Production of Strontium Sulfate and Strontium Carbonate from Brines

Abstract

The present invention relates to a process to produce high purity strontium sulfate and strontium carbonate from subterranean brines. The present disclosure also relates to chemical precipitations of subterranean brines to isolate strontium from divalent cations, such as calcium and barium. Such precipitations include the use of sulfate and subsequent solids separations and washing of the precipitate. In a latter step in the strontium carbonate process, a metathesis reaction with a carbonate is performed upon the strontium sulfate to produce strontium carbonate while allowing optional recycling of the sulfate. An additional rinse with acid or water of the strontium sulfate may be performed prior to metathesis to increase the purity of the resulting strontium carbonate.

Claims

1. A method for producing strontium carbonate from an aqueous brine solution having 300-30,000 mg/L of strontium, 50-10,000 mg/L barium, 5,000-150,000 mg/L sodium and 10-100,000 mg/L calcium, the method comprising the steps of: combining the brine solution with an effective amount of a first sulfate-containing reagent to precipitate barium sulfate in a first effluent; separating said barium sulfate from said first effluent; identifying the molar concentration of strontium in said first effluent; combining said first effluent with an effective amount of a second sulfate-containing reagent to precipitate substantially only strontium sulfate in a second effluent; separating said strontium sulfate from said second effluent; washing said strontium sulfate with an aqueous solvent; suspending said strontium sulfate precipitate in an aqueous suspension; and combining said strontium sulfate with a carbonate-based reagent to convert said strontium sulfate to strontium carbonate.

2. The method of claim 1, wherein said the first sulfate-containing reagent is selected from the group consisting of: sodium sulfate, lithium sulfate, potassium sulfate, ammonium sulfate or sulfuric acid.

3. The method of claim 2, wherein said first sulfate containing reagent is sodium sulfate and said concentration is 0.1%, up to 1%, up to 15%, or up to 30% molar excess of the barium concentration.

4. The method of claim 1, wherein said second sulfate-containing reagent is selected from the group consisting of: sodium sulfate, lithium sulfate, potassium sulfate, ammonium sulfate, strontium sulfate, or sulfuric acid.

5. The method of claim 4, wherein said second sulfate containing reagent is sodium sulfate and said effective amount is less than 0.1%, less than 1%, less than 15%, less than 50% or less than 70% of said molar concentration of strontium.

6. The method of claim 1, wherein the carbonate-containing reagent is selected from the group consisting of: sodium carbonate, lithium carbonate, potassium carbonate, ammonium carbonate, or carbon dioxide and an alkali.

7. The method of claim 6, wherein said carbonate-containing reagent is gaseous carbon dioxide introduced to said aqueous suspension combined with sodium hydroxide.

8. The method according to claim 1, further comprising the step of pretreating the brine solution utilizing a method selected from the group consisting of: a filtration separation, a density-based separation, a hydrocyclone, an oxidation process, an absorption process, a chelation process, or an ion-exchange process.

9. The method of claim 8, wherein said pretreating step utilizes filtration with a filter having a pore size of 10 to 100 nm, 100 to 1000 nm, or 1000 nm to 100 μm.

10. The method of claim 1, wherein the barium sulfate is separated from said first effluent by a method selected from the group consisting of: densification using a settling tank/clarifier, filtration, and use of a hydrocyclone.

11. The method of claim 1, wherein the strontium sulfate is separated from said second effluent by a method selected from the group consisting of: densification using a settling tank/clarifier, filtration, and use of a hydrocyclone.

12. The method of claim 1, wherein said aqueous solvent is water.

13. The method of claim 1, said aqueous suspension is a water slurry.

14. The method of claim 1, further comprising the step of separating the strontium carbonate from said aqueous suspension by a method selected from the group consisting of: densification using a settling tank/clarifier, filtration, and use of a hydrocyclone.

15. The method of claim 1, further comprising the step of washing said strontium carbonate with water.

16. The method of claim 1, wherein any separating step is performed by filtration with a filter having a pore size of 10 to 100 nm, 100 to 1000 nm, or 1000 nm to 100 μm.

