Biostimulant material, method of making and use thereof

Abstract

This invention relates to the field of soil remediation technology, and discloses a biostimulating material, its preparation method, and its application. The preparation method includes the following steps: (1) subjecting biochemically treated sludge to static sedimentation and centrifugation to obtain sludge supernatant and sludge precipitate; (2) mixing the sludge supernatant obtained in step (1) with a first coagulant and a toughening agent, then adding an oxygen-releasing agent and a reaction regulator, and performing a first freeze-drying to obtain a composite oxygen-releasing material; (3) mixing the sludge precipitate obtained in step (1) with a second coagulant, then adding the composite oxygen-releasing material obtained in step (2), and performing a second freeze-drying to obtain the biostimulating material. This biostimulating material can provide slow-release electron acceptors for microorganisms, while also supplementing microbial strains and providing co-metabolic carbon sources and nutrients such as N and P for microorganisms, thus providing excellent soil remediation effects.

Description

Technical Field

[0001] This invention relates to the field of soil remediation technology, specifically to a method for preparing a biostimulant material, the biostimulant material obtained by the method, and its application. Background Technology

[0002] Common soil and groundwater remediation technologies include in-situ remediation and ex-situ remediation. For sites with deep contamination and difficult excavation due to organic pollution, in-situ remediation is increasingly favored. In-situ remediation technologies primarily include bioremediation and chemical remediation. Chemical remediation techniques can easily damage soil structure and cause secondary soil pollution; in-situ bioremediation, due to its advantages of high efficiency, economy, and no secondary pollution, is considered an ideal technology for large-scale contaminated soil remediation. Enhanced in-situ bioremediation technologies mainly include bio-addition, biostimulation, bioventilation, and microbial fuel cells. Bio-addition increases bioremediation efficiency by increasing the number of microorganisms, including the addition of highly efficient degrading bacteria, immobilized bacteria, and microbial-plant synergistic remediation. Biostimulation improves the bioremediation rate by improving the microbial living environment, including the addition of nutrients, surfactants, co-metabolite substrates, and improved oxygen conditions.

[0003] In the removal of organic pollutants from soil and groundwater, aerobic microbial metabolism offers a significant technological advantage over anaerobic metabolism in mineralizing organic pollutants. During aerobic microbial metabolism of organic matter, the organic matter serves as both a carbon source and electron donor. However, complete oxidation of organic matter requires sufficient oxygen as an electron acceptor, converting it into inorganic substances and thus mineralizing the organic pollutants.

[0004] Currently, a limiting bottleneck in the biological remediation of soil and groundwater is the lack of sufficient electron acceptors, which restricts the degradation rate of pollutants. This necessitates measures such as air or oxygen injection, ozone injection, microbubble injection, hydrogen peroxide injection, and the application of solid oxygen-releasing agents to increase the oxygen content in soil and groundwater. These measures improve environmental conditions for microbial growth and degradation, enhancing microbial metabolism and degradation activity to accelerate pollutant degradation. However, while these methods release oxygen rapidly, they cannot provide stable, long-term oxygen release, and their operating costs are relatively high.

[0005] Oxygen-releasing compounds (ORCs) are a type of composite material commonly used in bioremediation of groundwater in recent years. The main oxygen-releasing components are generally peroxides, such as calcium peroxide (CaO2), magnesium peroxide (MgO2), and persulfate (Na2S2O8). The principle is that these compounds react with H2O to release O2, increasing the dissolved oxygen (DO) concentration in the water, thereby raising the water's redox potential and promoting the aerobic biodegradation of organic pollutants (2CaO2 + 2H2O = 2Ca(OH)2 + O2↑, 2Na2S2O8 + 2H2O = 2Na2SO4 + 2H2SO4 + O2↑). ORCs have attracted considerable attention due to their simple operation, low cost, significant effects, and ability to be used in conjunction with technologies such as permeable barriers. Related studies have demonstrated that ORCs can significantly increase the DO concentration in water.

[0006] The main ways in which slow-release oxygen materials are used in actual contaminated site remediation projects are as follows:

[0007] (1) Set up multiple oxygen release wells downstream of the contaminated site, put the oxygen release material into the porous filter bag and add it into the oxygen release well. When the oxygen release material fails, the filter bag can be removed and replaced with new oxygen release material.

[0008] (2) ORC is injected into the contaminated aquifer in powder or slurry form using a high-pressure pump;

[0009] (3) As a filler for Permeable Reactive Barrier (PRB), it is added to PRB and used in combination with other physical, chemical and biological groundwater remediation methods to achieve the purpose of pollutant degradation and removal.

[0010] Studies have shown that ORC can be used to remediate most aerobic biodegradable pollutants, such as benzene series compounds (BTEX) and other light oil components, MTBE, chlorinated olefins, chlorinated alkanes, and various herbicides (such as atrazine and acetochlor).

[0011] According to surveys, by the end of 2019, my country had over 10,000 wastewater treatment plants with an annual wastewater treatment capacity of 220 million tons, resulting in a significant increase in the amount of residual sludge generated during the wastewater treatment process. Currently, my country's annual residual sludge production reaches tens of millions of tons. If such a large amount of residual sludge cannot be effectively utilized, it will place a heavy burden on wastewater treatment plants. Therefore, it is necessary to consider fully utilizing the nutrients such as nitrogen, phosphorus, and potassium in the residual sludge, transforming waste into resources for secondary use, and improving both social and economic benefits.

[0012] The common problems with existing slow-release oxygen materials are: the oxygen-releasing agent is lost when it comes into direct contact with water during the preparation process; the pH rises or falls after being applied to soil or groundwater, affecting the degradation of pollutants by microorganisms; and existing remediation materials generally do not have the function of providing microbial strains, co-metabolic carbon sources and nutrients to contaminated sites.

[0013] Patent CN101407358B discloses a metal peroxide-based oxygen slow-release composite material. The method uses calcium peroxide as an oxygen-releasing agent and cement or similar materials as binders during the preparation process. Because calcium peroxide comes into direct contact with water during the preparation process, the oxygen-releasing agent will be lost. At the same time, the material will cause the environmental pH value to rise as calcium peroxide is consumed during use, which is not conducive to the growth and metabolism of microorganisms. Moreover, the material does not have the function of providing bacterial strains, co-metabolic carbon sources and nutrients.

