CN114276815A - Preparation method of modified fly ash, modified fly ash prepared by preparation method and application of modified fly ash - Google Patents
Preparation method of modified fly ash, modified fly ash prepared by preparation method and application of modified fly ash Download PDFInfo
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Abstract
The invention provides a preparation method of modified fly ash, the modified fly ash prepared by the method and application of the modified fly ash, wherein the preparation method comprises the following steps: sequentially carrying out first classified screening, magnetic separation, second classified screening and acid method modification on the fly ash to obtain the modified fly ash. The modified fly ash disclosed by the invention is low in heavy metal content and has extremely strong adsorption and pH regulation capabilities. The invention also provides a soil conditioner which comprises the modified fly ash. The soil conditioner prepared by the invention can reduce the salt alkalinity of soil, increase the organic matter content and soil porosity in the soil, improve the soil quality and has wide application prospect in the aspect of saline-alkali soil improvement. The invention takes the industrial waste fly ash as the raw material, solves the problems of land occupation and possible environmental pollution caused by fly ash accumulation, realizes waste utilization, and has important significance for improving agricultural production and the living standard of people.
Description
Technical Field
The invention belongs to the technical field of comprehensive utilization of solid waste fly ash, and particularly relates to a preparation method of modified fly ash, the prepared modified fly ash and application thereof.
Background
Saline-alkali soil is a widely distributed soil type, has 9.5 hundred million hectares of saline-alkali soil in the world, occupies about 10 percent of the total land area, and is widely distributed in more than 100 countries and regions. Saline-alkali soil contains excessive saline-alkali ions, so that the soil structure is lagged, the air permeability is poor, the soil temperature rises slowly, the biological activity in the soil is poor, the nutrient absorption is slow, the permeability coefficient is low, the physiological disorder of plants is caused, the nutritional status of the plants is influenced, and the growth of the plants is threatened.
Saline-alkali soil is an important factor for restricting agricultural development, and the yield and quality of crops are seriously influenced. At present, there are many reports on the improvement of saline-alkali soil. Zhang Yalan et al propose to use cotton stalk to prepare wood vinegar, and to improve saline-alkali soil after dilution. The results show that the pyroligneous acid has the effect of improving the pH, the salinity, the sodium absorption ratio and the alkalization degree of the saline-alkali soil and has certain sterilization effect. However, the method does not supplement organic fertilizer to the soil, can not further promote the growth of crops, has no selectivity on the sterilization effect of the wood vinegar, can remove beneficial bacteria in the soil, and is not beneficial to further improvement of the soil (see Zhang Yalan, etc., research on the saline-alkali soil improvement effect of the wood vinegar [ J ], Chinese academy of agricultural chemistry, 2014, 35(6), 292-295.).
CN110078564A discloses a compound microorganism coated long-acting saline-alkali soil improving fertilizer and a preparation method thereof, the compound microorganism coated long-acting saline-alkali soil improving fertilizer comprises saline-alkali soil improving materials, coating materials, a compound microorganism bacterial agent, a nitrogen fertilizer and essential medium and trace elements of plants, the modifying materials are combined with microorganisms, the saline-alkali soil of the soil can be improved, meanwhile, organic matters and beneficial bacteria in the soil are increased, and crops can be helped to grow better. However, the raw material components of the method are all powdery, can only improve factors such as pH, alkalinity and the like of the saline-alkali soil, cannot loosen the soil, solves the problems of soil hardening and low oxygen content, has high production cost, and is not suitable for large-scale use.
CN110105965A discloses a mixed type saline-alkali soil dry land soil conditioner and a preparation method thereof, wherein the conditioner consists of granules and a microbial agent, and the granules comprise a blocking agent, an acid regulator and an organic fertilizer; the blocking agent comprises fly ash and zeolite powder; the acidity regulator comprises hydrolytic polymaleic anhydride, phosphoric acid, oxalic acid, zinc sulfate and ammonium sulfate; the organic fertilizer comprises humic acid and fulvic acid. The method has the advantages that the acid regulator is added into the modifier, the functions of the microbial agent and the blocking agent are combined, the saline-alkali soil is well modified, the pH of the modified saline-alkali soil is reduced from 9.5 to 8.5, the salt content is reduced from 19.9 per mill to 2.4 per mill, the organic matter is increased from 3 per mill to 3.5 per mill, and the yield of the planted wheat is increased by 15%. However, the fly ash in the raw material of the blocking agent contains a large amount of heavy metals, the operation of removing the heavy metals is not performed before the blocking agent is used, the content of the heavy metals in the soil is overproof when the blocking agent is directly added into the soil, and the planted crops also contain a large amount of heavy metals, so that the blocking agent is not beneficial to the health.
The research on the saline-alkali soil improvement technology can not only relieve the problem of land salinization, but also has direct practical significance for agricultural development and improvement of the living standard of people. How to provide a method for improving saline-alkali soil, which can effectively improve the saline-alkali soil of the saline-alkali soil, increase organic matters in the soil, has low cost and does not cause secondary pollution to the soil, and has become a problem to be solved urgently.
Disclosure of Invention
Aiming at the defects and actual requirements of the prior art, the invention provides a preparation method of modified fly ash, the prepared modified fly ash and application thereof, wherein most heavy metals in the fly ash can be removed by carrying out twice classification screening and magnetic separation on the fly ash, and the particle structure of the fly ash is not damaged; the acid method is used for modification, partial impurities in the fly ash are removed, the adsorption capacity can be improved, and the pH value can be reduced. The soil conditioner using the modified fly ash as the main raw material can adjust the salt alkalinity of soil and adsorb salt ions and pollutants in the soil, and the components such as humic acid, excrement and the like in the soil can increase organic matters in the soil and promote the growth of crops, so that the soil conditioner has extremely high application value.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for preparing modified fly ash, comprising:
sequentially carrying out first classified screening, magnetic separation, second classified screening and acid method modification on the fly ash to obtain the modified fly ash.
