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Concentration of ore can be explained as a method by which gangue is separated from the ore of the metal. The process is also known as dressing or benefaction. Gangue is the combined name of the impurities like sand, clay, grit, etc.
Gangue needs to be separated because minerals are present in high concentration in its ore. These minerals are extracted by the processes given below:
- Concentration of ore
- Isolation of metal from concentrated ore
- Purification of metal
| Table of Content |
Keyterms: Ore, gangue, sand, clay, grit, metal, Cassiterite, minerals
Concentration Of Ore: Types
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Concentration of ore can be done by various methods depending on the characteristics of ore and gangue. Given below are 4 methods of concentration of ore:
1. Hydraulic Washing
Hydraulic washing is used for the concentration of ores in which there is a noticeable difference in weights of gangue and useful minerals. This happens by the gravity separation technique. The pressure created by the stream of water makes the heavy metal settle down and the lighter gangue particles separate.
2. Magnetic Separation
Magnetic separation method is based on the magnetic properties of the components of the ore. It involves grinding of ore into fine particles and placing them on a moving conveyor belt. The conveyor belt has electromagnetic rollers which attract the magnetic particles forming a heap near it and hence the non-magnetic particles form a separate heap.
3. Froth Floatation Method
Froth floatation method is used for the concentration of sulphide ores. This technique is based upon the wetting properties of the metal and gangue particles. Sulphide ore is grounded and is dropped in a mixture of water and pine oil (oil and water create a suspension). In this tank, the compressed air is blown through the agitator which is rotated. Due to agitation, the gangue particles settle down and sulphide ore floats upside down. These two are separated in different tanks and the sulphide ore is sent for further processing.
4. Leaching
Leaching is used for the ores which are soluble. This makes it easier for gangue particles to separate and extract minerals.
Also Read:
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| Ellingham Diagram | Calcination/Roasting | Leaching Process |
Things To Remember
- Concentration of ore is the process used to extract useful minerals by separating the gangue particles.
- Concentration of ore can be done by 4 methods: Hydraulic Washing, Magnetic Separation, Froth Floatation, Leaching.
- Hydraulic washing depends upon the weights of the metal and gangue particles.
- Magnetic separation depends on the magnetic properties of the metal and gangue particles.
- Froth floatation method depends on the wetting properties of the metal and gangue particles.
- Leaching depends on the solubility of the metal.
Also Read:
Sample Questions
Ques 1. Explain the magnetic separation process of ores with a labelled diagram. (3 marks)
Ans. Magnetic separation method is based on the magnetic properties of the components of the ore. It involves grinding of ore into fine particles and placing them on a moving conveyor belt. The conveyor belt has electromagnetic rollers which attract the magnetic particles forming a heap near it and hence the non-magnetic particles form a separate heap.
Ques 2. Why is the froth flotation method selected for the concentration of sulphide ores? (1 mark)
Ans. The froth floatation method depends on the wetting properties. Sulphide particles can be wetted by oil and gangue particles can be wetted by water. This makes the process of formation of form easier and hence, the froth flotation method is suitable for sulphide ores.
Ques 3. What is the difference between a mineral and an ore? (2 marks)
Ans. Mineral: Minerals are naturally occurring chemical compounds in which metals and impurities coexist in the earth's crust.
Ore: An ore is a mineral that can be used to extract the metal in a practical and cost-effective manner.
As a result, while all ores are minerals, not all minerals are ores.
Ques 4. Which of the following ore is concentrated by the chemical leaching method? (2 marks)
(a) Galena
(b) Copper pyrite
(c) CaO + SiO3
(d) SiO2 and CaSiO3
Ans. Native silver or gold or Argentite is finely powdered. This is treated with a dilute solution of sodium cyanide or potassium cyanide and the air current is passed through. Silver forms soluble cyanides and impurities are filtered.
4Ag + 8NaCN + O2 + 2H2O → 4Na[Ag(CN)2] + 4NaOH
Or
Ag2S + 4NaCN → 2Na[Ag(CN)2] + Na2S
(sodium dicyanoargentate)
Ques 5. What is the principle of gravity method of ore concentration? (1 mark)
Ans. The gravity method of ore concentration is dependent on the wetting properties of metal and gangue. When the suspension of water and oil is agitated it forms a froth containing mineral particles. This is separated from the entire mixture and is sent for further processing for the extraction of ore.
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