Graphene-hydroxyapatite composite material, preparation method, desulfurizer and heavy metal adsorbent

Abstract

The present invention discloses a graphene-hydroxyapatite composite material, a preparation method thereof, a desulfurizer and a heavy metal adsorbent, belonging to the technical field of composite material synthesis. The preparation method of the graphene-hydroxyapatite composite material is as follows: in an alcohol organic solvent, using polyethyleneimine as a modifier, graft treatment is carried out on hydroxyapatite to obtain amino-functionalized hydroxyapatite; the amino-functionalized hydroxyapatite is dispersed in water, a zinc precursor and a silver precursor are added, the pH is adjusted, and after stirring evenly, a hydrothermal reaction is carried out to prepare zinc-silver-loaded hydroxyapatite; it is added to a graphene oxide solution, and an electrostatic self-assembly reaction is carried out at room temperature to obtain a graphene-hydroxyapatite composite material. The present invention uses hydroxyapatite as a carrier, introduces transition metals zinc and silver, solves the problem of uneven dispersion of active sites, and then coats graphene oxide, reduces the loss of transition metals zinc and silver, and improves the service life of the graphene-hydroxyapatite composite material.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material synthesis, and more specifically to graphene-hydroxyapatite composites and their preparation methods, desulfurization agents, and heavy metal adsorbents. Background Art

[0002] Fossil fuels are mixtures of hydrocarbons or hydrocarbon derivatives, and their natural resources include coal, petroleum, natural gas, etc. Diesel, as an important fuel, is widely used as a power source for vehicles, ships, and internal combustion engine equipment due to its high volumetric calorific value, high efficiency, good power performance, etc. However, untreated diesel contains many sulfur-containing compounds. After the sulfur-containing compounds are burned, sulfur oxides will be produced, which will not only cause irreversible corrosion and damage to engine components, but also directly emitted into the air, and will combine with water to form acid rain, which will not only damage the growth of vegetation, but also reduce the lifespan of buildings, cultural heritages, and industrial equipment. Sulfur oxides will also cause the poisoning of the motor vehicle exhaust treatment catalyst, thereby reducing its catalytic activity, increasing the emissions of nitrogen oxides and particulate matter in the air, aggravating urban environmental pollution, and endangering human health. Diesel contains a variety of sulfides, mainly mercaptans, sulfides, thiophenes, benzothiophenes, dibenzothiophenes, and their derivatives. The sulfur-containing compounds with higher sulfur content are thiophene compounds. The sulfur content in this type of substance accounts for more than 80% of the total sulfur content in diesel, and among the thiophene compounds, the contents of benzothiophene and dibenzothiophene are the highest, which can account for 70% or even higher of the thiophene compounds. Among them, active sulfur-containing substances such as sulfur element, hydrogen sulfide, mercaptan, and sulfide have relatively low boiling points and relatively active chemical properties, and they can generally be removed by commonly used industrial technical means. However, non-active sulfur-containing compounds such as thiophene, benzothiophene, and dibenzothiophene have relatively stable chemical properties and are relatively difficult to remove.

[0003] Adsorption desulfurization is a method that, under mild conditions and without the participation of hydrogen, adsorbs sulfur-containing compounds onto an adsorbent through the adsorption of the adsorbent and sulfur-containing compounds, thereby achieving the purpose of removing sulfur-containing compounds from fuel oil. The metal active component forms a chemical bond with the sulfide in the fuel oil, thereby realizing the removal of sulfide. Researchers have studied adsorbents, such as using SBA-15 mesoporous molecular sieves as carriers, but due to the uneven dispersion of active sites and easy loss, it is not conducive to the regeneration and reuse of the adsorbent. Summary of the Invention

[0004] In view of the above problems, the present invention provides a graphene-hydroxyapatite composite material and its preparation method and application. In the preparation process, hydroxyapatite is used as a carrier, and transition metals zinc and silver are introduced to solve the problem of uneven dispersion of active sites. Then, graphene oxide is coated to reduce the loss of transition metals zinc and silver and improve the service life of the graphene-hydroxyapatite composite material.

[0005] The first object of the present invention is to provide a preparation method of a graphene-hydroxyapatite composite material, comprising the following steps:

[0006] In an alcoholic organic solvent, using polyethyleneimine as a modifier, graft treatment is carried out on hydroxyapatite to obtain amino-functionalized hydroxyapatite.

[0007] Disperse the amino-functionalized hydroxyapatite in water, add a zinc precursor and a silver precursor, adjust the pH to 9-10, stir evenly, and then carry out a hydrothermal reaction at 120°C to 130°C to prepare hydroxyapatite loaded with zinc and silver; for example, the pH is adjusted to 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10, etc.; but not limited to the listed values, other unlisted values within the above value range are equally applicable.

[0008] The hydrothermal temperature is 120°C, 121°C, 122°C, 123°C, 124°C, 125°C, 126°C, 127°C, 128°C, 129°C, 130°C, etc.; but not limited to the listed values, other unlisted values within the above value range are equally applicable.

[0009] Add the hydroxyapatite composite material loaded with zinc and silver to the graphene oxide solution, and carry out an electrostatic self-assembly reaction at room temperature to obtain the graphene-hydroxyapatite composite material.

[0010] In a preferred embodiment of the present invention, the mass ratio of the amino-functionalized hydroxyapatite, the zinc precursor and the silver precursor is 0.1-0.15:1-4, and the mass ratio of the zinc precursor and the silver precursor is 1-4:0.3-0.4.

