RU2276197C2 - Composition for demercurization of objects infested with mercury - Google Patents

Abstract

FIELD: ecology, in particular composition for demercurization.

SUBSTANCE: claimed composition contains sodium thiosulfate and water. Additionally it contains potassium permanganate and nitric acid in the next ratio (wt.%): potassium permanganate 0.52-0.12; sodium thiosulfate 4-6; nitric acid 0.5-1.5; and balance: water. Method for demercurization of objects infested with mercury includes treatment with abovementioned composition for 2 h followed by washing with water. Composition of present invention makes it possible to reduce mercury and mercury vapor concentration to maximum allowable concentration or lower without corrosive and toxic effects.

EFFECT: stable demercurization effect after single treatment of objects infested with mercury.

2 cl, 1 ex

Description

The present invention relates to methods for cleaning objects affected during operation by heavy metals, in this case mercury, and can be used to clean various objects from mercury (demercurization): enterprises producing or using mercury and mercury devices, vehicles, medical organizations, schools and preschool institutions, as well as residential premises. In addition, it can be useful in solving a number of other environmental and sanitary-hygienic issues related to the protection of labor and the environment.

A known composition for purification from mercury (demercurization), used in a method for cleaning rooms from metallic mercury, containing hydrogen peroxide H ₂ O ₂ and water (AS No. 266727, USSR).

According to the authors, the necessary effect of reducing the concentration of mercury vapor by repeated treatment with the specified composition after 24 hours is achieved at objects affected by mercury, using this method and composition.

The disadvantages of this composition is that:

- the use of hydrogen peroxide (H ₂ O ₂ ) only creates protective oxide films on drops of mercury, which, as it turns out, are destroyed by hydrogen sulfide and other “acid” vapors, as a result of which the evaporation of mercury from the surface of its drops increases, reducing the effect of demercurization to zero;

- the composition has a low mercury removal efficiency and strongly corrodes some materials;

- it is necessary to re-treat the proposed composition, which increases in time the process of demercurization (at least up to 24 hours).

Also known is a composition for demercurization containing sodium thiosulfate (TH), ethylenediaminetetraacetic acid (EDTA) and water (US Pat. No. 2,774,736, CL 252-192).

In objects affected by mercury, the use of this composition, according to the authors, achieves the removal of mercury to a certain harmless concentration.

The disadvantage of the composition is that its action is mainly aimed not at the removal of mercury, but at its, in fact, temporary disposal ("transfer into non-volatile form"), that is, there is no effective removal of mercury.

Another disadvantage is that it is not universal, in terms of corrosion, in relation to some materials and their combinations.

A disadvantage can be considered that the processing of the demercurizable object is carried out for a long time (the composition is left overnight), as well as every two weeks. In addition, the components of the composition of "TN" and "EDTA" are quite expensive.

Also known is the composition, an aqueous solution of which in 1 liter contains 1 g of potassium permanganate and 5 ml of hydrochloric acid (P.P. Pugachevich. "Work with mercury in laboratory and industrial conditions", M., publishing house "Chemistry", 1972, p .304). By using this composition, dusty and very small droplets of mercury are converted to calomel, and larger droplets are coated with a film of mercury (I) chloride. However, the effect of demercurization is unstable: initially, after 1 hour, the concentration of mercury vapor decreases by 40-50%, then, after some time, the concentration of mercury vapor increases again and you have to periodically process this solution.

The closest in technical essence to the claimed solution is a composition for demercurization of objects affected by mercury, containing potassium dichromate, sodium thiosulfate, nitric acid and water and the method of its application (RF patent No. 2185413, class 09 09 3/00, C 22 V 43/00).

On objects affected by mercury, the use of this composition also achieves the removal of mercury to a certain harmless concentration.

The claimed invention is directed to the development of compositions for demercurization, devoid of the above disadvantages.

