Experimental and theoretical analysis of reactive extraction of caproic acid by using TBP in green diluents

Abstract

Use of toxic diluent is harmful for producing caproic acid from fermentation unit. It led to consider green and non-toxic diluents: sunflower and soybean oils in the current study along with tributyl phosphate (TBP) as the reactive extractant. Important performance indicator parameters were estimated over the temperature range of 298 K–318 K. The changed of enthalpy and entropy because of mass transfer of caproic acid from aqueous phase to the interfaces, complexation reaction and overall acid transfer from aqueous phase to organic phase were estimated and analyzed. Best model among considered different acid concentration dependent distribution co-efficient models was identified following a newly developed method. Sunflower oil is identified as more efficient diluent than soybean oil. The new method has successfully determined the equilibrium complexation reaction stoichiometry. Further, concentrations of complex, free acid and dimer in the organic phase were determined which never were estimated previously. In spite of low loading ratio, less than 0.5 in the current experimental study, the estimated m has appeared greater than 1.0 for n=1. Current work has suggested to use presently studied microorganism friendly green and nontoxic diluents (sunflower and soybean oil) in biorefinary industry for recovering caproic acid from fermentation unit.