Soil heavy metal pollution treatment and ecological restoration method

Abstract

The invention discloses a soil heavy metal pollution treatment and ecological restoration method, and relates to the technical field of pollution treatment. Comprising the following steps: (1) soil pretreatment; (2) a bioremediation stage; (3) deep stabilization treatment; (4) detecting and circularly repairing; according to the invention, the modified clay and the magnetic nano material are used for synergistically adsorbing heavy metals, and the 72-hour removal rate exceeds 90%; the pericarp fermented environment-friendly enzyme fertilizer is used for activating heavy metals and promoting plant growth; heavy metals are enriched and the soil environment is improved through an earthworm-microorganism coupling remediation system; biomass charcoal and a low-temperature treatment technology are combined, so that the heavy metal forms a stable complex, and the method is efficient, low in cost and free of secondary pollution.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pollution treatment, more particularly to a soil heavy metal pollution treatment and ecological restoration method. BACKGROUND

[0002] With the rapid development of industry and agriculture and the accelerated urbanization process, the discharge amount of mine selection wastewater, chemical industry electroplating wastewater, domestic sewage and other industrial wastewater continues to increase, while the influence of atmospheric pollutants such as coal combustion and industrial waste gas is also increasingly significant. These pollutants continue to accumulate in the soil environment, resulting in a large number of cultivated land in China, especially basic farmland, facing serious threats from heavy metals and other pollutants.

[0003] With the intensification of human production activities, the problem of ecological environment pollution is becoming increasingly serious, and soil pollution has become a major environmental problem that needs to be addressed urgently. The common toxic heavy metals in agricultural land mainly include mercury, cadmium, arsenic, chromium and lead. The soil in these areas is mostly low-pH variable charge soil, and has weak buffering capacity to exogenous acidic substances and extremely limited ability to fix heavy metals. In some areas, the soil has even reached saturation state and faces the risk of pollution overflow. The heavy metals in the soil have high activity, and once the external environment changes, they can easily dissolve into soil solution, or contaminate groundwater and surface water with runoff, or be absorbed by plants, and then harm human and animal health through the food chain. Taking cadmium pollution as an example, the background value in the contaminated area is generally high, and the cadmium content in rice in some contaminated areas can be more than ten times that in clean irrigation areas, and the cadmium content in vegetables can even be several dozen times higher. As can be seen, agricultural land contaminated by heavy metals poses a serious potential threat to public health.

[0004] Due to the limited self-purification capacity of the soil, if the pollution problem cannot be effectively treated and restored, it will directly or indirectly lead to pollution of surface water and groundwater, decline in agricultural product yield and quality, and even harm human health and affect social sustainable development.

[0005] Therefore, it is an urgent problem for those skilled in the art to provide an efficient and feasible soil heavy metal pollution treatment and ecological restoration method. SUMMARY

[0006] Therefore, the present application provides a soil heavy metal pollution treatment and ecological restoration method.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A soil heavy metal pollution treatment and ecological restoration method, comprising the following steps:

[0009] (1) Soil pretreatment: The contaminated soil is broken to a particle size of less than 3 mm, modified clay mineral adsorbent and magnetic nanomaterial are added, mechanical stirring is carried out, and then magnetic separation is carried out to separate the magnetic material adsorbing heavy metals;

[0010] (2) Bioremediation stage: super-accumulating plants are planted, and earthworms and functional microbial flora are introduced, and environment-friendly enzyme fertilizer is applied regularly to promote the activation and plant absorption of heavy metals;

[0011] (3) Deep stabilization treatment: biomass charcoal composite repair agent is mixed with soil, and after low-temperature freezing treatment, acid treatment agent is sprayed to realize long-term fixation of heavy metals;

[0012] (4) Detection and cyclic repair: the content of heavy metals in the soil is detected, and steps (1)-(3) are repeated when the standard is not met.

[0013] Further, in step (1), the modified clay mineral adsorbent is prepared by mixing montmorillonite, bentonite and phosphoric acid modified attapulgite in a volume ratio of 1:2:1, and the dosage is 20 kg / mu;

[0014] The magnetic nanomaterial is neodymium-iron-boron magnetic core loaded with ferroferric oxide activated carbon particles, and the dosage is 15-55 g per kilogram of soil.

[0015] Further, in step (2), the super-accumulating plants are selected from at least two of Taraxacum officinale, Amorpha fruticosa and Bidens pilosa;

[0016] The earthworms are Eisenia foetida, and the density of the earthworms is 50-100 per square meter;

[0017] The functional microbial flora comprises Bacillus subtilis and arbuscular mycorrhizal fungi.

