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.