Preparation method of charcoal-based slow-release phosphate fertilizer based on foamed magnesium modified charcoal

Abstract

The invention provides a preparation method of a biochar-based slow-release phosphate fertilizer based on foamed magnesium modified biochar. The preparation method comprises the following steps: step 1, preparing foamed magnesium modified biochar by taking straw as a raw material; 2, phosphorus-containing wastewater is treated on the basis of the foamed magnesium modified biochar; and step 3, preparing the biochar-based slow-release phosphate fertilizer based on the foamed magnesium modified biochar after phosphorus-containing wastewater treatment. The magnesium modified biochar is prepared by a foaming technology, a phosphate adsorbent with a large specific surface area is obtained, the purification effect of the biochar on phosphorus-containing wastewater is effectively enhanced, and meanwhile, a method for preparing a slow-release phosphate fertilizer from the biochar which has treated the phosphorus-containing wastewater is provided. The phosphorus-containing wastewater is efficiently and stably treated, and meanwhile, the method has the advantages of being low in cost, convenient to use and good in environmental benefit.

Description

Technical Field

[0001] The invention relates to a method for preparing a biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar, and belongs to the technical field of sewage remediation. Background Art

[0002] With the rapid development of economy and society, the eutrophication of water bodies caused by excessive discharge of phosphorus-containing wastewater has put tremendous pressure on the environment, thus attracting extensive attention from researchers in various countries. Recycling pollutants in wastewater by adsorption is conducive to the recycling of resources.

[0003] Biochar is a solid material obtained by pyrolysis of biomass under anaerobic or anoxic conditions. It has the greatest potential in wastewater treatment due to its low price, stable properties, and excellent adsorption effect. However, raw biochar is usually negatively charged and reacts negatively with phosphate, which is also an anion. The adsorption of phosphorus on the surface of biochar can be effectively enhanced by increasing the specific surface area of ​​biochar, increasing the number of surface functional groups, and attaching cations on the surface. The physical and chemical reactions of active phosphorus can further improve the removal effect of biochar on phosphate.

[0004] my country is a big agricultural country with abundant straw resources. Biochar is a commonly used adsorbent and a soil conditioner with many excellent properties. It is one of the mainstream ways to recycle straw.

[0005] Foamed magnesium-modified biochar is prepared using straw as raw material, which is used to treat phosphorus-containing wastewater and then made into slow-release phosphate fertilizer for returning to the field. Based on this, the present invention proposes a method for preparing biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar. Summary of the invention

[0006] The present invention aims to solve the problem that the original biochar in the prior art reacts with phosphate, which is also an anion. In order to solve the technical problem that the active phosphorus has a repulsive effect, resulting in poor adsorption effect, a method for preparing a biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar is proposed.

[0007] The technical solution adopted by the present invention to solve the above problems is: the present invention proposes a method for preparing a biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar, comprising:

[0008] Step 1: preparing foamed magnesium-modified biochar using straw as raw material;

[0009] Step 2: Treatment of phosphorus-containing wastewater based on foamed magnesium-modified biochar;

[0010] Step 3: Preparation of biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar after treating phosphorus-containing wastewater.

[0011] Optionally, the foamed magnesium-modified biochar in step 1 is divalent magnesium-modified biochar, and divalent magnesium is attached to the surface and micropores.

[0012] Optionally, the step of preparing modified biochar in step 1 includes:

[0013] Step 1.1: Screen the corn stover and mix the screened corn stover and Mg(HCO 3 ) 2 The solution is mixed and stirred;

[0014] Step 1.2: Mix the corn stover and Mg(HCO 3 ) 2 The solution is filtered and separated to obtain a filter residue;

[0015] Step 1.3: drying the filter residue to constant weight, grinding and screening to obtain biomass powder;

[0016] Step 1.4: The biomass powder is placed in a tubular furnace, heated to 750°C under nitrogen protection, and pyrolyzed after heating. After the pyrolysis is completed, the powder is naturally cooled to room temperature to obtain foamed magnesium-modified biochar;

[0017] Step 1.5: Wash the foamed magnesium-modified biochar with deionized water for 3-5 times, centrifuge dry, and seal for storage.

