Preparation method of sustained-release material, prepared sustained-release material and application of sustained-release material

Abstract

The invention provides a preparation method of a sustained-release material, the prepared sustained-release material and application of the sustained-release material. The preparation method comprises the following steps: (1) dispersing first starch in water, then adding a first active substance, activated carbon and sodium alginate, and uniformly mixing to obtain a product I; (2) dispersing second starch in water, then adding a second active substance, and uniformly mixing to obtain a product II; and (3) mixing the product I obtained in the step (1), the product II obtained in the step (2), a strength agent, a matrix and a solvent, molding, and drying to obtain the sustained-release material. The slow-release material has the characteristics of environmental friendliness and long-term release, can be used for in-situ chemical oxidation, in-situ chemical reduction and bioremediation of polluted underground water in the aspects of nutrient maintenance of microorganisms and the like, and particularly can achieve long-term and efficient remediation when being used for remediation of organic pollutants in underground water.

Description

Technical Field

[0001] The present invention belongs to the technical field of sustained-release materials, and in particular relates to a method for preparing a sustained-release material, the prepared sustained-release material and applications thereof. Background Art

[0002] When organic matter leaks into the soil aquifer, it will dissolve and distribute between the water, gas and solid phases, and thus persist in the soil and groundwater for a long time. However, due to the low water solubility, high interfacial tension and adhesion to soil particles of organic pollutants, it may take decades or even hundreds of years for these pollutants to naturally degrade to harmless levels. Therefore, the development of efficient groundwater organic pollution remediation technology has become an important research topic. Commonly used remediation technologies for this type of organic pollutants include: extraction treatment technology, in-situ chemical oxidation technology (ISCO), bioremediation technology, permeable reaction wall technology, etc. Among them, ISCO is one of the most promising technologies for the efficient removal (degradation) of groundwater organic pollutants.

[0003] In the implementation of ISCO, full contact between oxidants and pollutants is the key to improving remediation efficiency. However, organic pollutants in groundwater, as hydrophobic substances, are usually adsorbed in soil particles in the aquifer and gradually released into the groundwater, forming a long-term pollution source. Oxidants, as water-soluble substances, are easily dispersed in groundwater, transported, diffused and diluted with water flow, but because their transmission rate is usually much greater than the release rate of organic pollutants, the contact efficiency between the two is low, and the oxidant is wasted. Therefore, in engineering practice, the injection time is often extended and the injection amount of the agent is increased to achieve full contact and degradation of the target pollutants, which not only increases the cost, but also easily causes secondary pollution. In addition, after the oxidant fails, low-concentration organic pollutants continue to be released in the aquifer medium, forming a tailing and rebound phenomenon of pollution, which requires repeated dosing, further aggravating the problem of excessive agent addition and secondary pollution.

[0004] CN102491425A discloses a slow-release potassium permanganate oxidant for in-situ chemical remediation of groundwater. 4 Dispersed into molten paraffin, and then cooled and solidified in a mold to make slow-release KMnO4 oxidants of different shapes, so as to achieve slow-release KMnO 4 The purpose of slow release of oxidants. However, in this study, harmful organic paraffin was used as one of the raw materials, which poses a great risk of secondary pollution.

[0005] CN107188361A discloses a slow-release sulfiding agent and a preparation method thereof, and a method for using the slow-release sulfiding agent to purify heavy metals and arsenic in an acidic solution. 2+ , Mn 2+ and Zn 2+A sulfur source and a surfactant are added to the solution to react, and a nano-micron metal sulfide sol slow-release sulfiding agent is obtained, which is used to remove heavy metals and arsenic in acidic solutions. It has the advantages of high removal efficiency, low usage of sulfiding agent, and low release of hydrogen sulfide. However, this agent is only effective for heavy metal pollutants, and cannot repair organically contaminated groundwater, and it is difficult to achieve long-term repair.

