Method for adsorbing and removing perfluorinated and polyfluoroalkyl compounds in water

Abstract

The invention provides a method for adsorbing and removing perfluoro and polyfluoroalkyl compounds in water, plastic particles are used as an adsorbent, the perfluoro and polyfluoroalkyl compounds in water are removed by a batch adsorption method or a fixed bed adsorption method, and the chain length of the perfluoro and polyfluoroalkyl compounds is not less than 4 carbon atoms. The plastic particles are made of synthetic high-molecular polymer particles. According to the method, waste plastic particles which are wide in source and low in cost are adopted as the adsorbent, and efficient removal of PFAS in water can be achieved. Meanwhile, the method for removing the PFAS in the water based on the waste plastic particles serving as the adsorbent is adopted, so that the environmental accumulation and pollution risks possibly caused by the solid wastes are avoided, and the synergistic target of resource utilization of the waste plastic particles and efficient removal of the PFAS in the water is also achieved.

Description

Technical Field

[0001] This invention relates to the fields of water treatment and groundwater remediation, and more specifically, to a method for adsorbing and removing perfluorinated and polyfluoroalkyl compounds from water. Background Technology

[0002] Per- and polyfluoroalkyl substances (PFAS) are a class of synthetic organic pollutants with high environmental persistence, bioaccumulation, and potential toxicity. The extremely high carbon-fluorine bond energy in their molecular structure (approximately 485 kJ / mol) makes PFAS difficult to remove effectively through natural degradation processes (such as chemical, biological, or photolytic degradation), thus allowing them to persist in water bodies, soil, and organisms for extended periods. PFAS have been proven to be associated with various health risks, including endocrine disruption, immunotoxicity, and carcinogenicity, and are therefore listed as priority pollutants for control.

[0003] Currently, the main technologies for treating PFAS in water include adsorption, chemical oxidation, membrane separation, and bioremediation. Among these, adsorption is one of the most widely used technologies due to its simplicity, relatively low cost, and stable performance. Commonly used adsorbents include activated carbon, ion exchange resins, and modified biochar. However, these materials still have certain limitations: activated carbon has limited adsorption capacity for short-chain PFAS and is difficult to regenerate; ion exchange resins are expensive and easily affected by water quality; and the adsorption performance of biochar is greatly affected by raw materials and preparation processes, resulting in insufficient stability.

[0004] On the other hand, waste plastic particulate matter, as a widespread environmental pollutant, has accumulated in enormous quantities and is difficult to degrade, becoming a global environmental problem. Common types of plastics include polyethylene (PE), polyvinyl chloride (PVC), and polystyrene (PS). Recent studies have found that some plastic particulate matter has a certain adsorption capacity for hydrophobic organic compounds, providing a theoretical basis for its use as an adsorbent in water pollution remediation. However, there is currently no technical solution for the systematic adsorption and removal of waste plastic particulate matter for PFAS, especially its application in the two typical processes of batch adsorption and fixed-bed adsorption columns, which has not yet been reported.

[0005] Therefore, developing a technology that uses waste plastic particles as an adsorbent to efficiently remove PFAS from water and realize the resource utilization of solid waste is of great environmental and economic significance. Summary of the Invention

[0006] To overcome the limitations of existing technologies, such as high cost of adsorbent materials, aggravated environmental pollution from waste plastic particles, and traditional PFAS treatment methods, this invention provides a method for adsorbing and removing perfluorinated and polyfluoroalkyl compounds from water. This method utilizes widely available and inexpensive waste plastic particles as an adsorbent, which can efficiently adsorb and remove PFAS with a chain length of at least 4 carbon atoms from water, achieving low-cost remediation of polluted water bodies. Furthermore, it enables the resource utilization of waste plastic particles, achieving the dual goals of "treating waste with waste" and synergistic treatment of pollutants.

[0007] This invention provides a method for adsorbing and removing perfluorinated and polyfluoroalkyl compounds from water. The method uses plastic particles as the adsorbent and employs batch adsorption or fixed-bed adsorption to remove the perfluorinated and polyfluoroalkyl compounds. The chain length of the perfluorinated and polyfluoroalkyl compounds is not less than 4 carbon atoms, and the plastic particles are made of synthetic polymer particles.

