De- fluorinating agent, and preparation method and application thereof
By preparing metal-doped carbon nitride materials as defluorinating agents, the problem of unsatisfactory defluorination effect of high-fluoride hydrochloric acid was solved, realizing an efficient and economical defluorination process and reducing the risk of environmental pollution.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HAOHUA ENG CO LTD
- Filing Date
- 2023-11-30
- Publication Date
- 2026-06-09
Smart Images
Figure CN117482889B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of fluorochemical technology, and in particular to a defluorinating agent, its preparation method, and its application. Background Technology
[0002] Fluorochemicals, with its superior product performance, diverse varieties, wide range of applications, and remarkable economic benefits, has become a rapidly developing and important industry. Its products are widely used in construction, automotive, electronics, aerospace, defense, and pharmaceutical industries, and its applications are expanding into even broader and deeper areas with technological advancements. However, the fluorochemical industry produces numerous byproducts, among which fluorinated hydrochloric acid is difficult to treat, posing significant safety and environmental challenges. With the large-scale expansion and development of the fluorochemical industry, the production of high-fluorinated hydrochloric acid is constantly increasing, posing risks of environmental pollution and resource waste. Therefore, it is urgent to overcome key technologies for purifying byproduct fluorinated hydrochloric acid to promote the green and sustainable development of the fluorochemical industry.
[0003] Currently, widely used defluorination methods for high-fluoride hydrochloric acid include reaction precipitation, distillation, and selective adsorption. However, these methods are not very effective and have not been widely adopted. Summary of the Invention
[0004] Therefore, it is necessary to provide new defluorinating agents that can improve the defluorination effect, as well as their preparation methods and applications.
[0005] One aspect of this application provides a method for preparing a defluorinating agent, comprising the following steps:
[0006] A transition metal precursor is mixed with a nitrogen source and a carbon source and heated to obtain a eutectic; and
[0007] The eutectic is calcined under a protective atmosphere.
[0008] In some embodiments of this application, the transition metal precursor includes one or more of cerium source, zirconium source, lanthanum source and cobalt source, and / or the nitrogen source and the carbon source are the same substance, which may be urea.
[0009] In some embodiments of this application, the molar ratio of urea to the transition metal precursor is 1:(0.002 to 0.1), and may be 1:(0.002 to 0.01).
[0010] In some embodiments of this application, the temperature at which the transition metal precursor and urea are mixed and heated is 40°C to 90°C.
[0011] In some embodiments of this application, the calcination includes a first-stage calcination and a second-stage calcination.
[0012] The calcination temperature in the first stage is 180℃~300℃, the heating rate is 1℃ / min~10℃ / min, and the holding time is 30min~240min;
[0013] The second stage of calcination is carried out at a temperature of 500℃~600℃, a heating rate of 5℃ / min~10℃ / min, and a holding time of 60min~240min.
[0014] In another aspect of this application, a defluorinating agent prepared by the described preparation method is provided.
[0015] In some embodiments of this application, the surface functional groups of the defluorinating agent include -Cl groups and / or -OH groups.
[0016] In some embodiments of this application, the specific surface area of the defluorinating agent is 40 m². 2 / g~120m 2 / g.
[0017] In another aspect, this application provides the application of the defluorinating agent in the defluorination of fluorinated hydrochloric acid.
[0018] In some embodiments of this application, the hydrochloric acid contains 1% to 30% hydrochloric acid by mass, and / or 50 ppm to 4000 ppm fluorine by mass.
[0019] In another aspect, this application provides a method for defluorinating fluorinated hydrochloric acid, comprising the following steps: adding the defluorinating agent to the fluorinated hydrochloric acid, wherein 0.5g to 10g of the defluorinating agent is added per liter of fluorinated hydrochloric acid.
[0020] In some embodiments of this application, the method for defluorinating with fluorine-containing hydrochloric acid further includes a step of desorbing the defluorinating agent. Optionally, the reagent used for desorption is an alkaline solution, an acid solution, or a saturated salt solution. More specifically, it may be a NaOH solution with a concentration of 1 mol / L to 10 mol / L, a hydrochloric acid solution with a concentration of 1 mol / L to 10 mol / L, or a saturated NaCl solution.
