A precious metal recovery adsorbent, a preparation method thereof, and a precious metal recovery method

Abstract

The application discloses a kind of adsorbents for noble metal recovery and preparation method thereof, further provide a kind to be used in the noble metal recovery method of the catalyst, wherein the adsorbents for noble metal recovery includes nitrogen-doped graphene-SiO2 Hybrid Material, the nitrogen-doped graphene-SiO2 Hybrid Material includes graphene-SiO2 Hybrid Material and nitrogen doped therein, wherein the molar amount of nitrogen in the nitrogen-doped graphene-SiO2 Hybrid Material and the total molar amount of C and Si are 1: (55-10050) ratio. The noble metal recovery adsorbent of the application can effectively recover noble metal Au in wastewater, has strong noble metal recovery adsorption capacity, high recovery rate, especially for the catalyst washing produced in the preparation process of vinyl acetate catalyst containing lower content of noble metal element Au has higher noble metal recovery adsorption capacity.

Description

Technical Field

[0001] This invention belongs to the field of precious metal recycling technology, specifically relating to a precious metal recycling adsorbent and its preparation method, and a precious metal recycling method. Background Technology

[0002] Vinyl acetate is an important chemical raw material, widely used in the manufacture of polyvinyl alcohol, vinyl copolymer resin, adhesives, coatings, textile processing, paper coatings, etc. There are two main production processes for vinyl acetate: the ethylene process and the acetylene process. The ethylene process dominates due to its good processability and economy, and the production capacity of vinyl acetate using this method accounts for 82% of the total production capacity. At present, most countries increase vinyl acetate production by upgrading and expanding existing plants and updating catalysts. The development trend of the ethylene process is mainly in the following directions: (1) The scale of production plants tends to be larger. For example, the expansion of VAC plants of USI and Hoechst in the United States is mainly achieved by increasing the space velocity of the plant and using highly active catalysts; (2) The ethylene process VAC process is being improved to reduce unit consumption and energy consumption; among them, the vinyl acetate process package and related catalysts of Sinopec Shanghai Petrochemical Research Institute have a strong competitive advantage in the industry. The acetylene process plant has a high investment and is difficult to be environmentally friendly, but in areas where oil resources are scarce, it will still maintain a considerable competitive advantage for a certain period of time and directly promote the research and development of C1 chemical methods.

[0003] The main method for producing vinyl acetate in the world today uses ethylene, oxygen, and acetic acid as raw materials, with palladium-gold-potassium acetate / silica as a catalyst, and produces vinyl acetate, water, and carbon dioxide as a byproduct, as well as trace amounts of ethyl acetate, methyl acetate, acetaldehyde, and other acetoxylated products. The preparation of the catalyst used in the ethylene process for producing vinyl acetate mainly includes noble metal impregnation of the support, aging, liquid-phase reduction with hydrazine hydrate, leaching of the reducing liquid followed by water washing, impregnation with a co-catalyst (e.g., potassium acetate), and drying to obtain the finished catalyst. The waste liquid obtained from the water washing step contains Au (mainly in the form of [Au(OH)2]). 4-x While the content of precious metals (in the form of Clx) is low and difficult to recover, the volume of catalyst washing waste liquid is large, still resulting in a considerable loss of Au. Therefore, research on methods for recovering precious metals during the preparation of vinyl acetate is of great significance. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a precious metal recovery adsorbent and its preparation method, and further to provide a precious metal recovery method using the catalyst.

[0005] Therefore, the first aspect of the present invention provides an adsorbent for precious metal recycling, comprising a nitrogen-doped graphene-SiO2 hybrid material, wherein the nitrogen-doped graphene-SiO2 hybrid material comprises a graphene-SiO2 hybrid material and nitrogen doped therein, wherein the molar ratio of nitrogen to the total molar ratio of C and Si in the nitrogen-doped graphene-SiO2 hybrid material is 1:(55-10050).

