RU2730619C1 - Agent for reducing arsenic mobility in soil - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention relates to the field of environmental protection and can be used for reclamation of lands contaminated with arsenic and other heavy metals. Agent contains a composition of silicon and iron preparations. Silicon preparation is amorphous silicon dioxide with surface area of 30 m/g to 400 m/g, which is selected from a group consisting of synthetic silicon, silicon, obtained from industrial waste, where iron is used as an iron preparation. Ratio of iron and silicon in weight ratio ranges from 1/10 to 1/30. Iron preparation is iron sulphate III. Synthetic amorphous silicon dioxide is selected from a group which includes pyrogenic silica, finely ground quartz or other natural silicon dioxide with SiOcontent of not less than 85 %. Amorphous silicon dioxide obtained from wastes from industry is selected from a group comprising ash, microsilica and other silicon-containing compounds with SiOcontent of not less than 85 %.EFFECT: agent reduces toxic effect of arsenic on living organisms and arsenic mobility in soils and grounds.4 cl, 2 tbl, 2 ex

Description

Technology area

The invention relates to the field of environmental protection and can be used for reclamation of land contaminated with arsenic and other heavy metals.

State of the art

Currently, arsenic pollution of the environment is one of the main negative factors affecting human health. The concentration of arsenic in drinking water over 10 μg per liter causes chronic poisoning [1]. Arsenic contamination mainly occurs as a result of the weathering of arsenic-containing minerals, coal combustion, the use of arsenic-containing pesticides, the use of arsenates in wood processing, in the extraction and smelting of certain metals [2]. It is known that wastewater from enterprises producing glass products, wood preservatives, ceramic products, leather goods, as well as factories producing paints, oil refineries may contain arsenic and heavy metals, which may enter the soil [3].

Continuous population growth and industrial development leads to the global pollution of soil and groundwater with arsenic. In some areas, this problem has reached a critical level [3]. Therefore, it is necessary to develop new technologies for the treatment and decontamination of arsenic-contaminated soil and wastewater.

Known compositions, which include iron salts, namely ferrous sulfate. US Pat. No. 4,723,992 (1988-02-09) discloses compositions for fixing pentavalent arsenic, such as arsenates and arsenic acid, commonly found in soil. The fixation is carried out in such a way that arsenic loses its mobility and activity even after a possible further increase in soil acidity. The compositions contain metal salts of iron, aluminum or chromium with a weak acid, preferably iron or aluminum acetate, which are spread over the soil containing arsenic compounds. The composition includes ferrous sulfate and at least one acetate of sodium, potassium or ammonium [4].

Chinese Invention Application No. CN 109570218 (2019-04-05) relates to the technical field of cleaning contaminated soils, in particular to a stabilizing agent for heavy metals contaminated with arsenic and antimony. The stabilizing agent is obtained from zirconium oxychloride, hydrotalcite, calcium oxide and ferrous sulfate, which are used as feedstock. The stabilizing agent has the advantage of using zirconium oxychloride, hydrotalcite, calcium oxide and ferrous sulfate as raw materials, which are of low cost. A good stabilizing effect is achieved up to 98% [5].

Chinese Invention Application No. CN 107254313 (2017-10-17) discloses an arsenic contaminated soil conditioner, a preparation method, and a soil contamination control method. It is proposed to use rice straw, ferrous sulfate heptahydrate and hydrogen peroxide as raw materials for the air conditioner. The method for preparing the air conditioner includes the following stages: cleaning and grinding rice straw, soaking rice straw in a solution _of FeSO ₄ ⋅7H ₂ O, adding Н ₂ О ₂ with a concentration of 30%, uniform mixing, filtration, drying, charring the raw material in a muffle at a temperature of 300 up to 400 ° C [6].

In the application for the invention of China No. CN 109575926 (2019-04-05) a conditioner for soils contaminated with cadmium and arsenic is proposed, which contains the following parts by weight of raw materials: 0-10 parts of hematite, 20-30 parts of ferrous sulfate; 10 parts of manganese dioxide; 15-20 parts of ash; 10-15 parts of quicklime; 10-15 parts of sepiolite; 10-15 parts of calcium dihydrogen phosphate; and 0-10 parts of wollastonite [7]. The proposed air conditioner firmly binds heavy metals cadmium and arsenic, forming chemically stable compounds, which leads to a decrease in the migration and diffusion of inorganic pollutants in the environment.

Chinese Patent Application No. CN 108085016 (2018-05-29) discloses a soil conditioner for reducing arsenic mobility and its use. The conditioner contains agent A and agent B, and agent A is obtained from raw materials in parts by weight as follows: 40-60 parts of iron poly-sulfate, 45-65 parts of ferrous sulfate and 0-15 parts of sodium humate; agent B is obtained from mass parts of raw materials as follows: 20-35 parts of pyrolusite powder, 25-45 parts of calcined bentonite and 30-50 parts of lime. Agent A and agent B are used in the conditioner in a mass ratio of 1: 1 [8].

