High-entropy Friedel's salt fluorine removal agent as well as preparation method and application thereof

Abstract

The invention discloses a high-entropy Friedel's salt fluorine removal agent as well as a preparation method and application thereof, and belongs to the technical field of wastewater treatment and environmental functional material preparation. The invention solves the problems of weak selectivity, low adsorption capacity, poor stability and the like of the existing defluorination material. Through co-doping of multiple metal ions including Bi, Fe, Mg, Ti and Zr, a high-entropy solid solution structure is formed in mayenite crystal lattices, then the crystal lattice distortion and charge imbalance effect is generated, the diversity and activity of surface sites are remarkably improved, and the affinity and exchange capacity of the fluorine removal agent to fluorine ions are improved. Experimental results show that the fluorine removal efficiency of the prepared high-entropy Friedel's salt fluorine removal agent on a fluorine-containing water sample with the initial concentration of 350 mg / L can reach 95% or above, and is far higher than that of an undoped fluorine removal agent (53.2%). In addition, the fluorine removal agent is simple in preparation process and easy to industrially amplify, and has good environmental benefits and wide application prospects.

Description

Technical Field

[0001] This invention relates to a high-entropy Fred salt defluorinating agent, its preparation method, and its application, belonging to the technical field of wastewater treatment and environmental functional material preparation. Background Technology

[0002] In industry, wastewater discharged from metallurgy, chemical, electronics, and phosphate fertilizer industries often contains high concentrations of fluoride ions, posing a serious threat to the ecological environment and human health. my country's "Integrated Wastewater Discharge Standard" (GB8978-1996) clearly stipulates that the first-level discharge standard for fluoride cannot exceed 10 mg / L.

[0003] Currently, mainstream defluoridation technologies include precipitation, adsorption, ion exchange, and membrane separation. Among these, precipitation methods, such as lime precipitation, are low-cost but require large amounts of reagents and produce high sludge yields. Adsorption methods commonly use materials such as activated alumina and zeolite, but suffer from limited adsorption capacity and regeneration difficulties. In recent years, calcium aluminate materials, due to their layered structure which can accommodate anions, have been used in defluoridation research. Their hydration product, Frederick salt, can capture fluoride ions through ion exchange. However, traditional calcium aluminate and Frederick salts have low defluoridation efficiency, and the defluoridation products are difficult to utilize as resources, limiting their practical application.

[0004] High-entropy materials, as a class of solid solutions composed of multiple elements, can form stable single-phase crystal structures and exhibit excellent physicochemical properties due to the high-entropy effect, achieving breakthroughs in fields such as alloys and ceramics. Studies have shown that introducing multiple metal ions to construct a high-entropy system can significantly enhance the surface site activity and ion exchange capacity of the material. However, the application of high-entropy design concepts to Frederick salt defluorination materials remains a gap in research. Current technologies have not yet achieved the ability to enhance the selective adsorption capacity of fluoride ions by controlling the lattice structure of calcium aluminum oxide or Frederick salt through multi-metal doping. Therefore, developing a Frederick salt defluorination agent based on the high-entropy effect has significant scientific and engineering value. Summary of the Invention

[0005] To address the problems of weak selectivity, low adsorption capacity, and poor stability of existing defluorination materials, this invention provides a high-entropy Fred salt defluorination agent, its preparation method, and its application.

[0006] The technical solution of the present invention: One objective of this invention is to provide a method for preparing a high-entropy Fred salt defluorinating agent, the method comprising the following steps: (1) Add deionized water to the mixed powder of CaO and Al2O3, stir into a paste, let stand, and obtain the matrix; (2) Add a compound containing Bi, Fe, Mg and Ti to the matrix, stir evenly, then add a compound containing Zr, mix thoroughly, and dry to obtain the calcination precursor; (3) The calcined precursor was calcined at 600-1200 °C, cooled, ground and sieved to obtain high-entropy material; (4) Soak the high-entropy material in a saturated sodium chloride solution. After soaking, filter and dry to obtain the high-entropy Fred salt defluorinating agent.

[0007] Further specifying, the molar ratio of CaO and Al2O3 in (1) is (1.5-2.5):1.

