RU2722697C1 - Agent for reducing arsenic mobility in soil - Google Patents

Abstract

FIELD: agriculture.SUBSTANCE: invention relates to the agriculture. Agent for reducing mobility and solubility of arsenic compounds in soil contains a composition of silicon and iron preparations, wherein the 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 natural silicon dioxide, synthetic silicon dioxide, silicon obtained from waste industry, where iron is used as iron (III) oxide, wherein ratio of iron and silicon in weight ratio is from 1/10 to 1/30.EFFECT: invention reduces arsenic toxicity to living organisms and arsenic mobility (solubility) in soils and grounds.4 cl, 2 tbl, 2 ex

Description

Technical field

The invention relates to the field of environmental protection and can be used for the restoration of lands contaminated with arsenic and other inorganic pollutants.

State of the art

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

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

Known compositions, which include iron salts, namely iron oxide. A well-known Chinese patent No. CN105733588 (2019-04-26), where a material based on nano-alpha-Fe ₂ O ₃ , which is immobilized in bio-carbon by means of oxygen-free high-temperature carbonization, is used for soil cleaning. The synthesized iron-based biocarbon material is uniformly mixed with the soil in a certain proportion and after a while a fixed proportion of arsenic in the water-soluble state and arsenic in the effective state in the arsenic-contaminated soil reaches 59.6% and 66.2%, respectively [4].

Known compositions, which include silicon dioxide. An air conditioner for the restoration of contaminated soils based on amorphous silicon dioxide is described in RF patent No. RU2122903 (12/10/1998). As a mineral component, a mixture of two or more solid silicon-containing substances with a Si content of 5-45%, at least one of these substances, the consumption of which is 50-10000 kg per 1 ha, is in non-crystalline form with particles not exceeding 1 mm in size, and other substances with a total consumption of 100-20000 kg per 1 ha are in non-crystalline or crystalline form with particles not exceeding 5 cm in size. Environmentally friendly solid silicon-containing wastes can be used as solid silicon-containing substances. industry and agriculture in the form of ash, slag, dust, etc., chemically pure silicon-containing compounds, for example amorphous silicon dioxide, silica sand, calcium silicate, magnesium silicate, etc., as well as ground silicon-containing rocks, for example: sand, sandstone, zeolite, tuff [5].

Compositions are known which comprise both silicon compounds and iron compounds. Chinese patent application CN 105199737 (2015-12-30) describes a soil conditioner used for treating contaminants with heavy metals and arsenic. The proposed conditioner is a mixture of calcium containing compounds (lime, dolomite), magnesium containing compounds (talc, sepionite), silicon containing compounds (sand, wallostonite, bentonite) and iron compounds (iron ore, feldspar, albite). The prepared mixture is subjected to heat treatment (from 1150 to 1250 ° C) and after cooling it is milled. [6]. The resulting conditioner is expensive due to the use of high heat and fine grinding.

Closest to the claimed composition is the application for the invention of China No. CN 107377600 (2017-11-24), which relates to an air conditioner used to restore soil contaminated with a mixture of cadmium-arsenic, and the method of its application. The composition of the air conditioner consists of 30-50 parts of hydroxyapatite, 10-30 parts of zeolite and 25-55 parts of modified carbonized straw. Hydroxyapatite contains calcium (22-27%) phosphorus (9-12%), the zeolite contains 62-70% SiO ₂ , 13-17% Ai ₂ O ₃ , 1-2% Fe ₂ O ₃ , 3.5-6% CaO and 1-3% Na ₂ O. Thus, iron and silicon are in the same compound — zeolite, and not a mixture of cuttings and iron-containing compounds [7]. The disadvantage of the air conditioner is also the low content of silicon (about 7% SiO ₂ ) and iron (about 0.2% Fe ₂ O ₃ ) of the volume of the product, which reduces its effectiveness with respect to arsenic.

The objective of the invention is the creation of an effective and safe composition of the means for soil remediation, stimulating growth and improving the vital activity of plants.

