Bio-based porous cobalt monatomic catalyst and preparation method and application thereof

Abstract

The invention provides a bio-based porous cobalt monatomic catalyst and a preparation method and application thereof, and relates to the technical field of sewage treatment. Urea, dicyandiamide, a pore-forming agent and a precursor silkworm excrement are mixed and dispersed in a solvent, then the mixture and a cobalt source are mixed and dispersed, drying and specific roasting treatment are performed, the bio-based porous cobalt monatomic catalyst is obtained, and the pore-forming agent is at least one of bicarbonate and carbonate. When the prepared bio-based porous cobalt monatomic catalyst is used for treating organic pollutants in a water body, the pollutants can be efficiently removed under the normal-temperature neutral condition, the adverse effect of DOC in the water can be effectively overcome, and the bio-based porous cobalt monatomic catalyst serves as an immobilized particle catalyst, is convenient to separate from water and recycle, and is good in cycling stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, and particularly relates to a biological-based porous cobalt monatomic catalyst as well as a preparation method and application thereof. BACKGROUND

[0002] In recent years, the acceleration of industrialization has led to the discharge of various types of refractory organic pollutants into water environments at an exponential scale, which has become a long-term and severe public health problem. In order to ensure the supply of clean drinking water and eliminate ecological risks, various water treatment technologies have been developed for application in the field of industrial wastewater and municipal sewage treatment to promote environmental sustainable development and protect drinking water safety. These technologies include physical adsorption, biochemical treatment, chemical conversion, Fenton oxidation, PMS activation, and ferrate oxidation. However, due to the complexity and stability of the structure of refractory organic pollutants, the above-mentioned technologies often fail to achieve efficient removal, and generally have the problem of high energy consumption. In addition, the widespread presence of dissolved organic carbon (DOC) in water bodies not only significantly inhibits the degradation process of organic pollutants, but also can promote the generation of harmful by-products, which undoubtedly makes the remediation of organic pollution in actual water bodies face more daunting challenges.

[0003] Recently, scholars have found that cation-pi interactions can promote the generation of electric fields by adjusting the charge rearrangement between metal ions and pi systems or the coordination of surface pollutants. Moreover, the strength of cation-pi interactions depends on the type of cations and the properties of pi systems, which indicates that the adjacent environment involved plays a key role in adjusting the strength of the electric field. This provides the possibility of utilizing cation-pi system coordination to generate electric field energy and achieve low-energy and efficient water treatment. In the past, the construction of cation-pi systems often relied on graphene, but the catalyst prepared from graphene is powdery and not suitable for actual water body treatment. Moreover, the high cost of graphene preparation greatly limits its practical application. SUMMARY

[0004] The present application aims to overcome the deficiencies of the prior art and provides a biological-based porous cobalt monatomic catalyst as well as a preparation method and application thereof.

[0005] To achieve the above-mentioned purpose, in a first aspect, the present application provides a preparation method of a biological-based porous cobalt monatomic catalyst, comprising the following steps: mixing and dispersing urea, dicyandiamide, a pore-forming agent, and silkworm excrement in a solvent to obtain dispersion liquid A; mixing and dispersing a cobalt source with the dispersion liquid A to obtain dispersion liquid B; drying the dispersion liquid B to obtain solid particles; The solid particles are calcined at 250-600 DEG C for 2-6 h, and then calcined at 650-900 DEG C for 1-3 h to obtain a solid product, i.e. a bio-based porous cobalt monatomic catalyst. The pore-forming agent is at least one of a bicarbonate and a carbonate.

[0006] The catalyst synthesized by the preparation method has monatomic Co sites and a graphene-like (GL) π system, wherein the monatomic Co has a large specific surface area, which is conducive to improving the utilization rate of Co atoms, and the monatomic Co has high spin, which helps to promote the catalytic degradation of organic pollutants and accelerate the transfer of electric charges; compared with carbon nitride, the graphene-like structure has stronger electron transport capacity, so that the catalytic degradation rate of organic pollutants is higher. Meanwhile, the monatomic Co is connected to the GL structure through Co-O-C and Co-N-C chemical coordination bonds, the π electrons on the GL are activated and transferred to the periphery of the monatomic Co through these chemical bond bridges, forming an electron high-density region, and an electron low-density region is formed near the GL, thereby forming a strong electric field on the surface of the catalyst. When the obtained catalyst is used for wastewater treatment, the synergistic coordination of DOC-organic pollutants-H2O at the high-spin monatomic Co sites and the GL sites causes strong surface charge rearrangement, generates very strong electric field energy, and makes the adsorption groups of the organic pollutants undergo continuous oxidation and homolytic cleavage of adjacent chemical bonds until complete mineralization. In the entire reaction process, the generated free radicals can continuously charge the catalyst function, and without external energy assistance, low-energy efficient purification of wastewater, especially composite wastewater, can be realized.

[0007] Urea is calcined at 250-600 DEG C to form a carbon nitride network structure through a condensation reaction, and can play a role of a binder in the condensation process, coating cobalt and silkworm excrement, and meanwhile, urea is compounded with dicyandiamide. Since urea and dicyandiamide have different condensation directions in the formation of the carbon nitride network structure, the formed carbon nitride network structure can better coat cobalt and silkworm excrement, and promote better complexation between cobalt and silkworm excrement, so that the synthesized catalyst has better stability. In addition, urea and dicyandiamide further carbonize at 650-900 DEG C to act as a template to make silkworm excrement directionally grow at high temperature to form a graphene-like structure.

