Process for removal of impurities including iron, organic, and color from metal halogen solutions

Abstract

The various embodiments of the disclosure relate generally to a process for converting industrial hydrohalide solutions to commercial metal halide solutions having a sufficient quality in terms of impurity content and color. An embodiment of the disclosure can include the steps of identifying a hydrohalide solution having organic and / or inorganic impurities neutralizing the hydrohalide solution with a basic material in one or more steps toa neutral or alkaline pH to produce a metal halide solution, filtering the metal halide solution to remove any alkaline insoluble impurities, and then adjusting pH of the metal halide solution to a pH of about 6.5 to about 8.

Description

PROCESS FOR REMOVAL OF IMPURITIES INCLUDING IRON, ORGANIC,AND COLOR FROM METAL HALOGEN SOLUTIONSTECHNICAL FIELD

[0001] The various embodiments of the disclosure relate generally to processes, methods, and systems for removing impurities from a hydrogen halide solution, it is particularly useful for post-halogenation byproduct streams.BACKGROUND

[0002] Among industrial processes, halogen oxidations (or oxidative halogenations) of organic compounds produces a significant number of commercial products. For example, brominated flame retardants such as tetrabromobisphenol A (TBBPA) are prepared by a bromine oxidation of an organic substrate, e.g. bisphenol, to produce TBBPA. The products of that bromine oxidation include the valuable flame retardant, but also an aqueous stream which typically includes HBr and impurities. Chlorine oxidations are also challenged by aqueous streams that must be addressed.

[0003] For an industrial process to be commercially competitive, the byproduct streams must be utilized or disposed of in an economical method. This could include recycling the stream back into the process, diverting the stream into another process, or converting the stream into a separate commercial product. In the absence of these options, disposal may be necessary, but simply disposing of an industrial stream is both environmentally challenging and commercially inefficient because it wastes atom-value from the process. Thus, recycling the stream back into the process, diverting the stream into another process, or converting the stream into a separate commercial product are much preferred, but the impurity profile of that byproduct stream becomes a significant hurdle to overcome.BRIEF SUMMARY

[0004] The various embodiments of the disclosure relate generally to a process for converting industrial hydrohalide solutions to commercial metal halide solutions having a sufficient quality in terms of impurity content and color.

[0005] An embodiment of the disclosure can include the steps of identifying a hydrohalide solution having organic and / or inorganic impurities neutralizing the hydrohalide solution with a basic material in one or more steps toa neutral or alkaline pH to produce a metal halide solution, filtering the metal halide solution to remove any alkaline insoluble impurities, and then adjusting pH of the metal halide solution to a pH of about 6.5 to about 8. Alternatively, an oxidizer or halogenating agent may be added to the solution during the course of the process. The role of the oxidizer or halogenating may be inclusive of halogenation and / or oxidation of organic impurities and oxidization of metal ions to insoluble ionic states.DETAILED DESCRIPTION

[0005] Although preferred embodiments of the disclosure are explained in detail, it is to be understood that other embodiments are contemplated. Accordingly, it is not intended that the disclosure is 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 disclosure is capable of other embodiments and of being practiced or carried out in various ways. Also, in describing the preferred embodiments, specific terminology will be resorted to for the sake of clarity,

[0006] It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” ‘"an” and “die” include plural referents unless the context clearly dictates otherwise.

[0007] Also, in describing the preferred 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 which operate in a similar manner to accomplish a similar purpose.

[0008] Ranges can 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, another embodiment includes from the one particular value and / or to the other particular value.

[0009] By ‘’comprising’’ or “containing” or “including” is meant that at least the named compound, element, particle, or method step is present in the composition or article or method, but does not exclude the presence of other compounds, materials, particles, method steps, even if the other such compounds, material, particles, method steps have the same function as what is named.

[0010] It is also to be understood that the mention of one or more method steps does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Similarly, it is also to be understood that the mention of one or more components in a device or system does not preclude the presence of additional components or intervening components between those components expressly identified.

[0011] Bromine oxidation (which is an electrophilic substitution of bromine on an aromatic ring) of organic compounds produces hydrobromic acid, also known as hydrogen bromide, which must be utilized or disposed. However, the HBr stream contains numerous challenges, including organic and iron impurities from the process and the plant equipment. One common option in any plant process is to recycle a stream into the process or related process, or to convert the stream to another product. However, recycling the untreated HBr stream can lead to precipitation of solids in equipment. One common product produced from an HBr stream can be sodium bromide solutions, commonly used as weighted solutions for drilling and other applications. However, both the organic and iron impurities make that material arc poorly suited for sales. Some comparable products on the market have a notable strong unpleasant organic odor and color issues that make them less desirable.

