Humin-like hydrothermal carbon as well as preparation method and application thereof

Abstract

The invention discloses humin-like hydrothermal carbon as well as a preparation method and application thereof, and belongs to the technical field of agricultural solid waste resource utilization. The humin-like hydrothermal carbon is prepared from corn straw through a hydrothermal carbon method, carbon-containing functional groups of the humin-like hydrothermal carbon comprise 24-28% of alkyl carbon, 8-12% of methoxyl carbon, 8-14% of oxyalkyl carbon, 6-9% of anomeric carbon, 35-38% of aromatic carbon, 5-12% of carboxyl carbon and 0-5% of C = O according to the peak area percentage of characteristic peaks, and the carbon structure of the humin-like hydrothermal carbon is basically consistent with that of natural humin. The humin hydrothermal carbon can be applied to soil remediation, heavy metal pollution of soil is eliminated, and the content of organic carbon in the soil is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural solid waste resource utilization, and specifically relates to a humin-like hydrothermal charcoal and a preparation method and application thereof. Background Art

[0002] Corn straw is a common biomass in farmland. Straw burning is a common way to deal with straw biomass, but it brings about environmental pollution and carbon loss in farmland. Therefore, the resource utilization of farmland straw biomass is an important environmental issue. Humus is the "black gold" in agricultural soil and an important component of the soil organic carbon pool. It has great resistance to microbial decomposition and can be preserved in the soil for a long time. It is of great significance in eliminating pollutants, maintaining carbon balance and increasing crop yields. Humin is the most stable carbon component in humus.

[0003] Humin plays an important role in restoring soil fertility and protecting the environment. It can promote the aggregation of soil colloidal particles, improve the adsorption capacity of colloidal particles, prevent surface water runoff and soil erosion, and thus improve soil permeability and suitability for cultivation. However, the current natural humin extraction process is complicated, the extraction cost is high, and it is difficult to mass produce. Therefore, there is an urgent need to provide a method for artificially preparing humin. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a humin-like hydrothermal charcoal and a preparation method and application thereof, so as to solve the problems of difficulty in extracting and mass producing existing natural humin.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: a humin-like hydrothermal carbon is provided, wherein the carbon-containing functional groups thereof include, by molar percentage, 24-28% alkyl carbon, 8-12% methoxy carbon, 8-14% oxyalkyl carbon, 6-9% anomeric carbon, 35-38% aromatic carbon, 5-12% carboxyl carbon and 0-5% C=O.

[0006] On the basis of the above technical solution, the present invention can also be improved as follows:

[0007] Furthermore, the carbon-containing functional groups thereof include, by mole percentage, 25% alkyl carbon, 9% methoxy carbon, 13% oxyalkyl carbon, 8% anomeric carbon, 36% aromatic carbon, 6% carboxyl carbon and 3% C=O.

[0008] The present invention also provides a method for preparing the above-mentioned humin-like hydrothermal carbon, comprising the following steps:

[0009] S1: mixing corn straw powder and water in a mass ratio of 3-5:30-50 to obtain corn straw slurry;

[0010] S2: heating the corn straw slurry to 240-260° C., isothermally cracking for 30-60 min, introducing an inert gas to a pressure of 19-21 MPa, and hydrothermally reacting for 4-8 h to obtain a hydrothermal reaction product;

[0011] S3: Drying the hydrothermal reaction product to obtain.

[0012] The beneficial effects of adopting the above technical scheme are as follows: the present invention uses corn straw as raw material, and prepares humin-like hydrothermal charcoal through high-temperature and high-pressure hydrothermal reaction. First, the straw is hydrolyzed at high temperature to generate small molecular organic matter, and then inert gas is used for pressurization to generate alkyl carbon and aromatic carbon. The product increases with the extension of reaction time. The combined effect of high temperature, high pressure and reaction time causes the straw oxyalkyl carbon to be gradually consumed and react to generate more stable alkyl carbon and aromatic carbon. Alkyl carbon and aromatic carbon are the most important structures of soil humin, so that the hydrothermal charcoal product generates a structure similar to that of soil humin.

[0013] Furthermore, the particle size of the corn stover powder is less than 100 mesh.

[0014] Furthermore, the mass ratio of corn straw powder to water is 1:10.

[0015] Furthermore, the inert gas is CO2.

[0016] Furthermore, the drying temperature in S3 is 65-75°C.

[0017] The present invention also provides an application of the humin-like hydrothermal charcoal in soil remediation.

[0018] Furthermore, the above-mentioned soil remediation is to reduce the content of heavy metal ions in the soil.