[0006] According to some embodiments of the present invention, the molar ratio of graphene to SiO2 in the nitrogen-doped graphene-SiO2 hybrid material, expressed as C / Si (molar ratio of C to Si), is (5-50):(50-10000).

[0007] According to some embodiments of the present invention, the molar ratio of nitrogen:carbon:silicon in the nitrogen-doped graphene-SiO2 hybrid material is 1:(5-50):(50-10000).

[0008] According to some embodiments of the present invention, the graphene-SiO2 hybrid material uses SiO2 as a carrier, and graphene is uniformly distributed in the carrier.

[0009] A second aspect of the present invention provides a method for preparing an adsorbent as described in the first aspect of the present invention, comprising the following steps:

[0010] (1) Graphene was treated with acid, filtered and dried to obtain adsorbent precursor I;

[0011] (2) The adsorbent precursor I is mixed with the first dispersing solvent, crosslinking agent and dehydrating agent and reacted under an inert atmosphere. After filtration and drying, adsorbent precursor II is obtained.

[0012] (3) Hydrolyze adsorbent precursor II to obtain adsorbent precursor III;

[0013] (4) The adsorbent precursor III was mixed with the second dispersion solvent and the carrier precursor and reacted, then filtered and dried to obtain the adsorbent precursor IV.

[0014] (5) The adsorbent precursor IV was calcined in a mixed atmosphere of inert gas and ammonia to obtain the adsorbent.

[0015] According to some embodiments of the present invention, in step (1), the graphene includes at least one of single-layer graphene, double-layer graphene and multilayer graphene, and the sheet size of the graphene is 5-15 micrometers.

[0016] According to some embodiments of the present invention, in step (1), at least one of sulfuric acid, nitric acid, formic acid, acetic acid and hydrochloric acid is used.

[0017] According to the present invention, in step (1), the graphene is treated with acid by mixing the graphene with an acid. The amount of acid added is not specifically limited, as long as the acid can impregnate the graphene. According to some preferred embodiments of the present invention, in step (1), the ratio of graphene to acid is not less than 1g:20mL, preferably 1g:50mL-1g:500mL.

[0018] According to some embodiments of the present invention, the crosslinking agent in step (2) includes a silane coupling agent, preferably at least one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane and 3-ureopropyltrimethoxysilane.

[0019] According to some embodiments of the present invention, the dehydrating agent is selected from at least one of dicyclohexylcarbodiimide and N,N'-carbonyldiimidazole.

[0020] According to the present invention, the first dispersing solvent is used to dissolve or disperse the adsorbent precursor I, the crosslinking agent, and the dehydrating agent. The type and amount of the first dispersing solvent are not specifically limited, but are designed to dissolve and disperse the adsorbent precursor I, the crosslinking agent, and the dehydrating agent without affecting their reaction. Preferably, the first dispersing solvent is selected from tetrahydrofuran and / or dimethyl sulfoxide. The amount of the first dispersing solvent is sufficient to at least submerge the reactants.

[0021] According to some embodiments of the present invention, the temperature of the reaction in step (2) is 40-80°C.

[0022] According to some embodiments of the present invention, the reaction time in step (2) is 12-36 h.

[0023] According to some embodiments of the present invention, in step (3), the hydrolysis includes mixing adsorbent precursor II with deionized water, preferably the ratio of adsorbent precursor II to deionized water is 1g:1000mL-1g:5000mL.

[0024] According to some embodiments of the present invention, in step (3), the hydrolysis temperature is 20-80°C.

[0025] According to some embodiments of the present invention, in step (3), the hydrolysis time is 6-24 hours.

[0026] According to some embodiments of the present invention, in step (4), the carrier precursor includes a silicon source and ammonia water, preferably the silicon source is selected from at least one of tetraethyl orthosilicate, methyl orthosilicate and propyl orthosilicate.

[0027] According to some embodiments of the present invention, the concentration of the ammonia water is 1-10%.

