SG MEM

Current state-of-the-art lab-scale methods for fabricating superhydrophobic membranes for membrane distillation often involve complex surface modifications or the use of nanomaterials. However, these methods are difficult to scale up. This technology relates to a pure rheological spray-assisted non-solvent induced phase separation (SANIPS) approach to fabricate superhydrophobic polyvinylidene fluoride (PVDF) membranes. The resulting membranes have high porosity, superhydrophobicity, high liquid entry pressure, and hierarchical micro/nanostructures. They can also be easily scaled up. The spraying step caused local distortion of the membrane surface, which induced a two-stage phase inversion. This led to the formation of multilevel polymeric crystal structures. The morphological structures and other membrane properties (e.g., mechanical strength and liquid entry pressure) could be tuned by applying spraying materials with different physicochemical properties. This facile fabrication method will pave the way for the large-scale production of superhydrophobic membranes for membrane distillation.

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.

Thin-film nanocomposite (TFN) membranes are a promising technology for desalination to increase water permeability of thin-film composite (TFC) membranes without compromising selectivity. However, their widespread use has been limited by the time and resources required to synthesise the necessary nanomaterials.  This invention relates to a methodology to form TFN membranes directly on TFC membranes, resulting in membranes with enhanced water permeability with little compromise on salt rejection.