[0018] Optionally, in step 1.1, the corn stalks are screened using a 100-mesh sieve, the rotation speed during the mixing and stirring process is 300 r / min, and the mixing and stirring time is 24 h.

[0019] Optionally, the temperature during the drying process in step 1.3 is 60° C., and a 100-mesh sieve is used to screen the filter residue after drying and grinding.

[0020] Optionally, the heating rate during the heating process in step 1.4 is 10°C / min and the pyrolysis time is 2h.

[0021] Optionally, the step of preparing the biochar-based slow-release phosphate fertilizer in step 3 includes:

[0022] Step 3.1: Prepare potassium dihydrogen phosphate solution;

[0023] Step 3.2: Add the foamed magnesium-modified biochar as an adsorbent into a potassium dihydrogen phosphate solution and shake to obtain a precipitate;

[0024] Step 3.3: Dry the precipitate at 60°C to constant weight to obtain biochar-based slow-release phosphate fertilizer.

[0025] Optionally, the step of preparing the potassium dihydrogen phosphate solution in step 3.1 comprises:

[0026] A potassium dihydrogen phosphate solution was obtained by dissolving 100 mg of potassium dihydrogen phosphate in 50 mL of deionized water.

[0027] Optionally, in step 3.2, the weight ratio of the foamed magnesium-modified biochar to the potassium dihydrogen phosphate solution is 1:50, the temperature during the oscillation process is 25° C., the oscillation rate is 140 r / min, and the oscillation time is 24 h.

[0028] The beneficial effects of the present invention are:

[0029] The present invention uses a foaming technique to prepare magnesium-modified biochar, obtains a phosphate adsorbent with a large specific surface area, effectively enhances the purification effect of biochar on phosphorus-containing wastewater, and proposes a method for preparing biochar that has treated phosphorus-containing wastewater into a slow-release phosphate fertilizer. While achieving efficient and stable treatment of phosphorus-containing wastewater, it also has the advantages of low cost, easy use, and good environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A flow chart of a method for preparing a biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar provided by the present invention;

[0031] Figure 2 A flow chart for preparing the foamed magnesium-modified biochar provided by the present invention;

[0032] Figure 3 A flow chart for preparing the biochar-based slow-release phosphate fertilizer provided by the present invention;

[0033] Figure 4 This is a rendering of the effect of preparing foamed magnesium-modified biochar using the foaming technology provided by the present invention;

[0034] Figure 5 This is a diagram showing the absorption and desorption effects of the foamed magnesium-modified biochar prepared by the foaming technology provided by the present invention;

[0035] Figure 6 A microscopic surface view of the prepared foamed magnesium-modified biochar provided by the present invention;

[0036] Figure 7 A comparison chart of the treatment of phosphorus-containing wastewater by using foamed magnesium-modified biochars of different concentrations provided by the present invention;

[0037] Figure 8 A comparison diagram of the dissolution effect of phosphorus after adding the biochar-based slow-release phosphate fertilizer provided by the present invention;

[0038] Fig. 9 A comparison chart of phosphate content after adding biochar-based slow-release phosphate fertilizer provided by the present invention;

[0039] Fig.10 This is a comparison diagram of the growth of plants after adding the biochar-based slow-release phosphate fertilizer provided by the present invention. DETAILED DESCRIPTION

[0040] Specific implementation method 1: Combination Figure 1 and Figure 4-6 To illustrate this embodiment, Figure 1 As shown, the method for preparing a biochar-based slow-release phosphate fertilizer using foamed magnesium-modified biochar in this embodiment includes the following steps:

[0041] S1: Preparation of foamed magnesium-modified biochar using straw as raw material;

[0042] S101: Pass corn stalks through a 100-mesh sieve, add Mg(HCO3) solution, mix, and stir at a speed of 300 r / min for 24 h;

[0043] S102: filtering and separating, drying the filter residue at 60° C. to constant weight, grinding, and passing through a 100-mesh sieve to obtain biomass powder;

[0044] S103: placing the biomass powder into a tubular furnace, passing nitrogen protection, and heating to 750°C at a heating rate of 10°C / min, pyrolyzing for 2 hours, and then naturally cooling to room temperature to obtain foamed magnesium-modified biochar;

[0045] S104: Wash the biochar with deionized water for 3-5 times, centrifuge and dry, and seal and store.

