Sustained-release agent component design method and sustained-release agent preparation method

Abstract

The invention relates to a sustained-release agent component design method and a sustained-release agent preparation method.The sustained-release agent comprises quartz sand, paraffin and an active ingredient, the sustained-release agent component design method comprises the steps that different component design schemes are preset, the volume of the sustained-release agent of each component design scheme is the same, each component design scheme has a first variable and a second variable, and the first variable and the second variable are different; the first variable is the mass of active ingredients contained in unit volume, and the second variable is a wax-sand ratio; simulating a rapid dissolution process of the active ingredients on the surface of the sustained-release agent to obtain a first release curve of the active ingredients changing along with time; the dissolving process of the active ingredients in the slow-release agent is simulated, a second release curve of the active ingredients changing along with time is obtained, and the simulation process comprises the steps that an effective diffusion coefficient is obtained according to the first variable and the second variable, and the second release curve is simulated and solved by combining the effective diffusion coefficient on the basis of the Fick's law; and determining a matched optimal component design scheme according to the matching degree of the expected stable concentration and the mass-time release curve.

Description

Technical Field

[0001] The present application relates to the field of groundwater remediation, and in particular to a method for designing a slow-release agent component and a method for preparing a slow-release agent. Background Art

[0002] Groundwater is an important component of my country's water resources, accounting for 13.8% of the country's total water supply. Its quality and safety are related to the healthy development of society. With the acceleration of urbanization, the groundwater environment has been polluted by various sources such as industrial wastewater, agricultural sewage, and urban domestic waste. Among them, difficult-to-degrade organic pollutants such as trichloroethylene, benzene rings, and aromatic hydrocarbons take hundreds of years to degrade in the natural environment. At the same time, the hydrogeological conditions of groundwater are relatively complex, and pollutant control is difficult. For difficult-to-degrade organic pollutants, the commonly used technical means are in-situ remediation and ex-situ remediation. In-situ chemical oxidation technology has the advantages of high remediation efficiency, wide treatment range, and low cost, but it will be affected by the oxidant material and the groundwater environment during the remediation process, and often has problems such as reverse diffusion, tailing, rebound, and low oxidant life of pollutants.

[0003] The slow-release agent (CRMs) technology studied in recent years is one of the effective methods to overcome the problems encountered by the current in-situ chemical oxidation technology: slow-release agents have the following advantages: stable and low release rate, can carry out long-term remediation of pollutants; low cost; can reduce non-selective consumption and loss of oxidants; green and environmentally friendly. Depending on the different oxidants used, the more common slow-release agents are permanganate slow-release agents and persulfate slow-release agents. Persulfate has the characteristics of high reduction potential, good stability and multiple activation methods, and is more suitable for long-term stable remediation of groundwater.

[0004] The stable release of slow-release agents is a key factor in the application of in-situ groundwater remediation, which will be affected by the composition and proportion of the slow-release agent itself, as well as the environmental medium conditions. Accurately grasping and characterizing the release law and characteristics of slow-release agents is an important part of the slow-release agent technology for in-situ applications. Mathematical algorithms and models are effective means to study the release of slow-release agents. At present, a small number of studies have analyzed the law of slow-release agent release. However, these methods are based on the fitting of experimental data and lack the exploration of the diffusion effect during the release process. Although, on this basis, the existing technology attempts to give a quantitative prediction of the release time of the slow-release agent based on the research and development model, the common research and development empirical model cannot deeply explain the release process, nor can it confirm its reliability for wide applicability, making it difficult to assist in the setting of slow-release agents. Summary of the invention

[0005] Based on this, it is necessary to provide a sustained-release agent component design method and a sustained-release agent preparation method to address the above technical problems.

[0006] The present application provides a method for designing components of a sustained-release agent, wherein the sustained-release agent comprises quartz sand, paraffin wax and an active ingredient, and the method for designing components of a sustained-release agent comprises:

[0007] Different component design schemes are preset, each of which has the same volume of sustained-release agent, and the component design scheme has a first variable and a second variable, wherein the first variable is the mass of active ingredient contained per unit volume, and the second variable is the wax-to-sand ratio of the mass of paraffin wax to the mass of quartz sand;

[0008] Simulate the sustained release process of different component design schemes to obtain the mass-time release curve of the active ingredient in each component design scheme, including:

[0009] Simulating the rapid dissolution process of the active ingredient at the surface of the sustained-release agent to obtain a first release curve of the active ingredient changing with time;

[0010] Simulating the dissolution process of the active ingredient in the sustained-release agent to obtain a second release curve of the active ingredient changing with time, the simulation process comprising: obtaining an effective diffusion coefficient according to the first variable and the second variable, simulating and solving the second release curve based on Fick's law and the effective diffusion coefficient, the second release curve and the first release curve forming the mass-time release curve;

[0011] According to the matching degree between the expected stable concentration in the application scenario and the mass-time release curve, a matching preferred component design scheme is determined.

