalysis reactor can faciliate potential application of photocatalytic oxidation process in drinking water treatment.

Influence of hydraulic retention time on efficiencies of high concentration PAC-MF bioreactor treating slightly polluted surface water

In this study,the influence of hydraulic retention time on feasibility,efficiency and membrane foul- ing of slightly polluted surface water treatment by a high concentration PAC-MF bioreactor were investigated. During three months operation,TOC,NH4 + -N,nitrobenzene,and TMP were measured to evaluate the MBR performance. The results show that,when HRT reduces from 3 h to 1 h,removal efficiency of TOC and ammonia-nitrite decrease a little. However,there is little effect of HRT on nitrobenzene. And the optimal hydraulic retention time is 1 h.

Start-up and contaminants removal characteristics of aerobic granules-membrane bioreactor at low temperature

In order to understand the effect of low temperature on the formation process of aerobic granules and contaminants removal characteristics,the aerobic granules-membrane bioreactor (AGS-MBR) has been started up and operated at low temperature using the carbon resource of sodium acetate. Aerobic granules cultivated in AGS-MBR possess smooth surface and compact structure in morphology as well as better settling property and higher biomass after 38 days. The average parameters of aerobic granules are: diameter 3. 1 mm,wet density 1. 041 g/mL,sludge volume index 42. 35 mL/g and settling velocity 20. 6 - 45. 2 cm/min. During the start-up of AGS-MBR,the respectively average contaminants removal efficiencies at low temperature are 91. 9% for chemical oxygen demand (COD) ,89. 2% for NH4 + -N and 86. 3% for PO43- -P,and the overgrowth of filamentous bacteria has been well controlled. In addition,the hollow fiber microfiltration (MF) membrane fouling is light and the regime membrane layer is capable of enhancing membrane filtration as well as the average growth of trans-membrane pressure (TMP) is 1. 07 kPa/d. Compared with the conventional cultivation of aerobic granules,the sludge granulation time significantly decreases from 73 days to 38 days by the application of microfiltration membrane at low temperature.

Optimization of Ceramic Paste Viscosity Use for the Elaboration of Tubular Membrane Support by Extrusion and Its Application

The objective of this work was to determine the optimum size and amount of raw materials which influence the viscosity of ceramic paste using the experimental design for the production of tubular support by the extrusion technique and its application in microfiltration. The Box Behnken design was used to optimize the viscosity of the ceramic paste. ANOVA was used to model the system represented by independent parameters and dependent output response and to optimize the system by estimating the statistical parameters. A three-factor and three-level design was used generating thus 15 experiments. The independent factors were the amount of porogen, size of porogen and amount of binder and dependent factor the viscosity of the ceramic paste. The minimum (−1), intermediate (0) and maximum (+1) level of the amount of porogen, size of porogen and amount of binder used were 20 g, 30 g and 40 g, 50 μm, 100 μm and 150 μm, and 2 g, 3.5 g and 5 g respectively. The statistical analyses showed that the values of the answers would adapt to a second degree polynomial model. The R-square value obtained was greater than 95%, the Biais factor was equal to the unit and the Absolute Average Deviation (AAD) equal to the zero thus validating the model. The optimal size of raw material was found to be 100 μm for an amount of clay of 66 g, amount of porogen of 30 g and amount of binder of 4 g. The optimum viscosity of the ceramic paste was found to be 26.7 Pa∙s which is close to the viscosity of the clay paste only found to be 28.5 Pa∙s, thus good for shaping by the extrusion technique. The ceramic paste showed a pseudo-plastic behavior. The tubular porous support was sintered at 950°C and the dimensions, such as outer and inner diameters and length of the tube were 4 cm, 2 cm, and 19 cm, respectively. The sintered membrane possesses a porosity of 43.5%, water permeability of 244.9 L/h∙m2 bar, an average pore size of 2.4 μm and mechanical strength of 9.2 MPa with very good corrosion resistance in acidic and basic conditions. The membrane was subjected to microfiltration of synthetic clay suspension at various combinations of applied pressures (0.5 - 2 bar) with a feed concentration of 100 NTU. An increase in the applied pressure leads to an increase in the flow rate and retention rate. The flow rate decreases steadily with time. The highest retention was obtained at 2 bar with permeability of 184.69 L/h∙m2 bar and a retention of 96% decreasing the turbidity to about 3.5 NTU which is below the acceptable value of 5 NTU.

