A remediation agent for high lead-contaminated soil and a method of use

Abstract

The application discloses a kind of repair reagent suitable for shooting field high lead pollution soil and use method, the repair reagent is as follows: modified bone meal 1-3 parts, soluble phosphate 0.2-1 part, low molecular organic acid 2-5 parts and humus 1-6 parts.The repair reagent of the application can be repaired to high lead soil, and Pb ion is converted into ore type compound by complexation, adsorption, precipitation and ion exchange, and the stability of Pb ion is well maintained, using the principle that ion mineralization stabilizing agent can quickly occur mineralization reaction with Pb ion, so that the processing reaction and curing time are greatly shortened, the processing capacity of contaminated soil per unit time is improved, when it is applied, equipment is simple, investment is less, cost is low, economic benefit is high, and secondary pollution is not caused in processing process.

Description

Technical Field

[0001] This invention belongs to the field of soil environmental pollution remediation technology, specifically relating to a remediation agent for soil with high lead content and its application method. Background Technology

[0002] Shooting ranges are among the primary sites where humans release lead (Pb) into the environment. Heavy metal pollutants in the soil of shooting ranges include lead, antimony, arsenic, copper, and zinc, originating from bullets and fragments, with Pb being the primary component. Approximately 97% of the heavy metals in the soil of shooting ranges are lead. Discarded bullets accumulate in the soil of target mounds, and after weathering, release their heavy metals into the soil, posing a potential risk to personnel at the shooting range and the surrounding ecosystem. According to reports from the United States, more than 70,000 tons of lead are used annually in ammunition manufacturing, most of which ultimately ends up in shooting ranges and accumulates in the soil there.

[0003] Remediation methods for lead contamination in soil include leaching, solidification / stabilization, electrochemical methods, phytoremediation, and microbial remediation. Among these, solidification / stabilization is a commonly used technique. This technique mainly utilizes materials to passivate lead in the soil, thereby reducing its bioavailability and toxicity. It has advantages such as low cost and rapid effectiveness.

[0004] Commonly used solidification / stabilization materials include lime, calcium carbonate, phosphorus-containing compounds, and organic substances that promote reduction. Among these remediation materials, phosphorus-containing materials have a very significant effect on the remediation of heavy metals and can significantly reduce the bioavailability of heavy metals in the soil by changing soil pH and chemical reaction conditions, thereby reducing their accumulation in plants. In domestic and international lead (Pb) contaminated soil remediation practices, phosphorus-containing materials have received widespread attention from scholars both at home and abroad due to their low cost, simple construction, and good remediation effect.

[0005] Currently, commonly used phosphorus-containing materials include soluble phosphorus-containing materials, phosphorus-containing fertilizers, hydroxyapatite, and phosphate rock. However, they have drawbacks such as low adsorption capacity and poor long-term remediation effect. In order to address the shortcomings of the above-mentioned phosphorus-containing materials in the process of Pb remediation, this invention develops a composite remediation material, which has a larger specific surface area and higher surface activity. It has the advantages of good stability, low cost, cleanliness and no pollution, and high practical application value, and can be directly applied in actual site remediation. Summary of the Invention

[0006] The technical problem to be solved by this invention is: given the high concentration of heavy metal Pb in the soil of shooting ranges and the alkalinity of the soil, in order to reduce the environmental risks it poses to the surrounding soil and groundwater, and to overcome the shortcomings of commonly used phosphorus-containing materials, such as low adsorption capacity and poor long-term remediation effect.

[0007] In a first aspect, the present invention provides a remediation agent suitable for lead-contaminated soil at shooting ranges, the remediation agent comprising the following components in parts by weight: 1-3 parts modified bone meal, 0.2-1 parts soluble phosphate, 2-5 parts low molecular weight organic acid, and 1-6 parts humic matter; wherein the modified bone meal is obtained by reacting animal bone meal at 300-400°C under a nitrogen atmosphere for 2-4 hours; and the molecular weight of the low molecular weight organic acid is not greater than 200.

[0008] Preferably, the animal bone meal is any one or a mixture of two or more of fish bone meal, pork bone meal, or beef bone meal.

[0009] Preferably, the modified bone powder has a specific surface area > 1.85 m² / g, and the mass content of hydroxyapatite in the modified bone powder is greater than 70%.

[0010] Preferably, the particle size of the modified bone powder is 20–50 μm.

[0011] Preferably, the soluble phosphate is any one or a mixture of two or more of potassium phosphate, potassium dihydrogen phosphate, and diammonium hydrogen phosphate.

