Preparation method of high-selectivity bromide ion selective adsorbent

Abstract

The invention belongs to the field of adsorbents, and particularly relates to a preparation method of a high-selectivity bromide ion selective adsorbent, which comprises the following steps: dissolving zircon salt, 2, 5-dihydroxy and phthalic acid, and reacting with glacial acetic acid to obtain a precursor; the precursor is subjected to a reaction with mercaptoethylamine hydrochloride and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and a sulfydryl functionalized adsorbent is obtained; carrying out protonation treatment on the sulfydryl functionalized adsorbent to obtain adsorbent particles; the preparation method comprises the following steps: doping adsorbent particles and a titanate coupling agent into combustible gel formed on the basis of ethanol, and igniting the combustible gel for firing treatment to obtain the high-selectivity bromide ion selective adsorbent. The material shows excellent selectivity and adsorption performance on low-concentration bromide ions in high-salinity brine, and has high stability, regeneration capacity and excellent freeze-thaw resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adsorbents, in particular to a preparation method of a high-selectivity bromide ion selective adsorbent. BACKGROUND

[0002] In the field of bromine resource extraction and water body debromination, developing a high-selectivity bromide ion adsorbent is the key to realizing efficient enrichment and recovery of bromine in brine. In the prior art, there are various adsorbents for bromide ions. Although some of these schemes have certain adsorption capacity, there is still room for improvement in terms of selectivity, adsorption capacity and cycle stability in complex ion coexistence systems.

[0003] Patent CN120618413A discloses a synthesis method of a bromide ion adsorbent for extracting bromine from salt lakes. The precursor is generated by reacting strontium chloride, manganese chloride with sodium phosphate and sodium hydroxide, and then treated with sodium bromide and sodium hydroxide to obtain the final adsorbent. The adsorbent exhibits certain selective adsorption capacity for low-concentration bromide ions in a high-chlorine environment. However, this method relies on multiple precipitation and ion exchange reactions, and the preparation process is relatively long. Moreover, the structural stability of the obtained material is greatly affected by pH fluctuations, and it is prone to phase change or loss of active sites after multiple cycles, which limits its applicability in industrial continuous operation.

[0004] Patent CN118988267A discloses a preparation method of a MOF-based silver monatomic adsorbent material and its application in low-concentration bromide ion adsorption. The nitrogen atoms on the MOF ligand anchor silver atoms, achieving single dispersion of silver and thus improving the adsorption efficiency of bromide ions and the utilization rate of noble metals. The material exhibits high adsorption capacity under low-concentration bromide ion conditions. However, this technology relies on noble silver as the active center, which has a high raw material cost. Moreover, the structural stability of the MOF framework is limited in strong acid, strong base or high-salt environments, which may affect the long-term performance. In addition, silver monatomic atoms are easily affected by interfering ions such as sulfides in actual water bodies, leading to a decrease in selectivity.

[0005] Although the above two technical solutions have certain adsorption effect on bromide ions under certain conditions, in harsh environments, such as in winter, repeated freezing and thawing of brine can significantly affect the repeated regeneration capacity of the adsorbent.

[0006] Based on this, the present application is proposed. SUMMARY

[0007] The purpose of the present application is to provide a preparation method of a high-selectivity bromide ion selective adsorbent to solve the above problems.

[0008] The purpose of the present application is to provide a preparation method of a high-selectivity bromide ion selective adsorbent, which can be achieved by the following technical solutions: A preparation method of a high-selectivity bromide ion selective adsorbent, comprising the following steps: S1: dissolving a zirconium salt and 2,5-dihydroxyterephthalic acid in a mixed solvent of N,N-dimethylformamide and deionized water, adding glacial acetic acid as an adjusting agent, heating and reacting, after the reaction is completed, cooling, centrifuging, washing, and vacuum drying to obtain a precursor; S2: dispersing the precursor in anhydrous ethanol, adding mercaptoethylamine hydrochloride and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and reacting under nitrogen protection, after the reaction is completed, filtering, washing, and vacuum drying to obtain a mercapto-functionalized adsorbent; S3: placing the mercapto-functionalized adsorbent in dilute hydrochloric acid for protonation treatment, controlling the pH to be in an acidic environment of 2.0-3.5, after the treatment is completed, repeatedly washing with deionized water until neutral, and drying to obtain adsorbent particles; S4: uniformly mixing the adsorbent particles, a titanate coupling agent, and ethanol, pouring into a saturated calcium acetate solution, stirring, standing, becoming a combustible gel, igniting the combustible gel, burning the combustible gel until it is extinguished, washing with deionized water, and drying to obtain the high-selectivity bromide ion selective adsorbent.

