Preparation Method and Application of a Composite Carbon Source

Abstract

The present invention discloses a preparation method and application of a composite carbon source. The composite carbon source is obtained by uniformly mixing a mixed powder as a skeleton with a starch-based hydrophobic material and then drying. The starch-based hydrophobic material provides a large amount of polysaccharide carbon source, while the biomass carbon source in the mixed powder is mainly composed of cellulose and is a high-quality carbon source. The biochar provides a good environment for the growth of denitrifying bacteria. During operation, the denitrifying bacteria in the sewage first utilize the starch-based material on the surface of the composite carbon source. After the mixed powder skeleton therein is exposed, sodium acetate and glucose can be rapidly utilized by the denitrifying bacteria, enhancing the growth and multiplication of the early-stage bacteria. Moreover, the pore structures of the biochar and the biomass carbon source also provide a good carrier for the growth and development of the bacteria, enabling the denitrifying bacteria to fully multiply on the composite carbon source, thereby effectively improving the utilization efficiency of the composite carbon source.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment. Specifically, it relates to a preparation method and application of a composite carbon source. Background Art

[0002] The development of urbanization has also brought greater challenges to the purification and treatment of sewage. The increase in the concentration of nitrogen and phosphorus in sewage will damage the water environment. Therefore, in the treatment of industrial sewage, nitrogen also needs to be treated. There are two common forms of nitrogen in sewage, one is ammonia nitrogen and the other is nitrate nitrogen. Among them, the treatment process of ammonia nitrogen is relatively simple. The lack of carbon source for nitrate nitrogen leads to a low C / N value. The denitrification process is seriously affected by the lack of carbon source, making it difficult for the total nitrogen to meet the discharge standard. Therefore, supplementing the carbon source in sewage is an important part of sewage denitrification.

[0003] The so-called carbon source is a class of nutrients containing carbon elements and can be utilized by the growth and reproduction of microorganisms. The use of a composite carbon source can effectively avoid the problem of reducing the diversity of microbial flora in activated sludge caused by the long-term use of a single carbon source. However, the existing composite carbon sources in the prior art still have problems such as low denitrification efficiency in the early stage, easy dissolution of the composite carbon source, resulting in low utilization efficiency of the composite carbon source, and low denitrification efficiency in the early stage. To solve the above problems, the present invention provides the following technical solutions. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method and application of a composite carbon source, and solve the problems of low utilization efficiency of the composite carbon source and low denitrification efficiency in the early stage in the prior art.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A preparation method of a composite carbon source includes the following steps:

[0007] In the first step, the biomass material is crushed to obtain biomass powder. After washing and drying the biomass powder, the dried biomass powder is subjected to alkali treatment, and the biomass powder obtained by alkali treatment is washed with water to neutrality and then dried to obtain a biomass carbon source;

[0008] Wherein the biomass material includes straw, branches, etc.;

[0009] The specific method of the alkali treatment is:

[0010] The biomass powder is added to 15%-30% ammonia water for immersion treatment. The conditions for immersion treatment are: temperature 60-180 degrees Celsius, time 0.5-4h;

[0011] Where OH -The saponification that weakens the hydrogen bonds between cellulose and hemicellulose and the ester bonds between xylan hemicellulose and internal molecules of other components. As the ester bonds decrease, the porosity of the lignocellulosic raw materials increases. The hemicellulose is partially dissolved, and the cellulose swells due to hydration;

[0012] In the second step, a mixed saturated aqueous solution of sodium acetate and glucose is prepared, and the biomass carbon source obtained in the first step is added thereto;

[0013] Under the condition of -0.05 Mpa to -0.08 Mpa, after negative pressure impregnation for 10 - 30 min, the biomass carbon source is dehydrated and dried to obtain a biomass core;

[0014] In this step, first, the biomass carbon source fully absorbs the saturated aqueous solution, and then through the drying method, the crystals of sodium acetate and glucose are distributed in the pore structure of the biomass carbon source;

[0015] In the third step, the biochar material is crushed to 200 - 400 mesh, and then the biomass core and the crushed biochar material are uniformly mixed according to a mass ratio of 1:0.01 - 0.05 to obtain a mixed powder for use;

