CN111662718A - Soil heavy metal passivator and preparation method and application thereof - Google Patents
Soil heavy metal passivator and preparation method and application thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of soil remediation, and particularly relates to a soil heavy metal passivator and a preparation method and application thereof. The soil heavy metal passivator comprises the following components, by weight, 33-75 parts of carbonized bone meal; 7-30 parts of a metal salt antagonist; 10-50 parts of solid alkali. The passivant takes carbonized animal bone powder and a metal salt antagonist as main components, has cheap and easily-obtained raw materials, and can provide mineral nutrients such as phosphorus, calcium and the like for soil; by adding the solid alkali as a precipitator of the metal salt antagonist, the rapid dissolution loss of the metal salt is avoided, so that the aim of releasing the metal antagonistic ions in a lasting manner is fulfilled, and the heavy metal absorption of crops is further reduced.
Description
Technical Field
The invention belongs to the technical field of soil remediation, and particularly relates to a soil heavy metal passivator and a preparation method and application thereof.
Background
In recent years, with the development of industry and the use of agricultural input products in large quantities, the world faces more and more serious soil environment safety problems, and the heavy metal pollution is the most concerned. Due to the current scientific level, heavy metal pollutants entering the soil cannot be separated from the soil simply and quickly. For the treatment of polluted soil, a passivation/stabilization method is mainly adopted at present, namely, the total amount of heavy metals in the soil is not reduced, but the mobility and the bioavailability of pollutants are reduced by technical means, so that the influence and ecological risks of the pollutants are restrained.
The passivation material which is efficient, cheap and environment-friendly is a research hotspot at present, wherein the passivation material which takes the biomass material as the main body can be naturally degraded in soil, has good environmental compatibility and can not cause secondary pollution to the soil. At present, a lot of related patents and academic reports are reported at home and abroad, for example, Chinese patent document CN106635046A discloses a preparation method and application of a cow dung-based biomass material, calcined cow dung and straw ash are mixed and then mixed with polluted soil and maintained, so that heavy metals in the soil are stabilized, and the leaching concentration of lead in the soil is effectively reduced; chinese patent document CN106811202A discloses a humic acid preparation for reducing the content of free heavy metal ions in soil and an application thereof, after the humic acid preparation is sprayed in the soil polluted by heavy metal, the heavy metal content in crops and plants and the migration amount of the heavy metal to other places can be effectively reduced, so as to achieve the purpose of reducing the heavy metal pollution, Chinese patent document CN107384433A discloses a soil heavy metal passivator which is prepared by adopting materials such as peanut shells, Korean pine needles, chitin and the like, so that the heavy metal content of the plants can be effectively reduced, and the purpose of passivation and restoration can be achieved; the soil heavy metal passivator shows a good passivation effect.
The bone meal contains abundant minerals, mainly hydroxyapatite crystal [ Ca ]10(PO4)6(OH)2]And amorphous calcium hydrogen phosphate (CaHPO)4) The biological organic fertilizer is a novel biomass component in the soil heavy metal passivator, has a certain passivation effect, can reduce the application of phosphate fertilizer, and improves economic benefit. Chinese patent document CN110252798A adopts inorganic phosphate, bone meal, pH regulator, bentonite and biochar as main raw materials to prepare the heavy metal contaminated soil composite remediation agent, but the dosage of the agent is 0.5-5 wt% of the soil weight, and approximately 11250-112500 kg/hm2The application amount is large, the cost is high, the components are complex, and the effects of damaging and passivating the soil structure are still to be further improved.
Disclosure of Invention
Therefore, the invention aims to overcome the defects that the passivating agent containing bone meal in the prior art is large in application amount, high in cost, complex in components, capable of damaging the soil structure, and still needs to be further improved in passivating effect, and the like, and provides the soil heavy metal passivating agent, and the preparation method and the application thereof.
Therefore, the invention provides the following technical scheme:
the invention provides a soil heavy metal passivator, which comprises the following components in parts by weight,
33-75 parts of carbonized bone meal;
7-30 parts of a metal salt antagonist;
10-50 parts of solid alkali.
Further comprises the following components in parts by weight,
40-60 parts of carbonized bone meal;
18-23 parts of a metal salt antagonist;
20-40 parts of solid alkali.
Further, the metal salt antagonist is at least one of iron-containing metal salt, manganese-containing metal salt, zinc-containing metal salt, calcium-containing metal salt and magnesium-containing metal salt.
