Flotation is a process used to separate minerals from gangue by taking advantage of differences in the abilities of minerals to wet or adhere to air bubbles. It involves grinding ore to liberate particles, rendering the desired mineral hydrophobic using surfactants, and introducing air bubbles. Hydrophobic minerals attach to the bubbles and are carried to the surface, forming a froth layer that is skimmed off. Reagents called collectors, frothers, and modifiers are used to control the selectivity and efficiency of the separation. Flotation is widely used in the mining industry to concentrate ores for further processing.

1. FLOTATION

2. Definition of flotation
The process of seperation of mixed liberated particles from each other if there
are sufficent differences in their wettability is called flotation.

3. Principle Of Operation
Froth flotation commences by comminution (that is, crushing and grinding), which is used to
increase the surface area of the ore for subsequent processing and break the rocks into the
desired mineral and gangue in a process known as liberation, which then has to be separated
from the desired mineral. The ore is ground into a fine powder and mixed with water to form a
slurry. The desired mineral is rendered hydrophobic (lacking affinity for water) by the addition of
a surfactant.
The particular chemical depends on which mineral is being refined. As an example,
pine oil is used to extract copper. This slurry (more properly called the
pulp) of hydrophobic mineral-bearing ore and hydrophilic (having a strong affinity for water
gangue is then introduced to a water
bath which is aerated, creating bubbles. The hydrophobic grains of mineral-bearing ore escape
the water by attaching to the air bubbles, which rise to the surface, forming a foam or a scum
(more properly called a froth). The froth is removed and the concentrated mineral is further
refined.

5. INTRODUCTON
The floatation process operates by preparing a water suspension of a
mixture of relatively fine sized particles (smaller than 150 micro meters)
and by contacting the suspension with a swarm of air bubbles of air in a
suitably designed process vessel. Particles that are not wetted by water
(hydrophobic) tend to be attached to air bubbles levitate (float) to the top
of the process vessel and collect in the forth layer.
Thus difference in the surface chemical properties of the solids are the
basis of separation by flotation.
surfaces that do not have strong surface chemical bonds that were broken
tend to be non-polar and are not readily wetted. e.g Graphite and Talc.
These solids are naturally floatable.

6. Froth Flotation CellFroth Flotation Cell

7. Effect of Variables on FlotationEffect of Variables on Flotation
• Physical and chemical nature of the material
• Pretreatment (grinding etc.)
• Water chemistry
• Reagents added
• Type flotation cell

8. APPLICATIONS
• Mineral applications: the floatation process is most widely
used in the mineral process industry to concentrate mineral values in the
ores.most of the world’s copper, lead, zinc, molybdenum and nickel are
produced from ores that are concentrated first by flotation.
In addition, floatation is commonly used for the recovery of fine coal and
for the concentration of wide range of mineral commodities including
fluorspar, mica, sponueme, bastnaesite, calcite, granite and talc.

9. OTHER APPLICATIONS
• Wastewater treatment: to remove particulate, organic and biological
contaminants.
• Extraction of metallic values from hydrometallurgical streams by
particulate floatation.
• Recovery of bitumen from tar sand.
• Deinking of waste paper.

10. APPLICATIONS
• Recovery of solids from white water in paper making.
• Recovery of glass water from industrial wastes.
• Removal of impurities from peas.
• Separation of proteins from milk.
• Clarification of fruit juices.
• Extraction of soluble particles

11. The following steps are followed:
•Grinding to liberate the mineral particles
•Reagent conditioning to achieve hydrophobic surface charges on the
desired particles.
•Collection and upward transport by bubbles in an intimate contact with
air or nitrogen
•Formation of a stable froth on the surface of the flotation cell
•Separation of the mineral laden froth from the bath (flotation cell)
Mechanics Of Flotation

13. UNIT OPERATION OF FLOTATION
Unit operation of flotation is based on two major
steps:
• Conditioning
• Separation

14. UNIT OPERATION OF FLOTATION
• Conditioning: is basically a pre treatment step. the slurry or the
pulp, consisting of particles to be separated, is fed to the conditioning unit,
to which the necessary flotation reagents are added.
the main purpose of conditioning step is to create physical-chemical
conditioning or the process of chemical changes necessary for forth
flotation.
The conditioner may be soluble, insoluble, and partially soluble.

