The influence of pH and solvent polarity on the mechanism and efficiency of folic acid extraction with Amberlite LA-2

Studies on the reactive extraction of folic acid with Amberlite LA-2 in three solvents of different polarity (n-heptane, chloroform, dichloromethane), at various extractant concentrations and pH-values of the aqueous solutions, indicated that the pH-value controls the extraction mechanism through the dissociation of carboxylic groups of folic acid. Thus, the solute and the extractant participate at the interfacial reaction at a molar ratio of 1:2 for pH below pK1, and 1:1 for pK1 < pH < pK2. The solvent polarity and pH-value exhibit a significant effect both on the extraction degree of folic acid (for an Amberlite LA-2 concentration of 80 g/l the extraction degree in dichloromethane was about 2-2.7 times greater than that corresponding to extraction in n-heptane, this difference increased with increasing pH of the aqueous solution) and on the extraction constant (by increasing the pH-value from 3 to 5.2, the extraction constants obtained for dichloromethane increased about 2.7 to 27.1 times compared with those obtained for extraction in n-heptane).