CN113337293B - Anti-freezing solidification stabilizing agent for antimony-polluted soil and preparation method and application thereof - Google Patents
Anti-freezing solidification stabilizing agent for antimony-polluted soil and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses an anti-freezing type solidification stabilizing agent for antimony-polluted soil, and a preparation method and application thereof, belongs to the field of soil remediation, and aims to solve the technical problems that an existing solidification stabilizing agent is poor in solidification effect, large in agent dosage and unstable in effect under a freeze-thaw cycle condition. The anti-freezing solidification stabilizing agent for the antimony-polluted soil is prepared by grinding and mixing ferric salt or ferrous salt, fly ash and calcium lignosulfonate. The anti-freezing solidification stabilizing agent for the antimony-contaminated soil is uniformly mixed with the contaminated soil, stirred and uniformly sprinkled with water in the stirring process; then covering the soil surface with a moisture-preserving material and curing. The solidification and stabilization medicament has high-efficiency complexing and freeze-thaw resistance, and can be used in the field of remediation of antimony-polluted soil, particularly in areas with high-frequency freeze-thaw phenomena.
Description
Technical Field
The invention relates to the field of soil remediation, in particular to an anti-freezing curing and stabilizing agent for antimony-polluted soil, and a preparation method and application thereof.
Background
In recent years, with the development and utilization of mineral resources, the rapid development of industrial production and the increase of the usage amount of pesticides and chemical fertilizers, the problem of heavy metal pollution of soil is increasingly prominent, and the human health and food safety are influenced. Antimony is a potentially toxic heavy metal, usually present in the environment in the inorganic form of trivalent sb (iii) or pentavalent sb (v), antimonite and antimonate being the most common sb (iii) and sb (v) compounds, respectively. In recent years, antimony concentrations in the environment have increased dramatically due to mining and smelting operations, waste incineration, coal and oil combustion, waste ammunition, polyethylene terephthalate industry, battery plants, and the use of pharmaceuticals and pesticides, and have entered the soil by percolation, runoff, sedimentation, and the like. In this background, it is very necessary to propose a reasonable prevention and control strategy for antimony-contaminated soil. The main remediation measures of the antimony in the soil include soil leaching, solidification and stabilization, phytoremediation, bioremediation and the like. Solidification/stabilization (S/S) is considered a practical, effective, and promising technology for remediation of heavy metal contaminated soil, with the advantages of relatively low cost and easy implementation.
Solidification stabilization can be divided into two steps, solidification and stabilization, wherein the solidification is to wrap the contaminated soil in an integral solidified body with high structural integrity to fix the pollutants and reduce the leaching rate of the pollutants, and the stabilization is to convert the pollutants into a form with lower solubility and fluidity so as to minimize the toxicity of the pollutants and reduce the environmental risk of the pollutants. The selection and addition of a curing stabilizer is an important step in the curing stabilization technique, and long-term effectiveness under ambient conditions is an important consideration in technical applications. The commonly used curing and stabilizing agents at the present stage mainly comprise cement, lime, organic materials, clay minerals, sulfides, phosphate substances, metal salts, oxides and the like. The method realizes the stability of the antimony in the soil by changing the physical and chemical properties of the soil, electrostatic adsorption, chemical precipitation, interlayer ion exchange, encapsulation and other modes. But the materials in the current stage have the defects of poor curing effect, large medicament dosage, unstable effect under complex environmental conditions such as freeze-thaw cycle and the like. Aiming at the problems, the invention provides the high-efficiency anti-freezing curing stabilizing material aiming at the antimony, so that the material using amount is reduced, and the material stabilizing effect and the freeze-thaw resistance are improved, thereby having strong practical significance.
Disclosure of Invention
The invention provides an anti-freezing curing and stabilizing agent for antimony-polluted soil, and a preparation method and application thereof, aiming at solving the technical problems of poor curing effect, large agent dosage and unstable effect under the condition of freeze-thaw cycle of the existing curing and stabilizing agent.
The anti-freezing solidification stabilizing agent for the antimony-polluted soil is prepared by mixing 24-55% of ferric salt or ferrous salt, 21-72% of fly ash and 4-24% of calcium lignosulphonate according to mass percentage.
