u will love to have the total info. abt the general principles and isolation of elements . the best project u can get all over the site...!!

1. 2013
General Principlesand Processes
of Isolation of Elements…
Aashirwad jindal
Chemistry project.
12/11/2013

2. Acknowledgment..!!
I would like to express my special thanks of gratitude to
my teacher vishal sir as well as our principal chakrapani
sir who gave me the golden opportunity to do this
wonderful project on the topic general principles and
isolation of elements which also helped me in doing a lot
of Research and i came to know about so many new things
I am really thankful to them.
Secondly i would also like to thank my parents and friends
who helped me a lot in finalizing this project within the
limited time frame.
Aashirwad jindal..

3. Magnetic separation..!!!
Magnetic separation takes advantage of differences in the
magnetic properties of minerals. Minerals fall into one of three
magnetic properties: ferromagnetic, paramagnetic and
diamagnetic. Ferromagnetic minerals are themselves magnetic
(i.e., magnetite and pyrrhotite) and can be easily separated from
other minerals with a
magnet since they will
stick to the poles of the
magnet. These minerals
can be separated by
wrapping the poles of a
magnet in paper, passing
the magnet over the
mineral mixture. The
ferromagnetic
minerals
will stick to the magnet
and
may
be
easily
separated by removing the
paper covering the magnet. Paramagnetic and diamagnetic
minerals are not magnetic, but they differ in how they interact
with a magnetic field. Paramagnetic minerals are weakly
attracted into a magnetic field and diamagnetic minerals are
weakly repelled by a magnetic field. Thus, if a mixture of
paramagnetic and diamagnetic minerals is passed through a
magnetic field, they will be pulled into the field (paramagnetic) or
repelled from the field (diamagnetic) and may be separated.
Furthermore, paramagnetic minerals with different degrees of
paramagnetism can be separated from one another in the same
way. The device used to separate minerals based on their

4. Magnetic separation..!!!
magnetic properties is called a Frantz Isodynamic Magnetic
Separator. The magnetic separator consists of a large
electromagnet through which mineral mixtures can be passed on
a metal trough which is divided near its exit end. Varying the
strength of the magnetic field and/or slope of the separation
trough is used to separate minerals.
All forms of mineral separation suffer from one difficulty. It is
impossible to completely eliminate impurities. Depending on what
the impurities are, that may or may not be a major problem. For
example, if you were separating hornblende from a granite for Zr
analysis, potential contamination by zircon inclusions in the
hornblende might be a major problem. A typical hornblende
crystal might have a Zr content of 50 ppm. A zircon crystal
(ZrSiO4) has approximately 500,000 ppm Zr. Thus, if the
hornblende separate contained only 0.01% Zr, the hornblende
would contribute 4999.5 units of Zr and the zircon impurity
would contribute 5000 units of Zr. The resulting concentration
you would measure would be 100 ppm, which is twice the correct
result. This is a major problem that cannot be eliminated when
mineral separations are involved in the analysis.

5. Leaching process…!!!
Leaching is the process by which constituents of a solid material
are released into a contacting water phase. Although some species
may be more of an environmental concern than others, the
leaching process is indiscriminant such that all constituents (e.g.,
major or minor matrix components as well as inorganic, organic
and radionuclide contaminants) are released under a common set
of chemical phenomena which may include mineral dissolution,
desorption and complexation, and mass transport processes. In
turn, these phenomena are affected by certain factors that can
alter the rate or extent of leaching. Among these factors are:
internal chemical and physical reactions
external stresses from the surrounding environment
physical degradation of the solid matrix due to erosion or
cracking, and
loss of matrix constituents due to the leaching process itself.
Physical and Chemical Factors Influencing Leaching

6. Leaching process…!!!
The process of leaching includes the partitioning of contaminants
between a solid and liquid phase (e.g., assuming local
equilibrium) coupled with the mass transport of aqueous or
dissolved constituents. Mass transport is the summation of
diffusion, hindered diffusion, tortuosity effects, and effective
surface area effects through the pore structure of the material to
the environment. Important chemical factors, those that
influence the liquid-solid partitioning (LSP) of a constituent,
include solution pH, redox, the presence of dissolved organic
matter, and biological activity. Physical factors, such as relative
hydraulic conductivity, porosity and fill geometry, play an
important role in determining the rate at which constituents
transport through a solid into a passing liquid phase.
The process itself is universal, as any material exposed to contact
with water will leach components from its surface or its interior
depending on the porosity of the material considered.

