Toshikuni Yonemoto

The effect of the hydrophobicity of microchannels and components in water and oil phases on droplet formation in microchannel water-in-oil emulsification

Abstract The effects of the hydrophobicity of silicon microchannels and components in the oil and water phases in the production of monodispersed water-in-oil (W/O) emulsions by microchannel emulsification was investigated. Several types of silane coupler reagents were applied to make the microchannel hydrophobic. The hydrophobicity of the surface was evaluated by contact angle measurements. Hexane, decane and oleic acid were used as the oil phase, and pure water and sucrose solution were used as the water phase. Tetraglycerol polyricinoleate, sodium bis(2-ethylhexyl) sulfosuccinate and sorbitan fatty acid esters were used as surfactants. The contact angle of a water droplet on the modified silicon microchannel plate in an oil phase was found to be dependent on the composition of the oil phase, the surfactant type and the silane coupler reagent used for surface modification. When the contact angle was greater than 120°, monodispersed water droplets were formed and the geometric standard deviation was below 1.06. The average droplet size varied from 17 to 23 μm, and was affected by the characteristics of the surfactant and the viscosities of the water and oil phases.

Kinetics of ultrasonic disinfection of Escherichia coli in the presence of titanium dioxide particles.

The ultrasonic disinfection of Escherichia coli was carried out in the presence of anatase‐type TiO2 particles, and the effectiveness of the combination of ultrasonic irradiation with TiO2 addition was verified. The rate constant was determined from the plot of the common logarithm of the survival cell ratio versus the ultrasonic irradiation time using first‐order kinetics. In the absence of particles, the rate constant was proportional to the ultrasonic power. When ultrasonic disinfection was carried out in the presence of TiO2 particles, which have a radical generation ability, the rate of disinfection was remarkably faster than that in the absence of TiO2. In the presence of silica particles, which have no radical generation ability, the rate of disinfection was the same as that in the absence of TiO2. These results suggest that the radical generation ability of TiO2 appeared as a result of the ultrasonic irradiation. The effect of the amount of TiO2 on the rate of disinfection was also examined. The rate constant for disinfection in the presence of TiO2 was saturated to a certain value and was represented using the Langmuir‐type equation. The proposed model well describes the effects of the ultrasonic power and the amount of TiO2 on the rate constant for disinfection.

Investigating the differences in acid separation behaviour on weak base ion exchange resins

Differences in acid separation behaviour on weak base ion exchange resins have been investigated in this work. Experimental data has been obtained on sorption equilibrium using various types of weak base resins and both inorganic and organic monobasic acids. A detailed analysis has been presented using the experimental data of present work and also that reported in the literature. Apart from acid concentration and type of acid, other factors such as resin type and basicity are also discussed. It was found that, resins with high basicity are most suitable for the acid removal applications. For resins with medium and weak basicity, large variation in the sorption capacity with concentration was observed. A new theoretical approach incorporating effect of resin basicity has been proposed and examined qualitatively and quantitatively using the sorption data. The results substantiate reversibility of sorption through lower values of protonation equilibrium constants and also indicate incomplete resin salt dissociation in some cases.

The desalination of a mixed solution of an amino acid and an inorganic salt by means of electrodialysis with charge-mosaic membranes

Abstract A new electrodialysis with charge-mosaic membranes was proposed to achieve efficient desalination of a mixed solution of an amino acid and an inorganic salt. For such a mixed solution, the conventional electrodialytic desalination with both cation-and anion-exchange membranes had resulted in a considerable loss of the amino acid through the membranes. In this method, however, the amino acid in the desalination channel of the electrodialyzer migrates away from the membranes so that the permeation loss of the amino acid through the membrane can be prevented. Batchwise desalination experiments by this method were carried out with a glutamic acid or arginine solution including NaCl under the condition of constant electric current density. Similar experiments by the conventional method were also carried out. As a result of comparing both methods, the amino acid loss in this method became much smaller than that in the conventional one. It was confirmed that this method was very useful for the desalination of an amino acid solution. The effects of operating conditions on the desalination process are also discussed.

THE DETERMINATION OF DIFFUSION COEFFICIENTS OF COUNTER-IONS IN THE ION-EXCHANGE MEMBRANE BY MEANS OF BATCHWISE DONNAN DIALYTIC EXPERIMENTS

Abstract A new method, based on the Nernst-Planck equation, has been proposed for determining diffusion coefficients of counter-ions in an ion-exchange membrane for bi-ionic Donnan dialysis. This method involves dialytic experiments in which both the solution concentration and the membrane potential are measured under the condition controlled by diffusion resistance in the membrane. It also involves mathematical optimization treatment of the experimental data. The K + −H + system with a cation-exchange membrane was studied, and the optimum diffusion coefficients of these counter-ions were obtained. The diffusion coefficients were found to vary with the ionic composition of the solution. The theoretical time courses of the concentration and membrane potential calculated by using the optimum diffusion coefficients agreed with the experimental results.

