A method for adsorbing and degrading perfluorinated and polyfluorinated compounds in water by using zero-valent magnesium material
By using zero-valent magnesium materials to adsorb and mechanically ball-mill the perfluorinated and polyfluorinated compounds in water, the high energy consumption and high cost problems of existing technologies are solved, achieving efficient and economical PFAS removal and degradation. It is suitable for environments with multiple pH values, and the materials are reusable.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INST OF SOIL SCI CHINESE ACAD OF SCI
- Filing Date
- 2024-05-08
- Publication Date
- 2026-07-07
AI Technical Summary
Existing technologies are insufficient for efficiently and economically removing perfluorinated and polyfluorinated compounds, especially short-chain PFAS, from water. Furthermore, conventional methods are energy-intensive and costly, making long-term remediation in groundwater difficult.
Zero-valent magnesium materials are used to adsorb perfluorinated and polyfluorinated compounds, and then oxidative free radicals are generated through mechanical ball milling for degradation. Combining the high adsorption capacity of zero-valent magnesium with the strong adsorption effect of the nano-magnesium surface generated by corrosion, rapid adsorption and complete degradation are achieved.
It achieves efficient and low-cost removal of perfluorinated and polyfluorinated compounds, degrading them into easily decomposable products, reducing environmental impact, with strong applicability, low operating costs, suitability for environments with multiple pH values, and reusable materials.
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Figure CN118343879B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of water treatment technology and relates to a method for treating water containing perfluorinated and polyfluorinated compounds, and more particularly to a method for adsorbing and degrading perfluorinated and polyfluorinated compounds in water using zero-valent magnesium materials. Background Technology
[0002] Per- and polyfluoroalkyl substances (PFAS) are a class of chemically stable, environmentally persistent, highly recalcitrant, and bioaccumulative new pollutants with significant toxicity. They are widely used in fire extinguishing agents, non-stick cookware coatings, food packaging, and textiles. Studies have shown that perfluorooctanoic acid (PFOA) and perfluorooctanesulfonates (PFOS), containing eight carbon atoms, can cause liver and kidney disease, increase the risk of cancer, and reduce fertility, posing a significant threat to human health. However, due to the extremely high bond energy of the CF bond in their structure, per- and polyfluoroalkyl substances possess extremely high chemical and thermal stability, making them very difficult to degrade.
[0003] Finding efficient methods for controlling PFAS pollution has always been a major challenge in the field of environmental remediation. Existing groundwater PFAS remediation technologies mainly employ advanced oxidation degradation based on persulfate or adsorption removal methods based on porous materials. However, conventional advanced oxidation methods are difficult to effectively degrade PFAS, often requiring high-temperature heating and external electrodes to improve removal efficiency, resulting in high energy consumption and costs, which is not conducive to long-term groundwater remediation. In comparison, using adsorption materials to enrich and immobilize PFAS is a simpler treatment method with greater economic viability. Furthermore, adsorption removal is also a crucial foundation for combining other degradation technologies, as researchers have found that the main reason short-chain PFAS are difficult to degrade is that the pollutants cannot be adsorbed onto the catalyst surface. Therefore, selecting remediation materials with both catalytic and adsorption functions is more meaningful for long-term PFAS removal goals. Summary of the Invention
[0004] To address the problem of efficient removal of PFAS pollutants, this invention provides a method for adsorbing and degrading perfluorinated and polyfluorinated compounds in water using zero-valent magnesium materials. This method utilizes the strong adsorption capacity of zero-valent magnesium for PFAS and the decomposition ability of strong oxidative free radicals generated by mechanical ball milling, enabling efficient, rapid, and thorough removal of PFAS. The method is simple, removes PFAS thoroughly and efficiently, has low operating costs, and is environmentally friendly.
[0005] To achieve the above objectives, the present invention provides a method for adsorbing and degrading perfluorinated and polyfluorinated compounds in water using zero-valent magnesium material, characterized by the following steps: Step 1, adding zero-valent magnesium material to the water to be treated containing perfluorinated and polyfluorinated compounds, mixing thoroughly, so that the perfluorinated and polyfluorinated compounds are adsorbed and fixed on the zero-valent magnesium material; Step 2, placing the adsorbed zero-valent magnesium material in a ball mill for mechanical ball milling, so that the perfluorinated and polyfluorinated compounds adsorbed on the zero-valent magnesium material are degraded.
