Process for preparing surface modified porous biochar based on industrial waste salt co-treatment

Abstract

The invention discloses a surface modified porous biochar preparation process based on industrial waste salt co-processing, which comprises the following steps: (1) uniformly mixing wetted industrial waste salt and agricultural straw biomass powder, and then continuously sealing and stirring at 50 DEG C for 1-2 hours to obtain a wetted mixture; (2) paving wet industrial waste salt with the thickness of 2-3cm on the surface of the wet mixture, then drying the wet industrial waste salt, covering a crucible cover on the wet industrial waste salt, heating to 600-800 DEG C at a heating rate of 1-10 DEG C / min for pyrolysis, keeping the constant temperature for 0.5-2 hours, and cooling to room temperature to obtain molten salt modified biochar; and (3) dissolving and eluting the molten salt with hot water and deionized water for 3-4 times, and drying to obtain black surface modified charcoal powder. By improving the pyrolysis process, the method has a good economic cost advantage; meanwhile, in the process of preparing the biochar, harmless treatment of the waste salt is achieved, and the method has outstanding social and ecological benefits and good application and popularization prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource recycling of industrial hazardous waste and synthesis of environmental functional materials, and specifically relates to a preparation process of surface-modified porous biochar based on the coordinated disposal of industrial waste salt. Background Art

[0002] With the rapid development of the global economy in recent years, energy consumption and environmental pollution have increased exponentially. The synthesis of inexpensive, environmentally friendly, and highly efficient environmentally functional materials is an effective approach to addressing these environmental pollution issues. Biochar, a highly aromatic, carbon-rich solid product typically prepared through high-temperature pyrolysis, is a low-cost, effectively dispersed, and stable carbonaceous material. Due to its surface charge, porous structure, and abundant functional groups, it holds great promise for the adsorption and removal of pollutants from diverse media.

[0003] my country's annual average production of industrial waste salt exceeds 5 million tons and continues to grow. Due to its complex composition, high toxicity, significant hazards, significant environmental risks, and difficulty in disposal, industrial waste salt cannot generally be recycled as an industrial raw material. Furthermore, as a hazardous waste, its improper disposal can potentially cause environmental pollution, while its high disposal costs can increase the environmental and economic burden on businesses. Therefore, the resource utilization of industrial waste salt has significant environmental and economic value.

[0004] Surface modification of biochar is the most effective means of enhancing its adsorption activity. However, previous studies have primarily employed two strategies for surface modification: direct addition of modifying agents during biochar synthesis, and subsequent post-treatment of the biochar surface to produce the modified biochar. Both approaches involve the use of highly corrosive, toxic, and costly modifying agents, increasing the cost of biochar preparation and potentially posing air or water pollution risks due to decomposition and elution of the modifying agents.

[0005] Although previous technical reports have involved the preparation process of biochar materials based on molten salt systems, the salt systems generally used are pure chemicals. Compared with traditional pyrolysis technology, although the overall biochar preparation cost can be reduced, the proportion of molten salt in the cost is still too large to support its large-scale preparation. Industrial waste salt is difficult to be recycled and reused as a resource because it contains impurities such as organic matter and heavy metals. It is urgent to achieve its harmlessness and resource utilization through technological innovation. Although the use of industrial waste salt as a molten salt system to prepare biochar can greatly reduce the preparation cost. However, the harmful flue gases and heavy metal residues generated by the pyrolysis of waste salt will increase the environmental burden of the biochar preparation process, and will also affect the quality and application range of biochar products. Summary of the Invention

[0006] The purpose of the present invention is to provide a process for preparing surface-modified porous biochar based on the coordinated disposal of industrial waste salt.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A process for preparing surface-modified porous biochar based on the coordinated disposal of industrial waste salts comprises the following steps:

[0009] (1) mixing the wetted industrial waste salt and the agricultural straw biomass powder uniformly, and then continuously stirring in a sealed state at 50° C. for 1-2 hours to obtain a wetted mixture; the mass of the industrial waste salt in the wetted mixture is 2.5-20% of the mass of the agricultural straw biomass powder;

[0010] (2) transferring the wetted mixture into a crucible and compacting it, and then spreading the wetted industrial waste salt with a thickness of 2-3 cm on the surface, then drying the wetted industrial waste salt to form a dense sealing layer, covering the crucible with a lid, and placing it in a muffle furnace, heating it to 600-800°C at a heating rate of 1-10°C / min for pyrolysis, and maintaining a constant temperature for 0.5-2h before cooling it to room temperature to obtain molten salt-modified biochar; the room temperature is 25°C;

[0011] (3) The molten salt-modified biochar was dissolved and eluted 3-4 times with 50°C hot deionized water, and then dried at 60-80°C for 16-24 hours to obtain a black powder. The black powder was ground and sieved to obtain the surface-modified biochar.