[0008] Compared with existing technologies, this invention innovatively transforms waste plastics into highly efficient adsorbents, achieving not only effective removal of persistent organic pollutants in water but also solving the problem of resource utilization of plastic waste. This method has significant advantages such as readily available raw materials, low cost, and environmental friendliness, providing a sustainable solution for PFAS remediation.

[0009] In the selection of plastic particles in this invention, the material of the plastic particles can be selected from at least one of polystyrene, polyethylene, and polyvinyl chloride, or other materials such as polypropylene, polyethylene terephthalate, polyamide, and polycarbonate. In one possible embodiment, the specific steps of the batch adsorption method are as follows: the plastic particles are added to water containing perfluorinated and polyfluoroalkyl compounds, and an adsorption reaction is carried out by stirring to obtain a reaction solution. After the adsorption reaction is completed, the reaction solution is filtered to complete the adsorption removal.

[0010] Compared with existing technologies, the present invention features a simple process, flexible operation, and rapid processing without the need for complex equipment. Stirring ensures full contact between the adsorbent and pollutants, significantly improving mass transfer efficiency. It is particularly suitable for intermittent wastewater treatment scenarios and has excellent engineering applicability.

[0011] In one possible implementation, the concentration of the plastic particles in water containing perfluorinated and polyfluoroalkyl compounds is ≥0.01 g / L. This concentration condition ensures effective adsorption while minimizing material consumption, making the treatment process more economical. Even at low dosages, an effective adsorption process can be initiated, making it suitable for wastewater treatment with varying degrees of pollution.

[0012] In one possible implementation, the stirring speed is >10 r / min. By optimizing the stirring conditions, the plastic particles are ensured to be uniformly dispersed in the solution, effectively preventing deposition and agglomeration, significantly improving the solid-liquid contact efficiency, and creating favorable kinetic conditions for the adsorption reaction.

[0013] In one possible implementation, the adsorption reaction is carried out at a temperature > 0°C for a time > 2 minutes. These conditions allow for efficient adsorption at room temperature, significantly reducing energy consumption. The short contact time enables effective removal, giving this method significant operational advantages in practical engineering applications.

[0014] In one possible implementation, the specific steps of the fixed-bed adsorption method are as follows: Step S1: A fixed bed containing plastic particles is prepared by filling the fixed bed layer with plastic particles alone, or by filling the fixed bed layer with a mixture of plastic particles and inert materials, or by injecting a suspension of plastic particles into a fixed bed layer filled with inert materials. Step S2: Water containing perfluorinated and polyfluoroalkyl compounds is injected into the fixed bed of step S1 at a constant flow rate to carry out the adsorption reaction.

[0015] Compared with existing technologies, this invention employs a fixed-bed adsorption method to treat PFAS-containing water. Its core advantage lies in integrating plastic particles as the adsorption medium into a fixed-bed reactor, achieving a highly efficient, stable, and continuously operating pollution control process. This method constructs the adsorption system by filling the bed with plastic particles alone, mixing them with inert materials, or injecting a suspension into the pre-filled bed. This flexible operation makes it easily adaptable to different engineering scenarios. By allowing polluted water to flow through the fixed bed at a constant flow rate, the adsorption capacity of the plastic particles for PFAS can be fully utilized, achieving continuous removal of pollutants. This process is not only simple to operate and manage, suitable for large-scale water remediation, but also provides a feasible path for the resource utilization of waste plastics while effectively degrading PFAS in water, combining high treatment efficiency, low cost, and environmental sustainability.

[0016] In one possible implementation, in step S1, the plastic particulate suspension further includes sodium carboxymethyl cellulose, and the mass concentration of sodium carboxymethyl cellulose in the plastic particulate suspension is 1-5 g / L, while the mass concentration of plastic particulates in the plastic particulate suspension is 0.1-1 g / L. The addition of sodium carboxymethyl cellulose significantly improves the dispersibility and stability of the plastic particles, effectively prevents fixed bed clogging, enhances the uniform distribution of the adsorbent in the bed, and thus improves the overall treatment efficiency.

[0017] In one possible implementation, in step S1, the mass percentage of plastic particles in the fixed bed is ≥0.1%. This ratio minimizes the amount of adsorbent used while ensuring treatment effectiveness, thereby reducing operating costs and avoiding excessive increases in bed resistance, achieving an optimal balance between technical and economic efficiency.

