CN109628099B - A passivation stabilizer for remediation of cadmium pollution in farmland soil and its preparation method and use method - Google Patents

Abstract

This invention relates to the field of cadmium-contaminated farmland soil remediation, and particularly to a passivation stabilizer for cadmium-contaminated farmland soil remediation, its preparation method, and its application method. The passivation stabilizer comprises calcium dihydrogen phosphate, biochar, and bio-fertilizer, in the following weight fractions: calcium dihydrogen phosphate 35-45%, biochar 10-20%, and bio-fertilizer 35-45%. The passivation agent material provided by this invention for cadmium-contaminated farmland soil combines various passivation materials. Calcium dihydrogen phosphate precipitates with cadmium, while biochar, with its large porosity, fixes cadmium through adsorption. Bio-fertilizer reduces the available cadmium content in the soil through ion adsorption and ion exchange, while simultaneously increasing soil organic matter content. Furthermore, it adjusts the soil pH, reducing the redissolution of pollutants. Through synergistic effects, this invention effectively meets the requirements of strong stability, no secondary pollution, and long-lasting and stable effects in the remediation of heavy metal-contaminated soil.

Description

A kind of passivation stabilizer for remediation of cadmium pollution in farmland soil and preparation method thereof Instructions

technical field

The invention relates to the field of farmland cadmium-contaminated soil treatment, in particular to a passivation stabilizer used for farmland soil cadmium-contaminated remediation and a preparation method and use method thereof.

Background technique

As one of the important resources for human survival, the safety of soil has always attracted people's attention. However, in recent years, due to the rapid development of industry, the increase of "three wastes" discharge, and the aggravation of urban pollution, the problem of heavy metal pollution in soil has become increasingly serious.

The main cause of cadmium pollution in my country's farmland is agricultural sewage irrigation, and the pollution sources mainly come from waste gas and wastewater discharged from factories, smelters, and enterprises. Heavy metal-contaminated soil remediation technologies mainly include physical remediation, chemical remediation, bioremediation, etc. Among them, in-situ passivation remediation technology has received extensive attention due to its low cost, simplicity and ease of operation. This method can be applied to heavy metal-contaminated farmland. Chemical stabilizers can effectively reduce the availability of heavy metals and improve soil fertility, which is the key to in situ remediation.

Phosphate is a kind of passivation stabilizer that is widely used in soil heavy metal pollution. The form of heavy metals in soil and the solubility of phosphate are important factors affecting phosphate passivation of heavy metal polluted soil. The effect of soluble phosphate passivation is better. However, the application of readily soluble phosphates in soil may pose the risk of causing eutrophication of surface water bodies. Biochar has a large specific surface area and strong adsorption, making it a remediation agent for heavy metal pollution. Biochar can reduce the mobility of heavy metal ions in the soil through the pH value of the soil, play a role in fixing heavy metals, and reduce the effective state in the soil through ion exchange, co-precipitation, physical adsorption, surface complexation, etc. cadmium. After using organic materials to remediate heavy metal-contaminated soil, the pH value of the soil is significantly increased, and the amount of cation substitution in the soil also increases significantly. The organic materials can complex with heavy metals in heavy metal-contaminated soil to form macromolecular organic complexes compounds that can significantly reduce the availability of heavy metals in soils.

SUMMARY OF THE INVENTION

In order to make up for the deficiency of different passivation stabilizer materials alone in the process of soil restoration, and improve the restoration efficiency, the present invention combines three restoration materials, calcium dihydrogen phosphate, biochar, and biological fertilizer, to passivate cadmium-contaminated farmland soil.

One object of the present invention is to provide a passivation stabilizer for remediation of cadmium pollution in farmland soil, which can effectively passivate and repair cadmium-contaminated farmland soil, effectively reduce the content of available cadmium in the farmland soil, and passivate the The effect is long-term and stable, and another object of the present invention is to provide the above-mentioned preparation and use method of the passivation stabilizer for the remediation of heavy metal complex pollution in farmland soil.

In order to achieve the above purpose of the invention, the technical solution adopted in the present invention is: a passivation stabilizer for remediation of cadmium pollution in farmland soil, characterized in that the passivation stabilizer comprises calcium dihydrogen phosphate, biochar, biological Bacterial fertilizer, according to weight fraction: calcium dihydrogen phosphate 35-45%, biochar 10-20%, biological bacterial fertilizer 35-45%.

More preferably, in terms of weight fraction: calcium dihydrogen phosphate 40-45%, biochar 10-20%, biological bacterial fertilizer 40-45%.