[0012] Preferably, in step (3), the particle size after grinding is 50-100 mesh.

[0013] Preferably, the agricultural straw biomass powder may be a mixture of one or more biological straws.

[0014] Preferably, the agricultural straw biomass powder is Juncao; the mass of the industrial waste salt is 5% of the mass of the agricultural straw biomass powder; and the particle size of the agricultural straw biomass powder is 50-200 mesh.

[0015] Preferably, in order to achieve better results, the wetted industrial waste salt is prepared by drying the industrial waste salt at 60°C for 2 hours, crushing the industrial waste salt into 50-200 mesh, and then adding water and mixing. The ratio of industrial waste salt to water is 3-9:1. Preferably, the ratio of industrial waste salt to water is 7:1.

[0016] In order to achieve better pyrolysis effect, preferably, in step (2), the heating rate is 5°C / min, the pyrolysis temperature is 700°C, and the constant temperature is maintained for 1 hour.

[0017] Preferably, the industrial waste salt is waste salt produced in the pesticide production process and having a sodium chloride content greater than 70 wt%.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1) Before pyrolysis, the present invention uses moist sodium chloride waste salt for a sealed pre-reaction to improve the bonding between the biomass powder and the organic matter in the waste salt, and promote the subsequent synergistic pyrolysis; the compaction and sealing link can form a compacted structure after drying, which improves the salt sealing effect, reduces the volatilization of harmful organic substances during the pyrolysis process of the waste salt, and reduces the environmental burden of the process; the present invention uses the dual sealing and activation functions of the waste salt to achieve carbonization and activation of the biomass precursor in the next step of air, greatly reducing the preparation cost of the material.

[0020] 2) Utilizing the chemical bonding between the organic components in waste salt and biomass to achieve synergistic pyrolysis of small organic molecules in waste salt and biomass, this can provide inexpensive, high-performance biochar for the synergistic adsorption and removal of heavy metals in multi-media and the catalytic degradation of organic pollutants, thereby achieving functional modification of biochar. Specifically, by leveraging the interaction between organic molecules and functional groups on the surface of biomass, chemical bonding is achieved on the biomass surface during the low-temperature heating stage, effectively avoiding the sublimation or carbonization of small organic molecules and promoting their in-situ, synchronous pyrolysis on the biochar surface under high-temperature conditions, forming rich nitrogen, phosphorus, and sulfur functional groups and doping sites, significantly improving the adsorption characteristics of heavy metal ions and organic pollutant molecules in multi-media.

[0021] 3) The biochar preparation process of the present invention is mainly based on pesticide industrial waste salt and agricultural organic waste. By improving the pyrolysis process, the harmful organic residues in the pyrolysis process of organic waste salt can be synergistically pyrolyzed with biomass, and beneficial defect structures can be formed on the surface of biochar. In the process of biochar preparation, not only the quality of biochar is improved, but also the harmful components in the waste salt are directionally removed, and the harmless treatment of the waste salt is achieved, which has good economic cost advantages; at the same time, it provides a high-added treatment and disposal method for the harmlessness and resource utilization of industrial hazardous waste and agricultural waste, which has outstanding social and ecological benefits and has good application and promotion prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The SEM analysis and energy spectrum surface scanning analysis diagrams of the comparative example and Example 1 of the present invention, as well as the C element distribution diagram, N element distribution diagram, and O element distribution diagram of Example 1 of the present invention; wherein (a) is the SEM analysis diagram of the comparative example, (b) is the SEM analysis diagram of Example 1 of the present invention, and (c) is the energy spectrum surface scanning analysis diagram of Example 1 of the present invention;

[0023] Figure 2The XRD patterns of Example 1 and the comparative example of the present invention are shown in FIG.

[0024] Figure 3 The Raman spectra of Example 1 of the present invention and the comparative example are shown below:

[0025] Figure 4 The N2 adsorption / desorption isotherms and pore size distribution diagrams of Example 1 of the present invention and the comparative example; wherein (a) is the N2 adsorption / desorption isotherm, and (b) is the pore size distribution diagram;

[0026] Figure 5 This is a comparison chart of the adsorption and activation of persulfate to degrade sulfonamide antibiotics according to Example 1 of the present invention and the comparative example. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the embodiments, but the protection scope of the present invention is not limited thereto.