[0016] A silane coupling agent solution is prepared, where the dosage of the silane coupling agent is 0.3% - 2% of the weight of the biomass carbon source. Then guar gum is added thereto to prepare an aqueous guar gum solution with a mass concentration of 1% - 1.3%. Then a nutrient agent is added thereto and uniformly mixed to obtain an adhesive;

[0017] The nutrient agent is a substance that can promote the growth of denitrifying bacteria, including at least one of amino acids such as methionine, arginine, threonine, nicotinic acid or alanine; and / or

[0018] At least one of high - protein materials such as tryptone, beef extract powder or corn steep liquor powder; and / or

[0019] At least one of trace elements such as potassium sulfate, magnesium sulfate, ferrous sulfate or sodium sulfide;

[0020] The adhesive is atomized and sprayed on the mixed powder to wet the mixed powder. Specifically, during the wetting process, the stirring and kneading of the mixed powder are maintained so that the adhesive can be attached to the surface of the mixed powder as evenly as possible;

[0021] The biomass core is dried at a temperature of 20 - 35 degrees Celsius to obtain a surface - treated mixed powder;

[0022] This step can form a guar gum film by spraying a guar gum solution containing silane coupling agent and nutrients on the surface of the biomass core and biochar powder, reducing the loss of glucose and sodium acetate in the biomass core during subsequent processing, and at the same time enabling the nutrients and silane coupling agent to be distributed as evenly as possible on the surface of the biomass core and biochar;

[0023] Fourth step, add starch to deionized water to prepare a starch milk, and then add sodium hydroxide to the starch milk to adjust the pH of the starch milk to 8-9;

[0024] Add maleic anhydride to the starch milk, react at a temperature of 20-40 °C for 2-10 h, and after the reaction, add acid to adjust the pH value of the starch milk to 6.5-7.0; after washing, dehydration and drying, obtain maleic anhydride-modified starch;

[0025] When preparing the starch milk, the mass ratio of starch to deionized water is 1:2.5-4;

[0026] The mass ratio of starch to maleic anhydride is 1:0.01-0.1;

[0027] After crushing the maleic anhydride-modified starch to 200-400 mesh, prepare it into a starch milk, then add soybean oil to it, stir and mix evenly, then add an initiator, and keep stirring and reacting at 100-170 °C for 2-10 h to obtain a starch-based hydrophobic material;

[0028] The mass ratio of maleic anhydride-modified starch to soybean oil is 1:0.3-0.5;

[0029] The initiator is benzoyl peroxide or dicumyl peroxide;

[0030] This step first introduces unsaturated double bonds on the starch surface through reaction under alkaline conditions, and then initiates the cross-linking reaction of the unsaturated double bonds with soybean oil through an initiator, so that the modified starch has good hydrophobicity;

[0031] Fifth step, uniformly stir and mix the surface-treated mixed powder and the starch-based hydrophobic material according to a weight ratio of 1:1-10, and then dry at low temperature and crush to obtain the composite carbon source, and the particle size of the composite carbon source is 10-200 mesh;

[0032] The low-temperature drying means drying in a temperature environment below 40 °C.

[0033] The beneficial effects of the present invention:

[0034] 1. The present invention uses a mixed powder as the skeleton, which is mixed evenly with the obtained starch-based hydrophobic material and then dried to obtain a composite carbon source. The starch-based hydrophobic material provides a large amount of polysaccharide carbon source, while the biomass carbon source in the mixed powder is mainly composed of cellulose and is a high-quality carbon source. There are abundant glucose and sodium acetate crystals in the pores of the biomass carbon source, and the biochar provides a good environment for the growth of denitrifying bacteria. During operation, the denitrifying bacteria in the sewage first utilize the starch-based material on the surface of the composite carbon source. After the mixed powder skeleton therein is exposed, sodium acetate and glucose can be quickly utilized by the denitrifying bacteria, promoting the development and proliferation of the bacteria in the early stage. The pore structures of the biochar and the biomass carbon source also provide a good carrier for the growth and development of the bacteria, enabling the denitrifying bacteria to fully proliferate on the composite carbon source, thereby effectively improving the utilization efficiency of the composite carbon source.

[0035] 2. The present invention uses a starch-based hydrophobic material as the main body and a mixed powder as the filler skeleton to improve the hydrophobic ability of the composite carbon source, avoid the composite carbon source from disintegrating when encountering water and causing situations such as turbid water quality, thereby improving the effective utilization rate of the composite carbon source.

