Nano filtration

Rather than use ion exchange, water can be deionized using membrane processes. Both nano-filtration and reverse... 

Reverse osmosis and nano-filtration are high-pressure membrane separation processes (typically 10 to 50 bar for reverse osmosis and 5 to 20 bar for nano-filtration), which can be used to reject dissolved inorganic salt or heavy metals. The processes were discussed in Chapter 10 and are particularly useful for removal of ionic species, such... 

Steam stripping Air stripping Biological nitrification Chemical oxidation Ion exchange Solvent extraction Biological oxidation (aerobic) Wet oxidation Activated carbon Chemical oxidation Chemical precipitation Ion exchange Adsorption Nano-filtration Reverse osmosis Electrodialysis... 

Ion exchange Reverse osmosis Nano-filtration Electro dialysis Crystallization Evaporation Acid Base Heat treatment UV light Chemical oxidation... 

To find a suitable membrane for a certain application, an important parameter is the molecular weight cut-off (MWCO). The MWCO is defined as the molecular weight at which 90% of the solutes are retained by the membrane. It should be taken into account that the pore size of many ultra- and nano filtration membranes is greatly influenced by the solvent and by the temperature used under experimental conditions. This particularly concerns polymeric membranes as will be discussed in the next paragraph. 

The most widely applied commercial nano filtration membrane is the MPF series of Koch Int.[19] (Figure 4.9). The series contains polymeric silicon-derived membranes in the MWCO range of 400-700 Da. [20] The membranes are supplied in a 50% ethanol / water mixture, and should under no circumstances be allowed to dry out. Before use, the membranes must be conditioned with the solvent of choice. 

Koschuh, W., V.H. Thang, S. Krasteva, S. Novalin and K.D. Kulbe, Flux and Retention Behaviour of Nano filtration and Fine Ultrafiltration Membranes in Filtrating Juice from a Green Biorefinery A Membrane Sreening, J. Membr. Sci., 261, 121-128 (2005). 

Micro-, ultra-, and nano-filtration can separate smaller particles using media with defined porous sizes (i.e., 10 1—1 pm in microfiltration, 10 2—10 pm in ultrafiltration, and 10 3— 10 2 pm in nanofiltration). Residual colloidal and suspended solids can be removed by microfiltration. Selected salts, most organic compounds, bacteria, protozoan cysts, oocysts and viruses are removed by nanofiltration, so that the treated water will be disinfected. This advanced filtration is used for the treatment of effluents for indirect potable reuse applications such as groundwater injection, water softening, decoloriza-tion, or removal of micropollution. 

A holy grail for DON (and DOM in general) remains a rapid and portable method to quantitatively isolate and desalt a large dissolved sample (Bronk, 2002). Such a method would not only allow a wealth of diverse techniques to be brought to bear on the largest unknown fraction of DON, but would allow direct isotopic measurements and compound-specific mass balances. Examples of some approaches currently being explored to improve DON recovery on both small and large scales include homemade ion-retardation resins (Bronk, unpublished data), electrodialysis (Vetter et al, 2007), and use of nano-filtration membranes coupled to standard ultrafiltration approaches (McCarthy et al unpubhshed data). 

Guizard C. Nano filtration Guide. Montpellier, France CFM Booklet N ISBN 2.9516158-0-9, 2000. 

Chitry, F. et al., Lanthanides(ttt)/actinides(III) separation by nano-filtration-complexation in aqueous medium, in Proceedings of International Conference, Nuclear waste From Research to Industrial Maturity, Montpellier, Oct. 2-4, 2000. 

Zaidi A, Buisson H, Sourirajan S, and Wood H. Ultra- and nano-filtration in advanced effluent treatment schemes for pollution control in the pulp and paper industry. Wat. Sci. Tech. 1992 25(10) 263-276. 

Nano filtration According to the International Union of Pure and Applied Chemistry (lUPAC) recommendations [16] nanofiltration is a pressure-driven membrane-based separation process in which particles and dissolved molecules smaller than about 2 nm are retained. ... 

Schafer, A.I., Pane, A.G., and Waite, T.D., Nano filtration Principles and Applications, Elsevier Advanced Technology, Oxford, United Kingdom, 2005. 

C. Guizard, A. Julbe, A. Larbot, L. Cot, Nanostructures in Sol-Gel Derived Materials. Application to the Elaboration of Nano filtration Membranes, Key Engineering Materials Vols. 61 62 (1991) pp. 47-56, Trans Tech Publications, Switzerland. 

Nano filtration (NF) is a relatively new process, though while the number of applications is growing rapidly, the transport mechanisms are still poorly understood (Raman et al. (1994)). NF shows a high selectivity between mono- and multivalent ions. Its popularity in water treatment stems from its softening abilities and high organics (and micropollutant) rejection. 

High-pressure homogenization, bead mills, sonication, enzymatic treatments Filtration (micro-, ultra-, nano-filtration), precipitation, solvent extraction, ion exchange, size exclusion, affinity chromatography Hydrophobic interaction/reversed-phase chromatography... 

Nano-filtration, heat, pH, chemical inactivation, ultraviolet, gamma irradiation... 

These cut-off values are nominal values (N.M.W C O ) and are therefore not always precise enough to be used as an exact parameter when fractioning continuously distributed polymers However ultra-filtration from nano filtration could have a scale of 100-lmil Dalton, Fig 3 illustrates a typical example of the membrane range... 

J.T. Scarpello, D. Nair, L.M. Freitas dos Santos, L.S. White, and A.G. Livingston, The separation of oiganometalhc catalysts using solvent resistant nano filtration, J. Membr. Sci. 180 (2002) 1-15. 

Van Gestel T, Kruidhof H, Blank DHA, and Bouwmeester HIM. Zr02 and Ti02 membranes for nanofiltration and per-vaporation. Part 1. Preparation and characterization of a corrosion-resistant Zr02 nano filtration membrane with a MWCO < 300. J. Membr. Set 2006 284 128-136. 

Ahmed S, Rasul MG, Hasib MA, Watanabe Y. Performance of nano filtration membrane in a vibrating module (VSEP-NF) for arsenic removal. Desalination 2010 252 127-134. 

Bhanushali, D., Kloos, S., and Bhattacharyya, D. (2002) Solute transport in solvent resistant nano filtration membranes for non-aqueous systems Experimental results and the role of solute-solvent coupling. Journal of Membrane Science 208, 343-359. 

Geng, A., Lin, H. T., and Tan, Y. (2002) Solvent recovery from edible oil extract using nano-filtration ceramic membranes. In World Conference and Exhibition on Oilseed and Edible, Industrial, and Specialty Oils (p. 17) abstracts. Istanbul, Turkey. 

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