[0012] Preferably, the low-molecular-weight organic acid is any one or a mixture of two or more of oxalic acid, citric acid, malic acid, etc.

[0013] Preferably, the humus is prepared by mixing 1-3 parts by weight of organic waste with 0.5-2 parts by weight of mushroom residue, 0.1-0.5 parts by weight of molasses and 0.5-1 parts by weight of soybean meal and stirring evenly; the organic waste is any one or a mixture of two or more of livestock and poultry manure, urban sludge or kitchen waste, and the particle size of the organic waste is ≤5mm; the particle size of the mushroom residue and soybean meal is ≤1cm.

[0014] Furthermore, the particle size of both the bacterial bran and soybean meal is 3mm to 5mm.

[0015] Secondly, the present invention provides a method for using the remediation agent described in the first aspect for the remediation of lead-containing soil: the phosphorus remediation agent is mixed and stirred with the soil to be remediated for remediation; the molar mass ratio of phosphorus in the remediation agent to lead in the soil to be remediated is not less than 0.1.

[0016] Furthermore, the mixed soil is aged at room temperature for 5 to 10 days, turned and stirred every 3 days, and water is added to keep the soil moisture content constant at 20% to 40% of the field capacity.

[0017] The beneficial effects of this invention are as follows: This invention uses modified bone meal as raw material, adds low-molecular-weight organic acids as activators, and humic substances as adsorbents and modifiers to prepare a low-cost, environmentally friendly agent that effectively remediates high Pb content in shooting range soil. This remediation agent can rapidly improve the soil compaction problem in shooting ranges, while providing nutrients and organic matter to the soil, which is beneficial for the revegetation of the shooting range soil and the restoration of the ecological environment of the shooting range area. Attached Figure Description

[0018] Figure 1 Schematic diagram of the principle of treating soil with remediation agents containing high lead content. Detailed Implementation

[0019] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0021] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0022] The following embodiments further illustrate the present invention so that those skilled in the art can better understand and implement it, but the embodiments are not intended to limit the present invention.

[0023] The contaminated soil samples in Examples 1-4 were taken from a bullet-avoidance soil pile at a shooting range in Nankou Town, Changping District, Beijing. This shooting range is mainly used for the type approval and reliability testing of small arms and has been in use for 8 years. The soil sampling depth was 30-50cm from the top layer. Three sampling points were taken and homogenized. After removing the more obvious bullets and cartridge cases, the pH value of the soil was measured to be 8.5, the average lead concentration was 3320mg / kg, and the lead concentration in the leachate was 366ug / L, exceeding the Class V water body standard in GB14848.

[0024] Example 1:

[0025] Bovine bone meal was reacted at 300℃ for 3 hours under nitrogen protection. Adsorbed water evaporated, and collagen and other organic substances decomposed, yielding modified bone meal. The main components of the modified bone meal were hydroxyapatite (72%), a small amount of char (10%), and carbonates (9%). After cooling, the modified bone meal was washed with ultrapure water and dried at 70℃ for later use. In the laboratory, 1000g of the soil from the bulletproof surface of the shooting range was weighed, and 10g of modified bone meal, 5g of potassium dihydrogen phosphate, 20g of oxalic acid, and 30g of humus were added sequentially. An appropriate amount of water was added and stirred evenly, maintaining the soil moisture at 30% of field capacity. After curing at room temperature for 5 days, the soil was collected to determine the lead concentration in the leachate and the soil pH value. Testing revealed that the pH of the remediated soil was 6.96, and the lead concentration in the leachate was 10.5 ug / L. Compared to the control sample, the lead concentration in the leachate was significantly reduced, indicating that the addition of the remediation agent effectively solidified / stabilized the lead, greatly reducing its migration and bioavailability. The remediated soil was now neutral.

[0026] Example 2:

[0027] Bone meal was reacted at 300℃ for 3 hours under nitrogen protection to obtain modified bone meal. The main components of the modified bone meal were hydroxyapatite (72%), a small amount of char (10%), and carbonate (9%). After cooling, the modified bone meal was washed with ultrapure water and dried at 70℃ for later use. In the laboratory, 1000g of the soil from the bulletproof surface of the shooting range was weighed, and 20g of modified bone meal, 2g of potassium dihydrogen phosphate, 30g of oxalic acid, and 40g of humus were added in sequence. An appropriate amount of water was added and stirred evenly, maintaining the soil moisture at 30% of field capacity. After curing at room temperature for 5 days, the soil was collected to determine the lead concentration in the leachate and the soil pH value. The test results showed that the pH of the remediated soil was 6.85, and the lead concentration in the leachate was not detected (detection limit 4.2ug / L). The remediation agent had a good effect on solidification / stabilization of lead, and the soil remained neutral after remediation.

