Motor vehicles produce many different pollutants. The principal pollutants of concern—those that have been demonstrated to have
significant effects on human, animal, plant, and environmental health and
welfare—include: Hydrocarbons, Carbon monoxide (CO),Nitrogen oxides
(NOx),Carbon dioxide (CO2), Particulates, Sulphur oxides (SOx).Air injection
,Exhaust gas recirculation, Catalytic converters are newly invented remedies to
control emission. Exhaust gas recirculation (EGR) is a reliable and
practice-proven method of emission control for diesel engines. Harmful nitrogen
oxides (NOx) are mainly produced at high temperatures and pressures, but it is
possible to reduce the NOx concentrates emitted to the environment by up to
50%.along with EGR system the three way catalysts can also be used in the
controlling process. Silica gel based EGR system is another remedy and the main
thing is that it can be applied in petrol engines also. Silica gel is a
granular, vitreous, highly porous form of silica made synthetically from sodium
silicate. Despite its name, silica gel is a solid.

Silica gel is most commonly encountered in everyday life as beads packed in a vapour-permeable plastic. In this form, it is used as
a desiccant to control local humidity in order to avoid spoilage or degradation
of some goods. Because of poisonous dopants and their very high adsorption of
moisture, silica gel packets usually bear warnings for the user not to eat the contents.
Silica gel's high surface area (around 800 m²/g) allows it to adsorb water
readily, making it useful as a desiccant (drying agent). Once saturated with
water, the gel can be regenerated by heating it to 120 °C (250 °F) for two hours.
Some types of silica gel will "pop" when exposed to enough water. So
concluding with abstract, the silica gel with some chemicals can be very
effectively used in EGR system to control the pollution