EP-4735173-A1 - METHOD FOR PURIFYING A PHOSPHATE CONTAINING SOLUTION

Abstract

The present invention concerns a method for purifying a phosphate containing solution using at least a first ion-exchange separation system and a second ion-exchange separation system, each IEX system comprising at least two columns connected in series; each column of said first IEX system comprising at least one strong acid cation resin, and each column of said second IEX system comprising at least one chelating resin.

Inventors

• HUEBER, Damien
• SONVEAUX, MARC

Assignees

• Prayon

Dates

Publication Date

20260506

Application Date

20240626

Claims (1)

1. CLAIMS 1 . A method for purifying a phosphate containing solution [hereafter, solution P] (101 ) using at least a first ion-exchange separation system (102) [hereafter, first IEX system] and a second ion-exchange separation system (103) [hereafter, second IEX system], each IEX system (102, 103) comprising at least two columns (202, 203) connected in series; each column (202, 203) of said first IEX system comprising at least one strong acid cation resin, and each column of said second IEX system comprising at least one chelating resin; wherein said method comprises a series of step sequences which are carried out in each IEX system (102, 103), each sequence comprising at least the steps of: a. feeding (201 , 20T) a solution P (101 ) to at least one column (202, 203); b. collecting (205, 205’) the solution P from at least one column (202, 203) different from the column used in step (a); c. regenerating at least one column (202, 203); and wherein in each sequence, a solution P (101 ) is fed (201 , 20T) in a column (202, 203) different than the column used in step (a) of the previous sequence; with the proviso that the solution P (101 ) fed in said second IEX system (103) is the solution P collected from said first IEX system (102) or that the solution P (101 ) fed in said first IEX system (102) is the solution P collected from said second IEX system (103). 2. A method according to claim 1 , wherein said step (c) comprises at least the steps of: c1. feeding at least one regenerating solution to said column being regenerated; and c2. collecting said regenerating solution from said column being regenerated; with the proviso that the regenerating solution fed in said first IEX system is a regenerating solution collected from said second IEX system. 3. A method according to claim 1 or claim 2, wherein said at least one strong acid cation resin is made of a crosslinked polymer comprising sulfonic acid moieties; and wherein said polymer is selected from the group consisting of polystyrene, polyacrylate, and combinations thereof. 4. A method according to any one of the preceding claims, wherein said at least one chelating resin comprises at least one crosslinked polymer and phosphonic acid and sulfonic acid moieties; and wherein said polymer is selected from the group consisting of polystyrene, polyacrylate, and combinations thereof. 5. A method according to any one of claims 2 to 4, wherein said regenerating solution is an acidic solution or an alkaline solution; preferably, said regenerating solution is an acidic solution comprising at least one acid selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid and mixtures thereof; wherein said acidic solution preferably comprises at least 5 wt.%, more preferably at least 10 wt.%, even more preferably at least 15 wt.% and preferably at most 25 wt.%, more preferably at most 35 wt.% of said acid, based on the total weight of said acidic solution. 6. A method according to claim 5, wherein said acidic solution has a pH of at most 2, preferably at most 1 , even more preferably at most 0.1 . 7. A method according to any one of the preceding claims, wherein each IEX system comprises at least three columns connected in series. 8. A method according to any one of the preceding claims, wherein said solution P comprises based on the total weight of said solution P, at least 5 wt.%, preferably at least 10 wt.%, more preferably at least 20 wt.% and preferably at most 40 wt.%, preferably at most 25 wt.% of P2O5. 9. A method according to any one of the preceding claims, wherein said solution P further comprises at least 100 ppm, preferably at least 1000 ppm, more preferably at least 5000 ppm of Ca ions. 10. A method according to any one of the preceding claims, wherein said solution P further comprises, at least 50 ppm, preferably at least 300 ppm, more preferably at least 1000 ppm of Mg ions. 11. A method according to any one of the preceding claims, wherein said solution P further comprises, at least 50 ppm, preferably at least 500 ppm, more preferably at least 5000 ppm of Fe ions. 12. A method according to any one of the preceding claims, wherein said solution P further comprises, at least 50 ppm, preferably at least 400 ppm, more preferably at least 2000 ppm of Al ions. 13. A method according to any one of the preceding claims, wherein said solution P comprises, at least 50 ppm, preferably at least 300 ppm, more preferably at least 1000 ppm of K ions. 14. A method according to any one of the preceding claims, wherein said solution P comprises, at least 10 ppm, more preferably at least 20 ppm, even more preferably at least 50 ppm, preferably at least 200 ppm, more preferably at least 350 ppm of Na ions. 15. A method according to claim 11 , comprising a step of reducing at least partially said Fe (III) ions; said step of reducing at least partially said Fe(lll) ions being preferably carried out before feeding said solution P into said first I EX system and/or said second I EX system.