In the present invention, theThe fly ash is fine ash captured from flue gas generated after coal combustion, and the main component of the fly ash is SiO2、Al2O3、Na2O、K2O、CaO、MgO、Fe2O3、TiO2And unburned carbon. The fly ash is one of industrial solid wastes with the largest discharge amount in China, a large amount of land area is occupied by piling, the air, water and soil are seriously polluted by flying dust, and heavy metals in the fly ash can cause harm to organisms. The coal ash is prepared into the soil conditioner by carrying out classification screening, magnetic separation and acid method modification on the coal ash, so that the waste is utilized, and the soil conditioner has a wide application prospect.
In the invention, the first classifying and screening, the magnetic classifying and the second classifying and screening are physical classifying processes, so that the particle structure of the fly ash is not damaged, and the comprehensive utilization of the screened fly ash is not influenced. The two grading screens and the magnetic screen are combined, so that most heavy metals in the fly ash are removed.
Preferably, the preparation method comprises:
(1) performing primary classification screening on the fly ash to obtain coarse-grain fly ash and fine-grain fly ash, and collecting the fine-grain fly ash;
(2) carrying out magnetic separation on the fine-grained fly ash obtained in the step (1), and collecting non-magnetic fly ash;
(3) carrying out secondary classification screening on the nonmagnetic fly ash obtained in the step (2), and collecting coarse-grained ash;
(4) and (4) carrying out acid method modification on the coarse-grained ash obtained in the step (3) to obtain the modified fly ash.
Preferably, the classification equipment used in the first classification screening in step (1) comprises any one of a linear vibrating screen, a circular vibrating screen or an air classifier or a combination of at least two of the linear vibrating screen, the circular vibrating screen and the air classifier, for example, the combination can be a circular vibrating screen, an air classifier, a combination of a circular vibrating screen and an air classifier or a combination of a linear vibrating screen and a circular vibrating screen.
Preferably, the particle size of the first classifying screen in step (1) is 80-150 μm, such as 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, 145 μm or 150 μm.
In the invention, most of large-particle substances in the fly ash are unburned coal which contains a large amount of heavy metal substances, and the unburned coal is separated by primary classified screening, so that the unburned coal can be reused, the energy is saved, and a key effect on heavy metal removal of the fly ash is achieved.
Preferably, the magnetic separation equipment used in the magnetic separation in the step (2) is a magnetic separator.
Preferably, the magnetic field strength of the magnetic separation in the step (2) is 480-1600 kA/m, such as 480kA/m, 500kA/m, 600kA/m, 700kA/m, 800kA/m, 900kA/m, 1000kA/m, 1100kA/m, 1200kA/m, 1300kA/m, 1400kA/m, 1500kA/m or 1600 kA/m.
In the invention, the magnetic particles in the fly ash have higher enrichment effect on heavy metal elements, the magnetic particles are separated out through magnetic separation, the heavy metal elements in the fly ash are removed again, and the possibility of secondary pollution to the environment caused by comprehensive utilization of the fly ash is reduced.
Preferably, the classifying equipment used in the second classifying screen in step (3) comprises any one or a combination of at least two of a linear vibrating screen, a circular vibrating screen and an air classifier, and for example, the classifying equipment can be a linear vibrating screen, an air classifier, a combination of a linear vibrating screen and a circular vibrating screen or a combination of a linear vibrating screen, a circular vibrating screen and an air classifier.
Preferably, the particle size of the second classifying screen in step (3) is 5 to 35 μm, for example, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm or 35 μm.
According to the invention, heavy metals are enriched in the fine-particle fly ash with the particle size of less than 35 μm, and the non-magnetic fly ash obtained after magnetic separation is subjected to secondary classification screening to separate out fine-particle ash, so that the heavy metals in the fly ash can be further removed, and coarse-particle ash with very low heavy metal content is obtained, thereby facilitating comprehensive utilization and changing waste into valuable.
Preferably, the acid-process modification of step (4) comprises: and (4) dipping and stirring the coarse-grained ash obtained in the step (3) in an acid solution, and performing solid-liquid separation to obtain the modified fly ash.
In the invention, the fly ash is soaked and stirred in an acid solution, on one hand, partial impurities and heavy metals in the fly ash are removed, and on the other hand, partial skeleton alumina pore channel structures in fly ash particles are rearranged to prepare the modified fly ash. Compared with the fly ash, the modified fly ash generates a new mesoporous structure, the pore volume is increased, the adsorption capacity is improved, the adsorption capacity to carbonate, bicarbonate and other alkaline ions is obviously enhanced, and the pH adjusting effect is better.
Preferably, the molar concentration of the acid solution is 0.1 to 3mol/L, and may be, for example, 0.1mol/L, 0.2mol/L, 0.3mol/L, 0.4mol/L, 0.5mol/L, 0.6mol/L, 0.7mol/L, 0.8mol/L, 0.9mol/L, 1mol/L, 1.2mol/L, 1.4mol/L, 1.6mol/L, 1.8mol/L, 2mol/L, 2.2mol/L, 2.4mol/L, 2.6mol/L, 2.8mol/L, or 3 mol/L.
In the invention, the concentration of the acid solution is controlled to be 0.1-3 mol/L, the damage to the skeleton structure of the fly ash is very small, the soil can be loosened, the volume weight of the soil is reduced, and the phenomenon of large-area collapse cannot occur.
Preferably, the acid solution comprises any one of sulfuric acid, phosphoric acid, acetic acid, citric acid, oxalic acid or hydrochloric acid or a combination of at least two of them, and may be, for example, sulfuric acid, phosphoric acid, oxalic acid, a combination of acetic acid and oxalic acid, a combination of phosphoric acid and hydrochloric acid or a combination of citric acid, oxalic acid and hydrochloric acid.
Preferably, the temperature of the dipping and stirring is 20 to 90 ℃, for example, 20 ℃, 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃ or 90 ℃.
Preferably, the time for the immersion stirring is 0.5 to 4 hours, for example, 0.5 hour, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours.
