Method for conversion of reaction masses produced in alkaline hydrolysis of lewisite into technical products

FIELD: chemistry.

SUBSTANCE: invention relates to the field of chemical weapons destruction, namely to methods for conversion of reaction masses (RM) produced in process of lewisite destruction by method of alkaline hydrolysis, and also products produced from RM in evaporation - "hydrolytic sodium arsenite" (HAS), or in electrolysis of RM - spent catholyte. Method includes filtering of initial product from water-insoluble substances, concentration of filtrate by evaporation to produce solution of sodium arsenite in concentration of 25.0-30.0 wt %, separation of sodium chloride deposit by means of filtration, neutralisation of sodium arsenite solution to produce arsenic oxide and its treatment by method of repulping, dissolution of sodium chloride deposit in water and treatment of produced solution from arsenic compounds, at the same time sodium chloride solution is cleaned from arsenic compounds by means of their recovery into element arsenic, recovery agent is represented by thiourea dioxide, or sodium or zinc dithionite, or their mixtures, which is taken in the ratio of 2.1-2.5 per 1 relative to total arsenic, and process of recovery is carried out in the range of temperatures from 20 to 100°C, produced element arsenic is cleaned by method of repulping. In process of arsenic oxide production, arsenic compounds (V) are recovered in arsenic compounds (III) at pH of medium equal to 3-4 with a recovery agent taken in the ratio of 1.5-2.5 per 1 relative to arsenic (V), at the same time recovery agent is represented by sulphite, or bisulphite, or sodium pyrosulphite, or rongaite or their mixtures. Process of arsenic oxide and element arsenic repulping is carried out with diluted solutions of mineral acids and water in ultrasonic field. On completion of element arsenic repulping process solution is filtered, deposit of element arsenic is washed on the filter with ethyl alcohol, then pressed in die with pressure of at least 70 kN and finally dried in vacuum at the temperature from 20 to 200°C. Solutions are filtered through a layer of microcellulose and carbon-fibre fabric of 0.5-3.0 cm, which makes it possible to separate water-insoluble substances, dying admixtures and metal admixtures.

EFFECT: invention makes it possible to increase efficiency and to simplify process, to expand assortment and to improve quality of produced technical products, to improve ecological safety of the process.

5 cl, 7 ex, 1 dwg

The invention relates to the field of chemical weapons destruction, and in particular to methods of processing reaction mass (RM), formed during the destruction of lewisite by the method of alkaline hydrolysis, as well as products derived from the Republic of Moldova in the process of evaporation - "sodium arsenite hydrolysis" (ANG) or during electrolysis RM-Catolica waste [1, 2].

The resulting RM that meets the technical requirements of THE 2112-123-04872702-2002, contains the main standardized components: sodium arsenite, sodium chloride, sodium hydroxide, mechanical water-insoluble impurities, water, as impurities are present arsenate sodium carbonate and sodium silicate, heavy metals (iron, copper), painted polimerobetonie organic compounds and other components.

There is a method of processing RM in the arsenate sodium [3] by its processing when heated in an aqueous solution of hydrogen peroxide, followed by evaporation to the content of the arsenate ion in the reaction mixture of 120 g/kg, cooling solution at pH>13 prior to crystallization of sodium arsenate and Department last filtering.

Na₃AsO₃+H₂O₂→Na₃AsO₄+H₂About

The advantages of this method include the simplicity of the hardware design process, the cheapness and availability of reagents used, the ability to obtain a commercial product - Arsen is the sodium. However, this method has significant drawbacks: explosion hazard when working with hydrogen peroxide when heated, receiving arsenic-bearing waste water after phase filtering, limiting the use of arsenate of sodium in the national economy, the lack of technical solutions for the removal of contaminated sodium chloride and other impurities.

A variation of the method of processing the RM associated with obtaining arsenate is a technical solution [4].

The proposed method of processing the Republic of Moldova lies in the allocation of metallic arsenic by oxidation of arsenite sodium arsenate sodium peroxide when heated with subsequent precipitation with calcium chloride in the form of hard soluble calcium arsenate. The obtained calcium arsenate may or stored, or to be further processed in metallic arsenic by heating with phosphorous acid in the environment of excess phosphoric acid.

