Reactive separation of nicotinic acid from aqueous solution using tri-n-octylamine in biocompatible modifier diluent mixture: Influencing parameters exploration, mechanism insights, thermodynamics, regeneration of solvents and column design

Abstract

In the current study, reactive extraction using tri-n-octylamine (TOA) with n-dodecane and lauryl alcohol (modifier) as biocompatible extraction system is investigated for intensification of recovery of nicotinic acid (NA), a pharmaceutical industrially important compound. The effect of important parameters such as initial NA concentration (0.014 - 0.083 mol.kg−1), TOA concentration (0.148–1.201 mol.kg−1), initial pH value (2.5–6) and temperature (298–328±1 K) are explored and optimized as NA concentration of 0.548 mol.kg−1, TOA concentration (0.706 mol.kg−1 or 20% w/w), pH (3.3) and Temp.298±1 K at 101.325±1 kPa for 92% of extraction degree. Equilibrium mechanism insights are determined as stoichiometry of reactions, overall equilibrium constant (KE) and individual equilibrium constant (K11 and K21) for 1:1 and 2:1 NA-TOA complexes. Theoretical reaction mechanisms are also supported by FT-IR data analysis. Evaluations of entropy (∆S0), enthalpy (∆H0) and Gibb's free energy (ΔG0) are carried out to find suitability of the process. A suitable column (RDC) design at optimized conditions is proposed and theoretical stages (NTS) are calculated which are found to be 5. Finally, solvent regeneration as 99% is achieved using 0.05 M NaOH solutions. This study is useful to intensify the process and design an economical industrial scale recovery of NA from dilute aqueous/fermentation broth.