Arsenic passivator and preparation method and application thereof

Abstract

The invention provides an arsenic passivator and a preparation method and application thereof, and belongs to the technical field of soil purification, the preparation method of the arsenic passivator comprises the following steps: S1, recycling a used spontaneous heating patch, taking out contents, and grinding the contents into powder by using a ball milling process; s2, performing ultrasonic water washing on the powder obtained in the step S1 to remove salt and impurities; and S3, the material obtained after washing in the step S2 is dried and ground through a spheroidal graphite technology, and the arsenic passivator is obtained. The arsenic passivator prepared by the method provided by the invention has the advantages of simple preparation method, low preparation cost and good curing effect.

Description

Technical Field

[0001] The present invention relates to the technical field of soil purification, and in particular to an arsenic passivator and a preparation method and application thereof. Background Art

[0002] In nature, arsenic (As) exists mainly in the form of trivalent arsenic (As(III)) and pentavalent arsenic (As(V). Among them, As(III) is the most toxic and mobile form of arsenic and is often detected in flooded soils or sediments. In these soils, dissimilatory arsenic or iron-reducing microorganisms are extremely active and can directly promote the reduction of As(V) to As(III), resulting in a large increase in soluble As(III). Rice is the only food crop that requires intermittent flooding. Even in paddy soils that are not contaminated by arsenic, the bioavailability of arsenic is very low. The arsenic absorption and transport efficiency of rice is also very high. In addition, rice has a very high efficiency in arsenic absorption and transport, and rice grains often accumulate a large amount of arsenic, which is more than 10 times higher than other grains. Rice is the staple food of more than half of the world's population, and the rice food chain poses a major threat to human arsenic exposure. Therefore, reducing arsenic accumulation in rice is a key measure to alleviate human arsenic exposure. Fe-C material is an arsenic passivator that contains iron oxide and activated carbon. It can be used for the stabilization and remediation of soil arsenic pollution and effectively reduce the bioavailability of arsenic. However, at present, the production cost of arsenic passivators is relatively high and cannot be used in the field for a long time. Summary of the Invention

[0003] The problem to be solved by the present invention is how to reduce the production cost of the arsenic passivator.

[0004] In order to solve the above technical problems, the first aspect of the present invention provides a method for preparing an arsenic passivation agent using discarded self-heating patches, comprising the following steps: S1: Recycle the used self-heating patch, remove the contents and grind them into powder using a ball milling process; S2: ultrasonically washing the powder obtained in step S1 to remove salt and impurities; S3: Dry the material obtained after washing in step S2 and grind it using a spherical graphite process to obtain an arsenic passivator.

[0005] This method extracts an arsenic passivator from used self-heating stickers through grinding and water washing. The arsenic passivator contains an Fe-C material that can be used to adsorb As(III) in soil. This three-step method recycles discarded self-heating stickers, addressing the high cost of traditional passivator raw materials. A staged ball milling process controls the particle size, combined with ultrasonic water washing to effectively remove impurities, ultimately producing an arsenic passivator with a high specific surface area.

[0006] Preferably, in step S1, the specific conditions of the ball milling process are: the ball milling environment temperature is 5-40°C; the single ball milling time is 0.5h, and the ball milling is stopped and cooled for 5-10min after each 0.5h, and the cycle is 5-10 times; the grinding ball diameter is 10-20mm, the mesh size of the sieve is greater than or equal to 100 mesh, and the ball milling speed is 150-400rpm.

[0007] The present invention can prevent the material from overheating and agglomerating by low-temperature intermittent ball milling.

[0008] Preferably, in step S2, the ultrasonic washing method is: washing the powder 2 to 3 times with ultrapure water or distilled water under ultrasonic conditions, with each washing time being 10 to 40 minutes.

[0009] Preferably, the ultrasonic frequency is 20-40 kHz, and the ultrasonic power is 50-500 W.

