RU2275260C2 - Method of neutralizing metallic surfaces, soils, and water solutions - Google Patents

Abstract

FIELD: environmental protection.

SUBSTANCE: method comprises oxidizing metallic surfaces contaminated by toxic agents by means of oxidizing reagents. The oxidizing reagents are made of solutions of nitrous acid and hydrogen peroxide with a concentration of 4-5% by mass.

EFFECT: enhanced safety and quality of cleaning.

6 tbl, 2 ex

Description

The invention relates to the field of chemical technology and can be used in the chemical, metallurgical and defense industries when cleaning soils and aqueous media from one of the components of rocket fuel (CMT) - asymmetric dimethylhydrazine (UDMH) and its transformation products.

UDMH, which is also called “heptyl” in technology, is used as a fuel component in rocket technology. UDMH is a highly toxic compound. So, the maximum permissible concentration for air in the working area is 0.1 ml / m ³ , for water in reservoirs - 0.02 ml / l (Kolla V.E., Berlinersky I.S. Pharmacology and chemistry of hydrazine derivatives, Yoshkar-Ola, 1976, 264 p.).

Storage, transportation of UDMH is carried out in hermetic containers made of steel and its alloys, in which an excess pressure of nitrogen or other gas is maintained.

One of the important problems that arise when using UDMH as a fuel is environmental pollution. The remains of UDMH in the separating parts of the launch vehicle (OCRN), when dropped to the surface, pose a threat to public health and pollute the environment. The Proton rocket is the most dangerous, the first and second stages of which in total contain more than 2 tons of highly toxic UDMH falling on the Earth’s surface, partially dissipating in the atmosphere when the spent steps fall. At present, there are no effective technologies for the purification of contaminated UDMH structures, soil, surface water, or OCRN surfaces. All existing technologies can be divided into three groups: thermal, methods of deep oxidation of UDMH to elementary components, methods of using aqueous solutions containing active substances that react with UDMH and in one case form insoluble or sparingly soluble complexes, and in the other, they promote decomposition to more simple compounds in their composition (Collection of methods. Environmental protection. L., Hydrosphere., 1985, 9 pp.). The OCHRN is thermally treated with an open flame using a free-burning hydrocarbon fuel torch, as well as with a special thermal chamber (Artamonov D.G., Pimkin V.G. Research report "Experimental development of soil neutralization technologies and fragments of products contaminated with toxic components.") . However, despite the rather effective removal of UDMH on the surface and in the cavities of the product, the combustion process does not occur completely. When burning a large amount of fuel, an upward “thermic” is formed, including UDMH fumes and products of their incomplete combustion. Subsequently, aerosols condense, which leads to secondary environmental pollution.

Another variety of methods involves the use of aqueous solutions containing active substances, in particular meta-nitrobenzoic acid, which, at certain pH-values, forms a complex compound with UDMH in the form of a solid phase. Solutions contaminated with UDMH, then according to the proposed method, are thermally neutralized in a special furnace (A.K. Buryak, Scientific and Technical Report on the component of the OKR "Update". Development and experimental development of methodological proposals for cleaning metal containers and building systems from combustible UDMH UZP ", stage 2, book 2, M. 2002. Institute of Physics and Chemistry RAS, 2002, 55 p.).

Closest to the proposed invention is a method of detoxification, based on the deep oxidation of UDMH to elemental components. So, to neutralize UDMH on the surface of the black hole, metal structures, walls of shelters, etc. calcium peroxide is used, the decomposition of which releases atomic oxygen, which is involved in the decomposition of UDMH. The total equations in this case have the form

To obtain one mole of oxygen, two moles of calcium peroxide are required. As follows from equations (3) - (5), 1 mole of UDMH is consumed according to stoichiometry of 4 moles of oxygen, and 1 mole of UDMA and DMA is consumed by about 3.38 moles with complete oxidation of toxicants, respectively. The content of UDMH, NDMA, DMA in soil samples after three days is reduced by 54.4, 55.6, 54.1%, i.e. approximately twice (Kruchinin N.A., et al. Russian Patent No. 2095105 of November 10, 1997). Using calcium peroxide, including alkali metal phosphates and soda ash, the soil was detoxified from aromatic compounds (Biomanagement Inc. US Pat. No. 6,268,205 A dated July 31, 2001).

The disadvantage of this method of neutralizing metal surfaces and detoxification of the soil is the low degree of purification of contaminated sites, a long detoxification process. The performance of the cleaning process is low due to the poor solubility of calcium peroxide in water (0.1 mg / l). All this leads to an increase in the cost of detoxification technology, an increase in the consumption of reagent - calcium peroxide, the installation of additional equipment, and an increase in water consumption.

The aim of the invention is the creation of an effective and technically simple method of neutralizing metal and other surfaces, solutions and media contaminated with toxic substances using a peroxide compound and an acid, characterized in that hydrogen peroxide is used as an inorganic peroxide compound and an aqueous solution of nitric acid is used. acid in amounts of 3 or more times the required stoichiometric ratio.

