Textile Materials in Liquid Filtration Practices: Current Status and Perspectives in Water and Wastewater Treatment

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Chapter 11
Textile Materials in Liquid Filtration Practices: Current
Status and Perspectives in Water and Wastewater
Treatment
Murat Eyvaz, Serkan Arslan, Ercan Gürbulak and
Ebubekir Yüksel
Additional information is available at the end of the chapter
http://dx.doi.org/10.5772/intechopen.69462
Abstract
Filtration is considered the keystone of water and wastewater treatment and is used for vari-
ous purposes, such as sludge dewatering and concentrating any solution. Moreover, as an
advanced ltration technology, membranes can remove materials ranging from large visible
particles to molecular and ionic chemical species. Proper selection of lter media/membrane
material in ltration processes is often the most important consideration for assuring e-
cient separation. Filter media can be classied by their materials of construction, such as
coon, wool, linen, glass ber, porous carbon, metals, and rayons. Recently, new polymeric
materials have been used both individually and/or blended in ltration processes for the
treatment of waters and wastewaters. The purpose of this chapter is to bring an overview
on the textile-originated lter materials in ltration applications from conventional ltration
to advanced membrane processes. Although many researches on lter media are available,
very few researches have been carried out on the cuing-edge technologies about using lter
materials on ltration processes from classical to advanced membrane processes. Therefore,
in this part of the book, following major and minor titles are stated truly on the aforemen-
tioned new technologies and linked with conventional methods in water and wastewater
treatment applications.
Keywords: ltration, membrane, textiles, woven, nonwoven, bers, nanobers,
electrospinning, water treatment, wastewater treatment
© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly cited.

1. Introduction
Physical, chemical, and biological methods are used in water treatment to convert raw water
to potable water. The selection of the treatment method depends on the properties of the raw
water. Water treatment methods can be based on simple physical processes, such as sedimen-
tation processes or more complex physicochemical processes, such as coagulation. Among
these purication methods, ltration is the process of removing solid substances from a uid/
liquid (water/wastewater) by passing them through a porous medium (ltration). Filtration
is commonly used in water treatment to remove solids, including microorganisms (bacteria,
viruses, etc.) and precipitated iron and manganese found in surface waters [1]. In addition to
conventional ltration, direct ltration, which is a simple and economically aractive process
in which the sedimentation phase is lifted, is often used. Direct ltration is suitable for raw
waters with a turbidity value lower than 10 NTU. It does not require sedimentation tanks
and, in some cases, oatation tanks, which leads to low installation and operating costs [2].
Filtration is a basic procedure widely used in environmental engineering applications for
the removal of suspended solids, such as clay and silt particles, microorganisms, colloid and
sediment humic substances, roen plant particles, and calcium carbonate and magnesium
hydroxide precipitates used in water softening [3]. Filtration is used in the treatment of drink-
ing water, especially in high-quality surface water. For the treatment of wastewater, dierent
kinds of ltration processes can be used at dierent stages of the process [4, 5]. In addition to
solid-liquid separation, the ltration process is used for dewatering. A classication based on
the operating mode of the ltration and the ltration unit used is shown in Figure 1.
Filters are selected in dierent qualities depending on the characteristics of the industries in
which they are used. For example, the reverse osmosis process used to desalinate water and
Figure 1. Operational modes of ltration (adopted from [6]).
Textiles for Advanced Applications294

the cellulose acetate and aramid hollow ber membranes used are among the rst applica-
tions of ber-based ltration. The important properties of the bers used in such a ltra-
tion are their hydrolytic nature, oxidative nature, and high biological resistance over a wide
pH range. In addition, the bers need to be resistant to temperature changes and chemicals
used in dierent industries. Poly (phenylene sulde), polysulfone, aramids, polyimide, PEEK
(Victrex), uorocarbon, and related bers are examples of high-performance bers eective
for liquid ltration under extreme and rapid changing environmental conditions [7].
Proper selection of filter media/membrane material in filtration processes is often the
most important consideration for assuring efficient separation. Filter media can be clas-
sified by their materials of construction, such as cotton, wool, linen, glass fiber, porous
carbon, metals, and rayons. Recently, new polymeric materials have been used both indi-
vidually and/or blended in filtration processes for the treatment of waters and wastewa-
ters. The purpose of this chapter is to bring an overview on the textile-originated filter
materials in filtration applications from conventional filtration to advanced membrane
processes. Although many researches on filter media are available, very few researches
have been carried out on the cutting-edge technologies about using filter materials on fil-
tration processes from classical to advanced membrane processes. Therefore, in this part
of the book, following major and minor titles are stated truly on the aforementioned new
technologies and linked with conventional methods in water and wastewater treatment
applications.
2. Principles of ltration
2.1. Filtration mechanisms
Filtration is based on the principle that water is passed through a porous medium at a cer-
tain rate. The lter does not allow particles to pass while allowing water to pass through.
Particles (0.01–5 mm) retained in the lter medium are smaller than the size of the lter
material (5–20 mm), and such retention takes the place in trapping in unltered extraneous
materials, which strikes and adheres to the lter material due to the rapid ow of the uid.
Although the ow in the porous media was announced by Darcy in 1856, the rst lters
were designed by trial and error until the publication of the Carman-Cozeny equation (1937),
which describes the ow in the lter bed. As research continues on the design of granule
lters, the earlier empirical equations used in design are still widely used [8].
The trapping of particles in the lter bed consists of two phases, collision and aachment.
In the rst stage, the particles in the uid approach the surface of the densities of the porous
lter media by mechanisms, such as sedimentation, impaction, diusion, and interception,
and become accessible to hold. In the second step, the retention of particles in the lter
depends on the balance between the supercial forces between the particles and the l-
ter medium. These steps and the mechanisms that play a role in each step are explained
elsewhere (Figure 2) [9, 10].
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2.2. Types of ltration processes
2.2.1. Surface (membrane) ltration
Membrane ltration is the process of separating a material from a medium through which it
can pass more easily than other materials in the same environment. In water and wastewater
treatment, membranes are used to remove unwanted suspended or dissolved substances.