[0021] Compared with the prior art, this application has at least the following beneficial effects:
[0022] The defluorinating agent preparation method provided in this application involves heating a transition metal precursor and urea to form a eutectic, followed by calcination of the eutectic to obtain metal-doped carbon nitride. The metal-doped carbon nitride prepared in this application, as a defluorinating agent, possesses a large specific surface area and exhibits extremely strong adsorption of fluoride in hydrochloric acid through complexation between the metal and fluorine, and hydrogen bonding between HF and the N atoms in the C3N4 main structure. Furthermore, it exhibits acid resistance and recyclability. The defluorinating agent preparation method provided in this application is highly efficient, simple, and low-cost, achieving a harmonious balance between high efficiency, pollution-free operation, and economic cost, thus possessing significant application potential. Attached Figure Description
[0023] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0024] Figure 1 SEM images of the defluorinating agents prepared in Examples 6-9;
[0025] Figure 2 EDS diagrams of the defluorinating agents prepared in Examples 6-9;
[0026] Figure 3 TEM images of the defluorinating agents prepared in Examples 6-9;
[0027] Figure 4 XRD patterns of the defluorinating agents prepared in Examples 6-9;
[0028] Figure 5 FTIR images of a metal precursor, urea, and eutectic in one embodiment;
[0029] Figure 6 DSC diagrams of eutectic mixtures formed by different proportions of metal precursors and urea;
[0030] Figure 7 FTIR images of a defluorinating agent according to one embodiment and the defluorinating agent after multiple cycles of recovery;
[0031] Figure 8 Nitrogen adsorption-desorption curve and pore size distribution diagram of a defluorinating agent according to one embodiment;
[0032] Figure 9 XPS images of a defluorinating agent before and after adsorption and desorption, according to one embodiment. Detailed Implementation
[0033] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.
[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0035] In this application, terms such as "first aspect," "second aspect," and "third aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features.
[0036] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.
[0037] In this application, "one or more" means any one, two or more of the listed items.
[0038] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.
[0039] Unless otherwise specified, the percentage content mentioned in this application refers to mass percentage for solid-liquid mixtures and solid-phase-solid mixtures, and volume percentage for liquid-phase-liquid mixtures.
[0040] Unless otherwise specified, all percentage concentrations mentioned in this application refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.
[0041] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows for temperature fluctuations within the precision range controlled by the instrument.
[0042] Method steps that do not specify temperature in this application generally refer to method steps performed at room temperature or ambient temperature. In this document, room temperature or ambient temperature is equivalent and can be used interchangeably; specifically, temperature refers to 22°C to 25°C.
[0043] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.
[0044] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.
[0045] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.
[0046] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.
[0047] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
[0048] In this application, "eutectic" refers to a homogeneous solid mixture that melts into a melt of the same composition when heated to a specific temperature. This melting temperature is lower than the melting point of these compounds or elements.
[0049] Carbon nitride (C3N4) has a highly ordered triazine ring framework, thus exhibiting good resistance to strong acids and bases. Furthermore, the presence of -NH2 and =NH groups on its surface endows it with excellent surface properties, enabling carbon nitride materials to adsorb various inorganic ions. The hydrogen bonding of the nitrogen atoms in the C3N4 main structure (N…HF hydrogen bonds) gives the material a certain affinity for fluorine. However, most carbon nitride materials exhibit low specific surface areas, and their adsorption capacity needs improvement. Metal doping of carbon nitride can alter its morphology and increase adsorption sites, but this process often requires high-temperature and high-pressure methods such as hydrothermal treatment to construct a uniform and ordered structure at the microscale, which is usually a bottleneck hindering cost reduction. Therefore, optimizing the structure and morphology of carbon nitride to prepare a simple, inexpensive, acid-resistant, and highly efficient defluorinating agent has great application potential.
[0050] To achieve the above objectives, the first aspect of this application provides a method for preparing a defluorinating agent, comprising the following steps:
[0051] S12, a transition metal precursor is mixed with a nitrogen source and a carbon source and heated to obtain a eutectic; and
[0052] S14, the eutectic is calcined under a protective atmosphere.
[0053] In the above preparation method, during the formation of the eutectic mixture of the metal precursor and urea, these two components act as hydrogen bond donors and acceptors, respectively, achieving a uniform distribution of the doped metal at a relatively low temperature. Further calcination induces a thermal polycondensation reaction, yielding a metal-composite carbon nitride material. These two processes not only effectively ensure the uniformity of metal doping but also significantly increase the material's specific surface area. The prepared material exhibits extremely strong acid resistance (very low metal leaching rate), and due to the complexation between the metal and fluorine, and the hydrogen bonding between HF and the N atoms in the C3N4 main structure, the prepared metal-doped carbon nitride material demonstrates a strong adsorption effect on fluorine in hydrochloric acid. Moreover, this metal-doped carbon nitride material can be repeatedly recycled as a defluorinating agent.
