RU2698800C1 - Method of producing strontium sorbent for solutions containing hardness salts - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to methods of producing sorption material for extraction of strontium radionuclides from solutions with high content of hardness salts. Method of producing strontium sorbent for solutions containing hardness salts, involving obtaining amorphous porous barium silicate. Prior to adding the strontium sorbent to the solution in the pores of the matrix of amorphous porous barium silicate, microcrystalline barium sulphate is formed. For this purpose, amorphous porous barium silicate is treated with solutions containing sulphate ions.

EFFECT: invention reduces washing out of weakly bound exchange barium without significant reduction in sorption efficiency.

1 cl, 6 dwg

Description

The invention relates to methods for producing sorption material for the extraction of strontium radionuclides from solutions with a high content of hardness salts and a method for extracting strontium radionuclides from solutions with a high content of hardness salts.

A known method of producing a strontium sorbent for natural unpopulated waters, comprising forming a thin-layer inorganic sorbent of barium manganite with a barium content of 0.120-0.180 g / g sorbent on wood-cellulose granular support (see Ryzhenkov A.P., Egorov Yu.V. Sorption of strontium-90 from fresh waters in the process of sulfate modification of barium manganite (Radiochemistry, 1995, v. 37, issue 6, pp. 549-553). At the same time, reagents containing sulfate anions, which interact with barium cations of the sorption-reagent material with the formation of insoluble barium sulfate, are additionally introduced into the water to be purified. Such interaction of the sorption-reagent material with the components of the solution containing the recoverable substance leads to a noticeable increase in the efficiency of strontium extraction due to its additional adsorption coprecipitation in the new sorption sulfate phase. The optimal concentration of sodium sulfate in solution is (5-10) × 10 ^-3 mol / dm ³ . The process is carried out in static conditions.

The disadvantages of the method are its low efficiency for cleaning solutions with a high content of hardness salts for reasons of low selectivity in the strontium-calcium system and the sensitivity of the sorbent to the content of organic substances due to the recovery of barium manganites.

There is also a method of producing a strontium sorbent for solutions containing hardness salts, including the production of amorphous porous barium silicate (TU 2164-012-02698192-2007, for the production of CPM sorbent).

The method provides an effective strontium sorbent, but its use in standard pressure filters used in LRW treatment systems has a number of negative aspects: the dynamic capacity of such filters is many times less than the static capacity, which reduces the efficiency of strontium radionuclide removal in LRW treatment systems. In addition, with a lack of sulfate ions in a solution containing hardness salts (in the form of magnesium carbonates, for example), exchange barium leaving the silicate matrix into the solution is partially carried out into the piping system, where it forms a precipitate (mainly barium carbonate), which leads to the need for regular additional chemical washing of pipelines, which also reduces the efficiency of treatment plants, and this problem cannot be solved by the additional introduction of sulfate ions into the solution technologically because of the requirements for the chemical composition of purified water (salinity not exceeding 1 g / l).

The problem to which the invention is directed is to obtain a sorbent suitable for use in pressure filters, LRW purification systems with reduced precipitation of barium salts in its pipelines.

The technical result manifested in solving the problem of the invention is to reduce the leaching of loosely coupled exchange barium without a significant decrease in the efficiency of sorption.

The problem is solved, and the claimed technical result is achieved by the fact that the method of producing strontium sorbent for solutions containing hardness salts, including the preparation of amorphous porous barium silicate, is characterized in that microcrystalline barium sulfate is formed in the pores of the matrix of amorphous porous barium silicate, for which amorphous porous barium silicate is treated with solutions containing sulfate ions.

A comparative analysis of the features of the claimed solution with the signs of the prototype and analogues indicates the conformity of the claimed solution to the criterion of "novelty."

The combination of features of the invention provide a solution to achieve the claimed technical result, and the features of the characterizing part of the claims provide a solution to the following functional problems.

The signs “in the pores of the matrix of amorphous porous barium silicate form microcrystalline barium sulfate” provide a decrease in the content of precisely weakly bound exchange barium, converting it to barium sulfate at the stage of sorbent synthesis.