In the first stage contained in aqueous solution sodium arsenite oxidized to arsenate 30% hydrogen peroxide at a temperature of 60°With:

Na₃AsO₃+H₂O₂→Na₃AsO₄+H₂About

In the second stage arsenate precipitated in the form of arsenate calcium by adding 1.5 to 2 molar excess of calcium chloride at a temperature of 100°C, arsenate calcium filter:

2Na₃AsO₄+3CaClsub> 2→CA₃(AsO₄)₂↓+6NaCl

In the third stage, carry out the restoration of arsenate of calcium taken in the form of sediment to elemental arsenic, phosphorous acid, taken in the amount of 150% of the arsenate of calcium, in the environment of phosphoric acid taken in the quantity of 400% of arsenate of calcium, at a temperature of 80-150°C.

CA₃(AsO₄)₂↓+5H₃RHO₃+5H₃PO₄→2As↓+s(H₂PO₄)₂+3H₂About

The disadvantages of this method are the possibility of formation of highly toxic and explosive compounds arsina cars and phosphine at the stage of obtaining arsenic; the difficulty of controlling the temperature in a given interval at the stage of oxidation of arsenite sodium peroxide (exothermic reaction) and the possibility of decomposition of the latter; the formation of waste - calcium phosphate contaminated with arsenic, large quantities of toxic waste arsenic mixture of acids of phosphorus, waste salts of calcium phosphate and sodium chloride contaminated with arsenic and acids, and acidic wastewater generated during the filtration and washing of the intermediate and target products.

Also known is a method of processing RM in the arsenic sulfide by the action of hydrochloric acid and sodium sulfide at pH 1-4 environment temperature 15÷50°C and mixing time 10-60 min [5].

2Na₃AsO₃+NS+3Na ₂S→As₂S₃↓+12NaCl+6H₂O

The precipitate of sulphide of arsenic is sent to storage. The disadvantage of this method is the product of sulphide of arsenic, which is not used in the direct purpose in the economy and must subsequently additional chemical processes to be transferred to other industrially useful compounds, such as arsenic oxide (III), as well as the formation of sulfide acidic waste cleanup.

Currently, as an industrial method for processing RM selected electrochemical process of obtaining elemental arsenic [2].

The authors state that the proposed method is electrolysis has several disadvantages: energy intensity, the complexity of the technical design of the electrolysis process because of the formation of highly toxic and explosive compounds (arsina cars, chlorine, hydrogen, and oxygen), low productivity, which allows to apply the method for processing the RM, resulting from the destruction of a relatively small number of lewisite.

The most widely used arsenic-bearing product in the economy is the oxide of arsenic (III), the annual demand in which the domestic and international markets is high and is growing every year.

In terms of implementation of this approach has been developed a method of processing RM [6], to the activities aimed at obtaining technical oxide of arsenic (III).

In this way the RM is separated from solids by filtration, subjected to the process of evaporation to about 40% excess water, and then with stirring, treated with hydrochloric acid to provide a pH at pH 7, to convert arsenite sodium oxide of arsenic (III) by the reaction:

2Na₃AsO₃+6l→As₂O₃↓+6NaCl+3H₂O

To the resulting neutral in acidity of the solution was added 60% solution of sulfuric acid until pH = 1÷5. This process of acidification is not only to create an acidic environment, but also to prevent the formation of soluble chloride arsenic. The precipitate is kept in the reactor for one hour at ambient temperature, filtered and dried.

To the filtrate after separating and washing the precipitate add alkaline to pH 10, and is subjected to the process of evaporation to remove most of the water (90%), which leads to crystallization of sodium chloride. Salt is separated on a filter and after washing it with cold 5% solution model HC1 sent for drying and storage. The residual portion of the filtrate, containing some amount of arsenic oxide (III) (due to its own solubility), is directed into the container, which is preparing a 60% solution of sulfuric acid, which is used in the next cycle of deposition of oxide of arsenic.

However, the method was developed for the model systems, and it did not take into account the presence of real objects arsenic (V)carbonate and sodium silicate, as well as admixtures of organic compounds.

The closest in technical essence and the achieved effect (prototype) is a method of processing ANG, which was aimed at obtaining technical products - oxide of arsenic and sodium chloride [7].

In this way ANG dissolved in an aqueous solution of hydrochloric acid to generate the pH of the system, equal to 8.0-9.0 units. After the establishment of equilibrium (~1÷1.5 hours of mixing) is produced by the filtering system to obtain a first filtrate and sludge "water-insoluble substances and sodium chloride.

