CN111040769A - Soil restoration improving agent and soil restoration improving method - Google Patents
Soil restoration improving agent and soil restoration improving method Download PDFInfo
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- CN111040769A CN111040769A CN201911304972.9A CN201911304972A CN111040769A CN 111040769 A CN111040769 A CN 111040769A CN 201911304972 A CN201911304972 A CN 201911304972A CN 111040769 A CN111040769 A CN 111040769A
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Abstract
The invention discloses a soil remediation improver and a soil remediation improvement method, and belongs to the technical field of heavy metal pollution treatment. The soil remediation improver is prepared from the following raw materials in parts by weight: 25-35 parts of cement, 35-55 parts of fly ash, 5-12 parts of quick lime, 7-15 parts of water glass and 2-7 parts of mixed acid; the mixed acid is prepared from concentrated sulfuric acid and concentrated nitric acid according to the volume ratio of (16-20) to 1. The soil restoration and improvement method comprises the following steps: crushing and screening soil to be repaired to obtain a soil pretreatment material; uniformly mixing the soil pretreatment material with water and a soil remediation agent to obtain slurry to be treated; the soil remediation agent is the soil remediation improver; and stacking and curing the slurry to be treated for 7-30 days. The soil remediation improver disclosed by the invention is low in cost, good in heavy metal solidification and stabilization effects, and suitable for large-scale application. The soil restoration and improvement method is simple to operate and good in restoration effect.
Description
Technical Field
The invention relates to the technical field of heavy metal pollution treatment, in particular to a soil remediation improver and a soil remediation and improvement method.
Background
Heavy metal pollution is an important aspect of environmental pollution, and is mainly environmental pollution caused by heavy metals or compounds thereof, including soil heavy metal pollution, water heavy metal pollution and the like. Wherein, heavy metals in the soil have nondegradable nature under the natural state, and can be continuously accumulated in the soil, so that the harm is more and more serious, and the treatment of the heavy metal polluted soil is more difficult. Heavy metals in soil mainly come from mining, waste water discharge, sewage irrigation, products with excessive heavy metals and the like.
Heavy metals in the soil exceed the standard, the human health can be directly harmed, the environmental quality is deteriorated, and the treatment of the heavy metal pollution of the soil needs to be timely and thorough. At present, two main approaches are available for treating soil heavy metal pollution: firstly, the existing form of heavy metal in soil is changed to fix the heavy metal, so that the mobility and the bioavailability of the heavy metal in the environment are reduced, and the main repairing technology comprises an immobilization/stabilization technology and a vitrification technology; and secondly, removing heavy metals from the soil by using a biological or engineering technical method, wherein the main repairing technologies comprise a soil leaching/extraction technology, an electric repairing technology, a thermal desorption technology and the like. The method for remedying the heavy metal pollution of the field soil can be divided into a physical remediation method, a chemical remediation method, a biological remediation method, an agricultural ecological remediation method and the like according to the remediation mechanism.
The solidification and stabilization technology of heavy metals in soil is a restoration technology which fixes or converts soil pollutants into a state with inactive chemical properties by using a physical or chemical method and prevents the soil pollutants from migrating and diffusing in the environment so as to reduce the toxic degree of the soil pollutants, has the characteristics of moderate cost, good effect, short period and the like, and is one of the best methods for treating the heavy metal polluted soil internationally at present.
Curing and stabilization differ in that the curing technique is to mix the contaminated medium with a curing agent, reduce permeability and encapsulate the contaminants into a solid material. The stabilization is to reduce the leachability and the migration capacity of pollutants through chemical reactions, generally, a stabilizing agent is added into soil to adjust and change the physical and chemical properties of heavy metals in the soil, so that the heavy metals generate a series of reactions such as adsorption, complexation, precipitation, ion exchange, oxidation reduction and the like, the biological effectiveness and the migration capacity of the heavy metals in the soil environment are reduced, and the hazard of the heavy metal elements is reduced.
Generally, in order to achieve better treatment effect, two technologies of curing and stabilizing are combined to reduce the pollution risk, and the cured/stabilized product can be conveniently transported for subsequent treatment. The method has the advantages of low investment, quick restoration and simple operation, and has certain superiority to the restoration of large-area medium-low soil pollution.