The problem is solved due to the fact that the composition of the means for soil remediation contains silicon containing material and iron oxide. Amorphous silicon dioxide is used as the silicon-containing material. The composition of the soil conditioner is carried out in the following ratio of iron and silicon components: from 1/10 to 1/30.

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

SUMMARY OF THE INVENTION

The subject of the present invention is a means for reducing the mobility and solubility of arsenic compounds in soil containing a composition of silicon and iron preparations. In this case, the silicon preparation is amorphous silicon dioxide with a surface area of 30 m ² / g to 400 m ² / g, which may be synthetic silicon dioxide, silicon-containing waste in the form of ash, microsilicon with a silicon dioxide content of at least 85% and ground natural silicon dioxide (quartz sand, tuff, diatomite) with a SiCO ₂ content _of at least 85%, where the iron preparation is a natural or synthetic iron (III) oxide, while the ratio of the iron and silicon preparation in a weight ratio is from 1 / 10 to 1/30.

Description of the invention

When studying the effective composition of the composition to reduce the mobility and solubility of arsenic compounds in the soil, it was found that the use of a composition consisting of amorphous silicon dioxide with a surface area of 30 m ² / g and an iron preparation can significantly reduce the mobility and solubility of arsenic compounds in the soil.

Amorphous (non-crystalline) silicon dioxide with a high specific surface almost never occurs in nature in its pure form. It can only be obtained in a technological way. Several grades of amorphous silica are known. One preparation is sold under the KOVELOS trademark and is a very light micronized (particle size depending on the brand from 6 to 40 microns) white powder without taste and odor with a nanoporous particle structure, with pronounced sorption properties. Its specific surface area is 350-400 m ² / g [8]. Another drug under the brand name MICROSILICA is produced by Kuznetsk Ferroalloys OJSC [9].

Due to the large specific surface area of amorphous silicon dioxide, more binding sites for arsenic are provided compared to traditional materials, thus significantly improving the removal efficiency of arsenic contaminants.

As amorphous silicon dioxide, natural silicon (tuffs, diatomites), synthetic silicon (fumed silica), and industrial wastes (ash, microsilica) can be used. The high surface area of silicon compounds provides high solubility with respect to silicon, which ensures their high chemical activity [10].

As an iron preparation, iron oxide was used. 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 agent allows for the maximum efficiency of arsenic deactivation due to the synergistic effect of reducing its mobility. Since the components of the agent do not show toxic effects in relation to microorganisms, their use does not lead to a decrease in the activity of microorganisms and a decrease in the efficiency of reclamation. A method of increasing the mobility and solubility of arsenic compounds in the soil involves adding funds to the surface of the selected soil site in doses of 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-iron mixture, a number of incubation, vegetation, and laboratory experiments were carried out using the following silicon-containing compounds: microsilicon 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 a source of iron, a soluble salt of iron oxide (Fe ₂ O ₃ ) was used as a source of iron. The following mixtures were made:

1) Microsilica: iron oxide in a ratio of 10: 1,

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

3) Silicon dioxide (30 m ² / g): iron oxide in a ratio of 30: 1,

4) Silicon dioxide (300 m ² / g): iron oxide in a ratio of 30: 1,

All initial preparations and mixtures were ground to a particle size of 0.1 mm.

Example 1

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

The use of iron oxide reduces the content of arsenic in plant roots by 48.4%, in the green mass of plants - by 41.8%. The iron preparation also reduced the mobility of arsenic in the soil by 30.8% for 0.1 n HCl extract and 43.7%) for 2 n HNO ₃ extract. The use of only silicon preparations also leads to a decrease in arsenic activity in the soil-plant system. However, the most significant decrease 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 arsenic content in the roots of plants decreased by 65.8-87.4%, its content in the leaves of barley decreased to 94.9-97.3%). The mobility of arsenic in the soil was reduced by 68.4-90.4%).