[0011] For example, the mass ratio of the amino-functionalized hydroxyapatite and the zinc precursor is 0.1:1, 0.1:2, 0.1:3, 0.1:4, 0.12:1, 0.12:2, 0.12:3, 0.12:4, 0.13:1, 0.13:2, 0.13:3, 0.13:4, 0.14:1, 0.14:2, 0.14:3, 0.14:4, 0.15:1, 0.15:2, 0.15:3, 0.15:4, etc., but not limited to the listed values, other unlisted values within the above value range are equally applicable.

[0012] For example, the mass ratio of the zinc precursor to the silver precursor is 1:0.3, 1:0.32, 1:0.34, 1:0.36, 1:0.38, 1:0.4, 2:0.3, 2:0.32, 2:0.34, 2:0.36, 2:0.38, 2:0.4, 3:0.3, 3:0.32, 3:0.34, 3:0.36, 3:0.38, 3:0.4, 4:0.3, 4:0.32, 4:0.34, 4:0.36, 4:0.38, 4:0.4, etc., but not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0013] In a preferred embodiment of the present invention, the reaction time of the hydrothermal reaction is 10 h to 12 h. For example, the reaction time of the hydrothermal reaction is 10 h, 10.5 h, 11 h, 11.5 h, 12 h, etc., but not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0014] In a preferred embodiment of the present invention, the mass ratio of the zinc-silver-loaded hydroxyapatite composite material to graphene oxide is 8:1 to 7. For example, the mass ratio of the zinc-silver-loaded hydroxyapatite composite material to graphene oxide is 8:1, 4:1, 8:3, 2:1, 8:5, 4:3, 8:7, etc., but not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0015] In a preferred embodiment of the present invention, the reaction time of the electrostatic self-assembly is 5 min to 15 min. The reaction time of the electrostatic self-assembly is 5 min, 7 min, 9 min, 11 min, 13 min, 15 min, etc., but not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0016] In a preferred embodiment of the present invention, the mass ratio of polyethyleneimine to hydroxyapatite is 1:5 to 6. For example, the mass ratio of polyethyleneimine to hydroxyapatite is 1:5, 1:5.2, 1:5.4, 1:5.6, 1:5.8, 1:6, etc., but not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0017] In a preferred embodiment of the present invention, the reaction time of the grafting treatment is 30 min to 40 min. For example, the reaction time of the grafting treatment is 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, etc., but not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0018] The second object of the present invention is to provide a graphene-hydroxyapatite composite material prepared by the above preparation method.

[0019] The third object of the present invention is to provide a desulfurizer, which comprises the above-mentioned graphene-hydroxyapatite composite material.

[0020] The fourth object of the present invention is to provide a heavy metal adsorbent, which comprises the above-mentioned graphene-hydroxyapatite composite material.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention provides a graphene-hydroxyapatite composite material. During the preparation process, hydroxyapatite has a pore structure and can better load oxides of zinc and silver as a carrier. And due to the pore structure, the oxides of zinc and silver have a good dispersion effect. Then, a layer of graphene oxide is introduced. Since the amino groups on the amino-functionalized hydroxyapatite facilitate the formation of hydrogen bonds through electrostatic self-assembly reaction with graphene oxide, thus coating on the hydroxyapatite loaded with zinc and silver, and the graphene-hydroxyapatite composite material is prepared. When the graphene-hydroxyapatite composite material prepared by the present invention is used as a desulfurizer, the oxides of zinc and silver serve as active centers. The oxides of transition metals zinc and silver provide empty orbitals for the lone pair electrons of the S atom on the dibenzothiophene molecule. The S in dibenzothiophene forms a π-complex adsorption with the transition metal. At the same time, graphene oxide and dibenzothiophene form a π-π interaction, improving the adsorption efficiency. Moreover, the loading of hydroxyapatite and the coating of graphene oxide reduce the loss of the oxides of transition metals zinc and silver, thereby improving the regenerability of the graphene-hydroxyapatite composite material. The synergistic effect among hydroxyapatite, zinc oxide, silver and graphene oxide can effectively remove sulfur-containing compounds.

[0023] (2) The graphene-hydroxyapatite composite material prepared by the present invention can be used to adsorb heavy metal ions. Based on the ion exchange and adsorption ability of hydroxyapatite, nickel ions can be effectively adsorbed. Then, the introduction of graphene oxide enables groups such as carboxyl and hydroxyl groups on the surface of graphene oxide to be used for adsorbing nickel ions, and graphene oxide provides a larger surface area and more adsorption sites, thus being more conducive to the adsorption of nickel. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Desulfurization rate of the graphene-hydroxyapatite composite material prepared in Example 3 with time when added to diesel with different concentrations.

[0025] Figure 2 Desulfurization rates of the graphene-hydroxyapatite composite materials prepared in different examples and comparative examples.

[0026] Figure 3Desulfurization rate of graphene-hydroxyapatite composite and simulated diesel at different ratios.

[0027] Figure 4 Reusability of the graphene-hydroxyapatite composite prepared in Example 3.

[0028] Figure 5 Chromium removal rate of the graphene-hydroxyapatite composite prepared in Example 3.

[0029] Figure 6 Nickel removal rate of the graphene-hydroxyapatite composite prepared in Example 3. Detailed implementation mode

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0031] Graphene is an allotrope of carbon, and carbon atoms are bonded by sp 2 hybridization to form a single-layer hexagonal honeycomb lattice graphene. Using this crystal structure of graphene, fullerenes, graphene quantum dots, carbon nanotubes, nanoribbons, multi-walled carbon nanotubes and nanohorns can be constructed. Stacked graphene layers (more than 10 layers) form graphite, and the layers are held together by van der Waals forces, with an interplanar spacing of 0.335 nanometers. Graphene has excellent optical, electrical and mechanical properties.