The technical result, in comparison with the prototype, is:

- increasing the efficiency of removing mercury from objects affected by it;

- expansion of the scope (universality) of the composition in relation to objects consisting of more heterogeneous structural materials;

- weakening the corrosive effects of demercurizator on the materials of the object;

- the economy of this composition.

The technical result is achieved in that the composition for demercurization of objects affected by mercury, containing sodium thiosulfate, nitric acid and water, additionally contains potassium permanganate in the following ratio of components, in wt.%:

potassium permanganate - 0.12-0.52 sodium thiosulfate - 4-6 Nitric acid - 0.5-1.5 water - the rest

The method of demercurization of objects affected by mercury includes treating the object affected by mercury with a composition containing sodium thiosulfate, nitric acid and water for 2 hours, followed by washing with water, the treatment being carried out with a composition additionally containing potassium permanganate in the indicated amount.

Replacing the proposed composition of the dichromate with potassium permanganate and changing the concentration of nitric acid, which together have strong oxidizing properties, can improve the efficiency of mercury removal due to its more complete oxidation.

The presence of sodium thiosulfate in the indicated amount creates strong complexes with mercury ions (logK _1,2 = 29.86; logK _1,2,3 = 32,26; logK _1,2,3,4 = 33,61).

Both sodium thiosulfate and potassium permanganate also simultaneously serve as corrosion inhibitors, expanding the scope of the composition to various materials affected by mercury (especially metals) and their combinations.

In addition, this selection of components allows you to create a more stable effect of demercurization after a single treatment of an object affected by mercury.

For experimental verification of the claimed composition was prepared 6 mixtures of ingredients, 4 of which showed optimal results.

Potassium permanganate and, in addition, nitric acid were used as an oxidizing agent, sodium thiosulfate was used as a complexing agent. Mixtures were prepared by sequentially dissolving the components in water under normal conditions. It was found that if the concentration of the components in the composition is less than the specified lower limits, there is a decrease in the efficiency of mercury removal; if their concentration is greater than the upper boundaries, the composition begins to exhibit corrosion aggressiveness.

Example.

Samples of demercurizable material (for example, common alloys of structural metals, reinforced concrete, plastic, religion, linoleum, painted wood, plastic compound, plexiglass), treated with mercury for 45 days, washed with distilled water. Then, the standard method is used to determine the mercury content on the samples before demercurization. Next, the samples are immersed in 1 liter of a solution of demercurizator with the following ratio of ingredients (in wt.%): Potassium permanganate - 0.12-0.52, sodium thiosulfate - 4-6, nitric acid - 0.5-1.5, water - rest. After 2 hours, the samples are removed from the solution, washed with water and the mercury content is determined by the same standard method or its absence is fixed.

From laboratory experiments and the results of application at real facilities, it follows that the proposed composition for demercurization, which we called "Composition 102a", has higher efficiency, which ensures an increase in the removal of mercury from the surfaces of demercurizable objects.

The use of the claimed invention, in comparison with the prototype, will allow:

- improve the quality (degree) of cleaning objects affected by mercury;

- expand the scope (universality) of the composition in relation to objects consisting of dissimilar structural materials;

- to weaken the corrosive effects of demercurizator on the materials of the object;

- create a stable effect of demercurization after a single treatment of a mercury-affected object;

- increase efficiency by reducing the cost of the components of the composition.

Claims (2)

1. The composition for demercurization of objects affected by mercury, containing sodium thiosulfate, nitric acid and water, characterized in that it additionally contains potassium paramanganate in the following ratio of components, wt.%: Potassium permanganate 0.12-0.52 Sodium thiosulfate 4-6 Nitric acid 0.5-1.5 Water Rest 2. The method of demercurization of objects affected by mercury, including their treatment with a composition containing sodium thiosulfate, nitric acid and water, for two hours with further washing with water, characterized in that the treatment is carried out with a composition additionally containing potassium permanganate in the following ratio of components, weight .%: Potassium permanganate 0.12-0.52 Sodium thiosulfate 4-6 Nitric acid 0.5-1.5 Water Rest