SOURCE OF PHOSPHATE FOR AGRICULTURE AND THE FOOD INDUSTRY

Abstract

SOURCE OF PHOSPHATE FOR AGRICULTURE AND THE FOOD INDUSTRY. The invention relates to a phosphate salt in solid form with the formula Mn(HPO4)y.zH2O, wherein M is Na, K, NH4, n = 2, and y = 1; or M is Ca, n = 1, y = 1; or M is Al or Fe, n = 2, y = 3; and wherein z is 0, 1 or 2; said phosphate salt having a phosphate content expressed as P2O5 content between 30 and 50% by weight of the phosphate salt, distinguished by having a cadmium content of less than 0.40 ppm.

Description

[001] Field of technique

[002] The present invention relates to a phosphate salt exhibiting a high degree of purity, i.e., a reduced presence of impurities, mainly radioactive impurities and / or those originating from heavy metals or transition metals of the periodic table of elements. The present invention also relates to a process for preparing this phosphate salt and its use in a formulation or composition intended for agriculture or the food industry, or for the preparation thereof. Preferably, said phosphate salt can be used for the preparation of single superphosphate (SSP), triple superphosphate (TSP), monoammonium phosphate (MAP), diammonium phosphate (DAP), phosphoric acid, NPK fertilizer, monocalcium phosphate (MCP) or monodicalcium phosphate (MDCP).

[003] Technological background of the invention

[004] Phosphate salts are regularly used in fertilizer compositions such as manures or in feed compositions to facilitate the supply of phosphorus, respectively, to soils or in animal or human food.

[005] In the agricultural field, fertilizers are, however, compounds that can cause serious contamination to the environment, especially to cultivated soils. Mineral fertilizers, given their intensive use to increase the supply of nutrients such as nitrogen or phosphorus, can contaminate soils for a long time if they contain an excessive amount of impurities. Phosphates constitute a privileged source for the introduction of phosphorus into the soil. These are generally produced or originate from mineral phosphate, which naturally contains high levels of metals such as cadmium, lead, mercury, uranium, chromium, or even arsenic. The dispersion of these toxic elements in cultivated soils will favor long-term environmental pollution of said cultivated soils. Petition 870160033568, dated 04 / 07 / 2016, page 6 / 49 2 / 42 Furthermore, some of these elements can be found in foods grown in these soils, in the water, and ultimately in the human or animal body. Several gastrointestinal, pulmonary, or renal diseases are known to be caused by the excessive presence of toxic elements.

[006] Among the phosphate salts currently used in agriculture are single superphosphate (SSP), triple superphosphate (TSP), or calcium phosphate salts, such as dicalcium phosphate (DCP). Dicalcium phosphate is prepared from phosphate ore. For example, the preparation of phosphate salts by means of a process comprising the following steps is known from document no. WO 2004 / 002888:

[007] - at least one attack on phosphate ore by a first aqueous solution of hydrochloric acid, with formation of an attack liquor,

[008] - a first separation, in the attack liquor, between an insoluble solid phase containing impurities and a separated aqueous phase comprising phosphate ions, chloride ions and calcium ions in solution,

[009] - an extraction of an aqueous solution containing phosphate ions, chloride ions and calcium ions by an organic extraction agent, to form an aqueous extraction phase comprising chloride ions and calcium ions and an organic extraction phase comprising chloride ions and calcium ions and an organic extraction phase containing phosphoric acid, and

[010] - a re-extraction of the organic extraction phase by an aqueous re-extraction agent, to isolate an aqueous re-extraction phase containing phosphate ions, as well as, optionally, a concentration of the aqueous re-extraction phase to form an aqueous solution of pure phosphoric acid.

[011] For this procedure carried out at room temperature, a dicalcium phosphate is obtained which has a P2O5 content of 36.27% by weight and a Ca content of 28.9% by weight. The impurity content, mainly heavy metals including cadmium, arsenic, nickel or lead, constitutes, respectively, 0.65 ppm, 2.01 ppm, 3.5 ppm and 3.7 ppm. The use of this salt in the field of fertilizers or livestock feed is considered. Petition 870160033568, dated 04 / 07 / 2016, page 7 / 49 3 / 42

[012] It is also known from document noWO 2005 / 066070 another process for attacking phosphate ore at room temperature to form a dicalcium phosphate precipitate. The process comprises especially the steps of:

[013] - a digestion of phosphate ore by an aqueous solution of hydrochloric acid with the formation of an attack liquor consisting of an aqueous phase, in which calcium phosphate is in solution, and an insoluble solid phase containing impurities,

[014] - a first separation between the insoluble solid phase and the aqueous phase of the attack liquor,

[015] - a prior neutralization of an aqueous medium containing calcium phosphate in solution to a first pH lower than the pH at which a significant portion of that calcium phosphate precipitates in the form of calcium monohydrogen phosphate (DCP), with precipitation of impurities,

[016] - isolation of precipitated impurities from the previously neutralized aqueous medium,

[017] - a further neutralization of said aqueous medium previously neutralized to a second pH higher than the first pH mentioned above, with precipitation of DCP, and

[018] - a second separation between the subsequently neutralized aqueous medium, which is an aqueous solution of calcium chloride, and the precipitated DCP.

[019] The applicant specifically noted that the precipitated DCP obtained by this process contained a cadmium content of 0.46 ppm.

[020] It is also known from document noFR 2115244 a process for preparing precipitated DCP produced from an attack on phosphate ore by dilute hydrochloric acid. The insoluble materials resulting from this reaction are separated while the liquid phase is subjected to two neutralization steps in the presence of a basic compound allowing the precipitation of DCP. The applicant noted that the heavy metal contents Petition 870160033568, dated 04 / 07 / 2016, page 8 / 49 4 / 42 in the DCP originating from this process were higher than in the DCP originating from the process of document no. WO 2005 / 066070 described above. The cadmium content was specifically 1.3 ppm.

[021] The levels of radioactive elements in several samples of dicalcium phosphate (DCP) are also known from Casacuberta et al., Journal of hazardous materials, 2009, 170, pages 814 to 823. The DCP samples 1-4, 9 and 10 mentioned in that document were not prepared by digestion of phosphate ore in the presence of hydrochloric acid followed by neutralization of the resulting aqueous phase to precipitate the DCP. The levels of U234, U238 and Pb210 are high, respectively, on the order of 900 Bq / kg, 1,100 Bq / kg and 2,000 Bq / kg, that is, almost 4,000 Bq / kg in these three radioactive elements alone. Casacuberta et al. They explain that these high levels of uranium and lead are due to the solubility of these elements in an acidic medium and their precipitation in the form of salts, along with the precipitation of dicalcium phosphate during its preparation. The cadmium content in these samples varies between 0.44 ppm and 6.5 ppm.

[022] It is also known from Taro et al. (Japan Kokai 74 / 148 / 685 and 74 / 148 / 686) the decomposition in an acidic medium of phosphate ore by a hydrochloric acid solution for the preparation of tricalcium phosphate. Hiroaki et al. also described the production of calcium hydrogen phosphate from phosphate rock (Japan Kokai 78 / 101959). The treatment of the rock with a hydrochloric acid solution is carried out at 70 °C for 3 hours. Raman Gopaliyengar et al. also described the treatment of phosphate rock with a concentrated hydrochloric acid solution followed by neutralization with an ammonium salt (Indian 116, 950).

[023] Under certain conditions, the magnesium content must also be controlled. The magnesium present in dicalcium phosphate (DCP) comes from the phosphate source used to produce DCP. An excessively high magnesium content in the phosphate source, exceeding 1% by weight of magnesium in the phosphate source, causes problems in the treatment of the liquor. Petition 870160033568, dated 04 / 07 / 2016, page 9 / 49 5 / 42 attack during the leaching of the phosphate source by an acid. Phosphate salts are therefore generally prepared from a phosphate source that is low in magnesium (less than 1% by weight in the phosphate source).

[024] The levels of radioactive elements or metals in phosphate salts, such as dicalcium phosphate, can be reduced by limiting the risks associated with contamination of soils and foods grown in those soils by using a wide variety of phosphate sources.

[025] The present invention aims to provide a phosphate salt suitable for use in a formulation or composition intended for agriculture or the food industry, or suitable for use in the preparation of a formulation or composition intended for agriculture or the food industry, in which at least part of the levels of radioactive elements or metallic impurities consisting of heavy metals or transition metals are reduced. The present invention also aims to provide a flexible process for preparing this phosphate salt, i.e., being able to use a wide range of phosphate sources regardless of their quality.

[026] Summary of the invention

[027] According to a first aspect, the present invention relates to a phosphate salt in solid form of formula Mn(HPO4)y.zH2O wherein M is Na, K, NH4, n = 2, and y = 1; or M is Ca, n = 1, y = 1; or M is Al or Fe, n = 2, y = 3; and wherein z is 0, 1 or 2; said phosphate salt has a phosphate content expressed as P2O5 content between 30 and 50% by weight of the phosphate salt.

[028] Said phosphate salt according to the present invention may have a cadmium content of less than 0.4 ppm. Said phosphate salt according to the present invention may have a magnesium content of less than or equal to 20 ppm, advantageously less than 15 ppm, preferably less than 10 ppm.

[029] The said phosphate salt according to the present invention may, moreover, have a Po210 content of less than 500 Bq / kg, advantageously less than 300 Bq / kg, preferably less than 200 Bq / kg. Petition 870160033568, dated 04 / 07 / 2016, page 10 / 49 6 / 42

[030] Said phosphate salt according to the present invention may have an Ra226 content of less than 50 Bq / kg, advantageously less than 25 Bq / kg, preferably less than 10 Bq / kg, and particularly less than 5 Bq / kg.

[031] Preferably, said phosphate salt may have a uranium content of less than 1,500 Bq / kg, preferably less than 1,000 Bq / kg, particularly less than 800 Bq / kg. The uranium content is determined by the sum of the respective contents in U234, U235 and U238.

[032] The said phosphate salt may have a Pb210 content of less than 1,500 Bq / kg, advantageously less than 1,000 Bq / kg, preferably less than 800 Bq / kg, particularly less than 500 Bq / kg.

