Adsorption and desorption of antimony acetate on sodium montmorillonite

The adsorption of antimony acetate (Sb(OAc)₃) on sodium montmorillonite (Na-MMT) was studied at five different initial concentrations, and data from the adsorption isotherm were modeled using the Langmuir, Freundlich and D-R isotherm equations. The kinetics of adsorption was also discussed using three kinetic models: the pseudo-first-order, the pseudo-second-order and the intraparticle diffusion model. The rate constants of pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetics, and the amount of Sb(OAc)₃ adsorbed at equilibrium were determined. Moreover, the desorption of Sb(OAc)₃ from several kinds of Sb-MMT (Na-MMT was intercalated by antimony acetate) was investigated at room temperature and 180°C. The results show that according to the maximum amounts of adsorbate and correlation coefficients calculated from the three isotherm equations mentioned above, the corresponding data from adsorption experiments fit fairly well to the Langmuir isotherm. The adsorption data show a good compliance with the pseudo-second-order kinetic model and also follow the intraparticle diffusion model up to 30min. The equilibrium adsorption capacity of Sb(OAc)₃ on MMT is close to the cation exchange capacity (CEC) of the montmorillonite. The desorption amount of Sb(OAc)₃ is correlated with both the temperature of desorption and the drying temperature of Sb-MMT.