Preferably, the rotation speed of the dipping and stirring is 10 to 700rpm, for example, 10rpm, 20rpm, 30rpm, 40rpm, 50rpm, 60rpm, 70rpm, 80rpm, 90rpm, 100rpm, 150rpm, 200rpm, 250rpm, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, 550rpm, 600rpm, 650rpm or 700rpm may be used.
Preferably, the method further comprises a drying step after the solid-liquid separation.
Preferably, the drying temperature is 50-150 ℃, for example, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃ or 150 ℃.
Preferably, the drying time is 1-24 h, for example, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h or 24 h.
In the invention, the modified fly ash soaked in the acid solution is not neutralized or washed, and the hydrogen ions contained in the modified fly ash can increase the neutralizing capacity of the modified fly ash to alkaline ions, so that the pH adjusting capacity is further enhanced.
As a preferred technical scheme, the preparation method of the modified fly ash provided by the invention specifically comprises the following steps:
(1) performing primary classification screening on the fly ash by using classification equipment with a screening particle size of 80-150 mu m to obtain coarse-grain fly ash and fine-grain fly ash, and collecting the fine-grain fly ash;
(2) adding the fine-grained fly ash obtained in the step (1) into a magnetic separator, carrying out magnetic separation at 480-1600 kA/m, and collecting non-magnetic fly ash;
(3) performing secondary classification screening on the nonmagnetic fly ash obtained in the step (2) by using classification equipment with the screening particle size of 5-35 mu m, and collecting coarse particle ash;
(4) adding the coarse-grained ash obtained in the step (3) into 0.1-3 mol/L acid solution, dipping and stirring for 0.5-4 h at the temperature of 20-90 ℃ and the rotating speed of 10-700 rpm, then carrying out solid-liquid separation, and drying for 1-24 h at the temperature of 50-150 ℃ to obtain the modified fly ash.
In the invention, unburned coal in the fly ash is removed by primary classified screening, magnetic particles rich in heavy metal elements in the fly ash are removed by magnetic separation, fine particle ash with high heavy metal content is removed by secondary classified screening, and fly ash with low heavy metal content and a pore structure is screened out by three times of physical sorting for subsequent comprehensive utilization; the modified fly ash is prepared by acid modification, a new mesoporous structure is formed, and the adsorption capacity is enhanced.
In a second aspect, the invention provides a modified fly ash prepared by the preparation method of the first aspect.
According to the invention, most of heavy metal ions such as cadmium, chromium, arsenic, mercury, lead and the like in the fly ash can be removed through twice grading screening and magnetic separation, the pore volume can be increased through acid method modification, and the prepared modified fly ash has excellent capacity of adsorbing and adjusting the pH value and has extremely high application value.
In a third aspect, the invention provides a soil conditioner, wherein the raw material of the soil conditioner comprises the modified fly ash of the second aspect.
In the invention, the modified fly ash prepared by physical separation and acid method modification has excellent adsorption capacity, can adsorb saline alkali ions in soil and improve the saline alkali of the soil; the modified fly ash has larger holes, can loosen soil, reduce the volume weight of the soil, improve the dispersibility of clay soil, increase the oxygen content in the soil and is more beneficial to the growth of crops.
Preferably, the raw material of the soil conditioner further comprises any one of slag scraps, feces or humic acid or a combination of at least two of the slag scraps, the feces, the slag scraps and the humic acid, and can be a combination of the slag scraps, the feces and the humic acid or a combination of the slag scraps, the feces and the humic acid.
Preferably, the sawdust comprises any one of or a combination of at least two of wine lees, vinegar lees, oil lees or wood chips, and may be, for example, wine lees, oil lees, wood chips, a combination of wine lees and vinegar lees, a combination of vinegar lees and wood chips or a combination of vinegar lees, oil lees and wood chips.
Preferably, the manure comprises cow manure and/or sheep manure.
In the invention, the slag scraps and the excrement belong to acidic organic matters, which are beneficial to reducing the pH of soil, improving the dispersibility of soil clay grains, improving the soil structure, coordinating the water, fertilizer and gas heat of the soil, providing a large amount of nutrients and providing a better growth environment for planting crops.
In the invention, the humic acid contains medium and trace elements required by plants, can stimulate the growth of crops, improves the stress resistance of the crops and improves the quality of the crops; calcium ions contained in the humic acid can replace sodium ions, so that the alkalization degree of the soil is reduced, and the toxic effect of the sodium ions on plants is reduced; in addition, the organic colloid in the humic acid can form gel with calcium ions in the soil, so that the fertilizer and water retention capacity of the soil is improved, and the fertilizer efficiency is improved.
In the invention, the slag scraps, the excrement, the humic acid and the modified fly ash act together, so that the saline-alkali degree of the soil can be improved, meanwhile, nutrient organic matters are provided for plants, and the growth of the plants is further promoted.
Preferably, the mass percentage of the modified fly ash in the raw material of the soil conditioner is 30% to 90%, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90%.
Preferably, the percentage by mass of the lees in the raw material of the soil improvement agent is 0.1% to 30%, and may be, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%.
Preferably, the content of the vinegar residue in the raw material of the soil improvement agent is 0.1 to 20% by mass, and may be, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20% by mass.
Preferably, the oil cake may be 0.1% to 10% by mass, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% by mass of the raw material of the soil conditioner.
Preferably, the wood chips are 0.1% to 10% by mass of the raw material of the soil conditioner, and may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, for example.
Preferably, the mass percentage of the cow dung and/or sheep dung in the raw material of the soil conditioner is 0.1% to 20%, and may be, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%.
Preferably, the humic acid may be present in an amount of 0.1 to 40% by mass, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35% or 40% by mass of the raw material of the soil conditioner.
Preferably, the raw materials of the soil conditioner comprise, by mass, 30-90% of modified fly ash, 0.1-30% of wine residue, 0.1-20% of vinegar residue, 0.1-10% of oil residue, 0.1-10% of wood chips, 0.1-20% of cow dung and/or sheep dung and 0.1-40% of humic acid.
In a fourth aspect, the invention provides a use of the modified fly ash of the second aspect or the soil conditioner of the third aspect in saline-alkali soil improvement.
