Method for manufacturing an ammonium phosphate fertilizer having low cadmium content
Abstract:
The invention relates to a method for manufacturing an ammonium phosphate fertilizer from a phosphoric acid aqueous solution that has less than 50% P2O5 concentration and is obtained by wet phosphate ore treatment, said phosphoric acid containing traces of cadmium, comprising the following steps: (a) neutralizing said phosphoric acid solution (1) with ammonia (3) up to a molar ratio N/P of between 0.1 and 0.8, (b) reacting said partially neutralized solution (4) with a sulfide source (6) so as to form a cadmium sulfide precipitate (9), (c) separating said precipitate (9) so as to obtain a refined ammoniated phosphoric acid solution (10), (d) ammoniating and granulating said refined solution (10) so as to form said fertilizer (12).
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