Organic pollution biostimulation sustained-release material as well as preparation method and application thereof

Abstract

The invention relates to the field of environmental protection, and discloses an organic pollution biostimulation sustained-release material as well as a preparation method and application thereof. The organic pollution biostimulation slow-release material is of a core-shell structure, an inner core contains porous carbon loaded with sulfate, and a shell layer contains nitrogen-doped porous carbon. Biomass charcoal is used as a matrix, charcoal fully etched and dispersed by molten sulfate is used as a sulfate radical slow-release center, and nitrogen-doped porous carbon is coated on the outer layer to perform slow-release control on a core medicament slow-release layer, so that the sulfate radical slow-release biomass-based carbon-carbon microsphere slow-release material is formed. And an electron acceptor can be continuously provided for sulfate reducing bacteria in a polluted site.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection, and particularly to an organic pollution biostimulation sustained-release material, a preparation method thereof, and an application thereof. Background Art

[0002] The high-speed development of the industrialization process has derived a series of industrial polluted sites. The polluted sites in the petrochemical industry are mostly represented by organic pollutants. The development of green and efficient remediation technologies is becoming increasingly important for the effective treatment of polluted sites.

[0003] Sulfate-reducing bacteria are widely present in various places in nature, such as soil, seawater, oil and gas fields, river bottom sludge, etc. Sulfate-reducing bacteria are anaerobic reducing bacteria that use sulfur oxides such as sulfate, sulfite, and thiosulfate as electron acceptors and organic matter as a carbon source for life activities. Through the dissimilatory action of sulfate-reducing bacteria, sulfate is reduced to S 2- , and part of the carbon source is converted into CO3 2- , S 2- , and CO3 2- can interact with metal ions to form insoluble precipitates. Through the life activities of sulfate-reducing bacteria, the conversion and removal of pollutants can be comprehensively achieved. Relying on sulfate-reducing bacteria in nature, providing a pharmaceutical system capable of slow release of sulfate has great significance for synchronously achieving pollutant removal.

[0004] Biochar is a porous solid with an aromatic structure formed by pyrolytic carbonization of waste biomass at a certain temperature. The aromatic structure ensures its biological and chemical stability and can exist in the environment for a long time without being decomposed and mineralized by microorganisms. The particularity of the porous structure endows it with many functionalizable characteristics. Existing research has found that the porous structure after biomass carbonization shows good effects such as rich porosity, increased cation exchange capacity, and enhanced water and fertilizer retention efficiency during soil utilization, and has a better soil improvement effect; there is also research based on the soil improvement effect of biochar, using biochar as a matrix, and obtaining biochar with a certain pharmaceutical slow-release function through operations such as blending and compounding. The slow-released pharmaceutical can participate in the remediation process of polluted soil, and the biochar matrix after slow release can continue to play a certain role in the soil improvement process. By adding slow-release functions, biochar is transformed into a soil conditioner with a certain remediation function. This type of research not only functionalizes waste biomass into a high-quality and efficient product for solving soil pollution, but also directly contributes to the overall goal of carbon sequestration and emission reduction under the background of "dual carbon" in the form of soil carbon sequestration.

[0005] The main types of traditional sustained-release agents include coated types, polymer matrix types, adsorptive types, etc. Natural components are mostly used as coating materials, such as chitosan, sodium alginate, starch, cellulose, etc. These coating materials are mixed with active substances such as biochar. The operation is simple and it has a wide application. The coating materials play a role in hindering the diffusion of the agent, extending the sustained-release period. However, most of the traditional coating components are microbial nutrient organic matters, which are easily preferentially utilized by microorganisms as metabolic substrates during the process of returning to the soil, thus affecting the sustained-release effect of the agent and limiting the multi-scenario application of the material. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems existing in the prior art, such as easy decomposition of the sustained-release coating, large limitations in usage scenarios, and complex preparation processes. The present invention provides an organic pollution biostimulation sustained-release material, its preparation method and application. This organic pollution biostimulation sustained-release material can continuously provide electron acceptors for sulfate-reducing bacteria in polluted sites by slowly releasing sulfate radicals.

[0007] In order to achieve the above purpose, on the one hand, the present invention provides an organic pollution biostimulation sustained-release material. The organic pollution biostimulation sustained-release material has a core-shell structure, wherein the inner core contains porous carbon loaded with sulfate, and the shell layer contains nitrogen-doped porous carbon.

[0008] Preferably, in the porous carbon loaded with sulfate, the sulfate is selected from two or more of magnesium sulfate, calcium sulfate, potassium sulfate, sodium sulfate, iron sulfate and lithium sulfate;

[0009] Preferably, in the porous carbon loaded with sulfate, the pore size of the porous carbon is 1-70 nm, preferably 1-30 nm;

[0010] Preferably, the raw material for preparing the porous carbon loaded with sulfate contains biomass.

[0011] Preferably, the pore size of the nitrogen-doped porous carbon is 1-30 nm, preferably 1-20 nm;

[0012] Preferably, the raw material for preparing the nitrogen-doped porous carbon contains biomass.

[0013] Preferably, the diameter of the organic pollution biostimulation sustained-release material is 1-3 mm, preferably 1.25-1.75 mm.

[0014] Preferably, the diameter of the inner core is 0.5-1.5 mm, preferably 0.65-0.95 mm;

[0015] Preferably, the thickness of the shell layer is 0.25-0.5 mm, preferably 0.3-0.4 mm.

[0016] The second aspect of the present invention provides a method for preparing the above-mentioned organic pollution biostimulation slow-release material, and the preparation method includes the following steps:

[0017] (1) Mix sulfate and biomass, then perform carbonization treatment, and then granulate to obtain a core;

[0018] (2) Mix biomass with urea to obtain a nitrogen-containing mixture;

[0019] (3) Mix the core obtained in step (1) with the nitrogen-containing mixture obtained in step (2), then granulate, and then perform roasting.

[0020] Preferably, in step (1), the weight ratio of the amount of the biomass to the amount of the sulfate is 1:1-8, preferably 1:3-6.

