A denitrification and dephosphorization agent and preparation method thereof

Abstract

The invention discloses a denitrification and dephosphorization agent and a preparation method thereof. First, corn stalks and a metal nitrate aqueous solution are used as raw materials to prepare metal-based biochar, and then acrylamide is polymerized in situ with the metal-based biochar as a matrix to prepare modified metal-based biochar; then acrylic acid is used to graft starch to obtain acrylic acid grafted starch, and then the acrylic acid grafted starch is reacted with ethylenediamine solution to obtain amino chelated starch, and enzymatic hydrolysis is performed to obtain porous amino chelated starch; finally, the modified metal-based biochar and the porous amino chelated starch are compounded to obtain the agent. The agent can simultaneously achieve denitrification and dephosphorization of sewage, and has very good application prospects.

Description

Technical Field

[0001] The present invention relates to a sewage treatment agent, in particular to a denitrification and dephosphorization agent and a preparation method thereof, belonging to the technical field of sewage treatment. Background Art

[0002] In recent years, with the continuous development of industrialization, a large amount of sewage rich in nitrogen and phosphorus has been generated in industrial production. In addition, the use of agricultural nitrogen and phosphorus fertilizers has also accumulated a considerable amount of nitrogen and phosphorus in the soil, and entered the water body with drainage. Livestock and poultry breeding also produces sewage with high nitrogen and phosphorus content. Sewage rich in nitrogen and phosphorus directly discharged into the water body will cause eutrophication of the water body in a short period of time, destroy the ecological balance, cause serious pollution to surface water and groundwater, and ultimately affect human health. Therefore, it is very important to remove nitrogen and phosphorus from sewage.

[0003] At present, there are four main methods for sewage treatment:

[0004] Physical method: Separate and remove insoluble suspended pollutants in wastewater through physical action, such as screening, interception, centrifugal separation, etc. The steps are relatively simple and the processing speed is fast, but it is difficult to treat impurities dissolved in sewage;

[0005] Chemical method: Add environmental protection chemicals for sewage treatment to water to separate pollutants in dissolved and colloidal states in water through chemical reactions, such as coagulation method, oxidation-reduction method, etc.; currently, the commonly used environmental protection chemicals for sewage treatment are inorganic treatment agents such as aluminum salts and iron salts;

[0006] Biological method: using the metabolism of microorganisms to convert organic pollutants in the wastewater in dissolved and alternating states into harmless substances to achieve purification; it can be divided into aerobic biological treatment and anaerobic biological treatment;

[0007] Physical and chemical method: Use physical and chemical effects to remove pollutants from water, including ion exchange, membrane separation and electroadsorption.

[0008] Among them, adsorption treatment by adding chemicals is the most common in sewage treatment practice, with simple operation and low treatment cost. However, nitrogen and phosphorus are indicators that are difficult to control, and it is even more difficult to achieve nitrogen removal and phosphorus removal at the same time. Therefore, it is of great significance to study simultaneous nitrogen removal and phosphorus removal.

[0009] Patent CN115367853B discloses an environmentally friendly agent for sewage treatment and its preparation method, which is made by mixing modified chitin, fungicide, volcanic rock and polyaspartic acid as raw materials. The agent of this patent technology has a relatively high COD removal rate and a removal rate of suspended solids in water, but the effect on nitrogen and phosphorus removal is relatively limited. Summary of the invention

[0010] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and to provide a denitrification and dephosphorization agent and a preparation method thereof.

[0011] To achieve the above object, the present invention adopts the following technical solutions:

[0012] The present invention provides a method for preparing a denitrification and dephosphorization agent, and the specific steps are as follows:

[0013] (1) First, corn straw and a metal nitrate aqueous solution are used as raw materials to prepare metal-based biochar, and then acrylamide is in situ polymerized on the metal-based biochar as a matrix to prepare modified metal-based biochar;

[0014] (2) then grafting the starch with acrylic acid to obtain acrylic acid grafted starch, and then reacting the acrylic acid grafted starch with an ethylenediamine solution to obtain amino chelated starch, and performing enzymatic hydrolysis to obtain porous amino chelated starch;

[0015] (3) Finally, the modified metal-based biochar is compounded with porous amino-chelated starch to prepare the denitrification and phosphorus removal agent.