Further, the metal salt antagonist is at least one of ferrous sulfate, ferric chloride, ferrous chloride, manganese sulfate, zinc chloride, zinc sulfate, calcium chloride, magnesium chloride and magnesium sulfate.
Further, the solid alkali is at least one of quicklime, slaked lime, limestone powder and plant ash.
The invention also provides a preparation method of the soil heavy metal passivator, which comprises the following steps:
dissolving the metal antagonist in water, then uniformly mixing with the carbonized bone meal, drying, and then mixing with solid alkali to obtain the soil heavy metal passivator.
Further, the preparation steps of the carbonized bone meal are as follows: carrying out low-temperature carbonization treatment on the bone meal in an inert gas atmosphere, wherein the temperature of the low-temperature carbonization treatment is 300-600 ℃, and the time is 2-5 h;
preferably, the temperature of the low-temperature carbonization treatment is 400-500 ℃, and the time is 2-3 h.
Further, the inert gas is nitrogen, and the nitrogen flow rate is 0.5-3.0L/min;
preferably, the nitrogen flow rate is 2.0L/min.
Further, the drying temperature is 70-90 ℃.
The invention also provides an application of the soil heavy metal passivator or prepared by the preparation method in heavy metal contaminated soil remediation.
The heavy metal of the invention contains one or more elements of cadmium, lead, copper, chromium, mercury and the like.
Further, the dosage of the passivator is 1500-2Can be used for passivating heavy metals in soil and reducing the content of heavy metals in agricultural products. The passivator is generally applied when the soil is ploughed, and the crop transplanting or sowing is carried out after 3-5 days.
The bone meal can be commercially available bone meal which meets the standard requirements of GB/T20193 & 2006 bone meal for feed and meat bone meal, and the raw material sources of the bone meal comprise but are not limited to livestock and poultry bones such as bovine bones, pig bones, sheep bones, chicken bones and the like.
The technical scheme of the invention has the following advantages:
1. the soil heavy metal passivator provided by the invention comprises the following components, by weight, 33-75 parts of carbonized bone meal; 7-30 parts of a metal salt antagonist; 10-50 parts of solid alkali. The passivant takes carbonized animal bone powder and a metal salt antagonist as main components, has cheap and easily-obtained raw materials, and can provide mineral nutrients such as phosphorus, calcium and the like for soil; by adding the solid alkali as a precipitator of the metal salt antagonist, the rapid dissolution loss of the metal salt is avoided, so that the aim of releasing the metal antagonistic ions in a lasting manner is fulfilled, and the heavy metal absorption of crops is further reduced. The composite passivator changes the form of heavy metal in soil into an insoluble state by improving the pH value of the soil through the combined action of the metal salt antagonist and the solid alkali, thereby reducing the effectiveness of the heavy metal. In all raw materials, the solid alkali plays a main role in improving the pH of the soil, and the carbonized bone meal contains more calcium elements, so that the concentration of calcium ions in the soil can be improved, the salinity saturation of the soil is improved, and the auxiliary effect on the improvement of the pH of the soil is achieved. The three components are matched according to a specific dosage proportion, so that the soil structure is not damaged, the application amount is small, the excellent effect of reducing the activity of heavy metals is shown, and meanwhile, the passivator is simple to apply, can effectively reduce the treatment cost, and has good environmental compatibility. According to the invention, through further optimization selection of the use amount of each component, the soil heavy metal passivator has a more excellent soil passivation effect.
The soil heavy metal passivator provided by the invention is prepared from bone meal, solid alkali and a metal salt antagonist, or is a biological material, or is a large amount or medium element contained in soil, and can be naturally degraded or decomposed in a soil environment, so that secondary pollution to the soil is avoided.
2. The preparation method of the soil heavy metal passivator provided by the invention comprises the steps of dissolving a metal antagonist in water, uniformly mixing the metal antagonist with carbonized bone meal, drying, and mixing with solid alkali to obtain the soil heavy metal passivator. The method can realize the sustained release of metal salt ions by loading the metal salt antagonist in the carbonized bone powder, and avoid the rapid loss of the metal salt antagonist ions in the soil. Under the action of solid alkali, the metal salt can form flocculent hydroxide precipitates in soil and carbonized bone powder, and the slow decomposition of the flocculent precipitates in the soil can further supply metal antagonistic ions to the soil continuously. The metal salt ion contained in the metal salt antagonist and the soil heavy metal ion generate competitive adsorption on the root surface of the crops, so that the absorption of the crops to the heavy metal is reduced. The invention can synergistically reduce the bioavailability of heavy metals through a plurality of action mechanisms, so that agricultural products meet the food sanitation standard.
