Abstract: An unsteady state mass transfer model of unstirred dead-end ultrafiltration module has been developed in the present study. The dynamic membrane surface concentration is evaluated using a modified self-consistent field theory, which enables the development of an algorithm to incorporate the contribution of solute adsorption in the membrane surface concentration dynamics. Knowing the corrected membrane surface concentration, permeate flux and permeate side concentration is determined using osmotic pressure model and flux-rejection relation as predicted by irreversible thermodynamics. The time evolution of all the different process variables is achieved by solving two component balance equations developed at the membrane surface and in the solution phase respectively. The basic feature of the model is the incorporation of adsorbed fraction in the unsteady state membrane surface concentration. For the validation of the proposed model, experiments were conducted with Bovine Serum Albumin (BSA)/water as feed in a standard unstirred batch ultrafiltration module fitted with Polyethersulfone (PES) membrane of 30 kDa molecular weight cut-off (MWCO). The model predicted flux and the permeate concentration were found to be in good agreement with the experimental data. (C) 2010 Elsevier B.V. All rights reserved.
Abstract: The membrane surface dynamics is very difficult to predict and can be roughly estimated by the available models but a true depiction is always difficult since the magnitude and direction of driving forces change as a function of time. The present study is an effort to address the issue, so that the combinatorial approach of deterministic and stochastic modelling might present a better understanding of membrane dynamics. The effect of diafiltration has also been incorporated to investigate the effects it has on the membrane. A stochastic model developed by a knowledge based hybrid neural network (KBHNN) was trained using the Levenberg-Marqurt algorithm where the film layer model was used as the deterministic layer, called the first principle model (FPM). Present work employs two different types of KBHNN architecture with an effort to understand the suitability and applicability of the hybrid network in case of predictions for an ultrafiltration (UF) process. In one sort of architecture neural part was in series with the FPM and in the other one it was in parallel with the FPM. The high correlation coefficient (R(2)) value portrays the correctness and preciseness of the underlining assumptions and establishes the validity of the developed network. (C) 2010 Elsevier B.V. All rights reserved.
Abstract: The present study primarily is an attempt to establish a technique on the disposal scheme for the wastewater coming out as an effluent from milk industries with proper environmental guides and regulations. Apart from the wastewater treatment methodology development, the present work mainly focuses on the attainment of high value product, such as the production of galactosyl-oligosaccharide (GOS) in batch reactor and as well as in recycle membrane reactor after hydrolyzing recovered lactose from the whey stream with beta-galactosidase enzyme originated, from Bacillus circulans. Around 77-78% purity of this GOS was achieved with three-step membrane separation techniques: the first one was the ultrafiltration followed by diafiltration equipped nanofiltration. In recycle membrane reactor, GOS production was found to be 33% higher than that in the batch reactor, and monosaccharide concentration was 78% lower with 23% remaining enzyme activity after 18,000 s of reaction time.
Notes: International Symposium on New Frontiers in Chemical and Biochemical Engineering, Thessaloniki, GREECE, NOV 26-27, 2009
Abstract: This study describes an innovative approach for recovery and concentration of sesame glucosides from defatted sesame cake using membrane separation route. Simple aqueous extraction of the seed meal at suitable pH value followed by two steps membrane fractionation (ultrafiltration-nanofiltration) was done to obtain sesame glucoside concentrate. In this process, about 0.7% +/- 0.29 recovery of total meal glucoside was achieved along with coproduct sesame protein isolate at yield value of 36.50%. Several in vitro analyses were carried out to assay the antioxidative potential of recovered glucosides in different reaction models. Recovered glucosides have shown comparable alpha,alpha’-diphenyl-1-picryl-hydrazyl radical scavenging activity and Cu(2+) ion chelation capacity with solvent extracted glucosides. Sesame glucosides have shown unique antioxidant activity for 29 h in an induced oxidation system of linoleic acid emulsion. This study includes a detail analysis on membrane performance parameters and fouling characteristics of ultrafiltration membrane, which are crucial factors to consider for industrial relevance. All findings point toward the potentiality of ultrafiltration-nanofiltration-based technique for recovery of polar antioxidants from various raw materials.
Abstract: A rigorous surface renewal model has been developed describing the aspects of mass transfer in a rotating disk-membrane (RDM) ultrafiltration cell. The model takes into consideration of two distribution functions of random surface elements, one with respect to their point of origin and the other related to the corresponding residence time on the membrane surface. The back transport flux and the permeate flux are evaluated at the membrane surface in order to develop a surface component balance equation. The component balance equation and a flux-rejection relationship arising from irreversible thermodynamics are solved simultaneously to develop a dynamic simulation. The simulation elucidates on permeate flux, membrane surface concentration and the permeate concentration under various operating conditions of transmembrane pressure, bulk concentration, membrane and stirrer speeds. For validation of the proposed model, experiments were conducted with bovine serum albumin (BSA)/water as feed in a standard rotating disk membrane module fitted with polyethersulfone (PES) membrane of 30 kDa molecular weight cut-off (MWCO). The model predicted flux and permeate concentration was found to be in good agreement with the experimental data, and the maximum absolute deviation for both cases was found to be well within +/- 5%. (C) 2011 Elsevier Ltd. All rights reserved.
Abstract: The article presents a detailed investigation of adsorption lead fouling characteristic of Bovine Serum Albumin (BSA) onto Polyethersulfone (PES) ultrafiltration membrane in a standard laboratory scale cross-flow module (Viva-flow 200). Isotherms were performed to determine the equilibrium adsorption behavior; in addition to that transient adsorption rate was also determined by measuring the adsorbed mass as a function of time. The effect of different process parameters like transmembrane pressure (TMP), solution pH and feed concentration on adsorption and permeate flux has been explored under steady as well as transient condition. It was found that at pH close to the Iso-electric point of BSA, adsorbed amount reaches its maxima and hence corresponding permeate flux decreases to its minima. The equilibrium adsorption data was analyzed with nonlinear regression methods in order to determine the best suitable isotherm model amongst that of Langmuir, Freundlich and Redlich-Peterson. It was observed that Langmuir and Redlich-Peterson model can best describe the equilibrium conditions at low and high pH ranges respectively, whereas with the increase of TMP Redlich-Peterson model becomes more appropriate over that of Langmuir.