[0008] To further specify, the molar ratio of CaO to Al2O3 in (1) is (1.8-2.1):1.

[0009] Further specifying, the settling time in (1) is 2 h.

[0010] Further specifying, in (2), the molar ratio of Bi, Fe, Mg and Ti is 1:1:1:1, the molar ratio of Bi to Al is (0.001-0.006):1, and the molar ratio of Zr to Al is (0-0.03):1.

[0011] To further specify, the molar ratio of Bi to Al in (2) is (0.002-0.004):1.

[0012] To further specify, the molar ratio of Zr to Al in (2) is (0.018-0.022):1.

[0013] Further specifying, (2) the Bi-containing compound is Bi2O3, Bi(NO3)3, Bi2(SO4)3, BiCl3, BiOCl or Bi2O2CO3.

[0014] Further specifying, (2) the Fe-containing compounds are Fe2O3, Fe(NO3)3, Fe2(SO4)3, FeCl3, FeOCl or Fe2(CO3)3.

[0015] Further specify that (2) contains Mg compounds such as MgO, Mg(NO3)2, MgSO4, MgCl2 or MgCO3.

[0016] Further specifying, (2) the Ti-containing compound is TiO2, Ti(NO3)4, Ti(SO4)2 or TiCl4.

[0017] Further specifying, (2) the Zr-containing compound is ZrO2, Zr(NO3)4, Zr(SO4)2, ZrCl4 or (Zr(CO3)2).

[0018] Further specifying, the drying temperature in (2) is 55-105 °C.

[0019] Further specified, in (3) the calcination time is 2 h and the heating rate is 10 °C / min.

[0020] Further specified, the calcination temperature in (3) is 800-900 °C.

[0021] Further specifying, (3) after cooling, grind through a 100-mesh sieve.

[0022] Further specifying, the soaking time in (4) is 24 h.

[0023] The second objective of this invention is to provide a high-entropy Fred salt defluorinating agent prepared by the above method.

[0024] The third objective of this invention is to provide an application of the above-mentioned high-entropy Fred salt defluorinating agent in the defluorination of fluoride-containing wastewater.

[0025] Beneficial effects: This invention introduces the high-entropy design concept into the calcium aluminum stone system. Through co-doping with multiple metal ions such as Bi, Fe, Mg, Ti, and Zr, a high-entropy solid solution structure is formed in the calcium aluminum stone lattice, resulting in lattice distortion and charge imbalance effects. This significantly increases the diversity and activity of surface sites, enhancing the affinity and exchange capacity for fluoride ions. Compared with traditional Fred salt defluorinators, the defluorination performance is greatly improved. Experimental results show that the high-entropy Fred salt defluorinator prepared in this invention can achieve a defluorination efficiency of over 95% for fluoride-containing water samples with an initial concentration of 350 mg / L, far exceeding that of the undoped defluorinator (53.2%). This is because the defluorination mechanism of the high-entropy Fred salt defluorinator prepared in this invention not only involves Ca... 2+ With F - The formation of CaF2 precipitate also includes interlayer ion exchange and the reaction of high-valence metal hydroxyl oxides with F. - The complexation and displacement effects of Bi and Zr are significant, with Bi increasing adsorption capacity, Ti enhancing surface active site density, and Zr improving selectivity for fluoride ions. Furthermore, the method for preparing high-entropy Fred salt defluorinating agents in this invention involves only conventional operations such as grinding, drying, high-temperature calcination, and filtration, requiring no complex equipment, having moderate energy consumption, a simple and controllable process, and being easy to scale up industrially, making it suitable for large-scale production. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the process for preparing the high-entropy Fred salt defluorinating agent according to the present invention; Figure 2 The XRD patterns of the defluorinating agents prepared in Example 2 and Comparative Example 1 are shown below. Figure 3 SEM images and EDS spectra of the high-entropy Fred salt defluorinating agent prepared in Example 2. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0028] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art may make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0029] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0030] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0031] Example 1: A method for preparing a high-entropy Fred salt defluorinating agent: like Figure 1 As shown, CaO and Al2O3 with a molar ratio of 1.8:1 were weighed as matrix raw materials, mixed, and then an equal mass of deionized water was added. The mixture was stirred into a uniform paste and allowed to stand for 2 hours to form a matrix. Four compounds, Bi(NO3)3, Fe(NO3)3, Mg(NO3)2, and Ti(SO4)2, were added to the matrix, providing a molar ratio of Bi, Fe, Mg, and Ti of 1:1:1:1, and a molar ratio of Bi to Al of 0.002:1. The mixture was stirred until homogeneous to obtain a high-entropy material precursor. ZrO2 was then added as a zirconium source, controlling the molar ratio of Zr to Al to be 0.018:1, and the mixture was thoroughly ground and mixed. The mixture was placed in an oven and dried at 60 °C for 6 hours to obtain a calcined precursor. The dried calcined precursor was placed in a muffle furnace and heated to 800 °C at a heating rate of 10 °C / min, and calcined for 2 hours. h, after naturally cooling to room temperature, grind and pass through a 100-mesh sieve to obtain high-entropy material; the obtained high-entropy material is immersed in a saturated sodium chloride solution for 24 h to activate, then filtered and dried in an 80 °C oven for 12 h to obtain high-entropy Fred salt defluorinating agent, labeled A.

