Crossflow Microfiltration Research Articles

Striping phenomenon during cross-flow microfiltration of oil-in-water emulsions

Abstract The striping phenomenon in membrane filtration, whereby the foulants deposit as regular streaks rather than a more uniform layer, was first observed more than 30 years ago (Jonsson, 1987), but the understanding has remained limited to a few subsequent studies (Henriksen and Hassager, 1993; Larsen, 1991; Li et al., 2016; Tanudjaja et al., 2017; Tarabara et al., 2002). In view of the potential practical implications of the stripes in terms of membrane fouling and fouling mitigation, this study was targeted at an in-depth characterization of the stripes. The direct observation through the membrane (DOTM) technique was employed to observe the conditions when the stripes formed by oil emulsions stabilized by three Tween surfactants at a lower cross-flow velocity, and higher oil concentrations and permeate fluxes. The results indicate that (i) other than hydrodynamic factors (e.g., permeate drag, tangential shear), foulant-membrane and foulant-foulant interactions played a role in stripe formation or disappearance, as evident in the formation of stripes only by the oil emulsion stabilized by the Tween surfactants and the effect of pH; (ii) stripes made up of oil droplets appeared to be easier to remove than the more uniform layer of oil droplets, as evident in the shorter time taken for the former to detach; and (iii) among the three Tween surfactants, the striping characteristics investigated were largely similar, except for the time taken for the deposits to detach. These are expected to have implications for fouling control and mitigation.

Erythrocyte fouling on micro-engineered membranes.

Crossflow microfiltration of plasma from blood through microsieves in a microchannel is potentially useful in many biomedical applications, including clinically as a wearable water removal device under development by the authors. We report experiments that correlate filtration rates, transmembrane pressures (TMP) and shear rates during filtration through a microscopically high channel bounded by a low intrinsic resistance photolithographically-produced porous semiconductor membrane. These experiments allowed observation of erythrocyte behavior at the filtering surface and showed how their unique deformability properties dominated filtration resistance. At low filtration rates (corresponding to low TMP), they rolled along the filter surface, but at higher filtration rates (corresponding to higher TMP), they anchored themselves to the filter membrane, forming a self-assembled, incomplete monolayer. The incompleteness of the layer was an essential feature of the monolayer's ability to support sustainable filtration. Maximum steady-state filtration flux was a function of wall shear rate, as predicted by conventional crossflow filtration theory, but, contrary to theories based on convective diffusion, showed weak dependence of filtration on erythrocyte concentration. Post-filtration scanning electron micrographs revealed significant capture and deformation of erythrocytes in all filter pores in the range 0.25 to 2 μm diameter. We report filtration rates through these filters and describe a largely unrecognized mechanism that allows stable filtration in the presence of substantial cell layers.

Analysis of process intensification and performance assessment for fermentative continuous production of bioethanol in a multi-staged membrane-integrated bioreactor system

The work analyses process intensification in production of fermentative biofuel (bioethanol) in a multi-staged membrane integrated bioreactor system from sugarcane juice (SCJ) using Saccharomyces cerevisiae (NCIM 3205). Membrane based clarification, sterilization and concentration of sugar cane juice could replace several energy-intensive and polluting steps of conventional production schemes. Integration of traditional bioreactor with membrane-based devices for downstream purification of bioethanol enabled the system for recycling of cells and residual sugars to the fermentation unit through largely fouling free cross flow microfiltration and nanofiltration membrane modules. The new process design is characterized by high yield (0.48 g/g), productivity (14.6 g/L/h) and concentration capability (97.6 g/L) using concentrated SCJ of 22 wt% under high cell density in a flexible, compact, eco-friendly and modular plant. The final membrane distillation stage concentrated ∼98% pure ethanol in a solar-driven direct contact membrane distillation configuration using PTFE/PET hydrophobic membrane with enhanced flux with vis-à-vis the existing processes. A rectangular flat sheet cross flow membrane module in counter-current flow mode of hot and cold streams was employed. The membrane-based system achieves quite high levels of process intensification essential to sustainable operation at industrial scale. The achieved process intensification in the new system has been analysed vis-a-vis the existing conventional systems in terms of eco-friendliness, flexibility, cost of equipment and production, consumption of energy and material, profitability, E-factor, atom efficiency and business sustainability.

