RU2541258C1 - Method of immobilising mercury in solid wastes - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of immobilising mercury in solid wastes, containing mercury oxide and metal mercury, includes oxidation of metal mercury with water hydrogen peroxide solution and precipitation of mercury in form of basic bivalent mercury carbonate (HgCO₃·2HgO). Precipitation of mercury simultaneously with oxidation or after oxidation is carried out by processing wastes with carbon dioxide in autoclave under pressure 15-20 atm at temperature 40-50°C for 4-5 hours.

EFFECT: reduction of consumption of reagents and elimination of formation of secondary wastes.

3 cl, 3 tbl, 3 ex

Description

FIELD OF THE INVENTION

The invention relates to environmental protection in the production and use of metallic mercury and its compounds and is intended for immobilization (curing / stabilization) of mercury and its compounds in solid mercury-containing wastes (brick, concrete, soil, etc.).

State of the art

Mercury, metallic and in the form of a compound, is a substance of the first hazard class. Of particular danger are metallic mercury vapors. Due to the high elasticity of mercury vapor above its surface, the concentration of the latter in air even at ordinary temperature can be many times higher than the maximum permissible concentration in the residential area (maximum permissible concentration).

Because of this, the main task when conducting demercurization of surfaces and / or volumes contaminated with mercury is the complete removal of metallic mercury or its transfer to the stationary form of stable chemical compounds (immobilization).

To neutralize metallic mercury through its chemical immobilization, a significant amount of chemical reagents has been proposed and used in practice that can oxidize mercury and convert it to compounds that are hardly soluble (or insoluble) in water.

A known method of demercurization of mercury-containing waste for their disposal according to the patent of the Russian Federation [1]. The method includes treating waste with a solution of calcium polysulfide. Before treatment with a solution of calcium polysulfide, the waste is mixed with an oxidizing agent containing active chlorine in an amount equal to 0.15-10.0 wt.% By weight of the waste, then water is introduced and the mixture is kept. The resulting mixture is subjected to treatment with a solution of calcium polysulfide at a ratio of a solution of calcium polysulfide to a mixture of 1-4: 10 wt.%, Respectively, followed by a long aging of the reaction mixture.

The disadvantage of this method is the secondary pollution of waste with an excess of oxidizing agent and calcium polysulfide.

A known method of immobilization of metallic mercury by ed. USSR No. 266727 [2], in which the treatment of surfaces contaminated with mercury and places of its accumulation is carried out with a 5% aqueous solution of H ₂ O ₂ .

The disadvantage of this method is the low stability created on the surface of the metallic mercury film of its oxide.

One of the water-insoluble mercury compounds is the basic carbonate of divalent mercury (HgCO ₃ · 2HgO). It can be obtained by reacting oxidized forms of mercury with carbonates.

A known method of the disposal of metallic mercury by immobilization in various materials (soil, brick, concrete, etc.) according to the patent of the Russian Federation No. 2342449 [3]. The method involves oxidizing mercury by treating with an aqueous solution of hydrogen peroxide. In addition, mercury is precipitated with oxidation by treating mercury-containing waste with an aqueous solution of a reagent that converts metallic mercury into a water-insoluble or sparingly soluble compound of natural or technogenic composition. As a reagent, water-soluble alkali metal carbonates with the addition of nitric acid are used.

The disadvantage of this method is the formation of secondary waste - nitrates of alkali metals.

Disclosure of invention

An object of the invention is to reduce reagent consumption and to prevent the generation of secondary waste.

This goal is achieved in that immobilization of mercury in solid wastes containing mercury oxide and metallic mercury, including oxidation of metallic mercury with an aqueous solution of hydrogen peroxide and precipitation of mercury as basic carbonate of divalent mercury (HgCO ₃ · 2HgO), precipitation of mercury simultaneously or sequentially with oxidation metallic mercury is carried out by treatment with carbon dioxide; immobilization of mercury in solid wastes containing mercury oxide and metallic mercury is carried out at a carbon dioxide pressure of 15-20 atm; immobilization of mercury in solid wastes containing mercury oxide and metallic mercury is carried out at a temperature of 40-50 ° C; immobilization of mercury in solid waste containing mercury oxide and metallic mercury is carried out for 4-5 hours.

