Process For The Conversion Of Lithium Phosphate Into A Low Phosphate Lithium Solution Suitable As Feedstock For The Production Of Saleable Lithium Products And For The Recovery Of Phosphorous For Re-Use In The Production Of Lithium Phosphate

Abstract

Some aspects of the present disclosure relate to systems and processes for the conversion of lithium phosphate into a low-phosphate solution containing lithium which may be suitable as feedstock for the production of saleable lithium products.

Claims

1. A process for converting lithium phosphate into a low-phosphate solution containing lithium which is suitable as feedstock for the production of saleable lithium products, the process comprising: dissolving the lithium phosphate in acid to form an acidic lithium phosphate bearing solution; treating the acidic lithium phosphate bearing solution with a hydroxide of a phosphate carrier to form a precipitate of phosphate and the phosphate carrier; and separating the precipitate of phosphate and the phosphate carrier leaving a low-phosphate solution containing lithium.

2. The process of claim 1, further comprising: treating the precipitate of phosphate and the phosphate carrier with a hydroxide base to convert the phosphate carrier to a precipitate of hydroxide and the phosphate carrier.

3. (canceled)

4. The process of claim 2, wherein the treatment with the hydroxide base is carried out at a temperature higher than ambient temperature.

5-7. (canceled)

8. The process of claim 2, wherein the treatment with the hydroxide base is carried out at an acidic pH.

9-12. (canceled)

13. The process of claim 2, wherein the treatment with the hydroxide base is carried out in two stages.

14. The process of claim 13, wherein the first stage and/or the second stage of treatment with the hydroxide base are carried out at a temperature higher than ambient temperature.

15. The process of claim 13, wherein the first stage and/or the second stage of treatment with the hydroxide base are carried out at a temperature about 70 C. to about 200 C.

16-17. (canceled)

18. The process of claim 13, wherein the first stage and/or the second stage of treatment with the hydroxide base are carried out at an acidic pH.

19. The process of claim 13, wherein the first stage and/or the second stage of treatment with the hydroxide base are carried out at a pH<2.75.

20. (canceled)

21. The process of claim 13, wherein the pH in the second stage is controlled to a pH greater than the pH of the first stage.

22. (canceled)

23. The process of claim 2, wherein treating the precipitate of phosphate and the phosphate carrier with a hydroxide base releases the phosphate into solution for re-use in a process to produce lithium phosphate.

24. The process of claim 2, wherein the precipitate of hydroxide and the phosphate carrier is separated and at least some of the phosphate carrier is re-used in the step of treating the acidic lithium phosphate bearing solution to form the precipitate of phosphate and the phosphate carrier.

25. The process of claim 2, wherein the precipitate of hydroxide and the phosphate carrier is separated and at least some of the phosphate carrier is dissolved in acid to form a solution of the phosphate carrier ion.

26. The process of claim 25, wherein the solution of the phosphate carrier ion is used to treat a solution containing residual phosphate from which the lithium phosphate has been separated prior to being dissolved in acid whereby the phosphate carrier forms a precipitate of the residual phosphate and the phosphate carrier.

27. The process of claim 26, wherein the solution containing residual phosphate is a brine and the precipitate of the residual phosphate and the phosphate carrier is separated from the brine, thereby leaving the brine substantially phosphate free for return to the environment.

28. The process of claim 27, wherein the precipitate of the residual phosphate and the phosphate carrier separated from the brine is treated with the hydroxide base.

29. The process of claim 1, wherein the phosphate carrier comprises an ion that forms an insoluble phosphate compound within a certain pH range and that releases the phosphate and forms an insoluble hydroxide compound at a higher pH.

