Membrane Seperation Processes like RO and NF Shinde Siddheshwar Bhagwanrao Shinde M. Tech Food Technology

1. REVERSE OSMOSIS & NANOFILTRATION
(Advanced Food Engineering FST-603)
COLLEGE OF FOOD TECHNOLOGY
V.N.M.K.V. PARBHANI
Submitted By Course Guide
Mr. S.B. Shinde
Reg. No: 2020T14M
M.Tech Food technology
College of Food Technology
VNMKV Parbhani 431402
Dr. R.B. Kshirsagar
Dept. Food Engineering
College of Food Technology
VNMKV Parbhani 431402
1
Siddheshwarshinde@hotmail.com

2. • What is Membrane technology
• Basic terminologies
• What exactly happens in osmosis
• Osmotic pressure & Laws
• Reverse osmosis phenomenon
• Theoretical background of RO
• Filters and modules
• Applications of RO technology
• Nanofiltration
• Transport theories of NF
• Applications of NF
• References
OUTPUT
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3. Membrane operations
Micro filtration Ultra filtration
Nano filtration
Reverse osmosis
Pore size: 0.1-10 micron
Pressure range: 0.1-3 bar
Pore size: 0.003-0.1 micron
Pressure range: 2-10 bar
Pore size: 0.0001 micron
Pressure range: 15-80 bar
Pore size: 0.001 micron
Pressure range: 5-35 bar
Pressure Driven
Operations
(PDOs)
• A number of membrane processes have evolved which make use of a pressure
driving force and a semipermeable membrane in order to effect a separation of
components in a solution or colloidal dispersion.
• Separation is based mainly on molecular size, but to a lesser extent on shape
and charge.
• They can be considered to be a continuous spectrum of processes, with no clear-
cut boundaries between them.
Membrane technology
3

4. Basic Terminologies
• The feed material is applied to one side of a membrane and subjected to a
pressure.
 Permeate (Filtrate)
The stream which passes through the membrane under the influence of
this pressure is termed the permeate (filtrate).
 Concentrate or Retentate
The stream left after the required amount of permeate is removed is
termed the concentrate or retentate.
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5. What is Osmosis ?
Osmosis is the spontaneous net movement of
solvent molecules through a selectively permeable
membrane into a region of higher solute
concentration, in the direction that tends to
equalize the solute concentrations on the two sides.
Osmosis is how plants are
able to absorb water from
soil.
Swelling of resins and
other seeds when they are
soaked in water
Phase 1
Phase 2
Phase 1
Phase 2
π
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6. WHAT
EXACTLY
HAPPENS
Mango shrinken in salt solution : Osmosis
Dates swells after soaked in water
Plasmolysis
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7. • Isotonic solution: Net movement is zero
• Hypotonic solution: Cell swells in hypotonic solution
• Hypertonic solution: Cell shrink in hypertonic solution
Solution
Cell/commodity
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8. What is Osmotic Pressure?
π = iCRT
Where,
π is the osmotic pressure
i is the van’t Hoff factor
C is the molar concentration of the solute in the solution
R is the universal gas constant
T is the temperature
If sufficient pressure is applied to the solution side of the semipermeable membrane, the
process of osmosis is halted. The minimum amount of pressure required to nullify the
process of osmosis is called osmotic pressure.
 Pressure to halt Osmosis Mechanism i.e. Movement of solvent to solution.
 Dependent on the concentration of solute particles in the solution
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9. Laws of osmotic pressure
• Solute partical in dilute solution posses kinetic energy & moves random
directon in solution. Thus, they are similar to gas molecules
Van’t Hoff’s theory of osmotic pressure
Van’t Hoff’s Boyle’s Law of solution
• At constant temperature, osmotic pressure (π) of dilute solution is directly
proposnal to its molar concentration (C) or Inversely proposnal to volume
(V) of the solution
Expression:
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10. Van’t Hoff’s Charle’s Law of solution
• When concentration remaining constant then osmotic pressure (π) of dilute
solution is directly proposnal to absolute temperature (T) of solution.
Expression:
Van’t Hoff’s Avagedro of solution
• At given temperature, equal volumes of the solutions having the same
osmotic pressure contain equal number of solute particles.
𝝅 ∝ 𝒏 10

