Saline-alkali soil improving material as well as preparation method and application thereof

Abstract

The invention provides a saline-alkali soil improving material and a preparation method and application thereof, the saline-alkali soil improving material comprises modified fly ash and a calcium agent, the content of the calcium agent is 1-20wt% of that of the saline-alkali soil improving material, and the calcium agent comprises gypsum, calcined gypsum, desulfurized gypsum, phosphogypsum, fluorgypsum, carbide slag, quick lime or slaked lime. The preparation method comprises the following steps: sequentially carrying out screening and ultrasonic modification on fly ash, mixing with a calcium agent, and curing, so as to obtain the saline-alkali soil improvement material which is applied to the improvement of mud flat saline-alkali soil. The saline-alkali soil improving material provided by the invention is simple in component, solid waste can be recycled, the fly ash is modified, heavy metal elements in the fly ash are removed, chemical agents are not contained, and secondary pollution is avoided; the soil conditioner is applied to the improvement of mudflat saline-alkali soil, effectively reduces the pH value and salt content of the saline-alkali soil, improves the organic matter content and soil porosity, and has a good saline-alkali soil improvement effect; the preparation method is simple in steps and easy to prepare.

Description

Technical Field

[0001] The invention belongs to the technical field of saline-alkali land improvement, and specifically relates to a saline-alkali land improvement material and a preparation method and application thereof. Background Art

[0002] Saline-alkali soil is a kind of obstructive soil widely distributed on the earth. Because saline-alkali soil contains excessive saline-alkali ions, the soil is easy to compact, which seriously affects the circulation of water, fertilizer, gas and heat in the soil, and then affects plant growth, which is an important factor restricting agricultural development. Therefore, the study of saline-alkali land improvement technology is of great significance to agricultural development and the improvement of farmers' living standards. In response to the demand for saline-alkali land improvement, many improvement technologies have been produced, such as the dark pipe salt discharge technology disclosed in CN115428611A, the ecological module technology based on the acid-base neutralization principle disclosed in CN115399173A, and the method for improving saline-alkali land and soil fertility improvement by humic acid activated phosphate rock powder disclosed in CN115287079A, etc., but these technologies only solve the saline-alkali land problem locally, and cannot fundamentally solve the problem of soil structure destruction caused by the invasion of saline-alkali ions, and therefore it is difficult to efficiently improve saline-alkali land. In particular, there are currently few public technologies for improving the vertical structure of saline-alkali soil.

[0003] Fly ash is one of the major solid wastes emitted by coal-fired power plants. However, the comprehensive utilization rate of fly ash is currently low. The large amount of fly ash accumulated from coal burning has caused serious pollution to the surrounding environment such as the atmosphere, water bodies and soil.

[0004] CN111363558A discloses a saline-alkali land improver, which includes 10-20 parts of desulfurized gypsum, 2-4 parts of biogas slurry and 3-5 parts of fly ash. This improver uses ordinary fly ash and adds biogas slurry, and its further improvement of saline-alkali land improvement effect mainly depends on biogas slurry.

[0005] CN105602569A discloses a saline-alkali land improvement fertilizer, the raw material composition of which includes 20-40 parts of soluble humic acid, 5-15 parts of amino acids, 5-10 parts of organic matter, 7-15 parts of composite microorganisms, 10-15 parts of fly ash and 13-27 parts of mixed grass powder. The fly ash used in this improved fertilizer has not been modified and is used in a small amount. The effect of fly ash in fertilizer is limited, and the consumption capacity of fly ash is limited. In the prior art, there is a lack of technology for applying a large amount of fly ash to improve saline-alkali soil. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a saline-alkali land improvement material and a preparation method and application thereof. The saline-alkali land improvement material has simple ingredients, is easy to prepare, has good saline-alkali land improvement effects, and can achieve solid waste recycling.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a saline-alkali land improvement material, wherein the saline-alkali land improvement material comprises modified fly ash and a calcium agent;

[0009] The content of the calcium agent is 1-20wt% of the saline-alkali land improvement material;

[0010] The calcium agent includes any one of raw gypsum, slaked gypsum, desulfurized gypsum, phosphogypsum, fluorite, carbide slag, quicklime or slaked lime, or a combination of at least two thereof.

