BACKGROUND: Reactive extraction is a promising technique for the recovery of amino acids from a queous solutions. The reactive extraction of L-valine with di(2-ethylhexyl)phosphate acid (D2EHPA) has been studied in this work. An expression for the equilibrium distribution ratio (D) was proposed to describe the experimental data. RESULTS: The diluents, equilibrium pH value (pH(eq)), the concentration of L-valine and D2EHPA were found to be the key factors that affected D. The highest D was observed at pH(eq) around 2.6 with 1-octanol as diluent. D value increased with increase of the concentration of D2EHPA. In contrast, with increase of the concentration of L-valine, D value decreased. The extraction mechanism was analyzed using Fourier infrared spectra. The reactive extraction mechanism of L-valine with D2EHPA was mainly via proton-transfer and ion-exchange process. By fitting the experimental data, (1: 1) complex of L-valine with D2EHPA was deduced. The comparison of theoretical D values with the experimental data verified the reliability of the proposed mechanism equations. CONCLUSIONS: L-valine was efficiently extracted from aqueous solutions using D2EHPA in 1-octanol, which provides preliminary practical information and theoretical basis for the separation of L-valine, as well as its purification and recovery. (C) 2016 Society of Chemical Industry