RU2513846C1 - Method of processing hydrolysed sodium arsenite into commercial product - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of processing hydrolysed technical sodium arsenite into a commercial product involves cyclic repetition of consecutive steps. First, arsenic salts are leached from material with hydrochloric acid solution, which is added until achieving pH 9.5-10.5, to form a heterogeneous system. The heterogeneous system is then divided into a solid phase and a working solution. Further, the working solution is concentrated through evaporation to arsenic (III) content greater than 10 g/100 g water and the concentrated working solution is separated from the formed precipitate. Arsenic (III) oxide is precipitated by acidifying the working solution and the arsenic (III) oxide precipitate is filtered off. The filtrate is returned to the first step of the process. After repeating the cycle of said operations 3 to 10 times, arsenic (IV) compounds are then extracted from the working solution via reduction thereof to arsenic (III) compounds or to elementary arsenic.

EFFECT: invention reduces the amount of process wastes and improves safety when processing hydrolysed sodium arsenite.

2 cl, 2 ex

Description

The invention relates to the field of chemical technology and can be used in a chemical production flow chart, the feedstock of which is hydrolytic sodium arsenite (technical), TU 2622-159-04872702-2005 (hereinafter - ANG). This raw material has the form of granules from light gray to dark brown in color and is a mixture of salts (mainly arsenite and sodium chloride), as well as a small amount of water-insoluble residue. According to chapter 5 of the report [1], a number of ANG batches did not meet the technical conditions, in particular, all investigated ANG batches contained arsenic (V) salt - sodium arsenate, in an amount from 2.4 wt.% To 14.5 wt.%, with an average value of 9.27 wt.%. The percentage of arsenic (V) of the total arsenic content was up to 38 wt.%.

The objective of the invention is to develop a method for processing ANG into commercial products suitable for processing raw materials with possible deviations from TU and universal for any batch number.

By the nature of the composition (salt mixture) and the limited scope of the problem (currently, the reserves of this type of raw material are approximately 12,500 tons), the hydrometallurgical technology with the selective dissolution of arsenic salts at the first stage and the isolation of arsenic (III) oxide from the solution as the final product seems optimal. However, the presence of arsenic (V) compounds in the feedstock complicates the task.

Consider the well-known technologies for processing arsenic-containing raw materials, based on the hydrometallurgical approach. Known technologies can be classified into 3 groups, depending on the product obtained:

1) Arsenic (III) oxide

A method of processing the reaction masses formed during the detoxification of lewisite [patent: Demakhin A.G. et al., 2001 (hereinafter - RU 2192297)].

A method of processing products of detoxification lewisite [patent: Demakhin A.G. et al., 2001 (hereinafter - RU 2198707)].

A method of processing the reaction masses formed in the process of detoxification of lewisite [patent: A. Demakhin et al., 2008 (hereinafter - RU2359725)], as well as the work of Eliseev A.D. “Physico-chemical principles of the process of separation of hydrolytic sodium arsenite into basic components”, Saratov, 2008.

A method of processing products of alkaline hydrolysis of lewisite into commercial products [patent: Demakhin A.G. et al., 2008 (hereinafter - RU2389526)].

2) Technical elemental arsenic

Method of utilization of mixtures containing inorganic arsenic compounds PL / [patent: Iwaniec Janusz et al., 2002 (hereinafter - PL 357396)].

The method of separation of elemental arsenic from the reaction mass obtained by the destruction of lewisite [patent: Baranov Yu.I. et al. 2002 (hereinafter - the RF 2009276)].

A method of obtaining elemental arsenic from aqueous and aqueous-organic solutions [patent: V.V. Sheluchenko et al., 2008 (hereinafter - RU 2371391)].

A method of processing the reaction masses formed during the alkaline hydrolysis of lewisite into technical products [patent: Rastegaev O.Yu. et al., 2009 (hereinafter - RU 2396099)].

A method of obtaining elemental arsenic [patent: Rastegaev O.Yu. et al., 2008 (hereinafter - RU 2409687)].

A method of obtaining elemental arsenic and sodium chloride from alkaline hydrolysis products of lewisite [patent: Demakhin A.G. et al., 2009 (hereinafter - RU 2412734)].

3) Other products

A method of processing the reaction masses of detoxification lewisite [patent: Petrov V.G. et al., 1995 (hereinafter - RF 2099116)].

