CN115351064A - Silicon-based curing agent, repairing agent and repairing method for repairing soil polluted by vanadium/cadmium - Google Patents

Silicon-based curing agent, repairing agent and repairing method for repairing soil polluted by vanadium/cadmium Download PDF

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CN115351064A
CN115351064A CN202210781311.0A CN202210781311A CN115351064A CN 115351064 A CN115351064 A CN 115351064A CN 202210781311 A CN202210781311 A CN 202210781311A CN 115351064 A CN115351064 A CN 115351064A
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curing agent
silicon
vanadium
soil
based curing
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CN115351064B (en
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郭勇军
周坚兵
李择桂
蔺俊鹏
郑逊麟
王泽钿
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Foshan Zhibao Ecological Technology Co ltd
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B09DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09CRECLAMATION OF CONTAMINATED SOIL
    • B09C1/00Reclamation of contaminated soil
    • B09C1/10Reclamation of contaminated soil microbiologically, biologically or by using enzymes
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B09DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09CRECLAMATION OF CONTAMINATED SOIL
    • B09C1/00Reclamation of contaminated soil
    • B09C1/08Reclamation of contaminated soil chemically
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Abstract

The invention discloses a silicon-based curing agent for repairing vanadium/cadmium pollution of soil, which comprises 10-40wt% of a curing agent A and 60-90wt% of a curing agent B, wherein the curing agent A is obtained by mixing silicon-rich tailings and an alkali activator according to a mass ratio of 7.0-9.0: 1.0 and then roasting the mixture; the curing agent B is biochar. Also discloses a soil vanadium/cadmium pollution repairing agent, which comprises a silicon-based curing agent and a microbial agent, wherein the microbial agent comprises reducing bacteria with V (V) reducing performance. The silicon-based curing agent coupled reducing bacteria repairing vanadium-cadmium contaminated soil synergistic system can realize the reduction of high-valence vanadium to be converted into low-valence vanadium, and can realize the continuous, efficient and stable repairing of vanadium-cadmium contaminated soil.

Description

Silicon-based curing agent, repairing agent and repairing method for repairing vanadium/cadmium polluted soil
Technical Field
The invention belongs to the technical field of soil heavy metal pollution remediation, and particularly relates to a silicon-based curing agent, a remediation agent and a remediation method for remedying vanadium/cadmium pollution in soil.
Background
Vanadium (V) has excellent properties and is widely used in modern society. Excessive exposure of vanadium has a highly toxic effect on organisms, causing damage to the respiratory system and leading to metabolic disorders. The united nations environmental planning agency (UNEP) has proposed the listing of vanadium as a priority environmental hazard element. Vanadium is present in a variety of species in different valence states, with pentavalent vanadium V (V) being the most toxic and mobile moiety, and V (IV) being less toxic and insoluble under neutral conditions.
During smelting, a large amount of dust containing V is discharged into the air, and the dust is settled on soil through dry and wet processes and is a main way for the pollution of the soil V. In addition, the production processes of mining, crushing, sintering, smelting and the like of some vanadium-containing minerals can cause vanadium and other accompanying heavy metals to be discharged into the environment, so that soil pollution is caused. In the process of mining stone coal mining areas and vanadium titano-magnetite, heavy metals such as cadmium (Cd) are associated, so that V and Cd in soil exceed standards.
Once contaminated, the release, migration and transformation of V, cd in soil is influenced by soil-indigenous microorganisms that constitute important soil functions in biogeochemical processes, such as microorganism-mediated leaching of vanadium from minerals and reduction of V (V) to V (IV) has been previously reported. In addition, V (V) bioreduction may compete with other electron acceptors in the soil, with oxygen and nitrate being the most prevalent. Vanadium also regulates microbial community structure, microbial activity and metabolism. Vanadium-cadmium contaminated soil environments are widely populated with indigenous microorganisms that are tolerant to vanadium contamination, not only are resistant to vanadium but also are capable of altering the valence state of vanadium, such as by reducing higher vanadium to lower vanadium to reduce the toxicity of vanadium.
