Reactive Separation of Caproic Acid From Aqueous Streams Using Tri-N-Butyl Phosphate in Natural Diluents

Caproic acid is gaining prominence as a chemical building block, exhibiting a wide array of applications across various industries. It serves as an antimicrobial agent, a feed additive, a promoter of plant growth, and a precursor for various products, including fragrances, lubricants, and pharmaceuticals. Consequently, the separation and purification of caproic acid are essential. Reactive extraction represents a sustainable and energy-efficient method for isolating carboxylic acids in downstream processes. This article elucidates the liquid-liquid equilibria involved in the extraction of caproic acid utilizing tri-n-butyl phosphate (TBP) dissolved in natural oils. The experimental results are explained in terms of distribution coefficient, overall equilibrium constant, partition coefficient, extraction efficiency, dimerization constant, and loading ratio. Further, the number of stages was also ascertained to design the extraction column. Additionally, diffusivity using the Wilke-Chang model and the Reddy-Doraiswamy correlation was approximated. The density and viscosity of the extract phase were vetted since both characteristics are the prime factors to facilitate the mass transport of caproic acid toward the interphase and design of the extraction process.