[0010] Ultrasonic cleaning can remove impurities, salts, and other organic matter from the contents of the self-heating patch, improving the quality of the final arsenic passivator product and eliminating the risk of soil salinization caused by exogenous materials. At the same time, the 20-40kHz ultrasonic frequency is matched with a 100-500W power to create an optimal cavitation effect, ensuring the cleaning effect while avoiding damage to the three-dimensional structure of the iron-based material caused by excessive power.

[0011] Preferably, in step S3, the drying temperature is 40-60° C., and the drying time is 12-36 hours.

[0012] Preferably, in step S3, the specific conditions of the ball milling process are: the ball milling environment temperature is 5-40°C; the single ball milling time is 0.5h, and the ball milling is stopped and cooled for 5-10min after each 0.5h, and the cycle is repeated 5-10 times; the grinding ball diameter is 10-20mm, the mesh size of the sieve is greater than or equal to 100 mesh, and the ball milling speed is 150-400rpm.

[0013] The ball milling process in step S3 can increase the specific surface area of the material, expose more Fe-O active sites and cavities, and enhance the arsenic adsorption capacity of the final product.

[0014] Furthermore, the second aspect of the present invention provides an arsenic passivator, which is prepared by the preparation method described in the first aspect.

[0015] Preferably, the arsenic passivator comprises the following components in parts by mass: 35% to 45% iron (Fe), 5% to 15% carbon (C), 20% to 30% oxygen (O), and the remainder being unavoidable impurities or common soil minerals.

[0016] Furthermore, the third aspect of the present invention provides a use of the arsenic passivator described in the second aspect, wherein the arsenic passivator is used for arsenic fixation in paddy soil.

[0017] Preferably, the arsenic curing agent is used by mixing the arsenic curing agent and paddy soil in a mass ratio of (0.4-1):100, and then flooding the soil to complete the arsenic curing of the paddy soil.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The raw material source of the arsenic curing agent provided by the present invention is used and discarded self-heating stickers. The raw material source is wide and easy to obtain, and the raw material cost is low; 2. The preparation method of the arsenic curing agent provided by the present invention is simple, does not require complex equipment, and is easy to industrialize; 3. The arsenic solidifying agent provided by the present invention is suitable for the remediation of arsenic pollution in various soils, especially for the remediation of arsenic pollution in paddy soil, and has a short remediation cycle, making it suitable for long-term use in the field. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The SEM scanning image and EDS energy spectrum scanning result of the arsenic passivator prepared in Example 1 of the present invention are shown; Figure 2 The pH, soluble salt concentration, and total salt removal test results of the arsenic passivator prepared by the method of the present invention and the arsenic passivator prepared by ordinary water washing in Example 1 of the present invention are shown; Figure 3 The heavy metal content determination results of the arsenic passivator prepared by the method of the present invention and the arsenic passivator prepared by ordinary water washing in Example 1 of the present invention; Figure 4 This is a graph showing the experimental results of reducing soil arsenic effectiveness using different doses of arsenic passivators in Example 2 of the present invention; Figure 5 The three-dimensional fluorescence analysis results in Example 2 of the present invention; Figure 6 This is the detection result of soil iron and arsenic metabolism genes in Example 3 of the present invention; Figure 7 These are the results of the effect of the arsenic passivator in Example 4 of the present invention on the effectiveness of arsenic in rice fields and the accumulation of arsenic in rice. DETAILED DESCRIPTION

[0020] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only intended to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter ranges described in the present invention. Reasonable variations derived therefrom are still within the scope of protection of the claims of the present invention.

[0021] It should be noted that the endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0022] As described in the background, arsenic curing agents currently have high production costs, making them impractical for long-term field use. In light of this, the present invention provides a low-cost arsenic curing agent comprising the following components, calculated by weight: 35% to 45% iron (Fe), 5% to 15% carbon (C), 20% to 30% oxygen (O), with the remainder being unavoidable impurities.

[0023] More specifically, the preparation method of the aforementioned arsenic curing agent is: S1: Recycle the used self-heating patch, remove the contents and grind them into powder using a ball milling process; S2: ultrasonically washing the powder obtained in step S1 to remove salt and impurities; S3: Dry the material obtained after washing in step S2 and grind it using a spherical graphite process to obtain an arsenic passivator.

