Radioactive wastewater treatment with modified aromatic polyamide reverse osmosis membranes via quaternary ammonium cation grafting

With the growing application of nuclear power, development of methods for the treatment of radioactive wastewater has become increasingly important. In this study, a positively charged aromatic polyamide reverse osmosis (RO) membrane was prepared using a quaternary ammonium salt (2, 3-epoxypropyl-trimethylammonium chloride, EPTAC) grafting to improve nuclide removal efficiency. After modification, the zeta potential of the RO membrane surface increased from -22.89 mV to 21.20 mV in neutral conditions. The positively charged RO membrane promoted more efficient removal of nuclides when compared with the original RO membrane. The decontamination factor (DF) of cesium (I) increased from 11.69 to 151.12 and the DF of cobalt (II) increased from 28.62 to 1670.84. In addition, the surface properties of the modified RO membrane were measured, including hydrophilicity, chemical elements, and morphology. The results of these analyses demonstrated that the hydrophilicity of the membrane was significantly improved as the water contact angle decreased from 65 degrees to 10 degrees. The analysis also demonstrated that the EPTAC-modified RO membrane had a stable nuclide DF under different pH conditions. A brief comparison of the DF of nuclides between commercial RO membranes and modified membranes demonstrated a potential application of EPTAC-modified RO membranes for the treatment of radioactive wastewater from nuclear power plants.