Air Pollution MCQ with answer and solution

Concept

In adsorption, gas molecules stick to the surface of a solid such as activated carbon. In absorption, gas dissolves into a liquid.

Step-by-step solution

1. Gaseous pollutant control methods are absorption (liquid), adsorption (solid surface) and combustion. 2. Spray tower and plate tower use a liquid, so they are absorption units. 3. A venturi scrubber is a wet scrubber, used mainly for particulates and some absorption. 4. An activated carbon unit uses a solid adsorbent, so it is an adsorption unit.

Explanation

Adsorption means pollutant gas molecules stick to the surface of a solid. Activated carbon has a very large surface area, so it is the most common adsorbent. So the activated carbon unit is the adsorption unit.

Why the other options are wrong

A: Spray tower is an absorption (liquid) unit. C: Plate tower is an absorption (liquid) unit. D: Venturi scrubber is a wet scrubber, mainly for particulate removal.

Shortcut

Solid adsorbent (activated carbon, silica gel) means adsorption. Liquid contact (tower, scrubber) means absorption.

Common mistake

Confusing adsorption (on a solid surface) with absorption (into a liquid).