Abstract: Adsorption over TiO(2) is used efficiently for reactive dyes removal from wastewater. This paper investigates adsorption efficiency for Reactive Red 198 (RR198) removal over TiO(2) adsorbent using response surface methodology. The main process parameters considered for optimisation were pH, adsorbent dose, and adsorption time. The experimental scheme was designed according to central composite rotatable design and second order regression model was developed. For regression analysis and ANOVA study, software MINITAB 15 was used. The optimum pH, TiO(2) dose, and time were found to be 4.3, 4.3 g L(-1), and 32.42 min, respectively. Complete removal was observed. Pareto analysis established pH the most influential parameter.
Abstract: Galactosyl oligosaccharides (COS) are prebiotics commonly manufactured by beta-galactosidase conversion of lactose, producing a mixture containing GUS, lactose, glucose and galactose. Enrichment of GUS in this mixture adds value to the product. This study aimed to determine whether the addition of ethanol to aqueous saccharide solutions could be used to selectively precipitate and enrich GUS from a reaction mixture. High concentrations of ethanol (>70% v/v) were required to induce precipitation. The total saccharide concentration was a significant variable, with higher GUS enrichment occurring at lower total saccharide concentrations. Varying the temperature between 10 and 40 degrees C had less impact than had changes in the concentration of saccharide or ethanol. GOS was enriched 2.3 (+/- 0.1) fold in the precipitate formed in a solution of 90% (v/v) ethanol with 28 g/L of total saccharide at 40 degrees C. Performing two such precipitations sequentially reduced the monosaccharides from 48% (w/w) of the total saccharides to 4% (w/w). COS precipitation has potential for industrial application as it is simple in operation and offers levels of purification similar to those by other techniques. (C) 2011 Elsevier Ltd. All rights reserved.
Abstract: This paper investigates the adsorptive removal of Cr (VI) from aqueous solution over commercial powdered activated carbon (PAC) and carries optimisation of removal efficiency for the process using response surface methodology (RSM). The effects of different parameters such as pH, initial Cr (VI) concentration, adsorbent dose, contact time and temperature on adsorption were studied to find the best operating conditions. This study showed that when initial concentration was 50 ppm, 100% Cr (VI) removal was possible with pH 2 and 2 g L(-1) PAC concentration. Different adsorption kinetic models and isotherms were compared respectively with the proposed kinetic model based on liquid phase adsorbate concentration and the developed new three-parameter isotherm. The new isotherm supported the experimental results with a better accuracy. The main process parameters considered for optimisation were pH, adsorbent dose and adsorption time. The experimental was designed according to central composite rotatable design (CCRD) and second order regression model was developed for regression analysis and ANOVA study. The optimum pH, PAC dose and time were found to be 2.32, 1.79 g L(-1) and 25.76 min. Pareto analysis established that PAC dose was the most influential parameter. (C) 2011 Elsevier B.V. All rights reserved.
Abstract: Present work primarily deals with an exhaustive investigation on the effect of beta-galactosidase (EC 3.2.1.23) immobilization on polymeric polyether sulfone, cellulose triacetate and thin film composite polyamide membrane to produce galacto-oligosaccharides from lactose. Fouling is one of the key issues that control any membrane separation process to obtain the desired product. Especially, this issue with membrane becomes multiplied after making any attachment of immobilization chemicals on its surface, i.e. in case of enzymatic membrane reactor. Present work thus aims to identify the insights of carbohydrate interactions with the membrane surface after immobilization and how far it controls the production of galacto-oligosaccharides in this membrane reactor. (C) 2011 Elsevier B.V. All rights reserved.
Abstract: A mass transfer model based on unsteady state component balance over the concentration boundary layer has been developed in the present study. The model uses semi-infinite consideration in order to solve the governing partial differential equation by Laplace transform that gives an analytical expression for the concentration profile. During the solution procedure, pseudo steady state assumption has been used, as a consequence of which permeate flux and membrane surface concentration have been taken constant over any small time interval. Once the expression for concentration profile is known, a time evolution loop has been developed to simulate the permeate flux, membrane surface concentration and permeate concentration under specified operating conditions of transmembrane pressure drop and bulk concentration. The prediction of the proposed model was found to be in good agreement with experimental results obtained during unstirred dead end ultrafiltration of polyethylene glycol (of average molecular weight 6000) solution using a cellulose acetate membrane of 5000 Da molecular weight cut-off.
Abstract: Emulsion Liquid Membrane (ELM) separation technique is an effective procedure for the removal of Chromium (VI) ions from the wastewater stream. In the present study, the effect of changes of different parameters such as the pH of feed solution, the stirring speed, and the emulsification time, carrier concentration, surfactant concentration, the effect on the presence of other metal ions, are systematically investigated. The membrane phase consists of kerosene with hexane as diluant, Aliquat 336 as extractant, sorbitan mono-oleate (span 80) as surfactant. 1 (N) Sodium hydroxide is the stripping solution. Results show that by the ELM process, 90% Cr(VI) can remove successfully in optimum condition from feed.
