RU2360039C2 - Method of bromine extraction from natural chloride water with receiving bromide concentrate - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: invention relates to technology of inorganic substances and bromide extraction from natural chloride waters and brines with receiving bromide concentrate. The method includes oxygenising bromide till elementary bromine appears on anode of two compartment cell, divided by cation-exchange membrane, whereupon bromine is separated from anolyte, bromine is extracted from contact carrier phase with back catholyte with further bromine reduction on cathode with receiving bromide salt concentration. Initial bromine-containing chloride solution is acidified by 4-7 g/l of hydrochloric acid. The portion of bromine containing chloride solution is acidified and after anode oxidation is combined with the main mass of the solution containing bromine. The chloride solution to 10 vol.% is delivered to anode chamber. Ferric bromide is added in catholyte till total concentration of ferrum is 5-6 g/l. Ferric bromide is regenerated and returned to the process. ^ EFFECT: enhancement of security when receiving bromide concentrate within processing of natural brome-containing chloride waters, prevention of toxic chlorine supply to production, transportation of non-toxic bromide salt concentrate to consumers, decrease of reactant and energy consumptions. ^ 5 cl, 4 dwg, 3 ex

Description

The invention relates to the field of technology of inorganic substances and relates to processes for the extraction of bromine from natural chloride waters and brines to obtain bromide concentrates.

A number of methods are known for the extraction of bromine from natural waters and brines to produce bromide concentrates that are safe for transportation. In particular, the bromide ion is oxidized with chlorine, the liberated elemental bromine is blown off with air or steam and absorbed from the vapor-gas mixture with alkaline reagents: alkali metal hydroxides or carbonates [V.I. Ksenzenko, D. S. Stasinevich. Chemistry and technology of bromine, iodine and their compounds. M. Chemistry. 1995 S. 163]. The disadvantages of these processes are the use of elemental chlorine, the delivery of which to remote areas where well-known deposits of bromine-containing brines are located is unsafe, as well as a significant consumption of alkaline reagents.

It is proposed to use chlorine for the oxidation of bromine, obtained electrochemically on the anode of the electrolyzer [RF patent No. 98123657, published 2000.12.27], or to conduct direct oxidation of bromine on the anode [RF patent No. 2171862, published 2001.08.10]. However, the elimination of the use of imported chlorine, according to the proposed methods, does not ensure the safe functioning of enterprises using these methods, due to the envisaged export of a toxic production product - elemental bromine. In addition, the proposed methods are characterized by increased energy consumption and its irrational use, which consists in its consumption not only for the evolution of chlorine, but also the decomposition of hydrochloric acid at the cathode with the evolution of hydrogen.

Closest to the proposed method is the traditional, used in practice in the CIS countries, the process of extraction of bromine with the production of bromine iron [V.I. Ksenzenko, D.S. Stasinevich. Chemistry and technology of bromine, iodine and their compounds. M. Chemistry. 1995], which consists in the oxidation of bromides with chlorine, separation of bromine from the initial chloride solution by blowing it with air or steam (liquid extraction or sorption), absorption of bromine with bromide iron and evaporation of bromide solution at the final stage.

The disadvantages of the method is the need to deliver large quantities of toxic chlorine to the place of processing of bromine-containing solutions (for Russia, often in hard-to-reach areas: Yakutia (tr. "Udachnaya"), Turukhansky district and Evenkiya of the Krasnoyarsk Territory, etc.), and with its electrochemical production - high electricity costs.

The aim of the proposed method is to increase production safety for the extraction of bromine from natural chloride waters, reducing reagent and energy costs.

The goal of ensuring production safety is achieved by eliminating the supply of toxic chlorine to the production and exporting bromide to the consumer in the form of a salt concentrate, which is ensured by the anodic oxidation of bromides in a two-chamber electrolyzer separated by a cation exchange membrane, by selective transfer of bromine from the initial solution (anolyte) to catholyte by traditional methods ( by blowing with air or steam, extraction, sorption), followed by cathodic reduction of bromine in reverse catholyte to obtain bromide wow concentrate.

Schematic diagram of the process is shown in figure 1.

