Tahei Tomida

Micelle formation of sodium alkylsulfate under high pressures

Abstract Under high pressures up to 3000 atm, the effects of added salt, chain length, and temperature on the critical micelle concentration (CMC) of sodium dodecylsulfate (SDS) were investigated. The linear relationship between the logarithm of the CMC and of the gegenion concentration was confirmed at high pressures up to 3000 atm. From the behavior of gegenion under pressure, the variation of the aggregation number of micelles with pressure was estimated; initial compression seems to cause the micelle to disaggregate, resulting in the formation of a number of small micelles. The well known fact, at atmospheric pressure, that the CMCs of SDS and its homologous surfactants decrease logarithmically with an increase in the number of carbon atoms in the alkyl chain was confirmed even at pressures up to 3000 atm. From these results, the contributions of hydrocarbon tail and ionic head to the standard free energy and partial molal volume changes on micellization are discussed. Finally, the CMC of SDS was determined at various pressures and temperatures of 17 to 40°C. The temperature at which the CMC becomes minimum tends to shift toward the lower temperature as the pressure increases. The changes of partial molal entropy and enthalpy on micellization, which decrease as the temperature is raised and increase as the pressure increases to a certain value, could be qualitatively explained by the formation of an “iceberg” structure of water around the hydrocarbon tail in the monomer state. Further, the micelle-forming properties are discussed in terms of the temperature and pressure dependence of the CMC.

Partial molal volumes of surfactant and its homologous salts under high pressure

Abstract The compressions of solutions of sodium alkylsulfates and alkyltrimethylammonium bromides and then the partial molal volumes of these salts under pressure were determined. The partial molal volume of surfactant in micellar state decreased with increase in pressure and that of alkyltrimethylammonium bromide in singly dispersed state decreased also with pressure, while the partial molal volume of sodium alkylsulfate in singly dispersed state increased with increase in pressure. The changes of the partial molal volume on micellization determined directly were compared with that obtained indirectly from the pressure dependence of the critical micelle concentration.

Studies on selective adsorbents for oxo-anions. Nitrate ion-exchange properties of layered double hydroxides with different metal atoms

Layered double hydroxides (LDHs) with different kinds of metal ions (Mg–Al, Co–Fe, Ni–Fe, and Mg–Fe) in the brucite layers were prepared and their anion exchange properties were studied by measurements of distribution coefficient (Kd) and ion exchange capacity. The basal spacing of LDHs varied depending on the kind of metal ions in the brucite layer. A relatively high Kd value for NO3− ions was observed on Ni–Fe type LDHs, and a markedly high Kd value for the hydrothermally-treated Ni–Fe type LDHs (Ni–Fe (HT)), prepared at 120 °C. These high Kd values correlated with the basal spacing of 0.81 nm observed for this sample, where the interlayer distance (0.33 nm) is suitable for the stable fixing of NO3− ions (ionic size = 0.33 nm). A chemical analysis study showed a Cl−/NO3− ion-exchange mechanism for NO3− adsorption on Ni–Fe (HT). The NO3− uptake by Ni–Fe (HT) was nearly constant (NO3/Fe = 0.7) over a pH range between 5 and 10, which also supports the adsorption mechanism of Cl−/NO3− ion exchange. The Ni–Fe (HT) could remove NO3− ions from seawater effectively (NO3− uptake = 168 μmol g−1) even though seawater contains an extremely large amount of coexisting anions. This novel adsorbent thus has a NO3− ion-sieve property and will prove beneficial for the selective removal of NO3− ions from industrial effluents and seawater to clean the environment.

Heavy metal immobilization in aqueous solution using calcium phosphate and calcium hydrogen phosphates

This study examines the possibilities for removing heavy metal cations from water with calcium phosphate, calcium hydrogen phosphate, and calcium dihydrogen phosphate at 293 K. It was reported that immobilization of aqueous heavy metal cations, which is known to be one of the characteristic properties of calcium hydroxyapatite, proceeded favorably with these phosphates. Calcium phosphate, calcium hydrogen phosphate, and calcium dihydrogen phosphate could favorably remove Pb2+ from aqueous solution. Calcium hydrogen phosphate also removed aqueous Cu2+, Co2+, and Cd2+, whereas these cations were not immobilized by calcium phosphate and calcium dihydrogen phosphate. A contribution of the dissolution-precipitation mechanism to immobilization with these phosphates is suggested.