[0006] CN114160558A discloses a contaminated soil in-situ chemical barrier material and its preparation and application. The material uses the in-situ clean soil of the site or the soil that meets the landfill disposal standard as the main matrix material, and adds clay minerals at the same time, which significantly reduces the permeability coefficient of the barrier mixture. In addition, the application of active materials in the mixture effectively controls and assists in reducing the pollution factors, thereby achieving the in-situ risk control and disposal goals of the contaminated site through a variety of functional characteristics. However, the material uses soil as the main matrix material. Experimental data show that soil and clay as matrix materials are very easy to absorb water, swell and disintegrate when exposed to water, which greatly reduces the release time of the active components in the material, and cannot achieve the purpose of slow release and long-term repair.

[0007] In summary, the slow-release remediation materials and remediation methods disclosed in the prior art are either only developed for heavy metal contaminated sites and have limited remediation effects on organic pollutants, or the base materials are not suitable for long-term release and the slow-release period is short, which makes it impossible to achieve the purpose of slow release and long-term remediation of slow-release materials. Therefore, it is urgent to develop an environmentally friendly, long-term release slow-release material. Summary of the invention

[0008] In view of the defects of the prior art, the present invention provides a method for preparing a slow-release material, a slow-release material prepared, and an application thereof. The slow-release material prepared by the method has the characteristics of being environmentally friendly and having a long-term release, and can be used for in-situ chemical oxidation, in-situ chemical reduction, and bioremediation of contaminated groundwater, and the maintenance of microbial nutrition, and in particular, can achieve long-term and efficient remediation when used for remediating organic pollutants in groundwater.

[0009] The first aspect of the present invention provides a method for preparing a sustained-release material. The method comprises:

[0010] (1) dispersing the first starch in water, then adding the first active substance, activated carbon, and sodium alginate and mixing them evenly to obtain product I;

[0011] (2) dispersing the second starch in water, and then adding the second active substance and mixing evenly to obtain product II;

[0012] (3) The product I obtained in step (1), the product II obtained in step (2), a strength agent, a matrix, and a solvent are mixed, molded, and dried to obtain a sustained-release material.

[0013] According to the present invention, in step (1), the first active substance includes one or more of sodium persulfate, potassium persulfate, ammonium persulfate, calcium persulfate, potassium permanganate, sodium permanganate, sodium sulfite, and microbial nutrients, preferably one or more of sodium persulfate, potassium persulfate, and ammonium persulfate. Further, the microbial nutrient includes at least one of glucose, lignin, nitrate, and ferrous salt. The first active substance does not produce harmful substances after being oxidized, reduced, or biologically utilized, and does not cause secondary pollution of groundwater.

[0014] According to the present invention, in step (1), the average particle size of the first starch is 15 to 20 μm.

[0015] According to the present invention, the particle diameter of the activated carbon in step (1) is 40-60 mesh. The activated carbon is wood activated carbon and / or coal-made activated carbon. In the activated carbon, the pore volume occupied by macropores (pore diameter>50nm) is more than 5% of the total pore volume, preferably 5%-8%.

[0016] According to the present invention, in step (1), the materials are fed in the following ratio, i.e., the mass ratio of water, sodium alginate, first starch, first active substance, and activated carbon is 100: (1-3): (5-15): (35-50): (30-45). The product prepared within this ratio range can maximize the loading of the first starch particles carrying the first active substance in the pores of the activated carbon.

[0017] According to the present invention, in step (1), the first starch is dispersed in water and then stirred thoroughly. Then, the first active substance, activated carbon, and finally sodium alginate are added in order. Each time a material is added, it is mixed evenly. Preferably, after adding the activated carbon, stirring is performed, preferably mechanical stirring. The mechanical stirring device can be a magnetic stirrer. Preferably, the mechanical stirring time is 1 to 2.5 hours. More preferably, sodium alginate is added during stirring.

[0018] According to the present invention, in step (1), the product I is shaken in a shaker. The shaking time is 30 to 50 minutes, so that the starch with the active substance is fully loaded into the activated carbon. The obtained product I is an activated carbon composite material loaded with the first active substance.

[0019] According to the present invention, the product I in step (1) can be filtered, washed and dried. The drying can be natural drying, such as drying at room temperature 10 to 25° C. for 10 to 48 hours.

