NanoFiltration.pptx

8/14/2019 NanoFiltration.pptx

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TYPES OF FILTRATION


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NF PROPERTIES

In general, NF has a MWCO near the 300-500 g/mole range. Hence theseparation of components with these molecular weights from higher moleculweight components can be accomplished

NF membranes have a slightly charged surface. Because the ion size andpore size are comparable, the charge plays a dominant role in separation


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POSSIBLE APPLICATIONS

Food :Demineralization of Whey

Recycle of nutrients in fermentation processes

Recovery of Cleaning-In-Place solutions

Textile :Removal of dyes from waste water

Water:Removal of degreasing agents from water

Hardness removal from water

Removal of heavy metals from water


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MASS TRANSFER IN NF

In a typical UF, MF and RO the Kedem Katachasky equations are used formodelling. This would be valid for NF with uncharged membrane

For a charged membrane though, a different methodology is followed. It usethe Nernst-Planck equation


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We get the above equation after rigorous solving in a ternary solution

The F1 and R 8,1 are functions of the valence of the solute ions andPermeability components


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RELATING MEMBRANE CHARGE TO PERFORMANCE

Performance of membrane i.e. Water Flux and Solute Rejection

In this experiment the membrane performance was investigated as a functionof pH.

It was done for various solutions like an indifferent electrolyte (NaCL), Hum Acid, and Anionic and Cationic surfactants

An NF-55 membrane was used for these measurements, operational pH of 3-9 and Temp range is 35 oC


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VARIANCE OF ZETA POTENTIAL WITH PH


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VARIANCE OF ZETA POTENTIAL WITH PH

In case of NaCl, we see that the membrane is positively charged at pH=3, and thenpasses through an isoelectric point at 3.2 and then is negatively charged above 3.2 .

But with SRHA, the zeta potential is always negative. Indicating that humic molecureadily adsorb to membrane surface and the negative groups of humic acid dominat

the membrane surface charge

At low pH, membrane and SRHA oppositely charged, hence attraction is bothelectrostatic and hydrophobic, whereas at high pH it is only hydrophobic


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SURFACTANTS

SDS, an anionic surfactant has similar effect as SRHA did on the membranezeta potential

At high pH, there is hydrophobic interaction and thus the adsorption of thesurfactant happens

At low pH, adsorption is even more because of electrostatic interaction


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SURFACTANTSDTAB, a cationic surfactant has markedly different interaction with the

membrane


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Water FluxandRejectionEffects


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NanoFiltration.pptx