CN115351064B - Silicon-based curing agent for repairing soil vanadium/cadmium pollution, repairing agent and repairing method - Google Patents
Silicon-based curing agent for repairing soil vanadium/cadmium pollution, repairing agent and repairing method Download PDFInfo
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Abstract
The invention discloses a silicon-based curing agent for repairing soil vanadium/cadmium pollution, which comprises 10-40wt% of curing agent A and 60-90wt% of curing agent B, wherein the curing agent A is obtained by mixing and roasting silicon-rich tailings and an alkali activator according to the mass ratio of 7.0-9.0:1.0; the curing agent B is biochar. Also disclosed is a soil vanadium/cadmium pollution remediation agent comprising a silicon-based curing agent and a microbial agent comprising a reducing bacterium having V (V) reducing properties. The synergistic system for restoring the vanadium-cadmium polluted soil by the silicon-based curing agent coupling reducing bacteria can realize the reduction and conversion of high-valence vanadium into low-valence vanadium, and can realize the continuous high-efficiency stabilization and restoration of the vanadium-cadmium polluted soil.
Description
Technical Field
The invention belongs to the technical field of soil heavy metal pollution restoration, and particularly relates to a silicon-based curing agent, a restoration agent and a restoration method for restoring soil vanadium/cadmium pollution.
Background
Vanadium (V) has excellent properties and is widely used in modern society. The overexposure of vanadium has a very toxic effect on the organism, causing damage to the respiratory system, leading to metabolic disorders. The united states environmental planning agency (UNEP) has proposed to list vanadium into a list of preferred environmental hazard elements. Vanadium is present in a variety of species of different valence states, with pentavalent vanadium V (V) being the most toxic and mobile part, while V (IV) is less toxic and insoluble under neutral conditions.
A large amount of V-containing dust is discharged into the air in the smelting process, and the dust is settled on the soil through dry and wet processes, so that the V-containing dust is a main way of polluting the soil. In addition, the production processes of exploitation, crushing, sintering, smelting and the like of some vanadium-containing minerals can lead to the discharge of other accompanying heavy metals such as vanadium into the environment, thereby causing soil pollution. In stone coal mining areas and vanadium titano-magnetite exploitation processes, heavy metals such as cadmium (Cd) and the like are often associated, and therefore, the V and Cd in soil are out of standard.
Once contaminated, the release, migration and transformation of V, cd in the soil is affected by soil-borne microorganisms that constitute important soil functions in the bio-geochemical process, such as microbial-mediated leaching of vanadium from minerals and V (V) reduction to V (IV) have 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. Indigenous microorganisms resistant to vanadium contamination widely exist in the environment of vanadium-cadmium contaminated soil, which are not only resistant to vanadium but also capable of changing the existing valence state of vanadium, such as reducing high valence vanadium to low valence vanadium, so that the toxicity of vanadium is reduced.
At present, less research is carried out on the vanadium-polluted soil, and no report on a method for repairing the vanadium-cadmium-polluted soil by using a curing agent and a microorganism is available. Chinese patent publication No. CN104772331B discloses a heavy metal curing agent for repairing vanadium ore contaminated soil, which comprises the following components in mass ratio: 65-75% of goethite, 25-35% of protonated chitosan, wherein the goethite belongs to natural minerals, and is nontoxic and pollution-free; the protonated chitosan is also beneficial to improving the organic matter content in the soil, increasing the soil fertility, avoiding greatly changing the pH value of the soil after mixed application, and effectively reducing the toxic leaching rate of vanadium and other heavy metals in the soil after restoration; the curing agent has the advantages that the reduction effect on toxic vanadium is more than 80%, the detoxification effect is to be improved, and no obvious curing effect on cadmium is achieved. Chinese patent application publication No. CN105670640A discloses a composite soil conditioner for treating heavy metal Cd pollution, which comprises the following formula 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 kind of iron-reducing bacteria, photosynthetic bacteria and bacillus, but the soil conditioner is mainly used for repairing 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 reducing pentavalent vanadium and hexavalent chromium, and discloses bacillus Bacillus amyloliquefaciens SM which can reduce vanadium and chromium simultaneously, has higher tolerance to vanadium and chromium in the environment, can adapt to living environment in high background pollution areas, has higher reduction rate to hexavalent chromium and pentavalent vanadium, and needs to add citric acid as an electron donor when in use, however, the repair technology needs to input a large amount of reducing bacteria and citric acid into the environment, and can influence microecological balance of soil.