[0009] Further, in step S1, the heating reaction temperature is 80-120℃.

[0010] Further, in step S2, the reaction temperature is 25-45℃.

[0011] Further, in step S3, the treatment temperature is 30-50℃.

[0012] Further, the zirconium salt is zirconyl chloride octahydrate or zirconium nitrate pentahydrate, and the molar ratio of the zirconium salt to 2,5-dihydroxyterephthalic acid is 1:0.8-1.2.

[0013] Further, the volume ratio of N,N-dimethylformamide to deionized water is 3:1-5:1. Further, the amount of glacial acetic acid added is 1%-5% of the total volume of the mixed solvent.

[0014] Further, the mass ratio of the precursor to mercaptoethylamine hydrochloride is 1:0.3-0.8. Further, the amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride added is 0.2-0.5 times the mass of the precursor.

[0015] Further, in step S3, the concentration of the dilute hydrochloric acid is 0.05-0.2 mol / L. Further, the drying temperature is 70-75℃.

[0016] Further, in step S4, the mass ratio of the adsorbent particles and the titanate coupling agent is 10:1; Further, the mass-volume ratio of the adsorbent particles and ethanol is 1:10 g / mL, and the volume ratio of ethanol and calcium acetate saturated solution is 10:2.5.

[0017] According to the present application, by introducing 2,5-dihydroxyterephthalic acid ligand in the framework, two phenolic hydroxyl sites are provided on the ligand, creating reactive sites for subsequent thiol functionalization modification. On this basis, EDC·HCl is used as a coupling agent to covalently graft the thiol group in mercaptoethylamine hydrochloride to the phenolic hydroxyl group of the ligand under mild conditions to form a stable thioether bond connection. The process is carried out in anhydrous ethanol medium, and nitrogen is introduced to exclude oxygen interference to prevent the oxidation of thiol to disulfide bond and reduce the effective functional group density. The final obtained UiO-66-DHBA-SH material is rich in free-SH groups on the surface, and these groups are partially protonated during the protonation treatment stage to form positively charged structural units. The synergistic effect of the electrostatic interaction and the strong polarization characteristics of bromide ions makes the material exhibit selective recognition ability superior to common anions such as chloride ions, sulfate ions, and nitrate ions. In addition, the pH is strictly controlled in the range of 2.0-3.5 during the protonation process to avoid too low pH leading to Zr-O bond rupture and damage to the MOF framework, and too high pH weakening the degree of protonation and reducing the affinity for bromide ions.

[0018] Glacial acetic acid acts as a regulator in this process, which regulates the hydrolysis rate of Zr 4+ by competitive coordination, inhibits the formation of amorphous phase, and promotes the formation of highly crystalline crystals. When the concentration of acetic acid is too low, it is difficult to effectively regulate the nucleation process, and when it is too high, it may excessively inhibit the coordination of ligand and metal cluster, leading to a decrease in yield.

[0019] In step S3, a pH lower than 2.0 easily causes Zr-O bond hydrolysis, and a pH higher than 3.5 is insufficient for protonation, which weakens the selectivity.

[0020] In a second aspect, the present application provides a high-selectivity bromide ion selective adsorbent obtained by the above preparation method, wherein the framework of the adsorbent is formed by connecting Zr6O4(OH)4 clusters and 2,5-dihydroxyterephthalic acid ligands through Zr-O bonds to form a three-dimensional ordered pore structure. Its special pore structure matches the kinetic diameter of hydrated bromide ions, forming a spatial confinement effect, which further enhances the selective screening ability for bromide ions. At the same time, the high specific surface area provides abundant adsorption sites for bromide ions, and the Zr-O bond endows the material with excellent chemical stability in the pH range of 2-11, which is suitable for various brine environments.

[0021] The technical scheme of the present application solves the problem of insufficient selectivity of the existing bromide ion adsorbent to low-concentration bromide ions in a high-salt background. Traditional phosphate materials rely on ion exchange mechanism and are difficult to effectively enrich bromide ions in brine with a much higher concentration of chloride ions than bromide ions. Although silver-based MOF has high capacity, it is high in cost and easy to be poisoned by interfering ions.

