Tangential Filtration Research Articles

Short communication: Isolation of a whey fraction rich in α-lactalbumin from skim milk using tangential flow ultrafiltration

The objective of this research was to evaluate the potential for separating α-lactalbumin from pasteurized milk by using tangential flow membrane filtration. Filtration was carried out with a Purosep 7000 series membrane filtration unit (SmartFlow Technologies) with a regenerated cellulose membrane at 26°C and a transmembrane pressure of 186kPa. The protein in the permeate was >80% α-lactalbumin, and this product could be used as a value-added ingredient in nutritional products.

Antifouling microfiltration strategies to harvest microalgae for biofuel

Microalgae are microorganisms that can fix CO2 by using the energy from the sun and transforming it into organic molecules such as lipids (i.e. feedstock for biodiesel production). Microfiltration is a promising method to be considered in the harvesting step. In this study, two antifouling methods were tested in order to minimize permeability decrease over time, at low trans-membrane pressure filtration.Preliminary experiments were performed to find optimum conditions of transmembrane pressure, rotational speed and membrane pore size. Pilot experiments were carried out in the optimal conditions using microalgae obtained from the culture step and from a previous concentration process based on sedimentation. Fouling was significantly minimized, and the permeability plateau increased up to 600L/h/m2/bar.Three microalgae species were tested: Phaeodactylum tricornutum (Pht), Nannochloropsis gaditana (Nng) and Chaetoceros calcitrans (Chc).An economic assessment was also performed, which demonstrated that dynamic filtration is economically more efficient than tangential cross-flow filtration.

Use of nanofiltration membrane technology for ceramic industry wastewater treatment

A study has been undertaken of an advanced wastewater treatment approach using polymer nanofiltration membranes, in an attempt to obtain water of sufficient quality to allow it to be reused in the same production process or, alternatively, to be discharged without any problems. The study has initially focused on the removal of organic matter (reduction of COD) and the most representative ions present in the wastewater, such as Na+, Mg2+, Cl-, and SO42-. In a first part of the study, with a view to optimising the experimental phase, a simulation has been performed of the nanofiltration process using the NanoFlux software. Among other things, the simulation allows the most suitable membranes to be selected as a function of the permeate flow rate and desired level of retention in the substances to be removed. The subsequent experimentation was carried out in a laboratory tangential filtration system that works with flat membranes. It was found that retention values of about 90% were obtained for the studied substances, with a good permeate flow rate, using low operating pressures. These results demonstrate the feasibility of the studied technology and its potential as a treatment for improving ceramic industry wastewater quality.

Extraction of amaranth starch from an aqueous medium using microfiltration: Membrane fouling and cleaning

A Millipore ProFlux M12 Tangential Filtration System, fitted with a 1000 kDa regenerated cellulose membrane has been used to separate starch granules from starch milk produced by the Al-Hakkak process. However, membrane fouling was observed, and significant difficulties in cleaning the membrane were encountered. This paper describes the multi-step cleaning cycle that was developed to adequately clean the membrane between runs. Key cleaning steps were: a cold water rinse to remove loosely bound material, a protease wash to remove protein, a sodium hydroxide wash to “pre-treat” any remaining starch granules, an amylase wash to degrade the starch granules, and a final sodium hydroxide wash to remove residues from the previous step. It is expected that this cleaning method will be applicable to any membrane materials that have been fouled by the feed stream, or similar feed streams to that used in this research as it uses conditions suitable for regenerated cellulose, which is the least tolerable membrane material as far as chemical resistance and temperature are concerned.

Extraction of amaranth starch from an aqueous medium using microfiltration: Membrane characterisation

The research reported here investigated microfiltration as an alternative to density-based processes for separating amaranth starch-milk produced by the pilot-scale Al-Hakkak process into a starch-rich concentrate and an aqueous stream containing the soluble proteins and carbohydrates. A Millipore ProFlux M12 Tangential Filtration System, fitted with a 1000 kDa regenerated cellulose membrane, was used as the experimental apparatus. The selected membrane retained all the starch granules, but also retained more protein than desired (protein retention was 67% and the starch-rich concentrate had a dry-basis protein content of 12%). Analysis of the feed liquor, and diafiltered concentrate, revealed the presence of some non-starch insoluble material. This material, which may have been protein-based, was present in the starch-milk produced using the pilot-scale method but not the laboratory-scale method, and its presence determined the final protein content of the diafiltered concentrate. The optimal transmembrane pressure was approximately 100–150 kPa, above which flux increased non-linearly with pressure. However, the flux–pressure relationship was weak, suggesting that higher operating pressures may be sustainable.

