CN110038890B - A kind of ecological, environmental protective soil remediation method - Google Patents

Abstract

The present invention relates to a kind of ecological, environmental protective soil remediation methods, include the following steps: the surface that soil-repairing agent is uniformly sprinkling upon to heavy-metal contaminated soil, then carrying out Soil tillage is sufficiently mixed soil-repairing agent and heavy-metal contaminated soil uniformly, balances 6-8 days completion heavy metal-polluted soil repair processes.In parts by weight, soil-repairing agent is by being modified 55-65 parts of hectorite, and 20-30 parts of organic fertilizer, 10-20 parts of humic acid and 1~3 part of microbial bacterial agent mix.The soil remediation method has at low cost, ecological, environmental protective, the advantages such as repairing efficiency is short, repairing effect is good, remediation efficiency is high suitable for repairing to heavy-metal contaminated soil.

Description

A kind of ecological environmental protection soil remediation method

technical field

The invention relates to an ecological environment-friendly soil restoration method.

Background technique

With soils serving as the foundation of natural and agricultural ecosystems, the level of toxic metal pollution in the biosphere has increased dramatically since the Industrial Revolution. Soil heavy metal pollution refers to the phenomenon that human activities bring heavy metal substances into the soil, causing the content of heavy metals in the soil to be significantly higher than its natural background content, destroying the ecosystem and deteriorating the environmental quality. The sources of heavy metals in soil are divided into natural sources and man-made sources, of which man-made factors account for the main part. Among natural sources, heavy metals mainly come from the natural weathering of rocks and soils, and their content is usually low, and they are not toxic to the environment, animals and plants. Affected by human factors, one or more heavy metals in the soil gradually accumulate and increase, and exceed their natural background value. When the content is high to a certain level, the safety of humans, animals, plants and the entire ecosystem will be threatened. Humans have a long history of heavy metal pollution to nature. The heavy metal elements released by wood burning are deposited on the surface, gradually changing the local soil environment. After the rise of mining and smelting in ancient times, the relationship of "human-heavy metal-pollution" was formed. Research by Hong et al. showed that mining and smelting in ancient Roman times had caused pollution. After the industrial revolution, with the rapid development of industrialization and urbanization, soil heavy metal pollution has become more serious, and it has shown a trend of pollution from industry to agriculture, city to countryside, and point to surface pollution. The pollution form has also changed from gradual accumulation to sudden , Chain, and regional outbreak stages. The middle of the 20th century was a period of high incidence of foreign soil heavy metal pollution incidents, and governments of various countries began to pay attention to the problem of heavy metal pollution at this time. In the 1990s, the United States invested about US$100 billion in soil remediation; in the 2006 EU soil protection theme report, it was conservatively estimated that 25 European countries would pay 17.3 billion euros per year for special remediation of soil pollution. At present, the soil heavy metal pollution in some countries has been improved, but local pollution in mining areas and factories still exists. According to statistics, about 137,000 square kilometers of agricultural land in Europe have heavy metal content exceeding the critical value; about 6 million square kilometers of brownfields in the United States are polluted by heavy metals to varying degrees. my country is the largest developing country in the world. With economic development, soil environmental problems are becoming more and more serious. According to the "National Soil Pollution Survey Bulletin" released on April 17, 2014, the total soil pollution rate in the country was 16.1%, and the rates of cadmium, zinc, lead, and copper were 7%, 0.9%, 1.5%, and 2.1%, respectively.

Man-made activities such as industry, mining, and agriculture are the main causes of soil heavy metals. Human factors lead to the sources of heavy metals in soil can be summarized as four ways. (1) Atmospheric deposition. Atmospheric deposition is divided into two methods: natural deposition and rain deposition. Except for Hg, other heavy metals basically enter the atmosphere in the form of aerosols and enter the soil through deposition. Exhaust gas from industrial production, vehicle exhaust emissions, and oil extraction and processing enters the soil mainly through atmospheric deposition. Among them, the settlement of heavy metal-containing waste gas discharged from non-ferrous metal mining and smelting is the main way of heavy metal pollution. Studies have shown that about ^0.2-0.9kg /km2 of heavy metal Cd is deposited into the soil through the atmosphere every year, and heavy metals such as Zn, Hg, Cr, and Pb are also discharged in large quantities, and finally enter the soil. A research and survey was conducted on a number of metal mines and farmlands near smelters in Jiangxi. The Cd content in the soil in this area reached 29.77mg/kg, which was 50 times higher than the second level of my country's soil environmental quality standards. (2) Accumulation of solid waste. With the development of urbanization, the discharge of urban solid waste and domestic waste in my country is increasing year by year.

