what is concentrationand explain the process with diagram by metallic ore with sulphide as an impurity is purified
Answers
An ore of a metal is an impure source, this means other than the metal it consists of many other impurities such as sand, grit, clay, rocks etc. These impurities are collectively known as gangue. Gangue is generally commercial valueless and we must separate it from the ore. This entire process is the concentration of ores or even dressing or benefaction.
Now there are numerous ways to carry out the concentration of ores. The correct method is chosen based on the physical and chemical properties of the metal. Let us take a look at some of the most common methods.
Learn the process of Refining the Metal.
Hydraulic Washing
This method is based on the differences in weight between the gangue and the metal. Generally, the metal particles of the ore are heavier than the impurities. So we use the principle of gravity separation to separate the two.
Here crushed ore is mixed with an upward stream of running water. The lighter particles of the gangue wash away in the running water. The heavier metal particles settle down and can be separated easily. We use this method for ores that contain lead and tin since these are relatively heavier.
Magnetic Separation
Just like we saw earlier, the physical properties of metals can allow us to separate them from the gangue. One such physical property is magnetic properties of metals. In this method of Magnetic Separation, we use the magnetic properties of certain metals to divide them from the non-magnetic gangue.
Here we place the powdered ore on a roller belt. One belt of this roller is a magnet. So the magnetic material attracts to the metal belt and stays on the belt. The non-magnetic gangue falls in a heap from the belt. Also, the reverse may be the case. The gangue may be the magnetic material in certain cases.
Iron ores and manganese ores are the main ones for which we use magnetic separation. Magnetite and Chromitite ores (both iron ores) use this method on a large scale to remove their impurities.
Learn the process of extracting Crude Metal from Concentrated Ore.
Froth Flotation Process
Concentration of ores
Another method of concentration of ores is the Froth Flotation Method. This is the process for concentration of primarily sulphide ores. It has the advantage over gravity separation because it can collect even the extremely fine particles of minerals.
The process uses the difference in the wetting characteristics of minerals and gangue. Minerals are generally wetted by oil and gangue is wetted by water. So they prepare a mixture of the crushed ore with water, oil and other substances.
And rotating paddles will then agitate such mixture and introduce air. The air will cause bubbles to form, which attaches itself to the solid particles of minerals. And then a froth will form and it will rise to the top. This froth will contain the mineral particles which we can now separate. There are three main types of additives in this process, namely