Analyses of Ethylenediaminetetraacetic Acid (Edta) in Selected Binary Immiscible Solvents: The Role of Partition Coefficient, kD

Abstract

Background: The focus is on the extraction of Ethylenediaminetetraacetic acid from contaminants using binary immiscible solvents. The molecular distributions of EDTA in the binary solvents that are involved are the key factors that determine the magnitude of the partition coefficient. Methods: Ethylenediaminetetraacetic acid was investigated in carbon tetrachloride-water, diethyl ether-water, and n-hexane-water binary solvents, at 30°C and atmospheric pressure, to determine the partition coefficients and the influence of interfering reactions, such as dimerization, ionization, etc. occurring with the distributions of the acid in the binary solvents and to ascertain the best binary solvent for the analyses of the acid. These analyses were done by titration. EDTA solute was introduced into the solvents and the concentrations of the pure molecules were calculated from the titration measurements. Results: Ethylenediaminetetraacetic acid has the distribution coefficient, kD value of 1.9213 in carbon tetrachloride-water system with the dimerization constant, K of -30.7821. It has the ionization constant, α of 0.0149 in this medium. Ethylenediaminetetraacetic acid has the kD value of 1.2186 in diethyl ether-water system and dimerization constant of -23.8972 with the ionization constant of 0.0687. The kD of EDTA in n-hexane-water system is 0.2035 with the dimerization constant of 2329.7237 and ionization constant of 0.0005. Conclusion: Distribution coefficient technique is used for solute-solvent extraction, and the beneficiation of minerals. A high distribution coefficient shows preferential solubility in the solvent that is involved and hence good separation. From the three systems used, carbon tetrachloride-water and diethyl etherwater systems are good for the analyses of Ethylenediaminetetraacetic acid. Carbon tetrachloride-water system is the best binary immiscible solvent, from the three systems investigated, for the extraction and purification of the acid. Good extraction and purification of EDTA in the recommended solvents will be done in several continuous steps.