However, in some cases, the membrane may move to remove contaminants from the waste-
water or to transfer special components (such as oxygen) into the liquid medium. Extraction
processes currently used include electrodialysis (ED), dialysis, pervaporation (PV), and gas
transfer (GT). In such cases, the membrane is used to allow selective penetration of specic
components dissolved in water. However, ltration processes such as reverse osmosis (RO),
nanoltration (NF), ultraltration (UF), and microltration (MF) are of much more industrial
signicance. In these processes, it is the bulk water that passes through the membrane under
an applied pressure, leaving the pollutants in a concentrated form on the unpermeated side
of the membrane [10, 11]. Membrane classication based on ltration is shown in Figure 3.
2.2.2. Depth ltration
Deep-bed lters are more than a century-old and are widely used in water and wastewater
treatment applications. The theory of deep-bed ltration is the same as the formation of wells
or springs in nature, which are drained from porous media, such as rocks and sand. In prac-
tice, deep-bed lters are obtained by placing the material to be ltered in a closed tank (pres-
surized) or in an open concrete pond. The lter tank is designed according to the properties
of the liquid to be ltered or ltration method (pressure or gravity operation). Particles in
the liquid are trapped in the lter bed by the abovementioned ltration mechanisms. During
Figure 2. Filtration mechanisms in deep-bed lter, (a) diusion, (b) interception [9, 10].
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Figure 3. Schematic illustration of membrane ltration spectrum [11].
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ltration, the particles that accumulate in the lter bed begin to clog the lter and reduce the
uid pressure. For this reason, solids are not required at high concentrations. Filtration is
generally applied for concentrations lower than 0.5 g/L. Alternative or pretreatment systems
should be considered as the solids concentration increases. Precoagulation and/or occula-
tion systems have to be applied before the ltration of submicron particles that are too small
to be ltered or seled readily. The common types of deep-bed ltrations are slow sand ltra-
tion, rapid ltration, and direct ltration, which are explained in detail elsewhere [6]. Both
surface and depth ltration are shown schematically in Figure 4.
2.3. Operating parameters of ltration
The lter medium is evaluated as the heart of any ltration process. Ideally, while the solids
to be retained are concentrated on the feed side of the membrane, the liquid portion is forced
to pass through the membrane and is transported to its other side. A lter medium, by its
nature, is not homogeneous, and its dimensions and geometries come from irregular pores.
These pores may also exhibit an irregular distribution over the membrane surface. Since the
ow in the environment only takes place through the pores, the microuidic velocity therein
can cause large dierences on the lter surface. This indicates that the top layers of the lter
cake produced on the membrane surface are not homogeneous and are also formed based
on the nature and properties of the lter medium. Since the number of passages in the lter
cake is larger than the number in the lter media, the primary structure of the cake is strongly
aached to the structure of the rst layers. This means that the lter crayon and lter material
are inuenced by each other.
The pores containing passages extending along the lter medium can catch solid particles
smaller than the narrowest cross section of the passageway. Such retention of the particles is
Figure 4. Schematic representation of surface ltration (on the left side) and depth ltration (on the right side) [12].
Textiles for Advanced Applications298

generally explained by particle bridging or, in some cases, physical adsorption. Depending on
the intended use, dierent lter media are used. The commonly used lter media are sand,
diatomite, coal, coon or wool fabrics, metal wire cloth, porous quar plates, chamoe, sintered
glass, metal dust, and powdered ebonite. The average pore size and conguration of the lter
material (including tortuosity and connectivity) is due to the size and form of each element from
which the material is produced. The manufacturing method of the lter material also inuences
the average pore size and shape. For example, pore characteristics vary when the brous media
is rst pressed. Pore properties also depend on the properties of the bers in the woven fabric
or on the methods of sintering glass and metal powders. In addition to all these, some lter
media, especially brous layers, are subject to signicant compression when subjected to typical
pressures used in industrial ltration processes. Other lter materials, such as sintered plates of
ceramics, glass, and metal powders, are stable under the same operating conditions.
The ltration/separation process also inuences pore properties. Because as ltering contin-
ues, eective pore size decreases and ow resistance increases. This is because the particles
penetrate into the pores of the lter media. The separation of solid particles from the liquid by
ltration is a complex process. In practice, it is desirable that the lter pores are larger than the
average size of the particles to be ltered. However, the selected lter medium must have the
ability to retain solids by adsorption, and cohesive forces between the particles must be large
enough to induce particle agglomeration around the pore openings [13].
2.4. Application of ltration
2.4.1. In drinking water treatment
The ltration process discussed in this section is used to remove particulate material from the
water. Filtration is one of the unit processes used in drinking water treatment. The particles
retained in the lter may be particles present in the spring water, or may come into play
during the purication process. Particulate materials include clay and silt particles; microor-
ganisms, such as bacteria, viruses, and protozoa cysts; humic substances and other natural
organic particles; calcium carbonate and magnesium hydroxide precipitates used in softening
processes; or alumina or iron precipitation used in coagulation processes [14]. High-quality
drinking water production and ltration units are shown schematically in Figure 5.
About 30–40 years ago, lead was considered among the dangerous harmful pollutants in drinking
water. Today, along with lead, pesticides, bacteria, viruses, coliphages, nitrates, chlorine, chloror-
ganic substances, and aluminum have been added to the list of health threats, and the pollutant
list is renewing day by day [15]. The contaminants typically found in water are shown in Table 1.
2.4.2. In wastewater treatment
The treatment of wastewater is a big deal when considering the volume of the water to be
treated. Most of the water used for domestic, commercial, institutional, and industrial purposes
is returned to the environment as waste. For this reason, a suitable treatment for a safe discharge
is needed, which can manage wastewater treatment, from collection of waters to treatment, from
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equipment selection to process design. In most of the developed areas, wastewaters are collected
by a municipality or a private operator and are directed to the treatment plant for collection
by the sewerage system and surface runo. The purpose of wastewater treatment is to convert
Contaminants Eects
Chlorine • Reacts with organics and forms trihalomethanes
Bacterial diseases • Cause cholera, the most widespread infection
The parasitic protozoan Cryptosporidium • Get into the water supply from animal excrement
• Can survive for long periods in water
• Self-limiting gastroenteritis to life-threatening situations
Cryptosporidium • Resist chlorine
• Cause disease
• Treatable with antibiotics
Giardia lamblia • Cause disease
• Treatable with antibiotics
Bacteria and viruses • Can be removed by ultraltration and activated carbon
Table 1. Typical contaminants found in water (adopted from [15]).
Figure 5. Drinking water production units.