The precipitate "water-insoluble substances and sodium chloride successively washed with three portions of 20% sodium chloride solution, the first of which connects with the first filtrate and the other two are sent at the beginning of the process for dissolution ANG, forming the principles of the closed-loop toxic reagents. Receive the second combined filtrate and basic first precipitate of sodium chloride.

The second combined filtrate is treated with 20% solution of lithium chloride, translating compounds of arsenic (V) in soluble form lithium arsenate. The separated precipitate of lithium arsenate dissolved in strong hydrochloric acid, and the resulting arsenic acid is recovered in trichloride arsenic combined composition of the reducing agent - sodium iodide and hydrochloric acid with hydrazine.

The filtrate after separation of arsenate lithium (Li₃AsO₄) is directed to the operation of evaporation from the receiving system, containing a solution of sodium arsenite at a concentration of 25.0% to 30.0 wt.% and the second precipitate of sodium chloride. The second precipitate of sodium chloride is connected with the main first precipitate of sodium chloride, obtained by dissolving ANG in hydrochloric acid solution, and the filtrate is directed to the operation of neutralization of sodium arsenite solution trichloride arsenic and hydrochloric acid according to the reaction:

Na₃AsO₃+AsCl₃→As₂O₃↓+3NaCl

2Na₃AsO₃+6HCl→As₂O₃↓+6NaCl+3H₂O

The precipitate of oxide of arsenic is separated from the remaining filtrate, which is sent at the beginning of the process for dissolution ANG, washed with cold water and goes to clear occluded sodium chloride method Raul is Pyromania. The described approach allowed to obtain commercial products of the brand's technical and refined grade 2.

The combined first and second precipitation of sodium chloride is washed from the adsorbed arsenic compounds and dissolved in water to obtain a 20% solution of sodium chloride. This solution was sequentially subjected to a process of purification from arsenic compounds chemical and adsorption methods.

The essence of the chemical method is the oxidation present in the solution of the arsenite ion in arsenate action of sodium hypochlorite, with further deposition of poorly soluble arsenate of iron:

Na₃AsO₃+NaOCl→Na₃AsO₄+NaCl

Na₃AsO₄+FeCl₃→FeAsO₄↓+3NaCl

The filtrate after separation of arsenate of iron (FeAsO₄)is supplied to the adsorption treatment using sorbent brand GZH-35 and then by the process of vacuum evaporation and drying of the resulting suspension. Get technical sodium chloride contains up to 96 wt.% the basic substance and is used for receiving drilling mud and in the chlor-alkali industry.

Described is a method of processing ANG has the following advantages: the simplicity of the technological design process, implemented on the basis of standard chemical equipment; mild conditions of the process; satisfactory environmental pok what indicators during the implementation of the principle of closed-loop toxic reagents, the use of available and cheap chemicals.

However, this method does not completely eliminate recovering the lithium arsenate, volatile and toxic trichloride arsenic released during the oxidation of hydrazine, nitrogen gas may contribute to increased gas removal of arsenic trichloride in the area and the atmosphere. In addition, the water system shall be made additional impurities lithium salts and iodine. Iodine ions in the presence of oxygen and in the presence of an alkaline environment in the subsequent stages of the process can lead to the oxidation of part of trivalent arsenic back into pentavalent, which reduces the efficiency of the recovery phase.

The objective of the invention is to increase the efficiency of the method, the simplification of the process, expanding the range and improving the quality of technical products, the improvement of environmental safety of the process by finding technical solutions for physico-chemical removal of coloring impurities, permanent restoration of pentavalent arsenic, eliminating the possibility of formation and removal from the system volatile and toxic arsenic trichloride, additional cleaning solution of sodium chloride of arsenic compounds by extraction in the form of elemental arsenic, which will lead to the reduced toxic emissions, discharges and waste.

