K.S. Venkateswarlu

Sorption properties of oxides VIII: sorption of uranium on hydrous oxides

Abstract Sorption of unranium from nitrate solution on four hydrous oxides, namely, hydrous titanium, zirconium, cerium and thorium oxides (TiO 2 , ZrO 2 , CeO 2 , ThO 2 ) has been studied at pH 3.5 as a function of uranyl concentration and temperature. The sorbed species was uranyl ion in the case of hydrous TiO 2 and CeO 2 , while in the case of hydrous ZrO 2 and ThO 2 , electrolyte sorption involving uranyl nitrate predominated. Sorption site densities calculated from saturation capacities, evaluated from Langmuir adsorption isotherm and surface areas, bear a direct relationship with the heat of sorption values. Results indicate that, in terms of sorption site density, hydrous CeO 2 seems to be a better sorbent than hydrous TiO 2 for the sorption of uranium.

Solvent extraction of some transition elements with sulphoxides and phosphine oxides

Abstract Transition elements are known to form anionic chloro complexes and some are efficiently extracted by tributyl phosphate (TBP) from hydrochloric acid medium. In this paper an attempt is made to compare the solvent extraction characteristics of di-n-butyl sulphoxide (DBSO) with TBP in respect of extraction of Cr(VI), Mn(II), Fe(III), Co(II), Cu(II), Zn(II) and Zr(IV) from HCl solutions. The effects of the organic group on the extraction behaviour has been studied by exploring the extraction of Fe(III) by diphenyl sulphoxide (DPSO) and triphenyl phosphine oxide (TPPO). Possible explanations for the extraction in terms of donor-acceptor interaction have been discussed.

A comparative study of donor properties of sulphoxides and phosphine oxides in solvent extraction

Abstract A comparative study of the donor properties of sulphoxides and phosphine oxides in solvent extraction is reported. It was believed earlier that the stretching frequency of the phosphoryl group could serve as a measure of its basicity. In sulphoxides, however, the S → O frequency in different sulphoxides is nearly constant and cannot be a guide to their donor properties. A new method of assessing the relative donor strengths of both phosphine oxides and sulphoxides is described, based on the shift of the symmetric stretching frequency of OH of water on coordination with the donor. It is found that both phosphine oxides and sulphoxides form a single group, whose solvent extraction properties are determined by their relative donor strengths, as determined by this procedure. The extractions of water, perchloric acid, hydrochloric acid and pertechnic acid by dibutyl sulphoxide (DBSO) are reported. The extracted species are H2O·2DBSO and H2O·HClO4.

Sorption properties of oxides. IV. Hydrous mixed oxides

Abstract Anion sorption of hydrous oxides can be enhanced by suitably substituting the metal ion in an oxide matrix with a metal ion of higher charge. These mixed oxides will behave as anion sorbers in neutral and alkaline media as a result of induced anion sorption ability. Hydrous mixed oxides, Bi(III)Ti(IV), Bi(III)Zr(IV), Bi(III)Th(IV), Ti(IV)Sb(V), and Zr(IV)Sb(V), have been prepared and sorption of some anions by them was tested under acidic, neutral, and alkaline conditions and the behavior compared with that of pure oxides. Results indicated that the sorption properties of mixed oxides depend very much on the nature and composition of the final product. Among the different mixed oxides studied, Bi(III)Th(IV) mixed oxide exhibited very good sorption for Cl − and I − ions even in alkaline medium.

Sorption properties of oxides—V anion—Exchanges studies on hydrous thorium oxide

Abstract Nitrate-chloride, nitrate-thiocyanate, sulphate-chloride and sulphate-thiocyanate ion exchanges on different preparations of hydrous thorium oxide have been studied at 298°K in solutions to total ionic strength of about 0.1 M and at two hydrogen ion concentrations (0.01 and 0.001 M). The forward and the reverse exchanges did not coincide in all the four ion exchange systems investigated, thus giving rise to an hysteresis loop. The free energy of exchange for the forward and reverse reactions have been calculated for all the four systems. A selectivity series: sulphate ⪢ chloride > nitrate > thiocyanate, has been obtained.

Emission Mössbauer spectroscopy in 57Co doped metal acetylacetonates of Al(III), Cr(III), Mn(III), Fe(III) and Co(III)

Abstract Metal acetylacetonates of Al(III), Cr(III), Mn(III), Fe(III) and Co(III) were doped with high specific activity carrier free 57Co2+ and their emission Mossbauer spectra taken against enriched Na4Fe(CN)6. In the case of Al(III), Cr(III) and Co(III) complexes a simple quadrupole split pattern is obtained, while with Mn(III) and Fe(III) acetylacetonates the spectra corresponds to that of 57Co(AcAc)3. These results have been discussed.

Sorption properties of oxides—VII: Reversibility of cation exchange on hydrous thorium oxide☆

Abstract Li+Ca2+, Na+Ca2+, K+Ca2+ and NH4+Ca2+ exchanges at 0.01 M OH− concentration and Co2+Cu2+, Ni2+Cu2+ and Zn2+Cu2+ exchanges from neutral solutions on hydrous thorium oxide were studied at room temperature. Except NH4+Ca2+ exchange, all other exchanges investigated were non-reversible. Results indicate that specific chemical interactions play an important role during the exchange and/or sorption process.

Estimation of substituted phosphates such as dibutyl and monobutyl phosphates, based on their reaction with lanthanum-Xylenol Orange complex

Development of a new method for the estimation of substituted phosphates such as dibutyl phosphate (DBP) and monobutyl phosphate (MBP) is described in this paper. The method is based on the decolouration of lanthanum-Xylenol Orange complex by DBP and MBP at pH 5.

Reactions of co-ordinated ligands: Kinetics and mechanisms in the charge transfer interaction between dichloro or diaquo triethylene tetramine Co(III) and ferrocyanide

The cherry red-coloured solid state product obtained by the reaction ofcis-σ diaquo Co (III) triethylene tetramine with ferrocyanide was examined by thermogravimetric, infrared and Mössbauer techniques. Its electronic spectrum in aqueous medium was interpreted to consist of charge transfer IT transition at 440 nm and a ligand field transition around 330 nm. The kinetics of formation of this 1:1 product in solution was also studied.

Sorption properties of oxides IX: Effect of anions on the sorption of uranium (VI) on hydrous oxides

Effect of anions such as nitrate, chloride, sulphate and carbonate on the sorption of U(VI), from aqueous solutions on hydrous oxides of Ti(IV), Ce(IV) Zr(IV) and Th(IV) has been studied. The sorption of U(VI) is markedly reduced in the presence of anions, like carbonate, whichform strong complexes with UO22+ in solution. The results are explained in terms of a competition for free UO22+ between surface hydroxyl groups and ligands (anions) present in solution. The sorption of U(VI) on these hydrous oxides was also studied from a bicarbonatecarbonate mixture. Sorption was less under conditions when tricarbonate complex of U(VI) was formed, but increased at higher pH values (>9), presumably due to the formation and sorption of hydroxo complexes of U(VI).