[0011] The saline-alkali land improvement material provided by the present invention has simple ingredients, only containing modified fly ash and calcium agent, can realize solid waste recycling, has good improvement effect on saline-alkali land, and the fly ash is modified to remove heavy metal elements in the fly ash, does not contain chemical agents, and avoids secondary pollution.

[0012] The content of the calcium agent is 1-20wt% of the saline-alkali land improvement material, for example, it can be 1wt%, 5wt%, 8wt%, 10wt%, 12wt%, 15wt%, 18wt% or 20wt%, but is not limited to the listed values, and values ​​not listed in the numerical range are also applicable.

[0013] The calcium agent includes any one of raw gypsum, calcine gypsum, desulfurized gypsum, phosphogypsum, fluorgypsum, carbide slag, quicklime or slaked lime, or a combination of at least two of them. Typical but non-limiting combinations include a combination of raw gypsum and calcine gypsum, a combination of desulfurized gypsum and phosphogypsum, a combination of fluorgypsum, carbide slag, quicklime and slaked lime, a combination of raw gypsum, calcine gypsum and desulfurized gypsum, or a combination of phosphogypsum, fluorgypsum, carbide slag, quicklime and slaked lime.

[0014] In a second aspect, the present invention provides a method for preparing the saline-alkali land improving material as described in the first aspect, the preparation method comprising the following steps:

[0015] (1) screening fly ash to obtain fly ash particles;

[0016] (2) subjecting the fly ash particles obtained in step (1) to ultrasonic modification to obtain modified fly ash;

[0017] (3) Mixing the calcium agent with the modified fly ash obtained in step (2) and aging to obtain a saline-alkali land improvement material.

[0018] After the fly ash is screened and ultrasonically modified, the heavy metal elements in the fly ash can be efficiently removed. The screening process is a physical sorting technology, and no chemical agents are used to avoid secondary pollution. The modified fly ash is mixed with a calcium agent. The alkalinity of the calcium agent can etch the surface of the modified fly ash particles. On the one hand, a large number of pores will be produced, thereby increasing the specific surface area of ​​the modified fly ash, improving the adsorption and solidification capacity of the modified fly ash for salt-alkali ions, and improving the water and fertilizer retention capacity of the modified fly ash. On the other hand, the hydrophilicity of the surface of the modified fly ash particles will be greatly improved, which will help the salt-alkali ions in the soil particles to dissolve and detach, participate in the reconstruction of the new soil aggregate structure, and accelerate the migration and removal of salt-alkali ions.

[0019] Preferably, the fly ash in step (1) is fine ash collected from the flue gas after coal combustion, and its components include silicon dioxide, aluminum oxide, sodium oxide, potassium oxide, calcium oxide, magnesium oxide, iron oxide, titanium dioxide and carbon.

[0020] Preferably, the screening in step (1) comprises sequentially performing a first classification screening, a magnetic separation and a second classification screening on the fly ash.

[0021] Preferably, the particle size of the fly ash screened by the first classification is ≤150 μm, for example, it can be 20 μm, 50 μm, 100 μm, 120 μm or 150 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] Preferably, the grading equipment used in the first grading screening includes any one of a linear vibrating screen, a circular vibrating screen or an air flow classifier, or a combination of at least two of them. Typical but non-limiting combinations include a combination of a linear vibrating screen and a circular vibrating screen, a combination of a circular vibrating screen and an air flow classifier, or a combination of a linear vibrating screen, a circular vibrating screen and an air flow classifier.

[0023] Preferably, the magnetic field strength of the magnetic separation is 500-1500 kA / m, for example, it can be 500 kA / m, 800 kA / m, 1000 kA / m, 1200 kA / m or 1500 kA / m, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] Preferably, the magnetic separation equipment for magnetic separation includes a medium magnetic field magnetic separator and / or a high magnetic field magnetic separator.

[0025] Preferably, the grading equipment used in the second grading screening includes any one of a linear vibrating screen, a circular vibrating screen or an air flow classifier, or a combination of at least two of them. Typical but non-limiting combinations include a combination of a linear vibrating screen and a circular vibrating screen, a combination of a circular vibrating screen and an air flow classifier, or a combination of a linear vibrating screen, a circular vibrating screen and an air flow classifier.