[0012] Optionally, the active ingredient is persulfate.

[0013] Optionally, the rapid dissolution process of the active ingredient at the surface of the sustained-release agent is simulated to obtain a first release curve of the active ingredient over time, using the following formula:

[0014]

[0015] Where M t1 The active ingredient at t 1 Time release mass, t 1 is the duration of the first release profile, M 总 is the total added mass of the active ingredients in each component design scheme, α is the correction coefficient, and k is the rapid release constant.

[0016] Optionally, the effective diffusion coefficient is obtained according to the first variable and the second variable using the following formula:

[0017] De=AB*ln(X 1 )+C*X 2

[0018] Where De is the effective diffusion coefficient, A, B, and C are all constants, and X 1 represents the second variable, X 2 represents the total added mass of the active ingredients in each component design scheme, X 2 Obtained according to the first variable and the sustained-release agent volume.

[0019] Optional, A is 1.36×10 -6 , B is 1.27×10 -5 , C is 2.45×10 -6 .

[0020] Optionally, the sustained-release agent is in a cubic shape.

[0021] Optionally, in the process of simulating and solving the second release curve, the mass of the active ingredient of the second release curve is simulated in the following manner:

[0022]

[0023] Where a is half the side length of the cube-shaped sustained-release dosage form;

[0024] x is half of the side length of the cube-shaped sustained-release agent that has not yet dissolved inside the sustained-release agent;

[0025] M 2 To simulate the mass of the active ingredient during the dissolution process of the active ingredient inside the sustained-release preparation;

[0026] V is the volume of the solution in the simulation scenario;

[0027] C S is the maximum solubility of the active ingredient in the simulated scenario solution;

[0028] C a is the solubility of the active ingredient at the end of the first release curve;

[0029] De is the effective diffusion coefficient;

[0030] C, is the concentration of active ingredients in the solution in the simulation scenario.

[0031] Optionally, an effective diffusion coefficient is obtained according to the first variable and the second variable, and the second release curve is simulated and solved in combination with the effective diffusion coefficient, and the following two equations are used to solve the curve:

[0032] M 2 =A(8a 3 -8x 3 )

[0033]

[0034] Where a is half the side length of the cube-shaped sustained-release dosage form;

[0035] x is half of the side length of the cube-shaped sustained-release agent that has not yet dissolved inside the sustained-release agent;

[0036] A is the first variable;

[0037] M 2 To simulate the mass of active ingredients released cumulatively after time t during the dissolution process of the active ingredients in the sustained-release preparation;

[0038] De is the effective diffusion coefficient;

[0039] t 1 is the duration of the first release profile;

[0040] V is the volume of the solution in the simulation scenario;

[0041] C S It is the maximum solubility of the active ingredient in the simulated scenario solution.

[0042] The present application provides a method for preparing a sustained-release agent, which is implemented using the preferred component design scheme obtained in the sustained-release agent component design method described in the present application, comprising:

[0043] Determine the volume of the sustained-release agent according to the preferred component design scheme, and determine the mass of the active ingredient in the sustained-release agent according to the volume of the sustained-release agent and the mass of the active ingredient contained in the unit volume;

[0044] Determine the wax-sand ratio of the mass of paraffin wax to the mass of quartz sand according to the preferred component design scheme;

[0045] The sustained-release preparation is prepared.

[0046] Optionally, the active ingredient is sodium persulfate, and the process for preparing the sustained-release agent includes:

[0047] (I) firstly adding paraffin wax into anhydrous ethanol, heating and melting, and then adding sodium persulfate, mesoporous manganese oxide, quartz sand, Span-80 and polyethylene glycol according to a ratio, mixing and stirring at 65° C. to obtain a molten material; the mesoporous manganese oxide is prepared by a hard template coupled nano-etching method;

[0048] (II) The molten material obtained in step (I) is quickly poured into a mold and cooled at room temperature to obtain the product.

[0049] Optionally, the polyethylene glycol is polyethylene glycol-4000.

[0050] The sustained-release agent component design method and sustained-release agent preparation method of the present application have at least the following technical effects:

[0051] The sustained-release simulation of different component design schemes in this application is divided into two processes, namely the first stage belonging to the liquid phase and the second stage belonging to the solid phase, forming a two-phase diffusion model as a whole. The first stage mainly simulates the rapid dissolution of the surface of the sustained-release agent when it first enters the solution, and the second stage mainly simulates the slow dissolution of the solid inside the sustained-release agent after the surface of the sustained-release agent is rapidly dissolved. The present application obtains the effective diffusion coefficient through the first variable and the second variable, and simulates the sustained-release process with discrimination for different component conditions, further improving the wide applicability of the simulated release of the sustained-release agent.

