CN118619792A - A water-soluble fertilizer for improving saline-alkali and its preparation method and application - Google Patents

Abstract

The invention belongs to the technical field of solid waste treatment and biological fertilizer, and discloses a water-soluble fertilizer for improving salt and alkali, and a preparation method and application thereof. The water-soluble fertilizer for improving the salt and alkali comprises the following components in parts by weight: 30-80 parts of water-soluble silicon fertilizer, 30-60 parts of potassium humate, 5-20 parts of porous silicon dioxide loaded carbon quantum dots and 1-10 parts of stabilizer. The porous silica loaded carbon quantum dot is prepared by taking antibiotic fungus residues as raw materials, performing hydrothermal reaction to obtain a carbon quantum dot solution, adding porous silica, stirring, adsorbing, and vacuum spray drying. The water-soluble fertilizer is compounded by water-soluble silicon fertilizer and potassium humate, and porous silicon dioxide loaded carbon quantum dots are used as an accelerator and a structure improver, so that the content of sodium in soil exchange and the soil alkalization degree can be effectively reduced, the fertilizer efficiency and the crop utilization rate can be obviously improved, and the effects of improving saline-alkali soil and improving crop yield are achieved.

Description

A water-soluble fertilizer for improving saline-alkali and its preparation method and application

Technical Field

The invention belongs to the technical field of solid waste treatment and biological fertilizer, and specifically relates to a saline-alkali improved water-soluble fertilizer and a preparation method and application thereof.

Background Art

Compared with normal soil, saline-alkali land has the following characteristics: the salt and alkali components contained in saline-alkali land are higher than those in normal soil, where salt refers to salts such as sodium chloride and sodium sulfate, and alkali refers to components such as sodium carbonate and sodium bicarbonate. These components exist in the form of sodium salts, and high sodium salt content is not conducive to plant growth. When plants absorb too much sodium ions, it will change the cell membrane structure and affect plant growth. At the same time, when the sodium ion content in plant cells is high, it will affect photosynthesis. In addition, excessive sodium ion content in the soil will lead to high soil osmotic pressure, which will reduce the ability of plants to absorb water, causing plants to lack water and eventually lead to plant death. Because saline-alkali land contains more alkaline substances, its pH is higher than 7, while the pH of normal soil is close to neutral. The soil in saline-alkali land is highly compacted, resulting in poor permeability.

At present, the main methods for treating saline-alkali land include washing salt, leveling the land, timely harrowing, applying organic fertilizers and using soil conditioners for improvement. CN 114368994A discloses an inorganic silicon fertilizer for improving saline-alkali soil, including liquid silicon fertilizer, colloidal silicon fertilizer and pH regulator, wherein the liquid silicon fertilizer is composed of water and silicon source according to a mass ratio of (6-8):1; the colloidal silicon fertilizer is composed of colloidal solution and silicon source according to a mass ratio of (3-4):1; the silicon source includes the following raw materials in parts by weight: 25-35 parts of silicon dioxide, 15-25 parts of humic acid, 5-10 parts of soil loosening agent, and 12-18 parts of clay minerals. The inorganic silicon fertilizer mainly uses liquid silicon fertilizer to improve the utilization rate of inorganic silicon fertilizer by plants, uses colloid to provide long-term and continuous slow release, and adjusts the pH value to 2-3 to neutralize the alkalinity of saline-alkali land. However, the inorganic silicon fertilizer has limited control effect on the sodium salt content in the soil. CN 118165736A discloses a saline-alkali land improver and a saline-alkali land improving method. The saline-alkali land improver is made of the following raw materials in parts by weight: 30-50 parts of a de-sodium agent, 10-20 parts of aluminum sulfate, and 5-9 parts of an acidifier. The de-sodium agent is prepared by mixing an Artemisia selengensis extract, a cationic polyacrylamide, a reed-based porous material, and reed stems. However, the improvement method is to wash the salt by immersion in water, which wastes water resources seriously. In addition, due to environmental factors, the soil after washing the salt will recover salinity after a period of planting, and the improvement effect is less sustainable.

