Enhancing Reverse Osmosis Desalination Performance of Thin-film Nanocomposite Membranes by Incorporating Tannic Acid-Modified Graphitic Carbon Nitride Nanosheets

Abstract

The advancement of nanotechnology has significantly facilitated the development of thin-film nanocomposite (TFN) reverse osmosis membranes for water desalination. Nevertheless, there are still several issues, including nanomaterial aggregation and low compatibility, that prevent the membrane's performance from reaching the desired level. In this study, graphitic carbon nitride modified with natural tannic acid (TA) macromolecules was adopted as a novel hydrophilic modifier for TFN membranes. The incorporation of this modifier significantly increased hydrophilicity of the active layer to improve the water permeation ability and formed covalent bonding between the phenolic hydroxyl groups of TA and unreacted acyl chloride groups during interfacial polymerization to enhance nanofiller compatibility with the PA matrix. Consequently, the water permeance of the TFN membrane attained 2.49 L∙m⁻²∙h⁻¹∙bar⁻¹, which was 2.2-fold higher compared to unmodified PA membranes (1.13 L∙m⁻²∙h⁻¹∙bar⁻¹), while a high NaCl rejection rate of 96.1% was maintained.