30. The process of claim 1, wherein the phosphate carrier ion is iron (lll).

31. The process of claim 1, wherein the phosphate carrier ion is magnesium (II).

32. (canceled)

33. The process of claim 1, wherein the phosphate carrier ion is an ion of a rare earth element.

34-38. (canceled)

Description

BRIEF DESCRIPTION OF THE FIGURES

[0032] The disclosure will now be described in more detail below with reference to embodiments illustrated in the accompanying figures, wherein:

[0033] FIG. 1 illustrates a schematic representation of a phosphate precipitation, conversion and recovery process employing Fe(III) as a phosphate carrier within a process for the separation of phosphate from a solution containing lithium for use as feedstock for the production of saleable lithium products;

[0034] FIG. 2 illustrates a schematic representation of a process and plant for the separation of phosphate from a solution containing lithium for use as feedstock for the production of saleable lithium products, the process employing the phosphate precipitation, conversion and recovery process illustrated in FIG. 1 wherein Fe(III) is employed as a phosphate carrier; and

[0035] FIG. 3 illustrates a flowchart of a process the conversion of lithium phosphate into a low-phosphate solution containing lithium which is suitable as feedstock for the production of saleable lithium products in accordance with an embodiment of the disclosure.

[0036] FIG. 4 illustrates a quantitative graph demonstrating the efficacy of iron hydroxide as the phosphate carrier.

[0037] FIG. 5 illustrates a quantitative graph demonstrating the efficacy of magnesium hydroxide as the phosphate carrier.

[0038] FIG. 6 illustrates a quantitative graph demonstrating the optimisation of phosphate recovery conditions.

DETAILED DESCRIPTION

[0039] Although example embodiments of the disclosed technology are explained in detail herein, it is to be understood that other embodiments are contemplated. Accordingly, it is not intended that the disclosed technology be limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The disclosed technology is capable of other embodiments and of being practiced or carried out in various ways.

[0040] It must also be noted that, as used in the specification and the appended claims, the singular forms a, an and the include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from about or approximately one particular value and/or to about or approximately another particular value. When such a range is expressed, other example embodiments include from the one particular value and/or to the other particular value. Furthermore, unless the context clearly requires otherwise, throughout the description and the claims, the words comprise, comprising, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of including, but not limited to.

[0041] In describing example embodiments, terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art and includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. It is also to be understood that the mention of one or more steps of a process or method does not preclude the presence of additional steps or intervening steps between those steps expressly identified. Steps of a process or method may be performed in a different order than those described herein without departing from the scope of the disclosure. Similarly, it is also to be understood that the mention of one or more components in a process or system does not preclude the presence of additional components or intervening components between those components expressly identified.

[0042] The present disclosure relates to a process for the conversion of a lithium phosphate solution into a low phosphate containing lithium solution which is suitable as feedstock for the production of saleable lithium products, such as lithium carbonate or lithium hydroxide. The disclosure allows the recovery of the phosphate either for re-use to produce more lithium phosphate, or for other purposes. The disclosure also allows for the recovery and re-use of residual phosphate from a lithium-depleted solution resulting from a lithium phosphate precipitation process. The present disclosure is particularly suitable for the conversion of lithium phosphate that has been precipitated from a natural brine.

[0043] Referring to FIG. 1, there is shown a schematic representation of a phosphate precipitation, conversion and recovery process in accordance with an embodiment of the present disclosure. The process relies on the use of a phosphate carrier, which is an ion that forms an insoluble phosphate compound within a certain pH range, and that releases the phosphate, forming a hydroxide, at a higher pH, for example, when treated with sodium hydroxide (i.e. caustic soda). Examples of such phosphate carriers are Fe(III), and Mg(II), with Fe(III) being most preferred although the disclosure can include other ions that behave in a similar fashion.

