Effect Of Transmembrane Pressure Research Articles

Clarification of pomegranate juice by ultrafiltration: study of juice quality and of the fouling mechanism

Introduction . Ultrafiltration (UF) is a single-unit operation for the clarification and fining of fruit juices. The purpose of the UF is to remove suspended solids as well as haze-inducing and turbidity-causing substances to obtain a clear juice during storage. Specifically, the polymerization of phenolic compounds and their interaction with other components (e.g. , proteins) could cause a haze complex and turbidity in fruit juices, which can foul the ultrafiltration membrane. Materials and methods . Fresh pomegranate juice was clarified by the ultrafiltration process on a laboratory scale. In experimental tests performed according to the total recycle and the batch concentration mode, the effects of transmembrane pressure (TMP) and enzyme pre-treatment on permeation flux and quality of juice were studied. Results . With the total recycle mode, the effect of TMP on the color and clarity of clarified pomegranate juice was significant. The initial color of the raw pomegranate juice was reduced from 74% to 33% and the clarity decreased from 77% to 42% by UF when the TMP increased from (1 to 3.6) bar. Total phenolic rejection decreased from 45% to 21% when the TMP rose from (1 to 2) bar and remained constant above this value. With the batch concentration mode at TMP = 2 bar and velocity 1 m·s–1 , the enzymatic treatment (5 U·mL–1 , 300 min, T = 20 °C) of pomegranate juice provided the highest permeate flux, a decrease in total phenolics of 50% and an increased clarity of 30%. Fouling of the UF membrane during pomegranate juice processing is mainly due to the retention of polyphenols and/or proteins; thus, several blocking mechanisms were studied, using a recently developed membrane-fouling model. Analysis revealed that the membrane separation process was controlled by the gel layer mechanism of raw pomegranate juice and complete pore blocking mechanism with enzymatic pre-treatment.

A Numerical Study of the Apparent Selectivity in the Fractionation of Two Macromolecules by Ultrafiltration

The fractionation of two macromolecules by ultrafiltration in a parallel plate cell was studied by computational fluid dynamics (CFD). The in-house code developed takes on account of the pressure drop, the variation of the permeate velocity along the cell, the concentration polarization over the membrane, and the variation of the transport properties and of the osmotic pressure with the concentration of the solutes. A convective-diffusive model, to simulate the solute transmission, was also adopted. The real and apparent selectivity, local and mean, were determined, in order to study the effect of transmembrane pressure, Reynolds number, inlet solute concentrations, specific area of the membrane pores, and membrane resistance. The code was applied to study the separation of Bovine Serum Albumin (BSA) and Dextran-T10 macromolecules. The mean apparent selectivity increases with increasing transmembrane pressures until it reaches a maximum after which it decreases. The mean apparent selectivity increases with increasing Reynolds number consequence of a polarization decrease. Moreover, the selectivity increases with a decrease of the pore size and, also, with an increase of the membrane resistance. For low inlet concentrations of the solutes, the variation of the physical properties with the concentration does not produce any appreciable effect on the apparent selectivity.

Performance characterization and CFD analysis of a novel shear enhanced membrane module in ultrafiltration of Bovine Serum Albumin (BSA)

In this article, design, performance characterization and hydrodynamic simulation of a novel shear enhanced membrane module has been presented. Considering its structural similarity with the well known spinning basket reactor the module has been named as Spinning Basket Membrane (SBM) module. The module is unique in terms of its hydrodynamic cleaning facility. For the present study, the test fluid was the aqueous solution of Bovine Serum Albumin (BSA) of different concentrations. And the process was the ultrafiltration (UF) of the same using Polyvinylidene Fluoride (PVDF) membrane of 50,000 Molecular weight Cut off (MWCO). In addition to feed concentration, the effect of transmembrane pressure and basket rotational speed on permeate flux as well as on rejection has been studied. The results of a detailed hydrodynamic simulation has been also presented in order to correctly understand the hydrodynamic picture inside the module. From the perspective of performance rating it is to be noted that after 5h of continuous run the final regenerated flux was found to be within 90% of its initial counterpart (i.e. flux at t=0).