[0036] 3. By adding a silane coupling agent and a nutrient agent to guar gum, the present invention can improve the compatibility effect between the mixed powder and the starch-based hydrophobic material, and at the same time, the nutrient agent can provide nutritional conditions for the growth and proliferation of denitrifying bacteria, further promoting the proliferation of denitrifying bacteria in the composite carbon source and improving the utilization efficiency of the denitrifying bacteria for the composite carbon source. Specific Embodiments

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0038] Embodiment 1

[0039] A preparation method of a composite carbon source includes the following steps:

[0040] In the first step, peanut shells are crushed to obtain biomass powder. The biomass powder is washed and then dried, and the dried biomass powder is subjected to alkali treatment. After the alkali-treated biomass powder is washed to neutrality, it is dried to obtain a biomass carbon source.

[0041] The specific method of the alkali treatment is as follows:

[0042] The biomass powder is added to 15% ammonia water for immersion treatment. The conditions for the immersion treatment are: temperature 80 °C, time 3 h.

[0043] Step 2: Prepare a mixed saturated aqueous solution of sodium acetate and glucose at 25 °C, and add the biomass carbon source obtained in the first step thereto;

[0044] Under the condition of -0.08 Mpa, impregnate under negative pressure for 10 min, and then dehydrate and dry the biomass carbon source to obtain a biomass core;

[0045] Step 3: Crush the biochar material to 200 mesh, and then uniformly mix the biomass core and the crushed biochar material according to a mass ratio of 1:0.01 to obtain a mixed powder for use;

[0046] Prepare a silane coupling agent solution, wherein the dosage of the silane coupling agent is 0.3% of the weight of the biomass carbon source, then add guar gum thereto to prepare an aqueous guar gum solution with a mass concentration of 1%, and then add a nutrient agent thereto and uniformly mix to obtain an adhesive;

[0047] Wherein the nutrient agent includes amino acids of methionine, arginine, threonine, nicotinic acid and alanine with a mass ratio of 1:1:1:1:1 and

[0048] high-protein materials of tryptone, beef extract powder and corn steep liquor powder with a mass ratio of 0.5:1:1.5 and

[0049] trace elements of potassium sulfate, magnesium sulfate, ferrous sulfate and sodium sulfide with a mass ratio of 1:1:1:1;

[0050] The mass ratio of amino acids, high-protein materials and trace elements is 1:7:0.05;

[0051] Atomize and spray the adhesive on the mixed powder to wet the mixed powder. Specifically, during the wetting process, keep stirring and kneading the mixed powder so that the adhesive can adhere to the surface of the mixed powder as evenly as possible;

[0052] Dry the biomass core at 30 °C to obtain a surface-treated mixed powder;

[0053] Step 4: Add starch to deionized water to prepare a starch milk, and then add sodium hydroxide to the starch milk to adjust the pH of the starch milk to 8-9;

[0054] Add maleic anhydride to the starch milk and react at 40 °C for 2 h. After the reaction, add an acid to adjust the pH value of the starch milk to 6.5-7.0; after washing, dehydrating and drying, obtain maleic anhydride-modified starch;

[0055] Wherein the mass ratio of starch to deionized water when preparing the starch milk is 1:2.5;

[0056] Wherein the mass ratio of starch to maleic anhydride is 1:0.05;

[0057] After crushing the maleic anhydride-modified starch to 200 mesh, a starch milk is prepared, and then soybean oil is added thereto. After stirring and mixing evenly, an initiator is added thereto, and the mixture is kept warm and stirred at 100 °C for 10 h to obtain a starch-based hydrophobic material;

[0058] The mass ratio of the maleic anhydride-modified starch to the soybean oil is 1:0.3;

[0059] The initiator is benzoyl peroxide;

[0060] In the fifth step, the surface-treated mixed powder and the starch-based hydrophobic material are evenly stirred and mixed according to a weight ratio of 1:1, and then dried at a low temperature below 40 °C and crushed to obtain the composite carbon source, and the particle size of the composite carbon source is 10 mesh.