A method of disposing of a poisonous substance of a skin-boiling effect of the lewisite type [patent: V. Gormay et al., 1999 (hereinafter - the Russian Federation 2172196)].

Consider the advantages and disadvantages of the technologies specified in the above patents.

Technologies for processing arsenic-containing raw materials into technical arsenic (III) oxide

All of the above technologies associated with the production of technical arsenic (III) oxide relate to the processing of another type of raw material - liquid reaction masses from the destruction of lewisite, corresponding to TU 2112-123-04872702-2002 (hereinafter - liquid reaction masses). In addition to the different state of aggregation, a significant difference between this raw material and ANT is the high content of pentavalent arsenic compounds in ANG.

The technologies described in patents RU 2192297, RU 2198707 describe the production of arsenic (III) oxide by concentration and acidification of liquid reaction masses, but the problem of removing arsenic (V) compounds from the working process is not considered, therefore, we can conclude that up to 38% of arsenic contained in raw materials will be in production waste if these technologies are used for processing ANG.

The technology RU 2359725 proposes the production of arsenic (III) oxide in a similar manner as in the two previous patents, but it contains a method for recovering arsenic (V) compounds into arsenic (III). The method includes the widespread use of arsenic (III) chloride, which is formed during the acidification of a solution of liquid reaction masses with hydrochloric acid to a pH of less than 1.

Arsenic (III) chloride is a volatile (t _boil = 130 ° C), highly toxic compound (LD ₅₀ = 48 mg / kg), and is also included in the List of 2 chemical weapons precursors established by the Chemical Weapons Convention [2]. Working with such a substance requires the application of the highest standards of industrial and environmental safety and greatly increases the cost of such a technical process.

In addition, the liquid reaction masses used in the technology as raw materials contain alkaline hydrolysis products of lewisite by reactions

Accordingly, the processing of raw materials with hydrochloric acid according to the technology under consideration is carried out until the stage of separation of insoluble organic impurities from the solution of arsenic salts, strong acidification of the reaction masses can lead to the reverse process:

Reaction (6) is a classical reaction to produce lewisite [3]; excess arsenic chloride acts as a catalyst - Lewis acid. Thus, the process described in RU2359725 is the opposite of alkaline hydrolysis, used to destroy lewisite reserves, and can lead to the re-formation of chemical weapons.

In technology RU 2389526, the reduction of arsenic (V) compounds to arsenic (III) is considered using a multi-stage treatment, including the isolation of arsenic (V) as a precipitate of lithium arsenate, the conversion of lithium arsenate to arsenic acid using hydrochloric acid, and the reduction of arsenic acid to arsenic chloride (III) using a combined reducing agent - sodium iodide and ascorbic acid or hydrazine.

The disadvantages of this technology:

- multi-stage process

-the use of rather expensive reagents (according to December 2012: lithium chloride - from 650 rubles / kg, sodium iodide - 1200 rubles / kg, ascorbic acid - 530 rubles / kg) in the manufacturing process;

- additional pollution of the resulting product - As ₂ O ₃ impurities of lithium compounds, iodine, oxidation products of ascorbic acid;

- similarly to patent RU 2359725, the technology RU 2389526 widely uses highly toxic and volatile arsenic (III) chloride, which is included in the List of 2 chemical weapons precursors established by the Chemical Weapons Convention.

Technologies for processing arsenic-containing raw materials into technical elemental arsenic

The technology described in PL 357396 describes the separation of elemental arsenic from an aqueous solution and includes the oxidation of As (III) to As (V) with hydrogen peroxide, the deposition of arsenic in the form of poorly soluble calcium arsenate, and the production of elemental arsenic by calcium phosphorous acid arsenate when heated to 80 -150 ° C in a large excess (400% of the amount of calcium arsenate) phosphoric acid. The disadvantages of the method are the large number of process steps, the use of an explosive oxidizing agent when heated, the use of a toxic compound - phosphorous acid - as a reducing agent, the formation of a large amount of arsenic contaminated waste in the process, the possibility of the formation of toxic and explosive phosphine when heating phosphorous acid by the disproportionation reaction:

The technology described in RF 2009276 formed the basis for the creation of an industrial electrolysis unit put into operation at the chemical weapons destruction facility in Gorny, Saratov Region in 2009. After two years of operation, it was decided to close the production due to low arsenic yield and formation 3-4 times the amount of arsenic-containing waste during electrolysis.

