Analytical Sciences

Abstract − Analytical Sciences, 15(8), 773 (1999).

Comparison of 1-Octanol with Benzene in the Extraction of Copper(II) with Various Phenylcarboxylic Acids
Hiromichi YAMADA * , Tetsuyoshi NAITO, Kazuto MIWA, Shinsuke YAMADA and Hiroko WADA
Department of Applied Chemistry, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555, Japan
The solvent extraction of copper(II) with 3-phenylpropanoic, 4-phenylbutanoic, and 2-phenylbutanoic acids was carried out using 1-octanol and benzene as solvents at 25°C and at an aqueous ionic strength of 0.1 mol dm-3 (NaClO4). Each extraction equilibrium for these systems was determined in detail by a slope analysis and curve-fitting method. In the aqueous solution, the formation constants of copper(II) with these phenylcarboxylate anions were potentiometrically determined. The present results have been compared with the previous results for the extraction of copper(II) with phenylacetic acid using 1-octanol and benzene as solvents. Between the partition constants of CuA2 and HA (HA: phenylcarboxylic acid), the following relationship was set up: log KD,CuA2=1.8log KD,HA-1.5 for four kinds of phenylcarboxylic acids in the 1-octanol systems. Although a remarkable difference in the extracted species between the benzene and 1-octanol systems was observed, the extraction constants of dimeric copper(II) species and dimerization constants in these extraction equilibria were found to show a high correlation between the 1-octanol and benzene systems. The dimerization constants of copper(II) carboxylates in the 1-octanol systems increased with the number of carbon atoms in the acids: phenylacetic < 3-phenylpropanoic < 4-phenylbutanoic =~ 2-phenylbutanoic acids, and the extraction constants of the dimeric species, Cu2A4(HA)2 in the benzene systems decreased in the order: 2-phenylbutanoic < henylacetic < 3-phenylpropanoic < 4-phenylbutanoic acids. In the systems using 1-octanol and benzene, 2-phenylbutanoic acid was superior to the other phenylcarboxylic acids as an extractant for copper(II). (Keywords: Phenylcarboxylic acids, solvent extraction, dimerization of copper(II) carboxylates, solvent effect, partition constant of copper(II) phenylcarboxylates)