[0008] The preparation method uses at least one of bicarbonate and carbonate as a pore-forming agent, which has two main functions. One is to act as a pore-forming agent, so that the synthesized catalyst has a uniform porous structure. The other is to act as a reducing agent to avoid the formation of cobalt oxide during the reaction calcination process, and to directionally induce the formation of single-atom Co. However, if a pore-forming agent without reducing properties, such as zinc chloride, zinc nitrate, aluminum chloride, etc., is used, although it has strong pore-forming ability and is uniformly dispersed with other raw materials, the pore structure is uniform, but it cannot form single-atom Co, resulting in low efficiency of the catalyst in catalyzing the degradation of organic pollutants. For example, ammonium chloride, which is weakly acidic, is not easy to disperse uniformly with other raw materials, resulting in uneven pore structure, and it cannot form single-atom Co, so the efficiency of the catalyst in catalyzing the degradation of organic pollutants is low.

[0009] The preparation method uses silkworm excrement as a carbon-based precursor to form a graphene-like structure. Compared with graphite, melamine, dicyandiamide, etc., using silkworm excrement as a carbon-based precursor can form a graphene-like structure, which has stronger electron transport capacity, resulting in a higher rate of catalytic degradation of organic pollutants. Compared with wood chips, silkworm excrement can be better coated with Co during the urea and dicyandiamide polycondensation reaction, and can chemically coordinate with Co. At the same time, using graphite, melamine, dicyandiamide, wood chips, etc. as a carbon-based precursor, the synthesized catalyst is powdery, while using silkworm excrement as a carbon-based precursor, the synthesized catalyst is granular, has good processing stability, is suitable for water treatment, is easy to separate and recover, and silkworm excrement contains various heteroatoms, which is conducive to regulating the coordination charge environment of Co single atoms, making the catalyst have stronger catalytic activity, and the cost is low and easy to obtain.

[0010] The preparation method needs to mix and disperse urea, dicyandiamide, pore-forming agent and precursor silkworm excrement in a solvent, and then mix and disperse with a cobalt source. This is conducive to the interaction between urea and dicyandiamide and the precursor silkworm excrement to form a molecular network complex, and the pore-forming agent is uniformly dispersed in it. After adding the cobalt source, the pore-forming agent reacts with the cobalt source to produce gas, which can open the silkworm excrement channels, allowing them to better adsorb cobalt ions and coordinate with them, and the polycondensation of urea and dicyandiamide is more uniform, and the dispersion of metal atoms in the catalyst is more uniform.

[0011] When the catalyst synthesized by the above preparation method is used to treat organic pollutants in water, it can achieve efficient removal of pollutants at room temperature and neutral conditions. Compared with conventional wastewater oxidation treatment methods, it can effectively overcome the adverse effects of natural organic carbon (DOC) in water on pollutant removal. In addition, the catalyst can retain the morphology of the precursor silkworm excrement particles, which belongs to a solid-supported granular catalyst, is easy to separate from water, and has good cycling stability.

[0012] Preferably, the mass ratio of the urea, the dicyandiamide, the pore-forming agent to the cocoon is (0.4-0.75):(1-1.9):(0.1-0.45):1, and the mass ratio of the cocoon to the amount of substance of cobalt element in the cobalt source is 1 g:(0.001-0.0019) mol.

[0013] For example, the mass ratio of the urea, the dicyandiamide, the pore forming agent, and the silk cocoon is 0.40:1.0:0.10:1, 0.50:1.2:0.20:1, 0.60:1.5:0.30:1, 0.70:1.7:0.40:1, 0.75:1.9:0.45:1, 0.40:1.2:0.20:1, 0.40:1.5:0.30:1, 0.40:1.7:0.40:1, 0.40:1.9:0.45:1, 0.50:1.0:0.10:1, 0.50:1.5:0.30:1, 0.50:1.7:0.40:1, 0.50:1.9:0.45:1, 0.60:1.0:0.10:1, 0.60:1.2:0.20:1, 0.60:1.7:0.40:1, 0.60:1.9:0.45:1, 0.70:1.0:0.10:1, 0.70:1.2:0.20:1, 0.70:1.5:0.30:1, 0.70:1.9:0.45:1, 0.75:1.0:0.10:1, 0.75:1.2:0.20:1, 0.75:1.5:0.30:1, 0.75:1.7:0.40:1, 0.50:1.0:0.20:1, 0.60:1.0:0.30:1, 0.70:1.0:0.40:1, 0.75:1.0:0.45:1, 0.40:1.2:0.10:1, 0.60:1.2:0.30:1, 0.70:1.2:0.40:1, 0.75:1.2:0.45:1, 0.40:1.5:0.10:1, 0.50:1.5:0.20:1, 0.70:1.5:0.40:1, 0.75:1.5:0.45:1, 0.40:1.7:0.10:1, 0.50:1.7:0.20:1, 0.60:1.7:0.30:1, 0.75:1.7:0.45:1, 0.40:1.9:0.10:1, 0.50:1.9:0.20:1, 0.60:1.9:0.30:1, 0.70:1.9:0.40:1, 0.50:1.2:0.10:1, 0.60:1.5:0.10:1, 0.70:1.7:0.10:1, 0.75:1.9:0.10:1, 0.40:1.0:0.20:1, 0.60:1.5:0.20:1, 0.70:1.7:0.20:1, 0.75:1.9:0.20:1, 0.40:1.0:0.30:1, 0.50:1.2:0.30:1, 0.70:1.7:0.30:1, 0.75:1.9:0.30:1, 0.40:1.0:0.40:1, 0.50:1.2:0.40:1, 0.60:1.5:0.40:1, 0.75:1.9: 0.40: 1, 0.40: 1.0: 0.45: 1, 0.50: 1.2: 0.45: 1, 0.60: 1.5: 0.45: 1 or 0.70: 1.7: 0.45: 1, etc.

