ZEOLITE OR PERMUTIT PROCESS

 

Zeolites are naturally occuring hydrated sodium alumino silicate minerals. 

Na2O. Al2O3. xSiO2. yH2O where x = 2 to 10 and   y = 2 to 6.

Natural zeolites are nonporous. The synthetic form of zeolite is known as permutit. Synthetic zeolite is represented by Na2Ze. Synthetic zeolites are porous and have a jelly structure. They are prepared by heating together china clay, feldspar and soda ash. These zeolites have higher exchange capacity per unit weight than natural zeolites.

In this synthetic zeolite process, the hard water is allowed to percolate through sodium zeolite. The sodium ions which are loosely held in Na2Ze are replaced by Ca2+ and Mg2+ ions present in the water.

Process:

In this process , the hard water is passed through a bed of sodium zeolite (Na2Ze). The hardness-causing ions (Ca2+, Mg2+) in hard water is replaced by loosely held sodium ions in zeolite bed. The outgoing soft water contains only sodium ions.

Na2Ze + Ca(HCO3)2  --> CaZe + 2NaHCO3

Na2Ze + Mg(HCO3)2  --> MgZe + 2NaHCO3

Na2Ze + CaCl2  -->  CaZe + 2NaCl

Na2Ze + MgCl2  --> MgZe + 2NaCl

Na2Ze + CaSO4  -->  CaZe + Na2SO4

Na2Ze + MgSO4  -->  MgZe + Na2SO4

As sodium ions do not give any hardness to water, the effluent water will be soft.

Regeneration:

After the softening process, the zeolite is completely converted into calcium and magnesium zeolites and it gets exhausted. At this stage, the hard-water supply is stopped and the exhausted bed is regenerated by treating with a concentrated 10% brine (Nacl) solution.

Exhausted zeolite with 10% NaCl --> Regenerated Zeolites

CaZe + 2NaCl                                --> Na2Ze + CaCl2

MgZe + 2NaCl                               --> Na2Ze + MgCl2

For Limitations, Advantages and Disadvantages of Zeolite Process refer https://meticulousperspectives.blogspot.com/2021/01/zeolites-limitations-advantages-and.html


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