[0054] Without limitation, transition metal precursors include nitrates, chlorides, sulfates, and chlorides of transition metals. In some embodiments, transition metal precursors include one or more of cerium, zirconium, lanthanum, and cobalt sources.
[0055] Without limitation, the nitrogen source may include inorganic nitrogen compounds such as ammonium nitrogen (NH4) + Nitrate nitrogen (NO3—) and simple organic nitrogen compounds (such as urea), etc.
[0056] Without limitation, carbon sources can include inorganic and organic carbon sources, such as methanol, sodium acetate, glucose, urea, and biomass carbon sources.
[0057] In some implementations, the nitrogen source and carbon source are the same substance, which may be urea.
[0058] In some embodiments, the molar ratio of urea to the transition metal precursor is 1:(0.002 to 0.1) or any ratio therebetween, such as 1:0.005, 1:0.006, 1:0.007, 1:0.008, 1:0.009, 1:0.01, 1:0.05, or 1:0.08. In some optional embodiments, the molar ratio of urea to the transition metal precursor is 1:(0.002 to 0.01).
[0059] In some embodiments, the mass ratio of the transition metal precursor to urea is 1:5 to 1:20 and any ratio therebetween, for example, it can also be 1:6, 1:8, 1:10, 1:12, 1:15, or 1:18.
[0060] In some embodiments, step S12 involves heating the mixture of the transition metal precursor and urea at a temperature of 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, or any value between them.
[0061] In some implementations, the protective atmosphere is air, nitrogen, or carbon dioxide.
[0062] In some embodiments, the calcination in step S14 includes a first-stage calcination and a second-stage calcination.
[0063] Optionally, the temperature of the first-stage calcination is 180℃ to 300℃ and any value between therewith, for example, 180℃, 200℃, 220℃, 250℃, or 280℃. Optionally, the heating rate of the first-stage calcination is 1℃ / min to 10℃ / min and any value between therewith, for example, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, or 9℃ / min. Further optionally, the holding time of the first-stage calcination is 30 min to 240 min and any value between therewith, for example, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 120 min, 140 min, 160 min, 180 min, 200 min, or 220 min.
[0064] Optionally, the temperature of the second-stage calcination is 500℃ to 600℃ and any value between therewith, for example, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, or 590℃. Optionally, the heating rate of the second-stage calcination is 5℃ / min to 10℃ / min and any value between therewith, for example, 6℃ / min, 7℃ / min, 8℃ / min, or 9℃ / min. Further optionally, the holding time of the first-stage calcination is 60min to 240min and any value between therewith, for example, 70min, 80min, 90min, 100min, 120min, 140min, 160min, 180min, 200min, or 220min.
[0065] The metal-doped carbon nitride prepared under the above calcination conditions has a better adsorption effect on fluorine as a defluorinating agent.
[0066] A second aspect of this application provides a defluorinating agent obtained by the preparation method of any of the above embodiments.
[0067] In some embodiments, the surface functional groups of the above-mentioned defluorinating agent include not only the -NH2, =NH and other groups present in carbon nitride itself, but also -Cl groups and / or -OH groups. The -Cl groups and -OH groups can form ion exchange interactions with F, thereby further improving the defluorination effect of the defluorinating agent.
[0068] In some embodiments, the specific surface area of the defluorinating agent is 40 m². 2 / g~120m 2 / g and any values between them. Specific surface area within this range is more conducive to the defluorination effect of the defluorinating agent.
[0069] A third aspect of this application provides the application of the above-mentioned defluorinating agent in the defluorination of fluorinated hydrochloric acid.
[0070] In some embodiments, the hydrochloric acid mass concentration in the fluorinated hydrochloric acid is 1% to 30%. Understandably, the hydrochloric acid mass concentration in the fluorinated hydrochloric acid may include, but is not limited to, 1%, 5%, 10%, 15%, 20%, 25%, and 30%. The defluorinating agent of this application is used in a strongly acidic environment.
[0071] In some embodiments, the fluorine concentration in the fluorinated hydrochloric acid is 50 ppm to 4000 ppm. Understandably, the fluorine concentration in the fluorinated hydrochloric acid may include, but is not limited to, 50 ppm, 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, and 400 ppm.
