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.

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.

Membrane Microfiltration Fermentation of Glucose Oxidase with Cell Recycling

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.

Mechanism of Coalescence Demulsification with Microfiltra- tion Membrane

A study on the membrane coalescence demulsification was carried out with four working systems of water/n-butyl alcohol, water/n-octanol, water/30% TBP(in kerosene) and water/kerosene. The membranes made of polytetrafluoroethylene (PTFE) with 1.0μm pore size were used. The results indicated that the excellent demulsification efficiency for emulsions with various oil contents was obtained. A conductivity probe was used to study the demulsification mechanism. An electrode probe was designed and used to determine the oil content near the membrane surface. The obtained data showed that the oil content in the permeated stream was much higher than that in the feed emulsion. A physical mechanism to explain the membrane demulsification was put forward.

Experimental and CFD Study on the Role of Fluid Flow Pattern on Membrane Permeate Flux

This paper reports a study on the role of fluid flow pattern and dynamic pressure on the permeate flux through a micro filtration membrane in laboratory scale.For this purpose,a dead-end membrane cell equipped with a marine type impeller was used.The impeller was set to rotate in the clockwise and counter clockwise directions with the same angular velocities in order to illustrate the effect of rotation direction on permeate flux.Consequently, permeate fluxes were measured at various impeller rotational speeds.The computational fluid dynamics（CFD）predicted dynamic pressure was related to the fluxes obtained in the experiments.Using the CFD modeling,it is proven that the change in dynamic pressure upon the membrane surface has direct effect on the permeate flux.

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.

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.

Experimental Study on Revolving Cross-flow Microfiltration of Highly Viscous Liquids

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.

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.

PVDF/SiC疏/亲水Janus复合膜的制备及其膜蒸馏处理酸性废水性能

着眼于采用直接接触式膜蒸馏(DCMD)技术对酸性废水进行处理和资源再利用,针对传统蒸馏膜机械稳定性不高、通量低等问题,使用刮涂法和非溶剂致相分离(NIPS)法在亲水碳化硅(SiC)微滤膜表面构建疏水聚偏氟乙烯(PVDF)多孔薄层,制备得到具有不对称润湿性的PVDF/SiC疏/亲水双层Janus复合膜,用于DCMD性能研究.使用N,N-二甲基乙酰胺(DMAc)为溶剂,水-乙醇体系为非溶剂凝固浴,探究了制膜过程中PVDF铸膜液浓度、凝固浴成分、凝固浴温度等因素对PVDF层表面形貌和浸润性的影响,研究了复合膜在DCMD浓缩稀硫酸和处理模拟酸性矿山废水中的性能.结果表明,铸膜液中质量分数10%PVDF和纯乙醇凝固浴为最佳制膜条件,所得复合膜水接触角达140°,分离层孔隙率为45%,平均孔径为0.6μm,并且PVDF层与SiC基体结合力强.复合膜在DCMD浓缩质量分数10%(107 g/L)稀硫酸溶液和处理模拟酸性矿山废水实验中水的膜通量均达10 L/(m^(2)·h)以上,对非水组分截留率近100%,并具有长期运行稳定性,表现出DCMD处理酸性废水的应用潜力.

铸膜液中水的含量对聚醚砜微滤膜结构和性能的影响

通过蒸汽诱导相分离(VIPS)耦合非溶剂诱导相分离(NIPS)制备窄孔径分布聚醚砜(PES)微滤膜。本研究以PES为成膜材料,聚乙二醇为致孔剂,以水作为添加剂制备微滤膜,探究了铸膜液中水的质量分数对VIPS阶段蒸汽暴露时间及微滤膜结构与性能的影响.结果表明,铸膜液中水的质量分数从0%增加到3%,相似孔结构的形成所需的蒸汽暴露时间从90 s降低到30 s.膜的表面由致密皮层转变为大孔结构,孔径从0.087μm增加到0.193μm,孔径分布显著变窄,水接触角从83.6°增加到113.2°,拉伸强度从1.86 MPa增加到3.85 MPa,断裂伸长率从7%增加到16%,膜的力学性能显著增强,同时膜的纯水渗透率从5840 L/(m^(2)·h·MPa)增加到42300 L/(m^(2)·h·MPa).这表明,少量水的添加显著缩短了VIPS蒸汽暴露时间,同时改善了微滤膜的结构和性能.

