Filtration

Ministry of Higher Education
and Scientific Research

Al-Muthanna University
Engineering College
Chemical Engineering Department
Filtration
By Student
Ahlam Shalal Drywall
Supervise
Prof.Dr.Raid Al-khateeb
Introduction:
Filtration is a physical, biological or chemical operation that
separates solid matter and fluid from a mixture with
a filter medium that has a complex structure through which only
the fluid can pass. Solid particles that cannot pass through the
filter medium are described as oversize and the fluid that passes
through is called the filtrate.[1] Oversize particles may form
a filter cake on top of the filter and may also block the filter
lattice, preventing the fluid phase from crossing the filter,
known as blinding. The size of the largest particles that can
successfully pass through a filter is called the effective pore
size of that filter. The separation of solid and fluid is imperfect;
solids will be contaminated with some fluid and filtrate will
contain fine particles (depending on the pore size, filter
thickness and biological activity). Filtration occurs both
in nature and in engineered systems; there
are biological, geological, and industrial forms. [2]
Methods:
There are many different methods of filtration; all aim to attain

the separation of substances. Separation is achieved by some
form of interaction between the substance or objects to be
removed and the filter. The substance that is to pass through the
filter must be a fluid, i.e. a liquid or gas. Methods of filtration
vary depending on the location of the targeted material, i.e.
whether it is dissolved in the fluid phase or suspended as a solid.
Hot Filtration, solution contained in the Erlenmeyer flask is heated on a hot plate in
order to prevent re-crystallization of solids in the flask itself
There are several filtration techniques depending on the desired

outcome namely, hot, cold and vacuum filtration. Some of the
major purposes of getting the desired outcome are, for the
removal of impurities from a mixture or, for the isolation of
solids from a mixture.
Hot Filtration for the separation of solids from a hot solution
Hot filtration method is mainly used to separate solids from a

hot solution. This is done in order to prevent crystal formation in
the filter funnel and other apparatuses that comes in contact with
the solution. As a result, the apparatus and the solution used are
heated in order to prevent the rapid decrease in temperature
which in turn, would lead to the crystallization of the solids in
the funnel and hinder the filtration process.[4] One of the most
important measures to prevent the formation of crystals in the
funnel and to undergo effective hot filtration is the use stemless
filter funnel. Due to the absence of stem in the filter funnel,
there is a decrease in the surface area of contact between the
solution and the stem of the filter funnel, hence preventing re-
crystallization of solid in the funnel, adversely affecting
filtration process.
Cold Filtration, the ice bath is used to cool down the temperature of the
solution before undergoing the filtration process
Cold Filtration method is the use of ice bath in order to rapidly
cool down the solution to be crystallized rather than leaving it
out to cool it down slowly in the room temperature. This
technique results to the formation of very small crystals as
opposed to getting large crystals by cooling the solution down at
room temperature.
Vacuum Filtration technique is most preferred for small batch
of solution in order to quickly dry out small crystals. This
method requires a Büchner funnel, filter paper of smaller
diameter than the funnel, Büchner flask, and rubber tubing to
connect to vacuum source.
Types of Filtration
There are many different ways to filter matter, and below are
just a few that we can use in the separating of substances.
1. Vacuum Filtration:
In vacuum filtration, a vacuum pump is used to rapidly draw the

fluid through a filter. Hirsch funnels and Buchner funnels, which
are the same kind of funnel in two different sizes, are used along
with filter paper. The funnels have a plate with holes in it, as we
can see below, and they are usually used when the substance to
be filtered is small in volume.
2. Centrifugal Filtration:
This kind of filtration is done by rotating the substance to be

filtered at very high speed. Due to the horizontal rotation, the
more dense matter is separated from the less dense matter.
3. Gravity Filtration:
This is where the mixture is poured from a higher point to a

lower one. It is commonly done through simple filtration, using
filter paper in a glass funnel, where the insoluble solid particles
are captured by the filter paper and the liquid goes right through
by gravity’s pull. Depending on the volume of the substance at
hand, filter cones, fluted filters, or filtering pipets can be used.
4. Cold Filtration:
Cold filtration makes use of very low temperatures, often by

