Kinetic and thermodynamic parameters of 99Mo sorption on thermally treated hydrotalcite

Summary Thermally treated hydrotalcite was synthesized and its ability to sorb ⁹⁹Mo from aqueous solutions was studied under static conditions as a function of initial concentration, amount of sorbent and pH. X-ray diffraction was used to characterize synthesized calcined hydrotalcite. The values of sorption data were fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) sorption isotherms. The mean energy of sorption was calculated as 5.24 kJ^. mol^-1from D-R sorption isotherm. The Lagergren equation has been used for the study of the kinetic process. The rate constants of ⁹⁹Mo sorption on calcined hydrotalcite were calculated at various temperatures (293-323 K). The thermodynamic constans have been calculated and the standard enthalpy of the system was found to be<span style='font-size:12.0pt; font-family:Symbol;mso-bidi-font-family:Symbol'>DH°=11.5±0.3 kJ^. mol^-1. The values of calculated<span style='font-size:12.0pt;font-family:Symbol;mso-bidi-font-family: Symbol'>DG° and<span style='font-size:12.0pt;font-family: Symbol;mso-bidi-font-family:Symbol'>DS° were</o:p>-13.9±2.0 kJ^. mol^-1and (8.7±0.2)^. 10^-2kJ^. K^-1. mol^-1, respectively. These results show that the sorption process is endothermic, spontaneous in nature and the degree of freedom of ions is increased by sorption.