[0026] Preferably, the particle size of the fly ash particles in step (1) is 10-150 μm, for example, 10 μm, 50 μm, 80 μm, 100 μm, 120 μm or 150 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0027] Preferably, the temperature of the ultrasound in step (2) is 20-90°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C or 90°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0028] Preferably, the ultrasonic time in step (2) is 0.5-20 min, for example, 0.5 min, 2 min, 5 min, 10 min, 12 min, 15 min, 18 min or 20 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] Preferably, the frequency of the ultrasound in step (2) is 20-132 kHz, for example, 20 kHz, 40 kHz, 60 kHz, 80 kHz, 100 kHz, 120 kHz or 132 kHz, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] Ultrasound is used to modify fly ash particles. The cavitation effect of ultrasound produces a huge impact pressure on the surface of fly ash, which can remove heavy metal elements adsorbed on the surface of fly ash and make them enter the liquid phase from the solid phase, thereby reducing the content of heavy metals in fly ash and effectively removing typical heavy metal elements in fly ash.

[0031] Preferably, the instrument used for the ultrasound is an industrial ultrasonic cleaning machine.

[0032] Preferably, the rotation speed of the stirring in the ultrasound in step (2) is 10-650 rpm, for example, it can be 10 rpm, 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm or 650 rpm, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0033] Preferably, the fly ash particles are mixed with water before the ultrasonic treatment in step (2).

[0034] Preferably, after the ultrasound in step (2), solid-liquid separation and drying are performed in sequence.

[0035] Preferably, the drying temperature is 60-140°C, for example, it can be 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C or 140°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] Preferably, the drying time is 2-20 h, for example, 2 h, 5 h, 8 h, 10 h, 12 h, 15 h, 18 h or 20 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] Preferably, the calcium agent in step (3) includes any one of raw gypsum, plaster of Paris, desulfurized gypsum, phosphogypsum, fluorgypsum, carbide slag, quicklime or slaked lime, or a combination of at least two of them. Typical but non-limiting combinations include a combination of raw gypsum and plaster of Paris, a combination of desulfurized gypsum and phosphogypsum, a combination of fluorgypsum, carbide slag, quicklime and slaked lime, a combination of raw gypsum, plaster of Paris and desulfurized gypsum, or a combination of phosphogypsum, fluorgypsum, carbide slag, quicklime and slaked lime.

[0038] Preferably, the content of the calcium agent mixed into the saline-alkali land improvement material in step (3) is 1-20wt%, for example, it can be 1wt%, 5wt%, 8wt%, 10wt%, 12wt%, 15wt%, 18wt% or 20wt%, but is not limited to the listed values, and values ​​not listed in the numerical range are also applicable.

[0039] Preferably, the aging temperature in step (3) is 10-40°C, for example, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C or 40°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] Preferably, the aging time in step (3) is 2-15 days, for example, 2 days, 5 days, 8 days, 10 days, 12 days or 15 days, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] In a third aspect, the present invention provides an application of the saline-alkali land improving material as described in the first aspect, wherein the saline-alkali land improving material is applied to improving tidal flat saline-alkali land.

[0042] Preferably, the application method comprises: mixing the saline-alkali land improvement material and fresh water with the tidal flat saline-alkali land, maintaining the mixture in a natural environment for 7-30 days, and then sequentially tilling the land and reducing alkali and draining salt.

[0043] Preferably, the added amount of the saline-alkali land improving material is 1-30wt% of the tidal flat saline-alkali land, for example, it can be 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt% or 30wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] Preferably, the soil depth of the tidal flat saline-alkali land is 10-50 cm, for example, it can be 10 cm, 20 cm, 30 cm, 40 cm or 50 cm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] Preferably, the method for reducing alkali and removing salt comprises: performing a first washing with fresh water and / or sea water, and then performing a second washing with fresh water.

[0046] Preferably, the first washing water consumption is 50-150m 3 , for example, it can be 50m 3 、80m 3 、100m 3 、120m 3 or 150m 3 , but not limited to the listed values, other unlisted values ​​within the numerical range are also applicable.

[0047] Preferably, the water consumption of the second washing is 50-500m 3 , for example, it can be 50m 3 、100m 3 、200m 3 、300m 3 、400m 3 or 500m 3 , but not limited to the listed values, other unlisted values ​​within the numerical range are also applicable.

