Attapulgite-based soil heavy metal repairing agent as well as preparation method and application thereof

Abstract

The invention provides an attapulgite-based soil heavy metal repairing agent as well as a preparation method and application thereof, and belongs to the technical field of soil repairing. The repairing agent disclosed by the invention is prepared from the following components in parts by mass: 40 to 70 parts of activated attapulgite; 10 to 25 parts of biochar; 5-15 parts of a phosphate compound; 5-15 parts of an organic polymer; and 3-10 parts of zero-valent iron powder. The soil remediation agent disclosed by the invention can efficiently fix various heavy metals such as Pb, Cd, Cr, As, Cu, Zn and Hg at the same time through cooperation of various mechanisms, and is wide in application range.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soil remediation, and particularly relates to a palygorskite-based soil heavy metal remediation agent and a preparation method and application thereof. BACKGROUND

[0002] Heavy metals are difficult to be degraded in soil, and have the characteristics of concealment, accumulation and long-term. At present, the remediation technologies for soil heavy metal pollution mainly include the guest soil method, the electrokinetic remediation, the leaching method and the stabilization / immobilization method. Among them, the stabilization / immobilization method is widely applied to the remediation of large-area medium and light pollution soil due to its low cost, simple operation and quick effect.

[0003] The core of the stabilization / immobilization method is to add a remediation agent to the contaminated soil, so as to change the existing form of heavy metals in the soil through adsorption, precipitation, complexation, oxidation and reduction, and reduce the migration and biological availability of heavy metals. Common remediation agents include lime, phosphate, clay mineral and biochar. Palygorskite is a natural one-dimensional nanochain layered structure of hydrous magnesium-aluminum silicate clay mineral, which has a unique pore structure, a large specific surface area and rich surface functional groups, and has good adsorption performance for heavy metal ions. However, the single use of natural palygorskite has the problems of limited adsorption capacity, poor immobilization effect on specific heavy metals (such as As and Cr), and poor stability in complex soil environment.

[0004] Therefore, it is of important practical significance and application value to develop a composite remediation agent based on palygorskite and compounded with other functional materials, which can synergistically, efficiently and durably immobilize various heavy metals. SUMMARY

[0005] The present application aims to provide a palygorskite-based soil heavy metal remediation agent and a preparation method and application thereof, so as to solve the above technical problems.

[0006] In order to achieve the above application purposes, the present application provides the following technical solutions: The present application provides a palygorskite-based soil heavy metal remediation agent, which is composed of the following components in mass fraction: 40-70 parts of activated palygorskite; 10-25 parts of biochar; 5-15 parts of phosphate compound; 5-15 parts of organic polymer; 3-10 parts of zero-valent iron powder.

[0007] Further, the activated palygorskite is palygorskite activated by acid solution or high-temperature calcination; the acid solution is hydrochloric acid or sulfuric acid with a concentration of 1-3 mol / L, and the high-temperature calcination is performed at a temperature of 300-500 DEG C.

[0008] Further, the biochar is biochar prepared by pyrolysis of straw, sawdust or rice husk under anaerobic conditions at 400-600 DEG C, and has a specific surface area of 200-400 m 2 / g.

[0009] Further, the phosphate compound is one or more of calcium dihydrogen phosphate, hydroxyapatite or superphosphate.

[0010] Further, the organic polymer is one or more of sodium alginate, carboxymethyl cellulose or chitosan.

[0011] The application further provides a preparation method of the soil heavy metal stabilization remediation agent, comprising the following steps: a. proportionally adding activated palygorskite, biochar, phosphate compound, organic polymer and zero-valent iron powder into a mixer and uniformly mixing them; b. packaging the uniformly mixed materials to obtain the soil heavy metal stabilization remediation agent.

[0012] Further, in the step a, the mixing rotation speed is 30-100 rpm, and the mixing time is 30-60 min.

[0013] The application further provides application of the above-mentioned soil heavy metal stabilization remediation agent in fixing heavy metals in soil, and the heavy metals include one or more of lead, cadmium, chromium, arsenic, copper, zinc and mercury.