[0018] In one possible implementation, in step S1, the inert material is a porous natural quartz sand medium. Quartz sand, as a supporting medium, effectively improves the bed structure, enhances hydraulic conductivity, prevents channeling, and provides a stable hydrodynamic environment for the adsorption process. Attached Figure Description

[0019] Figure 1 The curve of the adsorption and removal rate of 8 mg / L perfluorooctanoic acid (PFOA) in water by adding 20 g / L polystyrene (PS), polyethylene (PE) or polyvinyl chloride (PVC) in Example 1 of the present invention as a function of time. Figure 2 The curve showing the change over time of the adsorption and removal rate of 8 mg / L perfluorooctane sulfonic acid (PFOS) in water by adding 20 g / L PS, PE or PVC in Example 2 of the present invention. Figure 3 The curves showing the adsorption and removal rates of low concentrations (10, 20, 30, 40, 50, 60, 80 and 100 µg / L) of PFAS in water with the addition of 0.2 g / L PS, PE or PVC in Example 3 of the present invention are shown as curves of PFAS concentration. Figure 4 Example 4 of this invention shows the adsorption and removal rate of high concentrations (8, 10, 12, 15, 18 and 20 mg / L) of PFAS in water by adding 50 g / L PS, PE or PVC as a function of PFAS concentration. Figure 5 The curves showing the adsorption and removal rates of 50 µg / L PFAS in the injection solution over time in Example 5 of this invention, where 0.5% PS, PE, or PVC is added to a fixed-bed reactor. Detailed Implementation

[0020] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the present invention.

[0021] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0023] The following is a further explanation based on specific embodiments.

[0024] Example 1: 1) Weigh 0.04 g of perfluorooctanoic acid (PFOA) powder, dissolve it in 500 mL of simulated groundwater (AGW), stir well, and prepare a PFOA stock solution with a mass concentration of 80 mg / L; 2) Transfer 50 mL of the PFOA stock solution prepared in step 1) into a 500 mL volumetric flask, dilute to the mark with AGW and make up to volume to prepare a PFOA working solution with a mass concentration of 8 mg / L. 3) Weigh 0.08 g of polystyrene (PS), polyethylene (PE) and polyvinyl chloride (PVC) plastic granules respectively, and add them to 4 mL of PFOA working solution with a mass concentration of 8 mg / L prepared in step 2) to obtain a reaction solution. The mass concentrations of PS, PE and PVC in this reaction solution are all 20 g / L.

[0025] 4) The glass bottle containing the reaction solution was placed on a rotary mixer and the mixing and adsorption reaction was carried out at 40 rpm at 25 °C. To avoid interference from sampling operations, the sacrificial reagent bottle method was used in this study: three parallel reaction bottles were simultaneously removed at 1, 2, 3, 5, 7, 10, 15, and 30 minutes of the reaction (each time point corresponds to one set of parallel samples). Subsequently, the aqueous phase sample from each reaction bottle was aspirated using a syringe and filtered through a 0.45 μm filter membrane to remove plastic particles. Finally, the residual PFOA concentration in the filtrate at each time point was measured, and an adsorption curve was plotted with relative concentration (C / C0, i.e., the ratio of concentration C at time t to the initial concentration C0) as the ordinate and time (t) as the abscissa.

[0026] Figure 1 This example illustrates the change over time in the adsorption and removal rate of 8 mg / L PFOA in water by adding 20 g / L PS, PE, or PVC. Figure 1 It can be seen that, with the addition of PE, the adsorption and removal rate of PFOA basically stabilized after 10 minutes of reaction, with a maximum adsorption and removal rate of 25%. In contrast, the adsorption and removal rate of PFOA in the reaction solution with added PS and PVC was not significant. Figure 1 In this context, PFOA+PS indicates an aqueous solution containing 20 g / L PS (containing 8 mg / L PFOA); PFOA+PE indicates an aqueous solution containing 20 g / L PE (containing 8 mg / L PFOA); and PFOA+PVC indicates an aqueous solution containing 20 g / L PVC (containing 8 mg / L PFOA).