At present, the research on vanadium-polluted soil is less, and no report on a method for repairing vanadium-cadmium-polluted soil by using a curing agent and microorganisms is provided. Chinese patent publication No. CN104772331B discloses a heavy metal curing agent for repairing vanadium ore contaminated soil, which comprises the following components in percentage by mass: 65-75% of goethite and 25-35% of protonated chitosan, wherein the goethite belongs to natural minerals and is non-toxic and pollution-free; the protonated chitosan is also beneficial to improving the content of organic matters in soil and increasing the soil fertility, cannot greatly change the pH value of the soil after being mixed and applied, and can effectively reduce the toxic leaching rate of vanadium and other heavy metals in the soil after being repaired; the curing agent has a more than 80% effect of reducing toxic vanadium, the detoxification effect needs to be improved, and the curing agent has no obvious curing effect on cadmium. Chinese patent application publication No. CN105670640A discloses a composite soil conditioner for treating heavy metal Cd pollution, which comprises the following components in percentage by weight: 20-30% of clay mineral, 10-20% of peat, 10-20% of biochar, 25-35% of slaked lime, 5-15% of iron oxide and 5-10% of microbial agent, wherein the microbial agent at least contains one iron reducing bacterium, photosynthetic bacteria and bacillus, but the soil conditioner mainly repairs cadmium pollution in soil and has no obvious repairing effect on vanadium pollution in soil. Chinese patent application CN114317369A discloses Bacillus and application thereof in reduction of pentavalent vanadium and hexavalent chromium, and discloses Bacillus amyloliquefaciens SM01 capable of reducing vanadium and chromium simultaneously, high tolerance to vanadium and chromium in the environment, adaptability to living environment of high background pollution area, high reduction rate to hexavalent chromium and pentavalent vanadium, and the need of adding citric acid as an electron donor during use.
Disclosure of Invention
The invention aims to solve the problems and provides a silicon-based curing agent and a repairing agent for repairing soil polluted by vanadium/cadmium, which can cure heavy metals, improve soil environment and restore soil environment health while reducing and detoxifying high-valence vanadium.
In order to achieve the purpose, the invention adopts the technical scheme that:
a silicon-based curing agent for remedying the vanadium/cadmium pollution of soil comprises 10 to 40 weight percent of curing agent A and 60 to 90 weight percent of curing agent B,
the curing agent A is obtained by mixing the silicon-rich tailings and an alkali activator according to the mass ratio of 7.0-9.0: 1.0 and then roasting the mixture;
the curing agent B is biochar.
The silicon-rich tailings are selected from one or more of mica, quartz sand, kaolin, calcite, granite and potassium feldspar tailings, and preferably quartz sand tailings;
the alkali activator is selected from one or more of sodium hydroxide, potassium hydroxide and sodium carbonate, and is a solid alkali activator or is prepared into liquid and then is mixed with the silicon-rich tailings for roasting; roasting at 750-1000 deg.C for 30-120min, preferably roasting, cooling, grinding, and sieving with 100-200 mesh sieve.
The raw material biomass material of the biochar comprises one or more of plant source biomass, animal manure, domestic sludge, biogas residues and kitchen waste, wherein the plant source biomass comprises plant residues, straws, rice bran and sawdust;
preferably, the kitchen waste comprises vegetable and fruit residues, animal bones and food residues;
preferably, the biochar is hydrothermal biochar or high-temperature pyrolysis biochar.
The domestic sludge is a product in the domestic sewage treatment process, consists of slurry of solid impurities, suspended matters and colloidal substances, and is solid precipitate substances generated in the sewage treatment process.
The biogas residues are waste materials generated by biogas production, residues obtained by putting human and animal excreta, crop straws and the like into a biogas tank and fermenting the human and animal excreta, are collectively called biogas fertilizers, and the biogas fertilizers comprise biogas slurry and biogas residues.
The preparation method of the hydrothermal biochar comprises the following steps: adding biomass material and water into a high-pressure batch reactor according to a solid-liquid mass ratio of 0.5-1.5: 3 for reaction, introducing inert gas to create an oxygen-free environment, cooling, filtering and drying at 220-350 ℃ for 30-120 min.
The invention provides a soil vanadium/cadmium pollution remediation agent, which comprises a silicon-based curing agent and a microbial agent, wherein the microbial agent comprises a reducing bacterium with V (V) reducing performance, preferably Corynebacterium humosus (Corynebacterium humireducens), iron reducing bacterium (Fontibacter ferridum. Nov), comamonas Comamonas, bacillus sphaericus (Lysinibacter sphaericus), bacillus ocellatus (Oceanobacillus), enterobacter ludwigii and Pseudomonas saccharolyticus (Pseudomonas saccharolytica).
In the technical scheme, the microbial agent is a liquid microbial agent, and preferably, the cell density of active bacteria in the microbial agent is 10 7 ~10 10 Per mL;
the preferable mass volume ratio of the silicon-based curing agent to the microbial agent is as follows:
0.5-7.5kg; or
0.5-6.5kg or 0.7-5.5kg or 0.7-3.5kg or 1.0-3.5kg or 1kg of either;
preferably, the strain of the corynebacterium humireducens is CGMCC NO.2452, the strain of the iron reducing bacteria is CCTCC M2011498, the strain of the comamonas is CCTCC AB2011133, the strain of the spherical lysine bacillus is CGMCC1.8079, the strain of the marine bacillus is CGMCC1.8877, the strain of the Lodvisia enterobacter ledebensis is CGMCC NO.8801, and the strain of the saccharolytic pseudo-caneber is CGMCC 1.5315.
