Boron removal and antifouling properties of thin-film nanocomposite membrane incorporating PECVD-modified titanate nanotubes

Abstract

BACKGROUND: Incorporation of nanofillers into the polyamide (PA) layer of thin-film composite (TFC) membrane could improve membrane surface properties for enhanced water separation efficiency. However, most nanofillers do not disperse well in organic medium. In this work, the surface of titanate nanotubes (TNTs) was modified via the plasma-enhanced chemical vapour deposition (PECVD) method in order to promote its dispersion rate (in organic medium) during thin-film nanocomposite (TFN) membrane fabrication. RESULTS: Fourier transform infrared (FTIR) analysis confirmed the surface chemistry of TNTs coated by hexafluorobutyl acrylate (HFBA) or hydroxyethyl methacrylate (HEMA) via PECVD method. The effects of embedding modified TNTs into the PA layer on membrane surface morphology, hydrophilicity and performance were also investigated and the results were further compared with commercial reverse osmosis (RO) membranes. It was found that the incorporation of HFBA- and HEMA-modified TNTs could enhance the membrane water permeability by >25% and >40%, respectively, without compromising their salt rejection. The boron rejections of TFN membranes incorporated with HFBA- and HEMA-modified TNTs meanwhile were recorded at 75.56% and 70.73%, respectively; these values were relatively higher than those for the self-synthesized TFC (68.57%) and commercial RO membranes (37–39%). The developed TFN membranes also exhibited higher fouling tolerance than the commercial RO membranes, achieving >94% of water flux regeneration as a result of enhanced membrane surface hydrophilicity. CONCLUSION: Compared to hydrophilic modification using HEMA, nanofillers modified by hydrophobic HFBA proved more effective at producing a PA layer with better nanofiller distribution, making the resultant TFN membrane more suitable for desalination processes.