In the invention, the modified fly ash has extremely low heavy metal content and excellent adsorption and pH regulation capabilities; the soil conditioner takes the modified fly ash as a main component, humic acid, excrement and slag are added into the soil conditioner, the salt alkalinity of soil can be further adjusted, the soil structure can be improved, the organic matter of the soil can be increased, the growth of crops can be promoted, the microbial environment of the soil can be improved, and the soil can be further improved.
Compared with the prior art, the invention has the following beneficial effects:
(1) the method takes the industrial waste fly ash as a raw material, reduces the occupation of the fly ash accumulation on the land and possible pollution to the atmosphere, water and environment, changes waste into valuable, screens out unburned coal, magnetic particles, coarse particle ash and fine particle ash through three-step sorting treatment, wherein the unburned coal can be reused, the magnetic particles are iron-rich materials and can be used for recovering iron, the coarse particle ash can be used for preparing modified fly ash, and the fine particle ash can be used as an industrial cement production raw material, so that the full utilization of the fly ash is realized, and the method has direct practical significance for agricultural production and improvement of the standard of human life;
(2) according to the invention, through the first grading screening, the magnetic separation and the second grading screening, the removal rate of heavy metals such as cadmium, chromium, arsenic, mercury and lead can reach 30% -60%, the process is a physical process, the particle structure of the fly ash is not damaged, and the process is simple, efficient, energy-saving and environment-friendly; the fly ash particles are soaked in the acid solution with lower concentration, so that heavy metals can be further removed, part of the alumina framework is rearranged, the prepared modified fly ash has a new mesoporous structure, the adsorption capacity and the saline-alkali degree adjusting capacity are stronger, the skeleton structure of the fly ash cannot be damaged, the operation is simple and convenient, the cost is lower, and the wide application prospect is realized;
(3) the modified fly ash prepared by the invention has low heavy metal content, and cannot cause secondary pollution to the environment by comprehensive utilization; can adsorb saline alkali ions and other pollutants in the soil and reduce the saline alkali of the soil; the hole structure in the modified fly ash can also loosen soil, reduce the volume weight of the soil, improve the dispersibility of soil particles, improve the soil structure and coordinate the water, fertilizer and gas heat of the soil; the compound fertilizer is matched with slag scraps, excrement and humic acid, can further improve the salinity of soil, and simultaneously supplements organic substances, provides trace elements and nutrient substances for the growth of crops, promotes the growth, improves the quality of the crops, and has extremely high application value.
Detailed Description
To further illustrate the technical means and effects of the present invention, the present invention is further described with reference to the following examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention.
The examples do not show the specific techniques or conditions, according to the technical or conditions described in the literature in the field, or according to the product specifications. The reagents or apparatus used are conventional products commercially available from normal sources, not indicated by the manufacturer.
The materials such as fly ash, wine residue, vinegar residue, oil residue, wood chips, cow dung, sheep dung, humic acid and the like required by the invention can be obtained or purchased from corresponding production factories: for example, the fly ash used in the present invention is obtained from a power plant, and in the following examples, the fly ash is obtained from a power plant in Ningxia, and similarly, the fly ash may be obtained from a power plant in inner Mongolia or Shanxi;
the said lees, vinegar residues, oil residues and wood chips are also taken from the corresponding production plants, the lees, vinegar residues, oil residues and wood chips used in the following examples are taken from winery, vinegar plant, oil mill and wood plant of Ningxia respectively;
the cow dung and the sheep dung are taken from a farm, and the cow dung and the sheep dung used in the following examples are taken from a farm in inner Mongolia;
the humic acid was a humic acid commonly used in the art, and the humic acid used in the examples below was purchased from a humic acid plant of inner Mongolia.
Example 1
The embodiment provides a modified fly ash, and a preparation method of the modified fly ash comprises the following steps:
(1) performing primary classification screening on the fly ash by using a circular vibrating screen with the screening particle size of 80 mu m to obtain coarse-grain fly ash and fine-grain fly ash, and collecting the fine-grain fly ash;
(2) adding the fine-grained fly ash obtained in the step (1) into a magnetic separator, carrying out magnetic separation at 480kA/m, and collecting non-magnetic fly ash;
(3) performing secondary classification screening on the nonmagnetic fly ash obtained in the step (2) by using a linear vibrating screen with the screening particle size of 15 microns, and collecting coarse grained ash;
(4) and (4) adding the coarse-grained ash obtained in the step (3) into a 0.5mol/L citric acid solution, soaking and stirring for 3 hours at the rotating speed of 10rpm at the temperature of 55 ℃, performing solid-liquid separation, and drying for 24 hours at the temperature of 105 ℃ to obtain the modified fly ash.
The embodiment also provides a soil conditioner, and the soil conditioner comprises the raw materials of 80% of modified fly ash, 10% of wine residue, 5% of vinegar residue and 5% of sheep manure by mass percent.
And fully mixing the raw materials of the soil conditioner to prepare the soil conditioner.
Example 2
The embodiment provides a modified fly ash, and a preparation method of the modified fly ash comprises the following steps:
(1) performing primary classification screening on the fly ash by using an airflow classifier with the screening particle size of 120 mu m to obtain coarse-grained fly ash and fine-grained fly ash, and collecting the fine-grained fly ash;
(2) adding the fine-grained fly ash obtained in the step (1) into a magnetic separator, carrying out magnetic separation at 800kA/m, and collecting non-magnetic fly ash;
(3) performing secondary classification screening on the nonmagnetic fly ash obtained in the step (2) by using a circular vibrating screen with the screening particle size of 8 mu m, and collecting coarse grained ash;
(4) and (4) adding the coarse particle ash obtained in the step (3) into a mixed solution of citric acid with the final concentration of 0.6mol/L and sulfuric acid with the final concentration of 0.5mol/L, soaking and stirring for 2 hours at the rotation speed of 350rpm at the temperature of 50 ℃, performing solid-liquid separation, and drying for 20 hours at the temperature of 101 ℃ to obtain the modified fly ash.
