Fast, facile and scalable fabrication of novel microporous silicalite-1/PDMS mixed matrix membranes for efficient ethanol separation by pervaporation

Abstract

Ethanol pervaporation during its fermentative production alleviates product inhibition and hence enhances bioethanol production as a source of renewable energy. In this work, a novel microporous silicalite-1/PDMS mixed matrix membrane was fabricated by spraying as a facile, fast and low-cost method on a flat ceramic membrane. The effect of PDMS (0.05–0.15 g/ml), silica (0–0.06 g/ml) and curing temperature (80–150 °C) on the separation factor and permeation flux of the membranes was investigated using Box-Behnken design for separation 5 wt% ethanol/water solution at 30 °C which circulated at 400 (ml/min). Membranes were characterized by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and contact angle (CA). PDMS concentration acted as an influential factor. Higher curing temperatures led to separation factors less than one due to the higher density of the PDMS matrix. While lower temperatures caused low density, which decreased separation factors. Consequently, pervaporation performance improvement according to the hydrophobicity is possible as far as negative effects on the density of the polymer matrix can be controlled. Additionally, effects of temperature (30–70 °C), concentration (5–10 wt%), and flow rate (400–1000 ml/min) of the feed stream on the optimal membrane performances were examined. The best performances of permeation flux of 3.64 (kg/m2·h) and separation factor of 17.24 corresponded to the membrane (0.08 (g/ml) of PDMS, 0.06 (g/ml) of silica and curing temperature of 109.5 °C) with CA of 142° for separating 5 wt% solution at 60 °C and 400 ml/min. Eventually, this novel membrane can enhance bioethanol production and make it more affordable.