The Chinese patent with application publication number CN103881727A discloses a stabilizing and curing agent for repairing heavy metal and toxic organic compound contaminated soil, which comprises the following raw materials in percentage by mass: 10-30% of cement, 10-30% of fly ash, 20-50% of clay, 2-10% of activating agent and 2-20% of oxidizing agent, wherein the activating agent is one or more than two of magnesium oxide, aluminum oxide, titanium dioxide or molybdenum trioxide, and the oxidizing agent is one or more than two of sodium persulfate, calcium peroxide, potassium persulfate and ammonium persulfate, and the raw materials are put into a grinding machine to be ground and uniformly mixed to prepare the cement with the specific surface area of 400-800 m-2A stabilizing curing agent per kg.
The stabilizing and curing agent combines the curing agent, the activator and the oxidant, and can well fix and stabilize heavy metal elements in soil. However, the stabilizing and curing agent has few kinds of heavy metal elements which can be stably cured, and is not suitable for the remediation and treatment of the polluted soil containing various heavy metal elements.
Disclosure of Invention
Aiming at the defects in the prior art, the first purpose of the invention is to provide a soil remediation improver which can be used for remediation and treatment of contaminated soil containing various heavy metal elements.
The second purpose of the invention is to provide a soil remediation and improvement method which is simple in process, convenient to operate and low in cost.
In order to achieve the first object, the invention provides the following technical scheme:
a soil remediation improver is prepared from the following raw materials in parts by weight: 25-35 parts of cement, 35-55 parts of fly ash, 5-12 parts of quick lime, 7-15 parts of water glass and 2-7 parts of mixed acid; the mixed acid is prepared from concentrated sulfuric acid and concentrated nitric acid according to the volume ratio of (16-20) to 1.
By adopting the technical scheme, the soil remediation improver takes cement and fly ash as curing agents, and water glass is added, so that the water glass can promote the curing of the cement to generate a complex cross-linking structure, and the cured materials have high density and good curing effect. The repaired and improved soil has good stability in the subsequent treatment process, and secondary pollution of heavy metal elements caused by drying shrinkage and cracking can not occur. The soil restoration improver is also added with a small amount of mixed acid, the mixed acid is prepared by mixing sulfuric acid and nitric acid, and the mixed acid and the water glass act to promote the water glass and silicic acid groups to generate hydroxyl-linked reaction to generate a cross-linking material with larger molecular weight and complex structure, thereby greatly improving the solidification effect on heavy metal elements. Quicklime can be combined with soil particles, and promotes the cementation and conglomeration among the soil particles, so that the curing effect is improved.
The invention is further configured to: the soil remediation improver is prepared from the following raw materials in parts by weight: 31-35 parts of cement, 35-45 parts of fly ash, 5-12 parts of quick lime, 8-15 parts of water glass and 4-5 parts of mixed acid; the mixed acid is prepared from concentrated sulfuric acid and concentrated nitric acid according to the volume ratio of (18-19) to 1.
By adopting the technical scheme, the invention further optimizes the proportion of the raw materials, so that the soil remediation agent has better solidification effect and higher stabilization rate on various heavy metal elements.
The invention is further configured to: the cement is at least two of volcanic ash type cement, silicate type cement and fly ash type cement.
By adopting the technical scheme, the cement is matched with more than two types of cement, so that the adsorption and solidification effects can be better exerted by utilizing the characteristics of different cements.
The invention is further configured to: the fly ash is obtained by mixing class I fly ash and class II fly ash according to the mass ratio of (1-3) to 1.
By adopting the technical scheme, the fly ash in different grades is mixed according to a certain proportion for use, and the particles with different granularities of the graded fly ash are matched with each other, so that the gaps among the particles can be reduced, and the density of the solidified product is greatly improved. In addition, in general, the amount of the class I fly ash is set to be larger, so that the fly ash can be filled among other particles more easily, and the fly ash has very good dispersibility for soils with different physical properties.
The invention is further configured to: the raw materials also comprise chitosan and citric acid, wherein the mass ratio of the chitosan to the citric acid is (2.5-3.5): 1.
by adopting the technical scheme, the chitosan and the citric acid are added, the chitosan improves the adhesiveness of the soil remediation improver when the soil remediation improver acts on the soil, and meanwhile, the solidification rate of cement can be controlled, so that the whole process of the soil remediation improver for playing a role is stable and controllable. The citric acid has good complexing and stabilizing effects on heavy metal ions, and can reduce the activity of the heavy metal ions. In addition, citric acid and chitosan are combined with each other to form a macromolecular mixture, and the macromolecular mixture has a very good adsorption effect on heavy metal ions.
