Clarity On The Extraction Of Moderately Reactive Metals Introduction

Metals are elements that are found in ores in a mixture with other various types of elements. As a result of the same, once the metals are extracted from their ores, they have to be converted to the pure metal form. This process is also known as the extraction of metals. In this article, we will share the extraction process of metals that are moderately reactive.

How are Moderately Reactive Metals Extracted?

The moderately reactive metals found in the middle of the reactivity series such as tin, iron, zinc, lead, and so on, usually exist in the form of oxides in their natural form, while a few others can be found as sulphide ores or carbonates. However, it is easier to obtain pure metals by reducing their oxides, as compared to the process of reducing them from their carbonates or sulphides. Thus, no matter what ore the metal is found in, it needs to be transformed into some form of metal oxide, which is then further reduced. The processes of calcination and roasting are used to turn concentrated ores to some form of metal oxide. Thus the method that will be used depends upon the nature of the ore.  While calcination converts carbonates into oxides, roasting turns sulphide ores into oxides. 

• Calcination – calcination can be defined as the process where the carbonated ore is turned into a metal oxide through the process of quickly warming it up in an atmosphere that has no air. For instance, zinc exists in calamine ores in the form of zinc carbonate (ZnCO3). Thus in order to start the process of extraction of zinc from the zinc carbonate, the zinc carbonate has to be turned into zinc oxide first. Calcination is utilised to achieve this. The Calamine ore as well as the zinc carbonate will decompose to a zinc oxide and CO2 when it is warmed up rapidly in the lack of any air. Thus the result will be that the ZnO will be transformed into zinc oxide. 

ZnCO3             ZnO      +           CO2

• Roasting – roasting is when a sulphide ore is turned to a metal oxide as it has been quickly heated up in the lack of any air. For instance, if we consider a Zinc blend ore, it consists of zinc in the form of sulphide, that is ZnS. Thus, before the zinc is extracted from the zinc sulphide, the zinc sulphide has to be transformed into zinc oxide. To achieve the same, the process is utilised.  Both Zinc oxide as well as sulphur dioxide will be created when the zinc sulphide or zinc blend ore is quickly heated up in the lack of any air, or simply roasted. Thus, the zinc sulphide will turn to the zinc oxide.  

2ZnS       +         3O2                2ZnO          +         2SO2

How are Metal Oxides Reducted?

With the help of reducing agents like calcium, sodium, aluminium, or carbon, the metal oxide which is created due to calcination or roasting of the ores needs to be converted into free metals. The level of chemical reactivity of that specific metal that needs extraction is used to determine which reducing agent is going to be used. 

• Reducing metal oxide by using Carbon – the Carbon element is usually used in order to reduce oxides that are less reactive, such as iron, tin, copper, zinc, nickel, and lead. This metal oxide will first be mixed with the carbon which exists as coke, and then warmed up in the furnace in this process of carbon reduction. With the help of carbon, the metal oxide will be reduced to the form of free metal. 

ZnO + C   Zn + CO

• Reducing metal oxide by using Aluminium – The process of extracting metals from the existing oxides, a metal that is comparatively more reactive such as aluminium is used as the reducing agent. For instance, in the case that the metal is more reactive as compared to zinc and will not be reduced with the help of carbon, aluminium is usually used as a reducing agent. The process can be attributed to the reason that a metal that is comparatively more reactive like aluminium will be able to displace the metal that is less reactive from its existing metal oxide, leaving behind the free metal only. Thus, the reaction of the displacement can be used to transform metal oxides into free metal. This powdered aluminium will oxidise into an aluminium oxide once it has reduced the metal oxide into a metal. 

3MnO2    +     4Al                  3Mn          +      2Al2O3     +     Heat

Conclusion

Metals are usually found in ores in a combination with other types of elements. Thus they have to be extracted.

 This process of extraction of moderately reactive metals that fall in the middle of the reactivity series is done by reducing their specific oxides, such as calcium, sodium, carbon, aluminium, sodium, and so on.