Aplicação de microfiltração com membranas cerâmicas no processo de separação de biodiesel e glicerina

This study investigated the efficiency of microfiltration with ceramic membranes in separating biodiesel and glycerin. Synthetic blends (feed solution) were prepared with mass composition of 80% biodiesel, 10% glycerin and 10% anhydrous ethanol. Runs were performed in the micro and ultrafiltration module, in batch mode, using tangential filtration. Experiments were carried out with Al 2 O 3 /TiO 2 tubular ceramic membranes with average pore size of 0.2, 0.4 and 0.8 µm, filtration area of 0.005 m 2 , at 60oC and transmembrane pressures of 1.0, 2.0 and 3.0 bar. Membrane performance was evaluated based on its capacity to retain glycerin and permeate flux values. The low content of glycerin in the permeate, 0.04-0.1 wt%, demonstrates a high potential with respect to the use of ceramic membranes in the separation stage of biodiesel.

Combined biological processing and microfiltration in the treatment of unhairing wastewater

The unhairing step, a part of the beamhouse process, is particularly polluting, generating an alkaline wastewater with high concentrations of organic and inorganic matter. The aim of this study was to evaluate the treatment of this industrial wastewater using a combination of biological and microfiltration processes. The performance of the activated sludge system (AS) was evaluated under varying organic loading rate (OLR) from 0.9 to 3.4 kg chemical oxygen demand (COD) m(-3) day(-1) and decreasing hydraulic retention time (HRT) from 3 to 1.6 days. For an HRT of 3 days, the increase of OLR significantly affected the removal of organic matter. Therefore, the biological organic matter removal of unhairing wastewater decreased from 92% to 66% for COD and from 87 to 53% for biological oxygen demand (BOD(5)). GC-MS analyses showed that biological treatment of unhairing wastewater contributed to the removal of long chain fatty acids and their degradation products. Microfiltration of unhairing wastewater was performed using 0.2 μm pore-size membranes in tangential filtration. The highest removal efficiencies were obtained for bacteria (100%) and turbidity (98.4%) which confirmed the importance of the microfiltration step in treatment of unhairing wastewater. The result showed that the flux decay rate was greatest at the start of the microfiltration assay (90 L h(-1) m(2)), becoming 60.7 L h(-1) m(2) after 32 min. This change indicated that fouling occurred rapidly once the membrane module was put into operation.

Wall Shear Rates in Taylor Vortex Flow

Wall shear rate and its axial and azimuthal components were evaluated in stable Taylor vortices. The measurements were carried out in a broad interval of Taylor numbers (52-725) and several gap width (R1/R2 = 0.5 – 0.8) by two three-segment electrodiffusion probes and three single probes flush mounted in the wall of the outer fixed cylinder. The axial distribution of wall shear rate components was obtained by sweeping the vortices along the probes using a slow axial flow. The experimental results were verified by CFD simulations. The knowledge of local wall shear rates and its fluctuations is of primordial interest for industrial applications like tangential filtration, membrane reactors and bioreactors containing shear sensitive cells.

Selection of membranes for purification of fructooligosaccharides

The aim of this study was to purify fructooligosaccharides (FOS) present in a mixture of sugars, containing also glucose, fructose and sucrose through, nanofiltration membranes. Four membranes were used: NP010 and NP030 (Microdyn Nadir, Germany), Desal−5 DL and Desal−5 HL (GE Water & Process Technologies). Experimental assays were performed in a dead-end cell and tangential cell filtration to select the most appropriate membrane. Then, with the membrane selected performed diafi ltration in tangential cell fi ltration up to a concentration about 80% FOS. In the dead-end filtration cell experiments the NP010, NP030, HL and DL membranes were selected, since they performed the highest retentions of FOS, and lowest retention of glucose. The results showed that NP030 membrane performed the highest differences between the retention of FOS and sucrose, where the retentions of the different saccharides were: fructooligosaccharides (Robs = 0.66), glucose (R obs = 0.18), fructose (R obs = 0.15) and sucrose (R obs = 0.24). The results clearly demonstrate the potential of diafiltration using the NP030 membrane in the purification of FOS from mixtures containing mono and disaccharides.

