Katsumi Kurotaki

The composition and ion-exchange behavior of zinc hexacyanoferrate(II) analogues

Abstract The dependence of the composition of zinc hexacyanoferrate(II) complexes on the mixing ratio of sodium hexacyanoferrate(II) and zinc nitrate solutions is demonstrated, and the ion-exchange behavior of the different complexes is described. Depending on the mixing ratios of the two components, Zn2Fe(CN)6 or Na2Zn3[Fe(CN)6]2, or mixtures of these compounds, may be formed. The adsorption rate for cesium(I) on zinc hexacyanoferrate(II) is extremely slow, whereas it is very rapid on disodium trizinc hexacyanoferrate(II). The Zn-Cs and Na-Cs exchange rates for the different complexes are discussed.

Determination of rare earth elements, thorium and uranium by inductively coupled plasma mass spectrometry and strontium isotopes by thermal ionization mass spectrometry in soil samples of Bryansk region contaminated due to Chernobyl accident

The present paper describes the inductively coupled plasma mass spectrometric (ICP-MS) determination of rare earth elements (REEs), thorium and uranium in forest, pasture, field and kitchen garden soils from a Russian territory and in certified reference materials (JLK-1, JSD-2 and BCR-1). In addition to concentration data, strontium isotopic composition of the soil samples were measured by thermal ionization mass spectrometry. The measurements contributed to the understanding of the background levels of these elements in an area contaminated due to Chernobyl accident. There was not a significant variation in the concentration of REEs at different depth levels in forest soil samples, however, the ratio of Th/U varied from 3.32 to 3.60. Though concentration of U and Th varied to some extent, the ratio did not show much variation. The value of 87Sr/86Sr ratio, was in the top layer soil sample relatively higher than in the lower layers.

Adsorption characteristics of radionuclides on zirconium hexacyanoferrate(II)

Abstract Zirconium hexacyanoferrate(II) (FeZr) was prepared and shown to be a weak cation exchanger ; definite mesh sizes are readily made. The mole ratio of iron to zirconium in the FeZr is 1 :1. Adsorption rates of 59Fe, 60Co, 65Zn, 144Ce, 137Cs and 95Zr in 0.1 M hydrochloric acid and sea water were investigated by batch studies. Kd values of these radionuclides in 0.1 M hydrochloric acid and in concentrated salt solutions were determined together with those of 85Sr and 106RuNO. Batch studies indicated that only hydrogen ions are liberated in the exchange reaction. A Ge(Li) detector combined with adsorption on a FeZr column was used for a rapid and simple determination of 59Fe, 60Co, 65Zn, 137Cs, and 95Zr in 11 of sea water, the recoveries of these radionuclides being about 95 %.

Molar volumes of metal complex ions in water. Part 1.—Hexaammine and trisdiamine complexes

Partial molar volumes at infinite dilution text-decoration:overlineV0 have been examined [ML6]z+ in water at 25 °C on the basis of the scaled particle theory (SPT), where M = Cr, Mn, Fe, Co, Ni, Rh or Ir; z= 2 or 3; L = NH3, ethane-1,2-diamine/2 (en/2), propane-1,2-diamine/2 (pn/2), cyclohexane-1,2-diamine (chxn/2), 2,2′-bipyridine/2 (bipy/2) or 1,10-phenanthroline/2 (phen/2). text-decoration:overlineV0 decreases by 25 cm3 mol–1 as z increases from 2 to 3, keeping L and r(M–N) constant, where r(M–N) is the mean distance between metal and coordinated N atoms. Applying this difference to the Drude–Nernst equation Vel(the effect of z on the intrinsic volume Vint), is given as –5.0z2 cm3 mol–1. Linear relationships having the same slope were found between Vint(=text-decoration:overlineV0+ 5.0z2) and r(M–N) for all groups of [ML6]z+ whose L are fixed. This shows that Vint of [ML6]z+ is the sum of the core volume Vint(core) which determines Vel and the volume of additional parts grown from the core Vint(add). The slope of Vintvs. r(M–N) gives Vint(core), and suggests that the nearest water molecules to the core contact at the face centres of the octahedral core formed by six N atoms.

Thermodynamics of ion exchange of trivalent Coiii or Criii complex with cerium(III) ions on cation exchange resin

The thermodynamic values of ion exchange of [M(B)n(H2O)6-n]3+[M = CoIII or CrIII, B = NH3, (ethylenediamine = en)/2, (1,3-diaminopropane = tn)/2, (1,2-diaminopropane = pn)/2 or urea, 0 < n < 6] with Ce3+ ions on Dowex 50W resin of 2, 8 or 16% divinylbenzene (DVB) content were determined from selectivity coefficient and heat of exchange measurements at 25°C. Further, the equivalent volumes of [M(B)n(H2O)6-n]3+-form resins of 2% DVB content were measured. The heat and entropy of exchange were negative for the preferential uptake of [MB6]3+ by Ce3+-form resin of 2% DVB content and they vary significantly with the ligand, B. The sequence of their values was as follows: [Cr(urea)6]3+ < [Co(NH3)6]3+≈[Cr(NH3)6]3+ < [Co(en)3]3+ < [Co(tn)3]3+≈[Co(pn)3]3+. From the entropy of exchange on 2% DVB resin, we speculate that the interaction between the complex ion and water depends on the surface charge density of complex ion. Further, the heat of exchange on 2% DVB resin and the equivalent volume of resin are explained in terms of the interaction between the complex ion and water.

