New membrane developments expanding the horizon for the application of reverse osmosis technology

Two new composite reverse osmosis (RO) membranes were developed recently with significantly improved performance over commercially available conventional composite membranes. The ESPA membrane chemistry provides a high flux at low operating pressure, while maintaining very good salt and organics rejection. The membrane has been in operation successfully for over 3 years, Transmission and field emission electron micrographs of the membrane surface demonstrate that the structure of the membrane skin layer is the reason for the improved performance. Fouling behavior of the ESPA chemistry is similar to conventional membranes. The LFC 1 membrane is a low fouling composite RO membrane. The surface properties of the membrane have been permanently modified during the manufacturing process to reduce surface charge and increase membrane hydrophilicity. The surface charge of various membranes was determined quantitatively using Zeta potential measurements. Membrane charge plays an important factor role in the fouling mechanism because it can function as an absorption site for foulants. Performance of the LFC1 under high fouling conditions demonstrates a significantly better flux stability than conventional brackish water composite membranes. The ESPA and LFC1 membranes will reduce the operating cost and improve the reliability of RO systems, thus making membrane technology an even more attractive alternative to traditional demineralization technologies.