[0014] For example, the mass ratio of the cocoon dust to the amount of substance of cobalt element in the cobalt source is 1 g:0.001 mol, 1 g:0.0011 mol, 1 g:0.0012 mol, 1 g:0.0013 mol, 1 g:0.0014 mol, 1 g:0.0015 mol, 1 g:0.0016 mol, 1 g:0.0017 mol, 1 g:0.0018 mol or 1 g:0.0019 mol.

[0015] More preferably, the mass ratio of the urea, the dicyandiamide, the pore-forming agent and the cocoon dust is (0.47-0.58):(1.1-1.5):(0.355-0.395):1, and the mass ratio of the cocoon dust to the amount of substance of cobalt element in the cobalt source is 1 g:(0.0014-0.0015) mol, so that the catalytic activity of the catalyst is higher.

[0016] More preferably, the mass ratio of the urea, the dicyandiamide, the pore-forming agent and the cocoon dust is 0.5:1.25:0.375:1, and the mass ratio of the cocoon dust to the amount of substance of cobalt element in the cobalt source is 1 g:0.00145 mol, so that the catalytic activity of the catalyst is more optimal. Controlling the amounts of urea, dicyandiamide, pore-forming agent, cocoon dust and cobalt source to satisfy the mass ratio of urea, dicyandiamide, pore-forming agent and cocoon dust is (0.4-0.75):(1-1.9):(0.1-0.45):1 and the mass ratio of cocoon dust to the amount of substance of cobalt element in the cobalt source is 1 g:(0.001-0.0019) mol, particularly the mass ratio of urea, dicyandiamide, pore-forming agent and cocoon dust is (0.47-0.58):(1.1-1.5):(0.355-0.395):1 and the mass ratio of cocoon dust to the amount of substance of cobalt element in the cobalt source is 1 g:(0.0014-0.0015) mol, especially the mass ratio of urea, dicyandiamide, pore-forming agent and cocoon dust is 0.5:1.25:0.375:1 and the mass ratio of cocoon dust to the amount of substance of cobalt element in the cobalt source is 1 g:0.00145 mol, so that the urea, dicyandiamide and cocoon dust are more uniformly condensed and are less likely to be carbonized, the pore structure is more developed, the active sites are more, the cobalt species is less likely to be agglomerated, the surface oxide is less, and the catalytic activity is higher.

[0017] In the process of preparing the bio-based porous cobalt single-atom catalyst using the solid particles, the solid particles are calcined at 250-600°C (such as 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C or 600°C) for 2-6h (such as 2h, 3h, 4h, 5h or 6h), and then calcined at 650-900°C (such as 650°C, 680°C, 700°C, 720°C, 750°C, 780°C, 800°C, 820°C, 850°C, 870°C or 900°C) for 1-3h (such as 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h, 2.8h or 3h).

[0018] Preferably, the specific step of calcining the solid particles at 250-600°C for 2-6h is as follows: calcining the solid particles at 250-400°C for 1-3h, and then calcining the solid particles at 450-600°C for 1-3h. The solid particles are first calcined at 250-400°C (such as 250°C, 270°C, 300°C, 320°C, 340°C, 360°C, 380°C or 400°C) for 1-3h (such as 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h, 2.8h or 3h) to make them undergo semi-polycondensation, and then calcined at 450-600°C (such as 450°C, 470°C, 500°C, 520°C, 550°C, 570°C or 600°C) for 1-3h (such as 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h, 2.8h or 3h) to make them undergo complete polycondensation, so that the polycondensation of urea and dicyandiamide is more uniform, excessive carbonization does not occur, the network structure formed is more complete, and the electronic structure is more superior, thereby making the catalytic activity of the catalyst more superior.

[0019] Preferably, the pore-forming agent comprises at least one of sodium bicarbonate, ammonium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate.

[0020] More preferably, the pore-forming agent comprises ammonium bicarbonate. Using ammonium bicarbonate as the pore-forming agent makes the catalytic activity of the synthesized catalyst more superior.

[0021] Preferably, the cobalt source comprises at least one of cobalt chloride hexahydrate, cobaltous sulfate, cobalt acetate, cobalt sulfate heptahydrate, cobalt acetate tetrahydrate, cobalt nitrate hexahydrate.

[0022] Preferably, the heating rate during calcination is controlled in the range of 2-20℃ / min, which is beneficial to eliminate the trace adsorbed water in the solid product B, so that the active species can be dispersed and denatured, and uniformly doped into the graphene-like structure through chemical bonding, and the target catalyst particles are uniform and black. The heating rate of each stage of calcination is independently selected, which can be the same or different, such as 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min, 15℃ / min, 16℃ / min, 17℃ / min, 18℃ / min, 19℃ / min or 20℃ / min.

[0023] Preferably, the calcination is carried out in a protective gas atmosphere, and the protective gas includes at least one of nitrogen and inert gas.

[0024] Preferably, the ratio of the material liquid in the dispersion A is (urea + dicyandiamide + pore-forming agent + silkworm excrement) : solvent = 1g : (2-6) mL, such as 1g:2mL, 1g:2.5mL, 1g:3mL, 1g:3.5mL, 1g:4mL, 1g:4.5mL, 1g:5mL, 1g:5.5mL or 1g:6mL.

