Device and method for monitoring release migration capability of plastic additive in water environment

Abstract

The invention discloses a device and a method for monitoring the release migration capability of a plastic additive in a water environment. The device comprises a horizontal rotating shaking table and at least one plastic additive release bottle mounted on the horizontal rotating shaking table, each release bottle comprises a bottle body used for storing a water medium, a bottle plug capable of sealing the bottle body and a light shield used for shielding light from the bottle body, a micro-plastic release cage and a solid-phase adsorption film are arranged in the bottle body in a suspended manner, and the micro-plastic release cage comprises a cage body used for storing a micro-plastic sample; the solid-phase adsorption film is used for adsorbing the plastic additive released by the micro-plastic release cage; the micro-plastic release cage and the solid-phase adsorption film are located at the same height of the bottle body, the solid-phase adsorption film is vertically arranged, and a horizontal distance is formed between the micro-plastic release cage and the solid-phase adsorption film. According to the invention, the release behavior of the plastic additive can be accurately monitored under the condition of'infinite pool ', and the device has good stability, leakproofness and efficient adsorption characteristic, and is suitable for long-term experimental research under different environmental conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental pollutant monitoring, and particularly relates to a device and method for monitoring the release and migration ability of plastic additives in water environment. Background Art

[0002] Since the birth of plastics in 1907, the plastics industry has developed rapidly. Not only has the production, use, and abandonment volume of plastics continued to increase, but researchers have also found that plastic additives (PAs) are also one of the important reasons for the toxicity of some plastic materials. Plastic additives will be released, exposed throughout the life cycle of plastic products, and play a key role in the sublethal toxicity of aquatic organisms. They can accumulate in organisms, threatening the aquatic ecosystem and thus posing potential hazards to humans. Plastic additives are divided into additive additives and reactive additives. Additive plastic additives do not chemically react with the plastic matrix, and their molecular structure is relatively free, making it easy to diffuse out of the matrix and be released into the environment. For these plastic additives that are "non-covalently" added to plastic polymers, resulting in the release and exposure of additives, they will be referred to as enriched free-state plastic additives hereinafter. Common free-state plastic additives, such as flame retardants, plasticizers, antioxidants, and ultraviolet stabilizers, have biological toxicity, may be amplified through the food chain, and threaten the ecosystem. Some also have high chemical stability and are prone to accumulate in the environment, becoming persistent organic pollutants (POPs). The release behavior of free-state plastic additives is an important factor affecting their environmental migration and exposure, directly affecting the environmental exposure level and thus affecting the ecological toxicity assessment.

[0003] By studying the release mechanism of free-state plastic additives, it is possible to more accurately evaluate their migration ability in the natural environment, providing a scientific basis for relevant risk assessment and pollution control. By improving experimental design and technical methods, it is possible to better simulate and predict the release and migration ability of plastic additives in the natural environment. Revealing the migration kinetic behavior of free-state plastic additives helps to predict environmental risks on a long time scale, provides data support for mathematical models, and thus contributes to risk assessment and pollution control. At the same time, it also helps enterprises develop more environmentally friendly plastic additives or production processes with reduced additive release, reducing the potential risks of additives to the environment and human health, and helping to achieve the sustainable goal of plastic pollution control.

[0004] Current research on the release of plastic additives lacks a unified monitoring method, making it difficult to comprehensively evaluate environmental risks. Traditional experiments mostly use static systems and cannot simulate the complex migration behaviors in the natural environment. Since plastic additives released into natural water bodies have the characteristics of low solubility and high partition coefficients, such as phthalic acid plasticizers, this method has limitations for plastic additives. In practical applications, the "Infinite sink condition" is mainly applicable to simulate systems with strong environmental dilution and high fluidity, such as open environments like natural water bodies and rivers. The "Infinite sink condition" is a hypothetical condition used to describe the release or diffusion behavior of solutes. Its main assumptions include: (1) The released solute is diluted to an extremely low concentration and does not significantly change the initial state of the receiving environment; (2) When the solute diffuses from the release source to the receiving environment, the environment does not have a counteracting effect on the solute concentration at the release source. In practical applications, the "Infinite sink condition" is mainly applicable to systems with strong environmental dilution and high fluidity, such as open environments like natural water bodies and rivers. Methods for realizing the "Infinite sink condition" of the release device include flow-through experiments, large-volume simulation experiments, semi-dynamic leaching experiments, and on-site deployment. Research methods for the leaching of plastic additives in the environmental context have great limitations in terms of environmental relevance. For example, due to the limited solubility and the influence of release, they cannot reflect the leaching changes in the real water environment. Currently, in order to monitor the release and migration ability of plastic additives in the water environment, there are no relevant devices and methods that can achieve the "Infinite sink condition" publicly available. Summary of the Invention

[0005] The purpose of the present invention is to provide a device and method for monitoring the release and migration ability of plastic additives in the water environment, which can achieve the "Infinite sink condition". The "Infinite sink condition" has the advantages of a constant concentration gradient, infinite dilution, and a stable release end. By monitoring and analyzing the environmental levels of different forms of plastic additives, the release and migration ability of plastic additives can be evaluated and characterized.

[0006] In a first aspect, the present invention provides a device for monitoring the release and migration ability of plastic additives in the water environment, comprising a horizontal rotary shaker and at least one plastic additive release bottle mounted on the horizontal rotary shaker;

[0007] Each of the plastic additive release bottles includes a bottle body for storing an aqueous medium, a bottle stopper for sealing the bottle body, and a light-shielding cover for shading the bottle body. A microplastic release cage and a solid-phase adsorption membrane are suspended in the bottle body. The microplastic release cage includes a cage body for storing microplastic samples, and the solid-phase adsorption membrane is used to adsorb the plastic additives released by the microplastic release cage;

[0008] The microplastic release cage and the solid-phase adsorption membrane are located at the same height in the bottle body. The solid-phase adsorption membrane is arranged vertically, and there is a horizontal distance between the microplastic release cage and the solid-phase adsorption membrane.

[0009] In at least one embodiment of the present invention, the bottle body is an Erlenmeyer flask, and the microplastic release cage and the solid-phase adsorption membrane are suspended in the bottle body by a rigid wire fixed to the bottle stopper;

[0010] The horizontal distance between the microplastic release cage and the solid-phase adsorption membrane is 1-2 cm.

[0011] In at least one embodiment of the present invention, the average diameter of the pores of the cage body of the microplastic release cage is ≤2 mm;

[0012] The material of the cage body of the microplastic release cage is stainless steel;

[0013] The cage body of the microplastic release cage is spherical. In the bottle body with a capacity of 150-750 mL, the diameter of the cage body is 20 mm-50 mm, preferably 30 mm.

[0014] In at least one embodiment of the present invention, the solid-phase adsorption membrane is a triolein-embedded acetate membrane (TECAM) or a polystyrene-N-pyrrolidone copolymer-embedded acetate membrane (HECAM);

[0015] In the bottle body with a capacity of 150-750 mL, the size of the solid-phase adsorption membrane is 2 cm * 3 cm.

[0016] In at least one embodiment of the present invention, the device further includes a sealed box, which includes a box body and a box cover. The horizontal rotary shaker is installed in the box body;

[0017] A heater is provided on the lower surface of the box cover for heating the plastic additive release bottle, and a temperature detector is provided on the box body;

[0018] A heat dissipation device is provided on the box body;

[0019] A control panel is provided on the upper surface of the box cover for controlling the heating device and the horizontal rotary shaker.

[0020] In a second aspect, the present invention provides a method for monitoring the release and migration ability of plastic additives in the water environment, which is characterized in that the device for monitoring the release and migration ability of plastic additives in the water environment described in any one of the above is used, and it includes the following steps:

[0021] S1. Place the microplastic sample in the microplastic release cage and add an aqueous medium into the bottle body so that the microplastic cage is completely immersed in the aqueous medium;

[0022] S2. Start the horizontal rotary shaker for oscillation. The plastic additives released from the microplastic release cage are continuously adsorbed by the solid-phase adsorption membrane, and at predetermined time points, the contents of the plastic additives in the aqueous medium and the solid-phase adsorption membrane are measured respectively;

[0023] S3. Calculate the R value at the predetermined time point according to the following formula. Taking time as the abscissa and the R value as the ordinate, plot the release kinetic curve of the plastic additive;

[0024]

[0025] In formula (4-1), M t is the mass of the plastic additive in the solid-phase adsorption membrane at time t, and M0 represents the total mass of the plastic additive in the aqueous medium, the solid-phase adsorption membrane and the remaining microplastics at time 0.

