Science Class 10: Extraction of Metals

Extraction of Metals

Enrichment of ores is the physical and chemical separation of impurities or gangue from ore. It is the process of removing gangue particles from ore in order to enhance the proportion of metal in the ore.

Depending on the metal’s reactivity, different techniques are used to obtain it. The extraction of pure metal from ores entails several steps. 

• Metal extraction at the bottom of the activity series: By heating alone, these metals’ oxides can be reduced to metals. Mercury and copper are two examples.
• Metal extraction in the midst of an activity series: Metals such as iron, zinc, and others are typically found in nature as sulfides or carbonates. Due to the fact that it is easier to obtain metal from its oxide than it is from its sulfides and carbonates, metal sulfides and carbonates are converted into metal oxides prior to reduction.
• Metal extraction is a high-level activity Series: Electrolytic reduction is used to get these metals. Sodium, magnesium, and calcium, for example, are obtained by electrolysis of their molten chlorides.

The metal produced from the ore is not particularly pure. Refining is the process of eliminating impurities from metal in order to achieve a pure metal. Electrolytic refining is the most extensively utilised technique of refining.

Roasting and Calcination:

By rapidly heating the sulfide ores in the presence of excess air, they are converted to oxides. This is referred to as roasting.

By rapidly heating carbonate ores in confined air, they are converted to oxides. This is referred to as calcination.

Electrolytic Refining:

 Metals like copper, zinc, nickel, silver, tin, gold, etc. are electrolytic refining. 

Apparatus setup:

• The anode is a non-pure metal.
• Cathode: A thin, pure metal strip
• The aqueous phase of the metal salt is called an electrolyte.

Current is transmitted through the electrolyte and the electrolytic refining occurs:

• The anode’s pure metal dissolves in the electrolyte.
• On the cathode, an equal quantity of pure metal from the electrolyte is deposited.
• Impurities that are soluble in the solution are dissolved.
• Impurities that are insoluble in water sink to the bottom of the anode and are referred to as anode mud. In this way, the electrolytic refining has occurred.

Corrosion:

Corrosion is the process through which a metal gradually deteriorates due to the action of moisture, air, or chemicals in the surrounding environment. For instance,

• When exposed to air, silver becomes black. This corrosion occurs when a layer of silver sulfide is made on the surface which occurs when silver combines with sulfur in the air.
• Copper: When it comes into contact with the carbon dioxide that is found in the air in a moist state, it gradually loses its gleaming brown surface and develops a green coat. This green substance is copper carbonate in its simplest form.
• When iron is exposed to moist air for an extended period of time, it develops a coating of a brown flaky substance known as rust, known as corrosion.

Prevention from Corrosion:

Iron can be prevented from corrosion by painting, galvanising, chrome plating, anodizing, or alloying.

• Coating: Applying paint, oil, or grease to metal surfaces seals out air and moisture.
• Galvanizing: It is the process by which iron is coated with a thin layer of zinc.
• Alloying: It is a process that enhances the properties of a metal. For instance, iron is combined with nickel and chromium to create stainless steel, which is very strong and resistant to corrosion.

Alloy:

It is a homogeneous alloy composed of two or more metals, or of a metal and a non-metal.

• Firstly you need to heat and subsequently melt the primary metal. Then dissolve the other remaining elements in it in precise quantities. Following that, it is chilled to room temperature.
• Alloys have lower electrical conductivity and melting temperature than pure metals. For instance
  • Brass (a copper-zinc alloy) and Bronze (a copper-tin alloy) are poor conductors of electricity, while copper is utilised to build electrical circuits.
  • Solder (a lead-tin alloy) usually has a much lower melting point and it is used to join electrical lines.

Conclusion:

Extraction of Metals is the process of removing gangue particles from ore in order to enhance the proportion of metal in the ore. Impurities that are insoluble in water sink to the bottom of the anode and are referred to as anode mud. In this way, the electrolytic refining has occurred. Corrosion is the process through which a metal gradually deteriorates due to the action of moisture, air, or chemicals in the surrounding environment. For instance,