[033] The contents of uranium (U234, U235 and U238), Po210, Ra226 or magnesium or cadmium in said phosphate salt according to the invention are markedly reduced relative to equivalent phosphate salts of the prior art. Thus, as mentioned above, Casacuberta et al. described a series of DCP samples, obtained by a wet process, whose contents of uranium (U234 and U238), Po210, Pb210 and magnesium were, respectively, on the order of 2,000 Bq / kg, 1,000 Bq / kg, 2,000 Bq / kg and 200 ppm. Said phosphate salt according to the present invention may have one or more contents of radioactive elements mentioned in the present invention in combination with one or more contents of metals mentioned in the present invention. In addition to a low cadmium content, said phosphate salt may contain Po210, Pb210, U234, U235, U238, Ra226, Ra228, K40, Th228, Th230 or Th232 contents mentioned in this patent application.The content expressed with respect to a radioactive element, for example, a radionuclide, corresponds to the activity in Bq of the radionuclide per kg of the product considered, for example, per kg of phosphate salt according to the invention.

[034] According to a second aspect of the present invention, a process for preparing said phosphate salt is provided. The process is a wet and non-thermal process (i.e., by calcination of the ore of Petition 870160033568, dated 04 / 07 / 2016, page 11 / 49 7 / 42 phosphate). The process according to the present invention comprises the following steps: a) a digestion of a phosphate source by a first aqueous solution of hydrochloric acid with the formation of an attack liquor consisting of an aqueous phase comprising phosphate ions and chloride ions in solution, and a first insoluble solid phase containing impurities, b) a first separation between the aqueous phase comprising phosphate ions and chloride ions in solution and the first insoluble solid phase comprising impurities, (c) a neutralization of said aqueous phase comprising phosphate ions and chloride ions in solution at a pH sufficient for the formation of an aqueous medium comprising chloride ions and for the precipitation of phosphate ions in the form of said phosphate salt, (d) a second separation between said aqueous medium comprising chloride ions and said phosphate salt, distinguished by steps (a) and (b) being carried out at a temperature between 50 °C and 70 °C.

[035] Said phosphate salt has reduced levels of radioactive elements, such as uranium, polonium or Pb210, and metals, such as magnesium and cadmium, relative to the prior art due to carrying out steps (a) and (b) of the present process at a temperature between 50 °C and 70 °C.

[036] Step (a) of phosphate source digestion may have a duration of less than one hour, advantageously less than 30 minutes, preferably between 5 minutes and 20 minutes, particularly 15 minutes. The content of radioactive or metallic elements may also be controlled by this relatively short duration of phosphate source digestion.By controlling the temperature and / or digestion time of the phosphate source, the amount of impurities (radioactive elements or metals) dissolved in step a) is reduced, resulting in a fast and economically viable reaction.

[037] The duration of the neutralization performed in step c) may be less than Petition 870160033568, dated 04 / 07 / 2016, page 12 / 49 8 / 42 four hours, advantageously less than two hours, preferably less than one hour, particularly between 35 minutes and 50 minutes.

[038] Considering its purity, that is, especially due to its reduced content of radioactive elements, said phosphate salt according to the present invention can be used directly as one of the constituents of a composition intended for agriculture or a food composition. Said phosphate salt according to the present invention can also be used for the preparation of monoammonium phosphate or diammonium phosphate. Said phosphate salt according to the present invention can also be used for the preparation of a high-purity phosphoric acid, which has a particularly low content of radioactive elements. Said phosphate salt according to the present invention can also be used for the preparation of calcium sulfate or calcium chloride, which preferably has reduced levels of uranium Po210, Pb210e and / or cadmium.The said phosphate salt according to the present invention can also be used for the preparation of monocalcium phosphate or mono-dicalcium phosphate (MDCP).

[039] The present invention also provides compositions comprising said phosphate salt or one of the compounds mentioned above and prepared from said phosphate salt in accordance with the present invention.

[040] The process according to the present invention also allows the use of a low-quality phosphate source, that is, one that has a low phosphate content, expressed as a percentage by weight of P2O5 in the phosphate source, or that contains a high impurity content, contrary to the process described in the prior art.

[041] Brief description of the drawings

[042] Figure 1 represents a block diagram of the process for preparing said phosphate salt according to a particular embodiment of the present invention. Petition 870160033568, dated 04 / 07 / 2016, page 13 / 49 9 / 42

[043] Detailed description of the present invention

[044] According to the present invention, a phosphate salt depleted of metallic or radioactive impurities is provided. Said phosphate salt has a phosphate content expressed as P2O5 content between 30 and 50% by weight of the phosphate salt, preferably from 36 to 45% by weight of the phosphate salt. Said phosphate salt may be in solid form. Said phosphate salt may have the formula Mn(HPO4)y.zH2O, in which

[045] M is Na, K, NH4, n = 2, ey = 1; or

[046] M is Ca, n = 1, y = 1; or

[047] M is Al or Fe, n = 2, y = 3; and

[048] where z is 0, 1 or 2.

[049] Said phosphate salt according to the present invention may have a uranium content of less than 1,500 Bq / kg, preferably less than 1,000 Bq / kg, in particular less than 800 Bq / kg. The uranium content is determined by the respective contents of U234, U235 and U238. Said phosphate salt may have a U234 content of less than 800 Bq / kg, advantageously less than 600 Bq / kg, preferably less than 500 Bq / kg, in particular less than 400 Bq / kg. Said phosphate salt may have a U238 content of less than 900 Bq / kg, advantageously less than 700 Bq / kg, preferably less than 500 Bq / kg, in particular less than 400 Bq / kg. The said phosphate salt may have a uranium content of U235 of less than 100 Bq / kg, advantageously less than 75 Bq / kg, preferably less than 50 Bq / kg, in particular less than 20 Bq / kg.

[050] Said phosphate salt according to the present invention may have a Pb210 content of less than 1,500 Bq / kg, advantageously less than 1,000 Bq / kg, preferably less than 800 Bq / kg, in particular less than 500 Bq / kg.

[051] Said phosphate salt according to the present invention may have a Po210 content of less than 500 Bq / kg, advantageously less than 300 Bq / kg, preferably less than 200 Bq / kg, in particular less than 150 Bq / kg.

[052] Said phosphate salt according to the present invention may have a Th228 content of less than 100 Bq / kg, advantageously less than 50 Bq / kg, Petition 870160033568, dated 04 / 07 / 2016, p. 14 / 49 10 / 42 preferably, less than 25 Bq / kg, in particular, less than 10 Bq / kg. Said phosphate salt according to the present invention may have a Th230 content of less than 100 Bq / kg, advantageously less than 50 Bq / kg, preferably less than 25 Bq / kg, in particular, less than 10 Bq / kg. Said phosphate salt according to the present invention may have a Th232 content of less than 50 Bq / kg, advantageously less than 25 Bq / kg, preferably less than 10 Bq / kg, in particular, less than 1 Bq / kg. The said phosphate salt according to the present invention may have a thorium content, determined by the respective contents of Th230, Th228 and Th232, of less than 150 Bq / kg, advantageously less than 100 Bq / kg, preferably less than 50 Bq / kg, in particular less than 20 Bq / kg.

[053] Said phosphate salt according to the present invention may have an Ra226 content of less than 50 Bq / kg, advantageously less than 25 Bq / kg, preferably less than 10 Bq / kg, in particular less than 5 Bq / kg. Said phosphate salt according to the present invention may have an Ra228 content of less than 50 Bq / kg, advantageously less than 25 Bq / kg, preferably less than 10 Bq / kg, in particular less than 5 Bq / kg.

[054] Said phosphate salt according to the present invention may have a K40 content of less than 25 Bq / kg, advantageously less than 10 Bq / kg, preferably less than 5 Bq / kg.

[055] Advantageously, said phosphate salt according to the present invention is a calcium phosphate salt of formula Ca(HPO4).zH2O wherein z is 0, 1 or 2; in particular, a calcium phosphate salt of formula Ca(HPO4).2H2O. Said calcium phosphate salt may thus have a phosphate content expressed as P2O5 content between 30 and 50% by weight of the phosphate salt and a calcium content between 15 and 30% by weight of the phosphate salt. Advantageously, said calcium phosphate salt may have a phosphate content expressed as P2O5 content between 33 and 45% by weight of the phosphate salt and a calcium content between 15 and 30% by weight of the phosphate salt. Preferably, said calcium phosphate salt may have a phosphate content expressed as P2O5 of between 36 and 45% by weight of Petition 870160033568, dated 04 / 07 / 2016, page 15 / 49 11 / 42 phosphate salt and a calcium content between 15 and 30% by weight of the phosphate salt.

[056] In addition to reduced levels of radioactive impurities, said radioactive impurities include one or more of the radioactive elements detailed above, for example, U234, U235, U238, Po210, Th228, Th230, Th232, K40, Ra226, Ra228 or Pb210, said phosphate salt according to the present invention may have reduced levels of metallic impurities, for example, heavy metals and transition metals. Alternatively or concomitantly with the levels of one or more radioactive elements described in this patent application, said phosphate salt may have one or more of the levels of metals mentioned above.

[057] In particular, said phosphate salt may have a strontium content of less than 300 ppm, advantageously less than 280 ppm, preferably less than 250 ppm, in particular less than 100 ppm.

[058] The said phosphate salt may have a barium content of less than 50 ppm, advantageously less than 25 ppm, preferably less than 10 ppm.

[059] The said phosphate salt may have a cobalt content of less than 10 ppm, advantageously less than 5 ppm, preferably less than 1 ppm.

[060] The said phosphate salt may have a mercury content of less than 10 ppm, advantageously less than 5 ppm, preferably less than 1 ppm.

[061] The said phosphate salt may have an arsenic content of less than 5 ppm, advantageously less than 3 ppm, preferably less than 1.6 ppm, in particular less than 1 ppm.

[062] The said phosphate salt may have a copper content of less than 10 ppm, advantageously less than 5 ppm, preferably less than 1 ppm.

[063] The said phosphate salt may have a zinc content of less than 100 ppm, advantageously less than 50 ppm, preferably less than 35 ppm.