[0048] Preferably, the first washing time is 0.5-2 days, for example, 0.5 days, 1 day, 1.5 days or 2 days, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] Preferably, the second washing time is 1-3 days, for example, 1 day, 1.5 days, 2 days, 2.5 days or 3 days, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The saline-alkali land improvement material provided by the present invention has simple ingredients, only containing modified fly ash and calcium agent, and can realize solid waste recycling. The fly ash is modified to remove heavy metal elements in the fly ash, and does not contain chemical agents, thereby avoiding secondary pollution. The material is applied to the improvement of tidal flat saline-alkali land, has strong adsorption and solidification ability for tidal flat saline-alkali ions, effectively reduces the pH value and salt content of tidal flat saline-alkali land, increases the organic matter content and soil porosity, and has a good improvement effect on tidal flat saline-alkali land. The preparation method thereof effectively removes heavy metal ions in fly ash through screening and ultrasonic modification, and does not introduce chemical agents. The overall process steps are simple and the preparation is easy. DETAILED DESCRIPTION

[0052] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0053] Example 1

[0054] This embodiment provides a method for preparing a saline-alkali land improvement material, the preparation method comprising the following steps:

[0055] (1) using an air flow classifier to perform a first classification screening on fly ash, collecting fly ash with a particle size of ≤100 μm and adding it to a magnetic separator, performing magnetic separation under a magnetic field of 1000 kA / m to collect non-magnetic fly ash, and using an air flow classifier to perform a second classification screening on the non-magnetic fly ash to collect fly ash particles with a particle size of 50-100 μm;

[0056] (2) The fly ash particles obtained in step (1) are immersed in clean water, and ultrasonically treated at a frequency of 80 kHz for 10 min at a temperature of 50° C. and a rotation speed of 350 rpm, and then filtered, and the filter residue is dried at 105° C. for 12 h to obtain modified fly ash;

[0057] (3) Mixing slaked lime with the modified fly ash obtained in step (2), wherein the amount of slaked lime used is 10 wt % of the saline-alkali land improvement material, and aging at 25° C. for 9 days.

[0058] Example 2

[0059] This embodiment provides a method for preparing a saline-alkali land improvement material, the preparation method comprising the following steps:

[0060] (1) using an airflow classifier to perform a first classification screening on fly ash, collecting fly ash with a particle size of ≤150 μm and adding it to a magnetic separator, performing magnetic separation under a magnetic field of 1500 kA / m to collect non-magnetic fly ash, and using an airflow classifier to perform a second classification screening on the non-magnetic fly ash to collect fly ash particles with a particle size of 100-150 μm;

[0061] (2) The fly ash particles obtained in step (1) are immersed in clean water, and ultrasonically treated at a frequency of 132 kHz for 20 min at a temperature of 90° C. and a rotation speed of 650 rpm, and then filtered, and the filter residue is dried at 140° C. for 2 h to obtain modified fly ash;

[0062] (3) Mixing carbide slag and quicklime with the modified fly ash obtained in step (2), wherein the amount of carbide slag is 10wt% of the saline-alkali land improvement material, and the amount of quicklime is 10wt% of the saline-alkali land improvement material, and aging at 40°C for 2 days.

[0063] Example 3

[0064] This embodiment provides a method for preparing a saline-alkali land improvement material, the preparation method comprising the following steps:

[0065] (1) using an airflow classifier to perform a first classification screening on fly ash, collecting fly ash with a particle size of ≤70 μm and adding it to a magnetic separator, performing magnetic separation under a magnetic field of 500 kA / m to collect non-magnetic fly ash, and using an airflow classifier to perform a second classification screening on the non-magnetic fly ash to collect fly ash particles with a particle size of 10-70 μm;

[0066] (2) The fly ash particles obtained in step (1) are immersed in clean water, and ultrasonically treated at a frequency of 20 kHz for 0.5 min under stirring conditions of a temperature of 20° C. and a rotation speed of 10 rpm, and then filtered, and the filter residue is dried at 60° C. for 20 h to obtain modified fly ash;

[0067] (3) mixing gypsum with the modified fly ash obtained in step (2), wherein the amount of gypsum is 1wt% of the saline-alkali land improvement material, and aging at 10°C for 15 days.

[0068] Example 4

[0069] This embodiment provides a method for preparing a saline-alkali land improving material. Compared with Embodiment 1, the frequency of ultrasound in step (2) is 10 kHz, and the rest is the same as Embodiment 1.

