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.
* 1 Overview * 2 Range of applications * 3 Advantages and disadvantages
* 4 Design and operation
* 4.1 Concentration polarisation
* 4.2 Spiral wound module
* 4.3 Tubular module
* 5 Characterisation
* 5.1 Performance parameters * 5.2 Morphology parameters * 5.3 Solute Transport and Rejection
* 6 Typical figures for industrial applications
* 7 Post-treatment
* 7.1 Aeration * 7.2 Disinfection and stabilisation
* 8 New developments * 9 See also * 10 References * 11 External links
RANGE OF APPLICATIONS
Historically, nanofiltration and other membrane technology used for molecular separation was applied entirely on aqueous systems. The original uses for nanofiltration were water treatment and in particular water softening . Nanofilters can “soften” water by retaining scale-forming, hydrated divalent ions (e.g. Ca2+, Mg2+) while passing smaller hydrated monovalent ions .
In recent years, the use of nanofiltration has been extended into other industries such as milk and juice production. Research and development in solvent-stable membranes has allowed the application for nanofiltration membranes to extend into new areas such as pharmaceuticals , fine chemicals, and flavour and fragrance industries. Development in organic solvent nanofiltration technology and commercialization of membranes used has extended possibilities for applications in a variety of organic solvents ranging from non-polar through polar to polar aprotic.
Fine chemistry and Pharmaceuticals Non-thermal solvent recovery and management
Room temperature solvent exchange
Oil and Petroleum chemistry Removal of tar components in feed
Purification of gas condensates
Bulk Chemistry Product Polishing
Continuous recovery of homogeneous catalysts
Natural Essential Oils and similar products Fractionation of crude extracts
Enrichment of natural compounds Gentle Separations
Medicine Able to extract amino acids and lipids from blood and other cell culture.
ADVANTAGES AND DISADVANTAGES
One of the main advantages of nanofiltration as a method of softening
water is that during the process of retaining calcium and magnesium
ions while passing smaller hydrated monovalent ions, filtration is
performed without adding extra sodium ions, as used in ion exchangers.
Many separation processes do not operate at room temperature (e.g.
distillation ), which greatly increases the cost of the process when
continuous heating or cooling is applied. Performing gentle molecular
separation is linked with nanofiltration that is often not included
with other forms of separation processes (centrifugation ). These are
two of the main benefits that are associated with nanofiltration.