With a continuous process, the following reactions occur on the electrodes:

anode : MBr _{n (anolyte)} -ne ^- → n / 2Br _{2 (anolyte)} + M ^{n +} _(anolyte)

cathode : n / 2Br _{2 (catholyte)} + ne ^- + M ^{n +} _(catholyte) → MBr _{n (catholyte)}

The cation M ^{n + is} transferred from the anolyte phase (pos. 1, Fig. 1) to the catholyte phase (pos. 2) by electromigration through a cation exchange membrane (pos. 3):

M ^{n +} _(anolyte) → M ^{n +} _(catholyte)

bromine - by means of heterophasic processes at the stages (4) of extraction, for example, by extraction with an organic solvent and re-extraction with reverse catholyte.

A multiple reduction or complete elimination of the reagent costs in this process is achieved by using a natural chloride solution as a supplier of cations for binding bromine to bromide salt, and reducing energy costs by combining the oxidation of bromides at the anode of the electrolyzer with the reduction of the resulting bromine at the cathode and significant concentration of bromides in a concentrate when using reverse catholyte as the bromine of the absorbing phase.

To increase the efficiency of absorption of bromine by catholyte, for example, when using bromine extraction by air blowing, a small amount of iron bromide (0.05-0.1 mol / L) is added to the catholyte. In this case, the bromine uptake efficiency is ensured by the oxidation of iron (2+):

2Fe ²⁺ + Br ₂ → 2Fe ³⁺ + 2Br ^- ,

which is then regenerated at the cathode by the reaction:

Fe ³⁺ + e ^- → Fe ²⁺

The relative amount of iron bromide in the reverse catholyte (bromide concentrate) is small (0.05-0.1 mol / l, with the content of bromidion 4-6 mol / l). If necessary, the bromine concentrate is purified from iron by extraction with tributyl phosphate and re-extraction with water.

To prevent the formation of hydroxide precipitates in the cathode space caused by a slight decomposition of water (up to 2-5% of the total current efficiency), the solution is acidified, which can be achieved by introducing hydrochloric acid into the initial chloride solution and transferring the hydrogen cation through the cation exchange membrane.

Example 1. Electrochemical production of bromide concentrate using bromine extraction.

The general process flow diagram is shown in figure 2. The installation includes a two-chamber electrolyzer, including an anode (pos. 1, figure 2) and cathode (pos. 2) chambers separated by a cation exchange membrane (pos. 3), a laboratory five-stage countercurrent extractor of the mixer-settler type for carrying out extraction processes (pos. .6), flushing (item 7) and stripping (item 8), dosing laboratory pumps.

A titanium plate 2 mm thick with an oxide ruthenium-titanium coating ORTA (electrode area 10 cm ² ) is used as an anode of the electrolyzer, carbon-graphite porous material (batting, electrode thickness 5 mm, contact area with a membrane 10 cm ² ). The cathode space of the electrolyzer is separated by a MK-40 cation exchange membrane (area, respectively -10 cm ² ). The distance between the electrodes is 3-4 mm.

The volume of the chamber for mixing the extractors is 60 ml, the sludge chamber 300 ml.

The initial chloride brine (quarry water of the kimberlite pipe “Udachnaya” - Republic of Sakha-Yakutia), composition: Na ⁺ 25 g / l; K ⁺ 12.9 g / l; Ca ²⁺ 67 g / l; Mg ²⁺ 15.8 g / l; Cl ^- 210 g / l; Br ^- 3.9 g / l, acidified with hydrochloric acid (item 5, figure 2) to a concentration of 4-7% (0.15-0.2 M) and fed into the anode chamber of the electrolyzer (item 1) with a stream 0.8 l / h In the cathode chamber of the electrolyzer (pos. 2), reverse catholyte, initially containing iron bromide with a concentration of 5-6 g / l in iron (0.1 M), is fed with the same stream (0.8 l / h). The current value on the electrolyzer is set at 1.0 A, which ensures 90% oxidation of bromine (control of the redox potential of the anolyte). When establishing a stationary mode of the process, the voltage at the electrodes of the electrolyzer is 3.9-4.2 V. Anolyte from the electrolyzer is sent to a countercurrent 3-stage extraction (item 6). As an extractant, a saturated hydrocarbon is used - a dearomatized extraction solvent (industrial name RED). The magnitude of the flow of extractant 0.8 l / h Extraction of bromine into the organic phase at this stage is over 99.9%. To wash the organic phase from a small amount of chlorine, the extract is washed in a single-stage extractor with the initial brine supplied to the oxidation of bromine (item 7). Reextract bromine with a solution of catholyte fed to a single-stage extractor (speed 0.8 l / h) (pos. 8). For 1 stage, quantitative reduction of bromine and its complete extraction into an aqueous solution is achieved.