Textiles for Advanced Applications300

these mixed wastes into a liquid stream, which will not harm the environment. Wastewater dis-
charged without treatment threatens the life of plants and animals by consuming oxygen in the
receiving environment. The contaminated receiving environment waters can be transported to
the surface waters to be used for water supply and can adversely aect human health. Although
most of the industrial wastewater treatment process is the same as domestic wastewater treat-
ment, the characteristics of the industrial wastewater source should be taken into account.
Granular ltration is generally used for the treatment of water and wastewater containing
suspended solids. The lter medium is composed of materials, such as sand and anthracite,
which contain granular particles. The lter medium is contained in a basin, and underneath
the material there is a layer that serves both as a support and as a drain. As the water or
wastewater passes through the lter bed, the particles are trapped in and on the bed. When
the lter is clogged, backwash is performed at high speed. The backwash water contains sol-
ids at high concentration and is recycled to another treatment step or plant inlet. Filtration
is typically used for liquids with a solids content of 100–200 mg/L. As the concentration of
suspended solids in the water-wastewater to be treated increases, the lter blockage acceler-
ates and the frequency of backwash increases. Sudden and continuous ow changes in the
ltration are another factor aecting the ltrate quality. Sedimentation is generally applied
before ltration to reduce the suspended solids load. Filtration can also be applied to reduce
suspended solids before biological treatment or before activated carbon process. The particles
that can be removed by the granular ltration process are usually in colloidal size or may be
in larger sizes such as oc. Although the oc is more likely to remain in the lter, it clogs the
lter faster. Sometimes, however, occulation of the particles may not be possible (as in many
oil and water emulsions). In this case, some other equipment such as ultraltration may be
needed. In a typical physical/chemical treatment plant, there are three parallel lters having
three lter media layers (sand and anthracite) connected in parallel.
2.4.2.1. In municipal wastewater treatment
In most municipal wastewater treatment plants, the wastewater delivered to the treatment is
not continuously characterized. For this reason, considering that other pollutants may also be
transported to the plant wastewater inlet, the design of the treatment plant should be designed
to cope with the pollutant in a wide range. These contaminants may be suspended or dis-
solved, organic or inorganic, or toxic or not. The treatment plant should be able to reduce the
total amount of these pollutants below the limit values set by national and local regulators.
These limits are regulated according to the structure of the receiving water environment. The
units of a conventional municipal wastewater treatment plant are shown in Figure 6.
2.4.2.2. In industrial wastewater treatment
Industrial wastes dier from domestic wastes in three main ways:
(i) They contain more inorganic or biodegradable contaminants,
(ii) They generally have low or high pH, and
(iii) They often contain high amounts of toxic substances.
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The oil compounds are also a problem for the treatment process. Although the waste amount
of a plant that applies a certain production standard is generally constant in terms of com-
pound and content, the purication cost is also very high since large volumes of wastewater
and high amounts of sludge are formed. Although most industrialized countries have com-
prehensive legislation on industrial wastewater, this is not sucient in wastewater manage-
ment alone. It is also important that the industry owner knows the regulations and that the
audits are carried out in sucient frequency and extent. For this reason, wastewater treatment
is a complex process in environmental management. In the majority of industrial wastewater
treatment plants, there are two main parts: (i) to dispose of special wastes that are initially
dependent on the raw material of the industry and (ii) to remove other general wastes. In the
rst part, the main function is to minimize the loss of any product material carried with the
waste. If it is possible, the main thing is to recover the products in the waste [15].
2.4.2.3. Treatment of hazardous wastes
Membrane processes are used in many water and wastewater treatment applications. Most
of these applications involve the separation and concentration of organic and inorganic sub-
stances. Wastewater can originate from industrial processes, contaminated ground or surface
waters, or byproducts of other treatment processes. Membrane and ltration processes are
used in water and wastewater treatment from visible particles to ionic species in many pollut-
ant removal methods. Membrane processes are also preferred for the separation of hazardous
wastes. In the organic pollutant removal, the separation takes place depending on the size
Figure 6. Conventional municipal wastewater treatment plant.
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(molecular weights) and polarities of the pollutants. For this, a suitable membrane having
a dierent pore diameter is selected and used. The smaller the pores of the membrane, the
higher the removal of small molecular weight compounds. However, as the pore size of the
membrane decreases, the ux will also decrease. This will adversely aect the amount of
product water obtained.
The polarity of an organic component is a measure of the ability of ionization in solution. Polar
molecules include, for example, water, alcohols, and compounds having hydroxyl groups (e.g.,
phenols) and carboxyl groups (e.g., organic acids). Aliphatic hydrocarbons and polynuclear
aromatic hydrocarbons are examples of nonpolar organic molecules. The chemical properties
of the membrane can be used to separate nonpolar components from polar components in a
waste stream. For example, a membrane that is surface hydrophilic will allow the passage of
polar components while retaining nonpolar components. These membranes can be used to
separate dissolved and emulsied oils from aqueous waste streams. Inorganic contaminants,
such as salts and heavy metals, can be removed and concentrated by membrane processes from
waste streams. Suspended inorganic materials can be easily removed using microltration
membranes. These membranes have pore sizes ranging from 0.01 to several microns. Dissolved
inorganics can be removed by reverse osmosis membranes or by precipitation followed by
microltration. Only when reverse osmosis is used, a pretreatment is absolutely necessary, or
it is used in the treatment of relatively clean waters. Chemical precipitation, on the other hand,
provides higher ux with microltration membranes that are less sensitive to fouling [15].
3. Textile materials for ltration
3.1. Properties of lter media
There are a number of materials available for use in the lter medium that can be used to
meet the needs of the user (Table 2). The material to be used must be easy to place on the lter
tank/module. For this purpose, wool and nonwoven fabrics, natural or synthetic bers may be
preferred. In some cases, the weaving medium may be equipped with metal glands. The same
material may be incorporated into the hard porous media (porous ceramic, sintered metal,
woven wire, etc.), cartridge, and wax lter.
The proper selection of lter material is the most important factor in achieving ecient ltra-
tion. A good lter medium/lter should have the following characteristics: the lter medium
should be able to retain the particles contained in the suspension in a wide size distribution; in
order to obtain a high amount of ltrate in the desired quality, the lter must exhibit minimum
resistance to ow; the cake deposited in the lter should be suitable for easy removal; it must be
resistant to chemicals that can be transported to the lter medium and should not be a soluble
material; during the ltration or backwashing process, the lter material should not swell; it
must be suciently resistant to temperature changes in the uid or environment; it must be
resistant to the pressure applied in the lter and mechanical abrasion that may occur during
the ow; and the lter material must be capable of preventing particles from being wedged in
the pores [6]. The parameters to be considered in the lter selection are schematized in Figure 7.