The problem is solved as follows. In the method of processing the reaction mass formed by alkaline hydrolysis of lewisite, including the recovery of arsenic (V) arsenic compounds (III), subsequent evaporation of the filtrate, separating from one stripped off the filtrate, the precipitate of sodium chloride and water-insoluble substances by filtration, sedimentation from the obtained filtrate oxide of arsenic and its clearance to the required degree of purity by reformirovania, dissolve the precipitate of sodium chloride in water and cleaning the solution obtained from compounds of arsenic, according to the solution are two of the recovery process, the first process restore compounds of arsenic (V) into compounds of arsenic (III) at pH equal to 3-4, a reducing agent, taken in the ratio of 1.5÷2.5 to 1 with respect to arsenic (V), in use as a reducing agent sulfite, or bisulfite, or sodium pyrosulfite, or rongalit, or mixtures thereof, in the second process restores the connection of arsenic (III) and (V) in elemental arsenic, thereby purifying the sodium chloride solution from arsenic compounds, and as a reductant use of thiourea dioxide (DTM), or dithionite sodium or zinc, or mixtures thereof, taken in the ratio of 2.1÷2.5 to 1 respect to the total arsenic, and the recovery process are in the range of the tempo of the atur from 20 to 100°C. with continuous mixing and dosing of the reagent within 3.0÷5.0 hours for filtration of a solution of sodium arsenite using 0.5÷3.0 cm layer microcellulose and carbon fiber fabric for separation of water-insoluble substances, coloring admixtures, admixtures of metals obtained in the implementation processes of the oxide of arsenic, elemental arsenic purified by the method of reformirovania, which consists in washing the precipitate in aqueous dilute solutions of mineral acids and water, held in the ultrasonic field, after reformirovania precipitates is separated by filtration, the precipitate of elemental arsenic additionally washed on the filter with ethyl alcohol, and then pressed into the mold with a pressure of not less than 70 kN and finally dried in vacuum at a temperature of from 20 up to 200°C.

A solution of sodium chloride containing residual amounts of arsenic compounds, is sent on sorption purification, then vacuum residue and drying the resulting product.

As a separate stage of the process allows to obtain different products and in a sense complementary, if necessary, in the implementation of technology to focus on one of the products, for example, to obtain elemental arsenic to leave only the second recovery process, and to obtain the oxide of arsenic is the first process of recovery. In addition, because the second process is CE recovery of the used reagents allow you to recover as compounds of arsenic (III), and compounds of arsenic (V)in the case of low content of arsenic (V) in the Republic of Moldova the first recovery process can be excluded.

The proposed method involves the use as a reductant reagent from the category of the most cheap, allowing recovery in one stage, which increases the economic efficiency of the process. Cleaning solutions of sodium chloride of arsenic with obtaining elemental arsenic expands the range of derived technical products. Exclusion from lithium chloride, sodium iodide, hydrazine improves process reliability by eliminating the possibility of oxidation of part of the arsenic (III) arsenic compounds (V), which leads to increased technical and environmental performance of the process by reducing contaminants in the final product, a more complete selection of arsenic in the form of technical products and the absence of gaseous and volatile arsenic substances and as a consequence reducing the amount of harmful emissions, discharges, waste during the process.

The proposed solution is illustrated by the drawing, which shows a diagram of the basic process of obtaining a trademark of oxide of arsenic, elemental arsenic and sodium chloride showing the main blocks, material flows, turnover of water in the production cycle.

redlagaemyi method for processing RM, formed by alkaline hydrolysis of lewisite, is illustrated by the following examples.

Example 1. 12 kg RM was filtered through a 1.5 cm layer of microcellulose and carbon fiber fabrics for the Department "water-insoluble substances, coloring substances. The filtrate was subjected to evaporation process about 3 times to obtain a solution containing sodium arsenite at concentrations of 29 wt.%. The precipitation of sodium chloride with arsenic was filtered, the weight of the wet sludge (25% moisture) was 0.52 kg of a Solution of sodium arsenite after separation of sodium chloride was neutralized 1.9 kg of hydrochloric acid and gained 0.38 kg technical oxide, white arsenic containing 95.7% of the basic substance.

The filtrate after separation of the oxide of arsenic is fed to further purification from arsenic and processing in sodium chloride. To 3.5 kg of the filtrate, containing arsenic at a concentration of 6.3 wt.%, added with stirring for 4 hours and a temperature of 60-65°C, 504 d DTM.

The precipitation of elemental arsenic washed 1 time in 300 ml of 0.5%NaOH solution, 2-4 times in 300 ml of water until a negative iodine reaction, Reformirovanie conducted in water in the ULTRASONIC bath at 40°C, the precipitate was filtered, washed on the filter with 80 ml of ethyl alcohol. The residual amount of the liquid from the precipitate arsenic was removed by pressing in the mold with a pressure of at least the e CN. Final drying of elemental arsenic was carried out in vacuum at a temperature of 150°C. the Obtained elemental arsenic by weight 199 g, was identified by x-ray fluorescence method on line_βwith wavelength 1057 Å. According to chemical analysis, it contained 97.8 wt.% the basic substance.