Known compositions, which include silicon dioxide. RF patent No. RU 2122903 (10.12.1998) describes an air conditioner based on amorphous silicon dioxide, which is designed to restore contaminated soils. In the soil conditioner, a mixture of two or more solid silicon-containing substances with a Si content of 5-45% is used as a mineral component, while at least one of these substances, the consumption of which is 50-10000 kg per 1 ha, is located in non-crystalline form with particles no more than 1 mm in size, and other substances, the total consumption of which is 100-20000 kg per 1 ha, are in non-crystalline or crystalline form with particles no more than 5 cm in size.Environmentally safe substances can be used as solid silicon-containing substances solid silicon-containing industrial and agricultural waste in the form of ash, slag, dust, etc., chemically pure silicon-containing compounds, for example, amorphous silicon dioxide, quartz sand, calcium silicate, magnesium silicate, etc., as well as ground silicon-containing rocks , for example, sand, sandstone, zeolite, tuff [9].

Known compositions, which include compounds of silicon and iron.

Korean Patent No. KR 101184933 (2012-09-28) discloses a method for removing arsenic from waste water using steel mill slag with a high iron content. The crushed oxidized slag has an average particle diameter of 1 to 1000 micrometers. Crushed slag from oxidized slag contains 20-50 wt. % Fe, 15-35 wt. % CaO, 1-5 wt. % MnO, 0.01-1 wt. % Free lime, 0.1-5 wt. % MgO, 5-20 wt. % SiO ₂ and 0.1 ~ 30 wt. % Al ₂ O ₃ [10].

The closest technical solution is described in RF patent No. RU 2471849 (01/10/2013), which describes a composition for detoxification of soils contaminated mainly with arsenic. The composition includes diatomite, consisting of silicon dioxide and treated with iron chloride Fe ³⁺ , as well as blue clay with the following ratio of components, wt. %: diatomite treated with Fe ³⁺ - 50-60, blue clay - 40-50 [11]. The disadvantage of the technical solution can be attributed to the fact that the composition for soil detoxification includes blue clays, which are a source of such a toxic element as aluminum.

The objective of the present invention is to create an effective and safe composition of a means for soil reclamation, stimulating the growth and improving the vital activity of plants.

The problem is solved due to the fact that the composition of the soil reclamation agent contains silicon-containing material and ferrous sulfate. Amorphous silicon dioxide is used as the silicon-containing material. The composition of the soil conditioner is carried out with the following ratio of iron and silicon components: from 1/10 to 1/30.

The technical result consists in the fact that the claimed agent on the basis allows to reduce the toxic effect of arsenic on living organisms and the mobility (solubility) of arsenic in soils and grounds.

The essence of the invention

The subject of the present invention is an agent for reducing the mobility and solubility of arsenic compounds in soil, containing a composition of preparations of silicon and iron. In this case, the silicon preparation is an amorphous silicon dioxide with a surface area of 30 m ² / g to 400 m ² / g, which is selected from the group consisting of silicon obtained by a synthetic method, silicon obtained from waste slags. Ferrous sulfate is used as an iron preparation. In this case, the ratio of the preparation of iron and silicon in a weight ratio is from 1/10 to 1/30.

Description of the invention

When studying the composition of an effective means for reducing the mobility and solubility of arsenic compounds in soil it has been found that the use of a composition consisting of amorphous silica with a surface area of 30 m ² / g and a preparation of ferrous sulfate significantly reduces the mobility and solubility of arsenic compounds in soil.

Amorphous (noncrystalline) silicon dioxide with a high specific surface area almost never occurs in nature in its pure form. It can only be obtained by technological means. Several brands of amorphous silicon dioxide are known. One preparation is produced under the KOVELOS trade mark and is a very light micronized (particle size depending on the brand from 6 to 40 microns) white powder, tasteless and odorless with a nanoporous particle structure, with pronounced sorption properties. Its specific surface area is 350-400 m ² / g. [12] Another drug under the brand name MIKROSILIKA is produced by OJSC Kuznetsk Ferroalloys [13].

Due to the large specific surface area of amorphous silicon dioxide, more binding sites for arsenic are provided compared to traditional materials. As amorphous silicon dioxide, synthetic silicon (fumed silica), finely ground quartz or other natural silicon dioxide or other silicon containing compounds with SiO2 content of at least 85%, industrial waste (ash, microsilica) can be used. The high surface area of silicon compounds ensures high solubility in

to silicon, which ensures their high chemical activity [14].

