A KINETIC AND THERMODYNAMIC STUDY OF SILVER SORPTION ONTO MANGANESE-DIOXIDE FROM ACID-SOLUTIONS

The batch kinetics of silver sorption at the tracer level onto manganese dioxide along with the thermodynamic parameters from dilute nitric and perchloric acid solutions are described. The values of DELTA-H, DELTA-S, and DELTA-G found from both acid solutions are similar. The sorption equilibrium constant, K(C), has been calculated at different temperatures between 288 and 308 K. Tests of different isotherms have shown that the sorption data fit very well to the Freundlich and Dubinin-Radushkevich (D-R) models at different temperatures. The thermodynamic data indicate the endothermic nature of silver sorption onto the oxide. The sorption capacity in the 0.23-0.77 mmol/g range and a mean free energy of sorption of about 11.5-15.4 kJ/mol have been found by using the D-R approach. The values of B and the correlation factor (r) have been determined by using the D-R isotherm. These values are comparable with those reported earlier for other sorption systems.