[0021] Preferably, in step (1), the sulfate is selected from two or more of magnesium sulfate, calcium sulfate, potassium sulfate, sodium sulfate, iron sulfate and lithium sulfate;

[0022] Preferably, the sulfate is a mixture of sodium sulfate, potassium sulfate and magnesium sulfate, and based on the total amount of sodium sulfate, potassium sulfate and magnesium sulfate being 100 wt%, the amount of sodium sulfate is 45-55 wt%, the amount of potassium sulfate is 5-15 wt%, and the amount of magnesium sulfate is 35-50 wt%.

[0023] Preferably, in step (1), the operation of the carbonization treatment includes: heating to 600-1200 °C at a heating rate of 3-15 °C / min and holding for 1-6 h.

[0024] Preferably, the atmosphere of the carbonization treatment is an inert atmosphere or an oxygen-containing atmosphere.

[0025] Preferably, in step (2), the weight ratio of the amount of the biomass to the amount of urea is 1:0.5-1.5.

[0026] Preferably, in step (3), the conditions of the roasting include: heating to 400-600 °C at a heating rate of 3-15 °C / min and holding for 1-5 h.

[0027] Preferably, the atmosphere of the roasting is an inert atmosphere or an oxygen-containing atmosphere.

[0028] The third aspect of the present invention provides an application of the above-mentioned organic pollution biostimulation slow-release material in the remediation of organic-polluted soil and groundwater.

[0029] Starting from the functional development and reuse of waste biomass, the present invention fully explores the value of biochar itself in the field of realizing slow-release functions. Using biomass carbon as the matrix, molten sulfate is used to fully etch the dispersed biochar as the slow-release center of sulfate radicals, and the outer layer is wrapped with nitrogen-doped porous carbon to control the slow release of the core pharmaceutical slow-release layer, forming a bio-stimulating slow-release material for organic pollution with sulfate radical slow-release biomass-based carbon-carbon microspheres. By slowly releasing sulfate radicals, this slow-release material can continuously provide electron acceptors for sulfate-reducing bacteria in polluted sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the process flow chart for the preparation of the bio-stimulating slow-release material for organic pollution;

[0031] Figure 2 is the structural schematic diagram of the test device used in Test Examples 2-4.

[0032] DESCRIPTION OF THE REFERENCE NUMERALS

[0033] 1 Stirrer 2 Water storage container

[0034] 3 Peristaltic pump 4 Sample loading port

[0035] 5 Reaction soil column 6 Outlet water storage device

[0036] 7 Nitrogen gas balloon DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The following further describes in detail the specific embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0038] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0039] On the one hand, the present invention provides a bio-stimulating slow-release material for organic pollution, the bio-stimulating slow-release material for organic pollution having a core-shell structure, wherein the inner core contains porous carbon loaded with sulfate, and the shell layer contains nitrogen-doped porous carbon.

[0040] In the organic pollution biostimulation slow-release material of the present invention, in the porous carbon loaded with sulfate, the sulfate is filled in the pores of the porous carbon with a pore diameter of 1-70 nm (the pores in the porous carbon are mainly mesopores and micropores). In addition to being filled in the pores of the porous carbon, part of the sulfate is also loaded on the surface of the porous carbon, and can continuously dissolve and release the fixed sulfate radical in a certain environment, becoming the slow-release core of the sulfate radical. By granulating and coating (nitrogen-doped porous carbon), the slow-release period of the sulfate radical is extended to prepare the organic pollution biostimulation slow-release material.

[0041] In the present invention, in order to reduce the melting temperature of the sulfate and avoid the destruction of the structure of the activated carbon due to too high reaction temperature, and to obtain a mixed molten salt with a stable structure, preferably, in the porous carbon loaded with sulfate, the sulfate is selected from two or more of magnesium sulfate, calcium sulfate, potassium sulfate, sodium sulfate, iron sulfate and lithium sulfate.

[0042] In the present invention, in order to achieve a better slow-release effect, in the porous carbon loaded with sulfate, the pore diameter of the porous carbon is 1-30 nm.

[0043] Preferably, the raw material for preparing the porous carbon loaded with sulfate contains biomass.

[0044] In the organic pollution biostimulation slow-release material of the present invention, the raw material for preparing the nitrogen-doped porous carbon contains biomass. Among them, the pores in the nitrogen-doped porous carbon are mainly micropores, and the pore diameter of the nitrogen-doped porous carbon is 1-30 nm, preferably 1-20 nm.

[0045] In a preferred case, in the present invention, choosing biomass as the raw material for roasting to prepare porous carbon can play a role in the functional development and reuse of biomass. At the same time, the biomass has a rich organic carbon content and has great advantages in the preparation of porous carbon.

[0046] In a preferred embodiment of the present invention, the organic pollution biostimulation slow-release material is spherical, and its inner core is also spherical. Preferably, the diameter of the organic pollution biostimulation slow-release material is 1-3 mm, more preferably 1.25-1.75 mm, and the diameter of the inner core is 0.5-1.5 mm, preferably 0.65-0.95 mm.

[0047] In a specific embodiment, the diameter of the organic pollution biostimulation slow-release material is 1.5 mm, and the diameter of the inner core is 0.70 mm.

[0048] In the organic pollution biostimulation slow-release material of the present invention, the thickness of the shell layer is 0.25-0.5 mm, preferably 0.3-0.4 mm.

[0049] In a specific embodiment, the thickness of the shell layer is 0.40 mm.

[0050] Controlling the size of the organic pollution biostimulation slow-release material of the present invention within the above range can achieve a certain amount of sulfate storage and can better achieve sulfate slow release.

[0051] The second aspect of the present invention provides a preparation method of the above organic pollution biostimulation slow-release material, and its process flow chart is as Figure 1 shown, and the preparation method includes the following steps:

[0052] (1) Mix sulfate and biomass, then carry out carbonization treatment, and then granulate to obtain a core.

[0053] (2) Mix biomass and urea to obtain a nitrogen-containing mixture.