11. Van’t Hoff’s general solution equation
• With the help of above three equation we can conclude general solution
equation.
From above all laws
π = iCRT
Osmotic pressure
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12. Important processing parameters for all pressure
activated processes
 The concentration factor (f )
Where,
VF is the feed volume
VC is the final concentrate volume.
 As soon as the concentration factor exceeds 2.0, the volume of permeate
will exceed that of the concentrate.
 Concentration factors may be as low as 1.5 for some viscous materials and 5.0–
50 for some dilute protein solutions.
 Generally higher concentration factors are used for ultrafiltration than for RO:
 Over 50.0 can be achieved for UF treatment of cheese whey, compared to about
to 5 for RO treatment of cheese whey.
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13. Continue...
• Rejection or retention factor (R)
• where
CF is the concentration of component in the feed
CP is the concentration in the permeate
 It influences the extent (quality) of the separation that can be achieved.
 Rejection values normally range between 0 and 1.0; and sometimes they are
expressed as percentages (0–100%).
 Occasionally negative rejections are found for some charged ions (Donnan
effect).
1. When CP= 0, R= 1, all the component is retained in the feed.
2. When CP=CF, R= 0, the component is freely permeating.
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14. Continue…
• If the concentration factor and rejection value are known,
• Yield of any component, which is defined as the fraction of that component
present in the feed, which is recovered in the concentrate, can be estimated.
• Obviously for reverse osmosis, the yield for an ideal membrane is 1.0.
 The yield (Y) can be calculated from:
 The derivation of this equation is provided in Lewis.
 Thus for a component where R= 0.95, at a concentration factor of 20,
 By putting these values in above equation
 the yield is 0.86; i.e.
 86% is retained in the concentrate and 14% is lost in the permeate
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15. Flux Rate
• The permeate flux is usually expressed in terms of
• This permits a ready comparison of different membrane configurations of
different surface areas.
• Flux values may be from < 5 to > 500 .
• Factors affecting the flux rate are the applied pressure, the volumetric flow rate of
feed across the membrane surface, its temperature and its viscosity.
• The flux is also influenced by concentration polarization and fouling, which in
turn are influenced by the flow conditions across the membrane.
• Inducing turbulence increases the wall shear stress and promotes higher flux
rates.
𝑳/𝑴𝟐
𝒉𝟏
𝑳/𝑴𝟐𝒉𝟏 𝑳/𝑴𝟐𝒉𝟏
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16. Reverse Osmosis (RO)
Reverse osmosis is the process of forcing a solvent from region of high solute
concentration through semipermeable membrane to a region of low solute
concentration by Applying a pressure.
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Hydrostatic pressure must be
higher than the Osmotic pressure
P > Pi
Direction of flow from
High solute concentration
to low solute concentration