Soil heavy metal pollution has become an important global environmental problem. According to estimates, in temperate climates, the retention time of Cd in the soil is 75-380 years, that of Hg is 500-1000 years, and that of Ag, Cu, Ni, Pb, Se, Zn, etc. is 1000-3000 years. Once the soil is polluted, heavy metals will not only accumulate in the soil for a long time, but also transfer to other environmental media, causing secondary pollution of the atmosphere and water. Excessive heavy metal content in the soil will affect the yield and quality of crops, and endanger the health of animals and humans through the food chain or direct contact. Under normal circumstances, heavy metal elements such as Cu, Zn, and Mn that enter animals and humans are not easy to cause harm to organisms, but when their content exceeds a certain limit, they will produce toxicity; most heavy metals (such as Hg, Cd, Pb, As etc.) are not essential to organisms and have clear toxic effects, so their entry into the food chain should be strictly controlled. Most of the heavy metals entering the human body exist in the original form, and may also be converted into compounds that are more toxic to organisms. When they enter the adipose tissue or deposit in the circulatory system, they are not easy to be excreted, thus causing acute or chronic damage to the human body. For example, excessive cadmium can cause kidney damage, osteoporosis, cancer and other lesions; excessive manganese may cause symptoms similar to Parkinson's disease; and organ damage.

Cadmium is a relatively rare heavy metal element in soil, with an average content of 0.5 mg/kg in the earth's crust. In nature, cadmium mainly exists in the form of sulfide in copper, lead, zinc and other non-ferrous metal deposits. The background value of cadmium in the surface soil in my country is 0.017-0.333mg/Kg, but various production and living behaviors of human beings can bring cadmium into the soil, and the characteristics of cadmium migration are that it is not easy to be decomposed and transformed by organisms, and it is not easily discharged with water. The movement can only accumulate along the food chain, thereby endangering the health of organisms and affecting normal functions and metabolic balance. The main sources of heavy metal cadmium pollution in soil are wastewater, waste residue, and waste gas from mining, electroplating, and chemical industries. Cadmium-containing fertilizers and pesticides used in agricultural production are also important sources of cadmium. According to the statistics of the State Environmental Administration, the cadmium-contaminated area of farmland in my country reached 280,000 square kilometers in 2003, and the amount of cadmium-exceeding agricultural products reached 1.5 million tons.

In-situ passivation is a form of adding amendments to the soil to change the existing form of heavy metals in the soil, passivate the metal ions in the soil or solution, and reduce their utilization. Each modifier has a different passivation effect on heavy metals, and the mechanism of action is also different. Therefore, in the actual soil remediation process, the appropriate modifier should be selected according to local conditions in order to achieve the best effect. At present, the modifiers commonly used in the market mainly include lime, calcium carbonate, phosphate and so on. It has a good improvement effect on metals such as Cd, Cu, and Zn.

Chinese authorized patent CN105838382B discloses a high-efficiency cadmium-reducing soil remediation agent and its application. In parts by weight, the soil remediation agent consists of 40-60 parts of modified hectorite, 20-30 parts of organic fertilizer, and 5-38 parts of humic acid. It is prepared by mixing 1 to 5 parts of the microbial agent, and the modified hectorite is obtained by calcining the hectorite, adding calcium polysulfide, stirring and reacting, and finally grinding into granules or powder. The soil remediation agent is suitable for remediating cadmium-contaminated soil, and then planting rice on the remediated soil, and has obvious advantages such as low cost, short remediation period, good cadmium reduction effect, and high rice yield.

However, the effective concentration of cadmium in the soil after the above-mentioned patent treatment is still too high, and it is difficult to meet the high-quality requirements for heavy metal content in the soil, and it is also impossible to further reduce the heavy metal content in crops.