[0016] Preferably, in step (1), the metal-based biochar is prepared by the following method: first, the corn stalks are cut into sections, washed and dried, crushed and ground to 100 mesh, and the stalk powder is obtained; then, the stalk powder is added to a metal nitrate aqueous solution, impregnated, vacuum dried, and calcined to obtain the metal-based biochar.

[0017] Further preferably, the usage ratio of straw powder to metal nitrate aqueous solution is 1g:5-6mL; the metal nitrate aqueous solution is a copper nitrate-zinc nitrate-cerium nitrate mixed aqueous solution, and the mass concentrations of copper nitrate, zinc nitrate and cerium nitrate contained therein are 3-4%, 2-3% and 1-2% respectively.

[0018] Further preferably, the process conditions of the immersion treatment are: 300-400W ultrasonic oscillation treatment for 2-3 hours, and 300-400W microwave irradiation for 5-6 minutes.

[0019] More preferably, the calcination process conditions are: calcination at 350-450° C. for 2-3 hours.

[0020] Preferably, in step (1), the specific method of in-situ polymerization of acrylamide is: firstly ultrasonically disperse the metal-based biochar in water to obtain a biochar dispersion, then add acrylamide monomer to the biochar dispersion, stir and mix, add potassium persulfate solution, polymerize under ultrasonic conditions, centrifuge to obtain the precipitate, wash, and dry to obtain the modified metal-based biochar.

[0021] Further preferably, the usage ratio of the metal-based biochar, water, acrylamide monomer and potassium persulfate solution is 1 g: 10-12 mL: 0.1-0.2 g: 0.3-0.4 mL; and the mass concentration of the potassium persulfate solution is 0.2-0.3%.

[0022] Further preferably, the process conditions of the polymerization reaction are: ultrasonic treatment at 200-300W for 30-40 minutes at 25-30°C.

[0023] Preferably, in step (2), the acrylic acid grafted starch is prepared by the following method: firstly, starch is stirred and dispersed in water to obtain a 1-2 mol / L starch solution, then, under a nitrogen atmosphere, stirred at 80-90° C. for 30-40 minutes, naturally cooled to 45-50° C., acrylic acid and ammonium persulfate-sodium bisulfite aqueous solution are added dropwise, pH is adjusted to 4-5, and the mixture is kept warm and stirred for 3-4 hours under nitrogen protection, the precipitate is centrifuged, the homopolymer is removed, washed, and dried to obtain the product.

[0024] Further preferably, the usage ratio of starch, acrylic acid and ammonium persulfate-sodium bisulfite aqueous solution is 1 g: 1-2 mL: 5-7 mL, and the mass concentrations of ammonium persulfate and sodium bisulfite contained in the ammonium persulfate-sodium bisulfite aqueous solution are 0.3-0.4% and 0.1-0.2%, respectively.

[0025] More preferably, the specific method for removing the homopolymer is: using acetone as the extractant, extracting the precipitate using a Soxhlet extractor for 15 to 17 hours, and refluxing 5 to 6 times per hour.

[0026] Preferably, in step (2), the amino chelated starch is prepared by the following method: adding acrylic acid grafted starch to 0.5-0.6 mol / L ethylenediamine solution, adjusting the pH to 4-5, stirring and reacting at 50-60°C for 2-3 hours, centrifuging to obtain a precipitate, washing, and drying; wherein the molar ratio of ethylenediamine contained in the ethylenediamine solution to the acrylic acid grafted starch is 3-4:1.

[0027] Preferably, in step (2), the specific method of enzymatic hydrolysis treatment is: mixing the amino chelated starch and the sodium hydrogen phosphate-citric acid buffer solution with a pH value of 4.0 evenly, then adding the glucoamylase solution, treating with ultrasonic oscillation at 300-400W for 40-50 minutes, centrifuging to obtain the precipitate, washing, drying, and grinding to 100 mesh to obtain the porous amino chelated starch; wherein the dosage ratio of the amino chelated starch, the sodium hydrogen phosphate-citric acid buffer solution, and the glucoamylase solution is 1g:8-10mL:0.05-0.06mL.