[0054] (3) Mix the core obtained in step (1) with the nitrogen-containing mixture obtained in step (2), then granulate, and then carry out roasting.

[0055] In the preparation method of the present invention, the biomass used is common waste biomass in the art. In a specific embodiment, the biomass can be selected from one or more of straw, corn cobs, coconut shells, walnut shells, and various tree branches.

[0056] The present invention is obtained through the melting activation process of traditional porous carbon, that is, in step (1), after mixing sulfate and biomass and carrying out carbonization treatment, porous carbon loaded with sulfate is obtained. However, different from traditional activation, the present invention does not wash after carbonization treatment, so that sulfate is retained.

[0057] Since the melting point of a single sulfate is relatively high, in order to obtain a sulfate with a low melting point, reduce the temperature of the molten salt carbonization process, and obtain a better slow-release effect, further preferably, in step (1), the sulfate is selected from two or more of magnesium sulfate, calcium sulfate, potassium sulfate, sodium sulfate, iron sulfate, and lithium sulfate. Further preferably, the sulfate is a mixture of sodium sulfate, potassium sulfate, and magnesium sulfate, and based on the total amount of sodium sulfate, potassium sulfate, and magnesium sulfate being 100 wt%, the amount of sodium sulfate is 45-55 wt%, the amount of potassium sulfate is 5-15 wt%, and the amount of magnesium sulfate is 35-50 wt%.

[0058] In a specific embodiment, in step (1), the sulfate is a mixture of sodium sulfate, potassium sulfate and magnesium sulfate. Based on the total amount of sodium sulfate, potassium sulfate and magnesium sulfate being 100 wt%, the amount of sodium sulfate can be 45 wt%, 47 wt%, 49 wt%, 50 wt%, 52 wt% or 55 wt%, the amount of potassium sulfate can be 5 wt%, 7 wt%, 10 wt%, 13 wt% or 15 wt%, and the amount of magnesium sulfate is 35 wt%, 37 wt%, 40 wt%, 43 wt%, 45 wt%, 47 wt% or 50 wt%.

[0059] In a specific embodiment, the sulfate is a mixture of sodium sulfate, potassium sulfate and magnesium sulfate. Based on the total amount of sodium sulfate, potassium sulfate and magnesium sulfate being 100 wt%, the amount of sodium sulfate is 51 wt%, the amount of potassium sulfate is 6 wt%, and the amount of magnesium sulfate is 43 wt%.

[0060] In the preparation method of the present invention, in order to make the sulfate fill more fully, in step (1), the biomass can be crushed and then mixed with the sulfate and ground together (both the biomass and the sulfate should be fully dried before mixing). There is no special requirement for the particle size of the crushed biomass, and it can preferably be about 45 - 55 mesh to make the materials fully dispersed and mixed evenly, and then carbonization treatment is carried out.

[0061] In step (1), the weight ratio of the biomass to the amount of the sulfate is 1:1 - 8, preferably 1:3 - 6, and specifically can be 1:3, 1:4, 1:5 or 1:6.

[0062] In the carbonization treatment process of step (1) of the present invention, after reaching a certain temperature, the biomass begins to carbonize in advance to form porous carbon with certain pores. As the temperature rises, after reaching the melting temperature of the sulfate, the sulfate begins to melt, and a phase change occurs. The molten sulfate enters the pores inside the porous carbon and further etches the pore structure. At the same time, the molten salt ions also participate in the subsequent carbonization process in the form of a template agent, promoting the enrichment of the pore channels of the porous carbon and the shaping of the porous carbon material. After the carbonization treatment, a biomass-based porous carbon loaded with sulfate is obtained.

[0063] In step (1), in order to achieve a better pore-forming effect, it is also necessary to further control the conditions of the carbonization treatment. In the preferred case, the operation of the carbonization treatment includes: heating at a heating rate of 3 - 15 °C / min to 600 - 1200 °C and holding for 1 - 6 h.

[0064] In step (1) of the present invention, in the carbonization treatment operation, according to the different sulfates used, their corresponding melting properties vary greatly. Therefore, the holding temperature aims at complete melting of the sulfate. Preferably, the holding temperature is preferably 600°C - 1200°C.

[0065] In a specific embodiment, in step (1), the heating rate can be 3°C / min, 6°C / min, 9°C / min, 12°C / min or 15°C / min, and it can be heated to 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C or 1200°C, and the holding time can be 1h, 2h, 3h, 4h, 5h or 6h.

[0066] In step (1) of the present invention, the atmosphere of the carbonization treatment is an inert atmosphere or an oxygen-containing atmosphere, and further preferably an inert atmosphere.

[0067] In a specific embodiment of the present invention, in step (1), the operation of the carbonization treatment includes: heating at a heating rate of 5°C / min to 700°C and holding for 4h.

[0068] In a preferred case in step (1) of the present invention, after the carbonization treatment, a porous carbon loaded with sulfate is obtained, and it is also necessary to grind it sufficiently to 100 - 200 mesh, and then granulate it.

[0069] In the granulation process of step (1) of the present invention, a binder needs to be sprayed simultaneously to promote molding. There are no special requirements for the dosage of the binder used, as long as the final core size meets the corresponding requirements.

[0070] In the preparation method of the present invention, in step (2), similarly to ensure sufficient mixing of the materials, the biomass can be crushed and then mixed with urea in a certain proportion and ground together to make the materials fully dispersed and mixed evenly, obtaining a nitrogen-containing mixture. There are no special requirements for the particle size of the crushed biomass, and it can be preferably about 45 - 55 mesh. There are also no special requirements for the grinding time, as long as the materials can be fully mixed evenly. Preferably, the grinding time is about 5min.

[0071] Further preferably, in order to achieve a better slow-release effect, in step (2), the weight ratio of the biomass to urea is 1:0.5 - 1.5, specifically it can be 1:0.5, 1:0.7, 1:0.9, 1:1, 1:1.2 or 1:1.5.