[0052] The slow-release agent component design method provided in the present application can quantitatively adjust the content of quartz sand and sodium persulfate to change the release process, simulate and adjust the life of the slow-release agent, help to more accurately simulate the release mechanism and process of the slow-release agent, assist in the design of the slow-release agent and effectively apply it to in-situ groundwater remediation in different environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a schematic diagram of the process of preparing a sustained-release agent in an embodiment of the present application;

[0054] Figure 2 This is a schematic diagram of the preparation process of mesoporous manganese oxide used in the method for preparing a sustained-release agent in one embodiment of the present application;

[0055] Figure 3 This is a schematic diagram of a process for designing a sustained-release agent component in one embodiment of the present application;

[0056] Figure 4 for Figure 3 Schematic diagram of the simulation concept of step S220;

[0057] Figure 5a This is a schematic diagram of electron microscope scanning before the sustained-release agent is released in a static release experiment;

[0058] Figure 5b This is a schematic diagram of electron microscope scanning after the sustained-release agent is released in a static release experiment;

[0059] Figure 6a Schematic diagram of the effect of different wax-sand ratios on the release of sustained-release agent in static release experiments;

[0060] Figure 6b This is a schematic diagram showing the effect of different sodium persulfate contents on the release of the sustained-release agent in a static release experiment;

[0061] Figure 7a This is a data comparison chart of the static release experiment and the simulated control experiment (the wax-sand ratio in the figure is 1:1);

[0062] Figure 7b This is a data comparison chart of the static release experiment and the simulated control experiment (the wax-sand ratio in the figure is 1:2);

[0063] Figure 7c This is a data comparison chart of the static release experiment and the simulated control experiment (the wax-sand ratio in the figure is 1:4);

[0064] Figure 7d This is a data comparison chart of the static release experiment and the simulated control experiment (the wax-sand ratio in the figure is 1:6);

[0065] Figure 8a This is a data comparison chart of the static release experiment and the simulated control experiment (the sodium persulfate content is 2g);

[0066] Figure 8b This is a data comparison chart of the static release experiment and the simulated control experiment (the sodium persulfate content is 4g);

[0067] Figure 8c This is a data comparison chart of the static release experiment and the simulated control experiment (the sodium persulfate content is 6g);

[0068] Figure 8d This is a data comparison chart of the static release experiment and the simulated control experiment (the sodium persulfate content is 8g). DETAILED DESCRIPTION

[0069] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0071] See also Figure 1 In one embodiment of the present application, a method for preparing a sustained-release agent is provided, comprising preparing the sustained-release agent according to the volume of the sustained-release agent, the mass of the active ingredient contained per unit volume, and the wax-sand ratio of the mass of paraffin wax to the mass of quartz sand. The active ingredient is sodium persulfate, and the process of preparing the sustained-release agent comprises:

[0072] (I) firstly adding paraffin wax into anhydrous ethanol, heating and melting, and then adding sodium persulfate, mesoporous manganese oxide, quartz sand, Span-80 and polyethylene glycol according to a ratio, mixing and stirring at 65° C. to obtain a molten material; the mesoporous manganese oxide is prepared by a hard template coupled nano-etching method;

[0073] (II) The molten material obtained in step (I) is quickly poured into a mold and cooled at room temperature to obtain the product.

[0074] As the specific process of this embodiment discloses, specifically, sodium persulfate (Na 2 S 2 O 8 ), manganese nitrate (Mn(NO 3 ) 2 ) were all analytically pure, quartz sand (SiO 2 ) was purchased from Shanghai McLean Biochemical Technology Co., Ltd. Commercial manganese dioxide was purchased from Xilong Chemical Co., Ltd. Anhydrous ethanol (C 2 H 6 O) and sodium hydroxide (NaOH) were all analytically pure, paraffin wax and polyethylene glycol-4000 were purchased from Sinopharm Chemical Reagent Co., Ltd. of chemically pure. Span-80 was purchased from Shenzhen Biaole Industrial Co., Ltd. of analytically pure. SBA-15 was purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd. Sodium bicarbonate (NaHCO 3 ) and potassium iodide (KI) were analytically pure and purchased from Shanghai Lingfeng Chemical Reagent Co., Ltd. The preparation instruments included: HC-2518 high-speed centrifuge (Anhui Zhongke Zhongjia Scientific Instrument Co., Ltd.); DF-101S heat-collecting constant temperature heating magnetic stirrer (Hangzhou David Hangzhou David Science and Education Instrument Co., Ltd.); DL-I-15 desktop closed electric furnace (Tianjin Taisite Instrument Co., Ltd.).