[0014] Patent CN110184072A discloses a method for preparing a calcium peroxide slow-release oxygen material. This method uses polylactic acid as an encapsulating agent, which avoids the loss of oxygen-releasing agent caused by contact between calcium peroxide and water during the preparation process. Polylactic acid can also serve as a co-metabolic carbon source for microorganisms. However, organic solvents are still used in the preparation of the encapsulating material, which increases the production cost and air pollution. At the same time, the material will cause the environmental pH value to rise as calcium peroxide is consumed during use, which is not conducive to the growth and metabolism of microorganisms.

[0015] Existing biostimulant materials generally have the following problems: oxygen-releasing agents release oxygen too quickly, causing a rapid increase in environmental oxygen content in a short period of time, exceeding the needs of microbial growth and metabolism, which is not conducive to the long-term biodegradation of site pollutants; oxygen-releasing agents are lost due to direct contact with water during the preparation process; after being applied to soil or groundwater, they can cause the pH to rise or fall, affecting the degradation of pollutants by microorganisms; and existing remediation materials generally do not have the function of providing microbial strains, co-metabolic carbon sources, and nutrients to contaminated sites. Summary of the Invention

[0016] The purpose of this invention is to overcome the aforementioned problems in the prior art and provide a biostimulating material and its preparation method. This biostimulating material can provide microorganisms with slow-release electron acceptors, while also supplementing microbial strains and providing microorganisms with co-metabolic carbon sources and nutrients such as N and P, thus providing excellent soil remediation effects.

[0017] To achieve the above objectives, the present invention provides a method for preparing a biostimulating material, the method comprising the following steps:

[0018] (1) The biochemically treated sludge is subjected to static sedimentation and centrifugation in sequence to obtain sludge supernatant and sludge precipitate;

[0019] (2) After mixing the sludge supernatant obtained in step (1) with the first coagulant and toughening agent, oxygen release agent and reaction regulator are added and mixed, and then subjected to first freeze drying to obtain composite oxygen release material;

[0020] (3) After mixing the sludge precipitate obtained in step (1) with the second coagulant, add the composite oxygen-releasing material obtained in step (2) and mix, and then perform a second freeze-drying to obtain the biostimulating material.

[0021] Preferably, in step (1), the settling time is 12 to 24 hours.

[0022] Preferably, in step (1), the centrifugation conditions include: rotation speed of 3000-5000 r / min and centrifugation time of 5-15 min.

[0023] Preferably, in step (2), the first gelling agent is polyvinyl alcohol and / or sodium alginate; the toughening agent is polyether polyol, preferably polyoxypropylene triol.

[0024] Preferably, in step (2), the first gelling agent is polyvinyl alcohol and sodium alginate, and the mass ratio of polyvinyl alcohol to sodium alginate is 2 to 5:1.

[0025] Preferably, in step (2), the weight ratio of the sludge supernatant to the first coagulant and the toughening agent is 100:5~20:0.2~1.

[0026] Preferably, in step (2), the conditions for mixing the sludge supernatant with the first coagulant and toughening agent include: temperature 90-100℃, time 30-60min; mixing by mechanical stirring or ultrasonic stirring, with mechanical stirring speed 180-260r / min and ultrasonic stirring frequency 20-40Hz.

[0027] Preferably, in step (2), the oxygen-releasing agent is a metal peroxide and / or a persulfate; preferably, the metal peroxide is one or more of calcium peroxide, magnesium peroxide, beryllium peroxide and barium peroxide, and the persulfate is sodium persulfate and / or potassium persulfate.

[0028] Preferably, in step (2), the reaction regulator is potassium dihydrogen phosphate and / or sodium dihydrogen phosphate.

[0029] Preferably, in step (2), the weight ratio of the sludge supernatant to the mixture of the first coagulant and toughening agent, the oxygen release agent and the reaction regulator is 100:5-30:0.3-1.5.

[0030] Preferably, in step (2), the conditions for mixing the oxygen-releasing agent and the reaction regulator include: temperature 60-80℃, time 30-60min; mixing by mechanical stirring or ultrasonic stirring, with mechanical stirring speed of 180-260r / min and ultrasonic stirring frequency of 20-40Hz.

[0031] Preferably, in step (2), the temperature of the first freeze-drying is -50℃ to -80℃.

[0032] Preferably, in step (3), the second gelling agent is one or more of carrageenan, gelatin, ethyl cellulose, methyl cellulose and xanthan gum.

[0033] Preferably, in step (3), the weight ratio of the sludge precipitate to the second coagulant is 100:1 to 5.

[0034] Preferably, in step (3), the conditions for mixing sludge sedimentation with the second coagulant include: temperature 25-50℃, time 30-60min; mixing by mechanical stirring or ultrasonic stirring, with mechanical stirring speed 180-260r / min and ultrasonic stirring frequency 20-40Hz.

[0035] Preferably, in step (3), the weight ratio of the mixture of sludge sedimentation and the second coagulant to the composite oxygen-releasing material is 5 to 15:1.

[0036] Preferably, in step (3), the conditions for mixing the composite oxygen-releasing material include: temperature 25-50℃, time 60-120min; preferably, mechanical stirring or ultrasonic stirring is used, with mechanical stirring speed of 160-200r / min and ultrasonic stirring frequency of 20-40Hz.

[0037] Preferably, in step (3), the temperature of the second freeze-drying is -50℃ to -80℃.

[0038] A second aspect of the present invention provides a biostimulatory material prepared by the preparation method of the present invention described above.

[0039] A third aspect of the present invention provides the application of the biostimulant material of the present invention in soil remediation.

[0040] Through the above technical solution, the present invention uses metal peroxides and metal persulfates as oxygen-releasing agents, sodium dihydrogen phosphate or potassium dihydrogen phosphate as reaction regulators, and utilizes a secondary encapsulation technology. The supernatant after centrifuging concentrated sludge and a gelling agent are used to make the inner encapsulation material, and the concentrated liquid after centrifuging concentrated sludge, polyvinyl alcohol and sodium alginate are used to make the outer encapsulation material. Through secondary encapsulation, a biostimulant material for soil remediation is produced.

