The extraction of glycolic acid from an aqueous glycolonitrile hydrolysate with tri-n-octylamine (TOA) in diluents of I-octanol and kerosene was investigated in this article. The influences of TOA concentration, extraction temperature and phase ratio, O/W (Volume ratio of organic phase to aqueous phase) on the acid distribution coefficient and loading factor of TOA were measured. The liquid-liquid equilibrium data of glycolic acid distributed between the extract phase and the raffinate phase were determined, and correlated with a model developed from the mass action law and suitable assumptions. Additionally, the acid loaded extractants were regenerated by using pure water as the back-extractant. The results show that lower temperature is beneficial to the extraction of glycolic acid from the hydrolysate, while higher temperature and phase ratio (O/W) are favorable to the back-extraction. (c) 2005 Elsevier B.V. All rights reserved.