A method for efficient hydrolysis of hexafluorophosphate in wastewater catalyzed by high-valence metal cations

Abstract

This invention discloses a highly efficient hydrolysis method for hexafluorophosphate ions in wastewater catalyzed by high-valence metal cations. The hydrolysis method utilizes the strong Lewis acidity of high-valence metal cations in water, which can react with PF6. ‑ This characteristic of fluorine atoms bonding together makes PF6 ‑ The formation of Lewis acid-base pair intermediates that are susceptible to nucleophilic attack (water) significantly reduces PF6. ‑ High-temperature hydrolysis reaction energy barrier, and realization of PF6 ‑ Preliminary pyrolysis produces a large amount of H. + Subsequently, the H produced by hydrolysis + Due to its strong polarization effect, it interferes with PF6. ‑ The electronic structure can further reduce PF6 ‑ Thermal stability, high-valence metal cations and H + Synergistic catalysis enables highly efficient pyrolysis of hexafluorophosphate. This invention offers advantages such as high hydrolysis efficiency, low operating costs, no need for extreme acid or alkaline environments, low equipment corrosivity, and ease of engineering application.

Description

Technical Field

[0001] This invention relates to a highly efficient hydrolysis method for hexafluorophosphate in wastewater catalyzed by high-valence metal cations, belonging to the field of wastewater treatment technology. Background Technology

[0002] Lithium hexafluorophosphate (LiPF6) electrolyte components are widely used in new energy industries related to lithium batteries due to their excellent electrochemical stability. However, with the booming development of the new energy industry, the environmental problems associated with its upstream and downstream industrial chains are becoming increasingly prominent. The Helmholtz Centre for Environmental Research in Germany has simultaneously detected PF6 in multiple river basins and regions. - In conjunction with relevant toxicological studies, PF6 has been confirmed to be effective. - It has extremely high biotoxicity and environmental persistence, and was identified as a novel persistent and mobile chemical pollutant in 2021.

[0003] Due to PF6 - Its extremely high chemical stability makes traditional oxidation methods ineffective, and its high biotoxicity also limits the application of traditional biochemical methods. Currently, for PF6... - Hydrolysis processes are mostly acid-based pyrolysis, the core principle of which is PF6. - The intrinsic property of PF6's stability decreasing under high temperature and high pressure conditions can be addressed by using high temperature and hot acid conditions. - Hydrolysis produces phosphate and fluoride ions. However, this type of process requires highly corrosion-resistant equipment and also necessitates the additional handling of highly toxic HF vapor, resulting in high maintenance costs and demanding operating conditions.

[0004] For these types of fluorine-containing inorganic anions with extremely high chemical stability (such as PF6) - BF4 - AsF6 - Studies have shown that the stability of PF6 can be effectively reduced by constructing Lewis acid-base intermediates. Theoretically, this can be achieved by utilizing the strong Lewis acidity of high-valence metal cations, in conjunction with PF6... - One or more fluorine atoms combine to form a Lewis acid-base pair intermediate, thereby reducing its thermal stability and achieving PF6. - Preliminary pyrolysis produces a large amount of H. + Subsequently, the H produced by hydrolysis + Due to its strong polarization, it interferes with PF6. - The electronic structure can further reduce PF6 - thermal stability, achieving PF6 - Highly efficient hydrolysis.

[0005] Based on this, the present invention develops a method for catalyzing PF6 in wastewater using high-valence metal cations.- The highly efficient hydrolysis process utilizes the strong Lewis acidity of high-valence metal cations and H+ without requiring additional pH adjustment. + The polarization effect effectively reduces PF6 - This method overcomes the pyrolysis energy barrier, enabling highly efficient Lewis pyrolysis. Compared to traditional pyrolysis processes, this method effectively solves the problem of PF6... - It overcomes key challenges such as difficult hydrolysis and high requirements for equipment corrosion resistance, while also possessing advantages such as environmental friendliness, economic efficiency, ease of operation, and easy engineering application. Summary of the Invention

[0006] For existing wastewater containing hexafluorophosphate (PF6) - The present invention addresses the problems of severe equipment corrosion and high treatment costs in pyrolysis processes. It provides a highly efficient hydrolysis method for hexafluorophosphate in wastewater catalyzed by high-valence metal cations, which has the advantages of being environmentally friendly, economically efficient, easy to operate, and easy to implement in engineering.

