Recovery of bromide from sulfate comprising aqueous streams

Abstract

A solvent extraction process for recovering bromide from a sulfate-containing aqueous stream, the process comprises an extraction step wherein said aqueous stream is mixed with an extraction medium comprising a tertiary amine extractant dissolved in one or more water-immiscible organic solvents, wherein said mixing is carried out in a strongly acidic environment, thereby forming bromide-containing extract and a raffinate with a reduced bromide level, wherein the bromide-containing extract is optionally treated to further minimize the presence of sulfate and is subsequently combined with an aqueous calcium source to form calcium bromide.

Claims

1. A solvent extraction process for recovering bromide from a sulfate-containing aqueous stream, the process comprises an extraction step wherein said aqueous stream is mixed with an extraction medium comprising a tertiary amine extractant dissolved in one or more water-immiscible organic solvents, wherein said mixing is carried out in a strongly acidic environment, thereby forming bromide-containing extract and a raffinate with a reduced bromide level, wherein the extraction medium is devoid of extractants other than said tertiary amine, wherein the bromide-containing extract is optionally treated to further minimize the presence of sulfate and is subsequently combined with an aqueous calcium source to form calcium bromide.

2. A process according to claim 1, wherein the amine extractant is a mixture comprising trioctyl amine [N(C.sub.8H.sub.18).sub.3] and tridecyl amine [(N(C.sub.10H.sub.22).sub.3].

3. A process according to claim 1, wherein the tertiary amine extractant is dissolved in a mixture of one or more aliphatic hydrocarbon(s) and an alcohol containing not less than 6 carbon atoms.

4. A process according to claim 3, wherein the tertiary amine extractant is dissolved in petroleum distillate consisting of a mixture of different chains with molecular weight from about 130 to 250 g/mol.

5. A process according to claim 3, wherein the alcohol comprises decanol.

6. A solvent extraction process for recovering bromide from a sulfate-containing aqueous stream, comprising: an extraction step, wherein said aqueous stream is mixed with an extraction medium comprising a tertiary amine extractant dissolved in one or more water-immiscible organic solvents, wherein the extraction medium is devoid of extractants other than said tertiary amine, wherein said mixing is carried out in a strongly acidic environment, thereby forming a bromide-containing extract and a raffinate with reduced bromide levels; a purification step, wherein the bromide-containing extract is treated with an aqueous bromide solution to form a bromide- enriched extract; and a washing step, wherein the bromide-enriched extract undergoes gradual neutralization and sulfate removal by combining same with a plurality of aqueous bases applied in succession, with phase separation taking place between each stage of basification to produce, after each stage, an aqueous bromide salt solution corresponding to the base employed and an organic medium with progressively increasing content of the tertiary amine in its free base form, wherein at least one of said successively applied aqueous bases—with the exception of the first—comprises a calcium source.

7. A process according to claim 6, wherein at least one aqueous bromide salt solution generated in the washing step is directed to, and used in, the purification step, as a bromide source for converting the bromide-containing extract into a bromide-enriched extract.

8. A process according to claim 7, wherein the washing step comprises: mixing the bromide-enriched extract with a base M.sup.1(OH).sub.p to form a first mixture; separating said first mixture into a first organic phase, comprising an essentially sulfate-free bromide-containing extract and a first aqueous phase, comprising a solution of a bromide salt M.sup.1(Br).sub.p, mixing said essentially sulfate-free, bromide-containing extract with a calcium source, to form a second mixture; separating said second mixture into a second organic phase, consisting of a bromide-containing extract, and a second aqueous phase, comprising an aqueous solution of calcium bromide; mixing said bromide-containing extract with a base M.sup.3(OH).sub.p, to form a third mixture; separating said third mixture into a third organic phase, consisting of a bromide-free extraction medium in which the tertiary amine is present in its free base form, and a third aqueous phase, comprising an aqueous solution of a bromide salt M.sup.3(Br).sub.p, wherein the process further comprises directing the so-formed bromide solutions M.sup.1(Br).sub.p and M.sup.3(Br).sub.p to the purification step, and the bromide-free extraction medium to the extraction step.

9. A process according to claim 8, wherein M.sup.1 and M.sup.3 independently indicate an alkali metal and p is 1.

10. A process according to claim 1, wherein the extraction takes place at a temperature below 25° C.

11. A process according to claim 1, wherein nitrate present in the sulfate-containing aqueous stream is extracted along with the bromide.

12. A process according to claim 6, wherein the amine extractant is a mixture comprising trioctyl amine [N(C.sub.8H.sub.18).sub.3] and tridecyl amine [(N(C.sub.10H.sub.22).sub.3].

