Process for treating aluminum ores

Claim 1

IN A PROCESS FOR TREATING ALUMINA- AND SILICA-CONTAINING MINERALS SUCH AS BAUXITE AND THE LIKE BY THE STEPS OF DIGESTING THE AFORESAID MINERAL IN AN ALKALINE MEDIUM, SO AS TO OBTAIN A SODIUM ALUMINATE SOLUTION AND AN UNDISSOLVED RESIDUE WHICH CONTAINS SODIUM OXIDE BOUND IN WATER-INSOLUBLE FORM TO THE ALUMIA AND SILICA THEREIN, AND SEPARATING THE SOLUTION FROM THE RESIDUE, THE IMPROVEMENT WHICH CONSISTS ESSENTIALLY OF: (1) WASHING THE RESIDUE TO REDUCE ITS SODIUM ALUMINATE CONTENT, (2) SUSPENDING SAID RESIDUE IN A WEAKLY ALKALINE AQUEOUS SODIUM HYDROXIDE SOLUTION HAVING A CONCENTRATION OF UP TO 50 GRAMS NA2O PER LITER AND A CONCENTRATION OF LESS THAN 30 GRAMS OF DISSOLVED AL2O3 PER LITER, (3) ADDING LIME TO THE AQUEOUS SUSPENSION IN A RATIO OF 2.5-5 MOLS LIME PER MOL SODIUM OXIDE BOUND IN WATERINSOLUBLE FORM TO THE ALUMINA AND SILICA IN THE RESIDUE, THEREBY SOLUBILIZING THE SODIUM OXIDE BOUND IN WATER-INSOLUBLE FORM IN THE RESIDUE, WITHOUT SOLUBILIZING SUBSTANTIAL AMOUNTS OF ALUMINA THEREFROM, (4) SEPARATING THE RESULTING AQUEOUS SOLUTION CONTAINING DISSOLVED SODIUM OXIDE FROM THE STILL UNDISSOLVED MATTER.