微生物检验过程中微滤膜分离技术的应用价值

目的探讨微生物检验过程中微滤膜分离技术的应用价值。方法以2022年1月—2023年6月济南市疾病预防控制中心接收的86份微生物待检样本为研究对象。从每份待检样本中各取10 mL以平板计数法进行微生物检验,另各取10 mL基于微滤膜分离技术获取菌细胞进行微生物检验。比较2种检验方法的微生物检出率、微生物检验出报告时间与活菌回收率,评价检验效果。结果2种方法共检出阳性样本47份,其中微滤膜分离技术检出45份,占比为95.74%,平板计数法检出阳性样本47份,占比为100%。2种方法的初检86份样本的阳性检出率比较,差异无统计学意义(P>0.05);基于复检结果,微滤膜分离技术初诊漏检2例,2种方法的复检阳性率与漏检率比较,差异无统计学意义(P>0.05)。微滤膜分离技术的平均培养时间(20.24±3.17)h,短于平板计数法的(32.75±4.36)h,差异有统计学意义(P<0.05)。随机抽样回收率实验,微滤膜分离技术的阳性菌回收率分别为87.69%、87.50%、79.07%、67.86%、83.51%,高于平板计数法的72.01%、71.38%、64.19%、47.32%、65.64%,差异有统计学意义(P<0.05)。结论微生物检验中应用微滤膜分离技术的阳性检出率与平板计数法相当,但前者的培养时间更短,微生物检验出报告时间早,阳性菌回收率更高,效果优于平板计数法。

焦化废水深度处理零排放技术的应用实例

以山东兖州某焦化厂焦化废水深度处理项目为实例,对焦化废水的水质特征、处理工艺、主要设计参数及运行状况进行详细分析。结果表明,采用(深度处理+膜浓缩+多效蒸发结晶)组合工艺,废水处理系统综合回收率高于94%,结晶混盐含水率<0.5%,出水水质满足GB 50050-2017《工业循环冷却水处理设计规范》要求。另外,依据运行数据,分析了用电、氧气、循环水、蒸汽及药剂的成本,得出每吨水直接运行费用低于13.9元。

膜技术在水处理中的应用研究

目前,膜技术已广泛应用于水处理中,成为解决全球水资源问题的重要途径。微滤和超滤可以有效去除水中的悬浮物和细菌,反渗透广泛应用于海水淡化和饮用水净化,电渗析用于工业废水处理。这些膜技术不仅提高水资源利用效率,还改善水质,对环境保护和可持续发展具有积极意义。本文结合膜技术发展现状,分析膜技术在水处理中的应用,然后进行膜生物反应器的比选,以更好地将膜技术应用于水处理中。未来,要持续创新,进一步拓展膜技术在水处理领域的应用,为全球水资源管理和保护做出更大贡献。

膜生物反应污水处理技术对水质优化的影响研究

随着工业化和城市化进程的加速,水污染问题日益严峻。针对污水处理和水质优化的问题,研究设计了一种膜生物反应污水处理技术。过程中引入了膜污染概念,分析了膜生物反应性能影响情况,通过曝气控制的方式,对膜生物反应技术进行了优化。实验结果表明,优化方法的化学需氧量浓度,相比于传统方法,下降了18.75%;其含盐率可以降至5%~8%,相对减少了2%;提高了溶解氧浓度的控制精度,增强了系统对外界干扰的抗性。说明基于膜污染控制的膜生物反应技术优化,能够有效提升废水处理效果,对环境工程污水处理具有重要的理论和实践意义。优化技术的应用,有助于提高污水处理效率,降低运营成本,同时可为水资源的可持续利用和环境保护提供技术支持。