Example 2

The second experiment was carried out using the same mixtures of iron oxide and silicon compounds. 1 g of iron oxide and the corresponding amounts of mixtures or silicon compounds were added to 250 ml plastic flasks. 1 g of salt (NaCl) was also added to ensure the same ionic strength. Then, 200 ml of distilled water was poured into the flasks, and using a 0.1 N HCl solution or 0.1 N NaOH solution, the pH of the solutions was adjusted to 7.0 ± 0.1. After that, 10 ml of concentrated AsNaO ₂ solution (400 mmol) was added to each flask. The flasks were shaken in a biscuit 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 arsenic concentration was determined using ICP-MSI Cap-Q (USA). The experiment was performed in 4 replicates. The results obtained are shown in table 2.

Iron oxide reduced the concentration of arsenic in solution by 2 times. The presence of slag had a minimal effect on arsenic concentration. Amorphous silica 300 m ² / g reduced the concentration as well as iron oxide. The proposed mixtures had maximum sorption properties with respect to arsenic. The presence of both components (silicon and glandular) has a synergistic effect, which can 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 compounds of arsenic, which reinforce each other, or create conditions for the consistent implementation of the mechanisms. Iron oxide provides chemical sorption of arsenic, while silicon compounds can only provide physical sorption of arsenic. However, the presence of iron oxide and amorphous silica with a high degree of dispersion provide both types of adsorption of arsenic. In addition, amorphous silica provides a high concentration. Monosilicic acid in solution. Monosilicic acid, in turn, can increase the chemical sorption ability of iron in relation to arsenic. Most likely, all of the above mechanisms work in the resulting systems.

Industrial applicability

The resulting tool neutralizes the soluble compounds of arsenic by sorption, the formation of insoluble silicates of arsenic. Thus, the toxic effects of arsenic on living organisms and the mobility (solubility) of arsenic in soils and soils are reduced, which contributes to the production of environmentally safer products. The use of the agent additionally contributes to the improvement of soil aeration and the better development of the root system of the plant due to the high porosity of the components of the agent and to the increase of 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. YANG ZHIHUI, CHAI LIYUAN Iron-based biochar material as well as preparation and application thereof. China Application CN 105733588 (2019-04-26)

5. Matychenkov B.B. and others. SOIL CONDITIONER. RF patent №2122903 (12/10/1998).

6. LEI ZHIGANG, LEI XINGYU Soil conditioner used for treating heavy metal pollution. China Application CN 105199737 (2015-12-30).

7. LIAO BAIHAN, ZHOU HANG Efficient conditioner used for restoring cadmium-arsenic composite polluted soil and application method of efficient conditioner. China Application CN 107377600 (2017-11-24).

8. The list of materials produced by Ecokremniy LLC http://aerosil.su/ob-amorfhom-diokside-kremniya.

9. Materials produced by Kuznetsk Ferroalloys OJSC https://www.dobavkabeton.ru/about.

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

Claims (4)

1. A tool to reduce the mobility and solubility of arsenic compounds in the soil, containing a composition of silicon and iron preparations, characterized in that the silicon preparation is an amorphous silicon dioxide with a surface area of from 30 m ² / g to 400 m ² / g, which is selected from a group consisting of natural silicon dioxide, synthetic silicon dioxide, silicon obtained from industrial wastes, where iron (III) oxide is used as an iron preparation, while the ratio of the iron and silicon preparation in a weight ratio is from 1/10 to 1/30 . 2. The tool according to p. 1, characterized in that the synthetic amorphous silicon dioxide is fumed silica with a SiO ₂ content _of at least 85%. 3. The tool according to p. 1, characterized in that natural amorphous silicon dioxide is part of tuffs, diatomite, finely ground quartz with a SiO ₂ content _of at least 85%. 4. The tool according to claim 1, characterized in that the amorphous silicon dioxide obtained from industrial wastes is selected from the group consisting of ash, microsilica with a content of SiO _{2 of} at least 85%.