[0027] Example 2: 1) Weigh 0.04 g of perfluorooctane sulfonic acid (PFOS) powder, dissolve it in 500 mL of AGW, stir well, and prepare a PFOS stock solution with a mass concentration of 80 mg / L. 2) Transfer 50 mL of the PFOS stock solution prepared in step 1) into a 500 mL volumetric flask, dilute to the mark with AGW and make up to volume to prepare a PFOS working solution with a mass concentration of 8 mg / L. 3) Weigh 0.08 g of polystyrene (PS), polyethylene (PE) or polyvinyl chloride (PVC) plastic granules and add them to 4 mL of PFOS working solution with a mass concentration of 8 mg / L prepared in step 2) to obtain a reaction solution. The mass concentrations of PS, PE and PVC in this reaction solution are all 20 g / L.

[0028] 4) The glass bottle containing the reaction solution was placed on a rotary mixer and the mixing and adsorption reaction was carried out at 40 rpm at 25 °C. To avoid interference from sampling operations, the sacrificial reagent bottle method was also used in this study: three parallel reaction bottles were simultaneously removed at 1, 2, 3, 5, 7, 10, 15, and 30 minutes of the reaction (each time point corresponds to a set of parallel samples). Subsequently, the aqueous phase sample from each reaction bottle was aspirated using a syringe and filtered through a 0.45 μm filter membrane to remove plastic particles. Finally, the residual PFOS concentration in the filtrate at each time point was measured, and the adsorption kinetics curve was plotted with relative concentration (C / C0, i.e., the ratio of concentration C at time t to the initial concentration C0) as the ordinate and time (t) as the abscissa.

[0029] Figure 2 This example illustrates the change over time in the adsorption and removal rate of 8 mg / L PFOS in water by adding 20 g / L PS, PE, or PVC. Figure 2 It can be seen that, with the addition of PE, the adsorption and removal rate of PFOS reached 67% after 10 minutes of reaction. In contrast, the adsorption and removal efficiency of PFOS in reaction solutions with added PS and PVC was not significant. PFOS+PS represents an aqueous solution with 20 g / L PS (containing 8 mg / L PFOS); PFOS+PE represents an aqueous solution with 20 g / L PE (containing 8 mg / L PFOS); PFOS+PVC represents an aqueous solution with 20 g / L PVC (containing 8 mg / L PFOS).

[0030] Example 3: 1) Weigh 0.005 g of perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexanoic acid (PFHxA) or perfluorohexane sulfonic acid (PFHxS) powder, dissolve it in 1000 mL of AGW, stir well, and prepare a stock solution of PFOA, PFOS, PFHxA and PFHxS with a mass concentration of 5000 µg / L. 2) Transfer 0.4, 0.8, 1.2, 1.6, 2, 2.4, 3.2 and 4 mL of the PFOA, PFOS, PFHxA or PFHxS stock solutions prepared in step 1) into eight 200 mL volumetric flasks, dilute to the mark with AGW and make up to volume to prepare working solutions of PFOA, PFOS, PFHxA and PFHxS with mass concentrations of 10, 20, 30, 40, 50, 60, 80 and 100 µg / L respectively; 3) Weigh 0.008 g of polystyrene (PS), polyethylene (PE), or polyvinyl chloride (PVC) plastic granules and add them to 40 mL of PFAS working solutions prepared in step 2 with mass concentrations of 10, 20, 30, 40, 50, 60, 80, and 100 µg / L to obtain reaction solutions. The mass concentration of PS, PE, or PVC in this reaction solution is 0.2 g / L.

[0031] 4) Place the glass bottles containing the reaction solution on a rotary mixer and maintain the temperature at 25 °C for 24 hours at a constant speed of 40 rpm to ensure the adsorption system reaches dynamic equilibrium. After the reaction is complete, use a syringe to aspirate the aqueous phase sample from each reaction bottle and filter it through a 0.45 μm filter membrane to remove plastic particles. Finally, determine the residual PFAS concentration in the filtrate at different concentrations and express it as a relative concentration (C0). en / C in That is, the concentration C at the end time. en Compared with the initial concentration C in Plot the adsorption curve with the ratio of PFAS concentration to PFAS concentration on the ordinate and the PFAS concentration on the abscissa.

[0032] Figure 3 This example illustrates how the adsorption and removal rate of PFAS in water by adding 0.2 g / L PS, PE, or PVC varies with the concentration of PFAS.