[0028] More preferably, the glucoamylase solution is obtained by uniformly mixing glucoamylase with disodium hydrogen phosphate-citric acid buffer solution at pH=4.0 in a ratio of 1 g:5 mL.

[0029] Preferably, the specific method of step (3) is: stirring and dispersing the porous amino chelated starch in water to prepare a starch dispersion with a mass concentration of 5 to 7%, adjusting the pH to 4 to 5, adding modified metal-based biochar, stirring at room temperature for 50 to 60 minutes, and drying; wherein the mass ratio of the porous amino chelated starch to the modified metal-based biochar is 0.8 to 1:10.

[0030] The present invention also provides a denitrification and dephosphorization agent, which is obtained by the above-mentioned preparation method.

[0031] Beneficial effects of the present invention:

[0032] The invention first uses corn stalks and a metal nitrate aqueous solution as raw materials to prepare metal-based biochar, then uses the metal-based biochar as a matrix to perform in-situ polymerization of acrylamide to prepare modified metal-based biochar; then uses acrylic acid to graft starch to obtain acrylic acid grafted starch, then reacts the acrylic acid grafted starch with an ethylenediamine solution to obtain amino chelated starch, and performs enzymatic hydrolysis to obtain porous amino chelated starch; finally, the modified metal-based biochar is compounded with the porous amino chelated starch to prepare a denitrification and dephosphorization agent. The agent can simultaneously achieve denitrification and dephosphorization of sewage, and has very good application prospects.

[0033] The use of corn stalks to prepare biochar realizes the reuse of corn stalks, is green and environmentally friendly, has rich pore structures, and has good adsorption effects. In the process of preparing biochar, a metal nitrate aqueous solution is added, specifically a copper nitrate-zinc nitrate-cerium nitrate mixed aqueous solution is used to generate copper, zinc, and cerium oxides on the biochar, and further acrylamide is polymerized in situ to generate polyacrylamide, which increases more adsorption sites and has a better removal effect on nitrogen and phosphorus in sewage.

[0034] Porous amino chelated starch has a rich pore structure and has a good adsorption and removal effect on nitrogen and phosphorus in sewage. Acrylic acid grafting and amino chelation provide more adsorption sites, further enhancing the adsorption and removal effect on nitrogen and phosphorus in sewage.

[0035] The present invention further enhances the adsorption and removal of nitrogen and phosphorus in sewage by compounding modified metal-based biochar with porous amino chelated starch, and the two act synergistically. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with embodiments. It should be noted that the following description is only for explaining the present invention and does not limit its contents.

[0037] Embodiment 1:

[0038] A method for preparing a denitrification and dephosphorization agent, the specific steps are as follows:

[0039] (1) First, corn straw and a metal nitrate aqueous solution are used as raw materials to prepare metal-based biochar, and then acrylamide is in situ polymerized on the metal-based biochar as a matrix to prepare modified metal-based biochar;

[0040] The metal-based biochar is prepared by the following method: first, corn stalks are cut into sections, washed, dried, crushed and ground to 100 meshes to obtain stalk powder; then, 1 kg of stalk powder is added to 5 L of metal nitrate aqueous solution, impregnated, vacuum dried, and calcined to obtain metal-based biochar.

[0041] The metal nitrate aqueous solution is a copper nitrate-zinc nitrate-cerium nitrate mixed aqueous solution, and the mass concentrations of copper nitrate, zinc nitrate and cerium nitrate contained in the mixed aqueous solution are 3%, 2% and 1% respectively.

[0042] The process conditions of the immersion treatment are: 300W ultrasonic oscillation treatment for 2 hours and 300W microwave irradiation for 5 minutes.

[0043] The calcination process conditions are: calcination at 350°C for 2 hours.