Detoxification of aqueous solutions and soils containing UDMH is carried out by deep oxidation with a mixture of solutions of nitric acid and hydrogen peroxide. Neutralization experiments involving oxidizing agents were carried out on various objects: soils and aqueous solutions resulting from the washing of contaminated metal surfaces. To achieve this goal, we used compounds that are part of rocket fuel - hydrogen peroxide and nitric acid. In a concentrated state, these components, mixed with UDMH, create reactive thrust in the stage of the launch vehicle of the spacecraft in a short period of time. Dilution with water of these components (UDMH and oxidizing agent) leads to a decrease in the rate of the oxidation reaction and contributes to an increase in the conversion of UDMH.

In the case of detoxification of the soil contaminated with UDMH, the contaminated areas are exposed to solutions of nitric acid and (or) hydrogen peroxide, then the soil is dug up for better contact. Detoxification products are ammonium salts and nitrates, which by their nature are mineral fertilizers, as well as nitrogen, carbon dioxide and water vapor. Thus, detoxification products contribute to improving the environmental situation in the areas of the fall of the separating stages of launch vehicles.

The results of detoxification according to the claimed method are illustrated by the following experimental data.

Example 1. Tillage

Table 1 shows the results of experiments to neutralize a piece of land contaminated with UDMH using nitric acid and a mixture of peroxide and nitric acid. As an object for testing at the Baikonur Cosmodrome, a site with an area of 10 × 10 m ² (site 91 ZNS KBTKHM) was selected. Reference points were marked on the plot, marked with pegs in the amount of 9 sample points and one control sample (10) taken outside the plot. The experiments were carried out with an east wind (speed = 10-12 m / s) and air temperature + 14 ° С. Before processing the plot, 10 samples were taken (series 1). After sampling, the site was treated with an aqueous UDMH solution (calculated as 10 ml per 10 l of water). Then, from the reference points, 9 soil samples were taken (series 2).

Next, the plot was dug up, treated with a solution of nitric acid with a concentration of 4.9 wt.% In an amount of 20 l. The level of soil contamination corresponded to the maximum permissible UDMH level for the soil, equal to 0.1 mg / kg.

Table 2 presents the results of the neutralization of soil contaminated with UDMH using hydrogen peroxide and / or nitric acid in the area contaminated with UDMH. The site was treated first with hydrogen peroxide, then with an aqueous solution of nitric acid. The soil was dug up and after one hour they were taken for UDMH analysis.

Below is a diagram of the site with the coordinates and sampling points (x - No. 1-10).

Table 1 The results of the neutralization of the soil contaminated with UDMH using nitric acid No. of selection point Defined indicators The amount of UDMH in the soil, mg / kg The amount of UDMH in the soil after treatment with nitric acid before processing one. UDMH 0.10 0,0 2. -≪- 0.12 0,0 3. -≪- 0.12 0,0 four. -≪- 0.14 0,0 5. -≪- 0.13 0,0 6. -≪- 0.10 0,0 7. -≪- 0.00 - 8. -≪- 0.04 0,0 9. -≪- 0,025 0,0 10. -≪- 0.00 - eleven. -≪ 0.14 ^X 0,0 12. -≪- 0.14 ^XX 0.1 Note: treatment UDMH and neutralization with nitric acid sampling area No. 10 was not performed
^X treatment was carried out with 6% nitric acid (example No. 11)
^XX treatment was carried out with 3.5% nitric acid (example No. 12)

table 2 The results of the neutralization of soil contaminated with UDMH using hydrogen peroxide and / or nitric acid No. sampling point The initial amount of UDMH in the soil, mg / kg The concentration of the reagent in the used aqueous solution,% wt. The flow rate of an aqueous solution, l / m ² The degree of conversion of UDMH,% wt. H ₂ O ₂ HNO ₃ one. 1,5 5 5 3/1 100.0 2. 1,5 10 10 3/1 100.0 3. 1,5 3 3 3/1 71.5 four. 0.5 5 5 3/1 100.0 5. 0.5 10 10 3/1 100.0 6. 0.5 3 3 3/1 83,4 7. 3.0 5 5 3/1 95.6 8. 3.0 10 10 3/1 100.0 9. 3.0 3 3 3/1 56.4 10. UDMH treatment and neutralization with hydrogen peroxide and nitric acid were not performed.

Plot scheme

As can be seen from tables 1 and 2, after neutralization with hydrogen peroxide and nitric acid, the content of UDMH in soil samples is significantly reduced or practically absent.

Example 2. The neutralization of aqueous solutions

Table 3 presents the results of the neutralization of aqueous solutions containing UDMH in the presence of additives of nitric acid and hydrogen peroxide for various periods of time. From table 3 it follows that when neutralizing aqueous solutions containing UDMH within 24 hours or more, its decomposition proceeds 100%.

Table 4 presents the results of the neutralization of aqueous solutions containing UDMH in the presence of additives of hydrogen peroxide and / or nitric acid. Nitric acid solutions were prepared from reactive 56% concentrated acid and 30% hydrogen peroxide solution. The solutions used contain 5.4.6 mass fractions of water per 5.4 mass fractions (based on 100% nitric acid). Similarly, 5 mass fractions of hydrogen peroxide (calculated as 100% hydrogen peroxide) account for 95 mass fractions of water.