[0033] from Figure 3 As shown in (a), with the addition of PE, the adsorption removal rate of PFOA at different low concentrations remained between 30% and 39%. In contrast, the adsorption removal rates of PFOA in reaction solutions with added PS and PVC remained only between 8% and 14% and 11% and 19%, respectively. PS represents an aqueous solution with 0.2 g / L PS (containing 10, 20, 30, 40, 50, 60, 80, and 100 µg / L PFOA); PE represents an aqueous solution with 0.2 g / L PE (containing 10, 20, 30, 40, 50, 60, 80, and 100 µg / L PFOA); PVC represents an aqueous solution with 0.2 g / L PVC (containing 10, 20, 30, 40, 50, 60, 80, and 100 µg / L PFOA).

[0034] from Figure 3-(b) shows that, with the addition of PE, the adsorption removal rate of PFOS at different low concentrations remained between 82% and 85%. In contrast, the adsorption removal rates of PFOS in reaction solutions with added PS and PVC remained only between 26% and 37% and 33% and 38%, respectively. PS represents an aqueous solution with 0.2 g / L PS (containing 10, 20, 30, 40, 50, 60, 80, and 100 µg / L PFOS); PE represents an aqueous solution with 0.2 g / L PE (containing 10, 20, 30, 40, 50, 60, 80, and 100 µg / L PFOS); PVC represents an aqueous solution with 0.2 g / L PVC (containing 10, 20, 30, 40, 50, 60, 80, and 100 µg / L PFOS).

[0035] from Figure 3 -(c) shows that the adsorption and removal rates of different low concentrations of PFHxA were not significant when PS, PE, and PVC were added. PS represents an aqueous solution with 0.2 g / L PS (containing 10, 20, 30, 40, 50, 60, 80, and 100 µg / L PFHxA); PE represents an aqueous solution with 0.2 g / L PE (containing 10, 20, 30, 40, 50, 60, 80, and 100 µg / L PFHxA); PVC represents an aqueous solution with 0.2 g / L PVC (containing 10, 20, 30, 40, 50, 60, 80, and 100 µg / L PFHxA).

[0036] from Figure 3 As shown in (d), with the addition of PE, the adsorption removal rates of different low concentrations of PFHxS remained between 36% and 48%. In contrast, the adsorption removal rates of PFHxS in reaction solutions with added PS and PVC remained only between 8% and 21% and 14% and 23%, respectively. PS represents an aqueous solution with 0.2 g / L PS (containing 10, 20, 30, 40, 50, 60, 80, and 100 µg / L PFHxS); PE represents an aqueous solution with 0.2 g / L PE (containing 10, 20, 30, 40, 50, 60, 80, and 100 µg / L PFHxS); PVC represents an aqueous solution with 0.2 g / L PVC (containing 10, 20, 30, 40, 50, 60, 80, and 100 µg / L PFHxS).

[0037] Example 4: 1) Weigh 0.02 g of perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexanoic acid (PFHxA) or perfluorohexane sulfonic acid (PFHxS) powder, dissolve it in 1000 mL of simulated groundwater (AGW), stir well, and prepare a stock solution of PFOA, PFOS, PFHxA and PFHxS with a mass concentration of 20 mg / L; 2) Transfer 25, 40, 50, 60, 75 and 90 mL of the PFOA, PFOS, PFHxA or PFHxS stock solutions prepared in step 1) into six 100 mL volumetric flasks, dilute to the mark with AGW and make up to volume to prepare working solutions of PFOA, PFOS, PFHxA and PFHxS with mass concentrations of 5, 8, 10, 12, 15 and 18 mg / L respectively.

[0038] 3) Weigh 0.2 g of polystyrene (PS), polyethylene (PE), or polyvinyl chloride (PVC) plastic granules and add them to 4 mL of PFAS solutions prepared in steps 1) and 2) with mass concentrations of 5, 8, 10, 12, 15, 18, and 20 mg / L to obtain reaction solutions. The mass concentration of PS, PE, or PVC in this reaction solution is 50 g / L.

