RU2753230C1 - Method for obtaining sorbent based on activated carbons for the extraction of mercury from aqueous media - Google Patents

Abstract

FIELD: chemical industry and nature protection.

SUBSTANCE: invention relates to the chemical industry and environmental protection and can be used for the cleaning of wastewater from chemical enterprises from mercury. Granular activated carbon is treated with a modifying solution that ensures the production of an active component on its surface, manganese (II) sulfide, in two stages. At the first stage, granular activated carbon is impregnated with a solution of manganese (II) sulfate with a concentration of 0.25-7.5, weight percentage, at the ratio of the mass of activated carbon and the volume of the solution (V_P), which is determined by the formula: V_P = m_{a. с.} ⋅ V_Σ ⋅ C_imp, where m_a.с. is the mass of activated carbon, g; V_Σ is the total pore volume, cm³/g; C_imp is the impregnation coefficient (C_imp = 0.8), followed by curing of the impregnated activated carbon and drying to an air-dry state. At the second stage, the resulting modified intermediate semiproduct is placed for 0.5-1.5 hours in a 10% solution of sodium sulfide solution taken in 5% excess relative to the stoichiometry of the reaction equation of the interaction of manganese sulfate with sodium sulfide. The target product is separated from the liquid and dried.

EFFECT: resulting sorbent based on granular activated carbon, the surface of which is modified with manganese (II) sulfide in an amount of 1-10, weight percentage, has a maximum equilibrium capacity of 2.3 mg/g and provides a degree of mercury extraction from highly concentrated wastewater of more than 90%.

1 cl, 2 tbl, 2 ex

Description

The technical field to which the invention relates

The invention relates to the field of sorption extraction of mercury ions from wastewater of chemical plants with modified activated carbon. The invention can be used to solve environmental problems associated with the purification of wastewater from mercury generated as a result of the activities of a number of chemical enterprises.

State of the art

A known method of producing a sulfur-containing carbon sorbent, which consists in a one-stage treatment of the original activated carbon material with hydrogen sulfide at a temperature of 200-700 ° C until the material is completely saturated with hydrogen sulfide. As an activated carbon material, carbon fibers of both natural and artificial origin and / or macroporous coals are used (patent RU No. 2187362, IPC B01J 20/20, publ. 20.08.2002, bull. No. 23). The sorbent is designed to extract heavy metal ions (including mercury), which tend to form poorly soluble sulfides.

The disadvantages of this method include the conditions for obtaining the sorbent - saturation of activated carbon with hydrogen sulfide at high temperatures (200-700 ° C).

There is a known method of producing a sulfur-containing sorbent, including the polycondensation of sodium polysulfide with an organochlorine compound on the surface of petroleum coke particles. 1,4-dichlorobutin-2 is used as the organochlorine compound (RF patent No. 2525416, publ. 08/10/2014, bull. No. 22). The sorbent has increased activity in relation to mercury ions when removed from aqueous solutions.

The disadvantage of this method is the use of 1,4-dichlorobutin-2 as an organochlorine component for polycondensation. Its use under reaction conditions can lead to the formation of a polymer sorbent with a high content of residual chlorine, which will cause a decrease in the sorbent activity.

A known method of producing a sorbent for purifying wastewater from mercury by pretreating activated carbon with sodium thiosulfate solution. The process of purifying waste water from mercury using a sorbent obtained by this method is carried out in an acidic medium, which requires additional preparation (AS USSR No. 929590, IPC C02F 1/62, publ. 23.05.82, Bul. No. 19).

The disadvantages of this method include limiting the pH of the solution, preferably in an acidic environment, the conditions for obtaining - keeping activated carbon in solution for 24 hours, as well as the instability of Na ₂ S ₂ O ₃ .