13. A process according to claim 6, wherein the tertiary amine extractant is dissolved in a mixture of one or more aliphatic hydrocarbon(s) and an alcohol containing not less than 6 carbon atoms.

14. A process according to claim 13, wherein the alcohol comprises decanol.

15. A process according to claim 6, wherein the tertiary amine extractant is dissolved in petroleum distillate consisting of a mixture of different chains with molecular weight from about 130 to 250 g/mol.

Description

EXAMPLES

Materials

(1) The WFGD brine used in the following examples consists of:

(2) TABLE-US-00001 % eq/Kg Br− 1.40 0.17 Cl− 1.25 0.35 SO.sub.4.sup.2− 0.27 0.06 NO3− 0.12 0.02 Anions (eq/Kg) 0.60 TOC 33 ppm
32% hydrochloric acid was purchased from Bio-Lab Ltd Company, Germeny. 1-Decanol and Sodium Hydroxide pellets were purchased from Merck KGaA Company, Germany. Parasol (boiling range 200-260° C., composed of aliphatic hydrocarbon) was purchased from Paz & Oils Chemicals Ltd Company, Israel. Alamine 336 was purchased from Cognis Corporation Company, Germany. Ketrul D80 (petroleum) was purchased from Total Fluids Company, France. TBP (Tributylphosphate) was purchased from Sigma-Aldrich, Israel. TIBP (Tri-iso-butylphosphate), HALLOCOMID-M-10(N,N-dimethyldecanamide) and HALLOCOMIDE-M-8-10 (N,N-dimethyloctylamide and N,N-dimethyldecanamide) were purchased from Stepan Company, USA. All materials were used without further purification. The percentages here and throughout the document are by weight unless otherwise indicated.

Methods

(3) The analytical methods used are summarized in the following table:

(4) TABLE-US-00002 Species Methods Instrument Cl.sup.− Br.sup.− Potentiometric 848 Titrino plus, Aqueous phase titration: METROHM precipitation titration Br.sup.− Iodometric Aqueous phase titration Cl.sup.− Potentiometric 848 Titrino plus, Aqueous phase titration: METROHM precipitation titration Cl.sup.− Br.sup.− Argentometric Titrator Organic phase potentiometric titration Br.sup.− Argentometric Titrator Organic phase potentiometric titration Cl.sup.− Argentometric Titrator Organic phase potentiometric titration SO.sub.4.sup.2− ICP ICP-AES Vista AX, Aqueous phase Varian CO.sub.3.sup.− Aqueous pH 848 Titrino plus, Aqueous phase titration METROHM NO.sub.3.sup.− Ion Dionex DX 500 IC Aqueous phase Chromatograph EP40 pump ED40 detector AS9-HC column AG9-HC guard column Ca.sup.2+ AAS AA240FS, Varian Aqueous phase Na.sup.+ AAS AA240FS, Varian Aqueous phase Total Organic TOC Multi N/C 2100S Carbon Analytic jena Aqueous phase H.sub.2O Karl Fisher Karl Fischer Organic phase titrator Alamine 336 Acid base AVANCE III 500 MHz titration Bruker NMR H NMR Spectrometer LC-MS Bruker Esquire LC Agilent HPLC 1200 Parasol H NMR AVANCE III 500 MHz GC-MS Bruker NMR Spectrometer Agilent GC 7890 MS 5975C Decanol H NMR AVANCE III 500 MHz GC-MS Bruker NMR Spectrometer Agilent GC 7890 MS 5975C

Examples 1 to 8

(5) The seperability of various Alamine 336-containing organic/aqueous mixtures into an aqueous phase and a single organic phase was investigated. In Example 1, Alamine 336 was used alone. In Examples 2 to 7, Alamine 336 (1.11 mol, 393 g) was mixed with 518 gram of the tested diluent. In Example 8, Alamine 336 (1.11 mol, 393 g), Parasol as a diluent (518 g) and Decanol (0.56 mol, 89.9 g) were mixed together to form the organic medium. The organic mixture was then combined with 1250 ml of 0.8M of HCl aqueous solution in a separatory funnel. The resultant mixture was allowed to separate into an aqueous phase and organic phase(s).

(6) When good separation was achieved, i.e., the mixture separates into a single organic phase and an aqueous phase, the organic phase was analyzed for Cl.sup.− and water content and the corresponding aqueous phase was analyzed for Total Organic Carbon (TOC). The compositions tested and the results are tabulated in Table 1.