Abstract: A semi-analytical model based on unsteady state mass transfer has been developed for the prediction of permeate flux, membrane surface concentration and permeate side concentration during ultrafiltration in a standard single stirred cell. Starting from the basic fluid mechanical analysis of the system, stirrer induced back transport flux was evaluated considering the actual non-uniform velocity field and the final expression was incorporated in the fundamental mass balance equation. As a result the obtained partial differential equation (PDE) became associated with variable coefficients. The PDE after taking Laplace transform was reduced to standard confluent hypergeometric equation via a series of appropriate substitutions, which was finally mapped again in the time domain considering only the first four terms of the resulting series solution. Once the analytical form of a concentration field was obtained, permeate flux and the membrane surface concentration were evaluated using polymer solution theory and irreversible thermodynamics. Finally an iterative scheme has been designed to simulate the permeate flux and the membrane surface concentration under specified set of operating parameters. The prediction from this model was found to be in good agreement with experimental data obtained from PEG-6000/water system using cellulose acetate membrane of 5000 Da molecular weight cut-off. (C) 2010 Elsevier B.V. All rights reserved.
Abstract: Reduction in the permeate flux is a major fundamental problem in membrane separation process due to membrane fouling and concentration polarisation. To alleviate these scenarios with an objective to attain proper throughput from the membranes, different types of high-shear devices have been proposed in literatures. In the present work with the rotating disc membrane module (RDMM), a high-shear device, vanes with different geometries and arrangements were used as turbulence promoters. The aim of the work is to identify a vane which will be worthy to obtain moderate permeate flux at the expense of low energy consumptions, i.e. with low applied trans-membrane pressure (TMP) and low membrane speed. To meet the objective a simulated solution of bovine serum albumin (BSA) and glucose was introduced as feed to the rotating disc membrane module (RDMM) fitted with different arrangements of vanes at different combinations of trans-membrane pressure (TMP), feed concentration and membrane speed. It was found that 45 degrees blade angle vane having holes on the blade surface produce maximum permeate flux at low IMP and membrane speed for even high concentration of the feed solution, and thus responsible for the low rejection of glucose on the retentate side confirming maximum purity of BSA and glucose in either side of the membrane. ANOVA analysis was also done on the throughput of this vane to understand the effects of different operating parameters and the effect due to their mutual interactions. (C) 2010 Elsevier B.V. All rights reserved.
Abstract: Development of an automated wastewater treatment plant is very difficult as the parameters of an industrial effluent change severely; accordingly the change in output of treatment plant. A computer-simulated model is required for interrelating the input and output parameters of wastewater treatment plant. An artificial neural network model has been proposed for the prediction of adsorption and photocatalysis efficiency of TiO(2) photocatalyst. The network was trained using the experimental data obtained at different pH with different TiO(2) dose and initial dye concentration. Different algorithms and transfer functions for hidden layer have been tested to find the most suitable and reliable network. The optimum number of neurons in the hidden layer was found by trial and error method. These neural network models efficiently predict the adsorption efficiency (% dye removal), adsorption capacity (loading) and photocatalytic efficiency of the process. Solution of reactive black 5 was used as simulated dye wastewater for this study. The effect of different operating parameters on process efficiency was studied. (C) 2010 Elsevier Ltd. All rights reserved.
Abstract: Random Chain model is mathematically standardised using Taylor’s expansion series, second order partial differential equation and Laplace transformation in details to establish the most important physical properties like probability distribution function and mean square separation of end to end of a biopolymer chain. A multivariable function correlating mean end to end separation, number of monomer unit and length of each monomer unit is established. Finally the output equations are standardised by an object oriented programming language like C++ for biopolymers like Catalase, Myosin and Bushy shunt virus.
Abstract: Stirred rotating disk membrane modules (RDMM) have been found to provide maximum flux enhancement due to minimization of the concentration polarization layer by shear effect. But unfortunately rigorous theoretical modeling of RDMM has not been developed yet, which greatly affects the simulation and optimization of this device under applications in many fields. In this perspective, the work reported in this article was carried out to develop an efficient artificial neural network (ANN) capable of predicting permeate flux in case of RDMM. Different ANNs, like Feedforward, Elman, Hopfield and Radial Basis Network, were investigated to find the optimum network configuration and corresponding network parameters have been estimated. As a case Study, the focus was given to ultrafiltration (UF) of casein whey, a complex protein mixture. For this purpose the UF of whey was carried out in RDMM at different pH and transmembrane pressures, with and without rotating the membrane. A detailed comparative study was made on the validation results between the predicted flux and corresponding experimental values for different ANNs investigated. Based on the results, it was concluded that the Radial Basis Network was most accurate in terms Of flux prediction and stability for UF using RDMM.
Abstract: 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 200mM 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 JMP) 4.5 kgf cm(-2), stirring speed 200 rpm, pH 2.5 and CEW-solvent ratio 1:1. (C) 2009 Elsevier B.V. All rights reserved.
Abstract: In this study, effects of different operating parameters in ultrafiltration (UF) of casein whey in rotating disk ultrafiltration module, fitted with a 30 kD followed by a 5 kD molecular weight cut-off (MWCO) membrane have been analyzed and the benefits of membrane rotation with respect to stationary membrane module are highlighted. Prior to UF, centrifugation and microfiltration (MF) were carried out with the raw casein whey with an aim to remove the major membrane foulants like colloidal matters, suspended casein particles and lipid. The effects of pH, membrane rotation and transmembrame pressure (TMP) on UF flux and rejection were studied thoroughly, giving an emphasis on the effect of operating conditions in pressure and mass transfer controlled region as well. It was observed that solution pH was having a strong effect on UF flux and rejection for treating casein whey, which was explained in terms of prevailing monomer-dimer equilibrium of beta-lactoglobulin, a major constituent of casein whey, as well as due to conformational changes of protein molecules with respect to isoelectric point. It was observed that for the 30 kD membrane, after 20 min of operation, 28.5% higher flux was obtained at pH 2.8 compared to pH 5.5 at a pressure of 490 kPa for stationary membrane, whereas the same figure for rotating membrane was 49.5%. Further, 38.7% higher UF flux at 300 rpm membrane speed compared to stationary membrane in 20 min of operation at pH 2.8 and TMP 490 kPa suggests the importance of shear across the membrane in minimizing the effects of concentration polarization. In the 5 kD membrane alpha-lactalbumin, which was mainly in the permeate stream from the 30 kD membrane, was separated from the other low molecular weight component of whey, such as lactose. (C) 2009 Elsevier B.V. All rights reserved.