[064] The said phosphate salt may have a chromium content of less than 150 ppm, advantageously less than 100 ppm, preferably less than 75 ppm.

[065] The said phosphate salt may have a nickel content of less than 3 ppm, Petition 870160033568, dated 04 / 07 / 2016, page 16 / 49 12 / 42 preferably, at 2.5 ppm.

[066] The said phosphate salt may have a thallium content of less than 5 ppm, advantageously less than 2.5 ppm, preferably less than 1 ppm.

[067] The said phosphate salt may have a lead content of less than 3 ppm, advantageously less than 2 ppm, preferably less than 1.5 ppm.

[068] The said phosphate salt may have a cadmium content of less than 0.40 ppm, advantageously less than 0.30 ppm, preferably less than 0.20 ppm, in particular less than 0.10 ppm.

[069] The said phosphate salt may have a manganese content of less than 20 ppm, advantageously less than 15 ppm, preferably less than 10 ppm, in particular less than 5 ppm, more particularly less than 2.8 ppm.

[070] The said phosphate salt may have a molybdenum content of less than 3 ppm, advantageously less than 2 ppm, preferably less than 1 ppm.

[071] Said phosphate salt according to the present invention may also have a magnesium content of less than or equal to 20 ppm, advantageously less than 15 ppm, preferably less than 10 ppm. Said phosphate salt may contain less than 5% by weight of the magnesium initially comprised in said phosphate source, advantageously less than 3%, preferably less than 2.5%, in particular less than 1%.

[072] The said phosphate salt according to the present invention may optionally have a metallic impurity content of less than 1,000 ppm, preferably less than 750 ppm, in particular less than 500 ppm, said metallic impurity content being determined from the respective contents of barium, cobalt, mercury, manganese, magnesium, molybdenum, strontium, thallium, cadmium, arsenic, copper, lead, zinc, nickel and chromium in said phosphate salt.

[073] Said phosphate salt according to the present invention may be in the form of aggregates of solid particles having a diameter between 500 µm and 5 mm, advantageously between 500 µm and 3 mm, preferably between 1 mm and 2 mm. Petition 870160033568, dated 04 / 07 / 2016, page 17 / 49 13 / 42

[074] Alternatively, said phosphate salt according to the present invention may be in the form of aggregates of solid particles having a diameter of less than 500 pm, advantageously, a diameter between 50 and 500 pm, preferably between 100 pm and 200 pm.

[075] Preferably, said phosphate salt can be produced from a phosphate source selected from the group consisting of phosphate ore or secondary phosphate sources, such as ash, for example, volatile ash (bone ash or manure ash, or ash from the incineration of sewage sludge) or any other raw material containing more than 10% phosphate expressed as P2O5. The phosphate ore and secondary phosphate sources typically comprise more than 10% by weight of P2O5, advantageously more than 15% by weight of P2O5, preferably more than 20% by weight of P2O5.

[076] Said phosphate salt according to the present invention may have a solubility in water at room temperature (20 °C) between 0.01 and 2% by weight. When said phosphate salt is a calcium phosphate salt, it may have a solubility in water at room temperature (20 °C) between 0.01 and 0.1% by weight.

[077] Said phosphate salt according to the present invention, preferably when in the form of a calcium phosphate salt, can be used as an ingredient in a composition intended for agriculture, in a food composition, or as a starting material for the preparation of phosphoric acid, single or triple superphosphate, monocalcium phosphate (MCP), monodicalcium phosphate (MDCP), ammonium phosphate salts (monoammonium or diammonium), potassium phosphate salts, or NPK type fertilizer compounds.

[078] Said phosphate salt according to the present invention, preferably when in the form of a calcium phosphate salt, can be brought into contact with or mu several of compounds selected from among water, sulfuric acid, phosphoric acid, a nitrogen source or a source of Petition 870160033568, dated 04 / 07 / 2016, page 18 / 49 14 / 42 potassium, or mixtures thereof, and be mixed with them to advantageously form aggregates of solid particles suitable for use as an ingredient in compositions intended for agricultural or food compositions. Said nitrogen source may consist of ammonia, urea, a nitrate, an ammonium salt, such as ammonium sulfate, ammonium chloride, ammonium nitrate or mixtures thereof, or any other organic or mineral nitrogen source comprising a nitrogen atom. Said potassium source may consist of a potassium salt, such as potassium chloride, potassium sulfate, potassium nitrate, a mixture of potassium sulfate and magnesium sulfate, or mixtures thereof. The aggregates of solid particles may comprise said phosphate salt according to the present invention if the reaction with any of the reagents mentioned above is not complete.When said phosphate salt is brought into contact with sulfuric acid and, optionally, with water, single superphosphate (SSP) can be formed. When said phosphate salt is brought into contact with phosphoric acid and, optionally, with water and sulfuric acid, triple superphosphate (TSP) can be formed. The weight ratio between phosphoric acid and the phosphate salt is between 0.5 and 0.65. The phosphate content in TSP is generally between 40% and 55% by weight of P2O5. When said phosphate salt is brought into contact with sulfuric acid, said nitrogen source and, optionally, water and / or phosphoric acid, monoammonium phosphate (MAP), diammonium phosphate (DAP) or a mixture of the two can be formed. When said phosphate salt is brought into contact with sulfuric acid and a source of potassium and, optionally, water and / or phosphoric acid, potassium phosphate salt may be formed.When said phosphate salt is brought into contact with said nitrogen source and said potassium source and, optionally, with water and / or phosphoric acid and / or sulfuric acid, an “NPK” type composition may be formed. The term “NPK” designates a composition containing nitrogen, potassium, phosphorus and mixtures thereof. Preferably, the NPK composition may comprise a weight content. Petition 870160033568, dated 04 / 07 / 2016, page 19 / 49 15 / 42 different or equal in phosphorus, nitrogen or potassium based on the total weight of the composition. The phosphorus, nitrogen or potassium content may be adjusted depending on the compounds in contact and their respective proportions. When said phosphate salt is brought into contact with an appropriate amount of phosphoric acid, monocalcium phosphate may be formed. The weight ratio between the phosphoric acid and the phosphate salt is between 0.5 and 0.65. When said phosphate salt is brought into contact with an appropriate amount of phosphoric acid, monodicalcium phosphate may be formed. The weight ratio between the phosphoric acid and the phosphate salt is less than 0.5. The phosphoric acid used in the different processes described above preferably has a phosphate content expressed as a weight percentage of P2O5 between 45% and 60%, advantageously between 50% and 55%, preferably around 54%.

[079] The said phosphate salt according to the present invention can be prepared by the process comprising the following steps: a) a digestion of a phosphate source by a first aqueous solution of hydrochloric acid with the formation of an attack liquor consisting of an aqueous phase comprising phosphate ions and chloride ions in solution, and a first insoluble solid phase containing impurities, b) an initial separation between the aqueous phase, which comprises phosphate and chloride ions in solution, and the initial insoluble solid phase, which contains impurities, (c) a neutralization of said aqueous phase comprising phosphate ions and chloride ions in solution at a pH sufficient to form an aqueous medium comprising chloride ions and to precipitate the phosphate ions in the form of said phosphate salt, d) a second separation between said aqueous medium comprising chloride ions and said phosphate salt, distinguished by steps a) and b) being carried out at a temperature between 50 °C and 70 °C.

[080] Said process according to the present invention may Petition 870160033568, dated 04 / 07 / 2016, page 20 / 49 16 / 42 also includes a drying step of said phosphate salt obtained in step d).

[081] Step a) of phosphate source digestion may have a duration of less than two hours, advantageously less than one hour, preferably less than 30 minutes, in particular between 5 minutes and 20 minutes, and more particularly 15 minutes. Decreasing the duration of the digestion step allows for a reduction in the metal content in the phosphate salt obtained in step b), such as, for example, the manganese content.

[082] The duration of the neutralization performed in step c) may be less than four hours, advantageously less than three hours, preferably less than one hour, in particular between 35 minutes and 50 minutes.

[083] The impurities contained in the solid phase obtained in step a) and separated in step b) may be metallic impurities or radioactive elements or insoluble materials. The radioactive elements contained in this solid phase may constitute one or more of the following elements: U234, U235, U238, Po210, Th228, Th230, Th232, K40, Ra226, Ra228 or Pb210. The metallic elements may be any of the following metallic elements: barium, cobalt, mercury, manganese, magnesium, molybdenum, strontium, thallium, cadmium, arsenic, copper, lead, zinc, nickel and chromium. Performing steps a) and b) at a temperature between 50 °C and 70 °C, advantageously between 55 °C and 65 °C, allows control of the precipitation of impurities, radioactive or not. Additionally, even in the presence of a magnesium-rich phosphate source, carrying out the process at a temperature between 50 °C and 70 °C allows for control of the viscosity of the attack liquor and avoids processing problems from the rock leaching reaction.When steps a) and c) are carried out during a short reaction time, as mentioned above, the purity of said aqueous medium comprising chloride ions and said phosphate salt obtained in step d) is enhanced. Therefore, the presence of radioactive impurities and / or metals is strongly limited in said aqueous medium comprising chloride ions and said phosphate salt obtained in step d) due to the process according to a). Petition 870160033568, dated 04 / 07 / 2016, page 21 / 49 17 / 42 present invention.

[084] The said phosphate source used in step a) may be selected from the group consisting of phosphate ore or secondary phosphate sources, such as ash, for example, volatile ash (bone ash or manure ash, or ash from the incineration of sewage sludge) or any other feedstock containing more than 10% phosphate expressed as a percentage by weight of P2O5 in said feedstock. The ash, as used herein, may comprise more than 10% by weight of phosphate expressed as a percentage by weight of P2O5 in the ash, advantageously more than 15% by weight of P2O5.

[085] Said phosphate source may contain a magnesium content exceeding 15% by weight based on the total weight of the phosphate source. Advantageously, the magnesium content of said phosphate source may be between 1.5% and 20% by weight based on the total weight of the phosphate source, preferably between 1.5% and 10% by weight.