[0018] Further, in step (2), the environment-friendly enzyme fertilizer is a liquid fertilizer obtained by mixing sucrose, fruit peel and water in a mass ratio of 1:30-40:100-120, and then filtering after at least 3 months of fermentation, wherein the fruit peel is yellow peach peel.

[0019] Further, the daily application method of the environment-friendly enzyme fertilizer is to dilute it with water in a volume ratio of 1:500-1000, and then apply it to the soil around the roots of terrestrial plants by drip irrigation or sprinkling irrigation at a frequency of 30-50 days.

[0020] Further, in step (3), the biomass charcoal composite repair agent is prepared by mixing biomass charcoal, sulfonated chitosan and cellulose solution in a mass ratio of 3:1:2;

[0021] The acid treatment agent is a mixture of oxalic acid and acetic acid in a ratio of 1:2 (v:v), and the spraying amount is 50 times dilution with water, and the spraying amount is 20-35 mL / kg of soil.

[0022] The low-temperature treatment temperature is -10 DEG C to -2 DEG C, and the treatment time is 12-48 hours.

[0023] Further, the biomass charcoal is prepared by grinding (through a 100-mesh sieve) after high-temperature sealing carbonization of straw waste at 325 DEG C for 40 hours, and the specific surface area is greater than or equal to 500 m 2 / g.

[0024] Compared with the prior art, the beneficial effects of the application are as follows:

[0025] The application adopts the modified clay mineral adsorbent to efficiently remove heavy metals in contaminated soil, and combines with magnetic nanomaterial to separate the soil and the heavy metals, so that the modified clay and the magnetic material synergistically act to significantly improve the soil quality and create favorable conditions for subsequent crop planting.

[0026] The application uses the environment-friendly enzyme fertilizer prepared by fermentation of waste fruit peels as topdressing, has the functions of activating heavy metals, promoting crop growth and optimizing the living environment of earthworms, realizes resource utilization of waste, does not need to add chemical agents, reduces the remediation cost, and avoids the problems of residues and secondary pollution caused by traditional chemical leaching.

[0027] The earthworms are rich in various enzymes, which can not only play the functions of activation, absorption and enrichment of heavy metals (such as cadmium, arsenic, mercury, lead, copper and zinc) in the soil under single or combined pollution conditions, but also can improve the heavy metal contaminated soil environment, promote nutrient circulation and enhance plant growth through the activities of the earthworms and their excrement (earthworm manure). The microbial flora in the earthworm manure can also adjust the biological availability of heavy metals in the soil through activation or passivation mechanism, and effectively repair the heavy metal pollutants in the soil.

[0028] In the soil remediation process, the growth of cellulose crystals is regulated by low-temperature after the treatment of the remediation agent, the formation of complex three-dimensional network structure is promoted, the heavy metal ions are firmly wrapped and complexed, and due to the crystallization effect, the heavy metal ions are difficult to dissolve in the solvent, and finally deposited in the carbon layer and adsorbed, so that the heavy metal ions and organic pollutants are efficiently removed. After one round of remediation, the cadmium concentration in the soil is reduced from 48 mg / kg to 2.4 mg / kg (removal rate 95%), and the mercury concentration is reduced from 53 mg / kg to 4.1 mg / kg (removal rate 92.3%); in the case of lead-zinc combined pollution, the lead concentration is reduced from 35 mg / kg to 1.5 mg / kg (removal rate 95.7%), and the zinc concentration is reduced from 28 mg / kg to 1.2 mg / kg (removal rate 95.7%). DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0030] Embodiment 1

[0031] Treatment of a certain cadmium and mercury contaminated farmland (initial concentration of cadmium 48 mg / kg, mercury 53 mg / kg);

[0032] A soil heavy metal pollution treatment and ecological restoration method, comprising the following steps:

[0033] (1) Soil pretreatment: the contaminated soil is crushed to a particle size of less than 3 mm, modified clay mineral adsorbent and magnetic nanometer material are added, and after mechanical stirring, the magnetic material adsorbing heavy metals is separated by magnetic separation;

[0034] The modified clay mineral adsorbent is made by mixing montmorillonite, bentonite and phosphoric acid modified attapulgite in a volume ratio of 1:2:1, and the dosage is 20 kg per mu; the modified clay mineral adsorbent has a mercury adsorption capacity of 85 mg / kg;

[0035] The magnetic nanometer material is neodymium-iron-boron magnetic core loaded with ferroferric oxide activated carbon particles, and the dosage is 55 g per kilogram of soil; after magnetic separation, the magnetic nanometer material has a cadmium adsorption capacity of 0.8 mg / g.