[0032] The chemical composition of hydroxyapatite is Ca 10 (PO4)6(OH)2, and the calcium-phosphorus ratio is 1.67. Hydroxyapatite crystals are hexagonal, presenting six-sided columns, and each unit cell contains 10 Ca 2+ , 6 PO4 3- and 2 OH - . As the main inorganic component of bone tissue, hydroxyapatite has excellent osteoconductivity, biocompatibility and ion exchangeability.

[0033] In the prior art, the prepared graphene-hydroxyapatite composite materials are mainly applied in the fields of biomedicine, material reinforcement, biosensors, and 3D printing. For example, the graphene-hydroxyapatite composite material can be used as a bone graft substitute for bone repair. It not only retains the biological activity and biocompatibility of hydroxyapatite, which is beneficial to new bone growth and combination with human tissues, but also improves the overall strength of the material by virtue of the excellent mechanical properties of graphene, and can meet the mechanical requirements during the bone repair process, promoting the regeneration and repair of bone tissue. When the graphene-hydroxyapatite composite material is used as a drug carrier to deliver drugs, its large specific surface area and unique structure enable it to load drugs, and hydroxyapatite increases the biocompatibility and stability of the material. The graphene-hydroxyapatite composite material is added to other polymer materials, ceramic materials or metal materials as a reinforcing agent to improve the mechanical properties, thermal properties, electrical conductivity, etc. of the materials. The graphene-hydroxyapatite composite material is used to prepare biosensors to detect various substances in the body.

[0034] In order to solve the problems existing in the adsorbents for adsorption desulfurization in the background art, the present invention proposes a preparation method of a graphene-hydroxyapatite composite material, which includes the following steps:

[0035] In an alcoholic organic solvent, using polyethyleneimine as a modifier, hydroxyapatite is grafted to obtain amino-functionalized hydroxyapatite.

[0036] The amino-functionalized hydroxyapatite is dispersed in water, a zinc precursor and a silver precursor are added, the pH is adjusted to 9-10, and after stirring evenly, a hydrothermal reaction is carried out at 120 °C to 130 °C to prepare hydroxyapatite loaded with zinc and silver.

[0037] The hydroxyapatite composite material loaded with zinc and silver is added to the graphene oxide solution, and an electrostatic self-assembly reaction is carried out at room temperature to obtain a graphene-hydroxyapatite composite material.

[0038] During the preparation process, first, hydroxyapatite is surface-functionalized with polyethyleneimine, and polyethyleneimine is introduced on the surface of hydroxyapatite, which improves the dispersibility of hydroxyapatite, reduces the aggregation of hydroxyapatite, and at the same time, after the grafting treatment, the surface of hydroxyapatite is provided with amino groups, and the introduction of amino groups facilitates the subsequent loading of other nanomaterials. Subsequently, Zn 2+ is provided by the zinc precursor, and Ag + is provided by the silver precursor. Under the condition of pH 9-10, a hydrothermal reaction is carried out to prepare oxides of zinc and silver on the hydroxyapatite / graphene oxide, and hydroxyapatite loaded with zinc and silver is prepared. Graphene oxide contains functional groups such as hydroxyl and carboxyl groups, and forms hydrogen bonds with amino-functionalized hydroxyapatite through an electrostatic self-assembly reaction to prepare a graphene-hydroxyapatite composite material.

[0039] The preparation method of hydroxyapatite used in the present invention is as follows:

[0040] Step 1. Dissolve 2 mmol Ca(NO3)2·4H2O in 15 ml of deionized water and stir for 30 min. Then add 1.46 g C6H5Na3O7·2H2O and stir for 1 h. Mark it as the first solution.

[0041] Step 2: Weigh 0.363 g of CTAB and add it to 20 ml of deionized water. Stir it thoroughly for 30 min in a constant temperature water bath at 30°C until the solution becomes clear. Then add 0.16 g of (NH4)2HPO4 and stir it thoroughly for 30 min. Then, absorb 2 mol / L HNO3 to adjust the pH value to 5. This solution is marked as the second solution.

[0042] Step 3: Add the first solution dropwise to the second solution, stir thoroughly for half an hour, then slowly pour the mixed solution into a 100 ml polytetrafluoroethylene-lined autoclave, and react in a 180°C homogeneous reactor for 24 hours. After the autoclave is cooled to room temperature, remove and open the autoclave, and wash the precipitate with deionized water and anhydrous ethanol and centrifuge it three times. Place the obtained powder in a 60°C constant temperature blast drying oven for drying to obtain hydroxyapatite, which is recorded as HA.

[0043] The polyethyleneimine used in the present invention has an average molecular weight of 100,000 and is purchased from Shanghai MacLean Biochemical Technology Co., Ltd. The present invention has no particular limitation on the source of polyethyleneimine, and those skilled in the art can purchase it through commercial channels according to actual application conditions, product quality and product performance.

[0044] The graphene oxide used in the present invention has a sheet diameter of 0.5 μm to 5 μm and a thickness of 0.8 nm to 1.2 nm, and is purchased from Shanghai MacLean Biochemical Technology Co., Ltd. The present invention has no particular restriction on the source of graphene oxide, and those skilled in the art can purchase it through commercial channels according to actual application conditions, product quality and product performance, or can prepare it through existing preparation methods.

[0045] Example 1

[0046] This embodiment provides a method for preparing a graphene-hydroxyapatite composite material, comprising the following steps:

[0047] Step 1: Add 0.05 g of polyethyleneimine to 100 mL of anhydrous methanol, stir at 300 r / min at room temperature until the polyethyleneimine is dissolved, weigh 0.25 g of hydroxyapatite, and ultrasonically disperse it for 30 minutes. After the ultrasonication, centrifuge, filter, and dry to obtain amino hydroxyapatite.