[0041] The biostimulant material of this invention encapsulates oxygen-releasing agents, enabling it to continuously and stably provide electron-emitting acceptors (O2, SO4) to microorganisms in contaminated soil or groundwater. 2- This process promotes the degradation of pollutants by microorganisms. A reaction regulator is added to the raw materials, which simultaneously mitigates pH fluctuations caused by the release of the oxygen release agent and slows the reaction rate between the oxygen release agent and water, effectively solving the problem of increased pH caused by using a single metal peroxide as the oxygen release agent. During the encapsulation process of this slow-release material, the oxygen release agent is encapsulated in a gel made from sludge supernatant and a gelling agent, avoiding direct contact with water and significantly reducing premature loss of the oxygen release agent. The encapsulation material uses environmentally friendly biodegradable organic matter and excess sludge as raw materials, realizing the resource utilization of wastewater treatment plant sludge. This increases the quantity and variety of microorganisms on-site while providing co-metabolic carbon sources and nutrients for microorganisms.

[0042] The use of biochemical sludge as a raw material realizes the resource utilization of wastewater treatment residue sludge. The biostimulant material of this invention can also be used in conjunction with zero-valent iron, biochar, etc., as components of raw materials for soil pollution remediation. Attached Figure Description

[0043] Figure 1 This is a graph showing the degradation rate of petroleum hydrocarbons after 100 days of the biostimulant materials in the embodiments and comparative examples of the present invention. Detailed Implementation

[0044] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0045] A first aspect of the present invention provides a method for preparing a biostimulating material, the method comprising the following steps:

[0046] (1) The biochemically treated sludge is subjected to static sedimentation and centrifugation in sequence to obtain sludge supernatant and sludge precipitate;

[0047] (2) After mixing the sludge supernatant obtained in step (1) with the first coagulant and toughening agent, oxygen release agent and reaction regulator are added and mixed, and then subjected to first freeze drying to obtain composite oxygen release material;

[0048] (3) After mixing the sludge precipitate obtained in step (1) with the second coagulant, add the composite oxygen-releasing material obtained in step (2) and mix, and then perform a second freeze-drying to obtain the biostimulating material.

[0049] In this invention, step (1) is used to perform preliminary separation of biochemically treated sludge to obtain sludge supernatant and sludge precipitate, and to prepare the core layer and shell layer of biostimulant material respectively.

[0050] According to the present invention, the biochemical treatment sludge refers to sludge generated from the biochemical treatment of wastewater. In the specific preparation process, for better soil remediation, it is preferable to use sludge generated from the treatment of wastewater containing the same or similar pollutants as those in the soil to be remediated. For example, when remediating oil-contaminated soil, it is preferable to use sludge generated during the treatment of oily wastewater.

[0051] According to a preferred embodiment of the present invention, in step (1), the settling time is 12-24 hours, preferably 20-24 hours; preferably, the centrifugation conditions include: rotation speed of 3000-5000 r / min, preferably 4000-5000 r / min, and centrifugation time of 5-15 minutes, preferably 8-12 minutes.

[0052] In this invention, step (2) is used to prepare the core layer of the biostimulating material, namely the composite oxygen-releasing material.

[0053] According to a preferred embodiment of the present invention, the first gelling agent may be polyvinyl alcohol and / or sodium alginate; the toughening agent may be polyether polyol, preferably polyoxypropylene triol.

[0054] According to a more preferred embodiment of the present invention, the first gelling agent is polyvinyl alcohol and sodium alginate, and the mass ratio of polyvinyl alcohol to sodium alginate is 2 to 5:1, preferably 3 to 4:1.

[0055] According to the present invention, in step (2), the weight ratio of the sludge supernatant to the first coagulant and the toughening agent is 100:5~20:0.2~1, preferably 100:5~10:0.3~0.6.

[0056] In order to better mix the sludge supernatant with the first coagulant and toughening agent, the mixing conditions for the sludge supernatant with the first coagulant and toughening agent in step (2) include: temperature 90-100℃, time 30-60min; mixing by mechanical stirring or ultrasonic stirring, with mechanical stirring speed of 180-260r / min and ultrasonic stirring frequency of 20-40Hz.

[0057] According to a preferred embodiment of the present invention, the oxygen-releasing agent can be a metal peroxide and / or a persulfate; preferably, the metal peroxide is one or more of calcium peroxide, magnesium peroxide, beryllium peroxide, and barium peroxide, and the persulfate is sodium persulfate and / or potassium persulfate. Furthermore, by using a combination of metal peroxide and persulfate as an oxygen-releasing agent, the performance of the prepared biostimulant material can be further improved.

[0058] According to a preferred embodiment of the present invention, the reaction regulator may be potassium dihydrogen phosphate and / or sodium dihydrogen phosphate.

[0059] According to the present invention, in step (2), the weight ratio of the sludge supernatant to the mixture of the first coagulant and toughening agent, the oxygen release agent and the reaction regulator is 100:5-30:0.3-1.5, preferably 100:15-25:0.3-1.

[0060] In order to better mix the sludge supernatant with the mixture of the first coagulant and toughening agent, as well as the oxygen release agent and reaction regulator, the conditions for adding the oxygen release agent and reaction regulator in step (2) include: temperature 60-80℃, time 30-60min; mechanical stirring or ultrasonic stirring is used for mixing, with mechanical stirring speed of 180-260r / min and ultrasonic stirring frequency of 20-40Hz.

[0061] To prepare the composite oxygen-releasing material for coating, preferably, the temperature of the first freeze-drying is -50°C to -80°C.

[0062] In addition, the composite oxygen-releasing material can be appropriately pulverized, for example, by grinding, to obtain a composite oxygen-releasing material with a suitable particle size. The particle size of the pulverized composite oxygen-releasing material can be 10–120 mesh, preferably 80–120 mesh.

[0063] In this invention, step (3) is used to encapsulate the composite oxygen-releasing material, thereby obtaining the biostimulating material of this invention.

[0064] According to the present invention, the second gelling agent may be one or more selected from carrageenan, gelatin, ethyl cellulose, methyl cellulose, and xanthan gum. The weight ratio of the sludge sediment to the second gelling agent is 100:1 to 5, preferably 100:3 to 5.