[0036] (2) Biological remediation stage: super-accumulating plants are planted, and earthworms and functional microbial flora are introduced, and environment-friendly enzyme fertilizer is regularly applied to promote heavy metal activation and plant absorption;

[0037] The super-accumulating plants are dandelion and three-leaf bidens;

[0038] The earthworms are Eisenia foetida, and the density of the earthworms is 80 per square meter;

[0039] The functional microbial flora contains Bacillus subtilis.

[0040] The environment-friendly enzyme fertilizer is a liquid topdressing obtained by mixing sucrose, fruit peel and water in a mass ratio of 1:30:100 and then filtering after at least 3 months of fermentation, wherein the fruit peel is yellow peach peel.

[0041] The daily application method of the environment-friendly enzyme fertilizer is to dilute it with water in a volume ratio of 1:500, and then uniformly apply it to the soil around the roots of terrestrial plants at a frequency of 50 days once by drip irrigation or sprinkling irrigation.

[0042] After 6 months, the cadmium content of the plants reaches 1500 mg / kg.

[0043] (3) Deep stabilization treatment: the biomass charcoal composite remediation agent is mixed with the soil, and after low-temperature freezing treatment, an acid treatment agent is sprayed to achieve long-term fixation of heavy metals;

[0044] The biomass charcoal composite remediation agent is prepared by mixing biomass charcoal, sulfonated chitosan and cellulose solution at a mass ratio of 3:1:2; the low-temperature treatment temperature is -10°C, and the treatment time is 12 hours.

[0045] The biomass charcoal is prepared by grinding (through a 100-mesh sieve) after straw waste is carbonized at 325°C under high temperature and sealed for 40h, and the specific surface area is ≥500m2 / g; the acid treatment agent is a 1:2 (v:v) mixture of oxalic acid-acetic acid, the spraying amount is 50 times dilution with water, and 20-35mL / kg of soil is sprayed; after low-temperature treatment, the cadmium leaching concentration is reduced from 1.5mg / L to 0.05mg / L, and the mercury leaching concentration is reduced from 0.8mg / L to 0.2mg / L.

[0046] (4) Detection and cyclic remediation: detect the content of heavy metals in the soil, and repeat steps (1)-(3) when the standard is not met.

[0047] After one round of remediation, the cadmium content in the soil is 2.4mg / kg, and the mercury content is 4.1mg / kg.

[0048] Comparative Example 1

[0049] Example 1 is used to treat a cadmium and mercury contaminated farmland in the same plot (initial concentration of cadmium 48mg / kg, mercury 53mg / kg);

[0050] (1) Biological remediation stage: planting hyperaccumulating plants, introducing earthworms and functional microbial flora, and regularly applying environmentally friendly enzyme fertilizer to promote heavy metal activation and plant absorption;

[0051] The hyperaccumulating plants are dandelion and bidens pilosa;

[0052] The earthworms are Eisenia foetida, and the density of introduction is 80 per square meter;

[0053] The functional microbial flora contains Bacillus subtilis.

[0054] The environmentally friendly enzyme fertilizer is a liquid fertilizer obtained by filtering after at least 3 months of fermentation of a mixture of sucrose, fruit peel and water at a mass ratio of 1:30:100, wherein the fruit peel is yellow peach skin.

[0055] The daily application method of the environmentally friendly enzyme fertilizer is to dilute it with water at a volume ratio of 1:500 first, and then apply it to the soil around the roots of terrestrial plants evenly through drip irrigation or sprinkling irrigation at a frequency of 50 days.

[0056] The plant accumulated cadmium up to 820 mg / kg after 6 months.

[0057] (2) Deep stabilization treatment: the biomass charcoal composite remediation agent is mixed with the soil, and after low-temperature freezing treatment, an acidic treatment agent is sprayed to achieve long-term fixation of heavy metals;

[0058] The biomass charcoal composite remediation agent is prepared by mixing biomass charcoal, sulfonated chitosan and cellulose solution at a mass ratio of 3:1:2; the low-temperature treatment temperature is-10°C, and the treatment time is 12 hours.

[0059] The biomass charcoal is prepared by grinding (through a 100-mesh sieve) after straw waste is carbonized at 325°C under high temperature and sealed for 40h, and the specific surface area is ≥500m2 / g; the acidic treatment agent is a mixture of oxalic acid-acetic acid at a ratio of 1:2 (v:v), the spraying amount is 50 times dilution of water, and the spraying amount is 20-35mL / kg of soil;

[0060] After low-temperature treatment, the cadmium leaching concentration is reduced from 1.5mg / L to 0.3mg / L, and the mercury leaching concentration is reduced from 0.8mg / L to 0.5mg / L.

