Polymer membranes have been widely used at different levels of water purifications. Perhaps, the most challenging utilization of polymer membranes in water purification is desalination, where the chemical functionality and physical structures of the membranes (e.g. reverse osmosis (RO) membranes to treat brackish water or sea water) must be fine tuned to remove salt ions. With a slight reduction of the separation capability, nanofiltration (NF) membranes for water softening and removal of color, taste, odor and other small contaminants can be made. The thin film composite structure has been routinely adopted for fabrications of NF and RO membranes. One of the most common methods to prepare the selective top layer on support material is interfacial polymerization. The support material (e.g. ultrafiltration (UF) membranes with MWCO ～ 100k or higher) usually has only a relatively small surface area fraction as open pores (with pore sizes of a few nanometers), which impose severe flux restrictions. There have been several attempts to use highly porous supports as a substitute to replace the low flux UF membranes as support materials. One example is the anodiscTM type inorganic membranes for high flux NF applications. However, this technology is not so practical because of the difficulty in handling and high cost.
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