[0028] Example 3:

[0029] Bone meal was reacted at 400℃ for 2 hours under nitrogen protection to obtain modified bone meal. The main components of the modified bone meal included hydroxyapatite (75%), a small amount of char (11%), and carbonates (8%). After cooling, the modified bone meal was washed with ultrapure water and dried at 70℃ for later use. In the laboratory, 1000g of the soil from the bulletproof surface of the shooting range was weighed, and 10g of modified bone meal, 5g of potassium dihydrogen phosphate, 20g of oxalic acid, and 30g of humus were added sequentially. An appropriate amount of water was added and stirred evenly, maintaining the soil moisture at 30% of field capacity. The soil was cured at room temperature for 5 days, and the lead concentration in the leachate and the soil pH were measured. The results showed that the pH of the remediated soil was 6.79, and the lead concentration in the leachate was 18.8ug / L. The remediation agent had a good effect on solidifying / stabilizing lead, and the soil remained neutral after remediation.

[0030] Example 4:

[0031] Bone meal was reacted at 400℃ for 2 hours under nitrogen protection to obtain modified bone meal. The main components of the modified bone meal included hydroxyapatite (75%), a small amount of char (11%), and carbonates (8%). After cooling, the modified bone meal was washed with ultrapure water and dried at 70℃ for later use. In the laboratory, 1000g of the soil from the bulletproof surface of the shooting range was weighed, and 10g of modified bone meal, 2g of potassium dihydrogen phosphate, 30g of oxalic acid, and 40g of humus were added sequentially. An appropriate amount of water was added and stirred evenly, maintaining the soil moisture at 30% of field capacity. After curing at room temperature for 5 days, the soil was collected to determine the lead concentration in the leachate and the soil pH value. The test results showed that the pH of the remediated soil was 6.91, and the lead concentration in the leachate was not detected (detection limit 4.2ug / L). The remediation agent had a good effect on solidifying / stabilizing lead, and the soil remained neutral after remediation.

Claims

1. A remediation agent suitable for use in the remediation of high lead-contaminated soils at shooting ranges, characterised in that, The repair agent comprises the following components in parts by weight: 1-3 parts modified bone meal, 0.2-1 parts soluble phosphate, 2-5 parts low molecular weight organic acid, and 1-6 parts humic substances; The modified bone meal is prepared by reacting animal bone meal at 300-400°C under a nitrogen atmosphere for 2-4 hours. The molecular weight of the low-molecular-weight organic acid is no greater than 200; The modified bone meal is any one or a mixture of two or more of fish bone meal, pork bone meal, or beef bone meal; The low molecular weight organic acid is any one or a mixture of two or more of oxalic acid, citric acid, and malic acid. The humus is prepared by mixing 1-3 parts by weight of organic waste with 0.5-2 parts by weight of mushroom residue, 0.1-0.5 parts by weight of molasses and 0.5-1 parts by weight of soybean meal and stirring evenly; the organic waste is any one or a mixture of two or more of livestock and poultry manure, urban sludge or kitchen waste, and the particle size of the organic waste is ≤5mm; the particle size of the mushroom residue and soybean meal is ≤1cm.

2. The repair agent according to claim 1, characterized in that, The modified bone powder has a specific surface area >1.85 m² / g and a mass content of hydroxyapatite in the modified bone powder >70%.

3. The repair agent of claim 1, wherein The modified bone powder has a particle size of 20–50 μm.

4. The repair agent according to claim 1, characterized in that, The soluble phosphate is any one or a mixture of two or more of potassium phosphate, potassium dihydrogen phosphate, and diammonium hydrogen phosphate.

5. The repair agent according to claim 1, characterized in that, The particle size of the bacterial bran and soybean meal is 3mm to 5mm.

6. A method of using the remediation agent according to any one of claims 1 to 5 for lead-containing soil remediation, characterized in that, The remediation agent is mixed and stirred with the soil to be remediated; the molar mass ratio of phosphorus in the remediation agent to lead in the soil to be remediated is not less than 0.

1.

7. The method of use according to claim 6, characterized in that, The mixed soil is aged at room temperature for 5 to 10 days, and turned and stirred every 3 days, with water added to keep the soil moisture constant at 20% to 40% of the field capacity.

Images