17. The method of claim 1, wherein said first effluent is flowing at a first flow rate and second sulfate-containing reagent is combined with said first effluent through a fluid recycling loop having a second flow rate less than said first flow rate of said first effluent.

18. The method of claim 17, wherein a flow rate ratio between said first flow rate and said second flow rate is between 50 and 2000.

19. The method of claim 17, wherein said second sulfate-containing reagent is concentrated.

20. The method of claim 19, wherein said second sulfate-containing reagent is sodium sulfate and said concentration is between 1-40 percent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG. 1 is schematic diagram of a first embodiment of the process of the present invention.

[0041] FIG. 2 is a schematic diagram of a second embodiment of the invention illustrating recycling of the sodium sulfate from the third stage of process densification.

[0042] FIG. 3 is a schematic diagram of a third embodiment of the invention illustrating recycling of sodium sulfate and washing of the strontium carbonate.

[0043] FIG. 4 is a schematic diagram of a fourth embodiment of the invention illustrating a recycling option for the strontium carbonate wash water.

[0044] FIG. 5 is a schematic diagram of a fifth embodiment of the invention replacing clarifiers from FIG. 5 with filters.

[0045] FIG. 6 is a schematic diagram of a sixth embodiment of the invention with an added wash step for rinsing the strontium sulfate.

[0046] FIG. 7 is a graph showing the mass in moles per liter of solution of barium, strontium and calcium precipitated as respective sulfates from initial feed brine upon increasing dosage of sodium sulfate.

[0047] FIG. 8 is a graph of the modelled metals precipitated from a barium depleted brine using pH control.

DETAILED DESCRIPTION

[0048] The following description sets forth numerous exemplary configurations, parameters, and the like. It should be recognised, however, that such description is not intended as a limitation on the scope of the present invention but is instead provided as a description of exemplary embodiments.

[0049] The present invention describes methods for an economical process for producing substantially pure strontium carbonate or strontium sulfate from subterranean brines having low (<1%) concentrations of strontium such as those produced during oil and gas operations. Typically, the composition of these brines is dominated by chloride as the anion with sodium being the dominant cations followed by strontium, barium, calcium, potassium, magnesium, manganese and various other cations and anions as minor constituents. These brines are considered waste products in oil and gas operations. Creation of a valuable strontium carbonate or strontium sulfate from these brines is a beneficial and more sustainable utilization of resources as well providing an economic benefit.

Definitions

[0050] In each instance herein, in descriptions, embodiments, and examples of the present invention, the terms “comprising”, “including”, etc., are to be read open-ended and expansively, without limitation. Thus, 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 to opposed to an exclusive sense, that is to say in the sense of “including but not limited to”.

[0051] The term “about” or “approximately” as used herein means within 20%, more preferably within 10%, and most preferably still within 5% of a given value or range. Percent and mg/L may be used interchangeably where 1% is equivalent to 10,000 mg/L.

[0052] The term “brine” or “brine solution” as used herein means an aqueous solution including halide salts. The fraction of total halides in one embodiment are >99% chloride and less than 1% fluoride, less than 1% iodide, and less than 1% bromide. In another embodiment the halides are >95% chloride, and less than 5% fluoride, less than 5% iodide and less than 5% bromide. In another embodiment the fraction of total halides are >80% chloride and less than 20% fluoride, less than 20% iodide, and less than 20% bromide. The halide concentrations are defined by the cation concentrations. In one embodiment, the cations are sodium greater than 5,000 mg/l, barium greater than 100 mg/l, calcium greater 500 than mg/l, or magnesium greater than 100 mg/L, and strontium greater than 500 mg/l. In another embodiment, the cations are sodium less than 400,000 mg/l, barium less than 20,000 mg/l, calcium less than 10,0000 mg/l, or magnesium less than 100 mg/L, and strontium greater than 500 mg/l and less than 20,000 mg/L.

[0053] The term “subterranean brine” as used herein means a brine derived from below the surface of the earth.

[0054] The term “produced water” as used herein means fluid that is produced from an oil or gas well as a result of well operations in the drilling, mining or production of oil or gas, such as natural gas, from a subterranean well, such as but not limited to hydraulic fracturing (also known as hydrofracturing or fracking) flowback water. Produced water is a subset of subterranean brine.