[0061] (3) Detection and cyclic remediation: detecting the content of heavy metals in the soil;

[0062] After remediation, the cadmium content in the soil is 24mg / kg, and the mercury content is 26mg / kg.

[0063] Compared with Example 1, Comparative Example 1 reduces the soil pretreatment operation, does not use magnetic nanomaterials to directionally adsorb cadmium, and only relies on natural sedimentation to cause a high proportion of free heavy metals; the soil is not broken, resulting in insufficient contact area between the adsorbent and the pollutants, and mercury is difficult to be captured by the modified clay mineral; high concentration of free heavy metals directly inhibits the root activity of hyperaccumulating plants, and the enrichment efficiency decreases; the soil porosity is low without pretreatment, and the solidifying agent (step 3) is difficult to penetrate uniformly, resulting in poor long-term stability.

[0064] Comparative Example 2

[0065] Example 1 is used to treat a cadmium and mercury contaminated farmland (initial concentration of cadmium 48mg / kg, mercury 53mg / kg) in the same field;

[0066] A soil heavy metal pollution treatment and ecological remediation method, comprising the following steps:

[0067] (1) Soil pretreatment: the contaminated soil is broken to a particle size of less than 3mm, modified clay mineral adsorbent and magnetic nanomaterials are added, and after mechanical stirring, the magnetic materials adsorbing heavy metals are separated by magnetic separation;

[0068] The modified clay mineral adsorbent is prepared by mixing montmorillonite, bentonite and phosphoric acid modified attapulgite in a volume ratio of 1:2:1, and the dosage is 20 kg / acre; the adsorption capacity of the modified clay mineral adsorbent for mercury reaches 85 mg / kg;

[0069] The magnetic nanomaterial is neodymium-iron-boron magnetic core loaded with ferroferric oxide activated carbon particles, and the dosage is 55 g per kilogram of soil. After magnetic separation, the adsorption capacity of the magnetic nanomaterial for cadmium reaches 0.8 mg / g.

[0070] (2) Deep stabilization treatment: mix the biomass charcoal composite repair agent with the soil, spray the acid treatment agent after low-temperature freezing treatment, and realize long-term fixation of heavy metals;

[0071] The biomass charcoal composite repair agent is prepared by mixing biomass charcoal, sulfonated chitosan and cellulose solution in a mass ratio of 3:1:2; the low-temperature treatment temperature is-10℃, and the treatment time is 12 hours.

[0072] The biomass charcoal is prepared by grinding (through a 100-mesh screen) after straw waste is carbonized at 325℃ under high temperature and sealed for 40h, and the specific surface area is ≥500m2 / g; the acid treatment agent is a mixed solution of oxalic acid-acetic acid in a volume ratio of 1:2 (v:v), the spraying amount is 50 times dilution of water, and the spraying amount is 20-35mL / kg of soil;

[0073] After low-temperature treatment, the cadmium leaching concentration is reduced from 1.5mg / L to 0.1mg / L, and the mercury leaching concentration is reduced from 0.8mg / L to 0.3mg / L.

[0074] (3) Detection and cyclic repair: detect the content of heavy metals in the soil;

[0075] After repair, the cadmium content in the soil is 18mg / kg, and the mercury content is 18mg / kg.

[0076] Compared with Example 1, Comparative Example 2 reduces the biological repair stage, lacks the chelation of heavy metals by the environment-friendly enzyme fertilizer, and the cadmium in the soil is mainly in the form of insoluble state, which cannot be absorbed by plants; the functional bacteria (such as Bacillus subtilis) are not introduced, resulting in insufficient secretion of organic acid and reduced desorption efficiency of mercury; only relying on the adsorption in step 1 and the solidification in step 3, the total amount of heavy metals is not reduced by plant extraction, and the residual amount of mercury is still high; the absence of earthworms leads to soil compaction, uneven penetration of the repair agent, and limited solidification effect.

[0077] Comparative Example 3

[0078] Example 1 is used to treat the cadmium and mercury contaminated farmland (initial concentration of cadmium 48mg / kg, mercury 53mg / kg) in the same plot.

[0079] A soil heavy metal pollution treatment and ecological restoration method, comprising the following steps:

[0080] (1) Soil pretreatment: the contaminated soil is broken to a particle size of less than 3 mm, modified clay mineral adsorbent and magnetic nanomaterial are added, mechanical stirring is carried out, and then the magnetic material adsorbing heavy metals is separated by magnetic separation;

[0081] The modified clay mineral adsorbent is prepared by mixing montmorillonite, bentonite and phosphoric acid modified attapulgite in a volume ratio of 1:2:1, and the dosage is 20 kg / acre; the adsorption capacity of the modified clay mineral adsorbent for mercury is 85 mg / kg;

[0082] The magnetic nanomaterial is neodymium-iron-boron magnetic core loaded with ferroferric oxide activated carbon particles, and the dosage is 55 g per kg of soil. After magnetic separation, the adsorption capacity of the magnetic nanomaterial for cadmium is detected to be 0.8 mg / g.