Molar volumes of metal complex ions in water Part 2. Hexahalogeno, hexacyano and tris(ethane-1,2-dioate) complexes

The partial molar volumes at infinite dilution in water, °, of [MB6]z− have been determined at 25 °C and are discussed, together with the ° of [MB6]z+ reported earlier. M is the metal ion; 1 ⩽ z ⩽ 4; A is F−, Cl−, CN− or alkanedioato ion/2; B is NH3 or diamine/2. The intrinsic volumes of [ML6]z ± , Vcav(ML6), were obtained from ° − kz2, where L is A or B, kz2 is the electrostatic effect of charge on Vcav(ML6) and k is −7.2 cm3 mol−1 for [MF6]z− and −5.0 cm3 mol−1 for other [ML6]z ± . Linear relationships are observed between Var(ML6) and rMX which change over a small range for [ML6]z ± having an identical L, rMX being the bond distance between M and the coordination atoms X. dVcav(ML6)/drMX is independent of the magnitude of Vcav(ML6) and increases as rMX increases. These facts are explained by using the model of the MX6 core where the sphere M* (radius rM*) is overlapped by six spheres of X (radii rX) whose centres are at a distance rMX from the centre of M*. Assuming that rM* = (rMX + rX)cos θ, a self-consistent set of rM* and θ is determined from the experimental value of dVcav(ML6)/drMX on the basis of scaled particle theory (SPT). θ is the angle between the MX bond and the centres of solvent water molecules (as spheres) which are nearest to M and in contact with X. Thus Vcav(ML6) is given by Vcav(ML6) = Vcav(Msphere*) + 6Vcav(Xseg) + 6Vcav(LexcX)where Vcav(Msphere*), Vcav(Xseg) and Vcav(LexcX) are the intrinsic volumes of M*, the segment of X which does not overlap with M* and the ligand excluding the X atom, respectively. It is found that all plots of Vcav(ML6) vs. rM* for [ML6]z ± parallel the plot of Vcav(Msphere*) calculated by SPT, vs. rM*. A very similar relationship is observed for MO4z− using the MX4 model.

Interactions between metal-complex ions and water. Part 3.—Entropies of solution and heat capacity changes of metal-complex ions in water at 25 °C

The entropies of solution and the heat-capacity changes of [ML6]3+, ΔS°s([ML6]3+) and ΔCp,s([ML6]3+), have been determined at 25 °C and are plotted against the polarization surface change densities, σp of [ML6]3+, where M is CoIII or CrIII, L is 1,3-propanediamine/2 (= tn/2), 1,2-ethanediamine/2 (= en/2), biguanide/2 (= bigH/2), urea, NH3 or H2O. Further, the values of ΔS°s[Cr(acac)3] and ΔCp,s[Cr(acac)3] in the literature have been included in the plots, where acac is the acetylacetonato ion. The values of –ΔS°s([ML6]n+) and ΔCp,s([ML6]n+)(n= 0 or 3), which are positive and large at σp= 0 of [Cr(acac)3], decrease as σp increases up to that of [Cr(urea)6]3+, followed by an increase. This suggests that [ML6]n+ changes the water structure in the vicinity of itself as its σp increases from zero, from a well ordered structure caused by hydrophobic hydration to a disordered one and them to a well ordered one caused by ionic (electrostrictive) hydration. [Cr(urea)6]3+ has an anomalously large ΔCp,s([ML6]n+) in the plot of ΔCp,s([ML6]n+) against σp, although no anomaly is observed in the plot of ΔS°s([ML6]n+)vs. σp. This anomaly is explained in terms of the transition between the hydrophobic and electrostrictive structures of water in the vicinity of [ML6]n+, which is similar to the order–disorder transition (λ-transition).

Interactions between metal-complex ions and water. Part 2.—Osmotic and mean activity coefficients of trivalent metal-complex chlorides in aqueous solutions at their freezing points

The method of freezing-point depression has been used to determine the osmotic and activity coefficients of [ML6]Cl3, [M = CoIII or CrIII; L = NH3, H2O, urea, ethylenediamine/2(= en/2), 1,3-diaminopropane/2(= tn/2), or 2,2′-bipyridine/2 (=bpy/2)] in aqueous solutions. Measurements have been made in the molality range 0.01–0.65. The osmotic coefficients have been fitted to the Debye–Huckel (DH) equation and the mean activity coefficients have been calculated. At a given molality these values increase in the following order: [Co(tn)3]Cl3 < [Co(en)3]Cl3 < [Co(NH3)6]Cl3 < [Co(bpy)3]Cl3 < [Cr(urea)6]Cl3 < [Cr(H2O)6]Cl3. This order does not agree with that of the radii of the metal-complex ions. The value of the expression ar–2c–27.27σc,p changes with σc, p, where a, rc and σc, p are the ion size parameter of the DH equation, the ionic radius and the polarization surface charge density of a given metal-complex ion, respectively, and 27.27 is a constant derived from the critical distance of ion association. A similar relation was observed for alkali metal and tetra-alkylammonium chlorides using cation surface charge densities. These relationships suggest that the interactions between cations and the chloride ion are affected by the water structure.