Contaminated soil remediation agent and preparation method thereof

Abstract

The invention discloses a contaminated soil remediation agent and a preparation method thereof, and belongs to the technical field of soil remediation, the preparation method comprises the following steps: S1, steel casting residues are crushed and sieved; s2, adding an acid solution into the steel slag raw material, and acidizing; s3, mixing the acidified steel slag with a sodium bicarbonate solution, and stirring; and S4, uniformly mixing the treated steel slag with a silicate curing agent and a persulfuric acid oxidizing agent in proportion to obtain the contaminated soil remediation agent. According to the remediation agent for the contaminated soil, the remediation agent is prepared from the steel casting residues, and the heavy metal arsenic and the organic pollutant phenol can be effectively and synchronously removed. The repairing agent not only can effectively fix heavy metal arsenic in soil and promote advanced oxygenolysis of phenol, but also realizes resource utilization of the steel casting residues, improves the resource utilization efficiency of solid waste treatment and promotes sustainable development of the ecological environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil remediation, and in particular, relates to a contaminated soil remediation agent and a preparation method thereof. Background Art

[0002] Pesticide chemical and other enterprises often produce heavy metals and organic pollutants, especially arsenic and phenol, during the production process. Heavy metal arsenic is easily enriched in the soil surface and enters the food chain through crops (such as vegetables and grains), thus posing a serious threat to the ecological environment and human health. Phenol, as a common industrial intermediate, is highly toxic and can penetrate into the soil through water bodies. Long-term retention leads to ecological imbalance, inhibits biological activity, and hinders crop growth. Therefore, the effective removal of arsenic and phenol in the soil has become a key task to achieve ecological sustainable development.

[0003] Solidification and stabilization technology combines contaminated soil with specific binders to reduce the mobility of heavy metals, and is widely regarded as one of the best technologies for treating toxic and hazardous wastes. Chemical oxidation technology, on the other hand, adds oxidants to contaminated soil to cause pollutants to undergo oxidation reactions and convert them into non-toxic or low-toxic substances. It is widely used in the removal of organic pollutants due to its advantages such as fast processing speed, high efficiency, and environmental friendliness. Existing soil remediation agents require the mixture to be activated, such as low-temperature plasma irradiation treatment, to achieve uniform mixing of the remediation agent; in addition, traditional raw material processing methods (such as Chinese patent CN110125159A) require the raw materials to be cracked and treated at high temperatures, which is energy-intensive and the subsequent processing of the cracking products is complicated, and the emission of gases and pollutants needs to be controlled.

[0004] Solid waste comprehensive utilization technology aims to recover the effective components in solid waste. Although solid waste is considered to be the main source of environmental pollution and occupies a large amount of land, the resources contained in it can be recovered through slag recycling technology, which has significant economic and social value. However, there are few existing technologies that reuse solid waste in soil remediation technology. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a contaminated soil remediation agent and a preparation method thereof. The present invention uses dicalcium ferrite and calcium ferrite in steelmaking slag for soil remediation for the first time, providing a simple technical path for simultaneous removal of heavy metal arsenic and organic pollutant phenol at room temperature. This method is not only of great significance in the resource utilization of industrial solid waste, but also shows broad application prospects in the field of soil remediation.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a contaminated soil remediation agent comprises the following steps:

[0008] S1, crushing and sieving the steelmaking slag to obtain steel slag raw materials;

[0009] S2, adding acid solution to the steel slag raw material, soaking it for a period of time, then draining the soaking liquid, and continuously washing it with water until the pH value of the washing liquid is neutral, thereby obtaining acidified steel slag;

[0010] S3, mixing the acidified steel slag with the sodium bicarbonate solution, stirring for 2-3 hours, filtering, drying and crushing the filter cake to obtain the treated steel slag;

[0011] S4. The treated steel slag is mixed evenly with a silicate curing agent and a persulfate oxidizing agent in a certain proportion to obtain a contaminated soil remediation agent.

[0012] Furthermore, the steelmaking slag contains dicalcium ferrite, calcium ferrite and manganese dioxide.

[0013] Furthermore, the crushing treatment in step S1 is: ball milling and granulation at 20-30° C., zirconium oxide balls and water are selected as grinding media, wet ball milling is performed, the rotation speed is 100-200 rpm, and the ball milling time is 10-48 hours.