[0055] The term “aqueous subterranean halide brine solution”, unless otherwise specified, refers generally to subterranean brines produced from oil or gas conventional or shale formations. typically having a concentration of less than 20,000 mg/L strontium and often even less barium, such as but not limited to less than 3,000 mg/L barium. For instance, in at least one embodiment the aqueous subterranean halide brine solution includes 300 mg/L to 3,000 mg/L barium and 1,000 to 10,000 mg/L and strontium, in the presence of total dissolved solids (TDS) concentrations ranging from 100,000 to 500,000 mg/L. More commonly, barium concentrations may be in the range of 30 to 4,000 mg/L, and in some embodiments may be in the range of 500 to 3,000 mg/L, compared to TDS common ranges of 150,000 to 250,000 mg/L. Strontium concentrations may be in the range of 300 mg/L to 10,000 mg/L, and in some embodiments may be in the range of 3,000 to 9,000 mg/L, compared to TDS ranges 150,000 to 250,000 mg/L. Thus, strontium is typically a minor component of the overall ionic composition of aqueous subterranean halide brine solutions and the barium concentration is typically lower than the strontium concentration. Therefore, “aqueous subterranean halide brine solution” as defined and used herein, is a significant distinction from ore composition purification methodologies currently used to derive or produce strontium carbonate and/or strontium sulfate.

[0056] The term “halide” refers to any compound containing a halogen atom, or to a halogen anion. Examples of halides include chloride, fluoride, iodide and bromide. In at least one embodiment, chloride may be the dominant halide in subterranean brines but other lower concentration halides may also be present.

[0057] The present disclosure provides novel methods or processes to derive greater than 80% to 99.99% purity strontium carbonate or strontium sulfate from subterranean brines. Subterranean brines have heretofore not been a raw material for commercial strontium carbonate production. Subterranean brines are impure and thus require an economical separation and purification process for high purity strontium carbonate or strontium sulfate production which has yet to be achieved.

[0058] FIG. 1 shows a flow diagram of a first embodiment of the process of the present invention. In this embodiment, feed brine is blended with sodium sulfate to precipitate out the barium from the feed brine. The sodium sulfate dose is preferably 0.1% molar excess of the barium concentration, though in other embodiments it may be up to 1%, up to 15%, or up to 30% in molar excess thereof. The molar excess of sodium sulfate used may depend on the scale of processing. The larger the molar excess of sodium sulfate used in this precipitation step, the lower the ultimate yield of strontium sulfate. This results in complete precipitation of the barium from the feed brine as barium sulfate and some slight precipitation of strontium sulfate only to the extent of the molar excess quantity of sodium sulfate consumed by the barium. As a water solution, given the known solubility product of barium sulfate, the remaining barium in solution is approximately 10 μM (0.014%). In brine solutions it will be slightly different due to the influence of the ionic composition but will nonetheless be very low. The solid barium sulfate (including a small concentration of strontium sulfate) is separated by a densification process such as a clarifier, where the solid barium sulfate settles to the bottom of the clarifier, such as by gravity. The remaining solution may be referred to as intermediate brine and is a barium-depleted brine. This intermediate brine may be decanted to isolate from the precipitated barium sulfate.

[0059] The intermediate brine is added to a second stage mixer where is it blended with additional amounts of sodium sulfate to precipitate strontium sulfate. This Figure shows the sodium sulfate added in a recycling loop where a concentrated sodium sulfate solution may be added at a small flowrate into a larger flowrate in to and out of the intermediate brine tank. The sodium sulfate added in this step is quantitatively dosed at slightly under the molar concentration of the strontium, preferably less than 0.1% though in other embodiments at less than 1% or less than 15%, or in other embodiments less than 50% or in other embodiments, less than 70% to avoid precipitating materials such as calcium or to allow more than one batch operation on the same depleted brine. As before, the lower the molar equivalent concentration of sodium sulfate relative to the strontium ion concentration used, the lower the resulting yield of strontium sulfate, and may depend on the scale of processing.

[0060] The final step in this embodiment is the metathesis reaction of sodium carbonate with the strontium sulfate to form the solid strontium carbonate which is separated by a densification process.