[0012] References in the literature indicated that non could be removed at a pH <8. However, initial attempts at ~12% NaBr solution by neutralizing “dean" HBr with 50% NaOH to a pH of -7, produced a thin brown slurry. The clear solution obtained after filtration was still light brown which on concentration became darker. Treatment of the 12% NaBr solution with activated carbon improved the color, but still produced solutions not commercially preferable. The process is equally applicable to other halogen oxidation reactions and metal halide products

[0013] As is obvious to one skilled in the art, organic transformations are highly dependent on reaction matrix conditions. As will become obvious to one skilled in the art, a variation in matrix can lead to largely different products for a given set of reactants. For instance, bromination of acetone fully proceeds to perbromination and subsequent hydrolysis to yield carbonate and bromoform in a basic reaction matrix (the bromine equivalent of the well known haloform reaction with acetone and chlorine or sodium hypochlorite). In an acidic matrix, bromine and acetone react to form monobromoacetone in good yield as the major product. Alternatively, bromine may react with ethanol to generate a series of unbrominated and brominated aldehydes, organic and inorganic acids, and other brominated molecules. Lower pH will favor the formation of hydrates and acetals leading to deactivation of the organic molecule to further halogenation or oxidation Tire impact of pH may arrive either by modification of the active bromination agent, protonation or deprotonation or other modification of the organic reagent or reagents or a combination of the two. Non-aqueous bromination systems will largely proceed through reaction of dibrominc with an organic molecule. In aqueous systems, bromine disproportionates into numerous species including one or more of but not limited to hypobromous acid, hypobromite, bromite, bromous acid, bromic acid, bromate, and perbromate. Generated during the disproportionation or if otherwise present, bromide may react with dibromine to form a tribromide ion. This ion may further react with additional dibromine to some extent to form further oligomeric ionic species. In the presence of chlorine or chloride, these species may also form with a mixture of bromine and chlorine present in a given ion or molecule. In a mixed chlorine / bromine and chloride / bromide system, the reaction products with organic molecules will similarly be mixed.

[0014] Organic impurities may contribute to a number of unwanted properties. The organic molecules may be colored and lead to an unwanted color to a certain product or have an unfavorable odor, health and safety profile, or contribute to unwanted turbidity, viscosity or other physical phenomena. The organic contaminants may also react with a process stream to generate further unwanted compounds. Even during final processing and polishing to remove certain remaining impurities, for instance in the reduction of di bromine with hydrazine, excesshydrazine could react with aldehydic materials to produce hydrazone type compounds. These produced compounds may have unfavorable impacts to a product.

[0015] While not wanting to be limited to any one theory, introduction of more than one pH regime allows for modification of the matrix and allowance of numerous reaction pathways and products. These new pathways are able to further transform organic molecules and the products of such may be easily removed from an aqueous stream, either through stripping, hydrolysis, precipitation, crystallization, filtration, sedimentation, liquid / liquid extraction, or any combination of the aforementioned treatment steps. Once sufficiently removed, the residual impurities do not deleteriously impact the byproduct stream or subsequent recycles or commercial products. It is a feature of this invention to modify the pH one or more times to provide conversion of unwanted impurities to easily removable byproducts.

[0015] In chemical manufacturing processes, numerous intermediate and incidental chemicals may be formed. These may or may not be well characterized. Isolation from an aqueous system into a non-miscible solvent for subsequent analysis may not be possible. In the absence of absolute chemical identification, those skilled in the art may use general functional information about the chemicals that may be obtained, for instance, through HPLC-UV, HNMR, or HPLC-MS. TOC may also be used for determination of the relative total organic impurity concentration. Peaks in specific regions of the HNMR spectra may be monitored through a cleanup process. It is well known that polar compounds generally have HNMR shifts between 1.8 and 4.2 ppm relative to TMS. Additionally, aromatic compounds may exhibit shifts from about 6 ppm to about 8 ppm relative to TMS. Oxidation or halogenation of these components can be monitored through the loss of HNMR proton peaks, shifting of the peaks, or changes in the splitting pattern of said peaks. Once these transformations are complete, stripping, hydrolysis, and precipitation may be used to remove the produced and / or converted impurities. Analysis via NMR or other methods to analyze known compounds that may be present can then be compared against measured TOC methods to ensure adequate removal of unwanted impurities.