The embodiment also provides a soil conditioner, and the soil conditioner comprises the raw materials of 55% of modified fly ash, 5% of wine residue, 10% of vinegar residue, 5% of oil residue, 5% of wood chips and 20% of sheep manure by mass percent.
And fully mixing the raw materials of the soil conditioner to prepare the soil conditioner.
Example 3
The embodiment provides a modified fly ash, and a preparation method of the modified fly ash comprises the following steps:
(1) performing primary classification screening on the fly ash by using a linear vibrating screen with the screening particle size of 150 mu m and an air flow classifier to obtain coarse-grained fly ash and fine-grained fly ash, and collecting the fine-grained fly ash;
(2) adding the fine-grained fly ash obtained in the step (1) into a magnetic separator, carrying out magnetic separation at 1600kA/m, and collecting non-magnetic fly ash;
(3) performing secondary classification screening on the nonmagnetic fly ash obtained in the step (2) by using an airflow classifier with the screening particle size of 5 microns, and collecting coarse-grained ash;
(4) and (4) adding the coarse-grained ash obtained in the step (3) into a mixed solution of citric acid with the final concentration of 0.7mol/L, acetic acid with the final concentration of 2mol/L and hydrochloric acid with the final concentration of 0.1mol/L, soaking and stirring for 3 hours at the rotating speed of 700rpm at the temperature of 60 ℃, carrying out solid-liquid separation, and drying for 16 hours at the temperature of 50 ℃ to obtain the modified fly ash.
The embodiment also provides a soil conditioner, and the soil conditioner comprises the raw materials of 50% of modified fly ash, 20% of vinegar residue, 10% of oil residue, 10% of wood chips and 10% of sheep manure by mass percent.
And fully mixing the raw materials of the soil conditioner to prepare the soil conditioner.
Example 4
The embodiment provides a modified fly ash, and a preparation method of the modified fly ash comprises the following steps:
(1) performing primary classification screening on the fly ash by using a linear vibrating screen with the screening particle size of 140 microns to obtain coarse-grained fly ash and fine-grained fly ash, and collecting the fine-grained fly ash;
(2) adding the fine-grained fly ash obtained in the step (1) into a magnetic separator, carrying out magnetic separation at 1000kA/m, and collecting non-magnetic fly ash;
(3) performing secondary classification screening on the nonmagnetic fly ash obtained in the step (2) by using an airflow classifier and a circular vibrating screen with the screening particle size of 35 mu m, and collecting coarse particle ash;
(4) and (4) adding the coarse grained ash obtained in the step (3) into a 3mol/L sulfuric acid solution, soaking and stirring for 0.5h at the temperature of 90 ℃ and the rotating speed of 100rpm, carrying out solid-liquid separation, and drying for 1h at the temperature of 150 ℃ to obtain the modified fly ash.
The embodiment also provides a soil conditioner, and the soil conditioner comprises the following raw materials, by mass, 30% of modified fly ash, 20% of cow dung, 30% of wine residue, 0.1% of humic acid, 0.1% of wood chips and 19.8% of vinegar residue.
And fully mixing the raw materials of the soil conditioner to prepare the soil conditioner.
Example 5
The embodiment provides a modified fly ash, and a preparation method of the modified fly ash comprises the following steps:
(1) performing primary classification screening on the fly ash by using an airflow classifier with the screening particle size of 100 mu m to obtain coarse-grained fly ash and fine-grained fly ash, and collecting the fine-grained fly ash;
(2) adding the fine-grained fly ash obtained in the step (1) into a magnetic separator, carrying out magnetic separation at 500kA/m, and collecting non-magnetic fly ash;
(3) performing secondary classification screening on the nonmagnetic fly ash obtained in the step (2) by using a linear vibrating screen and a circular vibrating screen with the screening particle size of 20 microns, and collecting coarse particle ash;
(4) and (4) adding the coarse particle ash obtained in the step (3) into a mixed solution of phosphoric acid with the final concentration of 1.5mol/L and oxalic acid with the final concentration of 0.7mol/L, soaking and stirring for 4 hours at the rotation speed of 500rpm at the temperature of 20 ℃, performing solid-liquid separation, and drying for 1 hour at the temperature of 125 ℃ to obtain the modified fly ash.
The embodiment also provides a soil conditioner, and the soil conditioner comprises the raw materials of, by mass, 50% of modified fly ash, 1% of humic acid, 0.1% of vinegar residue, 0.1% of oil residue, 2% of wood chips, 0.1% of sheep manure, 6.7% of cow manure and 40% of humic acid.
And fully mixing the raw materials of the soil conditioner to prepare the soil conditioner.
Example 6
The embodiment provides a modified fly ash, and a preparation method of the modified fly ash comprises the following steps:
(1) performing primary classification screening on the fly ash by using a linear vibration machine with the screening particle size of 95 microns to obtain coarse-grained fly ash and fine-grained fly ash, and collecting the fine-grained fly ash;
(2) adding the fine-grained fly ash obtained in the step (1) into a magnetic separator, carrying out magnetic separation at 750kA/m, and collecting non-magnetic fly ash;
(3) performing secondary classification screening on the nonmagnetic fly ash obtained in the step (2) by using an airflow classifier with the screening particle size of 28 microns, and collecting coarse particle ash;
(4) and (4) adding the coarse fly ash obtained in the step (3) into a mixed solution of sulfuric acid with the final concentration of 0.1mol/L and citric acid with the final concentration of 2.5mol/L, soaking and stirring for 2.5 hours at the rotation speed of 50rpm at the temperature of 50 ℃, performing solid-liquid separation, and drying for 5 hours at the temperature of 90 ℃ to obtain the modified fly ash.
The embodiment also provides a soil conditioner, and the soil conditioner comprises 90% of modified fly ash, 0.1% of wine residue, 1% of vinegar residue, 1% of oil residue, 2% of wood chip, 5.7% of sheep manure, 0.1% of cow manure and 0.1% of humic acid by mass.