[0044] The specific method of in-situ polymerization of acrylamide is as follows: first, 1 kg of metal-based biochar is ultrasonically dispersed in 10 L of water to obtain a biochar dispersion, then 0.1 kg of acrylamide monomer is added to the biochar dispersion, stirred and mixed, 0.3 L of 0.2% potassium persulfate solution is added, polymerization reaction is carried out under ultrasonic conditions, the precipitate is centrifuged, washed, and dried to obtain the modified metal-based biochar.

[0045] The process conditions of the polymerization reaction are: ultrasonic treatment at 200 W for 30 minutes at 25°C.

[0046] (2) then grafting the starch with acrylic acid to obtain acrylic acid grafted starch, and then reacting the acrylic acid grafted starch with an ethylenediamine solution to obtain amino chelated starch, and performing enzymatic hydrolysis to obtain porous amino chelated starch;

[0047] The acrylic acid grafted starch is prepared by the following method: first, 1 kg of starch is stirred and dispersed in water to obtain a 1 mol / L starch solution, then stirred at 80° C. for 30 minutes under a nitrogen atmosphere, naturally cooled to 45° C., 1 L of acrylic acid and 5 L of ammonium persulfate-sodium bisulfite aqueous solution are added dropwise, the pH is adjusted to 4, and the mixture is kept warm and stirred for 3 hours under nitrogen protection, the precipitate is centrifuged, the homopolymer is removed, washed, and dried to obtain the product.

[0048] The mass concentrations of ammonium persulfate and sodium bisulfite contained in the ammonium persulfate-sodium bisulfite aqueous solution are 0.3% and 0.1%, respectively.

[0049] The specific method for removing the homopolymer is: using acetone as the extractant, extracting the precipitate using a Soxhlet extractor for 15 hours, and refluxing 5 times per hour.

[0050] The amino chelated starch is prepared by the following method: adding acrylic acid grafted starch to 0.5 mol / L ethylenediamine solution, adjusting pH=4, stirring and reacting at 50°C for 2 hours, centrifuging to obtain a precipitate, washing, and drying; wherein the molar ratio of ethylenediamine contained in the ethylenediamine solution to the acrylic acid grafted starch is 3:1.

[0051] The specific method of enzymatic hydrolysis treatment is as follows: 1 kg of amino chelated starch is evenly mixed with 8 L of sodium dihydrogen phosphate-citric acid buffer solution with a pH value of 4.0, and then 0.05 L of glucose amylase solution is added, and ultrasonic oscillation is performed at 300 W for 40 minutes, and the precipitate is centrifuged, washed, dried, and ground into 100 meshes to obtain porous amino chelated starch; wherein the glucose amylase solution is obtained by evenly mixing glucose amylase with sodium dihydrogen phosphate-citric acid buffer solution with a pH value of 4.0 at a ratio of 1 g:5 mL.

[0052] (3) Finally, the modified metal-based biochar is compounded with porous amino-chelated starch to prepare the denitrification and phosphorus removal agent.

[0053] The specific method is: take 0.08 kg of porous amino chelated starch and stir and disperse it in water to prepare a starch dispersion with a mass concentration of 5%, adjust the pH to 4, add 1 kg of modified metal-based biochar, stir at room temperature for 50 minutes, and dry.

[0054] Embodiment 2:

[0055] A method for preparing a denitrification and dephosphorization agent, the specific steps are as follows:

[0056] (1) First, corn straw and a metal nitrate aqueous solution are used as raw materials to prepare metal-based biochar, and then acrylamide is in situ polymerized on the metal-based biochar as a matrix to prepare modified metal-based biochar;

[0057] The metal-based biochar is prepared by the following method: first, corn stalks are cut into sections, washed, dried, crushed and ground to 100 meshes to obtain stalk powder; then, 1 kg of stalk powder is added to 6 L of metal nitrate aqueous solution, impregnated, vacuum dried, and calcined to obtain metal-based biochar.