The invention is further configured to: the mass ratio of the chitosan to the cement is (1.5-4.5) to (25-35).
By adopting the technical scheme, the amount of the chitosan and the citric acid is limited, when the chitosan-citric acid composite adsorbent is used, the chitosan can be combined with the citric acid to play a good adsorption and complexation effect if the addition amount of the chitosan is small, and in addition, the use amount of the chitosan is controlled to be low, so that the cost is favorably reduced.
In order to achieve the second object, the invention provides the following technical scheme:
a soil remediation and improvement method comprises the following steps:
1) crushing and screening soil to be repaired to obtain a soil pretreatment material;
2) uniformly mixing the soil pretreatment material with water and a soil remediation agent to obtain slurry to be treated; the soil remediation agent is the soil remediation amendment of claim 1;
3) and stacking and curing the slurry to be treated for 7-30 days.
By adopting the technical scheme, the method adopts the steps of simple pretreatment, mixing with a soil remediation agent, maintenance and the like, can realize remediation of the heavy metal contaminated soil, is simple to operate, and is suitable for large-scale soil remediation treatment.
The invention is further configured to: the mass ratio of the soil pretreatment material to the water in the step 2) is 60-75: 25-40.
By adopting the technical scheme, the adding amount of water is limited, the obtained slurry has proper solid content and viscosity, and the soil remediation agent added in the later period is conveniently and uniformly dispersed in the slurry.
The invention is further configured to: in the step 2), the soil pretreatment material and water are mixed to obtain slurry, and then the slurry is added with the soil remediation agent and mixed uniformly, wherein the addition amount of the soil remediation agent is 70-120kg per cubic meter of the slurry.
By adopting the technical scheme, the using amount of the soil remediation agent can be determined according to the specific soil type and the heavy metal content in the soil, the cost is easily increased due to the large using amount, and the using amount of the soil remediation agent is small. Moreover, due to the adoption of the specific soil remediation improver, a good stabilizing effect can be realized by using a small amount.
The invention is further configured to: and 3) after curing for 7-30 days in the step 3), detecting, and repeating the steps 1) -3) if the content of the heavy metal elements is higher than a set standard.
By adopting the technical scheme, after the maintenance is carried out for a period of time, if the heavy metal content is not reduced to the set standard, the repairing and improving steps are repeated until the set standard is reached. Therefore, the detection can be carried out after short curing time, and if the maintenance time does not reach the standard, the repair is immediately and repeatedly carried out, so that the problem that the ideal effect cannot be achieved even if the maintenance time is too long is avoided, and the efficiency is improved.
In conclusion, the invention has the following beneficial effects:
the soil restoration modifier is added with water glass besides cement, fly ash and quicklime, has low cost, can reduce the cost in large-scale application, and realizes good solidification effect by utilizing a complex cross-linking structure generated by the water glass. The soil remediation improver disclosed by the invention is low in cost, good in heavy metal solidification and stabilization effects, and suitable for large-scale application.
Detailed Description
The present invention will be described in further detail with reference to examples.
In the raw material of the soil restoration improver of the present invention, the cement is preferably a mixture of two or more of pozzolan-type cement, silicate-type cement, and fly ash-type cement. Further preferably, the cement is prepared from the following components in percentage by mass (10-30): (70-90) a pozzolan-type cement, a silicate-type cement. Further preferably, the cement is prepared from the following components in percentage by mass (10-20): (50-65): (15-40) volcanic ash type cement, silicate type cement and fly ash type cement.
The fly ash is at least one of class I fly ash and class II fly ash. Preferably, the fly ash is obtained by mixing class I fly ash and class II fly ash according to the mass ratio of (1-3) to 1.
