Question

The Chlor-alkali industry produces chlorine and sodium hydroxide through electrolysis of NaCl solution . But one of the problem is that the sodium hydroxide to form chlorate and chloride. This leads to production of sodium chlorate, NaClO, a component of household bleach. Construct a suitable design and provide technical discussion to overcome technical issues

Answer 1

During electrolysis of NaCl, Sodium and chlorine exists as cation and anion respectively.There is competition between H+ and Na+. H+ being smaller in size moves faster towards the cathode ( negative) and liberated as Hydrogen gas.

Out of Cl- and OH- , Cl- being smaller in size migrates faster and form chlorine gas.

For the process should be efficient, acidic pH is necessary so that chlorine does not combines with OH- ion. Low pH means more H+ ions and hence H+ will combine more effectively with OH- ion. And hence, Cl- liberates as Cl2 gas.

Hence, chlorine will liberate and NaOH will be formed more effectively.

Nowadays, many new types of electrolysis are carried out such as Diaphragm cell , Membrane cell and many other to improve the production of NaOH.