[0058] The metal nitrate aqueous solution is a copper nitrate-zinc nitrate-cerium nitrate mixed aqueous solution, and the mass concentrations of copper nitrate, zinc nitrate and cerium nitrate contained in the mixed aqueous solution are 4%, 3% and 2% respectively.

[0059] The process conditions of the immersion treatment are: 400W ultrasonic oscillation treatment for 3 hours and 400W microwave irradiation for 6 minutes.

[0060] The calcination process conditions are: calcination at 450°C for 3 hours.

[0061] The specific method of in-situ polymerization of acrylamide is as follows: first, 1 kg of metal-based biochar is ultrasonically dispersed in 12 L of water to obtain a biochar dispersion, then 0.2 kg of acrylamide monomer is added to the biochar dispersion, stirred and mixed, 0.4 L of 0.3% potassium persulfate solution is added, polymerization reaction is carried out under ultrasonic conditions, the precipitate is centrifuged, washed, and dried to obtain the modified metal-based biochar.

[0062] The process conditions of the polymerization reaction are: ultrasonic treatment at 300W for 40 minutes at 30°C.

[0063] (2) then grafting the starch with acrylic acid to obtain acrylic acid grafted starch, and then reacting the acrylic acid grafted starch with an ethylenediamine solution to obtain amino chelated starch, and performing enzymatic hydrolysis to obtain porous amino chelated starch;

[0064] The acrylic acid grafted starch is prepared by the following method: firstly, 1 kg of starch is stirred and dispersed in water to obtain a 2 mol / L starch solution, then stirred at 90° C. for 40 minutes under a nitrogen atmosphere, naturally cooled to 50° C., 2 L of acrylic acid and 7 L of ammonium persulfate-sodium bisulfite aqueous solution are added dropwise, the pH is adjusted to 5, and the mixture is kept warm and stirred for 4 hours under nitrogen protection, the precipitate is centrifuged, the homopolymer is removed, washed, and dried to obtain the product.

[0065] The mass concentrations of ammonium persulfate and sodium bisulfite contained in the ammonium persulfate-sodium bisulfite aqueous solution are 0.4% and 0.2%, respectively.

[0066] The specific method for removing the homopolymer is: using acetone as the extractant, extracting the precipitate using a Soxhlet extractor for 17 hours, and refluxing 6 times per hour.

[0067] The amino chelated starch is prepared by the following method: adding acrylic acid grafted starch into 0.6 mol / L ethylenediamine solution, adjusting pH=5, stirring and reacting at 60°C for 3 hours, centrifuging to obtain a precipitate, washing, and drying; wherein the molar ratio of ethylenediamine contained in the ethylenediamine solution to the acrylic acid grafted starch is 4:1.

[0068] The specific method of enzymatic hydrolysis treatment is as follows: 1 kg of amino chelated starch is evenly mixed with 10 L of sodium dihydrogen phosphate-citric acid buffer solution with a pH value of 4.0, and then 0.06 L of glucose amylase solution is added, and the mixture is subjected to 400 W ultrasonic oscillation treatment for 50 minutes, and the precipitate is centrifuged, washed, dried, and ground into 100 meshes to obtain porous amino chelated starch; wherein the glucose amylase solution is obtained by evenly mixing glucose amylase with sodium dihydrogen phosphate-citric acid buffer solution with a pH value of 4.0 in a ratio of 1 g:5 mL.

[0069] (3) Finally, the modified metal-based biochar is compounded with porous amino-chelated starch to prepare the denitrification and phosphorus removal agent.

[0070] The specific method is: take 0.1 kg of porous amino chelated starch and stir and disperse it in water to prepare a starch dispersion with a mass concentration of 7%, adjust the pH to 5, add 1 kg of modified metal-based biochar, stir at room temperature for 60 minutes, and dry.

[0071] Embodiment 3:

[0072] A method for preparing a denitrification and dephosphorization agent, the specific steps are as follows:

[0073] (1) First, corn straw and a metal nitrate aqueous solution are used as raw materials to prepare metal-based biochar, and then acrylamide is in situ polymerized on the metal-based biochar as a matrix to prepare modified metal-based biochar;

[0074] The metal-based biochar is prepared by the following method: first, corn stalks are cut into sections, washed, dried, crushed and ground to 100 meshes to obtain stalk powder; then, 1 kg of stalk powder is added to 5 L of metal nitrate aqueous solution, impregnated, vacuum dried, and calcined to obtain metal-based biochar.