[0065] According to a preferred embodiment of the present invention, in step (3), the conditions for mixing sludge sedimentation with the second coagulant include: temperature 25-50°C, time 30-60 min; mixing by mechanical stirring or ultrasonic stirring, with mechanical stirring speed 180-260 r / min and ultrasonic stirring frequency 20-40 Hz.

[0066] According to the present invention, in step (3), the weight ratio of the mixture of sludge sedimentation and the second coagulant to the composite oxygen-releasing material is 5 to 15:1, preferably 8 to 12:1.

[0067] According to a preferred embodiment of the present invention, in step (3), the conditions for adding the composite oxygen-releasing material for mixing include: temperature 25-50°C, time 60-120 min; preferably, mechanical stirring or ultrasonic stirring is used, with mechanical stirring speed of 160-200 r / min and ultrasonic stirring frequency of 20-40 Hz.

[0068] For the preparation of biostimulant materials, preferably, the temperature of the second freeze-drying is -50°C to -80°C.

[0069] In addition, to facilitate the use of biostimulant materials, they can be appropriately pulverized, for example, by grinding, to obtain a suitable particle size for use. The particle size of the pulverized biostimulant material can be 10–120 mesh, preferably 80–120 mesh.

[0070] A second aspect of the present invention provides a biostimulant material obtained by the above preparation method.

[0071] A third aspect of this invention provides the application of the biostimulant material obtained by the above preparation method in soil remediation. The biostimulant material of this invention can be applied to the remediation of contaminated soil and groundwater, specifically for the remediation of oil-contaminated soil, and has broad application prospects.

[0072] The present invention will be described in detail below through embodiments.

[0073] Example 1

[0074] Step 1: Take 2000ml of residual sludge from the secondary sedimentation tank of the biochemical treatment system of the municipal wastewater treatment plant, let it settle for 24 hours, and take the lower layer of gravity-concentrated sludge.

[0075] Step 2: Take 500ml of gravity-concentrated sludge and put it into a centrifuge for centrifugation at 5000r / min for 10min.

[0076] Step 3: Take 250ml of the concentrated sludge supernatant after centrifugation in Step 2, add 15g of polyvinyl alcohol, 4g of sodium alginate and 1g of polyoxypropylene triol to it, and mix thoroughly with a heated magnetic stirrer at a heating temperature of 95℃, a mechanical stirring speed of 250r / min and a stirring time of 40min.

[0077] Step 4: Add 7.5g of calcium peroxide powder, 15g of sodium persulfate powder and 1g of potassium dihydrogen phosphate to the mixture obtained in Step 3, and stir thoroughly until the mixture is uniform. The stirring method is magnetic stirring with heating, the stirring temperature is 60℃, the stirring speed is 200r / min, and the stirring time is 40min.

[0078] Step 5: The mixture obtained in Step 4 is vacuum freeze-dried and then ground into powder for later use. The vacuum freeze-drying temperature is -60℃.

[0079] Step 6: Take 150ml of the concentrated sludge after centrifugation in Step 2, add 5g of carrageenan, and mix thoroughly. Use ultrasonic stirring at a temperature of 40℃, a frequency of 30Hz, and a time of 40min.

[0080] Step 7: Take 20g of the powder obtained in Step 5 and add it to the mixture obtained in Step 6. Stir and mix thoroughly. Use ultrasonic stirring at a temperature of 40℃, a frequency of 30Hz, and a time of 75min.

[0081] Step 8: After vacuum freeze-drying the mixture obtained in Step 7, grind it into powder to obtain the finished biostimulant material. The vacuum freeze-drying temperature is -60℃.

[0082] Oil-contaminated soil samples were taken from an oil field, and after impurities were removed, crushed, and sieved through a 20-mesh sieve, the samples were divided into 10 portions. 100g of soil sample was taken from each portion, and 1g of biostimulant material was added. The samples were mixed and stirred evenly. Deionized water was added daily to adjust the moisture content of the soil samples to 15%.

[0083] Total petroleum hydrocarbons in soil were extracted using ultrasonic extraction and determined by gravimetric method: 3g of air-dried soil sample was weighed and placed in a centrifuge tube. 15.0mL of a 1:1 (v / v) mixture of dichloromethane and n-hexane was added. The mixture was ultrasonically extracted at 4℃ for 10min using an ultrasonic cell disruptor, followed by centrifugation at 8000r / min for 15min. The extract was filtered through quantitative filter paper into a pre-weighed weighing bottle. The extraction was repeated three times. The weighing bottle was placed in a fume hood to allow the extractant to evaporate completely to constant weight before weighing.

[0084] Soil samples were placed in a constant temperature and humidity environment of 25℃ and 75% relative humidity, and the total petroleum hydrocarbon content was measured periodically. After 90 days, the petroleum hydrocarbon degradation rate reached over 77%. The results are shown in Table 1.

[0085] Table 1

[0086]

[0087] Example 2

[0088] Step 1: Take 2000ml of residual sludge from the secondary sedimentation tank of the biochemical treatment system of the municipal wastewater treatment plant, let it settle for 24 hours, and take the lower layer of gravity-concentrated sludge.

[0089] Step 2: Take 500ml of gravity-concentrated sludge and put it into a centrifuge for centrifugation at 5000r / min for 10min.

[0090] Step 3: Take 250ml of the concentrated sludge supernatant after centrifugation in Step 2, add 15g of polyvinyl alcohol, 4g of sodium alginate and 1g of polyoxypropylene triol to it, and mix thoroughly with a heated magnetic stirrer at a heating temperature of 95℃, a mechanical stirring speed of 250r / min and a stirring time of 40min.

[0091] Step 4: Add 10g of calcium peroxide powder, 20g of sodium persulfate powder and 1.5g of potassium dihydrogen phosphate to the mixture obtained in Step 3, and stir thoroughly until the mixture is uniform. The stirring method is magnetic stirring with heating, the stirring temperature is 60℃, the stirring speed is 200r / min, and the stirring time is 40min.

[0092] Step 5: The mixture obtained in Step 4 is vacuum freeze-dried and then ground into powder for later use. The vacuum freeze-drying temperature is -60℃.

[0093] Step 6: Take 150ml of the concentrated sludge separated by centrifugation in Step 2, add 5g of carrageenan, and mix thoroughly. The mixing method is ultrasonic stirring, with a stirring temperature of 40℃, an ultrasonic stirring frequency of 30Hz, and a stirring time of 40min.