[0019] The beneficial effect of adopting the above technical scheme is that the humin-like hydrothermal carbon prepared by the present invention can react with heavy metal elements in the soil through ion exchange, electrostatic adsorption, physical adsorption, complex reaction and chemical precipitation, thereby reducing the biological effectiveness and mobility of heavy metals and reducing the concentration of heavy metal ions in the soil.

[0020] Furthermore, the above-mentioned soil remediation is to enhance the carbon sequestration capacity of the soil.

[0021] The beneficial effects of adopting the above technical scheme are as follows: the humin-like hydrothermal charcoal prepared by the present invention contains relatively high levels of aromatic carbon and alkyl carbon. These carbon-containing functional groups are relatively stable, which helps to stabilize and preserve organic carbon in the soil, and effectively participate in the carbon cycle process, thereby improving the stability and carbon fixation potential of the soil.

[0022] The present invention has the following beneficial effects:

[0023] 1. The present invention uses corn stalks to prepare humin-like hydrothermal charcoal through a hydrothermal charcoal method, thereby realizing the recycling of agricultural solid waste resources. The preparation method is simple, low-cost, and easy to expand production.

[0024] 2. The humin-like hydrothermal carbon prepared by the present invention has a structure that is basically consistent with that of natural humin, and can be used for soil remediation, and can effectively reduce soil heavy metal pollution and increase soil organic carbon content. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart of the specific steps of the method for preparing humin-like hydrothermal carbon of the present invention;

[0026] Figure 2 This is a sample of humin-like hydrothermal carbon prepared in Example 1;

[0027] Figure 3 The nuclear magnetic resonance (NMR) spectra of the humin-like hydrothermal charcoal and soil humin prepared in Example 1. DETAILED DESCRIPTION

[0028] The principles and features of the present invention are described below in conjunction with embodiments. Figure 1 The present invention is a flow chart of the specific steps of the humin hydrothermal carbon preparation method. The examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific conditions are specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are followed. The reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially.

[0029] Embodiment 1:

[0030] A method for preparing humin-like hydrothermal carbon comprises the following steps:

[0031] S1: Grind corn straw into corn straw powder with a particle size less than 100 mesh, weigh 5 g of corn straw powder and add it into 50 mL of water to obtain corn straw slurry;

[0032] S2: Place corn straw slurry in a 250 mL hydrothermal reactor, heat to 250°C, and pyrolyze at constant temperature for 30 min. Then, introduce CO2 gas at a flow rate of 6 L / h until the pressure reaches 20 MPa. Perform hydrothermal reaction for 4 h to obtain a hydrothermal reaction product.

[0033] S3: Completely drying the hydrothermal reaction product at 70° C. to obtain humin-like hydrothermal carbon.

[0034] Embodiment 2:

[0035] A method for preparing humin-like hydrothermal carbon comprises the following steps:

[0036] S1: Grind corn straw into corn straw powder with a particle size less than 100 mesh, weigh 3 g of corn straw powder and add it into 30 mL of water to obtain corn straw slurry;

[0037] S2: Place corn straw slurry in a 250 mL hydrothermal reactor, heat to 250°C, and pyrolyze at constant temperature for 30 min. Then, introduce CO2 gas at a flow rate of 6 L / h until the pressure reaches 20 MPa, and perform hydrothermal reaction for 6 h to obtain a hydrothermal reaction product.

[0038] S3: Completely drying the hydrothermal reaction product at 65° C. to obtain humin-like hydrothermal charcoal.

[0039] Embodiment 3:

[0040] A method for preparing humin-like hydrothermal carbon comprises the following steps:

[0041] S1: Grind corn straw into corn straw powder with a particle size less than 100 mesh, weigh 5 g of corn straw powder and add it into 50 mL of water to obtain corn straw slurry;

[0042] S2: Place corn straw slurry in a 250 mL hydrothermal reactor, heat to 250°C, and pyrolyze at constant temperature for 50 min. Then, introduce CO2 gas at a flow rate of 6 L / h until the pressure reaches 20 MPa. Perform hydrothermal reaction for 8 h to obtain a hydrothermal reaction product.

[0043] S3: Completely drying the hydrothermal reaction product at 65° C. to obtain humin-like hydrothermal charcoal.

[0044] Experimental example:

[0045] The humin-like hydrothermal carbons prepared in Examples 1 to 3 have similar properties and structures. The humin-like hydrothermal carbons prepared in Example 1 were used for NMR testing to compare their structures with those of humin. Figure 2 This is a picture of the humin-like hydrothermal carbon sample prepared in Example 1.

