Membranes have been used for separations since the 18th century, with significant developments in the 20th century. They are semi-permeable barriers that selectively restrict the transport of molecules. Key membrane processes include microfiltration, ultrafiltration, nanofiltration, reverse osmosis, gas separation, and pervaporation. Membranes are used in modules and the selection of module depends on factors like membrane area, costs, and fouling control. While membranes offer advantages like mild operating conditions, challenges include membrane fouling and costs.

2. It is defined essentially
as a “Barrier which
separates 2 phases
& restricts
transport of
various molecules
in a selective
manner”.
Driven by
• Pressure
• Concentration
• Temperature
• Electrical potential
Gradients
It can be
• Thick/Thin
• Liquid/Solid
• Symmetric/Asymmetric
• Natural/Synthetic
• Neutral/Charged
• Homogeneous/Heterog-
eneous

3.  In 1748 - Abbe Jean-Antoine Nollet; French physicist separated
degassed alcohol using pig’s bladder.
 1824, Rene-Joachim-Henri Dutrochet, French physiologist
introduced “Osmosis”: Movement of water through a biological
membrane.
 1846 – Discovery of nitrocellulose (gave scope to MF)
 1855 – Frick discovered Cellulose nitrate membranes.
 1861- Thomas Graham (Father of Modern Dialysis): Coined
“Dialysis “- Separated Dissolved substances based on mol.wt., n
concentration.
 1865 – Moritz Traube invented first artificial membrane using
copper ferrocyanide precipitates.
 1875- Wilhelm Friedrich Philipp Pferrer: Made the membranes
to withstand operational pressures.

4.  1906-Bechhold devised a technique to prepare nitrocellulose
membranes of graded pore size .
 1930’s-Micro porous colloidal membranes became commercially
available.
 1950’s- Development n Significant use of MF technology in the
filtration of drinking water samples at the end of World War II:
Research effort was sponsored by US army.
 1959- Samuel Yuster made a breakthrough in RO– by the invention of
Loeb-Sourirajan membrane at UCLA.
 By 1960-Elements of modern membrane science had been developed
such as Gas Separation, Membrane Distillation etc.
 In the early 80’s- Henis &Tripodi made industrial GS: economically
feasible.
 Kober and coworkers developed Pervaporation. Later in 2000’s
modified for large scale applications.

5. Gas Separation n
Pervaporation

6.  Membrane process: the feed stream is divided into two
streams:
 Retentate (concentrate) stream
 Permeate stream
 Either the concentrate or permeate stream is the product of our
interest.

7. IDEALMEMBRANE
Permeate Feed
Driving ForceREALMEMBRANE
Phase 1Phase 2

8. I

10.  First generation membrane processes
 Microfiltration (MF)
 Ultrafiltration (UF)
 Nanofiltration (NF)
 Hyper filtration (HF) /Reverse osmosis (RO)
 Electro dialysis (ED)
 Second generation membrane processes
 Gas separation (GS)
 Pervaporation (PV)
 Membrane Distillation (MD)

11.  Separates suspended solids and some colloidal materials (>0.1μ) from a
feed stream.
 The concentrate requires periodic removal or cleaning to prevent the
eventual plugging of membrane feed passage ways.
 Pore size : 0.1-10.0 microns
 Pressure difference : Apprx. 10-500 kPa

12.  Separates colloidal material, emulsified oils, micro
biological materials, and large organic molecules.
 Somewhat dependent on charge of the particle, and is
much more concerned with the size of the particle.
 Pore sizes ranges: 10-1000 A° (103-0.1 microns) :most typical
0.005 μ
 Pressure difference : Apprx. 0.1-1.0 MPa
 Typically not effective at separating organic streams

13. Feed
Permeate
Permeate
Feed Retentate
1. Dead-end 2. Cross-flow

14.  Used when low molecular weight solutes such as inorganic salts/
small organic molecules (glucose, sucrose) have to be separated.
 Uses a membrane that is partially permeable to perform the separation
(like in RO), but NF pores >> RO pores
 Can operate at much lower pressures, and passes some of the inorganic
salts due to larger pore size
 Pore size is typically 1 nm
 Pressure difference: 10-20 bar

15.  Specifically used for the separation of dissolved ions from water
(dissolved solids, bacteria, viruses, salts, proteins, and other germs)
 Charged ions and all other materials greater than or equal to .001 μ.
 Essentially a pressure driven membrane diffusion process for
separating dissolved solutes.
 Relatively a low energy process.
 Smallest pore structure, 5-15 A0 (0.5 nm - 1.5 nm)
 allows only the smallest organic molecules and unchanged solutes
to pass through the semi-permeable membrane along with the water
 >95-99% of inorganic salts and charged organics will also be rejected
by the membrane due to charge repulsion established at the
membrane surface

17. In the ED process a semi-permeable barrier allows passage of either
positively charged ions (cations) or negatively charged ions (anions) while
excluding passage of ions of the opposite charge. These semi-permeable
barriers are commonly known as ion-exchange, ion-selective or
electrodialysis membranes.
Electrodialysis:

18.  Used for separation of gas mixtures.
 Separation of gases is due to their different solubility n diffusivity in
the polymer membranes.
 Rate of permeation:
 Proportional to pressure differential across the membrane,
solubility of gas in the membrane, diffusivity of gas through
membrane.
 Inversely proportional to the membrane thickness.
 Driving force: Concentration difference.
 Pore size: < 1 nm.
 Ex: Palladium membranes –Hydrogen Separation.