Calcium dihydrogen phosphate is colorless triclinic flake, granular or crystalline powder; biochar is made from straws fired at high temperature in a closed container; biological bacterial fertilizer is Bacillus amyloliquefaciens BZ6-1 biological bacterial fertilizer, bacterial fertilizer It mainly contains Bacillus amyloliquefaciens BZ6-1, which can produce active substances such as surfactin, fengycin and iturin, and applied for a patent using this strain: BZ6-1 strain is in the preparation of Application of medicines for the treatment of plant peanut bacterial wilt disease, patent number: 2010102415773.

The passivator of the present invention is suitable for cadmium-contaminated farmland soil, and is composed of the above-mentioned porous adsorbents and passivators of various materials with specific contents, which complement each other's advantages and combine the principles of adsorption and stabilization. The exchange, complexation, chelation and adsorption methods can effectively enhance the binding state of heavy metals, convert them into more stable strong organic binding state and residue state, effectively reduce the effective state content of heavy metals in farmland soil, and have a long-term and stable passivation effect. It has a great remediation effect on cadmium-contaminated farmland soil.

A preparation method of a passivation stabilizer for remediation of cadmium pollution in farmland soil, comprising the following steps:

1. Weigh the corresponding mass fraction of calcium dihydrogen phosphate, biochar, and biological bacterial fertilizer;

2. Crushing and mixing the components described in step 1 to remove particles with a particle size larger than 50 μm-150 μm,

That is, the passivation stabilizer is obtained.

In step 1, the biochar preparation process is as follows: the straw is placed in a closed container and fired at 300-600 degrees Celsius to make biochar. 300-600 degrees Celsius is the carbonization temperature of biochar.

A method of using a passivation stabilizer for remediation of cadmium pollution in farmland soil, comprising the steps of:

Ploughing and drying the fields, crushing the soil mass, and adding the passivation stabilizer;

After sowing the passivation stabilizer, the dry soil is subjected to rotary tillage treatment, 3 times of vertical and horizontal rotary tillage, and the rotary tillage depth is 15-20cm to ensure that the horizontal and vertical mixing are uniform, and the rotary tillage is placed for 10-20 days;

After the rotary tillage is completed, add water until the water surface is 10-12cm higher than the soil surface, and age the soil. During the ageing period, use a rotary tiller to perform rotary tillage operations on the soil;

Leave the farmland with the passivation stabilizer added for 12-15 days, and then dry the farmland.

As a limitation, according to the degree of cadmium pollution, the application rate of passivator per mu of farmland soil cadmium content lower than 1mg/kg is 400-800kg; the application rate of passivator per mu of farmland soil cadmium content higher than 1mg/kg is 1000-1500kg.

Compared with the prior art, the technical progress achieved by the present invention is:

The passivation material for the cadmium-contaminated farmland soil provided by the present invention is a combination of various passivation materials, and the passivation effect is better than that of a single passivation material. The calcium dihydrogen phosphate is precipitated by cadmium, and the biochar has large voids. , cadmium is fixed by adsorption, while biological bacterial fertilizer reduces the effective content of cadmium in soil by ion adsorption and ion exchange. In addition, soil pH is adjusted to reduce re-dissolution of pollutants. Through the synergistic effect, the present invention can well meet the requirements of heavy metal-contaminated soil remediation for strong stability, no secondary pollution, lasting and stable effect, and low cost. Most of the passivator materials are industrial wastes and agricultural wastes from a wide range of sources, the preparation and use methods are simple, the repair cost is low, wastes are turned into treasures, and the resource utilization of industrial solid wastes and agricultural wastes is realized.

The preparation method of the passivating agent provided by the invention is simple, has industrial production and wide application prospect.

The passivating agent of the invention belongs to in-situ repairing of cadmium pollution of farmland soil, does not affect agricultural production, does not damage soil structure, and can improve soil fertility.

The invention is suitable for repairing cadmium-contaminated soil in farmland.

