Water treatment

摘要

The invention provides a method of reducing the sodium content of a water containing dissolved sodium ions, particularly a water with a sodium ion content of at least 100 ppm. Examples of such waters are effluents such as acid mine drainage and river waters. The method includes the steps of:
(i) removing sodium, calcium and magnesium ions from the water by contacting the water with a cation exchange resin/s to capture sodium, calcium and magnesium ions thereon,(ii) treating the cation exchange resin/s of step (i) with nitric acid to produce an eluant containing sodium ions, calcium ions, magnesium ions nitrate ions and nitric acid,(iii) adding a carbonate to the eluant to precipitate the calcium and magnesium ions as calcium and magnesium carbonates;(iv) separating the precipitated carbonates from the eluant; and(v) treating the eluant from step (iv) to obtain a sodium and/or potassium nitrate product.

主权项

1. A method of treating a water containing dissolved sodium, calcium and magnesium ions including the steps of:
(i) removing sodium, calcium and magnesium ions from the water by contacting the water with a cation exchange resin(s) to capture sodium, calcium and magnesium ions thereon, wherein the cation exchange resin(s) on which the calcium and magnesium ions are captured is the same as on which the sodium ions are captured, (ii) treating the cation exchange resin(s) of step (i) with nitric acid to produce an eluant containing sodium ions, calcium ions, magnesium ions, nitrate ions and nitric acid, (iii) adding potassium carbonate or sodium carbonate to the eluant to precipitate the calcium and magnesium ions as calcium carbonate and magnesium carbonate; (iv) separating the precipitated carbonates from the eluant; and (v) treating the eluant from step (iv) to obtain a sodium and/or potassium nitrate product, wherein the treatment of the eluant in step (v) includes the steps of: (vi) adding potassium chloride to the eluant of step (v), (vii) treating the eluant of step (vi) to cause sodium ions in the eluant to crystallize as sodium chloride, (viii) separating the crystallised sodium chloride from the eluant of step (vii) to produce crystals of the sodium chloride and an eluant containing potassium nitrate in solution, and (ix) recovering potassium nitrate from the eluant of step (viii).