Table 3 Neutralization of aqueous solutions containing UDMH in the presence of additives of nitric acid and hydrogen peroxide. No. p / p Detoxicant Concentration Solution number The exposure time, h The initial amount of UDMH, mg / l The amount of UDMH after treatment, mg / l The degree of conversion of UDMH% one. 5% HNO ₃ one one 0.10 0,0 100.0 2. 5.4% HNO ₃ one 72 0.16 0,0 100.0 3. 5.4% HNO ₃ one 72 12.98 7.6 41.50 four. 5.4% HNO ₃ one 192 12.84 0,0 100.0 5. 5.4% HNO ₃ 2 72 5.89 4,51 23.40 6. 5.0% H ₂ O ₂ one one 0.10 0.00 100.0 7. 5.0% H ₂ O ₂ 2 24 5.26 3,51 33,20 8. 5.0% H ₂ O ₂ 2 24 6.67 0.00 100.0 9. 5.0% H ₂ O ₂ 2 24 6.22 0.00 100.0 10. 5.0% H ₂ O ₂ 2 48 5.78 0.00 100.0 eleven. 5.0% H ₂ O ₂ 2 48 6.43 0.00 100.0 12. 5.0% H ₂ O ₂ one 96 15,64 11.01 100.0 13. 3.0% H ₂ O ₂ one one 4,50 4,50 0,0 fourteen. 6.0% H ₂ O ₂ one one 4,50 0,0 100.0

Solution No. 2 is stabilized with 0.01 M sulfuric acid

Table 4 Neutralization of aqueous solutions containing UDMH in the presence of additives of hydrogen peroxide and / or nitric acid Sampling Point No. The concentration of the reagent detoxifier in solution% wt. The exposure time, after mixing the two reagents, h The initial amount of UDMH, mg / l The amount of UDMH after treatment, mg / l The degree of conversion of UDMH,% Hydrogen peroxide Nitric acid one 5 5 1,0 5,0 0,0 100.0 5 5 1,0 25.0 0,0 100.0 5 5 1,0 50,0 0,0 100.0 2 3 3 1,0 5,0 4.25 25.0 1,0 25.0 20.11 19.6 1,0 50,0 42.70 14.6 3 10 10 1,0 5,0 0,0 100.0 1,0 25.0 0,0 100.0 1,0 50,0 0,0 100.0 four 5 - 1,0 25.0 12.5 50,0 - 5 1,0 25.0 19.1 23.6 5 3 - 1,0 25.0 20.1 19.6 - 3 1,0 25.0 22.4 10,4 6 10 - 1,0 25.0 18.7 25,2 - 10 1,0 25.0 14.3 42.8 7 5 5 0.5 5,0 0.53 89.4 5 5 1,0 50,0 27.8 44,4 8 one one 1,0 5,0 4.1 18.0 fifteen fifteen 0.5 50,0 0,0 100.0 9 fifteen fifteen 0.5 30,0 0,0 100.0 fifteen - - 50,0 4.9 90.2 10 - fifteen 0.5 50,0 26.1 47.8

Hydrogen peroxide also showed such high rates. It should be noted that the concentration of reagents should be maintained at the level of 5 wt.% In relation to the solution. In the case of an increase in the concentration of the oxidizing agent (nitric acid and hydrogen peroxide), a composition is formed having explosive and fire hazardous properties. The amount of neutralizer should be maintained with additional fresh additives at the initial level. Table No. 5 shows the low ability of those nitric acid solutions where the initial concentration of the oxidizing agent was maintained at the initial level below 5 wt.% (About 2-3 wt.%). The data shown in table No. 6 indicate a decrease by almost an order of magnitude of UDMH concentration when using 5% solutions, compared with 2% nitric acid solutions. From the presented experimental data, it follows that the proposed method of detoxification allows you to clean UDMH from both soil sections and aquatic environments.

Table 5 Change in the concentration of UDMH solutions subjected to detoxification using 5% solutions of H ₂ O ₂ . No. of solutions Change in concentration of ml / l UDMH in time, 9 days 11 days 12 days Rr. No. 2 2,51 2,3 2.05 Rr№1 9.02 8.4 8.2 Table 6 The change in the concentration of UDMH in aqueous solutions of nitric acid of various concentrations within 24 hours. The initial concentration of UDMH, mg / l After treatment with 2% nitric acid After treatment with 5% nitric acid UDMH content, mg / l (%) 0.217 (100.0) 0.162 (75.1) 0.031 (14.8)

Claims (1)

A method of neutralizing metal surfaces, soils and aqueous solutions contaminated with toxic substances, including the oxidation of metal surfaces, soils, aqueous solutions contaminated with toxic substances with oxidizing reagents, characterized in that a solution of nitric acid and hydrogen peroxide with a concentration of 4- is used as oxidizing reagents 5 wt.%, And oxidation uses oxidizing reagents in relation to the impurities of a toxic compound in a ratio exceeding their stoichiometric amount three times.