[0075] The metal nitrate aqueous solution is a copper nitrate-zinc nitrate-cerium nitrate mixed aqueous solution, and the mass concentrations of copper nitrate, zinc nitrate and cerium nitrate contained in the mixed aqueous solution are 4%, 2% and 2% respectively.

[0076] The process conditions of the immersion treatment are: 300W ultrasonic oscillation treatment for 3 hours and 300W microwave irradiation for 6 minutes.

[0077] The calcination process conditions are: calcination at 350°C for 3 hours.

[0078] The specific method of in-situ polymerization of acrylamide is as follows: first, 1 kg of metal-based biochar is ultrasonically dispersed in 10 L of water to obtain a biochar dispersion, then 0.2 kg of acrylamide monomer is added to the biochar dispersion, stirred and mixed, 0.3 L of 0.3% potassium persulfate solution is added, polymerization reaction is carried out under ultrasonic conditions, the precipitate is centrifuged, washed, and dried to obtain the modified metal-based biochar.

[0079] The process conditions of the polymerization reaction are: ultrasonic treatment at 300 W for 30 minutes at 25°C.

[0080] (2) then grafting the starch with acrylic acid to obtain acrylic acid grafted starch, and then reacting the acrylic acid grafted starch with an ethylenediamine solution to obtain amino chelated starch, and performing enzymatic hydrolysis to obtain porous amino chelated starch;

[0081] The acrylic acid grafted starch is prepared by the following method: first, 1 kg of starch is stirred and dispersed in water to obtain a 2 mol / L starch solution, then stirred at 80° C. for 40 minutes under a nitrogen atmosphere, naturally cooled to 45° C., 2 L of acrylic acid and 5 L of ammonium persulfate-sodium bisulfite aqueous solution are added dropwise, the pH is adjusted to 5, and the mixture is kept warm and stirred for 3 hours under nitrogen protection, the precipitate is centrifuged, the homopolymer is removed, washed, and dried to obtain the product.

[0082] The mass concentrations of ammonium persulfate and sodium bisulfite contained in the ammonium persulfate-sodium bisulfite aqueous solution were 0.4% and 0.1%, respectively.

[0083] The specific method for removing the homopolymer is: using acetone as the extractant, extracting the precipitate using a Soxhlet extractor for 17 hours, and refluxing 5 times per hour.

[0084] The amino chelated starch is prepared by the following method: adding acrylic acid grafted starch to 0.6 mol / L ethylenediamine solution, adjusting pH=4, stirring and reacting at 60°C for 2 hours, centrifuging to obtain a precipitate, washing, and drying; wherein the molar ratio of ethylenediamine contained in the ethylenediamine solution to the acrylic acid grafted starch is 4:1.

[0085] The specific method of enzymatic hydrolysis is as follows: 1 kg of amino chelated starch is evenly mixed with 8 L of sodium dihydrogen phosphate-citric acid buffer solution with a pH value of 4.0, and then 0.06 L of glucose amylase solution is added, and ultrasonic oscillation is performed at 300 W for 50 minutes, and the precipitate is obtained by centrifugation, washed, dried, and ground into 100 meshes to obtain porous amino chelated starch; wherein the glucose amylase solution is obtained by evenly mixing glucose amylase and sodium dihydrogen phosphate-citric acid buffer solution with a pH value of 4.0 at a ratio of 1 g: 5 mL.

[0086] (3) Finally, the modified metal-based biochar is compounded with porous amino-chelated starch to prepare the denitrification and phosphorus removal agent.

[0087] The specific method is: take 0.08 kg of porous amino chelated starch and stir and disperse it in water to prepare a starch dispersion with a mass concentration of 7%, adjust the pH to 4, add 1 kg of modified metal-based biochar, stir at room temperature for 60 minutes, and dry.