[0028] According to the present invention, the second dispersing solvent is used to dissolve or disperse the adsorbent precursor III and the support precursor. The type and amount of the second dispersing solvent are not specifically limited, but are designed to dissolve and disperse the adsorbent precursor I, precursor III, and support precursor without affecting their reaction. The second dispersing solvent is selected from at least one of alcohols and ketones.

[0029] According to some embodiments of the present invention, the amount of silicon source and ammonia is 1:(0.01-0.1).

[0030] According to some embodiments of the present invention, the weight ratio of the second dispersing solvent to the total weight of the raw materials for the mixed reaction is 1:(1.1-1.5). According to some embodiments of the present invention, the raw materials for the mixed reaction include adsorbent precursor III and carrier precursor.

[0031] According to some embodiments of the present invention, in step (4), the molar ratio of inert gas to ammonia in the mixed atmosphere is 3:1 to 1:3, and the volume hourly space velocity of the mixed atmosphere is 200-1000 hr. -1 .

[0032] According to some embodiments of the present invention, in step (4), the calcination temperature is 800-1200℃ and the calcination time is 4-12h.

[0033] A third aspect of the present invention provides a method for recovering precious metals from wastewater, comprising mixing the adsorbent with wastewater for adsorption, precipitating and filtering to obtain an adsorbent adsorbed with precious metals, and desorbing the adsorbent adsorbed with precious metals to obtain the precious metals.

[0034] According to some embodiments of the present invention, the precious metal in the recovery method is Au, preferably the precious metal exists in the wastewater in the form of a complex, such as [Au(OH)]. 4-x It exists in the form of Clx.

[0035] According to some embodiments of the present invention, the wastewater is catalyst washing wastewater during the preparation of vinyl acetate catalyst.

[0036] According to some embodiments of the present invention, the content of the precious metal Au in the wastewater is about 1-30 ppmw.

[0037] According to some embodiments of the present invention, the amount of adsorbent used is 0.01-0.1 g / L wastewater.

[0038] According to some embodiments of the present invention, the desorption includes treating the adsorbent adsorbed with noble metals with a strong acid and then reducing it.

[0039] According to some embodiments of the present invention, the strong acid is selected from at least one of concentrated hydrochloric acid and concentrated nitric acid.

[0040] According to some embodiments of the invention, the reduction includes displacing the noble metal from its acid solution using another metal.

[0041] According to some embodiments of the present invention, the other metal is zinc.

[0042] The beneficial effects of the present invention are as follows: The recovery adsorbent of the present invention can effectively recover the precious metal Au in wastewater. It has a strong precious metal recovery adsorption capacity and a high recovery rate. In particular, it has a high precious metal recovery adsorption capacity for catalyst washing generated during the preparation of vinyl acetate catalyst containing a low content of precious metal element Au. Detailed Implementation

[0043] To make the present invention easier to understand, the present invention will be described in detail below with reference to embodiments. These embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the materials used in the embodiments are commercially available or conventional products obtained by conventional or known methods.

[0044] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0045] Example 1

[0046] 1. Preparation of Adsorbent

[0047] (1) Take 0.5g of graphene and add it to 100ml of sulfuric acid and nitric acid (the molar ratio of sulfuric acid and nitric acid is 3:1). Treat it at room temperature for 30min, filter and dry to obtain adsorbent precursor I.

[0048] (2) Take 0.3g of adsorbent precursor I and add it to 2000ml of tetrahydrofuran solution, add 20g of dicyclohexylcarbodiimide and 200g of APTES (chemical formula H2NCH2CH2CH2Si(OC2H5)3), sonicate for 2 hours, react at 60℃ under nitrogen atmosphere for 24 hours, filter and dry to obtain adsorbent precursor II;

[0049] (3) Take 0.5g of adsorbent precursor II and add it to 2000ml of deionized water to hydrolyze for 12h to obtain adsorbent precursor III;

[0050] (4) Add 1000 ml of ethanol, 150 g of tetraethyl orthosilicate and 5 g of ammonia (mass fraction 18%) to the obtained adsorbent precursor III and react at room temperature for 8 h. Filter and dry to obtain adsorbent precursor IV.