[0028] In the following examples, the industrial waste salt is waste salt with a sodium chloride content of 80 wt% produced during the pesticide production process; and the agricultural straw biomass powder is Juncao.

[0029] Example 1

[0030] A process for preparing surface-modified porous biochar based on the coordinated disposal of industrial waste salts comprises the following steps:

[0031] (1) mixing the wetted industrial waste salt and the agricultural straw biomass powder uniformly, and then continuously stirring them in a sealed state at 50° C. for 1 hour to obtain a wetted mixture; the mass of the industrial waste salt in the wetted mixture is 5% of the mass of the agricultural straw biomass powder; and the particle size of the agricultural straw biomass powder is 100 mesh;

[0032] The preparation method of the wetted industrial waste salt is as follows: drying the industrial waste salt at 60° C. for 2 hours, crushing the industrial waste salt into 100 meshes, and then adding water to mix, wherein the ratio of industrial waste salt to water is 7:1;

[0033] (2) The wetted mixture was transferred to a crucible and compacted, and then a 3 cm thick layer of wetted industrial waste salt was spread on the surface. The wetted industrial waste salt was then dried, covered with a crucible lid, and placed in a muffle furnace. The temperature was raised to 700 °C at a heating rate of 5 °C / min for pyrolysis, and the temperature was kept constant for 1 hour and then dropped to 20-25 °C to obtain molten salt-modified biochar;

[0034] (3) The molten salt-modified biochar was dissolved and eluted four times with 50°C hot deionized water, and then dried at 60°C for 24 hours to obtain a black powder. The black powder was ground through an 80-mesh sieve to obtain surface-modified biochar.

[0035] Example 2

[0036] A process for preparing surface-modified porous biochar based on the coordinated disposal of industrial waste salts comprises the following steps:

[0037] (1) mixing the wetted industrial waste salt and the agricultural straw biomass powder uniformly, and then continuously stirring them in a sealed state at 50° C. for 2 hours to obtain a wetted mixture; the mass of the industrial waste salt in the wetted mixture is 2.5% of the mass of the agricultural straw biomass powder; and the particle size of the agricultural straw biomass powder is 200 mesh;

[0038] The preparation method of the wetted industrial waste salt is as follows: drying the industrial waste salt at 60° C. for 2 hours, crushing the industrial waste salt into 200 meshes, and then adding water to mix, wherein the ratio of industrial waste salt to water is 3:1;

[0039] (2) The wetted mixture was transferred to a crucible and compacted, and then a 2 cm thick layer of wetted industrial waste salt was spread on the surface. The wetted industrial waste salt was then dried, covered with a crucible lid, and placed in a muffle furnace. The temperature was raised to 800°C at a heating rate of 10°C / min for pyrolysis, and the temperature was kept constant for 0.5 h and then dropped to 20-25°C to obtain molten salt-modified biochar;

[0040] (3) The molten salt-modified biochar was dissolved and eluted three times with 50°C hot deionized water, and then dried at 80°C for 16 h to obtain a black powder. The black powder was ground through a 100-mesh sieve to obtain surface-modified biochar.

[0041] Example 3

[0042] A process for preparing surface-modified porous biochar based on the coordinated disposal of industrial waste salts comprises the following steps:

[0043] (1) mixing the wetted industrial waste salt and the agricultural straw biomass powder uniformly, and then continuously stirring in a sealed state at 50° C. for 1.5 hours to obtain a wetted mixture; the mass of the industrial waste salt in the wetted mixture is 20% of the mass of the agricultural straw biomass powder; and the particle size of the agricultural straw biomass powder is 50 mesh;

[0044] The preparation method of the wetted industrial waste salt is as follows: drying the industrial waste salt at 60° C. for 2 hours, crushing the industrial waste salt into 50 meshes, and then adding water to mix, wherein the ratio of industrial waste salt to water is 9:1;

[0045] (2) The wetted mixture was transferred to a crucible and compacted, and then a 3 cm thick layer of wetted industrial waste salt was spread on the surface. The wetted industrial waste salt was then dried, covered with a crucible lid, and placed in a muffle furnace. The temperature was raised to 600 °C at a heating rate of 1 °C / min for pyrolysis, and the temperature was kept constant for 2 h and then dropped to 20-25 °C to obtain molten salt-modified biochar;

[0046] (3) The molten salt-modified biochar was dissolved and eluted three times with 50°C hot deionized water, and then dried at 60°C for 24 hours to obtain a black powder. The black powder was ground through a 50-mesh sieve to obtain surface-modified biochar.