[0061] Example 2

[0062] A preparation method of a composite carbon source, comprising the following steps:

[0063] In the first step, the biomass material is crushed to obtain biomass powder, the biomass powder is washed and dried, and the dried biomass powder is subjected to alkali treatment, and the biomass powder obtained by alkali treatment is washed to neutrality and then dried to obtain a biomass carbon source;

[0064] The biomass material includes straw, branches, etc.;

[0065] The specific method of the alkali treatment is as follows:

[0066] The biomass powder is added to 30% ammonia water for immersion treatment, and the conditions for immersion treatment are: temperature 180 °C, time 0.5 h;

[0067] In the second step, a mixed saturated aqueous solution of sodium acetate and glucose is prepared, and the biomass carbon source obtained in the first step is added thereto;

[0068] After negative pressure impregnation for 30 min under the condition of -0.05 Mpa, the biomass carbon source is dehydrated and dried to obtain a biomass core;

[0069] In the third step, the biochar material is crushed to 400 mesh, and then the biomass core and the crushed biochar material are evenly mixed according to a mass ratio of 1:0.05 to obtain a mixed powder for use;

[0070] A silane coupling agent solution is prepared, wherein the amount of the silane coupling agent is 2% of the weight of the biomass carbon source, and then guar gum is added thereto to prepare an aqueous guar gum solution with a mass concentration of 1.3%. Then, a nutrient is added thereto, and after uniform mixing, an adhesive is obtained;

[0071] Among them, the nutrient agent includes amino acids of methionine, arginine, threonine, nicotinic acid and alanine with a mass ratio of 1:1:1:1:1 and

[0072] high-protein materials of tryptone, beef extract powder and corn steep liquor dry powder with a mass ratio of 0.5:1:1.5 and

[0073] trace elements of potassium sulfate, magnesium sulfate, ferrous sulfate and sodium sulfide with a mass ratio of 1:1:1:1;

[0074] The mass ratio of amino acids, high-protein materials and trace elements is 1:7:0.05;

[0075] The adhesive is atomized and sprayed on the mixed powder to wet the mixed powder. Specifically, during the wetting process, the mixed powder is continuously stirred and kneaded to enable the adhesive to adhere to the surface of the mixed powder as evenly as possible;

[0076] The biomass core is dried at a temperature of 20 °C to obtain the surface-treated mixed powder;

[0077] In the fourth step, starch is added to deionized water to prepare a starch milk, and then sodium hydroxide is added to the starch milk to adjust the pH of the starch milk to 8-9;

[0078] Maleic anhydride is added to the starch milk, and the reaction is carried out at a temperature of 20 °C for 10 h. After the reaction is completed, acid is added to adjust the pH value of the starch milk to 6.5-7.0; after washing, dehydration and drying, maleic anhydride-modified starch is obtained;

[0079] Among them, the mass ratio of starch to deionized water when preparing the starch milk is 1:3.5;

[0080] Among them, the mass ratio of starch to maleic anhydride is 1:0.02;

[0081] After the maleic anhydride-modified starch is crushed to 400 meshes, it is made into a starch milk, and then soybean oil is added to it. After stirring and mixing evenly, an initiator is added, and the reaction is carried out under stirring and heat preservation at 170 °C for 2 h to obtain a starch-based hydrophobic material;

[0082] Among them, the mass ratio of maleic anhydride-modified starch to soybean oil is 1:0.5;

[0083] The initiator is benzoyl peroxide or dicumyl peroxide;

[0084] In the fifth step, the surface-treated mixed powder and the starch-based hydrophobic material are evenly stirred and mixed according to a weight ratio of 1:10, and then dried at a low temperature and crushed to obtain the composite carbon source, and the particle size of the composite carbon source is 100 meshes;

[0085] The low-temperature drying refers to drying in a temperature environment below 40 degrees Celsius.

[0086] Example 3

[0087] A preparation method of a composite carbon source includes the following steps:

[0088] In the first step, the biomass material is crushed to obtain biomass powder. The biomass powder is washed and then dried, and the dried biomass powder is subjected to alkali treatment. After the biomass powder obtained by alkali treatment is washed with water until neutral and then dried, a biomass carbon source is obtained;

[0089] The biomass material includes straw, branches, etc.;

[0090] The specific method of the alkali treatment is as follows:

[0091] The biomass powder is added to 15% ammonia water for immersion treatment. The conditions for immersion treatment are: temperature 180 degrees Celsius, time 2 h;

[0092] In the second step, a mixed saturated aqueous solution of sodium acetate and glucose is prepared, and the biomass carbon source obtained in the first step is added thereto;