[0014] Further, the application amount of the remediation agent is 0.5-5% of the weight of the contaminated soil, and the remediation agent is uniformly mixed with the contaminated soil, and the water content of the soil is maintained at 60-80% of the field water capacity, and the curing time is 14-28 days.

[0015] The application has the following advantages: 1. The application can simultaneously and efficiently fix multiple heavy metals such as Pb, Cd, Cr, As, Cu, Zn and Hg through the synergy of multiple mechanisms, and has a wide application range.

[0016] 2. Long-term stability: the formed phosphate precipitate and stable complex are not easily released in the soil environment, and the remediation effect is durable.

[0017] 3. Low cost: the main raw materials palygorskite and biochar are widely available and inexpensive, and the preparation process is simple and easy to scale up.

[0018] 4. Environmentally friendly: all components are natural or environmentally friendly materials, which will not cause secondary pollution to the soil, and the addition of biochar and organic polymer also helps to improve the soil aggregate structure and fertility. DETAILED DESCRIPTION

[0019] The present application provides a soil heavy metal remediation agent based on attapulgite, which is composed of components including the following mass fractions: Activated attapulgite 40-70 parts; Biochar 10-25 parts; Phosphate compound 5-15 parts; Organic polymer 5-15 parts; Zero-valent iron powder 3-10 parts.

[0020] In the present application, the content of the activated attapulgite is preferably 45-65 parts, further preferably 50-60 parts, and more preferably 52-58 parts, in terms of mass fraction.

[0021] In the present application, the content of the biochar is preferably 12-23 parts, further preferably 15-20 parts, and more preferably 18 parts, in terms of mass fraction.

[0022] In the present application, the content of the phosphate compound is preferably 6-13 parts, further preferably 8-12 parts, and more preferably 9-10 parts, in terms of mass fraction.

[0023] In the present application, the content of the organic polymer is preferably 6-13 parts, further preferably 8-12 parts, and more preferably 9-10 parts, in terms of mass fraction.

[0024] In the present application, the content of the zero-valent iron powder is preferably 4-9 parts, further preferably 5-8 parts, in terms of mass fraction.

[0025] In the present application, the activated attapulgite is attapulgite activated by an acid solution or high-temperature calcination; the acid solution is hydrochloric acid or sulfuric acid with a concentration of 1-3 mol / L, preferably 1.5-2.5 mol / L; the high-temperature calcination temperature is 300-500℃, preferably 350-450℃, and further preferably 400℃.

[0026] In the present application, the biochar is biochar prepared by anaerobic pyrolysis of straw, sawdust or rice husk at 400-600℃, and its specific surface area is 200-400 m 2 / g.

[0027] In the present application, the phosphate compound is one or more of calcium dihydrogen phosphate, hydroxyapatite or superphosphoric acid calcium, and is preferably calcium dihydrogen phosphate.

[0028] In the present application, the organic polymer is one or more of sodium alginate, carboxymethyl cellulose or chitosan, preferably carboxymethyl cellulose.

[0029] The present application also provides a preparation method of the soil heavy metal stabilization remediation agent, comprising the following steps: a. proportionally adding activated attapulgite, biochar, phosphate compound, organic polymer and zero-valent iron powder into a mixer and mixing uniformly; b. packaging the uniformly mixed material to obtain the soil heavy metal stabilization remediation agent.

[0030] In the present application, in step a, the mixing rotation speed is 30-100 rpm, preferably 50-80 rpm; the mixing time is 30-60 min, preferably 40-50 min.

[0031] The present application also provides the application of the above-mentioned soil heavy metal stabilization remediation agent in fixing heavy metals in soil, and the heavy metals include one or more of lead, cadmium, chromium, arsenic, copper, zinc and mercury.

[0032] In the present application, the application amount of the remediation agent is 0.5-5%, preferably 1-4%, and further preferably 2-3% of the weight of the contaminated soil; the remediation is carried out by uniformly mixing the remediation agent with the contaminated soil, and the water content of the soil is maintained at 60-80%, preferably 65-75%, and further preferably 70-72% of the field water holding capacity; the curing time is 14-28 days, preferably 20-25 days.

