Lecture_8___membrane_processing - Membrane Separation in...

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1 Membrane Separation in the Dairy Industry Carmen I. Moraru Cornell University Principle of the separation process Feed Concentrate Permeate The solution to be concentrated or fractionated Also called retentate The liquid passing through the membrane (filtrate)
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2 Pressure driven membrane separation processes - It is a MEMBRANE TYPE RELATIVE SIZE OF COMMON MATERIALS Reverse Osmosis Nano- filtration Ultrafiltration Microfiltration Filtration Metal ions Oil emulsions Red blood cells Aqueous salts Bacteria Viruses Cysts Yeast cells Sand Human hair Sugars Proteins / Enzymes PARTICLE SIZE 10 -4 10 -3 10 -2 10 -1 1.0 10 10 2 10 3 (Microns) APPROXIMATE 100 200 20,000 500,000 MOLECULAR WEIGHT IONIC RANGE MACROMOLECULAR RANGE MICRON PARTICLE RANGE RANGE COARSE PARTICLE RANGE For milk/dairy applications: Photo : TetraPak Dairy Processing Handbook, 2003
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3 Characteristic pressures and membrane pore sizes: Photo : TetraPak Dairy Processing Handbook, 2003 Reverse Osmosis (RO) - The most complex membrane separation technique - RO membranes concentrate low molecular weight organic materials and salts, while allowing water and solvents to pass through. - RO uses high pressures (35-100 bar) to overcome the high osmotic pressures across the membrane. This allows water to flow from the concentrated feed to the dilute permeate side, against the direction of normal osmosis. - Most popular application: desalination of sea water and water purification. - In the Dairy Industry: used for dehydration / concentration of whey and UF permeate.
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4 Nanofiltration (NF) - NF membranes reject divalent ions and organic molecules with Mw= 200-300, but allow most monovalent ions to pass. - NF can be used to selectively concentrate / eliminate valuable / undesirable substances from processing liquids.
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Lecture_8___membrane_processing - Membrane Separation in...

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