The preparation method of the soil heavy metal passivator provided by the invention comprises the following steps: carrying out low-temperature carbonization treatment on the bone meal in an inert gas atmosphere, wherein the temperature of the low-temperature carbonization treatment is 300-600 ℃, and the time is 2-5 h; preferably, the temperature of the low-temperature carbonization treatment is 400-500 ℃, and the time is 2-3 h. Further, the inert gas is nitrogen, and the nitrogen flow rate is 0.5-3.0L/min; preferably, the nitrogen flow rate is 2.0L/min. The bone meal is a natural biological material, in the low-temperature carbonization process, fat, protein and organic matter components in the bone meal are partially decomposed and gasified, and a plurality of pores with the pore diameter of about 250nm are formed in the bone meal, so that the specific surface area of the bone meal is greatly increased, the physical adsorption effect of the bone meal on metal salt antagonists and soil heavy metals is enhanced, and the soil passivation effect is further improved. By optimizing the conditions of the low-temperature carbonization treatment, the physical adsorption effect of the bone meal on the metal salt antagonist and the soil heavy metal can be further enhanced, and a more excellent soil passivation effect can be obtained. Meanwhile, the total phosphorus content of the bone meal is more than or equal to 11 percent, the nutrient requirement of crops can be supplemented after the bone meal is applied to soil, and the application of phosphate fertilizers is reduced, so that the use cost of a passivating agent is further reduced. On the other hand, organic components are decomposed by low-temperature carbonization, so that the organic matter content of the bone meal is further reduced, the bone meal does not have a post-decomposition process after being applied to soil, the seedling burning phenomenon cannot occur, crops can be planted in a short time, and the adverse effect on the growth of the crops is reduced.
3. The passivation material provided by the invention overcomes the defects of large using amount and large labor amount of the traditional biological passivation material and solid alkali, effectively improves the passivation efficiency by compounding the metal salt antagonist, and has the characteristics of low cost and high efficiency. The low cost is mainly shown in that: in the same soil, the direct cost is about 50 percent of the quicklime cost and about 40 percent of the slaked lime cost when the Cd content in the paddy is reduced to 0.20 mg/kg; meanwhile, the application amount is only about 30 percent of that of the conventional lime, so that the transportation and labor cost can be greatly reduced. The high efficiency is mainly shown in that: in the same soil, the content of Cd in the rice needs to be reduced to below 0.20mg/kg, and the using amount of lime is 6000-sodium silicate 7500kg/hm2The usage amount of the compound material is only 1500-charge 1875kg/hm2The consumption of the passivator can be greatly reduced, and the labor cost is reduced.
Detailed Description
The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.
The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.
Example 1
The embodiment provides a soil heavy metal passivator, which comprises the following components:
75kg of carbonized bone meal; 30kg of metal salt antagonist, wherein 20kg of manganese chloride and 10kg of ferrous sulfate are contained; 50kg of solid alkali, wherein, 25kg of slaked lime and 25kg of plant ash.
The preparation method of the soil heavy metal passivator comprises the following steps:
carrying out low-temperature carbonization on commercially available bone meal (meeting the standard requirements of GB/T20193 & 2006 bone meal for feed and meat and bone meal) under the condition of nitrogen, wherein the carbonization temperature is 600 ℃, the carbonization time is 2h, and the nitrogen flow rate is 3.0L/min to obtain carbonized bone meal;
dissolving the metal antagonist in 90kg of water, then uniformly mixing with the carbonized bone meal, drying at 90 ℃ for 6h, and then uniformly mixing with solid alkali to obtain the soil heavy metal passivator.
Example 2
The embodiment provides a soil heavy metal passivator, which comprises the following components:
33kg of carbonized bone meal; 7kg of metal salt antagonist, wherein the zinc sulfate is 3kg, and the magnesium chloride is 4 kg; 10kg of solid alkali, wherein, 5kg of slaked lime and 5kg of limestone.
