Masashi Iwata

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 .

Application of Electroosmosis for Sludge Dewatering—A Review

This work aims at providing an outline of engineering applications for electroosmosis, especially for sludge dewatering. A review of the theoretical analysis of electroosmotic dewatering is presented. The equations representing electroosmotic flow through porous media are initially discussed. Consolidation theory, which describes the progress of dewatering, is then described. In addition, various empirical research results addressing the effects of operational conditions and conditioning of sludge on both energy consumption and final water content of the sludge are reviewed. It is anticipated that this review will provide useful information to researchers pursuing solid–liquid separation of difficult-to-dewater materials such as sludge.

Synthesis and Magnetic Properties of Ultrafine Iron Particles Prepared by Pyrolysis of Carbonyl Iron

Magnetic characteristics of fine iron particles prepared by a new chemical process, were studied. In this semi-industrial process, iron pentacarbonyl, Fe(CO)5 was used as a starting material, and it was thermally decomposed under a magnetic field. Diameter of obtained particles was between 150 and 250 A, and the particles were aligned along the magnetic field like a necklace. The highest coercive force appeared when particle diameter was about 200 A. To stabilize the particles, surfaces of particles were slightly oxidized before they were exposed to the open air. The saturation magnetization of treated particles was about 70% of the bulk value. Some test tapes were made by using these fine iron particles.

Analysis of Combined Electroosmotic Dewatering and Mechanical Expression Operation for Enhancement of Dewatering

This article presents an efficient approach for the analysis of combined electroosmotic dewatering (EOD) and mechanical expression (ME) using the Terzaghi-Voigt combined model by considering creep deformation of the material. The EOD-ME process enhances dewatering because it combines the advantage of electroosmosis and mechanical dewatering, resulting in reduced void ratio compared to individual operation. The basic differential equation based on the model is solved analytically by assuming that both an electroosmotic pressure gradient E pg and a modified consolidation coefficient C e of the material are constant, resulting in the equation of solid compressive pressure in the material as a function of time and position. The analysis also leads to the equation of the average consolidation ratio U c, which is a measure of the progress of dewatering; this equation can describe well the empirical results under various conditions. The proposed approach can clearly explain the relationship of the driving forces of individual mode of operation. The large water content of semisolid bentonite–water mixture can effectively be reduced by the EOD-ME combined operation analyzed in this research.

Concentration of Proteinaceous Solutions with Superabsorbent Hydrogels

Abstract A process is investigated quantitatively for concentrating dilute aqueous bovine serum albumin solutions with superabsorbent crosslinked hydrogels. In the process, the gel swells by absorbing water only while macromolecules are excluded, thus producing a concentrated retentate. The concentration of the retentate is about 5.8 times larger than that of the feed for a dosage of dry gels of 0.63% by weight. The dynamic behavior of the concentration process is described by using the equation of motion of the gel network on the basis of the kinetics of the swelling of the gel. The pore size of the hydrogen controlling the sieving property is estimated from measurements of the permeation rate of water through the compressed, packed bed of the swelling gels, known as the compression-permeability test. It is demonstrated that slight stirring during the concentration process is accompanied by a rapid removal of the BSA filter cake on the gel surface, leading to efficient concentration.

Rapid enzyme-linked immunosorbent assay with functional magnetite particles

Ultrafine magnetite particles were applied to enzyme-linked immunosorbent assay (ELISA). For the assay of mouse IgG, anti-mouse IgG antibody or protein A was immobilized on the magnetite particles. The assay strategy was based on the sandwich method. Using anti-mouse IgG-magnetite and the spectrofluorometry, the mouse IgG standard curve was linear when the IgG concentration was between 5 μ g/ l -5 mg/ l . Using these functional magnetite particles, we could shorten the assay time to one thirty-fifth that of the conventional method.

Effect of Operating Parameters on the Effectiveness of Electric Field-Enhanced Separations

The purpose of this work is to summarize our latest research results about constant-current electroosmotic dewatering (EOD). The Terzaghi-Voigt combined model is used for the analysis of EOD of various solid-liquid systems by considering the creep deformation of the material. Bentonite clay, KC-flock, zinc oxide, and some of their mixtures are used as experimental materials. It is assumed that the electroosmotic pressure gradient E pg and modified consolidation coefficient C e of the materials are constant. The relation between the ratio of creep deformation to total deformation B and the modified consolidation coefficient C e is determined and compared with previous observations for the case of mechanical expression. The effectiveness of dewatering is described depending on operating parameters such as preconsolidation pressure, material composition, electric current density, and total solid volume per unit cross-sectional area. The model is verified by comparing the calculations with experimental data.

DELIQUORING BY EXPRESSION -PART 1 CONSTANT-PRESSURE EXPRESSION

Abstract The basic analitical method for so-called expression operation, the separation of liquid from solid-liquid systems by compression, are presented in view of the flow through compressible porous media. It has become evident that the expression mechanism consists of two flow phenomena. These types of phenomena can be analyzed by consideration of the flow mechanism through compressible porous beds, first by the filtration theory and second by the so-called consolidation theory. A simplified equation is also presented. It is shown that the simplified equation is well applicable to industrial expression problems even when the creep effects of matarials to be expressed are appreciable

A New Method for the Theoretical Analysis of Electroforced Sedimentation Using Terzaghi‐Voigt Combined Model

Abstract In this article a new method for the theoretical analysis of electroforced sedimentation (EFS) by use of the Terzaghi‐Voigt combined model is presented. Zinc oxide and a mixture of zinc oxide and KC‐flock are used as experimental materials. Both the electro‐osmotic pressure gradient E pg and the modified consolidation coefficient C e of the materials are assumed to be constant. The analytical solution can explain the solid compressive pressure distribution with time and position. The progress of electroforced sedeimentation can be represented by an average consolidation ratio U c as in mechanical expression. Variations of the effectiveness of EFS with the percentage of KC‐flock in the mixture, electric current density, and total solid volume per unit cross‐sectional area are investigated. EFS is best applied for materials with permanent charge.

PRESS DEWATERING OF BROWN COAL : PART 2 -BATCH AND CONTINUOUS-SCREW OPERATIONS-

ABSTRACT The brown coal is wet-ground and expressed in a batch constant-pressure or constant-rate operation and in a continuous screw-press operation. It is found that 90% of the moisture of the as-mined coal can be removed under the pressure of about 100 ma. Batch operations under a constant-pressure or a con-stant-rate can be analyzed well by using the Terzaghi-Voigt model and constant-pressure analysis. In a continuous screw-press operation, the resistance of the filter medium, the feed concentration and the die resistance affect the screw performance. The volumetric discharge rate under the open discharge condition can be expressed well by a lubrication theory. With discharge restricted by a screw-type die, the slip factor decreases with increase in die resistance.