membrane separations 1

8/19/2019 Membrane Separations 1

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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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T9%7 :$,

membrane separations 1

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