聚偏氟乙烯微滤膜的制备及相转化工艺参数的优化

作者采用非溶剂致相分离的方法,以聚偏氟乙烯(polyvinylidene fluoride,PVDF)为原料,以N,N-二甲基乙酰胺为溶剂制备微滤膜,探究非溶剂添加剂的种类与含量、预蒸发时间、环境湿度等因素对膜的微观结构、纯水通量及表面亲疏水性的影响。结果表明:固定PVDF的质量分数为16%,将异丙醇(质量分数为16%)和甘油(质量分数为6%)混合物作为添加剂,放入相对湿度为80%的环境中预蒸发4min后浸入水浴凝固,可获得具有大孔径、高通量、高疏水性的PVDF微滤膜。该PVDF膜的表面结构完全开放,支撑层由连通的蜂窝状孔结构组成,浸润后的水通量可达到(8650.74±305.29)L/(m^(2)·h),同时,对200nm的聚苯乙烯微球的截留率为99%以上。此外,该PVDF微滤膜的表面接触角为(122±3)°,有望用于生物医药生产过程中的空气除菌过程。

微滤膜分离技术在微生物检验中的应用价值分析

目的探究微生物检验中使用微滤膜分离技术的有效性,以期为类似研究提供一定的参考。方法以仪征市疾病预防控制中心2021年8月至2023年10月接收的60份检验样本为对象,根据所用检验方法不同予以分组,对照组给予常规平板培养检验,研究组使用微滤膜分离技术实施检验,对比不同组别检验所用时间、样本污染率等指标情况。结果对照组样本检验时间为(28.71±4.38)h,研究组为(5.26±0.53)h,研究组样本检出率(93.33%)高于对照组(73.33%),且样本污染率比对照组低,差异存在统计学意义(P<0.05)。结论采用微滤膜分离技术对微生物实施检验,具有检出率高、样本污染率低等特点,还能缩短检测工作所用时间,具有在疾控中心推广使用的价值。

死端搅拌操作条件下平均膜污染度量指数变化

在死端搅拌微滤膜装置上,采用0.1μm孔径的PES平板微滤膜对酵母悬浮液进行过滤实验。研究瞬时膜污染度量指数(t)和平均膜污染度量指数■在不同操作条件下(搅拌速率、浓度、温度、压力和污染物)的变化规律。结果表明,搅拌速率200 rmp时(t)最小,而■随搅拌速率的增加先增大后降低;在浓度、温度以及压力下,(t)均随时间递增,■随浓度递增。另外,■(酵母悬浮液)>■(活性污泥悬浮液)>■(高岭土悬浮液)则说明在实际过滤过程中,选择2 g/L、25℃和0.08 MPa作为固定操作条件,选择尽可能高搅拌速率和低料液浓度的高岭土悬浮液时的膜污染程度最轻。

Highly Durable MIL-96 Membranes via a One-step Active γ-Alumina Conversion Strategy for Gas Separation

Metal-organic frameworks(MOFs)are attractive in membrane separation due to their special pore structure and suitable aperture size.The fabrication of defect-free and robust MOF membranes with excellent durability is highly demanded but remains challenging.In this work,we report a one-step activeγ-alumina conversion strategy for the facile and reliable fabrication of an MIL-96 membrane.In this case,theγ-Al_(2)O_(3) sol was dip-coated and sintered on theα-Al_(2)O_(3) disc as the active aluminum source and substrate for the nucleation and growth of MOF.A continuous and well-intergrown MIL-96 membrane was generated with exceptional stability due to the strong adhesion to the substrate.The resultant MIL-96 membrane yielded a satisfactory H_(2)/CO_(2) permselectivity and high-temperature resistance,delivering a selectivity of 12.35 with H_(2) permeance of 6.20×10^(−7) mol·m^(−2)·s^(−1)·Pa^(−1) at 150℃.Moreover,the probe membrane presented remarkable durability and recyclability under harsh hydrothermal conditions.This method paves the way for constructing highly stable and selective MOF membranes and could accelerate the development of advanced membrane separation technologies for gas purification and recycling in addressing the severe energy and environmental problems.