[0072] In a specific embodiment, in step (2), the weight ratio of the biomass to urea is 8:7.

[0073] In step (3) of the present invention, preferably, the nitrogen-containing mixture is sufficiently ground to 100-200 mesh, and then mixed with the core obtained in step (1) for granulation to form a coating layer of the nitrogen-containing mixture on the surface of the core, obtaining a composite microsphere with a core-shell structure, and then calcined to finally obtain the organic pollution biostimulation slow-release material of the present invention.

[0074] In the granulation process of step (3) of the present invention, a binder needs to be sprayed simultaneously to promote molding. There are no special requirements for the dosage of the binder used, as long as the thickness of the shell layer of the finally obtained organic pollution biostimulation slow-release material meets the corresponding requirements.

[0075] In the invention, there are no special requirements for the selection of the binder, as long as it can promote bonding and molding. In a specific embodiment, the binder is an aqueous solution of bentonite with a concentration of 15 wt%.

[0076] In step (3) of the present invention, there are no special requirements for the dosages of the core obtained in step (1) and the nitrogen-containing mixture obtained in step (2), as long as the size of the finally obtained organic pollution biostimulation slow-release material and the thickness of the shell layer meet the corresponding requirements.

[0077] In the preparation method of the present invention, in step (3), during the calcination operation, urea will interact with the carbon-based component to undergo carbonization to form nitrogen-doped porous carbon. Among them, bentonite undergoes carbonization during the calcination process to form a functional component of the composite microsphere. After the calcination is completed, an organic pollution biostimulation slow-release material with sulfate radicals can be obtained.

[0078] Preferably, in order to obtain a better slow-release effect, in step (3), the conditions for the calcination include: heating up to 400-600 °C at a heating rate of 3-15 °C / min and holding for 1-5 h.

[0079] The calcination temperature in step (3) is lower than the melting temperature of the sulfate to avoid the melting and flowing out of the core sulfate.

[0080] In a specific embodiment, in step (3), the heating rate can be 3 °C / min, 5 °C / min, 7 °C / min, 10 °C / min, 12 °C / min or 15 °C / min, and it can be heated up to 400 °C, 500 °C or 600 °C, and the holding time can be 1 h, 2 h, 3 h, 4 h or 5 h.

[0081] In step (3) of the present invention, the atmosphere for the calcination is an inert atmosphere or an oxygen-containing atmosphere, and further preferably an inert atmosphere.

[0082] In the present invention, the oxygen-containing atmosphere is preferably a mixture of an inert atmosphere and air.

[0083] In a specific embodiment of the present invention, in step (3), the conditions for roasting include: heating up to 500 °C at a heating rate of 5 °C / min and holding for 3 h.

[0084] The method of the present invention pre-obtains porous carbon loaded with sulfate under certain conditions, and then performs biomass re-coating and carbonization to form a structural form in which nitrogen-doped porous carbon wraps porous carbon loaded with sulfate. It is characterized by mainly including three steps: first, preparing biomass-based porous carbon loaded with sulfate; second, performing material compounding and granulation with biomass and urea; and finally, performing roasting.

[0085] Starting from fully exploiting the value of biochar itself in the field of slow-release function realization, combining with the typical preparation process of porous carbon, using porous carbon loaded with sulfate as the sulfate slow-release center, and wrapping the outer layer with nitrogen-doped porous carbon, which is rich in micropores and can effectively control the slow release of the core agent slow-release layer, to form an organic pollution biostimulation slow-release material in the form of a sulfate slow-release biomass-based microsphere. Through evaluation and design, a slow-release material formulation with better sulfate slow-release function is screened. Compared with the prior art, the core agent slow-release layer is porous carbon fully etched and dispersed by molten sulfate. Since the molten salt is dispersed in the large, medium, and micropores of the porous carbon, its release process is inherently a slow-release process different from simple coating treatment. At the same time, the coating layer of the organic pollution biostimulation slow-release material obtained by this method is nitrogen-doped porous carbon. After the core agent is released, it is slowly released through the pores of the coating layer. At the same time, the surface active groups of the nitrogen-doped porous carbon interact with the agent, which can further extend the release period, make full use of the porous structure and adsorption performance of resource-based biochar, has good economic value and practical significance, and has a simple preparation process, good economy, and low cost.

[0086] Among them, the porous carbon completely filled with inner-layer sulfate in the organic pollution biostimulation slow-release material of the present invention can continuously dissolve and release the sulfate in it in a certain environment. The rich microporous structure and special active sites of the nitrogen-doped porous carbon can effectively delay the release period of sulfate, thereby overall lengthening the release process of sulfate. The slow-release period is estimated to reach more than 180 days, and preferably, the slow-release concentration can still reach 40 ppm at 160 d.

[0087] The third aspect of the present invention provides an application of the above-mentioned organic pollution biostimulation slow-release material in the remediation of organic-polluted soil and groundwater, and is further preferably applied to the remediation of organic-polluted soil and groundwater such as petroleum hydrocarbons, benzene series, and methyl tert-butyl ether.

[0088] The present invention draws on the preparation method of coated slow-release agents in the research process of existing slow-release agents, and through optimized design, a double-layer sulfate slow-release microsphere based on biomass carbon is prepared, breaking through the limitations of the existing technical ideas. At the same time, the preparation process combines the traditional activation method of porous carbon, uses molten salt to etch biomass carbon, and does not perform rinsing after the carbonization treatment to obtain a porous carbon loaded with sulfate. Since the molten salt is dispersed in the large, medium, and micropores of the porous carbon, its release is inherently a slow-release process. Meanwhile, nitrogen-doped porous carbon is used to "coat" the porous carbon completely filled with sulfate. After the core agent is released, it is slowly released through the pores of the coating layer. The surface active groups of the outer nitrogen-doped porous carbon can also interact with the agent, further extending the release period and having a good sulfate slow-release effect.