[0026] The present invention has the following beneficial effects:

[0027] By introducing a solid-phase material with high adsorption capacity as a pollutant trap, the device of the present invention ensures that the release kinetics of the solute is controlled by the desorption process, reduces the interference of other factors such as adsorption and absorption, and aims to more effectively simulate low-solubility additives and simulate the release kinetics under natural environmental conditions.

[0028] The present invention can provide "infinite pool" conditions for an integrated plastic additive leaching experiment system to keep the solute concentration in the solution close to zero and achieve continuous release under kinetic control. This system is suitable for long-term leaching experiments, adsorbs specific forms of plastic additives through a membrane for precise quantitative analysis, can simulate the continuous release behavior of plastic additives in a natural water environment, and quantitatively analyze the release and migration ability of plastic additives by dynamically monitoring the levels of different forms of plastic additives. Among them, the TECAM membrane or HECAM membrane selected as the solid-phase adsorption material can be analyzed by solvent back-extraction after the leaching experiment to study the relationship between the pollutant release amount and time, recover the adsorbed plastic additives from the membrane, accurately measure their release amounts, and ensure the accuracy and repeatability of the experimental data.

[0029] The present invention uses a solid-phase material with high adsorption capacity to ensure that the kinetics is controlled by the desorption release of additives, reducing the interference in the adsorption and absorption processes. It can be used to monitor and study the release and migration ability of plastic additives in different environmental media (water, sediment or soil) to evaluate their potential impact on the ecosystem. For example, by trapping and analyzing pollutants, scientific data can be provided to regulatory agencies for formulating regulations and guidelines regarding plastic additives and their potential ecological and health risks, reducing the pollution risk of plastic products and plastic additives to the water environment. The present invention can also be applied to support the research and development of new environmentally friendly materials. At the initial and final stages of research and development, by accurately evaluating the release performance of additives, plastic products with low pollution or controlled release can be developed to ensure the safety and environmental friendliness of the products. Or it can give full play to the unique advantages of your system in desorption kinetics research and pollutant trapping in fields such as supporting scientific research and experimental teaching in related fields.

[0030] The present invention provides a method for quantitatively analyzing the release of different types of plastic additives (such as light stabilizers, antioxidants, etc.) in various water environmental media, and further evaluating their potential impact on the environment.

[0031] In summary, the device and method of the present invention can accurately monitor the release behavior of plastic additives, have good stability, airtightness and high adsorption characteristics, and are suitable for long-term experimental research under different environmental conditions. Brief Description of the Drawings

[0032] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0033] Figure 1 is a device of the present invention for monitoring the release and migration ability of plastic additives in the water environment.

[0034] Figure 2 is a schematic structural diagram of a plastic additive release bottle in the device of the present invention for monitoring the release and migration ability of plastic additives in the water environment.

[0035] Figure 3 is a scanning electron microscope effect diagram of HECAM in the second embodiment of the present invention.

[0036] Figure 4 is a scanning electron microscope effect diagram of TECAM in the second embodiment of the present invention.

[0037] Figure 5 is an enrichment kinetic curve of the HECAM membrane of the membrane sheet for hydrophilic plastic additives in the third embodiment of the present invention.

[0038] Figure 6 This is the release kinetic curve of antioxidant I168 in the fourth embodiment of the present invention.

[0039] Figure 1 - Figure 2 The markings in it are as follows:

[0040] 100 - Plastic additive release bottle; 101 - Bottle body; 102 - Bottle stopper; 103 - Microplastic release cage; 104 - Solid-phase adsorption membrane; 105 - Copper wire;

[0041] 201 - Box body; 202 - Box cover; 203 - Heater; 204 - Temperature detector; 205 - Heat dissipation device; 206 - Control panel; 301 - Motor; 302 - Vertical beam; 303 - Rocker; 304 - First support cross beam; 305 - Second support cross beam. Detailed implementation manners

[0042] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0043] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "upper", "lower", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the system or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation of the present invention. In addition, the use of terms such as "first", "second", etc. to limit components is only for the convenience of distinguishing the above components. Without further declaration, the above terms have no special meanings and cannot be construed as indicating or implying relative importance.

[0044] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "set", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] As described in the background art, the research methods for the leaching of plastic additives in the environmental background have great limitations in terms of environmental relevance. Therefore, in the present invention, passive sampling membranes (TECAM membrane and HECAM membrane) are introduced as solid-phase adsorption phases to achieve the "infinite pool" condition of the release device, ensure that the desorption kinetics of the solute can effectively control its release process, and thus simulate more realistic environmental conditions.

[0046] Based on this, in the first part, as Figure 1 shown, the device of the present invention for monitoring the release and migration ability of plastic additives in the water environment includes a horizontal rotary shaker and at least one plastic additive release bottle installed on the horizontal rotary shaker; as Figure 2 shown, each plastic additive release bottle 100 includes a bottle body 101 for storing the water medium, a bottle stopper 102 for sealing the bottle body, and a light-shielding cover (not shown in the figure) for shading the bottle body. A microplastic release cage 103 and a solid-phase adsorption membrane 104 are suspended in the bottle body 101. The microplastic release cage 103 includes a cage body for storing microplastic samples, and the solid-phase adsorption membrane 104 is used to adsorb the plastic additives released by the microplastic release cage; the microplastic release cage 103 and the solid-phase adsorption membrane 104 are at the same height in the bottle body 101, that is, the solid-phase adsorption membrane is parallel to the plastic release cage and at the same liquid level. The solid-phase adsorption membrane 104 is arranged vertically, and there is a horizontal distance between the microplastic release cage 103 and the solid-phase adsorption membrane 104.

[0047] The light-shielding cover is composed of aluminum foil or tin foil tightly wound and wrapped around the bottle body. The leaching process should be kept in the dark to prevent the photolysis of plastic polymers and plastic additives during the release process. Specifically, for experiments on polyethylene (PE), polyvinyl chloride (PVC), and polystyrene (PS) plastics, photoaging-induced photodegradation of the polymer structure and a decrease in crystallinity may occur, which may lead to changes in the polymer structure and should be leached in the dark.

[0048] The bottle stopper 102 is a ground glass bottle stopper. When in use, it is further sealed with laboratory sealing materials to prevent the bottle stopper from popping out and becoming a safety hazard. The sealing materials should be selected from laboratory sealing films or solid paraffin with ductility, sealing performance, and hydrophobicity, which can ensure the tightness of the system when assembling and integrating the plastic additive release device, make it complete and controllable, and prevent oxidation, evaporation, and cross-contamination; the bottle body should be of an appropriate capacity according to the volume of the leaching medium and microplastics, and its volume is estimated through a preliminary experiment. For example, for a conical flask and a conical flask bottle stopper, a glass conical flask with a capacity of 150 - 750 mL (such as 250 mL) and its matching bottle stopper can be selected.

[0049] In an embodiment, the bottle body is a conical flask, and the microplastic release cage 103 and the solid-phase adsorption membrane 104 are suspended in the bottle body 101 by a hard wire fixed to the bottle stopper 102.

[0050] Exemplarily, the microplastic release cage 103 and the solid-phase adsorption membrane 104 are fixed with copper wires 105 respectively, that is, the copper wire for hanging the solid-phase adsorption membrane and the copper wire for hanging the microplastic release cage hang down along the opposite sides of the bottle mouth respectively. The two copper wires are parallel and of equal length, and are suspended at the middle position of the liquid during use. According to the different sizes of the bottle mouth, the horizontal distance between the microplastic release cage 103 and the solid-phase adsorption membrane 104 is 1-2 cm. This horizontal distance is convenient for operation and can ensure that the swinging space and swinging amplitude are within a suitable range.

