Hexagonal layered nickel-cobalt hydrotalcite antimony removal material as well as preparation method and application thereof

Abstract

The invention provides a hexagonal layered nickel-cobalt hydrotalcite antimony removal material as well as a preparation method and application thereof, and belongs to the technical field of hydrotalcite materials. On the basis of common MgAl-LDH, the LDH is regulated and controlled by introducing transition metals (Ni and Co), and Ni and Co can change the type and metal proportion in an interlayer channel of hydrotalcite, increase and regulate active sites of a hydrotalcite structure and enhance the removal capacity of the hydrotalcite structure on Sb (V) in water. Chloride ions are adopted for intercalation between layers, urea is adopted as a nitrogen source in the synthesis process, a surfactant is added for morphology regulation, and the obtained nickel-cobalt hydrotalcite antimony removal material has a hexagonal layered structure, multiple active sites, high removal efficiency on antimony in water, high removal rate and high adsorption capacity; the adsorbent is higher than most existing hydrotalcite structure adsorbents.

Description

Technical Field

[0001] This invention relates to the field of hydrotalcite materials technology, specifically to a hexagonal layered nickel-cobalt hydrotalcite antimony removal material, its preparation method, and its application. Background Technology

[0002] China possesses the world's largest antimony resources, products, and consumption, producing over 80% of the world's antimony domestically. Antimony metal has irreplaceable and unique applications in modern industry (such as flame retardants, alloys, and semiconductors and electronics), and the increasing use of antimony and its compounds has led to a continuous increase in antimony concentrations in the environment. However, antimony is carcinogenic and has adverse effects on human health.

[0003] Layered bimetallic hydroxides (LDHs) are natural clay minerals widely found in nature and can also be synthesized artificially. They possess anion exchange capacity, adsorption capacity, high specific surface area, and a "memory effect," making them highly promising for adsorbing and removing oxygen-containing anions (such as antimonates and arsenates) from water. However, traditional LDHs primarily remove anions through interlayer anion exchange (such as with NO3-). - SO4 2- Cl - Due to its small adsorption capacity and limited affinity and selectivity, it is particularly susceptible to the influence of coexisting ions in complex groundwater environments, especially in the case of exchange and surface electrostatic interactions. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a hexagonal layered nickel-cobalt layered double hydroxide (LCD) antimony removal material, its preparation method, and its application. The hexagonal layered nickel-cobalt LTD antimony removal material provided by this invention can rapidly adsorb Sb(V) in water and has a high adsorption capacity for Sb(V).

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a hexagonal layered nickel-cobalt hydrotalcite antimony removal material, comprising the following steps: Magnesium chloride, nickel chloride, cobalt chloride, aluminum chloride, surfactant, nitrogen source and water are mixed to obtain a mixture; The mixture was subjected to a hydrothermal reaction to obtain a hexagonal layered nickel-cobalt hydrotalcite antimony removal material.

[0006] Preferably, in the mixture, (Ni 2+ +Co 2+ +Mg 2+ ):Al 3+ =1:1~2:1.

[0007] Preferably, in the mixture, Mg 2+ :Al3+ =1:1~2:1.

[0008] Preferably, in the mixture, Ni 2+ :Co 2+ =2:1~1:2.

[0009] Preferably, the surfactant is one or more of polyethylene glycol, polyvinylpyrrolidone, and hexadecyltrimethylammonium bromide; The mass ratio of magnesium chloride to surfactant is 5-10 mM:1 g.

[0010] Preferably, the nitrogen source is urea, and the molar ratio of magnesium chloride to the nitrogen source is 1:10 to 1:20.

[0011] Preferably, the hydrothermal reaction is carried out at a temperature of 120~180℃ for 12~24 h.

[0012] This invention provides a hexagonal layered nickel-cobalt hydrotalcite antimony removal material prepared by the above-described method.

[0013] Preferably, the particle size of the hexagonal layered nickel-cobalt hydrotalcite antimony removal material is 0.3~0.6 μm.

[0014] This invention provides the application of the above-mentioned hexagonal layered nickel-cobalt hydrotalcite antimony removal material in the adsorption of Sb(V) element in water.