[0032] Example 2: A method for preparing a high-entropy Fred salt defluorinating agent: CaO and Al₂O₃ with a molar ratio of 2.1:1 were weighed as matrix raw materials, mixed, and then an equal mass of deionized water was added. The mixture was stirred into a homogeneous paste and allowed to stand for 2 hours to form a matrix. BiCl₃, FeCl₃, MgCl₂, and TiCl₄ compounds were added to the matrix, providing a Bi, Fe, Mg, and Ti molar ratio of 1:1:1:1 and a Bi to Al molar ratio of 0.003:1. The mixture was stirred until homogeneous to obtain a high-entropy material precursor. Zr(NO₃)₄ was added as a zirconium source, controlling the Zr to Al molar ratio at 0.020:1, and the mixture was thoroughly ground and mixed. The mixture was dried at 80 °C for 4 hours to obtain a calcined precursor. The dried calcined precursor was heated to 900 °C at a rate of 10 °C / min and calcined at this temperature for 2 hours. After cooling, the precursor was ground and passed through a 100-mesh sieve to obtain the high-entropy material. The obtained high-entropy material was then immersed in a saturated sodium chloride solution for 24 hours. After activation by h, the solution is filtered and dried at 75 °C for 10 h to obtain the high-entropy Fred salt defluorinating agent, labeled as B.

[0033] Example 3: A method for preparing a high-entropy Fred salt defluorinating agent: CaO and Al₂O₃ with a molar ratio of 2.0:1 were weighed as matrix raw materials and mixed with an equal mass of deionized water to form a paste. The paste was allowed to stand for 2 hours to form the matrix. Bi₂O₃, Fe₂O₃, MgO, and ZrO₂ were added as metal ion sources, providing a Bi, Fe, Mg, and Ti molar ratio of 1:1:1:1 and a Bi to Al molar ratio of 0.004:1. The mixture was stirred until homogeneous to obtain a high-entropy material precursor. Zr(SO₄)₂ was further added as a zirconium source, maintaining a Zr to Al molar ratio of 0.022:1. The mixture was ball-milled for 30 minutes to ensure homogeneity. The precursor was dried at 105 °C for 3 hours to obtain a calcined precursor. The calcined precursor was heated to 850 °C at 10 °C / min and calcined for 2 hours. After cooling, it was ground through a 100-mesh sieve to obtain the high-entropy material. The obtained high-entropy material was activated in a saturated NaCl solution for 24 hours, filtered, and then dried in a vacuum drying oven at 80 °C for 12 hours. h, that is, the high-entropy Fred salt defluorinating agent, is obtained and labeled as C.