[0033] Technical principle of the present application: Attapulgite and biochar have developed porous structure and large specific surface area. They can be used as carriers to load and disperse zero-valent iron powder particles on their surface and in their pores. This effectively prevents the agglomeration of zero-valent iron powder due to its own magnetism, greatly increases the contact area of zero-valent iron powder with heavy metal ions, and improves the reaction efficiency.

[0034] Zero-valent iron powder (F ) can form countless micro-batteries in contact with carbon or other trace metal impurities in attapulgite and biochar.

[0035] Anode (iron): F -2 → Fe (Iron is oxidized and releases electrons)

[0036] Cathode (carbon / impurities): 2 +2 → H2↑; under aerobic conditions, +2H2O+4 → 4OH More importantly, heavy metal ions can be directly reduced by electrons at the cathode, for example: Cr2 + 14 + 6 → 2Cr + 7H2O.

[0037] Fe and Fe produced by the corrosion of zero-valent iron powder will further hydrolyze to form iron (hydroxide) oxides, such as goethite and siderite. These newly formed iron (hydroxide) oxides are amorphous or weakly crystalline, with a large specific surface area and extremely high surface activity. They will cover or wrap the surface of attapulgite and biochar, greatly enhancing their adsorption and co-precipitation capacity for heavy metal ions (especially for As, Cr, etc.).

[0038] Organic polymers (such as sodium alginate, chitosan) can first complex heavy metal ions in solution through their functional groups (-COOH, -N ), enriching them around zero-valent iron powder particles and locally increasing the concentration of heavy metals, thereby greatly accelerating the reduction reaction rate of zero-valent iron powder on them. Organic polymers can form an organic film on the surface of zero-valent iron powder particles. This film can selectively permeate water molecules and heavy metal ions, but at the same time prevent oxygen from entering too quickly, slowing down the oxidation of zero-valent iron powder and playing a role in slow release and protection.

[0039] Phosphates mainly form phosphate precipitates with Pb , Cd , etc., while zero-valent iron powder mainly treats Cr(VI), As, etc. through reduction and iron oxide adsorption. They have clear division of labor and cover different types of heavy metals. In soil environments containing ammonium nitrogen, Fe produced by the reduction reaction of zero-valent iron powder can form very stable ammonium iron phosphate precipitates with phosphate (P ) and ammonium ions (N ). This precipitate can simultaneously fix phosphorus, iron, and heavy metals, making them more difficult to release. Phosphate will form a thin iron phosphate protective film on the surface of zero-valent iron powder. Although this film will slightly slow down the initial reaction rate of iron, it can prevent iron from being oxidized too quickly and excessively (e.g. covered by silicates and carbonates in the soil), thereby prolonging the effective reaction time of zero-valent iron powder and achieving long-term, slow stabilization of heavy metals.

[0040] Therefore, the introduction of zero-valent iron powder into the attapulgite-based composite formula is not a simple physical mixing. It produces a profound synergistic effect with other components from multiple levels such as "physical dispersion-electrochemical reduction-chemical precipitation-surface complexation". This makes the entire composite material a multifunctional, multi-mechanism, synergistic "integrated reaction system", which can more quickly, more thoroughly and more durably fix various heavy metals in the soil, especially effectively handle the variable-valence heavy metals (such as chromium and arsenic) that single attapulgite is difficult to deal with, which is the core embodiment of the invention.

[0041] The technical solutions provided by the present application will be described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present application.

[0042] Example 1

[0043] Take 100 mesh natural attapulgite powder 100 g, activate it with 500 mL of 2 mol / L hydrochloric acid solution at 70°C for 3 hours. Filter, wash with deionized water until the filtrate pH is about 6, dry at 105°C, crush to obtain activated attapulgite.

[0044] Formula: activated attapulgite (2M HCl activated) 55 parts, rice husk biochar (pyrolyzed at 500°C) 20 parts, hydroxyapatite 10 parts, carboxymethyl cellulose 10 parts, zero-valent iron powder 5 parts.