The invention also aims to provide a method for synergistically repairing vanadium/cadmium contaminated soil by coupling silicon-based curing agent with reducing bacteria, which comprises the following steps: step 1) adding the silicon-based curing agent described in any one of the above into the contaminated soil at an application rate of 0.5-2.0wt% or at an application rate of 1.0-7.5t/ha, preferably at an application rate of 0.7-2.0wt%, or 0.8-1.8wt%, or 0.8-1.5wt%, or 1wt%, or 1.5-6.5t/ha, or 1.0-5.5t/ha, or 1.0-4.5t/ha, or 1.0-3.5t/ha, or 1.0-2.5t/ha, or 1.0-2.0t/ha, or 1.5t/ha.
The method for synergistically repairing vanadium/cadmium contaminated soil by coupling the silicon-based curing agent with the reducing bacteria further comprises the step 2) of applying the microbial agent in any one of the repairing agents into the contaminated soil or the farmland and uniformly mixing.
In the technical scheme, the liquid microbial agent is added into the polluted soil or the polluted farmland according to the application amount of 5-50mL/kg or 150-500L/ha; preferably 5-45mL/kg or 20-45mL/kg or 35-45mL/kg,150-450L/ha or 150-350L/ha or 150-250L/ha or 200L/ha.
In the technical scheme, the repairing time is 20-70 days, or 30-65 days, or 40-65 days, preferably 60 days; the field water capacity of the soil is kept between 60 and 80 percent or between 65 and 75 percent, and the preference is 70 percent during the restoration period.
The repairing principle of the invention is as follows:
reducing pentavalent vanadium into low-valent vanadium by using reducing bacteria, reducing the toxicity of soil and realizing the detoxification of high-valent vanadium; meanwhile, the silicon-based curing agent can effectively and continuously cure and stabilize heavy metals. Active silicon components and biochar in the silicon-based curing agent can convert exchangeable vanadium and cadmium into stable parts through electrostatic adsorption, complexation, precipitation and other actions, and soluble carbon components released by the biochar in soil can complex vanadium and serve as electron donors for metabolism of reducing bacteria and soil microorganisms, so that detoxification of high-valence vanadium is promoted to be converted into low-valence vanadium. In addition, the microbial reducing strains are fixedly planted and gathered on the surface of the curing agent, a biological film can be formed on the surface of the silicon-based curing agent, the coupling synergistic effect of the reducing strains is promoted, the stability of vanadium and cadmium in soil is further promoted, and the continuous and effective remediation of the vanadium and cadmium polluted soil is realized.
The invention has the beneficial effects that:
1) The raw materials of the vanadium-cadmium polluted soil solidification repairing agent are industrial solid waste, biomass and the like, the reducing bacteria are commercial bacteria reagents, the raw material sources are wide, the environment is protected, the material cost is low, the vanadium-cadmium polluted soil solidification repairing agent can be produced and prepared in a large scale, and the performance is stable.
2) The silicon-based curing agent coupled reducing bacteria repairing vanadium-cadmium contaminated soil synergistic system can realize the reduction of high-valence vanadium to be converted into low-valence vanadium, and can improve the contents of iron and manganese combined state, organic matter combined state and residue state of vanadium and cadmium in soil to more than 80% and 90%, and can realize the continuous, efficient, stable and repairing of vanadium-cadmium contaminated soil.
3) The vanadium-cadmium pollution remediation method is simple to operate and low in cost, reduces solid wastes, can be applied to large-scale remediation of vanadium-cadmium polluted sites and farmland soil, and has wide application prospects.
Drawings
FIG. 1 is a graph of rice growth and harvest in contaminated farmland as described in example 3.
FIG. 2 shows the rice yield results of different experimental groups in example 3.
FIG. 3 shows the heavy metal content of rice harvested in different experimental groups in example 3.
FIG. 4 shows the results of the morphological distribution of vanadium and cadmium in the field soil after harvesting rice of different experimental groups in example 3.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to be limiting.
The experimental methods in the following examples are all conventional methods unless otherwise specified; the biological and chemical reagents used are conventional reagents in the art unless otherwise specified.