Patents RU 2371391 and RU 2409687, which are close in content, describe a method for isolating elemental arsenic from solutions by reaction with a reducing agent, thiourea dioxide, in an alkaline medium.

и $$As{O}_4^{3-}$$

:Let us consider in more detail the processes occurring in an aqueous-alkaline solution of thiourea dioxide in the presence of ions $$As{O}_3^{3-}$$

and $$As{O}_{\mathrm{four}}^{3-}$$

:

Excess thiourea dioxide decomposes in solution with the formation of urea, hydrogen sulfide, elemental sulfur, sulfites and other sulfur compounds [4]. The resulting solution, containing sodium sulfite, urea and residual amounts of arsenic (at a level of 2-50 mg / l, which is 40-1000 times higher than the current MPC for arsenic in natural water), does not find practical application and requires additional resources for disposal. The cheapest option for the disposal of such a solution is natural or forced evaporation and burial of the resulting mixture of urea and inorganic salts at the waste landfill (tentatively, hazard class 3).

It is possible to calculate some technological parameters of the application of a similar method for processing ANG into elemental arsenic:

the average composition of ANG is 46.0% NaCl, 9.30% Na ₃ AsO ₄ , 44.1% Na ₃ AsO ₃ ;

- the amount of thiourea dioxide (DTM) needed to convert arsenic compounds to elemental arsenic can be estimated using the examples given in the patents: for RU 2409687 DTM is used in a weight ratio of 2.16 g DTM / 1 g As ³⁺ and 20 g DTM / 1 g As ⁵⁺ ; for RU 2371391, a larger ratio of 4.8 g DTM / 1 g As ^{3+ is used} ;

, где $$m_{A{s}^{n+}}$$

- масса мышьяка в степени окисления n+, m_АНГ - масса АНГ, 1000 г, ω_соли - массовая доля данного вида соли в сырье, M(As) - молярная масса мышьяка, 75 г/моль, М(соли) - молярная масса данного вида соли, 192 г/моль для Na₃AsO₄ и 208 г/моль для Na₃AsO₄;-1 kg of ANG contains an average of 172.3 g of As ³⁺ and 33.5 g of As ⁵⁺ (calculated by the formula $$m_{A{s}^{n+}}=m_{\mathrm{BUT}NG}\times {\omega }_{\mathrm{from}\mathrm{about}l\mathrm{and}}\frac{M\left(As\right)}{M\left(\mathrm{from}\mathrm{about}l\mathrm{and}\right)}$$

where $$m_{A{s}^{n+}}$$

is the mass of arsenic in the oxidation state n +, m _ANG is the mass of ANG, 1000 g, ω _salt is the mass fraction of this type of salt in the feed, M (As) is the molar mass of arsenic, 75 g / mol, M (salt) is the molar mass of this salt, 192 g / mol for Na ₃ AsO ₄ and 208 g / mol for Na ₃ AsO ₄ ;

- the amount of DTM required for processing 1 kg of ANG according to the method of RU 2409687 is obtained equal to 172.3 * 2.16 + 33.53 * 20 = 1042.8 g;

- the amount of technological waste per 1 kg of ANG: only elemental arsenic is removed from the reaction system (arsenic-DTM compound) as a useful product. Consequently, the approximate amount of dry waste (in the case of 100% yield of arsenic) will be equal to the sum of the masses of raw materials and reducing agent minus the mass of arsenic in raw materials: m _OTX = m _ANG + m _DTM -m _As = 1000 + 1042.8- (172, 3 + 33.5) = 1837.0 g of waste, i.e. - 180% of the amount of feedstock, which greatly limits the possibility of using these methods.

Patent RU 2396099 discloses yet another method for processing liquid reaction masses formed during alkaline hydrolysis of lewisite. The technology includes: concentration of the reaction masses and deposition of arsenic (III) oxide from them by acidification, as well as various options for treating tailings - purification of arsenic produced during concentration of sodium chloride by DTM, the possibility of treating the concentrate with sulfur-containing reducing agents to convert arsenic (V) compounds in (III).

