Question

The most effective concentration step for sulfide ores is

• A. Froth flotation
• B. Magnetic separation
• C. Gravity separation
• D. Electrostatic separation

Hint:

When you see "sulfide ore concentration," your first thought should always be "froth flotation." Similarly, for iron oxide ores like magnetite, think "magnetic separation," and for heavy minerals like gold or cassiterite, think "gravity separation."

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Ore concentration (or beneficiation) is the process of separating valuable mineral particles from the waste rock (gangue). The choice of method depends on the physical and chemical properties of the mineral and gangue. The question asks for the most effective method for sulfide ores.
Step 2: Detailed Explanation:
- (A) Froth flotation: This is the predominant method used for concentrating sulfide ores (e.g., chalcopyrite CuFeS\(_2\), galena PbS, sphalerite ZnS). The process exploits the differences in surface wettability between the sulfide minerals and the gangue. Specific chemical reagents called collectors are added to the ore pulp, which selectively adsorb onto the surface of the sulfide mineral particles, making them hydrophobic (water-repelling). When air is bubbled through the pulp, these hydrophobic particles attach to the air bubbles and rise to the surface to form a mineral-rich froth, which is then collected. This method is highly efficient and selective for sulfides.
- (B) Magnetic separation: This method separates minerals based on their magnetic susceptibility. It is effective for ferromagnetic or strongly paramagnetic minerals like magnetite (Fe\(_3\)O\(_4\)) or for removing magnetic impurities. Most common sulfide ores are not strongly magnetic, making this method generally unsuitable.
- (C) Gravity separation: This method separates minerals based on differences in their specific gravity (density). It is effective for heavy minerals like cassiterite (SnO\(_2\)) or gold. While some sulfide minerals are dense, flotation is typically far more efficient for separating them from gangue, especially for fine particles.
- (D) Electrostatic separation: This method separates minerals based on differences in their electrical conductivity. It is a more specialized technique and not the primary method for concentrating common sulfide ores.
Step 3: Final Answer:
Froth flotation is the most important and widely used concentration process for sulfide ores due to its high efficiency and selectivity.
Step 4: Why This is Correct:
The surface chemical properties of sulfide minerals make them uniquely suited for the froth flotation process, which has become the industry standard for their concentration. The other methods listed are less effective or applicable to different types of ores.