Extraction equilibria of citric acid from aqueous solutions with trioctylamine in isodecanol/n-parafrins mixtures, were studied as a function of acid, amine and isodecanol concentrations at 25°C. The equilibrium data were interpreted by “chemical modeling” approach in which existence of (1,1) and (1,2) acid-amine complexes in the organic phase, were assumed. The corresponding equilibrium constants, which represent the experimental results the best, were determined.
Simpler mathematical model which refer to modified Langmuir isotherm, was also used for interpretation of the equilibrium data. Extraction constants and overall acid stoichiometric coefficient, which represent the experimental results the best, were determined. This mathematical form could be suitable in the analysis and design of the process in dynamic conditions.

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The radial distribution of solid concentration in the fully-developed flow region of a slurry bubble column was measured by an ultrasonic penetration method. The method allows the measurement of the solid holdup separately from the gas holdup by measuring the transmission time of the ultrasound transmitted through the three-phase medium. The solid concentration is maximum in the region near the column wall. The peak is sharpened with an increase in either the gas superficial velocity or the particle diameter, and is flattened with an increase in the liquid superficial velocity. The mechanism of the particle distribution is discussed by considering the role of lift force, diffusion force, interaction force caused by impaction between particles and bubbles, and interaction between the particles and liquid vortices in the bubble wakes. The effect of the interaction force seems to be significant in determining the structure of the particle concentration profiles in the slurry bubble column.

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Microencapsulation of biphenyl was carried out by varying the colloid concentration to investigate the microencapsulation of large oil droplets by the complex coacervation method. In dilute colloid solutions, the traditional model of the complex coacervation method is supported where coacervate droplets formed in the bulk solution adhere to oil droplets. However, in a solution of 3.0 wt% colloid, it was clarified that the microcapsule membrane was formed not by adhesion of the full-grown coacervate droplets, but by growth of small coacervate droplets adhering to oil droplets.
Spherical gelatine/acacia microcapsules with thicker membrane were successfully prepared by repeating the conventional complex coacervation method. The affinity of coacervate droplets to a core material is found to be a dominant factor in microencapsulation in the complex coacervation method.
The multi-layered microcapsules endured the release of encapsulated biphenyl, however the single-layered microcapsules were ruptured within a short time in release experiments, and a serious initial burst was induced. The multi-layered microcapsules prepared by repeating the conventional complex coacervation can be applied as a dosage form in the controlled release of active agents.

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The recovery of toxic metal compounds is a deep concern in all industrial countries. Hexavalent chromium is particularly worrying because of its toxic influence on human health. Actually the wastewater norm (0.1 g·m^-3) is very strict and will become more severe in the near future.
We present in this paper experimental results of Micellar Enhanced Ultrafiltration (MEUF) which is a suitable treatment for large volumes of effluents. A well known surfactant cetyltrimethylammonium bromide (CTABr) is used as complexing agent to remove the hexavalent chromium from wastewaters. As long as the feed concentration is less than or equal to 200 times the standard, more than 99 % of hexavalent chromium are retained and the permeate is satisfactory.

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Ion permeation experiments across a nanofiltration membrane were performed with NaCl at several pHs. A remarkable dependence of ion rejection on pH is observed. This phenomenon is considered to be caused by the change of surface charge, which results from the adsorption of ions onto the membrane pore wall. A model, which describes the diffusion of free ions within the membrane by the Nernst-Planck equation and adsorption of ions on the surface of the membrane by a Langmuir-type adsorption isotherm, is successfully applied to explain the experimental data.

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Supercritical water oxidation was used to break down municipal excess sludge. The reaction was carried out in a batch reactor with hydrogen peroxide as an oxidant in the temperature range of 473 K–873 K. The reaction products were analyzed in terms of total organic carbon (TOC), organic acids and ammonium ion. TOC decreases with temperature and oxidant amount. Acetic acid and ammonia are detected as major refractory intermediates in the product. When more than the stoichiometric demand of oxidant is used, organic carbon in liquid phase is almost completely destroyed. Complete destruction of ammonia produced during the reaction requires higher temperatures than that of acetic acid.

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The mixing of water and air has been studied in an agitated tank with narrow baffles. In such an agitated tank, the gas induction could be formed by the dead impellers operated above the critical impeller speed. Experimental parameters considered were the impeller speed, the baffle width, the clearance between lower impeller and tank bottom, the impeller diameter, the space between two impellers and the liquid level. Dimensional analysis and data regression gave a good correlation between the mixing time, the tank geometry and operational variables. It was found that an increase in impeller speed reduced significantly the mixing time. Too much reduction of baffle width, a decrease in the impeller diameter or a raise of liquid level can increase the mixing time. However, after gas induction achieved, the clearance between the lower turbine and the tank bottom has no significant effect on the mixing time.