Disclosure of Invention
The invention aims at solving the problems and provides a silicon-based curing agent and a repairing agent for repairing the vanadium/cadmium pollution of soil, which are used for reducing and detoxifying high-valence vanadium, curing heavy metals, improving the soil environment and recovering the soil environment health.
In order to achieve the purpose, the invention adopts the following technical scheme:
a silicon-based curing agent for repairing soil vanadium/cadmium pollution comprises 10-40wt% of curing agent A and 60-90wt% of curing agent B,
the curing agent A is obtained by mixing and roasting the silicon-rich tailings and an alkali activator according to the mass ratio of 7.0-9.0:1.0;
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 mixed with the silicon-rich tailings for roasting after being prepared into liquid or adopting a solid alkali activator; the roasting temperature is 750-1000 ℃, the roasting time is 30-120min, and the powder is preferably ground and sieved by a 100-200 mesh sieve after roasting and cooling.
The raw biomass material of the biochar comprises one or more of plant biomass, animal manure, domestic sludge, biogas residues and kitchen waste, wherein the plant biomass comprises plant residues, straw, rice bran and sawdust;
preferably, the kitchen waste comprises vegetable and fruit residues, animal bones and food residues;
preferably, the biochar is a hydrothermal biochar or a pyrolysis biochar.
Domestic sludge is a product of the domestic sewage treatment process, and consists of solid impurities, suspended matters and slurry of colloidal substances, which are essentially solid precipitate substances generated in the sewage treatment process.
The biogas residue is waste after biogas production, and residues after fermentation of human and animal excreta, crop straws and the like are put into the biogas digester and are collectively called biogas manure, wherein the biogas manure comprises biogas slurry and biogas residue.
The preparation method of the hydrothermal biochar comprises the following steps: adding biomass material and water into a high-pressure intermittent reactor according to a solid-liquid mass ratio of 0.5-1.5:3, reacting, charging inert gas to create an anaerobic environment, cooling at 220-350 ℃ for 30-120min, filtering, and drying.
The invention provides a soil vanadium/cadmium pollution restoration agent, which comprises the silicon-based curing agent and a microbial agent, wherein the microbial agent comprises a reducing bacterium with V (V) reducing performance, preferably Corynebacterium humicola (Corynebacterium humireducens), corynebacterium ferroreducing bacteria (Fontibacter ferriducenssp. Nov), comamonas (Comamonas), bacillus sphaericus (Lysinibacillus sphaericus), bacillus Oceanobacillus (Ocenobacillus), enterobacter ludwigii (Enterobacter ludwigii) and Pseudomonas saccharolytica (Pseudochrobactrum saccharolyticum).
In the above technical scheme, the microbial agent is a liquid microbial agent, preferably the active bacterial cell density in the bacterial liquid is 10 7 ～10 10 individual/mL;
the mass volume ratio of the preferable silicon-based curing agent and the microbial agent is as follows:
0.5-7.5kg of the weight of the feed additive is 0.1-5L; or (b)
0.5-6.5kg or 0.7-5.5kg or 0.7-3.5kg or 1.0-3.5kg or 1kg:0.1-5L or 0.1-4L or 0.1-3L or 0.1-2L or 0.15-3L or 0.15-2L;
preferably, the strain of the humus reduction corynebacterium is CGMCC No.2452, the strain of the iron reduction bacterium 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 LodeVichs enterobacter is CGMCC No.8801, and the strain of the sugar-decomposing pseudomonas is CGMCC1.5315.
The invention further aims to provide a method for synergistic restoration of vanadium/cadmium contaminated soil by coupling reduction bacteria with a silicon-based curing agent, which comprises the following steps: step 1) adding the silicon-based curing agent according to any one of the above claims to contaminated soil or to contaminated farmland at an application level of 0.5-2.0wt%, preferably at an application level 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 synergistic restoration of vanadium/cadmium contaminated soil by coupling the silicon-based curing agent and the reducing bacteria further comprises the step 2) of taking the microbial agent in any one of the restoration agents, applying the microbial agent into the contaminated soil or the farmland, and uniformly mixing the microbial agent and the contaminated soil or the farmland.
