The potential of recovering propionic acid from discharged water in vitamin B-12 production by anaerobic fermentation was investigated in this paper. A primary amine, N-1923, Was used as the extractant, kerosene as diluter and n-octanol as modifier. The influences of the content of N-1923 in the organic phase, the phase ratio and the pH of aqueous phase on the extraction yield of propionic acid were studied. The organic phase composition with the volume ratio was proposed of N-1923: kerosene: n-octanol as 45:35:20. Under conditions of the phase ratio (o/w) as 1:4, the pH of aqueous phase of 3.0 and after 5 min extraction, the extraction yield of propionic acid can be over 97%. (c) 2008 Elsevier Ltd. All rights reserved.