17. How does Reverse Osmosis work?
 To remove ions, mineral
chemicals, and other impurities
from drinking water.
 In this process, greater
pressure is applied, forcing the
water to travel through the
semipermeable membrane in
opposite to natural osmosis.
1. Sediment Pre-Filter
2. Carbon Pre-Filters
3. Reverse osmosis Membrane
4. Post Carbon filters
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18. 1. Sediment Pre-Filter
It removes dirt, rust and sediment particles down
to 5 microns. There are several different types of
sediment cartridges.
Pleated filters feature increased surface area and
longer life. These cartridges are washable and
reusable.
Melt blown polypropylene filters are designed
for the removal of dirt, rust and sediment from
water. 5 and 20 micron are the most popular sizes
for drinking water applications.
String wound filters are an inexpensive solution
to your filtration needs. These cartridges come in
a variety of media types and have a wide range of
applications.
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19. 2. Carbon Pre-Filters
Coconut Shell Carbon Block Cartridges
of 10 Micron removes chlorine, taste,
odor and chemical contaminants.
Activated carbon block filters typically
have a 0.5 to 10 micron filtration
This Capability, makes it also helpful for
particulate filtration, removing taste and
odor from chlorine, insoluble lead
reduction.
A 5-stage reverse osmosis system has an
third housing to hold an additional carbon
block cartridge.
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20. • TFC (Thin Film Composite) rejects or removes 95% of total dissolved
solids (TDS) down to 0.0001 micron
• Different membrane modules are manufactured for use of water
purification or desalination system also in fuel cells.
3. Reverse osmosis Membrane
4. Post carbon Filters
• Coconut shell Activated carbon is final polishing.
• It is just before you use that water
• Inline post filters typically clip onto top of reverse osmosis systems
membrane housing
• This post filters removes any chlorine or contaminants missed by the other
cartilage or membrane.
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21. Theoretical background
 According to the solution-diffusion transport mechanism (Salt & Water
permeate reverse osmosis membranes)
 The water flux, Ji is linked to the pressure and concentration gradient
across the membrane by the equation
Where
p is the pressure difference across the membrane,
π is the osmotic pressure differential across the membrane
A is constant
 When the applied pressure is higher than the osmotic pressure ( p > π )
Water flows from the concentrated to dilute salt solution side of membrane
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22. The salt flux J(j) across a reverse osmosis membrane is described by the equation
Where
B is salt permeability constant
Cjo & CJi are the salt concentrations on the feed and permeate side of the membrane
Concentration of salt in the permeate solution is usually much smaller than the
concentration in feed , so the above equation can be simplified to,
It follows from these two equations that, the water flux is proposnal to the applied
pressure but the salt flux is independent of pressure
Thus it means the membrane becomes more selective as pressure increases
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23. • For the RO system to produce product water, a minimum pressure must be
applied to the membrane to overcome the natural Osmotic pressure of the water.
• This pressure depends on the type of ion present and their concentration in water
• Osmotic pressure doesn’t depend on the type of membrane
• Roughly, every 10 ppm of TDS contribute about 1 psi of osmotic pressure
• For instance, if the TDS of feed water is 2000 ppm, then the Osmotic Pressure for
this water is about 20 psi
• Generally, the applied pressure is at least twice the OP for the variable RO system
Table gives information about how the permeate quality and quantity for a
membrane may change as pressure is reduced
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24. RO: Cellulosic membrane
• Cellulose acetate was the first high-performance reverse osmosis membrane
material discovered. (year 1894)
• The water & salt permeability of CA membrane is extremely sensitive to the
degree of acetylation of the polymer used to make the membrane.
• These membrane achieve 98-99 % sodium chloride rejection in seawater
desalination process
FTIR
SEM
XRD
TGA
ANTIBACTERIAL
CHEMICAL RESISTANCE
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25. ADVANTAGES OF CELLULOSIC MEMBRANE
• Easy to make
• Mechanically tough
• Cellulose acetate has higher flux
• Resistance to free chlorine concentration
• Kept free of bacteria
• Suitable to feed water having biological loading
RO: Non Cellulosic polymer membrane
During in 1960s to 1970s
Good sea water salt rejection upto 99.5 % but fluxes are low 1-3 gal/ft2
High chlorine rejection ( able to withstand upto 10000 ppm h)
High flux ( especially for polysulfone and poly vinyl alcohol.
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26. RO: Interfacial Composite Membrane
Interfacial composite membrane are formed over porous support by in-situ
polycondensation of polyfunctional amines and acid chloride monomers at the interface
of solvent
Advantages
• High flux & High rejection RO due to interfacial polymerization
• Also be operated at 35 oc temperature
• Salt rejection 995 % and water flux of 30 gal/ft2 day at 800 psi
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27. RO Modules: Membrane Configurations
Four Different Types of RO Modules Used In Desalination Process
TUBULAR MODULE
FRAME MODULE & PLATE MODULE
SPIRAL MODULE
HOLLOW FIBER MODULE
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28. • Made up of cellulose triacetate or aromatic polyamides
• Module incorporate the membrane around the central, and feed solution
flowed rapidly outward to shell
• Because fibers are extremely tightly packed inside the pressure vessel, flow
of feed solution is quietly slow
• As much as 40-50 % of feed could be removed as permeate in a single pass
through the module
HOLLOW FIBER MODULE
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29. Hollow fiber Advantage Hollow fiber Disadvantage
With high packing density because of
small strand diameter
Irreversible fouling & fiber breakage
Can be back flushed from the permeate
side and air scoured
Break under high strain compared to other
method and high operating cost
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30. SPIRAL WOUND MODULE
• In last 20 years improvement of sea water spiral elements have been made
• The capacity of 8 inch element has been doubled wheras the salt passage is about three
times less.
• Operating pressure for spiral wound element was 69 bar (1000 psi) in the past recently
it is 89.7 bar (1200 psi) .
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Spiral wound Advantage Spiral wound Disadvantage
Very high packing density than others Fouling is greater than fouling in tubular
filtration process
Easy for cleaning through CIP and
prevent membrane breakage
Can not handle by mechanical cleaning
like tubular and have low packing
density than hollow fiber