However, the method has a lot of disadvantages: none of the cleaning paths has been brought to its logical conclusion. So, it is known that the DTM treatment of arsenic-containing solutions cannot lead to the complete removal of arsenic from the solution. The best experimental results obtained in December 2012 give a value of 2 mg / L of residual As concentration in solution. In addition to incomplete purification, the purified sodium chloride is contaminated with a large number of DTM decomposition products - sodium sulfite and urea. For another tail, the filtrate, after deposition of arsenic (III) oxide, no clear processing mechanism is also presented, although it should contain a significant amount of arsenic — the solubility of arsenic (III) oxide in water at n.a. is about 2%.

The method RU 2412734 describes the preparation of elemental arsenic from solutions containing sodium chloride by the action of a reducing agent, sodium borohydride, and the subsequent purification of the brine on iron-containing sorbents. The method is quite expensive, since the reducing agent used in prices for December 2012 costs about 16,000 rubles / kg.

Technologies for processing arsenic-containing raw materials into other products

The technology in patent RF2099116 describes acidification with sulfuric acid to a pH of 2.5 of a solution of raw materials and the subsequent addition of sodium sulfide with the formation of sparingly soluble arsenic sulfide AS ₂ S ₃ .

The disadvantages of the technology are:

- the creation of a strongly acidic environment in a system containing decomposition products of lewisite can lead to the formation of arsenic (III) chloride and lewisite, similar to the situation described in the discussion of patent RU 2359725;

- the release of uncontrolled quantities of hydrogen sulfide into the atmosphere;

- arsenic sulfide formed has an extremely small crystal size, which leads to great difficulties in filtering it.

в арсенат $$As{O}_4^{3-}$$

, упаривание реакционной массы до содержания арсенат-иона в 120 г/кг, охлаждение раствора при pH>13 до начала выкристаллизовывания арсената натрия и отделение последнего фильтрованием.The technology in patent RF2172196 includes adding to the solution of raw materials an aqueous solution of hydrogen peroxide in an amount that ensures the oxidation of arsenite ion $$As{O}_3^{3-}$$

to arsenate $$As{O}_{\mathrm{four}}^{3-}$$

evaporating the reaction mass to an arsenate ion content of 120 g / kg, cooling the solution at pH> 13 until crystallization of sodium arsenate begins and separating it by filtration.

However, this method has significant drawbacks: the explosion hazard when working with hydrogen peroxide when heated, the production of arsenic-containing wastewater after the filtering stage, the limited use of sodium arsenate in the national economy, the lack of technical solutions for the removal of contaminated sodium chloride and other impurities.

Marketing research shows that of the arsenic-containing compounds, the most widely used product in the national economy is arsenic (III) oxide, and there has recently been a steady increase in the production and consumption of semiconductor compounds based on gallium arsenide, the raw material for which is high-purity arsenic [5].

After consideration of the known hydrometallurgical technologies for processing arsenic-containing raw materials, the following requirements for the processing technology of ANG can be formulated:

- the possibility of processing into marketable products compounds of arsenic (III) and (V) available in raw materials;

- minimization of the amount of technological waste;

- the absence in the process of hazardous substances such as arsenic chloride, arsine and other volatile non-metal hydrides, hydrazine;

- the minimum cost of the reagents used in the technology.

To fulfill these requirements, new technical solutions were found:

- the use of leaching instead of dissolving ANG;

- the use of a closed cycle "leaching - solution preparation - precipitation of arsenic (III) oxide - return of the filtrate" exclusively to obtain arsenic (III) oxide;

- the use of a module for processing solutions unsuitable for further use in the production of arsenic (III) oxide.

The problem is solved in a two-stage way:

1) Initially, grinding of raw materials to a granule size of not more than 3 mm is carried out. Prepared raw materials are supplied to the measuring device dispenser of bulk solids. A sample of raw material is fed from a measuring device to a tank apparatus with a mixing device, where arsenic salts are leached. For leaching, a water-hydrochloric acid system or a filtrate-hydrochloric acid-water system are used. The first system is used if there is currently no suitable filtrate. The mass of water or filtrate is taken in 1.4-1.6 times the mass of raw materials. Hydrochloric acid is added until the pH of the system reaches 9.5-10.5, which is required for the conversion of arsenic-containing salts in the feed to sodium dihydroarsenate and dihydroarsenite, which have the highest solubility among the sodium salts of arsenic and arsenic acids [6]. The required amount of hydrochloric acid depends on the total alkali content in the batch of raw materials and invariably within the same batch. Leaching is carried out for 1-2 hours by the propagation method, the capacitive apparatus must be equipped with a device for discharging the suspension. Next, the suspension, consisting of a solution of salts and a solid phase, including sodium chloride (the main component), contaminated with arsenic salts, insoluble organic compounds and bentonite, is fed to a coarse filter, where the precipitate is filtered and washed. The precipitate is washed on the filter with water to wash out the well-soluble salts of arsenic. The method and number of washes depends on the technological design of the filter; as a rule, two washes are sufficient, the total volume of which is equal to the volume of the filtrate. The washed precipitate of sodium chloride after purification by a known method (dissolution, filtering on a thin filter, sorption purification) meets the standards applicable to technical sodium chloride, and is suitable for preparing solutions for killing oil and gas wells and other purposes. Wash water is combined with the filtrate and fed to the filtering operation on a fine filter. A filter press or other filter with a large filter surface is well suited for this operation. In this operation, a fine precipitate of bentonite and insoluble organic substances is separated from the solution. This precipitate is sent for neutralization by heat treatment. The filtrate contains a mixture of dissolved salts: sodium chloride (close to saturated), sodium dihydroarsenite, sodium dihydroarsenate. Next, the solution is sent to the evaporation operation. Evaporation is carried out in an evaporation apparatus in order to obtain a concentrated solution of arsenic (III) salts (to an arsenic (III) content above 10 g / 100 g of water). The precipitate of sodium chloride formed during evaporation is separated on the filter, washed and combined with sodium chloride obtained earlier. The stage of evaporation of the filtrate can be skipped in the case when the content of arsenic (III) in the feed is very high. The evaporator must be equipped with a device for unloading the suspension. After separation of the precipitate of sodium chloride, arsenic (III) oxide is precipitated from the evaporated solution by adding hydrochloric acid to a pH of 6-7. The suspension containing arsenic oxide is filtered, the arsenic oxide is washed with a small amount of water, which is combined with the filtrate. The precipitate containing from 80 wt.% Or more of arsenic (III) oxide, as well as water and an admixture of sodium chloride, is dried on a filter and sent to obtain technical arsenic (III) oxide by freeze-drying using known technologies. The filtrate obtained after separation of arsenic (III) oxide is sent to the beginning of the process to leach arsenic salts from a new batch of raw materials. This filtrate is saturated in sodium chloride and arsenic (III) oxide, which ensures its constant composition with the exception of the content of arsenic salts (V), which are not removed in a significant amount from the solution during the above operations.

Summing up, the first stage of the technology involves the cyclic repetition of successive stages:

- leaching of arsenic salts from raw materials with the formation of a heterogeneous system;

- separation of the heterogeneous system into a solid phase and a working solution;

- concentration of the working solution and separation of the concentrated solution from the precipitate formed;

- deposition of arsenic oxide (III) by acidification of the working solution and separation of the precipitate of arsenic oxide (III) by filtration;

- return of the filtrate to the first stage of the process.

2) The second stage of the technology is applied if arsenic (V) compounds are present in the batch of raw materials. It consists in the fact that after repeating the cycle of operations of the first stage from 3 to 10 times, an operation is performed to remove arsenic (V) compounds from the working solution by restoring them to arsenic (III) compounds or to elemental arsenic.

, где $$\omega {}_{N{a}_{3}As{O}_4}$$

- массовая доля арсената натрия в партии АНГ, n - искомое число циклов.The first stage of the ANG processing technology meets the task of converting arsenic (III) salts contained in the feed to arsenic (III) oxide, however, arsenic (V) salts are also present in the feed, the concentration of which in the working solution increases with each subsequent cycle. This leads to the possibility of contamination of precipitates of sodium chloride by a significant amount of arsenic (V) salts, which can negatively affect the entire technology. For this reason, a periodic withdrawal of arsenic (V) compounds from the working cycle should be carried out. The frequency of the withdrawal of arsenic (V) compounds from the working cycle depends on the content of sodium arsenate in the feedstock, the optimal value is from 1 operation for every 3 cycles of the first stage of the process to 1 operation for every 10 cycles. The removal of arsenic (V) from the solution should be carried out with the content of As (V) in the solution at the level of 10 g / 100 g of water. The concentration of As (V) in the solution increases linearly with each new cycle (losses of As (V) compounds falling into the precipitate are insignificant at As (V) concentrations less than 10 g / 100 g of water); therefore, the number of cycles of the first stage, after which to draw As (V) out of solution, can be estimated by solving the empirical equation $$\omega {}_{N{a}_{3}As{O}_{\mathrm{four}}}\times n\approx 40$$