And fully mixing the raw materials of the soil conditioner to prepare the soil conditioner.
Example 7
The embodiment provides a modified fly ash, and a preparation method of the modified fly ash comprises the following steps:
(1) performing primary classification screening on the fly ash by using an airflow classifier with a screening particle size of 105 mu m to obtain coarse-grained fly ash and fine-grained fly ash, and collecting the fine-grained fly ash;
(2) adding the fine-grained fly ash obtained in the step (1) into a magnetic separator, carrying out magnetic separation at 1600kA/m, and collecting non-magnetic fly ash;
(3) performing secondary classification screening on the nonmagnetic fly ash obtained in the step (2) by using an airflow classifier with the screening particle size of 15 mu m, and collecting coarse-grained ash;
(4) and (4) adding the coarse-grained ash obtained in the step (3) into a hydrochloric acid solution with the concentration of 0.7mol/L, soaking and stirring for 2 hours at the rotation speed of 400rpm at 70 ℃, carrying out solid-liquid separation, and drying for 24 hours at 100 ℃ to obtain the modified fly ash.
The embodiment also provides a soil conditioner, wherein the soil conditioner comprises 100% of modified fly ash by mass.
Example 8
The difference from the example 1 is only that the raw materials of the soil conditioner in the example comprise 20% of modified fly ash, 70% of wine residue, 5% of vinegar residue and 5% of sheep manure by mass percent, and the rest raw materials and the preparation method are the same as the example 1.
Example 9
The only difference from example 1 is that the first classification screening in the preparation of the modified fly ash in this example uses a circular vibrating screen with a screening particle size of 500 μm, and the rest of the raw materials and the preparation method are the same as in example 1.
Example 10
The difference from example 1 is only that the magnetic separation is carried out at 300kA/m in the preparation process of the modified fly ash in the example, and the rest of the raw materials and the preparation method are the same as those in example 1.
Example 11
The only difference from example 1 is that the second classification of the modified fly ash in this example was carried out using a linear vibrating screen having a screening particle size of 3 μm, and the rest of the raw materials and the preparation method were the same as in example 1.
Example 12
The difference from example 1 is only that in the preparation process of the modified fly ash in this example, 5mol/L citric acid solution is used in the acid method modification, and the rest of the raw materials and the preparation method are the same as example 1.
Comparative example 1
The only difference from example 1 is that the modified fly ash in this example was prepared without first classifying and screening, and the rest of the raw materials and preparation method were the same as example 1.
Comparative example 2
The only difference from example 1 is that the modified fly ash in this example is prepared without magnetic separation, and the rest of the raw materials and preparation method are the same as example 1.
Comparative example 3
The only difference from example 1 is that the modified fly ash in this example was prepared without secondary classification screening, and the rest of the raw materials and preparation method were the same as in example 1.
Comparative example 4
The only difference from example 1 is that the acid-method modification was not performed in the preparation of the modified fly ash in this example, and the rest of the raw materials and the preparation method are the same as example 1.
Comparative example 5
The difference from the example 1 is only that the raw materials of the soil conditioner in the example comprise 30% of the wine residue, 20% of the vinegar residue, 10% of the oil residue, 10% of the wood chips, 5% of the cow dung, 5% of the sheep dung and 20% of the humic acid by mass percent, and the rest raw materials and the preparation method are the same as the example 1.
Comparative example 6
In the comparative example, commercially available desulfurized gypsum was selected as the soil conditioner.
Determination of heavy Metal content
And respectively measuring the contents of cadmium, chromium, arsenic, mercury and lead by using an inductively coupled plasma mass spectrometer (ICP-MS), measuring the contents and mass changes of heavy metals before and after removal, and calculating the removal rates of different heavy metals. The removal rates of heavy metals in the modified fly ashes prepared in examples 1 to 12 of the present invention and comparative examples 1 to 4 were measured according to the above method (wherein comparative example 5 does not contain the modified fly ashes, and comparative example 6 is commercially available desulfurized gypsum, and therefore the removal rates of heavy metals were not measured), and the results are shown in table 1.
TABLE 1
As can be seen from table 1, the modified fly ash prepared in examples 1 to 8, 12 and 4 has a good heavy metal removal effect of 30% to 60%, wherein the removal rate of cadmium is up to 53.16%, the removal rate of chromium is up to 46.47%, the removal rate of arsenic is up to 35.94%, the removal rate of mercury is up to 36.95%, and the removal rate of lead is up to 60.00%.
Compared with the examples 1 to 8, the modified fly ash prepared in the examples 9 to 11 and the comparative examples 1 to 3 has a higher heavy metal content. In the preparation process of the modified fly ash of example 9, the screening particle size of the classification device used in the first classification screening is larger, and part of smaller unburnt coal is not screened out, so that the prepared modified fly ash has more heavy metals; the modified fly ash of example 10 is not subjected to magnetic separation in the preparation process, and part of the heavy metals enriched in the magnetic particles are not separated, so that more heavy metals remain in the prepared modified fly ash; in the preparation process of the modified fly ash of example 11, the screening particle size of the classification equipment used in the second classification screening is smaller, so that some fine particle ash with slightly larger particles is not screened out, and the prepared modified fly ash has higher heavy metal content; the modified fly ash of comparative example 1 was not subjected to the first classification screening in the preparation process, and unburnt coal could not be removed; the modified fly ash of the comparative example 2 is not subjected to magnetic separation in the preparation process, and the magnetic particles enriched with heavy metals are not removed; the modified fly ash of comparative example 3 is not subjected to secondary classification screening in the preparation process, and cannot remove fine particle ash enriched with heavy metals, so that the heavy metal content is also high.
According to the results, the first grading screening, the magnetic separation and the second grading screening are matched with each other, so that 30-60% of heavy metal elements in the fly ash can be removed, and the shortage of heavy metal elements is not acceptable; the acid method modification can further improve the heavy metal removal efficiency. The method is combined with each other, so that heavy metal elements in the fly ash can be well removed.