[0025] Preferably, the solvent in the dispersion A includes water.

[0026] Preferably, the solid product is further washed and dried to obtain the bio-based porous cobalt monatomic catalyst. The washing can use water as the washing agent, and the drying temperature can be selected as 60-120℃, and the drying time can be selected as 12-36h.

[0027] Preferably, in the process of mixing and dispersing the urea, dicyandiamide, pore-forming agent and silkworm excrement in the solvent to obtain the dispersion A, the dispersion is carried out by stirring at a stirring speed of 10-30rpm for 1-6h.

[0028] Preferably, in the process of mixing and dispersing the cobalt source with the dispersion A to obtain the dispersion B, the dispersion is carried out by stirring at a stirring speed of 10-30rpm for 1-24h.

[0029] Preferably, in the process of drying the dispersion B to obtain the solid particles A, the drying temperature is 80-150℃, and the drying time is 12-72h.

[0030] In a second aspect, the present application provides a bio-based porous cobalt monatomic catalyst prepared by the preparation method of the bio-based porous cobalt monatomic catalyst.

[0031] In a third aspect, the present application provides an application of the bio-based porous cobalt monatomic catalyst in degrading organic pollutants in water bodies.

[0032] Preferably, the organic pollutants include at least one of quinolones, phenols, antihistamines.

[0033] Preferably, the quinolones include at least one of ciprofloxacin (CIP), norfloxacin, tetracycline.

[0034] Preferably, the phenols include at least one of bisphenol A (BPA), bisphenol B, bisphenol S, bisphenol F, bisphenol AF.

[0035] Preferably, the ethanolamines include at least one of diphenhydramine (DP), cetirizine.

[0036] Compared with the prior art, the present application has the following beneficial effects: 1. The catalyst synthesized by the present application utilizes the synergistic coordination of high-spin monatomic Co sites and GL sites, causing strong surface charge rearrangement and generating very strong electric field energy, so that the adsorption groups of organic pollutants are continuously oxidized and homolytic cleavage of adjacent chemical bonds occurs until complete mineralization. The free radicals generated during the entire reaction process can continuously charge the catalyst, and without external energy assistance, the low-energy efficient purification of wastewater, especially composite wastewater, can be realized.

[0037] 2. When the catalyst synthesized by the present application is used to treat organic pollutants in water bodies, efficient removal of pollutants can be achieved under normal temperature and neutral conditions.

[0038] 3. Compared with conventional wastewater oxidation treatment methods, the catalyst synthesized by the present application can effectively overcome the adverse effects of DOC in water on pollutant removal.

[0039] 4. The catalyst synthesized by the present application belongs to a solid-supported particulate catalyst, which is easy to separate from water and recycle, and has good recycling stability. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The SEM (scanning electron microscope) image of Co SA -N2O2-GL prepared in Example 1; Figure 2 The HAADF-STEM (high-angle annular dark field scanning transmission electron microscope) image of Co SA -N2O2-GL prepared in Example 1; Figure 3 The EPR (electron paramagnetic resonance) spectrum of Co SA -N2O2-GL and NC prepared in Comparative Example 1; Figure 4 Co prepared for Example 1 SA -N2O2-GL degradation curves for CIP, BPA and DP; Figure 5 Co prepared for Example 1 SA -N2O2-GL TOC removal graph for CIP, BPA and DP; Figure 6 Co prepared for Example 1 SA -N2O2-GL degradation curves for CIP in municipal wastewater and source water for drinking water; Figure 7 Co prepared for Example 1 SA -N2O2-GL repeated experiment activity evaluation graph. DETAILED DESCRIPTION

[0041] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0042] In the present application, the technical features described in an open form include a closed technical solution consisting of listed features, and also an open technical solution containing listed features.

[0043] In the present application, when a numerical interval is involved, the numerical interval is regarded as continuous and includes the minimum value and the maximum value of the range and each value between the minimum value and the maximum value, unless otherwise specified. Further, when a plurality of ranges are provided to describe a feature or a characteristic, the ranges can be combined. In other words, unless otherwise specified, all the ranges disclosed herein should be understood as including any and all sub-ranges falling within the range.

[0044] In the present application, the specific dispersion and stirring treatment method is not particularly limited.

[0045] The reagents or instruments used in the present application are not specified by the manufacturer, and are all conventional products that can be obtained by purchase.

[0046] Example 1 The present embodiment provides a preparation method of a bio-based porous cobalt monatomic catalyst, comprising the following steps: Urea, dicyandiamide, pore-forming agent and silkworm excrement were added into water, stirred at 20 rpm for 2 h to obtain dispersion A, wherein the pore-forming agent was sodium bicarbonate, the mass ratio of urea, dicyandiamide, pore-forming agent and silkworm excrement was 0.5:1.25:0.375:1, and the ratio of solid to solvent in dispersion A was (urea+dicyandiamide+pore-forming agent+silkworm excrement): solvent = 1 g:3.2 mL; A cobalt source was added into dispersion A, stirred at 20 rpm for 4 h to obtain dispersion B, wherein the cobalt source was cobalt chloride hexahydrate, and the mass ratio of silkworm excrement to the amount of substance of cobalt element in the cobalt source was 1 g:0.00145 mol; Dispersion B was placed in a 100℃ oven and allowed to stand for 24 h to obtain solid particles A; Solid particles A were placed in a tube furnace and calcined under N2 atmosphere, first heated to 350℃ and calcined for 1 h, then heated to 550℃ and calcined for 1 h, and then heated to 700℃ and calcined for 2 h, the heating rate of calcination was 5℃ / min, and after calcination, the temperature was allowed to decrease naturally to obtain solid product B; Solid product B was washed with water three times and placed in a 60℃ oven for 24 h to obtain a biomass-based porous cobalt monatomic catalyst, denoted as Co SA -N2O2-GL.