[0016] The present disclosure thus relates to a process for converting industrial hydrohalide solutions to commercial metal halide solutions having a sufficient purity in terms of impurity content and color,

[0017] The process can include the steps of identifying a hydrohalide solution having an iron impurity, neutralizing the hydrohalide solution with caustic to a basic pH to product a metal halide solution, filtering the metal halide solution to remove the iron impurity, and then adjusting pH of the metal halide solution to a pH of about 6.5 to about 8.

[0018] The term hydrohalide includes halogen acids, such as hydrochloric acid, hydrobromic acid, and hydroiodic acid. ie. HC1, HBr and HI. The compounds can also be descibred as hydrogen chloride, hydrogen bromine, and hydrogen iodide. Hydrohalide can be abbreviated as HX, where X is well-recognized as a halogen, i.e. Cl, Br, or I. The hydrohalide solution can comprise an HC1 solution or HBr solution, or the hydrohalide solution can comprise an HBr solution. The hydrohalide solution can comprise an aqueous solution.

[0019] The term metal halide describes an ionic salt compound containing a metal cation and a halide anion. The halide anion can comprise chloride, bromide or iodide, preferably chloride or bromide. The halide anion can comprise bromide. The metal cation can comprise alkali or alkaline earth metals. The metal cation can comprise lithium (Li), sodium (Na), potassium (K), or calcium (Ca). The metal cation can comprise sodium. Thus the metal halide can include lithium chloride, sodium chloride, potassium chloride, or calcium chloride, lithium bromide, sodium bromide, potassium bromide, magnesium bromide, or calcium bromide; preferably lithium bromide, sodium bromide, potassium bromide, magnesium bromide or calcium bromide; and more preferably sodium bromide.

[0020] The initial hydrohalide stream can be any hydrohalide stream in an industrial process. The hydrohalide stream can be less than about 50 % w / w HX, less than about 40% w / w HX, or less than about 30% w / w HX. The process can be use a hydrohalide solution that has been depleted due to a previous chemical process. Thus, the hydrohalide stream can be less than about 20% w / w HX, less than about 15% w / w HX, or less than about 12 % w / w HX.

[0021] The process can include one or more optional further steps to produce a commercially significant metal halide solution. The metal halide solution can be concentrated to a density of about 10 to about 14 Ib. / gal. preferably about 11 to about 13 Ib / gal, more preferably about 11.7 to about 12.7 Ib / gal. The metal halide solution can be concentrated by any standard industrial evaporation process, such as but not limited to techniques involving one or more of mechanical vapor recompression, falling film evaporation, multiple effect evaporation, force circulation evaporation, and / or solar evaporation. The metal halide solution can alternatively or additionally be further treated with a second concentrated metal halide solution to achieve the densities above,

[0022] For the step of neutralizing the hydrohalide solution with caustic to a basic pH to produce a metal halide solution, the pH can be adjusted to at least about pH 9, preferably at least about pH 9.5. The pH can be adjusted to a range of between about 9 to about 11, preferably between about 9.5 to about 10.8. However, it is a feature of the current process to have a pH hold in the process during the neutralizing step while also adding additional halogen or oxidizer. For example, an amount of oxidizer is added to a hydrobalide solution if said solution does not have sufficient halogen or other oxidizer and a caustic is added to raise the pH to a level of at least about 1-3. The solution is then heated and held for at least about 5 minutes. Then, additional caustic is added to raise the pH to its final level of at least 9.

[0023] The term "caustic” can comprise any industrially suitable base used to neutralize acid solutions. Caustic can include metal hydroxides, metal oxides, metal carbonates, and metal bicarbonates, where the metal is equivalent to the metal halide described above. Preferably, the caustic comprises lithium hydroxide, sodium hydroxide, potassium hydroxide, or calcium hydroxide. The caustic can be sodium hydroxide.