[0051] In one embodiment, the average diameter of the pores of the cage body of the microplastic release cage 103 is ≤2 mm, and the pores are evenly distributed on the surface of the cage body to ensure that the microplastic samples placed in the microplastic release cage are retained in the release cage, that is, it can ensure that the microplastic particles are in contact with the external liquid medium but will not leak, and can ensure smooth water flow and minimize particle blockage. The material of the cage body of the microplastic release cage is stainless steel to avoid rusting and other phenomena during subsequent leaching. The cage body of the microplastic release cage is spherical. In a bottle with a capacity of 150-750 mL, the diameter of the cage body is 20 mm-50 mm, preferably 30 mm. Exemplarily, the microplastic release cage 103 is made of two hemispherical stainless steel metal sheets with pores. When manufacturing, the two hemispherical metal sheets can be fixed into a whole with copper wires. The spherical release cage with this cage body diameter can provide enough internal space to accommodate 2-5 g of microplastic samples, and at the same time ensure sufficient contact between the samples and the water medium to improve the release efficiency. It should be noted that the microplastic release cage 103 is suspended in the bottle, and it is necessary to ensure that the cage is stable in the stirring and operation process, completely in contact with the liquid but will not sink to the bottom, and can be affected by water flow disturbance throughout the leaching process.

[0052] In one embodiment, the solid-phase adsorption membrane 104 is a triolein-embedded acetate membrane (TECAM) or a polystyrene-N-pyrrolidone copolymer-embedded acetate membrane (HECAM). This semi-permeable composite membrane is the diffusion membrane in two common passive samplers. It can not only control the diffusion rate of target compounds but also enrich target pollutants in environmental media through the diffusion mechanism during passive sampling to form a stable time-weighted average (TWA). The plastic additive release bottle is a key component providing "infinite sink" conditions for the leaching system. It ensures that the desorption and release process of solutes from the plastic matrix is always under kinetic control by efficiently adsorbing additives. The solid-phase adsorption membrane 104 is used to collect plastic additives released into the aqueous phase, ensuring a small change in the additive concentration in the aqueous phase, thereby achieving "infinite sink" conditions. The material of the solid-phase adsorption membrane 104 can be selected accordingly according to the target compound of the experiment. For example, if more attention is paid to hydrophilic substances, the HECAM membrane is selected as the solid-phase adsorption membrane; if the target compound is a hydrophobic compound, the TECAM membrane is selected as the solid-phase adsorption membrane.

[0053] In a bottle body with a volume of 150 - 750 mL, the size of the solid-phase adsorption membrane 104 is 2 cm * 3 cm. The size of the solid-phase adsorption membrane can be appropriately adjusted according to the dosage of microplastics. Among them, the size of 2 cm × 3 cm is suitable for being hung inside a standard experimental bottle of 150 - 750 mL (such as a 250 mL conical flask) to ensure that the membrane is always in the water medium during the soaking process and maintains a reasonable distance from the microplastic release cage. The solid-phase adsorption membrane of this size can provide sufficient adsorption capacity during the experimental period, making the adsorption process conform to the pseudo-first-order kinetic model, ensuring the stability of experimental data, and improving the enrichment efficiency.

[0054] In one embodiment, the device further includes a sealed box, which includes a box body 201 and a box cover 202. The horizontal rotary shaker is installed inside the box body 201; a heater 203 is provided on the lower surface of the box cover 202 for heating the plastic additive release bottle, and a temperature detector 204 is provided on the box body; a heat dissipation device 205 is provided on the box body, specifically arranged at the bottom of the box body; a control panel 206 is provided on the upper surface of the box cover for controlling the heating device and the horizontal rotary shaker, such as starting and stopping the heating device and the heating temperature, starting and stopping the horizontal rotary shaker and its rotation speed. The temperature detector 204 is used to detect the temperature of the shaker, so that the plastic additive release device can still operate at a constant temperature in winter or summer; the control panel 206 is a button-type operation, and can realize the setting of temperature and horizontal rotation speed adjustment. In the specific implementation process of the experimental system, referring to the environmental conditions, the temperature can be set to 21-25 degrees Celsius, and the rotation speed can be 40-150 rpm, and it can be adjusted according to the water flow fluctuations of the desired simulated environment, such as 40 rpm for slow flow and 150 rpm for turbulent flow.

[0055] In one embodiment, the horizontal rotary shaker is a device used for mixing liquids or keeping solutions homogeneous. By operating at a fixed speed under constant temperature conditions, it includes a motor 301, a vertical beam 302, a rocker 303, a first support cross beam 304 and a second support cross beam 305. The motor 301 provides power drive for the entire experimental device. The vertical beam 302 is connected to the first support cross beam 304 through the rocker 303. The first support cross beam 304 is connected to the second support cross beam 305, and the second support cross beam 305 is fixed on the box body 201. The motor 301 drives the rocker 303 to rotate, causing the first support cross beam 304 to rotate horizontally. The plastic additive release bottle is fixed on the first support cross beam 304 through a pressure spring fixing clip. The specific connection method can refer to the relevant literature ([1] Yangzhou Ruijie Environmental Protection Technology Co., Ltd. Special shaker for reverse osmosis membrane solution: 202323184624.7 [P]. 2024-06-11.). Among them, the pressure spring fixing clip provides necessary support and shockproof effects. The conical flask is firmly fixed on the platform through the pressure spring fixing fixture, avoiding sliding and overflow. The oscillation of the horizontal rotary shaker can promote the full contact between plastic fragments and water, accelerate the release of additives, and simulate the turbulent flow phenomenon of water under natural conditions.

[0056] During use, select plastic fragments containing additives with known concentrations, and cut the plastic fragments into microplastic fragments with a size of about 3 mm to 5 mm. Place the target microplastics in the microplastic release cage, assemble the integrated plastic additive release device according to the above assembly method, install the plastic additive release bottle on a horizontal rotary shaker, and secure it with a compression spring clamp. Wrap a light-shielding sleeve around the outside of the conical flask to prevent light from entering and affecting the experimental process. Adjust the temperature and stirring speed, and set appropriate temperature and stirring frequencies according to the experimental requirements. The specific temperature and stirring frequency should be determined according to the actual environmental conditions of the target research object. Start the horizontal rotary shaker to ensure stable operation of the system under constant temperature conditions, and conduct a long-term leaching experiment for 1 to 2 weeks. The leaching medium is an aqueous medium. Specifically, ultrapure water can be selected according to the above environmental conditions. If other studies are carried out, other leaching media such as seawater and seawater simulation liquid can also be used. The liquid level shall not exceed 2 / 3 of the height of the conical flask, but it is necessary to ensure that the microplastic release cage can be completely immersed in the aqueous phase, without any part sinking to the bottom or floating on the water surface.

[0057] The second part, the method for monitoring the release and migration ability of plastic additives in the water environment according to the present invention, uses the device for monitoring the release and migration ability of plastic additives in the water environment described in any one of the above, and includes the following steps:

[0058] S1. Place the microplastic sample in the microplastic release cage and add an aqueous medium into the bottle body so that the microplastic cage is completely immersed in the aqueous medium;

[0059] S2. Start the horizontal rotary shaker for oscillation. The plastic additives released from the microplastic release cage are continuously adsorbed by the solid-phase adsorption membrane, and at predetermined time points, the contents of the plastic additives in the aqueous medium and the solid-phase adsorption membrane are measured respectively;

[0060] S3. Calculate the R value at the predetermined time point according to the following formula. Take time as the abscissa and the R value as the ordinate to plot the release kinetic curve of the plastic additive;

[0061]

[0062] In formula (4-1), M t is the mass of the plastic additive in the solid-phase adsorption membrane at time t, and M0 represents the total mass of the plastic additive in the aqueous medium, the solid-phase adsorption membrane and the remaining microplastics at time 0.

