Method for etching a phosphate source using acid

A process of acid attack of a phosphate source including calcium for the production of a phosphate-based purified compound comprising the steps of:

• a) an acid attack using sulphuric acid of said phosphate source, during a predetermined time period ranging from 20 to 180 minutes with a formation of a first suspension containing a first solid matter and a first liquid phase in which the first solid matter is in suspension, said first solid matter comprising at least calcium phosphate and impurities, said first liquid phase comprising phosphoric acid and dissolved monocalcium phosphate, said attack being conducted in input conditions wherein the molar ratio of the sulphate from the sulphuric acid and from the phosphate source to the calcium present in the phosphate source ranges from 0.6 to 0.8 and the P2O5 content is of less than 6% by weight,
• b) a first filtration of said first slurry with a separation of said first solid matter from said first liquid phase, and
• c) a retrieval from said first liquid phase of a purified phosphate-based compound.