The document discusses various filtration techniques used in pharmaceutical processing. It defines filtration as the removal of solids from fluids or fluids from other fluids. Clarification can be achieved through filtration or centrifugation. There are two main reasons for these processes in pharmaceuticals: to remove unwanted particles and to collect solids as the final product. The document describes various types of filtration like solid/fluid, solid/gas, fluid/fluid filtration and their applications. It also discusses filtration theory, factors affecting filtration rate, various filter media types, filter aids, selection of filtration equipment and systems for different applications.

1. FILTRATION

2. Clarification is the processes that
involve the removal or separation of a
solid from a fluid, or a fluid from another
fluid.
The term 'fluid' involve both
• liquids
• gases.

3. Clarification can be
achieved using either
• filtration or
• centrifugation
techniques.

4. • In pharmaceutical processing there are
two main reasons for such processes:
1. To remove unwanted solid particles
from either a liquid product or from air
2. To collect the solid as the product
itself (e.g. following crystallization )

5. Types of filtration
• Solid/fluid filtration : can be defined as
the separation of an insoluble solid from a
fluid by means of a porous medium that
retains the solid but allows the fluid to
pass.
• Solid/fluid filtration may be subdivided
into
• solid/liquid filtration
• solid/gas filtration

6. applications of solid/liquid filtration in
pharmaceutical processing:
• Improvement of the appearance of
solutions, mouthwashes etc.
• Removal of potential irritants, e.g. from
eye-drop preparatition
• Recovery of desired solid material from a
suspension or slurry, e.g. to obtain a drug or
excipient after a crystallization process
• Sterilization of liquid or semisolid products
where processes involving heat
• Detection of microorganisms present in

7. applications of solid/gas filtration in
pharmaceutical processing.
1. the removal of suspended solid material
from air in order to supply air of the
required standard for either processing
equipment or manufacturing areas.
2. remove particulate matter generated
during a manufacturing operation from
the process air in order to prevent the
material being vented to the
atmosphere. E.g. filtering of exhaust air
from fluidized-bed and coating

8. Fluid/fluid filtration is used to produce
the desired product appearance.
e.g. Flavoring oils are sometimes added to
liquid preparations in the form of a spirit. When
these spirits are added to aqueous-based
formulations some of the oil may come out of
solution, giving the product a degree of
turbidity. Removal of the oil droplets by
passing them through an appropriate filter

9. Filtration theory has deficiency. The
deficiency is its preoccupation with
resistance to flow.
• The mathematical models for flow
through aporus medium, cake filtration,
and granular bed filtration may differ ,but
all follow this basic rule :the energy lost
in filtration is proportional to the rate
of flow per unit area.

10. Rate = driving force / resistance
Resistance is not constant since it increases as solids
are deposited on filter medium .
The rate concept as expressed in modifications of
poiseuilles equation :
Dv/dt = AP / u (ά W/ A+R )
Where
V : volume of filtrate
T : time A :filter area ,
P : total pressure drop through cake and filter medium
U : filtrate viscosity , ά : cake resistance
W: weight of dry cake solids
R : resistance of filter medium and filter

11. Interpretation of the basic equation , however lead
to general set of rules:
• pressure increases usually cause a proportionate
in increases in flow unless the cake is highly
compressible.
• An increase in the area increases flow rate
• The filtration flow rate at any instant is inversely
proportion to viscosity
• Cake resistance is function of thickness
• Particle size of the cake solids affects flow
through effect on the specific cake resistance ,
The filter medium resistance ,r ,usually negligible or
about 0.1 ά in cake filtration, is the primary
resistance in clarification filtration.

12. • It is convenient to summarize the
theoretic relationship as :
Rate of filtration = area of filter * pressure
difference / viscosity *resistance of cake
and filter
Most clarification problems can be
resolved by varying one or more of
these factors

13. Filter media
‫ـــــــــــــــــــــــــ‬
•The surface upon which the solid
deposited is a filter.
•Filter media are available in different
materials and forms .
the filter fabrics are commonly woven
from natural fibers such as cotton and
synthetic fibers and glass.
Filter cloth , a surface type medium , is
woven from either natural or synthetic
fiber or metal.

14. • Cotton fabric is most common and is widely
used as a primary medium ,as backing for
paper or felts in plate and frame filters , and as
fabricated bags for coarse staining .
Nylon is superior for pharmaceutical use,
since
• it is unaffected by mold, fungus, or bacteria,
• provides an extremely smooth surface for
good cake discharge
• has negligible absorption properties.
Both cotton and nylon are suitable for coarse
straining in aseptic filterations.

15. •Teflon is superior for most liquid filtration
•chemically inert
•provides sufficient strength
• can with stand elevated temperature.
• Woven wire cloth , particularly stainless
steel is
•durable
•resistant to plugging
• and easily cleaned
•Metallic filter media provide good
surfaces for cake filtrations and used with
filter aids.
•Wire screens : clean rapidly and returned to
service.

16. • Non woven filter media include
•felts
• bonded
•fabrics
• Kraft papers
felts : is a fibrous mass that is free from
bonding agents and mechanically interlocked
to yield specific pore diameters that have
controlled particle retention.
• It function as depth media and are
recommended where gelatinous solutions or
fine particulate matter are involved .

