Which statement describes how aluminum oxide is activated?

Which statement describes how aluminum oxide is activated?

• A. Oxygen and heat
• B. Sulfuric acid and heat
• C. Heat and washing with sodium hydroxide
• D. Carbon dioxide wash with HCl and heat

Answer: (C)

Activation of aluminum oxide hinges on preparing its surface to provide many active adsorption sites. Washing the oxide with a sodium hydroxide solution cleans and modifies the surface, creating or exposing hydroxyl groups that act as active sites for adsorption. Heating then dries and stabilizes the material, preserving those sites and the porous structure so the activated alumina can effectively remove contaminants like fluoride or arsenic from water. Simply exposing to oxygen and heat doesn’t develop those reactive sites, acids would alter the surface differently and can damage it, and a carbon dioxide wash with acid isn’t a recognized activation method.

Activation of aluminum oxide hinges on preparing its surface to provide many active adsorption sites. Washing the oxide with a sodium hydroxide solution cleans and modifies the surface, creating or exposing hydroxyl groups that act as active sites for adsorption. Heating then dries and stabilizes the material, preserving those sites and the porous structure so the activated alumina can effectively remove contaminants like fluoride or arsenic from water. Simply exposing to oxygen and heat doesn’t develop those reactive sites, acids would alter the surface differently and can damage it, and a carbon dioxide wash with acid isn’t a recognized activation method.