[0063] In one embodiment, the plastic additive in the microplastic sample is an additive-type plastic additive, preferably one or two of an antioxidant and a light stabilizer, more preferably one or more selected from tris(2-chloroisopropyl) phosphate (TCIPP), tris(1,3-dichloro-2-propyl) phosphate (TDCIPP), tributyl phosphate (TNBP), benzyl butyl phthalate (BBP), cresyl diphenyl phosphate (CDPP), bis(2-butoxyethyl) phosphate (BMPP), di-n-hexyl phthalate (DNHP), diisononyl phthalate (DINP), tris(2-ethylhexyl) phosphate (TEHP); as an example, the microplastic additive is Irgafos 168. The particle size of the microplastic sample is 3 mm to 5 mm, and this particle size can ensure a large contact area between the plastic and water in the experiment, which is beneficial to the release of the additive. For each microplastic release cage with a diameter of 20 mm to 50 mm, the addition amount of the microplastic sample is 0.2 to 0.5 grams, and the ratio of the microplastic sample to the water medium, i.e., the solid-liquid ratio, is 0.8 to 1 g / L, and the liquid level does not exceed 2 / 3 of the height of the bottle body. This parameter setting is more conducive to achieving the "infinite pool" condition. The morphology of the microplastic sample is one or more of granular, flaky, and fibrous. The water medium is pure water, seawater or seawater simulation liquid, river water.

[0064] In one embodiment, the frequency of the oscillation is 40 to 150 rpm, and the continuous oscillation lasts for 7 to 14 days; optionally, the predetermined time points respectively include 0 hour, 6 hours, 12 hours, 24 hours, 2 days, 7 days, 14 days.

[0065] In one embodiment, optionally, the water changing step is further included during the oscillation, such as changing water at 8 h and 16 h respectively.

[0066] In one embodiment, the method further includes the step of evaluating the release and migration behavior of the plastic additive in the water environment, and the release and migration behavior is evaluated by the mass transfer coefficient B i and the formula for calculating B i is as follows:

[0067]

[0068] In the formula, D p is the diffusion coefficient in the plastic phase; l is the characteristic size of the plastic layer, which is represented by the radius of the plastic particle or half of the thickness of the plastic film; k m is the mass transfer coefficient of the plastic-water boundary layer, and the formula for calculating k m is as follows:

[0069]

[0070] In the formula, μ represents the dynamic viscosity of water (Pa·s); vm represents the LeBas molar volume (cm 3 / mol); c p represents the concentration of the plastic additive in the plastic matrix (μg / g); c w represents the concentration of the plastic additive in the aqueous phase (μg / L).

[0071] Furthermore, the diffusion coefficient D in the plastic phase p is obtained by fitting the migration of the plastic additive from the microplastics to the water environment, specifically obtained by fitting with the following formula:

[0072]

[0073] In the formula, M t is the mass of the plastic additive in the water medium at time t, and M0 represents the total mass of the plastic additive in the water medium, the solid-phase adsorption membrane and the remaining microplastics at time 0.

[0074] The present invention will be further described in detail below in conjunction with specific embodiments. The provided embodiments are only for clarifying the present invention, rather than limiting the scope of the present invention. The following provided embodiments can be used as a guide for those of ordinary skill in the art to make further improvements, and do not limit the present invention in any way.

[0075] The methods used in the following embodiments are all conventional methods unless otherwise specified, and are carried out according to the techniques or conditions described in the literature in this field or according to the product specifications. The materials, reagents, etc. used in the following embodiments can be obtained from commercial sources unless otherwise specified.

[0076] The TECAM membrane and HECAM membrane in the following embodiments are respectively prepared according to the preparation method disclosed in Example 1 of Chinese Patent Application No. 202310235514.4 (Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Preparation method of integrated flat membrane making machine and semi-permeable composite passive sampling membrane: 202310235514.4 [P]. 2023-08-11.).

[0077] Example 1: Prediction of the enrichment parameters of an unknown plastic additive by the solid-phase adsorption device in an integrated plastic additive leaching experiment system based on the "infinite pool" system

[0078] Since a complete pollutant database has not been established for the solid-phase adsorption device in the prior art, the applicant predicted the enrichment parameters of the solid-phase adsorption device for the target pollutant in the previous research, so as to predict the enrichment effect of the solid-phase adsorption device on the unknown plastic additive.

[0079] Specifically, the previous research was based on the theoretical speculation of the physical and chemical properties of known plastic additives (such as hydrophobicity, molecular structure, etc.) and combined with experimental verification to infer the enrichment behavior of unknown plastic additives. By systematically analyzing these known substances, a prediction model of the enrichment parameters of the target pollutants by the solid-phase adsorption device can be constructed, providing a theoretical basis for subsequent experiments and improving the accuracy and reliability of experimental results.

[0080] Among them, the data of organophosphate flame retardants and phthalate plasticizers obtained from the research of this research group were used as the estimated reference source for predicting the enrichment parameters of different plastic additives, mainly based on the following reasons: (1) As typical plastic additives, the physical and chemical properties such as molecular structure, hydrophobicity, and lipophilicity of organophosphate flame retardants and phthalate plasticizers are somewhat similar to those of other types of plastic additives. (2) The adsorption and enrichment behaviors of organophosphate flame retardants and phthalate plasticizers in the solid-phase adsorption device have been relatively deeply studied, which can provide reasonable theoretical support for the prediction of the enrichment parameters of other unknown plastic additives. Based on the existing research results, the enrichment trends and parameters of other plastic additives can be speculated.

[0081] By using organophosphate flame retardants and phthalate plasticizers as reference data, a prediction method applicable to other types of plastic additives can be gradually derived, and the accuracy of the prediction results can be improved through similar experimental verification, which can provide guidance for the prediction of different plastic additives in the future. Therefore, their enrichment behaviors in the solid-phase adsorption device can be used as an important reference for predicting the enrichment parameters of different types of plastic additives. The data in Table 1 have been publicly disclosed in the doctoral dissertation "Gao Xiaozhong, Passive Sampling Study on the Exposure Fate of Organophosphate Flame Retardants and Other PBT Pollutants in Water Bodies", and the public can consult it by themselves (Gao Xiaozhong. Passive Sampling Study on the Exposure Fate of Organophosphate Flame Retardants and Other PBT Pollutants in Water Bodies [D]. Beijing: University of Chinese Academy of Sciences, 2019.).

[0082] Table 1 Comparison Table of Enrichment Parameters of Reference Plastic Additives and Target Plastic Additives (Antioxidants and Light Stabilizers)

[0083]

[0084]

[0085] Example 2: Experimental design of an integrated plastic additive leaching experimental system based on the "infinite pool" system.

[0086] This embodiment provides a method for experimental design of the enrichment process of target plastic additives by a solid-phase adsorption device. Before the experiment starts, it is necessary to master the enrichment parameters of plastic additives under the condition of the same "infinite pool". Therefore, it is assumed that the experiment changes the medium (water) so that the concentration fluctuation of the target plastic additive in the medium is less than 20%, that is, it is ensured that the amount of the plastic additive enriched in the leaching medium should not affect the total amount of system pollutants, so as to simulate the same conditions as achieving the "infinite pool" with the solid-phase adsorption device. The focus of this embodiment is on the calculation method of the water change cycle before the experiment starts, providing a basis for subsequent evaluation of the release behavior of plastic additives in the water environment.

[0087] During the re-verification process, the hypothesis is proposed that the enrichment mass in the first hour is the total amount of the 50-fold LOQ concentration sample (V s = 1 mL).

[0088] M t = m×(C0×C×t) = (50×LOQ)×V s (2-1)

[0089] Wherein, m is the mass of the solid-phase adsorption membrane (ng), C0 is the initial concentration of the target substance (ng / L), C is the concentration in the solution (ng / L), and t is the experimental time (h). In the experimental design, it is assumed that the enrichment mass in the first hour is 50 times the amount of the LOQ concentration sample, and the solution volume Vs is set to 1 mL.

[0090] Assume 4×t 1 / 2 > 24 hr, then it is considered to reach the equilibrium state within 24 hours of the experiment. According to the previous research of the inventor team on reference plastic additives, the enrichment state of the solid-phase adsorption device (HECAM semi-permeable composite membrane or TECAM) of the target plastic additive at the end of the preliminary experiment (the 24th hour) is speculated, and it is judged whether water needs to be changed during the experiment in combination with the hypothesis of the "infinite pool" condition.