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3.1.1. Classical ltration media
The lter medium is described as a porous (or at least semipermeable) barrier used to hold
part or all of a suspension. When the pores of this barrier are much smaller than the diameter
of the smallest particle to be ltered, the entire ltration process will take place on the surface,
Figure 7. Parameters in lter selection.
Basic media format Types of media
Loose granules Deep bed
Loose bers Pads, felts
Structured granules Bonded, sintered
Structured ber Needlefelts, spun
Sheet Perforated, microporous
Woven/knied Spun yarn, monolament
Tubular Hollow ber
Block Rigid
Wound on core Spun yarn, monolament
Structured array Ribbon, rods, bars
Extruded mesh Netlon
Table 2. Filter media types [15].
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not the depth of the lter medium. If there is any particle smaller than the pore diameter, it
will point toward the pores. Larger particles will clog the pores while smaller particles will
clog the surface, thereby reducing the ltrate ow. At a certain point, the ltration process
should be stopped and cleaned.
The mechanism by which the relationship between the particle size of the ltration process
and the lter pore size depends strongly is called surface straining. As long as the particles are
not deformed, the surface of the lter is separated by pore size with the help of tension. A sec-
ond mechanism, referred to as deep stretching, occurs when a particle moves along the pore
and is retained completely at a narrower point of the eye due to particle size. At this point, the
clogged pore should be cleaned with backwash. The ne particles move on a tortuous path
in lter bed and are trapped in the lter pores through a direct or inertial retention/diusion
mechanisms. This process is known as depth ltration. Congestion in the lter bed also occurs
with these mechanisms. Particles retained in the lter material are compressed and do not
completely cover the pores. Thus, the ow continues until the lter is completely clogged. In
this case, the lter should be backwashed.
During the ltration process, particles in the pores are held together, and after a while they
begin to function like lter material and assume the responsibility of trapping the particles
that come after it in the uid. A similar mechanism is also seen in the cake layer formed by
the separated particles held on the lter media, and this separation is called cake ltration.
More complicated mechanisms can occur in cake ltration. Because the cake compressed less
or more by water pressure.
3.1.2. Membrane ltration media
Membranes are classied according to the size of the particles they separate. Macroltration is
used to separate the intrinsic particles in the range of about 1 mm to 5 μm (screening is used
for particles above 1 mm). Microltration is applied for particles from about 5 μm to about
0.1 μm, while ultraltration is used for lower dimensions. While ultraltration separates ner
particles such as colloids, the lower limit of the particle size is usually determined by the term
molecular weight, measured in Dalton. Further separation processes include nanoltration
and reverse osmosis. In both systems, a semipermeable membrane acts as a barrier in front
of the uid ow. However, the operating principle of NF and RO processes is dierent from
that of UF. The liquid to be used in NF and RO is a solution which does not contain suspended
solids or is preltered. The last two processes mentioned do not physically contain holes. The
molecules are distributed across the membrane under high transmembrane pressure, and the
liquid is removed from the other side of the membrane in pure form [15].
3.2. Textile media
Textile bers are obtained from many natural and synthetic sources. Natural sources include
materials of wood/cellulosic and vegetable origin, such as coon, towel (ax), and jute, and
materials of animal origin, such as silk, wool, fur, and hair. Synthetic materials are produced
from natural sources such as glass, ceramics, carbon, metals, or reconstituted cellulose. They
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can also be obtained synthetically, extruded from thermoplastic polymers. The natural bres
are extremely long by comparison with their diameters, except in the case of wood cellulose,
where the manufacturing process produces short bres (in millimetres).
Fabrics are the largest component of lter materials. They are composed of bers or laments
made of natural or synthetic material and are relatively soft. They are also not rigid like dry
paper. For this reason, they need some kind of support when they need to be used as a lter
medium. The bers or laments can be made into a fabric as is by a series of drylaying opera-
tions to produce a felt or the like. Such ‘noninterlaced’ fabrics are often referred to as ‘nonwo-
ven.’ They are mentioned in the following sections of nonwoven fabrics [15]. A lter media
classication (Ipurchas, 1967) based on rigidity is shown in Table 3.
3.2.1. Woven fabrics
Flexible and nonmetallic materials have been widely used as lter media for many years.
These materials can not only be found in the form of fabric or as preformed nonwoven mate-
rials, but also as perforated plates. The fabric lter media is characterized by the number of
weaves, mesh size, yarn size, and mesh type. The number of mesh or the number of thread of
a fabric is the number of threads per inch. The number of yarns in the warp and weft direction
are equal to each other and are represented by a single number.
The warp threads are placed longitudinally in a fabric and are parallel to the fabric edge. Weft
or ll yarns also pass through the width of the fabric across the width of the warp. The space
between the threads is the mesh opening and is measured in units of mm or inch. Dierent
yarn sizes are normally dened as a diameter measurement in micrometers or mils (thou-
sands of an inch). In warp and weft directions, the yarn sizes are normally the same and are
represented by a single number. Fabrics are available in dierent mesh openings and dierent
yarn diameters. The yarn diameter aects the amount of open space in the cloth to which it
belongs, which determines the ltration ow rate or yield.
The diameter of the natural bers varies according to their source, and is usually bigger than
1 mm. Synthetic bers and laments are formed by a kind of extrusion process that has a
diameter that matches that of the extruded bending mouth. For this reason, their diameters
may be in a much wider range than natural products, and in a wide range of sizes. The length
and diameter of a natural ber can be increased by turning the material into a yarn, but the
Type Example Minimum trapped particles (μm)
Edge lters Wire-wound tubes
Scalloped washers
5–25
Metallic sheets Perforated plates
Woven wire
100
5
Woven fabrics Woven cloths
Natural and synthetic bers
10
Cartridges Spools of yarns or ber 2
Table 3. Filter media classication [6].
Textiles for Advanced Applications306

yarns can also be made from bers at the same time. Because the lengths are much longer,
the bers can usually be brought together to make a yarn, but the bundles are usually twisted
to have a reasonably constant diameter. In order to impart sucient strength to the resulting
yarn, the shorter ber laments must be rmly twisted after being rotated for sequencing.
