Radiotracer technique in adsorption study—VII. Adsorption of iodide ions on chromium (IV) oxide powder

Abstract

The kinetics of adsorption of iodide ions on chromium (IV) oxide has been studied as a function of concentration (10 −7–10 −2 M), temperature (293–328 K) and pH value (3.2–11.2) of the adsorptive solution employing the radiotracer technique. The kinetics of adsorption of iodide ions follows the first order rate law and obeys the Freundlich isotherm. Exposure of the activated oxide adsorbent to neutrons and γ-radiation from a (Ra-Be) neutron source having an integral neutron flux of 3.85 × 10 6 neutrons/cm 2/s and associated with a nominal γ-dose of ca 172 rads/h results in a nominal increase in the rate of uptake for 24 h irradiation and thereafter decreases substantially when the irradiation time is increased to 60 h. The kinetics of desorption of preadsorbed iodide ions on oxide surface in water as well as in potassium iodide solution also follows first order rate law, and amount released increases with the increase of temperature (303–323 K). The adsorption is deduced to be of the “activated” type.