[0051] (5) Take 20g of adsorbent precursor IV and calcine it at 1000℃ for 10 hours in a mixed atmosphere of nitrogen and ammonia (molar ratio of nitrogen to ammonia is 1:1) to obtain precious metal recovery adsorbent.

[0052] The content of each element in the precious metal recovery adsorbent was analyzed by XRF, and the specific data are shown in Table 1.

[0053] 2. Precious metal recycling

[0054] At room temperature, 200L of catalyst washing wastewater (containing approximately 1-15 ppmw of precious metal Au) and 10g of the prepared precious metal recovery adsorbent were added to a wastewater storage tank. After stirring and adsorption for 1 hour, the adsorbent that had settled and filtered was treated with a mixed solution of 15ml concentrated hydrochloric acid and 5ml concentrated nitric acid at 80℃ for 30 minutes. After filtration, sufficient zinc powder was added to the acid solution to reduce the precious metal. The results of precious metal recovery are shown in Table 1.

[0055] Example 2

[0056] 1. Preparation of Adsorbent

[0057] (1) Take 0.5g of graphene and add it to 100ml of sulfuric acid and nitric acid (the molar ratio of sulfuric acid and nitric acid is 3:1). Treat it at room temperature for 30min, filter and dry to obtain adsorbent precursor I.

[0058] (2) Take 0.3g of adsorbent precursor I and add it to 2000ml of tetrahydrofuran solution, add 20g of dicyclohexylcarbodiimide and 200g of APTES (chemical formula H2NCH2CH2CH2Si(OC2H5)3), sonicate for 2 hours, react at 60℃ under nitrogen atmosphere for 24 hours, filter and dry to obtain adsorbent precursor II;

[0059] (3) Take 0.5g of adsorbent precursor II and add it to 2000ml of deionized water to hydrolyze for 12h to obtain adsorbent precursor III;

[0060] (4) Add 1000 ml of ethanol, 150 g of tetraethyl orthosilicate and 10 g of ammonia (mass fraction 18%) to the obtained adsorbent precursor III and react at room temperature for 8 h. Filter and dry to obtain adsorbent precursor IV.

[0061] (5) Take 20g of adsorbent precursor IV and calcine it at 1000℃ for 10 hours in a mixed atmosphere of nitrogen and ammonia (molar ratio of nitrogen to ammonia is 1:2) to obtain precious metal recovery adsorbent.

[0062] The content of each element in the precious metal recovery adsorbent was analyzed by XRF, and the specific data are shown in Table 1.

[0063] 2. Precious metal recycling

[0064] At room temperature, 200L of catalyst washing wastewater (containing approximately 10-30 ppmw of precious metal Au) and 10g of the prepared precious metal recovery adsorbent were added to a wastewater storage tank. After stirring and adsorption for 1 hour, the adsorbent that had settled and filtered was treated with a mixed solution of 15ml concentrated hydrochloric acid and 5ml concentrated nitric acid at 80℃ for 30 minutes. After filtration, sufficient zinc powder was added to the acid solution to reduce the precious metal. The results of precious metal recovery are shown in Table 1.

[0065] Example 3

[0066] 1. Preparation of Adsorbent

[0067] (1) Take 0.5g of graphene and add it to 100ml of sulfuric acid and nitric acid (the molar ratio of sulfuric acid and nitric acid is 3:1). Treat it at room temperature for 30min, filter and dry to obtain adsorbent precursor I.

