CN109777428B - Composite modified diatomite heavy metal passivator and application thereof - Google Patents
Composite modified diatomite heavy metal passivator and application thereof Download PDFInfo
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Abstract
The invention discloses a composite modified diatomite heavy metal passivator which is prepared from the following raw materials in parts by weight: 20-115 parts of straw charcoal powder and CaCO310-20 parts of modified diatomite, Mg (OH)25-10 parts of modified diatomite and Fe3O42-5 parts of modified diatomite. The invention also discloses an application of the composite modified diatomite heavy metal passivator. The method has the advantages of high restoration efficiency, reduction of secondary pollution, realization of the aims of reducing the heavy metal accumulation amount of agricultural products and improving the quality of the agricultural products, and provision of guarantee for the safe production of agricultural products in China.
Description
Technical Field
The invention relates to the technical field of heavy metal passivators, in particular to a composite modified diatomite heavy metal passivator and application thereof.
Background
Heavy metals are non-essential elements for growth of animals and plants, and after entering farmland soil, the heavy metals can be absorbed and accumulated by plant bodies and enter human bodies through food chain ways, thus threatening the health of human beings.
In 2014, the national soil pollution condition survey bulletin issued by the ministry of environmental protection and the ministry of land resources jointly shows that the exceeding rate of the soil point location of cultivated land in China reaches 19.4%, and the main pollutants are cadmium (Cd), nickel (Ni), copper (Cu), arsenic (As), mercury (Hg), lead (Pb) and the like. The investigation of 140 million hectares of sewage irrigation area in China by the Ministry of agriculture discovers that the exceeding area of heavy metals in soil accounts for 64.8 percent.
Aiming at the heavy metal polluted farmland soil, the remediation method mainly comprises ecological remediation, phytoremediation, stabilization/immobilization remediation and the like. In consideration of the problems of repair cost, repair efficiency, possible secondary pollution and the like, the in-situ passivation repair method has better repair superiority, and the heavy metal passivator is the key for success or failure of the application of the soil in-situ repair technology.
At present, the traditional heavy metal passivator is used for in-situ treatment of polluted soil, and the following problems need to be solved: firstly, the fixation efficiency is low; ② the immobilized heavy metals may be converted into bio-available state again and exist in the soil with the lapse of time.
Therefore, how to fix the heavy metal pollutants in the soil efficiently and stably is one of the problems to be solved urgently by the in-situ passivation remediation method.
Disclosure of Invention
The invention aims to solve the technical problems of low repair efficiency, secondary pollution and the like in the prior art by preparing a novel heavy metal passivator and applying the passivator, realize the aims of reducing the heavy metal accumulation of agricultural products and improving the quality of the agricultural products and provide guarantee for the safe production of agricultural products in China.
The invention solves the technical problems by the following technical means: the composite modified diatomite heavy metal passivator is prepared from the following raw materials in parts by weight: 30-115 parts of straw charcoal powder and CaCO310-20 parts of modified diatomite, Mg (OH)28-10 parts of modified diatomite and Fe3O42-5 parts of modified diatomite.
Preferably, the straw charcoal powder is prepared from the following raw materials in parts by weight: 0-30 parts of wheat straw charcoal powder, 0-35 parts of rape straw charcoal powder, 20-30 parts of corn straw charcoal powder and 10-20 parts of rice straw charcoal powder.
The straw carbonization process: removing impurities from one or more of crop straws (wheat straws, rape straws, corn straws and rice straws), cleaning, drying for 24h, crushing, and putting into a vacuum heat treatment furnace for pyrolysis at 600 ℃ for 2-6h under 300-.
Preferably, the CaCO3The modified diatomite is prepared by the following steps:
(1) mixing diatomite and a hydrochloric acid aqueous solution, washing until the pH value is neutral, drying and sieving to obtain pretreated diatomite;
(2) mixing the pretreated diatomite with Na2CO3Mixing the aqueous solutions, adding CaCl2Oscillating the aqueous solution, washing until the pH value is neutral, drying, grinding and sieving to obtain CaCO3Modified diatomite.
Preferably, the CaCO3The modified diatomite is prepared by the following steps:
(1) mixing diatomite and hydrochloric acid aqueous solution with the concentration of 1mol/L-2mol/L according to the solid-to-liquid ratio of 1g/5mL-1g/8mL, ultrasonically dispersing for 30-60min, washing the diatomite with ethanol and deionized water until the pH value of filtrate is neutral, drying to constant weight, and sieving with a 60-mesh standard sieve to obtain pretreated diatomite;
(2) according to the solid-to-liquid ratio of 1g/5mL-1g/10mL, the pretreated diatomite and Na with the concentration of 0.5mol/L2CO3Mixing the water solutions, oscillating at constant temperature of 25-30 ℃ for 1-2 h, and adding 4mol/L CaCl2Aqueous solution (Na)2CO3Aqueous solution with CaCl2The volume ratio of the water solution is 5:1-10:1), oscillating at constant temperature of 30 ℃ for 30min, washing the product with distilled water until the filtrate is neutral, drying at constant temperature of 105 ℃, grinding, sieving with a 200-mesh standard sieve to obtain CaCO3Modified diatomite.
Preferably, said Mg (OH)2The modified diatomite is prepared by the following steps:
(1) roasting and drying the diatomite to obtain roasted diatomite;
(2) will be provided withMixing the roasted diatomite, magnesium chloride and sodium hydroxide, standing the mixed product, washing, filtering, drying, grinding and sieving to obtain Mg (OH)2Modified diatomite.
Preferably, said Mg (OH)2The modified diatomite is prepared by the following steps:
(1) roasting the diatomite for 2-3h at 450 ℃ to obtain roasted diatomite;
(2) drying magnesium chloride at 100 ℃ for later use;
(3) weighing roasted diatomite, dried magnesium chloride and sodium hydroxide according to the mass ratio of 1:1: 1/2-2/3; firstly, grinding the diatomite and the magnesium chloride together for 5-10 min; adding sodium hydroxide solid into a diatomite-magnesium chloride reaction system, grinding until the reaction is finished, standing the mixed product in the air for 3-5h, repeatedly washing with distilled water, filtering, drying the mixed product at the constant temperature of 110 ℃ for 9-12h, grinding, and sieving with a 200-mesh standard sieve to obtain Mg (OH)2Modified diatomite.
Preferably, the Fe3O4The modified diatomite is prepared by the following steps:
(1) roasting diatomite, grinding and sieving to obtain pre-roasted and sieved diatomite;
(2) preparing diatomite aqueous solution by using diatomite which is pre-baked and sieved, and mixing diatomite suspension with Fe3O4Mixing the aqueous solutions, adding the mixture into a chitosan-acetic acid-aqueous solution with the pH value of 6, and reacting;
(3) after the reaction is finished, washing the precipitate to be neutral, drying the precipitate at constant temperature, grinding the precipitate, and sieving to obtain Fe3O4Modified diatomite.
Preferably, the Fe3O4The modified diatomite is prepared by the following steps:
(1) roasting diatomite at 450 ℃ for 2-4h, grinding and sieving by a 60-mesh standard sieve to obtain pre-roasted and sieved diatomite;
(2) mixing pre-calcined and sieved diatomite with distilled water according to the solid-to-liquid ratio of 1g/10mL-1g/15mL to obtain diatomite suspension;
dispersing Fe by 28kHz ultrasonic for 25min according to the solid-to-liquid ratio of 1g/40mL-1g/50mL3O4Completely dissolved in distilled water to obtain Fe3O4An aqueous solution;
1g of chitosan (degree of deacetylation: 85%) was dissolved in 400mL of 1% aqueous acetic acid solution, and after complete dissolution with stirring, the pH was adjusted to 6;
(3) mixing Fe3O4Pouring the aqueous solution into the kieselguhr suspension, stirring, adding the chitosan-acetic acid-aqueous solution, (Fe)3O4The volume ratio of the aqueous solution to the diatomite suspension to the chitosan-acetic acid-aqueous solution is 2: 20: 3) reacting in water bath at 60-70 deg.c for 3-5 hr; after the reaction is finished, washing the precipitate with distilled water to be neutral, drying the precipitate at the constant temperature of 70 ℃ for 8-10h, grinding the precipitate, and sieving the precipitate with a 60-mesh standard sieve to obtain Fe3O4Modified diatomite.