Description of drawings

Fig. 1 Effects of different combinations of passivation stabilizers on soil available cadmium content;

Fig. 2 Effects of different passivation stabilizers on soil pH;

Fig. 3 Effects of different passivation stabilizers on soil organic matter;

Among them, treatment 1: 10% calcium dihydrogen phosphate, 30% biochar, 60% biological fertilizer; treatment 2: 15% calcium dihydrogen phosphate, 10% biochar, 75% biological fertilizer; treatment 3: 40% dihydrogen phosphate Calcium, 20% biochar, 40% biofertilizer; Treatment 4: 40% monocalcium phosphate, 15% biochar, 45% biofertilizer; Treatment 5: 45% monocalcium phosphate, 10% biochar, 45% bio Fertilizer; Treatment 6: 65% calcium dihydrogen phosphate, 5% biochar, 30% bio-fertilizer; Treatment 7: 70% calcium dihydrogen phosphate, 15% biochar, 15% bio-fertilizer; Treatment 8: 75% dihydrogen phosphate Calcium, 10% biochar, 15% biofertilizer.

Detailed ways

In order to illustrate the technical solution and technical purpose of the present invention, the present invention will be further introduced below in conjunction with the accompanying drawings and specific embodiments.

1 Materials and methods

1.1 Experimental Design

A total of 8 treatments were set up in this experiment, as shown in Table 1. Each treatment was repeated three times. The specific experimental steps were as follows: the passivation stabilizer was fully mixed with the cadmium-contaminated farmland soil, and the water content of the soil was kept at 60% by weighing. 100 mesh spare. The addition levels of passivation stabilizers were all 1% by weight of the Cd-contaminated soil. The initial effective cadmium content of Cd-contaminated soil was 7.8 mg/kg.

Table 1 Composition of Passivation Stabilizers

1.2 Determination and analysis methods

1.2.1 Determination of DTPA-extracted cadmium content in soil

The soil available cadmium content was determined by DTPA extraction-atomic absorption spectrophotometry. Accurately weigh 2.50g of air-dried soil sample and put it in a 100ml plastic jar, add 5ml of DTPA, put it into a shaker for 2h, let stand for 30min and then filter, accurately pipette 1ml of the filtrate, add 4ml of DTPA, shake well and measure by AAS method Cadmium content. The method of making the determination time mark: accurately measure 1ml of 1000μg/ml cadmium standard solution and transfer it to a 10ml volumetric flask, add DTPA to dilute to obtain a 100μg/ml cadmium standard solution, repeat the above operation once to obtain 10μg/ml cadmium standard solution. Accurately pipette 5, 10, 15, 20, 25, 50ml of 10μg/ml cadmium standard solution into a 100ml volumetric flask, add DTPA to the volume, and obtain 0.5, 1, 1.5, 2, 2.5, 5μg/ml Cadmium standard solution.

1.2.2 Determination of soil pH

Accurately weigh 10g of the air-dried soil sample and place it in a centrifuge tube, add 25ml of pure water, put it into a shaker for 1 hour, take it out and let it stand for 30 minutes, until the supernatant liquid is completely separated from the soil sample to be tested, take out the supernatant liquid, and adjust the pH value. Insert the meter into it and record the pH value after the reading is stable.

2 Results and Analysis

2.1 Effect of adding passivation stabilizer on the content of available cadmium in soil

The effect of adding different proportions of calcium dihydrogen phosphate, biochar and bio-fertilizer on the content of available cadmium in soil is shown in Figure 1. The effective cadmium content of the original soil sample was 7.80 mg/kg. It can be seen from Figure 1 that the application of different passivation stabilizers can reduce the effective cadmium content in the soil by 36%-72% respectively. Treatments 3, 4, and 5 had the best passivation effect on cadmium, reaching 72%, 69%, and 71%, respectively.

2.2 Effect of adding passivation stabilizer on soil pH value

The pH value of soil is one of the important basic physical and chemical properties of soil, which is of great significance to heavy metals in soil. Generally speaking, the pH value of the soil is relatively high, the lower the ecotoxicity of the heavy metals in the soil, the lower the bioavailability; the lower the pH value of the soil, the higher the ecotoxicity of the heavy metals in the soil, the greater the bioavailability . Moreover, the pH value of soil is one of the main factors affecting the adsorption, precipitation and dissolution of heavy metals. Therefore, regulating the pH value of soil plays an important role in reducing the availability and migration ability of heavy metals in soil.

The effect of applying different proportions of calcium dihydrogen phosphate, biochar and bio-fertilizer on soil pH is shown in Figure 2, where the initial (before untreated) pH of the tested soil was 7.15. It can be seen from the figure that the addition of passivation stabilizer can increase the pH value of soil. Treatments 3, 4 and 5 had the greatest effect on soil pH, with pH reaching 8.13, 7.82 and 7.99, respectively. And it has the least effect on treatment 1 and treatment 2, only 7.36 and 7.52. 2.3 Effect of adding passivation stabilizer on soil organic matter

The effect of adding different proportions of calcium dihydrogen phosphate, biochar and bio-fertilizer on the content of available cadmium in soil is shown in Figure 3. The organic matter content of the original soil sample was 6.85g/kg. The addition of different passivating agents will increase soil organic matter content and soil nutrient content. It can be seen from the comparison between different treatments that biochar and bio-fertilizer have a greater impact on soil organic matter content, especially bio-fertilizer. Soil organic matter content reaches 20g/kg and 15g/kg.