When the soil remediation improver is prepared, when the chitosan and the citric acid are not required to be added, the water glass and the mixed acid are uniformly mixed to obtain a mixture, and then the mixture is uniformly mixed with the cement, the fly ash and the quicklime. When the mixture is uniformly mixed with the cement fly ash and the quicklime, the mixture can be mixed with the three materials together, or the mixture can be uniformly mixed with the cement fly ash and the quicklime first and then is uniformly mixed with the quicklime. When the chitosan and the citric acid are added, the water glass and the mixed acid are uniformly mixed to obtain a first mixture, then the chitosan and the citric acid are uniformly mixed to obtain a second mixture, and the first mixture and the second mixture are uniformly mixed with the cement, the fly ash and the quicklime. When the chitosan and the citric acid are added, the mass ratio of the chitosan to the cement is (1.5-4.5) to (25-35).
In the following examples, the silicate-type cement is portland cement or ordinary portland cement, preferably ordinary portland cement; the volcanic ash type cement is volcanic ash portland cement; the fly ash type cement is fly ash silicate cement.
The embodiment of the soil remediation improver of the invention is as follows:
example 1
The soil remediation improver is prepared from the following raw materials in parts by weight: 25 parts of cement, 53 parts of fly ash, 10 parts of quicklime, 7 parts of water glass and 5 parts of mixed acid. The cement is silicate cement. The fly ash is class II fly ash. The mixed acid is obtained by mixing concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 19: 1.
When the soil remediation improver is prepared, the water glass and the mixed acid are uniformly mixed, then the cement and the fly ash are added and uniformly mixed, and finally the quicklime is added and uniformly mixed.
Example 2
The soil remediation improver is prepared from the following raw materials in parts by weight: 35 parts of cement, 40 parts of fly ash, 6 parts of quicklime, 12 parts of water glass and 7 parts of mixed acid. The cement is silicate cement. The fly ash is class II fly ash. The mixed acid is obtained by mixing concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 19: 1.
When the soil remediation improver is prepared, the water glass and the mixed acid are uniformly mixed, then the cement and the fly ash are added and uniformly mixed, and finally the quicklime is added and uniformly mixed.
Example 3
The soil remediation improver is prepared from the following raw materials in parts by weight: 30 parts of cement, 48 parts of fly ash, 9 parts of quicklime, 10 parts of water glass and 3 parts of mixed acid. The cement is prepared from the following components in percentage by mass: 80 of pozzolana type cement and silicate type cement. The fly ash is class II fly ash. The mixed acid is obtained by mixing concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 19: 1.
When the soil remediation improver is prepared, the water glass and the mixed acid are uniformly mixed, then the cement and the fly ash are added and uniformly mixed, and finally the quicklime is added and uniformly mixed.
Example 4
The soil remediation improver is prepared from the following raw materials in parts by weight: 31 parts of cement, 43 parts of fly ash, 12 parts of quicklime, 8 parts of water glass, 4 parts of mixed acid, 1.5 parts of chitosan and 0.5 part of citric acid. The cement is prepared from the following components in percentage by mass: 80 of pozzolana type cement and silicate type cement. The fly ash is obtained by mixing class I fly ash and class II fly ash according to the mass ratio of 2: 1. The mixed acid is obtained by mixing concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 19: 1.
When the soil remediation improver is prepared, the water glass and the mixed acid are uniformly mixed to obtain a first mixture, the chitosan and the citric acid are uniformly mixed to obtain a second mixture, and the first mixture and the second mixture are uniformly mixed with the cement, the fly ash and the quicklime.
Example 5
The soil remediation improver is prepared from the following raw materials in parts by weight: 35 parts of cement, 40 parts of fly ash, 5 parts of quicklime, 12 parts of water glass, 4 parts of mixed acid, 3 parts of chitosan and 1 part of citric acid. The cement is prepared from the following components in percentage by mass of 30: 70 of pozzolana type cement and silicate type cement. The fly ash is obtained by mixing class I fly ash and class II fly ash according to the mass ratio of 2: 1. The mixed acid is obtained by mixing concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 19: 1.
When the soil remediation improver is prepared, the water glass and the mixed acid are uniformly mixed to obtain a first mixture, the chitosan and the citric acid are uniformly mixed to obtain a second mixture, and the first mixture and the second mixture are uniformly mixed with the cement, the fly ash and the quicklime.
Example 6
The soil remediation improver is prepared from the following raw materials in parts by weight: 32 parts of cement, 35 parts of fly ash, 8 parts of quicklime, 14 parts of water glass, 5 parts of mixed acid, 4.5 parts of chitosan and 1.5 parts of citric acid. The cement is formed by mixing volcanic ash type cement, silicate type cement and fly ash type cement in a mass ratio of 15:50: 35. The fly ash is obtained by mixing class I fly ash and class II fly ash according to the mass ratio of 2: 1. The mixed acid is obtained by mixing concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 19: 1.