The source of carbonates for the synthesis of the basic carbonate of divalent mercury (HgCO ₃ · 2HgO) is carbon dioxide, which when dissolved in water gives carbonic acid. Carbon dioxide in the immobilization of mercury in solid waste performs two tasks: firstly, acidification of the aqueous medium to create conditions for the effective oxidation of metallic mercury, and secondly, the subsequent binding of mercury ions to a sparingly soluble compound - the main carbonate of divalent mercury (HgCO ₃ · 2HgO) .

The immobilization of mercury in solid waste using a solution of hydrogen peroxide and carbon dioxide is carried out in an autoclave under pressure. An increase in pressure and temperature leads to an increase in the rate of formation of the basic carbonate of divalent mercury (HgCO ₃ · 2HgO).

The use of hydrogen peroxide and carbon dioxide to immobilize mercury in solid waste eliminates the use of toxic reagents and eliminates the formation of secondary waste.

Short description of tables

Table 1 shows data on the effect of carbon dioxide pressure on the treatment of mercury oxide (HgO); Table 2 shows the effect of temperature on the treatment of mercury oxide (HgO); Table 3 shows the effect of time on the treatment of mercury oxide (HgO).

The implementation of the invention

Examples of the method.

Example 1. The effect of carbon dioxide pressure on the immobilization of mercury oxide. Samples of mercury oxide (HgO) of Ch. Qualification according to GOST 5230-74 were immobilized. A portion of mercury oxide (HgO) 2.0 g was placed in a glass vessel into which 20 ml of a 2.5% solution of H ₂ O _{2 was} poured. The ratio of T: W = 1: 10. Next, the vessel was placed in an autoclave and carbon dioxide was supplied for 24 hours at a temperature of 20 ° C. Carbon dioxide pressure was varied in the range from 5 to 25 atm. The experimental results are presented in table 1.

Table 1 The effect of carbon dioxide pressure on the treatment of mercury oxide (HgO) Sample number P, atm t, ° C τ, hour The residual concentration of HgO, wt.% The concentration of the residue, wt.% The phase composition of the residue one 5 twenty 24 21 ± 5 79 HgCO ₃ · 2 (HgO) 2 10 twenty 24 19 ± 5 81 HgCO ₃ · 2 (HgO) 3 fifteen twenty 24 15 ± 4 85 HgCO ₃ · 2 (HgO) four twenty twenty 24 14 ± 4 86 HgCO ₃ · 2 (HgO)

By immobilizing mercury oxide (HgO) with carbon dioxide, mixtures of mercuric oxide (HgO) and red-brown basic divalent mercury carbonate (HgCO ₃ · 2HgO) were obtained. The content of the basic carbonate of divalent mercury (HgCO ₃ · 2HgO) according to x-ray studies of the obtained samples increased from 79% weight. at a pressure of 5 atm up to 86% weight. at a pressure of 25 atm (see table 1).

An increase in pressure above 25 atm does not produce a noticeable effect.

Example 2. The effect of temperature on the immobilization of mercury oxide with carbon dioxide

Samples of mercury oxide (HgO) of Ch. Qualification according to GOST 5230-74 were immobilized. A portion of mercury oxide (HgO) 2.0 g was placed in a glass vessel into which 40 ml of a 2.5% solution of H ₂ O _{2 was} poured. The ratio of T: W = 1: 20. Then the vessel was placed in an autoclave and carbon dioxide was supplied at a pressure of P = 25 atm for 5 hours in the temperature range from 20 to 50 ° C. The experimental results are presented in table.2.

table 2 Effect of temperature on the treatment of mercury oxide (HgO) Sample number P, atm t, ° C t, hour The residual concentration of HgO, wt.% The concentration of the residue, wt.% The phase composition of the residue one 25 thirty 5 50 ± 7 fifty HgCO ₃ · 2HgO 2 25 40 5 40 ± 5 60 HgCO ₃ · 2HgO 3 25 fifty 5 15 ± 4 85 HgCO ₃ · 2HgO

By immobilizing mercury oxide (HgO) with carbon dioxide, mixtures of mercuric oxide (HgO) and red-brown basic divalent mercury carbonate (HgCO ₃ · 2HgO) were obtained. The content of the basic carbonate of divalent mercury (HgCO ₃ · 2HgO) according to x-ray studies of the obtained samples increased from 40% weight. at a processing temperature of 20 ° C to 85% by weight. at a processing temperature of 50 ° C (see table 2). As the temperature rises above 50 ° C, the cost of heating the autoclave increases dramatically.