20.  Separation of miscible liquids
 Liquid is maintained at atmospheric pressure on the feed side of the
membrane, and permeate is removed as a vapour because of a low
vapour pressure existing on the permeate side.
 Differs from all other membrane processes because of the phase change
of the permeate.
 Transport is effected by maintaining a vapour pressure gradient across
the membrane.
 Membranes used: Zeolite n Poly Dimetyl Siloxane

21.  Three steps sequence:
 Selective sorption of one of the components of the liquid into the
membrane on the feed side
 Selective diffusion of this component across the membrane
 Evaporation, as permeate vapour, into the partial vacuum
applied to the underside of the membrane

22.  Is a process in which two liquid or solutions at different
temperatures are separated by a porous hydrophobic
membrane.
 The liquid/solution must not wet the membrane otherwise
the pores will be filled for capillary force.
 Membrane distillation is a type of low
temperature, reduced pressure distillation due at the use
porous hydrophobic polymeric membranes.

23. Feed
H2O
T1
Permeate
H2O
T2
Air/vapour
Hydrophobic
porous membrane
T1>T2
Liquid water Liquid water
Schematic representation:
Such transport occur in a sequence
of three steps:
Evaporation on the high-
temperature side.
Transport of vapour molecules
through the pores of the
hydrophobic porous membrane.
Condensation on the low-
temperature side.
 It is one of the membrane processes in which the membrane is not
directly involved in separation the only function of the membrane is to act
as a barrier between the twos phases. Selectivity is completely determined
by the vapour liquid equilibrium involves. This means that the component
with the highest partial pressure will show the highest permeation rate.

24. Fractionation by membrane distillation, 1, porous hydrophobic membrane polymer;
2, feed; 3, vapour space; 4, cooling water; 5, chilled wall; 6, condensed droplets.
2
1
3
6
5
4

25. Synthetic polymeric membranes:
a) Hydrophobic
b) Hydrophilic
Ceramic membranes
PolyTetraFluoroEthylene,
Teflon
PolyVinyliDineFluoride
PolyPropylene
PolyEthylene
Cellulose esters
PolyCarbonate
PSf/PES
PolyImide/PolyEtherImide
PolyEtherEtherKetone
Alumina, Al2O3
Zirconia, ZrO2
Titania, TiO2
Silicium Carbide, SiC

26. 26
A module is the simplest membrane element that can be used in
practice.
Module design must deal with the following issues:
3. Membrane integrity against
damage and leaks
2. Minimum waste of energy
4. Easy egress of permeate
5. Permit the membrane
to be cleaned
1. Economy of manufacture

27.  Plate-and-frame module
 Spiral-wound module
 Tubular module
 Capillary module
 Hollow-fiber module

28. Membrane
module
Membrane
area/unit vol.
(m2 m-3 )
Membrane
costs
Control of
Fouling
Application
Plate & frame
Module
400 - 800 medium good MF, UF, RO,
ED
Spiral-wound
module
800 - 1200 low good UF, RO, GS
Tubular
module
20 - 100 very high very good MF, UF, RO
Capillary
module
600 - 1200 low very good UF, MF,
Hollow fiber
module
2000 - 5000 very low very poor RO, GS

29.  It is a process where solute or particles deposit onto
a membrane surface or into membrane pores in a
way that degrades the membrane's performance.

30. Major Foulants:
 Organic materials
 Biological growth
 Colloidal n suspended
particles
 Soluble salts
 Membrane properties
 Solution properties
 Operating conditions
Influential factors

31. 1. Pre-treatment of the feed solution
2. Membrane
properties
3. Module and process
conditions
4. Cleaning
a. Reducing concentration
polarisation
a1. Increasing flux velocity
a2. Using low flux membranes
a. Narrow pore size distribution
b. Hydrophilic membranes
a. Heat treatment
b. pH adjustament
c. Addition of complexing agents
d. Chlorination
e. Adsorption onto active carbon
a. Hydraulic cleaning
b. Mechanical cleaning
c. Chemical cleaning

32.  No specific chemical knowledge is needed for operation
 No Complex instrumentation
 Basic concept is simple to understand
 Separation can be carried out continuously
 Membrane processes can easily be combined with other
separation processes
 Separation can be carried out under mild conditions
 Membrane properties are variable and can be adjusted
 Greater design flexibility in designing systems
 Clean technology with operational ease

33.  Membranes are relatively expensive
 Certain solvents, colloidal solids, especially graphite
and other residues can quickly and permanently
destroy the membrane surfaces
 Oil emulsions are not "chemically separated," so
secondary oil recovery can be difficult.
 Synthetics are not effectively treated by this method
 Biofouling/membrane fouling;
 Low membrane lifetime;
 Generally low selectivity

34.  Concentration: The desired component is present
in a low concentration and solvent has to be
removed;
 Purification: Undesirable impurities have to be
removed;
 Fractionation: A mixture must be separated into
two or more desired components.

35.  Development and Advancement of Nano-materials for
effective membrane strength n separations.
 Over-coming the problem of Membrane Fouling.
 To design membranes for high selectivity.