Yarns made from bers usually have a thin, smooth, and glossy appearance. Staple yarns are
generally thicker, more hairy, and with less or no shine in appearance. Yarns can also be made
from various types of tapes. For the lter medium, these bands are most likely brillated or
made from other perforated material. The woven fabrics then consist of monolaments or
multilament yarns or twisted staple yarns. The laer is normally used as a single yarn, but
two or more spun yarns may be joined to the yarns which are twisted together; this is usually
the opposite of the twist of each thread.
Fabric materials can be considered as a physically stronger alternative lter medium than
paper materials and are used in a similar way for pleated elements. Fabric elements are in
fact the most commonly used lter material for ne-size ltration and can be easily com-
pared with modern paper lters in terms of ltration performance. Until the appearance of
processed paper lters, fabric lters were more advantageous than conventional paper lters.
While processed papers are now more commonly preferred as lter material due to lower
cost, fabric lters can withstand higher working pressures with similar geometry. However,
the fabric elements have a lower specic resistance than the paper elements. Though thicker
than paper, fabric materials can carry a heavier pollutant load per unit area. However, when
the same volume of packaging is taken into consideration, this advantage is oset by the
decrease in surface area since the fabric material is thicker. Fabric lters may be preferred
when large size lters are needed or when adsorption is required in addition to mechanical
screening. The fabrics may contain a range of materials, woven and nonwoven, and may be
modied by impregnation with synthetic resin or the like. In the same way, ‘cloth’ is often
used to describe a natural or synthetic fabric media and even a woven wire cloth [15]. Some
typical ltration performance curves for fabrics and papers are shown in Figure 8.
Figure 8. Filtration performance comparison [15].
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Synthetic ber-produced fabrics are superior to natural fabrics due to their resistance to swell-
ing, acid-alkali, and various solvents and their resistance to the growth of fungi and bacteria,
such as natural bers. In addition, many synthetic bers are resistant to high temperatures
and can be easily cleaned due to their smooth surface. The physical properties of the most
commonly used synthetic lter materials are shown in Table 4 [14].
3.2.1.1. Woven yarn fabrics
Fabrics can be woven from a wide variety of yarns. Generally, the warp threads (extend-
ing longitudinally on the counter) are stronger, whereas the weft threads (running along the
counter) may be more bulky and more tightly twisted. A weft is a thread of a very dierent
material, while it is quite common that warp is a single, relatively sti staple. Equally, it is
normal to make both warp and weft from the same ber or yarn. The properties of a fab-
ric, especially as regards its behavior as a lter medium, are highly dependent on the way
yarns are woven together. Many properties of the lter media are aributed to the natural
properties of the ber or lament or to the method of conversion to yarn. There are three
basic yarn types commonly used for lter media: (i) monolament, a single continuous la-
ment composed of synthetic material (or silk); (ii) multilament, a large number of laments;
and (iii) staples, spun or twisted laments from natural materials such as coon and wool,
or synthetic ones cut from extruded laments. The main feature of yarn type aecting ltra-
tion performance varies with monolament and multilament/staple fabrics. In monober
fabrics, the ltration takes place in the spaces between the laments, while, in multilament
and staple fabrics, yarn twisting is also important as ltration can also occur within the yarns
as well as between them. The physical and chemical properties of a yarn are often due to the
Fibers Acids Alkalis Solvents Fiber tensile
strength
Temperature
limit (°F)
Acrilan Good Good Good High 275
Asbestos Poor Poor Poor Low 750
Coon Poor Fair Good High 300
Dacron Fair Fair Fair High 350
Glass High Fair Fair High 600
Orlon Good Fair Good High 275
Saran Good Good Good High 240
Teon High High High Fair 180
Wool Fair Poor Fair Low 300
Dyne1 Good Good Good Fair 200
Nylon Fair Good Good High 300
Table 4. Properties of woven lter cloth bers [14].
Textiles for Advanced Applications308

physical and chemical properties of the bers or laments that make up the yarn. In addi-
tion to the number of natural bers (mostly coon, but some wool and silk) and a small but
growing number of inorganic bers, the bulk of lter fabrics is based on an increasingly wide
variety of synthetic polymer bers. The physical and chemical properties can then be adapted
to the ltration needs by selecting the appropriate polymer.
In textile ltration, the basic material (ber or lament type) of a woven fabric and its shaping
are the most important parameters in the selection of the fabric. The variety of woven fabrics
available to be used in ltration is virtually unlimited, even if only the way in which the mate-
rials of the llers or yarns and the way the threads are touched is taken into account. Then
the weaving process and the nal process to be applied to the fabric after weaving should be
added to the fabric structure. Woven fabrics consist of a specic and regular thread which is
called kniing. There is no need for the warp and weft yarns to be parallel or perpendicular
to each other, but this is true for most fabrics and this structure is also present in the lter
medium. The basic properties of a woven fabric result from the geometric uniformity of its
components and are retained by friction at the contact points, not by any solid connection.
The binding system or weave is the fundamental factor that determines the character of the
woven fabric. Although there are many complex types of kniing in industrial textiles, three
main types of kniing (plain, twill, and satin) are used (Figure 9). The dierences between the
wefts are dependent on the length of the weft threads formed when the threads are touched
on or under the warp threads. In the plain weave, the weft thread passes over succeeding
warp threads along the loom. The return weft then passes through the opposite direction of
the subsequent warp threads, so that each weft is held rmly by engaging the warp threads
together. Plain weaves can give the most dense fabric and the most robust woven fabric with
the highest leverage eciency. The texture braids are characterized by a strong diagonal pat-
tern. The weft yarns are formed by being passed over two or more warps at one time, and then
one or more underneath, regularly along the counter. The next weft thread follows the same
and upper paern, but is replaced by a warp thread. The essential feature of a twill is due to
its regularity which leads to the diagonal paern. In a twill weave, more weft threads can be
crammed to a unit length fabric, which gives the fabric more bulk. Compared to a plain weave
with the same yarns, the twill fabrics are more exible and therefore it is easier to place them
in a lter [14, 15]. A summary of the main types of weaves for wire cloth is given in Table 5.
Figure 9. Weave paerns in woven cloths [6].
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Satin texture broadens the twill weave concept with wider spacing between touch points.