[0020] According to the present invention, in step (2), the second active substance includes one or more of sodium persulfate, potassium persulfate, ammonium persulfate, calcium persulfate, potassium permanganate, sodium permanganate, sodium sulfite, and microbial nutrients, preferably one or more of sodium persulfate, potassium persulfate, and ammonium persulfate. Further, the microbial nutrient includes at least one of glucose, lignin, nitrate, and ferrous salt. The second active substance does not produce harmful substances after being oxidized, reduced, or biologically utilized, and does not cause secondary pollution of groundwater. The first active substance and the second active substance may be the same or different.

[0021] According to the present invention, in step (2), the average particle size of the second starch is 15 to 20 μm.

[0022] According to the present invention, in step (2), the mass ratio of water, the second starch and the second active substance is 100:(20-30):(50-60).

[0023] According to the present invention, the strength agent in step (3) includes at least one of quartz sand and glass fiber. The strength agent can provide mechanical strength for the sustained-release material, while creating a large pore size and increasing the release rate of the drug. The matrix includes one or more of polytetrafluoroethylene (PTFE), polystyrene (PS), polyethylene (PE), and polypropylene (PP). The matrix serves as a skeleton material for the sustained-release material matrix and plays a supporting and bonding role. The solvent includes at least one of dichloromethane and n-hexane. Preferably, the solvent includes dichloromethane and n-hexane. Preferably, the volume ratio of dichloromethane to n-hexane is 1:(0.5~1). The solvent will evaporate after the material is formed and will not be present in the material.

[0024] According to the present invention, in step (3), the mass ratio of product I, product II, strength agent, matrix, and solvent is (80-95): (75-85): (1-3): 100: (50-70). This feed ratio can form a layered wrapped structure, with the matrix material wrapped with the second active substance as the outer shell, and the activated carbon composite material loaded with the first active substance as the inner core. In the sustained-release application, a graded release effect is formed, which prolongs the release time of the drug and increases the oxidation cycle.

[0025] According to the present invention, preferably, in step (3), the method for mixing product I, product II, a strength agent, a matrix, and a solvent comprises:

[0026] (31) mixing a matrix with a solvent;

[0027] (32) the mixture obtained in step (31) is uniformly mixed with product I;

[0028] (33) The mixture obtained in step (32), product II and a strength agent are mixed uniformly.

[0029] According to the present invention, the shape of the sustained-release material in step (3) includes at least one of a cylindrical shape, a spherical shape, a strip shape and a compressed tablet shape.

[0030] According to the present invention, the drying conditions in step (3) are: temperature 30-45° C., time 30-60 hours.

[0031] The second aspect of the present invention provides a sustained-release material prepared by the above method.

[0032] The third aspect of the present invention provides the use of the sustained-release material prepared by the above method in sustained-release of materials.

[0033] According to the present invention, the application includes the application of the slow-release material in remediating organic pollutants in groundwater.

[0034] According to the present invention, the application is to use the above-mentioned slow-release material as filler, fill it into permeable reaction walls, groundwater remediation wells and other remediation structures, and carry out in-situ chemical oxidation, in-situ chemical reduction and in-situ biological remediation of polluted groundwater. In the process of in-situ chemical oxidation and in-situ chemical reduction, when groundwater carries pollutants through the filler, it undergoes redox reaction with the active substances released by the above-mentioned slow-release material, so that the pollutants are removed and the groundwater is purified; in the process of in-situ biological remediation, the carbon source, nitrogen source, electron acceptor and other nutrients released by the slow-release material prepared by the above method provide continuous support for microbial agents, thereby accelerating the degradation of pollutants by microorganisms and achieving groundwater remediation.

[0035] Compared with the prior art, the present invention has achieved remarkable technical effects:

[0036] (1) In the method of the present invention, the method adopts a sequential batch mixing method to form a multi-layer wrapped multi-core structure of the sustained-release material. When the outer shell is completely decomposed, the multiple dispersed cores in the inner layer can release the active substance from the inner layer to the outer layer in relay, achieving the effect of layered multi-level release, thereby realizing long-term stable drug release.

[0037] (2) The unique material ratio scheme in the product of the present invention ensures the loading amount of active substances while achieving close integration of active substances with other materials, develops a high-strength skeleton structure, avoids the material from breaking and disintegrating in water, and prolongs the classification speed of the finished material in water.