[0083] (2) Biological remediation stage: planting hyperaccumulating plants, introducing earthworms and functional microbial flora, and regularly applying environmentally friendly enzyme fertilizer to promote heavy metal activation and plant absorption;

[0084] The hyperaccumulating plants are dandelion and three-leaf bidens;

[0085] The earthworms are Eisenia foetida, and the density of the earthworms is 80 per square meter;

[0086] The functional microbial flora contains Bacillus subtilis.

[0087] The environmentally friendly enzyme fertilizer is a liquid fertilizer obtained by mixing sucrose, fruit peel and water in a mass ratio of 1:30:100 and then filtering after at least 3 months of fermentation, wherein the fruit peel is yellow peach peel.

[0088] The daily application method of the environmentally friendly enzyme fertilizer is to dilute it with water in a volume ratio of 1:500, and then apply it to the soil around the roots of terrestrial plants by drip irrigation or sprinkling irrigation at a frequency of 50 days.

[0089] After 6 months, the plant enrichment of cadmium reaches 1500 mg / kg.

[0090] (3) Detection and cyclic remediation: detecting the content of heavy metals in the soil;

[0091] After remediation, the cadmium content in the soil is 15 mg / kg, and the mercury content is 37 mg / kg.

[0092] Compared with Example 1, Comparative Example 3 reduces the deep stabilization treatment, and does not pass Fe 3+ , Mg 2+The cadmium forms stable complexes with heavy metals and is easily re-dissolved under acid precipitation; the soil micropores are not filled in the absence of biomass carbon composite repair agent, and mercury is easily transported to groundwater with water; the soil particles are not contracted by freezing, the efficiency of heavy metal wrapping is reduced, and the long-term stability is insufficient; the cadmium enriched in the plant body is not fixed by the stabilization treatment, and may be released back to the soil after decay.

[0093] Example 2

[0094] Remediation of a farmland near an industrial site with lead-zinc composite pollution (initial concentration of lead 35 mg / kg, zinc 28 mg / kg)

[0095] A soil heavy metal pollution treatment and ecological remediation method, comprising the following steps:

[0096] (1) Soil pretreatment: the contaminated soil is crushed to a particle size of less than 3 mm, modified clay mineral adsorbent and magnetic nanometer material are added, mechanical stirring is carried out, and then the magnetic material adsorbing heavy metals is separated by magnetic separation;

[0097] The modified clay mineral adsorbent is made by mixing montmorillonite, bentonite and phosphoric acid modified attapulgite in a volume ratio of 1:2:1, and the dosage is 20 kg per mu; the adsorption capacity of the modified clay mineral adsorbent is: lead 223 mg / kg, zinc 163 mg / kg;

[0098] The magnetic nanometer material is neodymium-iron-boron magnetic core loaded with ferroferric oxide activated carbon particles, and the dosage is 15 g per kilogram of soil; the adsorption capacity of the magnetic nanometer material is: lead 1.98 mg / g, zinc 1.46 mg / g.

[0099] (2) Biological remediation stage: planting hyperaccumulating plants, introducing earthworms and functional microbial flora, and regularly applying environmentally friendly enzyme fertilizer to promote heavy metal activation and plant absorption;

[0100] The hyperaccumulating plants are Amorpha fruticosa and Ipomoea aquatica, and are inoculated with arbuscular mycorrhizal fungi, and the soil organic matter is increased by 30%;

[0101] The earthworms are Eisenia foetida, and the density of the earthworms is 80 per square meter;

[0102] The environmentally friendly enzyme fertilizer is a liquid fertilizer obtained by mixing sucrose, fruit peel and water in a mass ratio of 1:40:120 and then filtering after at least 3 months of fermentation, and the fruit peel is yellow peach peel.

[0103] The daily application method of the environmentally friendly enzyme fertilizer is to dilute it with water in a volume ratio of 1:1000, and then apply it to the soil around the roots of terrestrial plants by drip irrigation or sprinkling irrigation at a frequency of once every 30 days.

