NaOH Manufacturing
Caustic soda (NaOH)
available in solid flakes and liquid solution (different concentration. Caustic
soda production is done by any one of the following manufacturing processes.
Method of Manufacture:
1.
Chemical: lime soda
process,
2.
Electrochemical:
chloro alkali process
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Diaphragm Cell
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Mercury Cell Process
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Membrane Cell Process
Electrochemical Process
Castner-Kellner Cell (Mercury Cell Process)
Castner-Kellner process was
developed in the mid 1800’s. The cell had a positive electrode and a negative
electrode inside a tank. The reactions proceeded as follows:
- A sodium chloride brine (salt water) is put into the tank.
- The positive electrode (Titanium anode) attracts the chloride away from the sodium. The chloride builds up and combines to form chlorine gas ( an excellent disinfectant)
Anode Reaction (oxidation:
2Cl- (aq) = CL2 (g)+ 2e-
 |
| fig: mercury cell process |
3 3. The water is broken
apart with the negative electrode (Mercury cathode) into hydrogen ions) which
form into hydrogen gas) and hydroxide ions.
4. The negative electrode
(Mercury electrode) attract sodium ions forming.
Cathode
Reaction (reduction):
Na+(aq) + e- = Na(s)
5.Na(s) dissolves
in the liquid mercury to form an amalgam, which is removed to the decomposer.
6.In the decomposer the amalgam reacts with water to form sodium
hydroxide, hydrogen gas and mercury.
7. Sodium hydroxide solution and hydrogen gas are collected.