[086] The first aqueous hydrochloric acid solution used in step a) of the present process may have an HCl concentration of less than or equal to 15% by weight, preferably from 8 to 13% by weight, in particular from 10 to 13% by weight, more particularly 12% by weight of the first aqueous solution. The use of an HCl solution of less than or equal to 15% allows the obtaining of a filterable attack liquor. Indeed, the use of a solution containing a concentration greater than 20% does not allow the attack liquor to be filtered, and beyond an HCl concentration greater than or equal to 25%, the attack liquor is no longer amenable to agitation. The use of an HCl solution with a concentration between 8 and 13% by weight or of the order of 12% by weight allows step a) to be carried out in a dilute medium which favors the treatment of the magnesium-rich rock.

[087] Preferably, in the attack liquor, the molar ratio between HCl and Ca is between 1.2 and 2.6, advantageously between 1.6 and 2.4, preferably between 1.6 and 2.2, in particular between 1.6 and 2.0. Petition 870160033568, dated 04 / 07 / 2016, page 22 / 49 18 / 42

[088] The said neutralization of step c) can be carried out in the presence of a base, advantageously calcium carbonate, calcium hydroxide, calcium oxide or a calcium salt. In this case, the said precipitated phosphate salt is a calcium phosphate salt and the said aqueous medium, in step d), comprises chloride ions and calcium ions. The said aqueous medium is preferably a calcium chloride solution having a calcium chloride content between 8 and 20% by weight of the solution, advantageously between 12 and 18% by weight, preferably about 15% by weight.

[089] Alternatively, the use in step c) of a sodium, potassium or ammonium salt allows the preparation of a sodium, potassium or ammonium phosphate salt, respectively. The appropriate use of an aluminum or iron salt or hydroxide allows the preparation of the corresponding phosphate salt.

[090] The said neutralization carried out in step c) can be performed at a pH lower than 5, advantageously between 2.5 and 3.0. When the neutralization is carried out at a pH between 2.5 and 3.0, the magnesium remains in solution without precipitating concomitantly with said phosphate salt. Preferably, this neutralization step can be carried out at room temperature or at a temperature between 50 and 70 °C.

[091] The said phosphate salt obtained in step d) may contain less than 5% by weight of the magnesium initially contained in said phosphate source, advantageously less than 2.5%, preferably less than 1%.

[092] According to a preferred embodiment, step a) of the present process can be carried out in a first competitor reactor comprising one or more compartments, advantageously between 2 and 12 compartments, preferably between 2 and 5 compartments, in particular between 3 and 5 compartments. The compartments are arranged in series and communicate with each other from below. The rock and hydrochloric acid can, for example, be introduced into a first compartment. The attack liquor thus formed then passes through the interior of Petition 870160033568, dated 04 / 07 / 2016, page 23 / 49 19 / 42 each of the other compartments that can thus be used to modulate or control the reaction time and optimize the mixing of the compounds. The last compartment of said first concurrent reactor of step a) is connected to a filter by means of a conduit that allows the reaction mixture obtained at the end of step a) to be directed to the filter where step b) of the present process will be carried out. Optionally, a buffer storage tank can be placed between the last compartment of the first concurrent reactor used to carry out step a) and the filter used to carry out step b). In this case, the reaction mixture obtained at the end of step a) is transferred from the buffer tank to the filter of step b).The filtrate recovered in step b) is sent to a second competing reactor comprising one or more compartments, advantageously between 2 and 12 compartments, preferably between 2 and 5 compartments, in particular between 3 and 5 compartments. The neutralization of step c) of the present process is carried out inside said second competing reactor. The filtrate is first introduced into the first compartment of said second reactor. The flow of the filtrate allows it to be directed to the other compartments of said second competing reactor. When neutralization is carried out in the presence of a base, this can be introduced into each of the compartments of said second reactor during the passage of the filtrate inside each of them. The neutralization reaction proceeds in each of the compartments comprised in said second reactor to favor the precipitation of the phosphate salt according to the present invention.The use of this compartmentalized reactor for carrying out step c) of the present process allows the formation of crystals of said phosphate salt according to the present invention, which have an optimized shape and particle size for the subsequent step d). Thus, when said phosphate salt is DCP with the formula CaHPO4.2H2O, the DCP crystals obtained can be in the form of an aggregate (cluster), that is, agglomerates of spherical or elliptical shape. The largest dimension of... Petition 870160033568, dated 04 / 07 / 2016, page 24 / 49 20 / 42 clusters may be less than 500 pm, advantageously between 20 pm and 250 pm.

[093] According to a particular embodiment, the process according to the present invention further comprises the following steps: (e) an attack on all or part of said phosphate salt obtained in step (d) by an aqueous solution of strong acid to form a suspension of a first phosphoric acid in solution and a second solid phase, f) a third separation between the first phosphoric acid and said second solid phase.

[094] Preferably, step e) can be carried out at a temperature above 80 °C, in particular, at a temperature between 80 °C and 100 °C. Carrying out step e) at a temperature above 80 °C, preferably at a temperature between 80 °C and 100 °C, allows control of the viscosity of the reaction medium obtained in step e). Preferably, when said phosphate salt used in step e) is a calcium phosphate salt, said aqueous solution of strong acid can consist of sulfuric acid. In this way, the second solid phase of step e) comprises calcium sulfate hemihydrate. Alternatively, when said phosphate salt used in step e) is a calcium phosphate salt and step e) is carried out at a temperature below 80 °C, preferably between 60 °C and 80 °C, said aqueous solution of strong acid may consist of sulfuric acid and said second solid phase of step e) comprises calcium sulfate dihydrate.

[095] Preferably, in step e) the molar ratio between the aqueous solution of strong acid and said phosphate salt obtained in step d) can be between 0.6 and 1.6.

[096] The first phosphoric acid obtained in step f) may be treated with activated carbon or a sulfur compound or may be concentrated. Said first phosphoric acid may be used in a composition intended for agriculture, for example, a fertilizer composition, or may be used in Petition 870160033568, dated 04 / 07 / 2016, page 25 / 49 21 / 42 preparation of a food composition. The said first phosphoric acid can be used for the preparation of a triple superphosphate or superphosphoric acid. The content of radioactive elements or metallic elements in the products thus prepared will be reduced.

[097] According to a preferred embodiment, said aqueous medium comprising chloride ions and obtained in step d) can be treated with a basic compound to form a purified aqueous base and a solid phase comprising impurities. Said purified aqueous phase comprises chloride ions and preferably has a pH between 8 and 12, advantageously between 9 and 10. Advantageously, when the aqueous medium obtained in step d) comprises chloride ions and calcium ions, the basic compound is selected from calcium hydroxide, calcium oxide and calcium, sodium, potassium or ammonium salts to form a purified aqueous phase comprising calcium chloride. Said solid phase comprising impurities may comprise magnesium salts or radioactive elements or metallic impurities.The treatment of the said aqueous medium comprising chloride ions and obtained in step d) by a basic compound therefore allows the obtaining of a purified calcium chloride solution, that is, one that has reduced levels of radioactive elements and magnesium. This treatment can be carried out at a temperature between 50 and 70 °C. Alternatively, this treatment can be carried out at room temperature. Preferably, said purified aqueous phase has a calcium chloride content between 10 and 30% by weight of the purified aqueous phase, advantageously between 12 and 20% by weight, preferably about 15%.

[098] Thus, the present invention also relates to a calcium chloride depleted of radioactive elements. The calcium chloride may be in solution or in solid form. Said calcium chloride may have a uranium content of less than 1 Bq / kg, preferably less than 0.1 Bq / kg, the uranium content being determined by the respective contents of U234, U235 and U238. The Petition 870160033568, dated 04 / 07 / 2016, page 26 / 49 22 / 42 said calcium chloride may also have a Po210 content of less than 500 Bq / kg, advantageously less than 250 Bq / kg, preferably less than 100 Bq / kg. Said calcium chloride may also have a radium content, determined by the respective Ra226 and Ra228 contents, of less than 10 Bq / kg, advantageously less than 1 Bq / kg, preferably less than 0.5 Bq / kg. Said calcium chloride may also have a thorium content determined by the respective Th228, Th230 and Th232 contents, of less than 10 Bq / kg, preferably less than 1 Bq / kg. Said calcium chloride can be obtained by the process according to the present invention, for example, by steps a) to d) of the present process wherein step c) is carried out in the presence of a calcium salt, hydroxide or calcium oxide to obtain in step d) an aqueous medium comprising chloride ions and calcium ions, thus forming an aqueous medium comprising calcium chloride.This aqueous medium, which comprises calcium chloride, can be dried or concentrated.

[099] Advantageously, said aqueous medium comprising calcium chloride, and obtained in step d), can be purified to have even lower contents of different radioactive elements or metals. Thus, said calcium chloride can have a uranium content of less than 0.05 Bq / kg, the uranium content being determined by the respective contents of U234, U235 and U238. Said calcium chloride can also have a Po210 content of less than 50 Bq / kg, advantageously less than 10 Bq / kg, preferably less than 5 Bq / kg. Said calcium chloride can also have a radium content, determined by the respective contents of Ra226 and Ra228, of less than 1 Bq / kg, advantageously less than 0.5 Bq / kg, preferably less than 0.1 Bq / kg. The aforementioned calcium chloride may also have a Pb210 content of less than 10 Bq / kg.Said calcium chloride may also have a thorium content determined by the respective contents of Th228, Th230 and Th232, of less than 0.1 Bq / kg, and preferably, no thorium residue is detected. Preferably, said purified calcium chloride may be prepared by the present process by treating the previously obtained calcium chloride solution with a basic compound. Petition 870160033568, dated 04 / 07 / 2016, page 27 / 49 23 / 42 selected, for example, from calcium hydroxide, calcium oxide, and calcium, sodium, potassium, or ammonium salts as described in this patent application. The purified calcium chloride solution thus obtained may have a pH greater than 10. Said purified calcium chloride solution may be concentrated and / or dried. Thus, a calcium chloride solution having a CaCl2 concentration of 35-40% by weight of the total solution may be obtained. Alternatively, CaCl2 granules with a CaCl2 content greater than 95% by weight based on the total weight of the granules may be obtained. Alternatively, CaCl2 petals with a CaCl2 content greater than 70% by weight based on the total weight of the petals may be obtained. Alternatively, CaCl2 petals with a CaCl2 content greater than 70% by weight based on the total weight of the petals can be obtained, preferably with a content between 70 and 80% by weight.