[0045] Preparation and effect: Put the activated attapulgite, biochar, phosphate compound, organic polymer and zero-valent iron powder into the mixer according to the proportion and mix uniformly; package the uniformly mixed material to obtain the soil heavy metal stabilization and remediation agent.

[0046] Take a heavy metal contaminated soil (pH = 6.8) around a lead-zinc mine, the basic properties of which are: Pb 45.2±2.1 mg / L, Cd 3.05±0.15 mg / L, Cr(VI) 28.7±1.4 mg / L. Dry, grind and pass through a 2mm sieve.

[0047] Experimental group: add 15g of the remediation agent prepared in this example (1.5% of the soil weight) to 1 kg of contaminated soil, mix thoroughly, adjust the soil moisture content to 70% of the field water holding capacity, and maintain at room temperature for 21 days.

[0048] After remediation, the soil pH is 7.2, and the TCLP leaching concentration of Pb, Cd and Cr(VI) in the soil is reduced by 91%, 88% and 95% respectively, and the bioavailable state accounts for 12%, 15% and 8% respectively.

[0049] Conclusion: This example demonstrates that the composite remediation agent has excellent synergistic stabilization effect on multiple heavy metals under the optimal ratio.

[0050] Example 2

[0051] Formulation: activated attapulgite (400℃ calcined) 60 parts, sawdust biochar (pyrolyzed at 450℃) 18 parts, calcium dihydrogen phosphate 12 parts, sodium alginate 8 parts, zero-valent iron powder 6 parts.

[0052] Preparation and effect: the preparation method is the same as example 1. The repair effect of Pb, Cd, Cr(VI) reduces the leaching concentration by 89.4%, 86.6%, and 94%, respectively, confirming the adjustability and universality of the formulation.

[0053] Example 3

[0054] Formulation: activated attapulgite (2M HCl activation) 50 parts, straw biochar (pyrolyzed at 550℃) 22 parts, superphosphate 8 parts, chitosan 12 parts, zero-valent iron powder 8 parts.

[0055] Preparation and effect: the preparation method is the same as example 1. This formulation shows extremely high fixation efficiency for Cd and As (additional pollution indicators), with leaching concentration reduction rates of 90% and 92%, respectively.

[0056] Conclusion: emphasizes the targeted repair potential of the formulation for different heavy metals, and the significant synergistic fixation of chitosan and zero-valent iron powder on As.

[0057] Example 4

[0058] Formulation: activated attapulgite (1.5M S activation) 58 parts, rice husk biochar (pyrolyzed at 500℃) 15 parts, hydroxyapatite 9 parts, carboxymethyl cellulose 13 parts, zero-valent iron powder 5 parts.

[0059] Preparation and effect: the mixing time is shortened to 35 minutes, and the rotation speed is 80 rpm.

[0060] Soil repair is carried out using the experimental method of example 1: After repair, it is detected that the TCLP leaching concentration of Pb, Cd, Cr(VI) in the soil is reduced by 89%, 86%, and 93%, respectively, and the bioavailable state accounts for 10%, 18%, and 10%, respectively.

[0061] Example 5

[0062] Formulation: activated attapulgite (2M HCl activation) 45 parts, rice husk biochar (pyrolyzed at 500℃) 25 parts, calcium dihydrogen phosphate 15 parts, sodium alginate 5 parts, zero-valent iron powder 10 parts.

[0063] Preparation and effect: the preparation method is the same as example 1, and the formula focuses on adsorption and reduction. The repair effect on Cr(VI) is particularly prominent, and the leaching concentration reduction rate is 97%.

[0064] Comparative example 1

[0065] Formula: activated palygorskite 55 parts, rice husk biochar 20 parts, hydroxyapatite 10 parts, carboxymethyl cellulose 15 parts, and zero-valent iron powder 0 parts.

[0066] Effect: the fixation effect of Pb and Cd is acceptable (leaching concentration is reduced by 80%), but the fixation effect of Cr(VI) is sharply decreased, and the leaching concentration is only reduced by 35%. BCR morphological analysis shows that the acid extractable state proportion of Cr is still as high as 45%.