Comparative performance of flat sheet and spiral wound modules in the nanofiltration of reactive dye solution

Besides the opportunities for reuse, stringent regulations and growing public awareness demand an enhanced quality of effluent from dye industries. Treatment of an aqueous solution of dye (reactive red 198) was carried out in a nanofiltration unit using both flat sheet and spiral wound modules to obtain a comparative performance evaluation in terms of permeate flux and quality. Hydrophilized polyamide membrane with molecular weight cutoff of 150 was used for the experiments. Effects of trans-membrane pressure (TMP), feed concentration and addition of salt on permeate flux were investigated. Percent reduction of color, chemical oxygen demand (COD), total dissolved solid (TDS), and conductivity were determined to assess performance of the membrane. The maximum flux decline was 16.1% of its initial value at 490kPa TMP with 50ppm feed concentration in spiral wound module, whereas the same in flat sheet under same conditions was 7.2%. The effect of TMP showed a quasi-linear increase in flux with increasing pressure. Increased permeate concentration led to the reduction in observed retention of dye in the membrane. The average reduction in color, COD, and TDS were 96.88%, 97.38%, and 89.24%, respectively. The decline in permeate flux was more in case of spiral wound module compared to flat sheet. However, spiral wound module performed better in terms of color removal, COD reduction, and TDS removal. Substantial removal of color was achieved in the nanofiltration experiments with a marked reduction in COD and TDS. The process allowed the production of permeate stream with great reutilization possibilities.

Micellar Enhanced Ultrafiltration of Reactive Black 5 from Aqueous Solution by Cationic Surfactants

Reactive black 5 (RB-5) dye was removed from a water stream using two cationic surfactants, cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC), via micellar enhanced ultrafiltration. Three membranes with different pore size were used for the determination of rejection coefficient and permeate flux of the solution at 1.5 bar trans-membrane pressure (TMP). The two surfactants (CPC and CTAB) played an almost negligible role in rejection efficiency with 5000 and 10,000 molecular weight cut-off membrane (MWCO), respectively. In this case, high rejection and low permeate flux was the result of a larger molecular size of RB-5 DYE being retained by comparatively smaller sized pores of membrane via ultrafiltration. However, CPC and CTAB surfactants showed 83% and 98% rejection coefficient, respectively, at a concentration greater than their CMC values against 30,000 MWCO. Permeate flux remained low and constant in presence of 5000 and 10,000 MWCO with a small variation against 30,000 MWCO for the two surfactants, thereby no appreciable effect on both surfactant concentrations on concentration polarization was estimated. Thus, RB-5 dye alone was determined to be responsible for membrane plugging or concentration polarization and ultimately for low permeate flux. The effect of trans-membrane pressure was also investigated during this study.

Separation of Liquiritin from Glycyrrhizic Acid in Licorice Root Extract by Nanofiltration Membrane

The aim of this work was to study the separation of liquiritin (LQ) from glycyrrhizic acid (GA), in licorice aqueous solutions using nanofiltration (NRT-7450) membrane. The LQ and GA components are the main active ingredients of licorice root extract with various pharmacological effects, The effects of transmembrane pressure, feed temperature, feed pH, and cross-flow velocity on permeate flux and recovery were determined. A lab scale cross-flow set up using flat-sheet configuration membrane was employed for all experiments. SEM micrographs showed the changes in the fouled surface during operating time. The applied transmembrane pressure, feed temperature, feed pH, and cross-flow velocity were varied from 4 to 10 bars, 30 to 40°C, 3 to 9, and 0.8 to 3.1 m s−1 respectively. The obtained recoveries for GA and LQ varied between 0.65 to 1.86% and 16.89 to 41.65%, respectively. The optimum operating conditions for separation LQ from GA in licorice aqueous solutions using NRT-7450 nanofiltration membrane were 1.8 m s−1cross-flow velocity, 8 bars transmembrane pressure, 40°C of feed temperature and pH 7.

Influence of particle size and operating parameters on virus ultrafiltration efficiency

In water treatment, virus removal using ultrafiltration is a major step towards better water quality. In this paper, we study virus filtration efficiency using surrogate virus particles and via statistical surface-response approach. We focus on the effect of particle size (20–100 nm range) as a key factor along with the effects of transmembrane pressure (20–60 kPa range) and feed flowrate (0.3–1.0 L/F;min range) on the filtration virus removal efficiency (LRV). The particle size is shown to impart a great deal of influence on surrogate particle removal. The effect of particle-to-pore-size ratio is reported for comparison of membrane molecular weight cut off (MWCO) performance. It was shown experimentally and through the developed empirical regression model that transmembrane pressure plays a major role in controlling the filtration efficiency along with flowrate. In the studied experimental range, higher LRV values are obtained at lower transmembrane pressure (20 kPa) and at higher feed flowrate (1 L/F;min). Further the effect on LRV of the interaction between transmembrane pressure and particle size seems to be more significant than that of the interaction of flowrate with particle size.