[0006] Generally, porous carbon materials or clay minerals, as adsorbents, primarily capture PFAS through hydrophobic interactions and electrostatic adsorption. Long-chain PFAS are mainly controlled by the hydrophobic interactions of the material surface, while short-chain PFAS are more susceptible to the influence of pH, background ions, and ionic strength during adsorption. Zero-valent magnesium (ZV) carries a high density of positive charge (Zeta potential > 10 mV), attracting negatively charged PFAS. Furthermore, the amorphous Mg(OH)₂ formed on the surface of ZV after corrosion exhibits strong hydrophobic interactions with PFAS. In addition, micron-sized ZV can undergo self-decomposition through corrosion in solution to form nano-sized ZV, which has even stronger surface interactions and can further enhance PFAS adsorption. Therefore, ZV exhibits extremely strong adsorption affinity and high adsorption capacity for PFAS per unit mass.
[0007] The transient high temperature and high energy generated by the mechanical collision during the ball milling process cause structural strain in the perfluorinated compounds, which in turn leads to a defluorination reaction, degrading organic fluorine into inorganic fluoride ions, and the degradation is completed within a few hours.
[0008] Perfluorinated and polyfluorinated compounds include perfluorooctanoic acid, perfluorooctanoic acid, perfluorobutyric acid, perfluorobutyric acid, and perfluorobutyric acid. Chlorinated hydrocarbons are completely degraded. Taking perfluorooctanoic acid as an example, its degradation products mainly include fluoride ions and sulfate ions.
[0009] Further, in step one, the preparation method of the zero-valent magnesium material is as follows: magnesium powder and graphite are placed in a ball mill and mechanically ball-milled to obtain the zero-valent magnesium material.
[0010] Furthermore, in step one, the particle size of the zero-valent magnesium material does not exceed 147 μm (100 mesh sieve), and the mass fraction of graphite does not exceed 15%.
[0011] Furthermore, in step one, the dosage of the zero-valent magnesium material is 1.0–2.0 g / L.
[0012] Furthermore, in step one, the concentration of perfluorinated and polyfluorinated compounds in the water to be treated is 100-1000 g / L.
[0013] Furthermore, in step one, the adsorption temperature is 20-25℃ and the adsorption time is 0.5-2h.
[0014] Furthermore, in step one, the pH of the water to be treated is 3.0-11.0.
[0015] Furthermore, in step one, the water to be treated is surface water or groundwater.
[0016] Furthermore, in step two, the time for ball milling to degrade perfluorinated and polyfluorinated compounds is 8–10 h, and the ball milling speed is 500–600 r / min.
[0017] Furthermore, in step two, the adsorbed zero-valent magnesium material is separated from the treated water by filtration or centrifugation.
[0018] The beneficial effects of this invention are as follows:
[0019] I. This invention utilizes highly efficient adsorption materials and simple adsorption methods to maximize the mass and minimize the time required to fix perfluorinated and polyfluorinated compounds per unit mass of material. This firstly achieves rapid purification of polluted water bodies, and further optimizes the dosage of remediation agents and the concentration of pollutants in the polluted water body to achieve the highest efficiency in rapidly removing PFAS. Furthermore, the adsorption-saturated zero-valent magnesium material can be further mechanically ball-milled to completely degrade PFAS into easily decomposable products, thereby reducing the total amount of PFAS pollution in the environment and reducing the long-term impact of harmful substances on the environment. This is conducive to promoting the treatment and control of persistent new pollutants in the environment.
[0020] Second, the method of this invention is simple, easy to operate, requires minimal equipment, and has low operating costs. Furthermore, it is not sensitive to the pH of the polluted water during the adsorption and removal of PFAS, and is applicable within a pH range of 3.0-11.0, demonstrating strong applicability. Zero-valent magnesium can be repeatedly used for PFAS adsorption and removal, exhibiting long-term stability. After complete corrosion of zero-valent magnesium in solution, it mainly forms magnesium hydroxide precipitate, which is a common mineral in the environment and is environmentally friendly. After mechanical ball milling, the PFAS in the zero-valent magnesium or magnesium hydroxide are completely decomposed, and the material can be disposed of as general waste, reducing the risk of secondary pollution. Overall, utilizing zero-valent magnesium materials to adsorb and degrade PFAS can simultaneously achieve the dual requirements of high-efficiency removal and environmental protection. Attached Figure Description
[0021] Figure 1 This is a transmission electron microscope image of micron-sized zero-valent magnesium material;
[0022] Figure 2 This is the XRD pattern of micron-sized zero-valent magnesium material;
[0023] Figure 3 This is the XPS C 1s spectrum of micron-sized zero-valent magnesium material;
[0024] Figure 4 This is a diagram showing the removal effect of micron-sized zero-valent magnesium materials on PFOA and PFOS;
[0025] Figure 5 This is a graph showing the change in fluoride ion concentration in the extract of micron-sized zero-valent magnesium material after ball milling and adsorption.
