Imidazole assisted molecular-scale regulation of polyamide for preparing reverse osmosis membrane with enhanced water permeance

Abstract

The development of reverse osmosis (RO) technology is still hindered by many obstacles, especially the low water permeance of RO membrane. Herein, an interfacial polymerization regulated by N-acyl imidazole chemistry was proposed to fabricate high permeance RO membranes. The improvement of membrane performance was achieved by simply adding 2-Methylimidazole (Hmim) into aqueous phase. More angstrom-scale free volume elements, which acted as water molecule transport channels, were formed in the polyamide separation layer due to the reaction and hydrolysis of Hmim. As a result, a substantial increase in water permeance was achieved while maintaining high NaCl rejection. In addition, more carboxylic acid groups were formed on the membrane surface due to the hydrolysis of N-acyl imidazole, thereby imparting higher hydrophilicity and anti-fouling properties to the membrane. With the addition of 1.5 w/w% Hmim, the water permeance of the prepared RO membrane was improved to 4.4 L m−2 h−1 bar−1, nearly 4.5 times compared to the control group, while maintaining a high NaCl rejection of above 98 %, thus successfully overcoming the permeability-selectivity trade-off limit. This work paves a new idea for the development of additives in the preparation of RO membranes.