[0046] The prepared foamed magnesium-modified biochar is divalent magnesium-modified biochar, and divalent magnesium is attached to the surface and micropores.

[0047] like Figure 4 and Figure 5 As shown, this embodiment uses foaming technology to pyrolyze magnesium bicarbonate at 750 degrees Celsius to release a large amount of carbon dioxide. The release process will expand the pore structure of the biochar and obtain biochar with a larger specific surface area. The foamed magnesium modified biochar prepared in this embodiment is as follows Figure 6 As shown, the prepared foamed magnesium-modified biochar has a larger surface area, and the material has many pores and strong adsorption capacity, and can efficiently and stably treat phosphorus-containing wastewater.

[0048] S2: Treatment of phosphorus-containing wastewater based on foamed magnesium-modified biochar;

[0049] S3: Biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar after treatment of phosphorus-containing wastewater.

[0050] Specific implementation method 2: Combination Figure 2 To illustrate this embodiment, Figure 2 As shown, the steps for preparing the foamed magnesium-modified biochar described in this embodiment include:

[0051] S201: screening corn stalks and mixing them with magnesium bicarbonate solution;

[0052] In S201, the corn stalks are screened using a 100-mesh sieve, the rotation speed during the mixing and stirring process is 300 r / min, and the mixing and stirring time is 24 h;

[0053] S202: filtering and separating the mixed corn stalks and magnesium bicarbonate solution to obtain a filter residue;

[0054] S203: drying the filter residue to a constant weight, grinding and screening the residue to obtain biomass powder;

[0055] The temperature during the drying process in S203 is 60° C., and a 100-mesh sieve is used to screen the filter residue after drying and grinding.

[0056] S204: putting the biomass powder into a tubular furnace, heating and degrading after passing helium protection, and naturally cooling to room temperature to obtain foamed magnesium-modified biochar;

[0057] The heating rate of S204 during the heating process is 10°C / min and the pyrolysis time is 2h.

[0058] S205: Wash the foamed magnesium-modified biochar with deionized water for 3-5 times, centrifugally dry it, and seal it for storage.

[0059] Specific implementation method three: Combination Figure 3 The present embodiment is described. The steps for preparing the biochar-based slow-release phosphate fertilizer described in the present embodiment include:

[0060] S301: preparing potassium dihydrogen phosphate solution;

[0061] The step of preparing potassium dihydrogen phosphate solution in S301 comprises:

[0062] A potassium dihydrogen phosphate solution was obtained by dissolving 100 mg of potassium dihydrogen phosphate in 50 mL of deionized water.

[0063] S302: adding the foamed magnesium-modified biochar as an adsorbent into a potassium dihydrogen phosphate solution and shaking to obtain a precipitate;

[0064] The weight ratio of the foamed magnesium-modified biochar to the potassium dihydrogen phosphate solution in S302 was 1:50, the temperature during the oscillation was 25°C, the oscillation rate was 140 r / min, and the oscillation time was 24 h.

[0065] S303: Drying the precipitate at 60° C. to a constant weight to obtain a biochar-based slow-release phosphate fertilizer.

