method for making an ammonium phosphate fertilizer having low cadmium content

摘要

The invention relates to a method for the manufacture of an ammonium phosphate fertilizer from an aqueous phosphoric acid solution which has less than 50% concentration of p2o5 and is obtained by treatment of wet phosphate ore. said phosphoric acid containing traces of cadmium. said method includes the following steps: (a) neutralizing said phosphoric acid solution (1) with ammonia (3) to an n / w molar ratio of between 0.1 and 0.8; (b) reacting said partially neutralized solution (4) with a sulfide source (6) to form a cadmium sulfide precipitate (9); (c) separating said precipitate (9) to obtain a refined solution of ammonium phosphoric acid (10); and (d) ammoniating and granulating said refined solution (10) to form said fertilizer (12).