Abstract: Recycling and reuse of wastewater after purification will reduce the environmental pollution as well as fulfill the increasing demand of water. Adsorption-based water treatment process is very popular for dye-house wastewater treatment. The present study deals with treatment of wastewater contaminated by reactive dye. TiO(2) is used as adsorbent and the spent adsorbent has been regenerated by Advanced Oxidation Process (AOP), without using any other chemicals. TiO(2) adsorbs dye molecules and then those dye molecules have been oxidized via a photocatalytic reaction in presence of UV irradiation. Kinetics of dye adsorption and photocatalytic oxidation reaction has been developed in this study. Photocatalyst adsorbent (TiO(2)) has been reused several times after regeneration. The activity of catalyst decreases after each cycle; due to poisoning cause by intermediate by-products. Kinetic of this catalyst deactivation has been incorporated with L-H model to develop the photocatalytic reaction kinetic model. (C) 2009 Elsevier B. V. All rights reserved.
Abstract: The Stern-Volmer equation has been analysed statistically through linear regression or best fit method in presence of a quencher. Two important Statistical parameters like regression coefficient and correlation coefficient are calculated from the standard data. The data obtained by the tryptophan fluorescence by dissolved oxygen gas as quencher at 348 nm has been analysed. The values of two most important photochemical kinetic parameters, the rate constant in presence of quencher and observed fluorescence lifetime in absence of quencher are calculated. The values obtained by this type of analysis are: 1.276x10(10) L.mol(-1).s(-1) and 2.6x10(-10) s respectively, With a correlation coefficient value of 1.000. This statistical data analysis is used to interpret the mechanism of bimolecular quenching which can be applied to photobiological study in the accessibility of amino acid residues of a folded protein to solvent.
Abstract: An unsteady state mass transfer model has been developed for rotating disk ultrafiltration module. Starting from the basic physics of the system, analytical expression of back transport flux generated due to rotation-induced shear field is determined, which is subsequently incorporated in the fundamental material balance equation. In order to get an analytical solution of governing partial differential equation via Laplace transformation, pseudo steady state consideration is imposed both on permeate as well as back transport flux. Once the analytical form of concentration field is obtained using the expression permeate flux, membrane surface concentration are evaluated using polymer solution theory and irreversible thermodynamics. Finally an iterative scheme is designed to simulate the permeate flux and membrane surface concentration under specified set of operating parameters. The prediction from this model is found to be in good agreement with experimental data obtained from PEG-6000/water system using cellulose acetate membrane of 5000 Da molecular weight cut-off. (C) 2008 Published by Elsevier B.V.
Abstract: The aim of the present study is to obtain safe and pure drinking water from surface water, which has been polluted with pesticide. Pesticide contaminated surface water samples were prepared by spiking commonly used pesticide, Isoproturon, in different surface water samples collected from different parts of India. Attempts were made to evaluate the efficiency of different adsorbents in removing pesticide from distilled water. Dosages and contact time of the selected adsorbent, pH were varied in order to optimise the treatment parameters for maximum removal of pesticide. Langmuir and Freundlich adsorption isotherm were also established in this adsorption study. Coagulation and then adsorption studies were performed on pesticide contaminated surface water as pre-treatment to reduce membrane fouling. Nanofiltration was done on pre-treated water in a test cell in dead end mode. The NF permeate was analysed for pH, turbidity, TDS, COD, TOC, conductivity, hardness, and colony count. RO was suggested after NF if necessary. The quality of NF/RO permeate water compared well with the potable water of our laboratory.
Notes: 5th Conference on Desalination Strategies in South Mediterranean Countries (EuroMed 2006), Montpellier, FRANCE, MAY 21-25, 2006
Abstract: Kraft black liquor(KBL), the wastewater from digester house of pulp and paper industry using sodium hydroxide and sodium sulfide during chemical pulping, causes severe damage to a terrestrial ecosystem. In this study, first of all, KBL has been characterized in terms of wastewater quality parameters, i.e. total solids, BOD, COD, turbidity, etc. Sedimentation of KBL using lime and alum as coagulants was studied and the dosage was optimized. A 35.2% reduction of BOD was achieved using 17.5% alum solution after adjusting the solution pH to 9.5 using fresh lime solution. Tertiary treatment like adsorption/ultrafiltration was investigated so as to further remove the non-biodegradable products like lignin and their derivatives. Adsorption was carried out at two different solution pHs under ambient condition using activated carbon as adsorbent. Adsorption isotherms of kraft pulp mill effluents over activated carbon at both pHs were found to be well described by Freundlich equation. Ultrafiltration was carried out using cross-flow module (Vivaflow(TM) 200) at three different transmembrane pressures, i.e. 1.5, 2 and 2.5 kg/cm(2). The UF operation at a TMP of 2.5 kg/cm(2) was seen to be a little bit more efficient in reducing COD, BOD, turbidity compared to adsorption on activated carbon.
Abstract: The random coil model is analysed to establish the mathematical support behind it. In this approach Stirling’s approximation, weight factor and improper integral (gamma function) are analysed in detail. A correlation between the important modelling parameters like radius of gyration, root mean square separation, number of monomers and length of each monomer unit is established. Finally this model is validated by a standard object-oriented programming tool for a protein like serum albumin.