[0070] Example 5

[0071] This embodiment provides a method for preparing a saline-alkali land improving material. Compared with Embodiment 1, the frequency of ultrasound in step (2) is 200 kHz, and the rest is the same as Embodiment 1.

[0072] Example 6

[0073] This embodiment provides a method for preparing a saline-alkali land improvement material. Compared with Example 1, the ultrasonication time in step (2) is 0.1 min, and the rest is the same as Example 1.

[0074] Example 7

[0075] This embodiment provides a method for preparing a saline-alkali land improvement material. Compared with Example 1, the ultrasonication time in step (2) is 40 minutes, and the rest is the same as Example 1.

[0076] Example 8

[0077] This embodiment provides a method for preparing a saline-alkali land improvement material. Compared with Example 1, the amount of slaked lime used in step (3) is 0.5 wt %, and the rest is the same as Example 1.

[0078] Example 9

[0079] This embodiment provides a method for preparing a saline-alkali land improvement material. Compared with Example 1, the amount of slaked lime used in step (3) is 40 wt %, and the rest is the same as Example 1.

[0080] Example 10

[0081] This embodiment provides a method for preparing a saline-alkali land improvement material. Compared with Example 1, the aging temperature in step (3) is 5° C., and the rest is the same as Example 1.

[0082] Embodiment 11

[0083] This embodiment provides a method for preparing a saline-alkali land improvement material. Compared with Example 1, the aging temperature in step (3) is 50° C., and the rest is the same as Example 1.

[0084] Example 12

[0085] This embodiment provides a method for preparing a saline-alkali land improvement material. Compared with Example 1, the aging time in step (3) is 1 day, and the rest is the same as Example 1.

[0086] Example 13

[0087] This embodiment provides a method for preparing a saline-alkali land improvement material. Compared with Example 1, the aging time in step (3) is 18 days, and the rest is the same as Example 1.

[0088] Comparative Example 1

[0089] This comparative example provides a method for preparing a saline-alkali land improvement material. Compared with Example 1, ultrasound is not performed in step (2), and the rest is the same as Example 1.

[0090] Comparative Example 2

[0091] This comparative example provides a method for preparing a saline-alkali land improvement material. Compared with Example 1, the ultrasonic modification in step (2) is replaced by acid modification, and the rest is the same as Example 1.

[0092] The acid modification method comprises the following steps: adding the fly ash particles obtained in step (1) into a 0.5 mol / L citric acid solution, immersing and stirring at 55°C and 10 rpm for 3 hours, separating the solid and the liquid, and drying at 105°C for 24 hours to obtain modified fly ash.

[0093] The content and mass change of cadmium, chromium, arsenic, mercury and lead before and after removal were measured by inductively coupled plasma mass spectrometry (ICP-MS), and the removal rate of each heavy metal was calculated. The heavy metal removal rate of the modified fly ash obtained in step (2) of Examples 1-7 and Comparative Examples 1-2 was measured by this method, and the results are listed in Table 1.

[0094] Table 1

[0095]

[0096] It can be seen from Table 1 that the preparation method of the modified fly ash provided in Examples 1-3 of the present invention can effectively remove heavy metal elements in fly ash, and the obtained modified fly ash has a low content of heavy metal elements; compared with Example 1, the heavy metal removal rate of Examples 4-7 is reduced, and the use of the preferred ultrasonic frequency and time of the present invention can further improve the removal rate of heavy metal elements; compared with Example 1, the heavy metal removal rate in Comparative Examples 1-2 is significantly reduced, and ultrasonic modification is a key step in fly ash modification. Ultrasound can effectively remove heavy metal elements in fly ash.

[0097] Application Example 1

[0098] This application example provides an application method of a saline-alkali land improvement material, and the application method comprises the following steps:

[0099] (a) The saline-alkali land improving material prepared in Example 1 is mixed evenly with a tidal flat saline-alkali land with a soil depth of 30 cm, and then fresh water is added to fully moisten the tidal flat saline-alkali land, wherein the amount of the saline-alkali land improving material is 15 wt % of the tidal flat saline-alkali land;

[0100] (b) kept in natural environment for 10 days and tilled by agricultural machinery;

[0101] (c) Use 100m first 3 Wash with 300m of fresh water for 1 day, then 3 Wash with fresh water for 2 days.