Antibiotic residues usually refer to the residues left after the active ingredients are extracted from the fermentation liquid or culture medium during the production of antibiotics. These residues may include unextracted antibiotics, metabolites, cell fragments, proteins, polysaccharides, lipids and other biologically active substances. Antibiotic residues are rich in organic matter, organic acids, nitrogen, phosphorus, potassium and various trace elements, especially the high protein content in the residues, which can be used to make organic fertilizers. Composting is a method of producing fertilizers by degrading organic matter in antibiotic residues through microbial fermentation, but due to the inhibitory effect of residual antibiotics on microorganisms, the degradation effect of antibiotics is limited, and the fermentation time is long, and the processing efficiency is low. If the antibiotic residues are not completely treated, the produced organic fertilizer may contain residual antibiotics and metabolic intermediates, etc., which are easily accumulated in microorganisms and organisms during the use of organic fertilizers, forming drug resistance and leading to potential ecological risks. CN 113087552 B discloses a method for preparing organic fertilizers from antibiotic residues, which is obtained by mixing the antibiotic residues with organic solid wastes after microwave treatment under ultrasonic conditions and drying, crushing and granulating after aerobic composting fermentation. This invention uses microwave combined with ultrasonic treatment to remove residual antibiotics in antibiotic bacterial residue while simultaneously eliminating resistance genes in the antibiotic bacterial residue, thus avoiding the occurrence of secondary pollution problems caused by the reuse of antibiotic bacterial residue.

Carbon Quantom Dots (CQDs) are an emerging zero-dimensional carbon nanomaterial with a size less than 10nm. They have excellent tunable fluorescence properties, photoluminescence properties, chemical and optical stability and biocompatibility. They have cutting-edge applications in the fields of ion detection, biosensing, bioimaging, and drug loading. At present, there are many methods for preparing CQDs, which are mainly divided into top-down method and bottom-up method. Among them, the bottom-up method often uses natural biomass as a carbon source and is prepared by pyrolysis, hydrothermal method and other technologies. It has the advantages of simple process, easy raw materials, environmental protection and high efficiency. The application of biomass carbon quantum dots as fertilizers has been reported. For example, CN 112979353 A discloses a method for preparing a low-cost environmentally friendly carbon quantum dot nanofertilizer and its application. The nanofertilizer is made of biomass as a raw material, including one or a mixture of several biomasses such as peanut bran, rapeseed residue, tea residue, and bean dregs. The biomass raw material is crushed by a pulverizer, and then placed in a tubular furnace for heating, reacted at 150℃～350℃ for 1～12h, naturally cooled to room temperature, ground, added with tap water, and then filtered and purified to obtain a biomass carbon quantum dot aqueous solution, i.e., nano fertilizer. Its application method is to add a biomass carbon dot solution with a concentration of 0.01mg/mL～0.1mg/mL prepared by the above method to a conventional nutrient solution. CN 115259957 B discloses a preparation method and application of a cyanobacteria-based carbon quantum dot nano selenium fertilizer, wherein the preparation method uses cyanobacteria as a carbon source, and then mixes with a selenium-containing solution and obtains a nano selenium fertilizer by hydrothermal treatment at 200～300℃. The above-mentioned prior art mainly utilizes the structural characteristics and slow-release effect, good water solubility and biocompatibility of carbon quantum dots to improve the utilization efficiency of agricultural products to nutrient solution or selenium, but its effect on improving the cultivation of agricultural products in saline-alkali soil is limited. CN 118120561 A discloses an application of wolfberry carbon quantum dots as drip irrigation fertilizer for improving the salt tolerance of crops. The application method comprises dispersing the wolfberry carbon quantum dots in water to obtain a wolfberry carbon quantum dots solution, and then immersing the crop roots in the wolfberry carbon quantum dots solution to improve the salt tolerance of the crops. The invention also does not disclose the improvement effect of the carbon quantum dots on saline-alkali soil.