[0024] More specifically, in step S1 of the above embodiment, the specific conditions of the ball milling process are as follows: the ball milling environment temperature is 5-40°C; the single ball milling time is 0.5h, and the ball milling is stopped and cooled for 5-10min after each 0.5h, and the cycle is repeated 5-10 times; the grinding ball diameter is 10-20mm, the mesh size of the sieve is greater than or equal to 100 mesh, and the ball milling speed is 150-400rpm.

[0025] More specifically, in step S2 of the above embodiment, the ultrasonic water washing method is: using ultrapure water or distilled water to wash the powder 2 to 3 times under ultrasonic conditions, each washing time is 10 to 40 minutes, the ultrasonic frequency is 20 to 40 kHz, and the ultrasonic power is 50 to 500 W.

[0026] More specifically, in step S3 of the above embodiment, the drying temperature is 40~60°C, the drying time is 12~36h, and the specific conditions of the ball milling process are: the ball milling environment temperature is 5~40°C; the single ball milling time is 0.5h, and after each ball milling for 0.5h, it is stopped and cooled for 5~10min, and the cycle is repeated 5~10 times; the grinding ball diameter is 10~20mm, the mesh size of the sieve is greater than or equal to 100 mesh, and the ball milling speed is 150~400rpm.

[0027] The technical solutions of the present invention are further illustrated below by specific examples. Unless otherwise defined, all terms, symbols and other scientific terms used herein are intended to have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs. In some cases, terms with conventional understandings are defined herein for the purpose of illustrating or facilitating reference, and such definitions herein should not be construed as indicating significant differences from conventional understandings in the art. The technical methods described or cited herein are generally well understood by those skilled in the art and are adopted by conventional methods. Unless otherwise stated, the use of commercially available reagents and instruments is carried out in accordance with the protocols and parameters provided by the manufacturers.

[0028] Example 1 Preparation of arsenic curing agent S1: Recover the used self-heating patch. At 25°C, remove the contents of the used self-heating patch (10 kg). Place the waste in a grinding jar and grind the contents using a ball mill at 300 rpm for 0.5 h. Stop grinding for 5 minutes to prevent the ground material from overheating. Continue grinding for 0.5 h, and repeat this process for 3 hours.

[0029] S2: Add ultrapure water to the powder obtained in step S1, perform ultrasonic water washing in a 50W ultrasonicator for 20 minutes, and repeat the washing twice to remove salt and impurities; S3: The material obtained after washing in step S2 is dried in a blast drying oven at 55°C for 24 hours, the dried material is placed in a grinding jar, and ball milled at 300 rpm for 0.5 hours, the grinding is stopped for 5 minutes to prevent the temperature of the ground material from being too high, and the grinding is continued for 0.5 hours. The grinding is repeated for 3 hours, the ground powder is taken out, passed through a 100 mesh sieve, and the sieve is taken to obtain an arsenic passivation agent with an average particle size of 150 microns.

[0030] The arsenic passivator prepared in this embodiment was subjected to SEM scanning and EDS analysis, and the relevant results are as follows: Figure 1 As shown, Figure 1 a in the figure is the SEM scanning result. Figure 1 b in the table is the result of C content analysis. Figure 1 The analysis result of c is O, Figure 1 The d in the equation is the analysis result of Fe, which is given by Figure 1 The SEM results show that the arsenic passivator prepared in this embodiment has a smooth surface without grooves, a relatively uniform particle size, and is in a regular block shape. The EDS results show that the main materials of the arsenic passivator prepared in the present invention include Fe, C, and O. By mass, Fe accounts for 44.3%, C accounts for 10.8%, and O accounts for 27.5%.

[0031] The pH, soluble salt concentration, and total salt removal of the arsenic passivator prepared in this embodiment and the arsenic passivator prepared after water washing were measured respectively. The results are as follows: Figure 2 As shown by Figure 2 It can be seen that the indicators of arsenic passivator prepared by ultrasonic water washing are better than those prepared by ordinary water washing.

