RU2481266C1 - Method of extracting iodine from mineral sources - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used in chemical industry. The method of extracting iodine from solutions which contain iodide and bromide ions involves ion exchange with anions of quaternary ammonium salts and oxidation of the iodide ions. The quaternary ammonium salts are taken in form of a solution in an organic solvent - kerosene extraction agent, which contains a cosolvent. The cosolvent used is xylene or tributyl phosphate or chloroform in amount of 10% more than the mass of salt theoretically required to bind iodide and bromide ions from the aqueous phase. The organic phase is separated after emulsion with the aqueous phase. Oxidation of iodide ions is carried out in organic phase with chlorine or bromine water. Molecular iodine formed is converted to a solid concentrate by adding a sorbent. The quaternary ammonium salts contain alkyl radicals with an optimum number of carbon atoms - from 8 to 16 and bromine and chlorine anions.

EFFECT: invention simplifies the process of extracting iodine and conduct the process directly on sources of iodine-containing water without forming fixed enterprises.

4 cl, 1 dwg, 1 tbl, 6 ex

Description

The invention relates to a technology for the production of iodine, in particular to a technology for the extraction of iodine from natural raw materials - underground saline water and associated water from oil and gas fields. Associated water extracted in oil and gas production processes contains iodine in reduced form (J ^- ), often has an alkaline reaction of the medium, and contains organic compounds (in particular, salts of naphthenic acids). Low concentrations of iodide ions (≥15 mg / l) and these factors make the process of iodine extraction rather complicated and economically expensive.

At most industrial enterprises, the production of iodine is based on the classical technological process, which consists in acidifying large volumes of water (1 kg of iodine is contained in ≈50 tons of water) to pH≈2.5, followed by oxidation of iodide ions with various oxidizing agents (in the simplest case, chlorine or chlorine water), blowing off the resulting iodine with air. The gas stream with iodine enters the scrubber with a solution containing a reducing agent, for example Na ₂ SO ₃ , where it again passes into the J ^- form and is concentrated in this form to a content of ≥30 g / l. Further, iodine is recovered to the solid phase from the concentrated solution by repeated oxidation (Ksenzenko V.I., Stasinevich D.S. Chemistry and technology of bromine, iodine and their compounds. - M.: Chemistry, 1995, 432 pp.)

The main disadvantages of the method are as follows:

- high consumption of acid necessary for acidification of water (at a pH of 6-7, the consumption of sulfuric acid is up to 400-500 kg per 1 kg of extracted iodine);

- acidification of water determines the need for deoxidation of waste water before pumping it into underground formations;

- when acidified, naphthenic acids are formed, polluting the filtration systems and the product.

A certain kind of process is the replacement of the recovery operation of the resulting molecular iodine with sorption on synthetic anion exchange resin (see RF patent No. 2235059, IPC C01B 7/14, publ. 2004.08.27) or extraction with an individual or mixed organic solvent (tributyl phosphate or its solutions in kerosene) (see RF patent No. 2331576, IPC C01B 7/14, publ. 2008.08.20).

However, these methods are also implemented by acidification of the original mineral sources. In addition, the multi-stage process leads to its complexity. The operation of desorption of iodine from the sorbent does not proceed fully, which requires additional washing of the resin from iodine.

Closest to the proposed method, in essence, a technical solution (anion exchange) is the extraction of iodide ions by an anion exchange resin based on quaternary ammonium salts, the alkyl chain of which contains at least 12 carbon atoms exchanged by anions with the accumulation of iodide ions in the resin. When the resin is substantially saturated with iodide, an acidified aqueous solution of sodium iodate is passed through it to oxidize the adsorbed iodide to iodine. The cycle is repeated several times until the resin is saturated with iodine. Then iodine is washed with a solution of NaOH (see patent DE 19745106, IPC C01B 7/14, publ. 1999.03.25).

Despite the fruitfulness of the approach associated with the successful selection of polymer modifiers (quaternary ammonium salts), it has all the drawbacks of the sorption technologies described above, as well as the multiple (3-5) treatment of the sorbent with iodate solution for complete binding of iodide ions.

The basis of the claimed invention is the task of creating a method that would allow simpler technical solutions to isolate iodine from natural mineral sources.