[0061] A second embodiment of the process is illustrated in FIG. 2. In this embodiment, the clarified liquid from the strontium sulfate to strontium carbonate metathesis is primarily sodium sulfate and water. This stream is recycled to the strontium sulfate blender. The example illustrated is one example of where this stream may be directed but is not meant to be limiting. There may also be some residual strontium dissolved in this stream and rather than discharging it, it is conserved in the process through this recycle stream.

[0062] A third embodiment of the process is illustrated in FIG. 3. This embodiment builds upon the prior embodiments by incorporating a wash stage for the strontium carbonate to remove any potentially soluble salts before the separation process of the strontium carbonate.

[0063] In a fourth embodiment, illustrated in FIG. 4, based upon the prior embodiments, the discharge of the wash water for the strontium carbonate purification is recycled to an earlier point in the process. This embodiment conserves water as well as soluble yet low concentration strontium at this stage. The example illustrated is one example of where this stream may be directed but is not meant to be limiting. In this example, the used wash water is blended with solid sodium sulfate which is then added as a solution to the initial feed brine.

[0064] In a fifth embodiment, any or all of the clarification or densification stages may be replaced by fine filtration equipment. The filters may range preferably from 10 nm to 100 nm or optionally 100 nm to 1000 nm pore sizes or 1000 nm to 100 μm pore size. This embodiment is illustrated in FIG. 5 where all the clarifiers are replaced by filters. Any or all of these filters may be a hydrocyclone operation.

[0065] In a sixth embodiment, shown in FIG. 6, the strontium sulfate is rinsed to purify the strontium sulfate by removing calcium sulfate. Water or water containing a halogen salt such as sodium chloride up to the saturation concentration of the salt may be used for the rinse.

[0066] Notably, for all of the solid separation steps employed, common technologies for filtration, dewatering and/or drying such as filter presses or the addition of dewatering aids such as coagulants, flocculants or polymers may be employed to help in the drying process or the use of recycle loops to aid in the separation.

EXAMPLES

[0067] The examples described herein are provided for the purpose of illustrating specific embodiments of the invention and are not intended to limit the invention in any way. A list of general principles, in no particular order, demonstrated in the examples are: [0068] 1. Barium sulfate is greatly favored over strontium and calcium sulfate in terms of reaction with aqueous sulfates. [0069] 2. Strontium sulfate is favored over calcium sulfate by equilibrium reaction with aqueous sulfates, but the reaction is rate limited by mass transfer and crystallization induction kinetics thus calcium sulfate will often be an impurity not predicted by equilibrium modeling. [0070] 3. Carbonate solutions react with strontium and calcium sulfates to make strontium and calcium carbonates. [0071] 4. Iron and other metal impurities dissolve at low pH and precipitate at high pH. [0072] 5. Calcium sulfate is more soluble than strontium sulfate thus allowing washing options to separate calcium sulfate from strontium sulfate. [0073] 6. Calcium carbonate and strontium carbonate both dissolve in acid solutions.
Persons of ordinary skill can utilize the disclosures and teachings herein to produce other embodiments and variations without undue experimentation. All such embodiments and variations are considered to be part of this invention.

Example 1

Thermodynamic Modelling Data

[0074] As an example of the process equilibrium driving the embodiments, a simulation was done using OLI Systems Studio StreamAnalyzer (version 10) to guide and demonstrate the processes described in this publication. The starting material for the simulation was based upon the composition of a known subterranean brine and is shown below in Table 1:

TABLE-US-00001 TABLE 1 Subterranean brine soluble ionic composition used for precipitation simulation from actual brine used in purification embodiments. Ionic Concentration, Concentration, Species mg/L mM Cl−1 152095 4290.0 Na+1 61400 2670.7 Ca+2 23900 596.3 Sr+2 6930 79.1 Ba+2 3140 73.2 K+1 2480 63.4 Mg+2 1780 22.9 Br−1 299 13.5 Li+1 94 3.7 Fe+2 89 1.6 HCO3−1 55 0.9 Mn+2 20 0.4

[0075] The simulation of sulfate precipitation upon addition of sodium sulfate is shown in FIG. 7, the barium precipitates first in relation to the sodium sulfate dose, followed by the strontium, followed by the calcium for this simulation. When 0.025 M sodium sulfate is added, the barium is precipitated and separated as barium sulfate and the soluble aqueous composition of the solution is shown below in Table 2.

