This document discusses the use of textiles in filtration applications. It begins with an introduction to filtration principles and processes. It then focuses on how various textile fibers and fabric constructions, such as woven, nonwoven and knitted, can be used as filter media. Specific applications where textiles are used for filtration are described, including vacuum cleaners, medical devices, power plants, water purification and more. The document discusses factors that influence filtration performance, such as fiber type, fabric properties and finishing treatments. It also provides examples of how textiles can be applied to purify air and water. In summary, the document outlines the role of textiles in filtration and provides details on textile materials and constructions suitable for various filtration

1. Textiles in Filtration
By: Granch Berhe
2015

2. Introduction to Filtration
• Picking out
• Decanting
• Evaporation
• Dissolution
• Filtration etc …
Separation of particles, molecules, atoms
and ions from one another may be
performed by:
Filtration is one type of separation

3. Filtration
Filtration is a mechanical or physical operation, which is used for
the separation of solids from fluids (liquids or gases) by interposing
a medium through which only the fluid can pass. Oversize solids in
the fluid are retained, but the separation is not complete; solids will
be contaminated with some fluid and filtrate will contain fine
particles (depending on the pore size and filter thickness).
Filtration is used to separate particles and fluid in a
suspension, where the fluid can be a liquid, a gas or a
supercritical fluid. Depending on the application, either
one or both of the components may be isolated.

4. Particulate Sizes and Filtration RangesParticulate Sizes and Filtration Ranges
Ref. : http://www.gewater.com

5. Principles of filtration
• There are five principles of filtration:
– Interception
– Inertial disposition
– Random diffusion
– Electrostatic disposition
– Gravitational forces

6. Dust collection principles

7. Dust collection principles

8. Filtration and textiles
• Both textile fibers and fabric form an important
part of filtration.
• Filtration fabrics are used widely in:
– Vacuum cleaners
– Medical uses
– Power stations
– Petrochemical plants
– Sewage disposal
– Water filtration
– Geotextiles etc.

9. Applications
In vaccum cleaners -The bag used in vaccum
cleaners is the typical method to capture the
debris vacuumed up. It involves a paper or
fabric bag that allows air to pass through, but
attempts to trap all dust and debris in the bag.
The bag may be disposable, or designed to be
cleaned and re-used.
In medical uses -Woven filters set the
standard for safe and efficient filtration
solutions in medical devices. Precision woven
fabrics is a critical component for medical
filter devices, blood filtration : precision
woven fabrics set the standard for safe and
efficient filtration.

10. In Power Stations-A bag house(BH, B/H) or fabric
filter (FF) is an air pollution control device that
removes particulates out of air or gas released
from commercial processes or combustion for
electricity generation.
In Sewage disposal- a non-woven fabric filter was experimentally
evaluated for solid-liquid separation in an activated sludge
reactor as an alternative membrane. A polypropylene fabric filter
(70, 50 and 35g/m2) was used.
Power plants, steel mills, pharmaceutical producers, food manufacturers, chemical
producers and other industrial companies often use bag houses to control emission
of air pollutants. Bag houses came into wide spread use in the late 1970s after the
invention of high-temperature fabrics (for use in the filter media) capable of
withstanding temperatures over 350°F

11. Water filtration-This type of filter is a common
solution to the problem of obtaining clean water in
many parts of the world, especially rural parts of
developing nations. It is a fairly simple process that
involves only materials that are available inmost parts
of the world
In Geo-textiles-The non-woven geo-textile
fabric is a common choice for areas looking to
stabilize, separate or filter materials. All non-
woven fabrics come with a needle-punched
exterior that allows thin water particles to
filter through the fabric while keeping soil
from filtering through. This geo-textile filter
fabric helps to retain fine particles when
water passes from fine to coarse-grained soil
.

12. Yarn types and fabric constructions
The technologist has basically three types of yarn to choose from when
designing a filter fabric, namely :
1.monofilament
2.multifilament and
3.staple-fibre
Monofilament:
The diameters of the monofilaments used range from 0.1mm up to 1.0mm,
the smaller diameters being used mainly in applications involving filter
presses, pressure leaf and candle filters, rotary vacuum disc and rotary
vacuum drum filters, whereas the larger diameters are used mainly in
relatively coarse filtration applications involving heavy duty vacuum belt
filters or multiroll filter presses. Although normally extruded in round cross-
section, for special applications they may also be produced in flat or oval
form.

