CN111676022A - Methods for remediation of heavy metal pollution in soil - Google Patents

Abstract

The invention relates to the technical field of soil remediation, in particular to a method for remedying heavy metal pollution of soil, and firstly provides a heavy metal soil pollution remediation agent which is composed of a soil conditioning precursor and an adhesive component, wherein the soil conditioning precursor is composed of magnetic polyvinyl alcohol microspheres, iron magnesium acorus carbon and bentonite/polyvinyl alcohol composite resin, and the weight ratio of the magnetic polyvinyl alcohol microspheres to the bentonite/polyvinyl alcohol composite resin is 1.0: 3.0-5.0: 1.5-3.0; and applying the repairing agent to the surface of the heavy metal contaminated soil, turning over and mixing uniformly, slightly spraying water and maintaining to finish repairing the heavy metal contaminated soil. The repairing agent can efficiently repair heavy, medium and light heavy metal polluted soil, complete passivation and degradation of heavy metal elements such as cadmium, arsenic, lead, mercury, copper, chromium, nickel, manganese and the like in the soil, improve the water retention capacity of the soil, increase the soil moisture value, enhance the soil quality, perform the sustained-release passivation and degradation effect on the heavy metal elements, prolong the action time and reduce the cost.

Description

Methods for remediation of heavy metal pollution in soil

technical field

The invention relates to the technical field of soil remediation, in particular to a method for remediating soil heavy metal pollution.

Background technique

Heavy metals are more prominent among soil inorganic pollutants, mainly because heavy metals cannot be decomposed by soil microorganisms, but are easy to accumulate and convert into more toxic methyl compounds, and some even accumulate in the human body at harmful concentrations through the food chain, causing serious harm. Human health. Soil heavy metal pollutants mainly include mercury, cadmium, lead, copper, chromium, arsenic, nickel, iron, manganese, zinc, etc. Although arsenic is not a heavy metal, its behavior, source and harm are similar to heavy metals, so it is usually listed in Heavy metals are discussed. As far as the needs of plants are concerned, metal elements can be divided into two categories: 1. Elements that are not needed for plant growth and development, but are more harmful to human health, such as cadmium, mercury, and lead. ② Elements required for the normal growth and development of plants, and have certain physiological functions for the human body, such as copper, zinc, etc., but too much will cause pollution and hinder the growth and development of plants.

Due to the different forms of the same metals in the soil, their migration and transformation characteristics and pollution properties are also different. Therefore, when studying the harm of heavy metals in soil, not only their total content, but also the content of various forms must be paid attention to. Heavy metals are generally not easily leached with water in soil and cannot be decomposed by soil microorganisms; on the contrary, organisms can enrich heavy metals, often causing heavy metals to gradually accumulate in the soil environment, and even some heavy metal elements can be converted into more toxic and more toxic elements in the soil. Large methyl compounds, and some are accumulated in the human body through the food chain in harmful concentrations, seriously endangering human health. Compared with the pollution of the water environment, the pollution of heavy metals to the soil environment is more difficult to control, and the pollution is more harmful.

For soil remediation of heavy metal complex pollution, stabilization remediation is mainly used in China. Stabilization remediation is to add stabilizers to the soil to reduce the bioavailability and mobility of heavy metals through a series of reactions such as adsorption, precipitation, complexation, ion exchange, and redox, so as to achieve the purpose of remediation of heavy metal-contaminated soils. Therefore, the key to stabilization repair is to find a high-efficiency stabilizer that is cheap and easy to obtain without secondary pollution. Commonly used stabilizers include alkaline substances such as lime and phosphorus-containing materials such as hydroxyapatite, phosphate rock powder and phosphate fertilizers. These traditional stabilizers have problems such as high cost and certain environmental risks. For example, adding excessive phosphorus-containing materials to soil may cause eutrophication of water bodies. In recent years, foreign countries, especially South Korea, have used shell powder to stabilize heavy metals in soil, and have achieved certain results. Shells are a natural, readily available material. China's shellfish production ranks first in the world, exceeding 10 million tons per year, and a large number of discarded shells are then dumped in landfills or reclaimed as solid waste. Using these waste shells for the remediation of polluted soil can realize the resource utilization of waste.

For the remediation of heavy metal polluted soil, the prior art includes the Chinese invention patent with the authorization announcement number CN105713619B, which discloses a preparation method of an iron-silicon-sulfur multi-element composite biochar soil heavy metal conditioner. The method of the invention includes: adding silicate to agricultural waste and isolating the air for calcination, adsorbing iron-containing salt on kaolin, adsorbing sulfate on bentonite, and then mixing the above three materials in a certain proportion Homogenize and add diatomaceous earth and starch for granulation to prepare the iron-silicon-sulfur multi-element composite biochar soil heavy metal conditioner. The conditioner can be widely used in the treatment of heavy metal pollution in paddy soil, and can simultaneously passivate cadmium, arsenic, lead and other composite pollution under acidic or alkaline soil conditions, reduce the absorption and accumulation of rice, and realize the safe utilization of polluted farmland. However, the method of the invention can only passivate three heavy metal pollutants such as cadmium, arsenic and lead, but has no responsive passivation effect for other heavy metals such as mercury, copper, chromium, nickel, and manganese, and it can only be applied to medium and mild The remediation of heavy metal-contaminated soils has limited application scope.

The disclosure of the above background technology content is only used to assist the understanding of the inventive concept and technical solution of the present invention, and it does not necessarily belong to the prior art of this patent application. If there is no clear evidence that the above content has been disclosed on the filing date of this patent application The above background art should not be used to evaluate the novelty and inventive step of the present application.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide a heavy metal-contaminated soil remediation agent and a method for remediating heavy metal pollution in soil by using the same. , complete the passivation and degradation of heavy metal elements such as cadmium, arsenic, lead, mercury, copper, chromium, nickel, manganese in the soil, and also improve the soil water retention capacity, increase soil moisture value, enhance soil quality, and reduce heavy metal elements. Slow-release passivation and degradation, prolong the action time and reduce the cost.

