Post on 08-Jul-2018
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Mass TransferPE -3101
Membrane Separations (Lecture –1)
Taught by:Engr. Muzammil Mehmood
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Membrane Separations
Whilst efective product separation is crucial to economicoperation in the process industries, certain types o materials areinherently dicult and epensive to separate. !mportanteamples include:
". #inely dispersed solids, especially those $hich arecompressible, and $hich have a density close to that o theli%uid phase, have high viscosity, or are gelatinous.
2. &o$ molecular $eight, non'volatile organics orpharmaceuticals and dissolved salts.
3. (iological materials $hich are very sensitive to their physicaland chemical environment.
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Cont.
The processing o these categories o materials has becomeincreasingly important in recent years, especially $ith the gro$tho the ne$er biotechnological industries and $ith the increasinglysophisticated nature o processing in the ood industries.
When diculties arise in the processing o materials o biological
origin, it is $orth as)ing, ho$ does nature solve the problem* Thesolution $hich nature has developed is li)ely to be both highlyefective and energy ecient, though it may be slo$ in processterms.
+ature separates biologically active materials by means o
membranes.
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!at is a membrane"
membrane may be de-ned as an interphase separating t$ophases and selectively controlling the transport o materialsbet$een those phases/.
membrane is an interphase rather than an interace because itoccupies a -nite, though normally small, element o space.
0uman beings are all surrounded by a membrane, the s)in, andmembranes control the separation o materials at all levels o lie,do$n to the outer layers o bacteria and sub cellular components.
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T#pes $f Membranes
". +aturally occurring membranes 1 human s)in, animal s)in 2
3. 4ynthetic membranes 1 polyamide , polysulphones ,polycarbonates etc 2
5. symmetric membranes 1 having a dense outer layer and a highlyporous substructure over the rest o membrane 2
6. 4ymmetric membranes 1 having similar structure throughout 2
7. Thin -lm composite membranes 1 etremely thin layer o " umsupported on a porous structure2
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%&'antaes $f MembraneSeparations
". mbient temperature operation
3. &o$er capital cost than other competitors
5. &o$er running cost
6. Modular construction
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1. Micro +itration (M+)
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0ere the driving orce is pressure gradient and the size range oparticles separated is ">?>." @m.
Eamples include 4mall particles, large colloids, microbial cells.
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2. ,tra +itration (,+)
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0ere the driving orce is pressure gradient and the size range oparticles separated is
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3. ano +itration (+)
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0ere the driving orce is pressure gradient and the size range oparticles separated is A" nm.
Eamples include
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. /e'erse $smosis (/$)
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0ere the driving orce is pressure gradient and the size range oparticles separated is
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. Eectro ia#sis (E)
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0ere the driving orce is Electric -eld gradient and the size rangeo particles separated is
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. ia#sis
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0ere the driving orce is concentration gradient and the sizerange o particles separated is
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!at are iui&
membranes 4 t!eirt#pes an&
a&'antaes
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tec!niues4 t!eir
6or5in principaan& t#pica
appications/o o. 31 (7an8a aseer)
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