Question

Leaching of ore is done in the ___________ method of metal extraction.

• A. pyrometallurgical
• B. hydrometallurgical
• C. electrometallurgical
• D. either pyrometallurgical or hydrometallurgical

Hint:

Use the word roots to remember the categories:

• Pyro = Fire (High Temperature, Smelting)

• Hydro = Water (Aqueous Solutions, Leaching)

• Electro = Electricity (Electrolysis, Electrowinning)

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Metal extraction processes are broadly categorized based on the chemical and physical principles they employ. The main categories are pyrometallurgy, hydrometallurgy, and electrometallurgy.

Step 2: Detailed Explanation:

• Pyrometallurgy: This branch uses high temperatures to carry out reactions. Processes like roasting, smelting, and refining in a furnace fall under this category. The word root 'pyro' means fire.

• Hydrometallurgy: This branch uses aqueous solutions (water-based chemistry) at relatively low temperatures to extract and purify metals. The word root 'hydro' means water. The cornerstone of any hydrometallurgical process is

leaching, where a specific chemical agent in a solvent (usually water) is used to selectively dissolve the valuable metal from the ore, leaving the gangue behind as a solid residue. Examples include cyanide leaching for gold and sulfuric acid leaching for copper.

• Electrometallurgy: This branch uses electrical energy to extract or refine metals. Processes like electrowinning (extraction from a solution) and electrorefining (purification of an impure metal anode) are examples.
Since leaching is the process of dissolving a metal from its ore using a liquid solvent, it is the defining unit operation of the

hydrometallurgical method.

Step 3: Final Answer:
Leaching is the fundamental step in the hydrometallurgical method of metal extraction.