The preparation method of the soil heavy metal passivator comprises the following steps:
carrying out low-temperature carbonization on commercially available bone meal (meeting the standard requirements of GB/T20193 & 2006 bone meal for feed and meat and bone meal) under the condition of nitrogen, wherein the carbonization temperature is 300 ℃, the carbonization time is 5h, and the nitrogen flow rate is 0.5L/min to obtain carbonized bone meal;
dissolving a metal antagonist in 7kg of water, then uniformly mixing with the carbonized bone meal, drying at 70 ℃ for 6h, and then uniformly mixing with solid alkali to obtain the soil heavy metal passivator.
Example 3
The embodiment provides a soil heavy metal passivator, which comprises the following components:
60kg of carbonized bone meal; 23kg of metal salt antagonist, wherein the weight of manganese sulfate is 10kg, the weight of ferric chloride is 8kg, and the weight of calcium chloride is 5 kg; 40kg of solid alkali, wherein 40kg of quicklime.
The preparation method of the soil heavy metal passivator comprises the following steps:
carrying out low-temperature carbonization on commercially available bone meal (meeting the standard requirements of GB/T20193 & 2006 bone meal for feed and meat and bone meal) under the condition of nitrogen, wherein the carbonization temperature is 600 ℃, the carbonization time is 2h, and the nitrogen flow rate is 3.0L/min to obtain carbonized bone meal;
dissolving a metal antagonist in 46kg of water, then uniformly mixing the metal antagonist with the carbonized bone meal obtained by the method, drying the mixture at the temperature of 80 ℃ for 6 hours, and then uniformly mixing the dried mixture with solid alkali to obtain the soil heavy metal passivator.
Example 4
The embodiment provides a soil heavy metal passivator, which comprises the following components:
40kg of carbonized bone meal; 18kg of metal salt antagonist, wherein the weight of manganese sulfate is 10kg, and the weight of ferrous chloride is 8 kg; 20kg of solid alkali, wherein 15kg of quicklime and 5kg of plant ash are contained.
The preparation method of the soil heavy metal passivator comprises the following steps:
carrying out low-temperature carbonization on commercially available bone meal (meeting the standard requirements of GB/T20193 & 2006 bone meal for feed and meat and bone meal) under the condition of nitrogen, wherein the carbonization temperature is 300 ℃, the carbonization time is 5h, and the nitrogen flow rate is 0.5L/min to obtain carbonized bone meal;
dissolving a metal antagonist in 40kg of water, then uniformly mixing the metal antagonist with the carbonized bone meal obtained by the method, drying the mixture at 75 ℃ for 6 hours, and then uniformly mixing the dried mixture with solid alkali to obtain the soil heavy metal passivator.
Example 5
The embodiment provides a soil heavy metal passivator, which comprises the following components:
50kg of carbonized bone meal; 20kg of metal salt antagonist, wherein the metal salt antagonist comprises 10kg of manganese chloride, 5kg of zinc chloride and 5kg of magnesium sulfate; 30kg of solid alkali, wherein the slaked lime is 20kg, the limestone is 5kg, and the plant ash is 5 kg.
The preparation method of the soil heavy metal passivator comprises the following steps:
carrying out low-temperature carbonization on commercially available bone meal (meeting the standard requirements of GB/T20193 & 2006 bone meal for feed and meat bone meal) under the condition of nitrogen, wherein the carbonization temperature is 400 ℃, the carbonization time is 3h, and the nitrogen flow rate is 2L/min to obtain carbonized bone meal;
dissolving a metal antagonist in 40kg of water, then uniformly mixing the metal antagonist with the carbonized bone meal obtained by the method, drying the mixture at 85 ℃ for 6 hours, and then uniformly mixing the dried mixture with solid alkali to obtain the soil heavy metal passivator.
Example 6
The embodiment provides a soil heavy metal passivator, which comprises the following components:
50kg of carbonized bone meal; 22kg of metal salt antagonist, wherein 12kg of manganese chloride, 5kg of ferrous sulfate and 5kg of magnesium chloride; 25kg of solid alkali, wherein the quicklime is 20kg, and the limestone is 5 kg.