TABLE-US-00002 TABLE 2 Simulated composition of element species of aqueous phase mixture in Table 1 after addition of 0.025M sodium sulfate. Element Aqueous Solid Phase, Liquid Phase, Solid Phase, Species Phase, mM mM mg/L mg/L H(+1) 1.02E+05 0.00E+00 1.03E+05 0.00E+00 O(−2) 5.10E+04 2.37E−11 8.17E+05 7.59E−10 Cl(−1) 4.29E+03 0.00E+00 1.52E+05 0.00E+00 Na(+1) 2.72E+03 0.00E+00 6.25E+04 0.00E+00 Ca(+2) 5.96E+02 0.00E+00 2.39E+04 0.00E+00 Sr(+2) 7.73E+01 5.93E−12 6.77E+03 1.04E−09 Mg(+2) 7.32E+01 0.00E+00 1.78E+03 0.00E+00 K(+1) 6.34E+01 0.00E+00 2.48E+03 0.00E+00 Li(+1) 1.35E+01 0.00E+00 9.40E+01 0.00E+00 Br(−1) 3.74E+00 0.00E+00 2.99E+02 0.00E+00 Fe(+2) 1.59E+00 0.00E+00 8.90E+01 0.00E+00 C(+4) 9.01E−01 0.00E+00 1.08E+01 0.00E+00 S(+6) 4.18E−01 5.93E−12 1.34E+01 3.80E−10 Mn(+2) 3.64E−01 0.00E+00 2.00E+01 0.00E+00 Ba(+2) 4.47E−02 0.00E+00 6.14E+00 0.00E+00 Fe(+3) 5.11E−09 0.00E+00 2.85E−07 0.00E+00

[0076] In Table 2, it is noted that there are essentially no solids (solid strontium is calculated at 1 part per trillion), the barium remains soluble at 0.0447 mM (6.14 mg/L), the strontium concentration is 77 mM (6770 mg/L), and the calcium concentration is 596 mM (23900 mg/L).

[0077] At this step in the simulation, or an earlier step in practice, the iron, manganese and magnesium can be separated by raising the pH as shown in FIG. 8. Maximum removal of iron occurs above pH 8.5 followed manganese and magnesium above pH 10.5. After solids are removed, the simulated stream composition at pH 10.5 is shown below in Table 3:

TABLE-US-00003 TABLE 3 Simulated composition of element species of aqueous phase mixture at pH 10.5 of mixture from Table 2 after solids removal. Element Aqueous Aqueous Species Phase, mM Phase, mg/L H(+1) 1.02E+02 1.03E+05 K(+1) 6.33E−02 2.48E+03 Na(+1) 2.87E+00 6.60E+04 Ba(+2) 4.42E−05 6.07E+00 Ca(+2) 5.95E−01 2.38E+04 Fe(+2) 7.06E−08 3.94E−03 Mg(+2) 2.16E−04 5.26E+00 Mn(+2) 4.73E−06 2.60E−01 Fe(+3) 3.00E−12 1.68E−07 Cl(−1) 4.28E+00 1.52E+05 Br(−1) 3.74E−03 2.99E+02 Li(+1) 1.35E−02 9.38E+01 C(+4) 8.32E−05 9.99E−01 S(+6) 4.17E−01 1.34E+01 Sr(+2) 7.72E+01 6.76E+03

[0078] Thus, at pH 10.5, the soluble iron, magnesium, and manganese concentrations are very low. After the barium, iron, magnesium and manganese solids are removed, additional 0.07 M sodium sulfate is added to the mixture from Table 3. The solids are separated and are 99.93% strontium sulfate and 0.07 percent barium sulfate thus resulting in a high purity strontium sulfate.

[0079] To the separated high purity strontium sulfate, an aqueous solution with a 0.03 M excess is added. The strontium sulfate reacts with the sodium carbonate to form strontium carbonate and soluble sodium sulfate. The resulting solid from the simulation is 99.91% strontium carbonate with 0.09% barium sulfate.

