Controllable preparation method of co sa-ldh single-atom water treatment catalyst with high co atomic loading

Abstract

The controllable preparation method of the CoSA-LDH single-atom water treatment catalyst with high Co atomic loading of the application relates to a water treatment catalyst preparation method. The application takes layered double hydroxide (LDH) as the carrier of SACs, loads single-atom Co on the LDH to prepare Co SA -LDH single-atom catalyst. The LDH has good ion exchange characteristics and structural stability. Moreover, the LDH preparation process is simple, has high activity, large specific surface area and low toxicity. Through precise regulation of the oxygen vacancy content and specific morphology on the surface, more loading sites are provided for single Co atoms, thereby improving the loading amount and stability of single Co atoms, enhancing the catalytic activity, and realizing the controllable preparation of Co SA -LDH single-atom catalyst with high Co atomic loading. The catalyst shows good catalytic activity and stability for activating peroxymonosulfate (PMS) to degrade dyes, antibiotics and phenolic pollutants. The catalyst preparation method is simple, has high catalytic efficiency, small pollution and low cost, and has potential practical application value.

Description

TECHNICAL FIELD

[0001] The present application relates to a water treatment catalyst preparation method, in particular to a controllable preparation method of CoSA-LDH single-atom water treatment catalyst with high Co atomic loading. BACKGROUND

[0002] With the rapid development of China's economy, a large amount of toxic and harmful substances such as antibiotics, phenols, dyes, etc. are discharged into the water environment, which causes serious pollution to the water environment system. In addition, these pollutants may directly or indirectly enter the organisms and human bodies after a series of physical and chemical changes, causing serious threat to human health. Therefore, developing an efficient water treatment technology is a key problem that needs to be solved at present. Advanced oxidation technology (AOPs) is a kind of water treatment technology that can efficiently remove refractory organic pollutants in water, and has attracted widespread attention in recent years. Advanced oxidation technology includes ozone catalytic oxidation method, photocatalytic oxidation method, Fenton method, persulfate oxidation method. Compared with other water treatment technologies, the persulfate oxidation method is green, non-toxic, has mild reaction conditions, fast degradation rate and low operation cost, and has become a research hotspot at present. Persulfate oxidation method refers to the activation of persulfate (PS) by using various catalysts to break the O-O bond to produce active oxygen species such as sulfate radicals (SO4· - ), hydroxyl radicals (·OH), etc. These active oxygen species attack organic pollutants, resulting in their decomposition. However, the traditional catalysts still have problems such as limited catalytic effect, high metal ion leaching, poor catalyst stability, etc. Single-atom catalysts (SACs) have the advantages of high catalytic efficiency, easy recovery, high atom utilization rate, wide pH application range, etc., and have excellent application prospect in the field of water treatment.

[0003] However, SACs still face some problems to be solved. For example, the current reported carriers (carbon materials, carbon nitride, metal-organic frameworks, covalent organic frameworks, etc.) can provide few loading sites for SACs, resulting in low SACs loading and poor catalytic activity; the surface energy of SACs is high, which is easy to aggregate into clusters or nanoparticles, resulting in poor stability. Therefore, selecting a suitable carrier and designing a controllable synthesis method of SACs is crucial for stabilizing single metal atoms and increasing their loading. 2+ / M 3+The presence of metal ions and interlayer anions leads to great nanostructure variability, can provide single metal atoms with rich anchoring sites, thereby improving the loading capacity and stability of SACs. Moreover, LDH has simple preparation process, high activity, large specific surface area and low toxicity. By precisely regulating the oxygen vacancy content and specific morphology on its surface, more loading sites are provided for single metal atoms, thereby improving their loading capacity and stability, enhancing the catalytic activity, realizing high Co atom loading Co SA -LDH single atom catalysts. SUMMARY

[0004] The purpose of the present application is to provide a controllable preparation method of CoSA-LDH single atom water treatment catalyst with high Co atom loading, which is a synthesis method for controllable preparation of SACs with high metal atom loading, and has better catalytic activity, achieving the purpose of efficiently removing refractory organic pollutants in water.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] The controllable preparation method of CoSA-LDH single atom water treatment catalyst with high Co atom loading uses LDH as the carrier of single atom Co, and by adjusting the dosage of hexamethylenetetramine and the ratio of water and ethanol in the solvent during the preparation of LDH, LDH with specific oxygen vacancy content and specific morphology can be controllably synthesized. The specific preparation process includes the following steps:

[0007] First, LDH is prepared by a hydrothermal method; that is, 0.1-5.0 g of soluble metal salt and 0.5-5.0 g of hexamethylenetetramine are dissolved in 10-300 mL of ethanol / water and mixed uniformly, and the mixed solution is placed in a polytetrafluoroethylene high-pressure reaction kettle for hydrothermal reaction, and finally washed and dried to obtain LDH. Then, single atom Co is loaded on LDH by a solvothermal method; that is, 0.1-5.0 g of the carrier is dispersed in deionized water, then 0.1-5.0 g of soluble cobalt salt is added and stirred for 1-5 h; then 0.1-5.0 g of reducing agent is added, and the solution is heated and stirred in a water bath, and finally washed and dried to obtain Co SA -LDH single atom catalyst.