Application of asymmetric Si3N4 hollow fiber membrane for cross-flow microfiltration of oily waste water

The asymmetric morphology of silicon nitride (Si3N4) ceramic hollow fiber membrane with a selective spongiform outer layer was optimized by the air gap distance and the internal rate of coagulate for oil/water emulsion microfiltration. The effect of trans-membrane pressure (TMP), feed flow rate (FFR), and pH of the feeding emulsion on the separation performance were determined experimentally. Membrane fouling has increased by dissociation of oil droplets during filtration at high TMP and FFR values. Fouling phenomena were studied based on standard pore blocking model. The pH by affecting the surface charge of the Si3N4 hollow fibers and zeta potential of the feed emulsion has also been introduced as a prominent influential factor on separation efficiency. The highest values of permeate flux (390 Lm−2h-1) and oil rejection (95%) were recorded in alkaline pH. The fabricated Si3N4 ceramic membranes were completely recovered (≤99%) by simple thermal treatment at 400 °C.

Production of a β-d-glucan-rich extract from Shiitake mushrooms (Lentinula edodes) by an extraction/microfiltration/reverse osmosis (nanofiltration) process

A pilot-scale process combining extraction of Shiitake mushroom (Lentinula edodes) powder in water (98 °C, 1 h), cross-flow microfiltration and reverse osmosis (nanofiltration) was performed to obtain β-glucan-rich extracts. Suspensions (45–80 L) obtained after 3 extractions were clarified by microfiltration reducing their turbidity to <1 NTU. Membrane flux was completely recovered after filtration. One of the clarified extracts was concentrated (to 6–7 L) by reverse osmosis (Nanomax95) and the other two by nanofiltration (Nanomax50 and ALNF99-2517). Different physicochemical parameters (permeate flux, total soluble substances, total suspended particles and electrical conductivity) were monitored during filtration and the bioactive compounds present in the obtained fractions (β-glucans, total carbohydrates, chitins, eritadenine, lenthionine, ergosterol) were analyzed. The more adequate membrane for Shiitake extract concentration was Nanomax50 because it showed higher filtration flux and higher values of bioactive compounds in the obtained extract than the extracts obtained with the other two membranes. This work describes a pilot-scale procedure for obtaining β-d-glucan-rich extracts from Lentinula edodes (Shiitake mushrooms). The extracts might be used in novel functional foods due to their high content in hypocholesterolemic compounds. The process combines extraction with boiling water, cross-flow membrane clarification and reverse osmosis/nanofiltration concentration of β-d-glucans. The procedure is scalable to industrial level.

The use of fluid dynamic gauging in investigating the thickness and cohesive strength of cake fouling layers formed during cross-flow microfiltration

A common challenge during membrane filtration is cake fouling, whereby the build-up of material on the membrane surface reduces the permeate flux. Such fouling layers can also alter the selectivity of the separation. In this study, fluid dynamic gauging (FDG) is used in situ to investigate the cake fouling formed during cross-flow filtration of a model material: softwood Kraft lignin. FDG was used to estimate (i) the thickness of the cake layers (in the μm scale) and (ii) the local cohesive strength at different depths in the cake layer. Fouling layers formed at different transmembrane pressure (TMP) values were investigated. The estimated thickness of the cake layers increased with increasing TMP. However, it was difficult to capture the full cake thickness for the more loosely formed cakes layers. An increase in the cohesive strength of the cake was found to occur with increasing TMP values.