[0068] (2) Take 0.4g of adsorbent precursor I and add it to 2000ml of tetrahydrofuran solution, add 20g of dicyclohexylcarbodiimide and 200g of APTES (chemical formula H2NCH2CH2CH2Si(OC2H5)3), sonicate for 2 hours, react at 60℃ under nitrogen atmosphere for 24 hours, filter and dry to obtain adsorbent precursor II;

[0069] (3) Take 0.5g of adsorbent precursor II and add it to 2000ml of deionized water to hydrolyze for 12h to obtain adsorbent precursor III;

[0070] (4) Add 1000 ml of ethanol, 150 g of tetraethyl orthosilicate and 5 g of ammonia (mass fraction 18%) to the obtained adsorbent precursor III and react at room temperature for 8 h. Filter and dry to obtain adsorbent precursor IV.

[0071] (5) Take 20g of adsorbent precursor IV and calcine it at 1000℃ for 10 hours in a mixed atmosphere of nitrogen and ammonia (molar ratio of nitrogen to ammonia is 1:1) to obtain precious metal recovery adsorbent.

[0072] The content of each element in the precious metal recovery adsorbent was analyzed by XRF, and the specific data are shown in Table 1.

[0073] 2. Precious metal recycling

[0074] At room temperature, 200L of catalyst washing wastewater (containing approximately 1-15 ppmw of precious metal Au) and 10g of the prepared precious metal recovery adsorbent were added to a wastewater storage tank. After stirring and adsorption for 1 hour, the adsorbent that had settled and filtered was treated with a mixed solution of 15ml concentrated hydrochloric acid and 5ml concentrated nitric acid at 80℃ for 30 minutes. After filtration, sufficient zinc powder was added to the acid solution to reduce the precious metal. The results of precious metal recovery are shown in Table 1.

[0075] Comparative Example 1

[0076] 1. Preparation of Adsorbent

[0077] (1) Take 0.5g of graphene and add it to 100ml of sulfuric acid and nitric acid (the molar ratio of sulfuric acid and nitric acid is 3:1). Treat it at room temperature for 30min, filter and dry to obtain adsorbent precursor I.

[0078] (2) Take 0.3g of adsorbent precursor I and add it to 2000ml of tetrahydrofuran solution, add 20g of dicyclohexylcarbodiimide and 200g of APTES (chemical formula H2NCH2CH2CH2Si(OC2H5)3), sonicate for 2 hours, react at 60℃ under nitrogen atmosphere for 24 hours, filter and dry to obtain adsorbent precursor II;

[0079] (3) Take 0.5g of adsorbent precursor II and add it to 2000ml of deionized water to hydrolyze for 12h to obtain adsorbent precursor III;

[0080] (4) Add 1000 ml of ethanol, 150 g of tetraethyl orthosilicate and 5 g of ammonia (mass fraction 18%) to the adsorbent precursor III and react at room temperature for 8 h. Filter and dry to obtain the precious metal recovery adsorbent.

[0081] The content of each element in the precious metal recovery adsorbent was analyzed by XRF, and the specific data are shown in Table 1.

[0082] 2. Precious metal recycling

[0083] At room temperature, 200L of catalyst washing wastewater (same as in Example 1) and 10g of the prepared precious metal recovery adsorbent were added to a wastewater storage tank. After stirring and adsorption for 1 hour, the adsorbent that had settled and filtered was treated with a mixed solution of 15ml concentrated hydrochloric acid and 5ml concentrated nitric acid at 80°C for 30 minutes. After filtration, sufficient zinc powder was added to the acid solution to reduce the precious metal. The results of precious metal recovery are shown in Table 1.

[0084] Comparative Example 2

[0085] 1. Preparation of Adsorbent

[0086] Take 0.3g of APTES (chemical formula H2NCH2CH2CH2Si(OC2H5)3), add 1000ml of ethanol, 150g of tetraethyl orthosilicate and 5g of ammonia (mass fraction 18%), react at room temperature for 8h, filter and dry to obtain precious metal recovery adsorbent.

[0087] The content of each element in the obtained noble metal adsorbent was analyzed by XRF, and the specific data are shown in Table 1.