[0072] A fourth aspect of this application also provides a method for defluorinating fluorinated hydrochloric acid, comprising the following steps: adding a defluorinating agent according to any of the above embodiments to the fluorinated hydrochloric acid, wherein 0.5g to 10g of the defluorinating agent is added per liter of fluorinated hydrochloric acid.
[0073] In some embodiments, the method for defluorinating with fluorinated hydrochloric acid further includes a step of desorbing the defluorinating agent. Optionally, the reagent used for desorption is an alkaline solution, an acidic solution, or a saturated salt solution. The defluorinating agent of this application can be desorbed to achieve regeneration and recycling.
[0074] Specific examples of alkaline solutions include, but are not limited to, NaOH solutions with concentrations ranging from 1 mol / L to 10 mol / L. Specific examples of acidic solutions include, but are not limited to, hydrochloric acid solutions with concentrations ranging from 1 mol / L to 10 mol / L. Specific examples of saturated salt solutions include, but are not limited to, saturated NaCl solutions.
[0075] The following are specific embodiments. They are intended to provide a more detailed description of this application to help those skilled in the art and researchers better understand it. The technical conditions described do not constitute any limitation on this application. Any modifications made within the scope of the claims of this application are protected by the claims.
[0076] Unless otherwise stated, all raw materials and reagents used in the following examples are commercially available or can be prepared by known methods. Experimental methods not specifying particular conditions in the examples were performed under conventional conditions, such as those described in literature, books, or methods recommended by the manufacturer.
[0077] Example 1
[0078] 0.3123 g of cerium chloride and 10 g of urea were added to a 30 mL covered crucible and heated to 40 °C until the solid was completely dissolved. After cooling, the crucible was calcined in a muffle furnace under an air atmosphere. The heating program was as follows: the temperature was increased from 25 °C to 180 °C over 160 min, held at 180 °C for 30 min, then increased to 550 °C over 37 min, held at 550 °C for 60 min, and then allowed to cool naturally to room temperature. The mixture was then ground into powder. Fluorine adsorption was tested in a system with a fluorine concentration of 1000 ppm and a hydrochloric acid mass concentration of 20%, and the fluorine adsorption efficiency was measured to be 69.90 mg / g. After fluorine adsorption saturation, the composite material was sequentially immersed in 1 mol / L NaOH solution, 1 mol / L hydrochloric acid solution, and saturated NaCl solution for 60 min each time. After 5 cycles, the adsorption efficiency decreased to 81%.
[0079] Example 2
[0080] 0.6513 g of cerium nitrate and 10 g of urea were added to a 30 mL covered crucible and heated to 60 °C until the solid completely dissolved. After cooling, the crucible was calcined in a muffle furnace under an air atmosphere. The heating program was as follows: 25 °C was increased to 220 °C over 40 min, held at 220 °C for 90 min, then increased to 600 °C over 70 min, held at 600 °C for 120 min, and then allowed to cool naturally to room temperature before grinding into powder. Fluorine adsorption was tested in a system with a fluorine concentration of 500 ppm and a hydrochloric acid mass concentration of 30%, and the fluorine adsorption efficiency was measured to be 50.32 mg / g. After fluorine adsorption saturation, the composite material was sequentially immersed in 5 mol / L NaOH solution, 1 mol / L hydrochloric acid solution, and saturated NaCl solution for 60 min each time. After 5 cycles, the adsorption efficiency decreased to 78%.
[0081] Example 3
[0082] 0.3850 g of lanthanum chloride and 10 g of urea were added to a 30 mL covered crucible and heated to 75 °C until the solid completely dissolved. After cooling, the crucible was calcined in a muffle furnace under an air atmosphere. The heating program was as follows: the temperature was increased from 25 °C to 300 °C over 30 min, held at 300 °C for 150 min, then increased to 550 °C over 25 min, held at 550 °C for 120 min, and then allowed to cool naturally to room temperature before grinding into powder. Fluorine adsorption was tested in a system with a fluorine concentration of 1000 ppm and a hydrochloric acid mass concentration of 11%, and the fluorine adsorption efficiency was measured to be 68.72 mg / g. After fluorine adsorption saturation, the composite material was sequentially immersed in 10 mol / L NaOH solution, 1 mol / L hydrochloric acid solution, and saturated NaCl solution for 60 min each time. After 5 cycles, the adsorption efficiency decreased to 78%.