Antibiotic bacterial residue is an organic biomass pollutant with a large number of functional groups and high abundance. It is a potential carbon source for carbon quantum dots and has great development space and research potential. However, there is no report on the preparation of carbon quantum dots using antibiotic bacterial residue as raw material and its application in water-soluble compound fertilizer to improve its ability to improve saline-alkali.

Summary of the invention

In view of the shortcomings and deficiencies of the above prior art, the primary purpose of the present invention is to provide a water-soluble fertilizer for improving saline-alkali.

Another object of the present invention is to provide a method for preparing the above-mentioned improved saline-alkali water-soluble fertilizer.

Another object of the present invention is to provide the use of the above-mentioned water-soluble fertilizer for improving saline-alkali in the planting of crops in saline-alkali land.

The purpose of the present invention is achieved through the following technical solutions:

A saline-alkali improved water-soluble fertilizer comprises the following components in parts by weight:

30-80 parts of water-soluble silicon fertilizer, 30-60 parts of potassium humate, 5-20 parts of porous silica loaded carbon quantum dots, and 1-10 parts of stabilizer;

The porous silica-loaded carbon quantum dots are prepared by the following method:

(1) adding an acid solution and antibiotic bacterial residue to a hydrothermal reactor and mixing them evenly, heating them to 160-200° C. in a closed environment for a first hydrothermal reaction; after the reaction, centrifuging and separating the supernatant, adjusting the pH to neutral, and placing the supernatant in a hydrothermal reactor again for a second hydrothermal reaction by heating to 160-200° C. in a closed environment; after the reaction, filtering and collecting the filtrate to obtain a carbon quantum dot solution;

(2) adding porous silica to the carbon quantum dot solution of step (1) for stirring and adsorption treatment, and vacuum spray drying the mixed solution to obtain porous silica loaded with carbon quantum dots.

Furthermore, the water-soluble silicon fertilizer is a commonly used water-soluble fertilizer and soil conditioner in the art. The silicon content in the water-soluble silicon fertilizer is calculated as silicon dioxide (SiO ₂ ) mass percentage ≥ 50%, the phosphorus content is calculated as phosphorus pentoxide (P ₂ O ₅ ) mass percentage of 5% to 30%, the nitrogen element (N) mass percentage of 1% to 10%, and the potassium element is calculated as potassium oxide (K ₂ O) mass percentage of 0% to 6%.

Furthermore, the potassium humate is a highly efficient organic potassium fertilizer commonly used in the art, and its potassium content is 5% to 12%.

Furthermore, the stabilizer is one or more of carboxymethyl cellulose, hydroxyethyl cellulose, acrylamide polymer, and acrylic acid polymer.

Furthermore, the acid solution in step (1) is a nitric acid solution or a sulfuric acid solution with a concentration of 0.2 to 2 mol/L.

Furthermore, the antibiotic residue in step (1) refers to antibiotic residue with a moisture content of 20% to 90% and an antibiotic content of 20 to 500 mg/kg, including but not limited to tetracycline residue, cephalosporin residue, penicillin residue, and vancomycin residue.

Furthermore, in step (1), the mass ratio of the acid solution to the antibiotic residue is 1 to 5:1.

Furthermore, in step (1), potassium hydroxide or potassium carbonate is used to adjust the pH.

Furthermore, the time of the first hydrothermal reaction in step (1) is 3 to 10 hours, and the time of the second hydrothermal reaction is 1 to 5 hours.

Furthermore, the porous silica in step (2) preferably has a particle size of 5 to 6 μm and a pore size of 5 to 20 nm.

Furthermore, the amount of porous silica added in step (2) is 5% to 30% of the mass of the carbon quantum dot solution.

Furthermore, the stirring and adsorption treatment in step (2) is carried out for 6 to 48 hours.