[0039] 4) Place the glass bottles containing the reaction solution on a rotary mixer and maintain the temperature at 25 °C for 24 hours at a constant speed of 40 rpm to ensure the adsorption system reaches dynamic equilibrium. After the reaction is complete, use a syringe to aspirate the aqueous phase sample from each reaction bottle and filter it through a 0.45 μm filter membrane to remove plastic particles. Finally, determine the residual PFAS concentration in the filtrate at different concentrations and express it as a relative concentration (C0). en / C in That is, the concentration C at the end time. en Compared with the initial concentration C in Plot the adsorption curve with the ratio of PFAS concentration to PFAS concentration on the ordinate and the PFAS concentration on the abscissa.

[0040] Figure 4 This example illustrates how the adsorption and removal rate of PFAS in water by adding 50 g / L PS, PE, or PVC varies with the concentration of PFAS.

[0041] from Figure 4As shown in (a), with the addition of PE, the adsorption removal rate of PFOA at different high concentrations remained between 20% and 28%. In contrast, the adsorption removal rate of PFOA in reaction solutions with added PS and PVC was not significant. PS represents an aqueous solution with 50 g / L PS (containing 8, 10, 12, 15, 18, and 20 mg / L PFOA); PE represents an aqueous solution with 50 g / L PE (containing 8, 10, 12, 15, 18, and 20 mg / L PFOA); PVC represents an aqueous solution with 50 g / L PVC (containing 8, 10, 12, 15, 18, and 20 mg / L PFOA).

[0042] from Figure 4 -(b) shows that, with the addition of PE, the adsorption and removal rates of PFOS at different high concentrations remained between 63% and 68%. In contrast, the adsorption and removal rates of PFOS in reaction solutions with added PS and PVC remained only between 11% and 13% and 11% and 16%, respectively. PS represents an aqueous solution with 50 g / L PS (containing 8, 10, 12, 15, 18, and 20 mg / L PFOS); PE represents an aqueous solution with 50 g / L PE (containing 8, 10, 12, 15, 18, and 20 mg / L PFOS); PVC represents an aqueous solution with 50 g / L PVC (containing 8, 10, 12, 15, 18, and 20 mg / L PFOS).

[0043] from Figure 4 -(c) shows that the adsorption and removal rates of different high concentrations of PFHxA were not significant when PE, PS, and PVC were added. PS represents an aqueous solution with 50 g / L PS (containing 8, 10, 12, 15, 18, and 20 mg / L PFHxA); PE represents an aqueous solution with 50 g / L PE (containing 8, 10, 12, 15, 18, and 20 mg / L PFHxA); PVC represents an aqueous solution with 50 g / L PVC (containing 8, 10, 12, 15, 18, and 20 mg / L PFHxA).

[0044] from Figure 4As shown in (d), with the addition of PE, the adsorption removal rate of PFHxS at different high concentrations remained between 14% and 23%. In contrast, the adsorption removal rate of PFHxS in reaction solutions with added PS and PVC was not significant. PS represents an aqueous solution with 50 g / L PS (containing 8, 10, 12, 15, 18, and 20 mg / L PFHxS); PE represents an aqueous solution with 50 g / L PE (containing 8, 10, 12, 15, 18, and 20 mg / L PFHxS); PVC represents an aqueous solution with 50 g / L PVC (containing 8, 10, 12, 15, 18, and 20 mg / L PFHxS).

[0045] Example 5: 1) Weigh 0.005g of perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexanoic acid (PFHxA) or perfluorohexane sulfonic acid (PFHxS) powder, dissolve it in 1000 mL of simulated groundwater (AGW), stir well, and prepare a stock solution of PFOA, PFOS, PFHxA and PFHxS with a mass concentration of 5000 µg / L; 2) Transfer 5 mL of the PFOA, PFOS, PFHxA or PFHxS stock solution prepared in step 1) into a 500 mL volumetric flask, dilute to the mark with AGW and make up to volume to prepare a PFOA, PFOS, PFHxA and PFHxS working solution with a mass concentration of 50 µg / L. 3) Fill a glass-stainless steel column with an inner diameter of 2 cm and a length of 15 cm with porous natural quartz sand evenly. After compaction, introduce carbon dioxide gas into the quartz sand column to remove air. Use a valveless fluid pump to introduce AGW solution degassed by heating from the bottom of the quartz sand column until the sand column is saturated (the column maintains a constant weight).

[0046] 4) Weigh 2 g of sodium carboxymethyl cellulose (CMC) powder, dissolve it in 1000 mL of simulated groundwater (AGW), stir well, and prepare a CMC solution with a mass concentration of 2 g / L.