Abstract: The surface water bodies have become very much susceptible to pollution by pesticides due to their increased application in agriculture. The production of potable water from pesticide contaminated lake and river water was investigated by a coagulation-adsorption-nanofiltration approach. Isoproturon (IPU) was selected as a target pesticide and spiked in distilled water and then in surface water. Coagulation was done before adsorption and coagulant dosage was selected on the basis of turbidity removal. Various adsorbents such as powdered activated charcoal (PAC), bentonite, chitosan were tried at different dosages to evaluate their efficiency in IPU removal. The effect of initial pesticide concentration was studied on percent removal of pesticide when treated with selected adsorbent at a particular dosage. The values of adsorption capacity calculated from Langmuir and Freundlich equations were 104.21 mg/g and 69.4 mg/g respectively indicating favorable adsorption of IPU on powdered activated charcoal surface. After optimizing the coagulation and adsorption protocol, nanofiltration (NF) was performed on pretreated water in a test cell in dead end mode. The NF permeate was analyzed for pH, turbidity, TDS, COD, TOC, conductivity, hardness, and colony count. Reverse osmosis (RO) was done after NF if required. The quality of NF/RO permeate was found comparable to the standards of drinking water.
Abstract: One of the major reasons of reluctance by industries to implement ultrafiltration (UF) of black liquor (BL) is flux decline and associated fouling. Several attempts have been made in the past to study and to analyze the performance of ultrafiltration of BL using various module combinations under different conditions. BL, spent liquor from alkaline sulfite pulping industries, is known to contain organics (mainly lignosulphonates of wide range of molecular weights) as well as inorganics; thus posing design restrictions for its treatment. The present work employs a laboratory fabricated stirred and rotating disk batch UF cell in an attempt to minimize flux decline and thereby obtain enhanced flux for the treatment of BL obtained from sulfite pulping industries. Asymmetric cellulose triacetate membrane of 5000-molecular weight cut-off was used for experimentations. Reduction of concentration polarization was observed with membrane rotation in this shear induced dynamic filtration unit and correlations have been obtained with different operating variables, like transmembrane pressure (TMP), stirrer speed and membrane rotation speed. The rejection of solutes, measured in terms of total solids (mostly containing lignosulphonates) was also correlated with different operating parameters. Pretreatment methods like, centrifugation, followed by microfiltration were utilized to remove any traces of suspended solids; thus minimizing the occurrences of membrane fouling. Pretreatment steps proved to be highly efficient in restoring the permeability of the membrane during experimentations. Finally, a new model was developed based on pore-plugging theory in order to assess the performance of UF, which clearly showed the reduction in pore-plugging phenomenon as a result of membrane rotation. Further, membrane rotating was proved to be more efficient in reducing concentration polarization compared to stirring action. (c) 2005 Elsevier B.V. All rights reserved.
Abstract: Ultrafiltration of Kraft black liquor was carried out by using an asymmetric membrane in a stirred batch cell, modified to work on a continuous mode. Spigler-Kedem (SK) model fro. in irreversible thermodynamics was used for the estimation of different membrane-solute parameters, like solute permeability (P-m) and reflection coefficient (sigma). The P-m and sigma so calculated from the above model were used to study the variation of these parameters with other process variables, like bulk concentration, pressure difference and stirrer speed. Finally, a simulation model was developed with the objective to predict permeate flux and rejection, which coupled the film theory, osmotic pressure model and SK model. The simulation results obtained from this study were validated with the experimental data using cellulose acetate membrane of 5,000 Da MWCO. Reasonably good agreements between the predicted and experimental, values were observed and the average absolute deviation (AAD) for the prediction of flux and rejection using SK model was found to be 6.3%.
Abstract: The objective of this work is to obtain a relative separation of beta-lactoglobulin (beta-LG) from whey protein concentrate by fractionation of protein using two-stage ultrafiltrafion (UF) with 30 and 10 kg mol(-1) molecular weight cut-off (MWCO) flat-disk membranes in stirred rotating disk module followed by ion-exchange membrane chromatography (IEMC) using Vivapure (TM) Q Mini-H column. Prior to UF, centrifugation, microfiltration and a four-stage discontinuous diafiltration (DD) were carried out to obtain whey protein concentrate from raw casein whey. Centrifugation and microfiltration were carried out to remove the major foulants like colloidal matters, suspended casein particles and lipid. DD using 5 kg mol(-1) polyethersulphone (PES) membrane with volume concentration ratio (VCR) 2 in each stage was employed with an objective to enrich the whey proteins by removing most of lactose, minerals and salts. The effects of various parameters, like solution pH, trans-membrane pressure (TMP), stirrer speed and membrane rotation speed on UF flux and rejection were studied thoroughly. A 36% higher flux was obtained with a feed pH of 2.8 compared to that at pH of 5.6 at a fixed TMP of 5.0 X 10(5) Pa which has been explained with the help of the effect of pH on monomer-dimer equilibrium of beta-LG and prevailing protein charge. A 33% enhancement of flux was observed at 1 min with membrane disc rotating at 300 rpm compared to the corresponding value of stationary membrane due to reduction in concentration polarization, the main limiting phenomenon for flux decline. A suitable loading buffer pH was investigated during IEMC runs so as to get a facilitated transport of beta-LG over alpha-LA through the strong anion exchanger membrane. An 87.6% purity of beta-LG (on total protein basis) was obtained in the filtrate of ion-exchange membrane chromatography. (c) 2005 Elsevier B.V. All rights reserved.