The invention also discloses a method for applying the composite modified diatomite heavy metal passivator to a dry crop farmland, which comprises the following steps:
(1) selecting the heavy metal risk grade of the soil of the crop planting plot as low risk, wherein Pi is more than 1 and less than or equal to 2, Pimax is more than 1 and less than or equal to 2; or, moderate risk, wherein Pi is greater than 2 and less than or equal to 3, Pimax is greater than 2 and less than or equal to 3;
(2) soaking the soil at high temperature for 3-5 days, draining the water, and insolating for 2-3 days;
(3) when deeply ploughing a polluted farmland, uniformly mixing one or more of the piled and rotted rice straws, corn straws, wheat straws and rape straws with soil, wherein the addition amount of the piled and rotted straws is 110-plus-material 260 kg/mu, and then broadcasting the composite modified diatomite heavy metal passivator, and the addition amount of the composted and rotted straws is 150-plus-material 200 kg/mu;
(4) covering a mulching film on the deeply ploughed soil, and exposing for 8-10 days; then uncovering the mulching film for continuous ventilation and insolation for 5-10 days; rain wash is avoided during insolation;
(5) and planting crops on the farmland soil subjected to the in-situ passivation treatment.
The invention also discloses a method for applying the composite modified diatomite heavy metal passivator to a paddy field, which comprises the following steps:
(1) selecting the heavy metal risk grade of the paddy field as low risk, wherein Pi is more than 1 and less than or equal to 2, Pimax is more than 1 and less than or equal to 2; or, moderate risk, wherein Pi is greater than 2 and less than or equal to 3, Pimax is greater than 2 and less than or equal to 3;
(2) irrigating and soaking the soil for more than 12h, and draining water when the soil is soft and the depth of mud feet is 0.1-0.2 m;
(3) uniformly spreading the piled and rotted rice straws in the field, wherein the spreading amount is 200-300 kg/mu; the prepared composite modified diatomite heavy metal passivator is applied on the piled rotten rice straws in a spreading amount of 100 and 200 kg/mu;
(4) ploughing a polluted paddy field;
(5) irrigating water in the deeply ploughed paddy field to a depth of 1-3cm, maintaining the soaking state of the paddy field for 15-20 days, and avoiding rain wash;
(6) stopping adding irrigation water into the paddy field when the soaking period is nearly finished, naturally evaporating a surface water layer in the paddy field to dryness, and maintaining the wet state of the paddy field soil;
(7) rice seedlings are planted in the paddy field soil after the in-situ passivation treatment.
The invention has the advantages that:
(1) the composite modified diatomite heavy metal passivator prepared by the invention has obvious passivation effect on heavy metals, long duration, wide source of adopted raw materials, low price and no secondary pollution to soil; by utilizing the preparation method and the formula of the heavy metal passivator, the repaired soil can better meet the growth requirements of crops, the accumulation amount of heavy metals in agricultural products is reduced, and the quality of the agricultural products is improved; the heavy metal in-situ passivation method provided by the invention is simple and easy to learn in operation, easy to popularize in a large scale and low in cost.
In order to produce agricultural products lower than the pollutant limit in food (GB2762-2005) and form a generalizable heavy metal passivation technology system, the modified passivator provided by the invention has the following advantages: firstly, high reaction activity, high adsorptivity, high structural stability and passivation durability; ② the raw material has rich sources, low price, safety, no secondary pollution and other properties. On the other hand, the absorption and accumulation of heavy metals in crops are reduced by an efficient and generalizable application technology of the heavy metal passivator.
(2) The invention is suitable for farmlands with low risk or moderate risk of heavy metal risk grade, including large-scale farmlands and facility farmlands; the experimental method is scientific and reasonable, and all indexes meet the national standard of the people's republic of China and the relevant regulations of the agricultural rural area of the people's republic of China; the heavy metal content of the agricultural products can be reduced from the source, the safety of the agricultural products is guaranteed, the health of people is guaranteed, and the method has great practical significance and wide application prospect.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.
Example 1
And (4) selecting a target planting land (namely the heavy metal polluted soil to be repaired). The heavy metal content of the farmland soil was measured, and the results are shown in table 1. According to the national standard of the people's republic of China, namely the soil environmental quality standard (GB15618-1995), the national standard of the people's republic of China, namely the safety threshold of cadmium, lead, chromium, mercury and arsenic in soil produced by rice (GB/T36869-2018) and the technical regulation of the safety evaluation of heavy metals in soil of agricultural product producing areas of China (2015), the heavy metal risk grade of the paddy field is selected to be low (Pi is more than 1 and less than or equal to 2, and Pimax is more than 1 and less than or equal to 2).
TABLE 1 soil heavy metal content of sampled plot I
| Heavy metal content of soil | Cd(mg/kg) |
| Sampling plot I | 0.24 |
| GB15618-1995 Primary Standard | 0.20 |
| GB15618-1995 Secondary Standard | 0.30 |
| GB15618-1995 three-level standard | 1.00 |
1. The in-situ passivation method of the invention
(1) A preparation method of a composite modified diatomite heavy metal passivator comprises the following steps:
CaCO3preparing modified diatomite:
mixing diatomite and hydrochloric acid aqueous solution with the concentration of 2mol/L uniformly according to the solid-to-liquid ratio of 1g/5mL, placing the mixture in an ultrasonic dispersion instrument, dispersing for 30min, filtering precipitates, and repeatedly washing the precipitates with ethanol and deionized water until the pH value of filtrate is neutral. Drying the diatomite to constant weight, and sieving the diatomite through a 60-mesh standard sieve to obtain the pretreated diatomite.
② according to the solid-to-liquid ratio of 1g/5mL, the pretreated diatomite and Na with the concentration of 0.5mol/L2CO3The aqueous solution is evenly mixed,oscillating at constant temperature of 30 ℃ for 1h, and adding 4mol/L CaCl2Aqueous solution (Na)2CO3Aqueous solution with CaCl2The volume ratio of the water solution is 10:1), then oscillating at constant temperature of 30 ℃ for 30min, removing supernatant, washing with distilled water until the filtrate is neutral, drying at constant temperature of 105 ℃ for precipitation, fully grinding, and sieving with a 200-mesh standard sieve to obtain CaCO3Modified diatomite.
Mg(OH)2Preparing modified diatomite:
putting diatomite raw soil into a muffle furnace, and roasting for 2 hours at 450 ℃. Meanwhile, putting the magnesium chloride into a constant-temperature drying oven, and drying for 24 hours at 100 ℃ for later use.
② weighing the roasted diatomite, the dried magnesium chloride and the sodium hydroxide according to the mass ratio of 1:1: 2/3. Placing diatomite and magnesium chloride into the same mortar, fully grinding for 10min, adding sodium hydroxide solid into a diatomite-magnesium chloride reaction system, grinding until yellow hard blocks are generated, and continuously grinding until the yellow hard blocks disappear; standing the mixture in air for 5h, washing with distilled water, oven drying at 110 deg.C for 9h, grinding, sieving with 200 mesh standard sieve to obtain Mg (OH)2Modified diatomite.
Fe3O4Preparing modified diatomite:
putting diatomite raw soil into a muffle furnace, roasting for 3 hours at 450 ℃, grinding and sieving by a 60-mesh standard sieve for later use.
And secondly, uniformly mixing the pretreated diatomite with distilled water according to the solid-liquid ratio of 1g/13mL to obtain diatomite suspension. According to the solid-to-liquid ratio of 1g/40mL, adding Fe3O4Dissolving in distilled water, and ultrasonic dispersing at 28kHz for 25min to obtain Fe3O4An aqueous solution. 1g of chitosan (degree of deacetylation: 85%) was dissolved in 400mL of 1% aqueous acetic acid solution, and after complete dissolution with stirring, the pH was adjusted to 6 to obtain a chitosan-acetic acid-aqueous solution.
