Toshiro Murase

The Terzaghi-Voigt combined model for constant-pressure consolidation of filter cakes and homogeneous semi-solid materials

Abstract Theories of constant-pressure consolidation are reexamined in detail. A Voigt model for constant-pressure consolidation is solved and the time factors which govern a secondary consolidation process are obtained. It is found that three kinds of retardation times exist in the solution of the Terzaghi-Voigt combined model; the first factor, Θ 1 , is due to liquid flow resistance of the Terzaghi element; the second, Θ 2 , is due to liquid flow resistance of the Voigt element; and the third, Θ 3 , is due to creep deformation of the particulate bed. One can derive the conventional solutions of the Terzaghi-Voigt combined model for constant-pressure consolidation under the normal assumption that both Θ 1 and Θ 2 are much less than Θ 3 .

Upward Dead-End Ultrafiltration of Binary Protein Mixtures

Abstract Upward dead-end ultrafiltration of aqueous solutions of mixtures of bovine serum albumin (BSA) and egg white lysozyme was conducted using membranes which are almost completely retentive for BSA but permeable for lysozyme. The dependence of lysozyme rejection and the filtration flux rate on pH and the addition of salts has been investigated. The experimental data obtained in this study clearly demonstrate that the electrostatic interactions between dissimilar molecules may control the solute rejection and the filtration rate in upward ultrafiltration of binary protein mixtures. For instance, the BSA and lysozyme molecules have opposite electric charges at pH 7. Consequently, lysozyme rejection is large because both molecules within the filter cake pack more tightly due to heterocoagulation. On the other hand, the BSA and lysozyme molecules have the same electric charge at pH 4. Thus, lysozyme is rejected by the filter cake of the retained BSA molecules due to repulsive electrostatic interactions b...

Flux decline behavior in dead-end microfiltration of protein solutions

Constant pressure microfiltration of solutions of the protein bovine serum albumin (BSA) has been studied in a batch filtration cell without stirring. Flow resistance increased dramatically with time compared with the initial membrane resistance while most of the solutes passed through the membrane. The variation of the filtration flux rate with time during extended filtration periods could not be analysed by a unique blocking filtration law. The long-term decline in the filtration rate was accurately described by considering the variation of the value of the exponent i in the general characteristic form of the blocking filtration laws. It was found that the value of i continued to decrease with the progress of filtration. In addition, the effects on the filtration rate due to the solution pH, the filtration pressure, the fluid solute concentration, and the membrane type were described based on the general characteristic form of the blocking filtration laws.

Influence of protein adsorption on flow resistance of microfiltration membrane

Abstract It is well known that the flow resistance and sieving property of a membrane change when protein adsorption, which is a specific interaction between the protein and membrane, occurs within the pores. The influence of the protein adsorption on the membrane hydraulic permeability was examined using bovine serum albumin (BSA) as the model protein and a nitrocellulose microfiltration membrane. The Kozeny—Carman equation, which has been applied to the laminar flow in a granular bed, was employed for the description of the flow property of the tortuous pore membranes. The flow resistance of the membrane after BSA adsorption was well evaluated from the reduced porosity due to the protein adsorption in the pores. Also, the equivalent diameter of the pore space of both the clean and preadsorbed membranes was evaluated by introducing the expression for the hydraulic mean diameter. Furthermore, it was found that a more significant protein adsorption at around the isoelectric point brings about a larger increase of the flow resistance of the preadsorbed membrane.

Analysis of dead-end ultrafiltration based on ultracentrifugation method

Abstract In order to clarify the internal structures of the filter cake formed in protein ultrafiltration, ultracentrifugation experiments were conducted. The local specific flow resistance at the various solution concentrations was determined by the sedimentation velocity technique. The porosity was related to the solute compressive pressure by the high-speed sedimentation equilibrium technique. A method has been developed for evaluating the internal structures in the cake on the basis of a compressible cake resistance model using ultracentrifugation data. The decline in the filtration rate in dead-end ultrafiltration was accounted for by considering the internal structures of the compressible cake. The properties of the cake were determined from ultrafiltration experiments in which a filter was subjected to a sudden reduction in its filtration area. The results accorded well with the calculations. This study revealed that the filtration behavior of ultrafiltration can be accurately described by a compressible cake resistance model.