The preparation method of the soil heavy metal passivator comprises the following steps:
carrying out low-temperature carbonization on commercially available bone meal (meeting the standard requirements of GB/T20193 & 2006 bone meal for feed and meat bone meal) under the condition of nitrogen, wherein the carbonization temperature is 500 ℃, the carbonization time is 2h, and the nitrogen flow rate is 2L/min to obtain carbonized bone meal;
dissolving a metal antagonist in 40kg of water, then uniformly mixing the metal antagonist with the carbonized bone meal obtained by the method, drying the mixture at the temperature of 80 ℃ for 6 hours, and then uniformly mixing the dried mixture with solid alkali to obtain the soil heavy metal passivator.
Comparative example 1
The comparative example provides a soil heavy metal passivator, which comprises the following components:
50kg of carbonized bone meal; 20kg of metal salt antagonist, wherein the metal salt antagonist comprises 10kg of manganese chloride, 5kg of zinc chloride and 5kg of magnesium sulfate; 30kg of solid alkali, wherein the slaked lime is 20kg, the limestone is 5kg, and the plant ash is 5 kg.
The preparation method of the soil heavy metal passivator comprises the following steps:
carrying out low-temperature carbonization on commercially available bone meal (meeting the standard requirements of GB/T20193 & 2006 bone meal for feed and meat bone meal) under the condition of nitrogen, wherein the carbonization temperature is 400 ℃, the carbonization time is 3h, and the nitrogen flow rate is 2L/min to obtain carbonized bone meal;
and (3) fully and uniformly mixing the metal antagonist, the carbonized bone meal obtained by the method and solid alkali to obtain the soil heavy metal passivator.
Comparative example 2
The comparative example provides a soil heavy metal passivator, which comprises the following components: 50kg of carbonized bone meal; 20kg of metal salt antagonist, wherein the metal salt antagonist comprises 10kg of manganese chloride, 5kg of zinc chloride and 5kg of magnesium sulfate.
The preparation method of the soil heavy metal passivator comprises the following steps:
carrying out low-temperature carbonization on commercially available bone meal (meeting the standard requirements of GB/T20193 & 2006 bone meal for feed and meat bone meal) under the condition of nitrogen, wherein the carbonization temperature is 400 ℃, the carbonization time is 3h, and the nitrogen flow rate is 2L/min to obtain carbonized bone meal;
dissolving the metal antagonist in 40kg of water, then uniformly mixing with the carbonized bone meal obtained by the method, and drying at 85 ℃ for 6 hours to obtain the soil heavy metal passivator.
Comparative example 3
The comparative example provides a soil heavy metal passivator, which comprises the following components:
50kg of carbonized bone meal; 30kg of solid alkali, wherein the slaked lime is 20kg, the limestone is 5kg, and the plant ash is 5 kg.
The preparation method of the soil heavy metal passivator comprises the following steps:
carrying out low-temperature carbonization on commercially available bone meal (meeting the standard requirements of GB/T20193 & 2006 bone meal for feed and meat bone meal) under the condition of nitrogen, wherein the carbonization temperature is 450 ℃, the carbonization time is 3h, and the nitrogen flow rate is 2L/min to obtain carbonized bone meal;
and (3) uniformly mixing the carbonized bone meal obtained by the method with solid alkali to obtain the soil heavy metal passivator.
Comparative example 4
The comparative example provides a soil heavy metal passivator, which comprises the following components:
50kg of carbonized bone meal; 20kg of metal salt antagonist, wherein the metal salt antagonist comprises 10kg of manganese chloride, 5kg of zinc chloride and 5kg of magnesium sulfate; 30kg of solid alkali, wherein the slaked lime is 20kg, the limestone is 5kg, and the plant ash is 5 kg.
The preparation method of the soil heavy metal passivator comprises the following steps:
carrying out low-temperature carbonization on commercially available bone meal (meeting the standard requirements of GB/T20193 & 2006 bone meal for feed and meat bone meal) under the condition of nitrogen, wherein the carbonization temperature is 700 ℃, the carbonization time is 3h, and the nitrogen flow rate is 2L/min to obtain carbonized bone meal;
dissolving a metal antagonist in 40kg of water, then uniformly mixing the metal antagonist with the carbonized bone meal obtained by the method, drying the mixture at 85 ℃ for 6 hours, and then uniformly mixing the dried mixture with solid alkali to obtain the soil heavy metal passivator.