17. Bonded fabrics are made by binding
textile fibers with resins ,solvents , and
plasticizers.
These material inter act with additives.
Kraft paper is pharmaceutical standard .
• it offers controlled porosity ,
• limited absorption characteristic , and
•low cost
Porous stainless steel filters are used for removal
of small amounts of unwanted solid liquids such as
milk , syrup , sulfuric acid .
Membrane filter media
• micro filtration

18. Filter aids
‫ــــــــــــــــــــــــــــ‬
Filter aid are special type of filter medium .
ideally the filter aid forms affine surface
deposit that screens out all solids , preventing
them from contracting and plugging the
supporting filter medium .
The filter aid acts by forming a highly porous
and no compressible cake that retains solids ,
as does any depth filter.

19. • If too little filter aid is used ,the resistance
offered by the filter cake is greater than if
no filter aid is used , because of added
thickness to the cake.
•On the other hand ,if high amount of filter
aid are added , the filter aid merely adds to
the thickness of the cake without providing
additional cake porosity .
Figure 7-1

21. The important characteristics for filter
aids are the following :
1.it should have a structure that permits
formation of previous cake.
2.it should have a particle size
distribution suitable for the retention
of solids , as required
3.it should be able to remain suspended
in the liquid
4.it should be free of impurities
5.it should be inert to the liquid being
filtered

22. Filter aid are classified
• from low flow rate ( fine : mean
size in the range of 3- 6 micron )
•To fast flow rate ( coarse : mean
size in the range of 20 – 40
micron )
Table 7-2

24. Filter aid may be applied by
Pre coating :requires suspending the
filter aid in a liquid and recirculation the
slurry until the filter aid uniformily
deposited on the filter septum.
Body mix :( direct addition of filter aid to
the filter feed ) is more common in batch
pharmaceutical operation .
Filter aids are chosen by trial and error in
either laboratory or plant .

25. Filter selection
Ideally the equipment chosen should
allow
• a fast filtration rate to minimize
production costs, be cheap to buy and run
• be easily cleaned and resistant to
corrosion
• be capable of filtering large volumes of
product before the filter needs stripping
down for cleaning or replacing

26. There are a number of product-related
factors that should be considered when
selecting a filter. These include:
• the chemical nature of the product.
- Interactions with the filter medium
may lead to leaching of the filter
components
- degradation or swelling of the filter
medium
- adsorption of components of the
filtered product on the filter.

27. • the volume to be filtered and the filtration
rate required.
- These dictate the size and type of equipment
• the operating pressure needed.
• the amount of material to be removed.
• the degree of filtration required.
- This will dictate the pore size of
membrane filters or the filter grade to be
used.

28. •the product viscosity and filtration
temperature.
-A high product viscosity may require
elevated pressures to be used.
- The incoming formulation can be heated,
or steam-heated jackets be fitted
to the equipment.

29. Filtration equipment and system
commercial equipment : is classified by
• type of driving force (gravity , pressure , or
vacuum )
• end product desired ( filtrate of cake solid )
• method of operating ( batch or continuous )

30. Gravity filters
• simple and cheap
• frequently used in laboratory filtration
• small and a low filtration rate
• use on a large scale is limited.

31. .
Vacuum filters
•The rotary vacuum filter In large-scale
filtration.
•The rotary vacuum filter is continuous in
operation and has a system for removing
the cake so that it can be run for
long periods handling concentrated
slurries.

33. The advantages of the rotary vacuum filter:
1.It is automatic and continuous in operation,
so that costs are very low.
2. The filter has a large capacity.
3. Variation of the speed of rotation enables the
cake thickness to be controlled

34. Uses of the rotary filter
• it is most suitable for continuous operation
on large quantities of slurry, especially if the
slurry contains considerable amounts of
solids
Examples of pharmaceutical applications
include
• the collection of calcium carbonate,
• magnesium carbonate

35. Disadvantages include:
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1.The rotary filter is a complex piece of
equipment with many moving parts and is
very expensive.
2. The cake tends to crack because of the
air drawn through by the vacuum system,
so that washing and drying are not
efficient.
3. Being a vacuum filter, the pressure
difference is limited to 1 bar and hot
filtrates may boil.

36. 4. The rotary filter is suitable only for
Straight forward slurries, being less
satisfactory if the solids form an
impermeable cake or will not separate
cleanly from the cloth.

37. Cartridge filters and systems
• Cartridge filters have an integral
cylindrical configuration made with
disposable or cleanable filter media and
utilize either plastic or metal structure
hardware.
• Cartridge filters provide maximum
filtration area in the smallest possible
package , allow quick change out of the
media , and save money .

38. Membrane filter and housing
• It has become the unit of choice for
• high volume ,
• sterile filtrations
• ideal for final polish prior to
bottling of bulk parenterals.
• Membrane filter holders accept
membranes from 13 to 293 mm in
diameter.
.

39. Laboratory filtration equipment
Among the special types of laboratory
filter paper for pharmaceutical industry are
•filter papers impregnated with activated
carbon for adsorption of colors and
odors in pharmaceutical liquids
•filter paper impregnated with
diatomaceous earth for removal of
colloidal haze from liquids with low
turbidity

40. Membrane ultra filtration
• Un like conventional filtration , ultra filtration
is a process of selective molecular separation
• It is define as a process of removing
dissolved molecules on the basis of
membrane size and configuration by passing
a solution under pressure through a very fine
filter.
• The difference between micro filtration and
ultr afiltration is the former removes
particulates and bacteria , the latter
separates molecules .

41. Thank you