Equilibrium Study on Reactive Extraction of Acetic Acid with Tri-n-butyl Phosphate in N-hexane

Extraction of carboxylic acids from dilute aqueous solution using traditional solvents such as ketones, alcohols, ethers, and ester is inefficient because the distribution ratio is rather low. Reactive extraction which exploits reversible chemical complexation is an effective separation process for extraction of carboxylic acids from aqueous streams such as fermentation broths and wastewaters. Considering its solubility in water, cost and availability, tri-n-butyl phosphate (TBP) seems to be an attractive solvent for the extraction of acetic acid from aqueous solution. The purpose of this experiment is to study the equilibrium of the reactive extraction of acetic acid in aqueous solution with TBP in n-hexane. The parameters studied in this experiment were initial concentration of acetic acid in the aqueous phase, TBP concentration in n-hexane phase, and the extraction temperature. In this experiment, the initial concentration of acetic acid was varied from 0.1 to 0.5 gmol/dm. The range of initial TBP concentrations in n-hexane was 0.1 to 1.0 gmol/dm and the extraction temperature range was 283 to 313 K. The overall equilibrium constants (Kpq) for the experiments using TBP concentration ranging from 0.1 to 1.0 gmol/dm at the extraction temperature of 293 K are calculated to be 0.1779 to 0.9650. Kpq for the experiments at the temperature ranging from 283 to 313 K at the initial concentration of acetic acid of 0.2 gmol/L are found to be 0.1311 to 0.9912. The Kpq as a function of temperature (T) in K can be expressed as ln Kpq = 5,629/T 19.92 with sum of squared error of 0.21.