[0100] The second solid phase of step e) and separated in step f) comprises calcium sulfate hemihydrate or calcium sulfate dihydrate or a mixture of the two. The calcium sulfate hemihydrate, the calcium sulfate dihydrate or their mixture may be mixed with an acidic solution, preferably a strong acid, to form a solid phase comprising calcium sulfate dihydrate and an aqueous phase comprising phosphate ions. The calcium sulfate hemihydrate is thus transformed into calcium sulfate dihydrate. The acid solution may consist of a hydrochloric acid solution and thus the aqueous solution obtained consists of a hydrochloric acid solution also comprising phosphate ions.Alternatively, the strong acid solution may consist of a sulfuric acid solution, and the second solid phase separated in step f) may also be mixed with said purified aqueous phase, preferably said purified calcium chloride solution, or with said aqueous medium comprising chloride ions and calcium ions obtained in step d), or a mixture thereof. Thus, a solid phase comprising calcium sulfate dihydrate and an aqueous phase comprising hydrochloric acid are obtained. The aqueous phase comprising... Petition 870160033568, dated 04 / 07 / 2016, page 28 / 49 24 / 42 hydrochloric acid can be recycled to form all or part of said first aqueous hydrochloric acid solution used in step a).

[0101] Thus, the present invention allows the preparation of calcium sulfate dihydrate with a low content of radioactive elements. Said calcium sulfate thus prepared may have a K40 content of less than 50 Bq / kg, advantageously less than 30 Bq / kg, preferably less than 16 Bq / kg. Said calcium sulfate may have an Ra228 content of less than 50 Bq / kg, advantageously less than 25 Bq / kg, preferably less than 10 Bq / kg, in particular less than 5 Bq / kg. Said calcium sulfate may have an Ra226 content of less than 50 Bq / kg, advantageously less than 25 Bq / kg, preferably less than 10 Bq / kg, in particular less than 5 Bq / kg. Said calcium sulfate may have a Th228 content of less than 50 Bq / kg, advantageously less than 25 Bq / kg, preferably less than 10 Bq / kg, in particular less than 5 Bq / kg.Said calcium sulfate may have a U235 content of less than 50 Bq / kg, advantageously less than 25 Bq / kg, preferably less than 10 Bq / kg, in particular less than 5 Bq / kg. Said calcium sulfate may have a U238 content of less than 50 Bq / kg, advantageously less than 25 Bq / kg, preferably less than 15 Bq / kg.

[0102] According to a third aspect of the present invention, said phosphate salt according to the present invention can preferably be used in solid form, in a composition or for the preparation thereof. The composition can be a composition intended for agriculture or a food composition. Advantageously, said composition intended for agriculture is a liquid fertilizer composition, or a fertilizer composition that is partially or totally soluble in water. Said food composition is a composition for animal or livestock or human feed. Preferably, said phosphate salt thus used is prepared by the process according to the present invention.

[0103] According to a fourth aspect of the present invention, a composition intended for agriculture or a food composition is provided that Petition 870160033568, dated 04 / 07 / 2016, pp. 29 / 49 25 / 42 comprises said phosphate salt according to the present invention.

[0104] Said food composition may also additionally comprise a basic food substance. Said food composition may be prepared by a process comprising the following steps: A) preparation of said phosphate salt according to the present invention by means of the process according to the present invention, B) Mixture of said phosphate salt thus prepared with a basic foodstuff.

[0105] Said composition intended for agriculture may further comprise a source of potassium and / or a source of nitrogen, diammonium phosphate, monoammonium phosphate, potassium phosphate, single superphosphate, monocalcium phosphate, monodicalcium phosphate or triple superphosphate. Said composition intended for agriculture may be a fertilizer composition, preferably a liquid fertilizer composition, or a fertilizer composition that is partially or totally water-soluble. Said nitrogen source may consist of ammonia, urea, a nitrate, an ammonium salt, such as ammonium sulfate, ammonium chloride, ammonium nitrate or mixtures thereof, or any other organic or mineral nitrogen source comprising a nitrogen atom.Said potassium source may consist of a potassium salt, such as potassium chloride, potassium sulfate, potassium nitrate, potassium hydrogen sulfate, a mixture of potassium sulfate and magnesium sulfate, or mixtures thereof. Said composition intended for agriculture may be prepared by a process comprising the following steps:. A) preparation of said phosphate salt according to the present invention by means of the process according to the present invention, B) a mixture of said phosphate salt obtained in A) with one or more of the following compounds: a nitrogen source or a potassium source or a mixture thereof, water, sulfuric acid or phosphoric acid to form said composition.

[0106] In the different compositions described in this application of Petition 870160033568, dated 04 / 07 / 2016, pages 30 / 49 26 / 42 patent, said phosphate salt according to the present invention preferably consists of a calcium phosphate salt (CaHPO4.zH2O where z is 0, 1 or 2; preferably z is 2).

[0107] According to a particular embodiment of the invention, a process for the preparation of single superphosphate (SSP) is provided comprising the steps of: A) preparation of said phosphate salt according to the present invention, preferably by means of the process according to the present invention, B) Addition of sulfuric acid and, optionally, phosphoric acid, and water to said phosphate salt to form single superphosphate (SSP).

[0108] The molar ratio between sulfuric acid and said phosphate salt is between 0.1 and 1. The molar ratio between phosphoric acid and said phosphate salt is between 0 and 1.

[0109] According to a particular embodiment of the invention, a process for the preparation of triple superphosphate (TSP) is provided comprising the following steps: A) preparation of said phosphate salt according to the present invention, preferably by means of the process according to the present invention, B) Addition of phosphoric acid and, optionally, sulfuric acid, and / or water to said phosphate salt to form TSP.

[0110] The molar ratio between sulfuric acid and said phosphate salt is between 0 and 1, preferably between 0.1 and 0.15. The molar ratio between phosphoric acid and said phosphate salt is between 0.1 and 1, preferably between 0.1 and 0.5.

[0111] According to a particular embodiment of the invention, a process is provided for the preparation of monoammonium phosphate (MAP) or diammonium phosphate (DAP) comprising the steps of: A) preparation of a phosphate salt according to the present Petition 870160033568, dated 04 / 07 / 2016, pp. 31 / 49 27 / 42 invention, preferably by means of the process according to the present invention, B) addition of sulfuric acid and ammonia or an ammonium salt to said phosphate salt to form monoammonium phosphate or diammonium phosphate.

[0112] Preferably, the addition of sulfuric acid may precede that of ammonia or ammonium salt. Preferably, filtration is carried out after the addition of sulfuric acid to separate an aqueous phase comprising phosphoric acid and a solid phase comprising calcium sulfate. The addition of ammonia or ammonium salt is carried out on the filtrate resulting from said filtration, that is, on the aqueous phase comprising phosphoric acid. The molar ratio between sulfuric acid and said phosphate salt is between 0.5 and 1.5, preferably between 0.8 and 1.2. Preferably, the molar ratio between ammonia and said phosphate salt is between 0.5 and 2.5.

[0113] According to a particular embodiment of the invention, a process for the preparation of potassium phosphate is provided, comprising the steps of: A) preparation of a phosphate salt according to the present invention, preferably by means of the process according to the present invention, B) Addition of a potassium source to said phosphate salt and, optionally, of an acid, to form said potassium phosphate salt.

[0114] The acid may consist of phosphoric acid or sulfuric acid. Preferably, when sulfuric acid is added, this addition may be carried out prior to the addition of the potassium source. A filtration is advantageously carried out after the addition of sulfuric acid to separate an aqueous phase comprising phosphoric acid and a solid phase comprising calcium sulfate. The addition of the potassium source may then be carried out on the filtrate resulting from said filtration, i.e., on the aqueous phase comprising phosphoric acid. Alternatively, a filtration may be Petition 870160033568, dated 04 / 07 / 2016, pages 32 / 49 28 / 42 carried out after step b). The molar ratio between sulfuric acid and said phosphate salt is between 0.5 and 1.5, preferably between 0.8 and 1.2. Preferably, the molar ratio between the potassium source and said phosphate salt is between 0.5 and 2.5, preferably between 1 and 2. The process is particularly applicable in the preparation of monopotassium phosphate (MPK - KH2PO4). In this case, the potassium source can preferably be potassium chloride, potassium sulfate, potassium hydrogen sulfate (KHSO4) or another potassium salt. The molar ratio between the acid and said phosphate salt is between 0 and 1. The molar ratio between the potassium source and said phosphate salt is between 0.5 and 2.5, preferably between 1 and 2. The addition of acid is especially optional when the potassium source consists of potassium hydrogen sulfate.

[0115] Said potassium salt according to the present invention, when prepared, preferably, according to the process of the present invention, can be used in a composition intended for agriculture or in a food composition, or can serve as a starting material for the preparation of said compositions. These can be prepared using the processes described above. The present invention also allows the preparation of “NPK” type compositions. Compositions of this type are frequently used as fertilizer in agriculture. The present invention therefore provides compositions that have reduced levels of impurities (radioactive elements or metals), avoiding the contamination of soils and crops in which these compositions may be used.

[0116] According to a particular embodiment of the invention, a process is provided for the preparation of NPK compositions comprising the steps of: A) preparation of a phosphate salt according to the present invention, preferably by means of the process according to the present invention, B) addition of sulfuric acid, a nitrogen source and / or a Petition 870160033568, dated 04 / 07 / 2016, pp. 33 / 49 29 / 42 source of potassium, to said phosphate salt for the formation of an NPK composition.

[0117] The molar ratio between sulfuric acid and said phosphate salt is between 0.1 and 1.5.

[0118] According to a particular embodiment of the invention, a process for the preparation of monocalcium phosphate (MCP) is provided comprising the steps of: A) preparation of a phosphate salt according to the present invention, preferably by means of the process according to the present invention, B) Addition of an appropriate amount of phosphoric acid to obtain a monocalcium phosphate.

