Production of Halogens

Chlorine:

Chlorine is produced from the electrolysis of brine (saturated salt solution, NaCl+H2O).
This occurs in a diaphragm cell or a membrane cell.
The following reactions occur at each electrode in a diaphragm cell and membrane cell:
- Anode: 2Cl- –> Cl2 + 2e-
- Cathode: 2H+ + 2e- –> H2
The Cl2 and H2 gases are collected separately and the remaining solution contains sodium hydroxide (NaOH).
The chlorine gas produced reacts with cold, dilute sodium hydroxide to produce chlorate(I) bleach (NaClO).
It’s important to note that the process is not very energy efficient and a high current is often required.

Bromine:

Bromine is chiefly obtained from salt lakes and brine wells.
The process involves oxidation of bromide ions by chlorine: 2Br- + Cl2 –> 2Cl- + Br2
This oxidation process separates the bromine from the solution.
Bromine’s reddish-brown colour aids in identifying its presence following extraction.

Iodine:

Iodine is produced by oxidising iodide ions present in brine.
The oxidation of iodides is often carried out using chlorine.
The process goes as follows: 2I– + Cl2 –> 2Cl– + I2
The resulting iodine is sublimed – converted from a solid directly into a gas, bypassing the liquid phase – to purify it.
The presence of iodine can be confirmed by its characteristic violet colour.

Remember, understanding the production process of halogens is crucial, but it is also essential to understand the properties, uses, and impacts of these halogens on the environment for a well-rounded understanding of the topic.