Nanofiltration (NF) is a relatively recent membrane filtration process used most often with low total dissolved solids water such as surface water and fresh groundwater, with the purpose of softening (polyvalent cation removal) and removal of disinfection by-product precursors such as natural organic matter and synthetic organic matter.
Nanofiltration is also becoming more widely used in food processing applications such as dairy, for simultaneous concentration and partial (monovalent ion) demineralisation.
The membrane separation process known as nanofiltration is essentially a liquid phase one, because it separates a range of inorganic and organic substances from solution in a liquid – mainly, but by no means entirely, water. This is done by diffusion through a membrane, under pressure differentials that are considerable less than those for reverse osmosis, but still significantly greater than those for ultrafiltration. It was the development of a thin film composite membrane that gave the real impetus to nanofiltration as a recognised process, and its remarkable growth since then is largely because of its unique ability to separate and fractionate ionic and relatively low molecular weight organic species.
The membranes are key to the performance of nanofiltration systems. They are produced in plate and frame form, spiral wound, tubular, capillary and hollow fibre formats, from a range of materials, including cellulose derivatives and synthetic polymers, from inorganic materials, ceramics especially, and from organic/inorganic hybrids.
Recent developments of membranes for NF have greatly extended their capabilities in very high or low pH environments, and in their application to non-aqueous liquids. The plastic media are highly cross-linked, to give long-term stability and a practical lifetime in more aggressive environments. NF membranes tend to have a slightly charged surface, with a negative charge at neutral pH. This surface charge plays an important role in the transportation mechanism and separation properties of the membrane.
ScaleAwayTM offers the following filtration technologies:
ScaleAwayTM offers the following filtration systems:
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