Crossflow microfiltration coupled with diafiltration to concentrate and purify carotenoids and flavonoids from citrus juices

Abstract This work aimed to evaluate an eco-friendly process based on microfiltration with a diafiltration stage in order to concentrate and purify the main carotenoids and flavonoids in citrus juices. Pilot plant scale trial parameters were: tubular ceramic membranes with 0.2 μm pore diameter, 40 °C and 3 bar of transmembrane pressure. Different operating conditions were tested varying volumetric reduction ratio (VRR) from 2.5 to 10 and diavolume (DV) up to 1.7. Permeate flux ranged from 20 to 100 L h− 1 m− 2 according to the VRR. The concentration was multiplied by 5 to 10 for carotenoids and hesperidin but only by 2 to 3 for narirutin. Diafiltration increased the purity of carotenoids and hesperidin from 8 to 20 times. A model was validated for prediction of the concentration and purification factors vs. VRR and DV and the retentions were 100%, 97% and 63% for carotenoids, hesperidin and narirutin.

Combined enzymatic and crossflow microfiltration process to assure the colloidal stability of beer

In this work, two beers of the industrial and craft types were stabilized and clarified by combining a commercial enzyme preparation of fungal origin (Brewers Clarex®), which is commonly used for the production of gluten-free beers, with crossflow microfiltration.By resorting to some European Brewing Convention indicative forcing tests (i.e., sensitive proteins, alcohol chill haze, and chill haze development), it was possible to confirm the efficacy of the enzyme preparation for both beers examined. By combining the enzymatic and polyvinylpolypyrrolidone (PVPP) treatments, each beer exhibited a greater colloidal stability with respect to that achievable with any single treatment. Independently of the stabilizing pretreatment used, final membrane clarification gave rise to permeated beers with almost the same chill haze development. By coupling the enzymatic treatment to crossflow microfiltration, it would be possible to replace PVPP, and avoid its expensive recovery and regeneration processes, thus leading to a simpler one-step beer conditioning process.

Oxidative stress induced membrane biofouling and its implications to on-line chemical cleaning in MBR

On-line chemical cleaning with sodium hypochlorite (NaClO) offers an effective option for maintaining sustainable permeability in MBR. However, inevitable exposure of activated sludge to NaClO leads to the generation of oxidative stress in microorganisms. Therefore, this study filled up the knowledge gap by investigating the potential effects of the NaClO-induced oxidative stress on biofouling development. For this purpose, stressed and non-stressed microorganisms with the same cell viability were prepared and their fouling propensities were further examined in a crossflow microfiltration system. It was found that the membrane fouling potential of stressed biomass was significantly increased due to the faster colonization of survived bacteria on membrane surface. In the absence of oxidative stress, more dead bacteria preferentially adhered onto membrane surface, followed by the attachment of live cells. However, a stratified structure of fouling layer appeared during the filtration of stressed bacteria, i.e. viable bacteria more situated at the membrane surface on the top of which a layer of dead bacteria was formed. These suggested that the oxidative stress prompted survived bacteria to rapidly and predominantly adhere onto the membrane surface, which in fact could be considered as a protective strategy for bacteria to survive under harsh conditions. Consequently, the NaClO-induced oxidative stress may negatively impact on the long-term effectiveness of on-line chemical cleaning in MBR.

Preliminary Concentration of Skim Latex and Its Wastewater Use Plate Sheet Microfiltration

Skim latex is a by–product of the concentrated latex factory. In this study, plate sheet membrane and cross–flow microfiltration (MF) experiments on skim latex and its wastewater were carried out to initially identify the performance of membrane separation. The series of MF experiments were conducted by using a nitrocellulose plate sheet membrane with a pore size of 0.1 μm and 0.45 μm at the pressures driven at 0.5 and 1 bar. The skim latex, skim latex diluted with water and skim rubber wastewater were tested by membrane separation. Sodium dodecyl sulfate (SDS) and cationic polymer were also added to the skim latex and used to combine it with the membrane. The results implied that filtration of skim rubber wastewater with a 0.45 μm membrane at 1 bar pressure gave the highest flux of 152.6 l/m2–hr while the skim latex gave the highest flux of only 1.4 l/m2–hr. When SDS and cationic polymer at 8 mg/l were added to the skim latex and tested, the highest flux was observed to increase as 2.1 and 2.8 l/m2–hr, respectively. When skim latex diluted with 5 and 10 times the amount of water was tested, the highest flux was determined to be 13.9 and 20.8 l/m2–hr, respectively. Using MF to filtrate the skim latex gave 48% SCOD removal. This result reflects that the MF system might be an alternative technology applied in the concentrated latex factory, especially to the rubber skim process.