[0048] Step 2: Add 0.01 g of amino-functionalized hydroxyapatite to 70 mL of absolute ethanol. After ultrasonic dispersion for 30 min, add 0.3 g of Zn(NO₃)₂·6H₂O and 0.03 g of Ag(NO₃)₂, adjust the pH to 9, stir evenly, then transfer to a hydrothermal reaction kettle and react at 120 °C for 10 h to obtain zinc-silver-loaded hydroxyapatite.

[0049] Step 3: Add 0.01 g of graphene oxide to 100 ml of absolute ethanol, stir at 5 °C for 4 h to obtain a graphene oxide solution. Then add 0.08 g of zinc-silver-loaded hydroxyapatite to the above graphene oxide solution, let it stand at 30 °C for 10 min. After standing, centrifuge, filter and dry to obtain a graphene-hydroxyapatite composite material; denoted as HA-(Zn-Ag)-GO1-a.

[0050] Example 2

[0051] Step 1: Add 0.05 g of polyethyleneimine to 100 mL of absolute methanol, stir at 300 r / min at room temperature until the polyethyleneimine is dissolved, then weigh 0.25 g of hydroxyapatite, ultrasonically disperse for 30 min. After ultrasonic treatment, centrifuge, filter and dry to obtain amino-functionalized hydroxyapatite.

[0052] Step 2: Add 0.01 g of amino-functionalized hydroxyapatite to 70 mL of absolute ethanol. After ultrasonic dispersion for 30 min, add 0.3 g of Zn(NO₃)₂·6H₂O and 0.03 g of Ag(NO₃)₂, adjust the pH to 9, stir evenly, then transfer to a hydrothermal reaction kettle and react at 120 °C for 10 h to obtain zinc-silver-loaded hydroxyapatite.

[0053] Step 3: Add 0.03 g of graphene oxide to 100 ml of absolute ethanol, stir at 5 °C for 4 h to obtain a graphene oxide solution. Then add 0.08 g of zinc-silver-loaded hydroxyapatite to the above graphene oxide solution, let it stand at 30 °C for 10 min. After standing, centrifuge, filter and dry to obtain a graphene-hydroxyapatite composite material; denoted as HA-(Zn-Ag)-GO3-a.

[0054] Example 3

[0055] Step 1: Add 0.05 g of polyethyleneimine to 100 mL of absolute methanol, stir at 300 r / min at room temperature until the polyethyleneimine is dissolved, then weigh 0.25 g of hydroxyapatite, ultrasonically disperse for 30 min. After ultrasonic treatment, centrifuge, filter and dry to obtain amino-functionalized hydroxyapatite.

[0056] Step 2: Add 0.01 g of amino-functionalized hydroxyapatite to 70 mL of absolute ethanol. After ultrasonic dispersion for 30 min, add 0.3 g of Zn(NO3)2·6H2O and 0.03 g of Ag(NO3)2, adjust the pH to 9, stir evenly, then transfer to a hydrothermal reaction kettle and react at 120 °C for 10 h to obtain zinc-silver-loaded hydroxyapatite.

[0057] Step 3: Add 0.05 g of graphene oxide to 100 ml of absolute ethanol, stir at 5 °C for 4 h to obtain a graphene oxide solution. Then add 0.08 g of zinc-silver-loaded hydroxyapatite to the above graphene oxide solution, let it stand at 30 °C for 10 min. After standing, centrifuge, filter and dry to obtain a graphene-hydroxyapatite composite material; denoted as HA-(Zn-Ag)-GO5-a.

[0058] Example 4

[0059] Step 1: Add 0.05 g of polyethyleneimine to 100 mL of absolute methanol, stir at 300 r / min at room temperature until the polyethyleneimine is dissolved, then weigh 0.25 g of hydroxyapatite, ultrasonically disperse for 30 min. After ultrasonic treatment, centrifuge, filter and dry to obtain amino-functionalized hydroxyapatite.

[0060] Step 2: Add 0.01 g of amino-functionalized hydroxyapatite to 70 mL of absolute ethanol. After ultrasonic dispersion for 30 min, add 0.3 g of Zn(NO3)2·6H2O and 0.03 g of Ag(NO3)2, adjust the pH to 9, stir evenly, then transfer to a hydrothermal reaction kettle and react at 120 °C for 10 h to obtain zinc-silver-loaded hydroxyapatite.

[0061] Step 3: Add 0.07 g of graphene oxide to 100 ml of absolute ethanol, stir at 5 °C for 4 h to obtain a graphene oxide solution. Then add 0.08 g of zinc-silver-loaded hydroxyapatite to the above graphene oxide solution, let it stand at 30 °C for 10 min. After standing, centrifuge, filter and dry to obtain a graphene-hydroxyapatite composite material; denoted as HA-(Zn-Ag)-GO7-a.

[0062] Example 5

[0063] Step 1: Add 0.05 g of polyethyleneimine to 100 mL of absolute methanol, stir at 300 r / min at room temperature until the polyethyleneimine is dissolved, then weigh 0.25 g of hydroxyapatite, ultrasonically disperse for 30 min. After ultrasonic treatment, centrifuge, filter and dry to obtain amino-functionalized hydroxyapatite.