③ Fe3O4Pouring the aqueous solution into the diatomite suspension, stirring uniformly, adding the chitosan-acetic acid-aqueous solution, (Fe)3O4Aqueous solution, diatomaceous earth suspension, chitinThe volume ratio of the sugar to the acetic acid to the water solution is 2: 20: 3) reacting in water bath at 65 ℃ for 4 h; after the reaction is finished, repeatedly washing and precipitating with distilled water until the filtrate is neutral, drying the product at the constant temperature of 70 ℃ for 9h, fully grinding, and sieving with a 60-mesh standard sieve to obtain Fe3O4Modified diatomite.
(2) The design of a composite modified diatomite heavy metal passivator formula comprises the following steps:
preferably, the formula of the diatomite passivator is as follows: 35 parts of rape straw biochar powder, 20 parts of corn straw biochar powder, 20 parts of rice straw biochar powder and CaCO310 parts of modified diatomite, Mg (OH)210 parts of modified diatomite, Fe3O45 parts of modified diatomite.
The straw charcoal powder in each embodiment of the invention is prepared by respectively removing impurities from rape straws, corn straws and rice straws, cleaning, drying for 24 hours, crushing, putting into a vacuum heat treatment furnace, and pyrolyzing at 300 ℃ for 6 hours to finish the carbonization process of the straws. (3) The invention provides an application method of a composite modified diatomite heavy metal passivator for reducing the content of biologically effective heavy metals in paddy field soil, which comprises the following steps:
firstly, irrigating water to soak soil for 12 hours, and draining the water completely when the depth of mud feet is 0.15 m. Secondly, uniformly scattering the piled and rotten rice straws in the field, wherein the scattering amount is 260 kg/mu. Thirdly, the composite modified diatomite heavy metal passivator prepared in the embodiment 1 is applied on the rice straws in a spreading amount of 150 kg/mu. And fourthly, ploughing the polluted paddy field, wherein the optimal depth is 0.3 m. A straw returning machine is selected to turn over the paddy field, and the working procedures of turning over, straw biochar crushing, slurry lifting, leveling and the like are completed at one time, so that the soil can be fully mixed with the straws and the composite modified diatomite heavy metal passivator. Fifthly, irrigating water in the ploughed paddy field with the depth of 3cm, maintaining the soaking state of the paddy field for 20 days, and avoiding rain wash in the period. Near the end of the soaking period, water is stopped being added to the paddy field to naturally evaporate the surface water layer in the paddy field and maintain the wet state of the paddy field soil. Sixthly, inserting rice seedlings in the paddy field after the in-situ passivation treatment. And planting management measures of the rice are implemented according to the regulations in the technical regulation for producing rice with pollution-free food of agriculture industry standard of the people's republic of China (NY/T5117-2002).
2. Ex situ passivation treatment
Firstly, a straw returning machine is selected to turn over the paddy field, the working procedures of turning over, slurry lifting, leveling and the like are completed at one time, and the turning depth is 0.3 m. Secondly, transplanting rice seedlings in the ploughed and leveled paddy field. Thirdly, the planting management measures of the rice are implemented according to the regulations in the agricultural industry standard of the people's republic of China, namely the technical regulations on the production of pollution-free food rice (NY/T5117-2002).
3. Comparative example: the soil of the same 3 plots was subjected to a remediation test using 3 kinds of modified diatomaceous earth, respectively. The specific process is as follows.
The preparation method of the 3 composite modified diatomite heavy metal passivators comprises the following steps: example 1 "above the in situ passivation process of the present invention. "the step (1) is the same.
The application method of the 3 composite modified diatomite heavy metal passivators and the rice planting management measures are as follows: firstly, spreading the composite modified diatomite heavy metal passivator, wherein the application amount of the 3 composite modified diatomite heavy metal passivators is respectively as follows: CaCO3Modified diatomaceous earth 15 kg/acre, Mg (OH)2Modified diatomite 15 kg/mu, Fe3O4The modified diatomite accounts for 7.5 kg/mu. And secondly, ploughing the paddy field to a depth of 0.3m, so that the soil can be fully mixed with the composite modified diatomite heavy metal passivator. Thirdly, inserting rice seedlings in the paddy field after the in-situ passivation treatment. And fourthly, the planting management measures of the rice are executed according to the regulations in the technical regulation for producing rice as pollution-free food in the agricultural industry standard of the people's republic of China (NY/T5117-2002).
4. Verification example: the method adopts a composite modified diatomite heavy metal passivator, namely: the same plots were subjected to a remediation test using a mixture of 3 modified diatomaceous earths. The specific process is as follows.
A preparation method of a novel composite modified diatomite heavy metal passivator comprises the following steps: example 1 "above the in situ passivation process of the present invention. "the step (1) is the same.
Composite modified diatomite heavy metal passivator: 3 kinds of compound modified diatomite heavy metal passivator mixture. CaCO3Modified diatomaceous earth, Mg (OH)2Modified diatomite, Fe3O4The mass ratio of the modified diatomite is 2:2: 1.
An optimized passivant application method and rice planting management measures are as follows: firstly, the compound modified diatomite heavy metal passivator is applied in a spreading amount of 37.5 kg/mu. And secondly, ploughing the paddy field to a depth of 0.3m, so that the soil can be fully mixed with the composite modified diatomite heavy metal passivator. Thirdly, inserting rice seedlings in the paddy field after the in-situ passivation treatment. And fourthly, the planting management measures of the rice are executed according to the regulations in the technical regulation for producing rice as pollution-free food in the agricultural industry standard of the people's republic of China (NY/T5117-2002).
5. Soil remediation effect
The heavy metal content in the soil of plot I was determined and the results are shown in table 2. The method disclosed by the invention has the efficiency of repairing the available Cd in the soil of 55.56%. In contrast, the method shown in the verification example has the remediation efficiency of the available Cd in the soil of 44.44%. The application method of the passivator provided by the invention can improve the passivating/fixing efficiency of the passivator on Cd in the polluted soil.
Compared with Cd repair efficiency (44.44%) of the method shown in the validation example, the method has the advantages of high Cd repair efficiency through CaCO3Modified diatomaceous earth, Mg (OH)2Modified diatomite, Fe3O4After the modified diatomite is passivated independently, the remediation efficiency of the effective Cd in the soil is 11.11%, 16.67% and 11.11% respectively. To illustrate CaCO3Modified diatomaceous earth, Mg (OH)2Modified diatomaceous earth and Fe3O4After the modified diatomite is compounded, the repairing efficiency is higher than the sum of the repairing efficiencies of 3 diatomite passivators which are independently applied, and the 3 composite modified diatomite heavy metal passivators have a synergistic effect on the passivation/fixation of Cd in the polluted soil.
TABLE 2 content variation of heavy metal Cd in soil I of the restored plot
The reasons that the application of the composite modified diatomite heavy metal passivator can enhance the repair efficiency are as follows: the adsorption/immobilization performance of the modified diatomite on the heavy metal ions is related to factors such as the structure, functional groups, the distribution of layer charges, electrovalence and ionic radius of the diatomite. The different modified diatomite has different structures due to different functional groups carried by the diatomite and different related ionic radii, distribution of layer charges and electrovalence. Compared with the application of single-kind modified diatomite, the composite modified diatomite has the advantages that the number and the kinds of adsorption sites provided by the composite modified diatomite for heavy metal ions are increased, the repulsive force among various functional groups is weakened, the adsorption and fixation capacity for the heavy metal ions is enhanced, and the effectiveness and the long-acting property for heavy metal immobilization are improved.
6. Further confirmation of the repair Effect
In order to further confirm the repairing effect of the invention and the technical advantages compared with the prior art, the method which is not subjected to repairing treatment and is shown in the verification example is respectively selected on the same land, and the variety of the cell which is subjected to repairing treatment by the method shown in the invention is rice 1.