The purified solution of sodium chloride, separated from the elemental arsenic and containing residual amounts of dissolved arsenic, were directed to the operation of the adsorption treatment with the subsequent reception of sodium chloride, as described in the prototype.

Example 2. To 5 kg ANG added 5 kg of water and 3.2 kg of a solution of 35% hydrochloric acid. In the resulting solution was added 0.32 kg of sodium sulfite, the solution was stirred for 0.5 hour, added 0.6 kg of a solution of 35% hydrochloric acid to pH 3-4, the solution was stirred for 1 hour, added 3.3 kg of a solution of 50% caustic soda to a pH of 8.5-9, the solution was stirred for 1 hour and then sent to the operation of the precipitate, consisting of "water-insoluble substances, coloring admixtures of sodium chloride from the filtrate by filtration of the solution through a 1.5 cm layer of microcellulose and carbon fiber fabric. The total weight of the wet sludge (25% moisture) was 4.1 kg

16 kg of the filtrate, containing Na₂HAsO₃, NaCl and NaOH, were subjected to the evaporation process of obtaining a solution, the content is the future arsenite sodium at a concentration of 27.5 wt.%. A solution of sodium arsenite after separation of sodium chloride was neutralized 2.65 kg of hydrochloric acid, the precipitate was repulpable in water using ULTRASONIC baths, received 1.12 kg technical oxide, white arsenic containing 96.2% of the basic substance.

The filtrate is sent for further purification from arsenic and processing in sodium chloride. To 4.1 kg of sediment was added 10 kg of water to leaching of sodium chloride and the formation of a 20% solution of sodium chloride. Undissolved precipitate a mass of 1.6 kg in the form of paste separated from the filter and sent for recycling.

To 16 kg of 20% solution of NaCl was added 87 g of DTM with stirring for 4 hours and a temperature of 60-65°C.

The precipitation of elemental arsenic washed 1 time in 60 ml of 0.5% NaOH solution 2-4 times with 70 ml of water until a negative iodine reaction, Reformirovanie conducted in water in the ULTRASONIC bath at 40°C, the precipitate was filtered, washed on the filter with ethyl alcohol. The residual amount of the liquid from the precipitate of arsenic removed by pressing in the mold with a pressure of not less than 70 kN. Final drying of elemental arsenic was carried out in vacuum at a temperature of 150°C. the Obtained elemental arsenic mass of 36 g was identified by x-ray fluorescence method on line_βwith wavelength 1057 Å. According to chemical analysis, it contained 98.3 wt.% the basic substance.

About ewenny solution of sodium chloride, separated from the elemental arsenic and containing residual amounts of dissolved arsenic, directed at the operation of the adsorption treatment with the subsequent reception of sodium chloride, as described in the prototype.

Example 3. Analogously to example 2 for the recovery of arsenic (V) arsenic compounds (III) used at 0.26 kg of sodium bisulfite, and for the extraction of arsenic in the form of elemental arsenic is introduced into the reaction 92 g dithionite sodium and received, respectively, 1.1 kg technical arsenic oxide with a content of 96.5% of the basic substance and the elemental arsenic mass of 34.5 g with the content of 98.3 wt.% the basic substance. In the case of economic necessity dithionite sodium can be replaced by cheaper technological predecessor, from which he obtained the industry dithionite zinc.

Example 4. Analogously to example 2 for the recovery of arsenic (V) arsenic compounds (III) used 0.17 kg rongalite and received respectively 1.04 kg technical arsenic oxide with a content of 95.2% of the basic substance and the elemental arsenic mass of 35 g with a content of 96 wt.% the basic substance.

Example 5. Analogously to example 2 for the recovery of arsenic (V) arsenic compounds (III) used 0.24 kg of sodium pyrosulfite and received respectively 1.0 kg technical oxide arsenic content 95.9% cos the main substances and elemental arsenic by weight of 34 g content for 96.1 wt.% the basic substance.

Examples 2-5 show that different reagents allow at least equal to the recovery process as compounds of arsenic (V) arsenic compounds (III)and removing arsenic compounds from a solution of sodium chloride in the form of elemental arsenic with approximately the same characteristics, and the expansion of reagents increases the reliability of the technology and gives an opportunity to optimize economic and cost parameters.