[0047] Example 2 The present example provides a preparation method of a biomass-based porous cobalt monatomic catalyst, which is different from example 1 in that the mass ratio of urea, dicyandiamide, pore-forming agent and silkworm excrement is 0.47:1.5:0.355:1, and the mass ratio of silkworm excrement to the amount of substance of cobalt element in the cobalt source is 1 g:0.0014 mol.

[0048] Example 3 The present example provides a preparation method of a biomass-based porous cobalt monatomic catalyst, which is different from example 1 in that the mass ratio of urea, dicyandiamide, pore-forming agent and silkworm excrement is 0.58:1.1:0.395:1, and the mass ratio of silkworm excrement to the amount of substance of cobalt element in the cobalt source is 1 g:0.0015 mol.

[0049] Example 4 The present example provides a preparation method of a biomass-based porous cobalt monatomic catalyst, which is different from example 1 in that the mass ratio of urea, dicyandiamide, pore-forming agent and silkworm excrement is 0.4:1.9:0.1:1, and the mass ratio of silkworm excrement to the amount of substance of cobalt element in the cobalt source is 1 g:0.001 mol.

[0050] Example 5 The embodiment provides a preparation method of a bio-based porous cobalt monatomic catalyst, which is different from the embodiment 1 in that the mass ratio of urea, dicyandiamide, a pore forming agent and silkworm excrement is 0.75:1:0.45:1, and the mass ratio of the silkworm excrement to the substance amount of cobalt elements in the cobalt source is 1g:0.0019mol.

[0051] Embodiment 6 The embodiment provides a preparation method of a bio-based porous cobalt monatomic catalyst, which is different from the embodiment 1 in that the pore forming agent is ammonium bicarbonate.

[0052] Embodiment 7 The embodiment provides a preparation method of a bio-based porous cobalt monatomic catalyst, which is different from the embodiment 1 in that the cobalt source is cobaltous sulfate.

[0053] Embodiment 8 The embodiment provides a preparation method of a bio-based porous cobalt monatomic catalyst, which is different from the embodiment 1 in that, when the solid particles A are placed in a tube furnace and calcined under a N2 atmosphere, the solid particles A are first heated to 250 DEG C and calcined for 3h, then heated to 450 DEG C and calcined for 3h, and then heated to 600 DEG C and calcined for 3h, the heating rate of calcination is 2 DEG C / min, and the solid product A is obtained after natural cooling.

[0054] Embodiment 9 The embodiment provides a preparation method of a bio-based porous cobalt monatomic catalyst, which is different from the embodiment 1 in that, when the solid particles A are placed in a tube furnace and calcined under a N2 atmosphere, the solid particles A are first heated to 400 DEG C and calcined for 1h, then heated to 600 DEG C and calcined for 1h, and then heated to 900 DEG C and calcined for 1h, the heating rate of calcination is 20 DEG C / min, and the solid product A is obtained after natural cooling.

[0055] Embodiment 10 The embodiment provides a preparation method of a bio-based porous cobalt monatomic catalyst, which is different from the embodiment 1 in that, when the solid particles A are placed in a tube furnace and calcined under a N2 atmosphere, the solid particles A are first heated to 350 DEG C and calcined for 2h, and then heated to 700 DEG C and calcined for 2h, the heating rate of calcination is 5 DEG C / min, and the solid product A is obtained after natural cooling.

[0056] Embodiment 11 The embodiment provides a preparation method of a bio-based porous cobalt monatomic catalyst, which is different from the embodiment 1 in that, when the solid particles A are placed in a tube furnace and calcined under a N2 atmosphere, the solid particles A are first heated to 550 DEG C and calcined for 2h, and then heated to 700 DEG C and calcined for 2h, the heating rate of calcination is 5 DEG C / min, and the solid product A is obtained after natural cooling.

[0057] Comparative example 1 The comparative example provides a preparation method of a catalyst, which is different from that of Example 1 in that no cobalt source is used, i.e. dispersion liquid A is directly stirred at 20 rpm for 4 h to obtain dispersion liquid B. The catalyst obtained in the comparative example is denoted as NC.

[0058] Comparative Example 2 The comparative example provides a preparation method of a catalyst, which is different from that of Example 1 in that only urea is used instead of dicyandiamide, and the mass ratio of urea, pore-forming agent and silkworm excrement is 1.75:0.375:1.

[0059] Comparative Example 3 The comparative example provides a preparation method of a catalyst, which is different from that of Example 1 in that only dicyandiamide is used instead of urea, and the mass ratio of dicyandiamide, pore-forming agent and silkworm excrement is 1.75:0.375:1.

[0060] Comparative Example 4 The comparative example provides a preparation method of a catalyst, which is different from that of Example 1 in that the pore-forming agent is zinc chloride.

[0061] Comparative Example 5 The comparative example provides a preparation method of a catalyst, which is different from that of Example 1 in that sawdust is completely replaced with equal weight of silkworm excrement.

[0062] Comparative Example 6 The comparative example provides a preparation method of a catalyst, which is different from that of Example 1 in that solid particles A are placed in a tube furnace and calcined under N2atmosphere, the temperature is raised to 700℃for 3 h, the temperature raising rate of calcination is 5℃ / min, and the solid product B is obtained after natural cooling after calcination.