The tailings industrial waste raw materials used in the examples of the invention are derived from the following sources:
quartz sand tailings: comprises waste residues in ore mining, tailings and tailings in the processing process, wherein the tailings account for most of the waste residues, and the chemical components of quartz tailings are mainly SiO 2 . The quartz sand tailings in the embodiment of the invention are from a cloud floating quarry in Guangdong province.
Granite tailings: the granite tailing is rock tailing and leftover material with poor appearance left after being mined by granite stone factories, and the chemical components mainly comprise quartz, potash feldspar and acidic plagioclase feldspar. The granite tailings in the embodiment of the invention are from a cloud floating quarry in Guangdong province.
Potassium feldspar tailings: the mineral is rock tailings and leftover materials with poor appearance left after the potash feldspar stone factory is mined, and the chemical components are mainly aluminosilicate minerals. The potassium feldspar tailings in the embodiment of the invention are from a cloud floating quarry in Guangdong province.
Example 1 remediation of contaminated soil
The vanadium-cadmium contaminated soil was collected from the soil of a certain stone coal mining area in Hunan, air-dried, and then sieved through a 10-mesh sieve, and the basic physicochemical properties and heavy metal elements of the soil sample were analyzed (see Table 1).
TABLE 1 soil sample basic Properties and Metal element analysis
Figure BDA0003725651210000051
The preparation of the silicon-based curing agent of the invention comprises the following steps: the silicon-based curing agent is prepared by mixing the curing agent A and the curing agent B according to the mass ratio of 30% to 70%.
The curing agent A is prepared by utilizing silicon-rich industrial solid waste under an alkali activation roasting method, and the specific preparation process comprises the following steps: mixing the quartz sand tailings and a solid alkali activator (KOH) according to the ratio of 9: 1, fully ball-milling, roasting in a programmed temperature-rising high-temperature furnace at 800 ℃ for 60-120min, cooling, grinding and sieving with a 100-mesh sieve.
The curing agent B is prepared by a hydrothermal method: adding the crushed rice straw and water into a high-pressure batch reactor (HT-250J0, HTLAB, beijing, china) according to the ratio of 1: 3 for reaction, and injecting nitrogen with the purity of 99.9% into the reactor to create an anaerobic environment. Then heating to the set temperature (220 ℃), wherein the pressure is not regulated in the reaction process, the reaction is finished after 60min, and the reactor is naturally cooled to the room temperature. The solid residue was separated by filtration to give a hydrothermal charcoal, which was dried at 105 ℃ to give curing agent B.
Culturing a reducing bacterium solution: the strain of the saccharolytic pseudo-ochrobactrum CGMCC 1.5315 (purchased from China general microbiological culture Collection center (CGMCC)) is enriched and cultured to a logarithmic phase for later use, and the cell density in the standby bacterial solution is 3.6 multiplied by 10 8 one/mL.
Repairing the polluted soil: CK, T1, T2, T3, T4, T5, T6, T7 and T8 processing groups are set. CK is an untreated control group, T1 is a silicon-based curing agent treatment group, T2 is a silicon-based curing agent and reducing bacteria liquid coupling synergistic treatment group (namely the soil vanadium/cadmium pollution remediation agent of the invention), T3 is a curing agent A treatment group, T4 is a curing agent A and reducing bacteria liquid coupling synergistic treatment group, T5 is a curing agent B treatment group, T6 is a curing agent B and reducing bacteria liquid coupling synergistic treatment group, T7 is a quartz sand tailing curing agent treatment group which is not subjected to alkali activation, and T8 is a non-silicon-based material curing agent treatment group (the non-silicon-based material is lime).
Respectively putting 5kg of soil into a PVC tank (40 cm multiplied by 15cm multiplied by 20 cm), wherein the CK group is not added with a curing agent; adding the silicon-based curing agent into the T1 according to 1% (w/w), fully mixing uniformly and paving; adding a silicon-based curing agent into the T2 according to 1% (w/w), fully and uniformly mixing, and then inoculating 0.2L of reducing bacteria liquid; adding a curing agent A into the T3 according to 1% (w/w); adding the curing agent A into the T4 according to 1% (w/w), fully and uniformly mixing, and then inoculating 0.2L of reducing bacteria liquid; adding a curing agent B into the T5 according to 1% (w/w); adding a curing agent B into the T6 according to 1% (w/w), fully and uniformly mixing, and then inoculating 0.2L of reducing bacteria liquid; t7 is the quartz sand tailings added with 1% (w/w) without alkali activation treatment; t8 is a treatment group to which 1% (w/w) of a non-silicon-based material was added, well mixed and leveled. During the restoration period, the soil of all treatment groups is added with water to keep the water holding capacity of the soil at 70%, the leaching content of vanadium and cadmium in the soil is measured after 60 days of restoration, the concentration of V (V) and V (IV) is measured and analyzed by using a PAR spectrophotometry, the content of cadmium is detected by using an inductively coupled plasma emission spectrometry (ICP-MS), and the experimental result is shown in Table 2.