Rotating Cylinder Microfiltration of Oil–in–Water Emulsion Using Novel Slotted Pore Filter

Nowadays, oil–in–water emulsion has become an important topic in petroleum industry, which produces oil–inwater emulsion in the recovery of crude oil. Oil–in–water emulsion produced in crude oil recovery causes problems at different stages of the production in the petroleum industry. Recently, microfiltration has been applied in the separation of oil from water. In filtration of oil–in–water emulsion, there is the possibility of oil drops deforming and squeezing through the slot of membrane so the separation efficiency will decrease. This research has studied cross flow filtration of oil–in–water emulsion in a rotating system and also visualized the interaction of oil drops and slot shaped membrane pores. The drop or bubble–slot experiment used a slot with different width. It has been found that the squeezing of an oil drop in the slot is really determined by the pressure applied and velocity of the surrounding fluid. Cross flow microfiltration experiment was conducted using tubular slotted pore membrane with rotation to generate shear on the surface of membrane. Kerosene and crude oil were tested using 5.3 and 7.5 microns membrane at different rotation speed and permeate velocity. Experimental results indicated that in a no blocking condition, the movement of oil drops was determined by shear force and permeate drag force. While in blocking condition, the rejection of oil drops was determined by the formation and characteristic of the secondary membrane formed on the surface of membrane. Blocking will improve the filtration performance in relation to oil rejection, but it will increase the pressure needed or decrease the flux rate through the membrane.

Economic Assessment for Cold Sterilization and Clarification of Pineapple Juice and Coconut Water using Microfiltration

This study aims to assess the economical feasibility for production of sterilized/clarified pineapple juice and coconut water using cross flow microfiltration (MF). The data for microfiltration plant design is based on the experimental results from our previous studies. The capacity of processing plant for the juice production is assumed to be 20,000 L/day for each juice. The 0.2 m and 0.1 m hollow fiber membranes are used for producing clarified/sterilized pineapple juice and coconut water respectively. The investment cost and the operating cost under various operating conditions are summarized. The operating condition is found to be a major factor influencing capital cost as well as operation cost. The economic assessment is accomplished for production of 5,000 m3/year, yielding an interest rate of return of 38.3-53.6 % and payback period of 1.9-2.6 years for pineapple juice while the yielding an interest rate of return of 19.2-23.2% and payback period of 3.9-4.4 years for coconut water depending on operating conditions.

Thermal treatment of clay-based ceramic membranes for microfiltration of Acutodesmus obliquus

Tubular ceramic microfiltration membranes were prepared by extruding thermally treated clay (TC) and raw clay to form a porous tubular membrane with the addition of cationic manioc starch and toasted manioc flour. The influence of an applied thermal treatment on the proprieties of the clay and the microfiltration membranes was characterized by measuring the particle size distribution, pore size distribution, and mechanical strength and by conducting X-ray fluorescence analysis, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. The membranes were used for microfiltration of Acutodesmus obliquus microalgae with various applied pressures in the range of 2×104–1×105Pa with a volumetric flow rate of 6.94×10−5m3·s−1 at a temperature of 10±5°C. The efficiency of each of the ceramic membranes was evaluated in terms of the permeate flux for water and microalgae and the microalga retention. The addition of TC to the membrane resulted in an optimal microalga permeate flux of 3.24×10−2kg·m−2·s−1 and a microalga retention of 98.3% at 4×104Pa and had positive impacts on the other proprieties measured. Overall, these results demonstrate a potential application of TC in ceramic membranes for crossflow microfiltration processes.