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The process of freezing water which contains some impurities produces highly pure ice and concentrates impurities present in the liquid phase. It is found that during the freezing process, by agitating the interface of freezing ice, pure ice ran be made. We investigated the effects of supersonic radiation and the dissolved air concentration in the liquid on the efficiency of separation and concentration of glucose and sodium chloride under various freezing rates. The efficiency was greatly improved by supersonic radiation and increasing dissolved air concentration.

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The properties of adsorbents and adsorbates contributing to the enhancement in adsorption of binary gas mixtures were experimentally investigated. It is found that adsorbent is required to maintain the phenolic hydroxyl group and the carbonyl group as acidic surface oxides on the carbon surface, and to have a microporous structure for the main adsorption sites. Each gas component is required to be chemisorbed on the phenolic hydroxyl group or the carbonyl group on the adsorbent, and that both components are adsorbed in the micropores together. From the characterization of absorbents after adsorption-desorption runs, it is demonstrated that the adsorbates in the micropores exist at a higher density than in the bulk state through the promotion of micropore filling when adsorption enhancement appears.

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The problem of fluid transport inside ceramic, porous, multi-channel microfiltration membranes has been studied experimentally and computationally. The transport of permeate in a seven (star-shaped) channel tubular membrane is modeled according to Darcy’s equation for flow in porous media; the resultant Laplace equation is solved numerically on the complex, multi-connected geometry of interest using the Boundary Integral Method (BIM). Based on this model, we propose an efficient and novel procedure for determining the effective permeability (K_m) of the membrane module by comparing computational results with on-line experimental measurements of permeate flux at various levels of Trans-Membrane Pressure (TMP). Besides determining K_m, the proposed approach can be used to identify alternative designs and operating conditions in membrane modules of arbitrary geometrical complexity.

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A novel chitosan-supported sulfonic acid resin modified by propane sultone was prepared and the adsorption characteristics of metal ions are examined by using a crosslinked chitosan-supported sulfonic acid resin (PSC) and a crosslinked chitosan resin (CLC).
In the low acidity region, the metal selectivity of PSC is similar to that of CLC. This suggested that the selectivity of PSC was attributed not to the sulfonate group but to the chitosan matrix. The role of the sulfonate is believed to be enriching the metal concentration in the neighborhood of the chitosan matrix. At the same time, since the hydrogen ion is also enriched in a thin layer near the surface of the main, the characteristic adsorption curves of PSC shift to the high pH region compared with those of CLC. The adsorption equilibrium constants of metal ion on PSC and CLC are evaluated. The maximum adsorption capacity for PSC in the case of adsorption of copper is 1.6 times that of CLC. On the other hand, in the high acidity region, the maximum adsorption capacity for PSC in the case of adsorption of palladium is lower than that for CLC because of steric hindrance.

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Flow of liquid/liquid dispersions have been investigated in a Hele-Shaw cell which contained a thin disk held between two parallel plates. This device offers a well defined flow field and also permits visual observation of the dispersed drop movement. The dispersed drops coalesce with the disk for the systems where the dispersed phase wets the disk surface. The dispersed phase accumulate at the downstream end of the disk and they detach from there as blobs. Through an accurate measurement of accumulated dispersed phase volume, the coalescence rate was determined. The coalescence efficiency in the Hele Shaw cell is determined by dividing the coalescence rate by the undisturbed flow rate of the dispersed phase through an area equal to the projected area of the disk on a plane normal to the flow direction. The coalescence efficiency first increases and then decreases with the flow rate of dispersion. The coalescence rate/disk dimensions increases with the decrease in the disk dimensions. The rate of coalescence increases with the increase in the dispersed drop diameter and it decreases with the increase in the continuum phase viscosity. The presence of surfactants reduces the coalescence rate. All these results are quantitatively explained through a model, which takes into account several important features like various mechanism of drainage, the roles of dispersion and continuous phase viscosities, and the drop deformation.

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In the previous paper, we proposed fundamental techniques to model and simulate combined continuous processes and discrete event systems, including sequential control, and developed a simulation program package for general use. In this paper, we apply the combined simulation method to analyze a proposed design of spinning processes in the synthetic fiber production plant. Repeated simulation is effectively used to make an appropriate decision on the number of equipment items. This case study includes various concrete techniques for modeling and simulation, and will help the process designer to model large-scale and complicated systems, and to analyze system performances.

