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Dive into the research topics where Hirotaka Uchiyama is active.

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Featured researches published by Hirotaka Uchiyama.


Separation Science and Technology | 1994

Removal of divalent metal cations and their mixtures from aqueous streams using micellar-enhanced ultrafiltration

John F. Scamehorn; Sherril D. Christian; Dawlat A. El-Sayed; Hirotaka Uchiyama; Samia S. Younis

ABSTRACT Micellar-enhanced ultrafiltration (MEUF) is a novel membrane-based separation technique that can be used to remove multivalent metal cations from aqueous streams. In this technique an anionic surfactant is added to the aqueous stream containing the metal cations to be removed. The surfactant forms highly charged aggregates called micelles onto which the metal cations adsorb or bind. The aqueous stream is then passed through an ultrafiltration membrane with pores small enough to block the passage of the micelles and adsorbed metal cations. In this study, MEUF has been shown to remove divalent cadmium, zinc, copper, and calcium ions and their mixtures with rejections of at least 96%. A previously developed equilibrium binding model describes the results successfully. Under reasonable conditions the flux rates are not substantially below that of pure water, indicating the feasibility of MEUF for industrial application.


Journal of Colloid and Interface Science | 1992

Solubilization of synthetic perfumes by nonionic surfactants

Yoshikazu Tokuoka; Hirotaka Uchiyama; Masahiko Abe; Keizo Ogino

Abstract The solubilization of synthetic perfumes (eugenol, linalool, benzyl acetate, α-Ionone, α-hexylcinnamaldehyde, and d -limonene) by hexadecyl polyoxyethylene ethers (C 16 POE n , n = 10, 20, 30, and 40) has been studied in terms of cloud point, maximum additive concentration, solubilizing capacities, distribution coefficient, and micellar size. The greater the hydrophilic properties of synthetic perfumes, the more the cloud points of C 16 POE 10 solution are decreased. The maximum additive concentration and solubilizing power are increased with decreasing polyoxyethylene chain length, except for eugenol and linalool. The distribution coefficients of eugenol, linalool, and benzyl acetate between micelle and bulk phase are increased as the number of ethylene oxides in C 16 POE n decreases. The diameters of micelles containing solubilized synthetic perfumes are increased with increasing concentration of synthetic perfumes dissolved. Furthermore, for C 16 POE 10 solution, the diameters of micelles solubilizing eugenol and linalool are increased substantially in the vicinity of each maximum additive concentration.


Colloid and Polymer Science | 1994

Phase diagrams of surfactant/water/synthetic perfume ternary systems

Yoshikazu Tokuoka; Hirotaka Uchiyama; Masahiko Abe

The phase diagrams of hexadecyl polyoxyethylene ether (C16POE10)/water/synthetic perfume, and sodium dodecyl sulfate (SDS)/water/synthetic perfume ternary systems were prepared. The synthetic perfumes used are, d-limonene, α-hexylcinnamaldehyde, α-ionone, benzyl acetate, linalool, and eugenol. In a series of C16POE10/water/synthetic perfume ternary systems, as the hydrophilicity of synthetic perfume increases, the regions of normal and inverse micellar solution phases were found to be extended, while that of the lamellar liquid crystal phase was reduced. Moreover, every region of normal micellar solutions, inverse micellar solutions, and lamellar liquid crystal phases in SDS/water/synthetic perfume ternary systems was found to be smaller than those in C16POE10/water/synthetic perfume systems.


Colloids and Surfaces A: Physicochemical and Engineering Aspects | 1997

Use of polyelectrolyte-surfactant complexes in colloid-enhanced ultrafiltration

Wen Guo; Hirotaka Uchiyama; Edwin E. Tucker; Sherril D. Christian; John F. Scamehorn