In order to achieve the above objects, the present invention provides the following technical solutions.

[1] A heavy metal contaminated soil remediation agent, the remediation agent comprising:

a soil conditioning precursor consisting of magnetic polyvinyl alcohol microspheres, iron-magnesium calamus charcoal and bentonite/polyvinyl alcohol composite resin in a weight ratio of 1.0:3.0-5.0:1.5-3.0; and

adhesive composition;

Wherein, the saturation magnetization of the magnetic polyvinyl alcohol microspheres is not lower than 3.0 A·m ² ·kg ^-1 .

According to some specific embodiments of the present invention, the weight ratio of the magnetic polyvinyl alcohol microspheres, the iron-magnesium biomass charcoal and the bentonite/polyvinyl alcohol composite resin is preferably 1.0:4.0-5.0:1.5-2.0, and the weight ratio is more preferably 1.0: 4.0～4.5:1.5～2.0, the most preferable weight ratio is 1.0:4.5:1.5.

In the present application, the soil conditioning precursor ternary structure composed of magnetic polyvinyl alcohol microspheres, iron-magnesium calamus charcoal and bentonite/polyvinyl alcohol composite resin is used as the functional component of the heavy metal contaminated soil remediation agent. Biochar and bentonite come from a wide range of sources, and are easily degraded in the soil. After repairing heavy metal pollution, it can also increase soil quality; heavy metal contaminated soil remediation agent is a composite soil remediation agent containing iron, magnesium, silicon and other elements. It can efficiently remediate soil contaminated by heavy, medium and light heavy metals, and at the same time complete the passivation of heavy metal elements such as cadmium, arsenic, lead, mercury, copper, chromium, nickel, manganese in the soil, and increase soil fertility. To achieve the purpose of carrying out heavy metal soil remediation and agricultural safety production at the same time, significantly improve the current problem of agricultural soil waste caused by multiple heavy metal pollution in my country, and further improve the urgent situation of excessive heavy metal content in crops.

According to some embodiments of the present invention, the adhesive composition consists of diatomaceous earth and starch.

According to some specific embodiments of the present invention, the magnetic polyvinyl alcohol microspheres are prepared by a method comprising the following steps:

1) 0.3～0.5 weight part of gelatin is completely dissolved in enough distilled water at room temperature;

2) under stirring, successively add 0.3-0.5 parts by weight of benzoyl peroxide, 8-10 parts by weight of liquid wax, 8-10 parts by weight of divinylbenzene and 25-40 parts by weight of polyvinyl alcohol, and continue stirring for at least 45min;

3) be warming up to 48～50 ℃ and keep warm for at least 10min, add 0.6～0.8 weight part of sodium carbonate and 1.5～2.0 weight part magnesium sulfate;

4) The temperature is raised to 70～78℃ and kept for at least 15min, 2.5～4.0 parts by weight of magnetic powder is added and kept for at least 4h;

5) Heat the temperature to 90-98°C and keep the temperature for at least 2h. After the solution is cooled to below 80°C, wash, filter with suction, vacuum dry and pulverize through a sieve of at least 100 meshes.

According to some specific embodiments of the present invention, the stirring rate of the step 2) is 120-180 r/min.

According to some specific embodiments of the present invention, the weight-average molecular weight of the polyvinyl alcohol in the step 2) is not higher than 20,000.

According to some specific embodiments of the present invention, the heating rate of the steps 3) to 5) is 0.5 to 1.0 °C/min.

According to some specific embodiments of the present invention, the magnetic powder in step 4) is Fe ₃ O ₄ magnetic powder.

According to other specific embodiments of the present invention, the magnetic powder in step 4) is modified through the following steps: adding equal weight of Fe ₃ O ₄ magnetic powder and silane coupling agent to at least 50 times by weight of 50-75% ethanol solution to disperse Homogeneous, under nitrogen protection, slowly heat up to 42-45°C, stir at 800-1200 r/min for at least 18h, wash with ethanol and deionized water for several times, and vacuum dry at 60°C for at least 48h.

According to other specific embodiments of the present invention, the silane coupling agent is at least one of vinyltriethoxysilane, vinyltrimethoxysilane or vinyltris(β-methoxyethoxy)silane.

According to some specific embodiments of the present invention, the vacuum drying in step 5) refers to drying under vacuum not higher than 60° C. for at least 24 hours.

Using silane coupling agent as a surfactant to modify the surface of Fe ₃ O ₄ magnetic powder particles can make the final magnetic polyvinyl alcohol microspheres more regular, obtain narrower particle size distribution and better dispersion, and also help improve the The magnetization of the magnetic polyvinyl alcohol microspheres plays a positive role in strengthening the heavy metal-contaminated soil remediation agent to passivate heavy metals.

According to some specific embodiments of the present invention, the iron-magnesium calamus charcoal is prepared by a method comprising the following steps:

1) pulverize the washed and dried calamus, and sieve to obtain wood chips with a size not greater than 0.5 mm;

2) prepare a mixed impregnation stable solution containing Fe ³⁺ , Fe ²⁺ and Mg ²⁺ ;

3) Under nitrogen, according to the weight ratio of wood chips and metal cations of 100:1.0 to 3.0, the wood chips of step 1) are immersed into the mixed immersion stabilization solution of step 2) for at least 2 hours;

4) Under nitrogen, the mixed solution in step 3) is heated to 550-580°C for pyrolysis for at least 1.5h;

5) Wash the ash on the biochar multiple times in step 4), pulverize it after drying, and pass it through a 100-mesh sieve.