[0064] Step 2: Add 0.01 g of amino-functionalized hydroxyapatite to 70 mL of absolute ethanol. After ultrasonic dispersion for 30 min, add 0.2 g of Zn(NO3)2·6H2O and 0.03 g of Ag(NO3)2, adjust the pH to 9, stir evenly, then transfer to a hydrothermal reaction kettle and react at 120 °C for 10 h to obtain zinc-silver-loaded hydroxyapatite.

[0065] Step 3: Add 0.05 g of graphene oxide to 100 ml of absolute ethanol, stir at 5 °C for 4 h to obtain a graphene oxide solution. Then add 0.08 g of zinc-silver-loaded hydroxyapatite to the above graphene oxide solution, let it stand at 30 °C for 10 min. After standing, centrifuge, filter and dry to obtain a graphene-hydroxyapatite composite material; denoted as HA-(Zn-Ag)-GO5-b.

[0066] Example 6

[0067] Step 1: Add 0.05 g of polyethyleneimine to 100 mL of absolute methanol, stir at 300 r / min at room temperature until the polyethyleneimine is dissolved, then weigh 0.25 g of hydroxyapatite, ultrasonic disperse for 30 min. After ultrasonic treatment, centrifuge, filter and dry to obtain amino-functionalized hydroxyapatite.

[0068] Step 2: Add 0.01 g of amino-functionalized hydroxyapatite to 70 mL of absolute ethanol. After ultrasonic dispersion for 30 min, add 0.4 g of Zn(NO3)2·6H2O and 0.03 g of Ag(NO3)2, adjust the pH to 9, stir evenly, then transfer to a hydrothermal reaction kettle and react at 120 °C for 10 h to obtain zinc-silver-loaded hydroxyapatite.

[0069] Step 3: Add 0.05 g of graphene oxide to 100 ml of absolute ethanol, stir at 5 °C for 4 h to obtain a graphene oxide solution. Then add 0.08 g of zinc-silver-loaded hydroxyapatite to the above graphene oxide solution, let it stand at 30 °C for 10 min. After standing, centrifuge, filter and dry to obtain a graphene-hydroxyapatite composite material; denoted as HA-(Zn-Ag)-GO5-c.

[0070] Example 7

[0071] Step 1: Add 0.05 g of polyethyleneimine to 100 mL of absolute methanol, stir at 300 r / min at room temperature until the polyethyleneimine is dissolved, then weigh 0.25 g of hydroxyapatite, ultrasonic disperse for 30 min. After ultrasonic treatment, centrifuge, filter and dry to obtain amino-functionalized hydroxyapatite.

[0072] Step 2: Add 0.01 g of amino-functionalized hydroxyapatite to 70 mL of absolute ethanol. After ultrasonic dispersion for 30 min, add 0.1 g of Zn(NO3)2·6H2O and 0.03 g of Ag(NO3)2, adjust the pH to 9, stir evenly, then transfer to a hydrothermal reaction kettle and react at 120 °C for 10 h to obtain zinc-silver-loaded hydroxyapatite.

[0073] Step 3: Add 0.05 g of graphene oxide to 100 ml of absolute ethanol, stir at 5 °C for 4 h to obtain a graphene oxide solution. Then add 0.08 g of zinc-silver-loaded hydroxyapatite to the above graphene oxide solution, let it stand at 30 °C for 10 min. After standing, centrifuge, filter and dry to obtain a graphene-hydroxyapatite composite material; denoted as HA-(Zn-Ag)-GO5-d.

[0074] Example 8

[0075] Step 1: Add 0.05 g of polyethyleneimine to 100 mL of absolute methanol, stir at 300 r / min at room temperature until the polyethyleneimine is dissolved, then weigh 0.3 g of hydroxyapatite, ultrasonically disperse for 30 min. After ultrasonic treatment, centrifuge, filter and dry to obtain amino-functionalized hydroxyapatite.

[0076] Step 2: Add 0.01 g of amino-functionalized hydroxyapatite to 70 mL of absolute ethanol. After ultrasonic dispersion for 30 min, add 0.4 g of Zn(NO3)2·6H2O and 0.04 g of Ag(NO3)2, adjust the pH to 10, stir evenly, then transfer to a hydrothermal reaction kettle and react at 130 °C for 12 h to obtain zinc-silver-loaded hydroxyapatite.

[0077] Step 3: Add 0.01 g of graphene oxide to 100 ml of absolute ethanol, stir at 5 °C for 4 h to obtain a graphene oxide solution. Then add 0.08 g of zinc-silver-loaded hydroxyapatite to the above graphene oxide solution, let it stand at 30 °C for 5 min. After standing, centrifuge, filter and dry to obtain a graphene-hydroxyapatite composite material.

[0078] Example 8

[0079] Step 1: Add 0.05 g of polyethyleneimine to 100 mL of absolute methanol, stir at 300 r / min at room temperature until the polyethyleneimine is dissolved, then weigh 0.28 g of hydroxyapatite, ultrasonically disperse for 30 min. After ultrasonic treatment, centrifuge, filter and dry to obtain amino-functionalized hydroxyapatite.

[0080] Step 2: Add 0.01 g of amino-functionalized hydroxyapatite to 70 mL of absolute ethanol. After ultrasonic dispersion for 30 min, add 0.1 g of Zn(NO3)2·6H2O and 0.035 g of Ag(NO3)2, adjust the pH to 9.5, stir evenly, then transfer to a hydrothermal reaction kettle and react at 125 °C for 11 h to obtain zinc-silver-loaded hydroxyapatite.

[0081] Step 3: Add 0.07 g of graphene oxide to 100 ml of absolute ethanol, stir at 5 °C for 4 h to obtain a graphene oxide solution. Then add 0.08 g of zinc-silver-loaded hydroxyapatite to the above graphene oxide solution, let it stand at 30 °C for 15 min. After standing, centrifuge, filter and dry to obtain a graphene-hydroxyapatite composite material.

