Problem 128 - A Complete Resource Book in Chemistry for JEE Main

Question

For which of the following metals may be hydrometallurgical extractive method be employed? (a) copper (b) iron (c) chromium (d) tin

Step-by-Step Solution

Answer

The hydrometallurgical method applies to copper (a) and tin (d).

Step 1: Identifying Hydrometallurgy

Hydrometallurgy is a process of extracting metals from their ores using aqueous chemistry. It typically involves three main steps: leaching, concentration and purification, and metal recovery. It is often used for metals that dissolve well in aqueous solutions.

Step 2: Understanding the Metals

Let's consider each metal: - **Copper**: Commonly extracted using hydrometallurgy (e.g., from copper sulfide ores through bacterial leaching or solvent extraction). - **Iron**: Not typically extracted via hydrometallurgy, as physical extraction methods (like blast furnace) are more efficient. - **Chromium**: More often extracted using pyrometallurgical methods due to its chemical properties. - **Tin**: Can be extracted via hydrometallurgy from ores using methods like alkaline leaching.

Step 3: Analyzing Compatibility

Copper and tin can both be effectively extracted using hydrometallurgical methods because they dissolve into solutions through processes like leaching. Iron and chromium typically require pyrometallurgical methods.

Step 4: Conclusion

From the analysis, the metals that can be extracted using hydrometallurgical methods are copper and tin. Iron and chromium do not typically use these methods for extraction.

Key Concepts

Metal Extraction Methods

Metal extraction is a fascinating process that allows us to obtain metals from their ores. This is achieved through various techniques, each suited to different types of metals and ores. The two primary methods of metal extraction include:

• Pyrometallurgy: This involves the use of high temperatures to convert ores into metals. It includes processes like smelting, where heat is applied to cause chemical reactions that release metals from their ores.
• Hydrometallurgy: Unlike pyrometallurgy, this method uses aqueous chemistry to extract metals. It involves using water-based solutions to dissolve metals from their natural states.

Each method has its own advantages and is chosen based on the type of metal, its ore, and environmental considerations. While hydrometallurgy is often preferred for metals that dissolve easily in water, pyrometallurgy is more suited to metals that require high-temperature processing for extraction.

Leaching Process

Leaching is the cornerstone of hydrometallurgy and a critical step in metal extraction. It refers to the process of removing metals from their ores by dissolving them in liquids, most often water or acidic solutions. Here is how it works:

• Leaching Solution is applied to the crushed ore.
• The desired metal particles dissolve into the liquid.
• The solution, now containing the metal, is collected for further processing.

The efficiency of leaching depends on factors such as the type of metal, the composition of the ore, and the chemicals used in the solution. For example, copper is often leached using sulfuric acid solutions. It's a widely used method because it’s simple, cost-effective, and environmentally friendlier than some alternatives, like smelting.

Aqueous Chemistry in Metallurgy

Aqueous chemistry plays a crucial role in the realm of hydrometallurgy. It provides an alternative to traditional high-temperature extraction methods by utilizing the reactions that occur in liquid solutions. This method leverages the solubility properties of metals to separate them efficiently.

• The main role of aqueous chemistry is to dissolve the target metals through precisely balanced solutions.
• It is specific to each metal, requiring different pH levels, solvents, and additives to achieve optimal extraction.
• Subsequent steps involve removing impurities and recovering the metals from the solution.

Using aqueous chemistry, hydrometallurgy can achieve high-purity results with reduced environmental impacts. This is because it often produces fewer emissions and can utilize less energy compared to other extraction methods. As such, it is a critical area of research for developing more sustainable metal extraction techniques.