Efficient slow-release carbon source based on MDI chemical modification and processing method

Abstract

The invention relates to an efficient slow-release carbon source based on MDI chemical modification and a processing method, the efficient slow-release carbon source comprises PBAT, corncob, AIBN, BCTPA, MDI, industrial diffusion oil and a wetting dispersant, and the processing method comprises the following steps: uniformly mixing PBAT and corncob, then adding AIBN and BCTPA, and uniformly mixing at normal temperature; adding the mixture into a double-screw extruder, and controlling the temperature in stages during processing; performing liquid nitrogen freezing on the product, and then crushing into powder; adding corncob powder into the powder to enable the corncob content to be 50-80%; industrial diffusion oil and a wetting dispersant are firstly added into the powder, and then MDI is added; adding the mixture into a double-screw extruder, and controlling the temperature in stages during processing; and obtaining the MDI chemically modified efficient slow-release carbon source when the sample is stable. The preparation method has the beneficial effects that chemical bond connection is established between the corncob and PBAT, and the slow release performance of the product is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of slow-release carbon sources, and in particular to a high-efficiency slow-release carbon source based on MDI chemical modification and a processing method thereof. Background Art

[0002] Constructed wetlands are often used in wastewater resource utilization due to their economic and environmentally friendly properties, such as treating tailwater from sewage treatment plants. However, the tailwater from sewage treatment plants generally has a low carbon-nitrogen ratio, which is then transferred to constructed wetlands, resulting in insufficient denitrification in constructed wetlands and reduced removal rate of nitrate nitrogen, which in turn leads to excessive total nitrogen in the effluent. Carbon sources, as electron donors, are an important limiting factor in anaerobic denitrification reactions in constructed wetlands. Reasonable regulation of carbon sources in wetlands can effectively improve the denitrification performance of constructed wetlands. Traditional carbon sources (ethanol, glucose, etc.) can increase the carbon-nitrogen ratio in sewage, but there are problems such as high cost, risk of secondary pollution, and difficulty in controlling the dosage. Compared with liquid carbon sources that release carbon quickly, slow-release solid carbon sources are more suitable for constructed wetlands.

[0003] Corncobs have a high content of xylan, which can provide a large amount of carbon source for nitrogen microorganisms. The high surface roughness can be used as a biofilm carrier for microbial growth. The material is green and pollution-free, has no negative impact on artificial wetlands, and can achieve resource utilization. Comprehensive pollutant removal rate, denitrification rate and cost price analysis show that corncobs are more suitable as plant slow-release carbon sources than other wood materials such as wood chips and reeds. Despite its many advantages, corncobs alone as a carbon source still have unstable carbon release problems such as high carbon release in the early stage and low carbon release in the later stage, and may also induce ammonia pollution and other problems. Polymers such as PBS, PCL, PHBV and PLA have higher TN removal rates than plant carbon sources, but polymers have problems such as high cost, low strength and low carbon release rate. Plants + polymers solve the problems of unstable carbon release, high cost and harm to the environment of slow-release carbon sources. PBAT is a biodegradable material that will be gradually degraded by microorganisms when placed in artificial wetlands, while providing a stable carbon source. Compared with other polymers such as PCL, PBS, PLA, etc., carbon release is more stable and the price is relatively lower.

[0004] Corn cobs and PBAT were used as materials to prepare slow-release carbon sources, and static carbon release tests and subsurface artificial wetland pilot tests were used to evaluate the carbon release capacity of the slow-release carbon sources. It was found that once the proportion of corn cobs increased, corn cob powder and PBAT had many problems during the mixing process, such as poor fluidity, uneven mixing, and clogging of the preparation machinery. In addition, since there is no chemical bond between corn cobs and PBAT, corn cobs and PBAT are still two independent substances. During the test, there are still unstable carbon release problems such as high carbon release in the early stage and low carbon release in the later stage, but they are not as obvious as corn cobs alone. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a high-efficiency slow-release carbon source based on MDI chemical modification and a processing method to overcome the deficiencies in the above-mentioned prior art.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: a high-efficiency slow-release carbon source based on MDI chemical modification, including: PBAT, corn cob, AIBN, BCTPA, MDI, industrial diffusion oil and wetting dispersant.

[0007] Based on the above technical solution, the present invention can also be improved as follows.

[0008] Furthermore, the content of corncob is 50% to 80%.