7. Froth flotation is considered to be the most widely used method for ore
beneficiation. In ore beneficiation, flotation is a process in which valuable
Froth flotation…!!!
minerals are separated from worthless material or other valuable minerals
by inducing them to gather in and on the surface of a froth layer. Sulfide
and non-sulfide minerals as well as native metals are recovered by froth
flotation. This process is based on the ability of certain chemicals to
modify the surface properties of the mineral(s). Other chemicals are used
to generate the froth and still others are used to adjust the pH. Certain
chemicals are even capable of depressing the flotation of minerals that are
either to be recovered at a later time or are not to be recovered.
The process of froth flotation entails crushing and grinding the ore to a fine
size. This fine grinding separates the individual mineral particles from the
waste rock and other mineral particles. The grinding is normally done in
water with the resultant slurry called the pulp. The pulp is processed in the
flotation cells, which agitate the mixture and introduce air as small
bubbles.
The ability of a mineral to float depends upon its surface properties.
Chemical modification of these properties enables the mineral particles to
attach to an air bubble in the flotation cell. The air bubble and mineral
particle rise through the pulp to the surface of the froth or foam that is
present on the flotation cell. Even though the air bubbles often break at this
point, the mineral remains on the surface of the froth. The mineral is
physically separated from the remaining pulp material and is removed for
further processing.
Frothers Frothers are liquids that produce the froth or foam on which the flotation
process depends. The froth resembles soap suds and provides the
physical separation between the mineral(s) floated and the pulp containing
the waste. The froth must be strong enough to support the weight of the
mineral floated and yet not be tenacious and non-flowing. It should have
the tendency to break down when removed from the flotation cell. The

8. frother should not enhance the flotation of unwanted material. Many other
characteristics are required for a foaming agent to be a good flotation
frother. Typical frothers include:
pine oil
certain alcohols
low molecular weight polypropylene glycols
Froth flotation…!!!
Aluminum..!!!
Collectors A collector is a chemical that attaches to the mineral surface and produces
a hydrophobic (water-fearing) surface. While certain minerals are naturally
hydrophobic and do not require a collector, recovery is often improved
when a collector is used. This water-repellent film facilitates the attachment
of the mineral particle to the air bubble. Many different chemicals are used
as collectors, such as:
oils
xanthates
dithiophosphates
petroleum sulfonates
fatty amines
Depressants - O
Depressants are chemicals that inhibit the flotation of minerals. They are
used to improve the selectivity of a flotation process. They often make it
feasible to separate minerals that were initially floated together.
The response of many minerals to the flotation process is often
dramatically affected by pH. Flotation circuits are often operated at a pH
range of 7.5 to 11.5. The exact range at any given plant is optimized for the
ore at that site. Lime is often used to raise the pH of the pulp and also
reduce the flotation of iron pyrite.
Hall-Héroult process is used to produce aluminum in an electrolytic cell are shown.
Alumina, an aluminum oxide (Al203), is dissolved in molten cryolite (Na3AlF6). It is
decomposed electrolytic between carbon and aluminum electrodes at about 950° C to

9. Aluminum..!!!
aluminum and oxygen. The carbon anode is continuously consumed by reacting with
the oxygen to give carbon dioxide (CO2). The typical features of the electrolysis cells in
an aluminum plant are described. Technical cells are operated with a current intensity of
100 to 500 kA. They are equipped with devices to operate the cells in a highly automatic
i.e. computer controlled way. The waste gases of the process are collected and
thoroughly cleaned (scrubbed) before being exhausted to the atmosphere.
The discussion of alternative methods to produce aluminum in technical quantities
mentions the Direct Carbothermic Reduction Process and the Alcoa Smelting Process
which were developed to replace the classical Hall-Héroult process. Technical problems
which could not be solved stopped however these projects.
Inert anodes must sustain the chemical attack of the anodic oxygen and of the
electrolyte at electrolysis temperature. Several candidate materials were investigated
however without con-vincing success so far. Using materials which are wetted by
aluminum as cathode would avoid several problems essentially the magnetic effects and
the chemical reactions of the carbon lining. Several patents and publications propose
materials and arrangements to replace the aluminum metal pad as cathode.
In 1886 Hall of the USA and Héroult of France invented simultaneously
and independently of each other the process to produce aluminum by
electrolysis.

10. Alumina, an oxide of aluminum (Al2O3), is dissolved in molten cryolite
(Na3AlF6) and decomposed electrolytically to give liquid aluminum. The
anode of the electrolytic cell is made of carbon and the pool of already
produced aluminum acts as cathode. The oxygen of the alumina is
discharged at the anode where it reacts with the carbon anode to
produce carbon dioxide (CO2).
1.3 Schema of a Hall-Héroult Electrolytic Cell.
Figure 1.3 shows schematically such a Hall-Héroult electrolysis. A steel
shell which is lined with carbon blocks and thermal insulation material
contains the liquid cryolite electrolyte and liquid aluminum. The
process uses electrical energy to reduce electrolytically aluminum
oxide and to keep the electrolyte at a temperature of about 950° C.
During aluminum production the chemical reactions consume
continuously alumina and anodes which must be added respectively
replaced to the electrolytic cell. Aluminum and anode gases (in essence
carbon dioxide and carbon monoxide) are produced and removed from
the cell.

