The prospective function of a novel energy efficient fermentation technology has been getting great attention in the past fifty years due to the quick raise in petroleum costs. Fermentation chemicals are still limited in the modern market in huge part because of trouble in recovery of carboxylic acids. Therefore, it is needed considerable development in the current recovery technology. Carboxylic acids have been used as the majority of fermentation chemicals. This paper presents a state-of-the-art review on the reactive extraction of carboxylic acids from fermentation broths. This paper principally focuses on reactive extraction that is found to be a capable option to the proper recovery methods.

The present study deals with the equilibrium reactive extraction of glycolic acid from aqueous solution by two different extractants [tri-n-butyl phosphate (TBP) and tri-n-octylamine (TOA)] at constant concentration of 0.573 kmol·m−3 dissolving in a wide range of diluents [n-hexane, decane-1-ol, n-hexane + decane-1-ol (1:1 v/v), 4-methylpentan-2-one (MIBK), benzene, and dichloromethane (DCM)] at isothermal conditions (298 ± 1 K). The effects of various parameters such as acid concentration (0.10−0.57 kmol·m−3), extractant type, and type of diluent on the recovery of glycolic acid from aqueous solution are derived. The values of equilibrium constants (K E), number of reacting acid molecules (m) per extractant molecule, and also the equilibrium constants (K 11 and K 21) for individual complexes between acid and extractant are estimated through the proposed mathematical model. Further, the experimental values of the distribution coefficients (K D) are correlated using the linear solvation energy relationship (LSER) model which is based on solute−solvent interaction parameters. The extraction power of TBP and TOA in terms of K D increases in the order of DCM ≥ MIBK > decan-1-ol > n-hexane + decan-1-ol (1:1 v/v) ≥ benzene ≥ n-hexane, and DCM ≥ decan-1-ol > MIBK > n-hexane + decan-1-ol (1:1 v/v) > benzene > n-hexane, respectively.

In the present study, the reactive extraction of levulinic acid (4-oxopentanoic acid) was investigated by using Aliquat 336 in various organic solvents [benzene, dichloromethane (DCM), dodecane, methyl isobutyl ketone (MIBK), 1-octanol] from dilute aqueous solution. Equilibrium data obtained at 298 K and 101.325 kPa were used to determine the values of distribution coefficient (K D), degree of extraction (E%), loading factor (Z), and complexation constants (K E). Among the diluents tested, DCM gave the highest extraction efficiency. Using 0.5454 mol·kg–1 of Aliquat 336 in DCM, K D and E% were obtained as 2.082 and 67.55%, respectively, at 0.2795 mol·kg–1 initial acid concentration in the aqueous solution. Z values were found to be between 0.033 and 1.628 depending on the nature of the diluent used and Aliquat 336 concentration in the organic phase. Using mass action law modeling, the stoichiometry of the extraction reaction was determined. It was observed that mostly 1:1, 2:1, and 3:1 types of complexes were formed. The results inferred that the polarity and the molecular size of the solvent were the important critical factors which decide the solubilization of the solvates in the organic phase. DCM was found to be the most appropriate solvent among tested ones for the reactive extraction of levulinic acid. The feasibility of the extraction process was also assessed by calculating the minimum solvent (extractant + diluent) to feed ratio and the number of theoretical stages required for the recovery of levulinic acid in the extraction column.

The carboxylic acids such as ethanoic, propanoic, and butanoic acids are most widely used in pharmaceutical, agricultural, polymer, and chemical industries. The separation of acids from fermentation broth and aqueous waste stream can be intensified by reactive extraction. The reactive extraction of carboxylic acids (ethanoic, propanoic, and butanoic acids) by N,N-dioctyloctan-1-amine (TOA) with six different diluents [decane, benzene, 4-methyl-2-pentanone (MIBK), decan-1-ol, chloroform, and decane (w ) 0.725) + decan-1-ol (w ) 0.275)] is studied. The physical equilibria using pure diluents with the same conditions are also studied. Distribution coefficients, loading factors, and degree of extraction are calculated as a result of batch extraction experiments. In the present work, a population-based search algorithm, differential evolution (DE), is employed as an optimization routine to estimate the optimum values of equilibrium constants (K E ) and stoichiometries of reactive extraction (m:n) through proposed mathematical models. On the basis of stoichiometries, the equilibrium constants (K 11 , K 21 , and K 31 ) for individual complexes between acid and extractant are also estimated. In addition to these parameters, the linear solvation energy relationship (LSER) model is applied to evaluate distribution coefficients, and the LSER equation is presented for each acid. The extraction power of amine/diluent system increases in the order of chloroform g decan-1-ol > MIBK > decane (w ) 0.725) + decan-1-ol (w ) 0.275) g benzene > decane. † Part of the "Sir John S. Rowlinson Festschrift".

The reactive extraction of benzoic acid (BA) and pyridine-3-carboxylic acid (NA) using diluent mixtures, decane-1-ol (w = 0.36) + cyclohexane (w = 0.64) and 4-methylpentan-2-one (w = 0.63) + kerosene (w = 0.37) with and without reactive extractants such as tri-n-butylphosphate (TBP) and N,N-dioctyloctan-1-amine (TOA), is carried out. The effect of various parameters such as the type of acid, type of diluent mixture, type of extractant, and composition of aqueous and organic phases are studied to analyze the performance of reactive extraction. The maximum values of the distribution coefficient (K D ) are found to be 38.1 for BA and 7.4 for NA with TOA (0.229 mol 3 dm À3 ) in decane-1-ol (w = 0.36) + cyclohexane (w = 0.64). A mathematical model based on mass action law is proposed to estimate the values of partition coefficient (P) and dimerization constant (D) in physical extraction and equilibrium constants (K E ) and number of reacting extractant molecules per acid molecule in chemical extraction. The values of the loading ratio, Z (between 0.005 and 0.566), for the extraction of both acids using TBP and TOA in both diluent mixtures indicate a formation of a 1:1 acid/extractant complex in the organic phase. For the reactive extraction of both acids, the highest values of K E are found with TOA in decane-1-ol (w = 0.36) + cyclohexane (w = 0.64).