[0063] Comparative Example 7 The comparative example provides a preparation method of a catalyst, which is different from that of Example 1 in that solid particles A are placed in a tube furnace and calcined under N2atmosphere, the temperature is first raised to 200℃for 2 h, and then raised to 700℃for 2 h, the temperature raising rate of calcination is 5℃ / min, and the solid product B is obtained after natural cooling after calcination.

[0064] Comparative Example 8 The comparative example provides a preparation method of a catalyst, which is different from that of Example 1 in that solid particles A are placed in a tube furnace and calcined under N2atmosphere, the temperature is first raised to 650℃for 2 h, and then raised to 700℃for 2 h, the temperature raising rate of calcination is 5℃ / min, and the solid product B is obtained after natural cooling after calcination.

[0065] Comparative Example 9 The comparative example provides a preparation method of a catalyst, which is different from that of example 1 in that: when the solid particles A are calcined in a tube furnace under N2atmosphere, the temperature is first raised to 550°C and calcined for 2h, and then raised to 600°C and calcined for 2h, the temperature rising rate of calcination is 5°C / min, and after the end of calcination, the temperature is naturally lowered to obtain the solid product B.

[0066] Comparative example 10 The comparative example provides a preparation method of a catalyst, which is different from that of example 1 in that: when the solid particles A are calcined in a tube furnace under N2atmosphere, the temperature is first raised to 550°C and calcined for 2h, and then raised to 1000°C and calcined for 2h, the temperature rising rate of calcination is 5°C / min, and after the end of calcination, the temperature is naturally lowered to obtain the solid product B.

[0067] Comparative example 11 The comparative example provides a preparation method of a catalyst, which is different from that of example 1 in that: when the solid particles A are calcined in a tube furnace under N2atmosphere, the temperature is first raised to 550°C and calcined for 1h, and then raised to 700°C and calcined for 2h, the temperature rising rate of calcination is 5°C / min, and after the end of calcination, the temperature is naturally lowered to obtain the solid product B.

[0068] Comparative example 12 The comparative example provides a preparation method of a catalyst, which is different from that of example 1 in that: when the solid particles A are calcined in a tube furnace under N2atmosphere, the temperature is first raised to 550°C and calcined for 8h, and then raised to 700°C and calcined for 2h, the temperature rising rate of calcination is 5°C / min, and after the end of calcination, the temperature is naturally lowered to obtain the solid product B.

[0069] Comparative example 13 The comparative example provides a preparation method of a catalyst, which is different from that of example 1 in that: when the solid particles A are calcined in a tube furnace under N2atmosphere, the temperature is first raised to 550°C and calcined for 2h, and then raised to 700°C and calcined for 0.5h, the temperature rising rate of calcination is 5°C / min, and after the end of calcination, the temperature is naturally lowered to obtain the solid product B.

[0070] Comparative example 14 The comparative example provides a preparation method of a catalyst, which is different from that of example 1 in that: when the solid particles A are calcined in a tube furnace under N2atmosphere, the temperature is first raised to 550°C and calcined for 2h, and then raised to 700°C and calcined for 4h, the temperature rising rate of calcination is 5°C / min, and after the end of calcination, the temperature is naturally lowered to obtain the solid product B.

[0071] The catalysts prepared in each example and comparative example are subjected to structure analysis by SEM, HAADF-STEM and EPR. Figure 1 、 Figure 2 、 Figure 3Co catalyst prepared in Example 1 SA SEM, HAADF-STEM and EPR images of Co Figure 1 It can be seen that the catalyst Co SA -N2O2-GL has a honeycomb-like porous structure with pore size of 1-10 μm. Figure 2 In the catalyst Co SA -N2O2-GL, the surface has abundant isolated bright spots, which indicate that the ingenious complexation of Co with the graphenelike structure promotes the formation of abundant Co atomic sites on the catalyst surface. Figure 3 In the catalyst Co SA The EPR spectrum of Co

[0072] Co SA EXAFS oscillation fitting results of Co As shown in Table 1, the central Co atom has a coordination number of 4, 2.2 O atoms are directly connected in the first coordination layer, and 2.1 N atoms and 1.4 C atoms are directly connected in the second coordination layer. The results confirm that the Co SA -N2O2-GL has a symmetry-breaking configuration, which effectively improves the interface electron transfer ability and structural stability of the catalyst. Therefore, in the catalyst Co SA On the surface of Co

[0073] Application Experiment 1 The catalyst samples prepared in each example and the comparative example were put into 50 mL of a pollutant solution (prepared by using the pollutant and ultrapure water UPW, and the pollutant was BPA) with a concentration of 10 mg / L, and the degradation reaction was started under constant temperature of 35 °C and constant magnetic stirring, the stirring speed was 35 rpm, and the reaction was carried out for 120 min. After the reaction, the catalyst was separated, and the concentration of the pollutant in the solution after the reaction was detected. The separated catalyst was dried, and then the pollutant solution was treated according to the foregoing process. The pollutant degradation rates after the catalyst was run once and 6 times are shown in Table 2. The pollutant degradation rate after running once = (the initial concentration of the pollutant in the solution - the concentration of the pollutant in the solution after running once) / the initial concentration of the pollutant in the solution x 100%, and the pollutant degradation rate after running 6 times = (the initial concentration of the pollutant in the solution - the concentration of the pollutant in the solution after running 6 times) / the initial concentration of the pollutant in the solution x 100%. The pollutant degradation of the catalyst prepared in Example 1 after each run is shown in Table 2. Figure 7 It can be seen that the catalyst has good stability and can be recycled, and the removal rate of BPA remains above 99.5% after 6 consecutive runs, and the release amount of cobalt is only 0.06 mg / L.

