AMINE EXTRACTION OF CITRIC-ACID - EFFECT OF DILUENT

Distribution of citric acid between water and trialkylamine C-7-C-9 dissolved in 7 various diluents (p-xylene, toluene, benzene, MIBK, 1-octanol, methylene chloride, chloroform) was studied. Using a ''chemical modeling'' approach two acid: amine complexes, ACID. AMINE and ACID. (AMINE)2, have been assumed to exist in the organic phase in the case of proton-donating diluents (octanol, chloroform, methylene chloride), while the complexes ACID. AMINE and (ACID)2(AMINE)3 have been suggested in the case of aromatics and MIBK. The estimated values of overall extraction constants, K11, K12 and K23, were correlated with solvatochromic parameters of the diluents according to the linear solvation energy relationship (LSER). Using this correlation the extractability of citric acid can be predicted for a wide range of diluents or their mixtures. The coextraction of water with acid was explained in terms of the corrected physical solubility of water, m(w)*BAR, and hydration coefficients, h11, h12 and h23. The values of hydration coefficients were also correlated with the solvatochromic parameters of the diluents.