(212f) Sustainable Recovery of Butyric Acid through Salt-Induced Aqueous Two-Phase Extraction Using Non-Ionic Surfactants

Butyric is an important four-carbon volatile fatty acid (VFA) with broad applications in food, feed, polymer, pharmaceutical and biofuels industries. In line with the Food-Energy-Water Nexus and in response to the increasing demands for energy and chemicals while overcoming the issues associated with depleting fossil-based resources, butyric acid stimulates innovative advancement in the bio-based economy as it can be produced from urban waste streams. To simulate the enhanced recovery of butyric acid by valorization from fermented wastewater, a salt-induced aqueous system of Zigova’s medium, butyric acid and non-ionic surfactant was subjected to reactive extraction. In this study, non-ionic surfactant was utilized among the other amphiphilic materials as a separating agent due to its low toxicity and high extraction effectiveness for short-chain carboxylic acids. The main goal of this research is to determine how salting-out affects the cloud point of ethoxylated non-ionic surfactant, and consequently, the butyric acid separation. The effects of varying fermentation nutrients such as (NH₄)₂SO₄, KH₂PO₄, MgSO₄, FeSO₄ and MnSO₄ on the extraction of butyric acid were determined through the acid partition coefficient and recovery ratio as the main responses. Results show that the cloud point of the system which refers to the temperature at which the mixture starts to phase separate, was sensitive to the presence of electrolytes. This caused high butyric acid partition coefficient and recovery ratio for the system with enhanced salt concentrations versus the control with conventional concentration of salts in the Zigova’s medium. The salt changed the solvent structure by aggregation and formation of larger micelles. This translates into a lipophilic shift which reduced the cloud point and the surfactant hydrophilic-lipophilic balance (HLB). As this HLB was decreased, the surfactant turned to be more hydrophobic and formed better separation. Also, the type of salt influenced the interphase mass transfer. Compared with monovalent cations like NH₄⁺ and K⁺, the polyvalent cations such as Mg²⁺, Fe²⁺ and Mn²⁺ were found to be more effective in decreasing the HLB thereby increasing the butyric acid partition coefficient and recovery ratio. This is because of the polyvalent cations’ higher surface charge densities. The implementation of this non-energy requiring recovery of butyric acid using non-ionic surfactant induced with salt may serve as a good start-up to achieve an economical production of other VFAs, especially for upscale applications.