[0009] Furthermore, the amount of AIBN added is 0.005% to 0.02% of PBAT, and the amount of BCTPA added is 0.005% to 0.02% of PBAT.

[0010] Furthermore, the amount of MDI added is 0.5% to 3% of PBAT.

[0011] Furthermore, the addition amount of industrial diffusion oil is 1% to 5% of PBAT, and the addition amount of wetting and dispersing agent is 0.03% to 0.1% of PBAT.

[0012] Furthermore, the industrial diffusion oil is industrial diffusion oil 12, and the wetting dispersant is wetting dispersant RF-8.

[0013] Based on the above technical solution, the present invention also provides a processing method of a high-efficiency slow-release carbon source based on MDI chemical modification, and the specific steps are as follows:

[0014] S1. Mix PBAT and corncob evenly, then add AIBN and BCTPA, and mix evenly at room temperature;

[0015] S2, adding the mixed material in S1 into a twin-screw extruder, and controlling the temperature in 4 stages during processing, the temperatures are 180℃~185℃, 185℃~190℃, 185℃~190℃ and 180℃~185℃, the screw rotation speed is 15rpm~25rpm, and the mixing time is 2min~5min;

[0016] S3, freezing the product processed by the twin-screw extruder with liquid nitrogen and then crushing it into powder;

[0017] S4, adding corncob powder to the powder in S3 to make the corncob content be 50% to 80%;

[0018] S5, first add industrial diffusion oil and wetting dispersant to the powder in S4, and then add MDI;

[0019] S6, adding the mixed material in S5 into a twin-screw extruder, and controlling the temperature in 4 stages during processing, the temperatures are 180°C to 185°C, 185°C to 190°C, 185°C to 190°C, and 180°C to 185°C, the screw rotation speed is 15rpm to 25rpm, and the mixing time is 2min to 5min;

[0020] S7. When the sample is stable, the MDI chemically modified high-efficiency slow-release carbon source is obtained.

[0021] Furthermore, the mass ratio of PBAT to corncob in S1 is (60-80):(40-20).

[0022] Furthermore, the mass ratio of PBAT to corncob in S1 was 70:30.

[0023] Furthermore, the temperatures in S2 are 183° C., 185° C., 185° C. and 183° C., respectively, the screw rotation speed is 20 rpm, and the mixing time is 3 min.

[0024] Furthermore, in S4, the corncob content is set at 60%.

[0025] Furthermore, in S6, the temperatures are 185° C., 188° C., 188° C. and 185° C., respectively, the screw rotation speed is 20 rpm, and the mixing time is 3 min.

[0026] Further, S7 is specifically as follows: after the sample is stabilized for 5 minutes, the product is collected and the product is cut into a suitable size after cooling, thereby obtaining a chemically modified MDI high-efficiency slow-release carbon source.

[0027] The beneficial effects of the present invention are: it can effectively solve the problems of poor fluidity, uneven mixing and mechanical clogging caused by the increase in the proportion of corn cobs, and at the same time establish a chemical bond connection between the corn cobs and PBAT to make them a whole, thereby greatly improving the sustained release performance of the product. Through performance characterization, it can be found that a stable covalent bond is generated between the corn cobs and PBAT in the MDI chemically modified high-efficiency sustained-release carbon source. The static carbon release test found that the MDI chemically modified high-efficiency sustained-release carbon source has significantly enhanced sustained release performance compared with the ordinary sustained-release carbon source. The results of the small-scale test of pollutant removal in the subsurface artificial wetland show that the MDI chemically modified high-efficiency sustained-release carbon source can greatly improve the removal rate of TN in the wetland, and will not have a negative impact on the COD effluent of the wetland, and is an effective and stable carbon source. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 They are the product pictures of slow-release carbon source and MDI chemically modified high-efficiency slow-release carbon source;

[0029] Figure 2SEM images of the highly efficient slow-release carbon source chemically modified with MDI at different magnification scales;

[0030] Figure 3 It is the distribution diagram of slow-release carbon source elements;

[0031] Figure 4 This is the EDS spectrum analysis diagram of the slow-release carbon source;

[0032] Figure 5 Element distribution diagram of efficient slow-release carbon source for chemical modification of MDI;

[0033] Figure 6 EDS spectrum analysis diagram of high-efficiency slow-release carbon source chemically modified by MDI;

[0034] Figure 7 The infrared spectrum analysis diagram of the slow-release carbon source and the high-efficiency slow-release carbon source chemically modified by MDI;