According to some specific embodiments of the present invention, Fe ³⁺ , Fe ²⁺ and Mg ²⁺ in the step 2) can be selected from Fe ₂ (SO ₄ ) ₃ .9H ₂ O, FeSO ₄ .7H ₂ O, MgCl ₂ respectively. • 6H ₂ O formulation.

According to some specific embodiments of the present invention, the amount ratio of Fe ³⁺ , Fe ²⁺ and Mg ²⁺ in the step 2) is 2-3:1:0.3-1.

According to some specific embodiments of the present invention, the heating rate of the step 4) is 5-8°C/min.

Using calamus biochar as the structure, the iron-magnesium calamus charcoal was prepared by carrying iron and magnesium ions. After compounding it with magnetic polyvinyl alcohol microspheres and bentonite/polyvinyl alcohol composite resin, it not only has excellent passivation of heavy metals in soil, but also The iron-magnesium calamus charcoal is rich in iron and magnesium elements, which can enrich the element ratio in the soil. In addition, the iron-magnesium calamus charcoal also has the function of enriching nitrogen and phosphorus in the soil solution. The iron-magnesium calamus charcoal after enriching nitrogen and phosphorus can be used as nitrogen Phosphorus slow-release fertilizer to further improve soil quality.

According to some specific embodiments of the present invention, the bentonite/polyvinyl alcohol composite resin is prepared by a method comprising the following steps:

1) At room temperature, add a sufficient amount of oxalic acid solution to the natural bentonite for soaking, react in a shaking table at 120-150 times/min for at least 2 hours, add hemicellulose lye and sodium bisulfite, and ultrasonically disperse for at least 20 minutes;

2) Rapidly raise the temperature to 55-60°C, add polyvinyl alcohol aqueous solution, and react at a constant temperature for at least 30 minutes under stirring. The product is flocculated and washed with ethanol, fully ground after drying, and extracted with acetone for 12 hours and dried.

According to some specific embodiments of the present invention, in the preparation method of the bentonite/polyvinyl alcohol composite resin, the weight ratio of natural bentonite, oxalic acid, hemicellulose, sodium bisulfite and polyvinyl alcohol is 1:0.8～1.0:0.3 ~ 0.5: 0.01 ~ 0.015: 0.3 ~ 0.6.

According to some specific embodiments of the present invention, in the preparation method of the bentonite/polyvinyl alcohol composite resin, the ultrasonic frequency of ultrasonic dispersion is 50-80 KHz, and the ultrasonic energy density is 0.6-0.8 w/cm ² .

According to some specific embodiments of the present invention, in the preparation method of the bentonite/polyvinyl alcohol composite resin, the weight average molecular weight of the polyvinyl alcohol is not higher than 25,000.

According to some specific embodiments of the present invention, in the preparation method of the bentonite/polyvinyl alcohol composite resin, the drying temperature is 60-70° C., and the drying time is at least 12 hours.

According to some specific embodiments of the present invention, in the preparation method of the bentonite/polyvinyl alcohol composite resin, it is sufficiently ground to pass through a 120-mesh sieve.

By modifying natural bentonite with oxalic acid, then adding hemicellulose and reducing agent sodium bisulfite to react, and finally introducing polyvinyl alcohol into the hemicellulose/bentonite system to prepare bentonite/polyvinyl alcohol composite resin, which improves the resin quality. The three-dimensional network structure of bentonite/polyvinyl alcohol composite resin has excellent water absorption, water retention, salt resistance and thermal stability, and is easily degradable and non-polluting. It is combined with magnetic polyvinyl alcohol microspheres, iron-magnesium calamus Combining charcoal into a heavy metal contaminated soil remediation agent, on the one hand, is beneficial to increase the water retention capacity of the soil, increase the soil moisture value, and enhance the soil quality after degradation. On the other hand, its higher salt adsorption effect can also significantly enhance the remediation agent. The ability to gather heavy metal elements, adsorb heavy metal ions around the repair agent and then be degraded and removed by the repair agent, which significantly improves the ability to degrade heavy metals. On the other hand, the bentonite/polyvinyl alcohol composite resin can also coat magnetic polyvinyl alcohol microspheres , in the process of gradual degradation, it can play a good slow-release effect, improve the effect of heavy metal-contaminated soil remediation agent to degrade heavy metals to the fourth quarter, and significantly reduce the cost.

[2] The method for preparing the heavy metal-contaminated soil remediation agent of item [1], the method comprising:

1) Preparation of magnetic polyvinyl alcohol microspheres;

2) prepare iron-magnesium calamus charcoal;

3) preparation of bentonite/polyvinyl alcohol composite resin;

4) fully mixing the materials obtained in steps 1), 2) and 3) according to a weight ratio of 1.0:3.0-5.0:1.5-3.0 to obtain a soil conditioning precursor;

5) The soil conditioning precursor prepared in step 4) is uniformly mixed with diatomite and starch in a mass ratio of 100:1-10:1-10, sprayed with water to granulate, and dried to obtain a heavy metal contaminated soil remediation agent.

According to some specific embodiments of the present invention, the particle size of the heavy metal-contaminated soil remediation agent is 3-5 mm.

The soil conditioning precursor ternary structure composed of magnetic polyvinyl alcohol microspheres, iron-magnesium calamus charcoal and bentonite/polyvinyl alcohol composite resin is used as the effective component, supplemented by diatomite and starch granulation to prepare the heavy metal contaminated soil remediation agent. Its production process is simple and can be produced on a large scale. Raw materials such as polyvinyl alcohol, ferromagnetic powder, biomass charcoal and bentonite are widely sourced, and are easily degraded in the soil. After repairing heavy metal pollution, it can also increase soil quality; it can be used for heavy, medium and light. It can effectively repair soil contaminated by heavy metals, and at the same time complete the passivation of heavy metal elements such as cadmium, arsenic, lead, mercury, copper, chromium, nickel, manganese in the soil, and enrich the soil; rich in iron and magnesium elements, can It enriches the element ratio in the soil. In addition, the iron-magnesium calamus charcoal also has the function of enriching nitrogen and phosphorus in the soil solution. The iron-magnesium calamus charcoal after enriching nitrogen and phosphorus can be used as nitrogen and phosphorus slow-release fertilizer to further enrich the soil quality; bentonite The magnetic polyvinyl alcohol microspheres can also be coated with the polyvinyl alcohol composite resin, and the outside is further bonded by an adhesive, which can play a good slow-release effect in the process of gradual degradation, and improve the degradation of heavy metals by heavy metal-contaminated soil remediation agents. to the fourth quarter, significantly reducing costs.

