Water desalination by cationic and anionic exchange resins - regenerating resins using ammonia and magnesium oxide with nil nett consumption

摘要

Water is desalinated by passing through a cationic exchange resing and an anionic exchange resin, pref. in that order. The anionic resin is regenerated with ammonia soln. to form also ammonium chloride soln. which is treated with magnesium oxide to form ammonia, which is reused, and magnesium chloride; evapn. of the MgCl2 soln., and heating gives MgO, which is re-used, and hydrogen chloride, which is dissolved in water. The HCl soln. is then used to regenerate the cationic resin and form also a sodium chloride soln. which is sepd. The MgO treatment is pref. carried out at 60-100 degrees C, partic. 80 degrees C and the MgCl2 heating at 180-1,000 degrees, partic, 350-700 degrees C. Used for purifying brackish water contg. 1-35 g./1. of NaCl pref. is not 30g./-1. The simple process gives high purity water and requires little or no chemicals for the resin regeneration.