Abstract: In this study, a detailed analysis of protein fractionation from casein whey using two-stage ultrafiltration (UF) with 30 kD and 10 kD flat-disk membrane in stirred rotating disk module has been made with an objective to understand the effect of membrane rotation and other important parameters on permeate flux and rejection. The membrane rotation was found to enhance the flux and was highly efficient in reducing the concentration polarization. The other independent variables being studied were solution pH, trans-membrane pressure (TMP) and stirrer speed. In the first stage UF with 30 kD membrane, most of the bovine serum albumin (BSA), lactoferrin (Lf) and immunoglobulin (Ig) were found to be rejected, and in the other with 10 kD membrane, alpha-lactalbumin (alpha-La), beta-lactoglobulin (beta-Lg) were rejected to give clear permeate with low protein concentration. To understand the effect of pH on whey protein UF, all the UF runs were taken at two different pH levels, 2.8 and 5.7, with 4.6 being isoelectric point (pI) of the casein. The effect of monomer-dimer equilibrium at higher pH has been observed and investigated. At feed pH 2.8 and membrane rotation at 3 00 rpm or more, higher fluxes were observed within the TMP range of 4-5 kg/cm(2). A 75.1% beta-Lg purity (on total protein basis) was obtained in the final stage, i.e. in 10 kD retentate at a TMP of 4 kg/cm(2) in stirred rotating disc module with 600 rpm membrane rotation speed.
Abstract: Ultrafiltration of black liquor was carried out using an asymmetric membrane in a stirred batch cell, which was modified to work on a continuous mode. Different solute-membrane parameters like solute permeability (P-m) and reflection coefficient (sigma) were estimated, based on the theories derived from irreversible thermodynamics. Kedem-Katchalsky (KK) and Spiegler-Kedem (SK) models, from irreversible thermodynamics, were utilized for the parameter estimation. The P-m and sigma, so calculated from the above two models, were compared and their variations with other process variable like bulk concentration, pressure difference and stiffer speed were established. Finally, a three-parameter simulation model was developed based on film theory, osmotic pressure model and KK/SK models, which were capable to predict permeate flux and rejection at any operating conditions based on P-m, sigma and R-m. The results of simulation studies were compared with experimental results, using cellulose acetate membrane of 5000 MWCO. The simulation results (in terms of flux and rejection) were found to be in good agreement with experimental data; though, the predictions based on SK model were found to be better compared to KK model and the absolute average deviations were 6.3% and 8.4% for the prediction of flux and rejection using SK and KK models, respectively. (c) 2006 Elsevier B.V. All rights reserved.
Abstract: Concentration and purification of lignosulphonates (LS) present in spent sulfite liquor (SSL) obtained from the paper industry were carried out through ultrafiltration (UF). The salts of lignosulphonic acid, a product of acid hydrolysis of lignin, are a major component of technical LS. In respect of molecular weight composition, LS represent a polydispersed system with a wide range of molecular weight distributions, from 200 to 150,000 Da. They have good adhesive properties and are used as plasticizers, peptizers, and stabilizers in the industry. The usefulness of LS is dependent on the molecular weight composition. Higher molecular weight LS fractions show properties of amorphous polymeric substances, which may have much industrial use. Diafiltration operation was used for purification of LS. The LS present in SSL were estimated using different membranes (polysulphone, cellulose acetate, fluoropolymer) of varied cut-off sizes (I K, 5 K, 10 K, 20 K, 25 K, 50 K and 100 K). Sharp cut-off membranes in between 20 K and 100 KI)a show close rejections (80-84%). The effect of different operating conditions such as different transmembrane pressures, dilution of SSL, membrane materials and different cut-off sizes was studied on flux and rejection. The effect of sharp and diffused cut-off membranes on flux and rejection was also studied. Continuous diafiltration (CD) was conducted over a high MWCO membrane (GR100K). It was observed that CD with a sharp cut-off membrane gave steady flux and a very good rejection of LS.
Abstract: A new method, comprised of a biological treatment followed by membrane separation, has been suggested for the treatment of spent prehydrolysis liquor (PHL) from a rayon grade pulp mill. First, the PHL was treated biologically using the torula utilis strain for the conversion of sugar into yeast. Reductions of 57 % in the amount of total reducing sugar (TRS) and about 46 % in COD were achieved in the biological treatment step. A “shifting order type” rate equation, where the order shifts from (m-n) at high concentrations to m at lower concentrations, was found to predict the total reducing sugar with high accuracy. An ultracentrifuge was used to separate out the yeast formed during the biological treatment. The clarified biologically treated liquor was subjected to reverse osmosis (RO) to remove all the remaining solutes. The permeate obtained was observed to be of disposable/reusable grade (negligible COD and less than 0.9 mg/L sugar). An attempt was made to predict the permeate flux during reverse osmosis (RO) using an osmotic pressure model. Modified osmotic pressure and concentration polarization models were utilized for the estimation of the osmotic pressure of different concentrations of the PHL’s solute constituents. Three different concentration parameters (TRS, COD, and Brix) were chosen to estimate the osmotic pressures. The prediction of the permeate flux by the combination of these models was found to be in good agreement with experimental flux values.
Abstract: A novel technology combining biochemical degradation and membrane separations has been proposed for the treatment of prehydrolysis liquor (PHL), a major waste effluent of rayon grade paper mills in India. The article addresses the significance, advantages, limitations and industrial viability of the technology and offers an alternate route to an otherwise conventional chemical method currently adopted in treating the PHL. In the present work, the effluent constituting primarily reducing sugars was first subjected to biological treatment with Torula utilis. The products (yeast) formed due to microbial fermentation as well as some unreacted constituents were then removed employing ultrafiltration (UF) and reverse osmosis (RO). The biological treatment followed by these membrane processes thus resulted in a clear liquid with negligible chemical oxygen demand (COD) and less than 0.9 mg/l of total reducing sugar (TRS). A series of experiments carried out suggested suitable range of operating conditions, such as dilution ratio of effluent liquor (1: 1), growth rate of yeast formation (similar to 5 days) and quantity of culture (15%), apart from other chosen conditions, for sustaining the maximum growth of yeast. A relatively larger MWCO size membrane (similar to 100 000) was found to be advantageous during UF for the removal of yeast and other constituents. The UF permeate when subjected to RO (using thin-film composite membranes) resulted in the removal of practically remaining amount of TRS. A pressure of around 2.1 MPa was found to be sufficient to carry out RO separation, which in absence of biological treatment followed by UF, would increase the operating pressure to a much higher value. Thus a substantial reduction in operating pressure of RO could be achieved by this combined process. (C) 2005 Elsevier B.V. All rights reserved.