[0067] Conclusion: zero-valent iron powder is a key component for treating variable heavy metals (especially Cr(VI)), and its reduction effect cannot be replaced by phosphates and organic polymers. Without it, the repair agent is basically ineffective for Cr(VI).

[0068] Comparative example 2

[0069] Formula: activated palygorskite 55 parts, rice husk biochar 20 parts, hydroxyapatite 10 parts, organic polymer 0 parts, and zero-valent iron powder 15 parts.

[0070] Effect: the powder mixture is obviously layered during storage and application, and the uniformity of mixing with soil is poor. The repair effect is unstable, and there is a large difference in data from different sampling points. Moreover, the long-term effect of zero-valent iron powder is weakened due to rapid aggregation and oxidation, and there is a rebound trend in the leaching concentration of Cr after maintenance.

[0071] Conclusion: organic polymers not only fix heavy metals through complexation, but more importantly, their thickening and dispersing effects ensure product uniformity, application uniformity, and delay the passivation of zero-valent iron powder, which is the key to achieving long-term stability.

[0072] Comparative example 3

[0073] Formula: activated palygorskite 55 parts, rice husk biochar 20 parts, phosphate compound 0 parts, carboxymethyl cellulose 15 parts, and zero-valent iron powder 10 parts.

[0074] Effect: the leaching concentration reduction rates of Pb and Cd are 69.9% and 64.9% respectively, which are significantly lower than example 1. The bioavailable state proportions of Pb and Cd are 35.8% and 41.6% respectively, which are much higher than example 1. The fixation effect on Cr(VI) is still good (reduced by more than 90%), but the fixation ability on Pb and Cd is significantly insufficient, with TCLP leaching concentration reduction rates of only 70% and 65%.

[0075] Conclusion: Phosphate compound is the core component of stable lead phosphate / cadmium phosphate precipitate formation. This chemical precipitation is incomparable to the adsorption and reduction mechanism for long-term fixation of Pb and Cd. Without it, the fixation of lead and cadmium is not complete.

[0076] Comparative Example 4

[0077] Formulation: Activated attapulgite 75 parts, biochar 0 parts, hydroxyapatite 10 parts, carboxymethyl cellulose 10 parts, zero-valent iron powder 5 parts.

[0078] Effect: The overall adsorption capacity of the repair agent decreases, and the treatment effect of the low-concentration but multiple heavy metal coexisting pollution scene becomes poor. The dispersibility of zero-valent iron powder is poor, and the micro-battery effect is weakened. The bulk density of the product increases, and the application amount per unit weight of the covered area decreases.

[0079] Conclusion: Biochar not only provides a large additional adsorption capacity, but also provides an ideal dispersion carrier and cathode for the formation of micro-batteries for zero-valent iron powder, and improves the physical properties of the product. Without it, the adsorption capacity and electrochemical activity of the system are impaired.

[0080] Comparative Example 5

[0081] Formulation: Natural attapulgite 55 parts, rice husk biochar 20 parts, hydroxyapatite 10 parts, carboxymethyl cellulose 10 parts, zero-valent iron powder 5 parts.

[0082] Effect: The fixation effect of all heavy metals decreases, and the overall repair efficiency is about 15-20% lower than that of Example 1. The reason is that the natural attapulgite pore is blocked, the specific surface area is small, and the surface functional group activity is low, which fails to fully play its role as a main substrate and synergistic reaction platform.

[0083] Conclusion: Activation treatment is a necessary step to stimulate the potential of attapulgite. The natural attapulgite without activation cannot achieve the expected synergistic effect of the present application, which proves the necessity of the pretreatment step of "activation".

[0084] The repair effect of the repair agent of Examples 1-2 and Comparative Examples 1-5 on heavy metals in soil is shown in Table 1.

[0085] Table 1 Repair results

[0086] Comparative Example 6

[0087] Formulation: Activated attapulgite 50 parts, biochar 20 parts, hydroxyapatite 10 parts, carboxymethyl cellulose 10 parts, zero-valent iron powder 10 parts.

