Process of extracting alumina from raw calcium aluminates

Claim 1

A METHOD OF PRODUCING SUBSTANTIALLY PURE ALUMINA HAVING A LOW SILICA CONTENT FROM CALCIUM ALUMINATE CONTAINING SILICA AS AN IMPURITY, COMPRISING THE STEPS OF LEACHING AN ANHYDROUS CALCIUM ALUMINATED SELECTED FROM THE GROUP CONSISTING OF CAO.AL2O3, 3CAO.AL2O3 AND 5CAO.3AL2O, WITH A DILUTE AQUEOUS SOLUTION OF AN INORGANIC ALKALI METAL SALT THE ALKALINE CATIONS OF WHICH SALT REACT WITH THE AL2O3 OF SAID CALCIUM ALUMINATE OF FORM SOLUBLE ALKALINE ALUMINATE AND THE ANIONS OF WHICH SALT REACT WITH THE CAO OF SAID CALCIUM ALUMINATE TO FORM A CALCIUM COMPOUND LESS SOLUBLE THAT SAID CALCIUM ALUMINATE, SAID ALKALINE CATIONS BEING IN SAID SOLUTION IN AN AMOUNT MOLECULARLY EQUIVALENT TO BETWEEN 3-18.3 GRAMS NA2O PER LITER; ADJUSTING THE AMOUNT OF SAID CATIONS AND SAID ANIONS IN SAID SOLUTION WITH RESPECT TO SAID CALCIUM ALUMINATE THE CORREPOND TO THE EQUIVALENT OF BETWEEN 1-1.6 MOLES OF NA2O PER MOLE OF AL2O3 OF SAID CALCIUM ALUMINATE AND TO HAVE PRESENT LESS ANIONOS THAT THE AMOUNT NECESSARY TO REACT WITH ALL OF SAID CAO OF CALCIUM ALUMINATE SO AS TO FORN AQUEOUS ALUMINATE SOLUTION CONTAINING CALCIUM ALUMINATE IN SOLUTION, SAID CALCIUM ALUMINATE IN SOLUTION PREVENTING THE DISSOLUTION OF SILICA IN SOLUTION, THEREBY OBTAINING AN AQUEOYS ALUMINATE SOLUTION SUBSTANTIALLY FREE OF SILICA; AND RECOVERING SUBSTANTIALLY PURE SILICA-FREE ALUMINA FROM SAID SOLUTION.

Claim 2

A METHOD OF PRODUCING SUBSTANTIALLY PURE ALUMINA HAVING A LOW SILICA CONTENT FROM CALCIUM ALUMINATE CONTAINING SILICA AS AN IMPURITY, COMPRISING THE STEPS OF LEACHING AN ANHYDROUS CALCIUM ALUMINATED SELECTED FROM THE GROUP CONSISTING OF CAO.AL2O3, 3CAO.AL2O3 AND 5CAO.3AL2O, WITH A DILUTE AQUEOUS SOLUTION OF AN INORGANIC ALKALI METAL SALT THE ALKALINE CATIONS OF WHICH SALT REACT WITH THE AL2O3 OF SAID CALCIUM ALUMINATE OF FORM SOLUBLE ALKALINE ALUMINATE AND THE ANIONS OF WHICH SALT REACT WITH THE CAO OF SAID CALCIUM ALUMINATE TO FORM A CALCIUM COMPOUND LESS SOLUBLE THAT SAID CALCIUM ALUMINATE, SAID ALKALINE CATIONS BEING IN SAID SOLUTION IN AN AMOUNT MOLECULARLY EQUIVALENT TO BETWEEN 3-18.3 GRAMS NA2O PER LITER; ADJUSTING THE AMOUNT OF SAID CATIONS AND SAID ANIONS IN SAID SOLUTION WITH RESPECT TO SAID CALCIUM ALUMINATE THE CORREPOND TO THE EQUIVALENT OF BETWEEN 1-1.6 MOLES OF NA2O PER MOLE OF AL2O3 OF SAID CALCIUM ALUMINATE AND TO HAVE PRESENT LESS ANIONOS THAT THE AMOUNT NECESSARY TO REACT WITH ALL OF SAID CAO OF CALCIUM ALUMINATE SO AS TO FORN AQUEOUS ALUMINATE SOLUTION CONTAINING CALCIUM ALUMINATE IN SOLUTION, SAID CALCIUM ALUMINATE IN SOLUTION PREVENTING THE DISSOLUTION OF SILICA IN SOLUTION, THEREBY OBTAINING AN AQUEOYS ALUMINATE SOLUTION SUBSTANTIALLY FREE OF SILICA; AND RECOVERING SUBSTANTIALLY PURE SILICA-FREE ALUMINA FROM SAID SOLUTION.