Example 6. 12 kg RM was filtered through a 1.5 cm layer of microcellulose and carbon fiber fabrics for the Department "water-insoluble substances, coloring substances. To the filtrate, containing arsenic at a concentration of 4 wt.%, added under stirring during 2 hours and a temperature of 60-65°C 1.2 kg DTM.

The precipitation of elemental arsenic washed 1 time in 300 ml of 0.5% NaOH solution 2-4 times with 500 ml of water until a negative iodine reaction, Reformirovanie conducted in water in the ULTRASONIC bath at 40°C, the precipitate was filtered, washed on the filter with 150 ml of ethyl alcohol. The residual amount of the liquid from the precipitate arsenic was removed by pressing in the mold with a pressure of not less than 70 kN. Final drying of elemental arsenic was carried out in vacuum at a temperature of 150°C. the Obtained elemental arsenic mass 384 g was identified by x-ray fluorescence method on line is To _βwith wavelength 1057 Å. According to chemical analysis, it contained 97.1 wt.% the basic substance.

Example 7. Analogously to example 6 from 1 kg of Catolica waste containing arsenic at a concentration of 1 wt.%, and 25 g DTM received elemental arsenic mass of 8 g content to 96.8 wt.% the basic substance.

Examples 1, 6, 7 show that the proposed method has high variability and allows you to use technological methods to improve the competitiveness of the technology. Thus, the implemented process allowed us to obtain three commercial products:

the oxide of arsenic, elemental arsenic and sodium chloride brand technical.

Literature

1. Lewis W.L., Stiegler H.W. Amer. Chem. Soc., 1925, v.47, p.2550.

2. Petrunin, VA and other Mathematical modeling of the process of alkaline hydrolysis of lewisite.// Russian chemical journal, 1995, No. 4, p.15-16.

3. Patent RU 2172196, IPC 62D 3/00.

4. Patent PL357396, 2002 (Polish patent).

5. Patent RU 2099116, IPC A62D 3/00.

6. Patent RU 2192297, IPC A62D 3/00.

7. Demagin A.G., Oleskevich CENTURIES, Cinnagen O.A., Shevchenko A.V., Nikiforov G. Technological aspects of processing reaction mass obtained in detoxification of lewisite in arsenic-bearing marketable products. // Russian chemical journal, 2007, No. 2, p.29-31.

1. A method of processing reaction mass formed by alkaline hydrolysis of lewisite in the is clinical products, includes the filtering of the raw product from the water-insoluble substance, concentrating the filtrate by evaporation to obtain a solution of sodium arsenite at a concentration of 25.0-30.0 wt.%, the sludge separation of the sodium chloride by filtration, neutralization of a solution of sodium arsenite with obtaining the oxide of arsenic and its cleaning method reformirovania, dissolving the precipitate of sodium chloride in water and the purification of the obtained solution from arsenic compounds, characterized in that the cleaning solution of sodium chloride of arsenic compounds is carried out by their recovery of elemental arsenic, at the same time as reducing use of thiourea dioxide, or dithionite sodium or zinc, or mixtures thereof, the reducing agent taken in the ratio of 2.1 to 2.5 : 1 relative to the total arsenic, and the recovery process is carried out in the temperature range 20-100°C, obtained elemental arsenic cleanse method reformirovania.

2. The method according to claim 1, characterized in that upon receipt of the oxide of arsenic in the process of recovery of arsenic (V) into compounds of arsenic (III) at pH 3-4 reducing agent, taken in the ratio of 1.5-2.5 : 1 with respect to arsenic (V), while in use as a reducing agent sulfite, or bisulfite, or sodium pyrosulfite, or rongalit, or mixtures thereof.

3. The method according to claim 1, characterized in that the process repulbican the oxide of arsenic, elemental arsenic spend dilute solutions of mineral acids and water in an ultrasonic field.

4. The method according to claim 3, characterized in that after reformirovania elemental arsenic, the solution is filtered, the precipitate of elemental arsenic washed on the filter with ethyl alcohol, then pressed into the mold with a pressure of not less than 70 kN and finally dried in vacuum at a temperature of from 20 to 200°C.

5. The method according to claims 1 and/or 3, characterized in that the filtering solutions are carried out through the layer of microcellulose and carbon fiber fabrics 0.5 to 3.0 cm, allowing to separate the water-insoluble substances, coloring impurities and impurity metals.