[0014] Furthermore, the sieving in step S1 is through a 200-mesh sieve.

[0015] Furthermore, the soaking time in step S2 is 20-24 hours; the acid solution is a hydrochloric acid solution or a sulfuric acid solution, and the pH value of the acid solution is 2.

[0016] Furthermore, the concentration of the sodium bicarbonate solution in step S3 is 0.8-1 mol / L; the solid-liquid ratio of the mixture of the acidified slag and the sodium bicarbonate solution is 1 g:10-15 mL.

[0017] Furthermore, the silicate curing agent is a compound of one or more of potassium silicate, sodium silicate, lithium silicate and sodium fluorosilicate in any proportion.

[0018] Furthermore, the persulfate oxidant is a compound of one or more of ammonium persulfate, sodium persulfate, and potassium persulfate in any proportion.

[0019] Furthermore, the mass ratio of the treated steel slag, silicate curing agent and persulfate oxidizing agent is 10-20:3-5:1-4.

[0020] After the steel slag raw material is acidified with acid solution, impurity ions that are easily soluble and harmful to the soil, such as Fe, Mn, Al, etc., can be removed to a certain extent in the gaps and surface of the steel slag; in addition, the acidification treatment can increase the porosity of the steel slag to a certain extent, increase the contact opportunity between the repair agent and the pollutants in the soil, and improve the soil treatment efficiency; in addition, the increased porosity of the steel slag can also provide more sites for the subsequent attachment of sodium bicarbonate, thereby improving the subsequent treatment effect of sodium bicarbonate;

[0021] Further treatment with sodium bicarbonate can reduce the content of free alkaline oxides in steel slag. Therefore, when the treated steel slag is added to contaminated soil, the possibility of an immediate and substantial increase in pH can be avoided, providing weakly alkaline to near-neutral pH conditions for the formation of ferrous arsenate from ferrous iron and arsenic elements. In addition, sodium bicarbonate treatment of steel slag does not destroy the dicalcium ferrite, calcium ferrite and manganese dioxide in the steel slag itself. Its hydrolysis process can produce a gel substance with good adsorption properties for heavy metals, while slowly releasing calcium hydroxide to stabilize soil pH.

[0022] The treated steel slag in the present invention contains elements such as calcium (Ca), manganese (Mn) and iron (Fe). After being mixed with a silicate curing agent and a persulfate oxidant, the arsenic ions can be reduced and cured at the same time, and the advanced oxidation degradation of phenol can be promoted by activating persulfate. The simultaneous curing and stabilization of heavy metals and organic pollutants and chemical oxidation remediation can be achieved, and the method is particularly suitable for the treatment of soil pollution in pesticide production enterprises.

[0023] The method for repairing soil using the above contaminated soil repair agent is as follows:

[0024] Spread the soil remediation agent evenly on the contaminated soil, solidify and oxidize it simultaneously, and test the remediation effect after 3-5 days of maintenance.

[0025] Beneficial effects of the present invention:

[0026] The present invention provides a soil contaminated repair agent, which can effectively achieve the simultaneous removal of heavy metal arsenic and organic pollutant phenol by using steelmaking slag to prepare the repair agent. The repair agent can not only effectively fix the heavy metal arsenic in the soil and promote the advanced oxidation decomposition of phenol, but also realize the resource utilization of steelmaking slag, improve the resource utilization efficiency of solid waste treatment, and promote the sustainable development of the ecological environment. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Example 1

[0029] Prepare the contaminated soil remediation agent according to the following steps:

[0030] S1, the cast steel slag was ball-milled and granulated at 20°C, zirconia balls and water were selected as grinding media, wet ball-milled, the speed was 100 rpm, the ball-milling time was 48 hours, and passed through a 200-mesh sieve to obtain steel slag raw material;

[0031] S2. Add hydrochloric acid solution (pH value is 2) to the steel slag raw material, soak for 20 hours, then drain the soaking liquid, and rinse with water continuously until the pH value of the washing liquid is neutral to obtain acidified steel slag;

[0032] S3, then the acidified steel slag and sodium bicarbonate solution (concentration of 0.8 mol / L) according to the solid-liquid ratio of 1g: 15mL mixed, stirred for 2h, filtered, the filter cake was dried and crushed to obtain the treated steel slag;

[0033] S4. Evenly mix the treated steel slag with potassium silicate and ammonium persulfate in a mass ratio of 10:3:1 to obtain a contaminated soil remediation agent.

