Ion Exchange Behavior of Zeolites A and P Synthesized Using Natural Clinoptilolite

The main goal of this study is to investigate the capability of zeolites A and P synthesized from Iranian natural clinoptilolite for uranium uptak. The removal of uranium(VI) from aqueous solution via ion exchange by zeolites in a single component system with various contact times,  temperatures and initial concentrations of uranium(VI) was investigated. The experimental results were fitted to the Langmuir and Dubinin-Radushkevich isotherms to obtain the characteristic parameters of each model. Both the Langmuir and Dubinin-Radushkevich isotherms were found to good represent the measured adsorption data. Using the thermodynamic equilibrium constants obtained at two different temperatures, various thermodynamic parameters, such as ΔG˚, ΔH˚, and ΔS˚ have been calculated. The thermodynamics of uranium(VI) ion and zeolite system indicates the spontaneous and endothermic nature of the process. It was noted that an increase in temperature resulted in a higher uranium loading per unit weight of the adsorbent.