[0074] Table 2 Number Degradation of pollutants after 1 run (%) Degradation of pollutants after 6 runs (%) Example I 100.0 99.5 Example 2 92.1 911 Example 3 93.8 91.9 Example 4 67.7 63.4 Example 5 65.9 62.0 Example 6 100.0 99.7 Example 7 100.0 99.4 Example 8 98.7 97.9 Example 9 97.2 96.8 Example 10 68.5 64.1 Example 11 66.0 60.9 Comparative Example 1 15.7 9.8 Comparative Example 2 36.8 26.5 Comparative Example 3 34.1 22.6 Comparative Example 4 20.4 13.2 Comparative Example 5 41.9 Comparative Example 6 38.4 / Comparative Example 7 45.3 Comparative Example 8 42.5 / Comparative Example 9 47.2 / Comparative Example 10 46.8 Comparative Example 11 50.2 Comparative Example 12 48.7 Comparative Example 13 47.4 Comparative Example 14 49.3 It can be seen from the above data that the catalysts obtained in each example have good catalytic activity and stability, such as the BPA degradation rate after running once is above 63.5%, and the BPA degradation rate after running 6 times is above 60%.

[0075] The comparative example 1 does not use cobalt source, resulting in the deviation of catalytic activity and stability of the obtained catalyst; the comparative example 2 only uses urea, the condensation reaction is highly directional, and the carbon nitride network structure formed cannot effectively coat cobalt and silkworm sand, resulting in the deviation of catalytic activity and stability of the obtained catalyst; the comparative example 3 only uses dicyandiamide, which does not have the role of binder and cannot effectively coat cobalt and silkworm sand, resulting in the deviation of catalytic activity and stability of the obtained catalyst; the comparative example 4 uses zinc chloride as a pore former, which does not have reducing property, resulting in the formation of cobalt oxide in the calcination process, and the deviation of catalytic activity and stability of the obtained catalyst; the comparative example 5 uses sawdust as a carbon-based precursor, the obtained catalyst has low activity and is in powder form, which is not convenient for recycling; the comparative example 6 does not use staged calcination, the pore former decomposes too quickly, which is not conducive to the formation of single-atom Co, and urea and dicyandiamide are excessively carbonized, resulting in too low activity of the obtained catalyst; the comparative example 7 has too low temperature in the low-temperature stage of calcination, which makes the material prone to agglomeration in the calcination process and is not conducive to the condensation of urea and dicyandiamide to form carbon nitride, resulting in too low activity of the catalyst; the comparative example 8 has too high temperature in the low-temperature stage of calcination, which makes the pore former decompose too quickly and is not conducive to the formation of single-atom Co, and urea and dicyandiamide are excessively carbonized, resulting in too low activity of the obtained catalyst; the comparative example 9 has too low temperature in the high-temperature stage of calcination, which makes the material prone to agglomeration in the calcination process, resulting in too low activity of the catalyst; the comparative example 10 has too high temperature in the high-temperature stage of calcination, which makes urea, dicyandiamide and silkworm sand excessively carbonized, resulting in too low activity of the obtained catalyst; the comparative example 11 has too short time in the low-temperature stage of calcination, which is not conducive to the condensation of urea and dicyandiamide to form carbon nitride, resulting in too low activity of the catalyst; the comparative example 12 has too long time in the low-temperature stage of calcination, which makes cobalt species prone to agglomeration, resulting in too low activity of the obtained catalyst; the comparative example 13 has too short time in the high-temperature stage of calcination, which is not conducive to the formation of graphite-like structure of sandworm, resulting in too low activity of the catalyst; the comparative example 14 has too long time in the high-temperature stage of calcination, which makes the material excessively carbonized, resulting in too low activity of the obtained catalyst.

[0076] It can be known from the examples 1-5 that when the amounts of urea, dicyandiamide, pore former, silkworm sand and cobalt source meet the mass ratio of urea, dicyandiamide, pore former and silkworm sand (0.4-0.75):(1-1.9):(0.1-0.45):1 and the ratio of the mass of silkworm sand to the amount of substance of cobalt element in cobalt source (1g:(0.001-0.0019) mol, especially the mass ratio of urea, dicyandiamide, pore former and silkworm sand (0.47-0.58):(1.1-1.5):(0.355-0.395):1 and the ratio of the mass of silkworm sand to the amount of substance of cobalt element in cobalt source (1g:(0.0014-0.0015) mol, and especially the mass ratio of urea, dicyandiamide, pore former and silkworm sand 0.5:1.25:0.375:1 and the ratio of the mass of silkworm sand to the amount of substance of cobalt element in cobalt source (1g:0.00145 mol), the catalytic activity and cyclic stability of the synthesized catalyst are better.

[0077] From the comparison of Examples 1, 8-11, it can be seen that the low-temperature calcination stage is divided into two stages, specifically as follows: calcining the solid particles at 250-400°C for 1-3 h, and then calcining at 450-600°C for 1-3 h, which is more conducive to the polycondensation of urea and dicyandiamide, makes the network structure more complete, and the electronic structure more superior, thereby making the catalytic activity of the catalyst more superior.

[0078] Application Experiment 2 0.03 g of the catalyst sample prepared in Example 1 was put into 50 mL of a pollutant solution with a concentration of 10 mg / L, and the degradation reaction was started under constant temperature of 35°C and continuous magnetic stirring at a stirring speed of 35 rpm. Samples were taken at different time points and the concentration of pollutants therein was detected.