[0022] The present application thermally decomposes the enriched titanate coupling agent by calcination within a certain temperature range (below 600 DEG C), and the generated titanium dioxide is combined with and fixed on the surface of the bromide ion selective adsorbent. Short-time calcination is beneficial to the activation of the interface of the bromide ion selective adsorbent, thereby reinforcing and fine-tuning the internal pore structure of the bromide ion selective adsorbent, so that it can adapt to the freeze-thaw cycle test. Finally, the bromide ion selective adsorbent described in the present application can have a capacity retention rate of not less than 88% after 50 freeze-thaw cycles.

[0023] The preparation method described in the present application has clear process steps, raw materials are easy to obtain, no noble metal is needed, and the reaction conditions are mild. The obtained adsorbent has high selectivity, high stability, high capacity and good engineering applicability, and is suitable for salt lake brine, seawater bromine extraction, industrial bromine-containing wastewater treatment and other scenes, and has significant industrial application prospect. DETAILED DESCRIPTION

[0024] The present application will be further described in detail below through specific examples.

[0025] Example 1 S1: Take zirconium oxychloride octahydrate 5.00 g (13.6 mmol) and 2,5-dihydroxyterephthalic acid 3.38 g (18.5 mmol, molar ratio 1:1.36, considering the purity of the ligand 95%), add DMF (N,N-dimethylformamide) 60 mL and deionized water 15 mL (volume ratio 4:1) mixed solvent, then add glacial acetic acid 2.25 mL (3% by volume), ultrasonic dispersion for 30 min, then transfer to a 100 mL reaction kettle, solvent thermal reaction at 120 DEG C for 48 h. Naturally cool to room temperature, centrifuge, wash with DMF (3x50 mL), anhydrous ethanol (3x50 mL), deionized water (3x50 mL) in turn, and vacuum dry at 60 DEG C for 24 h to obtain UiO-66-DHBA precursor 4.2 g.

[0026] S2: UiO-66-DHBA precursor 1.00 g was dispersed in 20 mL of anhydrous ethanol, and then 0.50 g of mercaptoethylamine hydrochloride and 0.30 g of EDC-HCl (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride) were added. After being stirred under nitrogen for 10 min, the mixture was sealed and stirred at 35°C for 24 h. Filtration was performed, and the filter cake was washed with anhydrous ethanol 5 times (30 mL each time), washed with deionized water until neutral, and dried at 50°C under vacuum for 20 h to obtain 1.32 g of UiO-66-DHBA-SH.

[0027] S3: 1.32 g of UiO-66-DHBA-SH was added to 200 mL of 0.1 mol / L HCl solution, and stirred at 40°C. The pH was monitored and adjusted to 2.8±0.1 using an online pH meter, and the mixture was treated for 4 h. Filtration was performed, and the filter cake was washed with deionized water until the conductivity was less than 10 μS / cm, and dried at 70°C under vacuum for 10 h to obtain 1.28 g of UiO adsorbent particles.

[0028] S4: 1 g of UiO adsorbent particles and 0.1 g of titanate coupling agent were mixed with 10 mL of ethanol, and then uniformly dispersed using a homogenizer to obtain an adsorbent particle suspension. The adsorbent particle suspension was poured into 2.5 mL of a saturated calcium acetate solution (20°C, mass fraction 25.6%), and stirred for 1 min. After standing, the mixture became a UX gel. The UX gel was ignited and burned until it was extinguished. The mixture was washed with deionized water 3 times, and dried at 70°C under vacuum for 10 h to obtain the finished activated adsorbent product.

[0029] Example 2 S1: The molar ratio of zirconium salt (zirconyl chloride octahydrate 5.00 g) to ligand (2,5-dihydroxyterephthalic acid 2.48 g) was adjusted to 1:1.0, and the rest was the same as in Example 1 to obtain 4.0 g of UiO-66-DHBA.

[0030] S2: 1.00 g of UiO-66-DHBA was reacted with 0.60 g of mercaptoethylamine hydrochloride and 0.40 g of EDC-HCl, and the rest was the same as in Example 1 to obtain 1.38 g of UiO-66-DHBA-SH.

[0031] S3: The protonation pH was controlled at 2.6, and the rest was the same as in Example 1 to obtain 1.34 g of UiO adsorbent particles.

[0032] S4: The same as in Example 1.

[0033] Example 3 S1: Zirconium nitrate pentahydrate 5.20 g was used instead of zirconium oxynitrate, ligand 2.60 g (molar ratio 1:1.05), volume ratio of DMF / water 5:1 (62.5 mL / 12.5 mL), glacial acetic acid 3.75 mL (5%), 100 °C for 72 h, the rest was the same as Example 1, and UiO-66-DHBA precursor 4.1 g was obtained.

