Question

Column I presents common air pollutants, and column II presents treatment technologies commonly employed to control air pollutants.

	Air pollutant		Treatment technology
1	Dust (size 5-25 microns)	P	Cyclone separator
2	Carbon monoxide (CO)	Q	Wet lime-water scrubber
3	Sulfur dioxide (SO2)	R	Electrostatic precipitator
4	Fly ash (size < 2.5 microns)	S	Catalytic converter

The option that CORRECTLY matches the air pollutant with its treatment technology is:

• A. 1 - P ; 2 - S ; 3 - Q ; 4 - R
• B. 1 - P ; 2 - R ; 3 - S ; 4 - Q
• C. 1 - R ; 2 - Q ; 3 - P ; 4 - S
• D. 1 - R ; 2 - Q ; 3 - S ; 4 - P

Hint:

Match by pollutant type: coarse dust to cyclone, fine fly ash to ESP, acid gas SO2 to wet scrubbing, CO gas to catalytic oxidation.

Answer 1

The Correct Option is A

Step 1: Recall which control technology suits each type of pollutant.
Cyclone separators use centrifugal force to fling heavier, coarser particles to the outer wall of a conical chamber, so they work well for relatively large dust particles, typically in the range of about 5 to 25 microns and above, but are not efficient for very fine particulates.
Electrostatic precipitators (ESP) charge particles electrically and collect them on oppositely charged plates; this makes them highly efficient even for very fine particulate matter such as fly ash below about 2.5 microns, which cyclones cannot capture well.
Wet scrubbers that use a lime-water (alkaline) slurry are the standard method for absorbing acid gases, and Sulfur dioxide (SO₂) is a classic acid gas removed by wet lime or lime-water scrubbing (flue gas desulfurization).
Catalytic converters use a catalyst bed to oxidize incomplete combustion products; Carbon monoxide (CO) is oxidized to carbon dioxide over a catalyst, which is exactly how catalytic converters control CO emissions, as in vehicle exhaust systems.

Step 2: Match each pollutant to its technology.
1. Dust (5-25 microns), being coarse, matches P, Cyclone separator.
2. Carbon monoxide (CO) matches S, Catalytic converter.
3. Sulfur dioxide (SO₂) matches Q, Wet lime-water scrubber.
4. Fly ash (below 2.5 microns), being very fine, matches R, Electrostatic precipitator.

Step 3: Compare with the options.
The set 1-P, 2-S, 3-Q, 4-R corresponds exactly to option (A). The other options either pair CO with electrostatic precipitation, or SO₂ with electrostatic precipitation, or fly ash with cyclone separation, all of which mismatch a gas-phase pollutant with a particulate control method or a coarse-particle method with fine particulate matter.

Final Answer:
Option (A): 1 - P ; 2 - S ; 3 - Q ; 4 - R. \[ \boxed{\text{(A)}} \]