Furthermore, the antifreeze solidification stabilizing agent for the antimony-polluted soil is prepared by mixing 27-48% of ferric salt or ferrous salt, 28-66% of fly ash and 7-24% of calcium lignosulfonate according to mass percentage, and the stabilizing efficiency can reach more than 95%.
Further, the iron salt is ferric sulfate, ferric nitrate or ferric chloride.
Further, the ferrous salt is ferrous sulfate.
The preparation method of the anti-freezing solidification stabilizing agent for the antimony-polluted soil comprises the following steps:
firstly, 24-55% of ferric salt or ferrous salt, 21-72% of fly ash and 4-24% of calcium lignosulfonate are weighed according to the mass percentage and are respectively ground into powder;
and secondly, uniformly mixing the powder obtained in the step one to obtain the anti-freezing solidification stabilizing agent for the antimony-polluted soil.
Furthermore, the granularity of the powder in the first step is 100 meshes-200 meshes.
The application method of the anti-freezing solidification stabilizing agent for the antimony-polluted soil comprises the following steps:
uniformly mixing an anti-freezing solidification and stabilization agent for the antimony-contaminated soil with the contaminated soil, stirring, and uniformly sprinkling water in the stirring process;
and secondly, covering a moisturizing material on the soil surface after stirring and maintaining.
Furthermore, the stirring times in the first step are 3-6 times.
Further, the water content of the soil after the water spraying in the step one is kept between 20% and 30%.
Furthermore, the curing days in the second step are more than 5 days.
According to the invention, ferric salt or ferrous salt, fly ash and calcium lignosulfonate with a specific ratio are adopted, and ferric hydroxide having an adsorption effect on antimony is generated in soil mainly through ferric salt or ferrous salt, so that the leaching concentration of antimony is greatly reduced, and the environmental risk of antimony is limited. Meanwhile, the complex effect of the fly ash and the calcium lignosulfonate on antimony is utilized to further reduce the mobility of antimony in soil, strengthen the freeze-thaw resistance of the soil, reduce the leaching concentration of heavy metals after freeze-thaw cycling, strengthen the strength of a solidified body after freeze-thaw cycling, strengthen the long-term stability of the solidified stabilizing material under complex environmental conditions, and have good application prospects.
The freeze-thaw resistance is mainly two aspects, one is that the leaching concentration can still reach the standard after freeze-thaw, and the other is that the strength loss is not great. The fly ash can perform partial hydration reaction, fill soil pores and enhance compressive strength, and the fly ash also contains a plurality of glass beads which can enhance the activity of the surface of soil particles so as to accelerate chemical reaction. Calcium lignosulfonate has a number of reactive groups that can complex with metal ions, such as: hydroxyl, carboxyl, carbonyl, and sulfonic acid groups, etc., thereby forming lignin-metal ion complexes, and these functional groups may also undergo ion exchange with metals, thereby reducing the mobility of the metals. The fly ash is beneficial to increasing the compressive strength of soil, the calcium lignosulphonate has hydrophobicity, the water is limited from entering the soil body, and the damage of ice crystals to the soil structure under the freeze-thaw cycle alternating state is limited.
The materials adopted in the invention are common industrial products, and have wide sources and low cost. The fly ash is an industrial byproduct, the lignin is used as a natural material, the yield in China is huge, the lignosulfonate is sulfonate which is a lignin product most explored and applied, and the fly ash and the calcium lignosulfonate are used as additives, so that the repair effect is improved, the resource utilization rate is improved, and the popularization is realized.
The anti-freezing curing and stabilizing agent for the antimony-polluted soil can be used in the field of antimony-polluted soil remediation, particularly in areas with high-frequency freezing and thawing phenomena.
Drawings
FIG. 1 is a graph of a freeze-thaw cycle temperature test of an example;
FIG. 2 shows the leaching concentration and compressive strength of the soil after 40 times of freeze thawing in the three examples.
Detailed Description
The following examples demonstrate the beneficial effects of the present invention.
Example 1: the preparation method of the anti-freezing solidification stabilizing agent for the antimony-polluted soil comprises the following steps:
firstly, weighing 47.6% of ferrous sulfate, 28.6% of fly ash and 23.8% of calcium lignosulfonate according to the mass percentage, and respectively grinding into 200-mesh powder;
and secondly, uniformly mixing the powder obtained in the step one to obtain the anti-freezing solidification and stabilization agent for the antimony-polluted soil.
