A pervaporation–microfiltration–osmotic distillation hybrid process for the concentration of ethanol–water extracts of the Echinacea plant

A three-stage hybrid membrane process for the concentration of ethanol–water extracts of the Echinacea plant has been investigated. Preliminary investigations using osmotic distillation in a single-stage process resulted in severe membrane wet-out by the ethanol-soluble, sparingly water-soluble alkyl amides that precipitated from solution due to the preferential removal of ethanol. In Stage 1 of the hybrid process, ethanol removal from the neat extract was achieved by pervaporation (PV). This gave an ethanol-free aqueous product containing suspended alkyl amides that was suitable for marketing in tincture form. In Stage 2, the precipitated alkyl amides were removed from the Stage 1 product by microfiltration (MF). In Stage 3, the microfiltration permeate was concentrated several-fold by osmotic distillation, followed by adding-back of the microfiltration retentate containing the precipitated alkyl amides to the osmotic distillation retentate. This gave a highly concentrated product suitable for marketing in capsule form. In addition to process design and product characterisation, pervaporation operating conditions were optimised for greatest efficiency in this application.