Extraction mechanism and behavior of oxalic acid by trioctylamine

Oxalic acid in an aqueous solution was extracted by tri-octylamine (TOA) in n-octanol as well as in the mixture of n-octanol and kerosene. Infrared sp ectroscopic analysis was performed to study the stoichiometry of complex fo rmation. A model for the extraction equilibrium was presented and subsequen tly used to correlate the experimental data. The distribution coefficient i ncreases with TOA concentration, S-0. The TOA loading increases sharply at lower aqueous phase concentration of oxalic acid, and approaches 1.0 at hig her aqueous phase concentration of oxalic acid. The effect of diluent, kero sene, on the extraction of oxalic acid depends on S-0. Kerosene apparently affects the extraction behavior at lower S-0. The infrared spectroscopic an alysis result shows that (1,2) complex between oxalic acid and amine was fo rmed in this experimental system. The apparent chemical association constan ts, K-11 and K-12, were obtained by fitting the experimental data of extrac tion equilibrium, where K-11 was much larger than K-12. (C) 2001 Elsevier S cience B.V. All rights reserved.