Furthermore, the temperature of the vacuum spray drying in step (2) is 100-120° C., and the vacuum degree is >0.09 MPa.

The preparation method of the above-mentioned improved saline-alkali water-soluble fertilizer comprises the following preparation steps:

The components are weighed in parts by weight, and the water-soluble silicon fertilizer, potassium humate, porous silica loaded carbon quantum dots and stabilizer are stirred and mixed evenly to obtain a saline-alkali improved water-soluble fertilizer.

The application of the above-mentioned water-soluble fertilizer for improving saline-alkali in the planting of crops on saline-alkali land is as follows: the water-soluble fertilizer for improving saline-alkali is added into water to dissolve and disperse evenly, and then sprayed before planting crops or on saline-alkali land where crops are planted.

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

(1) The present invention uses porous silica loaded with carbon quantum dots as a modifier for water-soluble compound fertilizers, which can effectively reduce the soil exchangeable sodium content and soil alkalinity (ESP), reduce the absorption of sodium ions by plants, and effectively improve the soil compaction in saline-alkali land.

(2) The water-soluble fertilizer of the present invention adopts a compound of water-soluble silicon fertilizer and potassium humate, and combines porous silica loaded with carbon quantum dots as a promoter and structure modifier, which can significantly improve the fertilizer utilization rate; at the same time, the water-soluble silicon fertilizer and potassium humate are combined to achieve the slow release of Si, N, P, K and other elements, thereby improving the fertilizer efficiency and fertilizer retention capacity.

(3) The carbon quantum dots used in the present invention are obtained by a simple hydrothermal reaction using antibiotic bacterial residue as raw material, which has the advantages of wide raw material sources, low cost, and simple production; and can simultaneously achieve the degradation treatment and resource utilization of antibiotic bacterial residue, with good environmental and economic benefits.

DETAILED DESCRIPTION

The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

Example 1

A saline-alkali improved water-soluble fertilizer comprises the following components in parts by weight:

60 parts of water-soluble silicon fertilizer (SiO ₂ ≥50%, P ₂ O ₅ 18.6%, N 5.2%, K ₂ O 2.3%), 40 parts of potassium humate (K ₂ O 8.7%), 10 parts of porous silica-supported carbon quantum dots, and 6 parts of hydroxyethyl cellulose.

The porous silica-loaded carbon quantum dots are prepared by the following method:

(1) A nitric acid solution with a concentration of 1 mol/L and tetracycline residue (water content of 82.5%, tetracycline content of 102 mg/kg) were added to a hydrothermal reactor in a mass ratio of 3:1 and mixed evenly, and heated to 180°C in a closed environment for the first hydrothermal reaction for 5 hours; after the reaction, the supernatant was centrifuged and separated, and the pH was adjusted to neutral with potassium hydroxide, and the supernatant was put into the hydrothermal reactor again for a closed environment and heated to 180°C for a second hydrothermal reaction for 2 hours. After the reaction, the filtrate was filtered to obtain a carbon quantum dot solution. The average particle size of the obtained carbon quantum dots was 4.7 nm. After the treatment in this step, the reduction rate of tetracycline residue was 92.5% ((dry basis content of original tetracycline residue-dry basis content of residual solid residue after treatment)/dry basis content of original tetracycline residue * 100%), and tetracycline was not detected in the residual solid residue and the carbon quantum dot solution (HPLC detection), indicating that tetracycline has been completely degraded.

(2) Porous silica (particle size of 5 to 6 μm, pore size of 5 to 20 nm) is added to the carbon quantum dot solution of step (1) for stirring and adsorption treatment for 12 hours. The amount of porous silica added is 20% of the mass of the carbon quantum dot solution. The mixed solution is spray-dried at a temperature of 100 to 120° C. and a vacuum degree of >0.09 MPa to obtain porous silica-loaded carbon quantum dots.