[0035] Figure 8 The removal effect diagram of COD in pollutants by the slow-release carbon source and the high-efficiency slow-release carbon source treatment group chemically modified with MDI;

[0036] Fig. 9 The figure shows the removal effect of TN in pollutants by the slow-release carbon source and the high-efficiency slow-release carbon source treatment group chemically modified with MDI. DETAILED DESCRIPTION

[0037] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0038] A highly efficient slow-release carbon source based on chemical modification of MDI, comprising: PBAT (polybutylene adipate / terephthalate), corn cob, AIBN (azobisisobutyronitrile), BCTPA (3-[[(benzylthio)thiocarbonyl]thio]propionic acid), MDI (diphenylmethane diisocyanate), industrial diffusion oil, and a wetting dispersant.

[0039] In order to solve the problems of poor fluidity, uneven mixing, and mechanical clogging in the preparation process after the proportion of corn cobs is increased, industrial diffusion oil and wetting dispersant are added in the present invention, wherein the role of the industrial diffusion oil is to increase the fluidity of PBAT so that PBAT can better coat the corn cobs, and the role of the wetting dispersant is to reduce the surface tension of the corn cobs, improve their wettability in PBAT, and help to disperse them evenly.

[0040] In order to solve the problem of unstable carbon release such as high carbon release in the early stage and low carbon release in the later stage of slow-release carbon source, AIBN and BCTPA are first introduced. Their function is to generate free radicals during the mixing process with PBAT, and to undergo grafting reaction with the small amount of free radicals generated by the decomposition of PBAT, so as to introduce carboxyl groups, hydroxyl groups and other groups on the surface of PBAT. Then MDI is introduced. Its function is to form covalent bonds between the hydroxyl groups and carboxyl groups in PBAT and the hydroxyl groups on the surface of corn cobs through chemical reactions, so as to regulate the carbon release rate.

[0041] Furthermore: the content of corncob is 50% to 80%, and preferably 60%, the addition amount of AIBN is 0.005% to 0.02% of PBAT, the addition amount of BCTPA is 0.005% to 0.02% of PBAT, the addition amount of MDI is 0.5% to 3% of PBAT, the addition amount of industrial diffusion oil is 1% to 5% of PBAT, and the addition amount of wetting and dispersing agent is 0.03% to 0.1% of PBAT.

[0042] The industrial diffusion oil is industrial diffusion oil 12, and the wetting dispersant is wetting dispersant RF-8, wherein both industrial diffusion oil 12 and wetting dispersant RF-8 are commercially available products.

[0043] A processing method for a high-efficiency slow-release carbon source based on MDI chemical modification, the specific steps are as follows:

[0044] S1. Mix PBAT and corncob uniformly at a mass ratio of (60-80): (40-20), then add AIBN and BCTPA, the addition amount of AIBN and BCTPA is 0.005%-0.02% of PBAT, and mix uniformly at room temperature;

[0045] S2, adding the mixed material in S1 into a twin-screw extruder, and controlling the temperature in 4 stages during processing, the temperatures are 180℃~185℃, 185℃~190℃, 185℃~190℃ and 180℃~185℃, the screw rotation speed is 15rpm~25rpm, and the mixing time is 2min~5min;

[0046] S3. The product processed by the twin-screw extruder is first frozen with liquid nitrogen and then crushed into powder. The crushing can be carried out by a crusher;

[0047] S4, adding corncob powder to the powder in S3 to make the corncob content be 50% to 80%;

[0048] S5. First add industrial diffusion oil and wetting dispersant to the powder in S4. The addition amount of industrial diffusion oil and wetting dispersant is 1% to 5% and 0.03% to 0.1% of PBAT respectively. Then add MDI. The addition amount of MDI is 0.5% to 3% of PBAT. Premix evenly.

[0049] S6, adding the mixed material in S5 into a twin-screw extruder, and controlling the temperature in 4 stages during processing, the temperatures are 180°C to 185°C, 185°C to 190°C, 185°C to 190°C, and 180°C to 185°C, the screw rotation speed is 15rpm to 25rpm, and the mixing time is 2min to 5min;

[0050] S7. When the sample is stable, the MDI chemically modified high-efficiency slow-release carbon source is obtained.