[0075] The preparation process of persulfate sustained-release agent is shown in the figure. For example, the mass of quartz sand of the sustained-release agent is 12g, the mass of sodium persulfate is 4g, the wax-sand ratio is 1:1, 1:2, 1:4, 1:6, and the other components remain unchanged (the mass of polyethylene glycol-4000 is 1.0g, the mass of mesoporous manganese oxide is 0.5g, and the mass of Span-80 is 0.1ml). For another example, the sustained-release agent with sodium persulfate content of 2g, 4g, 6g, and 8g, the mass of quartz sand is 12g, the mass of paraffin is 12g, and the other components remain unchanged (the mass of polyethylene glycol-4000 is 1.0g, the mass of manganese dioxide is 0.5g, and the mass of Span-80 is 0.1ml). The mold for preparing a cubic sustained-release agent is, for example, a cube-shaped 1cm×1cm×1cm, and 12 sustained-release agents are obtained in each batch, each weighing about 2.5g. The above preparation processes can be used to conduct static release experiments to prove the rationality of the component design scheme. It is understandable that when preparing a sustained-release agent, the absolute mass of a single sustained-release agent is limited by various factors and is difficult to accurately control. However, this does not affect the implementation of the schemes of each embodiment of the present application. Each embodiment changes the preparation process of the sustained-release agent by controlling the wax-sand ratio and the mass of sodium persulfate contained per unit volume. The subsequent static release experiment and simulation control experiment are sufficient to prove the feasibility of each embodiment.

[0076] See also Figure 2 , ordered mesoporous manganese oxide was prepared by hard template coupled nanoetching method (Wang Ting, Xu Kunmiao, Wu Liguang, et al. Construction and performance of sustained-release agent based on tetracycline removal in groundwater [J]. Journal of Environmental Sciences, 2022, 42(06): 167-177.), and the preparation process is shown in the figure.

[0077] See also Figure 3 An embodiment of the present application provides a method for designing a sustained-release agent component. The sustained-release agent includes quartz sand, paraffin wax, and an active ingredient. The method for designing a sustained-release agent component includes:

[0078] Step S100, presetting different component design schemes, each component design scheme having the same volume of sustained-release agent, the component design scheme having a first variable and a second variable, the first variable being the mass of active ingredient contained per unit volume, and the second variable being the wax-to-sand ratio of the mass of paraffin wax to the mass of quartz sand;

[0079] Step S200, simulating the sustained release process of different component design schemes to obtain the mass-time release curve of the active ingredient in each component design scheme, including:

[0080] Step S210, simulating the rapid dissolution process of the active ingredient on the surface of the sustained-release agent to obtain a first release curve of the active ingredient changing with time;

[0081] Step S220, simulating the dissolution process of the active ingredient in the sustained-release agent to obtain a second release curve of the active ingredient changing with time, the simulation process comprising: obtaining an effective diffusion coefficient based on the first variable and the second variable, simulating and solving the second release curve based on Fick's law and the effective diffusion coefficient, and the second release curve is connected with the first release curve to form a mass-time release curve;

[0082] Step S300, determining a matching preferred component design scheme according to the matching degree between the expected stable concentration and the mass-time release curve in the application scenario.

[0083] In this embodiment, the sustained-release agent can be a cube, and the application scenario can be, for example, groundwater ecological restoration, which has the desired stable concentration required for the active ingredient. Since the first release curve and the second release curve play a leading role in different time periods, and both release the active ingredient in the corresponding time period, the mass-time release curve of the active ingredient can be obtained by connecting the curves to each other. The active ingredient can be selected as a persulfate, such as sodium persulfate, and each embodiment is further explained using sodium persulfate as an example of the active ingredient.

[0084] This embodiment simulates the sustained release of different component design schemes into two processes, namely step S210 and step S220, which improves the reliability of different component design schemes. Step S210 mainly simulates the rapid dissolution of the surface of the sustained-release agent when it first enters the solution, which belongs to the first stage of the liquid phase. Step S220 mainly simulates the slow dissolution of the internal solid after the surface of the sustained-release agent is rapidly dissolved, which belongs to the second stage of the solid phase.

[0085] In addition, this embodiment obtains the effective diffusion coefficient through the first variable and the second variable, and simulates the sustained release process with discrimination for different component conditions, further improving the wide applicability of the simulated release of the sustained release agent. The reliability of the auxiliary design component of this embodiment can be reflected by providing comparative static release experiments and simulated control experiments in the following examples.

[0086] Step S200 as a whole can be regarded as a mathematical model for the release of a sustained-release agent, which divides the release process into two stages, including a first stage corresponding to step S210 and a second stage corresponding to step S220. The first stage represents the rapid release process of the sustained-release agent, which mainly involves the process in which the surface of the sustained-release agent and the sodium persulfate within a certain range from the surface are directly in contact with water and are rapidly dissolved. The second stage is a stable release process, in which water enters the interior of the sustained-release agent along the pores, and the sodium persulfate is mainly released through the diffusion process. At this time, the amount of water in the pores is not enough to quickly dissolve the surrounding sodium persulfate, and the diffusion process becomes the main rate-limiting step in this stage.