11. Aluminum..!!!
Figure 1.5 shows the slide show of the schematic cross section for such a technical cell.
Electrolyte, Metal Pad, TopCrust and Side Ledge
1.4 The AP 30 Electrolytic Cell (Rio Tinto Alcan former Péchiney).
This figure shows the AP 30 electrolytic cell of Péchiney (now Rio Tinto Alcan). This cell is operatated at 300 kA and is equipped with
20 double anodes and five side raisers that carry the electric current to the anode beam (not shown).

12. Zone refining..!!!
zone melting, any of a group of techniques used to purify an
element or a compound or control its composition by melting a
short region (i.e., zone) and causing this liquid zone to travel
slowly through a relatively long ingot, or charge, of the solid. As
the zone travels, it redistributes impurities along the charge. The
final distribution of the impurity depends on its distribution in the
starting charge of material; its distribution between the liquid and
solid phase of the material (called its distribution
coefficient, k, which is a characteristic of the particular impurity);
and on the size, number, and travel direction of the zones.
Zone melting is a means of using the freezing process to
manipulate impurities. It combines the fact that a
freezing crystal differs in composition from the liquid from which
it crystallizes with the idea of passing a short liquid zone along a
lengthy solid.

13. Zone refining..!!!
Zone refining is the most important of the zone-melting
techniques. In zone refining, a solid is refined by passing a
number of molten zones through it in one direction. Each zone
carries a fraction of the impurities to the end of the solid charge,
thereby purifying the remainder. Zone refining was first described
by the U.S. scientist W.G. Pfann and was first used in the early
1950s to purify germanium for transistors. The purity achieved
was hitherto unheard of—less than one part of detectable impurity
in 10,000,000,000 parts of germanium. The method was adopted
in transistor manufacture around the world.
The principles of zone refining are quite general, and so
the method has been applied to many substances. More
than one-third of the elements and hundreds of inorganic
and organic compounds have been raised to their highest
purity by zone refining. Many of these were, for the first
time, made pure enough for their intrinsic properties to be
determined.

14. Column chromatography…!!!
The mobile and stationary phases of chromatographic systems
are arranged in such a way that migration is along a coordinate
much longer than its width. There are two basic geometries:
columnar and planar. In column chromatography the stationary
phase is contained in a tube called the column. Apacked column
contains particles that either constitute or support the stationary
phase, and the mobile phase flows through the channels of the
interstitial spaces. Theory has shown that performance is
enhanced if very small particles are used, which simultaneously
ensures the additional desired feature that these channels be very
narrow. The effect of mobile-phase mass transfer on band (peak)
broadening will then be reduced (see discussions of mass transfer
and peak broadening in Efficiency and resolution and Theoretical
considerations below). Constructing the stationary phase as a thin
layer or film will reduce band broadening due to stationary-phase
mass transfer. Porous particles, either as adsorbents or as
supports for liquids, may have deep pores, with some extending
through the entire particle. This contributes to band broadening.
Use of microparticles alleviates this because the channels are
shortened. An alternate packing method is to coat impermeable
macroparticles, such as glass beads, with a thin layer of
microparticles. These are the porous-layer, superficially porous,
or pellicular packings. As the particle size is reduced, however,
the diameter of the column must also be decreased. As a result,
the amount of stationary phase is less and the sample size must be
reduced. Detection methods must therefore respond to very small
amounts of solutes, and large pressures are required to force the
mobile phase through the column. The extreme cases are known
as microbore columns; an example is a column 35 centimetres (14

15. Column chromatography…!!!
inches) long of 320-micrometre (1 micrometre = 10−4 centimetre)
inside diameter packed with particles of 2-micrometre diameter.
A second column geometry involves coating the stationary phase
onto the inside wall of a small-diameter stainless steel or fused
silica tube. These are open tubular columns. The coating may be
a liquid or a solid. For gaseous mobile phases, the superior
performance is due to the length and the thin film of the
stationary phase. The columns are highly permeable to gases and
do not require excessive driving pressures. Columns in which a
liquid mobile phase is used are much shorter and require large
driving pressures.

16. Planer chromatography…!!!
In this geometry the stationary phase is configured as a
thin two-dimensional sheet. In paper chromatography a
sheet or a narrow strip of paper serves as the stationary
phase. In thin-layer chromatography a thin film of a
stationary phase of solid particles bound together for
mechanical strength with a binder, such as calcium sulfate,
is coated on a glass plate or plastic sheet. One edge of the
sheet is dipped in a reservoir of the mobile phase, which,
driven by capillary action, moves through the bed
perpendicular to the surface of the mobile phase. This
capillary motion is rapid compared to solute diffusion in
the mobile phase at right angles to the migration path, and
so the solute is confined to a narrow path.