When the soil remediation improver is prepared, the water glass and the mixed acid are uniformly mixed to obtain a first mixture, the chitosan and the citric acid are uniformly mixed to obtain a second mixture, and the first mixture and the second mixture are uniformly mixed with the cement, the fly ash and the quicklime.
The soil remediation and improvement method provided by the invention mainly aims at remediation and improvement of the soil polluted by heavy metals. The soil pretreatment material is uniformly mixed with water and the soil remediation agent by stirring for 30-60 min. And after the slurry to be treated is stacked and maintained for 7-30 days (namely after being repaired and improved), the water content is not more than 30 percent.
The soil pretreatment material is uniformly mixed with water and the soil remediation agent, namely, the soil pretreatment material is uniformly mixed with the water to obtain slurry, and then the soil remediation agent is added into the slurry and uniformly mixed. When the soil remediation agent is added into the slurry, stirring is carried out simultaneously. The stirring speed is 100-200 rpm.
The temperature for curing the slurry to be treated is 15-25 ℃. The humidity during curing is 80-90%.
The soil restoration and improvement method of the invention has the following embodiments:
example 1
The soil restoration and improvement method of the embodiment comprises the following steps:
1) and excavating the soil from the polluted land, loading and transporting the soil to a storage yard, and performing anti-seepage treatment on the bottom of the storage yard.
2) The soil to be polluted is crushed and then sieved to sort out stones and other larger impurities, and the aperture of a sieve hole during sieving is 50 mm.
3) Adding the screened polluted soil into a stirrer, adding water, stirring and uniformly mixing to obtain slurry, wherein the mass fraction of water in the slurry is 40%; then adding a repairing modifier into the slurry, wherein the adding amount of the repairing modifier is 100kg of the repairing modifier added into each cubic meter of the slurry; stirring for 30min to mix the materials uniformly, and discharging the stirred slurry from the stirrer. The remediation improver adopted in this example is the remediation improver of example 1 of the soil remediation improver.
4) Transferring the slurry discharged from the stirrer to a yard, piling up the slurry into a soil pile with the height of 1m by a forklift, and maintaining for 28 days, wherein the temperature during maintenance is controlled to be 20 ℃ and the humidity is controlled to be not less than 90%.
5) And after the maintenance is finished, sampling for detection, repeating the steps 2) -4) once, sampling again for detection, and finishing the restoration when the heavy metal content is lower than the set value.
Example 2
The soil restoration and improvement method of the embodiment comprises the following steps:
1) and excavating the soil from the polluted land, loading and transporting the soil to a storage yard, and performing anti-seepage treatment on the bottom of the storage yard.
2) The soil to be polluted is crushed and then sieved to sort out stones and other larger impurities, and the aperture of a sieve hole during sieving is 50 mm.
3) Adding the screened polluted soil into a stirrer, adding water, stirring and uniformly mixing to obtain slurry, wherein the mass fraction of water in the slurry is 35%; then adding a repairing modifier into the slurry, wherein the adding amount of the repairing modifier is 120kg of the repairing modifier added into each cubic meter of the slurry; stirring for 60min to mix the materials uniformly, and discharging the stirred slurry from the stirrer. The remediation improver adopted in this embodiment is the remediation improver of embodiment 2 of the soil remediation improver described above.
4) Transferring the slurry discharged from the stirrer to a yard, piling up the slurry into a soil pile with the height of 1m by a forklift, and maintaining for 21 days, wherein the temperature during maintenance is controlled to be 20 ℃ and the humidity is controlled to be not less than 90%.
5) And after the maintenance is finished, sampling and detecting, and finishing the repair when the content of the heavy metal is lower than a set value.
Example 3
The soil restoration and improvement method of the embodiment comprises the following steps:
1) and excavating the soil from the polluted land, loading and transporting the soil to a storage yard, and performing anti-seepage treatment on the bottom of the storage yard.
2) The soil to be polluted is crushed and then sieved to sort out stones and other larger impurities, and the aperture of a sieve hole during sieving is 50 mm.