[0015] This invention provides a method for preparing a hexagonal layered nickel-cobalt layered double hydroxide (LDH) antimony removal material, comprising the following steps: mixing magnesium chloride, nickel chloride, cobalt chloride, aluminum chloride, a surfactant, a nitrogen source, and water to obtain a mixed solution; subjecting the mixed solution to a hydrothermal reaction to obtain the hexagonal layered nickel-cobalt LDH antimony removal material. This invention, based on the commonly used MgAl-LDH, modulates the LDH through transition metals (Ni, Co), with Ni... 2+ and Co 2+ The introduction of [a specific adsorption method] can create high-density, highly active, and specific adsorption sites for the oxygen-containing anions of Sb(V), enhancing the adsorption driving force and its removal capacity of Sb(V) from water by forming strong surface complexes. In this invention, chloride ions are used for intercalation between layers, and urea is used as the nitrogen source during the synthesis process. In the hydrothermal synthesis of urea, nitrogen is supplied by hydrolysis at 120-200℃ (NH4+). + (Amino intercalation material), synchronously adjust pH to promote uniform nucleation and improve crystallinity, use hydrolysis regulation and surfactants to achieve specific morphology control of the material, and at the same time add surfactants to regulate morphology. The resulting nickel-cobalt hydrotalcite has a standard hexagonal layered structure with a lattice spacing of 0.3 nm.

[0016] Furthermore, the main raw materials for synthesizing the nickel-cobalt layered double hydroxide (TLD) antimony removal material of this invention are inorganic salts and urea, which are widely available, low in cost, simple in preparation process, short in preparation cycle, highly operable, require no special equipment, and are easy to produce. The resulting nickel-cobalt LTD antimony removal material has a hexagonal layered structure with multiple active sites, high antimony removal efficiency in water, fast removal rate, and high adsorption capacity, exceeding that of most existing LTD structure adsorbents. Fitting results from the examples show that the nickel-cobalt LTD antimony removal material obtained in this invention can adsorb up to 43 mg / g of Sb(V), and the maximum adsorption capacity fitted by the Langmuir adsorption isotherm reaches 60.043 mg / g. Attached Figure Description

[0017] Figure 1 Transmission electron microscope (TEM) images of LDH obtained in Examples 1-4 and Comparative Example 1; Figure 2 Selected area diffraction patterns and HAADF-STEM images of LDH obtained in Examples 1-4 and Comparative Example 1; Figure 3 The adsorption effect of LDH on Sb(V) obtained in Examples 1-4 and Comparative Example 1 under different solid-liquid ratio conditions; Figure 4 The adsorption effect of LDH on Sb(V) obtained in Examples 1-4 and Comparative Example 1 under different time conditions; Figure 5 The XRD patterns of LDH obtained in Examples 1-4 and Comparative Example 1 before and after Sb(V) removal are shown. Figure 6 The infrared spectra of LDH obtained in Examples 1-4 and Comparative Example 1 before and after Sb(V) removal are shown. Detailed Implementation

[0018] This invention provides a method for preparing a hexagonal layered nickel-cobalt hydrotalcite antimony removal material, comprising the following steps: Magnesium chloride, nickel chloride, cobalt chloride, aluminum chloride, surfactant, nitrogen source and water are mixed to obtain a mixture; The mixture was subjected to a hydrothermal reaction to obtain a hexagonal layered nickel-cobalt hydrotalcite antimony removal material.

[0019] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0020] This invention involves mixing magnesium chloride, nickel chloride, cobalt chloride, aluminum chloride, a surfactant, a nitrogen source, and water to obtain a mixed solution. In this invention, the water is preferably pure water. The magnesium chloride is preferably MgCl₂·6H₂O, the nickel chloride is preferably NiCl₂·6H₂O, the cobalt chloride is preferably CoCl₂·6H₂O, and the aluminum chloride is preferably AlCl₃·6H₂O.

[0021] In this invention, in the mixture, (Ni 2+ +Co 2+ +Mg 2+ ):Al 3+ =1:1~2:1, preferably 2:1, Mg 2+ :Al 3+ =1:1~2:1, preferably 1:1.

[0022] In this invention, the mixture contains Ni 2+ :Co 2+ =2:1 to 1:2, specifically 2:1, 1:2, 1:1, or 3:5, with 2:1 being more preferred.

[0023] In this invention, the surfactant is preferably one or more of polyethylene glycol, polyvinylpyrrolidone, and hexadecyltrimethylammonium bromide, more preferably polyvinylpyrrolidone; the mass ratio of magnesium chloride to surfactant is preferably 5-10 mM:1 g, more preferably 3-8 mM:1 g. This invention achieves morphology control by adding the surfactant polyvinylpyrrolidone.

