Nanofiltration and Reverse Osmosis Membranes with High Water Permeability
Thin film composite (TFC) membranes are the main membrane types for reverse osmosis (RO) and nanofiltration (NF) membranes. RO membranes can be used for desalination, utility water treatment, wastewater treatment and reuse as well as process water treatment. NF membranes can allow monovalent ions, such as sodium chloride, to pass through the membrane, while rejecting divalent and multivalent ions, such as sodium sulfate. It has applications in the diary, food, dye, biotech, pharmaceutical and industrial processes for concentrating targeted streams.
Boosting membrane permeability without a decrease in their rejection to target ions has been the objective of many membrane producers. Many methods have been proposed in literature to achieve the target, such as incorporating nanoparticles or surfactants. However, the synthesis of uniform nanoparticles in large scale is a problem and the long-term stability of nanoparticles in the polyamide layer is of concern. The process of adding surfactants is also not controllable, leading to a potential concern for quality control in the final membrane product.
This invention relates to a simple method to increase the water permeability of thin film composite membranes for nanofiltration and reverse osmosis by 2 to 5 times.