Question

Photocatalysis is useful in breakdown of

• A. Acids and alkalies
• B. Chemicals containing heavy metals
• C. Toxic chemicals
• D. All of the above

Answer 1

Answer: (C)

Toxic chemicals

Photocatalysis is the reaction in presence of a catalyst that accelerates the rate of reaction which in turn, is occurring in presence of light i.e. photoreaction. Photocatalysis of effluents discharged from industries is done to remove organic pollutants from them. The catalyst used in the reaction is either zinc oxide or titanium oxide. Titanium oxide is a photocatalyst. When it is illuminated by light, an electron and positive hole pair is produced. The positive hole reacts with water to break it into hydrogen gas and hydroxyl ion whereas the negative electron reacts with oxygen to form superoxide.

The hydroxyl ions can break the bonds of various toxic substances such as formaldehyde, gasoline, chlorofluorocarbons etc.

So, the correct answer is 'Toxic chemicals'.