[0051] Experimental example

[0052] A processing method for a high-efficiency slow-release carbon source based on MDI chemical modification, the specific steps are as follows:

[0053] S1. Mix PBAT and corncob evenly at a mass ratio of 70:30, then add AIBN and BCTPA, the addition amount of AIBN and BCTPA is 0.005% to 0.02% of PBAT, and mix evenly at room temperature;

[0054] S2, adding the mixed material in S1 into a twin-screw extruder, and controlling the temperature in 4 stages during processing, the temperatures are 183°C, 185°C, 185°C and 183°C, the screw rotation speed is 20rpm, and the mixing time is 3min;

[0055] S3. The product processed by the twin-screw extruder is first frozen with liquid nitrogen and then crushed into powder. The crushing can be carried out by a crusher;

[0056] S4, adding corncob powder to the powder in S3 so that the corncob content is 60%;

[0057] S5. First add industrial diffusion oil and wetting dispersant to the powder in S4. The addition amount of industrial diffusion oil and wetting dispersant is 1% to 5% and 0.03% to 0.1% of PBAT respectively. Then add MDI. The addition amount of MDI is 0.5% to 3% of PBAT. Premix evenly.

[0058] S6, adding the mixed material in S5 into a twin-screw extruder, and controlling the temperature in 4 stages during processing, the temperatures are 185°C, 188°C, 188°C and 185°C, the screw rotation speed is 20 rpm, and the mixing time is 3 min;

[0059] S7. After the sample has stabilized for 5 minutes, the product is collected and cut into suitable sizes after cooling to obtain a highly efficient slow-release carbon source of MDI chemical modification.

[0060] Comparative Example

[0061] A slow-release carbon source comprises: PBAT, corn cobs, industrial diffusion oil and a wetting and dispersing agent.

[0062] A method for processing a slow-release carbon source, the specific steps are as follows:

[0063] S1. Add industrial diffusion oil and wetting dispersant to PBAT. The addition amount of industrial diffusion oil and wetting dispersant is 1% to 5% and 0.03% to 0.1% of the mass of PBAT respectively. Premix evenly.

[0064] S2, first mix the mixture in S1 with corn cob powder at room temperature, then mix them evenly in a high-speed mixer for later use;

[0065] S3. Add the mixture in S2 into a twin-screw extruder. During processing, the temperature is controlled in 4 stages, and the temperatures are 175°C, 180°C, 180°C, and 180°C, respectively. The screw rotation speed is 20rpm, and the mixing time is 2min. Before extrusion processing, the twin-screw extruder is cleaned with pure PBAT to clean the residue in the machine. After stabilization for 5min, the product is collected and cut into a suitable size to obtain a slow-release carbon source product.

[0066] like Figure 1 Shown are product pictures of a slow-release carbon source and a high-efficiency slow-release carbon source chemically modified with MDI.

[0067] like Figure 2 As shown, the surface of the corn cob is coated with PBAT to form a protective layer to slow down its degradation rate. The figure shows photos of different magnifications, and the image scale lengths are as shown in the figure, which are 1mm, 200um and 100um respectively.

[0068] Figure 3 , Figure 5 Elemental analysis shows that the main elements on the surface of the obtained slow-release carbon source and the MDI chemically modified high-efficiency slow-release carbon source material are C and O, and their atomic weight ratio is 56:46.

[0069] Figure 4 , Figure 6 Elemental analysis shows that the main elements on the surface of the obtained material are C and O, which account for 96.9% of the slow-release carbon source components, with a specific mass ratio of 62.17:34.73. The two elements are evenly distributed in the material. Compared with the high-efficiency slow-release carbon source that has not been chemically modified by MDI, it can be seen that there are a small amount of N and S in the high-efficiency slow-release carbon source chemically modified by MDI, but their contents are relatively low, mainly due to the presence of a small amount of S in the MDI modifier, while N is mainly affected by nitrogen in the air. In addition, the C / O ratio of the MDI slow-release carbon source is significantly increased, indicating that the chemical modification of MDI introduces new functional groups.

[0070] Infrared spectroscopy analysis was performed on the slow-release carbon source and the MDI chemically modified high-efficiency slow-release carbon source. Figure 7(a), (b), and (c) are the full infrared spectrum, 3450cm -1 Enlarged image, 1720cm -1 In the enlarged image, it can be found that the MDI chemically modified high-efficiency slow-release carbon source is at 3450cm-1 compared with the slow-release carbon source. -1 The peak intensity at 1720 cm-1 increased, which indicates that the addition of MDI chemical modifier increases the content of hydroxyl groups in the system. -1 The peak at is the stretching vibration peak of -(C=O). The enhancement of this peak indicates that more -(C=O) is produced after adding MDI chain extension, which increases the intensity of its absorption peak, indicating that a covalent bond is successfully established between corncob and PBAT.