[0088] Comparative Example

[0089] A method for preparing a denitrification and dephosphorization agent, the specific steps are as follows:

[0090] (1) First, corn straw and metal nitrate aqueous solution are used as raw materials to prepare metal-based biochar;

[0091] The specific method is as follows: first, the corn stalks are cut into sections, washed, dried, crushed and ground into 100 meshes to obtain stalk powder; then, 1 kg of stalk powder is added into 5 L of metal nitrate aqueous solution, impregnated, vacuum dried, and calcined to obtain metal-based biochar.

[0092] The metal nitrate aqueous solution is a copper nitrate-zinc nitrate-cerium nitrate mixed aqueous solution, and the mass concentrations of copper nitrate, zinc nitrate and cerium nitrate contained in the mixed aqueous solution are 4%, 2% and 2% respectively.

[0093] The process conditions of the immersion treatment are: 300W ultrasonic oscillation treatment for 3 hours and 300W microwave irradiation for 6 minutes.

[0094] The calcination process conditions are: calcination at 350°C for 3 hours.

[0095] (2) Then, using the metal-based biomass carbon as a matrix, acrylamide is polymerized in situ to prepare a modified metal-based biomass carbon, which is the denitrification and phosphorus removal agent;

[0096] The specific method is: firstly, 1 kg of metal-based biochar is ultrasonically dispersed in 10 L of water to obtain a biochar dispersion, then 0.2 kg of acrylamide monomer is added to the biochar dispersion, stirred and mixed, 0.3 L of 0.3% potassium persulfate solution is added, polymerization reaction is carried out under ultrasonic conditions, centrifugation is performed to obtain a precipitate, washing, and drying to obtain the modified metal-based biochar. The process conditions of the polymerization reaction are: ultrasonic treatment at 300W for 30 minutes at 25°C.

[0097] Test example

[0098] Industrial sewage was randomly divided into 4 parts, and the reagents obtained in Examples 1 to 3 and the comparative example were added respectively. The dosage of the reagent was 3 g per liter of sewage. The mixture was stirred at 300 r / min for 10 minutes, allowed to stand for 10 minutes, and filtered to obtain purified sewage.

[0099] Refer to HJ 199-2023 "Determination of total nitrogen in water - Gas phase molecular absorption spectrometry" to determine the total nitrogen content;

[0100] Refer to HJ 671-2013 "Determination of total phosphorus in water quality - Flow injection-ammonium molybdate spectrophotometry" to determine the total phosphorus content.

[0101] The total nitrogen content in the sewage before purification was 151.253 mg / L, and the total phosphorus content was 6.725 mg / L.

[0102] The total nitrogen content and total phosphorus content in the purified wastewater are shown in Table 1.

[0103] Table 1. Total nitrogen and total phosphorus content in purified wastewater

[0104] Total nitrogen content (mg / L) Total phosphorus content (mg / L) Example 1 0.729 0.012 Example 2 0.725 0.011 Example 3 0.720 0.009 Comparative Example 2.574 0.238

[0105] As can be seen from Table 1, the agents obtained in Examples 1 to 3 have excellent denitrification and dephosphorization effects.

[0106] In the control example, when the porous amino chelated starch was omitted, the nitrogen removal and phosphorus removal effects were significantly deteriorated, indicating that the porous amino chelated starch and the modified metal-based biochar acted synergistically to improve the nitrogen removal and phosphorus removal effects.

[0107] Although the above describes the specific implementation methods of the present invention, it does not limit the scope of protection of the present invention. Based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present invention.