Effect of Transmembrane Pressure on Geosmin Release from Cyanobacterial Cell During Microfiltration

The mechanisms of increase in geosmin concentration in MF permeate with filtration time were investigated when inflow to the MF contained cyanobacteria incorporating geosmin inside and outside their cells. Whereas the geosmin concentration in the MF permeate was almost the same as the extracellular geosmin concentration in the MF inflow at the beginning of filtration, it increased and exceeded the extracellular geosmin concentration in MF inflow after 2 h of filtration. A cell viability test using a double-staining method revealed that a portion of the intracellular geosmin, which was incorporated in the cyanobacterial cells and therefore retained on the MF membrane, was released from the cells. This occurred probably because increased transmembrane pressure (TMP) with filtration time forced the cells to compress. However, geosmin release was not explained simply by cell breakage: other possible factors were implied.

Concentration of licorice aqueous solutions using nanofiltration and reverse osmosis membranes

The aim of this work was to study the concentration of licorice aqueous solutions using reverse osmosis (FT 30) and nanofiltration (BDX N-90) membranes. The effects of transmembrane pressure, feed temperature, feed pH and cross-flow velocity on permeate flux and rejection were determined. A lab scale cross-flow set-up using flat-sheet configuration membrane was employed for all experiments. SEM micrographs showed the changes in the cross-section of RO and NF membranes at various pH solutions and surface alteration fouled during operating time. The applied transmembrane pressure, feed temperature, feed pH and cross-flow velocity were varied from 6 to 14 bar, 25–45 °C, 3–11 and 0.5–3.2 m/s, respectively. The obtained rejection values varied between 93 and 99.6%. The optimum operating conditions for concentration of licorice aqueous solutions using FT 30 reverse osmosis membrane were 1.8 m/s cross-flow velocity, 12 bar transmembrane pressure, 35 °C of feed temperature and pH 5. For BDX N-90 nanofiltration membrane the optimum conditions were 2 m/s cross-flow velocity, 10 bar transmembrane pressure, feed temperature 35 °C and pH 5. The membranes were tested for 10 h. The permeate flux was gradually decreased during the operating time and eventually reached a constant value.

Corn syrup clarification by microfiltration with ceramic membranes

The performance in clarifying corn syrup of three different microfiltration ceramic membranes made in our laboratory was investigated. From preliminary MF tests at laboratory scale, it was found that the composite ceramic membrane with average hydraulic pore size radius of r h ≈ 0.5 μm (CM05) performed better than the other two membranes ( r h ≈ 0.14 μm and r h ≈ 0.75 μm). Further studies of corn syrup clarification with the CM05 membrane at bench scale, with and without air backpulsing, were performed. The effects of transmembrane pressure (Δ p = 10.3–103.4 kPa) and the feed flow velocities ( v = 1.32 – 3.18 m/s ) on permeate flux at T = 60 °C were analyzed. Permeate fluxes without back-flushing decreased considerably during the first hour of operation; around 60–70% of the initial permeate flux. Membrane fouling responsible for the permeate flux decline during the operation time was evaluated by applying different blocking models and cake filtration model. Results indicate that a good fitting correlation between the experimental data and pore blocking models was achieved. When back-flushing procedure was applied high efficiency of average permeate flux ( J ≈ 95–105 L/m 2 h) was obtained. From these experiments, sequential back-flushing is recommended to achieve the highest flux values and allow the filtration cycle to continue over longer periods of time. The turbidity, insoluble residue, and total protein rejection performances of CM05 membrane were significantly higher than those obtained using the traditional rotary vacuum filtration (RVF) process.

Tailoring the enzymatic synthesis and nanofiltration fractionation of galacto-oligosaccharides

Continuous galacto-oligosaccharides (GOS) synthesis by bead-immobilized β-galactosidase and nanofiltration fractionation of derived sugar mixtures by cellulose acetate membranes are investigated. Upon enzyme adsorption assays (8 mL/g of solution/resin ratio, 150 mg/mL of initial enzyme concentration and 14 ± 1.4 mg protein/g resin), a Langmuir-type isotherm is observed. Enzyme concentration of 10 U/mL, selected in batch reactor experiments, is used for continuous GOS production carried out at lactose concentrations of 150 g/L and 300 g/L, and at 40 °C. Total dissolved solids concentration influences both reaction and saccharide mixtures fractionation. All observed sugar retention coefficients, mainly for monosaccharides, increase with transmembrane pressure and a gap between the retention values of synthesized disaccharides and lactose (87% versus 77%, respectively, for 2 bar/40 °C) is displayed as a function of the effective transmembrane pressure and total sugars concentration. At 150 g/L total sugars in feed, trisaccharides are totally retained. Doubling sugars concentration, trisaccharides retentions decreased for all applied pressures, reaching 90%.