In the technical scheme, the liquid microbial agent is added into polluted soil according to the application amount of 5-50mL/kg or is added into polluted farmland according to the application amount of 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 above technical scheme, the repair time is 20-70 days or 30-65 days or 40-65 days, preferably 60 days; the field water holding capacity of the soil is maintained at 60-80% or 65-75%, preferably 70% during the restoration period.
The repairing principle of the invention is as follows:
reducing pentavalent vanadium into low-valent vanadium by utilizing reducing bacteria, reducing the toxicity of soil, and realizing detoxification of high-valent vanadium; meanwhile, the silicon-based curing agent can effectively and continuously cure and stabilize heavy metals. The active silicon component and the biochar in the silicon-based curing agent can convert exchangeable vanadium and cadmium into stable parts through the actions of electrostatic adsorption, complexation, precipitation and the like, and the soluble carbon component released by the biochar in soil not only can complex vanadium, but also can serve as an electron donor for reducing bacteria and soil microorganism metabolism to promote detoxification of high-valence vanadium to convert the high-valence vanadium into low-valence vanadium. In addition, microbial reduction strains are planted and aggregated 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 reduction bacteria is promoted, the stability of vanadium and cadmium in soil is further promoted, and the continuous and effective restoration of the vanadium and cadmium polluted soil is realized.
The beneficial effects of the invention are as follows:
1) The raw materials of the vanadium-cadmium polluted soil solidifying and repairing agent adopt industrial solid waste, biomass and the like, the reducing bacteria are commercial bacteria agents, the raw materials are wide in source and environment-friendly, the cost of the materials is low, mass production and preparation can be realized, and the performance is stable.
2) The synergistic system for restoring the vanadium-cadmium polluted soil by the silicon-based curing agent coupling reducing bacteria can realize the reduction and conversion of high-valence vanadium into low-valence vanadium, and can improve the contents of the iron-manganese combined state, the organic matter combined state and the residue state of the vanadium and cadmium in the soil to more than 80 percent and more than 90 percent, so that the continuous, efficient, stable and restoration of the vanadium-cadmium polluted soil can be realized.
3) The vanadium-cadmium pollution remediation method disclosed by the invention is simple to operate, low in cost, and capable of reducing solid waste, and can be applied to remediation of large-scale vanadium-cadmium polluted sites and farmland soil, and has a wide application prospect.
Drawings
FIG. 1 is a graph showing the growth and harvest of contaminated farmland rice in example 3.
FIG. 2 shows the rice yield results for the different experimental groups in example 3.
FIG. 3 is a graph showing the heavy metal content of rice harvested from different experimental groups in example 3.
FIG. 4 shows the results of the detection of the morphological distribution of vanadium and cadmium in field soil after harvesting of rice in different experimental groups in example 3.
Detailed Description
The invention is further illustrated, but is not limited, by the following examples.
The experimental methods in the following examples are conventional methods unless otherwise specified; the biological and chemical reagents used, unless otherwise specified, are all conventional in the art.
The sources of the tailing industrial waste raw materials used in the embodiment of the invention are as follows:
quartz sand tailings: comprises waste residues in ore exploitation, tailings and tail mud in the processing process, wherein the tailings account for most of the chemical components of the quartz tailings are mainly SiO 2 . The quartz sand tailings in the embodiment of the invention come from the Guangdong province cloud and float quarry.
Granite tailings: is rock tailings and leftovers with bad quality left after the exploitation of granite stone factories, and the chemical components mainly comprise quartz, potassium feldspar and acid plagioclase feldspar. The granite tailings in the embodiment of the invention come from the Guangdong cloud and float quarry.
Potassium feldspar tailings: is rock tailings and leftovers with poor quality left after the exploitation of potassium feldspar factories, and the chemical components are mainly aluminosilicate minerals. The potassium feldspar tailings in the embodiment of the invention come from the Guangdong province cloud and float quarry.
EXAMPLE 1 contaminated soil remediation
The soil polluted by vanadium and cadmium is collected in the soil of a stone coal mining area in Hunan, and after air drying, the soil is sieved by a 10-mesh sieve, and the soil sample is subjected to analysis of basic physicochemical properties and heavy metal elements (see table 1).
TABLE 1 soil sample basic Properties and elemental analysis of metals
The preparation of the silicon-based curing agent 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 percent to 70 percent.