The technical result consists in simplifying the method by carrying out the anion exchange process in the liquid phase, and not at the liquid-polymer interface.

The problem is solved in that in the method of extracting iodine from solutions containing iodide and bromide ions, by ion exchange with anions of quaternary ammonium salts followed by oxidation of iodide ions, according to the solution of the quaternary ammonium salt is taken in the form of a solution in an organic solvent - extractant: kerosene, including a co-solvent: xylene or tributyl phosphate or chloroform in an amount 10% higher than the mass of salt theoretically necessary for the binding of iodide and bromide ions from the aqueous phase, which is emulsified with water phase, the organic phase is separated after emulsification, iodide ions are oxidized in the organic phase with chlorine or bromine water, the resulting molecular iodine is converted into a solid concentrate by the addition of a sorbent, while quaternary ammonium salts contain alkyl radicals with the optimal number of carbon atoms - from 8 to 16 and the anions of bromine and chlorine.

The ratio of organic and aqueous phases during their mixing varies in the range (2.5-50): 100. The content of co-solvent in the organic solvent is from 5 to 50 vol.%. After extraction of iodine, the organic phase with the salts regenerated in it after the oxidation process with a solution of chlorine or bromine water is sent to the repeated extraction of iodine to ensure a closed technological cycle.

Distinctive features of this invention are:

- the introduction of a quaternary ammonium salt directly into the phase of the mixed solvent based on kerosene in an amount 10% higher than the mass of salt theoretically necessary for the binding of iodide and bromide ions from the aqueous phase;

- carrying out the process of anion exchange at the boundary of the organic and aqueous phases under the conditions of creating microemulsions;

- the implementation of the oxidation process J ^- such an oxidizing agent that regenerates the Quaternary ammonium salt, thereby causing a continuous closed cycle;

- the binding of the released iodine to a solid concentrate.

The process of extracting iodide ions is reflected more clearly in the attached illustrations, where the drawing shows a diagram of the process for obtaining iodine concentrates from various mineral sources, where L is an organic solvent, 1 is a reactor with an initial solution, 2 is a mixing device, and Table 1 shows the expanded data on systems based on tetraoctylammonium bromide.

The essence of the proposed approach is that to the waters containing halide ions (iodide and bromide), solutions of quaternary ammonium salts in an organic solvent are added with vigorous stirring, which exchange their anion with the iodide ion of the salt present in the aqueous solution, with the formation compounds of R ₄ NI. The mass of the quaternary ammonium salt in the solution used is 10% higher than the mass of salt theoretically necessary for the equivalent exchange with iodide and bromide ions present in the aqueous phase. After separation of the organic phase, a solution of chlorine or bromine water is added to it, which oxidizes J ^- to elemental iodine, while simultaneously regenerating the quaternary ammonium salt to extract a new portion of iodide ions. The solution of the regenerated salt is sent to a new operation for the extraction of iodide ions, which forms a closed process cycle. The molecular iodine formed in the organic phase is exposed to the action of a sorbent, for example, colloidal copper in the organic phase with the formation of a solid copper iodide concentrate at the outlet. As it accumulates, copper is regenerated by iron powder, and the resulting iron iodide is oxidized to molecular iodine by the action of any oxidizing agent (Cl ₂ , NaOCl, etc.). The method was carried out as follows.

A certain volume of an aqueous solution containing a variable amount of iodide ions (20-100 mg / l) was introduced into reactor 1. Then, a solution of a quaternary ammonium salt in an organic solvent was added to it (the ratio of aqueous and organic phases was from 10: 1 to 40: 1). The amount of salt was taken 10% more than calculated by the equation of the anion exchange reaction. Next, the resulting system was intensively mixed by device 2 for 10-15 minutes and held until the boundary of phase separation was established (about 30 minutes). The aqueous phase was separated and analyzed for the content of iodide ions by the titrimetric method with sodium thiosulfate, adding a starch solution in the final titration step. The organic phase, containing a quaternary salt with an anion in the form of iodide, is directed to the operation of iodine isolation and regeneration of the quaternary ammonium salt. Elemental iodine formed in the organic phase is exposed to colloidal copper in the organic phase to form a solid copper iodide concentrate at the outlet. As it accumulates, copper is regenerated by iron powder, and the resulting iron iodide is oxidized to molecular iodine by the action of any oxidizing agent (Cl ₂ , NaOCl, etc.)

