Salting-out: A novel purification technique in biorefinery

The separation and purification of bio-alcohols are hot fields because reducing energy consumption is concerned with the market completeness of these biofuels. This study proposes a salting-out process for purifying fermentation-based bio-butanol and bioethanol. In the one-step salting-out process, the iso-butanol in the aqueous phase can be fully recovered and purified to >95 wt% under saturated salt conditions. Under K3PO4-saturated conditions at 40 °C, iso-butanol can be purified up to 98.62 wt%; however, a one-step salting-out process cannot completely purify it due to the limitation of the salting-out effect. After the two-step salting-out process, the purity of iso-butanol, n-butanol, and ethanol was 99.85 wt%, 99.77 wt%, and 98.91 wt%, respectively. The two-step salting-out approach can replace the conventional rectification and molecular sieve adsorption processes, thereby introducing a novel bio-alcohol purification process to the biorefinery.