13. Monofilament fabric, five-end satin
weave
For most filtration applications involving monofilaments, the majority of
diameters used are in the range 0.15–0.35mm, yielding fabric area
densities between 180 and 450gm-2. Heavy-duty filter belt applications,
on the other hand, usually employ diameters from 0.3–1.0 mm resulting
in area densities from 500–1700 gm-2.

14. Multifilament
Fabric area densities in this category vary from as little as
100gm-2 to around 1000 gm-2.

15. Staple-fibre yarns
For this, and filtration purposes in general, the yarns are usually spun
with 3.3 decitex fibres in relatively coarse linear densities, typically
from 130–250 tex. Fabrics in this category are normally woven in area
densities ranging from 350–800 gm-2, the lighter and intermediate
fabrics generally being used in pressure leaf and rotary vacuum drum
filters and the heavier fabrics in filter presses.

16. Staple-fibre yarns
For this, and filtration purposes in general, the yarns are usually spun
with 3.3 decitex fibres in relatively coarse linear densities, typically
from 130–250 tex. Fabrics in this category are normally woven in area
densities ranging from 350–800 gm-2, the lighter and intermediate
fabrics generally being used in pressure leaf and rotary vacuum drum
filters and the heavier fabrics in filter presses.

17. Fabric construction
Three basic types of construction are
1.woven fabrics,
2.needle felts and
3.knitted structures.
The first two are produced in flat form and will
require (i) slitting to appropriate width and (ii)
converting into tubular sleeves, whereas knitted
fabrics may be produced directly in tubular
form.

18. Important Characteristics of
Filter Fabric
– With the fabric warp and weft density increases,
the filtration resistance of the filter cloth increases
gradually.
– With the increase in the fabric warp, weft twist,
the filtration resistance of the filter cloth is
reduced gradually.
– Porosity of the fabrics.
– Air permeability of the fabrics.

19. Woven fabrics
Used predominantly in shake collectors, this class
of filter fabric may comprise twisted continuous
filament yarns, short staple-fibre yarns (cotton or
woollen spinning system) or perhaps a combination
of both. Weave patterns may be in the form of
elementary twills, for example 2/1, 2/2 or 3/1, or
perhaps simple satin designs, the latter providing
greater flexibility and hence superior resistance to
flex fatigue and a smoother surface for superior
cake release.
Woven fabric area densities are typically in the
range 200–500gm-2.

20. Woven fabrics
Plain weave-this weave is particularly suitable for flexible
yarns of the multifilament and short staple-fibre types.
The weave is also ideally suited to applications where
thread displacement, due for example to high internal
pressures
Twill Weave: this facilitates the production of fabrics of
higher area density and hence greater bulk, Usually
produced in simple 2/2 or 2/1 style. Twill weave fabrics
are also marginally more flexible than plain weave
fabrics, which may be advantageous when fabricating
cloths of complex make up or indeed when fitting the
cloths on the filter

21. Woven fabrics
Satin weaves: Both regular and irregular satin weaves are
employed. The irregular weaves, such as the four-shaft
construction, are frequently found in more densely sett
high efficiency fabrics, often with two warp threads being
woven as one. From this it will be appreciated that the
weaves with the longer floats are normally used in
conjunction with monofilament yarns.
Link Fabric: link fabrics are produced by a novel
technique in which polyester monofilaments are wound
into spiral form then meshed with similar monofilaments,
which are spiral wound in the opposite direction.

22. Link fabrics

23. Needle felts
In the majority of cases they are produced by needle punching a batt
of fibre – a number of layers of carded fibre web formed by means of a
cross-laying . By far the most widespread in dust collection processes,
providing an infinitely larger number of pores and facilitating
considerably higher filtration velocities than woven fabrics.
The majority of needle felts actually
fall in the range 400–510 gm-2, these
facilitating generally higher filtration
velocities. However, in the event that
the dust is particularly abrasive, a
longer life may be expected from
felts in the 540–640gm-2 range.

24. Finishing treatments
These are designed essentially to improve
(i)Fabric stability,
(ii)Filtration collection efficiency,
(iii)Dust release, and
(iv)Resistance to damage from moisture and chemical agents.
A number of finishing processes are employed to achieve these
goals, for example heat setting, singeing, raising, calendaring,
‘special surface treatments’ and chemical treatments.
Knitting fabrics
It’s being produced in seamless tubular form, weft-knitted
fabrics provide, in theory, an attractive and economic alternative
to both woven and needled constructions.