[0102] Application Example 2

[0103] This application example provides an application method of a saline-alkali land improvement material, and the application method comprises the following steps:

[0104] (a) The saline-alkali land improvement material prepared in Example 1 is mixed evenly with a tidal flat saline-alkali land with a soil depth of 10 cm, and then fresh water is added to fully wet the tidal flat saline-alkali land. The amount of the saline-alkali land improvement material used is 1 wt % of the tidal flat saline-alkali land;

[0105] (b) kept in natural environment for 7 days and tilled by agricultural machinery;

[0106] (c) Use 50m first 3 Wash with seawater and fresh water for 0.5 days, and then use 50m 3 Wash with fresh water for 1 day.

[0107] Application Example 3

[0108] This application example provides an application method of a saline-alkali land improvement material, and the application method comprises the following steps:

[0109] (a) The saline-alkali land improving material prepared in Example 1 is mixed evenly with a tidal flat saline-alkali land with a soil depth of 50 cm, and then fresh water is added to fully wet the tidal flat saline-alkali land, wherein the amount of the saline-alkali land improving material is 30 wt % of the tidal flat saline-alkali land;

[0110] (b) maintained in a natural environment for 30 days, using agricultural machinery for tillage;

[0111] (c) Use 150m first 3 Wash with seawater and fresh water for 2 days, and then use 500m 3 Wash with fresh water for 3 days.

[0112] Application Example 4

[0113] This application example provides an application method of a saline-alkali land improvement material. Compared with Application Example 1, the amount of the saline-alkali land improvement material used is 0.1wt% of the mass of the tidal flat saline-alkali soil, and the rest is the same as Application Example 1.

[0114] Application Example 5

[0115] This application example provides an application method of a saline-alkali land improvement material. Compared with Application Example 1, the amount of the saline-alkali land improvement material used is 50wt% of the mass of the tidal flat saline-alkali soil, and the rest is the same as Application Example 1.

[0116] Application Example 6

[0117] This application example provides an application method of a saline-alkali land improvement material. Compared with Application Example 1, an equal amount of the saline-alkali land improvement material is replaced with the saline-alkali land improvement material prepared in Example 2, and the rest is the same as Application Example 1.

[0118] Application Example 7

[0119] This application example provides an application method of a saline-alkali land improvement material. Compared with Application Example 1, an equal amount of the saline-alkali land improvement material is replaced with the saline-alkali land improvement material prepared in Example 3, and the rest is the same as Application Example 1.

[0120] Application Example 8

[0121] This application example provides an application method of a saline-alkali land improvement material. Compared with Application Example 1, an equal amount of the saline-alkali land improvement material is replaced with the saline-alkali land improvement material prepared in Example 4, and the rest is the same as Application Example 1.

[0122] Application Example 9

[0123] This application example provides an application method of a saline-alkali land improvement material. Compared with Application Example 1, an equal amount of the saline-alkali land improvement material is replaced with the saline-alkali land improvement material prepared in Example 5, and the rest is the same as Application Example 1.

[0124] Application Example 10

[0125] This application example provides an application method of a saline-alkali land improvement material. Compared with Application Example 1, an equal amount of the saline-alkali land improvement material is replaced with the saline-alkali land improvement material prepared in Example 6, and the rest is the same as Application Example 1.

[0126] Application Example 11

[0127] This application example provides an application method of a saline-alkali land improvement material. Compared with Application Example 1, an equal amount of the saline-alkali land improvement material is replaced with the saline-alkali land improvement material prepared in Example 7, and the rest is the same as Application Example 1.

[0128] Application Example 12

[0129] This application example provides an application method of a saline-alkali land improving material. Compared with Application Example 1, an equal amount of the saline-alkali land improving material is replaced with the saline-alkali land improving material prepared in Example 8, and the rest is the same as Application Example 1.

[0130] Application Example 13

[0131] This application example provides an application method of a saline-alkali land improving material. Compared with Application Example 1, an equal amount of the saline-alkali land improving material is replaced with the saline-alkali land improving material prepared in Example 9, and the rest is the same as Application Example 1.

[0132] Application Example 14

[0133] This application example provides an application method of a saline-alkali land improving material. Compared with Application Example 1, an equal amount of the saline-alkali land improving material is replaced with the saline-alkali land improving material prepared in Example 10, and the rest is the same as Application Example 1.