where $$\omega {}_{N{a}_{3}As{O}_{\mathrm{four}}}$$

- mass fraction of sodium arsenate in the batch of ANG, n is the desired number of cycles.

To remove arsenic (V) compounds from the working solution, recovery to arsenic (III) or recovery to elemental arsenic can be used. Since arsenic (V) reduction operations lead to contamination of the solution with the decomposition products of the reducing agent, it is impossible to use the resulting solution in the cycle of the first stage, instead, residual amounts of arsenic are removed from the solution and the solution is sent for disposal. To convert arsenic (V) compounds to arsenic (III), any of the known medium strength reducing agents, for example sodium sulfite, can be used. The reaction is carried out in a slightly acidic medium, after which the pH of the medium rises to 6-7, arsenic (III) oxide is separated, and the filtrate is sent for disposal.

Another variant of the second stage procedure is the removal of arsenic (V) from the solution using thiourea dioxide. In this case, a solution containing a significant amount of arsenic salts (V) is fed into a capacitive apparatus with a mixing device, heated to 60-80 ° C, made alkaline to pH 10-10.5 by adding the calculated amount of solid sodium hydroxide (about 4 g per 1 g of arsenic (V) in solution.Then thiourea dioxide is added portionwise to the solution in an amount corresponding to a stoichiometric ratio plus an excess of 20% (4.32 g of thiourea dioxide per 1 g of arsenic (V) in solution). elemental arsenic otfi It is washed, dried in an inert atmosphere and sent to a freeze-drying operation or to an oxidative firing to produce arsenic (III) oxide using known technologies.In this case, the process of removing arsenic (V) compounds from circulation leads to contamination of the resulting solution with impurities of sodium sulfite and urea, therefore, after carrying out such operations and separating the precipitate of elemental arsenic, the filtrate should be sent for disposal. For disposal, the filtrate is evaporated and a dry salt mixture containing sodium chloride, sodium sulfite and urea, as well as arsenic compounds at the level of 40 mg / kg of waste, is sent for disposal at the waste landfill. The amount of waste generated can be estimated by the following examples:

Example 1

The content of As (V) in the feedstock is 14.5 wt.%, The content of bentonite and insoluble organic substances is 4 wt.%, A single charge of feedstock is 5 kg. 3rd cycle of the first stage with the subsequent withdrawal of arsenic (V) compounds using thiourea dioxide:

entrance Exit 1. Leaching of raw materials, 3rd cycle 1.1 Raw materials - ANG, 5 kg 1.4 Suspension - 15.045 kg Na ₃ AsO ₄ 0.725 kg NaH ₂ AsO ₄ 1,681 kg Na ₃ AsO ₃ 0.75 kg NaH ₂ AsO ₃ 0.817 kg bentonite 0.05 kg bentonite 0.05 kg Insoluble Polymers (HBB) 0.15 kg HBB 0.15 kg NaOH 0.325 kg NaCl 5.15 kg NaCl 3 kg H ₂ O 7.197 kg 1.2 The filtrate after 2 cycles processing raw materials into arsenic oxide - 8 kg H ₂ O 5.58 kg As ₂ O ₃ 0.16 kg H ₃ AsO ₄ 0.96Kr NaCl 1.3 kg 1.3 Hydrochloric acid 35% - 2.045 kg H ₂ O 1.515 kg HCl 0.53 kg Total: 15.045 kg Total: 15.045 kg entrance Exit 2. Filtering the suspension, washing the precipitate 1.4 Suspension - 15.045 kg 2.1 Sediment: NaH ₂ AsО ₄ 1,681 kg NaH ₂ AsO ₄ 0.017Kr NaH ₂ AsO ₃ 0.817 kg NaH ₂ AsO ₃ 0.008 kg bentonite - 0.05 kg bentonite 0.025 kg HBB 0.15 kg HBB 0.075 kg NaCl 5.15Kr NaCl 2.170 kg H ₂ O 7.197 kg H ₂ O 0.542 kg 1.5 Flushing water - 6.64 kg 2.2 Filtrate NaH ₂ AsO ₄ 1,664 kg NaH ₂ AsO ₃ 0.808 kg bentonite 0.025 kg HBB 0.075 kg NaCl 2.98 kg H ₂ O 13.294 kg Total: 21.685 kg Total: 21.685 kg entrance Exit 3. HBV filtering 2.2 Filtrate 3.1 Sediment NaH ₂ AsO ₄ 1,664 kg HBB 0.075 kg NaH ₂ AsO ₃ 0.808 kg bentonite 0.025 kg bentonite 0.025 kg HBB 0.075 kg 3.2 Filtrate NaCl 2.98 kg NaH ₂ AsO ₄ 1,664 kg H ₂ O 13.294 kg NaH ₂ AsO ₃ 0.808 kg NaCl 2.98 kg H ₂ O 13.294 kg Total: 18.846 kg Total: 18.846 kg entrance Exit 4. Evaporation 3.2 Filtrate 4.1 Steam NaH ₂ AsO ₄ 1,664 kg H ₂ O 9.2 kg NaH ₂ AsO ₃ 0.808 kg NaCl 2.98 kg 4.2 Suspension H ₂ O 13.294 kg NaH ₂ AsO ₄ 1,664 kg NaH ₂ AsO ₃ 0.808 kg NaCl 2.98 kg H ₂ O 4.095 kg Total: 18.746 kg Total: 18.746 kg entrance Exit 5. Filtration, washing 0.489 kg H20 4.2 Suspension 5.2 Filtrate NaH ₂ AsO ₄ 1,664 kg NaH ₂ AsO ₄ 1,648 kg NaH ₂ AsO ₃ 0.808 kg NaH ₂ AsO ₃ 0.80 kg NaCl 2.98 kg NaCl 1,024 kg H ₂ O 4.095 kg H ₂ O 4.095 kg

5.1 Wash water 5.3 Precipitation H ₂ O 0.489 kg NaCl 1,956 kg NaH ₂ AsO ₄ 0.016Kr NaH ₂ AsO ₃ 0.008 kg H ₂ O 0.489 kg Total: 10.036 kg Total: 10.036 kg entrance Exit 6. Precipitation of As ₂ O ₃ 6.1 Hydrochloric acid, 35% 6.2 Suspension HCl 0.564 kg H ₃ AsO ₄ 1,427 kg H ₂ O 1,614 kg As ₂ O ₃ 0.535 kg H ₂ O 5.855 kg 5.2 Filtrate NaCl 1,928 kg NaH ₂ AsO ₄ 1,648 kg NaH ₂ AsO ₃ 0.80 kg NaCl 1,024 kg H ₂ O 4.095 kg Total: 9.745 kg Total: 9.745 kg entrance Exit 7. Filtration, washing of arsenic (III) oxide 6.2 Suspension 7.2 Sediment H ₃ AsO ₄ 1,427 kg H ₃ AsO ₄ 0.014 kg As ₂ O ₃ 0.535 kg As ₂ O ₃ 0.418 kg H ₂ O 5.855 kg H ₂ O 0.04 kg NaCl 1,928 kg NaCl 0.042 kg 7.1 Water - 1.0 kg 7.3 Leachate H ₃ AsO ₄ 1.412 kg As ₂ O ₃ 0.117 kg H ₂ O 6.816 kg NaCl 1,886 kg Total: 10.745 kg Total: 10.745 kg entrance Exit 8. DTM filtrate treatment 8.1 Dry NaOH-2.15 kg 8.3 Suspension As 0.834 kg 8.2 Dry DTM-2.878 kg Na ₂ SO ₃ 3,354 kg (NH ₂ ) ₂ CO 1,597 kg 7.3 Leachate NaCl 1,886 kg H ₃ AsO ₄ 1.412 kg H ₂ O 7.588 kg As ₂ O ₃ 0.117 kg H ₂ O 6.816 kg