using an ice bath. Some substances, such as fatty acid particles,
become suspended in the mixture as they cool down, which then
allows us to filter them out more easily.
5 Hot Filtration:
This is often used for crystalline compounds that contain

impurities. The way this filtration is done is by melting down
the crystalline compound, removing the impurities as the
substance is still in liquid form, and finally recrystallizing the
now pure substance. Often, it is recommended that the apparatus
used in this filtration be heated up so that the filtered substance
doesn’t crystallize in the funnel and block the flow.
Filtering Force:
The fluid to be filtered will pass through the filter medium only
if some driving force is applied. This force may be caused by
gravity, centrifugation, application of pressure on the fluid
above the filter, or application of vacuum below the filter or by
a combination of such forces. Gravitational force alone may be
used in large sand-bed filters and in simple laboratory filtrations.
Centrifuges containing a bowl with a porous filter medium may
be considered as filters in which gravitational force is replaced
by centrifugal force many times greater than gravity. If a
laboratory filtration is difficult a partial vacuum is usually
applied to the container below the filter medium to increase the
rate of filtration. Most industrial filtration processes involve the
use of pressure or vacuum, depending upon the type of filter
used, to increase the rate of filtration and also to decrease the
size of the equipment required.
Filtration Examples:
The most common example is making tea. While preparing tea,

a filter or a sieve is used to separate tea leaves from the
water. Through the sieve pores, only water will pass. The liquid
which has obtained after filtration is called the filtrate; in this
case, water is the filtrate. The filter can be a paper, cloth, cotton-
wool, asbestos, slag- or glass-wool, unglazed earthenware, sand,
or any other porous material. Filtration is used in water
treatment and sewage treatment. To have a clear understanding
of the matter and its states checkout the three states of matter.
Process Of Filtration
Uses Filteration
1-Coffee filter to keep coffee separate from sediment .
2-In medicine: dialysis
3-Use air conditioning (HEPA: High Efficiency Air Particulate)

.filters to remove particles from the air
4-To separate a mixture of chemical compounds, a solvent is

selected that is able to dissolve the first component, and is
unable to dissolve the second component. The solution is then
filtered, then the first element passes through the filter, while the
.other element remains as a solution is excluded
This is one of the most important techniques that chemists use
to purify compounds
5-.Filtration is used to clean air currents or other gas streams .
6-Filters are used in furnaces to prevent harmful gases from

entering the atmosphere
7-In the food industry.
8-In purifying water.
9-.In the pharmacy and drug industry .
References:
1. Article on "Water treatment solution: Filtration", retrieved on

15 October 2013
from http://www.lenntech.com/chemistry/filtration.htm
2. Sparks, Trevor; Chase, George (2015). Filters and
Filtration Handbook (6th ed.). Butterworth-
Heinemann. ISBN 9780080993966.
3. Lecture notes, Postgraduate course on Filtration

and Size separation at the Department of Chemical
Engineering, University of Lougborough, England
"Filtration Methods" (PDF). University of Calgary. University

of Calgary. Retrieved 4 June 2015

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Ministry of Higher Education

and Scientific Research

There are many different methods of filtration; all aim to attain

There are several filtration techniques depending on the desired

Hot filtration method is mainly used to separate solids from a

In vacuum filtration, a vacuum pump is used to rapidly draw the

This kind of filtration is done by rotating the substance to be

This is where the mixture is poured from a higher point to a

Cold filtration makes use of very low temperatures, often by

This is often used for crystalline compounds that contain

The most common example is making tea. While preparing tea,

1-Coffee filter to keep coffee separate from sediment .

2-In medicine: dialysis

3-Use air conditioning (HEPA: High Efficiency Air Particulate)

4-To separate a mixture of chemical compounds, a solvent is

5-.Filtration is used to clean air currents or other gas streams .

6-Filters are used in furnaces to prevent harmful gases from

7-In the food industry.

8-In purifying water.

9-.In the pharmacy and drug industry .

1. Article on "Water treatment solution: Filtration", retrieved on

3. Lecture notes, Postgraduate course on Filtration

"Filtration Methods" (PDF). University of Calgary. University

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