Equilibrium, Thermodynamic, and Kinetic Studies of the Adsorption of 2,4-Dichlorophenoxyacetic Acid from Aqueous Solution by MIEX Resin

摘要

The study investigated the performance of 2,4-D adsorption on MIEX resin. The different temperatures affecting the adsorption performance were specifically evaluated. Equilibrium data followed the Freundlich and Langmuir isotherm model for all investigated temperatures (283 K to 333 K). The Langmuir model was slightly better than the Freundlich model at a lower temperature (283 K); however, with the increase of temperature the Freundlich model could well describe the isotherm data. The solute coefficient of distribution (K-d) could be better used to estimate the thermodynamic parameters compared with the Langmuir equilibrium constant (K-L). The thermodynamic parameters (Delta H-0, Delta S-0, and Delta G(0)) showed that the adsorption of 2,4-D was feasible, endothermic, and spontaneous at 283 K to 313 K. The activation energy (E-a, 47.70 kJ.mol(-1)) determined by using the rate constant k(2) of pseudo-second order model (the suitable kinetic model) and the mean free energy value (E-fe, 6.0348 kJ.mol(-1)) evaluated by using the Dubinin-Radushkevich (D-R) model indicated that chemical ion-exchange was the predominant mechanism of 2,4-D adsorption. The calculated film diffusion coefficient value (D-f) suggested film diffusion was the kinetic rate-limiting step. The adsorbent displayed excellent reusability with 0.1 mol.kg(-1) NaCl as the regeneration agent.