[0024] In this invention, the nitrogen source is preferably urea, and the molar ratio of magnesium chloride to the nitrogen source is preferably 1:10. In this invention, the nitrogen source functions as a nitrogen supply (NH4+) from the hydrolysis of urea at 120-200°C. + / Amino intercalation materials), synchronously adjust pH to promote uniform nucleation and improve crystallinity, and use hydrolysis regulation and CO2 template to achieve specific morphology control of materials.

[0025] In this invention, the preferred volume ratio of magnesium chloride to water is 5-10 mM:70 mL.

[0026] In this invention, the mixing is preferably stirred, more preferably magnetically stirred, the mixing rate is preferably 250~300 r / min, and the mixing time is preferably 30~60 min, more preferably 40~50 min.

[0027] The present invention preferably carries out the hydrothermal reaction in the inner liner of a polytetrafluoroethylene reactor. In the present invention, the temperature of the hydrothermal reaction is preferably 120~180 ℃, specifically 120 ℃, 150 ℃ or 180 ℃, and the time is preferably 12~24 h, more preferably 12 h, 18 h or 24 h.

[0028] In this invention, after the hydrothermal reaction, the resulting hydrothermal reaction liquid is preferably subjected to post-treatment, which preferably includes sequential cooling, solid-liquid separation, washing of the solid, drying and grinding.

[0029] In this invention, the cooling is preferably natural cooling to room temperature, the solid-liquid separation is preferably vacuum filtration, the washing is preferably washing three times with anhydrous ethanol and pure water respectively, and the drying temperature is preferably 60 °C, and the drying time is preferably 24 h. This invention does not have special requirements for the grinding method; any grinding method well known to those skilled in the art can be used.

[0030] This invention provides a hexagonal layered nickel-cobalt layered double hydroxide (LCD) antimony removal material prepared by the above-described method. In this invention, the particle size of the hexagonal layered nickel-cobalt LCD antimony removal material is preferably 0.3~0.6 μm, more preferably 0.4~0.5 μm. In this invention, the lattice spacing of the hexagonal layered nickel-cobalt LCD antimony removal material is preferably 0.3 nm, representing a typical Hydrotalcite phase (PDF#89-0460).

[0031] This invention provides the application of the above-mentioned hexagonal layered nickel-cobalt hydrotalcite antimony removal material in the adsorption of Sb(V) element in water.

[0032] In this invention, the method of application preferably includes the following steps: Hexagonal layered nickel-cobalt hydrotalcite antimony removal material is mixed with antimony-containing water by shaking to carry out an adsorption reaction, and then solid-liquid separation is performed after adsorption.

[0033] In this invention, the concentration of the antimony-containing water is preferably 1~100 mg / L, more preferably 5~50 mg / L; the solid-liquid ratio of the hexagonal layered nickel-cobalt hydrotalcite antimony removal material to the antimony-containing water is preferably 0.2~2 g / L, more preferably 1~2 g / L.

[0034] In this invention, the preferred rate of the oscillating mixing is 150-200 r / min, the preferred temperature of the adsorption reaction is 10-40℃, more preferably 10℃, 25℃ or 40℃, and the preferred time is 1-3 h, more preferably 2 h.

[0035] In this invention, the solid-liquid separation is preferably filtration, and the filtration is preferably through a 0.22 µm filter membrane.

[0036] The following detailed description, in conjunction with embodiments, illustrates the hexagonal layered nickel-cobalt hydrotalcite antimony removal material, its preparation method, and its application, but these should not be construed as limiting the scope of protection of this invention.

[0037] Example 1 The preparation of hexagonal layered nickel-cobalt hydrotalcite antimony removal material involves the following steps: Weigh out 5 mM of divalent metal salt MgCl2·6H2O, 5 mM of divalent transition metal salt NiCl2·6H2O+CoCl2·6H2O (Ni / Co molar ratio 2:1), and 5 mM of trivalent metal salt (AlCl3·6H2O). Add 1 g of polyvinylpyrrolidone (PVP) as a surfactant and 50 mM urea as a nitrogen source. After mixing, add the mixture to 70 mL of pure water and stir magnetically for 30 min. Then, transfer the mixture to a 100 mL polytetrafluoroethylene reactor liner and carry out a hydrothermal reaction at 150 °C. After the hydrothermal reaction is completed for 12 h, filter the product and wash it three times each with pure water and anhydrous ethanol. Finally, dry the product at 60 °C for 24 h and grind it to obtain a hexagonal layered nickel-cobalt hydrotalcite antimony removal material, denoted as Ni2Co1-MgAl-LDH(N2Cl).