[0104] (3) Deep stabilization treatment: the biomass charcoal composite remediation agent is mixed with the soil, and after low-temperature freezing treatment, an acid treatment agent is sprayed to achieve long-term fixation of heavy metals;

[0105] The biomass charcoal composite remediation agent is prepared by mixing biomass charcoal, sulfonated chitosan and cellulose solution at a mass ratio of 3:1:2; the low-temperature treatment temperature is -2°C, and the treatment time is 48 hours.

[0106] The biomass charcoal is prepared by grinding (through a 100-mesh sieve) after straw waste is carbonized at 325°C under high temperature and sealed for 40 hours, and the specific surface area is ≥500 m2 / g; the acid treatment agent is a mixed solution of oxalic acid-acetic acid at a ratio of 1:2 (v:v), the spraying amount is 50 times dilution of water, and the spraying amount is 20-35 mL / kg of soil;

[0107] The synergistic effect of biomass charcoal-low temperature treatment reduces the lead leaching toxicity from 1.1 mg / L to 0.1 mg / L, and the zinc leaching toxicity from 1.8 mg / L to 0.3 mg / L, which meets the limit value (lead 0.5 mg / L, zinc 1.0 mg / L) of GB 5085.3-2007.

[0108] (4) Detection and cyclic remediation: detect the content of heavy metals in the soil, and repeat steps (1)-(3) when the content does not meet the standard;

[0109] After one round of remediation, the final lead concentration is 1.5 mg / kg, and the final zinc concentration is 1.2 mg / kg.

[0110] Comparative Example 4

[0111] Example 2: Remediation of a farmland near an industrial site with lead-zinc composite pollution (initial concentration of lead 35 mg / kg, zinc 28 mg / kg)

[0112] A soil heavy metal pollution treatment and ecological remediation method, comprising the following steps:

[0113] (1) Biological remediation stage: planting hyperaccumulating plants, introducing earthworms and functional microbial flora, and regularly applying environmentally friendly enzyme fertilizer to promote heavy metal activation and plant absorption;

[0114] The hyperaccumulating plants are Amorpha fruticosa and Ipomoea aquatica, and are inoculated with arbuscular mycorrhizal fungi, and the soil organic matter is increased by 30%;

[0115] The earthworms are Eisenia foetida, and the feeding density is 80 per square meter;

[0116] The environmentally friendly enzyme fertilizer is a liquid fertilizer obtained by filtering after at least 3 months of fermentation of a mixture of sucrose, fruit peel and water at a mass ratio of 1:40:120, and the fruit peel is yellow peach skin.

[0117] The daily application method of the environment-friendly enzyme fertilizer is to dilute it with water at a volume ratio of 1:1000, and then uniformly apply it to the soil around the roots of terrestrial plants by drip irrigation or sprinkling irrigation at a frequency of once every 30 days.

[0118] (2) Deep stabilization treatment: mix the biomass charcoal composite repair agent with the soil, spray the acid treatment agent after low-temperature freezing treatment, and realize long-term fixation of heavy metals;

[0119] The biomass charcoal composite repair agent is prepared by mixing biomass charcoal, sulfonated chitosan and cellulose solution at a mass ratio of 3:1:2; the low-temperature treatment temperature is-2℃, and the treatment time is 48 hours.

[0120] The biomass charcoal is prepared by grinding (through a 100-mesh screen) after straw waste is carbonized at 325℃ under high temperature and sealed for 40h, and the specific surface area is ≥500m2 / g; the acid treatment agent is a mixture of oxalic acid and acetic acid at a ratio of 1:2 (v:v), the spraying amount is 50 times dilution of water, and the spraying amount is 20-35mL / kg of soil;

[0121] The synergistic effect of biomass charcoal-low temperature treatment reduces the lead leaching toxicity from 1.1mg / L to 0.8mg / L, and the zinc leaching toxicity from 1.8mg / L to 1.5mg / L.

[0122] (3) Detection and cyclic repair: detect the content of heavy metals in the soil;

[0123] After one round of repair, the final lead concentration is 30mg / kg, and the final zinc concentration is 25mg / kg.

[0124] Compared with Example 2, Comparative Example 4 reduces the soil pretreatment operation, does not adsorb lead and zinc by directional adsorption of magnetic nanomaterials, has a high proportion of free heavy metals, and has a large pressure on subsequent biological repair; large particles of soil hinder the contact between the adsorbent and the pollutants, and the fixation efficiency of the modified clay mineral to zinc decreases; high concentrations of lead and zinc directly damage the plant root system, and the growth of Amorpha fruticosa is stagnant, and the symbiosis of mycorrhizal fungi fails; residual heavy metals in the soil without pretreatment are easy to migrate with rainfall, and deep stabilization treatment cannot completely cover them.