The water-soluble fertilizer for improving saline-alkali in this embodiment is prepared by the following method:

The components are weighed in parts by weight, and the water-soluble silicon fertilizer, potassium humate, porous silica-loaded carbon quantum dots and hydroxyethyl cellulose are stirred and mixed evenly to obtain a saline-alkali improved water-soluble fertilizer.

The obtained improved saline-alkali water-soluble fertilizer meets the requirements of ecological-grade fertilizer after testing (total cadmium <0.5 mg/kg, total mercury <0.5 mg/kg, total arsenic <5 mg/kg, total lead <10 mg/kg, total chromium <50 mg/kg, total thallium <1.0 mg/kg, total nickel <300 mg/kg, total cobalt <50 mg/kg, total vanadium <200 mg/kg, total antimony <10 mg/kg, biuret <1.5%, phenyl[a]pyrene <0.01 mg/kg, total petroleum hydrocarbon content ≤0.20%, total phthalate content ≤10 m/kg, total antibiotic content <1.0 mg/kg, ascaris egg mortality rate 100%, fecal coliform count ≤100/g).

Example 2

A saline-alkali improved water-soluble fertilizer comprises the following components in parts by weight:

80 parts of water-soluble silicon fertilizer (SiO ₂ ≥50%, P ₂ O ₅ 18.6%, N 5.2%, K ₂ O 2.3%), 30 parts of potassium humate (K ₂ O 8.7%), 5 parts of porous silica-loaded carbon quantum dots, and 2 parts of hydroxyethyl cellulose.

The porous silica-loaded carbon quantum dots are prepared by the following method:

(1) A sulfuric acid solution with a concentration of 1 mol/L and penicillin residue (water content of 76.4%, penicillin content of 89 mg/kg) were added to a hydrothermal reactor in a mass ratio of 4:1 and mixed evenly, and heated to 200°C in a closed environment for the first hydrothermal reaction for 4 hours; after the reaction, the supernatant was centrifuged and separated, and the pH was adjusted to neutral with potassium hydroxide, and then put into the hydrothermal reactor again for a closed environment and heated to 200°C for a second hydrothermal reaction for 2 hours. After the reaction, the filtrate was filtered to obtain a carbon quantum dot solution. The average particle size of the obtained carbon quantum dots was 3.9 nm. After treatment in this step, the reduction rate of penicillin residue was 94.1%, and penicillin was not detected in the remaining solid residue and the carbon quantum dot solution (HPLC detection), indicating that penicillin has been completely degraded.

(2) Porous silica (particle size of 5 to 6 μm, pore size of 5 to 20 nm) is added to the carbon quantum dot solution of step (1) for stirring and adsorption treatment for 24 hours, and the amount of porous silica added is 10% of the mass of the carbon quantum dot solution. The mixed solution is spray-dried at a temperature of 100 to 120° C. and a vacuum degree of >0.09 MPa to obtain porous silica-loaded carbon quantum dots.

The preparation method of the saline-alkali improved water-soluble fertilizer in this embodiment is the same as that in embodiment 1. The obtained saline-alkali improved water-soluble fertilizer meets the requirements of ecological grade fertilizer after testing.

Example 3

A saline-alkali improved water-soluble fertilizer comprises the following components in parts by weight:

30 parts of water-soluble silicon fertilizer (SiO ₂ ≥50%, P ₂ O ₅ 18.6%, N 5.2%, K ₂ O 2.3%), 60 parts of potassium humate (K ₂ O 8.7%), 20 parts of porous silica-loaded carbon quantum dots, and 10 parts of hydroxyethyl cellulose.