[0094] Step 7: Take 20g of the powder obtained in Step 5 and add it to the mixture obtained in Step 6. Stir and mix thoroughly. Use ultrasonic stirring at a temperature of 40℃, a frequency of 30Hz, and a time of 75min.

[0095] Step 8: After vacuum freeze-drying the mixture obtained in Step 7, grind it into powder to obtain the finished biostimulant material. The vacuum freeze-drying temperature is -60℃.

[0096] Oil-contaminated soil samples were taken from an oil field, and after impurities were removed, crushed, and sieved through a 20-mesh sieve, the samples were divided into 10 portions. 100g of soil sample was taken from each portion, and 1g of biostimulant material was added. The samples were mixed and stirred evenly. Deionized water was added daily to adjust the moisture content of the soil samples to 15%.

[0097] Total petroleum hydrocarbons in soil were extracted using ultrasonic extraction and determined by gravimetric method: 3g of air-dried soil sample was weighed and placed in a centrifuge tube. 15.0mL of a 1:1 (v / v) mixture of dichloromethane and n-hexane was added. The mixture was ultrasonically extracted at 4℃ for 10min using an ultrasonic cell disruptor, followed by centrifugation at 8000r / min for 15min. The extract was filtered through quantitative filter paper into a pre-weighed weighing bottle. The extraction was repeated three times. The weighing bottle was placed in a fume hood to allow the extractant to evaporate completely to constant weight before weighing.

[0098] Soil samples were placed in a constant temperature and humidity environment of 25℃ and 75% relative humidity. Total petroleum hydrocarbon content was measured periodically. After 90 days, the petroleum hydrocarbon degradation rate reached over 82%. The results are shown in Table 2.

[0099] Table 2

[0100]

[0101] Example 3

[0102] Step 1: Take 2000ml of residual sludge from the secondary sedimentation tank of the biochemical treatment system of the municipal wastewater treatment plant, let it settle for 24 hours, and take the lower layer of gravity-concentrated sludge.

[0103] Step 2: Take 500ml of gravity-concentrated sludge and put it into a centrifuge for centrifugation at 5000r / min for 10min.

[0104] Step 3: Take 250ml of the concentrated sludge supernatant after centrifugation in Step 2, add 15g of polyvinyl alcohol, 4g of sodium alginate and 1g of polyoxypropylene triol to it, and mix thoroughly with a heated magnetic stirrer at a heating temperature of 95℃, a mechanical stirring speed of 250r / min and a stirring time of 40min.

[0105] Step 4: Add 15g of calcium peroxide powder, 30g of sodium persulfate powder and 2g of potassium dihydrogen phosphate to the mixture obtained in Step 3, and stir thoroughly until the mixture is uniform. The stirring method is to use heated magnetic stirring, with a stirring temperature of 60℃, a stirring speed of 200r / min and a stirring time of 40min.

[0106] Step 5: The mixture obtained in Step 4 is vacuum freeze-dried and then ground into powder for later use. The vacuum freeze-drying temperature is -60℃.

[0107] Step 6: Take 150ml of the concentrated sludge separated by centrifugation in Step 2, add 5g of carrageenan, and mix thoroughly. The mixing method is ultrasonic stirring, with a stirring temperature of 40℃, an ultrasonic stirring frequency of 30Hz, and a stirring time of 40min.

[0108] Step 7: Take 20g of the powder obtained in Step 5 and add it to the mixture obtained in Step 6. Stir and mix thoroughly. Use ultrasonic stirring at a temperature of 40℃, a frequency of 30Hz, and a time of 75min.

[0109] Step 8: After vacuum freeze-drying the mixture obtained in Step 7, grind it into powder to obtain the finished biostimulant material. The vacuum freeze-drying temperature is -60℃.

[0110] Oil-contaminated soil samples were taken from an oil field, and after impurities were removed, crushed, and sieved through a 20-mesh sieve, the samples were divided into 10 portions. 100g of soil sample was taken from each portion, and 1g of biostimulant material was added. The samples were mixed and stirred evenly. Deionized water was added daily to adjust the moisture content of the soil samples to 15%.

[0111] Total petroleum hydrocarbons in soil were extracted using ultrasonic extraction and determined by gravimetric method: 3g of air-dried soil sample was weighed and placed in a centrifuge tube. 15.0mL of a 1:1 (v / v) mixture of dichloromethane and n-hexane was added. The mixture was ultrasonically extracted at 4℃ for 10min using an ultrasonic cell disruptor, followed by centrifugation at 8000r / min for 15min. The extract was filtered through quantitative filter paper into a pre-weighed weighing bottle. The extraction was repeated three times. The weighing bottle was placed in a fume hood to allow the extractant to evaporate completely to constant weight before weighing.

[0112] Soil was placed in a constant temperature and humidity environment of 25℃ and 75% relative humidity, and a sample was taken periodically to test the total petroleum hydrocarbon content. After 100 days, the petroleum hydrocarbon degradation rate reached 77.71%. The results are shown in Table 3.

[0113] Table 3

[0114]

[0115] Example 4

[0116] Step 1: Take 2000ml of residual sludge from the secondary sedimentation tank of the biochemical treatment system of the municipal wastewater treatment plant, let it settle for 24 hours, and take the lower layer of gravity-concentrated sludge.

[0117] Step 2: Take 500ml of gravity-concentrated sludge and put it into a centrifuge for centrifugation at 5000r / min for 10min.

[0118] Step 3: Take 250ml of the concentrated sludge supernatant after centrifugation in Step 2, add 15g of polyvinyl alcohol, 4g of sodium alginate and 1g of polyoxypropylene triol to it, and mix thoroughly with a heated magnetic stirrer at a heating temperature of 95℃, a mechanical stirring speed of 250r / min and a stirring time of 40min.

[0119] Step 4: Add 45g of calcium peroxide powder and 2g of potassium dihydrogen phosphate to the mixture obtained in Step 3, and stir thoroughly until the mixture is uniform. The stirring method is magnetic stirring with heating, the stirring temperature is 60℃, the stirring speed is 200r / min, and the stirring time is 40min.