[0024] The metal bromide solution can be filtered one or more times, either at basic pH or after adjustment to neutral pH. Preferably the metal bromide solution can be filtered at basic. The filtration can remove any solids from the solution, including precipitated metal hydroxides, metal oxide hydroxides, and other metal precipitates as well as organic impurities. Preferably,the metal precipitate comprises iron hydroxide, iron oxide, iron oxide hydroxide, chromium hydroxide, magnesium hydroxide, magnesium carbonate, calcium carbonate, or others. Generally, the iron with be in a 3+ oxidation state due to oxidative conditions of some processes. However, the process is not limited to Fe(3+).

[0025] The basic metal halide solution can be adjusted to a neutral pH with a hydrohalide acid solution. Preferably, the hydrohalide acid can be equivalent to the original hydrohalide solution, but does not necessarily need to be. For example, if the starting solution was a hydrobromic acid solution, then the basic metal halide solution, e.g. a metal bromide solution, could be neutralized with an HBr solution. Adjusting the solution to neutral pH means a pH of between 6 to 8, between 6.5 and 8, and preferably between 6.5 to 7.5.

[0026] The metal bromide solution after filtration can have an iron content of less than about 1 ppm Fe, less than about 0.5 ppm Fe, less than about 0.2 ppm iron, or less than about 0.1 ppm Fe. The metal bromide solution after filtration can have an APHA color of less than about 50, less than about 40, or less than about 30.

[0027] The present disclosure can be a process for converting an aqueous HBr stream to a metal bromide product, including the steps of identifying an aqueous HBr stream having any impurities and converting to an appropriate purity metal halide solution; filtering the metal bromide solution to remove insoluble impurities; and treating the metal bromide solution with HBr to adjust the pH to about 6.5 to about 8. The metal bromide solution is subsequently concentrated to a density of about 10 Ib / gal to about 14 Ib / gal, either by evaporation, further treatment with a concentrated metal bromide solution, or both.

[0028] The final metal bromide solution can have an iron concentration of less than about 0.5 ppm iron and an APHA Color of less than about 30.

[0029] The present disclosure also includes the production of a commercial metal bromide solution that is low in iron and APHA color Hie disclosure can include the method for preparing a metal bromide solution having an iron content of less than 0.5 ppm iron and anAPHA color of less than 30. The method includes the steps of neutralizing an aqueous HBr stream with caustic in one or more steps, ultimately reaching a pH value of at least about pH 9 to produce the metal bromide solution; filtering the metal bromide solution to remove iron hydroxide; and treating the metal bromide solution with HBr to decrease the pH to about 6.5 to about 7,5. Alternatively the pH may be reduced further to about 1-3.5 and then caustic may be introduced to reach tire final product pH of about 6.5 to 7.5. The metal bromide solution can be a sodium bromide solution further treated with concentrated sodium bromide and / or concentrated by evaporation, where the final density can be about 11.7 to about 12. 7 Ib / gal.EXAMPLESExample 110030] A byproduct HBr stream containing iron and other impurities was reacted with 50% NaOH until a pH of 10.5 was reached, heated to 75 C and held 2 hours, cooled, and held overnight. The next day, the material was heated to boiling, with recovery of the distillate. Once the boiling flask reached 113 C, the heat was stopped. After the solution cooled to ~85 C, the apparatus was disassembled, and the solution was filtered through a Whatman GF / F. Final APHA color was 136.

[0032] Alternatively, 227.16 g of byproduct HBr and 2.31 g bromine was mixed and brought to pH 3.8 with 50% NaOH, heated to 95 C, and held 1 hour. The solution was then brought to pH 9.5 with 50% NaOH, held at 95 C 1 hour, cooled to 65 C and filtered through a Whatman GF / F. The dilute APHA was measured as 2.69.Example 2

[0031] 2.7 g bromine was added to 667 g byproduct HBr prior to splitting between two subsequent experiments.

[0034] Next, one sample was treated with an intermediate pH hold. 337 g '"clean” HBr with bromine was brought to a pH of 3.3 with 32.06 g 50% NaOH. The temperature was increasedto 70 C and held for 30 minutes 1.66 g 50% NaOH was then added to increase the pH to 10.3 and held at 78-80 C for 30 minutes. The solution was then filtered, concentrated, and filtered again to yield a solution with an APHA of 18.75. Addition of hydrazine reduced the APHA to 11.65

[0035] The second sample was treated without an intermediate hold. 339 g sample 3 '"clean HBr ’ was brought to a pH of 10 1 with 35.69 g 50% NaOH, held 1 hour at 75 C, filtered, concentrated, and filtered to yield a colorless solution with an APHA of 11.55. Hydrazine increased the APHA color to 17.63.Example 3

[0032] The first sample was treated with an intermediate hold. 593 g HBr with bromine was taken to a pH of 3.46 with 60.08 g 50% NaOH and held at 75 C for 30 minutes. 4.34 g 50% NaOH was then added to increase pH to 10.48 and held for 1 hour, followed by filtration, concentration, and filtration to yield a solution with an APHA of 29.84, or 1.17 after hydrazine addition.