When the concentration of bromide ion in catholyte reaches 4.5 M (360 g / l), the bromine concentrate is taken at a rate of about 7.5-8 ml / h with the addition of an equal volume (7.5-8 ml / h) of bromide solution to the catholyte iron with a concentration of 5-6 g / l for iron (0.1 M).

Upon reaching the stationary operating mode of the installation to achieve 90% bromine recovery, the current value is increased to 1.1 a. A slight increase in energy consumption is due to a slight 7–10% reverse transfer of bromide ion from the cathode to the anode space through a cation exchange membrane.

The result is a product composition: Na ⁺ 20.5 g / l; K ⁺ 8.5 g / l; Ca ²⁺ 55 g / l; Mg ²⁺ 4.0 g / l; Fe _total 5.9 g / l, Cl ^- 15 g / l; Br ^- 365 g / l.

Total bromine recovery was 91%; power consumption of 1.5 kWh / kg of bromine.

Example 2. Electrochemical production of bromide concentrate using bromine extraction

The installation diagram for the process has been changed (figure 3). In order to reduce the consumption of hydrochloric acid, 1/10 of the bromine-containing chloride brine stream (10 volume percent) was acidified with hydrochloric acid to a concentration of 7 g / L (about 0.2 M) (pos. 5, Fig. 3) and fed into the anode chamber ( item 1) of the electrolyzer. The rest (90 volume percent) of the neutral initial solution was bypassed by the electrolyzer, and for the oxidation of bromine it was mixed with an anolyte containing elemental chlorine (item 9). Reducing the feed rate of acidified brine into the anode chamber provided a more efficient consumption of hydrochloric acid. In this case, a change in conditions led to a slight increase in the voltage on the electrolyzer, which in the stationary mode amounted to 4.1-4.4 V.

Otherwise, the experimental conditions remained the same: bromine was extracted with an RED solvent (pos. 6), the organic phase was washed with an initial brine (pos. 7) and reextracted with catholyte (8) containing 10 g / l of iron supplied from the cathode space (pos. 2) ) electrolyzer.

As a result, the production of bromine concentrate with a bromine content of about 350 g / l (chloride 12 g / l) was achieved.

Total bromine recovery was also about 90%;

- power consumption of 1.6 kWh / kg of bromine;

- the consumption of 31% hydrochloric acid decreased by almost 7-8 times and amounted to 0.5 l / kg of bromine.

Example 3 Electrochemical production of bromide concentrate using bromine air blowing

The installation diagram for the electrochemical production of bromide concentrate using air stripping of bromine is shown in Fig.4. In this experiment, as well as in the previous case, in order to reduce the consumption of hydrochloric acid, part of the total brine stream (10%) was acidified with hydrochloric acid (5, 4) and sent to the anode chamber (1). Next, the main part of the bromine-containing brine was mixed with anolyte (item 9), which ensured the oxidation of bromine with chlorine, the solution was heated to 50-60 ° C (item 10), and bromine was blown off with air in a vertical glass column 1.5 m high, equipped with 5 plates (item 11). To clean the bromine-air mixture from chlorine impurities, it was passed through a bromine-containing starting brine (item 12). From the bromine-air mixture, bromine was extracted by passing it through a solution of catholyte (item 13).