[0032] The heavy metal content of the arsenic passivator prepared in this embodiment and the arsenic passivator prepared after washing with water were measured respectively. The results are as follows: Figure 3 As shown by Figure 3 It can be seen that the contents of the self-heating patch itself contains a certain amount of heavy metal impurities. Ultrasonic water washing can greatly reduce the heavy metal content and effectively improve the performance of the final product.

[0033] Example 2 Arsenic passivation agent performance determination Topsoil (0-20 cm) from a typical paddy field was collected, placed in a cool, dry place, and stored dry for later use. Using flooded culture to simulate paddy field conditions, 1.0 kg of paddy field soil was divided into four equal portions and added to four 350 mL culture jars at a soil depth of 10 cm. The arsenic passivator described in Example 1 was added to the soil at concentrations of no addition, 0.1%, 0.4%, and 1%, and evenly mixed. During the culture process, the soil was flooded to a depth of 3 cm above the soil surface, and microcosm culture was performed at room temperature.

[0034] During the 40-day incubation period, soil pore water was collected regularly (at days 0, 8, 16, 24, 32, and 40) using a Rhizonsampler (0.1 µm sampling tip aperture). The pH and redox potential of the pore water were measured using a portable pH and redox potential meter. After testing, the pore water was acidified with 1 M hydrochloric acid for preservation. Free Fe, Mn, and As in the pore water were measured using ICP-MS. Dissolved organic carbon content was measured using a TOC analyzer. Changes in organic matter structure in the pore water were assessed using three-dimensional fluorescence spectroscopy and further analyzed using Fourier transform ion cyclotron resonance mass spectrometry.

[0035] The results are as follows Figure 4As shown, arsenic passivators at different ratios showed significant differences in the effectiveness of arsenic in paddy soil. Among them, when added at 1%, the arsenic effectiveness of paddy soil was the lowest and the effect was the best. When added at 0.4%, the effect was close to that of 1%. Arsenic passivators at different ratios had little effect on the dissolved Fe content, pH and Eh of flooded soil; but showed large differences in the effects on soluble Mn content and conductivity Ec. Although the soil arsenic effectiveness was lowest when added at 1%, it significantly increased the soluble Mn content and soil Ec value in the soil, and had a significant change in soil properties. Therefore, the arsenic passivator of the present invention was added to the soil at a ratio of 0.4%.

[0036] At the same time, adding arsenic passivator into the soil at 0.4% significantly reduced the soluble organic carbon in the soil by 25.6%. The three-dimensional fluorescence analysis showed that (such as Figure 5 ), artificial aeration tissue not only reduces the soluble organic carbon in the soil, but also changes the structure of soluble organic carbon.

[0037] Example 3 Effects of arsenic passivators on soil iron and arsenic metabolism genes Paddy soil incubated with 0.4% arsenic passivator added in Example 2 was collected, and total RNA in the soil sample was extracted. After extraction, it was immediately reverse transcribed into cDNA, and then the abundance of arsenic metabolism genes (arrA, arsC, aioA, Geobacteraceae) and iron reduction genes (Geobacteraceae) were tested using real-time fluorescence quantitative PCR.

[0038] The results are as follows Figure 6 As shown, the addition of an arsenic passivator significantly reduced the expression of the arsenic metabolism gene arsC, while having minimal effects on arsenic metabolism genes (arrA, aioA) and iron reduction genes (Geobacteraceae). This indicates that the arsenic passivator inhibited the activity of arsenic metabolism genes in the soil. Simultaneously, the expression of the soil iron reduction gene Geo was significantly increased. This suggests that the arsenic passivator provides abundant substrate for iron-reducing bacteria, thereby promoting heterotrophic iron reduction by soil iron-reducing microorganisms. Activated heterotrophic iron reduction competes with arsenic metabolism genes for soluble organic carbon, further reducing arsenic release from the soil.