Analysis of Pollution and Blockage of Titanium Rod Sintered Microporous Filter Element

Microfiltration is widely used in fine filtration operations, with dead-end filtration and cross-flow filtration. The microfiltration filter element or the microfiltration membrane is easy to be polluted by impurities in the water and causes fouling, resulting in flux attenuation. The flux can be expressed by Darcy’s law and attenuation model. In this paper, two industrial titanium rod sintered filter elements (?60 × 960 mm and ?60 × 960 mm) of different specifications are selected, and tap water (1.0 NTU) is used for constant pressure dead-end filtration. The amount tends to be the same, about 0.435 m3·m?2·h?1, which has nothing to do with the filtration accuracy of the filter element but only depends on the characteristics of the filter cake and the filter membrane. Through the analysis of the two models, it is found that the two filtration flux models are not universal and difficult to be applied in engineering.

Comparison of CNT-PVA membrane and commercial polymeric membranes in treatment of emulsified oily wastewater

Membrane separation is an attractive technique for removal of emulsified oily wastewater.However,polymeric membranes which dominate the current market usually suffer from severe membrane fouling.Therefore,membranes with high fouling resistance are imperative to treat emulsified oily wastewater.In this study,carbon nanotube-polyvinyl alcohol(CNT-PVA)membrane was fabricated.And its separation performance for emulsified oily wastewater was compared with two commercial polymeric membranes(PVDF membrane and PES membrane)by filtration of two homemade emulsions and one cutting fluid emulsion.The results show that these membranes have similar oil retention efficiencies for the three emulsions.Whereas,the permeation flux of CNT-PVA membrane is 1.60 to 3.09 times of PVDF membrane and 1.41 to 11.4 times of PES membrane,respectively.Moreover,after five consecutive operation circles of filtration process and back flush,CNT-PVA membrane can recover 62.3% to 72.9% of its initial pure water flux.However,the pure water flux recovery rates are only 24.1% to 35.3% for PVDF membrane and 6.0% to 26.3% for PES membrane,respectively.Therefore,CNT-PVA membrane are more resistant to oil fouling compared with the two polymeric membranes,showing superior potential in treatment of emulsified oily wastewater.

Preparation and characterization of hydrothermally engineered TiO2-fly ash composite membrane

这个工作指向便宜 TiO 2-fly 灰的准备和描述为油性的废水处理的合成的膜。合成的膜被经由热水的方法在苍蝇灰膜上扔吸水的 TiO 2 层制作，并且它的结构、词法、机械的性质被评估。合成的膜的分离潜力为 100-200 mg 楤? 被评估 ?????????????? 吗？？

Preparation and Characterization of Multi-layer Poly(arylene sulfide sulfone) Nanofibers Membranes for Liquid Filtration

Owing to the excellent filtration performance and low energy cost,polymeric nanofibers microfiltration(MF)membranes have attracted increasing attentions.Poly(arylene sulfide sulfone)(PASS),as one of the structurally modified polymers based on poly-(phenylene sulfide)(PPS),has been selected as the raw material to fabricate nanofibers MF membranes via electrospun techniques.The effects of PASS solution and the electrospinning processing parameters on the structural morphology of nanofibers were investigated in detail.The average diameter of PASS nanofibers was(296±46)nm under the optimal condition:polymer concentration of 0.27 g·m L^–1 PASS/DMI,applied voltage of 20 kV,and speed of collector drum of 300 r·min^–1.And then the multi-layer PASS nanofibers MF membranes were fabricated from cold-pressing the optimized PASS nanofibers(as-prepared PASS nanofibers)membrane.The morphology,porosity,pore size,mechanical properties,and surface wettability of the multi-layer PASS nanofibers MF membranes could be tuned by the layers of as-prepared nanofibers membrane.The results demonstrated that the membrane with 6 layers(marked as PASS-6)exhibited the smallest porosity,smallest pore size,highest mechanical property,and best surface wettability.Meanwhile,the multi-layer PASS nanofibers MF membranes showed that the rejection ratio gradually increased,while the pure water flux decreased with increasing membranes thickness.The PASS-6 membrane exhibited large water flux of 747.76 L·m^–2·h^–1 and high separation efficiency of 99.9%to 0.2μm particles,making it a promising candidate for microfilter.