[0093] After negative pressure impregnation for 30 min under the condition of -0.08 Mpa, the biomass carbon source is dehydrated and dried to obtain a biomass core;

[0094] In the third step, the biochar material is crushed to 300 meshes, and then the biomass core and the crushed biochar material are uniformly mixed according to a mass ratio of 1:0.03 to obtain a mixed powder for use;

[0095] A silane coupling agent solution is prepared, wherein the amount of the silane coupling agent is 1% of the weight of the biomass carbon source. Then guar gum is added thereto to prepare an aqueous guar gum solution with a mass concentration of 1.2%. Then a nutrient agent is added thereto, and after uniform mixing, an adhesive is obtained;

[0096] The nutrient agent includes amino acids of methionine, arginine, threonine, nicotinic acid and alanine with a mass ratio of 1:1:1:1:1 and

[0097] high-protein materials of tryptone, beef extract powder and corn steep liquor powder with a mass ratio of 0.5:1:1.5 and

[0098] trace elements of potassium sulfate, magnesium sulfate, ferrous sulfate and sodium sulfide with a mass ratio of 1:1:1:1;

[0099] The mass ratio of amino acids, high-protein materials and trace elements is 1:7:0.05;

[0100] Atomize and spray the adhesive in the mixed powder to wet the mixed powder. Specifically, during the wetting process, keep stirring and kneading the mixed powder so that the adhesive can adhere to the surface of the mixed powder as evenly as possible;

[0101] Dry the biomass core at a temperature of 30 °C to obtain the surface-treated mixed powder;

[0102] In the fourth step, add starch to deionized water to prepare a starch milk, and then add sodium hydroxide to the starch milk to adjust the pH of the starch milk to 8-9;

[0103] Add maleic anhydride to the starch milk and react at a temperature of 30 °C for 6 h. After the reaction, add acid to adjust the pH value of the starch milk to 6.5-7.0; after washing, dehydrating and drying, obtain maleic anhydride-modified starch;

[0104] Wherein the mass ratio of starch to deionized water when preparing the starch milk is 1:3;

[0105] Wherein the mass ratio of starch to maleic anhydride is 1:0.06;

[0106] After crushing the maleic anhydride-modified starch to 300 mesh, prepare it into a starch milk, then add soybean oil to it, stir and mix evenly, and then add an initiator, and keep stirring and reacting at 140 °C for 2-10 h to obtain a starch-based hydrophobic material;

[0107] Wherein the mass ratio of maleic anhydride-modified starch to soybean oil is 1:0.4;

[0108] The initiator is benzoyl peroxide or dicumyl peroxide;

[0109] In the fifth step, uniformly stir and mix the surface-treated mixed powder and the starch-based hydrophobic material according to a weight ratio of 1:3, and then dry it at a low temperature and crush it to obtain the composite carbon source, and the particle size of the composite carbon source is 200 mesh;

[0110] The low-temperature drying means drying in a temperature environment below 40 °C.

[0111] Comparative Example 1

[0112] Compared with Example 1, the difference in Comparative Example 1 is that the second step is not carried out, and other conditions are the same;

[0113] Comparative Example 2

[0114] Compared with Example 1, the difference in Comparative Example 2 is that the starch-based hydrophobic material is replaced by gelatinized starch, and other conditions are the same;

[0115] Comparative Example 3

[0116] An aqueous glucose solution is used as a carbon source.

[0117] Test conditions and test results

[0118] The water from a sewage treatment plant is used as a sample for the test. The sludge concentration of the water sample is 2300 - 2700 mg / L, the total nitrogen concentration is 37 mg / L, and the COD concentration is 102 mg / L. The composite carbon sources prepared in Examples 1 to Comparative Example 2 and the aqueous glucose solution in Comparative Example 3 are added to the water sample, and the addition amount is 3 g / L.

[0119] The nitrogen removal rate is detected at 2 h, 5 h, and 8 h. The specific results are shown in the following table:

[0120]

[0121]

[0122] As can be seen from the above table, compared with a single carbon source, the composite carbon source described in the present invention can also ensure good denitrification efficiency in the initial stage, and can always maintain a high denitrification efficiency during the denitrification process, without the problem that the denitrification efficiency is fast in the initial stage and significantly decreases in the middle and later stages.