Statistics is carried out on the rice yield and the constituent factors thereof on the plots which are not subjected to restoration treatment and are subjected to restoration treatment by the methods shown in the verification examples, and the results are shown in table 3, and compared with the results which are not subjected to in-situ passivation treatment, the effective panicle number, the maturing rate, the thousand grain quality and the actual yield of the planted fragrant glutinous rice are obviously increased after farmland soil is treated by the methods shown in the invention and the comparative examples.
TABLE 3 yield of fragrant glutinous rice planted on in-situ passivated plots I and its constituent factors
| Treatment of | Effective spike number/m2 | Grain number per ear | Percentage of fruit set (%) | Thousand seed mass (g) | Actual production (kg/mu) |
| Ex situ passivation treatment | 252.0 | 121.5 | 77.6 | 26.17 | 651.5 |
| Method shown in the verification example | 289.0 | 149.8 | 89.3 | 26.83 | 719.8 |
| The method of the invention | 293.0 | 153.9 | 92.4 | 26.96 | 742.6 |
And (5) measuring the content of heavy metal. Harvesting rice in a rice harvesting period, measuring the content of heavy metals in the rice, and detecting according to the specification of national standard of the people's republic of China, namely determination of sodium, magnesium, potassium, calcium, chromium, manganese, iron, copper, zinc, arsenic, selenium, cadmium and lead in grains and products thereof by inductively coupled plasma mass spectrometry (GB/T35876-2018).
As shown in Table 4, the Cd content in the fragrant glutinous rice is higher than the specified value (i.e. Cd is less than or equal to 0.2mg/kgFW) in the pollutant Limit in food (GB2762-2017) of the national standard without in-situ passivation treatment. After the in-situ passivation method treatment shown in the invention and the method treatment shown in the verification example, the Cd content in the fragrant sticky rice is respectively reduced to 0.08mg/kg and 0.13mg/kg, which meets the requirements of the national standard of pollutant Limit in food (GB 2762-2017). Compared with the ex-situ passivation treatment, the in-situ passivation treatment shown in the invention and the method treatment shown in the verification example remarkably reduce the Cd content in the fragrant glutinous rice, and the reduction range is 61.90% and 39.00%, respectively. The application method of the passivator provided by the invention can be used for effectively reducing the heavy metal accumulation in rice.
TABLE 4 variation of heavy Metal content in fragrant Oryza Glutinosa before and after in-situ passivation treatment
As shown in Table 5, the contents of Ca, Mg, Mn, Zn, Cu and Fe of the planted fragrant glutinous rice were significantly increased after the farmland soil was treated by the method shown in the verification example and the method shown in the present invention, as compared with the method without in-situ passivation treatment.
TABLE 5 Change in the amount of nutrient elements accumulated in fragrant Oryza Glutinosa before and after in-situ passivation
As shown in table 6, the unpolished rice rate, polished rice rate, and amylopectin content of the planted fragrant glutinous rice were increased in different levels after the treatment of the farmland soil by the method shown in the verification example and the method shown in the present invention, as compared with the treatment without in-situ passivation.
TABLE 6 change in the quality of fragrant glutinous rice before and after in-situ passivation treatment (i)
As shown in Table 7, the protein content, the ratio of essential amino acids to total amino acid content, the ratio of essential amino acids to non-essential amino acids, the crude fat content, VB, and the protein content of the cultivated aromatic glutinous rice were measured after the treatment of the farmland soil by applying the method shown in the verification example and the method shown in the present invention, as compared with the case where the in-situ passivation treatment was not carried out2The content increases in different magnitudes.
TABLE 7 change in the quality of fragrant glutinous rice before and after in-situ passivation treatment (ii)
As shown in table 8, 11 new volatile substances were generated from the fragrant glutinous rice planted by the method of the present invention, compared to the non-in-situ passivation treatment; the aromatic glutinous rice planted by applying the method shown in the comparative example produced 8 new volatile substances. The content percentage of the original volatile substances shows an ascending trend of different degrees; the characteristic aroma of the fragrant glutinous rice is more obvious.
TABLE 8 composition change of volatile substances in fragrant Oryza Glutinosa before and after in-situ passivation treatment
The beneficial effect that this embodiment possesses is: the prepared composite modified diatomite heavy metal passivator has an obvious effect of passivating heavy metals, and the adopted raw materials do not cause secondary pollution to soil; by utilizing the preparation method, the formula and the application method of the heavy metal passivator provided by the invention, the restored paddy field can better meet the growth requirement of paddy rice, the accumulation amount of heavy metals in the paddy rice is reduced, and the quality of the paddy rice is improved.
Example 2
And (4) selecting a target planting land (namely the heavy metal polluted soil to be repaired). The soil heavy metal content was measured, and the results are shown in table 9. According to the national standard of the people's republic of China, namely the soil environmental quality standard (GB15618-1995) and the national agricultural product production place soil heavy metal safety assessment technical regulation (2015), the heavy metal risk grade of the selected soil of the crop planting land is moderate (Pi is more than 2 and less than or equal to 3, Pimax is more than 2 and less than or equal to 3).
TABLE 9 soil heavy metal content of sampled plot II
1. The in-situ passivation method of the invention
(1) A preparation method of a modified diatomite heavy metal passivator comprises the following steps:
CaCO3preparing modified diatomite:
mixing diatomite and hydrochloric acid aqueous solution with the concentration of 1mol/L uniformly according to the solid-to-liquid ratio of 1g/8mL, placing the mixture into an ultrasonic dispersion instrument, dispersing for 60min, filtering precipitates, and repeatedly washing the precipitates with ethanol and deionized water until the pH value of filtrate is neutral. Drying the diatomite to constant weight, and sieving the diatomite through a 60-mesh standard sieve to obtain the pretreated diatomite.
② according to the solid-to-liquid ratio of 1g/10mL, the pretreated diatomite and Na with the concentration of 0.5mol/L2CO3Mixing the aqueous solution evenly, oscillating for 2h at 25 ℃, and adding 4mol/L CaCl2Aqueous solution (Na)2CO3Aqueous solution with CaCl2The volume ratio of the aqueous solution is 5:1), shaking at constant temperature of 30 ℃ for 30min, and removing the supernatant. Then washing the product with distilled water until the filtrate is neutral, drying at constant temperature of 105 ℃, fully grinding, and sieving with a standard sieve of 200 meshes. To obtain CaCO3Modified diatomite.
Mg(OH)2Preparing modified diatomite:
putting diatomite raw soil into a muffle furnace, and roasting for 3 hours at 450 ℃. Meanwhile, putting the magnesium chloride into a constant-temperature drying oven, and drying for 24 hours at 100 ℃ for later use.
② weighing the roasted diatomite, the dried magnesium chloride and the sodium hydroxide according to the mass ratio of 1:1: 1/2. Placing diatomaceous earth and magnesium chloride into the same mortar, and fully grinding for 5 min; adding sodium hydroxide solid into a diatomite-magnesium chloride reaction system, grinding until yellow hard blocks are generated, and continuing grinding until the yellow hard blocks disappear; after leaving the mixture in air for 3 hours, it was washed with distilled water and the mixture was filtered. After the filtration is finished, the precipitate is dried for 12h at the constant temperature of 110 ℃, fully ground and sieved by a standard sieve of 200 meshes to obtain Mg (OH)2Modified diatomite.
Fe3O4Preparing modified diatomite:
putting diatomite raw soil into a muffle furnace, roasting for 2 hours at 450 ℃, grinding and sieving by a 60-mesh standard sieve for later use.
And secondly, uniformly mixing the pretreated diatomite with distilled water according to the solid-liquid ratio of 1g/15mL to obtain diatomite suspension. According to the solid-to-liquid ratio of 1g/50mL, adding Fe3O4Dissolving in distilled water, and ultrasonic dispersing at 28kHz for 25min to obtain Fe3O4An aqueous solution. 1g of chitosan (degree of deacetylation: 85%) was dissolved in 400mL of 1% aqueous acetic acid solution, and after complete dissolution with stirring, the pH was adjusted to 6 to obtain a chitosan-acetic acid-aqueous solution.