[0088] 2. Precious metal recycling

[0089] At room temperature, 200L of catalyst washing wastewater (same as in Example 1) and 10g of the prepared precious metal recovery adsorbent were added to a wastewater storage tank. After stirring and adsorption for 1 hour, the adsorbent that had settled and filtered was treated with a mixed solution of 15ml concentrated hydrochloric acid and 5ml concentrated nitric acid at 80°C for 30 minutes. After filtration, sufficient zinc powder was added to the acid solution to reduce the precious metal. The results of precious metal recovery are shown in Table 1.

[0090] Comparative Example 3

[0091] 1. Preparation of Adsorbent

[0092] (1) Take 100g of graphene and add it to 100ml of sulfuric acid and nitric acid (the molar ratio of sulfuric acid and nitric acid is 3:1). Treat it at room temperature for 30min, filter and dry to obtain adsorbent precursor I.

[0093] (2) Take 100g of adsorbent precursor I and calcine it at 1000℃ for 10 hours in a mixed atmosphere of nitrogen and ammonia (molar ratio of nitrogen to ammonia is 1:1) to obtain precious metal recovery adsorbent.

[0094] The content of each element in the precious metal recovery adsorbent was analyzed by XRF, and the specific data are shown in Table 1.

[0095] 2. Precious metal recycling

[0096] At room temperature, 200L of catalyst washing wastewater (same as in Example 1) and 10g of the prepared precious metal recovery adsorbent were added to a wastewater storage tank. After stirring and adsorption for 1 hour, the adsorbent that had settled and filtered was treated with a mixed solution of 15ml concentrated hydrochloric acid and 5ml concentrated nitric acid at 80°C for 30 minutes. After filtration, sufficient zinc powder was added to the acid solution to reduce the precious metal. The results of precious metal recovery are shown in Table 1.

[0097] Table 1

[0098]

[0099] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for producing an adsorbent for precious metal recovery, characterized by, The adsorbent comprises a nitrogen-doped graphene-SiO2 hybrid material, the nitrogen-doped graphene-SiO2 hybrid material comprises a graphene-SiO2 hybrid material and nitrogen doped therein, wherein the ratio of the molar amount of nitrogen to the total molar amount of C and Si in the nitrogen-doped graphene-SiO2 hybrid material is 1: (55-10050); the molar ratio of C to Si in the nitrogen-doped graphene-SiO2 hybrid material is (5-50): (50-10000). The preparation method comprises the following steps: (1) treating graphene with acid, filtering and drying to obtain an adsorbent precursor I; (2) mixing the adsorbent precursor I with a first dispersion solvent, a crosslinking agent and a dehydrating agent and carrying out a reaction under an inert atmosphere, filtering and drying to obtain an adsorbent precursor II; (3) hydrolyzing the adsorbent precursor II to obtain an adsorbent precursor III; (4) mixing the adsorbent precursor III with a second dispersion solvent and a carrier precursor, carrying out a reaction, filtering and drying to obtain an adsorbent precursor IV; (5) calcining the adsorbent precursor IV under a mixed atmosphere of inert gas and ammonia gas to obtain the adsorbent; In step (1), the treatment of graphene with acid refers to mixing the graphene with acid; The crosslinking agent in step (2) comprises at least one of 3-aminopropyl triethoxysilane, 3-aminopropyl trimethoxysilane, N-phenyl-gamma-aminopropyl trimethoxysilane and 3-ureidopropyl trimethoxysilane.

2. The production method according to claim 1, characterized by, In step (1), the graphene comprises at least one of single-layer graphene and multi-layer graphene, the size of the graphene sheet is 5-15 microns; and / or the acid is selected from at least one of sulfuric acid, nitric acid, formic acid, acetic acid and hydrochloric acid, and / or the use amount ratio of the graphene and the acid is not less than 1g:20mL.

3. The preparation method according to claim 2, characterized in that, In step (1), the multi-layer graphene comprises double-layer graphene, and / or the use amount ratio of the graphene and the acid is 1g:50mL-1g:500mL.