[0091] If a certain plastic additive reaches the equilibrium state at the end of the preliminary experiment and the loss of the plastic additive concentration in the leaching medium does not exceed 20%, it indicates that the substance meets the "infinite pool" condition assumption and there is no need to perform water change treatment. At this time, the concentration of the plastic additive in the solid-phase adsorption device can be calculated according to formula (2-2) below.

[0092] C0×V w = m×C w ×K SW +C w ×V w (2-2)

[0093] Among them, m is the mass (g) of the solid-phase adsorption device; C0 is the concentration of the target plastic additive in the solution at the start of the experiment, i.e., the initial concentration of the target substance (ng / L); C w is the concentration of the target plastic additive in the aqueous phase (ng / L); t is the experimental time (h); V w is the volume (L) of the aqueous-phase solution used to soak the plastic sample in the experiment; M t is the mass (ng) of the plastic additive in the membrane when changing the water. Ksw is the PSD-water partition coefficient; PSD - an inherent parameter of the target substance; there are two calculation methods. At equilibrium, Ksw = Cs / Cw, and when not at equilibrium, Ksw = 1000ku / ke (the coefficient 1000 is for unit conversion of ku, L / g / d → mL / g / d).

[0094] If a certain plastic additive does not reach the equilibrium state at the end of the preliminary experiment and the loss of the plastic additive concentration in the leaching medium exceeds 20%, it indicates that water replacement treatment is required to reduce the concentration fluctuation. At this time, the latest water replacement time should be deduced based on the 20% concentration loss. At this time, the concentration of the plastic additive in the solid-phase adsorption device can be calculated according to formula (2-3) in the following text.

[0095] C0×V w = m×C w ×K SW - M t + C w ×V w (2-3)

[0096] Among them, m is the mass (g) of the solid-phase adsorption device; C0 is the concentration of the target plastic additive in the solution at the start of the experiment, i.e., the initial concentration of the target substance (ng / L); C w is the concentration of the target plastic additive in the aqueous phase (ng / L); t is the experimental time (h); V w is the volume (L) of the aqueous-phase solution used to soak the plastic sample in the experiment; M t is the mass (ng) of the plastic additive in the membrane when changing the water; t is the exposure time after water replacement, 24 hours.

[0097] Similarly, if at the end of the preliminary experiment, the enrichment of the plastic additive by the solid-phase adsorption device does not reach the equilibrium state, that is, it is in the linear or curve stage of the enrichment process. Then the water replacement cycle is calculated through the following formulas (2-4) to (2-7).

[0098] Enrichment is linear and water replacement is required:

[0099] C0×V w = m×C w ×k u ×t + C w ×V w (2-4)

[0100] Enrichment curve stage and water change:

[0101]

[0102] During the linear enrichment stage, there is no need to change the water:

[0103] C0×V w = m×C w ×k u ×t + C w ×V w (2 - 6)

[0104] During the enrichment curve stage, there is no need to change the water:

[0105]

[0106] Wherein, m is the mass of the solid phase adsorption device (g); C0 is the concentration of the target plastic additive in the solution at the start of the experiment, i.e., the initial concentration of the target substance (ng / L); C w is the concentration of the target plastic additive in the aqueous phase (ng / L); t is the experimental time (h); V w is the volume of the aqueous phase solution used to soak the plastic sample in the experiment (L); M t is the mass of the plastic additive in the membrane during water change (ng); t is the exposure time after water change; K u and k e are the absorption rate constant and the elimination rate constant, respectively.

[0107] In this embodiment, taking 10 reference plastic additives as an example, assuming that the initial concentration C0 of the plastic additive in the leaching medium (water) with a leaching volume V w of 500 mL is 1000 ng / L. Substituting the physical and chemical parameters of the reference plastic additives in Example 1 (the physical and chemical parameters are all provided by the papers published by this research group, and the references are the same as Table 1), the following results can be obtained through the above calculations. The loss ratio is set to "not higher than 20%" to meet the desired "infinite pool" condition.

[0108] The SEM images of HECAM and TECAM are shown in Figure 3 - 4 .

[0109] Table 2 Calculation results of the loss ratio of reference plastic additives during enrichment

[0110]

[0111] The calculated latest water change interval is 7h. Since it is an estimated experimental method, and under the condition that the error is not too obvious, it is designed to change water every 8h. Therefore, when designing the verification experiment, water is changed at 8h and 16h respectively (changing water twice in total) to achieve the leaching condition of the "infinite pool".

[0112] Example 3: Determination of enrichment parameters of hydrophilic target plastic additives by solid-phase adsorption device

[0113] In this example, the hydrophilic plastic additive BP-12 in Table 2 is taken as an example. Using the HECAM membrane as the solid-phase adsorption device, the enrichment kinetic parameters of the HECAM membrane for it, such as Ke, Ku, etc., are determined through enrichment experiments.

[0114] Prepare the HECAM membrane in advance and cut it into a size of 2*3 cm; prepare a solution containing the standard product (500 ng / L) in a 500 mL conical flask, completely immerse the HECAM membrane in the liquid surface, and enrich it in a shaker for 24 hours. During the leaching process, keep the constant temperature at 25°C and the constant speed at 125 rpm under the condition of light-shielded horizontal oscillation.

[0115] After the experiment starts, water samples and HECAM membrane samples are collected at seven time points of 0h, 2h, 4h, 8h, 16h, and 24h, and the water is changed to a new standard product solution (500 ng / L) at 8h and 16h; three groups of parallel experiments are set in the experiment, and one group is used as a blank control.

[0116] The plastic additive is enriched and eluted from the aqueous phase using the method of solid-phase extraction. The plastic additive dissolved in water is concentrated and stored at minus 4 degrees Celsius for subsequent analysis. Techniques such as ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS) are used for analysis to accurately determine the concentrations of plastic additives in the aqueous phase and the solid phase.

[0117] The pre-experiment treatment methods include the treatment of water samples and membrane samples. For the pretreatment of water samples, first, a recovery internal standard indicator BP-246S is added to ensure the accuracy of the experiment. The water samples are treated by solid-phase extraction method using a tandem solid-phase extraction column, where the WAX column is placed upstream and the HLB column is placed downstream. The treatment process includes activation, loading, washing, elution, and volume fixation. In the operation, first, the solid-phase extraction column is activated by installing a vacuum filtration device, and the WAX column and HLB column are pretreated with 6 mL of methanol and 6 mL of water respectively. Subsequently, the water sample is loaded at a flow rate of about S10 out Win through the activated tandem column. After the water sample is enriched, the WAX column and HLB column are separated, and the two columns are washed with 6 mL of water respectively. After washing, they are dried under vacuum for about 30 minutes. The elution step is carried out in three times. The eluent used for the WAX column is 6 mL of ammonia-methanol solution (1%, v / v), 6 mL of methyl tert-butyl ether / methanol solution (volume ratio 9:1), and 6 mL of dichloromethane / methanol solution (volume ratio 8:2). The HLB column is eluted with 6 mL of dichloromethane. After the eluents of the two columns are combined, they are blown to dry under ammonia in a 40°C water bath and rinsed with methanol 2-3 times until concentrated to about 200 μL. Finally, the concentrated solution is fixed to 1 mL with methanol solution, filtered, and stored at 4°C.

[0118] For membrane samples, the ultrasonic-assisted extraction method is used for treatment. First, a mixed solution of n-hexane-dichloromethane (6:4) is selected as the elution solvent, and elution is carried out twice, and finally, elution is carried out once with methanol. The elution time for each time is 10 minutes. After all the eluents are combined, they are blown dry under ammonia in a 40°C water bath and rinsed with methanol 2-3 times, and concentrated to about 200 μL. Finally, the solution is fixed to 1 mL with methanol solution, filtered, and the sample is stored at 4°C.