[0087] The following table explains the relevant parameters in step S200:

[0088]

[0089] For step S210, in the first few days after the release, the release rate is very high and follows an exponential relationship that can be expressed by first-order kinetics:

[0090]

[0091] Where, t 1 is the duration of the first release curve. The first release curve is a rapid release process, and the end of the duration is the number of days when the rapid release ends;

[0092] M t1 is sodium persulfate at t 1 The release quality over time (i.e. the total amount of sodium persulfate released in the first stage);

[0093] M 总 is the total added mass of active ingredients in each component design, i.e., the raw material mass of sodium persulfate in one sustained-release agent. 总 It represents the release mass of sodium persulfate in the sustained-release formulation at infinite time.

[0094] α is a correction coefficient, with a value range of 0.50 to 0.85, and k is a rapid release constant, with a value range of 0.05 to 1.5. Accordingly, a curve of the change of the sodium persulfate release mass over time in the first stage is obtained, that is, a first release curve is obtained.

[0095] See also Figure 4 For step S220, i.e. the second stage, the dissolution and diffusion process of sodium persulfate in the sustained-release agent can be solved based on Fick's law, as shown in formula (2):

[0096]

[0097] J is the diffusion flux;

[0098] M 2 To simulate the mass of sodium persulfate in the dissolution process of sodium persulfate inside the sustained-release agent, it increases with time, that is, the cumulative release mass of sodium persulfate released after t time in the second stage;

[0099] C is the concentration of active ingredients in the solution in the simulation scenario, specifically the concentration of sodium persulfate dissolved in water constructed by the mathematical model;

[0100] De is the effective diffusion coefficient;

[0101] x is half of the side length of the cube-shaped sustained-release agent that has not yet dissolved inside the sustained-release agent, referred to as the length of the undissolved area;

[0102] S is the surface area of ​​the cubic sustained-release agent at a certain moment.

[0103] The effective diffusion coefficient can be obtained from the first and second variables using the following formula:

[0104] De=AB*ln(X 1 )+C*X 2

[0105] In the formula, De is the effective diffusion coefficient, A, B, and C are all constants, and X 1 represents the second variable, X 2 represents the total added mass of sodium persulfate in each component design scheme, X 2 Obtained according to the first variable and the volume of the sustained-release agent. Specifically, A is 1.36×10 -6 , B is 1.27×10 -5 , C is 2.45×10 -6 .

[0106] The surface area of ​​a cubic sustained-release agent at a certain moment can be calculated using the following formula:

[0107] S=24x 2 (3)

[0108] Substituting formula (3) into formula (2) and moving S to the right side of the formula, we can get formula (4)

[0109]

[0110] In the process of simulating and solving the second release curve, the mass of sodium persulfate of the second release curve is simulated in the following manner: Including: integrating equation (4) using boundary conditions, when x is between 0 and a, the concentration C at the boundary of the undissolved region = C s ; When x = a, C = C a , the formula (5) for the mass release of sodium persulfate in the sustained-release agent was obtained, and further arrangement gave the formula (6):

[0111]

[0112] In the formula, a is half of the side length of the cube-shaped sustained-release agent, referred to as the second-stage boundary length;

[0113] V is the volume of the solution in the simulation scenario, referred to as the volume of water;

[0114] C S is the maximum solubility of sodium persulfate in the simulated scenario solution, that is, the maximum solubility of sodium persulfate in water, which is 550 kg / m 3 ;

[0115] Ca is the concentration of sodium persulfate in the aqueous phase, where C a is the solubility of sodium persulfate at the end of the first release curve, i.e., the solubility of sodium persulfate at the end of the first stage.

[0116] The rate of the undissolved diffusion zone in the sustained-release agent to the dissolved diffusion zone is shown in Equation (7):

[0117]

[0118] In the formula, A is the first variable, specifically representing the mass of sodium persulfate contained in a unit volume of the sustained-release agent.

[0119] According to the law of conservation of mass, equating Equation (6) to Equation (7) gives Equation (8)

[0120]

[0121] The cumulative mass of sodium persulfate released after time t (t≥t 1 ) is given by Equation (9)

[0122] M 2 = A(8a 3 - 8x 3 ) (9)

[0123] At this time, the concentration of sodium persulfate in the aqueous phase (C a ) is expressed by Equation (10)

[0124]

[0125] Substituting Equation (10) into Equation (8) gives Equation (11)

[0126]

[0127] Simplifying Equation (11) gives Equation (12)

[0128]

[0129] According to the boundary conditions, when t = t 1 , x = a, and when t≥t 1 , integrating for x (0≤x < a) gives the controlled release equation (13)

[0130]

[0131] Define the following dimensionless parameters in the form shown in Equation (14):

[0132]

[0133] Based on the above dimensionless parameters, equation (13) is converted into equation (15)

[0134]

[0135] Since this equation is an implicit function, this paper uses Matlab software to jointly solve the second-stage release amount M using formulas (13) and (9): t2 Since in the simultaneous equations, under the premise that the volume of the cubic sustained-release agent is determined, the first variable (the mass of the active ingredient contained per unit volume) and the second variable (wax-sand ratio) are used as input parameters, and on the basis of the effective diffusion coefficient De being obtained in relation to the first variable and the second variable, the effective diffusion coefficient can be combined to obtain the second-stage release amount M. t2 Then the second stage release amount M is obtained t2 The curve of change over time is the second release curve obtained by simulation.