[0044] The process broadly includes a phosphate precipitation step (110) in which an acidic solution of lithium and phosphate ions is treated with a hydroxide of a phosphate carrier (Fe(III)), thereby partially neutralising the solution and precipitating the phosphate of the phosphate carrier ion. A phosphate recovery step (130) is carried out whereby residual phosphate in a lithium depleted solution, resulting from the treatment of a lithium bearing solution with a phosphate to precipitate lithium phosphate, is also treated with a solution of the phosphate carrier to precipitate the phosphate of the phosphate carrier ion. Preferably, the solution of the phosphate carrier is a chloride of the phosphate carrier cation produced with the addition of hydrochloric acid (135). The precipitates of the phosphate precipitation step (110) and the phosphate recovery step (130) are subjected to treatment with a hydroxide base in a phosphate conversion step (120). The hydroxide base, such as sodium hydroxide, increases the pH such that the solid phosphate of the phosphate carrier ion converts to a solid hydroxide of the phosphate carrier ion. The solid hydroxide of the phosphate carrier ion may then be reused in the phosphate precipitation step (110) and the phosphate recovery step (130) as described above.

[0045] Referring to FIG. 2, there is shown a schematic representation of a lithium phosphate dissolution and phosphate recovery process and plant in accordance with an embodiment of the present disclosure. The process provides for the conversion of lithium phosphate into a phosphate-free lithium solution which is suitable as feedstock for the production of saleable lithium products, such as lithium carbonate or lithium hydroxide.

[0046] The process broadly includes steps of dissolving the lithium phosphate in acid (210), treating the resulting solution with the hydroxide of a phosphate carrier (220) ion such as iron(III) or magnesium(II) to precipitate the phosphate of the phosphate carrier ion, separating the precipitate of the phosphate and the phosphate carrier ion (230) to leave a low phosphate lithium solution suitable (240) for use for the production of saleable lithium products.

[0047] The phosphate precipitate is treated with a hydroxide base (250) such as sodium hydroxide or potassium hydroxide to regenerate a hydroxide of the phosphate carrier ion (260) for treating the acidic solution of dissolved lithium phosphate (220) and to produce a solution of phosphate suitable for re-use to produce more lithium phosphate (270). Some of the hydroxide of the phosphate carrier ion can be used to generate a solution of the phosphate carrier as a chloride to precipitate residual phosphate ions in lithium depleted brine solution (280) which is then separated before returning the brine solution to the environment (290).

[0048] The lithium phosphate which forms the starting material for this disclosure can be produced from the processing of mineral sources such as spodumene, petalite and lepidolite, seawater and from natural brines containing lithium such as those found in Salars in the Andes Mountains. Following the removal of target impurities, such as calcium, magnesium and boron ions, from a feed stock such as brine containing lithium ions, the recovery of lithium from the pre-treated brine can be performed by the lithium phosphate precipitation process. The lithium phosphate precipitation process includes treating the brine containing aqueous lithium (Li+) with a phosphorus containing reagent to form a lithium phosphate precipitate.

[0049] In order to precipitate a high proportion of the lithium, a certain concentration of phosphorous must be maintained. After separation of the lithium phosphate precipitate some phosphate remains in the lithium-depleted brine and needs to be recovered for re-use. This is because phosphorous containing reagent is expensive and because the brine containing phosphate cannot be returned to the environment.

[0050] Examples of such phosphate carriers are Fe(III), and Mg(II), with Fe(III) being most preferred although the disclosure can include other ions that behave in a similar fashion. The suitability of Fe(III) as a phosphate carrier ion is due to its propensity to precipitate as a phosphate at a lower pH and as a hydroxide at a higher pH. The reversible reaction of the phosphate carrier ion Fe(III) between an insoluble hydroxide compound and an insoluble phosphate compound, which is pH dependent, is represented by:

Fe(OH).sub.3FePO.sub.4

[0051] FIG. 3 illustrates an embodiment of the disclosure involving a process comprising a sequence of steps. The process includes a step of separating lithium phosphate precipitate from brine by solid/liquid separation (310).