[0033] The second sample was treated without an intermediate hold. -200 g Sample 5 HBr with bromine was taken to pH=10.8 and held 1 hour, filtered, concentrated, and filtered to yield a solution with an APHA of 213, which only lightly reduced to 200 with addition of hydrazine.Example 4

[0034] 2400 g byproduct HBr containing 87 ppm dissolved iron was neutralized with 50% NaOH to a pH of between 7-8. The light brown slurry’ was filtered to remove the brown solids. The pale yellow solution of dilute NaBr had an APHA of 18 and iron level of 9 ppm. One 275 g aliquot was concentrated. The subsequent APHA was 97 and the iron concentration was 31.

[0035] 2400 g byproduct HBr containing 87 ppm dissolved iron was neutralized with 50% NaOH to a pH of 9.5. The solution was filtered to remove insoluble iron impurities yielding and APHA of 5 and a soluble iron concentration of <1 ppm. 900 g of solution was then concentrated by heating to a temperature of 110 C with distillation of water The resulting APHA was 23 with a dissolved iron concentration of <1 ppm.Example 5

[0036] 450g of a 45% w / w NaBr solution containing 85 ppm bromate, 2456 ppm carbonate, 86 ppm bicarbonate, 101 ppm phosphate, 147 ppm sulfate with a pH of 10.39 was reduced to a pH of 1.20 by the addition of 7.57 g 48% HBr and allowed to react for an hour with offgassing. To this 3.3g 2% Sodium Formate was added and allowed to react for an hour The mixture was adjusted to pH 7 65 by the addition of NaOH and allowed to mix for an hour. The mixture (intermediate product) was colorless with analysis listed in Table 1. To this 9.5g 20% BaCl2was added and allowed to react for 3h yielding a turbid solution. The final reaction mixture was filtered using 0.45-micron filter (Final product). Analysis of the solution is shown in Table 1.Properties Intermediate Product Final ProductBromate (ppm) by <15 <15ICPhosphate (ppm) 84 1 1by ICSulfate (ppm) by 169 21ICpH 7.65 7.59Color (APHA) 4.16Turbidity (NTU) 2.45Table 1. Properties of Final ProductExample 6

[0037] 200g of a 45 w' / w% NaBr solution containing 769 ppm bromate and 4842 ppm carbonate with a pH of 11 was heated to 40 C. The pH of the solution was reduced down to 1.5 by the addition of 48% HBr and allowed to react for an hour. To this 2.2g 10% sodium nitrite was added and allowed to react for an hour. The reaction mixture was adjusted to pH 4.0 by addition of NaOH and allowed to mix for an hour. Further tire reaction mixture was adjusted to pH 7.0 by the addition of NaOH and allowed to mix for an hour, The mixture was colorless.The final reaction mixture was filtered using 1 micron filter and analyzed. Final product: Bromate = <15 ppm, Color (APHA) = 10

[0038] It is to be understood that the embodiments and claims disclosed herein are not limited in their application to the details of construction and arrangement of the components set forth in the description and illustrated in the drawings. Rather, the description and the drawings provide examples of the embodiments envisioned. The embodiments and claims disclosed herein are further capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purposes of description and should not be regarded as limiting the claims.

[0039] Accordingly, those skilled in tire art will appreciate that the conception upon which the application and claims are based can be readily utilized as a basis for the design of other structures, methods, and systems for carrying out the several purposes of the embodiments and claims presented in this application. It is important, therefore, that the claims be regarded as including such equivalent constructions.

Claims

CLAIMSWe claim:

1. A process for converting an aqueous HBr stream to a metal bromide product, comprising(a) Identifying an aqueous HBr stream having inorganic and / or organic impurities. (b) Such stream should have sufficient halogen to react with impurities or halogen should be added before or during the process to sufficiently react(c) Neutralizing the aqueous HBr stream with base in one or more steps to at least pH about 5 to about 11 to produce a metal bromide solution.(d) Filtering the metal bromide solution to remove the inorganic and / or organic impurities.