[0083] Example 4
[0084] 0.2293 g of lanthanum nitrate and 10 g of urea were added to a 30 mL covered crucible and heated to 75 °C until the solid completely dissolved. After cooling, the crucible was calcined in a muffle furnace under a carbon dioxide atmosphere. The heating program was as follows: the temperature was increased from 25 °C to 200 °C over 37 min, held at 200 °C for 240 min, then increased to 600 °C over 70 min, held at 600 °C for 240 min, and then allowed to cool naturally to room temperature before grinding into powder. Fluorine adsorption was tested in a system with a fluorine concentration of 4000 ppm and a hydrochloric acid mass concentration of 5%, and the fluorine adsorption efficiency was measured to be 97.20 mg / g. After fluorine adsorption saturation, the composite material was sequentially immersed in 10 mol / L NaOH solution, 1 mol / L hydrochloric acid solution, and saturated NaCl solution for 60 min each time. After 5 cycles, the adsorption efficiency decreased to 82%.
[0085] Example 5
[0086] 0.4123 g of cobalt nitrate and 10 g of urea were added to a 30 mL covered crucible and heated to 90 °C until the solid was completely dissolved. After cooling, the crucible was calcined in a muffle furnace under a carbon dioxide atmosphere. The heating program was as follows: the temperature was increased from 25 °C to 300 °C over 40 min, held at 300 °C for 90 min, then increased to 550 °C over 60 min, held at 550 °C for 120 min, and then allowed to cool naturally to room temperature before grinding into powder. Fluorine adsorption was tested in a system with a fluorine concentration of 2500 ppm and a hydrochloric acid mass concentration of 30%, and the fluorine adsorption efficiency was measured to be 80.35 mg / g. After fluorine adsorption saturation, the composite material was sequentially immersed in 5 mol / L NaOH solution, 1 mol / L hydrochloric acid solution, and saturated NaCl solution for 60 min each time. After 5 cycles, the adsorption efficiency decreased to 80%.
[0087] Example 6
[0088] 0.3574 g of zirconium nitrate and 10 g of urea were added to a 30 mL covered crucible and heated to 60 °C until the solid was completely dissolved. After cooling, the crucible was calcined in a muffle furnace under a nitrogen atmosphere. The heating program was as follows: the temperature was increased from 25 °C to 300 °C over 40 min, held at 300 °C for 90 min, then increased to 550 °C over 60 min, held at 550 °C for 120 min, and then allowed to cool naturally to room temperature before grinding into powder. Fluorine adsorption was tested in a system with a fluorine concentration of 1000 ppm and a hydrochloric acid mass concentration of 20%, and the fluorine adsorption efficiency was measured to be 72.23 mg / g. After fluorine adsorption saturation, the composite material was sequentially immersed in 5 mol / L NaOH solution, 2 mol / L hydrochloric acid solution, and saturated NaCl solution for 60 min each time. After 5 cycles, the adsorption efficiency decreased to 79%.
[0089] Example 7
[0090] 0.2025 g of zirconium oxynitrate and 10 g of urea were added to a 30 mL covered crucible and heated to 60 °C until the solid was completely dissolved. After cooling, the crucible was calcined in a muffle furnace under a carbon dioxide atmosphere. The heating program was as follows: from 25 °C to 200 °C in 37 min, held at 200 °C for 90 min, then increased to 550 °C in 70 min, held at 550 °C for 120 min, and then allowed to cool naturally to room temperature. The mixture was then ground into powder. Fluorine adsorption was tested in a system with a fluorine concentration of 1000 ppm and a hydrochloric acid mass concentration of 20%, and the fluorine adsorption efficiency was measured to be 23.17 mg / g. After fluorine adsorption saturation, the composite material was sequentially immersed in 5 mol / L NaOH solution, 2 mol / L hydrochloric acid solution, and saturated NaCl solution for 60 min each time. After 5 cycles, the adsorption efficiency decreased to 79%.