[0038] Example 2 Compared with Example 1, the difference is that in the 5 mM of divalent transition metal salt NiCl2·6H2O+CoCl2·6H2O, the Ni / Co molar ratio is 1:2, resulting in a hexagonal layered nickel-cobalt hydrotalcite antimony removal material, denoted as Ni1Co2-MgAl-LDH(N1C2).

[0039] Example 3 Compared with Example 1, the difference is that in the 5 mM of divalent transition metal salt NiCl2·6H2O+CoCl2·6H2O, the Ni / Co molar ratio is 1:1, resulting in a hexagonal layered nickel-cobalt hydrotalcite antimony removal material, denoted as Ni1Co1-MgAl-LDH(N1Cl).

[0040] Example 4 Compared with Example 1, the difference is that in the 5 mM of divalent transition metal salt NiCl2·6H2O+CoCl2·6H2O, the Ni / Co molar ratio is 3:5, resulting in a hexagonal layered nickel-cobalt hydrotalcite antimony removal material, denoted as Ni3Co5-MgAl-LDH(N3C5).

[0041] Comparative Example 1 Compared with Example 1, the difference is that the divalent transition metal salts NiCl2·6H2O and CoCl2·6H2O are not added, and magnesium aluminum hydrotalcite (MgAl-LDH) is obtained.

[0042] Structural characterization (1) The morphology of the hydrotalcite LDH synthesized in Examples 1-4 and Comparative Example 1 was observed using transmission electron microscopy, such as... Figure 1As shown, the prepared LDHs all have a layered hexagonal structure with a particle size of 0.3~0.6 μm. The material has good crystallinity and is a standard hexagonal layered structure. The lattice spacing was measured to be 0.3 nm based on the lattice fringes.

[0043] Selected area diffraction and HAADF-STEM images of the hydrotalcite synthesized in Examples 1-4 and Comparative Example 1 are shown below. Figure 2 As shown, the reciprocal vectors of the diffraction spots measured in selected area diffraction yielded a lattice spacing of 0.3 nm, all conforming to the (0 03) crystal plane of the hydrotalcite structure. The elemental atomic ratio exhibits M... 2+ :M 3+ ≈2:1.

[0044] (2) The XRD patterns of the hydrotalcite LDH synthesized in Examples 1-4 and Comparative Example 1 are shown in the figure. Figure 4 XRD analysis showed that the five LDHs were typical Hydrotalcite phases (PDF#89-0460), and all of them had typical LDH layered structures with different Ni / Co ratios, indicating that the materials have been synthesized in terms of structure and morphology.

[0045] Test Example 1: N under different solid-liquid ratio conditions x C y -LDH removal of Sb(V) A 1 g / L Sb(V) stock solution was diluted to 10 mg / L, and 50 mL of each solution was taken for later use. In each 50 mL Sb(V) solution, 0.01 g, 0.025 g, 0.05 g, and 0.1 g of the hydrotalcite LDH material synthesized in Examples 1-4 and Comparative Example 1 were added, respectively. The solutions were then placed in a constant temperature shaking incubator at 25 ℃ and 180 r / min for 3 h. After removing the solutions and passing them through a 0.22 µm filter membrane, the remaining Sb content in the solutions was determined using flame atomic absorption spectrometry. The results are as follows: Figure 3 As shown.

[0046] The results showed that when the solid-liquid ratio of the material to the antimony-containing solution was 1 g / L, i.e., the dosage in the figure was 0.05 g, the removal rate of antimony by the four materials was greater than 85%. When the solid-liquid ratio was 2 g / L, the removal rate of antimony reached more than 99%. Therefore, the nickel-cobalt-containing hydrotalcite materials prepared in this invention with different proportions all have good removal effects on Sb(V) in water.

[0047] Test Example 2: Study on Antimony Removal Performance at Different Times After preparing a 50 mg / L Sb(V) solution, it was placed in a 100 mL white bottle. LDH material synthesized in Examples 1-4 and Comparative Example 1 was added at a solid-liquid ratio of 0.5 g / L. The bottle was then placed in a constant-temperature shaking incubator at 25 °C, a shaking speed of 180 r / min, and a reaction time of 3 h. At different reaction times, 10 mL samples were taken using a 10 mL disposable syringe, filtered through a 0.22 µm filter, and stored in dilute nitric acid. Adsorption kinetics at different times were determined using AAS. All experiments were repeated three times, and the average value and standard deviation were taken. Single-factor analysis was used for all experiments, and the consistency of other factors was controlled during the experiments. The adsorption effect of LDH on Sb(V) under different time conditions is as follows: Figure 4 As shown.