Comparative example 5
The embodiment provides a soil heavy metal passivator, which comprises the following components:
50kg of commercially available bone meal (the bone meal for the feed meeting the standard requirements of GB/T20193-2006 bone meal for the feed and meat and bone meal); 20kg of metal salt antagonist, wherein the metal salt antagonist comprises 10kg of manganese chloride, 5kg of zinc chloride and 5kg of magnesium sulfate; 30kg of solid alkali, wherein the slaked lime is 20kg, the limestone is 5kg, and the plant ash is 5 kg.
The preparation method of the soil heavy metal passivator comprises the following steps:
dissolving the metal antagonist in 40kg of water, then uniformly mixing with the bone meal, drying at 85 ℃ for 6h, and then uniformly mixing with solid alkali to obtain the soil heavy metal passivator.
Examples of the experiments
1. Experiment of soil passivation effect
The soil heavy metal passivator disclosed in the embodiments 1-6 and the comparative examples 1-5 is used for heavy metal contaminated soil, the soil heavy metal passivator is respectively added into the contaminated soil during ploughing, and the contents of effective Cd, Pb and Cr in the soil after remediation are determined, wherein the specific determination method comprises the following steps: 5.00g (accurate to 0.01g) of soil sample sieved by a 20-mesh sieve is weighed into a 50mL centrifuge tube, 25mL of 0.01mol/L dilute hydrochloric acid leaching agent is added, and the mixture is shaken for 2 hours at room temperature. Centrifuging for 4 minutes at 4000rpm by using a centrifuge, and measuring the contents of Cd, Pb and Cr in the supernatant by using a graphite furnace atomic absorption spectrophotometer.
Table 1 shows the measurement results of the contents of effective Cd, effective Pb and effective Cr before and after the restoration of the soil with the contents of initial effective Cd, effective Pb and effective Cr being 0.373mg/kg, 41.1mg/kg and 60.3mg/kg respectively, wherein the addition amount of the composite modifier is 2250kg/hm2The repair time is 120 days;
table 2 shows the results of measurements of the contents of available Cd, available Pb, available Cu and available Cu after remediation of five fields of different pollution levels with the passivator provided in example 5, wherein the addition amount of the composite improver is 2250kg/hm2The repair time is 120 days;
table 3 shows the passivates provided in example 5 at various addition levels (1500 kg/hm)2、1875kg/hm2、2250kg/hm2、2625kg/hm2、3000kg/hm2) Measuring the effective Cd content of the soil (the initial effective Cd content is 0.373mg/kg, the effective Pb content is 41.1mg/kg, the effective Cr content is 60.3mg/kg, and the effective Cu content is 90.4mg/kg), wherein the repairing time is 120 days;
table 4 shows that the soil heavy metal passivator provided in example 5 is added at the same amount of 2250kg/hm2And determining the effective Cd content after restoring the soil (the initial Cd content is 0.373mg/kg) under different passivation times.
TABLE 1 influence of different passivators on soil available heavy metal content and removal rate
As can be seen from the data in the table, the average reduction rates of effective Cd, effective Pb and effective Cr in all examples were 50.3%, 38.6% and 53.7%, respectively, and the average reduction rates of effective Cd, effective Pb and effective Cr in the comparative examples were 39.0%, 32.5% and 40.5%, respectively. It can be seen that the examples reduce the content of the three available heavy metals in the soil to a significantly higher level than the comparative examples. Wherein, the reducing effects of the contents of the soil available Cd, the soil available Pb and the soil available Cr in the embodiment 5 are 57.1%, 44.3% and 68.0% respectively, and the reducing effects of the embodiment 6 on the contents of the soil available Cd, the soil available Pb and the soil available Cr are 58.2%, 44.8% and 66.7% respectively, which are obviously higher than the reducing effects of the embodiments 1, 2, 3 and 4 on the available heavy metals.
TABLE 2 influence of passivator on the content and removal rate of heavy metals in the available state of different fields
As can be seen from the data in the table, for different fields, the removal rate of the effective Cd of the passivator prepared in example 5 is 48.4-63.8%, and the average removal rate is 56.0%; the removal rate of the available Pb is 37.3% -57.5%, and the average removal rate is 44.3%; the removal rate of the effective Cr is 63.2-77.9 percent, and the average removal rate is 68.9 percent; the removal rate of the effective Cu is 38.8-52.5%, and the average removal rate is 45.1%. From the removal results of heavy metals in different effective states, the passivator shows good removal effect on Cd, Pb, Cr and Cu in the effective states.