[0125] Comparative Example 5

[0126] Example 2 is the repair of a farmland near an industrial site with lead-zinc composite pollution (initial concentration of lead 35mg / kg, zinc 28mg / kg)

[0127] A soil heavy metal pollution treatment and ecological repair method, comprising the following steps:

[0128] (1) Soil pretreatment: break the contaminated soil to a particle size of less than 3mm, add a modified clay mineral adsorbent and a magnetic nanomaterial, stir mechanically, then stand, and separate the magnetic material adsorbing heavy metals by magnetic separation;

[0129] The modified clay mineral adsorbent is made by mixing montmorillonite, bentonite and phosphoric acid modified attapulgite in a volume ratio of 1:2:1, and the dosage is 20 kg / acre; the adsorption capacity of the modified clay mineral adsorbent: lead 223 mg / kg, zinc 163 mg / kg;

[0130] The magnetic nanomaterial is neodymium-iron-boron magnetic core loaded with ferroferric oxide activated carbon particles, and the dosage is 15 g per kg of soil; the adsorption capacity of the magnetic nanomaterial: lead 1.98 mg / g, zinc 1.46 mg / g.

[0131] (2) Deep stabilization treatment: mix the biomass charcoal composite repair agent with the soil, spray the acid treatment agent after low-temperature freezing treatment, and realize long-term fixation of heavy metals;

[0132] The biomass charcoal composite repair agent is made by mixing biomass charcoal, sulfonated chitosan and cellulose solution in a mass ratio of 3:1:2; the low-temperature treatment temperature is-2°C, and the treatment time is 48 hours.

[0133] The biomass charcoal is prepared by grinding (through a 100-mesh screen) after straw waste is carbonized at 325°C under high temperature and sealed for 40 hours, and the specific surface area is ≥500 m2 / g; the acid treatment agent is a 1:2 (v:v) mixture of oxalic acid-acetic acid, and the spraying amount is 50 times dilution of water, 20-35 mL / kg of soil;

[0134] The synergistic effect of biomass charcoal-low temperature treatment reduces the lead leaching toxicity from 1.1 mg / L to 0.4 mg / L, and the zinc leaching toxicity from 1.8 mg / L to 0.9 mg / L.

[0135] (3) Detection and cyclic repair: detect the content of heavy metals in the soil;

[0136] After one round of repair, the final lead concentration is 5.3 mg / kg, and the final zinc concentration is 6.2 mg / kg.

[0137] Compared with Example 2, Comparative Example 5 reduces the biological repair stage, lacks the chelation of the environmental protection enzyme fertilizer, and the lead and zinc exist in the form of inert oxides, so the plant absorption efficiency is extremely low; the plant root absorption area is reduced due to the lack of inoculation of arbuscular mycorrhizal fungi, and the zinc transport capacity is reduced; the soil is hardened due to the lack of earthworms, the biomass charcoal (step 3) is difficult to uniformly disperse, and the penetration of the solidifying agent is blocked; only steps 1 and 3 are used for adsorption and solidification, and the total amount of heavy metals is not reduced by plant extraction, so the residual amount of zinc still exceeds the standard.

[0138] Comparative Example 6

[0139] Example 2 is the same as the repair of the farmland near the industrial site with lead-zinc composite pollution (initial concentration of lead 35 mg / kg, zinc 28 mg / kg)

[0140] A soil heavy metal pollution treatment and ecological restoration method, comprising the following steps:

[0141] (1) Soil pretreatment: the contaminated soil is broken to a particle size of less than 3 mm, modified clay mineral adsorbent and magnetic nanometer material are added, mechanical stirring is carried out, and then the magnetic material adsorbing heavy metals is separated by magnetic separation;

[0142] The modified clay mineral adsorbent is prepared by mixing montmorillonite, bentonite and phosphoric acid modified attapulgite in a volume ratio of 1:2:1, and the dosage is 20 kg per mu; the adsorption capacity of the modified clay mineral adsorbent is 223 mg / kg for lead and 163 mg / kg for zinc;

[0143] The magnetic nanometer material is neodymium-iron-boron magnetic core loaded with ferroferric oxide activated carbon particles, and the dosage is 15 g per kg of soil; the adsorption capacity of the magnetic nanometer material is 1.98 mg / g for lead and 1.46 mg / g for zinc.

[0144] (2) Biological restoration stage: super-accumulating plants are planted, and earthworms and functional microbial flora are introduced, and environment-friendly enzyme fertilizer is regularly applied to promote heavy metal activation and plant absorption;

[0145] The super-accumulating plants are Amorpha fruticosa and Ipomoea aquatica, and are inoculated with arbuscular mycorrhizal fungi, and the soil organic matter is increased by 30%;

[0146] The earthworms are Eisenia foetida, and the density of the earthworms is 80 per square meter;

[0147] The environment-friendly enzyme fertilizer is a liquid fertilizer obtained by mixing sucrose, peel and water in a mass ratio of 1:40:120, fermenting for at least 3 months, and then filtering.