Example 2

Demonstration of Solubilities of Strontium and Calcium Sulfates

[0080] To produce a high purity material, the calcium sulfate can be rinsed from the strontium sulfate because it has a higher solubility in water and brines, than the strontium sulfate. Both materials were independently slurried in distilled water, as well as in a 20% sodium chloride brine to determine if salt content had any effect on solubility. The solids were settled and the supernatant liquid was filtered through a 0.45 μm filter and the resulting cation concentrations determined as shown in Table 4 below where “NA” means “Not Applicable”.

TABLE-US-00004 TABLE 4 Solubility of strontium and calcium sulfates. Ca Sr CaSO4 SrSO4 material mg/L mg/L mg/L mg/L distilled water <3 <3 <10 <6 distilled water saturated in Calcium 701 NA 2381 NA Sulfate distilled water saturated in Strontium NA 42.1 NA 88 Sulfate 20% sodium chloride brine 125 10.6 336 22 20% sodium chloride brine saturated in 2050 NA 6963 NA Calcium Sulfate 20% sodium chloride brine saturated in NA 177 NA 371  Strontium Sulfate

[0081] The data from Table 4 above indicates that calcium sulfate has a higher solubility than sodium sulfate in both water and sodium chloride brines. Thus, depending upon the availability at the process site, either water or sodium chloride brines may be used to gain additional purity of strontium sulfate. Though demonstrated using sodium chloride, other halide salts or brines could be used for the rinse step if needed or desired. These strontium and calcium sulfate solubilities are used to determine the minimum amount of water or brine needed for this optional purification rinse step. Such a step is only necessary for increasing process flexibility to make different grades of purity using different amounts of calcium sulfate precipitated with strontium sulfate.

Example 3

Demonstration of Strontium Sulfate Production at Larger Scale with Rinses

[0082] A 1200-gallon volume of feed brine which had previously been treated to remove barium through sulfate precipitation, contained 29300 mg/L Ca, 2080 mg/L Mg and 6860 mg/L Sr with a total TDS of 462000. A volume of 275 gallons of 2% sodium sulfate (50 kg) was added to a recycling loop of this material in a rate of 2.5 gpm. The amount of sulfate added was equivalent, on a molar basis, to 50% of the strontium in the brine. The resulting slurry containing strontium sulfate was rinsed twice with 1200 gallons of well water.

[0083] The resulting strontium sulfate solid contained calcium, iron, potassium, sodium, carbonate, and chloride as shown in Table 5 below. Thus, the strontium sulfate material was 98.5% strontium sulfate on a trace metals basis.

TABLE-US-00005 TABLE 5 strontium sulfate produced from subterranean brine at large scale. % SrSO4 % Ca % CO3 % Fe % Mg % Mn % K % Na % Cl purity 0.92 0.68 0.13 N.D. N.D. 0.17 0.32 0.24 98.5

[0084] Even with the use of well water, known to have bicarbonate, iron, magnesium and other metals and halides present, a relatively pure strontium sulfate was produced.

Example 4

Demonstration of Purification of Low-Quality Strontium Carbonate Product to High-Quality Strontium Sulfate

[0085] It is recognized that the procedures described above may not always produce the product purity desired due to actual operating scenarios such as impure wash water, inaccurate feed or reagent concentrations, insufficient mixing and other process conditions. Impure material produced from prior low-quality production from subterranean brine produced at large scale was purified in the two examples below:

[0086] The dried starting material had the composition shown in Table 6 of:

TABLE-US-00006 TABLE 6 Low-quality strontium carbonate produced from subterranean brine at large scale. Carbonate Ba Ca Fe Na Sr Cl Sulfate 28.6 7.15 6.57 0.586 0.261 38.8 0.018 17.1

[0087] On a cation purity basis which is 100%-percent total cation impurities, this material was 85.4% pure.

[0088] In a first step, carbonate metathesis of any calcium and strontium sulfate was carried out by slurrying the solids in water in a 2.4:1 ratio of solids to water to which a 20% molar excess of 21% sodium carbonate solution was added and stirred for 2 hours at room temperature. This step converted most of the remaining strontium sulfate to strontium carbonate. The iron was then solubilized, and carbonate removed by acidifying to a pH <2. The material was ultrafiltered. The filtrate brine pH was increased to >8.2 to precipitate the iron. The remaining solids in the filtrate brine were again filtered for a purified brine.

