Question

Among the following options, a process for liquid-liquid separation is

• A. Smelting
• B. Roasting
• C. Sintering
• D. Calcination

Hint:

Associate key phases with metallurgical processes:
- {Smelting} \(⇒\) Liquid Metal + Liquid Slag
- {Roasting} \(⇒\) Solid + Gas \(⇒\) Solid + Gas
- {Sintering} \(⇒\) Solid (powder) \(⇒\) Solid (lump)
- {Calcination} \(⇒\) Solid \(⇒\) Solid + Gas

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The question asks to identify a metallurgical process that fundamentally involves the separation of two immiscible liquids.
Step 2: Detailed Explanation:
Let's analyze each process: - (A) Smelting: This is a high-temperature pyrometallurgical process for extracting a base metal from its ore. The process involves melting the ore concentrate with a fluxing agent. This results in the formation of two immiscible liquid layers:
1. A dense layer of molten metal.
2. A less dense layer of molten slag (impurities combined with the flux).
The separation of these two liquid layers by tapping them from the furnace at different levels is a key part of smelting. Therefore, smelting is a process for liquid-liquid separation.
- (B) Roasting: This is a process of heating a solid sulfide ore in the presence of air to convert it to a solid oxide, releasing sulfur dioxide gas. This is a solid-gas reaction (e.g., \(2\text{ZnS(s)} + 3\text{O}_2\text{(g)} ⇒ 2\text{ZnO(s)} + 2\text{SO}_2\text{(g)}\)). It does not involve liquid phases.
- (C) Sintering: This is a process where fine solid particles are heated to a temperature below their melting point, causing them to bond together and form a single, porous solid mass. This is a solid-state process used for agglomeration.
- (D) Calcination: This is a thermal treatment process applied to solid ores and other materials to bring about thermal decomposition, phase transition, or removal of a volatile fraction. It typically involves heating a solid to a high temperature, often to remove CO\(_2\) or water (e.g., \(\text{CaCO}_3\text{(s)} ⇒ \text{CaO(s)} + \text{CO}_2\text{(g)}\)). This is a solid decomposition process.
Step 3: Final Answer:
Among the given options, only smelting involves the separation of two liquid phases (molten metal and molten slag).
Step 4: Why This is Correct:
The definition of smelting directly involves creating and separating two liquid phases. The other processes are primarily solid-gas reactions or solid-state transformations.