[0038] (3) The sustained-release material prepared by the method of the present invention can effectively prolong the release period of the agent and stabilize the release rate during application. In particular, when applied to the remediation of pollutants in groundwater, it can improve the removal efficiency of pollutants and the stability of technical operation, reduce the dosage of the agent, and prevent pollution rebound. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a diagram showing the sustained release performance test effect of Example 1;

[0040] Figure 2 This is a diagram showing the sustained release performance test effect of Example 2;

[0041] Figure 3 This is a diagram showing the sustained release performance test effect of Example 3;

[0042] Figure 4 This is a graph showing the sustained release performance test effect of Comparative Example 1;

[0043] Figure 5 A schematic diagram of a contaminated groundwater treatment device for an application example;

[0044] Figure 6 This is an application example of the remediation effect of slow-release materials on groundwater contaminated by petroleum hydrocarbons (TPH). DETAILED DESCRIPTION

[0045] The present invention will be further described below by way of examples, but the protection scope of the present invention is not limited by the examples.

[0046] In the present invention, the method for testing the sustained-release performance is: weigh 10g of the sustained-release material and place it in 1L of deionized water, and measure the content of the active substance in the water at regular intervals, and at the same time measure the level of organic matter in the water to detect whether the sustained-release material will cause secondary pollution of the water body. The test interval increases with the test time. For example, the test can be performed every 1 day in the initial stage, every 2 to 5 days in the middle stage, and every 10 days in the final stage. After each test, the deionized water that has been tested is replaced with fresh 1L of deionized water. Repeat the above steps regularly until the active substance cannot be detected in the deionized water. In the present invention, the content of the active substance in the water is tested by spectrophotometry. For example, in each case, when persulfate is used as the active substance, the test method for the persulfate content adopts the potassium iodide-ultraviolet spectrophotometry method. When ferrous salt is used as the active substance, the test method for the iron content adopts the o-phenanthroline spectrophotometry method. When glucose is used as the active substance, the glucose determination method is sampled by high-performance liquid chromatography.

[0047] In the present invention, the test method for organic matter in water adopts the method of "Determination of Volatile Organic Matter in Water Quality - Purge and Trap-Gas Chromatography (HJ 686-2014)".

[0048] In the present invention, the loading amount of active substances in the sustained-release materials prepared in each example is determined by an element analyzer. In the present invention, the release period is the time from the addition of the sustained-release material to the water until the active substances can no longer be detected in the water; the cumulative release rate of the sustained-release material is the sum of the mass of active substances measured each time during the release period, divided by the loading amount of active substances in the sustained-release material; the average release rate is the sum of the mass of active substances measured each time during the release period, divided by the release period.

[0049] Example 1

[0050] (1) 15 g of corn starch with an average particle size of 20 μm was added to 100 g of water, and the mixture was stirred to form an emulsion. Then, 50 g of sodium persulfate was added to the emulsion to dissolve and mix. After stirring evenly, 45 g of 60-mesh wood activated carbon (the pore volume occupied by macropores was 5.3% of the total pore volume) was added to the mixture. The mixture was placed in a magnetic stirrer and stirred for 2 h. Then, 3 g of sodium alginate was added while stirring to form a colloid. The colloid was placed in a shaker and shaken for 45 min to allow the starch with active substances to be fully loaded into the activated carbon. The activated carbon after adsorption was then filtered, washed, and air-dried at 25° C. for 48 h to obtain product I, i.e., an activated carbon composite material.

[0051] (2) Re-weigh some starch (average particle size of 20 μm) and sodium persulfate, mix the starch and sodium persulfate in water to obtain product II. The mass ratio of the feed materials is water: starch: sodium persulfate = 100:30:60.

[0052] (3) Mixing the product I obtained in step (1), the product II obtained in step (2), a strength agent, a matrix, and a solvent, and forming and drying them to obtain a sustained-release material. The specific steps are:

[0053] (31) mixing the matrix polytetrafluoroethylene powder with a solvent (dichloromethane and n-hexane in a volume ratio of 1:1);

[0054] (32) the mixture obtained in step (31) is uniformly mixed with product I;

[0055] (33) The mixture obtained in step (32), product II and strength agent quartz sand are fully mixed. The ratio of product I: product II: quartz sand: polytetrafluoroethylene: solvent is 95:85:3:100:70. After fully mixing, the material is extruded into strips, and dried at 45°C for 48 hours to obtain cylindrical granular sustained-release material A.