[0052] Lithium phosphate precipitate is reacted (dissolved) with a mineral acid, such as hydrochloric acid, which lowers the pH of the solution, and a hydroxide of a phosphate carrier ion, such as iron(III), is added thereby precipitating the phosphate of the phosphate carrier ion (320). As a further example, if magnesium(II) were used instead of iron(III), then the resulting precipitate would be magnesium phosphate instead of iron (III) phosphate. Preferably, and as illustrated in FIG. 2, the reaction of the hydroxide of the phosphate carrier and the acidic lithium phosphate solution is allowed to take place in two stages at about 80 C. The pH in the first stage is preferably controlled in a range of about pH 1.25 to 1.5, thus precipitating about 90% of phosphorus in solution. The second stage is preferably controlled to a higher pH where the remainder of the phosphorus is precipitated to <10 mg/L. The pH of the second stage is dependent on the specific phosphate carrier being used. For example, if iron(III) is used as the phosphate carrier ion, the pH of the second stage would preferably be controlled to about pH 2.25 to 2.75. It is to be appreciated, however, that the although the addition of the hydroxide of the phosphate carrier ion does, at least to some extent, neutralise the acidic lithium phosphate solution the precipitation of the phosphate of the phosphate carrier ion may occur preferably at a relatively low pH range, being a pH of less than or equal to about the hydrolysis pH of the phosphate carrier ion being used. In the case of Fe(III), the precipitation of the phosphate of the phosphate carrier ion may occur preferably at about pH 2.75. In the case of Mg(II), the precipitation of the phosphate of the phosphate carrier ion may occur preferably at about pH 4.

[0053] The precipitate of the phosphate and the phosphate ion carrier, and any unreacted hydroxide, is separated from the solution containing lithium ions by a solid liquid separation process leaving a low phosphate containing lithium solution (330). The low phosphate containing lithium solution may be used as a feedstock to produce saleable forms of lithium such as lithium carbonate or lithium hydroxide. As a further example, if sulphuric acid were used instead of hydrochloric acid to dissolve the lithium phosphate then the resulting solution would contain lithium sulphate instead of lithium chloride.

[0054] The precipitate of the phosphate and the phosphate carrier ion is treated with a solution of a hydroxide base, such as NaOH(aq) or KOH(aq). This increases the pH and precipitates the hydroxide of the phosphate carrier ion and releases phosphate ions into the solution (340). For example, if the phosphate carrier was iron(III) and the strong base sodium hydroxide solution then solid iron(III) hydroxide and a solution of sodium phosphate would be formed.

[0055] Preferably, and as illustrated in FIG. 2, the treatment with sodium hydroxide is preferably performed in two stages at about 90 C. In the first stage the sodium hydroxide is preferably in large excess to ensure maximum conversion to ferric hydroxide and maximum phosphate dissolution. The second stage is preferably controlled to about 5 g/L excess sodium hydroxide by further addition of the phosphate precipitate to minimise the excess hydroxide present in the sodium phosphate solution. A high conversion of phosphate precipitate to hydroxide is achieved under these conditions.

[0056] The hydroxide of the phosphate carrier ion and the phosphate ions in solution are separated by solid liquid separation and the phosphate ions are reused to produce more lithium phosphate and the hydroxide of the phosphate carrier is reused to treat the lithium phosphate dissolved in mineral acid and some is reused to recover residual phosphate ions from the lithium depleted brine (350). The hydroxide of the phosphate carrier that is reused to recover residual phosphate is first reacted with mineral acid, such as hydrochloric acid, to form a low pH solution of the phosphate carrier ion. This solution is used to treat lithium depleted brine which has previously been treated with a phosphate supplying reagent to precipitate out lithium ions as lithium phosphate thus leaving the brine depleted of lithium but containing some residual phosphate. The treatment of the lithium depleted brine with the solution of the phosphate carrier ion precipitates out residual phosphate which can be separated from the brine by solid liquid separation which can then be returned to the environment (360).

