Chemical process to produce bleach.

What is Electrochlorination and Electrolysis?

by Lewis Loflin


Electrolysis is a chemical process driven by passing an electric current through an electrolyte, an ionic substance, either in a solution or molten state.

For example, molten table salt (sodium chloride) becomes conductive, an ionic solution. When an electric current is passed through it, this "solution" breaks apart into chlorine gas and sodium metal. The process is energy-intensive.

During electrolysis, electrical energy is converted into chemical energy. When an electric current is applied, it forces a non-spontaneous chemical reaction by driving ions to migrate toward oppositely charged electrodes.

Applications: Electrolysis has various purposes, including:

Electroplating - to coat one metal onto another.
Electro refining - to purify metals.
Production of chemicals - like chlorine, hydrogen, and sodium hydroxide from brine solution.
Anodizing - to increase corrosion resistance in metals like aluminum.
Electrolysis of water - to produce hydrogen and oxygen gases.

Electrolysis requires an external source of electrical energy because the process is not spontaneous; it's endothermic, meaning it requires energy input to proceed.

The amount of chemical change during electrolysis is proportional to the quantity of electricity passed through the electrolyte.

In summary, electrolysis is a technique where electrical energy is used to drive a chemical change that would not occur naturally by moving ions and forcing them to react at electrodes.

Pool chlorination equipment.
Pool chlorination equipment.


Electrochlorination produces sodium hypochlorite (bleach) by passing an electric current through salt water (brine). This bleach disinfects the water and makes it safe for human use, such as drinking water or swimming pools.

A low-voltage DC is applied, and electrolysis happens, producing sodium hypochlorite and hydrogen gas (H2).

At the negative electrode (cathode), sodium ions (cations) are reduced (gain electrons), producing sodium metal. This sodium metal immediately attacks the water, producing sodium hydroxide (NaOH) and hydrogen gas.

At the positive electrode (anode), chlorine ions (anions) oxidize (lose electrons), becoming chlorine gas (Cl2).

It is the electrolysis of salt water to produce a chlorinated solution. The chlorine gas attacks the sodium hydroxide, producing sodium hypochlorite.

Chlorination electrolysis cell.
Chlorination electrolysis cell.


The first step is removing any solids from the saltwater. Next, the saltwater streams through an electrolyzer cell's channel of decreasing thickness. One side of the channel is a cathode, and the other is an anode.

The solution travels to a tank that separates the hydrogen gas based on its low density. The simplified chemical reaction is:

NaCl + H2O + energy → NaOCl + H2

That is, energy is added to sodium chloride (table salt) in water, producing sodium hypochlorite and hydrogen gas.

Because the reaction takes place in an unpartitioned cell and NaOH is present in the same solution as the Cl2:

2 NaCl + 2 H2O → 2 NaOH + H2 + Cl2 - any Cl2 disproportionates to hypochlorite and chloride.

Cl2 + 2 NaOH → NaCl + NaClO + H2O resulting in a hypochlorite solution.


The above material credit GROK the X AI with additions by Lewis Loflin.

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I've been a part-time adjunct professor at a local community college teaching electricity and electronics.

Today I do this for the shear love of electronics.

I have 45 years experience in electronics, from vacuum tubes to modern solid state and industrial controls. I tend to teach from a general science viewpoint.

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