25. Dimensional stability treatments
As in the production of fabrics for dust collection applications,
heat is again instrumental in inducing the necessary fabric
stability, which, on this occasion, may be achieved through:
•Hot aqueous treatment,
•Heat setting or a combination of both.
In the case of aqueous treatments these may also include
surfactants to remove unwanted fibre and yarn processing aids.
Once again media manufacturers will be aware of the machine
speeds and temperatures that will be necessary in these
processes to achieve the maximum effect

26. Surface modifications
Surface of a fabric can be significantly enhanced by physical/thermal
means such as singeing and calendaring, the development of chemical
coatings production of still more efficient filter media. As in dust
collection, where surface coatings have been available for many years,
the treatments are designed to present a microporous structure to the
slurry which effectively restricts the penetration of particles to all but a
few micrometres in depth.

27. Permeability regulation
The calendaring operation is able both to modify the surface and
also to regulate the fabric’s permeability by means of heat and
pressure.
Before calendering After calendering

28. Fabric test procedures
These are carried out in normal textile laboratories in order (i) to
ensure that the materials under test have been manufactured in
accordance with design specification, and (ii) to monitor any short,
medium or long term trends.
Such tests are concerned primarily with;
Area density,
Fabric sett (hole),
Yarn types and linear densities,
Fabric structure,
Air permeability,
Thickness and density (principally needlefelts),
Tensile properties and fabric stability.

29. Projected World Population
Growth
http://www.globalchange.umich.edu/globalchange2/current
/lectures/human_pop/human_pop.html
1950-ref 2000~2x 2050~3x
HealthHealth,, EnvironmentEnvironment andand EnergyEnergy are three major research areas!are three major research areas!

30. Problem: a Shortage of Clean Water
• 41% of the Earth’s population (2.3 billion) live in water-
stressed areas; 3.5 billion by 2025.
• 1.2 billion people live without clean, piped water (WHO).
• Water shortages limit economic development and
threaten human life.

31. U
nited
statesAsia/Pacific
Europe
M
iddle
East/Africa
Latin
Am
erica/Caribbean
$0
$200
$400
$600
$800
$1,000
$1,200
$1,400
Sales($millions)
NewDesalinationCapacity(millionm3
/d)
2010
2005
A B
0
2
4
6
8
10
BillionGallonsPerDay
Oil
production
Desalinated
water
• There are currently more than 15,000
desalination plants worldwide (1/4 in US).
• Membranes (reverse osmosis and nano-
filtration) are the most energy-efficient
technology.
• Costly pre-treatment of water (chlorination
and dechlorination) is required before
membranes to reduce membrane fouling.
Water Desalinization Report, 42(35), 1, 2006
www.bp.com
Ultrapure Water, 23(3), 14, 2006
VALUE OF REVERSE OSMOSIS (RO)
SYSTEM COMPONENTS
Annualsales($millions)
Prediction
U
nited
statesAsia/Pacific
Europe
M
iddle
East/Africa
Latin
Am
erica/Caribbean
$0
$200
$400
$600
$800
$1,000
$1,200
$1,400
Sales($millions)
NewDesalinationCapacity(millionm3
/d)
2010
2005
A B
0
2
4
6
8
10
BillionGallonsPerDay
Oil
production
Desalinated
water
• There are currently more than 15,000
desalination plants worldwide (1/4 in US).
• Membranes (reverse osmosis and nano-
filtration) are the most energy-efficient
technology.
• Costly pre-treatment of water (chlorination
and dechlorination) is required before
membranes to reduce membrane foul.
Water Desalinization Report, 42(35), 1, 2006
www.bp.com
Ultrapure Water, 23(3), 14, 2006
VALUE OF REVERSE OSMOSIS (RO)
SYSTEM COMPONENTS
Annualsales($millions)
Prediction
Desalination Market is Large and ScheduledDesalination Market is Large and Scheduled
to Grow Rapidlyto Grow Rapidly

32. Production Equipment
In a fibrous filtration system,
filtration medium is a layer piled
with a number of fiber-mass
blocks. Periodically filtrated
particles on the medium are
removed by counter washing
accompanied by aeration
Sand filtration is widely used for
water treatment.