Isolation of Peptides from Calf Brain Tissue and Evaluation of their Tissue-Specific and Stimulatory Activity

A method for separating a mixture of calf brain peptides by extraction with aqueous HOAc followed by fractionation of the extract by cross-flow (tangential) microfiltration and solid-phase extraction was developed. The isolated peptide mixture contained constituents with molecular masses within 0.1 – 3 kDa. Low-pressure ion-exchange chromatography of this mixture over Dowex 50WX8 sulfonated cation exchanger isolated a pure peptide consisting of the five amino acids Arg, Lys, Gly, Ser, and Leu. The biological activity of the obtained pentapeptide was estimated on organotypic brain slice culture explants of Wistar rats. It was established that the peptide possessed high tissue-specific and stimulatory activity for brain explants that was greater than those of the commercial preparations Cortexin and Cerebrolysin.

Water recovery from laundry wastewater by the cross flow microfiltration process: A strategy for water recycling in residential buildings

In this work, domestic laundry wastewater was treated through a membrane process using a mixed cellulose ester (MCE) microfiltration membrane with 0.22 μm pore size. A cross flow filtration was used and the effect of operating parameters such as trans-membrane pressure (TMP) and feed flow rate on permeate flux and rejection characteristics have been studied. A detailed analysis of the membrane fouling and the formed resistances against permeation which caused flux decline including membrane, cake layer, reversible and irreversible resistances have been offered and the effect of trans-membrane pressure and flow rate on each of the mentioned resistances was examined. Finally, the removal efficiencies for BOD, COD, TSS and turbidity at different trans-membrane pressures and feed flow rates are determined. It was observed that an increase of TMP and feed flow rate has positive effects on the permeate flux and membrane rejection performance. Moreover, the overall resistance increases with an increase in TMP and decreases with an increase in feed flow rate. The highest removal efficiency for BOD, COD, TSS and turbidity was obtained as 93.9, 90.8 and 98.7 percent, respectively which was obtained at a TMP of 1 bar and feed flow rate of 44 L/h. Modeling of the microfiltration system by the Hermia models revealed that the cake formation model (CFM) has the best agreement with the experimental results and it could be concluded that the cake layer formation on the membrane surface is the main mechanism for membrane fouling and flux decline. The results of this study showed that the microfiltration is a reliable and simple operation for recycling and reuse of domestic laundry wastewater in mixture with fresh water for use in washing machines, toilets and irrigation.

Effect of crossflow microfiltration on the clarification and stability of beer from 100% low-β-glucan barley or malt

The clarifying effect of crossflow microfiltration (CFMF) on two types of lager beers made of 100% low β-glucan barley (LBGB), as such using the commercial Ondea®Pro enzyme preparation or pre-malted, was assessed and compared to that obtained using a commercial Pils Malt beer. All rough beers resulted to be quite similar with some differences in viscosity, color, and β-glucan, arabinoxylan, and polyphenol contents. The use of malted LBGB grains gave rise to a beer with low β-glucan (13 ± 4 mg/L) and arabinoxylan (568 ± 40 mg/L) concentrations, but high and stable colloidal turbidity (43.9 ± 0.2 EBC unit), with a consequent reduction in both permeation flux [23 ± 2 L/(m2 h)] and clarified beer quality. The best results in terms of filterability and permeated beer quality were obtained using 100% LBGB beer. Despite its high β-glucan (233 ± 4 mg/L) and arabinoxylan (917 ± 39 mg/L) contents, the limiting permeation flux approached 147 ± 24 L/(m2 h), about three times higher than obtained with the conventional all malted beer. The commercial Ondea®Pro enzyme preparation and CFMF clarification of the resulting rough beer might represent a valid option to produce a 100% barley beer, even if the raw materials used are not well suited for malting.

Dynamic membranes of powder-activated carbon for removing microbes and organic matter from seawater