Soil quality detection
And mixing the soil sample with deionized water according to the mass: volume ratio of 1kg:5L, stirring for 5min, standing for 1h, and measuring the pH value of the supernatant by using a pH meter, namely the pH value of the soil. The pH of the soil before and after the treatment with the soil conditioner prepared in the examples of the present invention and the comparative examples was measured according to the above-described method.
The salt content of the soil before and after the treatment of the soil improvement agent prepared in the examples of the present invention and the comparative examples was measured according to DB 37/T1303-2009 (soil Total salt content gravimetric method).
The organic matter content of the soil before and after the treatment with the soil improvement agent prepared in examples of the present invention and comparative examples was measured according to NY/T1121.6-2006 (soil test part 6: determination of organic matter of soil).
The soil porosity before and after the treatment of the soil improvement agent prepared in the examples and comparative examples of the present invention was measured according to the ring-knife weighing method.
The soil conditioner prepared in examples 1 to 12 and comparative examples 1 to 6 was added to saline-alkali soil at an addition of 10 t/mu, and the soil conditioner was uniformly spread on the saline-alkali soil and turned by a turning machine at a depth of 20 cm. The pH, salt content, organic matter content and soil porosity of the soil before and after the treatment were measured, respectively, and the results are shown in table 2.
TABLE 2
As can be seen from Table 2, the soil conditioner prepared in the examples 1 to 7, 9 to 11 and the comparative examples 1 to 2 has a good effect of improving saline-alkali soil, the pH value of the saline-alkali soil is obviously reduced after the soil conditioner is used, and the pH value is reduced by about 0.6 to 1.5; the salt content is obviously reduced, the salt content in each kilogram of soil is reduced by more than 0.5g, wherein the salt content in the embodiment 6 is reduced by 2.01 g/kg; the organic content and the soil porosity are also obviously improved.
Compared with the soil conditioners prepared in the embodiments 1-7, 9-11 and the comparative examples 1-2, the soil conditioner prepared in the embodiment 8 has less content of the modified fly ash and has a poor effect of reducing the salt alkalinity; example 12 in the course of acid-method modification of fly ash, an acid solution with a higher concentration is used, which destroys the skeleton structure of fly ash, and thus the effect of improving the porosity of soil is slightly poor; comparative example 3 no second stage screening was performed during the preparation of modified fly ash, fly ash particles with smaller particles were not separated out, and although the influence on the ability to adjust the salt alkalinity was smaller, soil pores were blocked, which was not conducive to the improvement of soil quality; the fly ash in the soil conditioner prepared in the comparative example 4 is not modified by an acid method, and the pH regulation and the adsorption capacity are weak, so the quality improvement condition of the treated saline-alkali soil is not obvious; the soil conditioner prepared in the comparative example 5 does not contain modified fly ash, so that the improvement effect on the salinity and alkalinity is poor; the soil conditioner of the comparative example 6 has a certain effect of reducing the pH, but the adjusting effect is poorer than that of the soil conditioners prepared in the examples 1 to 7 of the invention, and in addition, the soil conditioner does not have the capabilities of reducing the salt content, improving the organic matter content and increasing the soil porosity, which shows that the soil conditioner prepared in the examples 1 to 7 of the invention has stronger adjusting capability, more comprehensive functions and higher application value.
Crop yield detection
Uniformly spreading the soil conditioner on saline-alkali soil, wherein the application amount is 10 t/mu, and ploughing by using a ploughing machine, wherein the ploughing depth is 20cm, so that the corn can be planted, and the planting number is 3500 plants/mu.
The soil improvement agents prepared in examples 1 to 3 and comparative example 6 were applied to saline-alkali soil according to the above method, and the yields of crops were measured with the saline-alkali soil to which no soil improvement agent was applied as a control, respectively, and the results are shown in table 3.
TABLE 3
As can be seen from Table 3, the soil conditioners prepared in examples 1 to 3 and comparative example 6 have the effect of improving saline-alkali soil, and compared with a control group without the soil conditioner, the crop yield of the groups of examples 1 to 3 and the crop yield of the group of comparative example 6 are obviously improved, wherein the corn yield of the groups of examples 1 to 3 is improved to about 400 kilograms from about 50 kilograms per mu, and can be stabilized at about 500 kilograms in the next year; the corn yield of the comparative example 6 group was increased from about 50 kg per acre to about 250 kg, and could be stabilized at about 300 kg in the second year. The soil conditioner prepared by the invention can adjust the salt alkalinity of the soil, increase the organic matter content in the soil, improve the dispersion degree of the soil, improve the soil structure, adjust the water, fertilizer and gas heat balance and has wide application value.
According to the experimental results, the heavy metal content of the modified fly ash prepared in the examples 1-7 is low, and the corresponding soil conditioner has the capability of well reducing the salinity and alkalinity and increasing the content of soil organic matters and the porosity of soil; the soil conditioner prepared in the example 8 has low content of the modified fly ash and poor capability of improving saline-alkali soil, and the soil conditioner prepared in the comparative example 5 does not contain the modified fly ash and has no capability of improving saline-alkali soil, so that the soil conditioner is not suitable for being applied to actual production practice; the soil conditioner prepared in the examples 9-11 and the comparative examples 1-3 also has good capacity of reducing the salinity and alkalinity, but in the preparation process of the modified fly ash, heavy metal removal is not thorough, and the actual application may cause heavy metal pollution to soil; example 12 in the preparation of the modified fly ash, an acid solution with a higher concentration is used, and although the ability of the soil conditioner to reduce pH is increased, the skeleton structure of the fly ash is also destroyed, and the effect of increasing the porosity of the soil is poor; comparative example 4 acid-method modification was not performed in the preparation of modified fly ash, and the soil improvement ability was weak; comparative example 6 had a certain pH lowering ability, but did not lower the salt content and increase the organic content and soil porosity. Therefore, the modified fly ash and the corresponding soil conditioner prepared in the embodiments 1 to 7 are the best technical scheme for improving saline-alkali soil, and have wide application value.