[0007] The technical solution provided by this invention to solve the above problems is: a highly efficient hydrolysis method for hexafluorophosphate ions in wastewater catalyzed by high-valence metal cations, the hydrolysis method comprising the following steps:

[0008] Step (1): [The text abruptly ends here, likely due to an incomplete sentence or a formatting error.] - Wastewater and a high-valence metal cation solution were added to a magnetically stirred reactor. The reactor was placed inside a heating jacket, and magnetic stirring was activated to initiate a high-temperature pyrolysis reaction. The high-valence metal cations reacted with PF6. - Formation of Lewis acid-base pair metastable intermediates, reducing PF6 - Thermal stability, i.e., reducing PF6 - The pyrolysis energy barrier is used to achieve PF6 - Preliminary pyrolysis;

[0009] Step (2): During the high-temperature pyrolysis process in the magnetically stirred reactor, water, as a nucleophile, reacts with the Lewis acid-base metastable intermediate formed in step (1), promoting the hydrolysis of PF6- and generating a large amount of H2O. + ;

[0010] Step (3): The H generated in step (2) + The pH level of the reaction environment inside the magnetically stirred reactor is adjusted, while H... + The strong polarization of H⁺ interferes with the electronic structure of PF⁶⁻, further weakening its thermal stability, thus allowing it to react with H⁺ via a high-valence metal Lewis acid-base intermediate. + Strong polarization enhances the efficient hydrolysis of PF6-, ultimately achieving the hydrolysis of PF6-.

[0011] Preferably, in step (2), the reaction equation for water with the Lewis acid-base metastable intermediate is shown in equation (1):

[0012]

[0013] Preferably, in step (3) H + The equations that interfere with the electronic structure of PF6- are shown in equations (2), (3), and (4):

[0014]

[0015] HF-PF5→PF5+HF (3)

[0016]

[0017] Preferably, the magnetically stirred reactor contains H... + The generation of [the substance] does not require additional adjustment of the pH value of the water environment inside the magnetically stirred reactor.

[0018] Preferably, in step (1), the amount of metal cation added to the high-valence metal cation solution is 50-100 mM, and the high-valence metal cation preferably includes Al. 3+ Zr 4+ Sn 4+ Fe 3+ Ti 4+ At least one of them.

[0019] Preferably, in step (1), PF6 in the wastewater - The concentration is 10–12 mM.

[0020] Preferably, in step (1), the temperature range of high-temperature pyrolysis in the magnetically stirred reactor is 60-100°C, and the high-temperature pyrolysis time is 3-6 hours.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. This invention utilizes high-valence metal cations and H+ + Co-catalysis, thereby achieving PF6 - It features highly efficient pyrolysis and eliminates the need for adding high-concentration inorganic acids, significantly reducing the corrosiveness to processing equipment.

[0023] 2. The metal salts used in this invention are inexpensive and readily available, economical and efficient, and suitable for large-scale production. Furthermore, this invention has the advantages of simple process, easy operation, stable operation, and easy engineering application. Attached Figure Description

[0024] Figure 1The graph shows the concentrations of fluoride ions and phosphate ions in the original reaction solutions before and after pyrolysis in this invention.

[0025] Figure 2 The low-valent metal cation catalyzed PF6 in this invention - Comparison chart of pyrolysis performance;

[0026] Figure 3 This invention provides a high-valence metal cation catalytic process for PF6. - Comparison chart of pyrolysis performance;

[0027] Figure 4 This is the high-valence metal cation and hexafluorophosphate (PF6) in this invention. - ) Schematic diagram of the formation of Lewis acid-base pair metastable intermediate. Detailed Implementation

[0028] This section will describe in detail the specific embodiments of the present invention. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods. The purpose of the accompanying drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0029] A preferred embodiment of the present invention provides a method for the efficient hydrolysis of hexafluorophosphate in wastewater catalyzed by high-valence metal cations, the hydrolysis method comprising the following steps:

[0030] Step (1): Add wastewater containing PF6- and a high-valence metal cation solution to a magnetically stirred reactor. Place the reactor inside a heating jacket and turn on the magnetic stirring to perform high-temperature pyrolysis. The high-valence metal cations form a Lewis acid-base metastable intermediate with PF6-, reducing the thermal stability of PF6-, i.e., lowering the pyrolysis energy barrier of PF6-, thus achieving the initial pyrolysis of PF6-. Figure 4 As shown;

[0031] Step (2): During the high-temperature pyrolysis process in the magnetically stirred reactor, water, as a nucleophile, reacts with the Lewis acid-base metastable intermediate formed in step (1), promoting the hydrolysis of PF6- and generating a large amount of H2O. + ;

[0032] Step (3): The H generated in step (2) + The pH level of the reaction environment inside the magnetically stirred reactor is adjusted, while H... + The strong polarization of H⁺ interferes with the electronic structure of PF⁶⁻, further weakening its thermal stability, thus allowing it to react with H⁺ via a high-valence metal Lewis acid-base intermediate. + Strong polarization enhances the efficient hydrolysis of PF6-, ultimately achieving the hydrolysis of PF6-.