[3] Application of the heavy metal-contaminated soil remediation agent according to any one of items [1] to [2] in the remediation of heavy metal pollution in soil.

[4] A method for remediating heavy metal pollution in soil, the method comprising:

Apply the heavy metal-contaminated soil remediation agent described in any of items [1] to [2] with a thickness of 0.2 to 1 cm on the surface of the heavy metal-contaminated soil, and then mix the soil layer at least 15 cm deep from the soil surface by ploughing. The restoration of heavy metal-contaminated soil can be completed after 3 to 5 months of maintenance after light spraying.

The beneficial effects of the present invention are:

1) The soil conditioning precursor ternary structure composed of magnetic polyvinyl alcohol microspheres, iron-magnesium calamus charcoal and bentonite/polyvinyl alcohol composite resin is used as the effective component, supplemented by diatomite and starch granulation to obtain heavy metal contaminated soil remediation The production process is simple and can be produced on a large scale. The raw materials such as polyvinyl alcohol, ferromagnetic powder, biomass charcoal and bentonite are widely sourced, and are easily degraded in the soil, and the soil can be fertilized after repairing heavy metal pollution;

2) It can efficiently remediate soils polluted by heavy, medium and mild heavy metals, and at the same time complete the passivation of heavy metal elements such as cadmium, arsenic, lead, mercury, copper, chromium, nickel, manganese in the soil, and increase soil growth. Fertilizer; rich in iron and magnesium elements, which can enrich the element ratio in the soil. In addition, iron and magnesium calamus charcoal also has the function of enriching nitrogen and phosphorus in soil solution. The iron and magnesium calamus charcoal after enriching nitrogen and phosphorus can be used as nitrogen and phosphorus buffer Release fertilizer to further increase soil quality;

3) Bentonite/polyvinyl alcohol composite resin, magnetic polyvinyl alcohol microspheres, and iron-magnesium calamus charcoal are compounded into heavy metal-contaminated soil remediation agent, which is beneficial to increase soil water retention capacity, increase soil moisture value, and synergize after degradation The soil quality, its higher salt adsorption effect can also significantly enhance the ability of the repair agent to gather heavy metal elements, adsorb heavy metal ions around the repair agent and then be degraded and removed, significantly improving the ability to degrade heavy metals;

4) The heavy metal contaminated soil remediation agent can play a good slow-release effect in the process of gradual degradation, improve the heavy metal contaminated soil remediation agent's effect of degrading heavy metals to the fourth season, prolong the action time, and significantly reduce the cost.

The present invention adopts the above-mentioned technical scheme to achieve the above-mentioned purpose, makes up for the deficiencies of the prior art, has a reasonable design and is convenient to operate.

Description of drawings

In order to make the above-mentioned and/or other objects, features, advantages and examples of the present invention more clearly understood, the accompanying drawings are described as follows:

Fig. 1 is the magnetization performance detection schematic diagram of the magnetic polyvinyl alcohol microsphere in some embodiments of the present invention;

Fig. 2 is a schematic diagram of the passivation of the heavy metal cadmium in soil by the repairing agent of some embodiments of the present invention through four seasons;

3 is a schematic diagram of the passivation effect of the remediators in some embodiments of the present invention on the heavy metal arsenic in the soil through four seasons;

FIG. 4 is a schematic diagram of the passivation effect of the repairing agent on the heavy metal lead in the soil through four seasons according to some embodiments of the present invention.

Detailed ways

Those skilled in the art can refer to the content of this document and appropriately replace and/or modify the process parameters to achieve, however, it should be pointed out that all similar replacements and/or modifications are obvious to those skilled in the art, and they are regarded as including in the present invention. The products and preparation methods of the present invention have been described through preferred examples, and relevant persons can obviously make changes or appropriate changes and combinations to the products and preparation methods described herein without departing from the content, spirit and scope of the present invention. Implement and apply the technology of the present invention.

Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The present invention employs the methods and materials described herein; however, other suitable methods and materials known in the art can also be used. The materials, methods, and examples described herein are illustrative only and not intended to be limiting. All publications, patent applications, patents, provisional applications, database entries, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control.

Unless otherwise stated, all percentages, parts, ratios, etc. are by weight; otherwise stated include, but are not limited to, "wt%" means weight percent, "mol%" means mole percent, "vol%" means volume percentage.

When an amount, concentration, or other value or parameter is given in terms of a range, preferred range, or a series of upper and lower preferred values, it is to be understood that it specifically discloses the limitation or preference from any larger range and any smaller value All ranges formed by any pair of numerical values of the range limits or preferred values, whether or not the ranges are separately disclosed. For example, when describing the range of "1 to 5 (1~5)", the described range should be understood to include "1 to 4 (1~4)", "1 to 3 (1~3)", "1" to 2 (1 to 2)", "1 to 2 (1 to 2) and 4 to 5 (4 to 5)", "1 to 3 (1 to 3) and 5", and the like. Unless otherwise indicated, where numerical ranges are described herein, the ranges are intended to include the endpoints of the range as well as all integers and fractions within the range.

When the term "about" is used to describe a value or an endpoint of a range, the disclosure should be understood to include the specific value or endpoint referred to.

