No abstract available

[en] A radioactive indicator study has been done to examine the feasibility of concentrating chromate, molybdate and tungstate species from extremely dilute solutions by using ignited lead sulphate and barium sulphate as carriers. The procedure consists of two steps; first, the radioactive tracer in dilute aqueous solution is carried under optimum conditions; secondly, the carried activity after washing can be leached back in minimal amount of water of specified acidity. An examination of working conditions e.g., (i) carrying as a function of pH₂, amount of carrier and that of added inactive CrO²₄; (ii) adsorption/desorption efficiency as a function of lattice/non-lattice ion concn, and (iii) desorption as a function of pH of the eluant have been carried out in case of chromate species. Centrifuge method has been used. 3-4 extractions are needed for the maximum recovery of activity. (author)

[en] Deposition of carrier free ³²P on ignited Pb(IO₃)₂, Ba(IO₃)₂ and Sr(IO₃)₂ is described as a function of pH and the ionic composition comprising of lattice and non-lattice ions. The carrying is explained in relation to these factors and surface adsorption by the mechanism of counter ion exchange. The deposition on Ba(IO₃)₂ and Sr(IO₃)₂ is favoured in presence of lead ions whereas the same is lowered on Pb(IO₃)₂ in presence of non-lattice cations (eg. Ba²⁺ and Sr²⁺ ions) having the same electric charge and comparable ionic dimensions. The findings are discussed in the light of possible anchoring of these non-lattice cations by the lattice anion on the Pb(IO₃)₂ surface. This postulated masking results in reduction of the active sites responsible for carrying on Pb(IO₃)₂. (author)

[en] Ageing and extraction characteristics of freshly precipitated iodates (Pb, Ba and Sr) towards phosphate ions are described. The observed difference in extractability of the fresh and ignited samples (using P-32 indicator) is postulated to be due to difference in morphological characteristics between the two types. (T.I.)

[en] Influence of pH and that of added ions on sorption characteristics of ⁶⁰Co(II) species on ignited sulphates of lead, barium and strontium as microcrystalline solids has been described in terms of counter ion exchange at low pH and hydrolysis of the tracer at higher pH. (author)

[en] Deposition of carrier-free ³²P on ignited PbF₂, BaF₂, CaF₂ and MgF₂ is described as a function of the pH and the concentration of added lattice and non-lattice ions. The influence of these factors in enhancing the carrying is explained. The carrying is explained in the light of surface adsorption taking place by the mechanism of counter-ion exchange. In contrast with expectations, the carrying is favoured in the presence of non-lattice cations (e.g. Ba²⁺ and Sr²⁺) having the same electric charge and comparable ionic radii. These observations are discussed in the light of findings made in the case of lead sulphate, where the carrying of the same tracer is adversely affected by the presence of these foreign cations. The structural characteristics which are assumed to be responsible for the anchoring of these non-lattice cations by the lattice anion on the lead sulphate surface are supposed not to exist in these cases. (T.G.)

No abstract available

[en] Instantaneous deposition of ⁵¹Cr (as chromate ions) on ignited PbSO₄, BaSO₄ and SrSO₄ is profoundly influenced by pH and concentration of added lattice and nonlattice ions. The carrying is considered on the basis of surface adsorption by the mechanism of counter ion exchange. The deposition follows the expected trend in presence of lattice ion whereas abnormality is observed in presence of certain non-lattice cations of similar charge and ionic dimensions. Thus, deposition on BaSO₄ and SrSO₄ is favoured in presence of Pb²⁺ whereas the same is lowered on PbSO₄ in presence of these nonlattice cations. Also, carrying on BaSO₄ is suppressed on addition of Sr²⁺ whereas Ba²⁺ augments the deposition on SrSO₄ surface. The adverse effect can be overcome by increasing pH or lattice cation concentration in the suspension medium. The supressing role of Ba²⁺ is observed to be greater than that of Sr²⁺. The observed effect is postulated to be due to possible anchoring of these nonlattice cations by lattice anion, resulting in reduction of absorption sites available for carrying. (author)

[en] The radioindicator method has been used to concentrate Cr(VI) ions from the aqueous solution. The study shows that under optimum conditions, 250 mg of V₂O₅ carries 0.005 mg of chromium. Further, the activity carried under the specified conditions can be recovered more or less quantitatively by leaching the carrier. (author). 4 refs., 1 tab

[en] Radiotracer technique has been used for the investigation of adsorption of chromium(VI) traces on bismuth trioxide from aqueous solution. The effect of pH (2-10), concentration of chromate solution (10^-6-10^-2M) and temperature (303-323 K) has been thoroughly investigated. The influence of certain foreign ions has also been studied. The calculated kinetic and thermodynamic parameters indicate the first order rate law, spontaneity and exothermic nature of the adsorption process. Further, IR studies have established the chemical interaction between the sorbate and sorbent and a possible mechanism of the sorption process based on ligand exchange has been proposed. (author) 23 refs.; 5 figs.; 2 tabs