[0089] In the present invention, the biomass carbon has a stable structure and is not easily mineralized and decomposed by microorganisms in the soil. Its porous structure endows it with an excellent slow-release matrix for agents. Nitrogen doping is an effective method to improve the adsorption performance of carbon materials. Nitrogen participates in the activation process during the preparation of porous carbon, making the pore structure of the carbon material richer, especially the micropore structure. Through the combination of nitrogen-doped modification and the self-porous slow-release effect of biochar, it becomes a better sulfate slow-release carrier. Then, as an in-situ remediation agent, it is added to the polluted site. Sulfate-reducing bacteria in the polluted site can effectively utilize the slowly released sulfate in the biochar for pollutant purification during its slow-release period. After the sulfate is slowly released, the porous carbon carrier can still participate in the operation process of the soil ecosystem as a soil improvement medium.

[0090] The organic pollution biostimulation slow-release material described in the present invention is derived from waste biomass and is mainly used as a slow-release agent in organic polluted sites to provide electron acceptors for the vital activities of sulfate-reducing bacteria in the soil for a long time, thereby achieving pollutant removal. At the same time, the S generated by the reduction of sulfate 2- can interact with heavy metal ions in the polluted soil to form stable precipitates and separate from the soil ecosystem. The biochar matrix after slow release can continue to play a certain role in the soil improvement process, directly contributing to the overall goal of carbon sequestration and emission reduction under the background of "dual carbon", and having great economic value and practical significance.

[0091] The present invention will be described in detail below through examples, but the scope protected by the present invention is not limited thereto.

[0092] Hereinafter, room temperature refers to 25 °C, and the waste straw biomass used comes from corn straw.

[0093] Example 1

[0094] (1) Mix sodium sulfate, potassium sulfate, and magnesium sulfate thoroughly to obtain a mixed sulfate. Based on the total amount of sodium sulfate, potassium sulfate, and magnesium sulfate being 100 wt%, the amount of sodium sulfate is 51 wt%, the amount of potassium sulfate is 6 wt%, and the amount of magnesium sulfate is 43 wt%. Use a crusher to grind the waste straw biomass to 50 mesh to obtain waste straw biomass powder. Then mix the waste straw biomass powder with the mixed sulfate in a weight ratio of 1:1, and grind thoroughly for 5 minutes to ensure that the materials are fully dispersed and evenly mixed. Then place it in a tubular furnace and carry out carbonization treatment under a N2 atmosphere. The operations of the carbonization treatment include: heating at a heating rate of 5 °C / min to 700 °C and holding at 700 °C for 3 hours to obtain porous carbon loaded with sulfate;

[0095] (2) Use a crusher to grind the waste straw biomass to 50 mesh to obtain waste straw biomass powder. Mix the waste straw biomass powder with urea in a weight ratio of 10:5 and grind thoroughly for 5 minutes to obtain a nitrogen-containing mixture;

[0096] (3) Grind the porous carbon loaded with sulfate to a particle size of 100 mesh, place it in a disk granulator for granulation, and spray an aqueous solution of bentonite with a concentration of 15 wt% during the granulation process to promote shaping. When the particle diameter grows to 0.70 mm, obtain a core with a preliminary spherical shape;

[0097] (4) Grind the nitrogen-containing mixture to a particle size of 100 mesh, then add the core obtained in step (3), and mix for granulation. Spray an aqueous solution of bentonite with a concentration of 15 wt% during the granulation process to promote shaping, and obtain a composite microsphere with a particle diameter of about 1.5 mm;

[0098] (5) Place the composite microsphere obtained in step (4) in a tubular furnace and carry out roasting under a N2 atmosphere. The conditions for roasting include: heating at a heating rate of 5 °C / min to 500 °C and holding at 500 °C for 2 hours to obtain an organic pollution biostimulation slow-release material M1 with a core-shell structure. The organic pollution biostimulation slow-release material is spherical, with a diameter of 1.5 mm, the core has a spherical shape, the diameter of the core is 0.70 mm, and the shell thickness is 0.40 mm; the organic pollution biostimulation slow-release material has a core-shell structure, where the core is porous carbon loaded with sulfate and the shell is nitrogen-doped porous carbon.

[0099] Example 2

[0100] Carry out according to the method of Example 1, the difference is that in step (1), the weight ratio of the waste straw biomass powder to the mixed sulfate is 1:2, and an organic pollution biostimulation slow-release material M2 is obtained.

[0101] Example 3

[0102] Implemented according to the method of Example 1, except that in step (1), the weight ratio of waste straw biomass powder to mixed sulfate is 1:3, obtaining the organic pollution biostimulation slow-release material M3.

[0103] Example 4

[0104] Implemented according to the method of Example 1, except that in step (1), the weight ratio of waste straw biomass powder to mixed sulfate is 1:4, obtaining the organic pollution biostimulation slow-release material M4.

[0105] Example 5

[0106] Implemented according to the method of Example 1, except that in step (1), the weight ratio of waste straw biomass powder to mixed sulfate is 1:5, obtaining the organic pollution biostimulation slow-release material M5.

[0107] Example 6

[0108] Implemented according to the method of Example 5, except that in step (1), the heating rate is 10 °C / min, and in step (5), the heating rate is 10 °C / min, obtaining the organic pollution biostimulation slow-release material M6.

[0109] Example 7

[0110] Implemented according to the method of Example 5, except that in step (1), the heat preservation temperature is 800 °C, and in step (5), the heat preservation temperature is 600 °C, obtaining the organic pollution biostimulation slow-release material M7.

[0111] Example 8

[0112] Implemented according to the method of Example 5, except that in step (1), the heat preservation time is 4 h, and in step (5), the heat preservation time is 3 h, obtaining the organic pollution biostimulation slow-release material M8.

[0113] Example 9

[0114] Implemented according to the method of Example 5, except that in step (1), the heat preservation time is 5 h, and in step (5), the heat preservation time is 4 h, obtaining the organic pollution biostimulation slow-release material M9.

[0115] Example 10

[0116] Implemented according to the method of Example 8, except that in step (2), the waste straw biomass powder and urea are mixed at a weight ratio of 9:6, obtaining the organic pollution biostimulation slow-release material M10.