[0026] Figure 6 This is a comparison chart of the effects of pH on the removal of PFOA and PFOS by micron-sized zero-valent magnesium. Detailed Implementation
[0027] The present invention will be further described below with reference to specific embodiments.
[0028] Example 1
[0029] This embodiment provides a method for adsorbing and degrading PFOA and PFOS in water using zero-valent magnesium materials, including the following steps:
[0030] Step 1: Micron-sized zero-valent magnesium material was added to water containing different concentrations of PFOA and PFOS. The dosage of micron-sized zero-valent magnesium material was 1.0 g / L; the pH of the system was adjusted to 6.2 with 0.1 M sodium hydroxide solution; the reaction temperature was maintained at 20–25 °C, and the reaction was carried out with shaking at 150 rpm for 1–4 hours. The results are as follows. Figure 4 As shown in Table 1.
[0031] The preparation method of micrometer-sized zero-valent magnesium material is as follows: 4.5g of commercial zero-valent magnesium and 0.5g of commercial graphite are weighed and placed in a ball mill jar. Then, 100g of zirconium oxide beads are added to the jar. Under a nitrogen atmosphere and at room temperature (20-25℃), the ball mill is run at 300 rpm for 2 hours, with the direction changed every 10 minutes, to obtain micrometer-sized zero-valent magnesium material (mZVMg). TEM-mapping ( Figure 1 ) and XRD patterns ( Figure 2 The results showed that after mechanical ball milling, graphite and zero-valent magnesium were uniformly distributed on the surface of the micron-sized zero-valent magnesium material. C1s(…) was analyzed by XPS. Figure 3 The spectrum shows that the high-energy mechanical ball milling process successfully promoted the formation of the new chemical bond Mg-C structure.
[0032] from Figure 4It can be seen that the micron-sized zero-valent magnesium material achieved removal rates of 88.70% and 96.49% for PFOA and PFOS at a concentration of 100 μg / L, respectively, and reached adsorption equilibrium within 30 min. However, as the concentrations of PFOA and PFOS increased from 100 μg / L to 5000 μg / L, the removal rates decreased to 26.88% and 69.88%, respectively, and the reaction equilibrium time increased to 2 h. The pseudo-first-order adsorption kinetics fitting results showed that when the concentrations of PFOA and PFOS in water increased to 5000 μg / L, the adsorption rate constant of the micron-sized zero-valent magnesium material for PFOA decreased from 16.18 h⁻¹. -1 It dropped to 5.41h -1 Meanwhile, its adsorption rate constant for PFOS increased from 32.25 h⁻¹. -1 Dropped to 16.35h -1 .
[0033] Table 1. Rate constants for the adsorption of different concentrations of PFOA and PFOS in water by micron-sized zero-valent magnesium materials.
[0034]
[0035] Step 2: The micron-sized zero-valent magnesium material, after adsorbing 100 μg / L PFOS for 4 hours, was placed in a ball mill. The ball milling speed was set to 500 r / min. Samples were removed at different milling times, and PFOS and fluoride ions in the zero-valent magnesium material were extracted with water. After 8 hours of reaction, the PFOS concentration on the material was below the detection limit, while the fluoride ion concentration in the extract gradually increased. The results are as follows: Figure 5 As shown, PFOS is gradually degraded during ball milling, and fluoride ions are generated.