[0066] Example

[0067] Example 1

[0068] This example explores the effect of the amount of adsorbent produced by the present invention on the adsorption effect. The preparation method of the foamed magnesium modified biochar in this example is the same as the preparation method in the second specific embodiment, wherein 0.1 mol / L, 0.5 mol / L, 1 mol / L Mg(HCO 3 ) 2 Three kinds of foamed magnesium-modified biochars were prepared according to solution concentration. 0.0025g, 0.005g, 0.01g, 0.015g, 0.02g and 0.025g of each biochar were respectively added into 50mL of potassium dihydrogen phosphate solution with a potassium dihydrogen phosphate concentration of 10mg / L and pH=7 at 25℃. The mixture was shaken in a shaker at a speed of 140r / min for 24h. After reaching adsorption equilibrium, the remaining phosphate content in the supernatant was tested by a UV spectrometer. The phosphate test method was molybdenum blue colorimetry.

[0069] like Figure 7 As shown, in this embodiment, the treatment effects of biochar-based slow-release phosphate fertilizers prepared with different masses of modified biochar on phosphorus-containing wastewater are compared. When the mass of the foamed magnesium modified biochar is 0.05 g / L, the treatment of phosphorus-containing wastewater is best.

[0070] Example 2

[0071] In this example, an isothermal adsorption test was carried out, and the experimental scheme was as follows: a potassium dihydrogen phosphate solution was used to prepare simulated wastewater containing different concentrations of phosphate. The concentrations of the potassium dihydrogen phosphate solution in this example were 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, and 30 mg / L, respectively, 50 mL each, and the pH was 7; the preparation method of the foamed magnesium-modified biochar in this example was the same as the preparation method in the second specific implementation method, and an adsorbent was added to the potassium dihydrogen phosphate solution with an adsorbent concentration of 0.1 g / L. Under 25°C, the mixture was shaken in a shaker at a speed of 140 r / min for 24 hours. After reaching adsorption equilibrium, the remaining phosphate content in the supernatant was tested with an ultraviolet grader, and the phosphate test method was molybdenum blue colorimetry.

[0072] Example 3

[0073] In this example, an adsorption kinetics test was carried out, and the test scheme is as follows: the concentration of the potassium dihydrogen phosphate solution in this example is 10 mg / L, 50 mL, and the pH is 7; the preparation method of the foamed magnesium-modified biochar in this example is the same as the preparation method in the second specific implementation method, and an adsorbent is added to the potassium dihydrogen phosphate solution, and the adsorbent concentration is 0.1 g / L. Each group of 5 tubes of solution is shaken in a shaker at a speed of 140 r / min for 24 hours at 25°C. The phosphate concentration is sampled and tested at 2h, 4h, 8h, 12h, and 24h. This example has three parallel groups, and the phosphate test method is the molybdenum blue colorimetric method.

[0074] Example 4

[0075] This example explores the effect of the adsorbent produced by the present invention on the adsorption effect under different pH conditions. The preparation method of the foamed magnesium modified biochar in this example is the same as the preparation method in the second specific implementation method. A group of 8 tubes of 50mL potassium dihydrogen phosphate solution with a concentration of 10mg / L is used to adjust the pH value with hydrochloric acid and sodium hydroxide. The pH is set to 3, 4, 5, 6, 7, 8, 9, and 10 respectively. The adsorbent is added to the potassium dihydrogen phosphate solution. The adsorbent concentration is 0.1g / L. Under 25°C, shake in a shaker with a speed of 140r / min for 24h. After reaching adsorption equilibrium, the remaining phosphate content in the supernatant is tested with a UV grader. This example has three parallel groups, and the phosphate test method is molybdenum blue colorimetry.

[0076] Example 5

[0077] This example explores the slow-release effect of the slow-release phosphate fertilizer produced by the present invention. In this example, a soil column is set to simulate the effect of rainfall on soil phosphorus under natural conditions. 1% biochar-based slow-release phosphate fertilizer is added to the soil. The soil column is cultivated for 35 days and leached every 7 days.

[0078] The leaching experiment is as follows: 240 mL of deionized water is leached into the soil column at a flow rate of 2 mL / min, and the leached solution is collected, 10 mL in each tube, and the phosphate content in the solution is tested with a UV spectrometer to compare the dissolution effect of phosphorus. The phosphate test method is the molybdenum blue colorimetric method.