The signs “amorphous porous barium silicate are treated with solutions containing sulfate ions” provide the formation of microcrystalline barium sulfate in the pores of the matrix of amorphous porous barium silicate. In addition, this allows us to simplify and shorten the procedure for obtaining the claimed sorbent, due to the possibility of using the finished material - selective sorbent sorbent, produced by the DalRAO DCC.

The description of the invention and specific examples of its embodiment are illustrated by the following figures, which show:

In FIG. Figure 1 shows the dynamics of purification of a model LRW solution from Sr-90. Here, the solution is 1.1-hardness (in Mg ²⁺ ) = 5 ° W (mEq / L); a solution of 1.4 - hardness (Mg ²⁺ )) = 15 ° W (mEq / l); in FIG. Figure 2 shows the dynamics of purification of a model LRW solution from Sr-90 (here, hardness (in Mg ²⁺ ) = 5 ° W (mEq / L), pH = 6); in FIG. Figure 3 shows the dynamics of purification of a model LRW solution from Sr-90 (here stiffness (in Mg ²⁺ ) = 5 ° W (mEq / l), pH = 9); FIG. 4 Dynamics of purification of a model LRW solution from Sr-90 at a salt content of solutions of 35 g / l (here solution 1.1 is hardness (in Mg ²⁺ ) = 5 ° W (mEq / l), solution 1.4 is hardness (in Mg ²⁺ ) = 15 ° W (mEq / L)); FIG. 5 Dynamics of purification of a model LRW solution from Sr-90 at a salt content of solutions of 5 g / l, (here the concentration of sulfanol is 1.5 mg / l, solution 1.7 is the hardness (in Mg ²⁺ ) = 0.5 ° W (mEq / l), solution 1.9 - hardness (in Mg ²⁺ ) = 33.2 ° W (mEq / l)); In FIG. Figure 6 shows the dynamics of barium leaching from the sorbent into the solution during the purification of the LRW model solution from Sr-90 (salinity 10 g / l, pH = 6). Here CPM-n is a new sorbent obtained by the claimed method.

For the production of the claimed sorbent, the following components are needed:

- selective sorbent CPM according to TU 2164-012-02698192-2007;

- sodium sulfate according to GOST 21458-75, or according to GOST 6318-77, or according to GOST 4171-76, or according to GOST 5644-75;

- barium chloride according to GOST 4108;

- hydrochloric acid 0.1N (standard titer) according to TU 2642-001-49415344-99, or according to TU 6-09-2540-88, or according to TU 2642-001-07500602-97;

- distilled water;

g drinking water according to SanPiN 2.4.1.1074.

For the production of the claimed sorbent using the following equipment:

- installation for the production of sorbent SRM (according to TU 2164-012-02698192-2007);

- frame filters;

- drying cabinets;

- roll crusher;

- apparatus for dispersing bulk media;

- sorption column (Wave Cyber, size 1354, China) or similar;

- pump grade PKm 60 (PEDROLLO) or similar,

- containers for the preparation of solutions, finished products, waste, auxiliary;

- tanks for transportation and storage of the finished sorbent.

The claimed sorbent is a mechanically strong granules of irregular shape, consisting of finely divided crystalline barium sulfate in a porous silicate matrix. Appearance, technical and physico-chemical characteristics of the sorbent: appearance - fine-grained crumb, particle size from 0.3 to 3.0 mm; bulk density, g / cm ³ 0.3-0.5; the proportion of non-exchange barium in the sorbent ≥ 0.5.

The production technology consists of two stages, including:

- preparation of equipment, preparation of raw materials, manufacturing of SRM according to TU 2164-012-02698192-2007 (preparation of working solutions, mixing of working solutions, sedimentation, filtration, washing, drying, fractionation) - according to the technological scheme for the production of SRM sorbent used in DalRAO ";

- treatment of the sorbent CPM with solutions containing sulfate ions, modification of the CPM (preparation of working solutions, washing).

The technological process is carried out in compliance with sanitary standards and safety rules for production using harmful chemicals.

Inspection and preparation of equipment is carried out in accordance with the current regulatory documentation for chemical production using reactive chemicals. Reagents used must comply with the above GOSTs. The synthesis of the CPM sorbent is carried out according to the instructions for the production of selective CPM sorbent (TU 2164-012-02698192-2007), operating in the DalRAO DC.