[0033] Furthermore, in step (2), the reaction equation for water with the Lewis acid-base metastable intermediate is shown in equation (1):

[0034]

[0035] Furthermore, in step (3) H + The equations that interfere with the electronic structure of PF6- are shown in equations (2), (3), and (4):

[0036]

[0037] HF-PF5→PF5+HF (3)

[0038]

[0039] Furthermore, within the magnetically stirred reactor, due to H... + The generation of [the substance] does not require additional adjustment of the pH value of the water environment inside the magnetically stirred reactor.

[0040] Further, in step (1), the amount of metal cation added to the high-valence metal cation solution is 50-100 mM, and the preferred high-valence metal cation is Al. 3+ Zr 4+ Sn 4+ Fe 3+ Ti 4+ At least one of them.

[0041] Furthermore, in step (1), PF6 in the wastewater - The concentration is 10–12 mM.

[0042] Further, in step (1), the temperature range of high-temperature pyrolysis in the magnetically stirred reactor is 60-100℃, and the high-temperature pyrolysis time is 3-6 hours.

[0043] The hydrolysis principle of this invention is based on the strong Lewis acidity of high-valence metal cations in water, which can react with PF6. - This characteristic of fluorine atoms bonding together makes PF6 - The formation of Lewis acid-base pair intermediates that are susceptible to nucleophilic attack (water) significantly reduces PF6. - High-temperature hydrolysis reaction energy barrier, and realization of PF6 - Preliminary pyrolysis produces a large amount of H. + Subsequently, the H produced by hydrolysis + Due to its strong polarization, it interferes with PF6. - The electronic structure can further reduce PF6 -Thermal stability, high-valence metal cations and H + Synergistic catalysis enables efficient pyrolysis of hexafluorophosphate.

[0044] Example 1

[0045] Formulating PF6 - An initial concentration of 10 mM was used to simulate the reaction solution. After preparation, the concentrations of fluoride ions and phosphate ions in the initial reaction solution were tested. Subsequently, 50 mL of the 10 mM hexafluorophosphate solution was transferred into a magnetically stirred reactor using a graduated cylinder. The reactor was then placed in a heating mantle, and magnetic stirring was activated while the temperature was increased. After heating to 100 degrees Celsius, the reaction was carried out for 6 hours. After the reaction was completed, the solution was cooled to room temperature, and the concentrations of fluoride ions and phosphate ions in the mother liquor after pyrolysis were tested.

[0046] like Figure 1 As shown, the concentrations of fluoride ions and phosphate ions in the mother liquor of the reaction solution did not change much before and after pyrolysis, indicating that only about 10% of hexafluorophosphate ions were completely hydrolyzed after pyrolysis. This shows that hexafluorophosphate ions are very stable. Without the addition of high-valence metal cations, it is difficult for hexafluorophosphate ions to be attacked by water and undergo pyrolysis in the absence of a metastable Lewis acid-base pair intermediate.

[0047] Example 2

[0048] Five 50 mL samples of 10 mM PF6 were measured using a graduated cylinder. - The solution was added to three 100mL beakers, and different low-valent metal ion salts (Sn) were added to each beaker. 2+ Ca 2+ Mg 2+ The concentration of low-valent metal cations in the reaction solution was adjusted to 50 mM. After the low-valent metal ion salts in the beaker were completely dissolved, the solutions were poured into three magnetically stirred reactors. The reactors were placed in heating mantles, and magnetic stirring was turned on while the temperature was increased. After reaching 100 degrees Celsius, the reaction was maintained at this temperature for 6 hours. After the reaction was completed, the solutions were cooled to room temperature, and the concentrations of fluoride and phosphate ions in the pyrolysis reaction solution containing the added low-valent metal cations were measured.

[0049] like Figure 2 As shown, Ca 2+ Mg 2+ Two low-valence metal cations against PF6 - The pyrolysis of PF6 did not have a catalytic effect, possibly because the low-valence metal cations could not react with PF6. - Metastable intermediates are formed; however, Sn 2+ Because it is readily oxidized to Sn by fluorine in acidic solutions. 4+ Therefore, it can play the same role as directly adding Sn. 4+With similar catalytic effects, this experiment demonstrates the catalytic effect of high-valence metal cations on the high-temperature pyrolysis of hexafluorophosphate.

[0050] Example 3

[0051] Five 50 mL samples of 10 mM PF6 were measured using a graduated cylinder. - The solution was added to five 100mL beakers, and five common high-valence metal ion salts (Al) were added to each beaker. 3+ Zr 4+ Sn 4+ Fe 3+ Ti 4+ The concentration of high-valence metal cations in the reaction solution was adjusted to 50 mM. After the high-valence metal ion salts in the beakers were completely dissolved, the solutions were poured into five magnetically stirred reactors. The reactors were placed in heating mantles, and magnetic stirring was turned on while the temperature was increased. The reaction was carried out for 6 hours after reaching 100 degrees Celsius. After the reaction was completed, the solutions were cooled to room temperature, and the concentrations of fluoride and phosphate ions in the pyrolysis reaction solution containing added high-valence metal cations were measured.

