Salting‐out effect of potassium pyrophosphate ( K 4 P 2 O 7 ) on the separation of biobutanol from an aqueous solution

BACKGROUND Recovering biobutanol is expensive because of the large amount of water in the fermentation broth. In this work, potassium pyrophosphate trihydrate ( K 4 P 2 O 7 · 3H 2 O ), saturated K 4 P 2 O 7 solution at 298.15 K, and saturated K 4 P 2 O 7 solution at 333.15 K were used to separate acetone, 1‐butanol, and ethanol ( ABE ) from an aqueous solution. The salting‐out of ABE resulted in the formation of an organic solvent‐rich phase and an aqueous phase. RESULTS The aqueous solution consisted of 26 wt% 1‐butanol, 10 wt% acetone, 4 wt% ethanol, and 60 wt% water. The water content of the organic phase was heavily dependent on the salt concentration and it was 5.21 wt% under K 4 P 2 O 7 ‐saturated condition at 298.15 K. More than 99.5% ABE from the aqueous solution was recovered at the salting‐out factor (volume ratio of a K 4 P 2 O 7 solution to the aqueous solution) of 1.0. CONCLUSION The water content of the organic phase could be predicted by the initial K 4 P 2 O 7 concentration. The water content of the organic phase and the mass fraction of K 4 P 2 O 7 in the aqueous phase were correlated satisfactorily by a new linear equation. More than 96% of the water from the aqueous solution was removed by the salting‐out method. © 2015 Society of Chemical Industry