[0034] Example 2

[0035] Prepare the contaminated soil remediation agent according to the following steps:

[0036] S1. The steel slag is ball-milled and granulated at 25°C, zirconia balls and water are selected as grinding media, and wet ball milling is performed at a speed of 150 rpm for 28 hours, and the slag is passed through a 200-mesh sieve to obtain a steel slag raw material;

[0037] S2. Add sulfuric acid solution (pH value is 2) to the steel slag raw material, soak for 22 hours, then drain the soaking liquid, and rinse with water continuously until the pH value of the washing liquid is neutral to obtain acidified steel slag;

[0038] S3, then the acidified steel slag and sodium bicarbonate solution (concentration of 0.9 mol / L) according to the solid-liquid ratio of 1g: 12mL mixed, stirred for 2.5h, filtered, the filter cake was dried and crushed to obtain the treated steel slag;

[0039] S4. Evenly mix the treated steel slag with sodium silicate and sodium persulfate in a mass ratio of 15:4:2 to obtain a contaminated soil remediation agent.

[0040] Example 3

[0041] Prepare the contaminated soil remediation agent according to the following steps:

[0042] S1, the cast steel slag was ball-milled and granulated at 30°C, zirconia balls and water were selected as grinding media, wet ball-milled, the speed was 200 rpm, the ball-milling time was 10 hours, and the slag was passed through a 200-mesh sieve to obtain a steel slag raw material;

[0043] S2. Add hydrochloric acid solution (pH value is 2) to the steel slag raw material, soak for 24 hours, then drain the soaking liquid, and rinse with water continuously until the pH value of the washing liquid is neutral to obtain acidified steel slag;

[0044] S3, then the acidified steel slag and sodium bicarbonate solution (concentration of 1 mol / L) according to the solid-liquid ratio of 1g: 10mL mixed, stirred for 3h, filtered, the filter cake was dried and crushed to obtain the treated steel slag;

[0045] S4. Evenly mix the treated steel slag with lithium silicate and potassium persulfate in a mass ratio of 20:5:4 to obtain a contaminated soil remediation agent.

[0046] Comparative Example 1

[0047] Prepare the contaminated soil remediation agent according to the following steps:

[0048] S1, the cast steel slag was ball-milled and granulated at 20°C, zirconia balls and water were selected as grinding media, wet ball-milled, the speed was 100 rpm, the ball-milling time was 48 hours, and passed through a 200-mesh sieve to obtain steel slag raw material;

[0049] S2. Evenly mix the steel slag raw material with potassium silicate and ammonium persulfate in a mass ratio of 10:3:1 to obtain a contaminated soil remediation agent.

[0050] Comparative Example 2

[0051] Preparation of soil remediation agent:

[0052] Potassium silicate and ammonium persulfate were uniformly mixed in a mass ratio of 3:1 to obtain a soil remediation agent.

[0053] The soil remediation agents obtained in Examples 1-3 and Comparative Examples 1-2 were used to remediate the soil:

[0054] The contaminated soil and soil remediation agent were prepared in a mass ratio of 5:1. The soil remediation agent was evenly spread on the contaminated soil, and the arsenic was solidified and the organic pollutants were oxidized twice simultaneously. The soil was cured for 5 days, and then the remediation effect was tested. The specific testing method is as follows:

[0055] 1) Take a certain amount of dried and sieved soil sample, add deionized water at a solid-liquid ratio of 1:10, place the mixture in an oscillator, and oscillate at 150-200 rpm for 18-24 hours at room temperature. After the oscillation is completed, filter the extract with filter paper to obtain a clear water extract for testing.

[0056] 2) The filtered water extract is introduced into a high temperature plasma mass spectrometer, where the arsenic element in the sample is ionized to form arsenic ions, which are then separated and detected according to the mass-to-charge ratio.

[0057] 3) Based on the signal intensity detected by the instrument, the arsenic concentration in the sample is calculated using a standard curve or the instrument automatically. The concentration of water-leached arsenic in the soil is calculated in mg / L based on the volume of the extract and the mass of the soil.