Effects of pH and solvent density on dead-end upward ultrafiltration

Abstract Upward ultrafiltration experiments, in which the filtrate flow is in the opposite direction of gravity, were conducted under a constant pressure of 98 kPa, using a dead-end filter. The filtration characteristics were studied using a protein (bovine serum albumin) solution of 0.6 wt.% to determine the effects of the solvent environment such as pH and the density of the solvent. A dynamically balanced rate of filtration can be obtained by this newly developed technique. This filtration rate ranges from 3.0 × 10 −4 cm/sec to 1.04 × 10 −3 cm/sec depending on the pH of the solution, with a distinct minimum near the isoelectric point (ca. 5.1). The results obtained from downward ultrafiltration experiments conducted by a batchwise filter having a sudden reduction in its filtration area show that a very compact gel-cake with an average porosity of 0.902, which is not exfoliated easily, forms on the membrane surface at the isoelectric pH. The dynamically balanced filtration rate in upward ultrafiltration is shown to be largely determined by the density of the solvent. A method was developed for determining the buoyant density of protein solutes on the basis of the results of upward ultrafiltration experiments performed at different values of the density of the solvent; a value of about 1.27 g/cm 3 was obtained for bovine serum albumin.

Filtrate flux in crossflow microfiltration of dilute suspension forming a highly compressible fouling cake-layer

The crossflow microfiltration characteristics of dilute suspension, which produces a highly compressible fouling cake-layer and/or a highly viscous filtrate, is studied under constant pressure. With the filtration conditions within a critical level, medium filtration at an earlier stage ceases, and crossflow microfiltration follows the principle of thin-cake filtration after operation begins. An equation for flux, which relates the cake resistance to a number of operational variables, is determined for the thin-cake filtration process by introducing a controlling parameter composed of the shear stress exerted at the cake surface and the coefficient of constant-pressure filtration. On the basis of an empirical correlation of the flux-controlling parameters, the effects of both cake-compressibility and filtrate-viscosity on the flux are evaluated.

Separation of binary protein mixtures by ultrafiltration

Ultrafiltration of aqueous solutions of mixtures of bovine serum albumin(BSA) and egg white lysozyme was conducted using membranes which were almost completely retentive for BSA, but permeable for lysozyme, in order to investigate the factors influencing the filtration rate and the lysozyme rejection. The experimental data obtained in this study clearly demonstrate that the electrostatic interactions between dissimilar molecules may control the filtration rate and solute rejection in ultrafiltration of binary protein mixtures to a significant degree. It is also shown that increasing the shear stress acting on the membrane causes an increase in the lysozyme rejection, resulting in a reduced fractionation efficiency, and that ultrasonic irradiation is quite effective for fractionation of binary protein mixtures. Furthermore, the properties of the filter cake formed on the retentive membranes in downward dead-end ultrafiltration of binary protein mixtures have been studied in a batchwise filter which has a sudden reduction in its filtration area. In the pH range where both proteins are electropositive, the filter cake becomes loose and wet, thus reducing the flow resistance, while the cake becomes compact and dry in the pH range where the two proteins have opposite electrical charges.

Fractionation Characteristics of Binary Protein Mixtures by Ultrafiltration

ABSTRACT Ultrafiltration (UF) of mixtures of bovine serum albumin (BSA) and egg white lysozyme was conducted using membranes which were almost completely retentive for BSA but permeable for lysozyme. The experimental data have clearly demonstrated that the separation properties of binary protein mixtures are largely influenced by the hydrodynamics above the membrane, the solution environment, and the adsorption of the protein solutes within the membrane. In particular, it must be noted that the increase of the shear stress acting on the membrane surface improves the filtration rate, but causes the increase of the lysozyme rejection, resulting in a reduction in the fractionation efficiency. Furthermore, the effects of ultrasonic irradiation on the UF properties have been tested experimentally. Although the filtration rate was enhanced significantly by ultrasonic irradiation, the lysozyme rejection remained unchanged. The results showed that ultrasonic irradiation is quite effective for protein fractionation.

Effect of protein charge on cake properties in dead-end ultrafiltration of protein solutions

Abstract The properties of the filter cake formed on the retentive membrane in dead-end ultrafiltration of bovine serum albumin (BSA) solutions were obtained by using a batchwise filter which had a sudden reduction in its filtration area. Moreover, the zeta potential of BSA was measured by the electrophoretic light scattering method in order to investigate the correlation with the properties of the protein cake. The experimental data clearly demonstrated that the plots of such properties of the filter cake as the average porosity ɛav and the average specific filtration resistance αav against the absolute value of the zeta potential can almost be represented by a unique curve, respectively, irrespective of the sign of the zeta potential.