The curing agent A is prepared by utilizing silicon-rich industrial solid waste under an alkali activation roasting method, and the specific preparation process is as follows: mixing quartz sand tailings and a solid alkali activator (KOH) according to the proportion of 9:1, fully ball-milling, placing in a programmed high-temperature furnace, roasting 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 crushed rice straw and water into a high-pressure batch reactor (HT-250J0, HTLAB, beijing, china) according to the proportion 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, and the reaction is finished after 60 minutes, and the reactor is naturally cooled to room temperature. The solid residue was separated by filtration to give a hydrothermal char, which was dried at 105℃to give curing agent B.
Culturing a reducing bacteria solution: enriching and culturing strain of Bacillus pseudochrous CGMCC1.5315 (CGMCC from China general microbiological culture collection center) until logarithmic phase is reached, wherein cell density in the strain is 3.6X10 8 And each mL.
Repairing contaminated soil: CK, T1, T2, T3, T4, T5, T6, T7 and T8 treatment groups were set. CK is a non-treatment 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 repairing agent), 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 (non-silicon-based material is lime).
Respectively placing 5kg of soil into PVC tanks (40 cm×15cm×20 cm), wherein the CK group is free from adding curing agent; adding the silicon-based curing agent according to the invention into T1 according to 1% (w/w), fully and uniformly mixing and paving; adding a silicon-based curing agent into T2 according to 1% (w/w), fully and uniformly mixing, and inoculating 0.2L of reducing bacteria liquid; adding a curing agent A according to 1% (w/w) in T3; adding a curing agent A into the T4 according to 1% (w/w), fully and uniformly mixing, and inoculating 0.2L of reducing bacteria liquid; adding a curing agent B according to 1% (w/w) in T5; adding a curing agent B into the T6 according to 1% (w/w), fully and uniformly mixing, and inoculating 0.2L of reducing bacteria liquid; t7 is added with 1% (w/w) of quartz sand tailings which are not subjected to alkali activation treatment; t8 is the addition of 1% (w/w) of the non-silicon-based material treatment group, thoroughly mixed and spread. The soil of all treatment groups is added with water during the restoration period to keep the water holding capacity of the soil to be 70%, the leaching content of vanadium and cadmium in the soil is measured after 60 days of restoration, the concentrations of V (V) and V (IV) are 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 results are shown in table 2.
TABLE 2 leaching of heavy metals and V morphology in soil after remediation
From the results in table 2, it can be seen that: compared with the CK in the control group, 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 applying the silicon-based curing agent has the effect of curing and stabilizing the heavy metal in the soil and is better than the effect of independently applying the curing agent A (T3 group) and the curing agent B (T5 group); the leaching content of the T7 group Cu, zn, cd, pb is not greatly different from that of the CK group, and the solidification effect on heavy metals is not obvious. In addition, compared with the control group CK, the leaching content of V (V) in T1, T2, T3, T4, T5 and T6 is reduced by 65%, 88%, 46%, 75%, 47% and 80%, respectively, compared with the CK, which also shows that the silicon-based curing agent can cure and stabilize high-valence V in soil to a certain extent, in addition, under the synergistic effect of reducing bacteria, the reducing bacteria can further reduce V (V), detoxify the high-valence V, reduce the ecological risk of the V in the soil, and the detoxify effect of the T7 and T8 on the high-valence V is obviously poorer than that of other treatment groups. Furthermore, from the results of T8, lime has a solidification stabilizing effect of heavy metals, but its repairing effect is lower than that of T2 group, and it has no effect on V (V) detoxification.
EXAMPLE 2 contaminated soil remediation
The soil polluted by vanadium and cadmium is collected in farmland soil of a stone coal mining area in Hunan, and after air drying, the soil is sieved by a 10-mesh sieve, and the soil sample is subjected to analysis of basic physicochemical properties and heavy metal elements, and the analysis is shown in Table 3.
TABLE 3 soil sample basic Properties and elemental analysis of metals
Preparation of a 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 percent to 80 percent.
The curing agent A is prepared by utilizing silicon-rich industrial solid waste under an alkali activation roasting method, and the specific preparation process is as follows: mixing granite tailings and a solid alkali activator (KOH) according to the proportion of 9:1, fully ball-milling, placing in a programmed high-temperature furnace, roasting for 120min at 800 ℃, cooling, grinding and sieving with a 100-mesh sieve.