[0134] Application Example 15

[0135] This application example provides an application method of a saline-alkali land improving material. Compared with Application Example 1, an equal amount of the saline-alkali land improving material is replaced with the saline-alkali land improving material prepared in Example 11, and the rest is the same as Application Example 1.

[0136] Application Example 16

[0137] This application example provides an application method of a saline-alkali land improving material. Compared with Application Example 1, an equal amount of the saline-alkali land improving material is replaced with the saline-alkali land improving material prepared in Example 12, and the rest is the same as Application Example 1.

[0138] Application Example 17

[0139] This application example provides an application method of a saline-alkali land improving material. Compared with Application Example 1, an equal amount of the saline-alkali land improving material is replaced with the saline-alkali land improving material prepared in Example 13, and the rest is the same as Application Example 1.

[0140] Comparative application example 1

[0141] This comparative application example provides an application method of a saline-alkali land improvement material. Compared with Application Example 1, step (c) of reducing alkali and removing salt is not performed, and the rest is the same as Application Example 1.

[0142] The pH value, salt content, organic matter content and soil porosity of the tidal flat saline-alkali soil before and after improvement in the application example of the present invention were measured respectively to illustrate the improvement effect.

[0143] The determination method comprises: mixing soil and deionized water at a solid-liquid ratio of 1:5, where the unit of the solid-liquid ratio is kg / L, stirring for 5 minutes, standing for 1 hour, and then using a pH meter to determine the pH value of the supernatant, which is the pH value of the soil; determining the soil salt content before and after treatment with the saline-alkali land soil conditioner of the present invention according to DB37 / T1303-2009 (gravimetric method for determining total salt content in soil); determining the soil organic matter content before and after treatment with the saline-alkali land soil conditioner of the present invention according to NY / T1121.6-2006 (Part 6 of soil testing: determination of soil organic matter); and determining the soil porosity before and after treatment with the saline-alkali land soil conditioner of the present invention according to a ring knife weighing method.

[0144] The measurement results of the saline-alkali soil before improvement, the saline-alkali soil after improvement in Application Examples 1-5 and Comparative Application Example 1 are listed in Table 2.

[0145] The measurement results of the saline-alkali soil before improvement and the saline-alkali soil after improvement in Application Example 1 and Application Examples 6-17 are listed in Table 3.

[0146] Table 2

[0147] pH Salt content (%) Organic matter content (%) Soil porosity (%) Saline-alkali soil before improvement 7.64 1.88 1.27 17.38 Application Example 1 7.14 0.20 1.38 35.27 Application Example 2 7.32 0.36 1.35 32.82 Application Example 3 7.27 0.40 1.40 34.56 Application Example 4 7.50 0.45 1.32 31.26 Application Example 5 7.39 0.52 1.49 34.89 Comparative application example 1 7.48 0.96 1.37 28.93

[0148] It can be seen from Table 2 that in Application Examples 1-3, by using the saline-alkali land improvement materials and the use method provided by the present invention, the pH value and salt content of the saline-alkali soil are significantly reduced, and the organic matter content and soil porosity are significantly improved, which can achieve a good saline-alkali soil improvement effect; compared with Application Example 1, the improvement effect of Application Examples 4-5 is reduced, and the use of the preferred saline-alkali land improvement materials of the present invention can further improve the improvement effect; compared with Application Example 1, the improvement effect of the soil pH value and salt content is not significant. In the improvement of tidal flat saline-alkali land, seawater or fresh water is needed to reduce the alkali and discharge the salt from the soil to achieve the maximum improvement effect.

[0149] Table 3

[0150]

[0151]

[0152] It can be seen from Table 3 that:

[0153] The saline-alkali land improvement materials of Application Examples 6-7 have a good improvement effect on tidal flat saline-alkali land. After use, the soil pH value is significantly reduced, the salt content is significantly reduced, and the organic matter content and soil porosity are significantly improved; compared with Application Example 1, the improvement effect of Application Examples 8-17 is reduced, and the improvement effect on soil salt content and porosity is slightly reduced. When preparing modified fly ash, the amount of calcium agent, the maturation temperature and time of the calcium agent and fly ash affect the application effect of the saline-alkali land improvement material. The saline-alkali land improvement material prepared by the preferred preparation parameters of the present invention is applied to the improvement of tidal flat saline-alkali land, which can achieve further improvement of the tidal flat saline-alkali land improvement effect.