Water-soluble polyelectrolyte-surfactant complexes, involving oppositely charged species, can form at quite low thermodynamic activities of the surfactant. This fact can be exploited in colloid-enhanced ultrafiltration separations, where both molecular organic pollutants and toxic ions are to be removed from contaminated aqueous streams. Investigations have been made of (a) the solubilization and ultrafiltration of solutions of organic solutes in polymer-surfactant solutions, for comparison with studies of micellar surfactant solutions in the absence of added polymers; (b) the penetration of surfactant through the membrane (leakage of monomer) in dialysis and ultrafiltration experiments; and (c) the utility of polyelectrolytes as ‘scavengers’ for surfactant species that enter the permeate or filtrate in colloid-enhanced ultrafiltration separations. Polyelectrolytes chosen for the studies are sodium poly(styrenesulfonate) and poly(dimethyldiallylammonium chloride); the surfactants are cetylpyridinium chloride (hexadecylpyridinium chloride) and sodium dodecylsulfate. A detailed study has been made of the solubilization and separation ofp-tert-butylphenol in aqueous mixtures of sodium poly(styrenesulfonate) and cetylpyridinium chloride, at polyelectrolyte to surfactant mole ratios of two to one.


Journal of the American Oil Chemists' Society | 1988

Solution properties of mixed surfactant system: sodium dodecyl sulfate and alkyl polyoxyethylene ether system

Keizo Ogino; Toshlaki Kakihara; Hirotaka Uchiyama; Masahiko Abe

The effect of oxyethylene groups in a nonionic surfactant on the solution properties of anionicnonionic systems is described; these systems are sodium dodecyl sulfate (SDS)—hexadecyl polyoxyethylene ethers (C16POEn, where n=10, 20, 30 and 40). The degree of ionic dissociation of the mixed micelles decreases with increasing numbers of oxyethylene groups in the nonionic surfactant. As polyoxyethylene chain lengths increase, the electrical conductivities of the mixed surfactant solutions decrease, in spite of the decrease in activation energy for conduction. The radius of the mixed micelle with the electric double layer is larger for a nonionic surfactant having a shorter polyoxyethylene chain length than for one having a long polyoxyethylene chain. This may be attributed to the fact that the mixed micelle is formed more easily by a nonionic surfactant with a shorter polyoxyethylene chain length than by one with a longer chain.


Colloids and Surfaces B: Biointerfaces | 1993

Stability of surfactant vesicles formed from cationic didodecyldimethylammonium bromide

Yukishige Kondo; Masahiko Abe; Keizo Ogino; Hirotaka Uchiyama; Edwin E. Tucker; John F. Scamehorn; Sherril D. Christian

Abstract The solution properties of didodecyldimethylammonium bromide (DDAB) vesicles, including their relative stability, were estimated by measuring the vesicular diameter, the trapping efficiency of glucose, the aggregation number, and the ζ potential. DDAB vesicles with diameters in the range 17–40 nm were stable for long periods of time. However, 50 nm vesicular solutions were unstable and showed phase separation after 4 days. The DDAB vesicles were observed to have positive ζ potential values independent of diameter. The stability of vesicles may be attributed to electrostatic repulsive forces between the vesicles. Also, the glucose trapping efficiency for the 17 nm vesicle solution was 0.57%, and increased with an increase in vesicular diameter up to 2%. The results indicate that DDAB vesicles with small diameters (17 nm) have an inner phase. Further, the surface charge density calculation showed that 8–13% of DDAB molecules constituting the outside of the vesicles are charged, preventing the vesicles from fusing or flocculating in the aqueous solution and stabilized vesicle solution.


Colloid and Polymer Science | 1994

On the interpretation of solubilization results obtained from semi-equilibrium dialysis experiments

Sherril D. Christian; Edwin E. Tucker; John F. Scamehorn; Hirotaka Uchiyama

The interpretation of intramicellar solubilization data obtained from semi-equilibrium dialysis (SED) experiments is described, and methods are presented for determining equilibrium constants for the solubilization of organic species by aqueous surfactant solutions as well as activity coefficients of both the organic solute and the surfactant within the micelle. The solubilization equilibrium constant of an organic solute in an aqueous micellar solution (K) is defined as the ratio of the mole fraction of organic solute in the micellar “pseudophase” (X) to the concentration of the unsolubilized monomeric organic solute in the aqueous phase (c0). Expressions compatible with the Gibbs-Duhem equation are used to represent the concentration dependence of activity coefficients of both the solubilizate and surfactant in the micellar pseudophase; the analysis leads to calculated values of the concentrations of free and intramicellar surfactant and organic solute in both compartments of the equilibrium dialysis cell. Solubilization equilibrium constants for many amphiphiles are well correlated by the simple expressionK=K0(1-BX)2, whereB is an empirical constant andK0 is the limiting value ofK asX approaches 0.