The closest method for the same purpose to the claimed invention in terms of a combination of features is a method for producing a sorbent based on activated carbons for extracting mercury from wastewater from chemical enterprises, described in the article by E.A. Farberova. et al., “The use of carbon sorbents in the technology of wastewater treatment from mercury (Vestnik VSUIT, 2018, v. 80, No. 4, pp. 322-329). The known method includes the treatment of granular activated carbon with modifying solutions, ensuring the production of an active component on its surface - manganese (II) sulfide.

The disadvantage of this method is the absence in the description of the method of applying an active additive - manganese sulfide (II), the content of the active additive in the sorbent is not determined, the low resource of the sorbent layer when cleaning waste water from mercury (the estimated service life of the sorbent layer obtained by the known method (prototype) was 35 dm ³ / kg).

Disclosure of invention

The technical problem solved by the invention, and the technical result that is objectively manifested in the implementation of the method, is the expansion of the arsenal of sorbents to ensure a high degree of purification of aqueous media from mercury, which is activated carbon modified with manganese sulfide.

The problem was solved due to the fact that in the known method of obtaining a sorbent based on activated carbons for the extraction of mercury from wastewater of chemical enterprises, including the treatment of granular activated carbon with a modifying solution, which ensures the production of an active component on its surface - manganese sulfide (II), according to manganese sulphide invention (II) is prepared in two stages: the first stage granular activated carbon impregnated with a solution of manganese sulfate (II) with a concentration of 0,25-7,5% by weight at weight ratio of activated charcoal and the solution volume (V _Ρ), which. determined by the formula:

V _Ρ = m _ay ⋅V _Σ ⋅K _pr. ,

where m _ay is the mass of activated carbon, g;

V _Σ - total pore volume, cm ³ / g;

K _pr. - impregnation coefficient (K _pr = 0.8)

followed by curing the impregnated activated carbon and drying to an air-dry state, and at the second stage, the resulting modified intermediate product is placed for 0.5-1.5 hours in a 10% solution of sodium sulfide solution, taken in a 5% excess relative to stoichiometry equations for the reaction of the interaction of manganese sulfate with sodium sulfide, followed by separation from the liquid and drying of the target product.

The sorbent for the extraction of mercury ions from wastewater of chemical enterprises is granular activated carbon impregnated with manganese (II) sulfide in an amount of 1-10% of the mass.

Important: * the sorbent with the addition of manganese sulfide less than 1% has a low absorption capacity of mercury and a low degree of wastewater treatment in the studied concentration range of 1.20-123.7 mg / dm ³ ;

* increasing the supplement more than 10% is not effective, because does not improve performance, but leads to an overrun of the active component.

At the first stage of the proposed method, the processing of granular activated carbon is carried out with a solution of manganese (II) sulfate with a concentration of 0.25-7.5 wt.%.

The above is a mathematical relationship that relates the volume of a solution of manganese sulfate (MnSO ₄ ) to the mass of activated carbon. In this formula, the volume of the solution acts as a constant value for a given mass of coal (for example, 1 gram), a specific type of AG-3 coal (with a certain total pore volume). The impregnation coefficient (K _pr. ) Is taken constant and equal to K _pr. = 0.8. At the same time, to increase the content of the active additive in the sorbent, it is necessary to increase the concentration of MnSO ₄ in accordance with Table 1.

At the second stage of obtaining the sorbent, a solution of sodium sulfide (Na ₂ S) with a concentration of 10% was used to extract mercury ions.

The binding of Μn ^{2+ ions} in the composition of activated carbon by S ^2- ions was carried out according to the reaction: MnSO ₄ + Na ₂ S = MnS + Na ₂ SO ₄ .

For the interaction, a 5% excess of Na ₂ S solution was used with respect to the stoichiometry of the presented process equation.

When processing the intermediate in an excess of sodium sulfide solution for less than 0.5 hours, the reaction of interaction with manganese (II) sulfate on the surface of the activated carbon does not have time to complete; an increase in the contact time of more than 1.5 hours is impractical, since the specified period of time is sufficient to establish equilibrium in the system.