Table 2 heavy metals leaching and V morphology in soil after remediation
Figure BDA0003725651210000061
From the results in table 2, it can be seen that: compared with a control group CK, the leaching content of Cu, zn and Cd in the restored soil T1, T2, T3, T4, T5, T6 and T8 is obviously reduced, the leaching content of Pb in the T2 group is reduced by 56%, and the T1 group applied with the silicon-based curing agent has the effect of curing and stabilizing the heavy metal in the soil and the effect is better than that of the curing agent A (T3 group) and the curing agent B (T5 group) which are applied independently; the leaching content of the T7 group to Cu, zn, cd and Pb is not much different from that of the CK group, and the solidifying effect on heavy metals is not obvious. In addition, compared with CK in a control group, the leaching content of V (V) in T1, T2, T3, T4, T5 and T6 is respectively reduced by 65%, 88%, 46%, 75%, 47% and 80% compared with CK, which also indicates that the silicon-based curing agent can solidify and stabilize the high-valence V in soil to a certain extent, and in addition, under the synergistic action of reducing bacteria, the reducing bacteria can further reduce V (V) and detoxify the high-valence V, so that the ecological risk of the high-valence V in soil is reduced, while the detoxifying effect of the T7 and T8 groups on the high-valence V is obviously poorer than that of other treatment groups. Further, from the results of T8, it is understood that lime has a solidification stabilizing effect of heavy metals, but its repairing effect is lower than that of the T2 group, and it has no effect on V (V) detoxification.
Example 2 remediation of contaminated soil
The vanadium-cadmium contaminated soil is soil collected from farmland soil in a certain stone coal mining area in Hunan, is dried in the air and then is sieved by a 10-mesh sieve, and basic physicochemical properties and heavy metal elements of soil samples are analyzed, which is shown in Table 3.
TABLE 3 basic Properties and elemental analysis of soil samples
Figure BDA0003725651210000071
Preparation of silicon-based curing agent: the silicon-based curing agent is prepared by mixing the curing agent A and the curing agent B according to the mass ratio of 20% to 80%.
The curing agent A is prepared by utilizing silicon-rich industrial solid waste under an alkali activation roasting method, and the specific preparation process comprises the following steps: mixing granite tailings and a solid alkali activator (KOH) according to the ratio of 9: 1, fully ball-milling, roasting in a programmed temperature-rising high-temperature furnace at 800 ℃ for 120min, cooling, grinding and sieving with a 100-mesh sieve.
The curing agent B is prepared by a hydrothermal method: adding crushed food residues (leftover of restaurant) and water at a ratio of 1: 3 into a high-pressure batch reactor (HT-250J0, HTLAB, beijing, china) for reaction, and injecting nitrogen gas with purity of 99.9% into the reactor to create an anaerobic environment. Then heating to the set temperature (300 ℃), wherein the pressure is not regulated in the reaction process, the reaction is finished after 60min, and the reactor is naturally cooled to the room temperature. The solid residue was separated by filtration to give a hydrothermal charcoal, which was dried at 105 ℃ to give curing agent B.
Culturing a reducing bacterium solution: CGMCC1.8877 (purchased from China general)CGMCC) strain enrichment and culture to logarithmic phase for later use, wherein the cell density in the standby bacterial liquid is 5 multiplied by 10 8 one/mL.
Contaminated soil remediation: CK, T1, T2, T3, T4, T5, T6 and T7 processing groups are set. CK is an untreated control group, T1 is a silicon-based curing agent treatment group of the invention, T2 is a silicon-based curing agent and reducing bacteria liquid coupling synergistic treatment group (namely the soil vanadium/cadmium pollution remediation agent of the invention), T3 is a curing agent A treatment group, T4 is a curing agent A and reducing bacteria liquid coupling synergistic treatment group, T5 is a curing agent B treatment group, T6 is a curing agent B and reducing bacteria liquid coupling synergistic treatment group, and T7 is a granite tailing curing agent treatment group which is not subjected to alkali activation.