③ Fe3O4Pouring the aqueous solution into the diatomite suspension, stirring uniformly, adding the chitosan-acetic acid-aqueous solution, (Fe)3O4Aqueous solution, diatomite suspension, chitosan-acetic acid-aqueous solutionThe volume ratio is 2: 20: 3) reacting in water bath at 60 ℃ for 5 h; after the reaction is finished, repeatedly washing the product to be neutral by using distilled water, and then drying the precipitate at the constant temperature of 70 ℃ for 8 hours. Fully grinding, sieving with a 60-mesh standard sieve to obtain Fe3O4Modified diatomite.
(2) The design of a composite modified diatomite heavy metal passivator formula comprises the following steps:
preferably, the formula of the diatomite passivator is as follows: 30 parts of wheat straw charcoal powder, 25 parts of corn straw charcoal powder, 10 parts of rice straw charcoal powder and CaCO315 parts of modified diatomite, Mg (OH)210 parts of modified diatomite, Fe3O43 parts of modified diatomite.
(3) The straw charcoal powder in each embodiment of the invention is prepared by respectively removing impurities from wheat straws, corn straws and rice straws, cleaning, drying for 24 hours, crushing, putting into a vacuum heat treatment furnace, and pyrolyzing at 600 ℃ for 2 hours to finish the carbonization process of the straws. The invention provides an application method of a composite modified diatomite heavy metal passivator for reducing the content of biologically effective heavy metals in soil, which comprises the following steps:
firstly, soaking the soil at high temperature for 5 days, then draining the water, and insolating for 2 days. Secondly, uniformly scattering one or more of the piled and rotten rice straws, corn straws, wheat straws and rape straws in the field, wherein the scattering amount is 260 kg/mu. Thirdly, the composite modified diatomite heavy metal passivator prepared in the embodiment 2 is applied on the straws in a spreading amount of 200 kg/mu. And (3) ploughing the farmland by using a straw returning machine, finishing the working procedures of rotary tillage, straw biochar crushing, leveling and the like at one time, and uniformly mixing the piled straw, the composite modified diatomite heavy metal passivator and the soil, wherein the preferred deep ploughing depth is 0.3 m. Fourthly, covering a mulching film on the deeply ploughed soil, and exposing for 8 days; then, uncovering the mulching film to continue ventilation and insolation for 10 days; during the insolation period, the farmland soil is kept moist, but rain wash is avoided. Planting tomatoes in the farmland soil subjected to the in-situ passivation treatment. Sixthly, the planting management measures of the tomatoes are implemented according to the regulations in the technical regulation for producing pollution-free food tomato protection places of the agricultural industry standard of the people's republic of China (NY/T5007-2001).
2. Ex situ passivation treatment
Firstly, a rotary cultivator is selected to turn over the farmland, and the depth is 0.3 m. And secondly, planting tomatoes in the farmland after rotary tillage and leveling. And thirdly, the planting management measures of the tomatoes are implemented according to the regulations in the agricultural industry standard of the people's republic of China, namely the production technical regulation of pollution-free food tomato protection land (NY/T5007-2001).
3. Comparative example: the soil of the same 3 plots was subjected to a remediation test using 3 kinds of modified diatomaceous earth, respectively. The specific process is as follows.
The preparation method of the 3 composite modified diatomite heavy metal passivators comprises the following steps: example 2 "1. above the in situ passivation process of the present invention. "the step (1) is the same.
The application method of the 3 composite modified diatomite heavy metal passivators and the rice planting management measures are as follows: firstly, spreading the composite modified diatomite heavy metal passivator, wherein the application amount of the 3 composite modified diatomite heavy metal passivators is respectively as follows: CaCO3Modified diatomaceous earth 30 kg/acre, Mg (OH)2Modified diatomite 20 kg/mu, Fe3O410 kg/mu of modified diatomite. And secondly, ploughing the farmland to a depth of 0.3m, so that the soil can be fully mixed with the composite modified diatomite heavy metal passivator. And thirdly, the planting management measures of the tomatoes are implemented according to the regulations in the agricultural industry standard of the people's republic of China, namely the production technical regulation of pollution-free food tomato protection land (NY/T5007-2001).
4. Verification example: the method adopts a composite modified diatomite heavy metal passivator, namely: the same plots were subjected to a remediation test using a mixture of 3 modified diatomaceous earths. The specific process is as follows.
A preparation method of a novel composite modified diatomite heavy metal passivator comprises the following steps: example 2 "1. above the in situ passivation process of the present invention. "the step (1) is the same.
Composite modified diatomite heavy metal passivator: 3 kinds of compound modified diatomite heavy metal passivator mixture. CaCO3Modified diatomaceous earth, Mg (OH)2Modified diatomite, Fe3O4The mass ratio of the modified diatomite is 3: 2: 1.
an optimized passivant application method and tomato planting management measures are as follows: firstly, the compound modified diatomite heavy metal passivator is applied in a spreading amount of 60 kg/mu. And secondly, ploughing the farmland to a depth of 0.3m, so that the soil can be fully mixed with the composite modified diatomite heavy metal passivator. And thirdly, the planting management measures of the tomatoes are implemented according to the regulations in the agricultural industry standard of the people's republic of China, namely the production technical regulation of pollution-free food tomato protection land (NY/T5007-2001).
5. Soil remediation effect
The heavy metal content in the plot II soil was examined and the results are shown in table 10. The method disclosed by the invention has 41.40% of remediation efficiency on available Pb in soil. In contrast, the method shown in the verification example has the repair efficiency of 33.33% on the available Pb in the soil. The application method of the passivator provided by the invention can improve the passivation/fixation efficiency of the passivator on Pb in the polluted soil.
Compared with the Pb repair efficiency (33.33%) of the method shown in the example, the method has a higher Pb repair efficiency through CaCO3Modified diatomaceous earth, Mg (OH)2Modified diatomite, Fe3O4After the modified diatomite is passivated independently, the repair efficiency of the effective Pb in the soil is 8.60%, 9.13% and 9.68% respectively. To illustrate CaCO3Modified diatomaceous earth, Mg (OH)2Modified diatomaceous earth and Fe3O4After the modified diatomite is compounded, the repairing efficiency is higher than the sum of the repairing efficiencies of 3 diatomite passivators which are independently applied, and the 3 composite modified diatomite heavy metal passivators have a synergistic effect on the passivation/fixation of Pb in the polluted soil.
TABLE 10 change in the content of heavy metals Pb in soil II of the restored plot
The heavy metal content in the plot II soil was examined and the results are shown in table 11. The method disclosed by the invention has the remediation efficiency of 45.16% on the available Cd in the soil. In contrast, the method shown in the verification example has the remediation efficiency of 38.71% on the available Cd in the soil. The application method of the passivator provided by the invention can improve the passivating/fixing efficiency of the passivator on Cd in the polluted soil.
Compared with Cd repair efficiency (33.33%) of the method shown in the validation example, the method has the advantages of high Cd repair efficiency through CaCO3Modified diatomaceous earth, Mg (OH)2Modified diatomite, Fe3O4After the modified diatomite is subjected to single passivation treatment, the remediation efficiency of the soil effective state Cd is 12.9%, 6.45% and 9.68% respectively. To illustrate CaCO3Modified diatomaceous earth, Mg (OH)2Modified diatomaceous earth and Fe3O4After the modified diatomite is compounded, the repairing efficiency is higher than the sum of the repairing efficiencies of 3 diatomite passivators which are independently applied.
Table 11 change in heavy metal Cd content in soil II of plots after remediation
6. Further confirmation of the repair Effect
In order to further confirm the repairing effect of the invention and the technical advantages compared with the prior art, the method without repairing treatment and the method shown in the verification example are respectively selected on the same land, and the varieties are Anhui miscellaneous 21 and Su fen 8.
The statistics of tomato fruit character data on the plots which are not subjected to the repairing treatment and are subjected to the repairing treatment by the method shown in the validation example and are subjected to the repairing treatment by the method shown in the invention are carried out, and the results are shown in table 12, compared with the results which are not subjected to the in-situ passivation treatment, the fruit yield, the fruit hardness and the single fresh fruit quality of the planted Anhui miscellaneous 21 and Su pink 8 are obviously increased after the farmland soil is treated by the method shown in the validation example and the method shown in the invention.