[0119] The appropriate amount of phosphoric acid is determined based on the weight of the phosphate salt. The weight ratio between phosphoric acid and phosphate salt is between 0.5 and 0.65.

[0120] According to a particular embodiment of the invention, a process for the preparation of mono-dicalcium phosphate (MDCP) is provided comprising the steps of: A) preparation of a phosphate salt according to the present invention, preferably by means of the process according to the present invention, B) Addition of an appropriate amount of phosphoric acid to obtain mono-dicalcium phosphate.

[0121] The appropriate amount of phosphoric acid is determined based on the weight of the phosphate salt. The weight ratio between the phosphoric acid and the phosphate salt is less than 0.5.

[0122] Advantageously, the process according to the invention is carried out continuously.

[0123] Figure 1 represents a block diagram of the preparation process of said phosphate salt according to a particular mode of Petition 870160033568, dated 04 / 07 / 2016, pp. 34 / 49 30 / 42 embodiment of the present invention. The particular embodiment described below relates especially to the preparation of dicalcium phosphate with a low content of radioactive elements, but also to the preparation of calcium chloride solutions or the preparation of calcium sulfate which also has a low content of radioactive elements. The process can be applied to the preparation of other types of phosphate salts, for example, sodium, potassium, ammonium, aluminum or iron phosphate salts.

[0124] The phosphate source 1, for example, phosphate ore, is treated with a hydrochloric acid solution 2 during a digestion step of the phosphate source in 3. The treatment is carried out at a temperature between 50 and 70 °C for a duration of less than one hour, advantageously less than 30 minutes, preferably between 5 and 20 minutes. The reaction medium 4 resulting from digestion 3 comprises a solid phase containing impurities (radioactive elements and / or metallic impurities) and a liquid phase containing phosphate ions and chloride ions. The reaction medium 4 is filtered to separate the solid phase 4' containing metallic impurities and / or radioactive elements from the aqueous phase 5 containing phosphate ions and chloride ions.

[0125] The aqueous phase 5 comprising phosphate and chloride ions is then treated, in 13, with a base 14, for example, CaCO3, to form a dicalcium phosphate precipitate 16 and an aqueous solution 15 comprising chloride and calcium ions, thus forming a calcium chloride solution. The dicalcium phosphate precipitate 16 and the aqueous solution 15 are separated by filtration, for example, using a band filter. The dicalcium phosphate 16 thus obtained is a phosphate salt according to the present invention, i.e., especially depleted in radioactive elements. This dicalcium phosphate 16 can be used as a raw material in a composition intended for agriculture or in a food composition. It can also be used as a starting reagent for the preparation of compounds such as, for example, single or triple superphosphate, phosphate Petition 870160033568, dated 04 / 07 / 2016, pages 35 / 49 31 / 42 of monoammonium or diammonium phosphate, or potassium phosphate, monocalcium phosphate (MCP) or monodicalcium phosphate (MDCP).

[0126] Dicalcium phosphate 16 can also be treated, preferably at a temperature above 80 °C, with a solution of sulfuric acid 18 in 17 to form a solid phase comprising calcium sulfate and an aqueous phase comprising phosphoric acid, subsequently separated from each other, for example, by filtration. The calcium sulfate 24 thus obtained contains calcium sulfate hemihydrate which can be treated in 31 with a solution of hydrochloric acid 30. After separation, an aqueous solution of hydrochloric acid 32 and a solid phase of calcium sulfate dihydrate 33 are obtained. The solid phase of calcium sulfate dihydrate 33 has reduced levels of radioactive or metallic elements. The calcium sulfate dihydrate 33 can thus be used in a paper bleaching process or in the preparation of plaster or compositions intended for the construction sector.The aqueous solution of hydrochloric acid 32 also contains residual phosphate ions.

[0127] The calcium chloride solution 15 can be purified in 26 by adding a base 25, for example, calcium hydroxide. After separation, for example by filtration, a solid phase 27 comprising impurities and a purified aqueous phase comprising calcium chloride are obtained. The purified aqueous phase containing calcium chloride 28 can be concentrated and / or dried to obtain calcium chloride in different forms (solution or solid) at different concentrations. The purified aqueous phase comprising calcium chloride 28 can also be treated in 29 with a sulfuric acid solution 34. The calcium chloride solution 15 and calcium sulfate 24 can also be added in 29 to form an aqueous hydrochloric acid phase 35 and a solid phase comprising calcium sulfate dihydrate 36.Hydrochloric acid solution 35, like hydrochloric acid solution 32, can be recycled for use in step 3 of the phosphate source digestion. The solid phase comprising sulfate of... Petition 870160033568, dated 04 / 07 / 2016, pages 36 / 49 32 / 42 calcium dihydrate 36 can be used like calcium sulfate dihydrate 33.

[0128] In addition to a phosphate salt depleted of radioactive elements, the present process allows the preparation of calcium chloride, in solution or solid form, and / or calcium sulfate dihydrate, each of which has low levels of radioactive elements. The preparation of these compounds and their subsequent use is another advantage of the present invention.

[0129] According to an alternative aspect of the invention, when said phosphate source used in step a) of the present process is a secondary phosphate source, such as fly ash originating from the incineration of bones, manure or sewage sludge, as described in the present patent application, digestion with a hydrochloric acid solution (step a)) forms an aqueous solution comprising phosphate ions and chloride ions in solution. This can be isolated after step b) of the process. This solution is purified to eliminate chloride ions for the production of phosphoric acid or MCP. The elimination of chloride ions can be carried out according to purification techniques known to a person skilled in the art.

[0130] Examples

[0131] Procedure for determining the levels of radioactive elements by gamma spectrometry

[0132] The contents of Pb210, K40, Ra226 and Ra228 were determined by gamma spectrometry. Measurements were made in the presence of a detector comprising an ultrapure germanium crystal (HPGe) Canberra (HPGe XtRa 50% relative efficiency or HPGe BEGe 34% relative efficiency) and disposed within a measuring device comprising a lead shield. Measurements were made between 3 keV and 3 MeV for a BEGe detector or between 3 keV and > 10 MeV for an XtEa detector. The detector is calibrated with the aid of samples disposed in Petition 870160033568, dated 04 / 07 / 2016, pp. 37 / 49 33 / 42 inside Marinelli™ type containers with a capacity of 1 ml to 2.5 l. The determination of Ra226 content was carried out by measuring the daughter radionuclides (short half-life) of Ra226. The sample to be analyzed is placed in contact with activated charcoal in water for absorption of the Ra226 present in the sample. The solid residue was disposed of in a container (coaxial HDPE - 250 ml) for 21 days. The Ra226 measurement was carried out using a Lucas cell type detector. The K40 content is determined by the emission line at 1460.82 keV. The Ra226 content was determined from the daughter radionuclides Bi214e and Pb214e, whose emission lines were considered to be located at 609.31 keV, 1120.28 keV, and 1764.5 keV for Bi214e, and at 241.99 keV, 295.22 keV, and 351.93 keV for Pb214e, respectively. The Ra228 content was determined considering the emission lines of Ac228a at 338.32 keV, 911.19 keV, and 968.96 keV. The Pb210 content was determined considering the emission line at 46.5 keV.

[0133] Procedure for determining the levels of radioactive elements by alpha spectrometry

[0134] The contents of Po210, Th228, Th230, Th232, U234, U235, U238 were determined by alpha spectrometry. The detector is a silicon detector also designated as a “PIPS detector” from Canberra. When the sample to be analyzed is solid (e.g., DCP or CaSO4), 1 gram of it is previously digested by microwaves in the presence of a mixture comprising 5 ml of hydrofluoric acid, 5 ml of hydrochloric acid, and 5 ml of nitric acid. When the sample to be analyzed is liquid, it (10 ml) is treated with an aqueous solution of FeCl3 (1 ml of a solution prepared from 7.3 g / 100 ml). The precipitate is centrifuged and calcined. For the determination of the polonium content Po210, the previously treated sample, as mentioned above, is mixed with 0.25 l of water and 20 ml of hydrochloric acid (6 M), with ascorbic acid before being deposited on a silver surface under agitation at a temperature between 80 °C and 90 °C for 6 hours.To determine the uranium and thorium content, a. Petition 870160033568, dated 04 / 07 / 2016, pages 38 / 49 34 / 42 sample is purified on an ion exchange resin (Biorad AG) in the presence of a marker (Po208 or Po209) to eliminate polonium and is subjected to a second separation between uranium and thorium on a column comprising a UTEVA® type resin (Eichorm) in the presence of a U232 and Th229 marker.

[0135] Procedure for determining transition metal content

[0136] The metal content in a sample is determined by inductively coupled plasma optical emission spectrometry (IPC-OES) using an Agilent 710 Axial series ICP optical emission spectrometer equipped with a nebulizer (One Neb insert concentric ICP) and a plasma cutting torch (lo-flw, Quartz, inlet tbg, axial). Samples and standards are prepared in containers previously cleaned with a diluted nitric acid solution (193 g of 96% nitric acid, diluted to 1000 ml with distilled water).

[0137] The apparatus is calibrated according to the following protocol using standard solutions of Pb(NO3)2 with a lead concentration of 100 mg / l, Cd(NO3)2 with a cadmium concentration of 100 mg / l, Hg(NO3)2 with a mercury concentration of 100 mg / l, H3AsO4 with an arsenic concentration of 100 mg / l, and Y(NO3)3 with a yttrium concentration of 100 mg / l. From each of the Pb(NO3)2, Cd(NO3)2, Hg(NO3)2 and H3AsO4 solutions, a series of 7 calibration samples is prepared at 0.01 ppm, 0.05 ppm, 0.1 ppm, 1 ppm and 5 ppm. In each sample, 200 µl of the standard Y(NO3)3 solution are added, and then each sample is diluted with the diluted nitric acid solution mentioned above to make up a volume of 100 ml.