Purification of plasmid DNA from Escherichia coli ferments using anion‐exchange membrane and hydrophobic chromatography

A novel downstream bioprocess was developed to obtain purified plasmid DNA (pDNA) from Escherichia coli ferments. The intermediate recovery and purification of the pDNA in cell lysate was conducted using hollow-fiber tangential filtration and frontal anion-exchange membrane and elution hydrophobic chromatographies. The purity of the solutions of pDNA obtained during each process stage was investigated. The results show that the pDNA solution purity increased 30-fold and more than 99% of RNA in the lysate was removed during the process operations. The combination of membrane operations and hydrophobic interaction chromatography resulted in an efficient way to recover pDNA from cell lysates. A better understanding of membrane-based technology for the purification of pDNA from clarified E. coli lysate was developed in this research.

Separation of biodiesel and glycerol using ceramic membranes

This study investigated the efficiency of microfiltration with ceramic membranes in the separation of biodiesel and glycerol. Runs in a micro- and ultrafiltration module were performed in batch mode using tangential filtration. The experiments were carried out with tubular Al 2O 3/TiO 2 ceramic membranes with average pore size of 0.2, 0.4, and 0.8 μm and filtration area of 0.005 m 2. In the first part of the experiment, synthetic blends (feed solution) prepared with mass composition of 80% biodiesel, 10% glycerol, and 10% anhydrous ethanol were microfiltered at 60 °C and transmembrane pressures of 1.0, 2.0, and 3.0 bar. Membrane performance was evaluated based on the capacity to retain glycerol and on the permeate flux values. Experimental results showed that transmembrane pressure has a strong influence on biodiesel microfiltration. The best performance was obtained with the 0.2 μm membrane and 2.0 bar transmembrane pressure. In these conditions and at the same temperature that was used in the previous experiments (60 °C), the influence of the ethanol concentration on the feed solution separation was evaluated. The highest ethanol concentration in the feed solution used, 20%, resulted in the highest glycerol concentration in the permeate. The lowest flux decline rate and the highest glycerol retention (99.6%), were achieved for the feed solution with 5% ethanol.

Purification of plasmid DNA using tangential flow filtration and tandem anion-exchange membrane chromatography

A new bioprocess using mainly membrane operations to obtain purified plasmid DNA from Escherechia coli ferments was developed. The intermediate recovery and purification of the plasmid DNA in cell lysate was conducted using hollow-fiber tangential filtration and tandem anion-exchange membrane chromatography. The purity of the solutions of plasmid DNA obtained during each process stage was investigated. The results show that more than 97% of RNA in the lysate was removed during the process operations and that the plasmid DNA solution purity increased 28-fold. One of the main characteristics of the developed process is to avoid the use of large quantities of precipitating agents such as salts or alcohols. A better understanding of membrane-based technology for the purification of plasmid DNA from clarified E. coli lysate was developed in this research. The convenience of anion-exchange membranes, configured in ready-to-use devices can further simplify large-scale plasmid purification strategies.

Electrokinetic characterization of the Al 2O 3 ceramic MF membrane by streaming potential measurements

The alumina microfiltration(MF) membrane was modified with nanocrystalline TiO 2 in the pore wall. The electrokinetic properties of unmodified and modified alumina membranes were characterized by streaming potential measurements during tangential filtration at various conditions of pH, ionic concentration and ionic species in solutions. The modified membrane reveals a more acidic characteristic. The influence of pH value on the streaming potential of both membranes is explained by the shifting of the proton equilibrium that occurs at the surface of the membrane. The modification of the alumina membrane with TiO 2 leads to the decrease of its isoelectric point (IEP) from 6.1 to 4.0 when filtered with NaCl solution. The ionic concentration and electrolyte species also have influence on the streaming potential of both membranes. The reversal of the streaming potential sign and the change of the isoelectric point of the membrane when filtered with CaCl 2 and Na 2SO 4 solutions show specific adsorption of Ca 2+ and SO 4 2- ions onto the surface.