[0091] Example 8
[0092] 0.3880 g of zirconium chloride and 10 g of urea were added to a 30 mL covered crucible and heated to 60 °C until the solid was completely dissolved. After cooling, the crucible was calcined in a muffle furnace under a carbon dioxide atmosphere. The heating program was as follows: from 25 °C to 220 °C in 37 min, held at 180 °C for 90 min, then increased to 550 °C in 70 min, held at 550 °C for 120 min, and then allowed to cool naturally to room temperature. The mixture was then ground into powder. Fluorine adsorption was tested in a system with a fluorine concentration of 500 ppm and a hydrochloric acid mass concentration of 15%, and the fluorine adsorption efficiency was measured to be 37.00 mg / g. After fluorine adsorption saturation, the composite material was sequentially immersed in 5 mol / L NaOH solution, 2 mol / L hydrochloric acid solution, and saturated NaCl solution for 60 min each time. After 5 cycles, the adsorption efficiency decreased to 79%.
[0093] Example 9
[0094] 0.26830 g of zirconium oxychloride and 10 g of urea were added to a 30 mL covered crucible and heated to 60 °C until the solid was completely dissolved. After cooling, the crucible was calcined in a muffle furnace under an air atmosphere. The heating program was as follows: from 25 °C to 160 °C in 37 min, held at 200 °C for 90 min, then increased to 550 °C in 70 min, held at 550 °C for 120 min, and then allowed to cool naturally to room temperature. The mixture was then ground into powder. Fluorine adsorption was tested in a system with a fluorine concentration of 50 ppm and a hydrochloric acid mass concentration of 30%, and the fluorine adsorption efficiency was measured to be 24.32 mg / g. After fluorine adsorption saturation, the composite material was sequentially immersed in 5 mol / L NaOH solution, 2 mol / L hydrochloric acid solution, and saturated NaCl solution for 60 min each time. After 5 cycles, the adsorption efficiency decreased to 79%.
[0095] Example 10
[0096] The preparation method is basically the same as that in Example 1, except that segmented calcination is not performed. The specific steps are as follows:
[0097] 0.3123 g of cerium chloride and 10 g of urea were added to a 30 mL covered crucible and heated to 40 °C until the solid was completely dissolved. After cooling, the crucible was placed in a muffle furnace for calcination in an air atmosphere. The heating program was as follows: the temperature was increased from 25 °C to 550 °C within 200 min, held for 60 min, and then allowed to cool naturally to room temperature. The mixture was then ground into powder. Fluorine adsorption was tested in a system with a fluorine concentration of 1000 ppm and a hydrochloric acid mass concentration of 20%, and the fluorine adsorption efficiency was measured to be 36.4 mg / g. After fluorine adsorption saturation, the composite material was sequentially immersed in 1 mol / L NaOH solution, 3 mol / L hydrochloric acid solution, and saturated NaCl solution for 60 min each time. After 5 cycles, the adsorption efficiency decreased to 70%.
[0098] Example 11
[0099] 0.5051 g of zirconium chloride and 10 g of urea were added to a 30 mL covered crucible and heated to 60 °C until the solid was completely dissolved. After cooling, the crucible was calcined in a muffle furnace under a carbon dioxide atmosphere. The heating program was as follows: from 25 °C to 220 °C in 37 min, held at 180 °C for 90 min, then increased to 550 °C in 70 min, held at 550 °C for 120 min, and then allowed to cool naturally to room temperature. The mixture was then ground into powder. Fluorine adsorption was tested in a system with a fluorine concentration of 500 ppm and a hydrochloric acid mass concentration of 15%, and the fluorine adsorption efficiency was measured to be 39.08 mg / g. After fluorine adsorption saturation, the composite material was sequentially immersed in 5 mol / L NaOH solution, 2 mol / L hydrochloric acid solution, and saturated NaCl solution for 60 min each time. After 5 cycles, the adsorption efficiency decreased to 79%.
[0100] Example 12
[0101] 1.031 g of zirconium chloride and 10 g of urea were added to a 30 mL covered crucible and heated to 60 °C until the solid was completely dissolved. After cooling, the crucible was calcined in a muffle furnace under a carbon dioxide atmosphere. The heating program was as follows: from 25 °C to 220 °C in 37 min, held at 180 °C for 90 min, then increased to 550 °C in 70 min, held at 550 °C for 120 min, and then allowed to cool naturally to room temperature. The mixture was then ground into powder. Fluorine adsorption was tested in a system with a fluorine concentration of 500 ppm and a hydrochloric acid mass concentration of 15%, and the fluorine adsorption efficiency was measured to be 48.10 mg / g. After fluorine adsorption saturation, the composite material was sequentially immersed in 5 mol / L NaOH solution, 2 mol / L hydrochloric acid solution, and saturated NaCl solution for 60 min each time. After 5 cycles, the adsorption efficiency decreased to 65%.