The effect of pressure on solubilities of ionic surfactants in water

Abstract The solubilities of ionic surfactants, sodium dodecylsulfate and dodecylamine hydrobromide, have been determined measuring the electric conductivity at pressures up to 3000 atm and at several temperatures in the range 7 to 35°C. Influences of pressure and temperature on the solubility were similar on these ionic surfactants. With increase in pressure, the solubility decreases abruptly until the “critical solution pressure” Pc, but decreases gradually above this pressure. The critical micelle concentration (CMC) has also been determined under pressure. The relation between the solubility, the CMC, and the pressure is given by a phase diagram. The CMC vs pressure curve and the solubility vs pressure curve cross at a point Q. (The pressure at which the point Q exists is designated Pc.) The point Q is found to be the Krafft point at the pressure Pc. Micelles above this pressure are in a state of superpressing and metastable. The pressure dependences of the solubility and of the CMC are considered thermodynamically. Comparisons are made among the partial molal volumes of surfactant in micellar state ( V m ), in singly dispersed state ( V s ) and in hydrated solid state ( V c ).

Lead immobilization by non-apatite-type calcium phosphates in aqueous solutions

Abstract The immobilization of lead (II) ion by β-Ca 3 (PO 4 ) 2 , CaHPO 4 ·2H 2 O and Ca(H 2 PO 4 ) 2 ·H 2 O was found to proceed more favorably than that by calcium hydroxyapatite (CaHAp), probably due to rather greater solubility of former three calcium phosphates than that of CaHAp. The contribution of dissolution–precipitation mechanism was suggested to the immobilization.

Effective interfacial area and liquid—side mass transfer coefficient in the upward two-phase flow of gas—liquid mixtures

Abstract The effective interfacial area a was measured, for upward two-phase flow in a tubular gas—liquid reactor in the regions of undeveloped slug, froth and annular flow, by absorbing pure oxygen into sodium sulphite solutions. The interfacial shear stress between the gas and the liquid phases was calculated from the interfacial area and the pressure gradient. The liquid—side mass transfer coefficient kL was estimated from a and the volumetric mass transfer coefficient kLa. Correlations are proposed for a, the interfacial friction factor and kL.

Metal complexes of poly(2-acetamidoacrylic acid)

Abstract Complexation constants of divalent and trivalent metal ions with 2-acetamidoacrylic acid (4A) and its polymer (P4A) were determined by the modified Bjerrum method. P4A has carboxyl and acetamido (acetyl) groups. Although an additive effect of two functional groups was expected in complexing with metal ions, the complexation constants of P4A were essentially the same as those for poly(acrylic acid), while P4A has greater complexing ability than 4A. The interactions of P4A and 4A with Cu(II) and Mn(II) ions were studied using 13 C n.m.r. The addition of Cu(II) ion to P4A and 4A solutions selectively broadens the α-carbon and carboxyl carbon signals, and the addition of Mn(II) ion broadens the acetyl and carboxyl carbonyl carbon signals. This finding suggests that Cu(II) and Mn(II) ions form five-membered and seven-membered chelate rings, respectively.

Adsorption of CO2 on FSM-type mesoporous silicas

FSM-type mesoporous silicas with different pore sizes (FSM-10 with 1.7 nm, FSM-12 with 2.1 nm, FSM-14 with 2.3 nm and FSM-16 with 2.8 nm) were prepared and studied to use as adsorbents for CO2. The amount of adsorbed CO2 and the IR spectra of surface silanol groups of FSM after CO2 adsorption were measured. The results of isosteric heat of adsorption of CO2 indicated that both FSM-10 and FSM-12 were energetically homogeneous adsorbents for adsorption of CO2. On the other hand, both FSM-14 and FSM-16 had energetically different adsorption sites. The number of energetically higher adsorption sites of FSM-14 was fewer than that of FSM-16. The results of the IR spectra for free silanol groups of FSM-14 and FSM-16 were compatible with the results for isosteric heat of adsorption. The amount of CO2 adsorbed on FSM-14 and FSM-16, except for FSM-12, from CO2–N2 gas mixtures (CO2/N2=20.1/79.9) as capillary condensation increased rapidly with an increase in the total pressure from 0.4 to 0.5 MPa.

Characterization of palladium and palladium-silver alloy layers on stainless steel support

Pd and Pd/Ag layers were prepared by a technique of electroless plating on stainless steel supports. To form Pd/Ag layers, Pd layer was plated on an activated stainless steel (SS) sheet followed by Ag plating. The Pd/Ag-SS sheet composite was annealed at 873 K-973 K for 10 h -12 h in helium. Before annealing, the thickness of Pd layer and Ag layer on Pd/Ag-SS sheet composite was 7.6 μm and 1.9 μm, respectively. The formation of Pd/Ag alloy was observed on the SS sheet after annealing at 873 K for 12 h in helium. The ratios of Ag/(Pd+Ag) were 0.28 on the surface by XRF and 0.29 in the bulk by XPS. This result showed the formation of homogeneous Pd/Ag alloy on the SS sheet at that annealing condition. Helium permeances were measured at a pressure difference of 1 atm and room temperature. The permeances of porous stainless steel (PSS) tubes without and with 78 μm Pd layer were 100 m3/m2h and 0.35 m3/m2h, respectively. This result showed the obtained membrane was an almost dense membrane.