Highly-permeable and antifouling thin-film nanocomposite reverse osmosis membrane: Beneficial effects of 1D/2D g-C3N4 nanohybrids

Abstract

The development of highly-permeable reverse osmosis membranes has yet been pursued as a basis for efficient water purification/desalination. In this study, graphitic carbon nitride (g-C3N4) nanomaterials with three structures, including one-dimensional (1D) g-C3N4 nanorods, two-dimensional (2D) g-C3N4 nanosheets and one/two-dimensional (1D/2D) g-C3N4 nanohybrids were dispersed into polyamide layer for preparation of thin-film nanocomposite (TFN) membranes. The effects of different structures of g-C3N4 nanomaterials on the microstructure and performance of membranes were investigated. Compared with polyamide membrane, 1D/2D nanohybrids incorporated TFN membrane had more open and larger nodular structures with abundant water channels. The surface roughness was decreased, the negativity and hydrophilicity were improved. The water permeability of resultant TFN membrane increased to 3.63 L·m−2·h−1·bar−1 for 2000 ppm NaCl brackish solution, 3.4 times that of PA membrane, with a high rejection of about 99.0 %. Even for 32,000 ppm NaCl solution, almost the same as the concentration of seawater, the water permeability of TFN membrane still maintained at 1.73 L·m−2·h−1·bar−1, 1.4 times that of PA membrane. Meanwhile, antifouling performance of membranes was systematically analyzed under organic foulant, inorganic foulant and mixed organic-inorganic foulants, which proved the excellent antifouling performance of resultant TFN membranes. In a word, the 1D/2D nanohybrids incorporated TFN membrane exhibited superior permeability and antifouling performance to 1D nanorods or 2D nanosheets incorporated ones, confirming the effectiveness of 1D/2D g-C3N4 nanohybrids for modification of reverse osmosis membrane and promising for more applications.