Claims

1. Application of a denitrification and dephosphorization agent in the adsorption and removal of nitrogen and phosphorus in sewage, characterized in that: The denitrification and dephosphorization agent is obtained by the following preparation method: (1) First, corn straw and metal nitrate aqueous solution are used as raw materials to prepare metal-based biochar, and then acrylamide is in situ polymerized on the metal-based biochar to prepare modified metal-based biochar; (2) Then, the starch is grafted with acrylic acid to obtain acrylic acid grafted starch, and the acrylic acid grafted starch is reacted with ethylenediamine solution to obtain amino chelated starch, and then enzymatically hydrolyzed to obtain porous amino chelated starch; (3) Finally, the modified metal-based biochar is compounded with porous amino-chelated starch to prepare the denitrification and phosphorus removal agent; In step (1), the metal-based biochar is prepared by the following method: first, the corn stalks are cut into sections, washed, dried, crushed and ground to 100 meshes to obtain stalk powder; then, the stalk powder is added to a metal nitrate aqueous solution, impregnated, vacuum dried, and calcined to obtain the metal-based biochar; The specific method of acrylamide in-situ polymerization is: firstly, ultrasonically disperse the metal-based biochar in water to obtain a biochar dispersion, then add acrylamide monomer to the biochar dispersion, stir and mix, add potassium persulfate solution, perform polymerization reaction under ultrasonic conditions, centrifuge to obtain a precipitate, wash, and dry to obtain the modified metal-based biochar; In step (2), the acrylic acid grafted starch is prepared by the following method: firstly, starch is stirred and dispersed in water to obtain a 1-2 mol / L starch solution, then, under a nitrogen atmosphere, stirred at 80-90° C. for 30-40 minutes, naturally cooled to 45-50° C., acrylic acid and ammonium persulfate-sodium bisulfite aqueous solution are added dropwise, pH is adjusted to 4-5, and, under nitrogen protection, the mixture is kept warm and stirred for 3-4 hours, centrifuged to obtain a precipitate, homopolymer is removed, washed, and dried to obtain the obtained product; The amino chelated starch is prepared by the following method: adding acrylic acid grafted starch to 0.5-0.6 mol / L ethylenediamine solution, adjusting pH to 4-5, stirring and reacting at 50-60°C for 2-3 hours, centrifuging to obtain a precipitate, washing, and drying; wherein the molar ratio of ethylenediamine to acrylic acid grafted starch in the ethylenediamine solution is 3-4:1; The specific method of enzymatic hydrolysis treatment is: evenly mix the amino chelated starch with disodium hydrogen phosphate-citric acid buffer solution of pH=4.0, then add glucose amylase solution, treat with 300-400W ultrasonic oscillation for 40-50 minutes, centrifuge to obtain the precipitate, wash, dry, grind to 100 mesh, and obtain porous amino chelated starch; wherein the dosage ratio of amino chelated starch, disodium hydrogen phosphate-citric acid buffer solution, and glucose amylase solution is 1g:8-10mL:0.05-0.06mL.

2. The use according to claim 1, characterized in that: The dosage ratio of straw powder to metal nitrate aqueous solution is 1g:5-6mL; the metal nitrate aqueous solution is a mixed aqueous solution of copper nitrate-zinc nitrate-cerium nitrate, and the mass concentrations of copper nitrate, zinc nitrate and cerium nitrate contained in it are 3-4%, 2-3% and 1-2% respectively; The process conditions of the immersion treatment are: 300-400W ultrasonic oscillation treatment for 2-3 hours, 300-400W microwave irradiation for 5-6 minutes; The calcination process conditions are: calcination at 350-450°C for 2-3 hours.

3. The use according to claim 1, characterized in that: The dosage ratio of metal-based biochar, water, acrylamide monomer and potassium persulfate solution is 1g: 10-12mL: 0.1-0.2g: 0.3-0.4mL; the mass concentration of the potassium persulfate solution is 0.2-0.3%; the process conditions of the polymerization reaction are: ultrasonic treatment at 200-300W for 30-40 minutes at 25-30°C.

4. The use according to claim 1, characterized in that: The specific method of step (3) is: stirring and dispersing the porous amino chelated starch in water to prepare a starch dispersion with a mass concentration of 5 to 7%, adjusting the pH to 4 to 5, adding the modified metal-based biochar, stirring at room temperature for 50 to 60 minutes, and drying; wherein the mass ratio of the porous amino chelated starch to the modified metal-based biochar is 0.8 to 1:10.