Synthesis and characterization of modified alumina membrane with carbon nano-tubes for separation of ethanol from water using sweeping gas membrane distillation

Abstract

As ethanol forms an azeotropic mixture with water, producing pure ethanol is challenging for conventional distillation columns. This study intends to examine a sweeping gas membrane distillation (SGMD) system. To synthesise a membrane, an alumina support is prepared using the anodisation of an aluminum foil, followed by the pyrolysis of CNTs at different temperatures and substrate dipping times to create a porous hydrophobic membrane for the membrane distillation process. XRD and Raman spectroscopy patterns demonstrate that the optimum membrane can be made at the pyrolysis temperature of 700 °C. At the same time, the SEM and contact angle measurement tests show that substrate dipping for 10 min is optimal for obtaining a hydrophobic membrane with an appropriate pore size. The flux and selectivity tests show that an ethanol feed concentration of 27 wt% offers the best flux and separation factor. The concentration of 27 wt% was chosen as it mirrors the typical ethanol concentration in industrial processes. Regarding temperature dependency, the same trend is observed for flux, with an increase in the feed temperature leading to a decline in selectivity. Ultimately, in the optimal operational condition (50 °C and 27 wt%), the flux and selectivity are 45 kg m⁻² h⁻¹ and 8.8, respectively. These operational conditions were meticulously selected based on their ability to maximize the flux and selectivity, a testament to the careful methodology of this study. The outcome of this study reveals that the CNT-modified SGMD can efficiently separate ethanol from water.