Extraction of Picric Acid from Wastewater by a Secondary Amine (Amberlite LA2) in Octan-1-ol: Equilibrium, Kinetics, Thermodynamics, and Molecular Dynamics Simulation

Abstract

The paper deals with the equilibrium and kinetic studies on the reactive extraction of picric acid (HPc: 0.021-0.061 kmol·m-3) using Amberlite LA2 (ALA2; 0.235-1.175 kmol·m-3), a secondary amine, dissolved in an active diluent, octan-1-ol. On the basis of the values of the loading factor (Z < 0.5), the interaction between the molecules of HPc and ALA2 takes place by forming 1:1 solvates in the organic solvent phase and was confirmed from Fourier transfoem infrared analysis. The effect of the temperature (298.2, 308.2, and 318.2 K) on the performance of extraction is evaluated, and the thermodynamic parameters (entropy and enthalpy) are determined. The mass-transfer coefficient (kL = 7.12 × 10-4 m·s-1) of picric acid in octan-1-ol is estimated experimentally to establish the kinetics of the reaction. The Hatta number is found to be in the range of 0.009-0.011, suggesting a very slow extraction reaction occurring in the bulk of the solvent phase. The reaction order is 1.2 with respect to HPc and 0.7 order with respect to ALA2 with rate constants of forward and backward reactions of 18.3 × 10-6 and 4.94 × 10-6 (kmol·m-3)-1.9·s-1, respectively. The molecular dynamics behavior of the HPc + ALA2 + octan-1-ol system in the organic solvent phase is predicted from the simulated results. (Figure Presented).