TABLE 3 influence of different application rates of passivator on soil available heavy metal content and removal rate
As can be seen from the data in the table, in example 5, the contents of heavy metals such as available Cd, available Pb, available Cr and available Cu in the soil can be greatly reduced, the removal rate of the available heavy metals also shows an increasing trend along with the increase of the addition amount of the composite passivator, and the dosage of the passivator is from 1500kg/hm2Increased to 3000kg/hm2The removal rate of the available heavy metals is gradually increased, wherein the removal rate of the available Cd is increased from 40.8 percent to 69.4 percent, the removal rate of the available Pb is increased from 21.2 percent to 59.9 percent, and the removal rate of the available Cr is increased from 38.1 percentTo 85.0%, the removal rate of Cu in the active state is increased from 35.6% to 64.8%. From the aspect of removal rate, when the application amount of the passivant is 2625kg/hm2Increased to 3000kg/hm2In the process, the removal rate of the four heavy metals is obviously increased slowly, and the application amount of the passivator is considered to be more than 3000kg/hm2And then, the passivation effect is not obviously improved by continuously increasing the use amount of the passivator.
TABLE 4 influence of different passivation times on the content and removal rate of Cd in soil in effective state
Soil samples are respectively collected from the 7 th day, the 30 th day, the 60 th day, the 90 th day and the 120 th day (which respectively correspond to a transplanting period, a tillering period, a heading period, a grouting period and a mature period) after the passivant is applied, and the content of the available Cd is analyzed. As can be seen from the data in the table, the removal rate of the effective Cd is the lowest at 53.9% in the transplanting period, which is related to the requirement of a certain balance time after the passivator is applied to the soil; on day 30, the removal rate of the available Cd was the highest, 66.8%, and then slowly decreased to 57.1% of that on day 120.
2. Influence of soil heavy metal passivator on Cd content in crops
In order to influence the soil heavy metal passivator on the growth of crops, rice is planted on the soil which is repaired by the soil heavy metal passivator provided by the embodiment and the comparative example, meanwhile, the treatment without adding any passivation material is designed, and the management is carried out according to the conventional water and fertilizer management. Specifically, the soil heavy metal passivator is applied to the soil of the embodiment in the turning over process, and the application amount is 2250kg/hm2And transplanting rice varieties 7 days after the passivant is applied, wherein the application amount of the fertilizer is as follows: 180kg/hm2，P2O5：75kg/hm2；KO2：150kg/hm2Applying, wherein the nitrogen fertilizer is prepared by the following steps: the tillering fertilizer is applied twice in 6:4 ratio and phosphorus is addedThe fertilizer is applied in a one-time base mode, and the potassium fertilizer is prepared by the following steps: the spike fertilizer is applied twice in 6: 4. After the rice is mature, harvesting and calculating the yield. Respectively adopting a nitric acid-perchloric acid digestion method and a graphite furnace atomic absorption spectrometry method to determine the content of Cd and Pb in the seeds, and using the nitric acid-perchloric acid digestion method and a flame atomic absorption spectrometry method to determine the content of Cr and Cu in the seeds; the content of Hg in the grains was determined by nitric acid-sulfuric acid digestion and atomic fluorescence spectrometry, and the results are shown in table 5.
TABLE 5 Effect of different deactivators on Rice yield and heavy Metal content in seed
As can be seen from the data in the table, the treatment with the passivating materials of the examples and the comparative examples can increase the yield of rice grains, wherein the best effect of increasing the yield is shown in example 6, which shows that bone meal (or carbonized bone meal), lime and metal salt all have certain growth promoting effects. Analysis on the heavy metal content of the grains shows that the contents of Cd, Pb, Cr, Cu and Hg in the rice grains can be well reduced in examples 5 and 6: in example 5, the reduction amplitude of Cd, Pb, Cr, Cu and Hg of rice grains is 47.7%, 39.6%, 43.2%, 31.1% and 46.7%, and the average reduction amplitude is 41.7%; in example 6, the reduction range of Cd, Pb, Cr, Cu and Hg of rice seeds is 45.4%, 30.6%, 34.6%, 38.8% and 53.3%, and the average reduction range is 40.5%. Examples 5 and 6 showed excellent effects of increasing the yield and reducing the heavy metal content of rice,
3. cost investigation experiment
In order to investigate the actual effects of the passivator and quicklime in reducing the content of Cd in the soil active state and Cd in the rice grain, a field contrast test was performed using quicklime and the passivator material prepared in example 5. The quicklime is applied at 1500, 3000, 4500, 6000 and 7500kg/hm2The dosage of the composite passivator in the embodiment 5 is 1500, 1875, 2250, 2625 and 3000kg/hm2. Transplanting rice varieties 7 days after lime or passivant is applied, wherein the application amount of the fertilizer is as follows: 180kg/hm2，P2O5：75kg/hm2；KO2：150kg/hm2Applying, wherein the nitrogen fertilizer is prepared by the following steps: the tillering fertilizer is applied twice in 6:4, the phosphate fertilizer is applied once, and the potassium fertilizer is applied according to the following base fertilizer: the spike fertilizer is applied twice in 6: 4. After the rice is mature, collecting rice grains, and determining the content of Cd in the grains by adopting nitric acid-perchlorate digestion and graphite furnace atomic absorption spectrometry.