[0071] Small-scale experimental research

[0072] 1) Static carbon release test study

[0073] The carbon release process of the slow-release carbon source satisfies the secondary kinetic formula. The larger the Cm, the higher the final COD concentration released by the material, indicating that the material has a greater carbon release capacity; the larger the K, the smaller the mass transfer resistance of the material, and the easier it is to release organic carbon; t 1 / 2 The smaller it is, the faster the organic carbon release reaches equilibrium.

[0074] Table 1 Secondary kinetic fitting parameters of slow-release carbon source

[0075]

[0076] From Table 1, it can be seen that the maximum carbon release potential of the high-efficiency slow-release carbon source chemically modified with MDI has no significant change, but the carbon release resistance coefficient K has decreased significantly compared with the group without chemical modification, that is, the slow-release performance is significantly enhanced, indicating that a chemical bond is established between the corn cob and PBAT, which greatly improves the slow-release performance of the slow-release carbon source, which is beneficial to improving the durability of the slow-release carbon source product and the uniformity of carbon release.

[0077] 2) Research on the application of slow-release carbon sources in subsurface constructed wetlands

[0078] The carbon supply capacity of slow-release carbon sources and their effect on TN removal were investigated using downward subsurface flow constructed wetlands. Crushed stones with a particle size of 3 mm to 5 mm were used as fillers, and the unsaturated ratio was set to 50%. The slow-release carbon source and the high-efficiency slow-release carbon source chemically modified by MDI were evenly mixed with the crushed stones in the saturated area (flooded area).

[0079] from Figure 8It can be seen that the COD removal rate of the slow-release carbon source and the MDI chemically modified high-efficiency slow-release carbon source treatment groups showed a trend of first decreasing and then increasing. This is because the activated sludge supernatant was added in the early stage of the experiment, and the dissolved oxygen condition of the wetland was good in the early stage. Therefore, the COD removal rate was mainly reduced and removed by microorganisms in the activated sludge supernatant. The addition of activated sludge supernatant was stopped in the middle stage, the biofilm of the device was not complete, and the microbial activity had not reached a high level. In the later stage of the experiment, with the completion of microbial biofilm, the COD removal rate increased accordingly. The COD removal rate of the treatment group without slow-release carbon source was significantly higher than that of the treatment group with slow-release carbon source, followed by the MDI chemically modified high-efficiency slow-release carbon source. The source treatment group, and finally the slow-release carbon source treatment group, indicate that both the high-efficiency slow-release carbon source and the slow-release carbon source chemically modified by MDI contribute carbon sources to the wetland, and the slow-release carbon source contributes a greater concentration, making the wetland effluent basically negative, which is not conducive to improving the COD removal rate of the wetland. The high-efficiency slow-release carbon source chemically modified by MDI has a better slow-release effect, and its contribution to COD is relatively gentle in the stable stage (middle and late stages of the experiment), making the COD removal rate of the wetland in the middle and late stages stable at 30% to 60%. Although it is not as high as the COD removal rate without a slow-release carbon source, the effluent quality is basically below 30 mg / L, which meets the surface water Class IV water quality standard.

[0080] from Fig. 9 It can be seen that the removal rate of TN in the pollutants by the slow-release carbon source and the high-efficiency slow-release carbon source treatment group modified by MDI chemically is significantly higher than that of the treatment group without slow-release carbon source. This is mainly because the carbon and nitrogen content of wetland influent is generally low, and the denitrification reaction process, which is the key link of microbial denitrification, requires sufficient carbon source, resulting in a low TN removal rate in the group without slow-release carbon source, with an average TN removal rate of only 10.07%. The removal rate of TN by the slow-release carbon source is slightly higher than that of the high-efficiency slow-release carbon source modified by MDI chemically, with average TN removal rates of 89.20% and 86.01%, respectively. The difference is not significant. From the combined COD removal effect and TN removal effect, it can be seen that the appropriate COD supply concentration can effectively improve the TN removal rate of the wetland. However, if the COD supply concentration is too high, the TN removal rate of the wetland is no longer significantly improved, but it is a waste of the slow-release carbon source. At the same time, too high COD concentration will also cause additional pollution risks to the wetland. Therefore, the high-efficiency slow-release carbon source chemically modified with MDI with good slow-release performance is used in subsurface artificial wetlands. It can not only replenish the carbon source for the wetland and greatly improve the TN removal rate of the wetland, but also will not cause pollution burden on the wetland. It is an ideal carbon source.