Diseño de un proceso experimental para la producción de papaína liofilizada

Experimental Process design for lyophilized papain production Abstract: A process for papain (cistein papainase) extraction and purifi- cation from fresh latex obtained from unripped fruits of Carica papaya is described. Samples of fresh collected latex were suspended in citrate- phosphate buffer containing reducing agents whose concentration and application conditions were found experimentally. The extract was cen- trifugated and the clarified solution subjected to ammonium sulphate precipitation. The insoluble fraction was resuspended in water, desalted and concentrated by tangential filtration and, the remaining water re - moved by liophylization. The process allowed 80% recovery of the initial protein content and 65% of the original activity, the product obtained can be described as a white powder very soluble in water. All the steps can be scaled-up for commercial papain production.

Impact of zeta potential and size of caseins as precursors of fouling deposit on limiting and critical fluxes in spiral ultrafiltration of modified skim milks

Caseins, the main proteins of milk, are known to be responsible of flux limitations in tangential filtration of skim milk. These proteins are well known to be versatile with the pH. Their initial form, corresponding to the so-called “native casein micelles” is due to a complex aggregation of monomers through calcium phosphate bridges that can be disrupted by small pH variations. This paper deals with the determination of both critical and limiting fluxes during ultrafiltration of natural and modified skim milks. pH ranging from 3.7 to 11.5 allowed to consider skim milk ultrafiltration (UF) for production purpose (pH 6.6–6.7) as well as acidic and alkaline concentrated effluents. The physico-chemical characteristics of caseins, as diameter and zeta potential, were measured according to the pH variations obtained by the addition of HCl and NaOH. Then, both limiting and critical fluxes variations were correlated to these characteristics. The critical and limiting fluxes varied in a quite complicated way with the pH, leading to four different regions. At acidic pH, zeta potential was null and fluxes were controlled by large particles of caseins that precipitated in the solution. Around neutral pH, the diameter of casein micelles remained constant whereas the zeta potential varied strongly. In this region the fluxes increased linearly with the zeta potential of caseins. Then at alkaline pH, the zeta potential of caseins remained constant whereas the diameter varied showing successively partial destructuration and partial “restructuration” of new types of micelles, both different from native casein micelles. In this region the fluxes varied with the rate of large micelles. Finally, retention of lactose (main neutral solute of milk) and whole proteins, mainly responsible of COD, were measured and discussed in relationship with above-mentioned parameters.

Experimental Investigation on the Separation of Bentonite using Ceramic Membranes: Effect of Turbulence Promoters

The static turbulence promoters presented in this work are designed to enhance filtration within tubular ceramic membranes of 0.5 micron pore size. Permeate flux enhancement still remains a topical problem during tangential crossflow filtration. The decline in flux with time is due to the usual phenomena of concentration polarization and membrane fouling, operating parameters including the system pressures, feed composition, membrane type and configuration, and the hydrodynamics within the membrane module. Solute accumulates on the membrane surface and forms a high concentration gel layer, thus increasing the effective membrane thickness and reduces its hydraulic permeability. Turbulence promoters of varying pitch lengths have been incorporated into the work to ultimately reduce the deposition of bentonite particles on the membrane surface during microfiltration. Yeast suspensions have previously been used as feed suspensions in order to compare the effectiveness of the turbulence promoters with an organic foulant. The objective of this work was to investigate the influence of static promoter geometry on flux sustainability enhancement during bentonite suspension filtration. All experiments have been conducted on a tubular ceramic membrane and the experimental membrane rig as shown in this paper. The effects of feed concentration, feed temperature, system pressures, and crossflow rates on the membrane flux sustainability were investigated. It was found that the promoters greatly improved flux sustainability and membrane efficiency over time and in some cases, a loss of 3% in membrane efficiency was realized with turbulence promoters at higher feed temperatures. The use of the turbulence promoter caused a large scouring of the membrane surface and membrane cleaning was significantly improved compared to the experiments without the promoters.

