Development of positively charged polyamide reverse osmosis membrane via polyethyleneimine spray coating for enhanced radionuclide rejection in water treatment

While reverse osmosis (RO) is effective for treating radionuclide-contaminated wastewater, it is confronted by some limitations including membrane fouling and limited rejection towards ions with relatively small hydrated radii like Cs⁺. In this study, surface modification of PA TFC membranes is explored for the improvement of radionuclide rejection efficiency. A convenient spray coating method was employed to introduce a polyethyleneimine (PEI) layer of different concentrations on the membrane surface, thereby rendering desired positive surface charges for efficient rejection of Cs⁺, Cd²⁺, and Cr³⁺ ions. The modified membranes were characterized in terms of their morphological changes, surface charge density, long-term stability and fouling resistance. The Cs⁺, Cd²⁺ and Cr³⁺ ion rejection of the optimized membrane, TFC membrane coated with 0.1 mg/l PEI, was significantly improved by 14.89 %, 17.39 % and 4.12 %, respectively. The surface features of the membrane remained unchanged over the 24-hour filtration testing, suggesting the stability of the coating layer. The findings of this study suggest that PEI spray coating can serve as a promising approach to improve radionuclide ion removal from aqueous systems and represents a promising approach for membrane-based wastewater treatment.