Problem 169 - A Complete Resource Book in Chemistry for JEE Main

Question

Which one of the following ores is best concentrated by froth-floatation method? (a) cassiterite (b) galena (c) malachite (d) magnetite

Step-by-Step Solution

Answer

Galena is best concentrated by froth flotation.

Step 1: Understanding Froth Flotation

Froth flotation is a process used primarily for the concentration of sulfide ores. This involves mixing the powdered ore with water and frothers, which help to create froth, enabling sulfide ores to be separated from gangue.

Step 2: Identifying Sulfide Ores

The ores listed in the options must be classified as either sulfide or non-sulfide ores. Among the given options, galena is a sulfide ore, as it contains lead sulfide (PbS), while the others are not sulfide ores.

Step 3: Applicability of Froth Flotation

Since froth flotation is particularly effective for sulfide ores, and the only sulfide ore listed is galena, this makes it the best candidate for concentration using this method.

Key Concepts

Sulfide Ores

Sulfide ores are an important class of minerals known for their rich metal content. These ores primarily consist of metal sulfides. Some common metals found in sulfide ores include copper, lead, zinc, and nickel. Galena, for instance, is a well-known sulfide ore of lead (PbS).
Sulfide ores form deep underground, often in volcanic regions or as precipitates from hydrothermal veins. They are the byproduct of the crystallization process where sulfur combines with metals. This type of ore is crucial in the mining industry due to its economic significance. Metal extraction from sulfide ores is an important process, influenced by their unique chemical properties.

• Composition: Typically composed of metal combined with sulfur.
• Examples: Galena (PbS), Chalcopyrite (CuFeS₂), Sphalerite (ZnS).
• Extraction: Metal is extracted from sulfide ores using various techniques, including smelting and froth flotation.

Understanding sulfide ores provides a foundation for recognizing why froth flotation is suitable for their concentration.

Ore Concentration

Ore concentration is an essential step in mineral processing. It involves increasing the metal content of the ore by removing impurities. This makes subsequent metal extraction processes more efficient. Froth flotation is one method used, especially effective for sulfide ores.
The process of ore concentration begins with crushing the raw ore to fine particles. After this, various methods are employed to concentrate the ore and separate valuable minerals from the gangue.

• Chemical Methods: These include froth flotation, where chemicals like collectors and frothers are added to aid in mineral separation.
• Physical Methods: Techniques like gravity separation and magnetic separation fall under this category.
• Factors: The choice of concentration method depends on ore type, mineral composition, and economic considerations.

By increasing the concentration of desired minerals, mining operations can enhance the quality and value of extracted metals.

Mineral Processing

Mineral processing encompasses all activities that aim to separate and extract valuable minerals from ores. This full lifecycle of ore treatment includes a range of mechanical and chemical techniques designed to optimize extraction.
The goal is to efficiently convert ore into a form where metal can be extracted with higher yield and purity. Key processes include crushing, grinding, concentration (such as flotation), and smelting. Each process is critical to achieving cost-effective and environmentally friendly mining operations.

• Crushing and Grinding: Reduce ore size to liberate minerals.
• Concentration: Methods like flotation improve metal content.
• Extracting Metals: Techniques like smelting further purify metals.
• Sustainability: Modern methods emphasize reducing environmental impact while maximizing recovery.

Mineral processing not only focuses on handling the ores but also includes environmental and economic considerations that aim at achieving sustainable mining.