Efficient removal of cadmium ions from aqueous solutions by hydrous ceric oxide - a radiotracer study

The adsorption of cadmium ions on hydrous ceric oxide has been studied as a function of concentration (10-2-10-7 M), temperature (303-333 K) and pH (7.08-10.47) of adsorptive solution, applying radiotracer technique. The kinetics of adsorption was found to follow first order rate law with respect to adsorptive concentration and agrees well with classical Freundlich isotherm. The effect of temperature on equilibrium adsorption values has been utilized to evaluate the change in standard thermodynamic quantities (viz. ΔHo, ΔSo and ΔGo). Pre-irradiation of adsorbent with neutrons and γ-radiations from a 11.1 GBq (Ra-Be) neutron source having an integral neutron flux of 3.85 x 106 neutrons/cm2/sec and associated with a nominal γ-dose of ca. 1.72 Gy/hour has practically no effect on the extent of adsorption of cadmium ions. The sorption process was found to be endothermic and irreversible in nature. (orig.)