[0046] The humin-like hydrothermal charcoal and soil humin were ground into powder using an agate mortar and passed through a 100-mesh sieve. Part of the powder was loaded into a nuclear magnetic rotor for compaction, and the carbon structure and relative content of carbon-containing functional groups were tested on a 500 Hz Bruker nuclear magnetic resonance spectrometer to obtain the characteristic peak area data of carbon-containing functional groups. Soil humin was extracted from three typical soils, namely black soil, red soil and tidal soil. The extraction method was to use hydrochloric acid and sodium hydroxide solution to adjust the soil pH to pH=1 and pH=7 respectively, and then remove the supernatant after standing overnight. The residue obtained was soil humin.

[0047] The specific test results are shown in Table 1 and Figure 3 .

[0048] Table 1 Carbon functional group content of soil humin and humin-like hydrothermal charcoal

[0049]

[0050] From the data in Table 1 and Figure 3 It can be seen that the carbon-containing functional group content of humin-like hydrothermal carbon is very similar to that of soil humin, indicating that the structure of humin-like hydrothermal carbon prepared by the present invention is very similar to that of soil humin, among which alkyl carbon and aromatic carbon are relatively stable carbon structures, and their content is basically consistent with that of soil humin; Figure 3 It can be seen that the peaks of the carbon-containing functional groups of humin-like hydrothermal charcoal are consistent with those of soil humin, and the NMR spectrum of the generated humin-like hydrothermal charcoal is very similar to that of soil humin, which indicates that the carbon structure of humin-like hydrothermal charcoal is basically consistent with that of soil humin.

[0051] Application Example 1:

[0052] The application of humin-like hydrothermal carbon in the remediation of soil heavy metal pollution includes the following steps:

[0053] S1: Take a certain amount of soil and artificially pollute it, where the heavy metal Cd content is 2.58 mg / kg;

[0054] S2: adding the humin-like hydrothermal carbon prepared in Example 1 to the contaminated soil at a mass ratio of 2%, and spraying an appropriate amount of water daily to achieve the purpose of moistening;

[0055] S3: After 30 days, samples were taken for testing, and the content of heavy metal Cd in the soil before and after calculation decreased to 0.8 mg / kg.

[0056] Application Example 2:

[0057] The application of humin-like hydrothermal charcoal in soil carbon fixation and restoration includes the following steps:

[0058] S1: adding the humin-like hydrothermal carbon prepared in Example 1 to 200 g of soil at addition amounts of 0.5% and 2%, and taking a soil sample without humin-like hydrothermal carbon as a control;

[0059] S2: After 30 days of the experiment, the organic carbon content in the soil was measured. The soil organic carbon content of the soil with the addition of 0.5% and 2% humin-like hydrochar was 14.9 g / kg and 18.7 g / kg, respectively, while the soil organic carbon content of the control group without the addition of humin-like hydrochar was 13.1 g / kg.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A humin-like hydrothermal charcoal, characterized in that: Its carbon-containing functional groups include, according to the peak area percentage of characteristic peaks, 24-28% alkyl carbon, 8-12% methoxy carbon, 8-14% oxyalkyl carbon, 6-9% anomeric carbon, 35-38% aromatic carbon, 5-12% carboxyl carbon and 0-5% C=O.

2. The humin-like hydrothermal carbon according to claim 1, characterized in that: The carbon-containing functional groups thereof include, by mole percentage, 25% alkyl carbon, 9% methoxy carbon, 13% oxyalkyl carbon, 8% anomeric carbon, 36% aromatic carbon, 6% carboxyl carbon and 3% C=O.

3. The method for preparing humin-like hydrothermal carbon according to claim 1 or 2, characterized in that: The following steps are involved: S1: mixing corn straw powder and water in a mass ratio of 3-5:30-50 to obtain corn straw slurry; S2: heating the corn stalk slurry to 240-260° C., isothermally cracking for 30-60 min, introducing an inert gas to a pressure of 19-21 MPa, and hydrothermally reacting for 4-8 h to obtain a hydrothermal reaction product; S3: drying the hydrothermal reaction product to obtain.

4. The preparation method according to claim 3, characterized in that: The particle size of the corn stalk powder is less than 100 meshes.

5. The preparation method according to claim 3, characterized in that: The mass ratio of the corn stalk powder to water is 1:

10.

6. The preparation method according to claim 3, characterized in that: The inert gas is CO2.

7. The preparation method according to claim 3, characterized in that: The drying temperature in S3 is 65-75°C.

8. Use of the humin-like hydrothermal carbon according to claim 1 or 2 in soil remediation.

9. The use according to claim 8, characterized in that: The soil remediation is to reduce the content of heavy metal ions in the soil.

10. The use according to claim 8, characterized in that: The soil remediation is to enhance the carbon sequestration capacity of the soil.

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