[0048] Adsorption kinetics studies revealed that the nickel-cobalt hydrotalcite material N2C1 has an adsorption capacity of 43 mg / g for Sb(V), which is 3.5 times that of magnesium-aluminum hydrotalcite (12 mg / g). This indicates that the addition of transition metals can effectively increase the adsorption capacity of hydrotalcite for Sb(V).

[0049] Test Example 3 The XRD patterns of the hydrotalcite LDH materials synthesized in Examples 1-4 and Comparative Example 1 before and after removing Sb(V) are shown below. Figure 5 As shown, MgAl-LDH exhibits five diffraction peaks at 2-Theta of 11.6°, 23.4°, 34.2°, 39.4°, and 46.9°, representing the (0 0 3), (0 0 6), (1 0 1), (0 1 5), and (0 1 8) crystal planes of Hydrotalcite (PDF#89-0460 card). The LDH with the addition of Ni and Co still exhibits these typical diffraction peaks, indicating the LDH structure. Furthermore, the LDH structure remains unchanged after Sb(V) removal, demonstrating good material structural stability.

[0050] Test Example 4: Infrared spectra of LDH before and after Sb(V) removal. The FTIR spectra of the hydrotalcite LDH materials synthesized in Examples 1-4 and Comparative Example 1 before and after Sb(V) removal are as follows: Figure 5 As shown, in the range of 3000~3550 cm -1 The broad peak corresponds to the OH stretching vibration of the hydroxyl group (-OH) in metal hydroxides. Hydrothermal processes occurring in the atmospheric environment introduce CO2, resulting in a peak at 2300–2400 cm⁻¹. -1 and 1355 cm -1 The absorption peak is attributed to CO3. 2- Isocarbonate species, 1572–1813 cm -1The absorption peaks in the range of 400–1000 cm⁻¹ are due to the bending vibration of -OH. -1 The absorption peaks in the range correspond to the vibrations of M-OH and MO (M being Mg, Al, Ni, or Co). The FTIR peak area of ​​N2Cl decreases after the reaction, suggesting that the reaction process may involve hydroxyl exchange reactions, i.e., surface complexation reactions.

[0051] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for the preparation of a hexagonal layered nickel cobalt hydrotalcite antimony-free material, characterized in that, The method comprises the following steps: mixing magnesium chloride, nickel chloride, cobalt chloride, aluminum chloride, a surfactant, a nitrogen source and water to obtain a mixed solution; performing a hydrothermal reaction on the mixed solution to obtain a hexagonal layered nickel-cobalt hydrotalcite antimony removal material.

2. The production method according to claim 1, characterized by, (Ni 2+ +Co 2+ +Mg 2+ ):Al 3+ =1:1~2:

1.

3. The production method according to claim 1 or 2, characterized by, Mg 2+ :Al 3+ =1:1~2:

1.

4. The production method according to claim 1 or 2, characterized by, Ni 2+ :Co 2+ =2:1~1:

2.

5. The method of claim 1, wherein, The surfactant is one or more of polyethylene glycol, polyvinylpyrrolidone and cetyltrimethylammonium bromide. The mass ratio of the amount of substance of the magnesium chloride to the mass of the surfactant is 5-10 mM:1 g.

6. The method of claim 1, wherein, The nitrogen source is urea, and the molar ratio of the magnesium chloride to the nitrogen source is 1:10-1:

20.

7. The preparation method according to claim 1, characterized in that, The temperature of the hydrothermal reaction is 120-180 DEG C, and the time is 12-24 h.

8. The hexagonal layered nickel-cobalt hydrotalcite antimony removal material prepared by the preparation method of any one of claims 1-7.

9. The hexagonal layered nickel cobalt hydrotalcite antimony removal material of claim 8, wherein, The particle size of the hexagonal layered nickel-cobalt hydrotalcite antimony removal material is 0.3-0.6 μm.

10. The hexagonal layered nickel-cobalt hydrotalcite antimony removal material of claim 8 or 9 for use in adsorbing Sb(V) elements in water.

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