Solvent extraction process for recovering tungsten values from contaminated aqueous solutions

Claim 1

IN A PROCESS FOR RECOVERY OF TUNGSTEN VALUES FROM MOLYBDENUM AND SILICON CONTAMINATED AQUEOUS SOLUTIONS OF TUNGSTEN WHEREIN SAID TUNGSTEN IS SEPARATED FROM OTHER ORE CONTAMINANTS BY EXRACTION WITH AN AMINE DISSOLVED IN AN ORGANIC LIQUID SOLVENT, THE IMPROVEMENT COMPRISING THE SEQUENTIAL STEPS OF FIRST TREATING SAID CONTAMINATED AQUEOUS TUNGSTEN BEARING SOLUTION, PRIOR TO THE AMINE ORGANIC SOLVENT EXTRACTION STEP, TO SELECTIVELY REMOVE MOLYBDENUM THEREFROM BY ADJUSTING THE PH OF SAID MOLYBDENUM CONTAMINATED AQUEOUS SOLUTION TO AT LEAST ABOUT 8, ADDING TO SAID AQUEOUS SOLUTION ESSENTIALLY AT LEAST 170 PERCENT OF THE AMOUNT OF ALKALI SULFIDE STOICHIOMETRICALLY REQUIRED TO CONVERT THE MOLYBDENUM CONTAMINANT IN SAID AQUEOUS SOLUTION TO THE THIOMOLYBDATE COMPLEX ION, DIGESTING SAID AQUEOUS SOLUTION AT ELEVATED TEMPERATURE UNTIL THE MOLYBDENUM CONTAMINANT IS CONVERTED TO THE THIOMOLYBDATE COMPLEX ION; ACIDIFYING SAID AQUEOUS SOLUTION TO A PH BELOW ABOUT 3.0 WHEREBY THE MOLYBDENUM CONTAMINANT IS PRECIPITATED AS MOLYBDENUM TRISULFIDE, SEPARATING THE MOLYBDENUM TRISULFIDE PRECIPITATE FROM THE AQUEOUS MOLYBDENUM FREE SOLUTION, CONTACTING THE AQUEOUS SOLUTION WITH SAID AMINE DISSOLVED IN AN ORGANIC LIQUID SOLVENT THEREBY EXTRACTING SAID TUNGSTEN AND SILICON CONTAMINANT INTO THE ORGANIC SOLVENT LIQUID PHASE SEPARATING THE ORGANIC SOLVENT PHASE AND THE AQUEOUS PHASE, CONTACTING SAID ORGANIC SOLVENT PHASE WITH AN AQUEOUS SOLUTION OF AMMONIUM HYDROXIDE AND STRIPPING SAID TUNGSTEN AND SILICON FROM THE ORGANIC PHASE INTO SAID AUQEOUS SOLUTION; SEPARATING SAID ORGANIC PHASE AND AQUEOUS SOLUTION, ADJUSTING AND MAINTAINING THE CONCENTRATION OF AMMONIUM HYDROXIDE IN THE SILICON-CONTAMINATED TUNGSTEN-CONTAINING AQUEOUS AMMONIUM HYDROXIDE SOLUTION TO AT LEAST ABOUT 2 MOLAR, ADJUSTING AND MAINTAINING THE TEMPERATURE OF THE AQUEOUS SILICON-CONTAMINATED AMMONIUM HYDROXIDE SOLUTION TO AT LEAST 50*C., DIGESTING THE AQUEOUS SILICON CONTAMINATED AND TUNGSTENBEARING AMMONIUM HYDROXIDE SOLUTION AT SAID TEMPERATURE WHILE MAINTAINING A CONCENTRATION OF AMMONIUM HYDROXIDE IN SAID SILICON CONTAMINATED SOLUTION OF AT LEAST 2 MOLAR TO CAUSE SELECTIVE PRECIPITATION OF SILICON OXIDE THEREFROM AND CONCENTRATING THE RESULTANT TUNGSTEN-BEARING SOLUTION TO PRECIPITATE AMMONIUM PARATUNGSTATE SUBSTANTIALLY FREE OF SILICON AND MOLYBDENUM THEREFROM.