[0047] 5) Weigh 0.2 g of polystyrene (PS), polyethylene (PE), or polyvinyl chloride (PVC) plastic granules and add them to the CMC solution prepared in step 4) to obtain a CMC-plastic granule suspension. The mass concentration of plastic granules in the suspension is 0.2 g / L.

[0048] 6) Immediately after the CMC-plastic particle suspension is prepared, a one-dimensional flow field packed column experiment is conducted. The column experiment is divided into two groups. In the first group of column experiments, the 50 µg / L PFOA, PFOS, PFHxA, and PFHxS working solutions prepared in step 2) are directly injected into the saturated sand columns prepared in step 3), respectively. The pore water flow rate is 1 mL / min, and the injection volume is approximately 5 pore volumes (PV). Before the second group of column experiments begins, the CMC-PS, CMC-PE, and CMC-PVC suspensions prepared in step 5) are continuously injected into the saturated sand columns prepared in step 3) at a flow rate of 1 mL / min using a valveless fluid pump until the mass percentage of plastic particles retained in the saturated column reaches the predetermined 0.5%. Then, the injection solution is immediately switched to AGW solution to rinse the column until the concentration of CMC in the effluent is 0, and the pre-filling of plastic particles is completed. During the experiment, the 50 µg / L working solutions of PFOA, PFOS, PFHxA, or PFHxS prepared in step 2) were injected into the saturated column pre-filled with plastic particles, respectively. The pore water flow rate was 1 mL / min, and the injection volume was approximately 5 PV. Effluent samples at different time points were filtered through a 0.22 μm aqueous filter membrane, and the residual PFAS concentration was determined using high-performance liquid chromatography-mass spectrometry (HPLC-MS). The concentrations were expressed as relative concentrations (C0.05). out / C in That is, the concentration of the effluent C out With the concentration of the injected solution C in Plot the penetration curve with the ratio of time (t) on the vertical axis and time (t) on the horizontal axis.

[0049] Figure 5 This shows the change over time in the adsorption and removal rate of 50 µg / L PFAS in the injection solution when 0.5% PS, PE, or PVC is filled into a fixed-bed reactor in Example 5 of the present invention.

[0050] from Figure 5-(a) shows that the adsorption and removal rate of PFOA by the inert material in the fixed bed reached 37.46%. Compared with the inert material, the adsorption and removal rate of PFOA by the fixed bed increased by 14.15% when PE was filled. In contrast, the adsorption and removal rate of PFOA by the fixed bed increased by less than 10% when PS and PVC were filled. PFOA refers to injecting a 50 µg / L PFOA solution into a fixed bed without plastic particles; PFOA+PS refers to injecting a 50 µg / L PFOA solution into a fixed bed containing a PS mixture (containing 0.5% PS by mass); PFOA+PE refers to injecting a 50 µg / L PFOA solution into a fixed bed containing a PE mixture (containing 0.5% PE by mass); PFOA+PVC refers to injecting a 50 µg / L PFOA solution into a fixed bed containing a PVC mixture (containing 0.5% PVC by mass).

[0051] from Figure 5 -(b) shows that the adsorption and removal rate of PFOS by the inert material in the fixed bed reached 55.29%. Compared with inert material, the adsorption and removal rate of PFOS by the fixed bed increased by 43.86% when PE was filled. In contrast, the adsorption and removal rate of PFOS by the fixed bed increased by only 26.78% and 27.83% when PS and PVC were filled, respectively. PFOS refers to injecting a 50 µg / L PFOS solution into a fixed bed without plastic particles; PFOS+PS refers to injecting a 50 µg / L PFOS solution into a fixed bed containing a PS mixture (containing 0.5% PS by mass); PFOS+PE refers to injecting a 50 µg / L PFOS solution into a fixed bed containing a PE mixture (containing 0.5% PE by mass); PFOS+PVC refers to injecting a 50 µg / L PFOS solution into a fixed bed containing a PVC mixture (containing 0.5% PVC by mass).

