The deposition of carrier-free orthophosphate ions on freshly-precipitated micro-crystalline sulphates has been studied. The
results indicate a significant influence of various factors e. g. the pH of the suspension medium, the concentration of lattice
and certain non-lattice ions, the age of the precipitate and the time of contact of the tracer with the carrier surface. The
carrying is considered in the light of surface adsorption. The role of non-lattice cations and the relative merits of freshly
precipitated SrSO4, BaSO4 and PbSO4 as carrier for phosphate tracer, are discussed. Though they show better efficiency as carriers, because of poor recovery
they are of limited applicability for quantitative concentration of traces of phosphate.
Deposition of carrier-free32P on ignited PbF2, BaF2, SrF2, 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.
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.
The carrier technique has been used to concentrate Cr(VI) radiometrically by studying the carrying efficiency as a function of pH of aqueous medium, added ions, carrying capacity, amount of carrier and subsequent desorption of the activity adsorbed under optimum experimental conditions. The study shows that under optimum experimental conditions, 0.15 g of ZrO2 and 0.25 g of TiO2 carry 0.01 mg and 0.001 mg of chromium respectively. Further, the activity carried under the specified conditions can be recovered more or less quantitatively by leaching the carrier.
Sorption of chromium radionuclide has been studied in the pH range of 1–10 on titanium dioxide from aqueous solutions. The adsorption isotherm obtained is of the Freundlich type. The kinetic study of adsorption and desorption of tagged chromate ions at different temperatures show that the adsorption process is exothermic innnature. Further, the feasibility of adsorption process is confirmed by calculating the thermodynamic parameters.
The kinetics of adsorption of chromate ions has been investigated radiometrically over a wide range of concentration of chromate ions (10–6–10–2M) and temperature (303–323 K). The kinetics of the process follows essentially a first order rate law with respect to adsorptive concentration and obeys the Freundlich adsorption isotherm in the concentration range studied. In addition, the kinetics of desorption of the preadsorbed species also follows a first order rate law and the activation energy for desorption is greater than that of the adsorption process. On the basis of an adsorption kinetic study, the thermodynamic parameters have been calculated. Infrared spectroscopy has shown the chemical interaction of chromate ions on the surface of MnO2.