TABLE 12 tomato fruit traits planted on in situ passivated plot II
And (5) measuring the content of heavy metal. The fruits of the tomatoes are harvested in the harvesting period of the tomatoes, the content of heavy metals in the tomatoes is measured, and the detection method is carried out according to the regulations in the national food safety standard determination of lead (GB5009.12-2017) and the national food safety standard determination of cadmium (GB 5009.15-2014).
As shown in Table 13, the Pb and Cd contents of Wanza 21 and Su powder No. 8 are respectively higher than the specified values (namely Pb is less than or equal to 0.1mg/kgFW and Cd is less than or equal to 0.05mg/kgFW) in the pollutant Limit in food (GB2762-2017) of the national standard, and after the in-situ passivation method disclosed by the invention is used for treatment, the Pb and Cd contents in the fruits of the 2 varieties are respectively lower than 0.1mg/kg and 0.05mg/kg and meet the requirements of the pollutant Limit in food (GB2762-2017) of the national standard. Compared with the method without in-situ passivation treatment, the method shown in the verification example remarkably reduces the Pb content in Anhui miscellaneous 21 and Su fen 8 fruits, and the reduction range is 52.63% and 50.00% respectively; the Cd contents in Anhui miscellaneous 21 and Su fen 8 fruits are obviously reduced by 68.75% and 53.84%, respectively. Compared with the method without in-situ passivation treatment, the method provided by the invention has the advantages that the Pb content in Anhui miscellaneous 21 and Su fen 8 fruits is obviously reduced, and the reduction ranges are 63.16% and 65.38% respectively; the Cd contents in Anhui miscellaneous 21 and Su fen 8 fruits are obviously reduced by 75.00% and 61.54%, respectively. The application method of the passivator provided by the invention can be used for effectively reducing the accumulation of heavy metals in tomato fruits.
TABLE 13 variation of heavy metals content in tomato fruits before and after in situ passivation treatment
As shown in table 14, compared with the farmland soil which is not subjected to in-situ passivation treatment, the farmland soil which is subjected to in-situ passivation treatment disclosed by the invention has the advantages that the soluble protein content, the soluble solid content, the dry matter content, the vitamin C content, the soluble sugar content and the sugar-acid ratio of the planted Anhui miscellaneous 21 and Su powder 8 fruits are obviously increased, and the tomato fruit quality is obviously improved.
TABLE 14 tomato fruit quality planted on in situ passivated plot II
The beneficial effect that this embodiment possesses is: the prepared composite modified diatomite heavy metal passivator has an obvious effect of passivating heavy metals, and the adopted raw materials do not cause secondary pollution to soil; by utilizing the formula of the heavy metal passivator and the application method of the passivator, the repaired soil can better meet the growth requirement of the tomatoes, the accumulation amount of heavy metals in the tomato fruits is reduced, and the quality of the tomatoes is improved.
Example 3
And (4) selecting a target planting land (namely the heavy metal polluted soil to be repaired). The soil heavy metal content was measured, and the results are shown in table 15. According to the national standard of the people's republic of China, namely the soil environmental quality standard (GB15618-1995), the national standard of the people's republic of China, namely the safety threshold of cadmium, lead, chromium, mercury and arsenic in dry land soil for planting rhizome vegetables (GB/T36783-2018) and the technical regulation of the national agricultural product producing land soil heavy metal safety assessment (2015), the heavy metal risk grade of the soil of the selected crop planting land block is moderate risk (2 & lt Pi & lt & lt3 & gt, and 2 & lt Pimax & lt 3 & gt).
TABLE 15 soil heavy metal content of sampled plot III
1. The in-situ passivation method of the invention
(1) A preparation method of a modified diatomite heavy metal passivator comprises the following steps:
CaCO3preparing modified diatomite:
mixing diatomite and hydrochloric acid aqueous solution with the concentration of 1.5mol/L uniformly according to the solid-to-liquid ratio of 1g/6mL, placing the mixture in an ultrasonic dispersion instrument, dispersing for 45min, filtering precipitates, and repeatedly washing a product by using ethanol and deionized water until the pH value is neutral. Drying the precipitate to constant weight, and sieving with a 60-mesh standard sieve to obtain pretreated diatomite.
② according to the solid-to-liquid ratio of 1g/8mL, the pretreated diatomite and Na with the concentration of 0.5mol/L2CO3Mixing the aqueous solution evenly, oscillating for 1.5h at 26 ℃, and adding 4mol/L CaCl2Aqueous solution (Na)2CO3Aqueous solution with CaCl2The volume ratio of the aqueous solution is 7:1), shaking at constant temperature of 30 ℃ for 30min, and removing the supernatant. Washing the precipitate with distilled water until the filtrate is neutral, oven drying at 105 deg.C, grinding, and sieving with 200 mesh standard sieve. To obtain CaCO3Modified diatomite.
Mg(OH)2Preparing modified diatomite:
putting diatomite raw soil into a muffle furnace, and roasting for 2.5 hours at 450 ℃. Meanwhile, putting the magnesium chloride into a constant-temperature drying oven, and drying for 24 hours at 100 ℃ for later use.
② weighing the roasted diatomite, the dried magnesium chloride and the sodium hydroxide according to the mass ratio of 1:1: 4/7. Placing diatomaceous earth and magnesium chloride into the same mortar, and fully grinding for 7 min; adding sodium hydroxide solid into a diatomite-magnesium chloride reaction system, grinding until yellow hard blocks are generated, and continuing grinding until the yellow hard blocks disappear; after leaving the mixture in air for 4 hours, it was washed with distilled water and the mixture was filtered. After the filtration is finished, the precipitate is dried for 10 hours at the constant temperature of 110 ℃, fully ground and sieved by a standard sieve of 200 meshes. Obtaining Mg (OH)2Modified diatomite.
Fe3O4Preparing modified diatomite:
putting diatomite raw soil into a muffle furnace, roasting for 4 hours at 450 ℃, grinding and sieving by a 60-mesh standard sieve for later use.
And secondly, uniformly mixing the pretreated diatomite with distilled water according to the solid-liquid ratio of 1g/10mL to obtain diatomite suspension. According to the solid-to-liquid ratio of 1g/45mLFe3O4Dissolving in distilled water, and ultrasonic dispersing at 28kHz for 25min to obtain Fe3O4An aqueous solution. 1g of chitosan (degree of deacetylation: 85%) was dissolved in 400mL of 1% aqueous acetic acid solution, and after complete dissolution with stirring, the pH was adjusted to 6 to obtain a chitosan-acetic acid-aqueous solution.
③ Fe3O4Pouring the aqueous solution into the diatomite suspension, stirring uniformly, adding the chitosan-acetic acid-aqueous solution, (Fe)3O4The volume ratio of the aqueous solution to the diatomite suspension to the chitosan-acetic acid-aqueous solution is 2: 20: 3) reacting in water bath at 70 ℃ for 3 h; after the reaction is finished, repeatedly washing the product to be neutral by using distilled water, and then drying the product at the constant temperature of 70 ℃ for 10 hours. Fully grinding, sieving with a 60-mesh standard sieve to obtain Fe3O4Modified diatomite.
(2) The design of a composite modified diatomite heavy metal passivator formula comprises the following steps:
preferably, the formula of the diatomite passivator is as follows: 20 parts of wheat straw charcoal powder, 15 parts of rape straw charcoal powder, 30 parts of corn straw charcoal powder, 15 parts of rice straw charcoal powder and CaCO3Modified diatomaceous earth 20 parts, Mg (OH)28 parts of modified diatomite, Fe3O42 parts of modified diatomite.
The straw charcoal powder in each embodiment of the invention is prepared by respectively removing impurities from wheat straws, rape straws and corn straws, cleaning, drying for 24 hours, crushing, putting into a vacuum heat treatment furnace, and pyrolyzing at 450 ℃ for 4 hours to finish the carbonization process of the straws.