Ferrous sulfate in this example: fly ash: calcium lignosulfonate 10:6: 5.
Example 2: the preparation method of the freeze-resistant solidification stabilizing agent for the antimony-polluted soil comprises the following steps:
firstly, weighing 35.7% of ferrous sulfate, 57.1% of fly ash and 7.2% of calcium lignosulfonate according to the mass percentage, and respectively grinding into powder of 200 meshes;
and secondly, uniformly mixing the powder obtained in the step one to obtain the anti-freezing solidification and stabilization agent for the antimony-polluted soil.
Ferrous sulfate in this example: fly ash: calcium lignosulfonate-5: 8: 1.
Example 3: the preparation method of the freeze-resistant solidification stabilizing agent for the antimony-polluted soil comprises the following steps:
firstly, weighing 27.6 percent of ferrous sulfate, 55.2 percent of fly ash and 17.2 percent of calcium lignosulfonate according to the mass percentage, and respectively grinding the materials into 200-mesh powder;
and secondly, uniformly mixing the powder obtained in the step one to obtain the anti-freezing solidification stabilizing agent for the antimony-polluted soil.
Ferrous sulfate in this example: fly ash: calcium lignosulfonate 8:16: 5.
The freeze-resistant solidification stabilizing agent for antimony-contaminated soil prepared in examples 1, 2 and 3 was subjected to an experiment according to the following procedure:
uniformly mixing an anti-freezing type solidification and stabilization agent for the antimony-polluted soil with the to-be-repaired polluted soil, wherein the ratio of the adding quality of the anti-freezing type solidification and stabilization agent for the antimony-polluted soil to the quality of the to-be-repaired polluted soil is 1:10, stirring for 3 times, and uniformly sprinkling water in the stirring process to enable the water content of the soil to reach 25%;
and secondly, covering a waterproof plastic film on the surface of the soil after stirring, maintaining for 5 days, and maintaining the water content at 20-30% in the maintenance period so that the active components in the ferrous sulfate, the fly ash and the calcium lignosulfonate fully react with the heavy metal antimony.
Contaminated soil to be restored for experiments is from a special equipment factory of Harbin, the content and leaching concentration of antimony contaminated soil to be processed are firstly measured, the content of antimony in a soil sample is measured by a detection method specified in management and control standards (trial) for risk of soil contamination of construction land (GB3600-2018), and the detection result is 90 mg/kg;
measuring the content of antimony in the leachate of the polluted soil by using a leaching mode specified in a solid waste leaching toxicity leaching method horizontal oscillation method (HJ 557-2010), wherein the measurement result is 0.306 mg/L;
the unconfined compressive strength of the cured product was measured by the measuring method specified in geotechnical test method Standard (GB/T50123-2019), and the measurement result was 0.33 MPa.
After completion of the curing, the antimony content in the contaminated soil leachate and the unconfined compressive strength of the solidified body were measured, and the results are shown in table 1.
After curing, 40 times of freeze-thaw cycle experiments were performed at-20 ℃ to-20 ℃, the temperature setting curve of the freeze-thaw cycles is shown in fig. 1, the content of antimony in the leachate of contaminated soil and the unconfined compressive strength of the solidified body were measured according to the leaching method specified in the "solid waste leaching toxicity leaching method horizontal oscillation method" (HJ 557-2010) and the measurement method specified in the "geotechnical test method standard" (GB/T50123-.
TABLE 1 results of leaching concentration and unconfined compressive strength before treatment, after maintenance and after freeze-thaw cycling of contaminated soil
Experimental results show that after 5 days of maintenance, after the antimony-polluted soil is treated by the anti-freezing solidification stabilizing agent for antimony-polluted soil in the three embodiments, the concentration of antimony in a polluted soil leachate can meet the IV-type underground water standard (0.01mg/L) in the underground water quality standard (GB/T14848-2017), the compressive strength can reach the regulation of unconfined compressive strength of light soil of a roadbed in the highway roadbed design standard (JTG D30-2015), and the compressive strength is more than 600kPa for an expressway and a first-class highway.