Journal of Colloid and Interface Science | 1987

Fading phenomenon of azo oil dye in anionic-nonionic surfactant solutions

Keizo Ogino; Hirotaka Uchiyama; Mitsuo Ohsato; Masahiko Abe

Abstract Fading phenomena of azo oil dyes in aqueous solutions of mixed surfactant systems have been studied by spectrophotometry. The fading phenomenon is observed when 4-phenylazo-1-naphthol (4-OH) is added to an aqueous solution of a mixed surfactant system (anionic-nonionic), although it does not occur in single surfactant solutions or in cationic-nonionic mixed surfactant system solutions. The fading rate of 4-OH is dependent on the concentrations of the mixed surfactant system and dye and on the molar ratios of the surfactants. A typical system occurs at 1.0 × 10 −2 mole/liter of mixed surfactant, about 6.0 × 10 −5 mole/liter of dye, and 0.5 molar ratio of surfactant. No fading phenomenon is observed when naphthalene-1-azobenzene (NA) is added to aqueous solutions of the mixed surfactant system at any mole fraction. This may be because, when a tautomer of azo oil dye penetrates the palisade layers of micelles, the singlet oxygen due to the hydrophilic-hydrophilic interaction between anionic and nonionic surfactant molecules attacks the azo groups of the tautomer.


Journal of Colloid and Interface Science | 1989

Solubilization of oil—soluble azo dye by anionic—nonionic mixed surfactants in aqueous solutions, II

Hirotaka Uchiyama; Yoshikazu Tokuoka; Masahiko Abe; Keizo Ogino

Abstract The solubilization of oil-soluble azo dyes by anionic—ninionic mixed surfactants was studied by spectrophotometric methods: these systems are sodium dodecyl sulfate (SDS)—alkyl polyoxyethylene ethers (C m POE n ; m = 10 and 18 at n = 10 and 40 m = 16). This maximum additive concentration and solubilizing capacity of pure C m POE n solutions exceeded those of pure SDS solutions. The influence on the maximum additive concentration and solubilizing capacity was due to a greater difference in hydrophobic groups in nonionic surfactants than in hydrophilic groups. In the mixed surfactant systems, the maximum additive concentrations are made larger by nonionic surfactants including longer alkyl chains and/or longer polyoxyethylene chains. The amount of increase was larger in the system in which two kinds of micelles, one rich in anionic surfactant and the other rich in nonionic surfactant, exist than in system of mixed micelles. The presence of the oil-soluble azo dye asissts the mixed micelle formation.


Journal of Colloid and Interface Science | 1990

Viscosities of anionic—nonionic mixed surfactant systems

Hirotaka Uchiyama; Masahiko Abe; Keizo Ogino

The viscous property of anionic-nonionic mixed surfactant systems in aqueous solutions is described. The systems studied are sodium dodecyl sulfate (SDS)-alkyl poly(oxyethylene) ethers (CmPOEn; m = 12, 14, 16, and 18, n = 10, 20, 30, and 40). In the single system, the relative viscosity of the nonionic surfactant is larger than that of SDS and increases with increasing number of ethylene oxide. In mixed systems the relative viscosity shows maximum at the mixed molar ratio of SDS around 0.3, except for the SDS-C16POE40 system. The mixed systems having longer alkyl and/or polyoxyethylene chain lengths in the nonionic surfactant have a larger relative viscosity at any mixed ratio. The system in which the mixed micelle forms easily has a positive deviation from the ideal value. The relative viscosities of the surfactants in 0.1 M NaCl solution decrease linearly with an increase in the mixed molar ratio of SDS. It is considered that the relative viscosities in the mixed solutions show a maximum due to the electroviscous effect of a mixed solution being larger than that of a single solution.

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Masahiko Abe

Tokyo University of Science

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