[0138] Preparation of CaCl2 samples to be analyzed by ICP-OES

[0139] 10 g of CaCl2 are added to a 100 ml narrow-necked flask containing 50 ml of the diluted nitric acid solution as prepared above, followed by 200 µl of the Y(NO3)3 standard solution. The volume is then adjusted to 100 ml by adding the diluted acid solution. Petition 870160033568, dated 04 / 07 / 2016, pages 39 / 49 35 / 42 nitric acid. The solution thus obtained is subjected to vigorous stirring.

[0140] Preparation of phosphate salt samples according to the present invention, of DCP and of gypsum to be analyzed by ICP-OES

[0141] In a 100 ml narrow-necked flask containing 25 ml of the diluted nitric acid solution as prepared above, 2 g of the sample to be analyzed are added, followed by 10 ml of a 37% hydrochloric acid solution. If necessary, the resulting solution can be brought to a boil to dissolve the sample to be analyzed. 200 µl of the standard Y(NO3)3 solution are added, and the volume is adjusted to 100 ml by adding the diluted nitric acid solution. The resulting solution is vigorously shaken and optionally filtered before analysis if necessary.

[0142] Example 1

[0143] A phosphate ore of North African origin with a P2O5 content of 29% by weight is considered. The ore is attacked using an aqueous solution with a weighted HCl content of 12% at a temperature of 60 °C. The amount of HCl added is determined by a molar ratio between the HCl added to the ore and the Ca present in it. The ore is attacked at an HCl / Ca ratio of 1.8. The residence time in the attack reactor is 15 minutes. The attack liquor is then transferred to a filter press where insoluble materials (especially residues in Table 1 below) are separated from the aqueous phase. The temperature is maintained at 60 °C for filtration. The solution exiting the filter press is sent to a neutralization reactor. Calcium carbonate is added at a Ca / P molar ratio of 1 and a pH of 2.5-3.0.After 45 minutes of reaction and formation of dicalcium phosphate (DCP), the neutralized reaction medium is then directed to a band filter. The resulting cake is dried and consists of DCP exhibiting the characteristics mentioned below, i.e., a low content of radioactive elements and / or low levels of metals. The DCP has a P2O5 content of 44% by weight (dry weight). Petition 870160033568, dated 04 / 07 / 2016, pages 40 / 49 36 / 42 a calcium content of 24% by weight (dry weight). The filtrate is a 15% by weight aqueous solution of calcium chloride. The calcium chloride solution can be purified by adding calcium hydroxide until the pH of the solution is between 9 and 10. Insoluble materials, mainly magnesium salts and radioactive elements, precipitate, thus depleting the calcium chloride solution of radioactive elements. A purified calcium chloride solution (15% by weight) is thus obtained.

[0144] Table 1 details the levels of radioactive elements in the ore, the dicalcium phosphate (DCP) obtained, the calcium chloride solution (CaCl2), the purified calcium chloride solution (CaCl2p), and the residues from filtration after the ore digestion stage (i.e., first solid phase). Example 1 was reproduced three times, and the different components mentioned above were analyzed each time. For each radioactive element, an average value was determined based on the three tests, and this value is used further down in Table 1. Table 1 - Content of radioactive elements (Bq / kg) in the rock, DCP, CaCl2, CaCl2p and the residues resulting from the attack liquor according to the process of the present invention. DCP Ore Residues CaCl2 CaCl2p Po210 607 120 1360 50 2 Th228 54 6 225 0 0 Th230 613 8 2620 0 0 Th232 52 0 223 0 0 J234 593 387 1283 0.03 0.015 U235 26 15 61 0 0 J238 583 340 1377 0.03 0.009 K40 31 4 52 1 0 Ra226 572 2 2127 0.38 0 Ra228 51 0 188 0 0 Petition 870160033568, dated 04 / 07 / 2016, pages 41 / 49 37 / 42 DCP Ore Residues CaCl2 CaCl2p Pb210 570 275 63 31 8 (0 = element content considered below the detection limit)

[0145] The results presented in Table 1 demonstrate unambiguously that the process according to the present invention allows the preparation of a phosphate salt depleted of radioactive elements, that is, a weaker concentration of radionuclides. A significant majority of the radioactive elements are precipitated in the insoluble materials originating from the filtration of the attack liquor. Performing the ore digestion step at a temperature between 50 and 70 °C, for example, 60 °C, favors the precipitation of radioactive elements. Thus, in addition to dicalcium phosphate, purified or unpurified calcium chloride is also obtained, which has reduced concentrations of radionuclides, that is, of radioactive elements. The levels of radioactive elements in the dicalcium phosphate obtained according to the invention are lower than the levels mentioned for different DCP samples by Casacuberta et al. (Journal of hazardous materials, 2009, 170, pages 814 to 823).The phosphate salt according to the present invention is therefore purer than the DCP of the prior art when the content of radioactive elements is considered. Furthermore, the cadmium content in the DCP obtained according to the present invention was 0.26 ppm.

[0146] Example 2 (comparative)

[0147] Example 1 is reproduced by carrying out the attack on the ore and filtering the attack liquor at room temperature. The levels of radioactive elements are distinctly higher than those obtained in dicalcium phosphate according to the present invention, that is, when steps a) and b) of the present process according to the invention are carried out at a temperature between 50 °C and 70 °C. The uranium content was greater than 1,500 Bq / kg. In particular, the levels in the DCP obtained according to Example 2 in K40, Ra228, Th232, Pb210 and U234 were, respectively, 9 Bq / kg, 580 Bq / kg, 72 Bq / kg, 1170 Bq / kg and 900 Bq / kg. The polonium content Po210 was 840 Bq / kg. Petition 870160033568, dated 04 / 07 / 2016, pages 42 / 49 38 / 42

[0148] Example 3

[0149] Example 1 is reproduced from ore of Syrian origin containing a P2O5 content of 30.9%. Dicalcium phosphate is obtained with a P2O5 content of 42% by weight and a calcium content of 27% by weight. The dicalcium phosphate obtained in Example 3 has the same characteristics, in terms of radioactive element content, as the dicalcium phosphate of Example 1. Table 2 below details the metal contents in the dicalcium phosphate obtained according to Example 3. The table also details the metal contents of a dicalcium phosphate described in document no. WO 2004 / 002888 produced by a comparative process in which the digestion and filtration steps of the attack liquor are carried out at ambient temperature. Table 2 - Metal content (in ppm) in dicalcium phosphate from Example 3 and in dicalcium phosphate from document no. WO 2004 / 002888 DCP (Ex. 3 Invention) DCP (comparative WO 2004 / 002888) As 1.5 2.01 Ba 3.5 nd Cd 0.096 0.65 Co 0.94 nd Cr 66 73 Cu 3.8 1.3 Hg < 0.1 nd Mg 20 23.5 Mn 3 nd Mo 0.83 nd Ni 2.2 3.5 Pb 1.3 3.7 Sr 240 nd Petition 870160033568, dated 04 / 07 / 2016, pages 43 / 49 39 / 42 TI < 0.05 and Zn 34 36

[0150] The process according to the present invention allows the production of a phosphate salt, such as dicalcium phosphate, in which the metal content is reduced. The cadmium, arsenic, and lead contents are significantly reduced in the dicalcium phosphate prepared by the present invention. The magnesium content in DCP represents less than 1% of the magnesium initially present in the phosphate ore.

[0151] Example 4 - Preparation of single superphosphate SSP

[0152] Dicalcium phosphate prepared according to Example 1 can be used for the preparation of single superphosphate. Dicalcium phosphate was mixed with a sulfuric acid solution (0.5 molar equivalent relative to the amount of dicalcium phosphate) in a counter-clockwise double helix mixer. The single superphosphate (Ca(H2PO4)2) obtained with a P2O5 content between 32 and 37% by weight is dried and subsequently sieved. The single superphosphate can be used as fertilizer in a composition intended for agriculture. The amount of sulfuric acid can be adjusted to form, in the presence of a bulking agent, single superphosphate with a P2O5 content between 16 and 18%.

[0153] Example 5 - Preparation of triple superphosphate TSP

[0154] Dicalcium phosphate prepared according to Example 1 can be used for the preparation of triple superphosphate. The dicalcium phosphate was mixed with a solution of sulfuric acid (0.33 molar equivalent relative to the amount of dicalcium phosphate) and phosphoric acid (0.33 molar equivalent relative to the amount of dicalcium phosphate) in a double helix mixer operating in opposite directions. The triple superphosphate (Ca(H2PO4)2) obtained with a P2O5 content of 45% by weight is dried and subsequently sieved. The triple superphosphate thus obtained can be used on its own as fertilizer or in a composition intended for Petition 870160033568, dated 04 / 07 / 2016, pages 44 / 49 40 / 42 agriculture.

[0155] Example 6 - Preparation of monoammonium phosphate and diammonium phosphate (MDP / DAP)

[0156] Dicalcium phosphate prepared according to Example 1 can be used for the preparation of monoammonium phosphate and diammonium phosphate. Dicalcium phosphate was mixed with a sulfuric acid solution (1 molar equivalent relative to the amount of dicalcium phosphate) to form phosphoric acid solution and a calcium sulfate precipitate. After filtration, ammonia (between 1 and 2 molar equivalents relative to the amount of dicalcium phosphate) is added to the phosphoric acid solution. The ratio between monoammonium phosphate and diammonium phosphate can vary depending on the amount of ammonia added. After drying and granulation, monoammonium phosphate and diammonium phosphate are used in their original form as fertilizer in a composition intended for agriculture.

[0157] Example 7 - Preparation of an NPK type composition

[0158] Dicalcium phosphate prepared according to Example 1 can be used for the preparation of NPK-type compositions. Dicalcium phosphate was mixed with a solution of sulfuric acid (1 molar equivalent relative to the amount of dicalcium phosphate) and then with ammonia and potassium chloride. The amounts of ammonia and potassium chloride added are determined based on the desired nitrogen and potassium contents in the final NPK composition. NPK compositions of 15 / 15 / 15, 10 / 10 / 10 and 20 / 20 / 20 were specially prepared. The phosphorus and potassium values ​​represent the amount of oxide in the form of P2O5 or K2O that would be present in the composition if all the elemental phosphorus or potassium had been oxidized in these forms. The nitrogen value is the weight value of elemental nitrogen in the composition.