[0034] S2: 45 °C magnetic stirring for 12 h, the rest was the same as Example 1, and UiO-66-DHBA-SH 1.30 g was obtained.

[0035] S3: HCl concentration 0.05 mol / L, pH 3.0, 50 °C for 2 h, the rest was the same as Example 1, and UiO adsorbent particles 1.26 g were obtained.

[0036] S4: The same as Example 1.

[0037] Comparative Example 1 S1: Terephthalic acid was used instead of 2,5-dihydroxyterephthalic acid, and the rest was the same as Example 1, and UiO-66 was obtained.

[0038] S2: Because there is no phenolic hydroxyl group, it is not possible to graft mercapto groups, so S3 treatment is directly performed, and comparative UiO adsorbent particles are obtained.

[0039] S4: The same as Example 1.

[0040] Comparative Example 2 S1: The same as Example 1.

[0041] S2: EDC·HCl was omitted, and only UiO-66-DHBA precursor was mixed and stirred with mercaptoethylamine hydrochloride, and the rest was the same as Example 1, and a direct mixing product was obtained, which was used instead of UiO-66-DHBA-SH.

[0042] S3-4: The same as Example 1.

[0043] Comparative Example 3 S1-2: The same as Example 1.

[0044] S3: The protonation treatment was omitted, and UiO-66-DHBA-SH was directly dried to obtain an unprotonated sample, which was used instead of UiO adsorbent particles.

[0045] S4: The same as Example 1.

[0046] Comparative Example 4 S4 was omitted, and the rest was the same as Example 1.

[0047] Comparative Example 5 S1-3: The same as Example 1.

[0048] S4: omit the titanate coupling agent, the rest is the same as example 1.

[0049] Comparative Example 6 S1~3: the same as example 1.

[0050] S4: replace the titanate coupling agent with a silane coupling agent, the rest is the same as example 1.

[0051] Comparative Example 7 S1~3: the same as example 1.

[0052] S4: calcine the UiO adsorbent particles at 600℃ for 10 min in an oxygen environment to obtain a control adsorbent product.

[0053] Comparative Example 8 S1~3: the same as example 1.

[0054] S4: calcine the UiO adsorbent particles at 700℃ for 10 min in an oxygen environment to obtain a control adsorbent product.

[0055] Product characterization test: 1. The materials obtained in the above examples and comparative examples were subjected to BET test (American Micromeritics ASAP2460), XRD (Bruker D8 Advance, Cu Kα), XPS (Thermo Scientific ESCALAB Xi+) and adsorption performance evaluation (simulated brine: NaCl 4 mol / L, MgCl21 mol / L, CaCl20.5 mol / L, Br - 5 mg / L, pH=6.5, 25℃, solid-liquid ratio 1 g / L, oscillation 2h). Among them, the capacity retention rate after 5 cycles refers to the adsorbent in 1 adsorption, 1 regeneration, which is 1 cycle. Regeneration is desorption by NaCl / NaOH mixed solution (1 mol / L NaCl + 0.1 mol / L NaOH). Generally, after 5 cycles, the adsorption capacity should still maintain more than 90% of the initial value, indicating that it has excellent stability.

[0056] 2. Freeze-thaw cycle test. The materials obtained in the above examples and comparative examples were soaked in simulated brine, frozen in a-20℃ refrigerator, and then thawed, which was 1 freeze-thaw cycle; after 50 freeze-thaw cycles, the capacity retention rate was tested.

[0057] The test results are shown in Table 1.

[0058] Table 1

[0059] According to the results of Table 1, the specific surface area of the adsorbents obtained in Examples 1-3 is higher than 800 m 2 / g, -SH content is higher than 1.55 mmol / g, Br - The distribution coefficient Kd is higher than 5000 mL / g, significantly better than the comparative examples.

[0060] Comparative Example 1 has almost no adsorption capacity due to the absence of thiol groups; Comparative Example 2 has a low -SH loading and the -SH groups are easily detached due to the lack of covalent attachment; Comparative Example 3 contains -SH groups but they are not protonated and the electrostatic interaction is weak, with a Kd of less than 800 mL / g. The capacity retention of the materials of the examples is higher than 92% after 5 desorption cycles with a mixture of NaCl / NaOH (1 mol / L NaCl + 0.1 mol / L NaOH).

[0061] As can be seen from Comparative Examples 7-8, if the temperature is too high when calcining the adsorbent, the pore structure is easily collapsed, which affects the adsorption capacity of the material after regeneration and freeze-thaw cycles.