[0119] Discuss whether the content of plastic additives enriched on HECAM during the experiment should satisfy the linear equation (3-1) or the pseudo-first-order kinetic equation (3-2):

[0120] C s =C w ×k u ×t (3-1)

[0121]

[0122] In the formula: t is the sampling time of HECAM, C s is the concentration of the target substance in HECAM at time t, C w represents the concentration of the target substance in the water body, k u and k e are the absorption rate constant and the elimination rate constant respectively.

[0123] The recovery indicator BP-246S and the target substance BP-12 have certain similarities in chemical structure. They have similar molecular structures and functional groups, so they have certain similarities in solubility, polarity, partition coefficient, etc. In the experiment, the HECAM passive sampling membrane mainly adsorbs the target substance through non-polar forces or interactions. If the affinity of the target substance with the internal standard is similar, they will be enriched by the membrane in a similar way. Therefore, the change in the recovery rate of the recovery indicator BP-246S can be used as a representative of the overall experimental recovery rate. Especially during the enrichment and recovery process of the substance, the target substance and the internal standard may have similar affinities and adsorption efficiencies on the membrane, so their loss or damage rates will show a similar trend. Therefore, the damage rate of BP-246S is used to estimate the recovery rate of the target substance. The recovery indicator BP-246S was randomly added to five samples before sample pretreatment, and the dosage was 500 ng / 500 mL. The recovered mass of the recovery indicator BP-246S in the experimental results was 437.06±16.30.

[0124] The experimental results are shown in Table 3:

[0125] Table 3. Test results at different time nodes

[0126]

[0127] According to the fitting results, the fitting results of the pseudo-first-order kinetic model show that the fitted ku value is 1.760039, the standard error is 0.4209942, and the ke value is -0.02346571, the standard error is 0.01994979. The R 2 value of this model is 0.9597526, indicating that the pseudo-first-order kinetic model can fit the experimental data well and has a high fitting accuracy. In contrast, in the fitting results of the linear model, the fitted ku value is 2.27874, the standard error is 0.1210667, and the R 2 value is 0.9407363. Although it is still relatively close to 1, showing a good fitting effect, it is slightly inferior to the performance of the pseudo-first-order kinetic model. Therefore, combining the fitting results and the characteristics of the experimental data, it can be speculated that the experiment entered the linear stage at 24 hours. In this stage, the system showed a nearly linear change trend, which may be due to the reaction or the system gradually stabilizing, resulting in a linear relationship in the data. Therefore, the end of the experiment (24 hours) can be regarded as the linear stage. The fitting results are shown in Figure 5 .

[0128] According to the main principle of the estimation calculation, mass conservation is the key basis. Specifically, the total mass in a bottle of solution should be equal to the sum of the mass in the membrane and the mass in the water. The mass conservation verification results for 8 hours showed a recovery rate of 111.77% ± 7.34%, indicating that mass conservation was satisfied before water replacement. In addition, when the concentration in the water was 0 after 8 hours, the concentration remained at 83.03% of the initial concentration, and the fluctuation was less than 80%, indicating that the concentration change was stable and met the expected requirements of mass conservation and concentration fluctuation.

[0129] Example 4: Monitoring the Release and Migration Ability of Integrated Plastic Additives in Water Based on the "Infinite Pool" System

[0130] In the experimental system of the present invention, the kinetic characteristics of the leaching process need to be compared with the theoretical model through experimental data to confirm the satisfaction of the "infinite pool" conditions. To evaluate the release behavior of plastic additives, two possible kinetic models were considered: the linear model and the pseudo-first-order kinetic model.

[0131] C s =C w ×k u ×t (3-1)

[0132]

[0133] Where: t is the sampling time of the solid-phase adsorption device; C s is the concentration of the target substance in the solid-phase adsorption device at time t; C w represents the concentration of the target substance in the water body; k u and k e are the absorption rate constant and the elimination rate constant, respectively.

[0134] In the experiment, if the release rate before the end of the experiment shows a linear trend with the change in the remaining added dose, it indicates that the "infinite pool" conditions are met, that is, the release process of the additive is not affected by the concentration accumulation effect in the system.

[0135] During the experiment, by monitoring Mt at different time points, we can depict the release kinetic curve of the additive. This index can reflect the release rate of the plastic additive and the change in the migration trend. For the determination of the occurrence levels of plastic additives in different forms, the experiment first enriches the free plastic additives at different time points through a sampling membrane. Combining the distribution characteristics of the additives released from different forms of plastics (such as granular, sheet-like, fibrous, etc.), the release behavior of plastic additives in different occurrence forms is further analyzed. By repeatedly measuring and comparing the concentration changes of additives in different forms, the occurrence state and migration ability of plastic additives can be accurately evaluated.

[0136] Among the deterministic models in the study of the migration model of plastic additives from the plastic matrix to the water environment, they are the most in-depth. They are mathematical models established based on the physical and chemical phenomena of mass transfer. The diffusion inside the matrix and the diffusion in the environmental medium generally follow Fick's law of diffusion:

[0137] (1) Diffusion inside the matrix

[0138]

[0139] (2) Diffusion in the environmental medium

[0140]

[0141] In the formula, D p represents the diffusion coefficient of the plastic matrix; c represents the local concentration of the plastic matrix; r represents the radius of the microplastic sphere; x represents the position of the pollutant.

[0142] To better explore the environmental risks caused by the release of additives in the source material, it is necessary to evaluate the migration behavior of additives in the material. Generally, the initial release of unstable surface components is relatively fast, followed by a relatively slow internal diffusion for a long time. To discuss the kinetic process of the three-stage migration process, it is necessary to further discuss its rate-determining step. The rate-determining step of the release of plastic additives depends on many characteristics such as the physical and chemical properties of the pollutant and the properties of the plastic matrix (polymer type, shape, size, crystallinity, glass transition temperature, etc.). The rate-controlling step in the mass transfer process can be evaluated by the mass transfer coefficient (Biot) B i which represents the ratio of the transport rate through the liquid boundary layer to the diffusion rate in the plastic phase.

[0143] B i can be calculated by the following formula:

[0144]

[0145] In the formula, D p is the diffusion coefficient in the plastic phase; l is the characteristic size of the plastic layer, which can be represented by the radius of the plastic particle or half of the thickness of the plastic film; k m is the mass transfer coefficient of the plastic-water boundary layer, which is related to parameters such as the mass transfer coefficient, partition coefficient, and boundary layer thickness of the pollutant in the environmental medium.

[0146] After derivation, it can be estimated by the following formula:

[0147]

[0148] In the formula, μ represents the dynamic viscosity of water (Pa·s), and the corresponding dynamic viscosity value is found in the physical property data table of water according to temperature and pressure. Under standard atmospheric pressure, the dynamic viscosity of water at 25°C is approximately 0.00089 Pa·s; v m represents the LeBas molar volume (cm 3 / mol); c p represents the concentration of plastic additives in the plastic matrix (μg / g); c w represents the concentration of plastic additives in the aqueous phase (μg / L).

[0149] The thickness δw of the ABL can be estimated corresponding to the level of environmental turbulence. When using stirring to simulate the turbulence of natural water bodies, there are the following estimation methods: The δw value in static experiments is above 2000 μm; when the rotation speed is 40 rpm, the δw value is approximately 100 μm; when the rotation speed is 150 rpm, the δw value is approximately 50 μm; when the rotation speed is above 300 rpm, the δw value is less than 30 μm.

[0150] On the other hand, according to the conclusion obtained by Sun et al. on the leaching process of brominated flame retardants (BFRs) from approximately spherical plastic particles under "infinite pool" conditions, the following formula can be further derived:

[0151]

[0152] The advantage of applying the passive sampling membrane as the absorption phase in the solid-phase "infinite pool" system is that the parameters in the above formula can be measured through experiments, and D P and B i values can be determined through simulation, so as to determine the rate-determining step in the leaching process of plastic additives under the proposed conditions and explain the plastic additive release process and degree.

[0153] M0 can be measured through the solvent extraction experiment of the plastic; while M t is determined by the enrichment amount of the passive sampling membrane in the plastic additive leaching experiment of the "infinite pool" system based on the passive sampling membrane.