4. The production method according to any one of claims 1 to 3, characterized by, The dehydrating agent is selected from at least one of dicyclohexyl carbodiimide and N,N'-carbonyl diimidazole; and / or the first dispersion solvent is selected from tetrahydrofuran and / or dimethyl sulfoxide; and / or the reaction temperature in step (2) is 40-80℃, and / or the reaction time is 12-36h.

5. The method of any one of claims 1-3, wherein, In step (3), the hydrolysis comprises mixing the adsorbent precursor II with deionized water; And / or the hydrolysis temperature is 20-80℃, and the hydrolysis time is 6-24h.

6. The production method according to claim 5, wherein The use amount ratio of the adsorbent precursor II to deionized water is 1g:1000mL-1g:5000mL.

7. The method of any one of claims 1-3, wherein the method further comprises, In step (4), the carrier precursor comprises a silicon source and ammonia water; and / or the second dispersion solvent is selected from at least one of an alcohol and a ketone; And / or the ratio of the second dispersion solvent to the total weight of the raw materials of the mixing reaction is 1: (1.1-1.5), the raw materials of the mixing reaction being the adsorbent precursor III and the carrier precursor; And / or the mixing reaction temperature is 20-40℃, and / or the mixing reaction time is 2-12h.

8. The preparation method according to claim 7, characterized in that, In step (4), the silicon source is selected from at least one of tetraethyl orthosilicate, tetramethyl orthosilicate and tetrapropyl orthosilicate; and / or the concentration of the ammonia water is 1-10% by weight; and / or the weight ratio of the silicon source and the ammonia water is 1: (0.01-0.1).

9. The method of any one of claims 1-3, wherein, In step (5), the molar ratio of inert gas to ammonia in the mixed atmosphere is 3:1 to 1:3, and the volume space velocity of the mixed atmosphere is 200 to 1000 hr -1 ; and / or the calcination temperature is 800-1200℃, and the calcination time is 4-12h.

10. An adsorbent for noble metal recovery, prepared by the preparation method of any one of claims 1-9.

11. The adsorbent of claim 10, wherein, The adsorbent comprises a nitrogen-doped graphene-SiO2 hybrid material, which comprises a graphene-SiO2 hybrid material and nitrogen doped therein, wherein the ratio of the molar amount of nitrogen to the total molar amount of C and Si in the nitrogen-doped graphene-SiO2 hybrid material is 1: (55-10050), and the molar ratio of C to Si in the nitrogen-doped graphene-SiO2 hybrid material is (5-50): (50-10000).

12. The adsorbent of claim 11, wherein, The molar ratio of nitrogen: carbon: silicon in the nitrogen-doped graphene-SiO2 hybrid material is 1: (5-50): (50-10000).

13. A method for recovering noble metal from wastewater, comprising mixing the adsorbent of any one of claims 10-12 with wastewater for adsorption, precipitating and filtering to obtain an adsorbent with adsorbed noble metal, and desorbing the adsorbent with adsorbed noble metal to obtain the noble metal.

14. The recycling method of claim 13, wherein, The noble metal is Au; and / or the noble metal exists in the wastewater in the form of a complex; and / or the wastewater is catalyst washing wastewater in the preparation process of a vinyl acetate catalyst.

15. The recycling method of claim 14, wherein, The noble metal is present in the waste water in the form of [Au(OH) 4-x ]Clx.

16. The recycling method according to any one of claims 13-15, characterized in that, The amount of the adsorbent is 0.01-0.1g / L of wastewater, and / or the desorption comprises reducing the adsorbent with adsorbed noble metal after treating the adsorbent with a strong acid, wherein the strong acid is at least one selected from concentrated hydrochloric acid and concentrated nitric acid, and the reduction comprises using another metal to displace the noble metal from its acid solution.

17. The recycling method of claim 16, wherein, The other metal is zinc.

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