[0082] Comparative Example 1

[0083] Step 1: Add 0.05 g of polyethyleneimine to 100 mL of absolute methanol, stir at 300 r / min at room temperature until the polyethyleneimine is dissolved, then weigh 0.25 g of hydroxyapatite, ultrasonic disperse for 30 min. After ultrasonic treatment, centrifuge, filter and dry to obtain amino-functionalized hydroxyapatite.

[0084] Step 2: Add 0.01 g of amino-functionalized hydroxyapatite to 70 mL of absolute ethanol. After ultrasonic dispersion for 30 min, add 0.1 g of Zn(NO3)2·6H2O, adjust the pH to 9, stir evenly, then transfer to a hydrothermal reaction kettle and react at 120 °C for 10 h to obtain zinc-loaded hydroxyapatite.

[0085] Step 3: Add 0.05 g of graphene oxide to 100 ml of absolute ethanol, stir at 5 °C for 4 h to obtain a graphene oxide solution. Then add 0.08 g of zinc-silver-loaded hydroxyapatite to the above graphene oxide solution, let it stand at 30 °C for 10 min. After standing, centrifuge, filter and dry to obtain a graphene-hydroxyapatite composite material; denoted as HA-Zn-GO5-c.

[0086] Comparative Example 2

[0087] Step 1: Add 0.05 g of polyethyleneimine to 100 mL of absolute methanol, stir at 300 r / min at room temperature until the polyethyleneimine is dissolved, then weigh 0.25 g of hydroxyapatite, ultrasonic disperse for 30 min. After ultrasonic treatment, centrifuge, filter and dry to obtain amino-functionalized hydroxyapatite.

[0088] Step 2: Add 0.01 g of amino-functionalized hydroxyapatite to 70 mL of absolute ethanol. After ultrasonic dispersion for 30 min, add 0.03 g of Ag(NO3)2, adjust the pH to 9, stir evenly, then transfer it to a hydrothermal reaction kettle and react at 120 °C for 10 h to obtain silver-loaded hydroxyapatite.

[0089] Step 3: Add 0.05 g of graphene oxide to 100 ml of absolute ethanol, stir at 5 °C for 4 h to obtain a graphene oxide solution. Then add 0.08 g of zinc-silver-loaded hydroxyapatite to the above graphene oxide solution, let it stand at 30 °C for 10 min. After standing, centrifuge, filter and dry to obtain a graphene-hydroxyapatite composite material; denoted as HA-Ag-GO5-c.

[0090] Comparative Example 3

[0091] Step 1: Add 0.05 g of polyethyleneimine to 100 mL of absolute methanol, stir at 300 r / min at room temperature until the polyethyleneimine is dissolved, then weigh 0.25 g of hydroxyapatite, ultrasonic disperse for 30 min. After ultrasonic treatment, centrifuge, filter and dry to obtain amino-functionalized hydroxyapatite.

[0092] Step 2: Add 0.01 g of amino-functionalized hydroxyapatite to 70 mL of absolute ethanol. After ultrasonic dispersion for 30 min, add 0.1 g of Zn(NO3)2·6H2O and 0.03 g of Ag(NO3)2, adjust the pH to 9, stir evenly, then transfer it to a hydrothermal reaction kettle and react at 120 °C for 10 h to obtain zinc-silver-loaded hydroxyapatite.

[0093] Step 3: Add 0.05 g of graphene oxide to 100 ml of absolute ethanol, stir at 5 °C for 4 h to obtain a graphene oxide solution. Then add 0.08 g of zinc-silver-loaded hydroxyapatite to the above graphene oxide solution, let it stand at 30 °C for 10 min. After standing, centrifuge, filter and dry to obtain a hydroxyapatite composite material; denoted as HA-(Zn-Ag).

[0094] The N2 isothermal adsorption-desorption analysis was carried out using a Micromeritics ASAP 2020HD88 physical adsorption instrument to test the N2 isothermal adsorption and desorption of the samples. The BET equation was used to calculate the specific surface area to characterize the specific surface area of the samples.

[0095] Table 1 Physical properties of different materials

[0096] <![CDATA[Specific surface area (m 2 / g)]]> HA 23.734±0.047 Example 1 28.678±0.064 Example 2 29.541±0.038 Example 3 32.527±0.051 Example 4 30.174±0.042 Example 5 31.346±0.035 Example 6 31.981±0.073 Example 7 30.463±0.066

[0097] It can be seen from Table 1 that compared with HA, the specific surface area of the graphene-hydroxyapatite composite material prepared by the preparation method of the present invention is increased, and the increase in the specific surface area is beneficial to improving the adsorption capacity of the material.

[0098] Dibenzothiophene was used to prepare simulated diesel for testing. Specifically, 1000 mL of isooctane was added to a conical flask as a solvent, and dibenzothiophene was added and stirred until evenly mixed to prepare simulated diesel with an initial sulfur concentration of 400 μg / g, 1000 μg / g, or 2000 μg / g.

[0099] In the present invention, a static adsorption method was adopted to measure the saturated adsorption capacity of the graphene-hydroxyapatite composite material to evaluate its adsorption desulfurization performance, and the regeneration performance of the adsorbent was investigated after regeneration.