[0148] The daily application method of the environment-friendly enzyme fertilizer is to dilute the environment-friendly enzyme fertilizer with water in a volume ratio of 1:1000, and then apply the diluted environment-friendly enzyme fertilizer to the soil around the roots of the terrestrial plants by drip irrigation or sprinkling irrigation at a frequency of once every 30 days.

[0149] The synergistic effect of the biomass charcoal and low-temperature treatment reduces the lead leaching toxicity from 1.1 mg / L to 0.5 mg / L, and reduces the zinc leaching toxicity from 1.8 mg / L to 1.2 mg / L.

[0150] (3) Detection and cyclic restoration: the content of heavy metals in the soil is detected;

[0151] After one round of restoration, the final lead concentration is 3.8 mg / kg, and the final zinc concentration is 4.5 mg / kg.

[0152] Compared with Example 2, Comparative Example 6 reduces the deep stabilization treatment, and does not pass Fe 3+ , Mg 2+Zinc forms stable precipitates with lead and zinc, which is easily redissolved under acidic conditions; the soil micropore is not filled by the absence of biomass charcoal composite remediation agent, and lead is easily floated to the surface layer by capillary action; the soil particles are not contracted by -2℃ freezing, the efficiency of heavy metal encapsulation is reduced, and the long-term stability is poor; the zinc enriched in the plant body is not fixed by the stabilization treatment, and may return to the soil after decay.

[0153] The above description of disclosed embodiments enables one of ordinary skill in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for soil heavy metal pollution control and ecological restoration, characterized in that: The following steps are involved: (1) Soil pretreatment: The contaminated soil is crushed to a particle size of less than 3 mm, modified clay mineral adsorbent and magnetic nanomaterials are added, mechanically stirred and then allowed to stand, and the magnetic material that adsorbs heavy metals is separated by magnetic separation; (2) Bioremediation stage: Planting hyperaccumulator plants, introducing earthworms and functional microbial flora, and regularly applying environmentally friendly enzyme fertilizers to promote heavy metal activation and plant absorption; (3) Deep stabilization treatment: the biochar composite remediation agent is mixed with the soil, and after low-temperature freezing treatment, the acid treatment agent is sprayed to achieve long-term fixation of heavy metals; (4) Detection and recycling remediation: Detect the heavy metal content in the soil and repeat steps (1) to (3) if it does not meet the standard.

2. The method according to claim 1, characterized in that In step (1), the modified clay mineral adsorbent is prepared by mixing montmorillonite, bentonite, and phosphoric acid-modified attapulgite in a volume ratio of 1:2:1, and the addition amount is 20 kg / mu; The magnetic nanomaterial is neodymium iron boron magnetic core loaded with ferroferric oxide activated carbon particles, and the addition amount is 15-55g per kilogram of soil.

3. The method according to claim 1, characterized in that In step (2), the hyperaccumulator plants are selected from at least two of dandelions, Amorpha fruticosa, and Bidens pilosa; The earthworms are Eisenia fetida, and the stocking density is 50-100 per square meter; The functional microbial flora comprises Bacillus subtilis and arbuscular mycorrhizal fungi.

4. The method according to claim 1, wherein In step (2), the environmentally friendly enzyme fertilizer is a liquid topdressing obtained by mixing sucrose, peel and water in a mass ratio of 1:30-40:100-120, fermenting for at least 3 months and then filtering, wherein the peel is yellow peach peel.

5. The method according to claim 4, characterized in that The daily application method of the environmentally friendly enzyme fertilizer is to first dilute it with water at a volume ratio of 1:500-1000, and then evenly apply it to the soil around the roots of terrestrial plants through drip irrigation or sprinkler irrigation at a frequency of once every 30-50 days.

6. The method according to claim 1, characterized in that In step (3), the biochar composite repair agent is prepared by mixing biochar, sulfonated chitosan and cellulose solution in a mass ratio of 3:1:2; The acidic treatment agent is a 1:2 (v:v) mixture of oxalic acid and acetic acid, and the spraying amount is 50 times diluted with clean water, 20-35mL / kg soil spray; The low temperature treatment temperature is -10℃ to -2℃, and the treatment time is 12-48 hours.

7. The method according to claim 6, characterized in that The biochar is prepared by carbonizing straw waste at 325°C for 40 hours and then grinding it, with a specific surface area of ​​500m 2 / g.