[0057] In a preferred embodiment, the process involves the following steps: [0058] (1) Dissolving lithium phosphate in acid to form a lithium phosphate-containing solution; [0059] (2) Treating the lithium phosphate-containing solution with the hydroxide of the phosphate carrier ion, which leads to the neutralisation of the acid leading to a pH less than or equal to the hydrolysis pH of the phosphate carrier ion, which if the phosphate carrier ion is Fe(III) leads to a pH less than about pH 2.75, and the precipitation of the phosphate; [0060] (3) Separating the phosphate precipitate leaving a substantially phosphate-free lithium solution; [0061] (4) Treating the phosphate precipitate with a solution of a hydroxide base, such as NaOH(aq) or KOH(aq), at a relatively higher pH to convert the precipitate phosphate precipitate of the phosphate carrier ion into the hydroxide precipitate of the phosphate carrier ion and releasing the phosphate into the solution; [0062] (5) Separating the hydroxide precipitate for use in Step (2), and leaving a phosphate solution suitable for re-use in a process to precipitate more lithium phosphate; and/or [0063] (6) Residual phosphate remaining in a solution that has been depleted of lithium by the addition of phosphate and precipitation and separation of lithium phosphate is recovered by the addition of the phosphate carrier cation, preferably as a chloride (or sulphate), which precipitates the phosphate ions. The precipitated phosphate is then separated from the depleted lithium solution. The precipitated phosphate is in the same form as in process step 2 and can therefore be recycled to Step 4 to recover the phosphate.

[0064] The phosphate-free lithium solution may then be treated by conventional, or other, means to recover the lithium. For example, the remaining lithium solution may be treated with an alkali carbonate to precipitate lithium carbonate, or treated to produce lithium hydroxide.

EXAMPLES

[0065] Various aspects of the disclosed solution may be still more fully understood from the following description of some example implementations and corresponding results. Some experimental data is presented herein for purposes of illustration and should not be construed as limiting the scope of the disclosed technology in any way or excluding any alternative or additional embodiments.

Example 1General Process

[0066] A first example of certain implementations of the disclosed technology and corresponding results will now be described with respect to a brine solution composed of 1.2 g/L Ca, 10.0 g/L K, 4.3 g/L Mg, 114 g/L Na, 3.2 g/L S, 190 g/L Cl, 440 mg/L Li and 350 mg/L B that was treated for lithium recovery.

[0067] The brine was first treated with sodium hydroxide and sodium carbonate to precipitate both the magnesium and calcium to <10 mg/L.

[0068] After solid/liquid separation the solution was then heated to >100 C. and then a 100-200 g/L solution of sodium phosphate was added to precipitate lithium phosphate. The Li precipitation is dependent on the residual P (phosphorus) in solution. Nominally 70 to 85% of the lithium is precipitated as lithium phosphate. The resultant solution contained 400 mg/L of phosphorous, which concentration was required to ensure a high degree of lithium precipitation.

[0069] The lithium-depleted solution was then treated with a stoichiometric quantity of ferric chloride solution, with the pH controlled between pH 4 and 7, to produce an iron precipitate. The residual P was <5 mg/L.

[0070] The lithium phosphate was dissolved in a stoichiometric quantity of hydrochloric acid to produce a solution containing 35-40 g/L Li.

[0071] This solution was treated with ferric hydroxide slurry in two stages at 80 C., to produce an iron precipitate. The pH in the first stage was controlled to pH 1.25 to 1.5 and precipitated 90% of the phosphorus. The second stage was controlled to pH 2.25 to 2.75, where the remainder of the phosphorus was precipitated to <10 mg/L.

[0072] The iron precipitates were mixed and treated with a sodium hydroxide solution at 90 C. in a two stage process. In the first stage the sodium hydroxide was in excess to ensure maximum conversion to ferric hydroxide (and maximum phosphate dissolution). The second stage was controlled to 5 g/L excess hydroxide by further addition of the ferric phosphate precipitate to minimise the excess hydroxide present in the sodium phosphate solution. A conversion of ferric phosphate to ferric hydroxide of >95% was achieved.

