A Study of Cobalt Ions Removal from Aqueous Solutions by Sodium X-Zeolite

Abstract

Investigations were made to determine the ion-exchange removal of cobalt ions from aqueous solutions over a pH range of 5.5-7.0 by synthetic zeolite NaX using the batch method with initial cobalt chloride solution concentration within the range 0.003 to 0.013 mol dm⁻³. The percentage Co²⁺exchange as a function of Co²⁺ ions concentration and temperature were determined by means of chemical method. It was found that Co²⁺ ion-exchange phenomenon depended on the concentration, temperature and diameter of the hydrated Co²⁺ ion. Furthermore, cobalt exchange studies showed that over the complete concentration range the adsorption ratios for Co²⁺ ions exchanged into NaX-zeolite correlated with the linear form of the Langmuir and Freundlich adsorption isotherms. Standard thermodynamic parameters (ΔG°, ΔH°, ΔS°) determined by using the values of Langmuir binding constants instead of the values of the thermodynamic equilibrium constant for the exchange process were found not appropriate in order to interpret the results of the ion-exchange reaction.