[0120] Step 5: The mixture obtained in Step 4 is vacuum freeze-dried and then ground into powder for later use. The vacuum freeze-drying temperature is -60℃.

[0121] Step 6: Take 150ml of the concentrated sludge separated by centrifugation in Step 2, add 5g of carrageenan, and mix thoroughly. The mixing method is ultrasonic stirring, with a stirring temperature of 40℃, an ultrasonic stirring frequency of 30Hz, and a stirring time of 40min.

[0122] Step 7: Take 20g of the powder obtained in Step 5 and add it to the mixture obtained in Step 6. Stir and mix thoroughly. Use ultrasonic stirring at a temperature of 40℃, a frequency of 30Hz, and a time of 75min.

[0123] Step 8: After vacuum freeze-drying the mixture obtained in Step 7, grind it into powder to obtain the finished biostimulant material. The vacuum freeze-drying temperature is -60℃.

[0124] Oil-contaminated soil samples were taken from an oil field, and after impurities were removed, crushed, and sieved through a 20-mesh sieve, the samples were divided into 10 portions. 100g of soil sample was taken from each portion, and 1g of biostimulant material was added. The samples were mixed and stirred evenly. Deionized water was added daily to adjust the moisture content of the soil samples to 15%.

[0125] Total petroleum hydrocarbons in soil were extracted using ultrasonic extraction and determined by gravimetric method: 3g of air-dried soil sample was weighed and placed in a centrifuge tube. 15.0mL of a 1:1 (v / v) mixture of dichloromethane and n-hexane was added. The mixture was ultrasonically extracted at 4℃ for 10min using an ultrasonic cell disruptor, followed by centrifugation at 8000r / min for 15min. The extract was filtered through quantitative filter paper into a pre-weighed weighing bottle. The extraction was repeated three times. The weighing bottle was placed in a fume hood to allow the extractant to evaporate completely to constant weight before weighing.

[0126] Soil was placed in a constant temperature and humidity environment of 25℃ and 75% relative humidity, and a sample was taken periodically to test the total petroleum hydrocarbon content. After 100 days, the petroleum hydrocarbon degradation rate reached more than 80%. The results are shown in Table 4.

[0127] Table 4

[0128]

[0129] Example 5

[0130] Step 1: Take 2000ml of residual sludge from the secondary sedimentation tank of the biochemical treatment system of the municipal wastewater treatment plant, let it settle for 24 hours, and take the lower layer of gravity-concentrated sludge.

[0131] Step 2: Take 500ml of gravity-concentrated sludge and put it into a centrifuge for centrifugation at 5000r / min for 10min.

[0132] Step 3: Take 250ml of the concentrated sludge supernatant after centrifugation in Step 2, add 15g of polyvinyl alcohol, 4g of sodium alginate and 1g of polyoxypropylene triol to it, and mix thoroughly with a heated magnetic stirrer at a heating temperature of 95℃, a mechanical stirring speed of 250r / min and a stirring time of 40min.

[0133] Step 4: Add 45g of sodium persulfate powder and 2g of potassium dihydrogen phosphate to the mixture obtained in Step 3, and stir thoroughly until the mixture is uniform. The stirring method is magnetic stirring with heating, the stirring temperature is 60℃, the stirring speed is 200r / min, and the stirring time is 40min.

[0134] Step 5: The mixture obtained in Step 4 is vacuum freeze-dried and then ground into powder for later use. The vacuum freeze-drying temperature is -60℃.

[0135] Step 6: Take 150ml of the concentrated sludge separated by centrifugation in Step 2, add 5g of carrageenan, and mix thoroughly. The mixing method is ultrasonic stirring, with a stirring temperature of 40℃, an ultrasonic stirring frequency of 30Hz, and a stirring time of 40min.

[0136] Step 7: Take 20g of the powder obtained in Step 5 and add it to the mixture obtained in Step 6. Stir and mix thoroughly. Use ultrasonic stirring at a temperature of 40℃, a frequency of 30Hz, and a time of 75min.

[0137] Step 8: After vacuum freeze-drying the mixture obtained in Step 7, grind it into powder to obtain the finished biostimulant material. The vacuum freeze-drying temperature is -60℃.

[0138] Oil-contaminated soil samples were taken from an oil field, and after impurities were removed, crushed, and sieved through a 20-mesh sieve, the samples were divided into 10 portions. 100g of soil sample was taken from each portion, and 1g of biostimulant material was added. The samples were mixed and stirred evenly. Deionized water was added daily to adjust the moisture content of the soil samples to 15%.

[0139] Total petroleum hydrocarbons in soil were extracted using ultrasonic extraction and determined by gravimetric method: 3g of air-dried soil sample was weighed and placed in a centrifuge tube. 15.0mL of a 1:1 (v / v) mixture of dichloromethane and n-hexane was added. The mixture was ultrasonically extracted at 4℃ for 10min using an ultrasonic cell disruptor, followed by centrifugation at 8000r / min for 15min. The extract was filtered through quantitative filter paper into a pre-weighed weighing bottle. The extraction was repeated three times. The weighing bottle was placed in a fume hood to allow the extractant to evaporate completely to constant weight before weighing.

[0140] Soil samples were placed in a constant temperature and humidity environment of 25℃ and 75% relative humidity. Total petroleum hydrocarbon content was measured periodically. After 100 days, the petroleum hydrocarbon degradation rate reached 72.61%. The results are shown in Table 5.

[0141] Table 5

[0142]

[0143] Comparative Example 1

[0144] Step 1: Take 2000ml of residual sludge from the secondary sedimentation tank of the biochemical treatment system of the municipal wastewater treatment plant, let it settle for 24 hours, and take the lower layer of gravity-concentrated sludge.

[0145] Step 2: Take 500ml of gravity-concentrated sludge and put it into a centrifuge for centrifugation at 5000r / min for 10min.

[0146] Step 3: Take 250ml of deionized water, add 15g of polyvinyl alcohol, 4g of sodium alginate and 1g of polyoxypropylene triol, and mix thoroughly with a heated magnetic stirrer at a temperature of 95℃, a mechanical stirring speed of 250r / min and a stirring time of 40min.

