LALI PDF DL-EDL - DIALYSIS and ELECTRODIALYSIS Maretva...

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1 DIALYSIS and ELECTRODIALYSIS Maretva Baricot Ronnie Juraske Course: Membrane Separations December, 2003
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2 Dialysis What is dialysis? Dialysis is a membrane process where solutes ( MW~<100 Da) diffuse from one side of the membrane (feed side) to the other (dialysate or permeate side) according to their concentration gradient. First application in the 70’s. General Principles Separation between solutes is obtained as a result of differences in diffusion rates. • These are arising from differences in molecular size and solubility. • This means that the resistance increases with increasing molecular weight.
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3 Dialysis A typical concentration profile for dialysis with boundary layer resistences contains low-molecular-weight solute, A intermediate size molecules, B , and a colloid, C
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4 Dialysis In order to obtain a high flux, the membrane should be as thin as possible membrane feed Purifed feed dialysate Schematic drawing of the dialysis process
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5 Dialysis The solutes separate by passing through the membrane that behaves like a fibre filter and separation occurs by a sieving action based on the pore diameter and particle size (i.e. smaller molecules will diffuse faster than larger molecules). Transport proceedes via diffusion through a nonporous membranes. Membranes are highly swollen to reduce diffusive resistence.
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6 Dialysis Separation of solutes is determined by the concentration of the molecules on either side of the membrane; the molecules will flow from a high concentration to a lower concentration. Dialysis is a diffusion process and at steady - state transport can be described by : Transport
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7 Dialysis homogeneous Thicknes : 10 100 m m Membrane material: hydrophilic polymers (regenerated cellulose such as cellophane, cellulose acetate, copolymers of ethylene - vinyl alcohol and ethylene - vinyl acetate) Membrane application: optimum between diffusion rate and swelling Membranes
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8 Dialysis Applications Dialysis is used in varying circumstances such as: when a large pressure difference on the sides of the membrane is impractical,
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This note was uploaded on 01/07/2011 for the course CHEM 6153 taught by Professor - during the Spring '10 term at University of Florida.

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LALI PDF DL-EDL - DIALYSIS and ELECTRODIALYSIS Maretva...

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