Q. Name the process used for concentration of MnO2 ore.

Q. Name the process used for concentration of MnO2 ore.

Grade:Upto college level

1 Answers

askIITians Faculty 747 Points
8 years ago
When an ore has a low percentage of the desired metal, a method of physical concentration must be used before the extraction process begins. In one such method, the ore is crushed and placed in a machine where, by shaking, the heavier particles containing the metal are separated from the lighter rock particles by gravity. Another method is theflotation process, used commonly for copper sulfide ores. In certain cases (as when gold, silver, or occasionally copper occur "free," i.e., uncombined chemically in sand or rock), mechanical or ore dressing methods alone are sufficient to obtain relatively pure metal. Waste material is washed away or separated by screening and gravity; the concentrated ore is then treated by various chemical processes.

Ore is an impure metal containing large amount of sand and rocky material. The impurities like sand, rocky materials, limestone, mica etc present in the ore is called gangue or matrix. These impurities must be removed from the ore before the extraction of the metal. The substance added to the ore to remove the matrix called flux results in the formation of a fusible compound called slag.

The processes used for removing the gangue from the ore are based on the differences between the physical or chemical properties of the gangue and the ore. At first the ore is crushed to powder. The pulverized ore is separated by physical processes like hydraulic washing, froth-floatation, and magnetic separation or by chemical processes, depending on the nature of the ore and its impurities. Concentration of the ore is also known as 'dressing' or 'enrichment' of ore.
Hydraulic Washing (Gravity Separation)
The ore particles are poured over a hydraulic classifier which is a vibrating sloped table with grooves and a jet of water is allowed to flow over it. The denser ore settle in the grooves while the lighter gangue particles are washed away. This method is used for concentration of heavy oxide ores of lead, tin, iron etc.

Froth Floatation
This method employs a mixture of water and pine oil which is made to froth in a tank to separate sulphide ores. The differences in the wetting properties of the ore and gangue particles separate them.

Magnetic Separation
Magnetic ores like pyrolusite (MnO2) and chromite (FeO.Cr2O3) are enriched by this method by making use of the difference in the magnetic properties of the ore and gangue particles.

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