[0147] Step 4: Add 15g of calcium peroxide powder, 30g of sodium persulfate powder and 2g of potassium dihydrogen phosphate to the mixture obtained in Step 3, and stir thoroughly until the mixture is uniform. The stirring method is to use heated magnetic stirring, with a stirring temperature of 60℃, a stirring speed of 200r / min and a stirring time of 40min.

[0148] Step 5: The mixture obtained in Step 4 is vacuum freeze-dried and then ground into powder for later use. The vacuum freeze-drying temperature is -60℃.

[0149] Step 6: Take 150ml of the concentrated sludge separated by centrifugation in Step 2, add 5g of carrageenan, and mix thoroughly. The mixing method is ultrasonic stirring, with a stirring temperature of 40℃, an ultrasonic stirring frequency of 30Hz, and a stirring time of 40min.

[0150] Step 7: Take 20g of the powder obtained in Step 5 and add it to the mixture obtained in Step 6. Stir and mix thoroughly. Use ultrasonic stirring at a temperature of 40℃, a frequency of 30Hz, and a time of 75min.

[0151] Step 8: After vacuum freeze-drying the mixture obtained in Step 7, grind it into powder to obtain the finished biostimulant material. The vacuum freeze-drying temperature is -60℃.

[0152] Oil-contaminated soil samples were taken from an oil field, and after impurities were removed, crushed, and sieved through a 20-mesh sieve, the samples were divided into 10 portions. 100g of soil sample was taken from each portion, and 1g of biostimulant material was added. The samples were mixed and stirred evenly. Deionized water was added daily to adjust the moisture content of the soil samples to 15%.

[0153] Total petroleum hydrocarbons in soil were extracted using ultrasonic extraction and determined by gravimetric method: 3g of air-dried soil sample was weighed and placed in a centrifuge tube. 15.0mL of a 1:1 (v / v) mixture of dichloromethane and n-hexane was added. The mixture was ultrasonically extracted at 4℃ for 10min using an ultrasonic cell disruptor, followed by centrifugation at 8000r / min for 15min. The extract was filtered through quantitative filter paper into a pre-weighed weighing bottle. The extraction was repeated three times. The weighing bottle was placed in a fume hood to allow the extractant to evaporate completely to constant weight before weighing.

[0154] Soil was placed in a constant temperature and humidity environment of 25℃ and 75% relative humidity, and a sample was taken periodically to test the total petroleum hydrocarbon content. After 80 days, the petroleum hydrocarbon degradation rate reached more than 80%. The results are shown in Table 6.

[0155] Table 6

[0156]

[0157] Comparative Example 2

[0158] Step 1: Take 2000ml of residual sludge from the secondary sedimentation tank of the biochemical treatment system of the municipal wastewater treatment plant, let it settle for 24 hours, and take the lower layer of gravity-concentrated sludge.

[0159] Step 2: Take 500ml of gravity-concentrated sludge and put it into a centrifuge for centrifugation at 5000r / min for 10min.

[0160] Step 3: Take 250ml of the concentrated sludge supernatant after centrifugation in Step 2, add 15g of polyvinyl alcohol, 4g of sodium alginate and 1g of polyoxypropylene triol to it, and mix thoroughly with a heated magnetic stirrer at a heating temperature of 95℃, a mechanical stirring speed of 250r / min and a stirring time of 40min.

[0161] Step 4: Add 15g of calcium peroxide powder, 30g of sodium persulfate powder and 2g of potassium dihydrogen phosphate to the mixture obtained in Step 3, and stir thoroughly until the mixture is uniform. The stirring method is to use heated magnetic stirring, with a stirring temperature of 60℃, a stirring speed of 200r / min and a stirring time of 40min.

[0162] Step 5: The mixture obtained in Step 4 is vacuum freeze-dried and then ground into powder for later use. The vacuum freeze-drying temperature is -60℃.

[0163] Step 6: Take 150ml of deionized water, add 5g of carrageenan, and mix thoroughly using ultrasonic stirring at a temperature of 40℃, a frequency of 30Hz, and a time of 40min.

[0164] Step 7: Take 20g of the powder obtained in Step 5 and add it to the mixture obtained in Step 6. Stir and mix thoroughly. Use ultrasonic stirring at a temperature of 40℃, a frequency of 30Hz, and a time of 75min.

[0165] Step 8: After vacuum freeze-drying the mixture obtained in Step 7, grind it into powder to obtain the finished biostimulant material. The vacuum freeze-drying temperature is -60℃.

[0166] Oil-contaminated soil samples were taken from an oil field, and after impurities were removed, crushed, and sieved through a 20-mesh sieve, the samples were divided into 10 portions. 100g of soil sample was taken from each portion, and 1g of biostimulant material was added. The samples were mixed and stirred evenly. Deionized water was added daily to adjust the moisture content of the soil samples to 15%.

[0167] Total petroleum hydrocarbons in soil were extracted using ultrasonic extraction and determined by gravimetric method: 3g of air-dried soil sample was weighed and placed in a centrifuge tube. 15.0mL of a 1:1 (v / v) mixture of dichloromethane and n-hexane was added. The mixture was ultrasonically extracted at 4℃ for 10min using an ultrasonic cell disruptor, followed by centrifugation at 8000r / min for 15min. The extract was filtered through quantitative filter paper into a pre-weighed weighing bottle. The extraction was repeated three times. The weighing bottle was placed in a fume hood to allow the extractant to evaporate completely to constant weight before weighing.

[0168] Soil samples were placed in a constant temperature and humidity environment of 25℃ and 75% relative humidity. Total petroleum hydrocarbon content was measured periodically. After 100 days, the petroleum hydrocarbon degradation rate reached 73.89%. The results are shown in Table 7.

[0169] Table 7

[0170]

[0171] Comparative Example 3

[0172] Step 1: Take 250ml of deionized water, add 15g of polyvinyl alcohol, 4g of sodium alginate and 1g of polyoxypropylene triol, and mix thoroughly with a heated magnetic stirrer at a temperature of 95℃, a mechanical stirring speed of 250r / min and a stirring time of 40min.

[0173] Step 2: Add 15g of calcium peroxide powder, 30g of sodium persulfate powder and 1.5g of potassium dihydrogen phosphate to the mixture obtained in Step 1, and stir thoroughly until the mixture is uniform. The stirring method is heating magnetic stirring, stirring temperature 60℃, stirring speed 200r / min, stirring time 40min.