[0154] C s = C w k u t (3-1)

[0155]

[0156] In the formula: t is the enrichment time of the passive sampling membrane, C s is the concentration of the target substance in the passive sampling membrane at time t, C w represents the concentration of the target substance in the water body; k u and k eThey are the absorption rate constant and the release rate constant respectively.

[0157] In this formula, R is a ratio representing the proportion between the total amount of additives in the initial system and the mass of the additives that have been released. The higher this value, the fewer plastic additives are released, and relatively speaking, the lower the migration ability; while the smaller the R value, the more plastic additives are released, and the stronger the migration ability. By observing the change of R, the release rate and migration ability of plastic additives can be understood. For example, within a certain period of time, an increase in M indicates that more plastic additives have been released into the environment. As time goes by, the value of R will gradually decrease as the release process progresses, indicating that the released plastic additives are gradually increasing and the migration ability is gradually enhanced in the environment.

[0158] If R tends to be stable or close to 1 over time, it means that almost no plastic additives in the system are released or the release is slow, and the migration ability is poor; while if R shows a significant decrease, it means that the release rate of the additives is fast, the migration ability of the plastic additives is strong, and the maximum release amount may have been reached or it is close to the "infinite pool" state, that is, the release rate tends to be constant. This ratio can help judge whether the release of plastic additives reaches equilibrium under specific environmental conditions, as well as the dynamic changes of the release rate and migration ability. This is of great significance for understanding the ecological risks and environmental impacts of plastic additives.

[0159] The following combines specific examples to elaborate in detail on the monitoring method for the release and migration ability of the plastic additives in the present invention in the water environment.

[0160] 1. Pretreatment method

[0161] (1) Pretreatment of water

[0162] Using pure water as the water sample. The water sample pretreatment method uses solid-phase extraction with a tandem of WAX column, C18 column and HLB column. Before enrichment with the SPE column, the columns are activated with 10 mL of methanol, 10 mL of dichloromethane and 10 mL of ultrapure water respectively. Then, the sample is loaded at a rate of 5 ml / min using a vacuum pump. The C18 column and the HLB column are eluted with 10 mL of dichloromethane solvent, and the eluate is collected in a small test tube. The WAX column is eluted with 6 mL of ammonia-methanol solution (1%, V / V), 6 mL of methyl tert-butyl ether / methanol solution (9:1, V / V), and 6 mL of dichloromethane / methanol solution (8:2, V / V) respectively. The eluate is collected in a round-bottom flask and concentrated to about 5 mL using a rotary evaporator. After elution of the SPE column, the packing in the column is removed, only the sleeve and the lower sieve plate are retained, 5 g of anhydrous sodium sulfate is added to the sleeve for drying, and the combined sample is collected in a K-D concentrator tube. The solvent in the K-D concentrator tube is concentrated using gentle nitrogen, and the bottle body of the K-D concentrator tube is washed twice with dichloromethane during the process. Finally, it is blown to about 0.1 mL with nitrogen, the solvent is replaced with methanol, and finally the methanol solvent is fixed volume to 1 mL. After filtering with a 0.22 μm polytetrafluoroethylene (PTFE) membrane, it is transferred to a brown injection vial and stored at -20 °C for analysis.

[0163] (2) Pretreatment of the membrane

[0164] The plastic additives enriched in the TECAM membrane and the HECAM membrane can both be extracted by solvent ultrasound. The taken-out TECAM membrane and HECAM membrane are placed in a thick-walled sample bottle, 5 mL of a mixed solvent of n-hexane / dichloromethane (6:4, V / V) is added, and ultrasonic extraction is carried out for 10 min using a probe-type ultrasonic extractor (150 W). The extraction is repeated 2 times, and finally extracted once with methanol solvent. The extraction solutions of the 3 times are combined into a K-D concentrator tube. The solvent in the K-D concentrator tube is concentrated using gentle nitrogen, and the bottle body of the K-D concentrator tube is washed twice with dichloromethane during the process. Finally, it is blown to about 0.1 mL with nitrogen, the solvent is replaced with methanol, and finally the methanol solvent is fixed volume to 1 mL. After filtering with a 0.22 μm polytetrafluoroethylene (PTFE) membrane, it is transferred to a brown injection vial and stored at -20 °C for analysis.

[0165] 2. Analytical method

[0166] (1) Extraction method of plastic additives in microplastics

[0167] Weigh a microplastic sample of approximately 0.2 g and transfer it to a 15 mL thick-walled sample vial. Add 5 mL of swelling solvent (cyclohexane / ethyl acetate (1:1, V / V)) and soak for 16 hours to swell the polymer and facilitate extraction. Add 15 mL of the mixed solvent of cyclohexane / ethyl acetate (1:1, V / V) to the vial and ultrasonically extract for 30 min using a probe-type ultrasonic extractor (150 W power). Then replace with fresh solvent (15 mL of methanol) and repeat the extraction 3 times. Combine the swelling solution and the extraction solution in a round-bottom flask, rotary evaporate and concentrate to about 20 mL, dry with anhydrous sodium sulfate and transfer to a K-D concentration tube. The sample is concentrated under a gentle nitrogen stream. During the nitrogen blowing process, rinse the inner wall of the K-D concentration tube 2 times with cyclohexane / ethyl acetate (1:1, V / V), and concentrate to about 0.1 mL and make up the volume to 1 mL with methanol solvent. The sample is filtered through a 0.22 μm PTFE filter membrane and stored in a brown sample vial at -20 °C for subsequent analysis.

[0168] (2) Analytical method for plastic additives in microplastics

[0169] The sample analysis is carried out using an ultra-high pressure liquid chromatography-triple quadrupole liquid mass spectrometer. The Agilent chromatographic column Eclipse plus C18 RRHD (1.8 μm, 2.1 mm × 50 mm) is selected for separation. The mobile phases used for analysis are 2 mM ammonium acetate aqueous solution (A) added with 0.04% formic acid and methanol (B) respectively. The flow rate is 0.25 mL / min, and the gradient elution program is shown in the following table. The injection volume is set to 10 μL, and the column temperature is set to 40 °C.

[0170] Table 4 Gradient elution program for targeted screening of light stabilizers and antioxidants

[0171]

[0172] The mass spectrometry detection conditions are as follows: electrospray ionization source (ESI source), positive and negative ion multiple reaction monitoring mode (MRM) is used simultaneously. The temperature of the electrospray ionization source is 120 °C, the desolvation temperature is 380 °C, the desolvation gas flow rate and the cone orifice flow rate are 600 L / h and 50 L / h respectively. The capillary voltage is 3.2 kV, and the collision gas flow rate is 0.07 mL / min.

[0173] (3) External standard method for quantification and standard curve

[0174] Determine the mixed standard solution of a series of gradient concentration standard solutions of the target substances, draw the standard curve, obtain the linear equation and linear correlation, and verify the stability of the method. The mixed standard concentration is 0 ppb, 20 ppb, 50 ppb, 100 ppb, 200 ppb, 500 ppb and 1000 ppb to ensure the linearity of the standard curve (R 2 > 0.99).

[0175] 3. Experimental Procedure

[0176] Experimental setup: The apparatus is as described above. A 250 mL conical flask with a ground glass stopper is used as the experimental flask. The microplastic release cage consists of two hemispherical stainless - steel metal sheets with pores, which are fixed into a whole using copper wires. The average diameter of the pores in the cage body is 2 mm, and the cage diameter is 30 mm. The size of the solid - phase adsorption membrane is 2 cm * 3 cm. The solid - phase adsorption membrane and the microplastic release cage are respectively hung down along the opposite sides of the bottle mouth using copper wires. The two copper wires are parallel and of equal length. During use, the solid - phase adsorption membrane and the microplastic release cage are suspended in the middle of the liquid. When at rest, the horizontal distance between the microplastic release cage and the solid - phase adsorption membrane is 1.5 cm. The plastic fragments are cut into microplastic fragments about 3 mm - 5 mm and passed through a 3 - mm sieve.

