Question

Why should the metal sulphides and carbonates be converted to metal oxides in the process of extraction of metal from them?

Answer 1

Extraction of metal:

• Mining is the extraction of metal ores buried deep beneath.
• Metal ores are found in different quantities in the earth's crust.
• Metal extraction from ores is what enables us to use the minerals in the ground!
• The ores are not the same as the finished metals found in structures and bridges.
• Ores are made up of the desired metal compound as well as impurities and earthy things known as Gangue.

Metal sulphides and carbonates to be converted to metal oxides in metal extraction:

• A metal's oxide is easier to obtain than its sulphides or carbonates.
• As a result, when metal is extracted from metal sulphides and carbonates, it is first transformed into metal oxides.
• This is due to the fact that metals are easier to get from their oxides (through a reduction) than from carbonate or sulphide ores.
• As a result, prior to reduction, the ore must be transformed into metal oxide, which may then be reduced.
• Depending on the type of the ore calcination or roasting is used to transform the ore into oxide.
• Calcination converts a carbonate ore to oxide, whereas roasting converts a sulphide ore to oxide.

Calcination:

• In simplest terms, calcination can be defined as the process of heating a solid or substance in a controlled atmosphere.
• The temperature is frequently controlled during the process.
• The purpose of calcination is to alter a substance's physical or chemical makeup.
• Solids are heated to extremely high temperatures during calcination.
• Generally, this is done to get rid of water, and volatile compounds, or to oxidise the substance. This procedure is occasionally referred to as a purifying procedure. ${\mathrm{CaCO}}_3\left(\mathrm{s}\right)\to \mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)$

Roasting:

• In brief, roasting is a metallurgical process where ore is heated below its melting point in the presence of extra air and transformed into its oxide.
• Roasting is a technique used to transform sulphide ores, whereas calcination is mostly utilised in the oxidation of carbonates.
• Moisture and non-metallic contaminants are emitted as volatile gases during roasting.
• The roasting process involves a solid-gas thermal reaction that includes pyrohydrolysis, oxidation, reduction, sulfation, and chlorination$2\mathrm{ZnS}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2\mathrm{ZnO}\left(\mathrm{s}\right)+2{\mathrm{SO}}_2\left(\mathrm{g}\right)$