15. UNIT OPERATION OF FLOTATION
• Separation: separation is then intended to generate and introduce
air bubbles into the process vessel for contacting them with particulate
species. Particles attached to the air bubbles are in most applications
removed from the process vessel as froth.
accordingly the unit operation of flotation is referred to as FROTH
FLOTATION.
The froth overflow stream is called a concentrate in the mineral industry.
the slurry underflow is called tailings.
depending on the application, these two steps may be carried out in two
distinctly different process units or in one combined unit.

16. FLOTATION PLANT OPERATION
• Ores must be ground to a point of complete or nearly complete liberation.
Even tough it might possibly be accomplished by coarse crushing.,
grinding. Grinding is done in closed circuit with classifier.
• In many instances, superior flotation is results are obtained by conditioning
the ore with the reagents before the flotation step. Oily type collectors are
sometimes added to the grinding circuit to ensure dispersion.
• Flotation machines are built in multiple units. Common practice is to feed
the pulp to several cells known as roughers. Which produce a barren
tailing. The conentrate is treated in cleaner cells and recleaner cells for
final concentration.

17. Types of flotation
•Ore flotation
•Macro flotation
•Microflotation
•Precipitate flotation
•Ion flotation
•Molecular flotation
•Adsorbing collide flotation

18. Macroscopic flotation
A type of flotation of flotation in which there is the removal of macroscopic
particles is called macroscopic flotation
Microscopic flotation
A type of flotation in which there is the removal of microscopic particles
particularly colloid or microorganisms is called microscopic flotation
It is also called colloid flotation
Adsorbing colloid flotation
A type of flotation in which there is the removal of dissolved material in
piggyback fashions by adsorbtions on colloidal particles is called adsorbing
colloid flotation

19. Molecular flotation
A type of flotation in which there is the removal of surface inactive molecules
through the use of collector (surfactant) which yields an insoluble product is
called Molecular flotation
Ion flotation
It is the type of flotation in which there is the removal of surface-inactive ion
via a collector which yields an insoluble product; especially a removal of scum
is called ion flotation
Precipitate flotation
A type of flotation in which precipitate is removed by a collector which is not
precipitating agent is called precipitate flotation.

20. Flotation Reagents
Three types of chemical reagents used during the froth
flotation process
•Collectors
•Frothers
•Modifiers

21. Collectors
These are surface active agents that are added to the flotation pulp where they
adsorbs selectively on the surface of the particles and render them hydrophobic.
Collectors increase the natural hydrophobicity of the surface. and increase the
separability of the hydrophobic and hydrophilic particles.
Collectors are added in a certain amount. Addition of excess quantities of a
collector is not desirable because it results in reducing the selectivity and
increasing the cost.
Types of collectors:
1.Ionizing collector
2.Non ionizing collector

22. Collectors contd….
• The non ionizing collectors are practically insoluble in water and cause the
particles to become hydrophobic by covering them with a thin film.
• The ionizing collector adsorb either physically or chemically on the particles
surface and can further b classified into anionic and cationic collectors depending
upon the nature of the non polar hydrocarbon group. common examples of the
ionizing collectors include
Fatty acids
Long chain sulphates
Sulphonates
Amines
Xanthates
Dithiophosphates

23. Frothers
•These are also surface active agents added to the flotation pulp primarily to stabilise air
bubbles for efffective particle bubble attachment and removal of the froth.
•The frother action is similar to the ionizing collectors except that thay concentrate
primarily at air-liquid interface.
Commonly used frothers are
Pine Oil
Short Chain Alcohol
Polypropylene glycol
Cresylic acid

24. Modifiers
Modifiers adsorb on the surface of particles or react chemically at the surface
and prevent the adsorption of the collector or promotor.
Flotation modifiers include several classes of chemicals
Activator
pH regulators
Depressants
Despersants and flocculants

25. Activators
Enhance the flotation by collectors that will not float in their absence e.g. calcium activated
flotation of Quartz using oleate
pH Regulators
Regulators such as lime, caustic soda, soda ash and sulphuric acid are used to control or
adjust pH , a very critical factor in many flotation separations.
Depressants
Depressants prevent the adsorption of collectors and help in selectivity or stop unwanted
mineral from floating. Typical are sodium to depress pyrite, zinc sulphate to depress
ZnS,lime to depress pyrite and lignin sulphonates to depress graphite.

26. Flotation Equipment
Various type of flotation machine designs can be classified into different
categories on the methods used for the generation and introduction of air
bubbles into the equipment . Each of the techniques has its own advantage and
limitations. These must be considered carefully in selecting the equipment for a
specific application. Following are some different flotation units used as
flotation equipment.

