Enhanced extraction of ethanol from ethanol-water mixture by pervaporation using PDMS membranes impregnated with the PDMS-derived silicon oxy-carbide particles

In this work, we report that extraction of ethanol from the ethanol-water mixture using polydimethylsiloxane (PDMS) membranes is enhanced when the membrane is impregnated by the SiOC particles close to one side. SiOC particles with a high surface area (192 m2g−1) are prepared by a novel route in which a sponge of PDMS is wrapped inside an aluminum foil and subjected to a heat treatment at 550 °C. A 10% cross-linked and cured PDMS membrane is infused with these particles on one side up to a depth of 100 µm by exposing that side to a suspension of SiOC particles in di-iso-propylamine. Infusion leads to increased surface hydrophilicity on that side and a significantly altered pore size distribution in the membrane. We observed enhanced transport of ethanol as compared to water when infused membranes were used for pervaporation of a fifty-fifty mixture of ethanol water. We propose an explanation that the impregnated particles adsorb water molecules forming a water-rich region inside the membrane, which thereby affords a liquid phase diffusion of ethanol and enhances its transport as compared to neat membranes which offer only solid phase diffusion. SiOC modification increased ethanol–water selectivity by ∼150% compared to native PDMS.