Furthermore, unless expressly stated to the contrary, "or (or)" refers to an inclusive "or (or)" rather than an exclusive "or (or)". For example, the condition A "or" B applies: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), and Both A and B are true (or exist).

Furthermore, the indefinite articles "a" and "an" preceding an element or component of the invention are intended to mean that the number of occurrences (ie, occurrences) of the element or component is not limiting. Thus "a" or "an" should be read to include one or at least one, and the singular form of said elements or components also includes the plural unless the number is expressly stated to be in the singular.

It should be noted that, in this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any relationship between these entities or operations. any such actual relationship or sequence exists. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device that includes a list of elements includes not only those elements, but also includes not explicitly listed or other elements inherent to such a process, method, article or apparatus. without more restrictions. An element defined by the phrase "comprising an... does not preclude the presence of additional identical elements in a process, method, article or apparatus comprising said element".

Unless specifically stated, the materials, methods, and examples described herein are illustrative and not restrictive. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

The present invention is described in detail below.

Example 1: A heavy metal contaminated soil remediation agent:

The present embodiment provides a heavy metal contaminated soil remediation agent, and the remediation agent includes:

a soil conditioning precursor consisting of magnetic polyvinyl alcohol microspheres, iron-magnesium calamus charcoal, and bentonite/polyvinyl alcohol composite resin in a weight ratio of 1:4.5:1.5; and

A binder composition consisting of bentonite and starch;

Wherein, the magnetization of the magnetic polyvinyl alcohol microspheres is not less than 2.5 A·m ² /kg.

The heavy metal contaminated soil remediation agent is prepared through a method comprising the following steps.

1) Preparation of magnetic polyvinyl alcohol microspheres:

1.1) 0.4 parts by weight of gelatin is completely dissolved in sufficient distilled water at room temperature;

1.2) 0.5 parts by weight of benzoyl peroxide, 10 parts by weight of liquid wax, 10 parts by weight of divinylbenzene and 30 parts by weight of polyvinyl alcohol (weight average molecular weight 16000) were added successively under stirring at 120r/min, and continued stirring for 45min;

1.3) At a rate of 1.0°C/min, the temperature was raised to 50°C and kept for 10min, and 0.8 parts by weight of sodium carbonate and 1.5 parts by weight of magnesium sulfate were added;

1.4) The temperature was raised to 75°C at a rate of 1.0°C/min and kept for 15min, and 3 parts by weight of Fe ₃ O ₄ magnetic powder was added and kept for 4h;

1.5) At a rate of 1.0°C/min, the temperature was raised to 95°C and kept for 2 hours. After the solution was cooled to 78°C for washing, suction filtration, vacuum drying at 60°C, and pulverizing through a 100-mesh sieve, the solution was obtained;

The magnetic powder is modified through the following steps: 1 part by weight of Fe ₃ O ₄ magnetic powder and 1 part by weight of vinyltrimethoxysilane are added to 100 parts by weight of 65% ethanol solution for uniform dispersion, and under nitrogen protection, the temperature is slowly raised to 42° C. And stirred at 1000r/min for 18h, washed with ethanol and deionized water for many times, and dried under vacuum at 60°C for 48h.

2) Preparation of iron-magnesium calamus charcoal:

2.1) pulverize the washed and dried calamus, and sieve to obtain wood chips with a size not greater than 0.5 mm;

2.2 ₎ ^{Fe 3+} _{, Fe 2+} ^and _{Fe 3+} , _{Fe 2+} and Mg ²⁺ mixed impregnation stabilization solution;

2.3) Under nitrogen, according to the weight ratio of wood chips and metal cations 50:1, the wood chips of step 2.1) were dipped into the mixed dipping stabilization solution of step 2.2) for 2h;

2.4) Under nitrogen, the mixed solution in step 2.3) was heated to 560°C for pyrolysis at a rate of 8°C/min for 2h;

2.5) Washing step 2.4) The ash on the biochar is 5 times, dried, pulverized and passed through a 100-mesh sieve.

3) preparation of bentonite/polyvinyl alcohol composite resin;

3.1) At room temperature, a sufficient amount of oxalic acid solution was added to the natural bentonite for soaking, and the reaction was carried out in a shaking table at 150 times/min for ^2h , then hemicellulose lye and sodium bisulfite were added, and 60KHz, 0.6w/cm was ultrasonically dispersed for 20min;

3.2) Rapidly raise the temperature to 60°C, add an aqueous solution of polyvinyl alcohol (weight average molecular weight 20000), and react at constant temperature for 45min under stirring. The product is flocculated and washed with ethanol, dried at 65°C for 12h, fully ground and passed through a 120-mesh sieve, extracted with acetone for 12h and dried. get it done;

Among them, the weight ratio of natural bentonite, oxalic acid, hemicellulose, sodium bisulfite and polyvinyl alcohol is 1:1:0.5:0.012:0.4.

4) Compounding:

The materials obtained in steps 1), 2) and 3) are fully mixed according to the formula to obtain a soil conditioning precursor;

5) Granulation:

The soil conditioning precursor prepared in step 4) is evenly mixed with diatomite and starch according to a mass ratio of 50:1:4, water is sprayed to granulate, the particle size is 4.0±0.5mm, and after drying, a heavy metal contaminated soil remediation agent is obtained.

Among them, the pH of diatomite is 7.5, the specific surface area is 2.6, and the thickness is 325 mesh, which was purchased from Shijiazhuang Hualang Mineral Products Trading Co., Ltd.; the pH of bentonite is 8.0, the whiteness is 55, the density is 1.3g/cm3, and the particle size is 180-220 It was purchased from Nanjing Hengfeng Calcium Carbonate Factory.

Example 2: Another heavy metal contaminated soil remediation agent:

This embodiment provides another heavy metal-contaminated soil remediation agent, whose components, proportions and preparation methods are basically the same as those in embodiment 1, the only difference is that the soil conditioning precursor of this embodiment does not contain magnetic polyethylene Alcohol microspheres.