[0052] like Figure 3 As shown, after adding high-valence metal cations and completing the pyrolysis reaction, a large amount of hexafluorophosphate ions in the reaction solution undergo hydrolysis. Among the five high-valence metal cations selected, the order of catalytic performance is: Al 3+ >Fe 3+ >Sn 4+ >Ti 4+ >Zr 4 + Al 3+ The catalytic effect is most significant for PF6. - The hydrolysis rate of Zr can reach 94%. 4+ The catalytic effect was the weakest, at only 56%, PF6 - The hydrolysis catalytic performance may be related to the content of metal cations in the reaction medium, Fe 3+ Sn 4+ Ti 4+ Zr 4+ In all four groups, significant precipitates were observed in the solutions after the reaction, presumably hydroxide precipitates. These precipitates are the main reason for the poor hydrolysis performance. Under high-temperature hydrothermal conditions, the formation of insoluble hydroxide precipitates leads to a reduction in free high-valence metal cations, thus causing a decrease in catalytic performance. Experimental results show that high-valence metal cations can effectively catalyze the efficient pyrolysis of hexafluorophosphate in water. Combined with the results obtained in Example 1, this further illustrates that the reaction of high-valence metal cations and H+... + In the synergistic catalytic pyrolysis of hexafluorophosphate, high-valence metal cations play a major catalytic role.

[0053] The above description only illustrates the preferred embodiments of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments; all variations made within the scope of the independent claims of the present invention are within the scope of protection of the present invention.

Claims

1. A highly efficient hydrolysis method for hexafluorophosphate ions in wastewater catalyzed by high-valence metal cations, characterized in that: The hydrolysis method includes the following steps: Step (1): [The text abruptly ends here, likely due to an incomplete sentence or a formatting error.] - Wastewater and a high-valence metal cation solution were added to a magnetically stirred reactor. The reactor was placed inside a heating jacket, and magnetic stirring was activated to initiate a high-temperature pyrolysis reaction. The high-valence metal cations reacted with PF6. - Formation of Lewis acid-base pair metastable intermediates, reducing PF6 - Thermal stability, i.e., reducing PF6 - The pyrolysis energy barrier is used to achieve PF6 - Preliminary pyrolysis yields high-valence metal cations, including Al. 3+ Sn 4+ Fe 3+ At least one of them; Step (2): During the high-temperature pyrolysis process in the magnetically stirred reactor, water, as a nucleophile, reacts with the Lewis acid-base metastable intermediate formed in step (1), promoting the reaction of PF6. - Hydrolysis, generating a large amount of H2 + ; Due to H in the magnetically stirred reactor + The generation of [the substance] does not require additional adjustment of the pH value of the water environment inside the magnetically stirred reactor; Step (3): The H generated in step (2) + The pH level of the reaction environment inside the magnetically stirred reactor is adjusted, while H... + The strong polarization effect interferes with PF6 - The electronic structure further weakens PF6. - The thermal stability, thus through the high-valence metal Lewis acid-base intermediate and H + Strong polarization effect on PF6 - The synergistic effect of efficient hydrolysis ultimately achieves PF6 - Hydrolysis.

2. The method for efficient hydrolysis of hexafluorophosphate in wastewater catalyzed by high-valence metal cations according to claim 1, characterized in that: In step (2), the reaction equation for water with the Lewis acid-base metastable intermediate is shown in equation (1): （1）。 3. The method for efficient hydrolysis of hexafluorophosphate in wastewater catalyzed by high-valence metal cations according to claim 1, characterized in that: In step (3) H + Interference PF6 - The equations for the electronic structure are shown in equations (2), (3), and (4): （2） （3） （4）。 4. The method for efficient hydrolysis of hexafluorophosphate in wastewater catalyzed by high-valence metal cations according to claim 1, characterized in that: In step (1), the amount of metal cation added to the high-valence metal cation solution is 50~100mM.

5. The method for efficient hydrolysis of hexafluorophosphate in wastewater catalyzed by high-valence metal cations according to claim 1, characterized in that: In step (1), PF6 in the wastewater - The concentration is 10~12mM.

6. The method for efficient hydrolysis of hexafluorophosphate in wastewater catalyzed by high-valence metal cations according to claim 1, characterized in that: Step (1): The temperature range of high-temperature pyrolysis in the magnetically stirred reactor is 60~100℃, and the high-temperature pyrolysis time is 3~6 hours.

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