[0136] Based on this, the total release percentage can be further calculated:

[0137]

[0138] Static release test

[0139] In order to verify the feasibility of the sustained-release agent component design method of each embodiment of the present application, the applicant conducted experimental verification based on several examples in the preparation process.

[0140] See also Figure 5a and Figure 5b , the sustained-release agent was characterized before and after release by scanning electron microscopy (SEM). It can be seen that the surface of the sustained-release agent is relatively smooth and has fewer holes before release, while larger holes and pores appear in the sustained-release agent after release. This may be mainly because during the release process, water dissolves the sodium persulfate near the surface of the sustained-release agent, and then penetrates into the interior of the sustained-release agent along the pores, dissolving the sodium persulfate in the matrix and diffusing it out. The specific instruments used are S-4800 scanning electron microscope (Hitachi, Japan); TU-1901 double-beam UV-visible spectrophotometer (Beijing Puxi General Instrument Co., Ltd.).

[0141] See also Figure 6a The figure shows the effect of different wax-sand ratios on the release of sustained-release agents. 总It refers to the mass of sodium persulfate released by the sustained-release agent over time / the maximum mass of sodium persulfate that can be released by one sustained-release agent. As shown in the figure, as the proportion of quartz sand gradually increases, the release rate of the sustained-release agent also accelerates. When the ratio of paraffin to quartz sand is 1:1, the initial release rate is slow, and on the 9th day, the release rate reaches 60%. This may be due to the large proportion of paraffin mass, and the relatively dense structure of the prepared sustained-release agent, making it difficult for the sodium persulfate in the sustained-release agent to dissolve and diffuse out. When the mass proportion of quartz sand increases, the initial release rate of the sustained-release agent increases significantly. This may be due to the larger particle size of quartz sand, which increases the porosity of the sustained-release agent and makes the structure loose, which is conducive to water entering the interior of the sustained-release agent and increasing the mass transfer efficiency. Therefore, the smaller the wax-sand ratio, the more conducive it is to the dissolution and diffusion of the sustained-release agent.

[0142] See also Figure 6b , the figure shows the effect of different sodium persulfate contents on the release of the sustained-release agent. As shown in the figure, an increase in the sodium persulfate content will lead to an accelerated initial release rate of the sustained-release agent. When the sodium persulfate content is 2g, it may be due to the low content, there is more paraffin around, and because paraffin is a hydrophobic substance, it is difficult for water to penetrate. When the sodium persulfate content increases to 4g and 6g, the release rate of the sustained-release agent increases significantly. When it is increased to 8g, the release rate reaches 60% on the first day. This shows that increasing the sodium persulfate content can change the release time of the sustained-release agent.

[0143] Simulated control experiment

[0144] In order to verify the feasibility of the sustained-release agent component design method of each embodiment of the present application, the applicant evaluated the sustained-release agent component design method based on several examples in the preparation process, specifically the evaluation of the simulation model provided in step S200. The model evaluation adopts the correlation coefficient (R 2 ) and root mean square error (RMSE), R 2 The larger the value, the closer it is to 1 and the smaller the RMSE value, the more accurate the model is. The calculation formula is as follows:

[0145]

[0146] In the formula, y i is the measured value, Y i is the predicted value, O i is the measured average value, i is the sample sequence, and n is the sample size.

[0147] As shown in the figure, the first-order kinetic model, the diffusion model and the two-phase diffusion model proposed in this paper are used to calculate the experimental conditions of the sustained-release agents of different components and fit the experimental data. The two-phase diffusion model, i.e., step S200, includes the first stage simulation belonging to the liquid phase and the second stage simulation belonging to the solid phase. The determination coefficient R is calculated specifically through the following table 2 The calculation accuracy of different models is analyzed by using the root mean square error (RMSE).

