RU2560365C2 - Method of obtaining sorbent for selective extraction of iodides - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of obtaining is based on application of complexes of nickel ions with aminomethylphosphonic acids, formed as a result of interaction of hexamethylenetetramine, calcium hypophosphite, hydroiodic acid and nickel iodide. Synthesis is carried out in two stages. First, nickel-containing oligomer mixture is prepared, after that, dispersion of transformer oil in non-polar medium is performed. Obtained sorbent granules are washed from remains of transformer oil with benzene, then water, alkali and with water again.

EFFECT: obtaining sorbent with increased capacity and selectivity to iodides.

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Description

The invention relates to the production of phosphorus-nitrogen-containing amphoteric ion exchangers containing metal ions of complexing agents, which can be used for the selective extraction of iodides in the processing of natural brines and drilling water [C02F 1/42, C08F 8/40].

Known ion-exchange resins against the background of a significant amount of chlorides and bromides practically do not extract iodides in the form of simple anions without the use of redox processes. This is due to the fact that the known ion-exchange resins (anion exchangers) do not have sufficient selectivity for iodides compared with bromides and chlorides.

Taking into account the fact that in all natural brines the chloride content is tens and hundreds of times higher than the iodide content, the use of ion exchangers available today becomes ineffective without the need for preliminary introduction of oxidizing agents into the brine and conversion of iodides to elemental form, after which sorption is carried out. The disadvantages of the known ion-exchange resins and the method for extracting iodine using them are: low exchange capacity and selectivity for iodides, the need to transfer iodides to elemental iodine using expensive or toxic oxidizing agents (chlorine), incomplete desorption, which leads to a rise in the cost of the target product and a decrease in the efficiency of the process generally.

Closest to the proposed method in technical essence is a method of purifying water from iodides or bromides using anion exchange resin with primary and secondary or tertiary amino groups, modified with metal salts (copper, silver, mercury) [SU 1838246, 05.22.1992].

The disadvantages of the sorbent described in this method are: low sorption capacity, as well as the fact that the sorbent extracts iodides and bromides at low concentrations of interfering chlorides.

The objective of the invention is to develop a method for producing a sorbent with increased capacity and selectivity, which can be used on an industrial scale for the selective extraction of iodides from natural mineral brines and drilling water.

The technical result is to obtain a nickel-containing sorbent in the form of spherical granules by polycondensation of a mixture of urotropine, calcium hypophosphite, hydroiodic acid in the presence of nickel iodide salts when dispersed in a non-polar medium, which leads to high sorption capacity and selectivity to iodides when removing them from brines.

The technical result is achieved in a method for producing a sorbent for the selective extraction of iodides, including the use of complex compounds of metal ions with functional groups of the sorbent, moreover, nickel iodide is used as a metal salt, and functional groups of aminomethylphosphonic acids formed during the interaction of a mixture of urotropine and hypophosphite are used as ligands calcium, iodic acid and nickel iodide, when carrying out the reaction in two stages: in the first stage at a temperature of 20-30 ° C I get t of a nickel-containing oligomer mixture by the interaction of the starting reagents: urotropin, calcium hypophosphite, hydroiodic acid in a molar ratio of 1: 1.25: 5 - 1: 1.75: 5, respectively, and nickel iodide in an amount of 4-7% of the reaction mass; in the second stage, by dispersing the obtained oligomeric mixture in a non-polar medium, sorbent granules are obtained.

The claimed technical solution in comparison with the prototype provides for the preparation of a nickel-containing sorbent in two stages by polycondensation of urotropine, calcium hypophosphite, hydroiodic acid and nickel iodide in a dispersion medium with preliminary oligomerization of the mixture in order to obtain a highly selective sorbent with iodides. This leads to the following advantages: increased sorbent capacity and selectivity in the presence of chlorides, which positively affects the complex of consumer properties of the sorbent and allows the extraction of iodides from highly concentrated brines. The reaction of obtaining the sorbent proceeds with the intermediate production of methylol derivatives during the decomposition of urotropine in an acidic environment of hydroiodic acid, which then enter into a condensation reaction with molecules of hypophosphorous acid formed from calcium hypophosphite and hydroiodic acid. The formation of specific structures is influenced by nickel ions, which act as complexing agents with respect to the formed aminomethylene phosphine functional groups of the sorbent.

The increase in sorption capacity and sorbent selectivity for iodine is presumably associated with a synergistic effect due to the complexing properties of nickel cation and aminomethylenephosphine groups, a combination of electronic and steric factors contributing to the sorption of iodides not only by the ion-exchange mechanism, but also due to complexation with vacant electronic nickel orbitals, which predominantly coordinates and forms stronger complexes with iodine ions than with chloride and bromide ions.

The optimal amount of introduced nickel ions is 4-6% in terms of nickel iodide from the reaction mass. An increase in the number of nickel ions leads to a decrease in the osmotic resistance of the sorbent. The exposure time upon receipt of the oligomeric mixture is 75-80 minutes. During this time, the reaction mixture is homogenized and a clear solution is obtained.

Raising the oligomerization temperature above 30 ° C leads to a sharp reduction in the oligomerization time and an increase in the viscosity of the mixture, which leads to the formation of granules in the form of agglomerates. When carrying out oligomerization below 20 ° C, the duration of homogenization of the reaction mixture increases (up to 15 hours).