[0100] The static adsorption method is to place a certain proportion of desulfurizer and diesel in a container at a certain temperature, soak for a period of time, filter out the adsorbent, and measure the sulfur content of the diesel. The specific operation steps are as follows: Weigh 1 g of simulated diesel with an initial sulfur concentration of 400 μg / g, 1000 μg / g, or 2000 μg / g, put it into a flask, and then put 0.1 g of graphene-hydroxyapatite composite material, stir and adsorb at room temperature for 20 min, 40 min, 60 min, 80 min, 100 min, and 120 min. After the adsorption is completed, stop stirring, centrifuge to separate the graphene-hydroxyapatite composite material after adsorbing dibenzothiophene and the supernatant. Take about 1.0 mL of simulated diesel from the supernatant as a gas chromatography detection sample, analyze its remaining sulfur content, and compare it with the initial sulfur content.

[0101] The model and specifications of the gas chromatography are: Agilent 19091N-233, 30.0 m×250 μm×0.50 μm. Nitrogen is used as the carrier gas, the injection volume is 0.4 μL; the vaporization chamber temperature is 220 °C; the split ratio is 50:1; the detector temperature is 250 °C; the programmed temperature rise process is to hold at 60 °C for 2 min, rise to 100 °C at a rate of 10 °C / min, and hold for 1 min; the residence time is 4.7 min; the stop time is 11 min; the FPD detection limit is 1 μg-S / g.

[0102] The desulfurization rate is calculated according to the following formula.

[0103]

[0104] Among them, η1 is the desulfurization rate, %; C0 is the initial concentration of the simulated diesel, mg-S / g; C e is the concentration of the simulated diesel after adsorption equilibrium, mg-S / g.

[0105] The specific steps for detecting the regeneration performance are as follows: The recycled composite material is washed three times with ethanol, and the washed adsorbent is vacuum dried at 100 °C for 12 h. Then, the dried composite material is placed in a tube furnace and heated to 350 °C at a heating rate of 5 °C / min under a N2 atmosphere flow, purged for 2 h, and subjected to high-temperature desorption regeneration. The regenerated graphene-hydroxyapatite composite material is repeated the above adsorption-regeneration operation steps for a certain number of cycles to investigate the change in the saturated adsorption capacity of the adsorbent.

[0106] In this invention, the desulfurization performance of the graphene-hydroxyapatite composite material prepared in Example 3 was studied under different sulfur contents. When the ratio of the graphene-hydroxyapatite composite material to the simulated diesel was 1 g:10 mL, at room temperature, the desulfurization rate changes were investigated by changing the concentration of the simulated diesel to 400 μg / g, 1000 μg / g, and 2000 μg / g over time. From Figure 1 It can be seen that when the initial sulfur content was 400 μg / g and the reaction time was 80 min, the desulfurization rate reached 90.17%. When the time was extended to 120 min, the desulfurization rate reached 93.59%. When the initial sulfur content increased to 1000 μg / g and the adsorption time was 120 min, the desulfurization rate reached 89.6%. When the initial sulfur content continued to increase to 2000 μg / g and the adsorption time was 120 min, the desulfurization rate still reached 78.37%. As the initial sulfur content increased, the desulfurization rate decreased. This may be because after the graphene-hydroxyapatite composite material was saturated with adsorption, dibenzothiophene desulfurization occurred. However, even when the initial sulfur content increased, the graphene-hydroxyapatite composite material prepared in this invention still had a high desulfurization rate and could effectively remove sulfur-containing compounds in diesel.

[0107] When the initial sulfur content in the simulated diesel was 400 μg / g and the ratio of the graphene-hydroxyapatite composite material to the simulated diesel was 1 g:10 mL, at room temperature, under the condition of adsorbing for 120 min, the desulfurization rates of the graphene-hydroxyapatite composite materials prepared in different examples and comparative examples were investigated. As Figure 2 shown, it can be seen from Examples 1 to 4 that as the addition amount of graphene oxide increased, when the addition amount of graphene oxide was 0.05 g, the desulfurization rate of the graphene-hydroxyapatite composite material prepared therefrom for dibenzothiophene in the simulated diesel was the highest. When the addition amount of graphene oxide was fixed at 0.05 g, as in Examples 3 and 5-7, as the addition amount of Zn(NO3)2·6H2O increased to 0.3 g, the desulfurization rate of the graphene-hydroxyapatite composite material prepared therefrom for dibenzothiophene in the simulated diesel was the highest. This is because the specific surface area of the graphene-hydroxyapatite composite material increased, resulting in an increase in the adsorption sites available for the graphene-hydroxyapatite composite material, thereby improving the adsorption of dibenzothiophene.

[0108] Compared with Example 3, the graphene-hydroxyapatite composite prepared in Comparative Example 1 lacks zinc oxide, the graphene-hydroxyapatite composite prepared in Comparative Example 2 lacks silver oxide, and the hydroxyapatite prepared in Comparative Example 3 lacks graphene oxide. The desulfurization rate of the graphene-hydroxyapatite composite prepared in Example 3 is significantly improved. This is because the desulfurization rate is increased by the π-complexation adsorption and π-π interaction between dibenzothiophene and the graphene-hydroxyapatite composite, and the presence of graphene oxide reduces the loss of zinc and silver oxides, enabling the zinc and silver oxides to serve as active centers to enhance the adsorption of dibenzothiophene.

[0109] When the initial sulfur content in the simulated diesel was 400 μg / g, at room temperature, and under the condition of adsorption for 120 min, the desulfurization rates of the graphene-hydroxyapatite composite and the simulated diesel at different ratios were investigated. As Figure 3 shown, when the ratio of the graphene-hydroxyapatite composite to the simulated diesel was 1:10 and the adsorption time was 120 min, the desulfurization rate reached 93.59%. When the ratios of the graphene-hydroxyapatite composite to the simulated diesel were 1:20 and 1:30, the desulfurization rates of the graphene-hydroxyapatite composite were 84.9% and 80.1% respectively. It can be seen that even when the addition amount of the graphene-hydroxyapatite composite is reduced, it still has a good desulfurization rate.