Satin does not have the normal tissue paern of the tissue, resulting in an irregular appear-
ance with a smooth surface with relatively long layer of warp threads. Most satin fabrics are
made from at, slightly twisted yarn, so visual eects are enhanced. Satin weave fabrics are
more exible than the other two weave types because of the increased ease of thread twist-
ing: this reduces the likelihood of trapped particles. The longer oats allow for the insertion
of more warp threads in proportion, thereby further improving the smoothness of the surface
resulting in easier cake drainage (Table 6). However, unless both warp- and weft-oriented
yarns are compacted tightly, satin weaves generally do not provide high ltration eects,
while long oats are more susceptible to abrasive wear. In addition to cleaning, all kinds of
fabrics are subjected to a number of nishing processes, usually after weaving, to stabilize the
fabric, modify surface properties, and regulate the permeability of the fabric. Calendering and
singeing are two familiar surface processing methods that change the permeability.
3.2.1.2. Synthetic monolament fabrics
Monolaments are woven by extruded synthetic bers produced with diameters from 30 μm
to 2–3 mm. These fabrics are important as lter material in a wide range of industries and
applications. Because they have corrosion resistance, vibration fatigue withstanding capacity,
Name Characteristics Absolute rating
range (μm)
Remarks
Square plain or twilled Largest open area and lowest ow
resistance. Aperture size is the same
in both directions
20–300 Most common type of
weave. Made in all grades
from coarse to ne
Plain Dutch single weave Good contaminant retention
properties with low ow resistance
20–100 Openings are triangular
Reverse plain Dutch weave Very strong with good contaminant
retention
15–115
Twilled Dutch double weave Regular and consistent aperture size 6–100 Used for ne and ultrane
ltering
Table 5. Principle weaves for wire cloths [15].
Property Weave
Plain Chain Twill Sateen
Rigidity 1 2 3 4
Bulk 4 3 1 1
Initial ow rate 4 3 2 1
Retention eciency 1 2 3 4
Cake release 2 3 4 1
Resistance to building 4 3 2 1
Table 6. Filtration requirements of weave [6].
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uniformity, and economic resilience, they have taken the place of several other lter media
types. Chemical and food processing industries, industrial hydraulics, and medical, automo-
tive, and appliance markets are the main users of monober fabrics. These fabrics are available
in a range of 5–5000 μm openings and are made from polymeric materials including nylon,
polyester, polypropylene, and uorocarbon. Synthetic monober fabrics, due to ductility and
memory, can be exed repeatedly without fatigue. Compared to a metal cloth, they can be
folded or dented with less damage and they are lighter in weight. Some applications, at the
same time, may require the lter medium properties of a synthetic monolament and a metal-
lized surface for static electricity dissipation. Accordingly, a metallized polyester monola-
ment fabric coated with nickel of 2 μm thickness is produced. Combined mono- and multiber
fabrics now have useful additional properties. Thus, such material is used in disc lter pieces
that are elastic and will expand in the kickback phase to help release the cake. New belt press
lters and large automatic lter presses are mainly used for fabric lters with heavy bers [15].
In selecting the ber to be used in the ltration process, the material with the highest chemi-
cal, thermal, and mechanical resistances should be preferred. For example, in Table 7, the
resistance of dierent ber materials to various chemical substances is roughly presented [14].
3.2.2. Nonwoven fabrics
The nonwoven medium is made from coon, wool, synthetic and asbestos bers, or mixtures
thereof and from paper mass in the form of belts or plates. They can be used in dierent
design lters such as lter presses, horizontal disc lters and rotary drum vacuum lters for
liquid ltration. Most of these applications have low suspension concentrations; examples
are milk, beverages, lacquers, and lubricating oils. The individual bers in the nonwoven
lter media are generally connected between them as a result of the mechanical treatment.
A less common approach is the addition of binding agents. Sometimes, loose woven fabrics
can be used on both sides of the lter to protect the lter media. Both absorbent and nonab-
sorbent raw materials can be used to produce nonwoven lter media with dierent materials
and properties, dierent weights, and dierent ltration eciencies. These lter media hold
particles that are less scaered on their surface (more than 100 pm) or particles that are more
dispersed in the depths of the lter media.
Wool felt is probably the oldest kind of textile fabrics and for many years is the only nonwo-
ven fabric in practice. A strong adhesivebonded felt is developed, and drylaid synthetic bers
are collected and transformed to the shape of nonwoven media. Thus, nonwoven fabrics can
sometimes be obtained by agglomeration of bers, and sometimes continuous laments are
glued together to obtain desired exibility.
The chemical properties of an untwisted fabric relate to the natural structure of the ber that
is used almost completely, as long as no binder is used that has signicantly dierent proper-
ties. Nonwoven materials are classied into two main groups. These two classes are based
largely on the methods and tools used to hold loose bers together:
(i) The felts that utilize the basic ber features to obtain mechanical strength or the me-
chanical processing (especially needling) and
(ii) Bonded cloths, which use some extra adhesive material to hold the bers together.
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Type of ber Insect proof Resistance to
aging
Acid Alkali Chlorocarbonic
hydride
Ketone Phenol Benzene
Coon Medium Low Unstable Low
resistance,
swelling
Resistant Resistant Resistant Resistant
Silk Medium Low Low R. Unstable Resistant Resistant Resistant Resistant
Wool Bad Low Low R. Unstable Resistant Resistant Resistant Resistant
Glass Good Good Low R. Unstable Resistant Resistant Resistant Resistant
Steel bers (Brunsmet®)Good Good Low R. Resistant Resistant Resistant Resistant Resistant
PA 6 (Perlon®)Good Good Unstable Resistant Resistant Resistant Unstable Resistant
PA 6.6 (Nylon) Good Good Unstable Resistant Resistant Resistant Unstable Resistant
PA 11 (Rislan®)Good Good Low R. Resistant Resistant Resistant Unstable Resistant
PA 12 (Vestamid®)Good Good Low R. Resistant Swelling Resistant Unstable Swelling
PA Nomex®Good Good Low R. Resistant Resistant Resistant Unstable Resistant
Polyester Good Good Resistant Low R. Resistant Resistant Unstable Resistant
Polyacrylonitrile Good Good Resistant Low R. Resistant Resistant Resistant Resistant
Polyvinylchloride Good Good Resistant Resistant Resistant Unstable Unstable Unstable
Polyvinylidenechloride(Saran®)Good Good Resistant Resistant
except NH4OH
Resistant Resistant Unstable Resistant
Polyolens
Polyethylene
High-pressure Good Good Resistant Resistant Swelling Resistant Resistant Resistant
Low-pressure Good Good Resistant Resistant Swelling Resistant Resistant Resistant
Polypropylene Good Good Resistant Resistant Resistant Resistant Resistant Resistant
Polytetrauoroethylene Good Good Resistant Resistant Resistant Resistant Resistant
Table 7. Chemical resistances of bers [14].
