Adsorption and thermodynamics studies of U(VI) by composite adsorbent in a batch system

The adsorption of U(VI) from aqueous solutions onto composite adsorbent (algistar) has been studied using a batch adsorber. The parameters that affect the U(VI) sorption, such as contact time, solution pH, initial U(VI) concentration, and temperature, have been investigated and optimized conditions determined. Equilibrium isotherm studies were used to evaluate the maximum sorption capacity of composite adsorbent, and experimental results showed this to be 43.10 mg/g. The adsorption patterns of metal ions on composite adsorbent followed the Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherms. The Freundlich, Langmuir, and D–R models have been applied, and the data correlate well with Langmuir model, and that the sorption is physical in nature (the sorption energy E _ads = 12.90 kJ/mol). Thermodynamic parameters (∆H _ads^o = −41.08 kJ/mol, ∆S _ads^o = −68.00 J/mol K, ∆G _ads (298.15 K) = −20.81 kJ/mol) showed the exothermic heat of adsorption and the feasibility of the process. The results suggested that the composite adsorbent is suitable as a sorbent material for recovery and biosorption/adsorption of uranium ions from aqueous solutions.