31. FRAME MODULE & PLATE MODULE
• Plate and frame membrane system utilizes membrane laid on the top of the plate like
structure which in turn is held together by frame like support.
• Flat sheet membrane bolted together with frame around the perimeter, similar to heat
exchanger and filter press.
• Two plate configuration : DEAD END & CROSS FLOW
• Dead End : Feed solution flows perpendicular to membrane
• Cross Flow : Flow tangential to membrane wall
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32. Frame & Plate Module Advantage Frame & Plate Module Disadvantage
Solid being able to be easily separated
from water and easy cleaning of filter
surface
Low packing density
Cross flow plates allow more shearing
force and fouling reduction
Low efficiency and high presuure drop
Handle high solid concentration For dead end system, buildup is much
greater than cross flow so efficiency is
become less
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33. • T.M. consist of minimum of two tubes, Inner tube, called membrane tube, &
outer tube which is the shell
• Feed stream goes across the length of the membrane tube & is filtered out
into the outer shell while concentrate collects at the opposite end of the
membrane tube
• Used for application such as oily wastewater treatment, MBR and other high
solids process
TUBULAR MEMBRANE MODULE
• Tube like structure with porous wall
• Tubular modules work through tangential cross flow & can handle high
dissolved solids, high suspended solids, oil, grease, or fats
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34. Tubular Module Advantage Tubular Module Disadvantage
It has less fouling compared to plate and
frame systems. And similar amount of
fouling when compared to spiral and
capillary.
Low packing density and large size
Allows robust cleaning methods such as
use of harsh chemicals, backwash and
mechanical cleaning which is unique
feature
Packing density higher than plate and
frame but lower than capillary, hollow
fiber, and spiral wound
Handle high solid and emulsified oil load
and can physically cleaned by sponge ball
Capital and operating cost is high
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35. USES OF RO TECHNOLOGY
• Drinking water purification
• Waste water purification
• Hydrogen production
• Maple syrup production in food industry
• Production of deionized water
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36. NANOFITRATION
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37. • Realm between reverse osmosis and ultrafiltration.
• Hydraulic pressure is used to overcome the feed solution osmotic pressure,
and to induce diffusion of pure water, which we also called as permeate
through a semi permeable nanofiltration membrane
Rejects
dissolved
organics
insecticide
s and
pesticides
herbicid
es
Antibioti
cs
nitrates,
sugars
What is Retentate??
size range of 1 nm or 10 Angstroms.
• Nanofiltration may achieve moderate to low
removal of monovalent ions.
For example, sodium, potassium, chloride etc
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38. • The features of nanofiltration membranes lie between those of non-porous
RO membrane and porous ultrafiltration membranes
• Commercial nanofiltration membranes possess a fixed charge developed by
dissociation of surface groups such as sulphurated or carboxylic acids.
NF Membrane allow ions
to be separated by a
combination of the size
and electrical effects of
UF and the ion interaction
mechanisms of RO
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39. Properties of NF
PLATE AND
FRAME FORM
HOLLOW FIBER
FORMATS
CAPILLARY
SPIRAL WOUND,
TUBULAR
MEMBRANES
• NF can withstand very high or low pH environment.
• Membrane tends to have a slightly charged surface with a negative charge at a
neutral pH.
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40. Transport theories or models are adapted to describe the
Nanofiltration transport
1. Sourirajan’s sorption surface capillary flow model
2. Solution diffusion model
Sourirajan’s sorption surface capillary flow theory
• sorption of water molecules in the membrane. And then the desorption of
multivalent ions by dielectric forces
• effective charge density, pore radius and ionic strength determine the
rejection of monovalent ions.
• For nanofiltration membranes the rejection of monovalent ions ranges
between 0% to 50%.
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41. Solution diffusion model
• Describes the membrane as a porous film into which both water and solute
ions dissolve.
• Solute moves in the membrane mainly under the concentration gradient
forces.
• Water transport is dependent on the hydraulic pressure gradient.
• Transport of the solute through the membrane depends on the hindered
diffusion as well as convection.
Transport mechanism of charged solute
• Three modes of transfer:
 Diffusion
 Convection
 Electromigration
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42. Parameters That Affect The Performance Of A
Nanofiltration Membrane
• Pressure
• Temperature
• Cross-Flow velocity
• Solution PH
NF Advantages NF Disadvantages
Lower discharge volumes, lower retained
concentrations than RO for low value salts
Higher energy consumption than
ultrafiltration and microfiltration
Reduction in heavy metals Limited retention for salts and univalent
ions
Reduced to nitrates and sulphates Expensive than reverse osmosis
membranes
Reduction in colour, tannins and turbidity Membranes are sensitive to free chlorine.
Most of the time chlorine is present in
water and water streams 42

43. NF Application
• Desalination of food, dairy and beverage products or by-products.
• Partial desalination of whey, UF permeate or retentate as required.
Desalination of dyes and optical brighteners.
• Purification of spent clean in place chemicals, CIP chemicals.
• Colour reduction or manipulation of food products.
• Concentration of food, dairy and beverage products or by-products.
• Fermentation byproduct concentration.
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44. REFRENCES
• Food Processing Handbook James G. Brennan
• M.H. Moulder, Basic techniques in membrane technology
• Https://www.Safewater.Org/fact-sheets1/2017/1/23/ultrafiltrationnanoandro
• B.K. Datta Mass transfer and seperation process 2007
• K. Nath Membrane seperation processes PHI 2008
• M.cheryan ultrafiltration and microfiltration hand book
• Membrane Technology Prof. Kaustubha Mohanty Department of
Chemical Engineering Indian Institute of Technology, Guwahati
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45. Mr. Shinde S.B. ( 2020T14M)
M. Tech food technology
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