[0102] Example 13
[0103] 1.4286 g of zirconium chloride and 10 g of urea were added to a 30 mL covered crucible and heated to 60 °C until the solid was completely dissolved. After cooling, the crucible was calcined in a muffle furnace under a carbon dioxide atmosphere. The heating program was as follows: from 25 °C to 220 °C in 37 min, held at 180 °C for 90 min, then increased to 550 °C in 70 min, held at 550 °C for 120 min, and then allowed to cool naturally to room temperature. The mixture was then ground into powder. Fluorine adsorption was tested in a system with a fluorine concentration of 500 ppm and a hydrochloric acid mass concentration of 15%, and the fluorine adsorption efficiency was measured to be 54.21 mg / g. After fluorine adsorption saturation, the composite material was sequentially immersed in 5 mol / L NaOH solution, 2 mol / L hydrochloric acid solution, and saturated NaCl solution for 60 min each time. After 5 cycles, the adsorption efficiency decreased to 61%.
[0104] Example 14
[0105] 2.063 g of zirconium chloride and 10 g of urea were added to a 30 mL covered crucible and heated to 60 °C until the solid was completely dissolved. After cooling, the crucible was calcined in a muffle furnace under a carbon dioxide atmosphere. The heating program was as follows: from 25 °C to 220 °C in 37 min, held at 180 °C for 90 min, then increased to 550 °C in 70 min, held at 550 °C for 120 min, and then allowed to cool naturally to room temperature. The mixture was then ground into powder. Fluorine adsorption was tested in a system with a fluorine concentration of 500 ppm and a hydrochloric acid mass concentration of 15%, and the fluorine adsorption efficiency was measured to be 59.30 mg / g. After fluorine adsorption saturation, the composite material was sequentially immersed in 5 mol / L NaOH solution, 2 mol / L hydrochloric acid solution, and saturated NaCl solution for 60 min each time. After 5 cycles, the adsorption efficiency decreased to 59%.
[0106] Test case
[0107] 1. Morphological test
[0108] Figure 1 SEM images of the defluorinating agents prepared in Examples 6-9 are shown. Figure 2 EDS diagrams of the defluorinating agents prepared in Examples 6-9 are shown. Figure 3 TEM images of the defluorinating agents prepared in Examples 6-9 are shown. Figure 4 The XRD patterns of the defluorinating agents prepared in Examples 6-9 are shown.
[0109] Figure 1 and Figure 3 The microstructure of the defluorinating agent material was revealed. Figure 2 This confirms the presence and distribution of elements such as C, N, Zr, Cl, and O in the defluorinating agent material. Figure 4 The crystal structure of the defluorinating agent material was revealed.
[0110] 2. Eutectic test
[0111] Figure 5 The infrared spectra of the metal precursor (labeled as metal precursor in the figure), urea, and the eutectic mixture formed by the two are shown. Figure 5 It can be seen that the heating of the metal precursor and urea did not lead to the formation of any new chemical bonds. In contrast, the changes in the relevant characteristic peaks in the eutectic indicate that new interactions such as hydrogen bonds may have been formed.
[0112] Figure 6 DSC diagrams of eutectic mixtures formed from metal precursors and urea at different ratios (Examples 11, 12, 13, and 14 are ratios 1, 2, 3, and 4, respectively) are shown. Figure 6 It was confirmed that the formed substance has a melting point lower than that of any component, meaning that the two raw materials formed a eutectic by heating.
[0113] 3. Defluorinating agent test
[0114] Figure 7 The infrared spectra of the defluorinating agent prepared in Example 8 (labeled as composite material in the figure) and the defluorinating agent after recycling are shown. Figure 7 It is known that the defluorinating agent contains a triazine ring, hydroxyl group and zirconium; at the same time, the retention of the main structure of the defluorinating agent after multiple cycles indicates that the defluorinating agent has a certain degree of acid resistance.
[0115] Figure 8 The nitrogen adsorption-desorption curves and pore size distribution diagrams of the defluorinating agent prepared in Example 8 (labeled as a composite material in the figure) and the defluorinating agent after recycling are shown. These diagrams were obtained from the test samples using a BET surface area analyzer and testing methods known in the art. Figure 8 Calculations show that the specific surface area of the defluorinating agent is 87.77 m². 2 / g, total pore volume is 0.1659cm³ 2 The average pore diameter is 3.78 nm. Furthermore, the retention of pore structure and size after multiple cycles indicates that the material possesses a certain degree of acid resistance.