Example 1. They took 20 ml of an aqueous solution containing 100 mg / l of iodide ions and 4 ml of an organic phase consisting of 8.69 mg (C ₈ H ₁₇ ) ₄ NCl, 3.8 ml of kerosene and 0.2 ml of chloroform ( 5 vol.%). The degree of extraction of iodide ions from the aqueous phase is 98.9%.

Example 2. We took 40 ml of an aqueous solution containing 30 mg / l of iodide ions and 4 ml of an organic phase consisting of 8.0 mg (C ₁₂ H ₂₅ ) ₄ NBr, 3.6 ml of kerosene and 0.4 ml of tributyl phosphate ( 10 vol.%). The degree of extraction of iodide ions from the aqueous phase is 93.7%.

Example 3. We took 100 ml of an aqueous solution containing 50 mg / l of iodide ions and 2.5 ml of the organic phase, consisting of 43.1 mg (C ₁₆ H ₃₃ ) ₄ NBr 1.25 ml of kerosene and 1.25 ml o -xylene (50 vol.%). The degree of extraction of iodide ions from the aqueous phase is 95.8%.

Example 4. We took 50 ml of an aqueous solution containing 100 mg / l of iodide ions, with a total salinity of 80 g / l and 5 ml of an organic phase consisting of 23.6 mg (C ₈ H ₁₇ ) ₄ NBr 4.75 ml of kerosene and 0.25 ml of chloroform (5 vol.%). The degree of extraction of iodide ions from the aqueous phase is 76.7%.

Example 5. 40 ml of an aqueous solution was taken containing 70 mg / l of iodide ions and 4 ml of an organic phase consisting of 9.2 mg (C ₅ H ₁₁ ) ₄ NBr 3.8 ml of kerosene and 0.2 ml of chloroform (5 about.%). The degree of extraction of iodide ions from the aqueous phase is 26.7%.

Example 6. In a separatory funnel, 80 ml of an aqueous solution containing 100 mg / l of iodide ions and 16 ml of the organic phase consisting of 81.3 mg (C ₂₀ H ₄₁ ) ₄ NCl of 14.4 ml of kerosene and 1.6 ml are placed tributyl phosphate (10 vol.%). In the organic phase, the salt does not completely dissolve. The degree of extraction of iodide ions from the aqueous phase is 32.3%.

The application of this method allows you to:

- carry out the process directly in the oil and gas fields or sources of iodine-containing water without creating stationary enterprises;

- save money on expensive drilling and the creation of production infrastructure;

- get away from the operation of acidification and subsequent deoxidation of produced water;

- get away from the process of allocation of naphthenic acids;

- discharge waste water into reservoir pressure maintenance systems.

Claims (4)

1. The method of extraction of iodine from solutions containing iodide and bromide ions by ion exchange of anions of quaternary ammonium salts, oxidation of iodide ions, characterized in that the quaternary ammonium salts are taken in the form of a solution in an organic solvent - extractant: kerosene, including a co-solvent: xylene, or tributyl phosphate, or chloroform in an amount 10% higher than the salt mass theoretically necessary for binding iodide and bromide ions from the aqueous phase, which is emulsified with the aqueous phase, the organic phase is separated after emulsions carbonation, iodide ions are oxidized in the organic phase with chlorine or bromine water, the resulting molecular iodine is converted into a solid concentrate by adding a sorbent, while quaternary ammonium salts contain alkyl radicals with an optimal number of carbon atoms from 8 to 16 and bromine anions and chlorine. 2. The method according to claim 1, characterized in that the ratio of the organic and aqueous phases when they are mixed varies between (2.5-50): 100. 3. The method according to claim 1, characterized in that the content of the co-solvent in the organic solvent is from 5 to 50 vol.%. 4. The method according to claim 1, characterized in that after the extraction of iodine, the organic phase with the salts regenerated therein after the oxidation process with a solution of chlorine or bromine water is sent to the repeated extraction of iodine to ensure a closed technological cycle.

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