The curing agent B is prepared by a hydrothermal method: adding crushed kitchen waste food residues (leftovers of restaurants) and water into a high-pressure intermittent reactor (HT-250J 0, HTLAB, beijing, china) according to the proportion 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, and the reaction is finished after 60 minutes, and the reactor is naturally cooled to the room temperature. The solid residue was separated by filtration to give a hydrothermal char, which was dried at 105℃to give curing agent B.
Culturing a reducing bacteria solution: enriching CGMCC1.8877 (CGMCC from China general microbiological culture collection center) and culturing until logarithmic phase is reached, wherein the cell density in the standby bacterial liquid is 5×10 8 And each mL.
Repairing contaminated soil: CK, T1, T2, T3, T4, T5, T6 and T7 treatment groups were set. CK is a non-treatment 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 repairing agent), 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 activated by alkali.
Respectively placing 5kg of soil into PVC tanks (40 cm×15cm×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 T2 according to 1% (w/w), fully and uniformly mixing, and inoculating 0.2L of reducing bacteria liquid; adding a curing agent A according to 1% (w/w) in T3; adding a curing agent A into the T4 according to 1% (w/w), fully and uniformly mixing, and inoculating 0.2L of reducing bacteria liquid; adding a curing agent B according to 1% (w/w) in T5; adding a curing agent B into the T6 according to 1% (w/w), fully and uniformly mixing, and inoculating 0.2L of reducing bacteria liquid; t7 is to add 1% (w/w) of granite tailing curing agent which is not activated by alkali, fully mix and spread. The soil of all treatment groups is added with water during the restoration period to keep the field water holding capacity of the soil to be 70%, the leaching content and the V (V) content of vanadium and cadmium in the soil are measured after 60 days of restoration, and relevant experimental results are shown in table 4.
TABLE 4 leaching of heavy metals from soil after remediation and V morphology
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 stabilization effect of the silicon-based curing agent synergistic coupling reducing bacteria (T2 group) on heavy metals in soil is better than that of the single silicon-based curing agent treatment (T1 group), and the curing stabilization effect of the silicon-based curing agent (T1 group) on heavy metals is better than that of the curing agent a (T3 group) and the curing agent B (T5 group); and the leaching contents of Cu, zn, cd and Pb in the T7 group are not obviously different from those in the CK group, and the T7 group has no obvious curing effect. For V, the silicon-based curing agent synergistically couples with the reducing bacteria (T2 group) to effectively reduce the leaching content of V (V) in soil, wherein the leaching content of V (V) in the soil 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 detoxify high-price 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 the reducing bacteria, the content of V (V) is further reduced, and the ecological risk of soil pollution is reduced due to the reduction of the V (V) into low-valence vanadium.
EXAMPLE 3 contaminated farmland remediation
Experiments were carried out in farmland surrounding a stone coal mining area in Hunan province.
Preparation of a silicon-based curing agent: the silicon-based curing agent is prepared by mixing the curing agent A and the curing agent B according to a mass ratio of 25% to 75%.
The curing agent A is prepared by utilizing silicon-rich industrial solid waste under an alkali activation roasting method, and the specific preparation process is as follows: mixing potassium feldspar tailings and a solid alkali activator (NaOH) according to the proportion of 9:1, fully ball-milling, placing in a programmed high-temperature furnace, roasting for 90min at 800 ℃, cooling, grinding and sieving with a 100-mesh sieve.
The curing agent B is prepared by a hydrothermal method: adding crushed rice straw and water into a high-pressure batch reactor (HT-250J0, HTLAB, beijing, china) according to the proportion 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, and the reaction is finished after 60 minutes, and the reactor is naturally cooled to the room temperature. The solid residue was separated by filtration to give a hydrothermal char, which was dried at 105℃to give curing agent B.
Culturing a reducing bacteria solution: enriching CGMCC1.8079 (CGMCC from China general microbiological culture collection center) and culturing until logarithmic phase, wherein the cell density in the standby bacterial liquid is 3.7X10 8 And each mL.