(7) TABLE-US-00003 TABLE 1 Cl— Loading after Aq. phase charging - Org. phase TOC Ex. Diluent % Cl— % Load H.sub.2O (ppm) Separation 1 Alamine 336 3 phases alone 2 Alamine 336 in 3 phases Ketrul D80 3 Alamine 336 in 3 phases Parasol 4 Alamine 336 in 2.72 94.56 7.98 2 phases TBP 5 Alamine 336 in 2.79 97 8.4 165-591 2 phases TIBP 6 Alamine 336 in 2.79 98 14 230-580 2 phases HALLOCOMID M-10 7 Alamine 336 in 2.72 97.34 16 2170-2698 2 phases HALLOCOMID M-8-10 8 Alamine 336 in 3.3 93.3 2.19  39-172 2 phases Parasol + decanol

(8) The results summarized in Table 1 show that an organic diluent based on the combination of aliphatic hydrocarbon solvent (e.g., Parasol) and C6-C13 alcohols, such as 1-decanol, allows both good phases separation and minimization of the amount of water remaining in the organic phase.

Example 9

(9) Alamine 336 (1.11 mol, 393 g), Decanol (0.56 mol, 89.9 g) and Parasol (518 g) were mixed together. The mixture was combined with 1250 ml of 0.8M of HCl aqueous solution in a separatory funnel. The resultant mixture, which consists of two phases, was separated into organic and aqueous phases. The organic phase was analyzed for Cl.sup.−, H.sub.2O and Total Organic Carbon (TOC) and gave the following results: 3.3% Cl.sup.−, 2.2% H.sub.2O, 130-200.sub.ppm TOC and 93% loading of the Alamine 336 extractant.

(10) The charged organic phase was equilibrated with an excess of bromide-containing aqueous solution at 1.sub.aq:20.sub.org weight ratio. The composition of the bromide-containing aqueous solution is as set out above.

(11) The resultant mixture was allowed to settle and was then separated into organic and aqueous phases, which were analyzed for Br.sup.−, Cl.sup.− and TOC. The results are tabulated in Table 2.

(12) TABLE-US-00004 TABLE 2 Phase pH TOC (ppm) % Cl.sup.− % Br.sup.− Organic — — 3.23 0.056 Aqueous 2.9 80 2.23 0.006

Example 10

(13) The procedure set out in Example 9 was repeated, but this time the bromide-containing aqueous solution was equilibrated with an excess of charged organic phase (loaded with 3.3% Cl.sup.−) at 1.sub.org:30.sub.aq weight ratio and the mixture was acidified to pH=3 by the addition of 0.1% HCl solution.

(14) The resultant mixture was allowed to settle and was then separated into the organic and aqueous phases, which were analyzed for Br.sup.−, Cl.sup.− and TOC. The results are tabulated in Table 3.

(15) TABLE-US-00005 TABLE 3 Loading TOC Phase (%) (ppm) % Cl.sup.− % Br.sup.− Organic 80 — 0.7 4.23 Aqueous — 105 1.58 1.23

Example 11

(16) The procedure set out in Example 9 was repeated, but this time the charged organic phase was equilibrated at 1.sub.org:5.2.sub.aq weight ratio in order to obtain 1:1 equivalent ratio of Br.sup.− in the aqueous phase and Cl.sup.− in the organic phase.

(17) The mixture formed was allowed to settle and was then separated into the organic and aqueous phases, which were submitted for analysis.

(18) The organic phase was analyzed for % Br.sup.− and % Cl.sup.− and the aqueous phase was analyzed for % Br.sup.−, % Cl.sup.−, % NO.sub.3.sup.−, % SO.sub.4.sup.2− and TOC. The results are shown in Table 3 below. The organic phase (extract) was then taken and purified with 40% NaBr aqueous solution at 1.sub.aq:1.sub.org weight ratio. The resultant mixture was separated into two phases, organic and aqueous. The organic phase was analyzed for % Br.sup.−, % Cl.sup.− and H.sub.2O and the aqueous phase was analyzed for % Br.sup.−, % Cl.sup.−, % NO.sub.3.sup.−, % SO.sub.4.sup.2− and TOC. The results are summarized in Table 4.