TABLE 6 influence of different amounts of quicklime on Cd content in effective state and Cd content in grains of soil
TABLE 7 influence of different quantities of passivators on the Cd content in soil active state and grain Cd content
As can be seen from the comparison of the data in tables 6 and 7, the safety production of rice grains (Cd content is less than or equal to 0.20mg/kg) is used as a measure, and about 6000kg/hm of quicklime needs to be applied2The composite passivator only needs 1500-1875kg/hm2And (4) finishing. The cost accounting shows that about 4200 yuan/hm is needed for quick lime2The cost of the composite passivator is 1900-2400 yuan/hm2The direct cost is saved by 42.9-54.8%, and the practical use cost of the passivator is less than 50% of the application cost of the quicklime in consideration of the labor cost of transportation and application. Considering the difference of the effective Cd contents in different soils, the reasonable application amount of the composite passivator can be determined to be 1500-3000kg/hm2。
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the spirit or scope of the invention.
Claims (11)
1. A soil heavy metal passivator is characterized by comprising the following components in parts by weight,
33-75 parts of carbonized bone meal;
7-30 parts of a metal salt antagonist;
10-50 parts of solid alkali.
2. The soil heavy metal passivator of claim 1 comprising, in parts by weight,
40-60 parts of carbonized bone meal;
18-23 parts of a metal salt antagonist;
20-40 parts of solid alkali.
3. The soil heavy metal passivator of claim 1 or 2, wherein the metal salt antagonist is at least one of an iron containing metal salt, a manganese containing metal salt, a zinc containing metal salt, a calcium containing metal salt, a magnesium containing metal salt.
4. The soil heavy metal passivator of claim 3, wherein the metal salt antagonist is at least one of ferrous sulphate, ferric chloride, ferrous chloride, manganese sulphate, zinc chloride, zinc sulphate, calcium chloride, magnesium sulphate.
5. The soil heavy metal passivator of claim 1 or 2, wherein the solid alkali is at least one of quicklime, slaked lime, calcium carbonate, plant ash.
6. The preparation method of the soil heavy metal passivator is characterized by comprising the following steps:
dissolving the metal antagonist in water, then uniformly mixing with the carbonized bone meal, drying, and then mixing with solid alkali to obtain the soil heavy metal passivator.
7. The preparation method of the soil heavy metal passivator as claimed in claim 6, wherein the preparation steps of the carbonized bone meal are as follows: carrying out low-temperature carbonization treatment on the bone meal under the condition of inert gas, wherein the temperature of the low-temperature carbonization treatment is 300-600 ℃, and the time is 2-5 h;
preferably, the temperature of the low-temperature carbonization treatment is 400-500 ℃, and the time is 2-3 h.
8. The preparation method of the soil heavy metal passivator of claim 7, wherein the inert gas is nitrogen, and the nitrogen flow rate is 0.5-3.0L/min;
preferably, the nitrogen flow rate is 2.0L/min.
9. The method for preparing the soil heavy metal passivator of claim 7, wherein the drying temperature is 70-90 ℃.
10. The application of the soil heavy metal passivator prepared by the preparation method of any one of claims 1-5 or 6-9 in remediation of heavy metal contaminated soil.
11. The use as claimed in claim 10, wherein the amount of the passivating agent is 1500-2；
Preferably, the fertilizer is applied during soil plowing, and the crop transplanting or sowing is carried out after 3-5 days.
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