Abstract: In this study an attempt has been made to obtain a dimensional analysis based empirical model of ultrafiltration process under stirred condition, which for a given membrane will predict the permeate flux and the rejection during the dynamic as well as the steady state phases of operation from the process conditions applied, viz. pressure drop, stirrer speed, bulk concentration of the filtered species etc. A dimensional analysis by Rayleigh’s method was performed and the obtained dimensionless groups were related with the help of experimentally obtained data in this study, by non-linear regression employing Levenberg and Marquardt technique. Two equations have been obtained, one for the prediction of flux and other for the rejection. The computed results are found to be in good agreement with the experimental data obtained in this study during the ultrafiltration of PEG-6000 by cellulose acetate membrane and the absolute average deviation was found to be within less than 7%.
Abstract: A mass transfer model based on unsteady state mass balance over concentration boundary layer coupled with gradual development of so called “gel” or “cake” layer has been formulated in this study. The model considers the boundary layer problem simultaneously with the film theory of mass transfer and resistance in series model. The resulting equations are solved first by reducing the set of partial differential equations to nonlinear equations utilizing orthogonal collocation technique and then applying multidimensional Newton-Raphson method with suitable seeding scheme to solve the above-mentioned nonlinear equations together with some additional constraints. The problem of determination of membrane surface concentration is eliminated by this simultaneous solution of boundary layer equation together with gel layer. The model is found to be capable of predicting permeate flux and rejection under different experimental conditions. The main feature of this model is that it takes into account realistically the effect of gel layer formation within concentration boundary layer whereas in most of the previous studies this effect has not been considered. The dependency of concentration profile, gel thickness, and permeate concentration with different operating variables are also studied and the variations are found to be quite reasonable.
Abstract: A mass transfer model based on unsteady state mass balance over the concentration boundary layer, coupled with back transport resulting from the stirring action, opposing ultrafiltrate flux, has been developed in the present study. This model uses semi-infinite consideration to solve the governing partial differential equation by the Laplace transformation method, which gives the analytical solution of the concentration profile. During the solution procedure, pseudo-steady state assumption has been used, as a consequence of which volumetric flux and turbulent back transport flux have been taken as constants. Once the analytical expression for the concentration profile has been found, an iterative technique has been developed for simulating flux and rejection under any specified operating condition. The prediction from this model is found to be in good agreement with experimental results obtained during continuous stirred ultrafiltration of PEG-6000 solution using a cellulose acetate membrane of 5000 Da molecular weight cut-off. The average absolute deviation in the prediction of permeate flux has been found to be 5.6% and that for the prediction of rejection was 6.4%. (C) 2003 Society of Chemical Industry.
Abstract: A mathematical model based on filtration theory, coupled with resistance in series model and gel polarization/film model has been developed in the present study. Unlike the cake filtration equipment where cake deposition continues until the wash cycle comes, in case of continuous stirred ultrafiltration the deposited solutes are allowed to build up over the membrane indefinitely, along with continuous back transport of deposited solutes into bulk by the turbulence created by stirring action. To account for this back transport, a coefficient called back transport coefficient has been defined which is found to be independent of any operating variables. Variation of polarized layer resistance was also studied with different operating variables like bulk concentration, stirrer speed and pressure differential. A correlation was also developed relating polarized layer resistance with those operating variables. A comparative study has been made between experimentally found polarized layer resistance value, using ultrafiltration data of Bhattacharjee and Bhattacharya, with those found from correlation and this developed model based on filtration theory. The model has been found to predict the polarized layer resistance reasonably well once the three parameters describing the model viz. permeability coefficient, back transport coefficient and membrane hydraulic resistance are known along with the operating condition. Using the above-mentioned parameters, it is also possible to predict flux and/or total permeate volume at any time under a given operating condition. (C) 2003 Published by Elsevier B.V.
Abstract: An artificial neural network model of a continuous stirred ultrafiltration process, is proposed in the present study, which is able to predict permeate volumetric flux and permeate concentration at different bulk concentration, stirrer speed, pressure and time. Because of the complexity in generalization of the phenomenon of ultrafiltration by any mathematical model, the neural network proves to be a very promising method for the purpose of process simulation. The network uses the Back-propagation Algorithm for evaluating the connection strengths, representing the correlations between inputs (bulk concentration, stirrer speed, pressure and time) and output (permeate concentration and flux). The network employed in the present study uses four input nodes corresponding to the operating variables, and two output nodes corresponding to the measurement of the performance of the network (flux and permeate concentration). Experiments were performed to constitute the learning databases for the continuous stirred ultrafiltration process using PEG-6000 solute, and cellulose acetate membrane of 5000 MWCO. The network employed in the present study uses two hidden layers, with the optimum number of nodes being thirty and twenty. A leaning rate of 0.3, and momentum factor of 0.4 was used. The results predicted by the model were in good agreement with the experimental data, and the average deviations for all the cases are found to be well within +/-10 %.