Example 3. The influence of processing time on the immobilization of mercury oxide carbon dioxide

Samples of mercury oxide (HgO) of Ch. Qualification according to GOST 5230-74 were immobilized. A portion of mercury oxide (HgO) 0.5 g was placed in a glass vessel into which 20 ml of a 2.5% solution of H ₂ O _{2 was} poured. The ratio of T: W = 1: 40. Then the vessel was placed in an autoclave and carbon dioxide was supplied at a pressure of P = 25 atm at a temperature of t = 20 ° C for 1 to 24 hours. The experimental results are presented in table.3.

Table 3 Effect of time on the treatment of mercury oxide (HgO) Sample number HgO processing time, hour The concentration of HgO,% wt. The concentration of HgCO ₃ · 2HgO,% wt. one 0 one hundred 0 2 one 90 10 3 2 85 fifteen four 3 40 60 5 5 thirty 70 6 24 25 75

By immobilizing mercury oxide (HgO) with carbon dioxide, mixtures of mercuric oxide (HgO) and red-brown basic divalent mercury carbonate (HgCO ₃ · 2HgO) were obtained. The content of the main carbonate of divalent mercury (HgCO ₃ · 2HgO) according to x-ray studies of the obtained samples increased from 10% weight. when processing time 1 hour to 75% weight. with a processing time of 24 hours (see table 3).

Processing is optimal for 4-5 hours, a further increase in processing time does not give a significant effect.

Example 4. Immobilization of mercury-containing wastes containing mercury oxide and metallic mercury

Building wastes containing mercury in an amount of 80 mg / kg (40% in the form of metallic mercury) and soils containing mercury in an amount of 50 mg / kg (9% in the form of metallic mercury) were immobilized.

A weighed portion of 200 g of mercury-containing waste was placed in a glass vessel into which 200 ml of a 2.5% solution of H ₂ O _{2 was} poured. The ratio of T: W = 1: 1. Next, the vessel was placed in an autoclave and carbon dioxide was supplied at a pressure of P = 25 atm. The autoclave was kept for 2 days at a temperature of t = 20 ° C. Next, the waste was filtered and biotested at the Federal State Institution “TsLATI in the Siberian Federal District” (Novosibirsk).

As a result of the immobilization of mercury-containing waste with carbon dioxide, their hazard class decreased: for construction waste from the 3rd — moderately hazardous waste, to the 4th — low-hazardous waste, and for soils from the 4th — low-hazardous waste, up to the 5th — practically not hazardous waste.

Thus, the use of the method of immobilization of mercury in solid waste using carbon dioxide can reduce the consumption of the reagent and eliminate the formation of secondary waste.

Literature

1. RF patent No. 2400545. The method of demercurization of mercury-containing waste for their disposal / Auth. Levchenko L.M., Kosenko V.V., Mitkin V.N., Galitsky A.A. // Stated March 11, 2009

2. A.S. USSR No. 266727. A method of cleaning rooms from metallic mercury / Auth. Gavrikov L.A., Golubev V.G. // Stated November 6, 1968

3. RF patent No. 2342449. The method of neutralization of metallic mercury by immobilization / Auth. Chapaev I.G., Babushkin A.V., Belozerov I.M., Vladimirov A.G., Zabortsev G.M., Krivenko A.P., Ostrovsky Yu.V., Stepanov V.I., Tkachenko V .V., Shpak A.A. // Declared December 21, 2006

Claims (3)

1. A method of immobilizing mercury in solid wastes containing mercury oxide and metallic mercury, comprising oxidizing metallic mercury with an aqueous solution of hydrogen peroxide and precipitating mercury as the basic carbonate of divalent mercury (HgCO ₃ · 2HgO), characterized in that the deposition of mercury is carried out simultaneously with oxidation metallic mercury or after oxidation by treating solid waste with carbon dioxide in an autoclave at a carbon dioxide pressure of 15-25 atm. 2. The method according to claim 1, characterized in that the treatment of solid waste with carbon dioxide is carried out at a temperature of 40-50 ° C. 3. The method according to claim 1, characterized in that the treatment of solid waste with carbon dioxide is carried out for 4-5 hours.