SELECTIVE ADSORPTION STUDIES OF MANGANESE ON LEAD DIOXIDE FROM AQUEOUS-SOLUTIONS

The adsorption of manganese on lead dioxide from aqueous solutions has been studied as a function of shaking time, amount of adsorbent, pH, concentration of the adsorbate and temperature. The adsorption process is endothermic and values of the distribution coefficient K(D) increase with increase in temperature T. The data fitted very well to Langmuir, Freundlich, and Dubinin-Raduskevich isotherms and their corresponding constants were calculated. The thermodynamic parameters DELTAH-degrees and DELTAS-degrees were calculated from the slope and intercept of the plots of 1n K(D) vs. 1/T. Values of the free energy of specific adsorption DELTAG-degrees, decrease with increase in temperature and show that adsorption is more favourable at high temperature. The influence of different anions and cations has been examined. Tartrate, citrate, oxalate, thiocyanate, thiosulfate, EDTA, U(VI), AI(III), Fe(III), Cr(III) and Th(IV) ions drastically reduced the adsorption of manganese. Therefore these anions and cations ought to be removed before the adsorption of manganese on lead dioxide. The adsorption of other metal ions on the oxide were measured under identical conditions. The K(D) values indicate that manganese can be separated successfully from Hg(II), Ag(I), Ta(V), ln(III) and Tc(VII).