[0073] The above steps were repeated a number of times to new treated brine solutions without the addition of any new ferric hydroxide or ferric phosphate. The results were similar for each cycle. Thus, a locked cycle test was achieved and shown to be successful, proving the suitability of Fe(III) as a phosphate carrier ion.

[0074] It is to be appreciated that similar parameters may be applied to a magnesium system, where magnesium is used as the phosphate carrier ion in place of iron (III). In the case of a magnesium system, the main differences to the ferric system, and embodiments thereof described herein, are in the control of the pH of the system.

[0075] For example, in a magnesium system, in the phosphate recovery step after the lithium phosphate precipitation, the magnesium chloride addition reaction takes place at a higher pH than the equivalent reaction in the ferric system, e.g. at pH 10 or above. Hydrochloric acid can then be added to reduce the pH to neutral in the spent brine.

[0076] In the phosphate precipitation step after the lithium phosphate dissolution, the magnesium hydroxide can be added in two stages with the pH being controlled at about pH 4 in the first stage and about pH 5-6 in the second stage to achieve high phosphorus precipitation.

[0077] In the magnesium phosphate precipitate conversion to magnesium hydroxide and sodium phosphate step, the pH and temperature is similar to the ferric equivalent. The magnesium phosphate conversion is slightly lower at >90%. However the pH can be raised to increase the percentage of magnesium phosphate that reacts.

Example 2Ferric Phosphate Precipitation

[0078] In this second example, the efficacy of ferric hydroxide as the phosphate carrier was quantitatively tested in the step of treating the lithium phosphate bearing solution to form a ferric phosphate precipitate. Details of the concentrations of free phosphorous, iron and lithium ions, and the pH of the solution, over the course of this experiment can be found in FIG. 4.

[0079] An initial amount of lithium phosphate precipitate was added with hydrochloric acid to provide a solution of phosphoric acid and lithium phosphate. The phosphorus precipitation was then conducted in two stages, both controlled to 80 C.

[0080] In stage 1 (time 0-180 min), ferric hydroxide filter cake and the solution were simultaneously added to a vessel, containing a small heel of solution at pH 1.25. The phosphate solution was added at a set flowrate over 180 minutes while the ferric hydroxide addition was controlled to maintain pH 1.25. Approximately 95% of the ferric hydroxide was added in this stage.

[0081] As shown in FIG. 4, the addition of ferric hydroxide significantly increased the free lithium ions in the solution as a ferric phosphate precipitate was formed. While the skilled person would appreciate that the lithium may be extracted to be processed into a saleable form after this first stage, the inventors have found that the solution may be further treated in a second stage to provide additional recovery and recycling capabilities for the phosphorous in solution.

[0082] Accordingly, in stage 2 (time 180-300 min), further ferric hydroxide was added to raise the pH to 2.5 over 0.5 hours and then controlled at that pH for a further 1.5 hours. This addition of further ferric hydroxide caused a decrease in the phosphorous in solution from 1100 mg/L to 2 mg/L. The ferric ion concentration in solution was <5 mg/L throughout stage 2.

Example 3Magnesium Phosphate Precipitation

[0083] In this third example, the efficacy of magnesium hydroxide as the phosphate carrier was quantitatively tested in the step of treating the lithium phosphate bearing solution to form a magnesium phosphate precipitate. Details of the concentrations of free phosphorous, magnesium and lithium ions, and the pH of the solution, over the course of this experiment can be found in FIG. 5.

[0084] An initial amount of lithium phosphate precipitate was added with hydrochloric acid to provide a solution of phosphoric acid and lithium phosphate. The phosphorus precipitation was then conducted in two stages, both controlled to 80 C.

[0085] In stage 1 (time 0-125 min), magnesium hydroxide filter cake and the solution were simultaneously added to a vessel, containing a small heel of solution at pH 5.5. The phosphate solution was added at a set flowrate over 125 minutes while the magnesium hydroxide addition was controlled to maintain pH 5.5. Approximately 85% of the magnesium hydroxide was added in this stage.

