Enviromental Chemistry
5.0 Control Of Air Pollution
5.0 Control Of Air Pollution
Air pollution can be checked either at source or at the dispersal stage of various pollutants. Although the Prob. of controlling air pollution at source is not easy, yet it can be reduced to some extent by taking steps such as,
Use of appropriate raw materials, selection of proper sites for industrial units & use of modern techniques for efficient reduction of emission & effluents.
Different methods for the control of various air pollutants are as follows:
1. Control of CO
Some of the measures which can be adopted for control of CO pollution are:
(a) Use of anti pollution exhaust catalyst.
(b) Modification & improvement in internal combustion engine.
(c) Use of other fuels such as CNG, LPG & LHG.
2. Control of $C{O_2}$
$C{O_2}$ level can be maintained by reducing its release from industrial units & controlling vehicular exhaust etc. Hydrogen is being looked upon as pollution less future fuel.
3. Control of ${{\bf{N}}{{\bf{O}}_{\bf{x}}}}$ Pollution
(i) Power plants & industrial units emit large amounts of $N{O_X}$ Such emission can be reduced by almost 90% with the help of two step combustion.
(a) In the first step, the fuel is burnt at high temperature in a limited supply of air.
(b) In the second step, the unburnt fuel is burnt at lower temperature in excess of air.
(ii) Acidic scrubbing of fuel gases: The large amounts of nitrogen oxides emitted form power plants & industrial units can also be removed by scrubbing the fuel gases with sulphuric acid.
(iii) $N{O_X}$in vehicular exhaust is converted into ${N_2}$ & trace amount of $N{H_3}$ with the help of
anti-pollution exhaust catalyst.
4. Control of $S{O_2}$ pollution
The process of removal of $S{O_2}$ is known as flue as flue gas desulphurisation (FGD). Sulphuridioxide from flue gases is commonly removed by using chemical scrubbers consisting of a slurry of $CaC{O_3}$where $S{O_2}$ is absorbed forming $CaS{O_3}.$
Smog & its ill effects
Smog is a mixture of smoke & fog. The principal source of classical smog is the combustion of industrial household fuels. Because of the presence of $S{O_2}$ & carbon (soot particles), classical smog has a reducing character.
Photo Chemical Smog
This is another type of smog which is distinctly different from the classical smog.
The principal constituents of the photo chemical smog are ozone & oxides of nitrogen.
It causes irritation in eyes due to the presence of ozone. This type of smog is formed through photo chemical reactions involving solar radiations, hence is named as photo chemical smog.
Harmful effects of smog
(i) Smog causes respiratory Problems
(ii) It reduces visibility
(iii) It damages plants & other material like electronic & electrical equipment.