(19) TABLE-US-00006 TABLE 4 Aqueous phase Organic phase TOC % Loading pH (ppm) % SO.sub.4 % NO.sub.3 % Cl % Br H.sub.2O Tot. Br Cl S.sup.Br.sub.Cl % Cl % Br 4.4 85.1 0.215 0.06 1.83 0.81 1.215 71.22 43.62 27.60 8.02 0.91 3.23 Extraction 6.15 40.6 0.41 0.28 0.94 28.6 0.67 79.87 79.26 0.61 9.68 0.02 5.89 Purification

(20) The purified organic phase was treated with 17.5% NaOH solution, arriving at pH around 9. The phases were separated, the organic solution was analyzed for % Br.sup.−, % Cl.sup.−, H.sub.2O and the aqueous phase was analyzed for % NaBr, % Cl.sup.− % NO.sub.3.sup.−, % SO.sub.4.sup.2− and TOC. The results are summarized in Table 5.

(21) TABLE-US-00007 TABLE 5 Aqueous phase Eq. Ratio Organic phase TOC BI.sup.−:OH.sup.− % Cl % Br % H.sub.2O pH ppm % SO.sub.4 % NaBr % NO.sub.3 % Cl % Br aq org <0.002 <0.002 0.11 9.3 335 <0.01 32 0.15 0.09 24.6 1 1.25

Example 12

(22) The set of experiments reported in this Example illustrates the effect of temperature variation on the extraction efficiency of bromide, chloride and sulphate by a tertiary amine extractant such as Alamine 336. The procedure set out below was carried out at temperatures of 10° C., 25° C. and 50° C.

(23) Alamine 336 (0.22 mol, 80 g), Decanol (0.11 mol, 18.36 g) and Parasol (105.6 g) were mixed together. The mixture was equilibrated with a bromide-containing aqueous solution at 1.sub.aq:2.5.sub.org weight ratio. 20% HCl (39 g) was added dropwise until pH=2 was reached (the composition of the bromide-containing aqueous solution is as set out above). The resultant mixture was allowed to settle and was then separated into organic and aqueous phases. The organic phase was analyzed for % Br—, % Cl—, % H.sup.+ and % H.sub.2O and the aqueous phase was analyzed for % Br—, % Cl—, % NO.sub.3—, % SO.sub.4— and TOC. The measured results are tabulated in Table 6 below.

(24) TABLE-US-00008 TABLE 6 10° C. 25° C. 50° C. Aqueous Organic Aqueous Organic Aqueous Organic phase phase phase phase phase phase % Br− 0.35 2.76 0.43/0.42 2.76 0.47 2.59 % Cl− 1.99 1.86 1.99 1.91 1.99 1.97 % SO4−− 0.15 0.2198 0.15 0.2201 0.15 0.2184 % NO3− 0.0072 0.1761 0.0093 0.1737 0.0119 0.166 TOC.sub.ppm 108 123 128 % H+ 0.0907 0.0908 0.0909 % H.sub.2O 1.74 1.56 1.7 H+ (eq/Kg) 0.9000 0.9010 0.9020 Anions (eq/Kg) 0.9441 0.958 0.9521

(25) The results set out in Table 6 were used to calculate some useful quantities which are tabulated in Table 7 below. The quantities of interest are:

(26) The distribution coefficient K.sub.x (x=Br.sup.−, Cl.sup.−, NO.sub.3.sup.−, SO.sub.4.sup.2−): the ratio (at equilibrium) of the concentration of the anion X in the extract and aqueous phases. The distribution coefficient is a measure of the affinity of the anion towards the two phases.

(27) The selectivity S.sup.Br.sub.Y (y=Cl.sup.−, NO.sub.3.sup.−, SO.sub.4.sup.2−): the ratio of the distribution coefficient of bromide to the distribution coefficient of anion Y. Thus, S.sup.Br.sub.Y is a measure of the selectivity for the extractant to bromide as against anion Y, i.e., the ability of Alamine 336 to selectively extract bromide from an aqueous solution in which a competitor Y is also present.

(28) TABLE-US-00009 TABLE 7 10° C. 25° C. 50° C. Loading H+ 91.34% 89.75% 88.27% Loading Anions 95.82% 95.45% 93.19% NO3− loading 2.88% 2.79% 2.62% SO4−− loading 4.62% 4.56% 4.45% Br− loading 35.06% 34.41% 31.73% Cl− loading 53.26% 53.68% 54.39% K.sub.Br 7.89 6.42 5.51 K.sub.Cl 0.93 0.97 0.99 K.sub.NO3 24.46 18.68 13.95 K.sub.SO4 1.47 1.47 1.46 S.sup.Br.sub.SO4 5.38 4.38 3.78 S.sup.Br.sub.No3 0.32 0.34 0.39 S.sup.Br.sub.Cl 8.44 6.62 5.57 H.sub.2O 1.74 1.56 1.70

(29) The results set out in Table 7 show that Alamine 336 has higher selectivity for bromide against sulfate over a broad temperature range. Furthermore, the distribution coefficients of sulfate and chloride are not affected by temperature variation, whereas the extraction efficiency of bromide is increased with decreasing temperature.

