Continuous countercurrent salting-out extraction of 1,3-propanediol from fermentation broth in a packed column

The possibility of continuous extraction of 1,3-propanediol in a experimental packed column was investigated using a salting-out extraction system of dipotassium phosphate/ethanol. Mass transfer of 1,3-propanediol takes place from the dispersed phase (salt-rich solution) to the continuous phase (ethanol). The influences of flow rate of dispersed phase and size of packing material on partition coefficient and recovery of 1,3-propanediol were investigated and the results were compared with those obtained in spray column and test tube. Furthermore, the influences of various system compositions on hold up of dispersed phase, mass transfer coefficient, and system stability were also studied in the column packed by stainless steel Dixon 3 × 3 mm. It was found that the packed column showed a good extraction efficiency and stability. Besides, 1,3-propanediol recovery of 90.30% was obtained during a 11 h continuous operation when the real fermentation broth was used. At the same time, 94.4% of phosphate could be recovered when 0.2 volume of anhydrous ethanol was added into the raffinate phase at pH 4.0.