Preparation of high purity magnesium oxide from magnesium salt solutions

Claim 1

A METHOD FOR THE PREPARATION OF HIGH PURITY MAGNESIUM OXIDE FROM A WATER-SOLUBLE MAGNESIUM SALT COMPRISING: (A) ADDING A CALCIUM ION SEQUESTERING AGENT TO AN AQUEOUS SOLUTION OF A MAGNESIUM SALT FEED MATERIAL; (B) ADDING AN AQUEOUS BASIC SOLUTION SELECTED FROM THE GROUP CONSISTING OF AQUEOUS ALKALI METAL HYDROXIDES AND AMMONIUM HYDROXIDE TO SAID MIXTURE SO AS TO RAISE THE PH OF SAID MIXTURE TO AT LEAST 11.0 THEREBY PRECIPITATING MAGNESIUM HYDROXIDE; (C) SEPARATING SAID MAGNESIUM HYDROXIDE FROM THE RESIDUAL AQUEOUS LIQUOR; (D) DISSOLVING SAID MAGNESIUM HYDROXIDE IN AN AQUEOUS SOLUTION OF A MINERAL ACID THUS FORMING A CORRESPONDING MAGNESIUM SALT SOLUTION; (E) ADDING AN AQUEOUS SOLUTION OF A SOLUBLE SALT OF A METAL SELECTED FROM THE GROUP CONSISTING OF IRON AND ALUMINUM TO THE MAGNESIUM SALT SOLUTION; (F) ADDING AN AQUEOUS BASIC SOLUTION SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL HYDROXIDES AND AMMONIUM HYDROXIDE TO SAID SOLUTION THEREBY RAISING THE PH OF SAID SOLUTION TO AT LEAST 8 AND NOT GREATER THAN ABOUT 9 THEREBY PRECIPITATING OUT SAID HYDROXIDE OF THE METAL SALT; (G) REMOVING THE INSOLUBLES FROM SAID SOLUTION; (H) PASSING THE SUBSTANTIALLY SOLID FREE SOLUTION THROUGH AN ION EXCHANGE RESIN BED, SAID RESIN BED HAVING A STRONGER AFFINITY FOR ALUMINUM AND IRON IONS THAN FOR MAGNESIUM IONS; (I) ADDING TO SAID SOLUTION FROM RESIN BED, A COMPOUND SELECTED FROM THE GROUP CONSISTING OF SODIUM OXALATE, POTASSIUM OXALATE, AMMONIUM OXALATE, SODIUM LACTATE, POTASSIUM LACTATE, AMMONIUM LACTATE, SODIUM CARBONATE, POTASSIUM CARBONATE, AND AMMONIUM CARBONATE, IN AN AMOUNT SUFFICIENT TO PRECIPITATE FROM SOLUTION THE CORRESPONDING MAGNESIUM SALT; (J) SEPARATING SAID PRECIPITATED MAGNESIUM SALT FROM SAID SOLUTION; AND (K) CALCINING SAID MAGNESIUM SALT THEREBY PRODUCING HIGH PURITY MAGNESIUM OXIDE.

Claim 2

A METHOD FOR THE PREPARATION OF HIGH PURITY MAGNESIUM OXIDE FROM A WATER-SOLUBLE MAGNESIUM SALT COMPRISING: (A) ADDING A CALCIUM ION SEQUESTERING AGENT TO AN AQUEOUS SOLUTION OF A MAGNESIUM SALT FEED MATERIAL; (B) ADDING AN AQUEOUS BASIC SOLUTION SELECTED FROM THE GROUP CONSISTING OF AQUEOUS ALKALI METAL HYDROXIDES AND AMMONIUM HYDROXIDE TO SAID MIXTURE SO AS TO RAISE THE PH OF SAID MIXTURE TO AT LEAST 11.0 THEREBY PRECIPITATING MAGNESIUM HYDROXIDE; (C) SEPARATING SAID MAGNESIUM HYDROXIDE FROM THE RESIDUAL AQUEOUS LIQUOR; (D) DISSOLVING SAID MAGNESIUM HYDROXIDE IN AN AQUEOUS SOLUTION OF A MINERAL ACID THUS FORMING A CORRESPONDING MAGNESIUM SALT SOLUTION; (E) ADDING AN AQUEOUS SOLUTION OF A SOLUBLE SALT OF A METAL SELECTED FROM THE GROUP CONSISTING OF IRON AND ALUMINUM TO THE MAGNESIUM SALT SOLUTION; (F) ADDING AN AQUEOUS BASIC SOLUTION SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL HYDROXIDES AND AMMONIUM HYDROXIDE TO SAID SOLUTION THEREBY RAISING THE PH OF SAID SOLUTION TO AT LEAST 8 AND NOT GREATER THAN ABOUT 9 THEREBY PRECIPITATING OUT SAID HYDROXIDE OF THE METAL SALT; (G) REMOVING THE INSOLUBLES FROM SAID SOLUTION; (H) PASSING THE SUBSTANTIALLY SOLID FREE SOLUTION THROUGH AN ION EXCHANGE RESIN BED, SAID RESIN BED HAVING A STRONGER AFFINITY FOR ALUMINUM AND IRON IONS THAN FOR MAGNESIUM IONS; (I) ADDING TO SAID SOLUTION FROM RESIN BED, A COMPOUND SELECTED FROM THE GROUP CONSISTING OF SODIUM OXALATE, POTASSIUM OXALATE, AMMONIUM OXALATE, SODIUM LACTATE, POTASSIUM LACTATE, AMMONIUM LACTATE, SODIUM CARBONATE, POTASSIUM CARBONATE, AND AMMONIUM CARBONATE, IN AN AMOUNT SUFFICIENT TO PRECIPITATE FROM SOLUTION THE CORRESPONDING MAGNESIUM SALT; (J) SEPARATING SAID PRECIPITATED MAGNESIUM SALT FROM SAID SOLUTION; AND (K) CALCINING SAID MAGNESIUM SALT THEREBY PRODUCING HIGH PURITY MAGNESIUM OXIDE.