[0117] Example 11

[0118] It is implemented according to the method of Example 8. The difference is that in step (2), the waste straw biomass powder and urea are mixed at a weight ratio of 8:7 to obtain the organic pollution biostimulation slow-release material M11;

[0119] The porous carbon loaded with sulfate obtained in step (1) of this example is fully soaked and rinsed in water to completely dissolve and remove the sulfate. After drying the porous carbon after removing the sulfate, pore size characterization is carried out on it by a physical adsorption instrument. It is found that the pore size distribution of this porous carbon is 1-21 nm, with a relatively large proportion of mesopores and a secondary micropore distribution; by analyzing the pore size of the shell (nitrogen-doped porous carbon) of M11 by a physical adsorption instrument, it is found that its pore size distribution is 1-13 nm, with a relatively large proportion of micropores.

[0120] Example 12

[0121] It is implemented according to the method of Example 8. The difference is that in step (2), the waste straw biomass powder and urea are mixed at a weight ratio of 7:8 to obtain the organic pollution biostimulation slow-release material M12.

[0122] Example 13

[0123] It is implemented according to the method of Example 8. The difference is that in step (2), the waste straw biomass powder and urea are mixed at a weight ratio of 6:9 to obtain the organic pollution biostimulation slow-release material M13.

[0124] Example 14

[0125] It is implemented according to the method of Example 11. The difference is that in step (1), the atmosphere passed during carbonization treatment is a mixed atmosphere of N2 and air with a volume ratio of 4:1 to obtain the organic pollution biostimulation slow-release material M14.

[0126] Example 15

[0127] It is implemented according to the method of Example 11. The difference is that in step (1), the atmosphere passed during carbonization treatment is a mixed atmosphere of N2 and air with a volume ratio of 3:2 to obtain the organic pollution biostimulation slow-release material M15.

[0128] Comparative Example 1

[0129] It is implemented according to the method of Example 11. The difference is that in step (1), no mixed sulfate is used. The waste straw biomass powder is ground to 50 meshes and then directly placed in a tube furnace. Under a N2 atmosphere, carbonization treatment is carried out to obtain porous carbon. In step (3), the porous carbon loaded with sulfate is replaced with porous carbon to obtain the organic pollution biostimulation slow-release material D1.

[0130] Comparative Example 2

[0131] It was carried out according to the method of Example 11, except that in step (1), waste straw biomass was not used, and the mixed sulfate was sufficiently ground for 5 min, then placed in a tubular furnace, and under a N2 atmosphere, it was heated to 700 °C at a heating rate of 5 °C / min and held at 700 °C for 4 h to obtain a multi-component sulfate after melting and mixing; in step (3), the porous carbon loaded with sulfate was replaced with the multi-component sulfate after melting and mixing to obtain an organic pollution biostimulation slow-release material D2.

[0132] Test Example 1

[0133] The 24-hour sulfate radical slow-release rate W of M1-M15 and D1-D2 was measured respectively, and the calculation formula of W is as follows:

[0134]

[0135] Among them,

[0136] R 24 is the amount of sulfate radical precipitated in the aqueous phase in the constant-speed shaker for 24 h under light-shielding conditions.

[0137] T is the total amount of sulfate radicals fixed by the slow-release material.

[0138] The test implementation process was as follows: First, the organic pollution biostimulation slow-release material was rinsed in ultrapure water for 30 min and dried thoroughly to remove the unfixed sulfate radicals. 2 g of the rinsed and dried organic pollution biostimulation slow-release material was placed in a conical flask containing 250 mL of ultrapure water, and continuously oscillated in a shaker at 150 rad / min for 24 h under light-shielding conditions, and the sulfate radical concentration in the supernatant was measured and recorded as R 24 . 10 g of the rinsed and dried organic pollution biostimulation slow-release material was placed in an alumina crucible, heated to 1000 °C in a muffle furnace and calcined for 2 h to release the fixed sulfate radicals. After cooling, the calcined sample was taken out and redissolved, and the sulfate radical concentration in the supernatant was measured and recorded as T, which is the total amount of sulfate radicals fixed by the slow-release material. The test method for sulfate radical concentration refers to HJ84-2016 "Determination of Inorganic Anions in Water - Ion Chromatography Method".

[0139] The results are shown in Table 1.

[0140] Table 1

[0141]

[0142] Test Example 2

[0143] Adopt as Figure 1The following test device is used to simulate the slow-release effect of organic pollution biostimulation slow-release materials in the soil and groundwater environment. The test device is as shown in Figure 2 Figure Figure 2 . The device includes: a water storage container 2, a stirrer 1, a peristaltic pump 3, a reaction soil column 5 (with a length of 30 cm and a diameter of 10 cm), an outlet water storage container 6, and a nitrogen gas balloon 7. Among them, the stirrer 1, the water storage container 2, the peristaltic pump 3, the reaction soil column 5, and the outlet water storage container 6 are connected in sequence. The reaction soil column 5 is provided with a sample loading port 4, an inlet and an outlet. The inlet is connected to the peristaltic pump 3, and the outlet is connected to the outlet water storage container 6. The nitrogen gas balloon 7 is connected to the water storage container 2.

[0144] The reaction soil column 5 of the test device is filled with a mixed filler of humic acid, soil, and quartz sand. After loading the organic pollution biostimulation slow-release material through the sample loading port 4, it is spread flat on the entire cross-section. As shown in Figure 2 Figure Figure 2 , after the organic pollution biostimulation slow-release material is loaded through the sample loading port 4, the internal flow of soil and groundwater can be simulated in the device, and relevant indicators can be monitored to evaluate the slow-release performance of the material.