2.4 Correlation analysis

The correlation between the content of soil available cadmium and pH value, biochar, bio-fertilizer and calcium dihydrogen phosphate is shown in Table 3. The correlation between the available cadmium content in soil and pH reached a very significant negative correlation. The correlation analysis showed that the increase of soil pH could promote the transformation of soil cadmium from the available state to the refractory state, and reduce its bioavailability and toxicity. So as to achieve the purpose of soil restoration. At the same time, it can be found that calcium dihydrogen phosphate is significantly negatively correlated with pH, indicating that calcium dihydrogen phosphate reduces the availability of soil cadmium by increasing soil pH. It can also be seen from the table that biochar is also significantly negatively correlated with soil available cadmium content, indicating that biochar can significantly reduce the available cadmium content in soil. Singh et al. showed that after the application of biochar, the cadmium in the soil can be reduced to a reducible state. and extractable states decreased, while both oxidizable and residue states increased. The application amount and application time of biochar can affect the content of available cadmium. With the increase of biochar application ratio and application time, the pH value of soil increases, which promotes the conversion of cadmium in soil to refractory cadmium .

Table 2 Correlation analysis

Note: * means significant correlation, ** means extremely significant correlation.

The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and the descriptions in the above-mentioned embodiments and the description are only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (6)

1. The passivation stabilizer for farmland soil cadmium pollution remediation is characterized by comprising monocalcium phosphate, biochar and biological bacterial fertilizer, and is prepared from the following components in parts by weight: 35-45% of monocalcium phosphate, 10-20% of biochar and 35-45% of biological bacterial fertilizer; the calcium dihydrogen phosphate is colorless triclinic tablet, granule or crystalline powder; the biochar is formed by burning straws in a closed container at a high temperature; the biological bacterial fertilizer is Bacillus amyloliquefaciens BZ6-1, and produces surfactin, fengycin and iturin.

2. The passivation stabilizer for farmland soil cadmium pollution remediation as claimed in claim 1, wherein the passivation stabilizer comprises, in terms of weight fraction: 40-45% of monocalcium phosphate, 10-20% of biochar and 40-45% of biological bacterial fertilizer.

3. The preparation method of the passivation stabilizer for farmland soil cadmium pollution remediation, which is characterized by comprising the following steps of:

firstly, weighing calcium dihydrogen phosphate, biochar and biological bacterial manure with corresponding mass fractions;

secondly, crushing and uniformly mixing the components in the step one, and removing particles with the particle size of more than 50-150 microns to obtain the passivation stabilizer.

4. The preparation method of the passivation stabilizer for farmland soil cadmium pollution remediation, as claimed in claim 3, wherein in the first step, the biochar preparation process comprises: the straws are placed in a closed container and are fired into the biochar at the temperature of 300-600 ℃.

5. The use method of the passivation stabilizer for farmland soil cadmium pollution remediation as claimed in any one of claims 1-2, is characterized by comprising the following steps:

ploughing and drying the field, crushing the soil block mass, and adding the passivation stabilizer;

after the passivation stabilizer is sowed, carrying out rotary tillage on the dry soil, carrying out longitudinal and transverse rotary tillage for 3 times, wherein the rotary tillage depth is 15-20cm, ensuring that the dry soil is uniformly mixed horizontally and vertically, and standing for 10-20 days after the rotary tillage;

after the rotary tillage is finished, adding water until the water level is 10-12cm higher than the surface of the soil, aging the soil, and carrying out rotary tillage operation on the soil by using a rotary cultivator during the aging period;

and (5) standing the farmland added with the passivation stabilizer for 12-15 days, and drying the farmland in the sun.

6. The use method of the passivation stabilizer for farmland soil cadmium pollution remediation as claimed in claim 5, wherein when the farmland soil cadmium content is lower than 1mg/kg, the application amount of the passivation stabilizer per mu is 400-800 kg; when the cadmium content of the farmland soil is higher than 1mg/kg, the application amount of the passivation stabilizer per mu is 1000-1500 kg.

Images