[0174] Step 3: The mixture obtained in Step 2 is vacuum freeze-dried and then ground into powder to obtain a slow-release oxygen material. The vacuum freeze-drying temperature is -60℃.

[0175] Oil-contaminated soil samples were taken from an oil field, and after impurities were removed, crushed, and sieved through a 20-mesh sieve, the samples were divided into 10 portions. 100g of soil sample was taken from each portion, and 1g of biostimulant material was added. The samples were mixed and stirred evenly. Deionized water was added daily to adjust the moisture content of the soil samples to 15%.

[0176] Total petroleum hydrocarbons in soil were extracted using ultrasonic extraction and determined by gravimetric method: 3g of air-dried soil sample was weighed and placed in a centrifuge tube. 15.0mL of a 1:1 (v / v) mixture of dichloromethane and n-hexane was added. The mixture was ultrasonically extracted at 4℃ for 10min using an ultrasonic cell disruptor, followed by centrifugation at 8000r / min for 15min. The extract was filtered through quantitative filter paper into a pre-weighed weighing bottle. The extraction was repeated three times. The weighing bottle was placed in a fume hood to allow the extractant to evaporate completely to constant weight before weighing.

[0177] Soil samples were placed in a constant temperature and humidity environment of 25℃ and 75% relative humidity. Total petroleum hydrocarbon content was measured periodically. After 100 days, the petroleum hydrocarbon degradation rate reached 67.52%. The results are shown in Table 8.

[0178] Table 8

[0179]

[0180] The degradation rate of petroleum hydrocarbons of the biostimulant materials in the above embodiments and comparative examples after 100 days is as follows: Figure 1 As shown. By Figure 1 As can be seen from the results in Tables 1-8, by comparing Examples 1-5 with Comparative Examples 1-3, the biostimulant material of the present invention has better petroleum hydrocarbon degradation performance.

[0181] As can be seen from the comparison between Example 3 and Comparative Examples 1-2, the biostimulant material of the present invention can further improve the petroleum hydrocarbon degradation performance of the biostimulant material by using biochemically treated sludge.

[0182] A comparison of Examples 3 and 4-5 shows that by using metal peroxides and persulfates as composite oxygen-releasing agents, the petroleum hydrocarbon degradation performance of biostimulated materials can be further improved.

[0183] 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 inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a bio-stimulating material, characterized by, The preparation method comprises the following steps: (1) sequentially performing standing precipitation and centrifugal separation on the biochemical treatment sludge to obtain sludge supernatant and sludge precipitate; (2) mixing the sludge supernatant obtained in step (1) with a first gelling agent and a toughening agent, then adding an oxygen releasing agent and a reaction adjusting agent, mixing, and performing first freeze drying to obtain a composite oxygen releasing material; (3) mixing the sludge precipitate obtained in step (1) with a second gelling agent, then adding the composite oxygen releasing material obtained in step (2) and mixing, and performing second freeze drying to obtain a biological stimulating material; In step (2), the reaction adjusting agent is potassium dihydrogen phosphate and / or sodium dihydrogen phosphate; in step (2), the oxygen releasing agent is a metal peroxide and a persulfate salt; In step (2), the first gelling agent is polyvinyl alcohol and sodium alginate; the toughening agent is a polyether polyol; in step (3), the second gelling agent is one or more of carrageenan, gelatin, ethyl cellulose, methyl cellulose and xanthan gum; In step (2), the weight ratio of the sludge supernatant to the first gelling agent and the toughening agent is 100:5-20:0.2-1; in step (2), the weight ratio of the mixture of the sludge supernatant, the first gelling agent and the toughening agent to the oxygen releasing agent and the reaction adjusting agent is 100:5-30:0.3-1.5; In step (3), the weight ratio of the sludge precipitate to the second gelling agent is 100:1-5; in step (3), the weight ratio of the mixture of the sludge precipitate and the second gelling agent to the composite oxygen releasing material is 5-15:

1.

2. The production method according to claim 1, wherein, In step (2), the toughening agent is polyoxypropylene triol.

3. The production method according to claim 2, wherein In step (2), the mass ratio of polyvinyl alcohol to sodium alginate in the first gelling agent is 2-5:

1.

4. The production method according to any one of claims 1 to 3, wherein In step (2), the mixing conditions of the sludge supernatant with the first gelling agent and the toughening agent include: temperature 90-100℃, time 30-60min; mechanical stirring or ultrasonic stirring is adopted for mixing, the mechanical stirring speed is 180-260r / min, and the ultrasonic stirring frequency is 20-40Hz.

5. The production method according to claim 1, wherein The metal peroxide is one or more of calcium peroxide, magnesium peroxide, beryllium peroxide and barium peroxide; the persulfate salt is sodium persulfate and / or potassium persulfate.

6. The production method according to any one of claims 1 and 5, wherein In step (2), the mixing conditions of adding the oxygen releasing agent and the reaction adjusting agent include: temperature 60-80℃, time 30-60min; mechanical stirring or ultrasonic stirring is adopted for mixing, the mechanical stirring speed is 180-260r / min, and the ultrasonic stirring frequency is 20-40Hz.

7. The production method according to any one of claims 1 and 5, wherein The temperature of the first freeze drying is -50℃ to -80℃.

8. The production method according to claim 1, wherein In step (3), the mixing conditions of the sludge precipitate with the second gelling agent include: temperature 25-50℃, time 30-60min; mechanical stirring or ultrasonic stirring is adopted for mixing, the mechanical stirring speed is 180-260r / min, and the ultrasonic stirring frequency is 20-40Hz.

9. The production method according to claim 1, wherein In step (3), the mixing conditions of adding the composite oxygen releasing material include: temperature 25-50℃, time 60-120min.

10. The production method according to claim 1, wherein, The temperature of the second freeze drying is -50℃ to -80℃.

11. The method of producing according to claim 1, wherein, In step (1), the standing precipitation time is 12-24h.

12. The method of producing according to claim 1, wherein, The centrifugal separation conditions include: 3000-5000 r / min, centrifugal time 5-15 min.

13. The bio-stimulating material produced by the method according to any one of claims 1-12.

14. Use of the bio-stimulating material according to claim 13 for soil remediation.

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