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The effects of unsteady agitation, which was carried out by counter rotation, or raising and lowering of an impeller, on mixing of viscous liquids in an agitated vessel are investigated experimentally. A decoloration reaction is adopted to observe the mixing pattern and to measure the mixing time. By steady agitation, the segregated regions are formed in a vessel equipped with a 4-bladed pitched paddle in the range of relative low Reynolds numbers less than 200. It is demonstrated that these segregated regions are readily destroyed when counter rotation is carried out and are prevented from forming when the impeller is raised and lowered.

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The effective thermal conductivities of porous coke-pitch mixtures were measured during cooling and heating processes. The thermal conductivity of the solid phase (λ_s) is estimated using a heat transfer model far a porous body. In the estimation, porosity was given based on experiments and thermal conductivity of gas phase is estimated using a pyrolysis model. The results demonstrated that λ_s is independent of temperature when no change in true density occurs, and that λ_s increases with increasing true density. λ_s is correlated with hydrogen content. The derived equation is used to predict the effective thermal conductivities of the mixtures and packed coals during carbonization. Pyrolysis models, heat transfer models and models describing macroscopic physical changes am constructed. The models agree with the experiments. This fact shows the applicability of the developed equation to coal.

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A methodology for molecular dynamics simulation of alkaloid adsorption onto solid surfaces from solutions is developed by employing berberine as a model alkaloid, and water, methanol and N,N-dimethylformamide (DMF) as model solvents. A single berberine molecule and a solvation shell around it are considered as the solution madel. The behavior of berberine at the vacuum-solid interface and at the solution-solid interface were simulated, and it is found that a berberine molecule adsorbed with its molecular plane parallel to the graphite surface is most stable, and the molecular conformation does not change considerably during dissolution in the solvents and adsorption onto the graphite. Also, the solvent effects on the adsorption are focused on by analyzing the potential energy change of berberine molecule being adsorbed onto the graphite surface from the solutions by molecular dynamics calculations, and discussed quantitatively by combining solvophobic theory and calculations of the potential energy by molecular simulation. It is known that the presence of water or methanol has little effect on the adsorption of berberine onto the graphite surface, and that the presence of DMF inhibits the adsorption of berberine significantly. It can be said that the methodology developed in this work is useful for studying the solvent effects on adsorption, and for choosing proper solvents in adsorptive separation and purification processes for alkaloids.

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A disaster in a process plant is sometimes enlarged by its propagation to another part of the plant, and only a properly arranged process plant can prevent such a chain disaster. Therefore, safety must be considered in arranging equipment modules in the early design phase. Previously, only economical factors were focused on, and safety was considered after decided the plant layout. The purpose of this study is to develop a method to arrange the equipment modules with consideration of required safety. To consider chain disasters, not only the positions of the equipment modules, but also their directions become the decision variables, thus the problem is an enormous combinatorial optimization one. In this sturdy, a characteristic of this problem is considered, and an evolutionary searching method is found to be suitable. In the proposed method, the equipment modules are divided into module groups for the first step, and sub-arrangements within each group are generated under the consideration of safety. An initial arrangement is obtained by merging these sub-arrangements, and this arrangement is brushed up by alternating the location and the direction of the equipment modules. Finally, the effectiveness of the proposed method is demonstrated by solving an example problem.

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A corona-discharge reactor is applied to removal of CH₃I from N₂ in the presence of H₂O and O₂. In the reactor, CH₃I is converted to negative ions, negative-ion clusters or particles by electron attachment or O₃ in the presence of H₂O and O₂. In the removal of CH₃I from N₂, since one electron contributes to remove about three CH₃I molecules, radicals reactive with CH₃I are thought to be produced by the dissociative electron attachment. The removal efficiency of CH₃I is greatly improved by mixing H₂O or O₂ with gas. In these removals, one electron removes about seven CH₃I molecules from a N₂-H₂O mixture, about ten CH₃I molecules from a N₂-O₂ mixture, and about twelve CH₃I molecules from a N₂-O₂-H₂O mixture. A long term removal experiment indicates that the high removal efficiency of CH₃I from the N₂-O₂ mixture is maintained for an extended period, even after the anode surface is covered with the deposit of removed CH₃I. In the removal of CH₃I from a N₂-O₂ mixture, O₃ reaction improves the removal efficiency. Alan, the formation of negative-ion clusters is important for this high removal efficiency. Ab initio MO calculations suggest that the negative-ion clusters, O^–[CH₃I]_m (m = 1, 2, 4), OH^–[CH₃I]_m (m = 1, 2, 4) and H^–[CH₃I]_m (m = 1,2), are produced with a high probability. It is also suggested that O radicals do not influence the removal of CH₃I.