[0148] Evaluation results of three models (R 2 , RMSE)

[0149]

[0150] See also Figure 7a to Figure 7d The slow-release agent showed a trend of rapid release at the beginning. The main reason was that the sodium persulfate on the surface of the slow-release agent and nearby was able to directly contact with water and was quickly dissolved. As the oxidant was released, the concentration difference in the solution continued to decrease, and diffusion became the main rate-limiting step in the later stage of release. The R of the first-order kinetic model 2 When the wax-sand ratio is 1:1, it reaches 0.976. However, as the wax-sand ratio decreases, R 2 The RMSE value also decreases, reaching 0.0325. This is because the first-order kinetics mainly considers the concentration of sodium persulfate itself, ignores the effect of diffusion, and does not take diffusion as the main rate-limiting step, resulting in the predicted value being higher than the experimental value and an increase in error. The predicted value of the diffusion model is higher than the experimental value when the wax-sand ratio is 1:1. When the wax-sand ratio increases, the predicted value of the model in the early stage is lower than the experimental value, and R 2 It drops below 0.9, and the RMSE is greater than 0.01. This may be because the model does not take into account the rapid release of the slow-release agent in the early stage. As the proportion of quartz sand in the slow-release agent increases, the permeability of the slow-release agent increases. As more water penetrates, more oxidants are released in the early stage, making the concentration gradient change smaller in the later stage. Therefore, the diffusion driven by the concentration gradient in the later stage will become more stable and fit the experimental value better. The two-phase diffusion model proposed in this paper takes into account the rapid release of the slow-release agent in the early stage and the diffusion process in the later stage. The determination coefficient R 2 Both are greater than 0.9, and RMSE is less than 0.007. Compared with the first two models, the fitting accuracy is the highest and can better calculate the release of sustained-release agents.

[0151] See also Figure 8a to Figure 8d , which are the release conditions of the sustained-release agents with different sodium persulfate contents and the simulation results of the first-order kinetic model, diffusion model and two-phase diffusion model. As can be seen from the figure, the two-phase diffusion model has the best overall fit, R 2The fitting degree of the first-order kinetic model is better when the sodium persulfate content is 2g and 4g, but when the sodium persulfate content increases to more than 4g, R 2 Less than 0.9. As the sodium persulfate content increases, the fitting curve of the diffusion model shifts to the right. This is because the sodium persulfate near the surface of the initial sustained-release agent will be dissolved by water, resulting in a higher concentration of sodium persulfate in the water. The diffusion model is calculated based on the concentration difference at the boundary. Too much sodium persulfate will make the model unable to identify the error caused by the early rapid dissolution. When the sodium persulfate content is 0.6g, R 2 reached 0.984, and when the sodium persulfate content increased to 8g, R 2 The two-phase diffusion model can stably calculate the release process of different sodium persulfate contents. 2 All are above 0.95.

[0152] In each embodiment of the present application, sodium persulfate is used as an oxidant, paraffin wax and quartz sand are used as adhesives, and reaction kinetics and diffusion theory are combined to construct a two-phase diffusion model corresponding to step S200 that describes the release behavior of the sustained-release agent.

[0153] In order to demonstrate the feasibility of the sustained-release agent component design method of each embodiment, this application prepared sustained-release agents with different wax-sand ratios and sodium persulfate contents, conducted static release experiments, and simulated the release experimental data using a first-order kinetic model, a diffusion model, and the two-phase diffusion model of this study. The results were compared with the experimental results to evaluate the accuracy and reliability of the model. Finally, the parameter change law of the two-phase diffusion model was explored.

[0154] The release experiment designed the release of slow-release agents with different wax-sand ratios and different persulfate contents, obtained the release data for more than 15 days, and used the first-order kinetics, diffusion model and the two-phase diffusion model proposed in this paper for simulation calculation. The results showed that the determination coefficient R of the two-phase diffusion model 2 The two-phase diffusion model is used as the implementation method of step S200, and the determination coefficient R 2 Most of them are above 0.95, which is higher than the first-order kinetic model and diffusion model.

[0155] The above data comparison with the static release experiment and the first-order kinetic model and the diffusion model is sufficient to prove the reliability of the slow-release agent component design method of each embodiment of the present application. The quartz sand and sodium persulfate content can effectively change the release rate of the slow-release agent. The slow-release agent component design method provided in each embodiment can quantitatively adjust the content of quartz sand and sodium persulfate to change the release process and simulate the life of the slow-release agent. The slow-release agent component design method provided in each embodiment helps to more accurately simulate the release mechanism and process of the slow-release agent, assist in the design of the slow-release agent and effectively apply it to in-situ groundwater remediation in different environments. It is of great significance to guide the design optimization of persulfate slow-release agents, as well as the preparation and field application of persulfate slow-release agents based on groundwater remediation.

[0156] The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. When the technical features in different embodiments are embodied in the same figure, it can be regarded that the figure also discloses the combination examples of the various embodiments involved.

