Recovery of malic acid using trioctylamine in 1–decanol: equilibrium studies by response surface methodology using Box Behkhen optimisation technique

Reactive extraction is a significant technique employed for the removal of organic acids from dilute aqueous solutions. This technique was explored by applying Response Surface Methodology (RSM) in process parameter optimisation for malic acid recovery from aqueous streams using Trioctylamine as the extractant and 1-decanol as the organic diluent. Malic acid, a C4 dicarboxylic acid, has a wide variety of applications in the polymer, food, chemical and pharmaceutical industries. Extraction efficiency was systematically carried out using three process parameters for reactive extraction: temperature, initial malic acid concentration and extractant (Trioctylamine) composition. Response Surface Methodology in combination with Box-Behnken design involving seventeen experimental runs was employed for malic acid reactive extraction in this study. A statistical second order polynomial predicted an extraction efficiency of 97.98%. The optimum conditions of the process variables were found to be: temperature: 308.65 K, acid concentration: 0.711 Kmol/m³, Trioctylamine composition: 21.706% (v/v). Under these optimum conditions, the experimental response of extraction efficiency of 98.35% was obtained. The experimental results obtained were in close conformity with the predicted values by numerical optimisation using Response Surface Methodology. These findings can pave the way for the reactive separation process design for recovery of carboxylic acids from dilute aqueous waste streams as well as a fermentation broth.