[0047] Example 4

[0048] A process for preparing surface-modified porous biochar based on the coordinated disposal of industrial waste salts comprises the following steps:

[0049] (1) mixing the wetted industrial waste salt and the agricultural straw biomass powder uniformly, and then continuously stirring in a sealed state at 50° C. for 1 hour to obtain a wetted mixture; the mass of the industrial waste salt in the wetted mixture is 10% of the mass of the agricultural straw biomass powder; and the particle size of the agricultural straw biomass powder is 150 mesh;

[0050] The preparation method of the wetted industrial waste salt is as follows: drying the industrial waste salt at 60° C. for 2 hours, crushing the industrial waste salt into 150 meshes, and then adding water and mixing. The ratio of industrial waste salt to water is 8:1.

[0051] (2) The wetted mixture was transferred to a crucible and compacted, and then a 3 cm thick layer of wetted industrial waste salt was spread on the surface. The wetted industrial waste salt was then dried, covered with a crucible lid, and placed in a muffle furnace. The temperature was raised to 600 °C at a heating rate of 4 °C / min for pyrolysis, and the temperature was kept constant for 1.5 h and then dropped to 20-25 °C to obtain molten salt-modified biochar;

[0052] (3) The molten salt-modified biochar was dissolved and eluted four times with 50°C hot deionized water, and then dried at 70°C for 20 h to obtain a black powder. The black powder was ground through a 60-mesh sieve to obtain surface-modified biochar.

[0053] Example 5

[0054] A process for preparing surface-modified porous biochar based on the coordinated disposal of industrial waste salts comprises the following steps:

[0055] (1) mixing the wetted industrial waste salt and the agricultural straw biomass powder uniformly, and then continuously stirring them in a sealed state at 50° C. for 2 hours to obtain a wetted mixture; the mass of the industrial waste salt in the wetted mixture is 5% of the mass of the agricultural straw biomass powder; and the particle size of the agricultural straw biomass powder is 100 mesh;

[0056] The preparation method of the wetted industrial waste salt is as follows: drying the industrial waste salt at 60° C. for 2 hours, crushing the industrial waste salt into 100 meshes, and then adding water to mix, wherein the ratio of industrial waste salt to water is 7:1;

[0057] (2) The wetted mixture is transferred to a crucible and compacted, and then a 2-3 cm thick layer of wetted industrial waste salt is spread on the surface. The wetted industrial waste salt is then dried, covered with a crucible lid, and placed in a muffle furnace. The temperature is raised to 800°C at a heating rate of 5°C / min for pyrolysis, and the temperature is maintained constant for 1 hour and then lowered to 20-25°C to obtain molten salt-modified biochar;

[0058] (3) The molten salt-modified biochar was dissolved and eluted three times with 50°C hot deionized water, and then dried at 60°C for 24 hours to obtain a black powder. The black powder was ground through a 100-mesh sieve to obtain surface-modified biochar.

[0059] Comparative Example

[0060] A method for preparing surface-modified porous biochar:

[0061] Add the Juncao biomass powder to a crucible, and spread a 3cm thick layer of moistened sodium chloride waste salt on its surface. After drying, form a dense sealing layer. Cover the crucible with a lid and place it in a muffle furnace. Raise the temperature to 700°C at a rate of 5°C / minute, maintain a constant temperature for 1 hour, and then cool it down to 20-25°C. Dissolve and elute the molten salt with hot deionized water 3-4 times, then dry it at 60°C for 24 hours. Grind and sieve the resulting black biochar to form surface-modified biochar.

[0062] In order to verify the effect of the product obtained by the method of the present invention, the products obtained in Example 1 and the comparative example were subjected to SEM analysis and energy spectrum scanning analysis. Figure 1 As shown in the SEM analysis and energy spectrum scanning analysis, as well as the C element distribution map, N element distribution map and O element distribution map, according to the structure in the figure, it can be seen that the biochar formed by pyrolysis according to the method of the present invention has a better defect structure and is incorporated with a large number of nitrogen doping sites.