[0088] Theoretical risk: Excessive zero-valent iron powder will consume a large amount of soil , resulting in a significant increase in soil pH (alkalization) and possible re-dissolution of some amphoteric metal hydroxides (e.g. Cr(III)). Meanwhile, a large amount of iron powder will occupy the effective space of other components, destroying the structural balance of the formula.

[0089] pH change: the pH of the soil after remediation rose to 8.5 (7.2 after remediation in Example 1).

[0090] Remediation effect: Pb leaching concentration: 5.8 mg / L (lower than 4.1 mg / L in Example 1) Cd leaching concentration: 0.45 mg / L (lower than 0.37 mg / L in Example 1) Cr(VI) leaching concentration: 3.05 mg / L (significantly higher than 1.44 mg / L in Example 1) Analysis: Although the fixation of Pb and Cd is acceptable, the alkalization of the soil leads to the reactivation and leaching of some reduced Cr(III), making the overall remediation effect, especially the stability of Cr, worse. This proves that the more zero-valent iron powder is not necessarily better.

[0091] Comparative Example 7

[0092] Formula: activated palygorskite 57 parts, biochar 20 parts, hydroxyapatite 10 parts, carboxymethyl cellulose 10 parts, zero-valent iron powder 3 parts.

[0093] Theoretical risk: the amount of iron powder is not enough to completely reduce and fix all Cr(VI), and the reduction capacity is saturated, resulting in incomplete remediation.

[0094] Remediation effect: Pb leaching concentration: 4.5 mg / L Cd leaching concentration: 0.39 mg / L Cr(VI) leaching concentration: 8.90 mg / L (much higher than Example 1, incomplete reduction) Analysis: the fixation rate of Cr(VI) is only 69%, much lower than 95% in Example 1. This proves that when the concentration of pollutants is high, 3 parts of zero-valent iron powder cannot provide enough reduction capacity, and is at the lower limit of the dosage range, with poor results.

[0095] Comparative Example 8

[0096] Formula: activated palygorskite 50 parts, biochar 20 parts, hydroxyapatite 15 parts, carboxymethyl cellulose 10 parts, zero-valent iron powder 5 parts.

[0097] Theoretical risk: excessive phosphates may cause leaching of water-soluble phosphorus in the soil, causing environmental risks of water eutrophication. At the same time, it may form precipitates with other essential elements (such as zinc), affecting the soil ecology.

[0098] Repair effect: Pb leaching concentration: 3.9 mg / L (slightly better than Example 1) Cd leaching concentration: 0.35 mg / L (slightly better than Example 1) Cr(VI) leaching concentration: 1.50 mg / L (equivalent to Example 1) Environmental risk: The water-soluble phosphorus content of the repaired soil is as high as 25 mg / kg (only 8 mg / kg in Example 1), which poses a potential risk of phosphorus leaching.

[0099] Analysis: Although the fixation effect of Pb and Cd is slightly improved, it brings the risk of secondary pollution, which does not meet the principle of environmental-friendly invention, and proves that the amount of phosphate is not the higher the better.

[0100] Comparative Example 9

[0101] Formulation: Activated attapulgite 45 parts, biochar 30 parts, hydroxyapatite 10 parts, carboxymethyl cellulose 10 parts, zero-valent iron powder 5 parts.

[0102] Theoretical risk: Excessive biochar will excessively adsorb soil moisture and nutrients, which may affect plant growth. At the same time, it will seriously dilute the concentration of other active components (such as attapulgite and zero-valent iron), affecting their chemical reactions.

[0103] Repair effect: Pb leaching concentration: 6.2 mg / L Cd leaching concentration: 0.52 mg / L Cr(VI) leaching concentration: 2.20 mg / L Physical properties: The product is too loose, and the effective components per unit volume decrease.

[0104] Analysis: The fixation effect of all heavy metals is significantly worse than Example 1. Because biochar is mainly physical adsorption, it cannot provide strong chemical fixation like phosphate or zero-valent iron. Excessive use actually weakens the strength of the overall chemical reaction.