2. A process of Claim 1 further comprising and additional step after (d) of treating the metal bromide solution with acid HBr or a caustic to adjust the pH to 6.5-8, as necessary.

3. The process of Claim 1 wherein the inorganic impurities comprise a metal.

4. The process of Claim 3 wherein the inorganic impurities comprise iron.

5. The process of Claim 1 wherein the acid of step (e) is one or more of HBr, HC1, sulfuric acid, acetic acid, and / or formic acid.

6. The process of Claim 5 wherein the acid of step (e) is at least HBr.

7. The process of Claim 1 wherein as part of step (c), the HBr stream is partially neutralized to a pH between 0.5 and 8.5, preferably 1.0 to 7.0 and more preferably 1.25-4 and held for a time prior to further neutralization.

8. The process of Claim 7 wherein the partial neutralization and hold occur over greater than 5 minutes, preferably greater than 15 minutes, and more preferably greater than 45 minutes.

9. The process of Claim I wherein additional halogen is added during the process.

10. The process of Claim 9 wherein additional halogen is added at step (b).

11. The process of Claims 9 or 10 wherein additional halogen or other oxidant is added prior to the final pH adjustment step of step (e).

12. The process of any of the above claims wherein said halogen or other oxidant is one or more of bromine, chlorine, hydrogen peroxide, a bromate salt or solution, sodium perchlorate, oxygen, UV irradiation, ozone or an electrolytic oxidation process.

13. The process of any of the previous claims wherein the amount of halogen or other oxidant added is sufficient to react with organic impurities present and leave <5000, preferably <1500, and most preferably' < 500 ppm, halogen or other oxidant as bromine present at the end.

14. The process of any of the previous claims, wherein excess halogen or other oxidant is removed via a treatment step including but limited to addition of one or more of hydrazine, hydrogen peroxide, a sulfite salt, sodium sulfite, sodium thiosulfate, any of the alkali metal aluminum or borohydrides, methanol, alkali metal percarbonates, formaldehyde, formic acid, a formate salt, or an electrolytic reduction process.

15. The process of claim 14 wherein the treatment step comprises adjustment of the post evaporation pH to < 4.5 followed by stripping or reaction of the bromine.

16. The process of claim 15 wherein the low pH material is then adjusted to 6-8.

17. The process of claim 16 wherein the treatment step is includes sparging of the solution and / or sweeping of the vapor space with nitrogen, air. CO2 depleted air or similar gases w ith minimal CO218. The process of any of the previous claims wherein the treatment step also removes other unwanted impurities.

19. The process of Claim 18 wherein the other unwanted impurities comprises CO2.

20. The process of any of the previous claims, wherein the metal bromide solution is subsequently concentrated to a density of about 10 Ib / gal to about 14 Ib / gal.

21. The process of any of the previous claims, wherein the metal bromide solution is further treated with a concentrated metal bromide to a density of 10 Ib / gal to about 14 Ib / gal.

22. The process of any of the previous claims, wherein the pH is adjusted to about 9.5 to about 10.5 before filtering the iron hydroxide.

23. The process of any of the previous claims, wherein the metal bromide solution after filtration contains less than about 5 ppm iron, preferably less than about 1,5 ppm, or more preferably less than about 0.5 ppm iron.

24. The process of any of the previous claims, wherein the metal bromide solution after treatment has an APHA Color of <30.

25. The process of any of the previous claims, wherein the metal bromide solution comprises alkali bromide, alkaline earth bromides, and / or combinations thereof,26. The process of any of the previous claims, wherein the metal bromide comprises lithium bromide, sodium bromide, potassium bromide, magnesium bromide, or calcium bromide.

27. The process of any of the previous claims, wherein the caustic comprises sodium hydroxide.

28. The process of any of the previous claims, wherein the HBr stream is less than about 50% w / w HBr, preferably 25% w / w, and most preferably 15% w / w HBr.

29. The process of any of the previous claims, wherein the HBr stream is less than about 12% w / w HBr.

30. The process of Claim 29, wherein the metal bromide solution is further treated with concentrated metal bromide to a density of 1.1 SGU to 1.6 SGU

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