Bromine was extracted from the brine of the composition (brine of the Sukhotunguska deposit of the Krasnoyarsk Territory): Na ⁺ 60 g / l; K ⁺ 20.5 g / l; Ca ²⁺ 55 g / l; Mg ⁺ 8.6 g / l; Cl ^- 220 g / l; Br ^- 4.9 g / l. The brine supplied to the anode chamber is acidified to a concentration of 4-7 g / l (0.15-0.2 M). The total flow rate of the brine is 0.8 l / h, the flow rate of the reverse catholyte is 0.8 l / h. The content of iron bromide in catholyte is 5-6 g / l (0.1 M). The magnitude of the current on the electrolyzer is 1.2-1.3 A, the voltage on the electrodes of the electrolyzer is 3.7-4.1 V.

The result is an intermediate product composition: Na ⁺ 30.5 g / l; K ⁺ 23 g / l; Ca ²⁺ 19.5 g / l; Mg ²⁺ 3.0 g / l; Fe _total 5.8 g / l, Cl ^- 11 g / l; Br ^- 240 g / l.

To purify the product from iron and return it to the process, a 2-stage extraction of iron bromide with an 80% solution of tributyl phosphate in kerosene was carried out with an equal ratio of the volumes of the aqueous and organic phases (pos. 14, Fig. 4). The extraction of iron into the organic phase is at this stage more than 99.9%.

The resulting product contains 200 g / l of bromine, the residual concentration of iron is 0.005 g / l.

From the organic phase, iron bromide is back-extracted with water at O: B = 1: 1 (POS. 15, FIG. 4). A single treatment provides a quantitative extraction of iron in the aqueous phase.

The total bromine recovery in the product is about 89%;

- power consumption of 1.5 kW · h / kg of bromine;

- the consumption of 31% hydrochloric acid is 0.4 l / kg of bromine.

Thus, the proposed method allows to extract bromine from natural chloride waters by no less than 89-90% and to obtain bromide salt concentrate with a bromine content of 200-350 g / l with an electric power consumption of 1.5-1.6 kWh / kg of bromine and a flow rate of hydrochloric acid of 0.4-0.5 l / kg of bromine. During the extraction purification of the product, the consumption of iron bromide to obtain a concentrate can be practically reduced to zero and will not exceed 1-2 g / kg of bromine.

The use of bromine oxidation in the electrolyzer at the extraction and reduction stage when it is isolated into the product ensures production safety by eliminating the supply of toxic chlorine to production and exporting bromine to the consumer in the form of salt concentrate.

The list of drawings for the application for the invention "METHOD FOR EXTRACTION OF BROMINE FROM NATURAL CHLORIDE WATERS WITH PRODUCTION OF BROMIDE CONCENTRATE".

Figure 1. Schematic diagram of the production of bromine concentrate in the processing of chloride-bromide natural waters and brines.

Figure 2. Scheme for the electrochemical production of bromide concentrate using bromine extraction (for example 1).

Figure 3. Scheme for the electrochemical production of bromide concentrate using bromine extraction (for example 2).

Figure 4. Scheme for the electrochemical production of bromide concentrate with air stripping of bromine (for example 3) and the return of iron to the cycle

Claims (5)

1. The method of extraction of bromine from natural chloride waters to obtain a bromide concentrate, including the oxidation of bromide to elemental bromine, separation of bromine from the initial solution by blowing, extraction or sorption, characterized in that the oxidation of bromide to elemental bromine is carried out on the anode of a two-chamber electrolyzer separated by a cation exchange membrane bromine is separated from the anolyte, bromine is removed from the carrier phase by contact with reverse catholyte, followed by reduction of bromine at the cathode to obtain bromide salt of concentrate. 2. The method according to claim 1, characterized in that the initial bromine-containing chloride solution is acidified with hydrochloric acid to 4-7 g / L. 3. The method according to claim 1, characterized in that a portion of the bromine-containing chloride solution is sent to the anode chamber to 10 vol.%, Which is acidified and combined after the anodic oxidation with the bulk of the bromine-containing solution. 4. The method according to claim 1, characterized in that iron bromide is added to the catholyte to a total iron concentration of 5-6 g / l. 5. The method according to claim 4, characterized in that the iron bromide is regenerated and returned to the process by extraction from bromide concentrate by extraction with tributyl phosphate and reextraction with water.

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