The leaching concentration after 40 times of freeze-thaw cycles can meet IV-type underground water standards (0.01mg/L) in underground water quality standards (GB/T14848-2017), the compressive strength can reach the regulations of highway subgrade design specifications (JTG D30-2015) on the unconfined compressive strength of the light soil of the subgrade, and the unconfined compressive strength is larger than 600kPa for expressways and first-level highways.
In summary, the repairing agent of the present invention employs ferric salt or ferrous salt, fly ash and calcium lignosulfonate in a specific ratio. Ferric salt and ferrous salt can form hydroxyl ferric oxide, and the substance can form an inner sphere surface complex with antimony in soil, so that the leaching concentration of heavy metal antimony is obviously reduced, as shown in a formula (1).
4Fe 2+ +6H 2 O+O 2 →4FeOOH+8H + (1)
The fly ash can perform partial hydration reaction, fill soil pores and enhance the compressive strength, and the glass beads contained in the fly ash can enhance the activity of the surface of soil particles and improve the chemical reaction speed. Calcium lignosulphonate presents a number of reactive groups that can complex with metal ions, such as: hydroxyl, carboxyl, carbonyl, sulfonic group and the like, the migration activity of antimony is reduced through complexation and ion exchange, and the generated complex can keep stability under the condition of freeze-thaw cycle, so that the freeze-thaw resistance of the material is enhanced. On the other hand, the calcium lignosulphonate has hydrophobicity, limits water from entering soil, limits the damage of ice crystals to a soil structure in a freeze-thaw cycle alternating state, and strengthens the strength of the soil after the freeze-thaw cycle. The composite medicament of the ferric salt, the fly ash and the calcium lignosulfonate can obviously improve the stabilization performance of the heavy metal and greatly enhance the freeze-thaw resistance of the material. Compared with the traditional medicament, the composite medicament can quickly meet the environmental quality requirement within five days, has freeze-thaw resistance, has application prospect in severe cold areas, still maintains the stabilization capability and compressive strength of heavy metal antimony after 40 times of freeze thawing, has good repair effect and long-term stability. The raw materials designed by the invention are common industrial products, are low in addition, wide in source, low in cost, easy to operate, simple in maintenance process and strong in demonstration and popularization capacity, can be widely applied to the heavy metal antimony-polluted soil remediation work, and particularly has strong application potential in areas with frequent freeze-thaw cycles.
Claims (7)
1. An anti-freezing solidification stabilizing agent for treating antimony contaminated soil is characterized by being prepared by mixing 27-48% of ferrous sulfate, 28-66% of fly ash and 7-24% of calcium lignosulphonate in percentage by mass.
2. The method for preparing the freeze-resistant solidification stabilizing agent for antimony-contaminated soil according to claim 1, which is characterized by comprising the following steps:
firstly, 24-55% of ferrous sulfate, 21-72% of fly ash and 4-24% of calcium lignosulfonate are weighed according to the mass percentage and are respectively ground into powder;
and secondly, uniformly mixing the powder obtained in the step one to obtain the anti-freezing solidification stabilizing agent for the antimony-polluted soil.
3. The method for preparing the freeze-resistant solidification stabilizing agent for antimony-contaminated soil according to claim 2, wherein the particle size of the powder in the first step is 100-200 meshes.
4. The method for using the anti-freezing solidification stabilizing agent for the antimony contaminated soil as claimed in claim 1, wherein the method is carried out by the following steps:
uniformly mixing an anti-freezing solidification and stabilization agent for the antimony-contaminated soil with the contaminated soil, stirring, and uniformly sprinkling water in the stirring process;
and secondly, covering a moisturizing material on the soil surface after stirring and maintaining.
5. The use method of the anti-freezing solidification stabilizing agent for antimony-contaminated soil according to claim 4, wherein the number of stirring in the first step is 3 to 6.
6. The use method of the anti-freezing solidification stabilizing agent for antimony-contaminated soil according to claim 4, wherein the water content of the soil after the water spraying in the first step is kept between 20% and 30%.
7. The use method of the anti-freezing solidification stabilizing agent for antimony-contaminated soil according to claim 4, wherein the curing days in the second step are more than 5 days.
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