[0105] Comparative Example 10

[0106] Formulation: Activated attapulgite 30 parts, biochar 20 parts, hydroxyapatite 15 parts, carboxymethyl cellulose 15 parts, zero-valent iron powder 10 parts.

[0107] Theoretical risk: The proportion of attapulgite as the main matrix and reaction platform is too low, resulting in poor structure of the mixture, and other components cannot be effectively loaded and dispersed, and the synergistic effect is weakened.

[0108] Repair effect: Pb leaching concentration: 7.8 mg / L Cd leaching concentration: 0.68 mg / L Cr(VI) leaching concentration: 3.85 mg / L Analysis: all indicators are significantly worse. It is proved that the attapulgite is the "skeleton" of the whole composite material system, when the amount is too low, the stability, dispersibility and synergistic reaction efficiency of the system are greatly reduced.

[0109] From the above examples, the present application provides a kind of attapulgite-based soil heavy metal remediation agent and its preparation method and application. As can be seen from the above examples and comparative examples, zero-valent iron powder provides indispensable reduction function, for Cr(VI), As(III / V) and other variable valence heavy metals. Phosphate compounds provide irreplaceable chemical precipitation function, for Pb, Cd, Zn and other heavy metals. Organic polymers provide key physical and chemical stability function, ensure the uniformity and long-acting of the remediation process. Biochar provides important adsorption enhancement and structural support function, optimizes the overall performance. Activated attapulgite as an efficient main matrix is the basis platform for other components to play a role. The components in the remediation agent of the present application cooperate with each other to have synergistic effect, and have excellent remediation effect for heavy metal contaminated soil.

[0110] The above is only the preferred embodiment of the present application, it should be noted that for those skilled in the art, without departing from the principles of the present application, can make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. An attapulgite-based soil heavy metal remediation agent, characterized in that, It consists of components comprising the following parts by mass: 40-70 parts of activated attapulgite; 10-25 parts biochar; 5-15 parts of phosphate compounds; 5-15 parts of organic polymer; 3-10 servings of zero-price iron powder.

2. The soil heavy metal stabilizing and remediating agent according to claim 1, characterized in that, The activated attapulgite is attapulgite activated by acid solution or high-temperature calcination; the acid solution is hydrochloric acid or sulfuric acid with a concentration of 1~3 mol / L, and the high-temperature calcination temperature is 300~500℃.

3. The soil heavy metal stabilizing and remediating agent according to claim 1 or 2, characterized in that, The biochar is obtained by anaerobic pyrolysis of straw, sawdust, or rice husks at 400-600℃, and has a specific surface area of ​​200-400 m². 2 / g.

4. The soil heavy metal stabilizing and remediating agent according to claim 3, characterized in that, The phosphate compound is one or more of calcium dihydrogen phosphate, hydroxyapatite, or superphosphate.

5. The soil heavy metal stabilizing and remediating agent according to claim 1 or 4, characterized in that, The organic polymer is one or more of sodium alginate, carboxymethyl cellulose, or chitosan.

6. The method for preparing the soil heavy metal stabilizing and remediating agent according to any one of claims 1 to 5, characterized in that, Includes the following steps: a. Add activated attapulgite, biochar, phosphate compounds, organic polymers and zero-valent iron powder into a mixer in proportion and mix evenly; b. Package the evenly mixed materials to obtain the soil heavy metal stabilizing and remediating agent.

7. The preparation method according to claim 6, characterized in that, In step a, the mixing speed is 30~100 rpm and the mixing time is 30~60 min.

8. The application of the soil heavy metal stabilizing and remediating agent according to any one of claims 1 to 5 in the fixation of heavy metals in soil, characterized in that, The heavy metals include one or more of lead, cadmium, chromium, arsenic, copper, zinc, and mercury.

9. The application according to claim 8, characterized in that, The remediation agent is applied at a rate of 0.5-5% of the weight of the contaminated soil. During remediation, it is mixed evenly with the contaminated soil, and the soil moisture content is maintained at 60-80% of field capacity. The maintenance period is 14-28 days.

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