[0056] It was determined that the mass fraction of sulfur in the sustained-release material A in this example was 4.75wt%, and the loading amount of sodium persulfate in the sustained-release material A was calculated to be 17.66wt%. The sustained-release performance test results of the sustained-release material in this example are shown in FIG. Figure 1As shown, it can be seen that the release of active substances can be divided into two stages: the first stage is from 0 to 7 days, which is the decomposition and release stage of the outer shell, characterized by a faster release rate change and a steeper release curve; the second stage is from 8 to 80 days, which is the sustained release stage of the inner core, characterized by a stable release rate and a smooth curve; the relay release of the first and second stages achieves the effect of layered multi-level sustained release. The final test results show that the release period of sustained-release material A is 80 days. The cumulative release rate of sodium persulfate during the release period is 96wt%, and the average release rate is 2.21mg / (gd). During the entire sustained-release period, no organic matter was detected in the water, and the particles of the sustained-release material were never broken or disintegrated.

[0057] Example 2

[0058] (1) Add 5 g of corn starch with an average particle size of 15 μm to 100 g of water, stir and mix thoroughly to form an emulsion, then add 35 g of potassium persulfate to the emulsion to dissolve and mix, stir evenly, add 30 g of 40 mesh wood activated carbon (the pore volume occupied by macropores is 7.8% of the total pore volume) to the mixture, put the mixture into a magnetic stirrer and stir and mix thoroughly for 1 hour, then add 1 g of sodium alginate while stirring to form a colloid, put the colloid into a shaker, and shake for 30 minutes, so that the starch with active substances is fully loaded into the activated carbon. Then filter and wash the activated carbon after adsorption, and air-dry it at 25°C for 24 hours to obtain product I, i.e., an activated carbon composite material.

[0059] (2) Re-weigh some starch (average particle size of 15 μm) and calcium persulfate, mix the starch and calcium persulfate in water to obtain product II. The mass ratio of the feed materials is water: starch: calcium persulfate = 100:20:50.

[0060] (3) Mixing the product I obtained in step (1), the product II obtained in step (2), a strength agent, a matrix, and a solvent, and forming and drying them to obtain a sustained-release material. The specific steps are:

[0061] (31) mixing the matrix polytetrafluoroethylene powder with a solvent (dichloromethane and n-hexane in a volume ratio of 1:0.5);

[0062] (32) the mixture obtained in step (31) is uniformly mixed with product I;

[0063] (33) The mixture obtained in step (32), product II and strength agent quartz sand are fully mixed. The ratio of product I: product II: quartz sand: polytetrafluoroethylene: solvent is 80:75:1:100:50. After fully mixing, the material is extruded into strips, and dried at 40°C for 60 hours to obtain cylindrical granular sustained-release material B.

[0064] The mass fraction of sulfur in the sustained-release material B in this example was determined to be 4.57 wt %, and the loading amount of active substances (potassium persulfate and calcium persulfate) in the sustained-release material B was calculated to be 17.49 wt %. The sustained-release performance test results of the sustained-release material in this example are shown in FIG. Figure 2 As shown, it can be seen that the release of active substances can be divided into two stages: the first stage is from 0 to 9 days, which is the decomposition and release stage of the outer shell, characterized by a rapid change in release rate and a steep release curve; the second stage is from 10 to 81 days, which is the sustained release stage of the inner core, characterized by a stable release rate and a smooth curve; the relay release of the first and second stages achieves the effect of layered multi-level sustained release. The final test results show that the release period of sustained-release material B is 81 days. The cumulative release rate of active substances during the release period is 97wt%, and the average release rate is 2.13mg / (gd). During the entire sustained-release period, no organic matter was detected in the water, and the particles of the sustained-release material were never broken or disintegrated.