NaCl 1,886 kg Total: 15,259 kg Total: 15,259 kg entrance Exit 9. Filtering and rinsing As 8.3 Suspension 9.2 Filtrate As 0.834 kg As 0.833 kg Na ₂ SO ₃ 3,354 kg H ₂ O 1.0 kg (NH ₂ ) ₂ CO 1,597 kg NaCl 1,886 kg 9.3 Sediment H ₂ O 7.588 kg Na ₂ SO ₃ 3,354 kg (NH ₂ ) ₂ CO 1,597 kg 9.1 Wash water - 1.0 kg NaCl 1,886 kg H ₂ O 7.588 kg Total: 16,259 kg Total: 16,259 kg entrance Exit 10. Evaporation of the filtrate 9.2 Filtrate 10.1 Draft - 6.837 kg Na ₂ SO ₃ 3,354 kg Na ₂ SO ₃ 3,354 kg (NH ₂ ) ₂ CO 1,597 kg (NH ₂ ) ₂ CO 1,597 kg NaCl 1,886 kg NaCl 1,886 kg H ₂ O 7.588 kg 10.2 Water - 7.588 kg Total: 14.425 kg Total: 14.425 kg

The total amount of waste is 15 * 4% + 6.837 = 7.437 kg per 15 kg of processed raw materials, which is 49.6% of the mass of raw materials.

Example 2

For raw materials with a lower content of As (V), reduction with the reducing agent is required less often, the suspension of paragraph 1.4 corresponds to the 10th cycle of the first stage of processing of raw materials with an As (V) content of 4.3 wt.%. In this case, if the total content of bentonite and HBB is 4 wt.% And DTM is used as a reducing agent, then the total amount of waste per 50 kg of processed raw materials will be 50 * 4% + 6.837 = 8.837 kg, which is 17.7% of mass of raw materials.

The examples show that this method of two-stage processing of raw materials is suitable for processing arsenic compounds (III) and (V) contained in ANG into commercial products and can significantly reduce waste generation - from 180% for a reducing agent according to RU technology 2409687 to 17.7% - 49.6% and reduce the consumption of reducing agent by 5 or more times depending on the composition of the feedstock. It is also seen that at the first stage of the process, hydrochloric acid is used exclusively as a reagent, which ensures low processing costs.

Literature

[1] Report on the implementation of an integral part of work for state needs on the topic “Scientific and technical support of operational work at a chemical weapons destruction facility in the village of Gorny, Saratov Region”, name of the component “Operation of production, auxiliary buildings and structures, and provision of work, associated with the processing of reaction masses and industrial wastes resulting from the destruction of chemical weapons at the facility ”, Saratov, 2009

[2] URL: http://www.opcw.org/en/konvencija-o-khimicheskom-oruzhii/prilozhenie-po-khimikatam/v-spiski-khimikatov/ dated 12/05/2012

[3] Alexandrov V.N., Emelyanov V.I. Poisoning substances / ed. G.A. Sokolsky. - 2nd ed. - M .: Military Publishing House, 1990 .-- 272 p.

[4] Budanov VV, Makarov SV. Chemistry of sulfur-containing reducing agents: (Rongalit, dithionite, thiourea dioxide). M.: Chemistry 1994 .-- 139 p.

[5] Marketing research of markets for the consumption of arsenic-containing commercial products. Final report on research. Code "Products - M". GNIIHITEOS.M., 2005.

[6] Kaminsky Yu.D., Kopylov N.I. Arsenic. Novosibirsk: Siberian University Publishing House, 2004, 368 p.

Claims (2)

1. A method of processing technical hydrolytic sodium arsenite into commercial products, including the cyclic repetition of successive stages:
- leaching of arsenic salts from raw materials using a solution of hydrochloric acid, added to a pH of 9.5-10.5, with the formation of a heterogeneous system;
- separation of the heterogeneous system into a solid phase and a working solution;
- concentration of the working solution by evaporation to an arsenic (III) content above 10 g / 100 g of water and separation of the concentrated working solution from the precipitate formed;
- deposition of arsenic oxide (III) by acidification of the working solution and separation of the precipitate of arsenic oxide (III) by filtration;
- return of the filtrate to the first stage of the process. 2. The method according to claim 1, characterized in that after repeating the cycle of these operations from 3 to 10 times, an operation is performed to remove arsenic (V) compounds from the working solution by restoring them to arsenic (III) compounds or to elemental arsenic.