[0177] Weigh 0.2 g of microplastic samples and place them in the plastic additive release cage. Before the start of the experiment, the plastic additive release cage and the solid - phase absorption device are hung down into a glass conical flask using thin copper wires, and 200 mL of ultrapure water is added. The liquid level does not exceed 2 / 3 of the bottle height. The conical flask is wrapped with aluminum foil and sealed with a sealing film. Start the horizontal shaking device for shaking. The shaking conditions are set at 150 rpm, and the leaching experiment lasts for 7 days with continuous shaking. During the experiment, samples are taken at 7 pre - determined time points (0 day, 0.5 day, 1 day, 2 days, 3.5 days, 5 days, 7 days), and the water samples are retained. The microplastic samples are filtered through a fine nylon cloth, dried, and weighed; the solid - phase absorption membranes (TECAM membrane and HECAM membrane) are dried, weighed, then wrapped with aluminum foil respectively, and stored at - 20 °C.

[0178] Sampling is divided into two parts: (1) The amount of plastic additives in the solid - phase adsorption device: The concentration of additives in the aqueous phase is collected and measured through the solid - phase adsorption device. Each time a sample is taken, the amount of additives collected in the adsorption device is recorded. (2) The amount of plastic additives in the aqueous phase: The amount of plastic additives in the aqueous phase is collected through the SPE enrichment and elution process and analyzed.

[0179] The contents of plastic additives in the aqueous medium, the solid - phase adsorption membrane, and the remaining microplastic fragments at different time points are shown in Table 5.

[0180] Table 5 Contents of plastic additives in the aqueous medium, the solid - phase adsorption membrane, and the remaining microplastic fragments

[0181]

[0182] Where H represents the content (ng) of antioxidant I168 in the HECAM membrane of the solid - phase adsorption membrane; W represents the content (ng) of antioxidant I168 in the aqueous medium; P represents the content (ng) of antioxidant I168 in the remaining microplastic fragments.

[0183] According to the values at each time node in Table 5, calculate the R value at each time node. Taking the time node as the abscissa and the R value as the ordinate, plot the release kinetic curve of antioxidant I168, as shown in Figure 6 .

[0184] Furthermore, in this embodiment, by fitting the migration data of I168 plastic additive from microplastics to the water environment, the best estimated value of the diffusion coefficient DP = 2.35×10 -12 m 2 / s, and the confidence interval is (1.21×10 -12 , 3.48×10 -12 ); the residuals have no obvious pattern (RSE = 0.082), indicating that the model has good explanatory power. Residual analysis shows that the model has good explanatory power (RSE = 0.082), but the solvent extraction mass on the first day is abnormally low, which may be due to experimental errors or the early rapid desorption process.

[0185] Substitute the obtained DP value into formula (4-4), and the calculated Biot number (Bi≈680, much larger than 100) indicates that the release process is controlled by mass transfer in the aqueous boundary layer, that is, the diffusion of the additive from the plastic surface into the water is the rate-limiting step. The early rapid release may be due to the rapid desorption of the surface-adsorbed additive (non-diffusion-controlled). The fitting curve of the later diffusion behavior fits well with the √t relationship (RSE = 0.082), which conforms to the theoretical expectation of boundary layer control.

[0186] Parameter sensitivity analysis shows that increasing the stirring intensity (decreasing the boundary layer thickness δ) or decreasing the particle radius (R) can strengthen the boundary layer control, while increasing the diffusion coefficient (DP) may shift the mechanism to mixed control. In practical applications, the release can be accelerated by optimizing the stirring conditions (such as increasing the rotation speed), or the migration rate can be affected by regulating the size of the microplastics.

[0187] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for monitoring the release and migration ability of plastic additives in the water environment, characterized in that Comprising a horizontal rotary shaker and at least one plastic additive release bottle mounted on the horizontal rotary shaker; Each of the plastic additive release bottles includes a bottle body for storing an aqueous medium, a bottle stopper for sealing the bottle body, and a light-shielding cover for shielding the bottle body from light. A microplastic release cage and a solid-phase adsorption membrane are suspended in the bottle body. The microplastic release cage includes a cage body for storing a microplastic sample, and the solid-phase adsorption membrane is used for adsorbing plastic additives released from the microplastic release cage; The microplastic release cage and the solid-phase adsorption membrane are at the same height in the bottle body. The solid-phase adsorption membrane is arranged vertically, and there is a horizontal distance between the microplastic release cage and the solid-phase adsorption membrane.

2. The device for simulating the release behavior of plastic additives in an aqueous environment according to claim 1, characterized in that: The bottle body is a conical flask, and the microplastic release cage and the solid-phase adsorption membrane are suspended in the bottle body by a rigid wire fixed to the bottle stopper; The horizontal distance between the microplastic release cage and the solid-phase adsorption membrane is 1 - 2 cm.

3. The device for simulating the release behavior of plastic additives in an aqueous environment according to any one of claims 1-2, characterized in that: The average diameter of the pores of the cage body of the microplastic release cage is ≤ 2 mm; The material of the cage body of the microplastic release cage is stainless steel; The cage body of the microplastic release cage is spherical. In the bottle body with a capacity of 150 - 750 mL, the diameter of the cage body is 20 mm - 50 mm.

4. The device for simulating the release behavior of plastic additives in an aqueous environment according to any one of claims 1-3, characterized in that: The solid-phase adsorption membrane is a triolein - cellulose acetate semipermeable composite membrane or a polystyrene - N - pyrrolidone copolymer - cellulose acetate semipermeable composite membrane; In the bottle body with a capacity of 150 - 750 mL, the size of the solid-phase adsorption membrane is 2 cm * 3 cm.

5. The device for simulating the release behavior of plastic additives in an aqueous environment according to any one of claims 1-4, characterized in that: The device further includes a sealed box, which includes a box body and a box cover. The horizontal rotary shaker is installed in the box body; A heater is provided on the lower surface of the box cover for heating the plastic additive release bottle, and a temperature detector is provided on the box body; A heat dissipation device is provided on the box body; A control panel is provided on the upper surface of the box cover for controlling the heating device and the horizontal rotary shaker.

6. A method for monitoring the release and migration ability of plastic additives in the water environment, characterized in that, Using the device for monitoring the release and migration ability of plastic additives in the water environment according to any one of claims 1 - 5, comprising the following steps: S1. Place the microplastic sample in the microplastic release cage and add an aqueous medium into the bottle body so that the microplastic cage is completely immersed in the aqueous medium; S2. Start the horizontal rotary shaker to oscillate. The plastic additives released from the microplastic release cage are continuously adsorbed by the solid-phase adsorption membrane, and at predetermined time points, the contents of plastic additives in the aqueous medium, the solid-phase adsorption membrane, and the remaining microplastics are measured respectively; S3. Calculate the R value at the predetermined time point according to the following formula. Taking time as the abscissa and the R value as the ordinate, plot the release kinetic curve of the plastic additive; In formula (4-1), M t is the mass of the plastic additive in the solid-phase adsorption membrane at time t, and M _0 represents the total mass of the plastic additive in the water medium, the solid-phase adsorption membrane, and the remaining microplastics at time 0.

7. The method for monitoring the release and migration ability of plastic additives in the water environment according to claim 6, characterized in that: The plastic additives in the microplastic sample are additive plastic additives, preferably one or two of antioxidants and light stabilizers; The particle size of the microplastic sample is 3 mm - 5 mm; The morphology of the microplastic sample is one or several of granular, flaky, and fibrous.

8. The method for monitoring the release and migration ability of plastic additives in the water environment according to any one of claims 6-7, characterized in that: For each microplastic release cage with a diameter of 20 mm to 50 mm, the addition amount of the microplastic sample is 0.2 g to 0.5 g.

9. The method for monitoring the release and migration ability of plastic additives in the water environment according to any one of claims 6-8, characterized in that: The ratio of the microplastic sample to the water medium, i.e., the solid-liquid ratio, is 0.8 g / L to 1 g / L; The liquid level of the water medium in the bottle body does not exceed 2 / 3 of the height of the bottle body; The water medium is pure water, seawater, seawater simulation liquid or river water.

10. The method for monitoring the release and migration ability of plastic additives in the water environment according to any one of claims 6-9, characterized in that: The frequency of the oscillation is 40 rpm to 150 rpm, and the oscillation lasts for 7 days to 14 days.

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