The farmland restoration treatment is divided into CK control groups, T1, T2, T3, T4, T5, T6 and T7 treatment groups, wherein CK is a non-treatment control 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 reduction bacteria treatment group, the silicon-based curing agent is sprayed into soil according to 1.5T/ha, and then bacterial liquid is sprayed according to 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 reduction 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 reduction 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 applying a potassium feldspar tailing curing agent which is not activated by alkali in the T7 group, wherein the dosage is 1.5T/ha, uniformly spraying the potassium feldspar tailing curing agent into soil, uniformly mixing ploughing, ploughing to 20cm deep, irregularly supplementing water, keeping the water surface to be 1-2cm deep beyond the soil, and planting rice after two weeks. The rice variety is two-excellent 290, the direct seeding method is adopted to plant the rice, the rice planting follows the local farm work operation and the water and fertilizer management mode, and the rice growth and harvesting conditions are shown in figure 1.
The statistical yield of rice and the heavy metal content in rice were harvested after 120 days. The heavy metal content in the rice is detected and analyzed according to a method specified by national standard GB5009.12-2017, and the detection and analysis of Cu, zn, cd, V are respectively carried out according to methods specified in GB 5009.13-2017 national food safety standard food copper determination, GB 5009.14-2017 national food safety standard food zinc determination, GB5009.15-2014 national food safety standard food cadmium determination and GB 5009.268-2016 national food multi-element determination.
The rice yield results are shown in FIG. 2, and relative to CK group, T1 group yield is increased by 15%, T2 group yield is increased by 23%, T3 group yield is increased by 7%, T4 group yield is increased by 12%, T5 group yield is increased by 9%, and T6 group yield is increased by 16%; t7 has no obvious yield increasing effect basically. The heavy metal content results in the rice are shown in the figure 3, and in combination, the heavy metal content in the rice in the T1 and T2 groups is less than that in other treatment groups, the content difference of Pb, cd and V is obvious, and 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 the control group CK, the Pb content in the rice of the T1 group and the rice of the T2 group are respectively reduced by 44% and 56%, the Cd content is respectively reduced by 32% and 48%, and the V content is respectively reduced by 65% and 71%. The result shows 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 better effect than the independent application treatment of curing agents A and B, and the heavy metals Cd and Pb content of rice in T1 and T2 are lower than the pollutant limit in national food safety standard (GB 2762-2017).
The heavy metal forms of the field soil after harvesting the rice are distributed, the soil is continuously extracted according to a Tessier 5-step extraction method, and the leaching solution is analyzed by ICP-MS. As shown in FIG. 4, the combined and synergistic reduction bacteria of the silicon-based curing agent can effectively improve the contents of the combined state and the residual state of the iron and manganese oxides of Cd and V in the soil, compared with CK, the combined state, the organic matter combined state and the residual state of the cadmium in the soil in the T1 and T2 groups are improved by 19 percent and 21 percent respectively relative to other treatment groups, the combined state, the organic matter combined state and the residual state of the vanadium in the soil are improved by 16 percent and 20 percent respectively, which indicates that the silicon-based curing agent can effectively reduce the bioavailability of heavy metals in the soil, and the treatment effect of the combined and synergistic reduction bacteria of the silicon-based curing agent is further improved, so that the effect is optimal in each treatment group.
Claims (11)
1. A soil vanadium/cadmium pollution repairing agent is characterized in that: comprising a silicon-based solidifying agent and a microbial agent comprising a reducing bacterium having V (V) reducing properties selected from the group consisting of corynebacterium humicola (Corynebacterium humireducens), corynebacterium ferrugineum (nov), comamonas (Comamonas), bacillus sphaericus (Lysinibacillus sphaericus), bacillus marinus (Oceanobacillus), escherichia coli (Enterobacter ludwigii), and candida saccharolytica (Pseudochrobactrum saccharolyticum); wherein, the strain of Comamonas is CCTCC AB2011133, and the strain of marine bacillus is CGMCC1.8877;
the microbial agent is a liquid microbial agent, and the mass volume ratio of the silicon-based curing agent to the microbial agent is as follows: 0.5-7.5kg of the weight of the feed additive is 0.1-5L;
the silicon-based curing agent comprises 10-40wt% of curing agent A and 60-90wt% of curing agent B, wherein the curing agent A is obtained by mixing and roasting silicon-rich tailings and an alkali activator according to the mass ratio of 7.0-9.0:1.0; 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;
the alkali activator is selected from one or more of sodium hydroxide, potassium hydroxide and sodium carbonate, and is mixed with the silicon-rich tailings for roasting after being prepared into liquid or adopting a solid alkali activator; the roasting temperature is 750-1000 ℃ and the roasting time is 30-120min.
