Adsorption of I^- on Calcined Mg-Al Hydrotalcite

The layered double hydroxides (LDH) containing Mg²⁺ and Al³⁺ in the brucite like layers and interlayer carbonate ions were prepared by co-precipitation method and characterized by XRD, FT-IR and SEM. The adsorption behavior of I^- on LDH was investigated as a function of calcination temperature, initial pH, contact time and initial I^- concentration. The results show that the calcined LDH under 500 ℃ (CLDH-500) has the highest adsorption capacity for I^-. The maximum adsorption capacity of 217.22 mg/g is achieved at pH=6 with 8 h contact time when initial I^- concentration is 500 mg/L. Pseudo-first-order and pseudo-second-order kinetic models and intraparticle diffusion model were used to describe the adsorption process, and the results indicate that the adsorption data correlate well with pseudo-first-order kinetic model and intraparticle diffusion model (R²>0.96). The fitting results of Langmuir isotherm model (R²>0.99) show that the adsorption of I^- on CLDH-500 is monolayer. This method can provide technical and theoretical support for the removal of I^- from radioactive waste water.