Scalable coating of zeolite on alumina hollow fiber membranes for selective water removal from ethanol via pervaporation

Abstract

The separation of ethanol from water in an azeotropic mixture remains a major industrial challenge. To address this problem, the membrane-based pervaporation has emerged as a viable option due to its molecular selectivity and low temperature requirement. In this study, LTA type zeolite particles were coated on outer surface of alumina hollow fiber (AHF) to make defect free zeolite membrane by dip coating method. Coating method was optimized to enhance scalability as well as to reduce the wastage of synthesis gel. The phase, growth, and morphology of LTA on AHF was confirmed by XRD, FE-SEM, and HRTEM. The thickness of zeolite coating was ranged from 4 μm to 7 μm. Pervaporation tests of ethanol/water (90/10 vol%) mixture with various temperatures revealed strong water selectivity, a steady permeation flux and capacity to break the azeotrope. Permeate flux was increased with increase in temperature from 3.4 to 13 kg.m⁻²h^− 1, and separation factor varies from 6926.1 to 25754.5 for a feed flow of 2 mL min^− 1. The activation energy was estimated using the Arrhenius model to describe the temperature dependence of permeation. The activation energy for the CH₃CH₂OH and H₂O was ~ 86.83 and ~ 40 kJ mol^− 1, respectively; higher activation energy alludes to stronger sensitivity of water permeance to temperature, indicating its potential in water separation through pervaporation.