Study on Adsorption Behavior and Mechanism of U(Ⅵ) by Modified Rice Stem

The adsorption behavior of uranium on modified rice stem was studied through static adsorption experiments. The adsorption process was analyzed by thermodynamics and kinetics, and the adsorption mechanism was analyzed with FT-IR, SEM, EDS and XRD. The results show that the equilibrium adsorption process well fits to Langmuir isotherms model with relation coefficient greater than 0.98, and the monolayer adsorption is predominant form. The kinetic analysis shows that the UO²⁺₂ adsorption rate on modified rice stem is mainly controlled by surface adsorption. The process of adsorption can be well described by pseudo-second-order model with the relation coefficient to 0.999 2. The thermodynamic study indicates that the adsorption process is spontaneous, endothermic and unreversible. The adsorption of uranium on modified rice stem changes the morphology and the crystal characteristics of rice stem. In the adsorption, UO²⁺₂ mainly reacts with —OH, CCDS1O, SiCDS1O and P—O, etc. on the cell’s surface of modified rice stem. The adsorption of UO²⁺₂ on modified rice stem should be of chelated surface mechanism.