Its about membrane filtration technology used in food engg. It describes types of membrane, RO, UF, MF, troubleshooting occurred during membrane filtration etc.

1. MEMBRANE
FILTRATION

2. CONTENTS
• Introduction
• Types of membrane filtration
• Molecular weight cut off
• RO, UF and MF
• Recovery percentage
• Problems in membrane filtration
• Equipments
• applications

3. INTRODUCTION
•A feed consisting of mixture of two or more components
is partially separated.
•Separation by a semi permeable barrier namely
membrane.
•Feed is separated into retentate and permeate.
•Separation occurs by the membrane controlling the rate
of movement of various molecules between two liquid
phases, two gas phases, or a liquid and a gas phase.
•The driving force of separation is the pressure difference
across the membrane.
•The two products of feed are usually miscible.
•A sharp separation is often difficult to achieve.

4. i. Reverse Osmosis
ii. Ultrafiltration
iii. Microfiltration
iv. Dialysis
v. Electrodialysis
vi. Gas permeation
vii. Pervaporation.
Membrane separation processes include:

5. Reverse osmosis, ultrafiltration and microfiltration are the
classical membrane processes.

7. MOLECULAR WEIGHT CUTOFF (MWCO)

8. MWCOs can be defined as the molecular weight at
which 80% of the solutes are prohibited from
membrane diffusion.
An ideal membrane will retain all species with
molecular weight greater than the MWCO but will allow
all species with lower molecular weight to pass.
Membranes are available in a number of MWCO ranges
from 1,000 up to 100,000. For e.g., the MWCO range of
reverse osmosis is below 300, whereas that for
ultrafiltration membranes is between 300 and 300,000.

9. DIALYSIS
Transport of solute A
and B through
membrane is called
dialysis, and,
transport of solvent is
called osmosis.
It uses a semipremeable membrane to separate species
by virtue of their different diffusion rates in the
membranes.
Small solute of type A are separated from the solvent
and large solute of type B.

10. ELECRODIALYSIS
Electrodialysis (ED) is a membrane separation process
that utilizes an electrical potential difference as a driving
force for moving salt ions in solutions.
The membrane is selective and only permit the passage
of either anions or cations but not both.
Thus separation is due to charge rather than size
differences.
This process can be used to separate differently charged
molecules of similar sizes.

12. GAS PERMEATION
The gas components are separated through the
difference in pressure and concentration across the
membrane.
The permeation rate of a gas depends on its solubility
in the membrane material, as well as its molecular
structure.

13. PERVAPORATION
Permeation + Evaporation = Pervaporation
i.e. separation through the membrane by the permeate,
then its evaporation into the vapor phase.
Separation of components is based on a difference in
transport rate of individual components through the
membrane.

14. REVERSE OSMOSIS
What is osmosis?

15. The osmotic pressure 𝝅 for
dilute solutions can be
established as a function of
pressure and temperature,
using fundamental thermo-
dynamics, as follows:
𝝅= MRT
For ionized solutes:
𝝅= i MRT
The equation is known as
Van’t Hoff equation.

16. Liquid Approximate
Total Solid (%)
Osmotic Pressure
(bar)
Milk 11 6.7
Whey 6 6.7
Orange juice 11 15.3
Apple juice 14 20.0
Sea water 3.5 14.1
Casein solution 3.5 0.03
Osmotic Pressure Of Some Fluids:
 𝝅 of any species is inversely proportional to the
molecular weight. i.e. materials having more molecular
weights contribute lesser to the total osmotic pressure.

17. Transport:
Various theories have
been given:
The solvent actually
dissolve in the
membrane material
and diffuses through,
under the driving
force of pressure,
whereas solutes are
relatively insoluble
and are held back.

18. Rejection is based on electrostatic repulsion due to
formation of a pure layer of water over the membrane, and
the virtual charges on this layer reject charges of ionic free
species of salt solutions.

19. Simultaneously, by a complex mechanism of sorption,
diffusion, and desorption, pure water passes through the
membrane performing the separation process

20. In any event, RO requires that the applied pressure
should exceed the osmotic pressure of the feed.
Also, the rate of solvent transport across the membrane
is directly proportional to the pressure difference. Hence:
Jw ∝ A (ΔP-Δ 𝝅)
•As the feed become more concentrated, the osmotic
pressure rises. Hence the applied pressure must be
increased to maintain the flux.
•This limits the level of concentration.
•Pressure upto 70 bar may be applied in RO.

21. ULTRAFILTRATION and MICROFILTRATION
Pure sieving phenomena.
The pore network is randomly distributed, with pores
passing directly through the membrane.
There is no definite distinction between the two
processes, only difference being the pore size, even that is
not an absolute distinction.
Osmotic pressure is not much of importance.
Pressure, and hence the pumping power required are
much lower than RO.
Typically UF is carried out at 2-10 bar, with MF at lower
end of this range.

22. Transport:
•The separating ability is based
primarily on particle size, wherein
particles and molecules larger than
the largest pore are completely
retained, whereas species smaller
than the smallest pore are totally
permeated.
•UF and MF can be considered as an extension of
conventional filtration, with its separating ability ranging to
the molecular level.