[0089] To purified brine, a molar excess of 10% sodium sulfate relative to the expected Sr concentration was dosed over a period of 8 hours in a mixer. The solids were decanted and rinsed twice with deionized water to remove solid calcium sulfate. The solids were then dried and the resulting material had the composition shown in Table 7, in percent, of:

TABLE-US-00007 TABLE 7 strontium sulfate purified from material in Table 6. Carbonate Ba Ca Fe Na Sr Cl Sulfate not detected 0.53 0.16 not detected 0.19 48.9 0.23 50.0

[0090] On a cation purity basis this material was 99.1% pure strontium sulfate.

[0091] A similar experiment was done on a different starting material a second time and the resulting composition in percent compared to the starting material is shown in Table 8:

TABLE-US-00008 TABLE 8 strontium sulfate purified from subterranean brine impure strontium carbonate, second example. Carbonate Ba Ca Fe Na Sr Cl Sulfate Starting 25.2 1.26 3.95 1.3  .27 44.4  .03  17   material Final not 0.44 0.17 ND 0.12 48   0.0014 48.4 material detected

[0092] On a cation purity basis, this material was 99.3% pure strontium sulfate. Thus, even poor-quality material may be purified by a combination of rinsing, pH washing and filtration following the examples, principles, and results indicated above.

Example 5

Preparation of Purified Strontium Carbonate from Strontium Sulfate

[0093] A batch of strontium sulfate was prepared from a subterranean with a higher mole ratio of sulfate using otherwise the same purification procedure as in Example 5. The resulting strontium sulfate composition in percent, is shown in Table 9:

TABLE-US-00009 TABLE 9 strontium sulfate produced from subterranean brine. Carbonate Ba Ca Fe Na Sr Cl Sulfate not 0.284 1.39 not 0.114 46.9 0.019 54 detected detected

[0094] The resulting purity was 98.2%, somewhat lower than the examples in Example 5 due to the higher mole ratio of sulfate used in preparation. Nonetheless, the steps employed below were undertaken to demonstrate the preparation of a purified strontium carbonate.

[0095] The strontium sulfate was rinsed with water equivalent to 11 times the mass of the solid. The solids were separated by filtration and mixed with 10% excess of 11% sodium carbonate for 18 hours to make a crude strontium carbonate. The resulting wet cake from the crude strontium carbonate was acidified to less than pH 2 to convert the strontium carbonate to soluble strontium chloride. The pH was increased to 10.7 and the remaining sulfate solids were separated by ultrafiltration.

[0096] The ultrafiltered solution containing strontium chloride was mixed with at least a molar excess of 10% sodium carbonate at a concentration of 10% for 175 minutes. The wet cake was washed with water to remove excess sodium carbonate and chloride and then dried to produce a purified strontium carbonate with the following composition in percent shown in Table 10 below:

TABLE-US-00010 TABLE 10 Strontium carbonate purified from material in Table 9. Carbonate sulfate Ba Ca Fe Na Sr Cl 41.05 not 0.109 0.54 <.016 0.19 58.4 0.057 detected

[0097] On a cation purity basis, this material was 99.2% pure strontium carbonate.

[0098] The above results demonstrate that the steps employed can be used to prepare purified strontium sulfate and strontium carbonate from a subterranean brine.

[0099] The present invention and its embodiments have been described in detail. However, the scope of the present invention is not intended to be limited to the embodiments of any process, manufacture, composition of matter, compounds, means, methods, and/or steps described in the specification. Various modifications, substitutions, and variations can be made to the disclosed material without departing from the spirit and/or essential characteristics of the present invention. Accordingly, one of ordinary skill in the art will readily appreciate from the disclosure that later modifications, substitutions, and/or variations performing substantially the same function or achieving substantially the same result as embodiments described herein may be utilized according to such related embodiments of the present invention. Thus, the following claims are intended to encompass within their scope modifications, substitutions, and variations to combinations, kits, compounds, means, methods, and/or steps disclosed herein.