27. Electrolytic flotation units
Electrolytic or electroflotaion is based on the generation of hydrogen and oxygen bubbles
in a dilute aqueous solution by passing direct current between two electrodes.Electrical
power to the electrodes is supplied at a low voltage potential of 5 to 10 volts. The power
consumption is in the reage of 0.5 to 0.7kW/m of flotaion tank surface depending in the
conductivity of the liquid and the distance between the electrodes.

28. The main drawback of the electroflocation units is associated with the
electrodes in terms of their fouling requiring mechanical energy and their
consumption needing replacement at frequent intervals.
Electroflocation is not expected to suitable for potable water treatment because
of the possibly water treatment because of the possible heavy metals
contamination that can arise due to dissolution of the electrodes.
Electrolytic flotation contd......

29. Dissolved air flotation units
Vacuum flotation and pressure flotation are the two main types of dissolved air
flotation processes,with the latter being most widely used.
Vacuum flotation
In vacuum flotation the process stream is saturated with air at atmospheric pressure
and introduced to the flotation tank on which a vacuum is applied giving rise to the
generation of the air bubbles. The process can be run only as a batch process and
requires sophisticated equipment to produce and maintain the vacuum. By and large
the amount of air released during flotation is limted by the vacuum achievable.
Pressure flotation
In contrast to vacuum flotation dissolved air flotation unit can be operated on
continued basis by the application of pressure.this consist of pressurising and aerating
process stream and introducing it into the flotation vesel that is maintained at low
atmospheric pressure.the reduction of pressier resultys in the formaiton of fine air
bubbles and the collection of fine pariculates to be floated and removed as sludge.

30. Pressure flotation cont...
Pressurisation could be carried out on the entire feed stream or a fraction of the feed
stream while the remainder is introduced directly without aeration into the flotation
tank.the split flotation system offers a cost saving over the full flow units.in both
cases however is the solid particles in the feed stream are flocullated before
introducing top the flotation tank,the high shear during pressurisation,aeration and
pressre release can destroy flocs.
The dissolved air flotation process is more commonly used for sewage and potable
water treatment.it is gaining popularity for thetreatment of slaughter house,poultry
processing,sea food processing and food processing in wastes.

32. Dispersed air flotation units
Dispersed air flotation involves the generation iof air bubbles either pneumetically
Or by mechanical means.in both cases relatively large air bubbles are generated.in
order to control the size and stability of air bubbles frothere are added to the
flotation devices.
Mechanical flotation machines are most commonly used in mineral industry while
pneumatic column type unit are gaining popularity in recnt.
Mechanical Cells
In a typical installation a number of flotation cells are connected in series such that
each cell output froth into a launder.and the underflow from one cell goes to the
next one.The cell design may be such that the flow of slurry from one cell to
another can neither be restricted by weirs or unrestricted.
The mechanical cells that are most widely used today in sulfide,coal and non
metallic flotation operation are made by Fagergren,Denver and Outokumpy.

34. Mechanical cells cont...
These machines provide mechanical agitation and aeration by means of a rotation
impeller on an upright shaft.in addition the agitair and Denver cells also utilise air
from a blower to help aerate the pulp.
.Large scale flotation machine offer advantages of lower installed cost, lower
operating cost,lower floor space requirement.However it should be noted that large
flotation cells do not permit a reduction in the number of cells in a series.The use of
large flotation cells does enable a few number of parallel rows and therby permits a
reduction in pumps piping and other auxiliaries.

36. Flotation columns
Flotations columns belong the class of pneumatic devices in that air bubble
generation is accomplished by a gas sparging system and no mechanical agitation
is employed.Inputs to the column include pre conditioned slurry feed and air and
wash water spray which are introduced at about two third of height from the
bottom,in the bottom region and at the top of the column respectively.The outputs
are froth overflow consisting of hydrophobic particles from the top and underflow
from the bottom of the tank,carrying the non floatable hydrophilic particles.
The main advantages of the flotation
column technology include :
- Improved recovery
- Optimized grade
- Increased throughput

37. Column FlotationColumn Flotation
COLUMN FLOTATION CELLS BETTER SUITED TO FLOTATION
OF FINES

39. Flotation columns cont....
Advantages
•Improved seperation performance particularly for fine materials.
•Low Capital cost.
•Low operating cost.
•Low plant floor space requirments
•Easy adaptability to automatic control
•Simplicity in construction
•Flexibility in operation.
Uses
It is used in
Iron ore Copper,Lead Zinc and coal flotation processes.