Description

“METHOD FOR PURIFYING A PHOSPHATE CONTAINING SOLUTION” FIELD OF THE INVENTION The present invention relates to the technical field of phosphate purification, such as phosphoric acid purification, via ion-exchange. STATE OF THE ART Phosphates such as for example phosphoric acid and phosphate salts such as for example potassium phosphate (mono, di, tri), calcium phosphate (mono, di, tri), sodium phosphates, iron phosphates are used in many applications in the food and animal feed sector, agriculture and in the pharma industry. Phosphoric acid is also used in the production of semiconductors and integrated circuits. Depending on the final application, different levels of purity are required. However, phosphates are often produced from materials containing many impurities. These materials include for example phosphates rocks such as apatite, hydroxyapatite, chlorapatite or rocks containing low levels of P2O5, ashes from wastewater treatment sludges incineration, bone ashes, residual acids from metallurgical treatments, industry side streams such as washing solutions from the chemical, phosphate, pharmaceutical, food-processing industries. The present invention is concerned with the removal of metal ions, in particular Na, Ca, Mg, Fe, Cd, Pb, and Al ions from phosphate containing solutions. EP 0647205 A1 discloses a process for removing iron from phosphoric acid prepared from a wet process. The document further discloses that iron (III) is reduced to iron (II) which can then be removed by cationic ion exchange. US 2015166343 A1 discloses processes and methods for the recovery or the removal of metals, including the so-called “Minor Elements” consisting of iron, aluminum and magnesium, or their respective oxides, from a wet-process phosphoric acid using a continuous ion exchange approach. The document further discloses the use of a strong cationic exchange resin or equivalent material or composition capable of binding the minor element (ME) components, wherein the strong cationic resin is in the H+ form. However, some of the processes of the prior art do not always enable an efficient removal of Na, Ca, Mg, Fe, Cd, Pb, and Al ions and an efficient regeneration of the resins. There is thus a need for an alternative or im proved versatile method for purifying a phosphate containing solutions. SUMMARY OF THE INVENTION The inventors have surprisingly found that the present invention can at least partially fulfill the above identified need. The present invention is concerned with a method for purifying a phosphate containing solution [hereafter, solution P] using at least a first ion-exchange separation system [hereafter, first IEX system] and a second ion-exchange separation system [hereafter, second IEX system], each IEX system comprising at least two columns connected in series; each column of said first IEX system comprising at least one strong acid cation resin, and each column of said second IEX system comprising at least one chelating resin; wherein said method comprises a series of steps sequences which are carried out in each IEX system, each sequence comprising at least the steps of: a. feeding a solution P to at least one column; b. collecting the solution P from at least one column different to the column used in step (a); c. regenerating at least one column; and wherein in each sequence, the solution P is fed in step (a) in a different column than the column used in step (a) of the previous sequence; with the proviso that the solution P fed in said second IEX system is the solution P collected from said first IEX system or that the solution P fed in said first IEX system is the solution P collected from said second IEX system. In the context of the present invention, the term “comprising” should not be interpreted as excluding features or elements other than those explicitly mentioned. It should be construed as specifying the presence of the features or elements indicated, but does not exclude the presence or addition of one or more other features or elements. Thus, the scope of the expression "a method comprising steps A and B" should not be limited to methods consisting only of steps A and B. Similarly, a composition comprising components A and B should not be limited to compositions consisting only of components A and B. Accordingly, the terms "comprising" and "including" encompass the terms more restrictive “consisting essentially of’ and “consisting of”. In the context of the present invention, if an element or component is said to be selected from a list of recited elements or components, it should be understood that the element or component can also be any one of the individual recited elements or components in said list, or can also be selected from a group consisting of any two or more of the explicitly listed elements or components. Furthermore, the terms “first”, “second”, “third” and the like in the description and in the claims, are used for distinguishing between similar elements and no