Example 13

(30) The set of experiments reported in this Example illustrates the effect of washing in stages the organic phase collected following an extraction step, with a strong base being used in the first stage to partially neutralize the extractant, i.e., arriving at pH in the range from 4 to 6. The procedure set out below was carried out at different temperatures of 10° C., 25° C. and 50° C.

(31) The organic phase (extract) obtained in Example 12 was taken and partially washed with concentrated NaOH aqueous solution until pH=5 was reached. The resultant mixture was separated into two phases, organic and aqueous. The organic phase was analyzed for % Br—, % Cl—, % NO.sub.3—, % SO.sub.4—, % H.sup.+ and % H.sub.2O. The aqueous phase was analyzed for % Br—, % Cl—, % NO.sub.3—, % SO.sub.4— and TOC. The results are summarized in Table 8.

(32) TABLE-US-00010 TABLE 8 10° C. 25° C. 50° C. Aqueous Organic Aqueous Organic Aqueous Organic phase phase phase phase phase phase % Br− 5.12 1.9 4.95 1.83 5.06 1.69 % Cl− 7.34 0.33 7.59 0.39 7.64 0.33 % SO4−− 1.15 0.0072 1.06 0.0254 1.09 0.0116 % NO3− 0.34 0.1192 0.34 0.1163 0.34 0.1059 % H+ 0.0349 0.0331 0.0351 % H.sub.2O 0.48 0.475 0.52 TOC.sub.ppm 55 40.4 43 H+ 0.3462 0.3284 0.3482 (eq/Kg) Anions 0.353 0.3631 0.3664 (eq/Kg)

(33) The results set out in Table 8 demonstrate that the incomplete neutralization of the extractant allows an effective removal of the sulfate from the organic phase, which still remains bromide-loaded. The so-formed sulfate-free, bromide-loaded organic phase may proceed to the next washing stage, to be combined with an aqueous solution of calcium ion.

(34) The next set of examples (Examples 14 and 15) illustrates the results of experiments which were conducted in a bench scale continuous pilot plant in which batteries of mixer-settlers were arranged in succession according to the stages set forth in FIG. 1. In both examples, the bromide-containing solution had approximately the following composition: 1% Br.sup.−, 1.5% Cl.sup.−, 0.1% NO.sub.3.sup.− and 0.4% 50.sub.4.sup.2−. The extraction medium employed was a mixture consisting of parasol, Alamine 336 (at a concentration of 0.8 M, about 39 wt %) and Decanol (at a concentration of 0.45 M, about 9 wt %).

Example 14

(35) The various streams were fed at the following flow rates [kg/hr]: bromide-containing aqueous stream: 2.0; extraction medium: 0.8; HCl 20%: 0.1; NaOH 23%: 0.13.

(36) Production rate: 0.082 kg/hr of 3% Cl.sup.−, 2% NO.sub.3.sup.− (in the 30% NaBr solution).

(37) Yield of Br.sup.− extraction: 98-99%.

(38) Representative Concentrations:

(39) Depleted brine: Br.sup.− 200 ppm; Cl.sup.− 2.5-3.5%; NO.sub.3.sup.− 10-100 ppm, pH=1-3

(40) Extract: Br.sup.− 2.3-2.5%; Cl.sup.− 1.9-2.1%.

(41) Washed solvent: Br.sup.−-50-200 ppm.

Example 15

(42) The various streams were fed at the following flow rates [kg/hr]: bromide-containing aqueous stream: 2.0; extraction medium: 0.8; HCl 20%: 0.1; NaOH 23%: 0.07, Ca(OH).sub.2 (3% solids in 50% CaBr.sub.2) 0.4.

(43) Production rate: 0.04 kg/hr of 1.2-1.8% Cl.sup.−, 1.5-2% NO.sub.3.sup.− (in 50% CaBr.sub.2 solution).

(44) Yield of Br— extraction: 98-99%.

(45) Representative Concentrations:

(46) Depleted brine: Br.sup.− 200 ppm, Cl.sup.− 2.5-3.5%, NO.sub.3.sup.− 10-100 ppm, pH=1-3

(47) Extract: Br.sup.− 3.0-3.5%, Cl.sup.− 1.5-1.8%

(48) Washed solvent Br.sup.− 100-300 ppm