[0065] Example 3

[0066] (1) 10 g of corn starch with an average particle size of 20 μm was added to 100 g of water, and the mixture was stirred and mixed to form an emulsion. Then 40 g of ferrous sulfate was added to the emulsion to dissolve and mix. After stirring evenly, 40 g of 50-mesh wood activated carbon (the pore volume occupied by macropores was 6.7% of the total pore volume) was added to the mixture. The mixture was placed in a magnetic stirrer and stirred for 1.5 h. Then 2 g of sodium alginate was added while stirring to form a colloid. The colloid was placed in a shaker and shaken for 50 min to allow the starch with active substances to be fully loaded into the activated carbon. The activated carbon after adsorption was then filtered, washed, and air-dried at 25° C. for 48 h to obtain product I, i.e., an activated carbon composite material.

[0067] (2) Re-weigh some starch (average particle size of 20 μm) and ferrous sulfate, mix the starch and ferrous sulfate in water to obtain product II. The mass ratio of the feed materials is water: starch: ferrous sulfate = 100: 25: 55.

[0068] (3) Mixing the product I obtained in step (1), the product II obtained in step (2), a strength agent, a matrix, and a solvent, and forming and drying them to obtain a sustained-release material. The specific steps are:

[0069] (31) mixing the matrix polytetrafluoroethylene powder with a solvent (dichloromethane and n-hexane in a volume ratio of 1:0.8);

[0070] (32) the mixture obtained in step (31) is uniformly mixed with product I;

[0071] (33) The mixture obtained in step (32), product II and strength agent quartz sand are fully mixed. The ratio of product I: product II: quartz sand: polytetrafluoroethylene: solvent is 85:80:2:100:60. After fully mixing, the material is extruded into strips, and dried at 45°C for 60 hours to obtain cylindrical granular sustained-release material C.

[0072] It was determined that the mass fraction of iron in the sustained-release material C in this example was 6.97 wt %, and the loading amount of ferrous sulfate in the sustained-release material C was calculated to be 18.92 wt %. The sustained-release performance test results of the sustained-release material in this example are shown in FIG. Figure 3 As shown, it can be seen that the release of active substances can be divided into two stages: the first stage is about 0 to 15 days, which is the decomposition and release stage of the outer shell, characterized by a faster change in release rate and a steeper release curve; the second stage is about 16 to 80 days, which is the sustained release stage of the inner core, characterized by a stable release rate and a smooth curve; the relay release of the first and second stages achieves the effect of layered multi-level sustained release. The final test results show that the release period of sustained-release material C is 80 days. The cumulative release rate of ferrous sulfate during the release period is 97wt%, and the average release rate is 2.29mg / (gd). During the entire sustained-release period, no organic matter was detected in the water, and the particles of the sustained-release material were never broken or disintegrated.

[0073] Example 4

[0074] The difference from Example 1 is that the active substances in steps (1) and (2) are both glucose, and the rest is the same as Example 1.

[0075] After determination, the sustained release performance test results of this example of sustained release material are similar to Figure 1 . The release of active substances can be divided into two stages: the first stage is from 0 to 6 days; the second stage is from 7 to 77 days; the relay release of the first and second stages achieves the effect of layered multi-level sustained release. The final test results show that the release cycle of the sustained-release material is 77 days. The cumulative release rate of sodium persulfate during the release cycle is 96wt%, and the average release rate is 2.53mg / (gd). During the entire sustained-release cycle, no organic matter other than glucose was detected in the water, and the sustained-release material particles were never broken or disintegrated.

[0076] Comparative Example 1

[0077] The difference between this example and Example 1 is that the active substance sodium persulfate is not added in steps, but all at once. That is, all the materials in steps (1) and (2) of Example 1 are added at once in step (1) of Example 1. The material feeding amount and other operation steps are the same as in Example 1.

[0078] After determination, the sustained release performance test results of this example sustained release material are as follows Figure 4As shown, the results showed that the release period of the sustained-release material was only 8 days, and the slow-release effect was not achieved.

