Method for the treatment of waste acid resulting from titanium dioxide production

Claim 1

A PROCESS FOR PRODUCING AMMONIUM ALUM, AMMONIUM SULFATE, CRYSTALLINE IRON OXIDE AND METAL HYDROXIDE, EASILY SEPARABLE BY FILTRATION AND CONSISTING ESSENTIALLY OF FROM ONE TO FOUR MEMBERS SELECTED FROM THE GROUP CONSISTING OF THE HYDROXIDES OF ALUMINUM, TITANIUM, VANADIUM AND CHROMIUM, WHICH COMPRISES ADDING FROM ONE TO TWO MEMBERS SELECTED FROM THE GROUP CONSISTING OF AMMONIA AND AMMONIUM SULFATE TO WASTE ACID LIQUOR DERIVED FROM HYDROLSIS OF TIANIUM SULFATE SOLUTION, UNTIL THE AMONIUM SULFATE CONCENTRATION REACHES 40 TO 120 GRAMS PER LITER, COOLING THE MIXTURE TO ABOVE 5* TO 20* C. TO CRYSTALLIZE AMMONIUM ALUM THEREFROM, AND SEPARATING SAID ALUM FROM THE RESULTING AQUEOUS SOLUTION OF FERROUS SULFATE, INTRODUCING THE LATTER SOLUTION AND AMMONIA INTO AN AQUEOUS LIQUOR SEEDED WITH SAID METAL HYDROXIDE WHILE STIRRING, HEATING AT A TEMPERATURE OF FROM ABOUT 60* C TO THE BOILING POINT AND REMOVING A PORTION OF THE RESULTING MIXTURE CORRESPONDING TO THE AMOUNT OF THE INTRODUCED AQUEOUS SOLUTION OF FERROUS SULFATE AND AMMONIA, WHILE MAINTAINING A CONSTANT PH WITHIN THE RANGE OF 4.5 TO 7.0 THEREIN, THEREBY STIMULATING THE GROWTH OF THE HYDROXIDE PARTICLES IN SAID PORTION, SEPARTING SAID HYDROXIDR FROM THE REMOVED PORTION OF THE MIXUTRE, INTRODUCING AMMONIA INTO THE RESULTING MOTHER LIQUOR SO AS TO MAINTAIN A PH OF 3.0 TO 9.0 AND CONCURRENTLY FEEDING GAS CONTAINING MOLECULAR OXYGEN IN A FINELY DISPERSED FORM THEREINTO, THEREBY PRODUCING CRYSTALLINE IRON OXIDE AND AN AMMONIUM SULFATE SOLUTION, AND FINALLY SEPARATING THE CRYSTALLINE IRON FROM THE AMMONIUM SULFATE SOLUTION, AND FINALLY SEPARATING THE CRYSTALLINE IRON OXIDE FROM THE AMMONIUM SULFATE SOLUTION.