Respectively putting 5kg of soil into a PVC tank (40 cm multiplied by 15cm multiplied by 20 cm), wherein the CK group is not added with a treating agent; adding a silicon-based curing agent into the T1 according to 1% (w/w), fully and uniformly mixing and paving; adding a silicon-based curing agent into the T2 according to 1% (w/w), fully and uniformly mixing, and then inoculating 0.2L of reducing bacteria liquid; adding a curing agent A into the T3 according to 1% (w/w); adding the curing agent A into the T4 according to 1% (w/w), fully and uniformly mixing, and then inoculating 0.2L of reducing bacteria liquid; adding a curing agent B into the T5 according to 1% (w/w); adding a curing agent B into the T6 according to 1% (w/w), fully and uniformly mixing, and then inoculating 0.2L of reducing bacteria liquid; and T7 is the granite tailing curing agent which is added with 1 percent (w/w) and is not activated by alkali, and the mixture is fully mixed and paved. During the restoration period, the soil of all treatment groups is added with water to keep the field water holding capacity of the soil at 70%, the leaching content and the V (V) content of vanadium and cadmium in the soil are measured after 60 days of restoration, and the related experimental results are shown in table 4.
Table 4 heavy metal leaching and V morphology in the soil after remediation
Figure BDA0003725651210000081
As can be seen from the results in table 4, compared with CK, the leaching contents of Cu, zn, cd and Pb in the T1, T2, T3, T4, T5 and T6 treatment groups are all significantly reduced, the curing and stabilizing effects of the silicon-based curing agent synergistically coupled with the reducing bacteria (T2 group) on heavy metals in soil are superior to those of the single silicon-based curing agent treatment (T1 group), and the curing and stabilizing effects of the silicon-based curing agent (T1 group) on heavy metals are superior to those of the curing agent a (T3 group) and the curing agent B (T5 group); and compared with the CK group, the leaching contents of Cu, zn, cd and Pb in the T7 group have no obvious difference, and no obvious curing effect. For V, the silicon-based curing agent is synergistically coupled with the reducing bacteria (T2 group) to effectively reduce the leaching content of V (V) in soil, the V (V) content is reduced by 94% compared with CK, and the leaching amount of V (V) in the T1 group is reduced by only 40%; the T4 and T6 groups can also effectively reduce the leaching content of V (V) in soil, which indicates that the reducing bacteria can further reduce V (V) and detoxicate high-valence V, but the T2 group has the best detoxication effect.
The result shows that the application of the silicon-based curing agent can reduce the content of heavy metals in soil, and in addition, under the synergistic treatment of reducing bacteria, the content of V (V) is further reduced, so that the V is reduced into low-valence vanadium, and the ecological risk of soil pollution is reduced.
Example 3 remediation of contaminated Farmland
The experiment was carried out in the field around a certain stone coal mine area in Hunan province.
Preparation of silicon-based curing agent: the silicon-based curing agent is prepared by mixing 25% and 75% of curing agent A and curing agent B in a mass ratio.
The curing agent A is prepared by utilizing silicon-rich industrial solid waste under an alkali activation roasting method, and the specific preparation process comprises the following steps: mixing the potash feldspar tailings and a solid alkali activator (NaOH) according to the ratio of 9: 1, fully ball-milling, roasting in a programmed temperature-rising high-temperature furnace at 800 ℃ for 90min, cooling, and grinding through a 100-mesh sieve.
The curing agent B is prepared by a hydrothermal method: adding the crushed rice straw and water into a high-pressure batch reactor (HT-250J0, HTLAB, beijing, china) according to the ratio of 1: 3 for reaction, and injecting nitrogen with the purity of 99.9% into the reactor to create an anaerobic environment. Then heating to the set temperature (300 ℃), wherein the pressure is not regulated in the reaction process, the reaction is finished after 60min, and the reactor is naturally cooled to the room temperature. The solid residue was separated by filtration to give a hydrothermal charcoal, which was dried at 105 ℃ to give curing agent B.
Culturing a reducing bacterium solution: enriching CGMCC1.8079 (purchased from China general microbiological culture Collection center (CGMCC)) strain, and culturing to logarithmic phase for later use, wherein the cell density in the spare bacterial solution is 3.7×10 8 One per mL.
