Detailed Information on the Methods of concentration of Ores

Ores are a mixture of minerals and various other particles that need to be processed to extract minerals in their pure form. Also known as enrichment, the concentration of ores is the method of removing impurities and other unwanted particles from the ore. The removal method of the gangue particles or the unwanted particles depends on the difference in physical or chemical properties of the ore and the impurities. The minerals present in ores are found in the form of compounds with other elements, and their extraction process is called metal extraction. The various techniques used for extracting the metals from ores are called metallurgy, and there is no one way of extraction that is suitable for every kind of metal to be extracted. The extraction method depends on what metal is to be extracted. The different methods used for the concentration of ores are the froth floatation method,  gravity separation, leaching method and electromagnetic separation. 

Methods of Concentration of Ores

Without ore enrichment, the metals present cannot be used as their chemical and physical properties will differ from the pure form. The different methods used for separating the metals are collectively known as metallurgy, and there are several methods for extracting each metal. The methods used will depend on the metal required to be extracted and the difference in physical and chemical properties of the unwanted minerals and the metals present in the ore. 

Let us look at the different methods used for the concentration of ores. 

• Leaching method

This process is relatively easy but is not considered very efficient. In this method, the ore is treated with chemicals which causes the desired metals to turn into salts. While the metal is converted into soluble salts, the gangue particles remain insoluble, thereby getting separated from the metal. The salts are washed out after converting it back into metals and then processed, which gives the pure form of the metal. 

• Gravity separation or hydraulic washing

The gravity separation method, also known as hydraulic washing, is used for metals that are heavier than the gangue particles. In this method, water is used to enrich the ore. The ore is passed through a stream that goes upward, pushing up all the lighter particles mainly comprising impurities, while the metals that are heavier than the impurities settle down as they cannot be pushed. Before passing it through the stream, the ore is first crushed into a fine powder form, and the lighter particles, which are the impure particles, get washed away and separated from the metals. The gravity separation method is mostly used for concentrating tin and lead oxide from their ores. 

• Froth floatation method

In the froth floatation method, water is used but in a different way and for different metals. This method is suitable for separating hydrophobic materials from hydrophilic materials and was first used in the mining industry during the 20th century, specifically for sulphide ores. The ore particles are crushed into a fine powder and are then added to water that forms suspension to which collectors such as pine oil, fatty acids, etc., and froth stabilisers are added. The collectors boost the metal particles of the ore’s non-wettability, making the powdered ore form a froth on the water’s surface. Froth stabilisers like cresols, aniline, or any other type of stabilisers keep the froth forming while the water lubricates the impure particles and oil lubricates the metal. For the froth to keep forming, the suspension needs to be constantly stirred with the help of paddles. This method is carried out in tanks full of water, and after the process is complete, the froth of the metal is collected to be dried for use.

• Electromagnetic separation

As the name suggests, magnetised material, such as a magnet-equipped roller, is used for separating the unwanted particles to enrich the ore. The magnetic characteristics of the ore or the gangue particles are used for separation. The ore is powdered and is laid on a conveyor belt that passes through a magnetic roller. Metals that are magnetic stick to the magnetic roller, and the unwanted particles slide off. This magnetic separation method is suitable for metals that are attracted to a magnetised material and are separated from the non-magnetic particles, thereby enhancing the ore concentration. For this method, a magnetic separator is best suited to process iron ores like magnetite, chromite, and manganese, which are magnetic ores. 

Conclusion

Ores are present in the form of rocks and form naturally. These ores comprise metals of different kinds as well as other elements and particles that have no industrial use. The metal compounds are present in sufficient amounts in the ore, making them worthwhile to extract for use. However, the ore cannot be used if the necessary metals are not separated from the gangue particles, which are the unwanted particles that make it inconvenient for use. The concentration of the ores varies on the amount of metal and gangue present in the ore, and the methods used for the concentration of ore depend on the chemical and physical properties of the ore. There are four basic methods for enhancing the concentration of the ore, leaching method, gravity separation, froth floatation method, and electromagnetic separation, all used for extracting different kinds of metals.