• In general zeolites are micro porous, alumino-silicate minerals generally used as commercial adsorbents and catalysts. Zeolites have a porous structure that can contain a broad range of cations, such as Na+, K+, Ca2+, Mg2+ and others. These positive ions are quite loosely held and can readily be exchanged for others in a solution.
• Zeolites are solids that oppose the environmental situation that challenge many other materials. High temperatures don't bother them because they have relatively high melting points (over 1000°C), and they don't burn.

• Zeolites are unreactive and based on naturally occurring minerals; they're not believed to have any harmful environmental impacts. Although zeolites might sound incredibly boring, their stable and unreactive nature isn't what makes them useful. Zeolites are widely used as ion-exchange beds in domestic and commercial water purification, softening, and other applications.

   

Process: -

• Softening of water can be done by zeolite process, hard water is percolated at a specified rate through a bed of zeolite; kept in a cylinder. The Hardness causing ions (Ca+2,Mg+2 etc.) are retained by the zeolite as CaZe and MgZe; while the outgoing water contains sodium salts. Reactions taking place during the softening process are

$Na_2 Ze +Ca(HCO_3 )_2 → CaZe +2NaHCO_3$

$Na_2 Ze +Mg(HCO_3 )_2 → MgZe +2NaHCO_3$

​$Na_2Ze +CaCl_2 (or CaSO_4) → CaZe +2NaCl( or Na_2SO_4 ) $

$Na_2Ze +MgCl_2 (or MgSO_4) → MgZe +2NaCl( or Na_2SO_4 )$

• After Some time the zeolite is completely converted into calcium and magnesium Zeolites and it ceases to soften water. At this stage the supply of hard water is stopped and the exhausted zeolite is reclaimed by treating the bed with a concentrated NACL solution.

$CaZe(\text{ or } MgZe) + 2NaCl → Na_2 Ze + CaCl_2 (or MgCl_2 )$

There are few limitations of this process and these are as follows:

• If the supply of water is turbid in will clog the pores of zeolite blocked
• Water contains large quantities of colored ions such as Mn+2 and Fe+2 they may be removed first because these ions produce Mn and Fe zeolites ,which can’t be easily regenerated

There are some advantages of this process:-

1. It removes the hardness of water completely.
2. It consumes a small space.
3. It takes minimal time to complete the process
4. It a clean and suitable process.