Polydopamine-modified halloysite nanotube-incorporated polyvinyl alcohol membrane for pervaporation of water-isopropanol mixture

In reference, the mussel-encouraged surface adhesion chemistry, dopamine oxidative autopolymerization on the surface of halloysite nanotubes (HNTs) was performed to confer hydrophilicity to the HNTs. The additional hydrophilic moieties with surface coating by polydopamine (PDA) was assured with transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) techniques. A PDA/HNT-incorporated polyvinyl alcohol/polyvinyl amine (PVA-PVAm) membrane was fabricated for the pervaporation-dehydration of isopropanol/water (IPA/water), and the filler dispersion, crystallinity, and hydrophilicity of the membrane were confirmed by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and contact angle measurements, respectively. The pervaporation test was performed with membranes having different PDA/HNT contents, where the flux increased from 0.19 to 0.39 kg/m(2)h, and the separation factor decreased from 479 to 63 with the 80/20 (w/w, IPA/water) feed mixture at 40 degrees C. Compared to the unmodified HNT-incorporated membrane, the membrane with 5 wt.% PDA/HNT exhibited superior performance. Upon increasing the feed (85/15 IPA/water w/w) temperature from 40 to 70 degrees C, the flux of water and IPA increased from 0.062 to 0.13 kg/m(2)h and 0.000063 to 0.00144 kg/m(2)h, respectively. The apparent energy of activation calculated using the Arrhenius equation was positive for both IPA and water. The higher energy required for permeation of IPA (99.65 kJ/mol) compared to water (22.69 kJ/mol) is attributed to facile permeation of water compared to IPA through the hydrophilic channel created by PDA-HNT. In long-term operation (120 h), the IPA and water flux of the 5 wt.% PDA/HNT-incorporated PVA-PVAm membrane was maintained using a feed composition of 80/20 (w/w %) IPA/water at 40 degrees C, indicating remarkable reusability of the membrane. (C) 2021 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Automated summary

By performing dopamine oxidative autopolymerization on the surface of halloysite nanotubes (HNTs) and creating a PDA/HNT-incorporated polyvinyl alcohol/polyvinyl amine (PVA-PVAm) membrane, a stable and efficient pervaporation-dehydration system for isopropanol/water separation was achieved. The membrane showed superior performance in terms of flux and separation factor, with remarkable reusability over long-term operation.