The farmland restoration treatment is divided into CK contrast groups, T1, T2, T3, T4, T5, T6 and T7 treatment groups, CK is an untreated contrast group, and soil is not treated; the T1 group is a silicon-based curing agent treatment group, and the application dosage of the silicon-based curing agent is 1.5T/ha; t2 is a silicon-based curing agent coupling synergistic reducing bacteria treatment group, the silicon-based curing agent is sprayed in the soil according to the proportion of 1.5T/ha, and then bacterial liquid is sprayed according to the proportion of 200L/ha; the T3 group is a curing agent A treatment group, and the application dosage of the curing agent A is 1.5T/ha; the T4 group is a curing agent A coupling synergistic reducing bacteria treatment group, the application dosage of the curing agent A is 1.5T/ha, and then bacterial liquid is sprayed according to 200L/ha; the T5 group is a curing agent B treatment group, and the application dosage of the curing agent B is 1.5T/ha; the T6 group is a curing agent B coupling synergistic reducing bacteria treatment group, the application dosage of the curing agent B is 1.5T/ha, and then bacterial liquid is sprayed according to 200L/ha; and the group T7 applies the potash feldspar tailing curing agent which is not subjected to alkali activation, the dosage of the potash feldspar tailing curing agent is 1.5T/ha, the potash feldspar tailing curing agent is uniformly sprayed in the soil, plowing and mixing are carried out uniformly, the plowing depth is 20cm, water is replenished irregularly, the water level is kept to be 1-2cm higher than the soil, and rice planting is carried out after two weeks. The rice variety is the second best 290, the direct seeding method is adopted to plant the rice, the rice planting follows the local farming operation and water and fertilizer management mode, and the growth and harvesting conditions of the rice are shown in figure 1.
And after 120 days, the rice is harvested, and the statistical yield and the heavy metal content in the rice are obtained. The heavy metal content in the rice is detected and analyzed according to a method specified in national standard GB5009.12-2017 for Pb in the rice, and the detection and analysis of Cu, zn, cd and V are respectively performed according to methods specified in GB 5009.13-2017 national food safety standard determination for copper, GB 5009.14-2017 national food safety standard determination for zinc, GB5009.15-2014 national food safety standard determination for cadmium and GB 5009.268-2016 national food safety standard determination for multielement.
The rice yield results are shown in fig. 2, and compared with the CK group, the yield of the T1 group is increased by 15%, the yield of the T2 group is increased by 23%, the yield of the T3 group is increased by 7%, the yield of the T4 group is increased by 12%, the yield of the T5 group is increased by 9%, and the yield of the T6 group is increased by 16%; t7 basically has no obvious yield increasing effect. The results of the heavy metal contents in the rice are shown in fig. 3, and comprehensively, the heavy metal contents in the rice in the T1 group and the rice in the T2 group are less than those in other treatment groups, the content difference of Pb, cd and V is obvious, particularly, the content difference of Cd and V is more obvious, and the content of Cd and V in the rice in the T7 group is the highest in each treatment group; compared with CK of a control group, pb content of rice of T1 and T2 groups is respectively reduced by 44% and 56%, cd content is respectively reduced by 32% and 48%, and V content is respectively reduced by 65% and 71%. The results show that in the vanadium-polluted farmland, the silicon-based curing agent coupled synergistic reducing bacteria can effectively promote the yield increase of rice, reduce the enrichment of heavy metals in rice, and have the effect superior to that of the single application treatment of the curing agents A and B, and the heavy metals Cd and Pb in the rice in T1 and T2 are lower than the pollutant limit in national food standards for food safety (GB 2762-2017).
Heavy metal forms of field soil after rice harvesting are distributed, the soil is continuously extracted according to a 5-step extraction method of Tessier, and ICP-MS is adopted to analyze leaching liquor. As shown in fig. 4, the silicon-based curing agent coupled synergistic reducing bacteria can effectively improve the content of the iron-manganese oxide binding state and the residue state of Cd and V in soil, compared with CK, the content of the iron-manganese binding state, the organic matter binding state and the residue state of cadmium in soil of T1 and T2 groups is improved most compared with other treatment groups, the content of T1 and T2 groups is respectively improved by 19% and 21%, and the content of T1 and T2 groups of iron-manganese binding state, organic matter binding state and residue state of vanadium in soil is respectively improved by 16% and 20%, which shows that the silicon-based curing agent can effectively reduce the bioavailability of heavy metals in soil, while the treatment effect of the silicon-based curing agent coupled synergistic reducing bacteria is further improved, and the effect is optimal in each treatment group.

Claims (10)

1. A silicon-based curing agent for remedying vanadium/cadmium pollution of soil is characterized in that: the silicon-based curing agent comprises 10-40wt% of a curing agent A and 60-90wt% of a curing agent B,
the curing agent A is obtained by mixing the silicon-rich tailings and an alkali activator according to the mass ratio of 7.0-9.0: 1.0 and then roasting the mixture;
the curing agent B is biochar.
