Question

Electrostatic precipitators remove particulate matter by which of the following methods ?

• A. Coating dust particles with negative charge and collecting them on grounded plates
• B. Coating dust particles with positive charge and collecting them on grounded plates
• C. Washing dust particles away by spraying water
• D. Using catalysts to breakdown particulate matter

Answer 1

The correct option is A Coating dust particles with negative charge and collecting them on grounded plates

Electrostatic precipitators are devices that are capable of removing 99 percent of the particulate matter present in the exhaust coming from industries.

These devices consist of negatively charged electrode wires that are maintained at several thousand volts. The electrodes produce a discharge corona (a region of air that undergoes electrical breakdown and becomes conductive) that releases electrons which attach to the dust particles and give them a net negative charge. The collecting plates which are positively charged and grounded to attract the negatively charged dust particles.

Low velocity of air between the collecting plates is maintained to allow the dust to fall. These dust particles are collected and removed. Clean air from the electrostatic precipitator is let out to the smokestack (a chimney or funnel for discharging smoke) which is later released into the atmosphere. Hence option a is correct and option b is incorrect.

Figure : Electrostatic precipitator

Air scrubbers devices that can remove gases like sulphur dioxide. They wash away pollutants from exhausts by subjecting them to a spray of water or lime. Hence option c is incorrect.

Catalytic converters use catalysts such as palladium, platinum, etc., to speed up redox reactions that would convert harmful pollutants in the exhausts into non-harmful ones. Hence option d is incorrect.