Contents of the invention

In order to solve the technical problem that the effective state concentration of soil cadmium is still too large after being treated with soil remediation agent in the prior art and is difficult to meet the requirements of high-quality soil, the present invention proposes the following technical scheme:

An ecological environment-friendly soil remediation method, characterized in that: comprising the following steps: evenly sprinkle the soil remediation agent on the surface of the heavy metal-contaminated soil, and then perform soil plowing so that the soil remediation agent and the heavy metal-contaminated soil are fully mixed evenly, and the balance is 6-8 Complete the soil heavy metal remediation process in 10 days;

In parts by weight, the soil remediation agent is mixed with 55-65 parts of modified hectorite, 20-30 parts of organic fertilizer, 10-20 parts of humic acid and 1-3 parts of microbial agent. The hectorite is prepared by the following method: calcining the hectorite, then adding a mixed modifier to stir the reaction, carrying out microwave irradiation treatment while stirring, and finally grinding it into particles or powder, and the stirring reaction is carried out at a temperature of 280 ~ Carried out at 320°C for 1 hour;

The consumption of described mixed modifying agent accounts for the 10wt% of modified hectorite, and described mixed modifying agent is made up of calcium polysulfide and modifying agent I by mass ratio as 2:1, and the structural formula of described modifying agent I as follows:

The number of viable bacteria per gram of the microbial bacterial agent is 150 to 250 million.

Preferably, the microwave irradiation power is 750-850W, more preferably, the microwave irradiation power is 800W.

Preferably, the organic fertilizer is chicken manure, pig manure or cow manure.

Preferably, the microbial agent is Bacillus.

Preferably, the particle size of the modified hectorite is between 150 mesh and 250 mesh.

Technical scheme of the present invention has following benefit effect:

(1) The modification of hectorite with a composite modifier can greatly improve the modification effect, which is better than that of a single modifier, and then remove heavy metals such as cadmium in the soil to the greatest extent, and the removal efficiency is better than that of the existing one. Some soil remediation agents. The composite modifier can not only replace the impurities in the hectorite pores, enlarge the space, improve the adsorption and fixation of cadmium, but also realize the grafting and crosslinking of the hectorite microstructure reaction, to further improve the hydrophobic performance of hectorite, improve the ability to adsorb heavy metal ions in soil, and widen the distance between hectorite layers.

(2) On the basis of chemical modification, the parallel use of microwave modification can improve the modification effect of hectorite. After microwave modification, the mass transfer rate in the porous interior of hectorite is accelerated, and the influence of internal diffusion is reduced. Not only The activity of the hectorite can be improved, and at the same time, the composite modifier can better enter into the microstructure of the hectorite. What is important is that through a large number of experiments, it can be found that the microwave irradiation power is not as high as possible, and there is an optimal range value, that is, when the microwave irradiation power is in the range of 750-850W, the effect of microwave modification is the best, which can Remove heavy metals such as cadmium in the soil as much as possible. In addition, the use of microwave modification shortens the modification time of hectorite, improves the production efficiency and reduces the production cost.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with examples and comparative examples.

Example 1

An ecological environment-friendly soil remediation method, characterized in that: comprising the following steps: evenly sprinkle the soil remediation agent on the surface of the heavy metal-contaminated soil, then perform soil plowing to fully mix the soil remediation agent and the heavy metal-contaminated soil, and complete the balance in 6 days Soil heavy metal remediation process;

In parts by weight, the soil remediation agent is mixed with 55 parts of modified hectorite, 20 parts of organic fertilizer, 10 parts of humic acid and 1 part of microbial agent, and the modified hectorite is prepared by the following method : Calcining the hectorite, then adding a mixed modifier to stir the reaction, carrying out microwave irradiation treatment while stirring, and finally grinding it into granules or powder, the stirring reaction is carried out at a temperature of 280° C. for 1 hour;

The consumption of described mixed modifying agent accounts for the 10wt% of modified hectorite, and described mixed modifying agent is made up of calcium polysulfide and modifying agent I by mass ratio as 2:1, and the structural formula of described modifying agent I as follows:

Wherein, the microwave irradiation power is 750W, the organic fertilizer is chicken manure, the microbial agent is bacillus, and the particle size of the modified hectorite is between 150 mesh.

Example 2

An ecological environment-friendly soil remediation method, characterized in that: comprising the following steps: evenly sprinkle the soil remediation agent on the surface of the heavy metal-contaminated soil, and then perform soil plowing to fully mix the soil remediation agent and the heavy metal-contaminated soil, and complete the balance within 7 days Soil heavy metal remediation process;

In parts by weight, the soil remediation agent is mixed with 60 parts of modified hectorite, 25 parts of organic fertilizer, 15 parts of humic acid and 2 parts of microbial agent, and the modified hectorite is prepared by the following method : Calcining the hectorite, then adding a mixed modifier to stir the reaction, carrying out microwave irradiation treatment while stirring, and finally grinding it into granules or powder, the stirring reaction is carried out at a temperature of 300° C. for 1 hour;

The consumption of described mixed modifying agent accounts for the 10wt% of modified hectorite, and described mixed modifying agent is made up of calcium polysulfide and modifying agent I by mass ratio as 2:1, and the structural formula of described modifying agent I as follows:

Wherein, the microwave irradiation power is 800W, the organic fertilizer is pig manure, the microbial agent is bacillus, and the particle size of the modified hectorite is between 200 mesh.

