Why Zeolite softner cannot be used for softening Water containing Fe and Mn salts
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If the supply of water is turbid, the suspended matte must be removed (by coagulation, filtration, etc.), before the water is admitted to the zeolite bed; otherwise the turbidity will clog the pores of zeolite bed, thereby making it inactive.If water contains large quantities of coloured ions such as Mn2+ and Fe2+,they must be removed first, because these ions produce manganese and iron zeolites, which cannot be easily regenerated.Mineral acids, if present in water, destroy the zeolite bed and, therefore, they must be neutralized with soda, before admitting the water to the zeolite softening plant.
Disadvantages
The treated-water contains more sodium salts than in lime-soda process.The method only replaces Ca2+and Mg2+ions by Na+ ions, but leaves all the acidic ions like HCO3 and CO3 2- as such in the softened water. When such softened water (containing NaHCO3, Na2CO3 etc.) is used in boilers for steam generation, sodium bicarbonate decomposes producing CO2, which causes corrosion ; and sodium carbonate hydrolysis to sodium hydroxide, which causes caustic embrittlement.High turbidity water cannot be treated efficiently by this method, because fine impurities get deposited on the zeolite bed, thereby creating problem for its working.
If the supply of water is turbid, the suspended matte must be removed (by coagulation, filtration, etc.), before the water is admitted to the zeolite bed; otherwise the turbidity will clog the pores of zeolite bed, thereby making it inactive.If water contains large quantities of coloured ions such as Mn2+ and Fe2+,they must be removed first, because these ions produce manganese and iron zeolites, which cannot be easily regenerated.Mineral acids, if present in water, destroy the zeolite bed and, therefore, they must be neutralized with soda, before admitting the water to the zeolite softening plant.
Disadvantages
The treated-water contains more sodium salts than in lime-soda process.The method only replaces Ca2+and Mg2+ions by Na+ ions, but leaves all the acidic ions like HCO3 and CO3 2- as such in the softened water. When such softened water (containing NaHCO3, Na2CO3 etc.) is used in boilers for steam generation, sodium bicarbonate decomposes producing CO2, which causes corrosion ; and sodium carbonate hydrolysis to sodium hydroxide, which causes caustic embrittlement.High turbidity water cannot be treated efficiently by this method, because fine impurities get deposited on the zeolite bed, thereby creating problem for its working.
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