[0079] When the pollutant was CIP, BPA or DP, and the pollutant solution was prepared from the pollutant and ultrapure water (UPW), the test results were as follows: Figure 4 and Figure 5 , wherein the pollutant degradation rate = (initial concentration of the pollutant in the solution - concentration of the pollutant in the solution after reaction) / initial concentration of the pollutant in the solution x 100%, and the TOC (total organic carbon) removal rate = (initial concentration of TOC in the solution - concentration of TOC in the solution after reaction) / initial concentration of TOC in the solution x 100%.

[0080] When the pollutant was CIP, and the pollutant solution was prepared from one of ultrapure water (UPW), municipal wastewater (MW) and drinking water source water (RDW) and the pollutant, the test results were as follows: Figure 6 .

[0081] From Figure 4 and Figure 5 , it can be seen that, without external energy assistance, Co SA -N2O2-GL can completely remove CIP, BPA and DP by 100% through the self-purification process within 120 minutes, and the corresponding TOC removal rates are as high as 74.0%, 76.1 and 55.8%, respectively. It is worth noting that when Co SA -N2O2-GL is used to treat the pollutant solution prepared from municipal wastewater (MW) or drinking water source water (RDW), CIP can be removed by 100% within 30 minutes Figure 6 , which shows that DOC can greatly promote the degradation of BPA, which is completely different from the usual oxidation process.

[0082] Finally, it should be noted that the above examples are only used to illustrate the technical solutions herein and not to limit the scope of protection herein, and although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions herein can be modified or equivalently replaced without departing from the essence and scope of the technical solutions herein.

Claims

1. A method for preparing a biobased porous cobalt single-atom catalyst, characterized in that, The method comprises the following steps: mixing and dispersing urea, dicyandiamide, pore-forming agent and silkworm excrement in a solvent to obtain dispersion A; mixing and dispersing a cobalt source in the dispersion A to obtain dispersion B; drying the dispersion B to obtain solid particles; firing the solid particles at 250-600℃ for 2-6h, and then firing at 650-900℃ for 1-3h to obtain a solid product, i.e. a bio-based porous cobalt monatomic catalyst; the pore-forming agent is at least one of bicarbonate and carbonate.

2. The method of producing a bio-based porous cobalt single-atom catalyst according to claim 1, wherein, The mass ratio of the urea, the dicyandiamide, the pore-forming agent and the silkworm excrement is (0.4-0.75):(1-1.9):(0.1-0.45):1, and the mass ratio of the silkworm excrement to the cobalt element in the cobalt source is 1g:(0.001-0.0019)mol.

3. The method of producing a biobased porous cobalt single-atom catalyst according to claim 2, wherein, The mass ratio of the urea, the dicyandiamide, the pore-forming agent and the silkworm excrement is (0.47-0.58):(1.1-1.5):(0.355-0.395):1, and the mass ratio of the silkworm excrement to the cobalt element in the cobalt source is 1g:(0.0014-0.0015)mol.

4. The method of producing a bio-based porous cobalt single-atom catalyst according to claim 3, wherein, The mass ratio of the urea, the dicyandiamide, the pore-forming agent and the silkworm excrement is 0.5:1.25:0.375:1, and the mass ratio of the silkworm excrement to the cobalt element in the cobalt source is 1g:0.00145mol.

5. The method of producing a biobased porous cobalt single-atom catalyst according to claim 1, wherein, The specific steps of firing the solid particles at 250-600℃ for 2-6h are as follows: firing the solid particles at 250-400℃ for 1-3h, and then firing at 450-600℃ for 1-3h.

6. The method of producing a biobased porous cobalt single-atom catalyst according to claim 1, wherein, The pore-forming agent comprises at least one of sodium bicarbonate, ammonium bicarbonate, sodium carbonate, potassium bicarbonate and potassium carbonate; and / or, The cobalt source is a water-soluble cobalt source, comprising at least one of cobalt chloride hexahydrate, cobaltous sulfate, cobalt acetate, cobalt sulfate heptahydrate, cobalt acetate tetrahydrate and cobalt nitrate hexahydrate.

7. The method of producing a biobased porous cobalt single-atom catalyst according to claim 1, wherein, At least one of the following conditions is met: S1. When the solid particles are fired, the heating rate is controlled in the range of 2-20℃ / min; S2. When the solid particles are fired, the firing is carried out in a protective gas atmosphere, and the protective gas comprises at least one of nitrogen and inert gas; S3. The ratio of the dispersion A is (urea+dicyandiamide+pore-forming agent+silkworm excrement): solvent = 1g:(2-6)mL; S4. The solvent in the dispersion A comprises water; S5. The solid product is further cleaned and dried to obtain a bio-based porous cobalt monatomic catalyst.

8. The bio-based porous cobalt monatomic catalyst prepared by the method of any one of claims 1-7.

9. The bio-based porous cobalt monatomic catalyst of claim 8 is used for degrading organic pollutants in water.

10. Use according to claim 9, wherein The organic pollutants comprise at least one of quinolones, phenols and ethanolamines.

11. Use according to claim 10, wherein the compound is ###0002### The quinolones comprise at least one of ciprofloxacin, norfloxacin and tetracycline; and / or, The phenols comprise at least one of bisphenol A, bisphenol B, bisphenol S, bisphenol F and bisphenol AF; and / or, The antihistamines include at least one of diphenhydramine, cetirizine. The antihistamines include at least one of diphenhydramine, cetirizine.

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