Shuji Ikoma

Photostability enhancement of anionic natural dye by intercalation into hydrotalcite.

The aim of this study is the improvement of the photostability of several natural anionic dyes, carmine (CM), carthamus yellow (CY), and annatto dye (ANA), by complexation with hydrotalcite. The composite of the dyes and hydrotalcite is prepared by the coprecipitation method. CM is successfully intercalated in the hydrotalcite layer when the amount of introduced CM is large. The photostability of CM in CM/HT composites is superior to the CM adsorbed on silica surface. The effect of the stability enhancement is larger when the amount of introduced CM exceeds 0.23 g/g-host, or when the layer charge density of the hydrotalcite is larger. CY is also stabilized by complexation with hydrotalcite, whereas ANA is not stabilized by complexation with hydrotalcite. The photostability of an anionic natural dye can be improved by intercalation into the hydrotalcite layer, if the dye has a hydrophilic nature and a rather planar structure. The intercalated dye is stabilized by the protection from the attack of the atmospheric oxygen. In addition, contribution of the electrostatic interaction between the positively charged hydrotalcite layer and the intercalated anionic dye is also proposed.

The extraction of vanadium(IV) from hydrochloric acid solutions by long-chain alkyl amine and alkyl ammonium compound

Abstract The distribution of vanadium(IV) between hydrochloric acid solutions and organic solutions of tri- n -octylamine or tricaprylmethylammonium chloride has been investigated under different conditions. Both phases have been examined by spectrophometry, and the IR spectral measurement and the measurements of the apparent molecular weight and magnetic moment have been carried out for the organic extracts. The mechanism of the extractions is discussed and structures proposed for the complexes formed.

Optical absorption and electron spin resonance spectral studies of vanadyl chloro complexes formed in the solvent extraction systems with Aliquat-336, TOA, TOPO and TBP

Abstract Optical absorption and electron spin resonance (ESR) spectral studies have been carried out for the complexes formed in the extractions of vanadium(IV) by tricaprylmethylammonium chloride (R 3 R′NCl; Aliquat-336), tri- n -octylamine (R 3 N; TOA), tri- n -octylphosphine oxide (R 3 PO; TOPO) and tri- n -butylphosphate ((RO) 3 PO: TBP) in benzene from hydrochloric acid solutions or mixed solutions of hydrochloric acid and lithium chloride. As a result, it is found that the species VOCl 2 · n L, VO(OH)Cl· n L and VO 2 Cl· n L (L = R 3 R′NCl, R 3 NHCl, R 3 PO, (RO) 3 PO; n = 1 for R 3 R′NCl and R 3 NHCl, n = 2 for R 3 PO and (RO) 3 PO) are formed in the organic phase.

Comparative studies on the silica gels doped with polyamine copper(II) complexes by ion-exchange and sol-gel techniques☆

Abstract Silica gels doped with polyamine copper(II) complexes were prepared by hydrolysis of tetraethyl orthosilicate solution containing the complexes (sol-gel technique) and by ion-exchange of the cations of those complexes for silanol protons on the silica surface (ion-exchange technique). The copper species trapped within silica gels by the ion-exchange technique were attached to two neighbouring silanol oxygens, well-dispersed in gel bodies and little eluted with water, whereas silica gels prepared by the sol-gel technique contained the copper(II) complexes as aggregates and most of the complexes were leached with water. The copper(II) complexes on silica gels thermally decomposed to copper(II) oxide and copper metal particles under atmospheres of air and nitrogen, respectively. The formation temperatures of these particles in the ion-exchange silica glasses were 200 ∼ 300 °C higher than those in the sol-gel glasses. The particle sizes of the oxide and metal of copper in the ion-exchange silica glasses were about 200 A and considerably smaller than those in the sol-gel glasses.

Characterization of polyamine copper(II) complex-doped alumina gels prepared by the sol-gel technique

Abstract Alumina gels doped with polyamine copper(II) complexes were prepared by the sol-gel technique. The gels and the adsorbed water were characterized by ESR and optical absorption spectroscopies and thermogravimetry for the copper(II) complexes. The complex molecules are almost free in tumbling motion in air at room temperature to the same extent as those in viscous fluid solutions (such as aqueous ethylene glycol), but they aggregate gradually and the motion stops with decreasing amount of adsorbed water. The reversible interconversion of two dynamic states of the copper(II) complex molecule was observed according to whether the alumina gel surface was covered by adsorbed water, the amount of which was enough to form a monomolecular layer, or not. The variation of the amount of adsorbed water in the gels also causes reversibly the complex formation and dissociation between polyamine ligands and copper(II) ions for less stable complexes. As reported previously, silica gels catch tightly the complex molecules within the matrices by forming direct chemical bonding, and never show such an effect of adsorbed water as described above even though they contain adsorbed water in amounts comparable with the alumina gels.

Thermal decomposition of organic basic aluminium salts—formate and acetate

Abstract The thermal transformation of anhydrous alumina by the decomposition of the formate and acetate of basic aluminium has been examined by thermal analysis (TG and DTA), infrared spectrophotometry and X-ray diffraction studies. It is found that under an atmosphere of air the organic basic aluminium salts decompose to anhydrous amorphous alumina which transforms to α-alumina via γ-, δ- and θ-aluminas

Solvent extraction of vanadium(IV) from hydrochloric acid solutions by neutral organophosphorus compounds

Abstract The extraction of vanadium(IV) from hydrochloric acid solutions by tri-n-octylphosphine oxide (TOPO) or tri-n-butylphosphate (TBP) in benzene has been investigated under different conditions. The organic phases have been analysed stoichiometrically and spectrophotometrically. As a result, it has been found that the extraction equilibrium can be expressed as VOCl2(aq) + nTOPO(org) ⇌ VOCl2 · nTOPO(org) or VOCl2(aq) + nTBP(org) ⇌ VOCl2 · nTBP(org), in which n = 1 or 2. The structure for the complexes formed in the organic phase is proposed on the basis of the results obtained.

Thermal decomposition of zirconium hydroxide

Abstract The thermal decomposition of zirconium hydroxides prepared from aqueous ammonium hydroxide solutions on the addition of potassium fluorozirconate, K 2 ZrF 6 , under various conditions has been examined by thermogravimetry, differential thermal analysis, X-ray diffraction study and infrared spectrophotometry. As a result, it is found that the thermal decomposition of zirconium hydroxide proceeds according to In this process, the transformation of amorphous ZrO 2 to either the metastable tetragonal or monoclinic form depends on the composition of the original starting material as an hydrated oxyhydroxide, ZrO 2− x (OH) 2 x · y H 2 O where x ⩽ 2 and y ⋍ 1.

Reversible formation of iron(III) ion clusters in the poly(acrylic acid)–Fe3+ complex gel with changes in the water content

The hydrogel made by adding poly(acrylic acid)(PAA) to iron(III) chloride solution has been investigated as a function of the water content of the gel by means of EPR, visible and infrared spectroscopies. The red–brown PAA–Fe3+ complex gel formed is homogeneous and transparent as is the solution, while the xerogel obtained by drying the gel was yellow. Iron(III) ions in the gel aggregate [as iron(III) ion clusters] and disperse (as mononuclear species) reversibly with repeated wetting with water and drying of the gel. In the hydrated gel PAA carboxyl groups bond strongly to the cluster iron(III) ions, thus networks of intermolecularly cross-linked PAA cause gelation, whereas in the dry gel the networks are loosened.

Thermal Transformation of Aluminium Hydroxide to Alumina

The thermal transformation of crystalline and gelatinous aluminium hydroxide by thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffraction study and infrared spectrophotometry.