The above set of essential features allows obtaining the following technical result - expanding the arsenal of sorbents to ensure a high degree of purification of aqueous media from mercury, which is activated carbon modified with manganese sulfide, increasing the degree of purification of highly concentrated solutions from mercury ions, increasing the service life of the sorbent, obtaining a sorbent with stable characteristics while reducing the time to obtain it.

The invention is illustrated below by the following examples and table data. The sorbent was obtained and tested in laboratory conditions.

Example 1.

At the first stage, granular activated carbon of industrial production, grade AG-3, was treated with a solution of manganese (II) sulfate of 2.5% concentration. The ratio of the mass of activated carbon and the volume of the solution (V _P ) was determined by the formula:

V _Ρ = m _a.y. ⋅V _Σ ⋅K _pr. ,

where m _a.y. - mass of activated carbon, g;

V _Σ - total pore volume, cm ³ / g;

K _pr. - impregnation coefficient (K _pr. = 0.8).

After treatment with a MnSO ₄ solution, the activated carbon was aged and brought to an air-dry state.

At the second stage, the obtained modified intermediate was placed in a 5% excess in a solution of sodium sulfide with a concentration of 10% for 1 hour, taken in a 5% excess relative to the stoichiometry of the reaction equation for the interaction of manganese sulfate with sodium sulfide. After treatment, the sample was separated from the liquid and dried. Samples were obtained with different MnS content (0.5; 1.0; 5.0; 10.0; 15.0 wt%).

Concentrations of manganese sulfate solutions (l) when applying different amounts of additives are presented in table l.

Example 2.

The study of the efficiency of the obtained samples was carried out under static conditions with the following parameters of the cleaning process:

Sample weight 2.5 g. The volume of the solution to be cleaned is 50 cm ³ . Contact time 1 hour. Stirring speed 100-120 rpm. The concentration of the used solutions of mercury: 1.2 mg / dm ³ ; 1.7 mg / dm ³ ; 6.9 mg / dm ³ ; 11.7 mg / dm ³ ; 24.2 mg / dm ³ ; 36.0 mg / dm ³ ; 123.7 mg / dm ³ .

After the contact time elapsed, the sorbent was separated from the solution to be cleaned, in which the residual mercury content was analyzed.

The determination was carried out by the method of atomic emission spectral analysis with inductively coupled plasma on a Thermo iCAP 6500 Duo device with a flow-through mercury-hydride system, the detection limit of mercury is 0.01 μg / dm ³ .

The results of the study are shown in Table 2.

The service life of 1 kg of sorbent (~ 2 dm ³ ) was more than 106 dm ^{3 of} purified water at a solution concentration of 24 mg / dm ³ or less.

The maximum equilibrium sorbent capacity was 2.3 mg / g.

This description is considered as material illustrating the invention, the essence of which and the scope of patent claims are defined in the following claims, a set of essential features and their equivalents.

Claims (6)

A method of obtaining a sorbent based on activated carbons for the extraction of mercury from wastewater of chemical enterprises, including the treatment of granular activated carbon with a modifying solution, providing an active component on its surface - manganese (II) sulfide, characterized in that manganese (II) sulfide is obtained in two stages: at the first stage, granular activated carbon is impregnated with a solution of manganese (II) sulfate with a concentration of 0.25-7.5 wt.% at the ratio of the mass of activated carbon and the volume of the solution (V _P ), which is determined by the formula: V _P = m _ay ⋅ V _Σ ⋅ Κ _pr. , where m _ay is the mass of activated carbon, g; V _Σ - total pore volume, cm ³ / g; K _pr. - impregnation coefficient (K _pr = 0.8) followed by curing the impregnated activated carbon and drying to an air-dry state, and at the second stage, the resulting modified intermediate product is placed for 0.5-1.5 hours in a 10% solution of sodium sulfide solution, taken in a 5% excess relative to stoichiometry equations for the reaction of the interaction of manganese sulfate with sodium sulfide, followed by separation from the liquid and drying of the target product.