The porous silica-loaded carbon quantum dots are prepared by the following method:

(1) A nitric acid solution with a concentration of 2 mol/L and vancomycin residue (water content of 81.2%, vancomycin content of 110 mg/kg) were added to a hydrothermal reactor in a mass ratio of 2:1 and mixed evenly, and heated to 160°C in a closed environment for the first hydrothermal reaction for 8 hours; after the reaction, the supernatant was centrifuged and separated, and the pH was adjusted to neutral with potassium hydroxide, and then placed in a hydrothermal reactor again for a closed environment and heated to 160°C for a second hydrothermal reaction for 4 hours. After the reaction, the filtrate was filtered to obtain a carbon quantum dot solution. The average particle size of the obtained carbon quantum dots was 5.2 nm. After treatment in this step, the reduction rate of vancomycin residue was 90.6%, and no vancomycin was detected in the remaining solid residue and the carbon quantum dot solution (HPLC detection), indicating that vancomycin has been completely degraded.

(2) Porous silica (particle size of 5 to 6 μm, pore size of 5 to 20 nm) is added to the carbon quantum dot solution of step (1) for stirring and adsorption treatment for 12 hours, and the amount of porous silica added is 30% of the mass of the carbon quantum dot solution. The mixed solution is spray-dried at a temperature of 100 to 120° C. and a vacuum degree of >0.09 MPa to obtain porous silica-loaded carbon quantum dots.

The preparation method of the saline-alkali improved water-soluble fertilizer in this embodiment is the same as that in embodiment 1. The obtained saline-alkali improved water-soluble fertilizer meets the requirements of ecological grade fertilizer after testing.

Comparative Example 1

A saline-alkali improved water-soluble fertilizer comprises the following components in parts by weight:

60 parts of water-soluble silicon fertilizer (SiO ₂ ≥50%, P ₂ O ₅ 18.6%, N 5.2%, K ₂ O 2.3%), 40 parts of potassium humate (K ₂ O 8.7%), and 6 parts of hydroxyethyl cellulose.

Comparative Example 2

A saline-alkali-improving water-soluble fertilizer comprises the following components in parts by weight:

60 parts of water-soluble silicon fertilizer (SiO ₂ ≥50%, P ₂ O ₅ 18.6%, N 5.2%, K ₂ O 2.3%), 40 parts of potassium humate (K ₂ O 8.7%), 10 parts of porous silicon dioxide (particle size of 5-6 μm, pore size of 5-20 nm), and 6 parts of hydroxyethyl cellulose.

Comparative Example 3

A saline-alkali improved water-soluble fertilizer comprises the following components in parts by weight:

60 parts of water-soluble silicon fertilizer (SiO ₂ ≥50%, P ₂ O ₅ 18.6%, N 5.2%, K ₂ O 2.3%), 40 parts of potassium humate (K ₂ O 8.7%), 10 parts of carbon quantum dots (obtained by vacuum spray drying the carbon quantum dots solution in Example 1), and 6 parts of hydroxyethyl cellulose.

1. The water-soluble fertilizers of the improved saline-alkali of the above-mentioned Example 1 and Comparative Examples 1 to 3 are respectively applied to saline-alkali land for fertilization treatment. The application method is to add the water-soluble fertilizers of the improved saline-alkali to 500 times water to dissolve and disperse evenly, and then spray them on the saline-alkali land before planting crops, and the application amount is 25kg water-soluble fertilizer/mu. After 24 hours of application, samples are taken to test the exchangeable sodium content, soil alkalinity (ESP) and soil EC value of the soil. Three parallel samples are tested for each group of samples, and the average value is taken. The saline-alkali land without fertilization treatment is used as the control group. The test results are shown in Table 1 below.

Table 1

Test sample Exchangeable sodium content/cmol·kg ^-1 ESP/% EC value/dS/m Example 1 6.3 5.8 9.1 Comparative Example 1 16.0 13.7 18.4 Comparative Example 2 11.5 9.6 15.7 Comparative Example 3 9.1 11.4 14.5 Control group 17.6 15.6 24.2

From the results in Table 1, it can be seen that the present invention uses porous silica loaded with carbon quantum dots as a modifier for water-soluble compound fertilizer, which can effectively reduce the soil exchangeable sodium content, soil alkalinity (ESP) and soil EC value. At the same time, the loading combination of porous silica and carbon quantum dots has an obvious synergistic effect, which may be due to the combination of the two improving its pore transmission channel and adsorption active sites, effectively improving the adsorption and exchange of ions in saline-alkali soil, thereby achieving the effect of significantly reducing the soil exchangeable sodium content, soil alkalinity and soil EC value.