Example 3

An ecological environment-friendly soil repair method, characterized in that: comprising the following steps: evenly sprinkle the soil repair agent on the surface of the heavy metal-contaminated soil, and then perform soil plowing to fully mix the soil repair agent and the heavy metal-contaminated soil, and complete the balance in 8 days Soil heavy metal remediation process;

In parts by weight, the soil remediation agent is mixed with 65 parts of modified hectorite, 30 parts of organic fertilizer, 20 parts of humic acid and 3 parts of microbial agent, and the modified hectorite is prepared by the following method : Calcining the hectorite, then adding a mixed modifier to stir the reaction, carrying out microwave irradiation treatment while stirring, and finally grinding it into granules or powder, the stirring reaction is carried out at a temperature of 320° C. for 1 hour;

The consumption of described mixed modifying agent accounts for the 10wt% of modified hectorite, and described mixed modifying agent is made up of calcium polysulfide and modifying agent I by mass ratio as 2:1, and the structural formula of described modifying agent I as follows:

Wherein, the microwave irradiation power is 850W, the organic fertilizer is cow dung, the microbial agent is bacillus, and the particle size of the modified hectorite is between 250 mesh.

Comparative example 1

An ecological environment-friendly soil remediation method, characterized in that: comprising the following steps: evenly sprinkle the soil remediation agent on the surface of the heavy metal-contaminated soil, and then perform soil plowing to fully mix the soil remediation agent and the heavy metal-contaminated soil, and complete the balance within 7 days Soil heavy metal remediation process;

In parts by weight, the soil remediation agent is mixed with 60 parts of modified hectorite, 25 parts of organic fertilizer, 15 parts of humic acid and 2 parts of microbial agent, and the modified hectorite is prepared by the following method : Calcining the hectorite, then adding a mixed modifier to stir the reaction, carrying out microwave irradiation treatment while stirring, and finally grinding it into granules or powder, the stirring reaction is carried out at a temperature of 300° C. for 1 hour;

The consumption of described mixed modifying agent accounts for the 10wt% of modified hectorite, and described mixed modifying agent is only made of modifying agent I, and the structural formula of described modifying agent I is as follows:

Wherein, the microwave irradiation power is 800W, the organic fertilizer is pig manure, the microbial agent is bacillus, and the particle size of the modified hectorite is between 200 mesh.

Comparative example 2

An ecological environment-friendly soil remediation method, characterized in that: comprising the following steps: evenly sprinkle the soil remediation agent on the surface of the heavy metal-contaminated soil, and then perform soil plowing to fully mix the soil remediation agent and the heavy metal-contaminated soil, and complete the balance within 7 days Soil heavy metal remediation process;

In parts by weight, the soil remediation agent is mixed with 60 parts of modified hectorite, 25 parts of organic fertilizer, 15 parts of humic acid and 2 parts of microbial agent, and the modified hectorite is prepared by the following method : Calcining the hectorite, then adding a mixed modifier to stir the reaction, carrying out microwave irradiation treatment while stirring, and finally grinding it into granules or powder, the stirring reaction is carried out at a temperature of 300° C. for 1 hour;

The consumption of described mixed modifying agent accounts for the 10wt% of modified hectorite, and described mixed modifying agent is made up of calcium polysulfide and modifying agent I by mass ratio as 2:1, and the structural formula of described modifying agent I as follows:

Wherein, the microwave irradiation power is 600W, the organic fertilizer is pig manure, the microbial agent is bacillus, and the particle size of the modified hectorite is between 200 mesh.

Comparative example 3

An ecological environment-friendly soil remediation method, characterized in that: comprising the following steps: evenly sprinkle the soil remediation agent on the surface of the heavy metal-contaminated soil, and then perform soil plowing to fully mix the soil remediation agent and the heavy metal-contaminated soil, and complete the balance within 7 days Soil heavy metal remediation process;

In parts by weight, the soil remediation agent is mixed with 60 parts of modified hectorite, 25 parts of organic fertilizer, 15 parts of humic acid and 2 parts of microbial agent, and the modified hectorite is prepared by the following method : Calcining the hectorite, then adding a mixed modifier to stir the reaction, carrying out microwave irradiation treatment while stirring, and finally grinding it into granules or powder, the stirring reaction is carried out at a temperature of 300° C. for 1 hour;

The consumption of described mixed modifying agent accounts for the 10wt% of modified hectorite, and described mixed modifying agent is made up of calcium polysulfide and modifying agent I by mass ratio as 2:1, and the structural formula of described modifying agent I as follows:

Wherein, the microwave irradiation power is 1000W, the organic fertilizer is pig manure, the microbial agent is bacillus, and the particle size of the modified hectorite is between 200 mesh.