[0159] Example 8

[0160] Example 1 was reproduced from a phosphate rock that Petition 870160033568, dated 04 / 07 / 2016, pages 45 / 49 41 / 42 comprises 2.3% by weight of magnesium. The dicalcium phosphate obtained had the same characteristics as the dicalcium phosphate of Example 1 in terms of radioactive element and cadmium content. Additionally, less than 0.7% by weight of the magnesium present in the initial phosphate rock was present in this dicalcium phosphate.

[0161] Example 9

[0162] The purified calcium chloride (CaCbp) solution obtained in Example 1 is treated with a sulfuric acid solution (96% by weight) to form gypsum dihydrate CaSO4, 2H2O and a hydrochloric acid solution. The gypsum dihydrate CaSO4, 2H2O is analyzed and the contents of metals and radioactive elements are presented below in Table 3. The gypsum dihydrate CaSO4, 2H2O comprises a CaO content of 32.7% by weight and an SO3 content of 46.4% by weight. Table 3 - Metal content (in ppm) and radioactive elements (Bq / kg) in gypsum dihydrate CaSO4, 2H2O according to Example 9 Magnesium (ppm) 20 Strontium (ppm) 600 Total P2O5 (% by weight) 0.042 K40 (Bq / kg) < 16 Ra228 (Bq / kg) < 4 Ra226 (Bq / kg) < 2.2 Th228 (Bq / kg) < 1.7 U235 (Bq / kg) < 1.2 U238 (Bq / kg) < 13

[0163] The process according to the present invention allows the preparation of gypsum which has very low levels of radioactive elements.

[0164] Example 10

[0165] Example 1 is repeated using ash as the phosphate source Petition 870160033568, dated 04 / 07 / 2016, pages 46 / 49 42 / 42 originating from the calcination of sewage sludge. The phosphate content in the phosphate source is 23.6% by weight of P2O5 from the phosphate source. The phosphate salt obtained is a dicalcium phosphate comprising a phosphate content of 33.1% by weight of P2O5 and 15% by weight of calcium in the dicalcium phosphate. The cadmium, chromium, and mercury contents in the DCP obtained are, respectively, 0.28 ppm, 50 ppm, and less than 0.1 ppm. The contents of radioactive elements are similar to those obtained for the DCP obtained in Example 1.

Claims

1. Process for the preparation of a phosphate salt in solid form with the formula Mn(HPO4)y.zH2O where M is Na, K, NH4, n = 2 and y = 1; or M is Ca, n = 1, y = 1; or M is Al or Fe, n = 2, y = 3; and where z is 0, 1 or 2; wherein said phosphate salt has a phosphate content expressed as P2O5 content between 30 and 50% by weight of the phosphate salt, and wherein the cadmium content in said phosphate salt is less than 0.40 ppm, a) a digestion of a phosphate source (3) by a first aqueous solution of hydrochloric acid (2) with the formation of an attack liquor (4) consisting of an aqueous phase comprising phosphate ions and chloride ions in solution and a first insoluble solid phase containing impurities, b) a first separation between the aqueous phase (5) comprising phosphate ions and chloride ions in solution and the first insoluble solid phase (4') containing impurities,c) a neutralization (13) of said aqueous phase (5) comprising phosphate ions and chloride ions in solution with a base (14) to form an aqueous medium (15) comprising chloride ions and to precipitate the phosphate ions in the form of said phosphate salt (16), d) a second separation between said aqueous medium (15) comprising chloride ions and said phosphate salt (16), characterized in that steps a) and b) are carried out at a temperature between 50 °C and 70 °C for a duration of less than two hours and in that said first aqueous hydrochloric acid solution has an HCl concentration between 12% and 15% by weight, the neutralization carried out in step c) has a duration of less than one hour, and in step c) the pH is between 2.5 and 3.

0.

2. Process, according to claim 1, characterized by: - ​​step a) having a duration of less than one hour. Petition 870260077329, dated 04 / 08 / 2026, page 17 / 21 2 / 5 3. Process, according to claim 1 or 2, characterized in that: - said phosphate source (1) comprising a magnesium content greater than 1.5% by weight based on the total weight of the phosphate source, and / or - said phosphate source (1) of step a) being selected from the group consisting of phosphate ore or secondary phosphate sources, such as ash or any other feedstock containing more than 10% phosphate expressed as P2O5 content by weight in the phosphate source.

4. Process according to any one of claims 1 to 3, characterized in that: - in the attack liquor (4), the molar ratio between HCl and Ca is between 1.2 and 2.

6.

5. Process, according to any one of claims 1 to 4, characterized in that said neutralization of step c) - is carried out in the presence of calcium carbonate, calcium hydroxide, calcium oxide or one or more calcium, sodium or ammonium salts, and / or - is carried out in the presence of calcium carbonate, calcium hydroxide, calcium oxide or a water-soluble calcium salt; wherein said precipitated phosphate salt is a calcium phosphate salt and said aqueous medium comprises chloride ions and calcium ions, - is carried out in the presence of calcium carbonate, calcium hydroxide, calcium oxide or a water-soluble calcium salt;wherein said precipitated phosphate salt is a calcium phosphate salt and said aqueous medium is a calcium chloride solution having a calcium chloride content between 8 and 20% by weight of the solution, and / or - being carried out in the presence of calcium carbonate, calcium hydroxide, calcium oxide or a water-soluble calcium salt; wherein said precipitated phosphate salt is a calcium phosphate salt and said aqueous medium (5) comprises chloride ions and calcium ions forming a solution of Petition 870260077329, dated 04 / 08 / 2026, page 18 / 21 3 / 5 calcium chloride; and by the fact that a basic compound (14) selected from calcium hydroxide, calcium oxide and calcium, sodium, potassium or ammonium salts is added to said calcium chloride solution to form a purified calcium chloride solution having a pH between 8 and 12 and a solid phase comprising impurities comprising magnesium salts.; 6. Process, according to any one of claims 1 to 5, characterized by: - ​​a basic compound (25) being added to said aqueous medium (15) comprising chloride ions obtained in step d) to form a purified aqueous phase (28) comprising chloride ions and having a pH between 8 and 12, and a solid phase (27) comprising impurities.

7. Process, according to any one of claims 1 to 6, characterized by further comprising the following steps: e) an attack (17) of all or part of said phosphate salt (16) obtained in step d) by an aqueous solution of strong acid (18) to form a suspension of a first phosphoric acid in solution and a second solid phase, f) a third separation between the first phosphoric acid and said second solid phase.

8. Process according to claim 7, characterized in that in step e), the molar ratio between the aqueous solution of strong acid (18) and said phosphate salt obtained in step d) is between 0.6 and 1.

6.

9. Process according to claim 7 or 8, characterized in that the aqueous solution of strong acid used in step e) is an aqueous solution of sulfuric acid (18) and the second solid phase formed in step e) comprises calcium sulfate hemihydrate, calcium sulfate dihydrate or a mixture thereof.

10. Process, according to any one of claims 7 to 9, characterized in that the second solid phase obtained in step f) and that Petition 870260077329, dated 04 / 08 / 2026, page 19 / 21 4 / 5 comprises calcium sulfate hemihydrate, calcium sulfate dihydrate or a mixture thereof is mixed (31) with an acidic solution (30) to form a solid phase comprising calcium sulfate dihydrate and an acidic aqueous phase comprising phosphate ions.

11. Process according to claim 10, characterized in that: the acidic solution is a sulfuric acid solution (18) and the second solid phase obtained in step f) is similarly mixed with said purified aqueous phase, as defined in claim 5 or 6, or with said aqueous medium (15) comprising chloride ions obtained in step d) or with said aqueous medium comprising chloride ions or calcium ions obtained as defined in claim 6, or mixtures thereof, to form a solid phase comprising calcium sulfate dihydrate and an aqueous phase comprising hydrochloric acid, and / or the aqueous phase comprising hydrochloric acid is recycled to form all or part of said first aqueous hydrochloric acid solution used in step a).

12. Preparation process characterized by comprising the steps of: A) preparation of a phosphate salt in solid form with the formula Mn(HPO4)y.zH2O where M is Na, K, NH4, n = 2 and y = 1; or M is Ca, n = 1, y = 1; or M is Al or Fe, n = 2, y = 3; and where z is 0, 1 or 2; wherein said phosphate salt has a phosphate content expressed as P2O5 content between 30 and 50% by weight of the phosphate salt, and wherein the cadmium content in said phosphate salt is less than 0.40 ppm, and a step B) chosen from: - addition of sulfuric acid to said phosphate salt obtained in A) to form single superphosphate (SSP), or - addition of sulfuric acid and ammonia or an ammonium salt to said phosphate salt obtained in A) to form monoammonium phosphate or diammonium phosphate, or - addition of sulfuric acid, a nitrogen source or a source Petition 870260077329, dated 04 / 08 / 2026, page.20 / 21 5 / 5 of potassium or both, to said phosphate salt obtained in A) for the formation of said NPK type composition, or - addition of phosphoric acid and water to said phosphate salt obtained in A) for the formation of triple superphosphate (TSP), or - addition of a potassium source to said phosphate salt obtained in A) for the formation of said potassium phosphate.

13. Process for preparing monocalcium phosphate (MCP) or monodicalcium phosphate (MDCP) characterized by comprising the following steps: A) preparation of a phosphate salt in solid form with the formula Mn(HPO4)y.zH2O where M is Na, K, NH4, n = 2 and y = 1; or M is Ca, n = 1, y = 1; or M is Al or Fe, n = 2, y = 3; and where z is 0, 1 or 2; wherein said phosphate salt has a phosphate content expressed as P2O5 content between 30 and 50% by weight of the phosphate salt, and wherein the cadmium content in said phosphate salt is less than 0.40 ppm, B) addition of phosphoric acid to said phosphate salt obtained in A) for the formation of monocalcium phosphate, - wherein the weight ratio between phosphoric acid and said phosphate salt is between 0.5 and 0.65 for the preparation of monocalcium phosphate (MCP), - wherein the weight ratio between phosphoric acid and said phosphate salt is less than 0.5 for the preparation of monodicalcium phosphate (MDCP).

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