[0081] In summary, the MDI chemically modified high-efficiency slow-release carbon source not only improves the fluidity of PBAT powder during the preparation process, allowing the addition ratio of corn cobs to be increased accordingly, but also successfully establishes a chemical bond between PBAT and corn cobs, so that the MDI chemically modified high-efficiency slow-release carbon source has no significant change in the maximum carbon release potential compared to the slow-release carbon source, greatly improving the slow-release performance. The results of the pilot test show that the MDI chemically modified high-efficiency slow-release carbon source can greatly improve the TN removal rate of the subsurface flow constructed wetland without causing a negative impact on the COD of the subsurface flow wetland effluent, and is an efficient and stable denitrification carbon source.

[0082] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A high-efficiency slow-release carbon source based on chemical modification of MDI, characterized in that: include: PBAT, corncob, AIBN, BCTPA, MDI, industrial diffusion oils and wetting and dispersing agents.

2. The high-efficiency slow-release carbon source based on MDI chemical modification according to claim 1, characterized in that: The content of the corncob is 50% to 80%.

3. A high-efficiency slow-release carbon source based on MDI chemical modification according to claim 1 or 2, characterized in that: The amount of AIBN added is 0.005% to 0.02% of PBAT, and the amount of BCTPA added is 0.005% to 0.02% of PBAT.

4. A high-efficiency slow-release carbon source based on chemical modification of MDI according to any one of claims 1 to 3, characterized in that: The added amount of the MDI is 0.5% to 3% of the PBAT.

5. The high-efficiency slow-release carbon source based on MDI chemical modification according to claim 1, characterized in that: The added amount of the industrial diffusion oil is 1% to 5% of the PBAT, and the added amount of the wetting and dispersing agent is 0.03% to 0.1% of the PBAT.

6. The high-efficiency slow-release carbon source based on MDI chemical modification according to claim 1, characterized in that: The industrial diffusion oil is industrial diffusion oil 12, and the wetting dispersant is wetting dispersant RF-8.

7. A method for processing a high-efficiency slow-release carbon source based on chemical modification of MDI as claimed in any one of claims 1 to 6, characterized in that: The specific steps are as follows: S1. Mix PBAT and corncob evenly, then add AIBN and BCTPA, and mix evenly at room temperature; S2, adding the mixed material in S1 into a twin-screw extruder, and controlling the temperature in 4 stages during processing, the temperatures are 180℃~185℃, 185℃~190℃, 185℃~190℃ and 180℃~185℃, the screw rotation speed is 15rpm~25rpm, and the mixing time is 2min~5min; S3, freezing the product processed by the twin-screw extruder with liquid nitrogen and then crushing it into powder; S4, adding corncob powder to the powder in S3 to make the corncob content be 50% to 80%; S5, first add industrial diffusion oil and wetting dispersant to the powder in S4, and then add MDI; S6, adding the mixed material in S5 into a twin-screw extruder, and controlling the temperature in 4 stages during processing, the temperatures are 180°C to 185°C, 185°C to 190°C, 185°C to 190°C, and 180°C to 185°C, the screw rotation speed is 15rpm to 25rpm, and the mixing time is 2min to 5min; S7. When the sample is stable, the MDI chemically modified high-efficiency slow-release carbon source is obtained.

8. The processing method according to claim 6, characterized in that: The mass ratio of PBAT to corncob in S1 is (60-80):(40-20).

9. The processing method according to claim 7, characterized in that: The temperatures in S2 were 183°C, 185°C, 185°C and 183°C, the screw rotation speed was 20 rpm, and the mixing time was 3 min; the temperatures in S6 were 185°C, 188°C, 188°C and 185°C, the screw rotation speed was 20 rpm, and the mixing time was 3 min.

10. The processing method according to claim 7, characterized in that: S7 is specifically as follows: after the sample is stable for 5 minutes, the product is collected and the product is cut into a suitable size after cooling, thereby obtaining a chemically modified MDI high-efficiency slow-release carbon source.

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