Question

In hydrometallurgical process of leaching of copper ore, _____________ acid is used for the purpose.

• A. nitric
• B. acetic
• C. sulphuric
• D. hydrochloric

Hint:

In extractive metallurgy, economics is key. Sulphuric acid is often called the "workhorse" of hydrometallurgy because it is cheap and effective for many common ores, particularly copper oxides and uranium ores.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Hydrometallurgy is a branch of extractive metallurgy that uses aqueous solutions to extract metals from their ores. Leaching is the key step in hydrometallurgy where the desired metal is selectively dissolved from the ore using a chemical agent called a lixiviant. The question asks for the common acid used for leaching copper ores.

Step 2: Detailed Explanation:
The choice of lixiviant depends on the type of ore and economic factors. For copper ores, especially low-grade oxide and sulfide ores, acid leaching is a very common method. -

Leaching of Copper Oxide Ores: Ores like azurite (\(\text{Cu}_3(\text{CO}_3)_2(\text{OH})_2\)) or malachite (\(\text{Cu}_2\text{CO}_3(\text{OH})_2\)) are readily dissolved by acids. -

Leaching of Copper Sulfide Ores: Ores like chalcocite (\(\text{Cu}_2\text{S}\)) or chalcopyrite (\(\text{CuFeS}_2\)) can also be leached, often with the help of oxidizing bacteria (bioleaching). Let's consider the acids listed: - Sulphuric acid (H₂SO₄): This is the most widely used and economically viable lixiviant for copper ores. It is relatively inexpensive (often produced on-site from roasting sulfide ores), effective at dissolving many copper minerals to form copper sulfate (\(\text{CuSO}_4\)), and the resulting solution is suitable for subsequent recovery processes like solvent extraction and electrowinning (SX-EW). A typical reaction is: \[ \text{CuO} + \text{H}_2\text{SO}_4 \rightarrow \text{CuSO}_4 + \text{H}_2\text{O} \] - Nitric acid (HNO₃) and Hydrochloric acid (HCl): These are strong acids but are generally more expensive and more corrosive than sulfuric acid, making them less favorable for large-scale industrial leaching of copper. - Acetic acid (CH₃COOH): This is a weak organic acid and is not strong enough or economically practical for leaching most copper ores. Given its effectiveness, low cost, and compatibility with downstream processes, sulphuric acid is the standard choice in the hydrometallurgy of copper.

Step 3: Final Answer:
In the hydrometallurgical leaching of copper ore, sulphuric acid is commonly used. This corresponds to option (C).