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As a novel procedure to immobilize enzymes, lysozyme was dissolved in the molecular assembly of the nonionic surfactant Triton X-100 adsorbed on silica gel. The adsorption isotherms of Triton X-100 on silica gel, and of lysozyme in the molecular assembly of adsorbed Triton X-100 on silica gel, were obtained. The isotherm for the latter are significantly influenced by pH and buffering agents, while the isotherms for the former are not. Moreover, the adsorption of lysozyme was affected by the ionic strength of the buffering agents. Leakage of immobilized lysozyme is influenced by pH and temperature; it is found that much lysozyme leaked when pH and temperature were low. However, under limited conditions the immobilized enzyme is very stable. The immobilized lysozyme was used in the enzymatic hydrolysis reaction of the water-soluble chitin derivative glycol chitin. The enzymatic reaction obeys the Michaelis-Menten mechanism and the values of kinetic parameter, Michaelis constant K_m and maximum velocity V_max, are estimated. The apparent activation energy E_a is also obtained.

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Energy transformation is discussed from the viewpoint of the intermediary energy released or accepted by a change of substance. To display the results on a microscopic EUD (Energy-Utilization Diagram), the internal transformation in the process itself and the external transformation between different processes are demonstrated separately. The method is applied to two kinds of exothermic reactions and an endothermic reaction, energy-conserved processes with ΔH = 0 such as heat conduction, pressure drop and osmotic pressure and the energy transformation in the electrolyte in a fuel cell. It is found that this method reveals the internal mechanisms in complex energy transformation quite clearly.

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Supported ruthenium catalysts which showed high activity for high-molecular-weight hydrocarbon synthesis from CO and H₂ are studied in under gas-phase, liquid-phase, and supercritical-phase reaction conditions. The calcination temperature effect of the catalysts is investigated. The supercritical phase reaction process is most favorable for high-molecular-weight hydrocarbon synthesis, due to its stable activity, strong extraction capacity and high mass transfer efficiency. Addition of a small amount of middle olefins into a supercritical-phase Fischer-Tropsch (F-T) reaction medium significantly promotes carbon-chain growth and greatly enhances the selectivity of waxy products with slightly-decreased CO conversion, while suppressing methane selectivity and carbon dioxide selectivity. The hydrocarbon products thus formed exhibit anti-ASF distribution.

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Non-uniform radial and axial flow structures are characteristic of circulating fluidized beds (CFB). As a result, gas solids contact is still relatively poor in the riser although much better than in the bubbling bed. In this study, the influence of ring-type internals on the reduction of nonuniformity in a riser of 7.6 cm in diameter and 3 m in height was investigated. Three ring internals with open areas of 70%, 90% and 95% were installed in five axial positions in the riser. Measurement results for solids hold-up distribution of sand particles obtained using a fibre optic probe indicate that the internals can reduce radial nonuniformity, and evenly redistribute solids in the radial direction. Under high superficial gas velocities and low solids circulation rates, reversed radial solids distribution profiles with more dilute flow in the wall region than in the core region were also observed. A detailed study on the radial solids distributions around the ring internals shows the formation of a denser region above the 70% opening ring as compared to above the 90% and 95% opening internals and a mom dilute region below all three rings. Results of the axial voidage distribution with the presence of internals show the formation of a zigzag type axial profile instead of the regular S-shape profile.

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Fe oxide and composite Ti-Fe oxide ultrafine particles have been prepared using sodium big (2-ethylhexyl) suffosoccinate (Aerosol OT; AOT)/isooctane reverse micellar solutions. Fe₂O₃ particles were prepared by mixing a miceller solution containing sulfuric acid solution of ammonium irom (III) sulfate with an “alkaline” or a “neutral” micellar solution containing NaOH solution or distilled water, respectively. The formation of TiO₂ particles by adding titanium tetrabutoxide (TTB) to a micellar solution was also facilitated by NaOH. Simultaneous feeding of both TTB and Fe³⁺ solutions did not form composite particles but only Fe₂O₃ particles, indicating that the presence of Fe³⁺ prevented the formation of cores of TiO₂. The TiO₂ particles were thus prepared at first in the micellar solution, to which Fe³⁺-containing micellar solution was fed. The resulting particles possibly have a structure in which TiO₂ particles are coated by Fe₂O₃ thin layer.

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