[0154] In summary, the saline-alkali land improvement material provided by the present invention has simple ingredients, containing only modified fly ash and calcium agent, and can realize solid waste recycling. The fly ash is modified to remove heavy metal elements in the fly ash, and does not contain chemical agents, thereby avoiding secondary pollution. It is applied to the improvement of tidal flat saline-alkali land, has strong adsorption and solidification ability for tidal flat saline-alkali ions, effectively reduces the pH value and salt content of tidal flat saline-alkali land, increases the organic matter content and soil porosity, and has a good improvement effect on tidal flat saline-alkali land. Its preparation method effectively removes heavy metal ions in fly ash through screening and ultrasonic modification, and does not introduce chemical agents. The overall process steps are simple and easy to prepare.

[0155] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A saline-alkali land improvement material, characterized in that: The components of the saline-alkali land improvement material include modified fly ash and calcium agent; The content of the calcium agent is 1-20wt% of the saline-alkali land improvement material; The calcium agent includes any one of raw gypsum, slaked gypsum, desulfurized gypsum, phosphogypsum, fluorite, carbide slag, quicklime or slaked lime, or a combination of at least two thereof.

2. A method for preparing the saline-alkali land improving material according to claim 1, characterized in that: The preparation method comprises the following steps: (1) screening fly ash to obtain fly ash particles; (2) subjecting the fly ash particles obtained in step (1) to ultrasonic modification to obtain modified fly ash; (3) Mixing the calcium agent with the modified fly ash obtained in step (2) and aging to obtain a saline-alkali land improvement material.

3. The preparation method according to claim 2, characterized in that: The screening in step (1) comprises sequentially performing a first classification screening, a magnetic separation and a second classification screening on the fly ash; Preferably, the particle size of the fly ash screened by the first classification is ≤150 μm; Preferably, the magnetic field strength of the magnetic separation is 500-1500 kA / m.

4. The preparation method according to claim 2 or 3, characterized in that: The particle size of the fly ash particles in step (1) is 10-150 μm.

5. The preparation method according to any one of claims 2 to 4, characterized in that: The temperature of the ultrasound in step (2) is 20-90° C. Preferably, the ultrasonic time in step (2) is 0.5-20 min; Preferably, the frequency of the ultrasound in step (2) is 20-132kHz; Preferably, the rotation speed of the stirring during ultrasound in step (2) is 10-650 rpm.

6. The preparation method according to any one of claims 2 to 5, characterized in that: In step (2), the fly ash particles are mixed with water before the ultrasonic treatment; Preferably, the ultrasound in step (2) is followed by solid-liquid separation and drying; Preferably, the drying temperature is 60-140°C; Preferably, the drying time is 2-20 hours.

7. The preparation method according to any one of claims 2 to 6, characterized in that: The calcium agent in step (3) includes any one of raw gypsum, plaster of Paris, desulfurized gypsum, phosphogypsum, fluorsulphite, carbide slag, quicklime or slaked lime, or a combination of at least two thereof; Preferably, the content of the calcium agent mixed in step (3) is 1-20wt% of the saline-alkali land improvement material.

8. The preparation method according to any one of claims 2 to 7, characterized in that: The aging temperature in step (3) is 10-40°C; Preferably, the ripening time in step (3) is 2-15 days.

9. An application of the saline-alkali land improvement material according to claim 1, characterized in that: The saline-alkali land improvement material is used for improving tidal flat saline-alkali land.

10. The use according to claim 9, characterized in that: The application method comprises: mixing the saline-alkali land improvement material and fresh water with the tidal flat saline-alkali land, keeping it in a natural environment for 7-30 days, and then sequentially plowing and reducing alkali and draining salt; Preferably, the amount of the saline-alkali land improvement material added is 1-30wt% of the tidal flat saline-alkali land; Preferably, the soil depth of the tidal flat saline-alkali land is 10-50 cm; Preferably, the method for reducing alkali and removing salt comprises: using fresh water and / or sea water for a first wash, and then using fresh water for a second wash; Preferably, the first washing water consumption is 50-150m 3 ; Preferably, the water consumption of the second washing is 50-500m 3 ; Preferably, the first washing time is 0.5-2 days; Preferably, the second washing period is 1-3 days.

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