Example 3: Another heavy metal contaminated soil remediation agent:

This embodiment provides another heavy metal-contaminated soil remediation agent, and its components, proportions and preparation methods are basically the same as those in embodiment 1, the only difference is that the soil conditioning precursor of this embodiment does not contain iron-magnesium calamus carbon.

Example 4: Another heavy metal contaminated soil remediation agent:

This embodiment provides another heavy metal-contaminated soil remediation agent, and its components, proportions and preparation methods are basically the same as those in embodiment 1, the only difference is that the soil conditioning precursor of this embodiment does not contain bentonite/polyethylene Vinyl alcohol composite resin.

Example 5: Another heavy metal contaminated soil remediation agent:

This embodiment provides another heavy metal-contaminated soil remediation agent, and its components, proportions and preparation methods are basically the same as those in Embodiment 1, the only difference is that the magnetic polyvinyl alcohol microparticles in the soil conditioning precursor of this embodiment are The weight ratio of balls, calamus charcoal and bentonite/polyvinyl alcohol composite resin is 1:1:1.

Example 6: Another heavy metal contaminated soil remediation agent:

This example provides another heavy metal-contaminated soil remediation agent, and its components, proportions and preparation methods are basically the same as those in Example 1, the only difference is that in the preparation of magnetic polyvinyl alcohol microspheres in this example, heavy metals are used. Polystyrene with an average molecular weight of 16,000 replaces polyvinyl alcohol.

Example 7: Another heavy metal contaminated soil remediation agent:

This embodiment provides another heavy metal contaminated soil remediation agent, and its components, proportions and preparation methods are basically the same as those in embodiment 1, the only difference is that when preparing magnetic polyvinyl alcohol microspheres in this embodiment, Fe ₃ The O ₄ magnetic powder was used to prepare magnetic polyvinyl alcohol microspheres without any silane coupling agent modification.

Example 8: Another heavy metal contaminated soil remediation agent:

This embodiment provides another heavy metal-contaminated soil remediation agent, and its components, proportions and preparation methods are basically the same as those in embodiment 1, the only difference is that in this embodiment, cotton straw is used instead of calamus to prepare iron-magnesium cotton straw charcoal, and it was combined with magnetic polyvinyl alcohol microspheres and bentonite/polyvinyl alcohol composite resin to prepare a heavy metal contaminated soil remediation agent according to the ratio and method of Example 1.

Example 9: Another heavy metal contaminated soil remediation agent:

This embodiment provides another heavy metal contaminated soil remediation agent, and its components, proportions and preparation methods are basically the same as those in embodiment 1, the only difference is that in this embodiment, when preparing iron-magnesium calamus charcoal, it is mixed with an impregnating stable solution does not contain Fe ³⁺ .

Example 10: Another heavy metal contaminated soil remediation agent:

This embodiment provides another heavy metal contaminated soil remediation agent, and its components, proportions and preparation methods are basically the same as those in embodiment 1, the only difference is that when preparing iron-magnesium calamus charcoal in this embodiment, the immersion stabilization solution is mixed does not contain Fe ²⁺ .

Example 11: Another heavy metal contaminated soil remediation agent:

This embodiment provides another heavy metal contaminated soil remediation agent, and its components, proportions and preparation methods are basically the same as those in embodiment 1, the only difference is that when preparing iron-magnesium calamus charcoal in this embodiment, the immersion stabilization solution is mixed does not contain Mg ²⁺ .

Example 12: Another heavy metal contaminated soil remediation agent:

This embodiment provides another heavy metal-contaminated soil remediation agent, and its components, proportions and preparation methods are basically the same as those in embodiment 1, the only difference is that when the bentonite/polyvinyl alcohol composite resin is prepared in this embodiment, natural The bentonite was not soaked in oxalic acid solution, and after dispersing the natural bentonite in water, hemicellulose lye and sodium bisulfite were added, and the heavy metal contaminated soil remediation agent was prepared with the same subsequent steps and other steps as in Example 1.

Experimental example 1: Physical and chemical detection of magnetic polyvinyl alcohol microspheres:

The magnetic properties of the magnetic polyvinyl alcohol microspheres can be detected by the VSM-4HF vibrating sample magnetometer, and the Fe ₃ O ₄ coating rate of the magnetic polyvinyl alcohol microspheres can be detected by thermogravimetric analysis. , 6 and 7 were tested for magnetic properties and coverage, and the test results are shown in Figure 1 and Table 1.

Table 1. Physical and chemical detection results of magnetic polyvinyl alcohol microspheres

Example group Fe₃O₄ Coverage (%) Example 1 8.89 Example 6 6.62 Example 7 4.15

It can be seen from Figure 1 and Table 1 that, compared with polystyrene instead of polyvinyl alcohol, Fe ₃ O ₄ powder without silane coupling agent modification has the maximum saturation magnetization of magnetic polyvinyl alcohol microspheres and Fe ₃ The O ₄ coating ratio has a more significant effect, and the maximum saturation magnetization of the magnetic polyvinyl alcohol microspheres prepared without silane coupling agent modification is even lower than 3.0 A·m ² /kg.