2. The silicon-based curing agent of claim 1, wherein: the silicon-rich tailings are selected from one or more of mica, quartz sand, kaolin, calcite, granite and potassium feldspar tailings, and preferably quartz sand tailings;
the alkali activator is selected from one or more of sodium hydroxide, potassium hydroxide and sodium carbonate, and is a solid alkali activator or is prepared into liquid and then is mixed with the silicon-rich tailings for roasting; roasting at 750-1000 deg.C for 30-120min, preferably roasting, cooling, grinding, and sieving with 100-200 mesh sieve.
3. The silicon-based curing agent of claim 1, wherein: the raw material biomass material of the biochar comprises one or more of plant source biomass, animal manure, domestic sludge, biogas residues and kitchen waste, wherein the plant source biomass comprises plant residues, straws, rice bran and sawdust;
preferably, the kitchen waste comprises vegetable and fruit residues, animal bones and food residues;
preferably, the biochar is hydrothermal biochar or high-temperature pyrolysis biochar.
4. The silicon-based curing agent of claim 3, wherein: the preparation method of the hydrothermal biochar comprises the following steps: adding biomass material and water into a high-pressure batch reactor according to a solid-liquid mass ratio of 0.5-1.5: 3 for reaction, introducing inert gas to create an oxygen-free environment, cooling, filtering and drying at 220-350 ℃ for 30-120 min.
5. A soil vanadium/cadmium pollution repairing agent is characterized in that: comprising the silicon-based curing agent of any one of claims 1 to 4 and a microbial agent comprising a reducing bacterium having V (V) reducing ability, preferably Corynebacterium humus (Corynebacterium humireducens), iron-reducing bacterium (Fontibacter reducens), comamonas (Commamonas), lysinibacillus sphaericus (Lysinibacillus sphaericus), bacillus marinus (Oceanobacterium), enterobacter ludwigii (Enterobacter ludwigii), pseudocerobacter saccharolyticus (Pseudomonas saccharolyticus).
6. The soil vanadium/cadmium pollution remediation agent of claim 5 further comprising: the microbial agent is a liquid microbial agent, and preferably, the cell density of active bacteria in the microbial agent is 10 7 ~10 10 Per mL;
the preferable mass volume ratio of the silicon-based curing agent to the microbial agent is as follows:
0.5-7.5kg; or
0.5-6.5kg or 0.7-5.5kg or 0.7-3.5kg or 1.0-3.5kg or 1kg of either;
preferably, the strain of the corynebacterium humireducens is CGMCC NO.2452, the strain of the iron reducing bacteria is CCTCC M2011498, the strain of the comamonas is CCTCC AB2011133, the strain of the spherical lysine bacillus is CGMCC1.8079, the strain of the marine bacillus is CGMCC1.8877, the strain of the Lodvisia enterobacter ledebensis is CGMCC NO.8801, and the strain of the saccharolytic pseudo-caneber is CGMCC 1.5315.
7. A method for synergistically repairing vanadium/cadmium contaminated soil by coupling silicon-based curing agent with reducing bacteria is characterized by comprising the following steps: step 1) the silicon-based curing agent according to any one of claims 1 to 4 is added to the contaminated soil at an application rate of 0.5 to 2.0wt% or at an application rate of 1.0 to 7.5t/ha, preferably at an application rate of 0.7 to 2.0wt%, or 0.8 to 1.8wt%, or 0.8 to 1.5wt%, or 1wt%, or 1.5 to 6.5t/ha, or 1.0 to 5.5t/ha, or 1.0 to 4.5t/ha, or 1.0 to 3.5t/ha, or 1.0 to 2.5t/ha, or 1.0 to 2.0t/ha, or 1.5t/ha.
8. The method for cooperative remediation of vanadium/cadmium contaminated soil by using the silicon-based curing agent coupled with reducing bacteria as claimed in claim 7, wherein the method comprises the following steps: further comprises the step 2) of applying the microbial agent in the repairing agent of claim 5 or 6 into polluted soil or farmland and mixing uniformly.
9. The method for the cooperative remediation of vanadium/cadmium contaminated soil with the silicon-based curing agent coupled with reducing bacteria according to claim 8, wherein: adding the liquid microbial agent into the polluted soil or the polluted farmland according to the application amount of 5-50mL/kg or 150-500L/ha; preferably 5-45mL/kg or 20-45mL/kg or 35-45mL/kg,150-450L/ha or 150-350L/ha or 150-250L/ha or 200L/ha.
10. The method for cooperative remediation of vanadium/cadmium contaminated soil by using the silicon-based curing agent coupled with reducing bacteria as claimed in claim 7 or 8, wherein: the repairing time is 20-70 days, 30-65 days, 40-65 days, preferably 60 days; the field water capacity of the soil is kept between 60 and 80 percent or between 65 and 75 percent, and the preference is 70 percent during the restoration period.
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