[0086] As shown in FIG. 5, the addition of magnesium hydroxide significantly increased the free lithium ions in the solution as a magnesium phosphate precipitate was formed. Similar to the ferric phosphate example, the skilled person would appreciate that the lithium may be extracted to be processed into a saleable form after this first stage; however, the solution may also be further treated in a second stage to provide additional recovery and recycling capabilities for the phosphorous in solution.

[0087] Accordingly, in stage 2 (time 125-160 min), more magnesium hydroxide was added to raise the pH to 6.0 and then controlled at that pH for a further 30 minutes. This addition of further magnesium hydroxide caused a decrease in the phosphorous in solution from 235 mg/L to 126 mg/L. The remaining magnesium in solution after stage 2 was 1460 mg/L.

[0088] In further tests (not shown) conducted by adding stoichiometric amounts of magnesium hydroxide, it was found that the phosphorus concentration in solution could be reduced to <50 mg/L; however, the magnesium in solution was higher than in the above test.

Example 4Phosphate Recovery

[0089] In this fourth example, the optimisation of phosphate recovery conditions was tested.

[0090] A solution of spent brine (after the lithium phosphate precipitation step) was placed in a reaction vessel. A 230 g/L ferric chloride solution was slowly added to the spent brine over a four hour period at ambient temperature. As the ferric chloride was added, a precipitate formed and the pH slowly decreased. Solution samples were taken every 15 minutes and the pH monitored throughout.

[0091] The solution analyses, particularly the concentrations of phosphorous and iron ions in solution, have been plotted against pH in the FIG. 6.

[0092] As shown in FIG. 6, the ferric chloride gradually reduced the pH of the brine solution by forming ferric hydroxide. The ferric chloride also decreased the phosphate in solution by precipitating it as ferric phosphate. The graph shows that at pH 6.2 the phosphorus in solution was reduced to 2 g/L, and remained low (as did the iron) until the pH dropped to below 2.5.

[0093] These results indicate a preferable operating window for phosphate recovery of between pH 2.5 and 6.2. It also indicates that the preferable operating pH for stage 2 of ferric phosphate precipitation is pH 2.5, as at that pH the iron and phosphorus in solution was minimal.

[0094] Any of the herein described components and processes discussed may take on various forms to provide and meet the environmental, structural demands, and operational requirements. The specific configurations can be varied according to particular design specifications or constraints requiring a process or system according to the principles of the disclosed technology. Such changes are intended to be embraced within the scope of the disclosed technology. The presently disclosed embodiments, therefore, are considered in all respects to be illustrative and not restrictive. The scope of the present solution is indicated by the appended claims, rather than the foregoing description, and all changes that come within the meaning and range of equivalents thereof are intended to be embraced therein.

[0095] The definitions of the words or elements of the following claims are, therefore, defined in this specification to not only include the combination of elements which are literally set forth. It is also contemplated that an equivalent substitution of two or more elements may be made for any one of the elements in the claims below or that a single element may be substituted for two or more elements in a claim. Although elements may be described above as acting in certain combinations and even initially claimed as such, it is to be expressly understood that one or more elements from a claimed combination can in some cases be excised from the combination and that the claimed combination may be directed to a subcombination or variation of a subcombination(s).

[0096] Insubstantial changes from the claimed subject matter as viewed by a person with ordinary skill in the art, now known or later devised, are expressly contemplated as being equivalently within the scope of the claims. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are defined to be within the scope of the defined elements. The claims are thus to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, what can be obviously substituted and also what incorporates the essential idea of the embodiments.

[0097] What has been described above includes examples of one or more embodiments. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned embodiments, but one of ordinary skill in the art may recognize that many further combinations and permutations of various embodiments are possible. Accordingly, the described embodiments are intended to embrace all such combinations, alterations, modifications and variations that fall within the spirit and scope of the appended claims.