Textiles for Advanced Applications312

The more common method is to rely on the natural thermoplastic properties of the poly-
meric material to obtain adhesion when properly heated. Bonded cloths are divided into two
groups based on whether the ber formation is an integral part of the manufacture of the lter
medium or not. The basic felt does not contain binders: some wooly bers have the ability to
assemble together to form a coherent mass due to protrusions on the ber surface [14, 15].
The rst step in making any felt is to scan the bers so that the bers are roughly aligned
in one direction and drawn into a thin web. The pieces of this web are placed on top of one
another to achieve the desired thickness of the felting. Consecutive layers can be placed in the
same direction as the bers or they can be aligned in dierent directions to increase strength.
When sucient thickness is achieved, the felt is compressed, heated, and often nalized after
the dampening process has been carried out. The strength of this felt is basically weak. For
this reason, the strength of most felts is reinforced by the inclusion of a woven layer called
scrim.
Since the bers in a felt are not tightly bonded to the mass of the fabric, there is a risk of
bers moving away from the lter media during ltration. For this reason, the use of vari-
ous bonding elements, the integration of the thermoplastic bers into the fabric, and the
consolidation of the bers in the lter medium by means of various mechanical joining
processes based on needling or suturing braids are done. Modern felts are produced from
synthetic or natural bers or mixtures thereof. The bers are mechanically or with the help
of an adhesive bonded and passed through a controlled production to obtain a consistent
density, pore size, and mesh geometry. Thus cuto performance can be reasonably pre-
dicted. The structure of the felt is much looser than the paper, so depth ltration could be
performed, the specic resistance is reduced, and higher ow rates can be achieved with
smaller lter volumes and at lower pressure drop. The high-temperature-resistant meta-
aramid lter has helped the industry to move one step closer to the zero emission target by
providing a combination of high separation eciency and low dierential pressure of hot
gas ltration technology.
3.2.2.1. Wool resin media
In solid-gas ltration and, more rarely, in solid-liquid ltration, the particles desired to be
retained in the lter may carry an electrostatic charge. In this case, the use of lter material
carrying an electrostatic charge opposite to that of the particles will provide a more eective
ltration. For this purpose, many dierent lter media can be electrostatically charged. For
example, long-term electrostatic eects can be obtained by adding a special resin to the wool
felts used in the submicroscope aerosol ltration. Electrostatic charge is achieved by resin
transfer by adding the resin powder into the wool matrix enabling charge transfer. The wool
then has a positive charge and the resin has a negative charge. In this case, the lter is electri-
cally neutral in general. The random distribution of resin powder on the wool bers and the
random arrangement of the wool bers in the lter means that the electric eld is not uniform
and is therefore very eective for trapping both charged and unloaded particles. This electric
charge gives wool resin a very low resistance to airow, allowing submicrometer particles
to achieve a higher than 99.5% eciency in their ltration. Thanks to the resin’s very high
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electrical resistance, the resin lter can maintain its ltration eciency for many years despite
the adverse eects of tropical conditions. Wool resins were rst developed for use in respira-
tory devices for World War I and are still widely used in the respiratory industry, 90 years
after its development. It is preferred against many new materials with low resistance to
breathing and high ltration eciency. Vacuum cleaners and other independent dust col-
lectors also benet from the high retention of wool resin against asbestos and other harmful
dusts. In addition, wool resins are used as prelters for high efciency particulate air (HEPA)
lters and for heating and ventilation in clean rooms for computer suites.
3.2.2.2. Needlefelts
For some simple ltration applications, it is possible to use the felt directly. In most other
applications, however, mechanical or chemical treatment is required because of the low
mechanical resistance of the felts and because of the disassembly of the bers and mixing to
the ltrate. Needle punching is one of the mechanical strengthening methods used for this
purpose. This method has emerged as the most preferred mechanical strengthening tech-
nique for natural bers in the 1880s, but since the early 1970s, it has been suitable for many
synthetic bers for processing the felts. In this method, carded bers are pounded and com-
pressed into a more dense structure by punching with a series of specially barbed needles
moving back and forth at 2000 strokes/min and moving perpendicular to the felt layer. With
100 needle punches/cm2, it is possible to circulate the bers in the felt thickness both together
and to reduce the felt thickness considerably. The punching operation can be carried out by
one or both sides of the felt, so that the felt has a homogeneous structure. Needle felts are
commonly used as bag lters for ltering dust and gases. Typical applications include cement
industry, steel and aluminum plants, spray drying, coal grinding, sandblasting, food indus-
try, detergent manufacturing, pneumatic conveying, and hot gas ltration using metal ber
felts and ceramic bers. Some typical applications for lter fabrics of various kinds are shown
in Table 8 with their key characteristics. Felt is mechanically strengthened by needling, but
alternatively the hydroentanglement method is used as a more professional technique. In this
method, the bers are tried to be xed with the help of pressure water jet.
3.2.2.3. Meltspun materials
The use of new synthetic meltspun bers has begun to spread quickly, while ltration appli-
cations are commonly used with needle felts and woven fabrics. These bers are obtained
by extruding a molten thermopolymer from a ne nozzle. As the ber leaves the syringe, it
is quickly quenched in an air stream and then collected on a moving collecting belt running
underneath the nozzle. The laments on the collector are then pressed at a certain tempera-
ture for consolidation. Thus, the bers adhere to the points where they touch each other, and
the ber network is strengthened. This consolidation process is called spun bonding. If the
airow is placed immediately at the exit of the nozzle and along the line where the lament
falls onto the collector, the bers break o due to the air ow and fall on the collector in short
pieces. When these bers are pressed and sintered, this process is called melt blowing [15].
