Advanced reverse osmosis membranes prepared by counter-diffusion of organic phase monomers induced by polypyrrole additives

Highly permeable thin film composite (TFC) reverse osmosis (RO) membranes with abundant free volume are desirable for water treatment. However, the strategy of controlling the microstructure of the separation layer with high free volume rate is still a challenge. In this work, a modified strategy for the preparation of high-performance TFC RO membrane with inverse diffusible polypyrrole nanoparticles (PPYN) as organic phase additive was developed. The combination of PPYN and trimesoyl chloride (TMC) would diffuse backwards from the organic phase into the aqueous phase during the reaction process to disrupt the normal interfacial polymerization (IP) and thus introduce more free volume in the RO membrane due to the nanobubbles from violent reactions. Moreover, the thickness of the modified membrane decreased and the hydrophilicity increased based on the modulation of IP by PPYN, which facilitated the water molecules to transport. The prepared RO-PPYN membranes showed nearly three times the flux compared with the pristine RO membrane without sacrificing separation selectivity. Furthermore, the anti-biofouling property of the modified membrane was also improved. This work successfully demonstrated the potential use of PPYN as an organic filler to enhance the performance of seawater desalination in RO membranes. Our modification strategy provides an efficient and convenient way to prepare novel RO membranes with high permeability.