[0058] 4) Take representative soil samples from the target area, dry them in the shade and pass them through a 2mm sieve to ensure uniform soil particles.

[0059] 5) Weigh 10-20 g of the sieved dry soil sample, put it into an extraction bottle, add methanol as the extraction solvent, shake at a speed of 150-200 rpm for 30-60 minutes, and centrifuge after the extraction to obtain a phenol extract.

[0060] 6) After filtering the extract, inject it into a high performance liquid chromatograph, use a C18 reverse phase chromatographic column, separate phenol with an appropriate mobile phase, detect it under ultraviolet wavelength, and calculate the content of phenol.

[0061] The results are shown in Table 1 below:

[0062] Table 1

[0063]

[0064] The groundwater quality meets the Class IV water quality standard in the Groundwater Environmental Standard (GB 14848-2017). According to the present invention, the set soil flooding index should reach Class IV of the Surface Water Environmental Quality Standard (GB 3838-2002), that is, the arsenic content is less than 0.1 mg / L.

[0065] It can be seen from the data in Table 1 above that the soil waterlogging index after restoration by the soil restoration agent obtained by the present invention reaches Class IV of the "Surface Water Environmental Quality Standard" (GB 3838-2002); and it has a better effect on the removal of phenol in the soil; combined with the data of Comparative Example 1, it can be seen that after pre-treatment, the steel slag can effectively improve the restoration and treatment ability of the soil; combined with the data of Comparative Example 2, it can be seen that the steel slag itself has certain advantages for soil restoration.

[0066] The above specific implementation method part specifically introduces the analytical method involved in the present invention. It should be noted that the above introduction is only to help those skilled in the art better understand the method and ideas of the present invention, rather than limiting the relevant content. Without departing from the principle of the present invention, those skilled in the art may also make appropriate adjustments or modifications to the present invention, and the above adjustments and modifications shall also fall within the scope of protection of the present invention.

Claims

1. A method for preparing a contaminated soil remediation agent, characterized in that: The following steps are involved: S1, crushing and sieving the steelmaking slag to obtain steel slag raw material; S2, adding acid solution to the steel slag raw material, soaking it for a period of time, then draining the soaking liquid, and continuously washing it with water until the pH value of the washing liquid is neutral, thereby obtaining acidified steel slag; S3, mixing the acidified steel slag with the sodium bicarbonate solution, stirring for 2-3 hours, filtering, drying and crushing the filter cake to obtain the treated steel slag; S4. The treated steel slag is mixed evenly with a silicate curing agent and a persulfate oxidizing agent in a certain proportion to obtain a contaminated soil remediation agent.

2. The method for preparing a contaminated soil remediation agent according to claim 1, characterized in that: The crushing treatment in step S1 is: ball milling and granulation at 20-30° C., zirconium oxide balls and water are selected as grinding media, wet ball milling is performed, the rotation speed is 100-200 rpm, and the ball milling time is 10-48 hours.

3. The method for preparing a contaminated soil remediation agent according to claim 1, characterized in that: The sieving in step S1 is through a 200-mesh sieve.

4. The method for preparing a contaminated soil remediation agent according to claim 1, characterized in that: The soaking time in step S2 is 20-24 hours; the acid solution is a hydrochloric acid solution or a sulfuric acid solution, and the pH value of the acid solution is 2.

5. The method for preparing a contaminated soil remediation agent according to claim 1, characterized in that: The concentration of the sodium bicarbonate solution in step S3 is 0.8-1 mol / L; the solid-liquid ratio of the mixture of the acidified slag and the sodium bicarbonate solution is 1 g:10-15 mL.

6. The method for preparing a contaminated soil remediation agent according to claim 1, characterized in that: The silicate curing agent is a compound of one or more of potassium silicate, sodium silicate, lithium silicate and sodium fluorosilicate in any proportion.

7. The method for preparing a contaminated soil remediation agent according to claim 1, characterized in that: The persulfate oxidant is a compound of one or more of ammonium persulfate, sodium persulfate and potassium persulfate in any proportion.

8. The method for preparing a contaminated soil remediation agent according to claim 1, characterized in that: The mass ratio of the treated steel slag, silicate curing agent and persulfate oxidizing agent is 10-20:3-5:1-4.

9. A contaminated soil remediation agent, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 8.

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