[0157] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. A method for designing a sustained-release agent component, characterized in that: The sustained-release agent comprises quartz sand, paraffin and active ingredients, and the sustained-release agent component design method comprises: Different component design schemes are preset, each of which has the same volume of sustained-release agent, and the component design scheme has a first variable and a second variable, wherein the first variable is the mass of active ingredient contained per unit volume, and the second variable is the wax-to-sand ratio of the mass of paraffin wax to the mass of quartz sand; Simulate the sustained release process of different component design schemes to obtain the mass-time release curve of the active ingredient in each component design scheme, including: Simulating the rapid dissolution process of the active ingredient at the surface of the sustained-release agent to obtain a first release curve of the active ingredient changing with time; Simulating the dissolution process of the active ingredient in the sustained-release agent to obtain a second release curve of the active ingredient changing with time, the simulation process comprising: obtaining an effective diffusion coefficient according to the first variable and the second variable, simulating and solving the second release curve based on Fick's law and the effective diffusion coefficient, the second release curve and the first release curve forming the mass-time release curve; According to the matching degree between the expected stable concentration in the application scenario and the mass-time release curve, a matching preferred component design scheme is determined.

2. The method for designing sustained-release agent components according to claim 1, characterized in that: The active ingredient is persulfate.

3. The method for designing sustained-release agent components according to claim 1, characterized in that: The rapid dissolution process of the active ingredient at the surface of the sustained-release agent is simulated to obtain the first release curve of the active ingredient over time, using the following formula: Where M t1 is the release mass of the active ingredient at time t1, t1 is the duration of the first release curve, M 总 is the total added mass of the active ingredients in each component design scheme, α is the correction coefficient, and k is the rapid release constant.

4. The method for designing sustained-release agent components according to claim 1, wherein: The effective diffusion coefficient is obtained according to the first variable and the second variable using the following formula: De=AB*ln(X1)+C*X2 In the formula, De is the effective diffusion coefficient, A, B, and C are all constants, X1 represents the second variable, X2 represents the total added mass of the active ingredient in each component design scheme, and X2 is obtained based on the first variable and the volume of the sustained-release agent.

5. The method for designing sustained-release agent components according to claim 4, characterized in that: A is 1.36×10 -6 , B is 1.27×10 -5 , C is 2.45×10 -6 .

6. The method for designing sustained-release agent components according to claim 1, characterized in that: The sustained-release agent is in a cubic shape.

7. The method for designing sustained-release agent components according to claim 6, characterized in that: In the process of simulating and solving the second release curve, the mass of the active ingredient of the second release curve is simulated in the following manner: Where a is half the side length of the cube-shaped sustained-release dosage form; x is half of the side length of the cube-shaped sustained-release agent that has not yet dissolved inside the sustained-release agent; M2 is the mass of the active ingredient in the process of simulating the dissolution of the active ingredient in the sustained-release agent; V is the volume of the solution in the simulation scenario; C S is the maximum solubility of the active ingredient in the simulated scenario solution; C a is the solubility of the active ingredient at the end of the first release curve; De is the effective diffusion coefficient; C, is the concentration of active ingredients in the solution in the simulation scenario.

8. The method for designing sustained-release agent components according to claim 6, characterized in that: The effective diffusion coefficient is obtained according to the first variable and the second variable, and the second release curve is simulated and solved by combining the effective diffusion coefficient, and the following two equations are used to solve the curve: M2=A(8a3-8x3) Where a is half the side length of the cube-shaped sustained-release dosage form; x is half of the side length of the cube-shaped sustained-release agent that has not yet dissolved inside the sustained-release agent; A is the first variable; M2 is the mass of the active ingredient released cumulatively after t time in the process of simulating the dissolution of the active ingredient in the sustained-release agent; De is the effective diffusion coefficient; t1 is the duration of the first release curve; V is the volume of the solution in the simulation scenario; C S It is the maximum solubility of the active ingredient in the simulated scenario solution.

9. A method for preparing a sustained-release agent, characterized in that: The preferred component design scheme obtained in the sustained-release agent component design method according to any one of claims 1 to 8 is implemented, comprising: Determine the volume of the sustained-release agent according to the preferred component design scheme, and determine the mass of the active ingredient in the sustained-release agent according to the volume of the sustained-release agent and the mass of the active ingredient contained in the unit volume; Determine the wax-sand ratio of the mass of paraffin wax to the mass of quartz sand according to the preferred component design scheme; The sustained-release preparation is prepared.

10. The method for preparing a sustained-release agent according to claim 9, characterized in that: The active ingredient is sodium persulfate, and the process of preparing the sustained-release agent includes: (I) firstly adding paraffin wax into anhydrous ethanol, heating and melting, and then adding sodium persulfate, mesoporous manganese oxide, quartz sand, Span-80 and polyethylene glycol according to a ratio, mixing and stirring at 65° C. to obtain a molten material; the mesoporous manganese oxide is prepared by a hard template coupled nano-etching method; (II) The molten material obtained in step (I) is quickly poured into a mold and cooled at room temperature to obtain the product.

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