Problem 14 - A Complete Resource Book in Chemistry for JEE Main

Question

Tin stone is contaminated with Wolframite. Which one of the following methods can be employed to dress the tin stone ore? (a) electromagnetic separation (b) levigation (c) roasting (d) floatation process

Step-by-Step Solution

Answer

Electromagnetic separation (option a) is the most suitable method.

Step 1: Identify the minerals involved in the ore

Tin stone consists primarily of cassiterite (SnO₂), and it is contaminated with wolframite (FeWO₄ or MnWO₄). These minerals display different magnetic properties, with wolframite being magnetic.

Step 2: Analyze separation methods based on properties

Different separation techniques are selected based on the physical or chemical properties of the minerals involved. For cassiterite and wolframite, we note that wolframite is magnetic, while cassiterite is non-magnetic.

Step 3: Evaluate applicability of separation methods

Examine the given options: (a) Electromagnetic separation uses magnetic properties and can separate magnetic wolframite from non-magnetic cassiterite. (b) Levigation uses differences in density but both minerals have similar densities. (c) Roasting involves heating and altering chemical properties, not suitable for separating based on magnetism. (d) Floatation targets differences in surface properties, less effective here.

Step 4: Select the appropriate method

Electromagnetic separation is the most effective method since it leverages the magnetic properties of wolframite to separate it from cassiterite.

Key Concepts

Electromagnetic Separation

When dealing with mining and mineral dressing, identifying the best method to separate different minerals is vital. Electromagnetic separation is a method that leverages magnetic fields to separate magnetic minerals from non-magnetic ones. This technique is particularly useful if the materials differ significantly in magnetic properties. By using a powerful magnetic field, it can extract magnetic minerals like wolframite from non-magnetic minerals such as cassiterite. This method is efficient and effective, especially when one of the ores has distinct magnetic properties.

Cassiterite

Cassiterite, primarily known as SnO₂, is the principal ore of tin. It often appears in the form of fine-grained, dark, opaque crystals. One of its distinct features is that cassiterite is non-magnetic. Unlike some other ores, cassiterite does not respond to magnetic fields which makes electromagnetic separation a suitable method for its processing when it is mixed with magnetic minerals like wolframite. This quality allows for efficient separation when electromagnetic techniques are applied, ensuring purity in subsequent extraction processes.

Wolframite

Wolframite is an iron manganese tungstate mineral, with the chemical formula often written as FeWO₄ or MnWO₄. A key characteristic of wolframite is that it is magnetic. This is an important feature in the context of ore dressing because the ability to react to a magnetic field makes wolframite easy to separate from non-magnetic minerals in a mixed ore. Its magnetic nature means that when processing ores like tin stone, which are contaminated with wolframite, electromagnetic separation can effectively distinguish these two minerals.

Magnetic Properties

The magnetic properties of a mineral are a defining factor in choosing the appropriate mineral separation technique. Minerals can be broadly classified based on their magnetic susceptibilities, either being magnetic or non-magnetic. For example, in the case of separating cassiterite from wolframite, understanding that wolframite is magnetic allows for the deployment of electromagnetic separation to achieve purification. This separation exploits the magnetic susceptibility of wolframite and results in an effective method of mineral dressing. The knowledge of magnetic properties is crucial in mining operations to enhance the efficiency and efficacy of the separation process.