In conclusion, the heavy metal elements in the fly ash can be effectively removed through two times of classified screening and magnetic separation, the skeleton in the fly ash is rearranged through stirring and soaking in the acid solution, a mesoporous structure is generated, the adsorption capacity is increased, the preparation process is simple and efficient, and large-scale production can be realized; the modified fly ash prepared by the method has excellent capacity of adjusting the pH value, and is prepared into a soil conditioner after being reasonably matched with slag scraps, excrement and humic acid, so that the pH value and the salt content of saline-alkali soil can be reduced, the content of organic matters is increased, the dispersibility of the soil is increased, the improved saline-alkali soil is more suitable for plant growth, and the crop yield is obviously improved; the invention selects the industrial waste fly ash and the domestic waste wine residue, vinegar residue, oil residue and the like as raw materials, realizes waste utilization, saves energy and has wide application prospect.
The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. A preparation method of modified fly ash is characterized by comprising the following steps:
sequentially carrying out first classified screening, magnetic separation, second classified screening and acid method modification on the fly ash to obtain the modified fly ash.
2. The method of manufacturing according to claim 1, comprising:
(1) performing primary classification screening on the fly ash to obtain coarse-grain fly ash and fine-grain fly ash, and collecting the fine-grain fly ash;
(2) carrying out magnetic separation on the fine-grained fly ash obtained in the step (1), and collecting non-magnetic fly ash;
(3) carrying out secondary classification screening on the nonmagnetic fly ash obtained in the step (2), and collecting coarse-grained ash;
(4) and (4) carrying out acid method modification on the coarse-grained ash obtained in the step (3) to obtain the modified fly ash.
3. The method according to claim 2, wherein the classification equipment used in the first classification screening in step (1) comprises any one of a linear vibrating screen, a circular vibrating screen or an air classifier or a combination of at least two of the above;
preferably, the particle size of the first classifying and screening in the step (1) is 80-150 μm;
preferably, the magnetic separation equipment used in the magnetic separation in the step (2) is a magnetic separator;
preferably, the magnetic field intensity of the magnetic separation in the step (2) is 480-1600 kA/m;
preferably, the classifying equipment used in the second classifying and screening in the step (3) comprises any one of a linear vibrating screen, a circular vibrating screen or an airflow classifier or a combination of at least two of the linear vibrating screen, the circular vibrating screen and the airflow classifier;
preferably, the screening particle size of the second classifying and screening in the step (3) is 5-35 μm.
4. The method according to claim 2 or 3, wherein the acid-modifying of step (4) comprises: dipping and stirring the coarse-grained ash obtained in the step (3) in an acid solution, and performing solid-liquid separation to obtain the modified fly ash;
preferably, the molar concentration of the acid solution is 0.1-3 mol/L;
preferably, the acid solution comprises any one of sulfuric acid, phosphoric acid, acetic acid, citric acid, oxalic acid or hydrochloric acid or a combination of at least two of them;
preferably, the temperature of the dipping and stirring is 20-90 ℃;
preferably, the time for dipping and stirring is 0.5-4 h;
preferably, the rotating speed of the dipping and stirring is 10-700 rpm;
preferably, the method further comprises the step of drying after the solid-liquid separation;
preferably, the drying temperature is 50-150 ℃;
preferably, the drying time is 1-24 h.
5. The production method according to any one of claims 1 to 4, characterized by comprising:
(1) performing primary classification screening on the fly ash by using classification equipment with a screening particle size of 80-150 mu m to obtain coarse-grain fly ash and fine-grain fly ash, and collecting the fine-grain fly ash;
(2) adding the fine-grained fly ash obtained in the step (1) into a magnetic separator, carrying out magnetic separation at 480-1600 kA/m, and collecting non-magnetic fly ash;
(3) performing secondary classification screening on the nonmagnetic fly ash obtained in the step (2) by using classification equipment with the screening particle size of 5-35 mu m, and collecting coarse particle ash;
(4) adding the coarse-grained ash obtained in the step (3) into 0.1-3 mol/L acid solution, dipping and stirring for 0.5-4 h at the temperature of 20-90 ℃ and the rotating speed of 10-700 rpm, then carrying out solid-liquid separation, and drying for 1-24 h at the temperature of 50-150 ℃ to obtain the modified fly ash.
6. The modified fly ash prepared by the method according to any one of claims 1 to 5.
7. A soil conditioner characterized in that a raw material of the soil conditioner comprises the modified fly ash of claim 6;
preferably, the raw material of the soil conditioner further comprises any one or a combination of at least two of slag scraps, excrement or humic acid;
preferably, the slag chip comprises any one of wine residue, vinegar residue, oil residue or wood chip or a combination of at least two of the wine residue, the vinegar residue, the oil residue or the wood chip;
preferably, the manure comprises cow manure and/or sheep manure.
8. The soil conditioner according to claim 7, wherein the mass percentage of the modified fly ash in the raw material of the soil conditioner is 30-90%;
preferably, the mass percentage of the wine lees in the raw materials of the soil conditioner is 0.1-30%;
preferably, the mass percentage of the vinegar residue in the raw material of the soil conditioner is 0.1-20%;
preferably, the mass percentage of the oil residue in the raw material of the soil conditioner is 0.1-10%;
preferably, the mass percentage of the wood chips in the raw material of the soil conditioner is 0.1-10%;
preferably, the mass percentage of the cow dung and/or the sheep dung in the raw material of the soil conditioner is 0.1-20%;
preferably, the mass percentage of the humic acid in the raw material of the soil conditioner is 0.1-40%.
9. A soil conditioner according to claim 7 or 8, characterized in that the raw materials of the soil conditioner comprise, by mass, 30-90% of modified fly ash, 0.1-30% of wine residue, 0.1-20% of vinegar residue, 0.1-10% of oil residue, 0.1-10% of wood chips, 0.1-20% of cow dung and/or sheep dung and 0.1-40% of humic acid.
10. Use of a modified fly ash as claimed in claim 6 or a soil conditioner as claimed in any one of claims 7 to 9 for the conditioning of saline and alkaline land.
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