Simultaneous production of high quality biodiesel and glycerin from Jatropha oil using ion-exchange resins as catalysts and adsorbent.

The simultaneous production of high quality biodiesel and glycerin was realized by a bench-scale process using expanded-bed reactors packed with cation- and anion-exchange resins. The mixed-solution of crude Jatropha oil and methanol at a stoichiometric molar ratio was supplied to the process. The free fatty acid as well as triglyceride was completely converted to biodiesel. All by-products were adsorbed on the resin and the effluent from the process was free from them. The effluent fully met the international biodiesel standard specifications without any downstream purification processes except for removing methanol. The glycerin adsorbed on the resin was completely recovered as a transparent methanol solution during regeneration of the resin.

Pretreatment combining ultrasound and sodium percarbonate under mild conditions for efficient degradation of corn stover.

Ultrasound (US) can be used to disrupt microcrystalline cellulose to give nanofibers via ultrasonic cavitation. Sodium percarbonate (SP), consisting of sodium carbonate and hydrogen peroxide, generates highly reactive radicals, which cause oxidative delignification. Here, we describe a novel pretreatment technique using a combination of US and SP (US-SP) for the efficient saccharification of cellulose and hemicellulose in lignocellulosic corn stover. Although US-SP pretreatment was conducted under mild condition (i.e., at room temperature and atmospheric pressure), the pretreatment greatly increased lignin removal and cellulose digestibility. We also determined the optimum US-SP treatment conditions, such as ultrasonic power output, pretreatment time, pretreatment temperature, and SP concentration for an efficient cellulose saccharification. Moreover, xylose could be effectively recovered from US-SP pretreated biomass without the formation of microbial inhibitor furfural.

Biodiesel Production from Waste Cooking Oil Using Anion-Exchange Resin as Both Catalyst and Adsorbent

A novel production process of biodiesel fuel was developed using an expanded-bed reactor packed with an anion-exchange resin having catalytic and adsorption abilities. Waste cooking oil was used as a cheaper feedstock, and methanol was added at the stoichiometric molar ratio of 3:1. The main constituent of the feedstock, triglyceride was completely converted to the biodiesel by the resin’s catalytic ability. The impurities of the feedstock, free fatty acid, water, and dark brown pigment were removed from the product by the adsorption on the resin. In addition, the by-product glycerin was also removed from the product by the adsorption on the resin. The product eluted from the reactor was directly used for the standard tests of the biodiesel properties. The eluted product almost met the biodiesel quality standards (EN14214 in Europe and ASTM D6751 in North America). Thus, the proposed system permitted the simple production of biodiesel from the waste cooking oil without the upstream processing to remove the impurities (free fatty acid and water) and the downstream processing to remove the catalyst and by-products (glycerin and soap).

Improvement of Catechin Productivity in Suspension Cultures of Tea Callus Cells

In the suspension cultures of tea callus cells, C.sinensiscv. Yabukita, the effects of the culture conditions, such as culture period and light irradiation, on cell growth and catechin production were investigated. The production of flavonoids (catechins + proanthocyanidins) was promoted by inoculating the cells into the fresh medium at the culture period giving the maximum flavonoid content in the cells. The cultivation under light irradiation was repeated several times by inoculating the cells with the maximum flavonoid content. The flavonoid production was significantly increased without inhibiting the cell growth. We obtained the maximum flavonoid production, 1.5 g/dm3 medium, and the maximum content, 150 mg/(g of dry cell weight (DCW)). The latter value was larger than that in the leaves of the tea plant.

Continuous Synthesis of Titanium Dioxide Fine Particles Using a Slug Flow Ageing Tube Reactor

A continuous reactor system for titanium dioxide fine particle synthesis has been proposed, in which a packed bed for the nucleation of fine particles was connected in series with a slug flow ageing tube for growth of the particles. By injection of nitrogen gas into the inlet of the ageing tube, the continuous liquid feed was separated into small portions so that slug flow was formed. Spherical unagglomerated fine particles of titanium dioxide were obtained using this reactor system, and the effectiveness of using slug flow was elucidated. The effects of some operation variables such as liquid flow rate in the ageing tube and tube diameter were also examined. The particles obtained under the slug flow condition had narrower particle size distribution than those under a laminar flow condition at any flow rate. Particle geometric standard derivation (GSD) was found to be as small as that obtained in a batch process. No quality difference in particle GSD exists between ageing tubes of 2 mm i.d. and 3 mm i.d. for the slug flow. Chronomal analysis assuming diffusion-controlled growth was applied and was found to be effective for simulating a continuous particle synthesis process of titanium dioxide.