Second, the water-soluble fertilizers of the improved saline-alkali fertilizers of the above-mentioned embodiment 1 and comparative examples 1 to 3 are respectively applied to the saline-alkali land soybean planting fertilization treatment after the treatment in step 1, and the water-soluble fertilizers of the improved saline-alkali fertilizers are added to 500 times of water to dissolve and disperse evenly, and then sprayed on the saline-alkali land where soybeans are planted. The number of applications during the period from soybean planting to maturity is 3 times, and the application amount each time is 15kg of water-soluble fertilizer/mu. After harvest, the yield increase effect of each experimental group relative to the control group is calculated, and 3 parallels are set for each group, and the average value is taken. The results are shown in Table 2 below.

Table 2

Test sample Yield per mu Production increase rate Example 1 189.5kg 42.7% Comparative Example 1 164.0kg 23.5% Comparative Example 2 169.9kg 27.9% Comparative Example 3 180.1kg 35.6% Control group 132.8kg ----

It can be seen from the results in Table 2 that the addition of carbon quantum dots can effectively improve the yield-increasing effect of water-soluble fertilizers, and the yield-increasing effect of using porous silica to load carbon quantum dots is more significant.

Comparative Example 4

This comparative example adopts a one-step hydrothermal method to prepare a carbon quantum dot solution, and the specific preparation steps are as follows:

A nitric acid solution with a concentration of 1 mol/L and tetracycline residue (water content of 82.5%, tetracycline content of 102 mg/kg) were added to a hydrothermal reactor in a mass ratio of 3:1 and mixed evenly, and heated to 180 ° C in a closed environment for hydrothermal reaction for 7 hours; after the reaction, potassium hydroxide was used to adjust the pH to neutral, and the filtrate was filtered to obtain a carbon quantum dot solution. The average particle size of the obtained carbon quantum dots was 13.2 nm. After this step, the reduction rate of tetracycline residue was 92.7%, and no tetracycline was detected in the remaining solid residue and the carbon quantum dot solution (HPLC detection), indicating that tetracycline has been completely degraded.

By comparing the results of this comparative example with those of Example 1, it can be seen that the particle size of the obtained carbon quantum dots can be significantly reduced by the two-step hydrothermal method of the present invention.

Comparative Example 5

In the preparation process of the carbon quantum dot solution of this comparative example, no acid solution was added, and the specific preparation steps were as follows:

Deionized water and tetracycline residue (water content of 82.5%, tetracycline content of 102mg/kg) were added to the hydrothermal reactor in a mass ratio of 3:1 and mixed evenly, and heated to 180°C in a closed environment for the first hydrothermal reaction for 5h; after the reaction, the supernatant was centrifuged and separated, and the pH was adjusted to neutral with potassium hydroxide, and then put into the hydrothermal reactor again for a closed environment and heated to 180°C for the second hydrothermal reaction for 2h. After the reaction, the filtrate was filtered to obtain a carbon quantum dot solution. The average particle size of the obtained carbon quantum dots was 16.9nm. After this step, the reduction rate of tetracycline residue was 72.8%, and tetracycline was not detected in the remaining solid residue and the carbon quantum dot solution (HPLC detection), indicating that tetracycline has been completely degraded.

By comparing the results of this comparative example with those of Example 1, it can be seen that the present invention can significantly improve the reduction rate of antibiotic residue and significantly reduce the particle size of the obtained carbon quantum dots by acid-assisted hydrothermal degradation of antibiotic residue.