Demonstration of “Dynamic Tangential Filtration” at Palm Beach County to Produce High Quality Reuse Water

Demonstration of “Dynamic Tangential Filtration” at Palm Beach County to Produce High Quality Reuse Water

Elimination of organic matter present in wastewaters from the cork industry by membrane filtration

AbstractBACKGROUND: The first stage of the cork industrial process generates great volumes of wastewater with moderate to high organic pollutant content that must be purified using different procedures, such as filtration by membranes.RESULTS: The tangential filtration of these wastewaters was studied using two different laboratory equipments. In the first one, three ultrafiltration (UF) membranes were tested, with molecular weight cut‐off (MWCO) 100 kDa and 30 kDa, and two operating modes were used: total recycling of permeate and retentate streams, and in continuous mode, without recycling both streams. In the total recycling UF experiments, the influence of the operating variables on the permeate flux was first established. The effectiveness of the different membranes was determined by evaluating the rejection coefficients for several parameters that measure the global pollutant content of the effluent. The values found for these rejection coefficients were in the following order: ellagic acid and color > absorbance at 254 nm > tannic content > COD (chemical oxygen demand). In the continuous mode experiments, the fouling mechanism for each membrane was established by fitting the experimental data to various filtration fouling models given in the literature. The operating mode in the second equipment was batch concentration, and additional experiments were carried out with an UF membrane (2 kDa), and with a NF membrane (with MWCO in the range 150–300 Da).CONCLUSIONS: The three operating modes tested provided different rejection levels of organic matter; among them, the most effective procedure tested was batch concentration mode using a NF membrane. Copyright © 2007 Society of Chemical Industry

Hybrid modeling of convective laminar flow in a permeable tube associated with the cross-flow process

The confined flows in tubes with permeable surfaces are associated to tangential filtration processes (microfiltration or ultrafiltration). The complexity of the phenomena do not allow for the development of exact analytical solutions, however, approximate solutions are of great interest for the calculation of the transmembrane outflow and estimate of the concentration polarization phenomenon. In the present work, the generalized integral transform technique (GITT) was employed in solving the laminar and permanent flow in permeable tubes of Newtonian and incompressible fluid. The mathematical formulation employed the parabolic differential equation of chemical species conservation (convective–diffusive equation). The velocity profiles for the entrance region flow, which are found in the connective terms of the equation, were assessed by solutions obtained from literature. The velocity at the permeable wall was considered uniform, with the concentration at the tube wall regarded as variable with an axial position. A computational methodology using global error control was applied to determine the concentration in the wall and concentration boundary layer thickness. The results obtained for the local transmembrane flux and the concentration boundary layer thickness were compared against others in literature.

Laminar flow in a two-dimensional plane channel with local pressure-dependent crossflow

Long ducts (or pipes) composed of transpiring (e.g. porous) walls are at the root of numerous industrial devices for species separation, as tangential filtration or membrane desalination. Similar configurations can also be involved in fluid supply systems, as irrigation or biological fluids in capillaries. A transverse leakage (or permeate flux), the strength of which is assumed to depend linearly on local pressure (as in Starling's law for capillary), takes place through permeable walls. All other dependences, as osmotic pressure or partial fouling due to polarization of species concentration, are neglected. To analyse this open problem we consider the simplest situation: the steady laminar flow in a two-dimensional channel composed of two symmetrical porous walls.First, dimensional analysis helps us to determine the relevant parameters. We then revisit the Berman problem that considers a uniform crossflow (i.e. pressure-independent leakage). We expand the solution in a series of Rt, the transverse Reynolds number. We note this series has a rapid convergence in the considered range of Rt (i.e. Rt ≤ O(1)). A particular method of variable separation then allows us to derive from the Navier–Stokes equations two new ordinary differential equations (ODE), which correspond to first and second orders in the development in Rt, whereas the zero order recovers the Regirer linear theory. Finally, both new ODEs are used to study the occurrence of two undesirable events in the filtration process: axial flow exhaustion (AFE) and crossflow reversal (CFR). This study is compared with a numerical approach.