Explain demineralization of water by ion exchange method.
1 Answer
  1. Demineralization is the removal of minerals and nitrate from the water
  2. Ion exchange is primarily used for the removal of hardness ions like magnesium and calcium for water demineralization.
  3. Ion exchange method
    • Inorganic removal is accomplished through the adsorption of contaminant ions onto a resin exchange medium
    • One ion is substituted for another on the charged surface of the mediu, that is usually a plastic resin
    • This type of surface is designed as either cationic - positively charged or anionic - negatively charged. The medium is saturated with exchangeable ions before the treatment operations.
    • The contaminant ions during ion exchange, replace the regenerant ions because they are preferred by the exchange medium. When no ions are left to take the place of the contaminant ions, the medium is regenerated with a suitable solution that saturates the medium with the appropriate ions.
    • Since there is a required down time, the regeneration cycles are done only once per day.
    • Calculation of the breakthrough time for an ion exchange unit requires knowing the resin exchange capacity, influent contaminant concentration and the desired effluent quality.
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