Kinetic and equilibrium studies of chromium (III) removal from aqueous solution by IRN-77 cation-exchange resin

The kinetic and thermodynamic characteristics of adsorption of Cr (III) on IRN77 cation-exchange resin was investigated in the present study. Cr (III) sorption on cation-exchange resin IRN77 was studied as a function of time and temperature. The temperature was found to have a positive effect on film and particle diffusion processes. The activation energy was calculated using Arrhenius equation based on the rate constants and indicated that the activation energy of the particle diffusion process was higher than that of the film diffusion process. The film diffusion equation was well-fitted with a correlation coefficient over 0.99. The results showed that the film diffusion process was the rate-limiting step during Cr (III) sorption process. After the rate constants of adsorption isotherm of Cr (III) obtained from the Langmuir equation, the thermodynamic parameters Delta S-theta, Delta H-theta and Delta G(theta) were further calculated using the Eyring equation. The Delta S-theta and Delta H-theta were found to be -128.07 J/mol.K and 42.98 kJ/mol, respectively. The Delta G(theta) at temperature 298K, 313K and 328K were 81.14, 83.07 and 84.99 kJ/mol, respectively. The thermodynamic characteristics revealed that the mechanism of Cr (III) sorption was endothermic and the entropy-driving ion exchange. (C) 2012 Selection and/or peer-review under responsibility of Basel Convention Coordinating Centre for Asia and the Pacific and National Center of Solid Waste Management, Ministry of Environmental Protection of China.