[0034] Example 4: A method for preparing a high-entropy Fred salt defluorinating agent: CaO and Al2O3 with a molar ratio of 1.5:1 were weighed as matrix raw materials and mixed with an equal mass of deionized water to form a paste. The paste was allowed to stand for 2 hours to form the matrix. Bi2O2CO3, Fe2(SO4)3, MgCO3, and Ti(NO3)4 were added as metal ion sources, with a molar ratio of Bi, Fe, Mg, and Ti of 1:1:1:1 and a molar ratio of Bi to Al of 0.006:1. The mixture was stirred until homogeneous to obtain a high-entropy material precursor. ZrCl4 was then added as a zirconium source, with a molar ratio of Zr to Al of 0.03:1, and the mixture was thoroughly mixed. The precursor was dried at 55 °C for 8 hours to obtain a calcined precursor. The calcined precursor was calcined at 1200 °C for 2 hours at a rate of 10 °C / min, cooled, and ground to below 100 mesh to obtain the high-entropy material. The obtained high-entropy material was soaked in a saturated sodium chloride solution for 24 hours, filtered, and then... Drying at °C yields the high-entropy Fred salt defluorinating agent, labeled as D.

[0035] Comparative Example 1: A method for preparing a high-entropy Fred salt defluorinating agent: CaO and Al2O3 with a molar ratio of 2.1:1 were weighed as matrix raw materials, mixed, and then an equal mass of deionized water was added. The mixture was stirred into a homogeneous paste and allowed to stand for 2 h to form a matrix. Four compounds, BiCl3, FeCl3, MgCl2, and TiCl4, were added to the matrix, providing a molar ratio of Bi, Fe, Mg, and Ti of 1:1:1:1 and a molar ratio of Bi to Al of 0.003:1. The mixture was dried at 80 °C for 4 h to obtain a calcination precursor. The dried calcination precursor was heated to 900 °C at a rate of 10 °C / min and calcined at a constant temperature for 2 h. After cooling, it was ground and passed through a 100-mesh sieve to obtain a high-entropy material. The obtained high-entropy material was activated by soaking in a saturated sodium chloride solution for 24 h, filtered, and dried at 75 °C for 10 h to obtain a defluorinating agent, labeled as E.

[0036] Comparative Example 2: A method for preparing a defluorinating agent: CaO and Al2O3 with a molar ratio of 2.1:1 were weighed as matrix raw materials, mixed, and then an equal mass of deionized water was added. The mixture was stirred into a uniform paste and allowed to stand for 2 h to form a matrix. Zr(NO3)4 was added to the matrix as a zirconium source, and the molar ratio of Zr to Al was controlled at 0.020:1. The mixture was thoroughly ground and mixed evenly. The mixture was dried at 80 °C for 4 h to obtain a calcination precursor. The dried calcination precursor was heated to 900 °C at a rate of 10 °C / min and calcined at a constant temperature for 2 h. After cooling, it was ground and passed through a 100-mesh sieve to obtain zircon-loaded calcium aluminum stone material. The material was activated by soaking in a saturated sodium chloride solution for 24 h, filtered, and dried at 75 °C for 10 h to obtain a defluorinating agent, labeled as F.

[0037] Comparative Example 3: A method for preparing a defluorinating agent: CaO and Al2O3 with a molar ratio of 2.1:1 were weighed as matrix raw materials, mixed, and then an equal mass of deionized water was added. The mixture was stirred into a uniform paste and allowed to stand for 2 h to form a matrix. The matrix was dried at 80 °C for 4 h to obtain a calcination precursor. The dried calcination precursor was heated to 900 °C at a rate of 10 °C / min and calcined at a constant temperature for 2 h. After cooling, it was ground and passed through a 100-mesh sieve to obtain a calcium aluminum stone material. The material was activated by soaking in a saturated sodium chloride solution for 24 h, filtered, and dried at 75 °C for 10 h to obtain a defluorinating agent, labeled as G.

[0038] The structures of the defluorinating agents prepared in Example 2 and Comparative Example 1 were characterized. Figure 1 The image shows an XRD pattern, where the red line corresponds to Example 2 and the black line corresponds to Example 1. Figure 1 It can be seen that the characteristic peak of Fred salt appeared in the defluorinating agent prepared in Example 2, indicating that Fred salt was successfully prepared. Compared with the defluorinating agent prepared in Comparative Example 1, it can be seen that the introduction of zirconium can reduce the impurity peak to a certain extent, thereby improving the crystal stability and facilitating the formation of high-entropy Fred salt.

