Ethanol recovery from an aqueous medium using a pervaporation membrane

Pervaporation may be used to separate ethanol from the supernatant of fermented lignocellulosic materials. Ethanol in a dilute solution dissolves into an ethanol selective membrane and emerges on the other side as permeate at increased concentration. The main objective of this work was to study the effect of temperature, solution flow rate (Reynolds number), permeate-side pressure and various solutes on permeate flux and selectivity of polydimethyl-siloxane (PDMS) membrane for ethanol at a concentration of 2% w/w. Solution flow rate had no significant effect on either flux or selectivity. Solution temperature and permeate-side pressure had significant effects on both. Glucose in the solution decreased flux and selectivity but this effect was not significant at concentrations lower than 10 g/L. Xylose decreased flux at 10 g/L but had either very little effect or slightly increased selectivity. The effect of xylose on selectivity interacted with temperature. The presence of protein had little effect on either flux or selectivity. Maximal flux was obtained at the highest temperature and the lowest permeate-side pressure used while maximal ethanol selectivity was obtained at low solution temperature combined with a higher permeate-side pressure. No sugar or protein was found in the permeate.