3) Adding the screened polluted soil into a stirrer, adding water, stirring and uniformly mixing to obtain slurry, wherein the mass fraction of water in the slurry is 35%; then adding a repairing modifier into the slurry, wherein the adding amount of the repairing modifier is 120kg of the repairing modifier added into each cubic meter of the slurry; stirring for 60min to mix the materials uniformly, and discharging the stirred slurry from the stirrer. The remediation improver adopted in this embodiment is the remediation improver in embodiment 3 of the soil remediation improver.
4) Transferring the slurry discharged from the stirrer to a yard, piling up the slurry into a soil pile with the height of 1m by a forklift, and maintaining for 21 days, wherein the temperature during maintenance is controlled to be 20 ℃ and the humidity is controlled to be not less than 90%.
5) And after the maintenance is finished, sampling and detecting, and finishing the repair when the content of the heavy metal is lower than a set value.
Example 4
The soil restoration and improvement method of the embodiment comprises the following steps:
1) and excavating the soil from the polluted land, loading and transporting the soil to a storage yard, and performing anti-seepage treatment on the bottom of the storage yard.
2) The soil to be polluted is crushed and then sieved to sort out stones and other larger impurities, and the aperture of a sieve hole during sieving is 40 mm.
3) Adding the screened polluted soil into a stirrer, adding water, stirring and mixing uniformly to obtain slurry, wherein the mass fraction of water in the slurry is 28.5%; then adding a repair modifier into the slurry, wherein the addition amount of the repair modifier is 80kg per cubic meter of the slurry; stirring for 45min to mix the materials uniformly, and discharging the stirred slurry from the stirrer. The remediation improver adopted in this embodiment is the remediation improver of embodiment 4 of the soil remediation improver described above.
4) Transferring the slurry discharged from the stirrer to a yard, piling up the slurry into a soil pile with the height of 1m by a forklift, and maintaining for 15 days, wherein the temperature during maintenance is controlled to be 25 ℃ and the humidity is controlled to be not less than 80%.
5) And after the maintenance is finished, sampling and detecting, and finishing the repair when the content of the heavy metal is lower than a set value.
Example 5
The soil restoration and improvement method of the embodiment comprises the following steps:
1) and excavating the soil from the polluted land, loading and transporting the soil to a storage yard, and performing anti-seepage treatment on the bottom of the storage yard.
2) The soil to be polluted is crushed and then sieved to sort out stones and other larger impurities, and the aperture of a sieve hole during sieving is 40 mm.
3) Adding the screened polluted soil into a stirrer, adding water, stirring and mixing uniformly to obtain slurry, wherein the mass fraction of water in the slurry is 28.5%; then adding a repairing modifier into the slurry, wherein the adding amount of the repairing modifier is 75kg of the repairing modifier added into each cubic meter of the slurry; stirring for 30min to mix the materials uniformly, and discharging the stirred slurry from the stirrer. The remediation improver adopted in this example is the remediation improver of example 5 of the soil remediation improver described above.
4) Transferring the slurry discharged from the stirrer to a yard, piling up the slurry into a soil pile with the height of 1m by a forklift, and maintaining for 10 days, wherein the temperature during maintenance is controlled to be 25 ℃ and the humidity is controlled to be not less than 80%.
5) And after the maintenance is finished, sampling and detecting, and finishing the repair when the content of the heavy metal is lower than a set value.
Example 6
The soil restoration and improvement method of the embodiment comprises the following steps:
1) and excavating the soil from the polluted land, loading and transporting the soil to a storage yard, and performing anti-seepage treatment on the bottom of the storage yard.
2) The soil to be polluted is crushed and then sieved to sort out stones and other larger impurities, and the aperture of a sieve hole during sieving is 40 mm.
3) Adding the screened polluted soil into a stirrer, adding water, stirring and mixing uniformly to obtain slurry, wherein the mass fraction of water in the slurry is 28.5%; then adding a repairing modifier into the slurry, wherein the adding amount of the repairing modifier is 70kg of the repairing modifier added into each cubic meter of the slurry; stirring for 30min to mix the materials uniformly, and discharging the stirred slurry from the stirrer. The remediation improver adopted in this example is the remediation improver of example 6 of the soil remediation improver described above.