Ferrous sulfate was used as an iron preparation. It is preferable to choose an iron preparation in the form of iron III sulfate. In the manufacture of the product, the ratio of iron and silicon preparations in a weight ratio is from 1/10 to 1/30.

The combination of two components with different properties in the product allows for maximum efficiency of arsenic neutralization due to the synergistic effect of reducing the mobility of arsenic. Since the components of the agent are not used by microorganisms as a food product, this does not lead to a decrease in the activity of microorganisms and a decrease in the effectiveness of reclamation. A method for increasing the decrease in the mobility and solubility of arsenic compounds in the soil includes applying the agent to the surface of the selected soil area in doses from 0.1 to 3 tons per hectare, followed by disking or loosening the treated soil using a plow.

To obtain evidence of the possibility of creating a silicon-ferrous mixture, a number of incubation, vegetation and laboratory experiments were carried out using the following silicon-containing compounds: microsilica of a metallurgical plant (Kuznetsk Ferroalloys Metallurgical Plant, Novokuznetsk, Russia) and chemically pure amorphous silicon dioxide ( surface area 30 and 300 m ² / g). As the iron source, a soluble iron sulfate salt was used as a solid iron source. The following mixtures were made:

1) Microsilica: ferrous sulfate in a ratio of 10: 1,

2) Microsilica: iron sulfate in a ratio of 30: 1,

3) Silicon dioxide (30 m ² / g): ferrous sulfate in a ratio of 10: 1,

4) Silicon dioxide (300 m ² / g): ferrous sulfate in a ratio of 10: 1,

Example 1.

The vegetation experiment was carried out using peat as a soil matrix and a barley culture (Hordeum vulgare, cultivar Moskovskaya 9) in plastic vessels with a volume of 1 liter. Before planting the seeds, arsenic salt (AsNaO ₂ ) was added to the peat in an amount of 50 ml and an arsenic concentration of 50 mmol to ensure a high level of arsenic contamination. For 1 week, the arsenic-treated peat was incubated at a humidity of 40-50% and stirred to obtain a homogeneous contamination. After that, mixtures of silicon compounds with iron were introduced at doses of 100 kg / ha for iron compounds, and separately for iron compounds (100 kg / ha) and silicon (1 t / ha and 3 t / ha), where, in terms of 1 liter of soil, 100 kg / ha corresponds to 0.1 g per vessel, 1 t / ha - 1 g per vessel and 3 t / ha - 3 g per vessel, respectively. Then the barley seeds were planted. The plants were grown for 4 weeks. The air temperature was + 24 ° С during the day and + 20 ° С at night with a light regime of 12 hours and an air humidity of 90%. Watering was carried out regularly and the moisture content of the substrate was 50-60%) by weight. After that, samples of soil and plants were taken. The plants were dried and then the total arsenic content in the roots and leaves was determined using the ICP-MSI Cap-Q (USA). The content of mobile (0.1 n HCl extract) and potentially mobile (2 n HNO ₃ extract) forms of arsenic was determined in the soil using ICP-MSI Cap-Q (USA). All experiments were performed in 3-fold repetition. The data obtained are presented in table 1.

The use of iron preparations reduces the content of arsenic in plant roots to 44.8%, in the green mass of plants - to 37.3%. Iron preparations also reduce the mobility of arsenic in the soil to 39.4%. The use of only silicon preparations also leads to a decrease in the activity of arsenic in the soil-plant system. However, the most significant reductions in the accumulation of arsenic by plants and a decrease in the mobility of this metalloid in the soil were obtained using mixtures of silicon-containing and iron-containing preparations. The content of arsenic in plant roots decreased to 84.2%, its content in barley leaves decreased to 93-97%. The mobility of arsenic in the soil has been reduced by 56-88%.

Example 2

The second experiment was carried out using the same mixtures, iron oxide and silicon compounds. In plastic flasks with a volume of 250 ml was added 1 g of ferrous sulfate and the corresponding amounts of mixtures or silicon compounds. Added the same 1 g of salt (NaCl) to ensure the same ionic strength. Then, 200 ml of distilled water was poured into the flasks, and the pH of the solutions was adjusted to 7.0 ± 0.1 using a 0.1 N HCl solution or 0.1 N NaOH solution. Thereafter, 10 ml of concentrated AsNaO ₂ solution (400 mmol) was added to each flask. The flasks were shaken in a cookie for 1 hour on a rotator and then the resulting solutions were centrifuged at 15,000 rpm for 15 minutes. In the resulting solutions, the concentration of arsenic was determined using ICP-MSI Cap-Q (USA). The experiment was carried out in 4-fold repetition. The results are shown in Table 2.