[0145] Slow-release performance test: Load the organic pollution biostimulation slow-release material through the sample loading port 4 so that the filling thickness of the organic pollution biostimulation slow-release material in the reaction soil column 5 is 1 cm. Tap water is contained in the lower part of the water storage container 2. At the same time, nitrogen gas is filled into the water storage container 2 through the nitrogen gas balloon 7 so that the upper part of the water storage container 2 is filled with nitrogen gas to remove the oxygen in the upper headspace of the aqueous solution. The tap water in the water storage container 2 is continuously injected into the reaction soil column 5 from the inlet of the reaction soil column 5 at a certain rate through the peristaltic pump 3 to simulate the permeable reactive barrier technology. Regularly monitor the outflow concentration of sulfate in the water outlet of the outlet water storage container 6 (i.e., the sulfate at the outlet of the reaction soil column 5) to evaluate the slow-release effect of sulfate in the material and determine the slow-release time of the material in the simulated soil and groundwater. During the test process, adjust the water intake of the peristaltic pump 3 so that the water outflow rate at the outlet water storage container 6 is 3 mL / h.

[0146] Among them, the outflow concentration of sulfate in the water outlet of the outlet water storage container 6 monitored at different times after injecting the organic pollution biostimulation slow-release material is shown in Table 2.

[0147] Table 2

[0148]

[0149]

[0150] Tables 1 and 2 examined the sulfate release performance of the sustained-release materials obtained under different preparation conditions. Since there was no sulfate in D1, there was no relevant data. According to the results in Table 2, by comparing M1 - M5, it was found through the stage experiment that the sulfate concentration in each effluent showed a trend of first increasing and then decreasing. Among them, the peak concentration of M5 on the 50th day was as high as 93 ppm. From the concentration change trend, it was not difficult to infer that after 180 days, the sulfate concentration in the effluent of M5 could still be guaranteed to be above 27 ppm.

[0151] By comparing M5 and M6, it can be obtained that M6 reached the peak around the 30th day, and the peak concentration was slightly lower than that of M5, indicating that a slower heating rate was beneficial to extending the slow-release period.

[0152] By comparing M5 and M7, it can be obtained that the sulfate release trends of M5 and M7 were basically the same, but the peak of M7 was lower than that of M5, indicating that after the holding temperature was increased, the slow-release peak decreased to a certain extent.

[0153] By comparing M5, M8, and M9, it can be obtained that the sulfate release peaks of M8 and M9 lagged behind that of M5, and the peaks were basically equivalent, indicating that extending the holding time was beneficial to improving the slow-release performance of the material.

[0154] By comparing M8, M10, M11, M12, and M13, it can be obtained that when the mixing ratio of waste straw biomass powder and urea changed, it directly affected the functional structure of the nitrogen-doped porous carbon formed by calcination. When the mixing ratio of waste straw biomass powder and urea was 8:7, the slow-release performance was better.

[0155] According to M14 and M15, it is easy to know that a low-concentration oxygen atmosphere is beneficial to improving the slow-release performance. However, considering the actual operation and risk, it is better to carry out the process in an inert atmosphere.

[0156] According to D2, it is easy to know that when preparing materials with pure mixed sulfate as the core, there is no slow-release regulation of porous carbon on its slow release during the sulfate slow-release process, and the overall effect is relatively poor.

[0157] According to Table 1, the slow-release performance of M11 was better, and the 24-hour aqueous phase slow-release rate reached 25.78%. Through the long-term slow-release performance test in Table 2, it was not difficult to see that in the slow-release performance of M11, the peak was relatively good, and in the 160-day test results, it was not difficult to see that the slow-release level was still relatively good. From the long-term results, it can be predicted that the slow-release period of M11 can reach 220 days, and the slow-release concentration is estimated to still reach 40 ppm at 180 days.

[0158] Test Example 3

[0159] The actual pollutant removal performance of the organic bio-stimulating slow-release material was detected using the same test device as in Test Example 2.

[0160] The contaminated aquifer sediment used below is the petroleum hydrocarbon-contaminated aquifer sediment obtained from the contaminated soil of an enterprise site. The initial concentration of petroleum hydrocarbons measured by GS-MS is 103 mg / kg, and the water content of the contaminated aquifer sediment is 32%. The contaminated aquifer sediment taken for the experiment is placed in a tube and directly placed in a glove box after being sent to the laboratory. Air contact is avoided throughout this process.

[0161] The reaction soil column 5 is filled with contaminated aquifer sediment. After loading M11, D1, and D2 through the sample loading port 4, they are spread evenly across the entire cross-section, such that the filling thickness of the sample in the reaction soil column 5 is 1 cm. On both sides are contaminated aquifer sediments, simulating a permeable reactive barrier. The lower part of the water storage container 2 contains an aqueous solution of petroleum hydrocarbons with a concentration of 100 mg / L. Similarly, nitrogen gas is filled into the water storage container 2 through the nitrogen gas balloon 7, such that the upper part of the water storage container 2 is filled with nitrogen, removing the oxygen in the headspace above the aqueous solution of petroleum hydrocarbons. The aqueous solution of petroleum hydrocarbons in the water storage container 2 is continuously injected into the reaction soil column 5 from the water inlet of the reaction soil column 5 at a certain rate through the peristaltic pump 3, simulating the permeable reactive barrier technology. During the test, the water inflow of the peristaltic pump 3 is adjusted to make the water outlet rate of the water outlet water storage device 6 3 mL / h.

[0162] By regularly monitoring the data of the sulfate ion concentration and the petroleum hydrocarbon pollutant concentration in the water outlet from the water outlet water storage device 6, the organic pollution removal effect of the material is evaluated. The results are shown in Table 3.

[0163] Table 3

[0164]

[0165] As can be seen from Table 3, within 200 days after the addition of the material, the change in the pollutant concentration mainly occurs in three stages:

[0166] In the first stage, around the first 15 days or so, that is, in the initial stage of material addition, the change in the pollutant concentration is small, basically remaining at around 100 ppm. This may be because sulfate-reducing bacteria do not carry out life activities in the dominant strain position, or it may be due to the heterogeneity during the mixing process of the sediment and the reagent in the early stage and the systematic errors existing in the testing process; sulfate ions are continuously released and accumulated, and the concentration gradually increases.