(3) The invention provides an application method of a composite modified diatomite heavy metal passivator for reducing the content of biologically effective heavy metals in soil, which comprises the following steps:
firstly, soaking the soil at high temperature for 4 days, then draining the water, and insolating for 3 days. Secondly, uniformly scattering one or more of the piled and rotten rice straws, corn straws, wheat straws and rape straws in the field, wherein the scattering amount is 110 kg/mu. Thirdly, the composite modified diatomite heavy metal passivator prepared in the embodiment 3 is applied on the straws in a spreading amount of 150 kg/mu. And (3) ploughing the farmland by using a straw returning machine, finishing the working procedures of rotary tillage, straw biochar crushing, leveling and the like at one time, and uniformly mixing the piled straw, the composite modified diatomite heavy metal passivator and the soil, wherein the preferred deep ploughing depth is 0.4 m. Fourthly, covering a mulching film on the deeply ploughed soil, and exposing for 10 days; then, uncovering the mulching film to continue ventilation and insolation for 5 days; during the insolation period, the soil is kept moist, but rain wash is avoided. Fifthly, planting ginger on the farmland soil subjected to in-situ passivation treatment. Sixthly, the planting management measures of the ginger are executed according to the regulation of a national standard guiding technical document of ginger production (GB/Z26584-2011) of the people's republic of China.
2. Ex situ passivation treatment
Firstly, a rotary cultivator is selected to turn over the farmland, and the turning depth is 0.4 m. And secondly, planting ginger in the ploughed and leveled farmland. And thirdly, the planting management measures of the ginger are executed according to the regulations in the national standard guiding technical document of ginger production (GB/Z26584-2011) of the people's republic of China.
3. Comparative example: the soil of the same 3 plots was subjected to a remediation test using 3 kinds of modified diatomaceous earth, respectively. The specific process is as follows.
The preparation method of the 3 composite modified diatomite heavy metal passivators comprises the following steps: example 3 "1. above the in situ passivation process of the present invention. "the step (1) is the same.
The application method of the 3 composite modified diatomite heavy metal passivators and the rice planting management measures are as follows: firstly, spreading the composite modified diatomite heavy metal passivator, wherein the application amount of the 3 composite modified diatomite heavy metal passivators is respectively as follows: CaCO3Modified diatomaceous earth 22.5 kg/acre, Mg (OH)212 kg/mu of modified diatomite and Fe3O43 kg/mu of modified diatomite. And secondly, ploughing the farmland to a depth of 0.4m, so that the soil can be fully mixed with the composite modified diatomite heavy metal passivator. And thirdly, the planting management measures of the ginger are executed according to the regulations in the national standard guiding technical document of ginger production (GB/Z26584-2011) of the people's republic of China.
4. Verification example: the method adopts a composite modified diatomite heavy metal passivator, namely: the same plots were subjected to a remediation test using a mixture of 3 modified diatomaceous earths. The specific process is as follows.
A preparation method of a novel composite modified diatomite heavy metal passivator comprises the following steps: example 3 "1. above the in situ passivation process of the present invention. "the step (1) is the same.
Composite modified diatomite heavy metal passivator: 3 kinds of compound modified diatomite heavy metal passivator mixture. CaCO3Modified diatomaceous earth, Mg (OH)2Modified diatomite, Fe3O4The mass ratio of the modified diatomite is 15: 8: 2.
an optimized passivant application method and rice planting management measures are as follows: firstly, the compound modified diatomite heavy metal passivator is applied in a spreading amount of 37.5 kg/mu. And secondly, ploughing the farmland to a depth of 0.4m, so that the soil can be fully mixed with the composite modified diatomite heavy metal passivator. And thirdly, the planting management measures of the ginger are executed according to the regulations in the national standard guiding technical document of ginger production (GB/Z26584-2011) of the people's republic of China.
5. Soil remediation effect
The heavy metal content in the plot III soil was examined and the results are shown in table 16. The method disclosed by the invention has the efficiency of repairing the available Pb in the soil of 50.54%. In contrast, the method shown in the verification example has the repair efficiency of 41.94% on the available Pb in the soil. The application method of the passivator provided by the invention can improve the passivation/fixation efficiency of the passivator on Pb in the polluted soil.
Compared with the Pb repair efficiency (41.94%) of the method shown in the verification example, the method has the advantages of high Pb repair efficiency through CaCO3Modified diatomaceous earth, Mg (OH)2Modified diatomite, Fe3O4After the modified diatomite is passivated independently, the repair efficiency of the effective Pb in the soil is 11.02%, 7.80% and 14.24% respectively. To illustrate CaCO3Modified diatomaceous earth, Mg (OH)2Modified diatomaceous earth and Fe3O4After the modified diatomite is compounded, the repairing efficiency is higher than that of 3 kinds of diatomite which are independently appliedSum of the repair efficiency of the agent.
TABLE 16 Change in the content of heavy metals Pb in soil III of the restored plot
The heavy metal content in the plot III soil was examined and the results are shown in table 17. The method disclosed by the invention has the remediation efficiency of 52.63% on the available Cd in the soil. In contrast, the method shown in the verification example has the remediation efficiency of 31.58% on the available Cd in the soil. The application method of the passivator provided by the invention can improve the passivating/fixing efficiency of the passivator on Cd in the polluted soil.
Compared with Cd repair efficiency (31.58%) of the method shown in the verification example, the method has the advantages of high Cd repair efficiency through CaCO3Modified diatomaceous earth, Mg (OH)2Modified diatomite, Fe3O4After the modified diatomite is subjected to single passivation treatment, the remediation efficiency of the soil effective state Cd is 10.53%, 15.79% and 10.53% respectively. To illustrate CaCO3Modified diatomaceous earth, Mg (OH)2Modified diatomaceous earth and Fe3O4After the modified diatomite is compounded, the repairing efficiency is higher than the sum of the repairing efficiencies of 3 diatomite passivators which are independently applied.
Table 17 content change of heavy metal Cd in soil III of plot after remediation
The heavy metal content of the plot III soil was examined and the results are shown in table 18. The repair efficiency of the method disclosed by the invention on the As in the effective state in the soil is 48.74%. In contrast, the method shown in the verification example has the repair efficiency of 27.36% on the As in the available state in the soil. The application method of the passivator provided by the invention can improve the passivation/fixation efficiency of the passivator on As in the polluted soil.
As repair efficiency (27.36%) by CaCO As compared to that of the method shown in the test example3Modified siliconAlgae soil, Mg (OH)2Modified diatomite, Fe3O4After the modified diatomite is passivated independently, the repair efficiency of the effective As of the soil is 7.59 percent, 8.28 percent and 8.97 percent respectively. To illustrate CaCO3Modified diatomaceous earth, Mg (OH)2Modified diatomaceous earth and Fe3O4After the modified diatomite is compounded, the repairing efficiency is higher than the sum of the repairing efficiencies of 3 diatomite passivators which are independently applied.
TABLE 18 Change in the content of As in soil of plot III after remediation
6. Further confirmation of the repair Effect
In order to further confirm the repairing effect of the method and the technical advantages of the method in the invention compared with the prior art, ginger is planted in the plot which is not repaired and is repaired by the method shown in the verification example and is repaired by the method shown in the invention on the same plot, and the variety is the holy white ginger.
The statistics of the ginger character data of the plot which is not repaired and is repaired by the method shown in the comparative example and repaired by the method shown in the invention are carried out, and the results are shown in table 19.
TABLE 19 ginger traits planted on in situ passivated plots III
And (5) measuring the content of heavy metal. Fruits of the ginger are harvested in the harvesting period of the ginger, the heavy metal content of the ginger is measured, and the detection method is carried out according to the regulations in the national food safety standard determination of lead (GB5009.12-2010), the national food safety standard determination of cadmium (GB5009.15-2014) and the national food safety standard determination of total arsenic and inorganic arsenic (GB 5009.11-2014).
