Analysis of Reverse Osmosis Separation Performances of Ethanol/Water Mixtures and Design of Ethanol Concentration Processes

Abstract

This study successfully analyzed the reverse osmosis (RO) separation performances of ethanol/water mixture (1–37 wt% of ethanol) with polymeric RO membranes using transport equations derived on the basis of the solution-diffusion mechanism in which the permeation flux is proportional to the chemical potential gradient. It was demonstrated that the obtained permeation data were well correlated with the transport equations. By utilizing the analyzed results, multi-stage RO processes for ethanol concentration from 5 to 40 wt% were evaluated in terms of required energy with the conventional distillation design. According to the process evaluation, existing polymeric RO membranes for desalination were not applicable to the ethanol concentration since estimated required energy was larger than distillation. Instead, RO membrane having assumed hypothetical permeance values for ethanol of 0.1 times and water of 2 times was proved to be feasible to achieve lower energy consumption, which can be used as a design guide.

Graphical abstract

Keywords:

• Transport equation
• Chemical potential
• Reverse osmosis
• Ethanol
• Concentration process

Acknowledgements

We thank Toray Industries, Inc, Japan and Nitto Denko Corporation, Japan for kindly supplying RO membranes. We also thank Austin Schultz, PhD, from Edanz (https://jp.edanz.com/ac) for editing a draft of this manuscript.