Facilitated transport separation of propylene–propane: Experimental and modeling study

Supported liquid membrane, as one type of facilitated transport membranes, was used for the separation of propylene–propane mixtures. The effect of trans-membrane pressure and carrier concentration on membrane separation performance were evaluated in terms of mixed-gas selectivity, propylene and propane permeances and propylene and propane permeation fluxes. A general dimensionless model for the transport of components across the membrane was proposed and solved numerically by orthogonal collocation method. Experimental results showed that for a 70:30 (vol.%) propylene–propane mixture, at pressure 120 kPa and carrier concentration 20 wt.%, a propylene permeation flux of 1.46 × 10 −4 mol/m 2 s was obtained. Mathematical results are in well agreement with experimental results. The average deviation between experimental and modeling results was found to be 5.3% for propylene permeation flux and 0.03% for propane permeation flux.

Effect of operating parameters and membrane characteristics on the permeate rate and selectivity of ultra- and microfiltration membranes in the depth filtration model

The effect of transmembrane pressure, pore depth and initial radius, inlet concentration of suspended particles, and particle-collection efficiency of pore walls on the permeate rate and selectivity of ultraand microfiltration membranes with pores of the same radius operated under standard blocking conditions is studied using the previously developed depth filtration model, which takes into account the nonuniform capture of particles over the pore depth. It is shown that the variation of permeate rate and selectivity with time in standard blocking strongly depends on the studied parameters. Simple analytical formulas for calculating the membrane permeate rate and selectivity as well as the time at which the pore diameter reaches the cutoff value (time at which the transition to cake filtration takes place) are proposed. The formulas make it possible to find the values of the filter coefficient, which accounts for the particle-collection efficiency of membrane pore walls, and the cutoff pore diameter using the experimental curve of the membrane selectivity. It is demonstrated that the use of the classical Hermia standard blocking model for describing the experimental data on membrane permeate rate can lead to high errors, which are caused by its assumption on the uniform profile of the layer of particles caught inside the pore.

Chromate removal from wastewater using micellar enhanced crossflow filtration: Effect of transmembrane pressure and crossflow velocity

Removal of chromate from wastewater was investigated using Micellar Enhanced Crossflow Microfiltration Technique (MEMF) with cationic surfactant, cetyltrimetylammoniumbromide (CTAB). The variation of chromate, surfactant rejections and permeate flux with time were measured at two different CTAB concentrations as a function of transmembrane pressure drop (Δ P) and crossflow velocity, while CTAB/chromate, membrane pore size, temperature and pH of the feed solution was kept constant. For low CTAB concentration, it was observed that the efficiencies of chromate and surfactant removal increased with increasing Δ P, but decreased with increasing crossflow velocities. It was also observed that the effects of crossflow velocities and Δ Ps on the rejections decreased for high CTAB concentration. It was found that fouling of the membrane by surfactant is very rapid at low crossflow velocity and high Δ Ps at low CTAB concentration. As a result of this case, both transient permeate flux ( J) and steady state permeate flux ( J ⁎) decreased with decreasing crossflow velocity and increasing Δ P for both CTAB concentration. Unlike, modified fouling index (MFI) values increase with decreasing crossflow velocity and increasing Δ P. It was also observed that the effect of surfactant concentration in the 150, 200, and 250 kPa pressure and 3, 4, and 5 m/s crossflow velocity intervals dominates at high surfactant concentration.

The effect of transmembrane pressure and pH on treatment of paper machine process waters by using a two-step nanofiltration process: Flux decline analysis

In this work, the treatment of paper machine whitewater obtained from paper production by using loose and tight Nanofiltration (NF) membranes in a lab-scale plant with a plate and frame module was investigated. The NF membranes were evaluated for fouling, flux decline due to concentration polarization and their suitability for removing of components present in wastewater. The loose NF membrane was used for the first step under different transmembrane pressure (8 to 32bars) and pH (3, 5.6 and 10) values. The best filtration performances were provided under a pressure of 32bar and a pH of 5.6. The fouling mechanism at different transmembrane pressures and pH values was investigated by “Hermia's model”. Also, fouling on pores and on the surface of NF membranes was characterized by Scanning electron microscopy (SEM) and contact angle measurements, respectively. For the advanced treatment of permeate obtained from the loose NF membrane that provided the lowest fouling and flux decline, a tight NF membrane was used in the second step. Even better retentions were achieved from experiments with this NF membrane. Results obtained in this study showed that the combination loose and tight NF membranes achieved reuse of paper machine white water for use as shower water of paper machine.

