Zeolite process for water softening

What is zeolite
Zeolite is micro-porous mineral which is used as catalyst in many industrial purposes such as water purification and air purification. The zeolites are hydrated aluminosilicates and general composition Al_xSi_yO_2(x+y)  (without water molecules). Zeolites are two types natural and synthetic or artificial. The natural zeolite that is used for water softening is gluconites or greensand. Permutit is the synthetic zeolite that is most used in water softening and its chemical formula is Na₂O, Al₂O₃, nSiO₂, xH₂O. These are used as ion exchanger and odor removal in water softener. Permutit are more porous, glassy, and have higher softening capacity than greensand.
Zeolites are characteristically soft to moderately hard, light in density, insoluble in water but can act as base exchangers in contact with water containing cations. Hence these can remove Ca²⁺ and Mg²⁺ ions from water when hard water is passes through.

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Zeolite process for water softening
Zeolite process for water softening has become a commercial success for the reason that zeolite can be easily regenerated. When Ca²⁺ and Mg²⁺ ions containing hard water is passes through a bed of sodium zeolite, the sodium ions are replace by the calcium and magnesium ions.

Na₂Ze  + Ca(HCO₃)₂ → 2NaHCO₃ + CaZe
Na₂Ze  + Mg(HCO₃)₂ → 2NaHCO₃ + MgZe
Na₂Ze  + CaSO₄  → Na₂SO₄ + CaZe
Na₂Ze  + MgSO₄ → Na₂SO₄ + MgZe

When all sodium ions are replaced by calcium and magnesium ions, the zeolite becomes inactive. Then the zeolite needs to be regenerated. Brine solutions are passing through the bed of inactivated zeolite. The following reactions are taken place and form Na₂Ze.

CaZe + 2NaCl → Na₂Ze + CaCl₂
MgZe + 2NaCl → Na₂Ze + MgCl₂

The softening water by this process is used for laundry process and cannot be used for boiler purpose. Because this water softening system contains NaHCO₃ in the water; when this water is heated, it produces CO₂ which is corrosive for boilerplates.

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