As shown in Table 20, the contents of Pb, Cd and As in the ginger are respectively higher than the specified values in the national standard pollutant Limit in food (GB2762-2017) without in-situ passivation treatment (namely Pb is less than or equal to 0.1mg/kgFW, Cd is less than or equal to 0.05mg/kgFW and As is less than or equal to 0.5mg/kgFW), and after the treatment by the method shown in the verification example and the in-situ passivation method shown in the invention, the contents of Pb, Cd and As in the ginger are respectively lower than 0.1mg/kg, 0.05mg/kg and 0.5mg/kg, which meets the requirements of the national standard pollutant Limit in food (GB 2762-2017). Compared with the method without in-situ passivation treatment, the method shown in the verification example reduces the contents of Pb, Cd and As of the ginger, and the reduction ranges are 30.77%, 44.44% and 26.15% respectively; the method provided by the invention obviously reduces the Pb, Cd and As contents of the ginger, and the reduction ranges are 46.15%, 55.56% and 43.08% respectively. The application method of the passivator provided by the invention can be used for effectively reducing the heavy metal accumulation in the ginger.
TABLE 20 content variation of heavy metals in ginger before and after in situ passivation treatment
As shown in table 21, compared with the farmland soil which is not subjected to the in-situ passivation treatment, the farmland soil which is subjected to the in-situ passivation treatment of the invention has the advantages that the soluble sugar content, the soluble protein content and the vitamin C content of the planted ginger are obviously increased, the crude fiber content is reduced, and the ginger quality is obviously improved.
TABLE 21 quality of ginger planted on in situ passivated plots III
The beneficial effect that this embodiment possesses is: the prepared composite modified diatomite heavy metal passivator has an obvious effect of passivating heavy metals, and the adopted raw materials do not cause secondary pollution to soil; by utilizing the heavy metal passivator formula and the passivator application method provided by the invention, the repaired soil can better meet the growth requirement of the ginger, the accumulation amount of heavy metals in the ginger is reduced, and the quality of the ginger is improved.
It is noted that, in this document, relational terms such as first and second, and the like, if any, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (3)
1. The composite modified diatomite heavy metal passivator is characterized by being prepared from the following raw materials in parts by mass: 20-115 parts of straw charcoal powder and CaCO310-20 parts of modified diatomite, Mg (OH)25-10 parts of modified diatomite and Fe3O42-5 parts of modified diatomite;
the straw charcoal powder is prepared from the following raw materials in parts by weight: 0-30 parts of wheat straw charcoal powder, 0-35 parts of rape straw charcoal powder, 10-30 parts of corn charcoal straw charcoal powder and 10-20 parts of rice charcoal straw charcoal powder;
the CaCO3The modified diatomite is prepared by the following steps:
(1) mixing diatomite and hydrochloric acid aqueous solution with the concentration of 1mol/L-2mol/L according to the solid-to-liquid ratio of 1g/5mL-1g/8mL, ultrasonically dispersing for 30-60min, washing the diatomite with ethanol and deionized water until the pH value of filtrate is neutral, drying to constant weight, and sieving to obtain pretreated diatomite;
(2) according to the solid-to-liquid ratio of 1g/5mL-1g/10mL, the pretreated diatomite and Na with the concentration of 0.5mol/L2CO3Mixing the aqueous solutions, oscillating at constant temperature of 25-30 ℃, and adding 4mol/L CaCl2Oscillating the aqueous solution at constant temperature for 30min, washing the product with distilled water until the filtrate is neutral, oven drying at constant temperature of 105 deg.C, grinding, and sieving with 200 mesh standard sieve to obtain CaCO3Modified diatomite;
the Mg (OH)2The modified diatomite is prepared by the following steps:
(1) roasting the diatomite for 2-3h at 450 ℃ to obtain roasted diatomite;
(2) drying magnesium chloride at constant temperature for later use;
(3) weighing roasted diatomite, dried magnesium chloride and sodium hydroxide according to the mass ratio of 1:1: 1/2-2/3; firstly, grinding the diatomite and the magnesium chloride together for 5-10 min; adding sodium hydroxide solid into the reaction system, grinding until the reaction is finished, standing the mixed product in the air for 3-5h, repeatedly washing with distilled water, filtering, drying the mixed product at the constant temperature of 110 ℃ for 9-12h, grinding, and sieving with a 200-mesh standard sieve to obtain Mg (OH)2Modified diatomite;
said Fe3O4The modified diatomite is prepared by the following steps:
(1) roasting diatomite at 450 ℃ for 2-4h, grinding and sieving by a 60-mesh standard sieve to obtain pre-roasted and sieved diatomite;
(2) mixing pre-calcined and sieved diatomite with distilled water according to the solid-to-liquid ratio of 1g/10mL-1g/15mL to obtain diatomite suspension;
according to the solid-to-liquid ratio of 1g/40mL-1g/50mL, adding Fe3O4Dissolving in distilled water to obtain Fe3O4An aqueous solution;
dissolving chitosan in 1% acetic acid water solution according to the solid-to-liquid ratio of 1g/400mL, and adjusting the pH value to 6 after completely stirring and dissolving;
(3) mixing the Fe subjected to ultrasonic treatment3O4Pouring the aqueous solution into the diatomite suspension, stirring, adding the chitosan-acetic acid-aqueous solution, and reacting in a water bath at 60-70 ℃ for 3-5 h; after the reaction is finished, washing the precipitate with distilled water to be neutral, drying the precipitate at the constant temperature of 70 ℃ for 8-10h, grinding the precipitate, and sieving the precipitate with a 60-mesh standard sieve to obtain Fe3O4Modified diatomite.
2. A method for applying the composite modified diatomite heavy metal passivator as claimed in claim 1 to the farmland of a dry crop, which comprises the following steps:
(1) selecting the heavy metal risk grade of the soil of the crop planting plot as low risk, wherein Pi is more than 1 and less than or equal to 2, Pimax is more than 1 and less than or equal to 2; or, moderate risk, wherein Pi is greater than 2 and less than or equal to 3, Pimax is greater than 2 and less than or equal to 3;
(2) soaking the soil at high temperature for 3-5 days, draining the water, and insolating for 2-3 days;
(3) when deeply ploughing a polluted farmland, uniformly mixing straws, passivation materials and soil, wherein the addition amount of the straws is 500 kg/mu, and the addition amount of the composite modified diatomite heavy metal passivator is 200 kg/mu;
(4) covering a mulching film on the deeply ploughed soil, and insolating for 5-10 days; then uncovering the mulching film for continuous ventilation and insolation for 5-10 days; rain wash is avoided during insolation;
(5) and planting crops on the farmland soil subjected to the in-situ passivation treatment.
3. The method for applying the composite modified diatomite heavy metal passivator as claimed in claim 1 to the paddy field, which is characterized by comprising the following steps:
(1) selecting the heavy metal risk grade of the paddy field as low risk, wherein Pi is more than 1 and less than or equal to 2, Pimax is more than 1 and less than or equal to 2; or, a moderate risk, wherein, Pi is more than 2 and less than or equal to 3, Pimax is more than 2 and less than or equal to 3;
(2) irrigating and soaking the soil for 12h or more, and draining water when the soil is soft and the depth of mud feet is 0.1-0.2 m;
(3) uniformly spreading the rice straws in the field, wherein the spreading amount is 200-350 kg/mu; spreading the composite modified diatomite heavy metal passivator on the rice straws at a spreading amount of 100-200 kg/mu;
(4) ploughing a polluted paddy field;
(5) irrigating water in the deeply ploughed paddy field to a depth of 1-3cm, maintaining the soaking state of the paddy field for 15-20 days, and avoiding rain wash;
(6) stopping adding irrigation water into the paddy field when the soaking period is nearly finished, naturally evaporating a surface water layer in the paddy field to dryness, and maintaining the wet state of the paddy field soil;
(7) rice seedlings are planted in the paddy field soil after the in-situ passivation treatment.
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| CN112029504B (en) * | 2020-09-02 | 2021-08-10 | 中冶一局环境科技有限公司 | Modification method of porous substrate, modified porous substrate prepared by modification method, metal passivator containing modified porous substrate and application of metal passivator |
| CN113621383A (en) * | 2021-09-09 | 2021-11-09 | 安徽省农业科学院土壤肥料研究所 | Acidic soil conditioner and preparation and application methods thereof |
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