33. Water purification by some specific
fibers
Activated carbon fiber. Activated carbon fiber is often used in
combination with the membrane hollow fiber as a major
component of water-purifying equipment for drinking water. The
main role of activated fiber in the equipment is to remove such
substance as chlorinated organic chemical and smell constituents.
Ion-exchangeable fibers. There are some kinds of ion-
exchangeable fibers. They can be effective to remove toxic
ingredients of heavy metal from water. The fiber made of ion-
exchangeable polystyrene resin is used for purification of recycled
water from atomic power plants.

34. Reverse osmosis

35. Separation of oil and water
• Oil barrier- sheet fence made of woven fabric
reinforced by belt, (b) float made of foamed
polystyrene covered with woven fabric, and
(c) weight for stabilization.
• oil-adsorptive fibrous sheet. The material of
this sheet is usually nonwoven made of
polypropylene (PP), kapok, or cotton.
• Separating water from oil

36. Air purification
• Bag filters are widely used for cleaning the exhaust gas
from several kinds of incinerators.
• They are usually made of glass fiber-woven fabric or
synthetic fiber needle felt or its combination with
woven fabric.
• Polyphenylene sulfide, m-aramid, polyimide, and
polytetrafluorocarbon are typically used as the
synthetic fiber material
• Acid gas and some other harmful gas substances can
also be removed by introducing such materials as
slaked lime and activated carbon in the bag.
• Air filters used for the removal of dust for clean room
and office
• The filter medium is usually nonwoven.
• Filter medium is usually pleated in the filter of high
removal efficiency.

37. Air purification
Air filters
• Air filters used for the removal of dust for
clean room and office
• The filter medium is usually nonwoven.
• Filter medium is usually pleated in the filter of
high removal efficiency.

38. Toxic-gas removal and solvent
recovery
• Activated carbon fiber is useful as the key
material for both the removal system of toxic
gas and the solvent recovery system

39. Presented at the Fifteenth Annual Technical Conference & Expo of the American Filtration &
Separations Society, Galveston, Texas, April 9-12, 2002.
Electrospun
fibers
Contaminant
Melt blown
fibers
Air filtration using functional nanofibers
Filtration of aerosol particles
 Antimicrobial air filtration
Respiratory and breathing air filtration

40. Air filtration by nanofibrous web
Substrate
Fiber
Nanofibers
covered
with
submicron
NaCl

41. Nanofiber based adsorbents and
ion exchangers
Schematic diagram of the nanofiber network composite fuel cell proton-exchange
membrane. The inset shows the polymer matrix (a) which restricts swelling of the
nanofibers and imparts mechanical strength to the membrane. The water-swollen fiber
network (b) is composed of a sulfonated cation-exchange polymer shown (c)
schematically and (d) in actual chemical structure form

42. Nanofiber based adsorbents and
ion exchangers
Adsorption of heavy metal ions
Adsorption of organic compounds
Ion exchange

43. Nanofibrous Microfiltration Membranes
for Water Purification
∼100 nm
diameter
Non-woven
fiber mat
Breakthroughs in microfiltration:
low-cost & extremely high throughput
Non-woven
support, with pores
like coffee filter
•With comparable porosity, the smaller the fiber diameter, the smaller the pore size.
0.02-1 µm thick
5 nm fiber diameter
Flow
direction
Water with bacteria
Water without bacteria
Key Features
Ex: Typhoid, cholera, dysentery

44. Schematic View of E-spun/Coating
Composite Water Filtration
Membrane
Hydrophilic polymer-
Impregnated E-spun layer
Hydrophilic polymer coating
Fine e-spun layer
Coarse e-spun layer
+
+
2 µm
Coarse e-spun layer

45. Applications

47. Applications

48. Abrams M1A1 tank with self-
cleaning nanofiber filter

49. Filtration plays a major role in cleaning the environment

50. Cont…
adopted
three nozzles and
electrospun the PA 6
nanofiber membranes with
initial width of around 17
cm and the final width of
14.9 cm.
the preparation process
was composed of
electrospinning,
wetting, tension heat
setting, relaxation heat
setting, and coiling
on the roller
Fig.1—infusion pump, 2—spiral cone, 3—metallic
collector, 4—electrospun nanofibrous membrane,
5—stripping rollers, 6—water bath, 7—drying
rollers, 8—tension heat setting zone, 9—
relaxation heat setting, 10—finished nanofiber