[0123] In the description of the specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0124] The above content is only an example and explanation of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should all belong to the protection scope of the present invention.

Claims

1. A preparation method of a composite carbon source, characterized in that, It includes the following steps: In the first step, the biomass material is crushed to obtain biomass powder. After washing and drying the biomass powder, the dried biomass powder is subjected to alkali treatment, and the biomass powder obtained from the alkali treatment is washed with water until neutral and then dried to obtain a biomass carbon source; In the second step, a mixed saturated aqueous solution of sodium acetate and glucose is prepared, and the biomass carbon source obtained in the first step is added thereto; After the impregnation treatment, the biomass carbon source is dehydrated and dried to obtain a biomass core; In the third step, the biochar material is crushed to 200-400 mesh, and then the biomass core and the crushed biochar material are uniformly mixed according to a mass ratio of 1:0.01-0.05 to obtain a mixed powder for use; A silane coupling agent solution is prepared, wherein the amount of the silane coupling agent is 0.3%-2% of the weight of the biomass carbon source. Then, guar gum is added thereto to prepare an aqueous guar gum solution with a mass concentration of 1%-1.3%. Then, a nutrient agent is added thereto, and after uniform mixing, an adhesive is obtained; Wherein the nutrient agent is a substance that can promote the growth of denitrifying bacteria; The adhesive is atomized and sprayed into the mixed powder to wet the mixed powder; The biomass core is dried at a temperature of 20-35 °C to obtain a surface-treated mixed powder; In the fourth step, a starch-based hydrophobic material is prepared; In the fifth step, the surface-treated mixed powder and the starch-based hydrophobic material are uniformly stirred and mixed according to a weight ratio of 1:1-10, and after low-temperature drying and crushing, the composite carbon source is obtained. The particle size of the composite carbon source is 10-200 mesh.

2. The preparation method of a composite carbon source according to claim 1, characterized in that, Wherein the biomass material includes straw and branches.

3. The preparation method of a composite carbon source according to claim 1, characterized in that, The specific method of the alkali treatment is as follows: The biomass powder is added to 15%-30% ammonia water for immersion treatment. The conditions for the immersion treatment are: temperature 60-180 °C, time 0.5-4 h.

4. The preparation method of a composite carbon source according to claim 1, characterized in that, During the impregnation treatment in the second step, negative pressure impregnation is carried out for 10-30 min under the conditions of -0.05 Mpa to -0.08 Mpa.

5. The preparation method of a composite carbon source according to claim 1, characterized in that, The nutrient agent includes at least one of methionine, arginine, threonine, nicotinic acid or alanine; and / or At least one of tryptone, beef extract powder or corn steep liquor powder; and / or At least one of potassium sulfate, magnesium sulfate, ferrous sulfate or sodium sulfide.

6. The preparation method of a composite carbon source according to claim 1, wherein The preparation method of the starch-based hydrophobic material is: starch is added to deionized water to prepare a starch milk, and then sodium hydroxide is added to the starch milk to adjust the pH of the starch milk to 8-9; Maleic anhydride is added to the starch milk, and the reaction is carried out at a temperature of 20-40 °C for 2-10 h. After the reaction, acid is added to adjust the pH value of the starch milk to 6.5-7.0; after washing, dehydration and drying, maleic anhydride-modified starch is obtained; Wherein the mass ratio of starch to deionized water when preparing the starch milk is 1:2.5-4; Wherein the mass ratio of starch to maleic anhydride is 1:0.01-0.1; After the maleic anhydride-modified starch is crushed to 200-400 mesh, it is made into a starch milk, and then soybean oil is added thereto. After stirring and mixing evenly, an initiator is added thereto, and the reaction is carried out under the conditions of 100-170 °C with heat preservation and stirring for 2-10 h to obtain a starch-based hydrophobic material; The mass ratio of maleic anhydride-modified starch to soybean oil is 1:0.3 - 0.

5.

7. The preparation method of a composite carbon source according to claim 6, wherein, The initiator is benzoyl peroxide or dicumyl peroxide.

8. The preparation method of a composite carbon source according to claim 1, characterized in that, The low-temperature drying means drying is carried out in a temperature environment below 40 °C.

9. Application of a composite carbon source prepared by the preparation method according to any one of claims 1 to 8 in sewage purification.

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