Treatment of stable oil/water emulsion by novel felt-metal supported PVA composite hydrophilic membrane using cross flow ultrafiltration

The novel felt-metal supported PVA composite hydrophilic ultrafiltration membrane was used for the treatment of oil/water(O/W) emulsion. The effects of transmembrane pressure(TMP), cross flow velocity, feed concentration on membrane performance were investigated, and ultrasonic cleaning of the fouled membrane was also investigated. The results show the flux increases with the increase of cross-flow velocity and TMP within the given TMP range from 0.20 MPa to 0.40 MPa. With increase of initial oil concentration increases, the oil rejection increases while the permeate flux decreases. The composite membrane shows more than 90% oil rejection within the initial oil concentration range from 0.05% to 0.50% (mass fraction) at TMP of 0.30 MPa. The fouling of the composite membrane increases rapidly during the initial 20 min at given TMP range from 0.20 MPa to 0.40 MPa, and it increases slowly after 30 min. The results also show that ultrasound is very effective in removing oil fouling of the fouled membrane, and the properties of the composite ultrafiltration membrane can be completely recovered by 10 min of sonication.

Characterization of polysulfone hollow-fiber ultrafiltration membrane and its cleaning efficiency by streaming potential and flux method

Polysulfone (PS) hollow-fiber ultrafiltration membrane was characterized combined with flux and streaming potential in single electrolyte solutions. The effects of trans-membrane pressure, electrolyte concentration, ion valence and pH value of electrolyte solution on the streaming potential (SP) of the membrane were investigated. The zeta potential and surface charge density of the membrane were calculated on the basis of Helmholtz-Smoluchowski equation and Gouy-Chapmann theory. The results indicate that the valence and concentration of cation have a greater influence on the SP and surface charge density of PS membrane than those of anion, and the pH value of electrolyte solution has great effects on the SP and zeta potential of the membrane surface. Both the absolute value of the streaming potential and water flux of the adsorbed membrane decrease, compared with those of the clean membrane. The streaming potential and flux of the cleaned membrane can be completely recovered by cleaning with the mass fraction of 0.8% EDTA at pH=10.

A unified model of the time dependence of flux decline for the long-term ultrafiltration of whey

The performance of industrial membrane processes is affected by the time dependence of permeate flux, which includes both the absolute value and the rate of decrease in permeate flux at a given time. In particular, long-term fouling will affect the performance of industrial membrane processes that operate continuously for long periods of time, such as industrial whey ultrafiltration processes that can operate for up to 14 h every day. Results of whey ultrafiltration experiments conducted on a pilot scale membrane rig were used to establish a unified model for the time dependence of permeate flux during long-term ultrafiltration. Experimental results indicate that the effects of trans-membrane pressure and feed concentration on the rate of decrease in the permeate flux due to long-term fouling are statistically insignificant. The unified model from this paper can be applied in conjunction with the process dynamics models to study the performance of automatic controllers prior to controller design.

Cross-Flow Ultrafiltration Model Based on Concentration Polarization

A cross-flow ultrafiltration model which couples the formation of a cake layer and the existence of a polarized layer above the cake has been developed. The model contains three constants and the specific cake resistance to be evaluated from experiments. The model gave an excellent prediction on the performance of the cross-flow ultrafiltration of polyethylene glycol solutions. Experimental observations on the effects of transmembrane pressure, solute concentration and cross-flow velocity agreed well with the predicted permeate fluxes.

Separation of ovalbumin from chicken egg white using two-stage ultrafiltration technique

With increasing demand of high quality proteins in different aspects of bio-pharmaceuticals, ultrafiltration (UF) techniques are emerging as an attractive route for separation of ovalbumin from chicken egg white (CEW). In this study, the feasibility of separation of ovalbumin from CEW was investigated using Amicon stirred cell fitted with polyether sulfone (PES) membrane. A two-stage ultrafiltration scheme employing 30 and 50 kDa flat disk PES membranes was used for accomplishing the desired separation. Prior to UF, centrifugation and dilution by 200 mM NaCl solution to required CEW concentration were carried out to prepare feed for ultrafiltration. The effects of trans-membrane pressure, stirrer speed, solution pH, feed dilution on permeate flux and rejection have been studied thoroughly. In this study, total protein concentration and individual protein concentrations were observed at each stage of separation along with the permeation rate. Results of the investigation showed that a high purity ovalbumin (98.7% dry basis) could be produced by the proposed separation train with operating trans membrane pressure (TMP) 4.5 kgf cm −2, stirring speed 200 rpm, pH 2.5 and CEW–solvent ratio 1:1.