In this paper, experiments were conducted on equilibrium distribution of citric acid between aqueous solutions and tri-n-octylamine (TOA)-impregnated resins in the 288-318 K temperature range. Analysis of the results showed that the sorption of citric acid could be explained by the formation of acid-TOA complexes in the resin phase with the general composition (H3A)p(TOA)qBAR. Mole fraction of the complexes formed in the resin phase as a function of citric acid concentration in the aqueous solution was obtained. The effect of temperature on equilibrium distribution was also studied, and the apparent thermodynamic data for sorption reactions were determined. Finally, the distribution of citric acid between aqueous solutions and the resins impregnating with a mixture of TOA and bis(2-ethylhexyl)phosphoric acid was examined.