[0110] The recycling performance of the adsorbent is also an important parameter for measuring the performance of the adsorbent. Therefore, after the first adsorption was completed and the simulated diesel was removed, the graphene-hydroxyapatite composite prepared in Example 3 was then investigated for its recycling performance using fresh simulated diesel with an initial sulfur concentration of 400 μg / g. The results are as Figure 4 shown. The graphene-hydroxyapatite composite prepared in the present invention remained stable during the repeated experiments. After being reused 6 times, the desulfurization rate still reached 76.77%, indicating that the loading of hydroxyapatite and the coating of graphene oxide reduced the loss of transition metal zinc and silver oxides, enabling the graphene-hydroxyapatite composite to have good regeneration performance.

[0111] In addition, heavy metal ions may eventually enter the water environment through diesel combustion, diesel leakage, or diesel waste, which can cause harm to the water environment. For example, researchers have detected the presence of nickel and chromium in the Antarctic surface soil, presumably related to diesel combustion or leakage. Next, the graphene-hydroxyapatite composite prepared in Example 3 of the present invention was added to the wastewater containing heavy metal ions to investigate the removal effect of the graphene-hydroxyapatite composite on heavy metal ions.

[0112] A solution was prepared with potassium dichromate (K2Cr2O7) to simulate chromium-containing wastewater, and the removal effect of the graphene-hydroxyapatite composite material on heavy metal ion chromium was studied. Specifically, 0.2 g of the graphene-hydroxyapatite composite material was added to 100 mL of chromium-containing wastewater with a concentration of 40 mg / L or 100 mg / L. After mixing evenly, it was adsorbed at 40 °C for 1 h, then centrifuged at 2000 r / min for 5 min, and finally the supernatant was taken to measure the remaining chromium concentration.

[0113] A solution was prepared with NiSO4·6H2O to simulate nickel ion-containing wastewater, and the removal effect of the graphene-hydroxyapatite composite material on heavy metal ion nickel was studied. Specifically, 0.2 g of the graphene-hydroxyapatite composite material was added to 100 mL of nickel-containing wastewater with a concentration of 40 mg / L or 100 mg / L. After mixing evenly, it was adsorbed at 40 °C for 1 h, then centrifuged at 2000 r / min for 5 min, and finally the supernatant was taken to measure the remaining nickel concentration.

[0114] The removal rate of heavy metal ions was calculated according to the following formula

[0115]

[0116] Among them, η2 is the removal rate of heavy metal ions, %; C1 is the concentration of heavy metal ions in the solution before the reaction, mg / L; C0 is the concentration of Cr(VI) in the solution after the reaction, mg / L.

[0117] From Figure 5 and Figure 6 It can be seen that compared with Comparative Example 3, the graphene-hydroxyapatite composite material prepared in Example 3 has excellent removal effects on both chromium and nickel. This is because the presence of graphene oxide provides a large specific surface area, thus providing adsorption sites, and the carboxyl and hydroxyl groups on the surface of graphene oxide can effectively adsorb nickel ions and chromium ions. When the heavy metal ion concentration is increased from 40 mg / L to 100 mg / L, the graphene-hydroxyapatite composite material prepared in Example 3 still has relatively good removal effects on nickel ions and chromium ions, indicating that the graphene-hydroxyapatite composite material prepared in the present invention can effectively remove nickel ions and chromium ions from wastewater.

[0118] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0119] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A preparation method of a graphene-hydroxyapatite composite material, characterized in that, Including the following steps: In an alcohol organic solvent, using polyethyleneimine as a modifier, graft treatment is carried out on hydroxyapatite to obtain amino-functionalized hydroxyapatite; Disperse the amino-functionalized hydroxyapatite in water, add a zinc precursor and a silver precursor, adjust the pH to 9 - 10, stir evenly, and then carry out a hydrothermal reaction at 120 °C to 130 °C to prepare hydroxyapatite loaded with zinc and silver; the mass ratio of amino-functionalized hydroxyapatite to the zinc precursor is 0.1 - 0.15:1 - 4; the mass ratio of the zinc precursor to the silver precursor is 1 - 4:0.3 - 0.4; the reaction time of the hydrothermal reaction is 10 h to 12 h; Add the hydroxyapatite composite loaded with zinc and silver to the graphene oxide solution, and carry out an electrostatic self-assembly reaction at room temperature to obtain a graphene-hydroxyapatite composite.

2. According to the preparation method of a graphene-hydroxyapatite composite as described in claim 1, the mass ratio of the hydroxyapatite composite loaded with zinc and silver to graphene oxide is 8:1 - 7.

3. According to the preparation method of a graphene-hydroxyapatite composite as described in claim 1, the reaction time of the electrostatic self-assembly is 5 min to 15 min.

4. According to the preparation method of a graphene-hydroxyapatite composite as described in claim 1, the mass ratio of polyethyleneimine to hydroxyapatite is 1:5 - 6.

5. According to the preparation method of a graphene-hydroxyapatite composite as described in claim 1, the reaction time of the graft treatment is 30 min to 40 min.

6. A graphene-hydroxyapatite composite prepared by the preparation method as described in any one of claims 1 - 5.

7. A desulfurizer, characterized in that, Including the graphene-hydroxyapatite composite as described in claim 6.

8. A heavy metal adsorbent, characterized in that, Including the graphene-hydroxyapatite composite as described in claim 6.

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