Experimental example 2: Detection of the passivation effect of heavy metal contaminated soil remediation agent on heavy metal contaminated acidic soil:

The heavy metal-contaminated acidic soil in this experimental example was collected from the topsoil of a heavy-metal-contaminated farmland in Zhejiang Province. It was naturally air-dried and passed through a 10-mesh sieve. The measured pH was about 4.5, the total cadmium content was 48.52 ppm, the total arsenic content was 435.65 ppm, and the total lead content was 435.65 ppm. The content is 865.33pm, which belongs to heavy heavy metal polluted soil. Divide the soil into 12 groups, each group of 10kG is placed in a plastic bucket with an inner diameter of 40cm, and the repairing agents in Examples 1 to 12 are respectively laid in the above 12 groups of plastic buckets with a thickness of 0.5cm, and then each group of plastic buckets are placed in The soils were evenly mixed, sprayed with 500 g of clean water and left for 3 months indoors, analyzed the heavy metal cadmium, arsenic, and lead contents, and calculated the reduction value compared with the control soil without remediation agent treatment. Rice was planted after ploughing again. When the rice was harvested, samples were collected to analyze the contents of heavy metals cadmium, arsenic and lead in the grains, and the reduction values were calculated compared with the control soil without remediation agent treatment. Statistics are shown in Table 2.

Table 2. The passivation effect of the remediators of different embodiments on cadmium, arsenic and lead in heavy metal polluted acidic soil

It can be seen from Table 2 that the restoration agent in Example 1 of the preferred embodiment of the present application can not only significantly reduce the contents of cadmium, arsenic and lead in the acid soil polluted by heavy metals, but also effectively prevent the aforementioned three heavy metals from entering the rice grains. Therefore, while remediating heavy metal-contaminated soil, it reduces the absorption and accumulation effect of rice and protects human health.

Experimental Example 3: Detection of the passivation effect of heavy metal contaminated soil remediation agent on heavy metal contaminated alkaline soil:

The heavy metal-contaminated acidic soil in this experimental example was collected from the topsoil of a heavy-metal-contaminated farmland in Zhejiang Province, and was naturally air-dried and passed through a 10-mesh sieve. The measured pH was about 8.0, the total cadmium content was 62.58 ppm, the total arsenic content was 502.84 ppm, and the total lead content was 502.84 ppm. The content is 755.59pm, which belongs to heavy heavy metal polluted soil. In the same way as in Experimental Example 2, the restoration agents in Examples 1 to 12 were used to restore it, and the heavy metal cadmium, arsenic, and lead contents were analyzed, and the reduction value was calculated compared with the control soil without the restoration agent treatment. The rice was planted and harvested, and samples were collected to analyze the heavy metal cadmium, arsenic, and lead contents in the grains, and the reduction values were calculated compared with the control soil without remediation agent treatment. Statistics are shown in Table 3.

Table 3. The passivation effect of different embodiment remediation agents on cadmium, arsenic and lead in heavy metal polluted alkaline soil

It can be seen from Table 3 that the remediation agent in Example 1 of the preferred embodiment of the present application can also be applied to the remediation work of heavy metal-contaminated alkaline soil, and at the same time of remediating the heavy metal-contaminated soil, it can reduce the amount of heavy metals in the heavy metal-contaminated alkaline soil caused by rice. The cumulative effect of absorption of cadmium, arsenic and lead to protect human health.

Experimental example 4:

Collected from the farmland near a mine in Zhejiang Province, it was simultaneously enriched with cadmium (32.68ppm), arsenic (322.50ppm), lead (558.84ppm), mercury (12.55ppm), copper (598.65ppm), chromium (45.26ppm), nickel (22.69ppm) and manganese (458.33ppm) and other heavy metals polluted soil, according to the remediation method in Example 2, the reduction value was calculated compared with the control soil without remediation agent treatment. Statistics are shown in Table 4.

Table 4. The passivation effect of remediators of different embodiments on multiple heavy metals in heavy metal contaminated soil

As can be seen from Table 4, the remediation agent in Example 1 of the present application can efficiently passivate and remove heavy metal elements such as cadmium, arsenic, lead, mercury, copper, chromium, nickel, and manganese in the soil, which is concise and rapid. To remediate soil polluted by heavy metals, improve the current problem of agricultural soil waste caused by multiple heavy metal pollution in my country, and further improve the urgent situation of excessive heavy metal content in crops.

Experimental example 5:

On the basis of Experimental Example 3, Example 1, Example 6, Example 7, and Example 12 were selected respectively, and the continuous remediation effect of their corresponding remediators on heavy metal-contaminated soil was continued to be tested. The content of heavy metals in the soil before rice planting in the season, the third season, and the fourth season (two seasons each year), the statistical results are shown in Figures 2-4 respectively. It can be clearly seen that the restoration agent in Example 1 of the preferred embodiment of the present application can efficiently and continuously passivate heavy metals in the soil, can continuously act on four growth agents, and has higher passivation efficiency than ordinary iron-based biochar. The action time is longer; at the same time, it should be seen that soaking bentonite with oxalic acid and modifying Fe ₃ O ₄ magnetic powder with silane coupling agent have a greater impact on the continuous passivation of heavy metals by the repair agent.

The conventional technology in the above-mentioned embodiment is the prior art known to those skilled in the art, so it will not be described in detail here.

In view of the numerous embodiments of the solution of the present invention, and the experimental data of each embodiment is huge and numerous, it is not suitable to enumerate and describe one by one here, but the content to be verified in each embodiment and the final conclusion obtained are close. Therefore, the verification content of each embodiment will not be described one by one here, and only Examples 1 to 12 and Experimental Examples 1 to 5 are used as representatives to illustrate the advantages of the present application.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which the present invention pertains can make various modifications or additions to the described specific embodiments or substitute in similar manners, but will not deviate from the spirit of the present invention or go beyond the scope defined by the appended claims.

Although the present invention has been described in detail and cited some specific embodiments, it will be apparent to those skilled in the art that various changes or modifications can be made without departing from the spirit and scope of the present invention.

While the foregoing detailed description has shown, described and indicated novel features applicable to the various embodiments, it should be understood that changes may be made in the form and detail of the illustrated apparatus or method without departing from the spirit of the present disclosure. Various omissions, substitutions and changes. In addition, the various features and methods described above may be used independently of each other or in various combinations. All possible combinations and subcombinations are intended to fall within the scope of this disclosure. Many of the above-described embodiments include similar components, and thus, these similar components are interchangeable in different embodiments. While the invention has been disclosed in the context of certain embodiments and examples, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or applications as well as their obvious Modifications and Equivalents. Therefore, it is not intended that the present invention be limited by the specific disclosure of the preferred embodiments herein.

