Design of organosilica membranes to optimize reverse osmosis for the concentration of alcohols

Abstract

Short-chain alcohols like methanol, ethanol, and isopropyl alcohol are essential in various industries but require energy-intensive distillation for concentration and purification. Reverse osmosis (RO) offers an energy-efficient alternative, yet high osmotic pressures demand robust membranes. This study optimized robust organosilica membranes for alcohol concentration via RO by exploring different intermediate and separation layers. First, methylene-bridged organosilica membranes were prepared with silica-zirconia and organosilica intermediate layers. The use of an organosilica intermediate layer exhibited a water permeance, nearly three times higher than that with a silica-zirconia intermediate layer, without compromising alcohol rejection. Further investigation into separation layers with varying organic linking units in organosilica structure— methylene (-CH₂-), ethylene (-CH₂CH₂-), and propylene (-CH₂CH₂CH₂-)—revealed that membranes with fewer carbon atoms showed superior throughput with superior selectivity due to reduced preferential alcohol adsorption. These findings indicate that organosilica membranes with an organosilica intermediate layer and a methylene-bridged organosilica separation layer are promising for energy-efficient alcohol concentration.