Reactive Extraction of Citric Acid from Fermentation Broth Using Tri-n-Octylamine in Kerosene Diluent

Abstract

Citric acid is an important organic acid widely used in food, pharmaceutical, and biochemical industries, and its efficient recovery from fermentation broth remains a significant challenge in downstream processing. This study investigates the reactive extraction of citric acid from fermentation broth using tri-n-octylamine (TOA) dissolved in kerosene as an extractive solvent system. The research focuses on evaluating extraction efficiency, phase behavior, and mass transfer characteristics under varying operational conditions. Experimental analyses were conducted to examine the effects of extractant concentration, aqueous phase pH, temperature, phase ratio, mixing time, and initial citric acid concentration on extraction performance and acid recovery efficiency. Results demonstrated that tri-n-octylamine effectively forms acid–amine complexes with citric acid, resulting in enhanced extraction capacity and improved selectivity compared with conventional physical extraction methods. The kerosene diluent provided favorable phase separation behavior and stable extraction characteristics during operation. Equilibrium and kinetic studies indicated that extraction efficiency is strongly influenced by pH and extractant concentration, while optimized operating conditions significantly improved citric acid transfer from the aqueous fermentation medium to the organic phase. The reactive extraction process also minimized energy consumption and reduced downstream purification requirements, contributing to more economical and sustainable production practices. Furthermore, stripping and regeneration analyses confirmed the potential for solvent reuse and continuous process application. The findings highlight the suitability of tri-n-octylamine-based reactive extraction as an efficient and scalable approach for citric acid recovery from fermentation broths, supporting enhanced downstream processing and industrial biotechnology applications.