[0039] The morphology of the defluorinating agent prepared in Example 2 was characterized, and the SEM images and EDS spectra are shown below. Figure 3 As shown in (a) and (b), the defluorinating agent prepared in Example 2 exhibits a hexagonal morphology, and a large number of small particles containing high-entropy metal components are attached to the surface of the Fred salt, further indicating the formation of a high-entropy Fred salt defluorinating agent. Figure 3 (b) It can be seen that the high-entropy Fred salt defluorinating agent prepared in Example 2 contains Bi, Fe, Mg, Ti, and Zr components, and adsorbs a large amount of Cl during the activation process with saturated sodium chloride. - These characteristics lay the foundation for high defluorination rate and high adsorption capacity.

[0040] The defluorination efficiency of the defluorinating agents prepared in Examples 1-4 and Comparative Examples 1-3 was characterized. Specifically, 0.5 g of the defluorinating agent prepared above was added to 50 mL of a solution with an initial fluoride ion concentration of 350 mg / L. After stirring at 300 rpm for 4 h, the solution was filtered, and the residual fluoride ion concentration in the solution was measured. Based on this, the saturated adsorption capacity and fluoride ion removal rate of the defluorinating agent were calculated. The test results are shown in Table 1 below.

[0041] Table 1. Defluorination efficiency and adsorption capacity of various defluorinating agents

[0042] As shown in Table 1 above, the defluoridating agents prepared in the above embodiments and comparative examples, as tested, demonstrate that the high-entropy Fred salt defluoridating agents achieve a removal rate of over 95% for fluoride-containing water samples with an initial concentration of 350 mg / L, significantly outperforming traditional Fred salt materials without multi-metal doping. Among them, Examples 2 and 3 exhibit even higher defluoridation efficiency and adsorption capacity, making them suitable for highly efficient defluorination of fluoride-containing wastewater.

[0043] The above description is only a preferred embodiment of the present invention. Given that those skilled in the art can make appropriate changes and modifications to the above embodiments, the present invention is not limited to the specific embodiments described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a high-entropy Fred salt defluorinating agent, characterized in that, include: (1) Add deionized water to the mixed powder of CaO and Al2O3, stir into a paste, let stand, and obtain the matrix; (2) Add a compound containing Bi, Fe, Mg and Ti to the matrix, stir evenly, then add a compound containing Zr, mix thoroughly, and dry to obtain the calcination precursor; (3) The calcined precursor was calcined at 600-1200 °C, cooled, ground and sieved to obtain high-entropy material; (4) Soak the high-entropy material in a saturated sodium chloride solution. After soaking, filter and dry to obtain the high-entropy Fred salt defluorinating agent.

2. The preparation method according to claim 1, characterized in that, (1) The molar ratio of CaO to Al2O3 is (1.5-2.5):

1.

3. The preparation method according to claim 1, characterized in that, (2) The molar ratio of Bi, Fe, Mg and Ti is 1:1:1:1, the molar ratio of Bi to Al is (0.001-0.006):1, and the molar ratio of Zr to Al is (0-0.03):

1.

4. The preparation method according to claim 1, characterized in that, (2) The Bi-containing compounds are Bi2O3, Bi(NO3)3, Bi2(SO4)3, BiCl3, BiOCl or Bi2O2CO3.

5. The preparation method according to claim 1, characterized in that, (2) The Fe-containing compounds are Fe2O3, Fe(NO3)3, Fe2(SO4)3, FeCl3, FeOCl or Fe2(CO3)3.

6. The preparation method according to claim 1, characterized in that, (2) The Mg-containing compounds are MgO, Mg(NO3)2, MgSO4, MgCl2 or MgCO3.

7. The preparation method according to claim 1, characterized in that, (2) The Ti-containing compounds are TiO2, Ti(NO3)4, Ti(SO4)2 or TiCl4.

8. The preparation method according to claim 1, characterized in that, (2) The Zr-containing compounds are ZrO2, Zr(NO3)4, Zr(SO4)2, ZrCl4 or (Zr(CO3)2).

9. A high-entropy Fred salt defluorinating agent prepared by the method according to any one of claims 1 to 8.

10. The application of the high-entropy Fred salt defluorinating agent according to claim 9 in the defluorination of fluoride-containing wastewater.

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