23. Performance during UF and MF can be described by two
quantities:
1) Rejection (R): for any molecule or ionic species:
Thus, if a component is completely rejected by te
membrane, CP = 0 and R= 1. Similarly, for component
which freely permeate the membrane, CP = CF ,and R=0
The yield of any component if the quantity remaining at the
end of processing, and may be calculated as
C1 = C0 .fR
R frequently increases during process.

24. 2) Permeate flux:
The rate of flow is
given as:
(P1 – P2) = hydrodynamic pressure gradient: causes
continuous flow of the stream.
ΔP = transmembrane pressure (TMP) = the pressure
gradient that exits through the membrane from the feed
side to permeate side at each point along the membrane
surface, maximum at inlet, minimum at outlet.
Average TMP is given by:

25. RECOVERY PERCENTAGE
It shows the relation of the permeate flow rate to the feed
flow rate.
Depend on the feed concentration, being higher at
lower concentrations of feed solids.
A fraction of liquid approximately equal to that of the
solids should remain in the concentrate to make it flow.

26. The more dilute the feed, the higher the recovery
percentage.

27. Problems During Membrane Separation
1. CONCENTRATION POLARIZATION: a local increase in
solids as the permeate is removed from the stream.

28. The extent of concentration polarization depends upon
the chemical composition and the physical properties of
the feed, like presence of high molecular component,
shape etc.
It is reversible and original permeate flux can be
restored.

29. Concentration polarization determines the relationship of
permeate flux with the pressure.
At lower pressure, where concentration polarization is
minimal, flux is linearly related to transmembrane pressure.
As pressure increases, a
point will be found where flux
deviates from the pressure
dependent region such that
increase in pressure no longer
produces increased flux. This
is due to formation of a
consolidated polarized layer,
which takes over control of
the flux.

30. 2. FOULING:

31. Some factors which affect permeate flux during
membrane processing:

32. MEMBRANE SEPARATION EQUIPMENT
1. MEMBRANES:
Over the years, three generations of
membrane material have appeared on the
market.

33. I. The first generation
comprised cellulosic
materials. These are
prepared as a thin (0.1-1.0
μm) ‘skin’ on a much thicker
porous support. Their
application is limited to a
narrow pH range (2-8 at
most) and limited
temperature (<400 C).

34. II. The second generation included polymeric materials
such as polyamide, polysulphone or polyvinylidine
flouride.
• They are much
more resistant to pH
variation and can
withstand much
higher temperature
than cellulosic
membranes.
• These are again prepared as a skin on a porous
support, and can be manufactured in a range of pore
sizes.

35. III. The third generation was mainly based on inorganic
materials, like glass, metals and compounds of
aluminium, zirconium and titanium, again coated onto a
solid support. They are very rugged with high
mechanical, pH and temperature resistance.

36. In general terms, fabrication sources for membrane
materials can be classified as organic, inorganic, and
synthetic.
Properties of some membrane manufacturing materials

37. Common Membrane Shapes
Flat sheet membrane Tubular membrane
Hollow fibre membrane Monolithic or honey
comb membrane

38. 2. MEMBRANE MODULES:
In practice, membranes are configured into modules, the
design of which must incorporate several features:
• Support of membrane under required hydraulic
pressures.
• Large surface area of membrane, preferably in compact
volume.
• Flow stream must be established in which correct
hydrodynamic conditions can prevail- e.g., flow rate,
turbulence, pressure drop.
• Good hygienic conditions
• Ease of cleaning and membrane replacement.

39. COMMON MEMBRANE MODULES
1. Plate And Frame
Module:

40. 2. Spiral Wound Module

41. 3. Hollow Fiber Membrane Module
4. Tubular Membrane Module

42. 5. Monolithic Membrane Module

43. Reverse osmosis: Treatment of waste water and desalinization of
brackish water, Concentration of foods, Removing alcohol from beer
and wine
Ultrafiltration : pre-concentration of milk before making cheese,
clarification of fruit juices, recovery of vaccines and antibiotics from
fermentation broth
Microfiltration: clarification and biological stabilization of
beverages, separation of mammalian cells from a liquid
Dialysis: Chemical separations, hemodialysis
Electrodialysis: Concentration of brines, demineralization of cheese
whey, production of ultrapure water
Pervaporation: dehydration of ethanol-water azeotrope, removal of
water from organic solvents
Gas permeation: recovery of methane from biogas, adjustments of
H2/CO2 ratio in synthesis gas
APPLICATIONS

44. REFERENCES :-
• Enrique Ortega-Rivas(2012), Membrane Separations,
Non-Thermal Food Engineering Operations, p.199,
Springer Science+Business Media, e-ISBN 978-1-4614-
2038-5.
• Peter Zeuthen, Leif Bogh-Sorensen, Membrane Filtration
Techniques In Food Preservation, Food Preservation
Techniques, p. 276, Wood Head Publishing Limited, novel
food packaging techniques ISBN: 1 85573 675 6.
• J.D. Seader, Ernest J. Henley (2009), Membrane
Separations, Separation Process Principles, p.493, John
Wiley And Sons, ISBN-13: 978-81-265-0927-0.
• C. J. Geankoplis(2011), Membrane Separation Process,
Transport Processes And Separation Process Principles,
p. 840, PHI Learning Private Ltd, ISBN-978-81-2614-

45. THANK
YOU