A dynamic membrane was formed by introducing powder-activated carbon (PAC) prior to the cross-flow microfiltration of seawater. The microbes and organic matter in the seawater were removed efficiently through the interception, adsorption, and biodegradation of the PAC dynamic membrane. The properties of PAC dynamic membranes formed under various operating conditions were analyzed. The relationship between the specific filtration resistance of a dynamic membrane and transmembrane pressure was regressed as a power-type empirical equation for a given cross-flow velocity. An increase in cross-flow velocity led to higher specific filtration resistance because of the smaller particle size distribution. The thickness of a dynamic membrane increased with the transmembrane pressure but decreased with the cross-flow velocity. The thickness was correlated with the ratio of tangential to normal drag forces exerted on the PAC particles on the membrane surface. The filtrate quality for PAC dynamic membrane filtration was analyzed. Humic acid (HA) and turbidity were not detected. The chemical oxygen demand (COD) and dissolved organic carbon (DOC) had maximum removals of approximately 80% and 92%, respectively. The behavior by which HA was adsorbed on a PAC conformed to the Freundlich isotherm, and the modified Wheeler equation produced appropriate estimates of the breakthrough time. The breakthrough time increased with the thickness of the dynamic membrane. This study presents a method by which the filtration performance, such as filtration flux, thickness, and breakthrough time of the dynamic membrane, can be predicted directly from operating conditions.

Improving the performance of silica-based crossflow membranes by surface crystallization for treatment of oily wastewater

Today, hundreds of billions of barrels of oily wastewater is generated per day by a wide range of industrial applications. Depending on its hazardous nature, it is not possible to reuse or discharge the wastewater without any treatment. This study exhibits the fabrication of a ceramic filter, which is designed to obtain high recovery with high filtrate rate during the treatment of oily wastewaters. Tubular type ceramic filter was fabricated using an extrusion technique from local silica source, glass waste, and some organic additives. The length of the ceramic filter is 200 mm where the outer diameter and wall thickness are 12 and 3 mm, respectively. Dried samples were sintered at a temperature of 900, 950, and 1000 °C for 1 and 3 h of time, respectively. The effects of sintering conditions on the crystalline phase pore size and distribution, porosity, and permeability is discussed. The fabricated filters have high corrosion resistance for acidic (pH = 1.5) and basic (pH=13) conditions (<1% mass loss in both acid and basic media). The filtration performances of the ceramic filters are investigated by crossflow microfiltration via transmembrane pressure of 0.5–1 bar for synthetic oily wastewater. The relatively coarse pore size of the ceramic filter produced than the alternatives of the literature, achieves the oil separation efficiency rate up to 99.75%, which is attributed to the surface properties of the produced filter where the surfaces are negatively charged. According to the results, it could be said that the fabricated ceramic filter has high potential for microfiltration applications (oil level of the filtrate obtained is as less as 2 mg/L) and can be used as a support for ultrafiltration and nanofiltration technologies.

Выделение пептидов из ткани головного мозга телят и оценка их тканеспецифической и стимулирующей активности

Разработан метод выделения смеси пептидов из головного мозга телят экстрагированием водным раствором уксусной кислоты с последующим фракционированием экстракта тангенциальной микрофильтрацией и твёрдофазной экстракцией. Выделенная смесь пептидов содержит компоненты с молекулярными массами от 0,1 до 3 кДа. Из этой смеси методом ионообменной хроматографии низкого давления на сульфокатионите Dowex 50WX8 выделен индивидуальный пептид, состоящий из 5 аминокислот: Arg, Lys, Gly, Ser, Leu. Биологическую активность полученного пентапептида оценивали в органотипической культуре эксплантатов мозга крыс линии «Вистар». Показано, что пептид проявляет выраженную тканеспецифическую и стимулирующую активность по отношению к эксплантатам мозга, превышающую активность коммерческих препаратов кортексин и церебролизин.

Data-driven Modelling of Microfiltration Process with Embedded Static Mixer for Steepwater from Corn Starch Industry

Cross-flow microfiltration using ceramic tubular membrane was applied for treatment of steepwater from corn starch industry. Experiments are conducted according to the faced centered central composite design at three different transmembrane pressures (1, 2 and 3 bar) and cross-flow velocities (100, 150 and 200 L/h) with and without the usage of Kenics static mixer. For examination of the influence of the selected operating conditions at which usage of the static mixer is justified, a response surface methodology and desirability function approach were used. Obtained results showed improvement in the average permeate flux by using Kenics static mixer for 211 % to 269 % depending on experimental conditions when compared to the system without the static mixer. As a result of optimization, the best results considering flux improvement as well as reduction of specific energy consumption were obtained at low transmembrane pressure and lower feed cross-flow rates.