[0063] The XRD patterns and Raman patterns of the products obtained in Example 1 and the comparative example were taken, and the results were as follows: Figure 2 and 3 As shown by Figure 2 It can be seen from the above that the amorphous content of the carbon material formed by the waste salt assisted pyrolysis of the present invention increases, which is mainly caused by the defective structure formed on its surface; Figure 3 It can be seen that the biochar formed by the waste salt-assisted pyrolysis of the present invention has more surface defect structures, which can provide more active sites for processes such as adsorption and catalysis.

[0064] In order to further verify the effect of the method of the present invention, the N2 adsorption / desorption isotherms and pore size distribution of Example 1 and the comparative example were measured. The results are as follows: Figure 4 As shown in the figure, the biochar formed by waste salt assisted pyrolysis of the present invention has a higher specific surface area (422.03m2 g -1 Compare 344.08m 2 g -1 ), larger pore size (2.3nm vs. 2.0nm) and pore volume (0.24cm 3 g -1 Contrast 0.17cm 3 g -1 ).

[0065] In order to further demonstrate the superiority of the method of the present invention, the products of Example 1 of the present invention and the comparative example were used to perform adsorption and activation of persulfate to degrade sulfonamide antibiotics. The experimental method was to disperse the biochar products of Example 1 of the present invention and the comparative example into a 20 mg / L sulfamethoxazole solution (100 mL) at a ratio of 10 mg / L at room temperature of 25°C, place them in a shaker and shake for 50 minutes before sampling. The adsorption performance of the biochar was calculated according to the change in its concentration. Subsequently, 3 mmol / L of potassium persulfate was added, and the shaking was continued for 60 minutes. The samples were taken four times at intervals of 5 minutes, 15 minutes, 20 minutes, and 20 minutes to detect the change in the concentration of the sulfamethoxazole solution. The ratio of the measured concentration to the initial concentration was used as the vertical coordinate, and time was used as the horizontal coordinate to plot as shown below. Figure 5 As shown in the figure, it can be seen that the biochar obtained by the method of the present invention has better performance in both the adsorption and catalysis stages.

Claims

1. A process for preparing surface-modified porous biochar based on the coordinated disposal of industrial waste salt, characterized in that: The following steps are involved: (1) mixing the wetted industrial waste salt and the agricultural straw biomass powder uniformly, and then continuously stirring in a sealed state at 50° C. for 1-2 hours to obtain a wetted mixture; the mass of the industrial waste salt in the wetted mixture is 2.5-20% of the mass of the agricultural straw biomass powder; (2) The wetted mixture is transferred to a crucible and compacted, and then a 2-3 cm thick layer of wetted industrial waste salt is spread on the surface. The wetted industrial waste salt is then dried and covered with a crucible lid. The crucible is heated to 600-800°C at a heating rate of 1-10°C / min for pyrolysis, and the temperature is maintained constant for 0.5-2h before being cooled to room temperature to obtain molten salt-modified biochar; (3) The molten salt-modified biochar was dissolved and eluted 3-4 times with 50°C hot deionized water, and then dried at 60-80°C for 16-24 hours to obtain a black powder. The black powder was ground and sieved to obtain surface-modified porous biochar.

2. The process for preparing surface-modified porous biochar based on the coordinated disposal of industrial waste salt according to claim 1, characterized in that: The agricultural straw biomass powder is Juncao; the mass of the industrial waste salt in the wetting mixture is 5% of the mass of the agricultural straw biomass powder; and the particle size of the agricultural straw biomass powder is 50-200 meshes.

3. The process for preparing surface-modified porous biochar based on the coordinated disposal of industrial waste salt according to claim 2, characterized in that: The preparation method of the wetted industrial waste salt is as follows: drying the industrial waste salt at 60° C. for 2 hours, crushing the industrial waste salt into 50-200 meshes, and then adding water to mix, wherein the ratio of the industrial waste salt to the water is 3-9:

1.

4. The process for preparing surface-modified porous biochar based on the coordinated disposal of industrial waste salt according to claim 3, characterized in that: In step (2), the heating rate is 5°C / min, the pyrolysis temperature is 700°C, and the constant temperature is maintained for 1 hour.

5. The process for preparing surface-modified porous biochar based on the coordinated disposal of industrial waste salt according to claim 4, characterized in that: The industrial waste salt is waste salt generated in the pesticide production process and has a sodium chloride content greater than 70 wt%.

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