[0079] like Figure 8 and Fig. 9 As shown, after adding the biochar-based slow-release phosphate fertilizer prepared by the present invention to the soil, the phosphate content is significantly reduced within 7-35 days without affecting other beneficial nutrients in the soil.

[0080] like Fig.10As shown, the right side shows the growth of the plants after the addition of biochar-based slow-release phosphate fertilizer in this embodiment. It can be seen that compared with the other two pots of plants, the addition of biochar-based slow-release phosphate fertilizer can effectively promote plant growth, indicating that the biochar-based slow-release phosphate fertilizer prepared in the present invention has the advantages of low cost, easy use and good environmental benefits.

[0081] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar, characterized in that: The method for preparing a biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar comprises the following steps: Step 1: preparing foamed magnesium-modified biochar using straw as raw material; Step 2: treating phosphorus-containing wastewater based on the foamed magnesium-modified biochar; Step 3: Prepare biochar-based slow-release phosphate fertilizer based on the foamed magnesium-modified biochar after treating phosphorus-containing wastewater.

2. The method for preparing a biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar according to claim 1, characterized in that: The foamed magnesium-modified biochar in step 1 is divalent magnesium-modified biochar, and divalent magnesium is attached to the surface and micropores.

3. The method for preparing a biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar according to claim 1, characterized in that: The step of preparing foamed magnesium-modified biochar in step 1 comprises: Step 1.1: Screen the corn stalks, and mix and stir the screened corn stalks and the Mg(HCO3)2 solution; Step 1.2: filtering and separating the mixed corn stalks and Mg(HCO3)2 solution to obtain a filter residue; Step 1.3: drying the filter residue to a constant weight, grinding and screening to obtain biomass powder; Step 1.4: placing the biomass powder into a tubular furnace, heating it to 750° C. under nitrogen protection, performing pyrolysis after heating, and naturally cooling it to room temperature after the pyrolysis to obtain foamed magnesium-modified biochar; Step 1.5: Wash the foamed magnesium-modified biochar with deionized water for 3-5 times, centrifuge dry, and seal for storage.

4. The method for preparing a biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar according to claim 3, characterized in that: In step 1.1, the corn stalks were screened using a 100-mesh sieve, the rotation speed during the mixing and stirring process was 300 r / min, and the mixing and stirring time was 24 h.

5. The method for preparing a biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar according to claim 3, characterized in that: The temperature during the drying process in step 1.3 is 60° C., and a 100-mesh sieve is used to screen the filter residue after drying and grinding.

6. The method for preparing a biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar according to claim 3, characterized in that: The heating rate during the heating process in step 1.4 is 10°C / min and the pyrolysis time is 2h.

7. The method for preparing a biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar according to claim 1, characterized in that: The steps of preparing the biochar-based slow-release phosphate fertilizer in step 3 include: Step 3.1: Prepare potassium dihydrogen phosphate solution; Step 3.2: adding the foamed magnesium-modified biochar as an adsorbent into a potassium dihydrogen phosphate solution and shaking to obtain a precipitate; Step 3.3: Dry the precipitate at 60° C. to a constant weight to obtain a biochar-based slow-release phosphate fertilizer.

8. The method for preparing a biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar according to claim 7, characterized in that: The steps of preparing potassium dihydrogen phosphate solution in step 3.1 include: A potassium dihydrogen phosphate solution was obtained by dissolving 100 mg of potassium dihydrogen phosphate in 50 mL of deionized water.

9. The method for preparing a biochar-based slow-release phosphate fertilizer based on foamed magnesium-modified biochar according to claim 7, characterized in that: In step 3.2, the weight ratio of the foamed magnesium-modified biochar to the potassium dihydrogen phosphate solution is 1:50, the temperature during the oscillation process is 25°C, the oscillation rate is 140 r / min, and the oscillation time is 24 h.

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