Department “ORGANIC CHEMISRTY AND TECHNOLOGY”
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Chemistry for Engineering Logistics
SEPARATION AND PURIFICATION OF
SUBSTANCES
1. Introduction
2. Methods of Separation
3. Simple Distillation
Assoc. Prof. V. Grozev
1. Introduction
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Definition - separation and purification, in chemistry, separation of a
substance into its components and the removal of impurities
In chemical engineering, a separation process (separation), is any
mass transfer process that converts a mixture of substances into its
constituents. In some cases, a separation may fully divide the mixture into
its pure constituents.
Separations are carried out based on
differences in chemical or physical properties
such as size, shape, mass, density, or
chemical affinity, between the constituents of a
mixture.
Separation and purification are used for:
- production of pure chemicals, medicines,
pesticides;
- environmental protection from different hazardous wastes.
2. Methods of Separation and Purification
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Mixtures can be separated into their constituents by using different
methods. The particular method used for separating any given mixture
depends on the nature of its constituents (eg. solubility, different states,
boiling and melting points, adsorbtion).
Below lists some of the most common separation techniques for
separation:
1. Physical methods – precipitation, filtration, recrystallization,
evaporation, distillation.
2. Physical-chemical methods – adsorption, absorption, floatation.
3. Chemical methods – eg. chlorination
of drink water.
Diagram of simple filtration: oversize
particles in the feed cannot pass through
the lattice structure of the filter, while
fluid and small particles pass through,
becoming filtrate
3. Simple Distillation
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3.1. Distillation Principles
Consider an example of a liquid mixture containing two components
(methanol 20% and 80% water) - a binary mixture. Methanol boils at 65°C,
whereas water boils at 100°C. In this example, methanol is the more
volatile component than water. When the mixture is heated it starts to boil.
The vapour evolved during the boiling has the composition approximately
80% methanol and 20% water. This is four times richer in methanol than
the original liquid.
This difference between liquid and vapour compositions is the
basis for distillation operations.
3. Simple Distillation
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3.2. Laboratory equipment
thermometer
Distilled
mixture
flask
condenser
Boiling chips
distillate
3. Simple Distillation
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Vapour enters
Direction of water flow
condenser
Water out
Cold water in
3. Simple Distillation
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3.3. Laboratory operations
The distilled mixture is heated and
begins to boil
The obtained vapour is richer in
methanol (80%) than the original
liquid.
The condenser is cold, so the
vapour condenses to liquid with
content 80% methanol
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THANK YOU