[0079] Application Examples

[0080] The principle of using slow-release materials to repair contaminated groundwater is as follows Figure 5 As shown, the slow-release material A of Example 1 of the present invention is used as a filler and filled into a permeable reaction wall, and the permeable reaction wall is arranged in the flow path of organic contaminated groundwater. The contaminated groundwater penetrates through the wall, and the organic pollutants are oxidized and degraded by the active substances released by the slow-release material, and the pollutants are removed. The pollution removal rate can be calculated by testing the pollutant concentrations in the groundwater upstream and downstream of the permeable reaction wall respectively. In this application example, groundwater contaminated by petroleum hydrocarbons (TPH) was selected, and the concentration of influent petroleum hydrocarbons was (100±5) mg / L. The wall size was set to 10m*0.6m*6m, and 2 tons of slow-release material was filled as the wall filler at one time, and a 100-day pollution remediation application was carried out. During this period, the TPH concentrations in the groundwater upstream and downstream of the permeable reaction wall were measured at regular intervals, and the pollution removal rate was calculated. The pollution remediation effect is shown in the figure. Figure 6 As shown. Within the 0th to 80th day, the TPH removal rate remained above 90wt%, and the highest could reach 96.3wt%. After the 80th day, most of the oxidants in the slow-release material had been released, and the pollution removal rate changed from high to low. This result shows that the slow-release performance of the slow-release material is stable, and the material can be continuously released within the slow-release period, successfully repairing the contaminated groundwater.

Claims

1. A method for preparing a sustained-release material, It is characterized in that The method comprises: (1) dispersing the first starch in water, then adding the first active substance, activated carbon, and sodium alginate and mixing them evenly to obtain product I; (2) dispersing the second starch in water, and then adding the second active substance and mixing evenly to obtain product II; (3) The product I obtained in step (1), the product II obtained in step (2), a strength agent, a matrix, and a solvent are mixed, molded, and dried to obtain a sustained-release material.

2. The preparation method according to claim 1, It is characterized in that In step (1), the first active substance comprises one or more of sodium persulfate, potassium persulfate, ammonium persulfate, calcium persulfate, potassium permanganate, sodium permanganate, sodium sulfite, and microbial nutrients, preferably one or more of sodium persulfate, potassium persulfate, and ammonium persulfate; Furthermore, the microbial nutrient includes at least one of glucose, lignin, nitrate and ferrous salt.

3. The preparation method according to claim 1, It is characterized in that The particle diameter of the activated carbon in step (1) is 40 to 60 mesh; And / or, the activated carbon is wood activated carbon and / or coal-made activated carbon; And / or, in the activated carbon, the pore volume occupied by macropores (pore diameter>50 nm) is more than 5% of the total pore volume, preferably 5% to 8%.

4. The preparation method according to claim 1, It is characterized in that In step (1), the materials are fed in the following ratio, i.e., the mass ratio of water, sodium alginate, the first starch, the first active substance, and activated carbon is 100: (1-3): (5-15): (35-50): (30-45).

5. The preparation method according to claim 1, It is characterized in that In step (1), the average particle size of the first starch is 15 to 20 μm.

6. The preparation method according to claim 1, It is characterized in that In step (2), the second active substance comprises one or more of sodium persulfate, potassium persulfate, ammonium persulfate, calcium persulfate, potassium permanganate, sodium permanganate, sodium sulfite, and microbial nutrients, preferably one or more of sodium persulfate, potassium persulfate, and ammonium persulfate; Furthermore, the microbial nutrient includes at least one of glucose, lignin, nitrate and ferrous salt.

7. The preparation method according to claim 1, It is characterized in that In step (2), the mass ratio of water, the second starch and the second active substance is 100:(20-30):(50-60).

8. The preparation method according to claim 1, It is characterized in that In step (2), the average particle size of the second starch is 15 to 20 μm.

9. The preparation method according to claim 1, It is characterized in that In step (3), the mass ratio of product I, product II, strength agent, matrix and solvent is (80-95):(75-85):(1-3):100:(50-70).

10. The preparation method according to claim 1, It is characterized in that The mixing method of step (3) product I, product II, strength agent, matrix and solvent comprises: (31) mixing a substrate with a solvent; (32) the mixture obtained in step (31) is uniformly mixed with product I; (33) The mixture obtained in step (32), product II and a strength agent are mixed uniformly.

11. A sustained-release material prepared by the method according to any one of claims 1 to 10.

12. Use of a sustained-release material prepared by the method according to any one of claims 1 to 10 in sustained-release of materials.

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