[0116] Figure 9 The figure shows the XPS images of the defluorinating agent prepared in Example 8 (labeled as composite material), CN (C3N4), the defluorinating agent after adsorption (F), and the defluorinating agent after desorption. Figure 9 It can be seen that the defluorinating agent contains elements such as nitrogen, oxygen, zirconium, and chlorine. At the same time, the F element peak appears before and after adsorption, and disappears completely before and after desorption, which proves the effectiveness of adsorption and desorption.
[0117] As can be seen from the above embodiments, the method of this application has great market value:
[0118] 1) A eutectic can be obtained by simple mixing and heating, which ensures the uniform distribution of the doped metal at a lower temperature. The calcination thermopolymerization step is carried out under normal pressure, and the process is simple and easy to operate and control.
[0119] 2) Compared with similar materials, the material of this application has a higher defluorination efficiency, and the process is not affected by anions commonly found in industrial production processes. It can be recycled and reused, is acid resistant and does not easily leach metals, and has no secondary pollution.
[0120] 3) The entire material preparation process only requires readily available and low-cost urea and metal compounds as raw materials. The temperature for heating to prepare the eutectic is below 90°C, and the thermal polycondensation reaction condition is 600°C under normal pressure, both of which are easy to achieve in industrial production.
[0121] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0122] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.
Claims
1. A method for preparing a defluorinating agent, characterized in that, Includes the following steps: A transition metal precursor is mixed with a nitrogen source and a carbon source and heated to obtain a eutectic; and The eutectic is calcined under a protective atmosphere; the transition metal precursor includes one or more of cerium source, zirconium source, lanthanum source and cobalt source, the nitrogen source and the carbon source are the same substance, and the nitrogen source and the carbon source are urea; The molar ratio of urea to the transition metal precursor is 1:(0.002~0.1).
2. The method for preparing the defluorinating agent according to claim 1, characterized in that, The molar ratio of urea to the transition metal precursor is 1:(0.002~0.01).
3. The method for preparing the defluorinating agent according to claim 1, characterized in that, The temperature at which the transition metal precursor and urea are mixed and heated is 40°C to 90°C.
4. The method for preparing the defluorinating agent according to claim 1, characterized in that, The calcination includes a first-stage calcination and a second-stage calcination. The calcination temperature in the first stage is 180℃~300℃, the heating rate is 1℃ / min~10℃ / min, and the holding time is 30 min~240 min; The second stage of calcination is carried out at a temperature of 500℃~600℃, a heating rate of 5℃ / min~10℃ / min, and a holding time of 60 min~240 min.
5. The defluorinating agent prepared by the preparation method according to any one of claims 1 to 4.
6. The defluorinating agent according to claim 5, characterized in that, The surface functional groups of the defluorinating agent include -Cl groups and / or -OH groups.
7. The defluorinating agent according to claim 5, characterized in that, The specific surface area of the defluorinating agent is 40 m² / g to 120 m² / g.
8. The application of the defluorinating agent as described in any one of claims 5 to 7 in the defluorination of fluorinated hydrochloric acid.
9. The application according to claim 8, characterized in that, The fluorinated hydrochloric acid has a hydrochloric acid mass concentration of 1% to 30% and / or a fluorine concentration of 50 ppm to 4000 ppm.
10. A method for defluorinating fluoride-containing hydrochloric acid, characterized in that, Includes the following steps: Add the defluorinating agent as described in any one of claims 5 to 7 to fluorinated hydrochloric acid, wherein 0.5 g to 10 g of the defluorinating agent is added per liter of fluorinated hydrochloric acid.
11. The method for defluorinating fluoride-containing hydrochloric acid according to claim 10, characterized in that, It also includes the step of desorbing the defluorinating agent.
12. The method for defluorinating fluoride-containing hydrochloric acid according to claim 11, characterized in that, The reagents used for desorption are alkaline solutions, acidic solutions, or saturated salt solutions.
13. The method for defluorinating fluoride-containing hydrochloric acid according to claim 12, characterized in that, The reagents used for desorption are NaOH solution with a concentration of 1 mol / L to 10 mol / L, hydrochloric acid solution with a concentration of 1 mol / L to 10 mol / L, or saturated NaCl solution.