Claims (10)

1. A heavy metal contaminated soil remediation agent, the remediation agent comprising:

a soil conditioning precursor consisting of magnetic polyvinyl alcohol microspheres, acorus gramineus carbon and bentonite/polyvinyl alcohol composite resin in a weight ratio of 1.0: 3.0-5.0: 1.5-3.0; and

a binder component;

wherein the saturation magnetization intensity of the magnetic polyvinyl alcohol microspheres is not less than 3.0 A.m²·kg^-1。

2. The heavy metal contaminated soil remediation agent of claim 1, wherein: the magnetic polyvinyl alcohol microspheres are prepared by a method comprising the following steps:

1) 0.3-0.5 weight part of gelatin is completely dissolved in sufficient distilled water at room temperature;

2) sequentially adding 0.3-0.5 part by weight of benzoyl peroxide, 8-10 parts by weight of liquid wax, 8-10 parts by weight of divinylbenzene and 25-40 parts by weight of polyvinyl alcohol under stirring, and continuously stirring for at least 45 min;

3) heating to 48-50 ℃, preserving the temperature for at least 10min, and adding 0.6-0.8 part by weight of sodium carbonate and 1.5-2.0 parts by weight of magnesium sulfate;

4) heating to 70-78 ℃, preserving heat for at least 15min, adding 2.5-4.0 parts by weight of magnetic powder, and preserving heat for at least 4 h;

5) heating to 90-98 ℃, keeping the temperature for at least 2h, cooling the solution to below 80 ℃, washing, filtering, drying in vacuum, crushing, and sieving with at least 100-mesh sieve.

3. The heavy metal contaminated soil remediation agent of claim 2, wherein:

the magnetic powder of the step 4) is Fe₃O₄Magnetic powder of said Fe₃O₄The magnetic powder is preferably modified by a silane coupling agent.

4. The heavy metal contaminated soil remediation agent of claim 2 or 3, wherein: the magnetic powder of the step 4) is modified through the following steps: equal weight of Fe₃O₄Magnetic powder andadding a silane coupling agent into 50-75% ethanol solution which is at least 50 times the weight of the silane coupling agent, uniformly dispersing, slowly heating to 42-45 ℃ under the protection of nitrogen, stirring for at least 18h at 800-1200 r/min, washing for multiple times by using ethanol and deionized water, and drying in vacuum at 60 ℃ for at least 48 h.

5. The heavy metal contaminated soil remediation agent of any one of claims 1 to 4, wherein: the calamus carbon is prepared by a method comprising the following steps:

1) pulverizing cleaned and dried rhizoma Acori Calami, and sieving to obtain sawdust with size not greater than 0.5 mm;

2) preparation of a composition containing Fe³⁺、Fe²⁺And Mg²⁺The mixed impregnation stabilizing solution of (1);

3) under nitrogen, soaking the sawdust in the step 1) into the mixed soaking stable solution in the step 2) for at least 2 hours according to the weight ratio of the sawdust to the metal cations of 100: 1.0-3.0;

4) heating the mixed solution obtained in the step 3) to 550-580 ℃ under nitrogen, and pyrolyzing for at least 1.5 h;

5) and (5) washing ash on the biochar in the step 4) for multiple times, drying, crushing and sieving by a 100-mesh sieve to obtain the biological carbon.

6. The heavy metal contaminated soil remediation agent of claim 5, wherein: fe in the step 2)³⁺、Fe²⁺And Mg²⁺The amount ratio of the substances (A) is 2-3: 1: 0.3-1.

7. The heavy metal contaminated soil remediation agent of any one of claims 1 to 5, wherein: the bentonite/polyvinyl alcohol composite resin is prepared by a method comprising the following steps:

1) at room temperature, adding sufficient oxalic acid solution into natural bentonite, soaking, reacting for at least 2 hours in a shaking table for 120-150 times/min, adding hemicellulose alkali liquor and sodium bisulfite, and performing ultrasonic dispersion for at least 20 min;

2) and (3) rapidly heating to 55-60 ℃, adding a polyvinyl alcohol aqueous solution, reacting at a constant temperature for at least 30min under stirring, flocculating and washing a product with ethanol, drying, fully grinding, extracting with acetone for 12h, and drying to obtain the product.

8. The method for preparing the heavy metal contaminated soil remediation agent of any one of claims 1 to 7, wherein the method comprises:

1) preparing magnetic polyvinyl alcohol microspheres;

2) preparing iron magnesium calamus carbon;

3) preparing bentonite/polyvinyl alcohol composite resin;

4) fully mixing the materials prepared in the steps 1), 2) and 3) according to the weight ratio of 1.0: 3.0-5.0: 1.5-3.0 to obtain a soil conditioning precursor;

5) uniformly mixing the soil conditioning precursor prepared in the step 4) with diatomite and starch according to the mass ratio of 100: 1-10, spraying water for granulation, and drying to obtain the heavy metal contaminated soil remediation agent.

9. The use of the heavy metal contaminated soil remediation agent of any one of claims 1 to 8 for remediating heavy metal contaminated soil.

10. A method of remediating heavy metal contamination of soil, the method comprising:

the heavy metal contaminated soil remediation agent according to any one of claims 1 to 8 is applied to the surface of heavy metal contaminated soil, wherein the thickness of the heavy metal contaminated soil remediation agent is 0.2 to 1cm, then soil layers at least 15cm deep away from the surface layer of the soil are uniformly mixed in a turning mode, and the heavy metal contaminated soil is remedied after maintenance for 3 to 5 months after slight water spraying.

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