[0062] As can be seen from Example 1 and Comparative Examples 4-6, the titanium ester coupling agent is very flammable after the formation of the gel based on ethanol, and the temperature generated by the combustion does not exceed 600°C. The combustion time of the example is generally not more than 10 min, which will cause the titanium ester coupling agent to decompose, and the titanium dioxide produced by the decomposition will be combined and fixed on the surface of the bromide ion selective adsorbent. A short burning time is beneficial to the activation of the interface of the bromide ion selective adsorbent, thereby reinforcing and fine-tuning the pore structure of the bromide ion selective adsorbent, so that it can adapt to freeze-thaw cycle tests. Ultimately, the bromide ion selective adsorbent described in the present application can have a capacity retention rate of not less than 88% after 50 freeze-thaw cycles.

[0063] Although preferred embodiments of the application have been described, those skilled in the art will be able to make additional changes and modifications to these embodiments once they have been given the basic inventive concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0064] Obviously, various modifications and changes can be made to the present application by those skilled in the art without departing from the spirit and scope of the present application. Thus, if these modifications and changes fall within the scope of the claims and their equivalents, they are intended to be included in the present application.

Claims

1. A method for preparing a highly selective bromide ion adsorbent, characterized in that, Includes the following steps: S1: Dissolve zirconium salt and 2,5-dihydroxyterephthalic acid in a mixed solvent of N,N-dimethylformamide and deionized water, add glacial acetic acid as a regulator, heat the reaction, and after the reaction is completed, cool, centrifuge, wash, and vacuum dry to obtain the precursor; S2: The precursor was dispersed in anhydrous ethanol, and mercaptoethylamine hydrochloride and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added. The reaction was carried out under nitrogen protection. After the reaction was completed, the mixture was filtered, washed and vacuum dried to obtain the mercapto-functionalized adsorbent. S3: The thiol-functionalized adsorbent is placed in dilute hydrochloric acid for protonation treatment. The treatment is carried out in an acidic environment with a pH of 2.0~3.

5. After the treatment, it is repeatedly washed with deionized water until neutral and dried to obtain adsorbent particles. S4: After mixing the adsorbent particles, titanate coupling agent, and ethanol evenly, pour the mixture into a saturated calcium acetate solution, stir, and let it stand to form a flammable gel; ignite the flammable gel, and let it burn until it is extinguished; wash with deionized water and dry to obtain the highly selective bromide ion selective adsorbent.

2. The method for preparing a highly selective bromide ion adsorbent according to claim 1, characterized in that: In step S1, the heating reaction temperature is 80~120℃.

3. The method for preparing a highly selective bromide ion adsorbent according to claim 1, characterized in that: In step S2, the reaction temperature is 25~45℃.

4. The method for preparing a highly selective bromide ion adsorbent according to claim 1, characterized in that: In step S3, the processing temperature is 30~50℃.

5. The method for preparing a highly selective bromide ion adsorbent according to claim 1, characterized in that: The zirconium salt is zirconium oxychloride octahydrate or zirconium nitrate pentahydrate, and its molar ratio with 2,5-dihydroxyterephthalic acid is 1:0.8~1.

2.

6. The method for preparing a highly selective bromide ion adsorbent according to claim 1, characterized in that: The volume ratio of N,N-dimethylformamide to deionized water is 3:1 to 5:1; And / or, The amount of glacial acetic acid added is 1% to 5% of the total volume of the mixed solvent.

7. The method for preparing a highly selective bromide ion adsorbent according to claim 1, characterized in that: The mass ratio of the precursor to mercaptoethylamine hydrochloride is 1:0.3~0.8; And / or, The amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride added is 0.2 to 0.5 times the mass of the precursor.

8. The method for preparing a highly selective bromide ion adsorbent according to claim 1, characterized in that: In step S3, the concentration of the dilute hydrochloric acid is 0.05~0.2 mol / L; And / or, The drying temperature is 70~75℃.

9. The method for preparing a highly selective bromide ion adsorbent according to claim 1, characterized in that: In step S4, the mass ratio of adsorbent particles to titanate coupling agent is 10:1; And / or, The mass-to-volume ratio of adsorbent particles to ethanol is 1:10 g / mL, and the volume ratio of ethanol to saturated calcium acetate solution is 10:2.

5.

10. A highly selective bromide ion adsorbent, characterized in that: Obtained by the preparation method according to any one of claims 1 to 9.

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