4) Transferring the slurry discharged from the stirrer to a yard, piling up the slurry into a soil pile with the height of 1m by a forklift, and maintaining for 7 days, wherein the temperature during maintenance is controlled to be 25 ℃ and the humidity is controlled to be not less than 80%.
5) And after the maintenance is finished, sampling and detecting, and finishing the repair when the content of the heavy metal is lower than a set value.
Comparative example 1
The soil remediation agent of the comparative example is obtained by mixing cement and fly ash according to the mass ratio of 1: 1.
The soil remediation and improvement method of this comparative example was carried out in accordance with the method of example 1 of the soil remediation and improvement method of the present invention using the above-mentioned soil remediation agent.
Comparative example 2
The soil remediation agent of the comparative example is obtained by mixing water glass and mixed acid according to the mass ratio of 2: 1.
The soil remediation and improvement method of this comparative example was carried out in accordance with the method of example 1 of the soil remediation and improvement method of the present invention using the above-mentioned soil remediation agent.
Test examples
Taking the soil after screening in the step 2) (before repairing) and the soil after curing in the step 4) (after repairing) in the soil repairing and improving method examples 1-6 and the comparative example, adopting a TCLP toxicity leaching method to determine the heavy metal content in the soil, wherein the heavy metal content before repairing is approximately the same for each sample, and taking the average value as follows: the content of Pb is 593mg/kg, Zn is 147mg/kg, Cd is 7.7mg/kg and Cr is 118mg/kg, the detected contents of As and Hg are less and do not exceed the standard, so the two elements are not detected after repair.
The results of the detection after repair are shown in the following table.
TABLE 1 detection results of heavy metal content in soil after remediation in examples 1 to 6 and comparative examples 1 to 2
As can be seen from Table 1, when the soil remediation improver is used for remediation and improvement of heavy metal contaminated soil, the soil after remediation is cured and stabilized, and when the soil is leached, the detected heavy metal content is low, and the soil has a high stabilization rate on heavy metal elements.
Claims (10)
1. A soil remediation improver is characterized in that: the feed is prepared from the following raw materials in parts by weight: 25-35 parts of cement, 35-55 parts of fly ash, 5-12 parts of quick lime, 7-15 parts of water glass and 2-7 parts of mixed acid; the mixed acid is prepared from concentrated sulfuric acid and concentrated nitric acid according to the volume ratio of (16-20) to 1.
2. A soil remediation amendment according to claim 1, characterised in that: the feed is prepared from the following raw materials in parts by weight: 31-35 parts of cement, 35-45 parts of fly ash, 5-12 parts of quick lime, 8-15 parts of water glass and 4-5 parts of mixed acid; the mixed acid is prepared from concentrated sulfuric acid and concentrated nitric acid according to the volume ratio of (18-19) to 1.
3. A soil remediation amendment according to claim 1 or 2, characterised in that: the cement is at least two of volcanic ash type cement, silicate type cement and fly ash type cement.
4. A soil remediation amendment according to claim 1 or 2, characterised in that: the fly ash is obtained by mixing class I fly ash and class II fly ash according to the mass ratio of (1-3) to 1.
5. A soil remediation amendment according to claim 1 or 2, characterised in that: the raw materials also comprise chitosan and citric acid, wherein the mass ratio of the chitosan to the citric acid is (2.5-3.5): 1.
6. a soil remediation amendment according to claim 5, further comprising: the mass ratio of the chitosan to the cement is (1.5-4.5) to (25-35).
7. A soil restoration and improvement method is characterized by comprising the following steps:
1) crushing and screening soil to be repaired to obtain a soil pretreatment material;
2) uniformly mixing the soil pretreatment material with water and a soil remediation agent to obtain slurry to be treated; the soil remediation agent is the soil remediation amendment of claim 1;
3) and stacking and curing the slurry to be treated for 7-30 days.
8. The soil improvement method of claim 7, wherein the mass ratio of the soil pretreatment material to water in step 2) is 60-75: 25-40.
9. The soil remediation method of claim 7 wherein the soil pretreatment material is mixed with water in step 2) to form a slurry, and then the soil remediation agent is added to the slurry to mix evenly, the amount of soil remediation agent added is 70-120kg per cubic meter of slurry.
10. The soil improvement method according to any one of claims 7 to 9, wherein the steps 1) to 3) are repeated when the heavy metal content is higher than a predetermined standard by testing after 7 to 30 days of maintenance in the step 3).
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