Abstract: An unsteady state mass transfer model has been developed taking into account the effect of reversible pore plugging by the diffusing solute molecules. The osmotic pressure model has been used to predict the membrane surface concentration. The rate of available fractional area of the membrane that is blocked at any time due to pore plugging phenomenon has been assumed to be the function of dimensionless membrane surface concentration prevailing at that time. Experimental data generated in this study using cellulose acetate membrane of 5000 MWCO and polyethylene glycol (PEG)-6000 as solute in unstirred batch configuration has been used to find the appropriate nature of the above-mentioned function. Once the functional dependency between the rate of fractional area blocked and dimensionless membrane surface concentration has been found, it can be used to simulate flux and rejection behaviour during unstirred batch ultrafiltration (UF). The predicted results show very good agreement with the experimental data and the average deviations for all the cases are found to be well within +/-10%. (C) 2000 Elsevier Science B.V. All rights reserved.
Abstract: A mass transfer model based on an unsteady-state mass balance over the concentration boundary layer, coupled with diffusive backtransport opposing the ultrafiltrate flux, has been developed in the present study. This model can be used to simulate flux and rejection at any desired time in an unstirred batch ultrafiltration module. This model uses the semi-infinite consideration to solve the governing partial differential equation by the Laplace transform technique, which gives the analytical solution of the concentration profile. In the partial differential equation, volumetric flux is assumed to be constant in accordance with pseudosteady-state assumption, often used in diffusive mass transfer analysis. Once the analytical expression for the concentration profile has been found, an iterative technique has been used in conjunction with other membrane and solute properties to predict the flux and rejection at any desired time under a specified operating condition. Concentration profiles as a function of time for different experiments are also computed in order to analyze the effect of different operating parameters on the concentration boundary layer. The prediction from this model is found to be in good agreement with the experimental results obtained during ultrafiltration of PEG-6000 in an unstirred batch module using a cellulose acetate membrane of MWCO-5000, and in most cases the variation of concentration within the boundary layer is found to be limited within a very short distance over the membrane surface.
Abstract: An unsteady-state mass transfer model has been developed which takes into account the variation of diffusivity with solute concentration in the boundary layer. The main aim of this model is to study the effect of variation of diffusivity on membrane surface concentration as well as on the concentration profile prevailing within the boundary layer. Experimental data generated in this study have been used to validate the model. The resulting complex nonlinear partial differential equation has been solved by a numerical technique. The developed model is also capable of simulating volumetric flux and the permeate volume collected at any time under specified operating conditions. The simulated results show excellent fitting of the present model with variable diffusivity consideration when compared with experimental data. On the other hand, prediction based on constant diffusivity deviates considerably, indicating the importance of consideration of variable diffusivity in unsteady-state batch ultrafiltration.
Abstract: A mass transfer model based on a concentration boundary layer, as suggested by film theory, is proposed in this study. The mass transfer coefficient for the case of an unstirred batch cell was predicted using an extrapolation technique based on a suitable curve fitted equation. The parabolic partial differential equation resulting from the unsteady state mass balance over the concentration boundary layer was solved by a numerical technique using a second order implicit method. The solution process also couples the osmotic pressure model for the prediction of flux and an equation from irreversible thermodynamics for the prediction of real rejection. All equations were solved simultaneously by the multidimensional Newton-Raphson technique using Broyden’s correction factor to enhance the rate of convergence. The final predicted flux and rejection was found to be in good agreement with the experimental data, and the absolute average deviation in both cases was found to be well within 10%. (C) 1999 Elsevier Science B.V. All rights reserved.
Abstract: A mass transfer model in case of ultrafiltration is proposed in the present study which is capable of predicting the permeate volumetric flux and rejection at different pressure, concentration and stirrer speed. The model is based on the steady state mass balance over the boundary layer, coupled with the results from irreversible thermodynamics. It first predicts the membrane surface and permeate concentrations which are then utilized to calculate rejection. Permeate flux is then predicted using the result obtained from filtration theory. The model utilizes four parameters, namely, solvent permeability, solute permeability, reflection coefficient and specific cake resistance. These parameters along with the known values of the operating conditions and solution properties enable one to predict the flux as a function of time and rejection. The computed results are found to be in good agreement with the previously published data of Bhattacharjee and Bhattacharya during ultrafiltration of PEG-6000 by cellulose acetate membrane.
Abstract: A mathematical model based on steady-state mass balance over a boundary layer, coupled with the results from irreversible thermodynamics, is proposed in the present study for ultrafiltration of PEG-6000 rising a cellulose acetate membrane. The model is capable of predicting both the membrane surface concentration and permeate concentration, and can be utilized to predict the value of rejection at any operating condition. Three parameters (solvent permeability, solute permeability, and reflection coefficient) were taken into account while developing this model, These parameters, along with the known values of operating conditions and solution properties, allow prediction of rejection. The computed results are in good agreement with the previously published experimental data of Bhattacharjee and Bhattacharya.
Abstract: A mass transfer model based on an unsteady state mass balance over the concentration boundary layer, coupled with the back transport opposing the ultrafiltrate flux, has been developed in the present study. The model is capable of predicting permeate flux and rejection at different pressures, concentrations and stirrer speeds. This model first uses the experimental data of Bhattacharjee and Bhattacharya to integrate the governing partial differential equation and in the process, it calculates the back transport coefficient by a least squares fit. Once this coefficient along with other membrane and solute properties are known, permeate flux and rejection can be predicted at any desired operating conditions. Concentration profiles as a function of time for different experiments were also computed in order to analyze the effects of different operating parameters on the concentration boundary layer. The model predicts that the flux decline during ultrafiltration of PEG-6000 in a continuous stirred cell using a cellulose acetate membrane, occurs mainly due to the resistance offered by solute molecules during their transport back to the bulk. The effects of osmotic pressure and cake/gel formation are assumed to be negligible in this study.