[0039] Example 4 Effects of arsenic passivators on the availability of arsenic in rice fields and the accumulation of arsenic in rice The same paddy soil as in Example 2 was collected and set up a pot experiment with the addition of 0.4% arsenic passivator and a blank control. Widely planted rice varieties were transplanted. Soil pore water was collected using a Rhizon sampler (sampling head pore size: 0.1 μm) on the day of rice transplanting, 10 days, 20 days, 48 days, 64 days after rice transplanting, and on the day of harvest to test the arsenic content in the paddy soil pore water. The results are shown in Figure 2. Figure 7 As shown in Figure A, 10 days after rice transplanting, the arsenic content in the soil pore water was significantly lower than that in the control group without the addition of the arsenic passivator. This shows that the arsenic passivator provided by the present invention can effectively reduce the effectiveness of arsenic in rice fields.

[0040] In addition, after the rice matured, rice from the rice plant with 0.4% arsenic passivator added and the blank control group was collected to test the arsenic accumulation in the rice. Figure 7 As shown in Figure B, the arsenic content in the rice grains of the group with 0.4% arsenic passivator added was significantly lower than that of the blank control group. This shows that the arsenic passivator provided by the present invention can significantly reduce the accumulation of arsenic in rice in rice fields and effectively reduce the bioavailability of arsenic.

[0041] As can be seen from the above examples, the arsenic curing agent provided by the present invention is prepared using used self-heating patches as raw materials. Focusing on "waste treatment with waste", it has the three advantages of environmental protection, high efficiency, and low cost, providing a green and sustainable solution for the remediation of arsenic-contaminated soil. It is particularly suitable for the field of heavy metal treatment in agricultural soil and has significant social, environmental and economic benefits.

[0042] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for preparing an arsenic passivator, characterized in that: The following steps are involved: S1: Recycle the used self-heating patch, remove the contents and grind them into powder using a ball milling process; S2: ultrasonically washing the powder obtained in step S1 to remove salt and impurities; S3: Dry the material obtained after washing in step S2 and grind it using a spherical graphite process to obtain an arsenic passivator.

2. The method according to claim 1, wherein In step S1, the specific conditions of the ball milling process are as follows: the ball milling environment temperature is 5-40°C; the single ball milling time is 0.5h, and the ball milling is stopped and cooled for 5-10min after each 0.5h, and the cycle is repeated 5-10 times; the grinding ball diameter is 10-20mm, the mesh size of the sieve is greater than or equal to 100 mesh, and the ball milling speed is 150-400rpm.

3. The method according to claim 1, wherein In step S2, the ultrasonic washing method is: using ultrapure water or distilled water to wash the powder 2 to 3 times under ultrasonic conditions, with each washing time being 10 to 40 minutes.

4. The method according to claim 3, wherein The ultrasonic frequency is 20~40kHz and the ultrasonic power is 50~500W.

5. The method according to claim 1, wherein In step S3, the drying temperature is 40-60° C., and the drying time is 12-36 hours.

6. The method according to claim 1, wherein In step S3, the specific conditions of the ball milling process are as follows: the ball milling environment temperature is 5-40°C; the single ball milling time is 0.5h, and the ball milling is stopped and cooled for 5-10min after each 0.5h, and the cycle is repeated 5-10 times; the grinding ball diameter is 10-20mm, the mesh size of the sieve is greater than or equal to 100 mesh, and the ball milling speed is 150-400rpm.

7. An arsenic passivator, characterized in that The method is prepared by any one of claims 1 to 6.

8. The arsenic passivating agent according to claim 7, wherein The arsenic passivator includes the following components by mass: 35% to 45% iron, 5% to 15% carbon, 20% to 30% oxygen, and the remainder is inevitable impurities.

9. Use of the arsenic passivator according to claim 7 or 8, characterized in that: The arsenic passivator is used for arsenic fixation in paddy soil.

10. The use according to claim 9, characterized in that The method of using the arsenic solidifier is: mix the arsenic solidifier and paddy soil in a mass ratio of (0.4~1):100, and then flood the soil with water to complete the arsenic solidification of the paddy soil.

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