The presence of silica with a minimum surface area had a minimal effect on arsenic concentration. Amorphous silica 300 m ² / g reduced the concentration by 75.1%. The proposed mixtures had the maximum sorption properties in relation to arsenic. The presence of both components (silicon and ferrous) has a synergistic effect, which makes it possible to significantly increase the sorption properties in relation to arsenic. This can be explained by the presence of several mechanisms of interaction of the mixture with soluble arsenic compounds, which reinforce each other, or create conditions for the sequential implementation of the mechanisms. Ferrous sulfate provides the formation of insoluble arsenic compounds, while silicon compounds can only provide physical sorption of arsenic. However, the presence of ferrous sulfate and highly dispersed amorphous silica provide both ways to reduce the mobility and activity of arsenic. In addition, amorphous silica allows high concentrations to be obtained. Monosilicic acid in solution. Monosilicic acid, in turn, can increase the chemical sorption capacity of iron in relation to arsenic. Most likely, all of the above mechanisms work in the resulting systems.

Industrial applicability

The resulting product neutralizes soluble arsenic compounds by sorption, the formation of insoluble arsenic silicates. Thus, the toxic effect of arsenic on living organisms and the mobility (solubility) of arsenic in soils and grounds are reduced, which contributes to the production of environmentally safer products. The use of the product additionally contributes to the improvement of soil aeration and better development of the plant root system due to the high porosity of the components of the product and an increase in the water-holding capacity of the soil. Industrial applicability is further confirmed by examples 1 and 2.

Sources of information

1. Bradham KD, Diamond GL, Burgess M, Juhasz A, Klotzbach JM, Maddaloni M et al (2018) In vivo and in vitro methods for evaluating soil arsenic bioavailability: relevant to human health risk assessment. J Toxicol Env Heal B 21 (2): 83-114.

2. Kumar M, Ramanathan AL, Rahman MM, Naidu R (2016) Concentrations of inorganic arsenic in groundwater, agricultural soils and subsurface sediments from the middle Gangetic plain of Bihar, India. Sci Total Environ 573: 1103-1114.

3. Vodyanitsky, Yu.H. Chromium and arsenic in contaminated soils. Literature review Soil science. 2009. No. 5. - S. 551-559.

4. HAGER BROR About Fixation of arsenic in soil. US patent US 4723992 (1988-02-09).

5. LEI MING JIANG ZHANRU Stabilizing agent for arsenic and antimony heavy metal contaminated soil. Application of China CN 109570218 (2019-04-05).

6. WU CHUAN XUE SHENGGUO Arsenic-polluted soil passivator, preparation method and method for controlling arsenic-polluted soil. China application CN 107254313 (2017-10-17).

7. TAN WENFENG Cadmium-arsenic composite polluted soil remediation agent. Application of China CN 109575926 (2019-04-05).

8. ZHU HUIKE Arsenic passivator and application thereof. Application of China CN 108085016 (2018-05-29).

9. Matychenkov B.B. and others. SOIL CONDITIONER. RF patent №2122903 (10.12.1998).

10. METHOD FOR REMOVING ARSENIC USING STEEL PLANT SLAG AND SYSTEM THEREOF KR 101184933 (2012-09-28)

11. Kireicheva L.V. and others. COMPOSITION FOR DETOXIFICATION OF SOILS CONTAMINATED PREVIOUSLY WITH ARSENIC. RF patent No. 2471849 (10.01.2013).

12. List of materials produced by LLC "Eco-silicon" http://aerosil.su/ob-amorfnom-diokside-kxemniya.

13. Materials produced by JSC "Kuznetsk Ferroalloys"

https://www.dobavkabeton.ru/about

14. Ji, X., Liu, S., Huang, J., Bocharnikova, E., & Matichenkov, V. (2016). Monosilic acid potential in phytoremediation of the contaminated areas. Chemosphere, 157, 132-136.

Claims (4)

1. An agent for reducing the mobility of arsenic compounds in the soil, containing a composition of preparations of silicon and iron, characterized in that the preparation of silicon is amorphous silicon dioxide with a surface area of 30 m ² / g to 400 m ² / g, which is selected from the group, consisting of synthetic silicon, silicon obtained from industrial waste, where iron sulfate is used as an iron preparation, while the ratio of the preparation of iron and silicon in a weight ratio is from 1/10 to 1/30. 2. The agent according to claim 1, characterized in that the iron preparation is iron III sulfate. 3. The agent according to claim 1, characterized in that the synthetic amorphous silicon dioxide is selected from the group that includes fumed silica, finely ground quartz or other natural silicon dioxide with a SiO ₂ content _of at least 85%. 4. A tool according to claim 1, characterized in that amorphous silicon dioxide obtained from industrial waste is selected from the group consisting of ash, microsilica and other silicon-containing compounds with a SiO ₂ content _of at least 85%.