[0052] from Figure 5-(c) shows that the adsorption and removal rate of PFHxA by the inert material in the fixed bed reached 25.59%. Compared with the inert material, the adsorption and removal rate of PFHxA by the fixed bed increased by less than 10% when PE was filled. In contrast, the increase in the adsorption and removal rate of PFHxA by the fixed bed was not significant when PS and PVC were filled. PFHxA represents the injection of a 50 µg / L PFHxA solution into a fixed bed without plastic particles; PFHxA+PS represents the injection of a 50 µg / L PFHxA solution into a fixed bed containing a PS mixture (containing 0.5% PS by mass); PFHxA+PE represents the injection of a 50 µg / L PFHxA solution into a fixed bed containing a PE mixture (containing 0.5% PE by mass); PFHxA+PVC represents the injection of a 50 µg / L PFHxA solution into a fixed bed containing a PVC mixture (containing 0.5% PVC by mass).

[0053] from Figure 5 As shown in (d), the adsorption and removal rate of PFHxS by the inert material in the fixed bed reached 28.21%. Compared with inert material, the adsorption and removal rate of PFHxS by the fixed bed increased by 25.98% when PE was filled. In contrast, the adsorption and removal rate of PFHxS by the fixed bed increased by only 11.41% and 14.15% when PS and PVC were filled, respectively. PFHxS indicates that a 50 µg / L PFHxS solution is injected into a fixed bed containing no plastic particles; PFHxS+PS indicates that a 50 µg / L PFHxS solution is injected into a fixed bed containing a PS mixture (0.5% by mass); PFHxS+PE indicates that a 50 µg / L PFHxS solution is injected into a fixed bed containing a PE mixture (0.5% by mass); PFHxS+PVC indicates that a 50 µg / L PFHxS solution is injected into a fixed bed containing a PVC mixture (0.5% by mass).

[0054] Therefore, this invention utilizes widely available and inexpensive waste plastic particles as an adsorbent to achieve highly efficient removal of PFAS from water. Furthermore, this method of removing PFAS from water using waste plastic particles as an adsorbent not only avoids the environmental accumulation and pollution risks that such solid waste may cause, but also achieves the synergistic goal of resource utilization of waste plastic particles and efficient removal of PFAS from water. This method is applicable to water remediation technologies based on adsorption principles, providing an economical, efficient, and sustainable solution for the treatment of PFAS-contaminated water.

[0055] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A method for adsorbing and removing perfluorinated and polyfluoroalkyl compounds from water, characterized in that, Using plastic particles as adsorbents, batch adsorption or fixed-bed adsorption is employed to remove perfluorinated and polyfluoroalkyl compounds from water, wherein the chain length of the perfluorinated and polyfluoroalkyl compounds is not less than 4 carbon atoms, and the plastic particles are made of synthetic polymer particles.

2. The method as described in claim 1, characterized in that, The specific steps of the batch adsorption method are as follows: plastic particles are added to water containing perfluorinated and polyfluoroalkyl compounds, and the adsorption reaction is carried out by stirring to obtain a reaction solution. After the adsorption reaction is completed, the reaction solution is filtered to complete the adsorption removal.

3. The method as described in claim 2, characterized in that, The concentration of the plastic particles in water containing perfluorinated and polyfluoroalkyl compounds is ≥0.01 g / L.

4. The method as described in claim 2, characterized in that, The stirring speed is >10 r / min.

5. The method as described in claim 2, characterized in that, The adsorption reaction is carried out at a temperature greater than 0°C and for a time greater than 2 minutes.

6. The method as described in claim 1, characterized in that, The specific steps of the fixed-bed adsorption method are as follows: Step S1: A fixed bed containing plastic particles is prepared by filling the fixed bed layer with plastic particles alone, or by filling the fixed bed layer with a mixture of plastic particles and inert materials, or by injecting a suspension of plastic particles into a fixed bed layer filled with inert materials. Step S2: Water containing perfluorinated and polyfluoroalkyl compounds is injected into the fixed bed of step S1 at a constant flow rate to carry out the adsorption reaction.

7. The method as described in claim 6, characterized in that, In step S1, the plastic particulate suspension also includes sodium carboxymethyl cellulose, and the mass concentration of sodium carboxymethyl cellulose in the plastic particulate suspension is 1-5 g / L, and the mass concentration of plastic particulate matter in the plastic particulate suspension is 0.1-1 g / L.

8. The method as described in claim 6, characterized in that, In step S1, the mass percentage of plastic particles in the fixed bed is ≥0.1%.

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