[0036] Example 2
[0037] This embodiment provides a method for adsorbing PFOA and PFOS in water using zero-valent magnesium materials. The method is basically the same as step one of Embodiment 1, with the specific parameters as follows:
[0038] The dosage of micron-sized zero-valent magnesium material ranged from 0.2 to 10.0 g / L, with PFOA and PFOS concentrations of 500 μg / L and 5000 μg / L, respectively. The pH was 6.2, and the reaction time was 1–4 h. The results are shown in Table 2. When the pollutant concentration was 500 μg / L, as the mZVMg dosage increased from 0.2 g / L to 2.0 g / L, the PFOA removal rate increased from 20.18% to 91.44%, and the PFOS removal rate increased from 51.91% to 98.97%. When the PFOA and PFOS concentrations were 5000 μg / L, as the material dosage increased from 1.0 g / L to 10.0 g / L, the PFOA removal rate increased from 25.71% to 94.92%, while the PFOS removal rate increased from 66.27% to 95.19%. This indicates that the micron-sized zero-valent magnesium material maintains high removal rates for PFOA and PFOS over a wide concentration range.
[0039] Table 2. Removal rates of PFOA and PFOS at different concentrations in water by adsorption of micron-sized zero-valent magnesium materials with different dosages.
[0040]
[0041] Example 3
[0042] This embodiment provides a method for adsorbing PFOA and PFOS in water using zero-valent magnesium material. The method is basically the same as step one of Example 1, with the following specific parameters: the dosage of micron-sized zero-valent magnesium material is 1.0 g / L, the concentrations of PFOA and PFOS are set to 500 μg / L respectively, and the initial pH range is 3.0–11.0. The results after 8 hours of reaction are as follows... Figure 6 As shown, the initial pH has little effect on PFOS removal; the PFOS removal rate is above 93.59% across a wide pH range (3.0-11.0). Within the pH range of 3.0-9.0, the PFOA removal rate remains above 66.46%; however, at pH 11.0, the PFOA removal rate drops to 34.41%. In summary, the micron-sized zero-valent magnesium material prepared in this invention can achieve efficient adsorption of PFOA and PFOS across a wide pH range, indicating that the environmental pH value has little impact on the reaction system.
[0043] In this invention, unless otherwise stated, scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, the reagents, materials, and procedures used herein are all widely used in the relevant fields.
[0044] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for adsorbing and degrading perfluorinated and polyfluorinated compounds in water using zero-valent magnesium materials, characterized in that: Includes the following steps: Step 1: Add the zero-valent magnesium material to the water to be treated containing perfluorinated and polyfluorinated compounds, mix thoroughly, and allow the perfluorinated and polyfluorinated compounds to be adsorbed and fixed on the zero-valent magnesium material. The preparation method of the zero-valent magnesium material is as follows: magnesium powder and graphite are placed in a ball mill and mechanically ball-milled to obtain the zero-valent magnesium material; The dosage of the zero-valent magnesium material is 1.0~2.0 g / L; the concentration of perfluorinated and polyfluorinated compounds in the water to be treated is 100-1000 μg / L; the adsorption temperature is 20-25℃, and the adsorption time is 0.5-2 h. Step 2: Place the adsorbed zero-valent magnesium material in a ball mill for mechanical ball milling to degrade the perfluorinated and polyfluorinated compounds adsorbed on the zero-valent magnesium material; The perfluorinated and polyfluorinated compounds are specifically PFOS and PFOA.
2. The method for adsorbing and degrading perfluorinated and polyfluorinated compounds in water using zero-valent magnesium materials according to claim 1, characterized in that: In step one, the particle size of the zero-valent magnesium material does not exceed 147 μm, and the mass fraction of graphite does not exceed 15%.
3. The method for adsorbing and degrading perfluorinated and polyfluorinated compounds in water using zero-valent magnesium materials according to claim 1, characterized in that: In step one, the pH of the water to be treated is 3.0-11.
0.
4. The method for adsorbing and degrading perfluorinated and polyfluorinated compounds in water using zero-valent magnesium materials according to claim 1, characterized in that: In step one, the water to be treated is surface water or groundwater.
5. The method for adsorbing and degrading perfluorinated and polyfluorinated compounds in water using zero-valent magnesium materials according to claim 1, characterized in that: In step two, the time for ball milling to degrade perfluorinated and polyfluorinated compounds is 8-10 h, and the ball milling speed is 500-600 r / min.
6. The method for adsorbing and degrading perfluorinated and polyfluorinated compounds in water using zero-valent magnesium materials according to claim 1, characterized in that: In step two, the adsorbed zero-valent magnesium material is separated from the treated water by filtration or centrifugation.