Sorbent treatment

1 - processing in a sorption column - preparation of solutions of sodium sulfate, barium chloride (for analysis), is carried out in accordance with the general current technological instructions in compliance with safety regulations when working with harmful chemicals. A solution of sodium sulfate is prepared in a 150 l supply tank. The volume of the solution is 100 liters. The concentration of the working solution of sodium sulfate is 6-10 g / l. The volume of a solution of barium chloride is 1 l, the concentration of a solution of barium chloride is 1 g / l.

- loading the column (the sorption column with the installed drain pipe is filled to 2/3 of its volume with the initial selective sorbent CPM (fraction 0.3-3 mm) - 80 l, after which the column is prepared for pumping the working solution).

- pumping working solutions. The column is filled with sodium sulfate solution (50 L). Pumping through the column of the working solution of sodium sulfate from the supply tank is carried out from the bottom to the top in a closed cycle with filtration through the sintepon of the suspended suspension, the solution is returned to the supply tank. Pumping speed - 40 l / min. Pumping time - 6 hours.

- washing the sorbent from excess sulfate is carried out with tap water until complete washing from sodium sulfate. Control is carried out using a qualitative reaction with barium chloride - the formation of a precipitate of barium sulfate. To do this, 10 ml of barium chloride solution is added to a 100 ml wash water sample. The turbidity of the solution is visually assessed. Flushing continues until precipitation stops.

- unloading the washed sorbent is carried out in a polymer tank using a siphon with the supply of tap water to the column. If transportation is necessary, the sorbent is dried in ovens on pallets at 105 ° C. When used within the enterprise - packaged and stored raw.

2 - processing in a plastic container

- the preparation of solutions of sodium sulfate should be carried out similarly to the above example. A solution of sodium sulfate is prepared in a supply tank of 250 l. The volume of the solution is 200 liters. The concentration of the working solution of sodium sulfate is 10-20 g / l (up to 4 kg per 200 l of solution),

- pumping working solutions. A hard filter is installed on the supply tank. A polymer container filled with a sorbent (40 l) is installed on the filter, the pump hose is fixed in the container in such a way as to ensure the flow direction of the solution from the bottom up. The solution from the supply tank is pumped into the container with the sorbent in a closed cycle with filtration through the synthetic winterizer, the suspension is carried out by the solution, the solution is returned to the supply tank. Pumping speed - 25-30 l / min. Pumping time - 4 hours. Then everything repeats.

- washing the sorbent from excess sulfate. The container with the sorbent after treatment with a sulfate solution is transferred to a drain pan. Rinsing is carried out with tap water. Visually assess the turbidity of the solution. Flushing is continued until clear wash water. The output of the initial sorbent CPM as a result of one standard synthesis is 240 l (6 containers X 40 l). The required amount of sodium sulfate for processing one batch is: 4 kg + (5 × 1 kg) = 9 kg (37.5 g / 1 l of sorbent).

In the manufacturing process of the claimed sorbent, the staff monitors the technological parameters.

The control points of sampling and the scope of control of technological parameters are determined by the manufacturer of the sorbent, depending on the organization of the process.

The results of determining the comparative effectiveness of the claimed sorbent and prototype (the original sorbent CPM) showed that:

- the claimed sorbent is more effective than CPM in solutions with a high content of hardness salts (magnesium ions) (with a sufficient amount of sulfates (hereinafter 2 g / l)) (see Fig. 1);

- the effect of total salinity on the effectiveness of the claimed sorbent is significant in the first ten column volumes, then it is not significant (see Fig. 2 and Fig. 3);

- the effect of the stiffness of the LRW solution on the claimed sorbent: the higher the stiffness, the better the sorption even at high salinity (see Fig. 4) and even in the presence of moderate concentrations of surfactants (see Fig. 5);

- leaching of barium from the claimed sorbent is much less than from the starting material (sorbent CPM) (see Fig. 6).

Claims (1)

A method of producing a strontium sorbent for solutions containing hardness salts, comprising producing an amorphous porous barium silicate, characterized in that microcrystalline barium sulfate is formed in the pores of the matrix of amorphous porous barium sulfate before the introduction of the strontium sorbent into the solution, for which amorphous porous barium silicate is treated with solutions containing sulfate ions.

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