In a second step, spherical granules are obtained from an oligomer mixture in a non-polar medium, for example, transformer oil. The initial temperature of introducing the oligomeric mixture into a non-polar dispersion medium is 60-70 ° C.

Final exposure is carried out at a temperature of 100-105 ° C. The exposure time of the granules at each temperature is 1 hour. Lowering the inlet temperature below 60 ° C results in granules with a dispersion medium included in the volume. Raising the initial input temperature above 70 ° C leads to the formation of granules in the form of agglomerates.

Then the sorbent granules are separated from the dispersion medium and the product is washed from the dispersion medium with benzene, then the product is dried at a temperature of 20-25 ° C and washed with distilled water until it is completely washed from calcium iodide, and then washed with a 5% alkali solution, then washed with water until neutral reaction.

The invention is illustrated by the following examples.

Example 1. In a three-neck round-bottomed flask with a volume of 250 ml, equipped with a reflux condenser, a mechanical stirring device, 142.2 g of hydroiodic acid were charged, then 13.6 g of calcium hypophosphite were dosed. The mixture was stirred for 20 minutes. To the resulting mixture was added 7.2 g of nickel iodide (6% of the reaction mass) at 30 ° C. After the dosage of nickel iodide is completed, 14 g of urotropine are introduced into the reaction mixture (molar ratio of urotropine: calcium hypophosphite: hydroiodic acid 1: 1.25: 5). Then stirring is carried out until the reaction mixture is completely homogenized, maintaining the temperature in the flask 20-30 ° C for 80 minutes.

From the resulting mixture, the formation of sorbent granules is carried out in a 1-liter three-neck round-bottom flask equipped with a mixing device, a reflux condenser and a thermocouple, in which 450 g of a dispersion medium (transformer oil) are loaded, the mixing speed is set at 200 rpm, heated to a temperature of 60 ° С and then a nickel-containing oligomer mixture is introduced. The exposure time at this temperature is 1 h, then the temperature is increased to 100 ° C and can also withstand 1 h.

After completion of exposure at the indicated temperature, the reaction system is cooled to 80 ° C and the product granules are separated from the transformer oil on a suction filter and washed in Soxhlet with benzene from excess transformer oil. Then the product is loaded into the column and washed successively with distilled water until the removal of calcium iodide, 5% alkali solution and water until neutral. Yield 170.5 g. Nickel content 97% of the total sorbent capacity (7.9 mEq / g). The phosphorus content of 18.0%, nitrogen 7%. Humidity 70%.

Example 2. In contrast to example 1, we take the molar ratio of urotropine: calcium hypophosphite: hydroiodic acid 1: 1.75: 5, which corresponds to a weighting of calcium hypophosphite of 30.5 g.

Yield 190.3 g. Nickel content 98% of the total sorbent capacity (7.9 mEq / g). The phosphorus content of 19.0%, nitrogen 8.5%. Humidity 68%.

Example 3. In contrast to example 1, the oligomeric mixture is prepared at a temperature of 30 ° C.

Yield 168.8 g. Nickel content 97% of the sorbent capacity (7.6 mEq / g). The phosphorus content of 18.5%, nitrogen 7.3%. Humidity 72%.

Example 4. In contrast to example 1, the oligomeric mixture is prepared with the introduction of nickel iodide 6% of the reaction mass (10.9 g of nickel iodide).

Yield 183.6 g. Nickel content 99% of the sorbent capacity (8.1 mEq / g). The phosphorus content of 16.0%, nitrogen 6.1%. Humidity 68.5%.

Example 5. The main sorption indicators (static exchange capacity (SOE) and iodide selectivity were determined by sorption of iodides from an underground brine of the following composition 12 mg / l iodides, 550 mg / l bromides, 154345 mg / l chlorides.

A sample of a wet sample of a sorbent weighing 2,000 g was placed in a 50 ml brine and kept for 24 hours at a temperature of 20 ° С, after which the solution was analyzed for the residual content of iodides, bromides, chlorides by iodometric and titrometric methods of analysis.

Other conditions for determining the static exchange capacity correspond to GOST 20255.1-89 "Ionites, methods for determining the exchange capacity".

The SOI for iodides for the sorbents obtained in Examples 1–4 was 3.8–4.2 mEq / g, the selectivity for the extraction of iodides from natural brine was 75–78%. For the sorbent of the prototype, the capacity was 0.25-0.3 mEq / g, the selectivity of iodide extraction was 50-55%.

Claims (1)

A method of producing a sorbent for selective extraction of iodides, including the use of complex compounds of metal ions with functional groups of the sorbent, characterized in that nickel iodide is used as a metal salt, and functional groups of aminomethylene phosphonic acids formed during the interaction of a mixture of urotropine and calcium hypophosphite are used as ligands , iodic acid and nickel iodide, and the sorbent reaction is carried out in two stages: in the first stage, at a temperature of 20-30 ° C nickel-containing oligomeric mixture by the interaction of the starting reagents: urotropine, calcium hypophosphite and hydroiodic acid in a molar ratio of 1: 1.25: 5-1: 1.75: 5, respectively, and nickel iodide in an amount of 4-7% of the reaction mass; in the second stage, by dispersing the obtained oligomeric mixture in a non-polar medium, sorbent granules are obtained.