[0167] The second stage is from the 15th day to the 80th day. After dozens of days of adaptation period, sulfate-reducing bacteria begin to grow dominantly and continuously utilize the pollutant concentration inside the system for life activities. The increase in sulfate concentration slows down, and the pollutant concentration begins to drop sharply. By the 80th day, the degradation of 60%-70% of the pollutants has basically been completed.

[0168] The third stage is from the 80th day to the 200th day. The pollutant concentration is basically at a low level, remaining at around ten ppm. The degradation rate slows down. The slow-release material is still releasing sulfate radicals. After the sulfate ions maintain a certain concentration for a period of time, due to the action of water flow, the concentration begins to gradually decrease.

[0169] Comparative Example 1 is a porous carbon material without injecting sulfate radicals into the core. From the pollutant degradation data, it can be seen that this type of carbon material exhibits weak pollutant degradation ability and poor performance. The possible reason for its pollutant degradation is that there are certain free radicals on the surface of the porous carbon, which can play a part of the role of electron acceptors; D2 prepared in Comparative Example 2 is a simple core-shell structure of molten sulfate @ nitrogen-doped porous carbon. From the sulfate monitoring data, it can be seen that within the first 25 days, sulfate radicals are rapidly released and quickly reach the concentration peak. A part of the sulfate radicals flow out with the water without being utilized. Although it still releases at a certain level in the later stage, the overall effect is not as good as M11. Through the application comparison of M11 and D2, it can be seen that the core-shell structure of nitrogen-doped porous carbon has a certain slow-release effect, and the slow-release material with the core-shell structure provided by the present invention has a better slow-release effect.

[0170] Test Example 4

[0171] M11 was tested according to the test method of Test Example 3, except that the pollutant was replaced with a benzene solution of 100 mg / kg instead of petroleum hydrocarbons, and other steps were the same. The sulfate radical concentration and pollutant concentration data in the water outlet water storage device 6 were regularly monitored, and the results are shown in Table 4.

[0172] Table 4

[0173]

[0174]

[0175] The pollutant degradation trend in Table 4 is basically the same as that in Table 3, further corroborating the wide applicability of the slow-release material.

[0176] Based on the above-mentioned examples and comparative examples, it can be obtained that the organic pollution biostimulation slow-release material provided by the present invention has a better slow-release effect and can be applied to the remediation process of organic pollution soil such as petroleum hydrocarbons and benzene.

[0177] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. An organic pollution biostimulation slow-release material, characterized in that, The organic pollution biostimulation slow-release material has a core-shell structure, wherein the core contains porous carbon loaded with sulfate, and the shell layer contains nitrogen-doped porous carbon.

2. The organic pollution biostimulation sustained-release material according to claim 1, wherein In the porous carbon loaded with sulfate, the sulfate is selected from two or more of magnesium sulfate, calcium sulfate, potassium sulfate, sodium sulfate, iron sulfate and lithium sulfate.

3. The organic pollution biostimulation sustained-release material according to claim 1, characterized in that, In the porous carbon loaded with sulfate, the pore diameter of the porous carbon is 1-70 nm, preferably 1-30 nm; Preferably, the raw material for preparing the porous carbon loaded with sulfate contains biomass.

4. The organic pollution biostimulation sustained-release material according to any one of claims 1 to 3, characterized in that, The pore diameter of the nitrogen-doped porous carbon is 1-30 nm, preferably 1-20 nm; Preferably, the raw material for preparing the nitrogen-doped porous carbon contains biomass.

5. The organic pollution biostimulation slow-release material according to claim 1, characterized in that, The diameter of the organic pollution biostimulation slow-release material is 1-3 mm, preferably 1.25-1.75 mm.

6. The organic pollution biostimulation sustained-release material according to claim 1, wherein The diameter of the core is 0.5-1.5 mm, preferably 0.65-0.95 mm; Preferably, the thickness of the shell layer is 0.25-0.5 mm, preferably 0.3-0.4 mm.

7. The preparation method of the organic pollution biostimulation sustained-release material according to any one of claims 1-6, characterized in that, The preparation method includes the following steps: (1) Mix sulfate and biomass, then carry out carbonization treatment, and then granulate to obtain the core; (2) Mix biomass and urea to obtain a nitrogen-containing mixture; (3) Mix the core obtained in step (1) with the nitrogen-containing mixture obtained in step (2), then granulate, and then carry out roasting.

8. The preparation method according to claim 7, wherein In step (1), the weight ratio of the biomass to the dosage of the sulfate is 1:1-8, preferably 1:3-6.

9. The preparation method according to claim 7 or 8, characterized in that, In step (1), the sulfate is selected from two or more of magnesium sulfate, calcium sulfate, potassium sulfate, sodium sulfate, iron sulfate and lithium sulfate; Preferably, the sulfate is a mixture of sodium sulfate, potassium sulfate and magnesium sulfate, and based on the total dosage of sodium sulfate, potassium sulfate and magnesium sulfate being 100 wt%, the dosage of sodium sulfate is 45-55 wt%, the dosage of potassium sulfate is 5-15 wt%, and the dosage of magnesium sulfate is 35-50 wt%.

10. The preparation method according to claim 7 or 8, characterized in that, In step (1), the operation of the carbonization treatment includes: heating to 600-1200 °C at a heating rate of 3-15 °C / min and holding for 1-6 h; Preferably, the atmosphere of the carbonization treatment is an inert atmosphere or an oxygen-containing atmosphere.

11. The preparation method according to claim 7 or 8, characterized in that, In step (2), the weight ratio of the biomass to the dosage of urea is 1:0.5-1.

5.

12. The preparation method according to claim 7, characterized in that, In step (3), the conditions of the roasting include: heating to 400-600 °C at a heating rate of 3-15 °C / min and holding for 1-5 h; Preferably, the atmosphere of the roasting is an inert atmosphere or an oxygen-containing atmosphere.

13. Application of the organic pollution biostimulation slow-release material according to any one of claims 1-6 in the remediation of organic-polluted soil and groundwater.

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