2. The soil vanadium/cadmium pollution remediation agent of claim 1, wherein: the raw biomass material of the biochar comprises one or more of plant biomass, animal manure, domestic sludge, biogas residues and kitchen waste, wherein the plant biomass comprises plant residues, straw, rice bran and sawdust;
the kitchen waste comprises vegetable and fruit residues, animal bones and food residues;
the biochar is hydrothermal biochar or thermal pyrolysis biochar.
3. The soil vanadium/cadmium pollution remediation agent of claim 2, wherein: the preparation method of the hydrothermal biochar comprises the following steps: adding biomass material and water into a high-pressure intermittent reactor according to a solid-liquid mass ratio of 0.5-1.5:3, reacting, charging inert gas to create an anaerobic environment, cooling at 220-350 ℃ for 30-120min, filtering, and drying.
4. The soil vanadium/cadmium pollution remediation agent of claim 1, wherein: the silicon-rich tailings are quartz sand tailings; the alkali activator is solid alkali activator or liquid, and is mixed with the silicon-rich tailings for roasting, cooling and grinding to 100-200 mesh sieve.
5. The soil vanadium/cadmium pollution remediation agent of claim 1, wherein: the active bacterial cell density in the bacterial liquid of the microbial agent is 10 7 ～10 10 individual/mL;
the mass volume ratio of the silicon-based curing agent to the microbial agent is as follows: 0.5-6.5kg of the weight of the feed additive is 0.1-4L;
the strain of the humic substance reducing corynebacterium is CGMCC NO.2452, the strain of the iron reducing bacterium is CCTCC M2011498, the strain of the spherical lysine bacillus is CGMCC1.8079, the strain of the ludwigia bowel is CGMCC NO.8801, and the strain of the sugar-decomposing pseudo-pallor is CGMCC1.5315.
6. A method for synergistic remediation of vanadium/cadmium contaminated soil by coupling a silicon-based curing agent with a reducing bacterium, characterized in that the soil is remediated by the soil vanadium/cadmium contaminated remediation agent according to any one of claims 1 to 5, comprising:
step 1) adding the silicon-based curing agent into polluted soil according to the application amount of 0.5-2.0wt% or adding the silicon-based curing agent into polluted farmland according to the application amount of 1.0-7.5 t/ha;
and 2) taking the microbial agent in the repairing agent, applying the microbial agent into the polluted soil or the farmland, and uniformly mixing.
7. The method for synergistically restoring vanadium/cadmium contaminated soil by using the silicon-based curing agent coupled with reducing bacteria as set forth in claim 6, which is characterized in that: the silicon-based curing agent in the step 1) is added into polluted soil according to the application amount of 0.7-2.0wt% or is added into polluted farmland according to the application amount of 1.5-6.5 t/ha.
8. The method for synergistically restoring vanadium/cadmium contaminated soil by using the silicon-based curing agent coupled with reducing bacteria as set forth in claim 6, which is characterized in that: in the step 2), the liquid microbial agent is added into polluted soil according to the application amount of 5-50mL/kg or is added into polluted farmland according to the application amount of 150-500L/ha.
9. The method for synergistically restoring vanadium/cadmium contaminated soil by using the silicon-based curing agent coupled with reducing bacteria as set forth in claim 8, which is characterized in that: in the step 2), the liquid microbial agent is added into polluted soil according to the application amount of 5-45mL/kg or is added into polluted farmland according to the application amount of 150-450L/ha.
10. The method for synergistically restoring vanadium/cadmium contaminated soil by using the silicon-based curing agent coupled with reducing bacteria as set forth in claim 6, which is characterized in that: the restoration time is 20-70 days, and the field water holding capacity of the soil is kept to be 60-80% during the restoration period.
11. The method for synergistically restoring vanadium/cadmium contaminated soil by using the silicon-based curing agent coupled with reducing bacteria as set forth in claim 10, which is characterized in that: the restoration time is 30-65 days, and the field water holding capacity of the soil is kept to be 65-75% during the restoration period.
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