The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims (10)

1. The water-soluble fertilizer for improving the salt and alkali is characterized by comprising the following components in parts by weight:

30-80 parts of water-soluble silicon fertilizer, 30-60 parts of potassium humate, 5-20 parts of porous silicon dioxide loaded carbon quantum dots and 1-10 parts of stabilizer;

The porous silica supported carbon quantum dot is prepared by the following method:

(1) Adding the acid solution and the antibiotic residues into a hydrothermal reactor, uniformly mixing, and heating to 160-200 ℃ in a closed environment to perform a first hydrothermal reaction; centrifuging to obtain supernatant after the reaction is finished, regulating the pH to be neutral, putting the supernatant into a hydrothermal reactor again, heating the mixture to 160-200 ℃ in a closed environment, performing a second hydrothermal reaction, and filtering the filtrate after the reaction is finished to obtain a carbon quantum dot solution;

(2) Adding porous silicon dioxide into the carbon quantum dot solution in the step (1) for stirring and adsorbing treatment, and carrying out vacuum spray drying on the mixed solution to obtain the porous silicon dioxide loaded carbon quantum dot.

2. The water-soluble fertilizer for improving the salt and alkali according to claim 1, wherein the silicon content in the water-soluble silicon fertilizer is more than or equal to 50 percent by mass of silicon dioxide, the phosphorus content is 5-30 percent by mass of phosphorus pentoxide, the nitrogen element content is 1-10 percent by mass, and the potassium element content is 0-6 percent by mass; the potassium content in the potassium humate is 5-12%.

3. The saline-alkali-tolerant water-soluble fertilizer according to claim 1, wherein the stabilizer is one or more of carboxymethyl cellulose, hydroxyethyl cellulose, acrylamide polymer and acrylic acid polymer.

4. The water-soluble fertilizer for improving saline and alkaline according to claim 1, wherein the acid solution in the step (1) is a nitric acid solution or a sulfuric acid solution with a concentration of 0.2-2 mol/L; the antibiotic dregs are antibiotic dregs with water content of 20-90% and antibiotic content of 20-500 mg/kg, including tetracycline dregs, cephalosporin dregs, penicillin dregs and vancomycin dregs.

5. The saline-alkali-improved water-soluble fertilizer according to claim 4, wherein the mass ratio of the acid solution to the antibiotic residues is 1-5:1.

6. The saline-alkali-improved water-soluble fertilizer according to claim 1, wherein in the step (1), potassium hydroxide or potassium carbonate is used for adjusting the pH; the time of the first hydrothermal reaction is 3-10 h, and the time of the second hydrothermal reaction is 1-5 h.

7. The saline-alkali-improved water-soluble fertilizer according to claim 1, wherein the porous silica in the step (2) is porous silica with a particle size of 5-6 μm and a pore size of 5-20 nm; the addition amount of the porous silicon dioxide is 5-30% of the mass of the carbon quantum dot solution.

8. The water-soluble fertilizer for improving saline and alkaline according to claim 1, wherein the stirring and adsorbing treatment time in the step (2) is 6-48 h; the temperature of the vacuum spray drying is 100-120 ℃, and the vacuum degree is more than 0.09MPa.

9. The method for preparing the saline-alkali-improved water-soluble fertilizer as claimed in any one of claims 1 to 8, which is characterized by comprising the following preparation steps:

weighing the components in parts by weight, and uniformly stirring and mixing the water-soluble silicon fertilizer, the potassium humate, the porous silicon dioxide loaded carbon quantum dots and the stabilizer to obtain the water-soluble fertilizer with improved salt and alkali.

10. The application method of the saline-alkali-improved water-soluble fertilizer in saline-alkali soil crop planting comprises the steps of adding the saline-alkali-improved water-soluble fertilizer into water, dissolving and dispersing uniformly, and then spraying the saline-alkali-improved water-soluble fertilizer on the saline-alkali soil before planting crops or on the saline-alkali soil with the crops.