Textiles for Advanced Applications314

4. Recent processes in fabric ltration
4.1. Nanober spun membranes
Compared to other polymeric membranes, nanober membranes have aracted great interest
in recent years due to their advantages such as high selectivity, hydrophilicity, and mechani-
cal strength. Nanobers are very thin polymeric bers with a thickness of less than 100 nm
Material Suitable for Maximum service
temp (°C)
Principal advantage(s) Principal disadvantage(s)
Coon Aqueous solutions, oils,
fats, waxes, cold acids,
and volatile organic acids
90 Inexpensive Subject to aack by
mildew and fungi
Jute wool Aqueous solutions 85 Easy to seal joints in
lter presses
High shrinkage, subject
to moth aack in store
Nylon Acids, petrochemicals,
organic solvents, alkaline
suspensions
150 High strength or
exibility
Absorbs water; not
suitable for alkalis
Polyester
(Terylene)
Acids, common organic
solvents, oxidizing agents
100 Easy cake discharge.
Long life. Good
strength and exibility.
Initial shrinkage
Not suitable for alkalis
PVC Acids and alkalis Up to 90 May become brile.
Heat resistance poor
PTFE Virtually all chemicals 200 Extreme chemical
resistance. Excellent
cake discharge
High cost
Polyethylene Acids and alkalis 70 Easy cake discharge Soften at moderate
temperatures
Polypropylene Acids, alkalis, solvents
(except aromatics
and chlorinated
hydrocarbons)
130 Low moisture
absorption
Dynel Acids, alkalis, solvents,
petrochemicals
110
Orlon Acids (including chromic
acid), petrochemicals
Over 150
Vinyon Acids, alkalis, solvents,
petroleum products
110
Glass ber Concentrated hot acids,
chemical solutions
250 Suitable for a wide
range of chemical
solutions, hot or cold
(except alkalis)
Lacks fatigue strength
for exing. Abrasive
resistance poor
Table 8. Typical applications for lter fabrics [15].
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which are preferred in various industrial elds, such as electronics [16], biomedical [17], tex-
tile [18], and environment [19]. Nanobers stand out among similar polymeric membranes
with high specic surface area, high porosity, and interconnected pore networks [20]. The
nanobers used in applications where microltration and ultraltration are used provide
high water ux by reducing membrane resistance in water and wastewater treatment [21].
4.2. Electrospinning processes
Nanobers can be obtained by one of the methods: drawing, template synthesis, phase sepa-
ration, or electrospinning. Electrospinning is a frequently preferred method in recent times
in obtaining high porosity nanober mat. In this method, nanobers are obtained from a
charged polymer solution under a high electric eld. Parameters aecting the process (volt-
age intensity, feed rate of the polymer solution, nozzle-collector distance, polymer concen-
tration and type, and duration of electrospinning) can easily be changed and controlled
(Figure 10). Conditions such as room temperature and humidity are also factors that aect
nanober morphology [22]. The molecular weight of the selected polymer directly aects
the ber properties. The uniformity of the pore size of the nanober mats is obtained when
uniform and continuous collection of nanobers from the nozzles to the collector is achieved
[23]. The nanober layer, consisting of nanobers ranging from 50 nm to 10 mm, oers many
advantages such as high aspect ratio (length to diameter ratio), broad specic surface area,
unique physicochemical properties, and design exibility for chemical/physical surface func-
tionalization [24].
4.3. Nanobers in water and wastewater treatment
Nanober membrane processes are preferred in many industrial applications due to energy-
saving use, environmental friendliness, operational simplicity, and exibility during design.
As the nanober production technology improves, the use of nanobers as an alternative to
membrane processes, such as conventional microltration, ultraltration, and nanoltration,
has opened the way [21]. In one study, nanobers produced from the polysulfone polymer
were used for preltration to remove microscale particles prior to the ultra/nanoltration pro-
cess, thus extending the ultra/nanoltration membranes' life span [26]. The performance of
Figure 10. Schematic illustration of electrospinning setup: (1) rotating backing material, (2) conductive wire, (3) nozzle
tray, (4) syringe pump, (5) high voltage power [25].
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the membrane processes (retention of particles and the amount of permeate ux) strongly
depends on the particle size. It has also been reported that the addition of nanober mate-
rial and additives (such as nanoparticles and nanotubes) to the polymer solution aects the
separation performance [27].
One of the latest nanober studies is the work of Aslan et al. [25]. In this study, nanobers
were obtained at the scale of ultra/microltration by means of electrospinning from the solu-
tion prepared by polyacrylonitrile polymer. For the rst time in the literature, nanobers
were collected on a tubular support layer. The new membrane was tested with both standard
particle solution and a surface water. The novel tubular nanober membrane removes 95%
turbidity and 29% total organic carbon, which can be evaluated as high removal eciencies
when compared to the commercial microltration membrane. Membrane surface and cross
section SEM images are given in Figure 11.
5. Conclusions and recommendations
Filtration is considered the keystone of water and wastewater treatment and is used for vari-
ous purposes such as sludge dewatering and concentrating any solution. Moreover, as an
advanced ltration technology, membranes can remove materials ranging from large vis-
ible particles to molecular and ionic chemical species. Filtration performance depends on
Figure 11. SEM images of tubular backing material and nanober layer at dierent scales [25].
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operating conditions, such as uid characteristics, ltration rates, and lter media. Among
them, proper selection of lter media/membrane material in ltration processes is often the
most important consideration for assuring ecient separation.
Filter media can be classied by their materials of construction, such as coon, wool, linen,
glass ber, porous carbon, metals, and rayons. Recently, new polymeric materials have been
used both individually and/or blended in ltration processes for the treatment of waters and
wastewaters. The purpose of this chapter is to bring an overview on the textile-originated
lter materials in ltration applications from conventional ltration to advanced membrane
processes. Although many researches on lter media are available, very few reports are rep-
resented on the cuing-edge technologies about using lter materials on ltration processes
from classical to advanced membrane processes.
Textile materials and membranes are two important elements of surface ltration. The
performance of surface ltration is closely related to the physicochemical properties of
the lter surface. New materials are produced or the surface of the existing material is
modied in order to improve the performance of the lter surface. These modications
may involve the use of dierent chemicals (e.g., polymer blends) in the production of the
lter material, as well as the addition of additives to the base material (e.g., nanoparticles,
nanotubes). In recent years, textile nanobers have emerged in liquid ltration with their
unique properties such as high aspect ratio, broad specic surface area, unique physico-
chemical properties, and design exibility for chemical/physical surface functionalization,
and they will aract more aention in near future as lter material in both liquid and gas
ltration.
Author details
Murat Eyvaz*, Serkan Arslan, Ercan Gürbulak and Ebubekir Yüksel
*Address all correspondence to: meyvaz@gtu.edu.tr
Environmental Engineering Department, Gebze Technical University, Gebze, Kocaeli, Turkey
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