Removal of uranium(VI) and thorium(IV) ions from aqueous solutions by functionalized silica: kinetic and thermodynamic studies

摘要

Adsorption behavior of uranyl and thorium ions from synthetic radioactive solutions onto functionalized silica as sorbent has been investigated. The effect of contact time, initial concentration of radioactive solutions, sorbent mass, pH value and temperature on the adsorption capacity of the sorbent was investigated. Negative values of Gibbs free energy of adsorption suggested the spontaneity of the adsorption process on both functionalized silica with –NH_2 groups andwith –SHgroups. Positive values obtained for △H° indicates that the adsorption is an endothermic process. The adsorption isotherms were better fitted by Freundlich model and the adsorption kinetic was well described by the pseudosecond order equation. Desorption studies indicated that the most favorable desorptive reagents for UO_2~(2+) is HNO_3 1 M and for Th~(4+) is EDTA 1 M solutions.