Modeling and Optimization of Reactive Extraction of Citric Acid

Reactive extraction of citric acid from dilute aqueous solutions was studied using three different extractants, namely tri-n-butylphosphate (TBP), tri-n-octylamine (TOA), and Aliquat 336 (A336), dissolved in three different diluents: butyl acetate, decanol, and benzene. The isothermal batch equilibrium experiments were carried out at T = 300.15 +/- 1 K. The extraction was interpreted in terms of the distribution coefficient (K-D). Maximum extraction efficiency (E = 95.5%) was obtained at 20% (v/v) TOA in butyl acetate with complexation constant K-E2 = 1039.7 (kg mol(-1))(2) for the (2:1) complex. In addition to having a higher loading ratio (Z > 0.5), the overloading of amine(TOA) in the case of the citric acid + TOA + decanol system was also confirmed by spectroscopic (FTIR) analysis. The linear solvation energy relationship model was successfully applied to predict the distribution coefficient. The complex stoichiometry was also optimized using differential evolution. A close resemblance was observed between experimental and model values.