The following table details the composition of the mixed modifier and the power of microwave irradiation in Example 2 and Comparative Examples 1-3.

Numbering Mix modifier Microwave irradiation power Example 2 Calcium polysulfide + modifier I 800W Comparative example 1 Modifier I 800W Comparative example 2 Calcium polysulfide + modifier I 600W Comparative example 3 Calcium polysulfide + modifier I 1000W

Effect characterization: the soil remediation agent in Example 2 and Comparative Examples 1-3 is evenly mixed and sprinkled on the surface of the heavy metal cadmium contaminated soil, 150kg per mu, then the soil is plowed, and the soil heavy metal remediation process is completed in 7 days after balancing. The repaired soil was tested and the results are as follows:

Numbering Effective concentration of cadmium in untreated soil Effective concentration of cadmium in soil after treatment Example 2 0.613ug/L 0.059ug/L Comparative example 1 0.613ug/L 0.102ug/L Comparative example 2 0.613ug/L 0.086ug/L Comparative example 3 0.613ug/L 0.074ug/L

The above results show that: (1) from the experimental results of Examples and Comparative Example 1, prior art CN105838382B, it can be found that the use of composite modifiers can greatly improve the modification effect, which is better than the modification effect of using a single modifier, In turn, it can remove heavy metals such as cadmium in the soil to the greatest extent. The composite modifier can not only replace the impurities in the hectorite pores, make the space larger, and improve the adsorption and fixation of cadmium. The composite modifier can also realize water retention. The grafting and cross-linking reactions on the microstructure of pyroxene further improve the hydrophobic performance of hectorite, improve the ability to adsorb heavy metal ions in soil, and widen the distance between hectorite layers. (2) From the experimental results of Examples and Comparative Examples 3-4, it can be found that on the basis of chemical modification, parallel use of microwave modification can improve the modification effect of hectorite, and hectorite is porous after microwave modification The internal mass transfer speed is accelerated and the influence of internal diffusion is reduced, which not only improves the activity of hectorite, but also enables the composite modifier to better enter the microstructure of hectorite. Importantly, through a large number of experiments, it can be found that the microwave irradiation power is not as high as possible. When the microwave irradiation power is in the range of 750-850W, the effect of microwave modification is the best, which can remove heavy metals such as cadmium in the soil to the greatest extent.

Claims (6)

1. An eco-environmental protection soil restoration method is characterized in that: comprise the steps: soil restoration agent is evenly sprinkled on the surface of heavy metal contaminated soil, then soil plowing is carried out to make soil restoration agent and heavy metal contamination soil fully mix, balance 6 -8 days to complete the soil heavy metal remediation process; In parts by weight, the soil restoration agent is mixed with 55-65 parts of modified hectorite, 20-30 parts of organic fertilizer, 10-20 parts of humic acid and 1-3 parts of microbial agent. The hectorite is prepared by the following method: calcining the hectorite, then adding a mixed modifier to stir the reaction, carrying out microwave irradiation treatment while stirring, and finally grinding it into particles or powder, and the stirring reaction is carried out at a temperature of 280 ~ Carried out at 320°C for 1 hour; The consumption of described mixed modifying agent accounts for the 10wt% of modified hectorite, and described mixed modifying agent is made of calcium polysulfide and modifying agent I by mass ratio as 2:1, and the structural formula of described modifying agent I as follows: ; Wherein, the power of the microwave irradiation is 750-850W. 2. The ecological and environmental protection soil restoration method according to claim 1, characterized in that: the power of the microwave irradiation is 800W. 3. The ecological environment-friendly soil restoration method according to claim 1, characterized in that: the organic fertilizer is chicken manure, pig manure or cow manure. 4. The eco-environmental protection soil restoration method according to claim 1, characterized in that: the microbial agent is a bacillus. 5. The ecological and environmental protection soil restoration method according to claim 1, characterized in that: the particle size of the modified hectorite is between 150 mesh and 250 mesh. 6. The ecological and environmental protection soil restoration method according to claim 1, characterized in that: the number of viable bacteria per gram of the microbial agent is 150-250 million.