[0008] The controllable preparation method of the high-Co-atom-loading CoSA-LDH single-atom water treatment catalyst, the preparation of the single-atom catalyst, the LDH is prepared by a hydrothermal method with soluble metal salt and hexamethylenetetramine as precursors, the hydrothermal temperature is 100-500 DEG C, and the hydrothermal time is 1-24 h; after the single atom Co is doped, the Co SA -LDH is prepared by a solvothermal method, and the water bath heating temperature is 40-100 DEG C, and the water bath heating time is 1-10 h.

[0009] The controllable preparation method of the high-Co-atom-loading CoSA-LDH single-atom water treatment catalyst, the catalyst removes organic pollutants in water, takes potassium monopersulfate (PMS) as an oxidant, takes Co SA -LDH as the catalyst, takes dyes, antibiotics and phenols as target pollutants, and establishes a water treatment application system.

[0010] The present application has the following beneficial effects:

[0011] The present application adopts a solvothermal method to prepare Co SA -LDH with high Co atom loading, and the successful synthesis of the catalyst realizes high Co atom loading of Co SA -LDH catalyst. The increase of the content of oxygen vacancies on the LDH surface is beneficial to fixing single-atom Co, improving the loading (theoretically more than 10 wt.%) and stability of single-atom Co, reducing the aggregation of Co atoms, and improving the catalytic activity of the single-atom catalyst. The catalyst not only has high catalytic efficiency, but also is easy to recover, has less metal ion leaching, and has excellent catalytic activity and stability. Under certain conditions, the Co SA -LDH system can remove 100% of dyes and antibiotics with a concentration of 10-100 mg / L in 5 min; and for phenolic pollutants with a concentration of 10-50 mg / L, the catalyst can remove more than 90% in 5 min. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 Co SA -LDH single-atom catalyst.

[0013] Figure 2 Co SA -LDH on rhodamine B (RhB), tetracycline (TC), methylene blue (MB) and bisphenol A (BPA).

[0014] Figure 3 Co SA -LDH stability effect diagram. EMBODIMENT

[0015] The application will be further described in connection with the following examples, and the application is not limited to the following examples.

[0016] The application selects LDH as a carrier of monatomic Co, and the content regulation method of oxygen vacancies in LDH and the loading method of monatomic Co are as follows:

[0017] The soluble metal salt and hexamethylenetetramine are dissolved in an ethanol / water solution, and then put into a polytetrafluoroethylene high-pressure reaction kettle for hydrothermal reaction.

[0018] The mass of the soluble metal salt is 0.1-5.0 g, the mass of hexamethylenetetramine is 0.5-5.0 g, the ethanol concentration is 69-99%, and the volume of the ethanol / water solution is 10-100 mL.

[0019] The hydrothermal temperature is 100-500 ℃, and the hydrothermal time is 1-24 h.

[0020] The content of oxygen vacancies in LDH is regulated by adjusting the dosage of hexamethylenetetramine.

[0021] The morphology of LDH is regulated by adjusting the ratio of water and ethanol in the solvent.

[0022] Monatomic Co is loaded on LDH by using a solvothermal method.

[0023] The Co element in the soluble cobalt salt is reduced to the form of monatomic Co by adding a reducing agent.

[0024] The soluble cobalt salt is mixed with LDH and deionized water is added to disperse them uniformly.

[0025] The mass of the soluble cobalt salt and LDH is 0.1-5.0 g, and the volume of the deionized water is 10-100 mL.

[0026] The reducing agent is added and mixed uniformly.

[0027] The mass of the reducing agent is 0.1-5.0 g.

[0028] The mixed solution is put into a water bath kettle for heating and stirring.

[0029] The water bath heating temperature is 40-100 ℃, and the water bath heating time is 1-10 h.

[0030] The obtained solid is put into a centrifuge and washed with ethanol and deionized water.

[0031] The rotation speed of the centrifuge is 5000-8000 r / min, and the ethanol concentration is 69-99%.

[0032] The obtained solid is put into a vacuum drying oven for drying.

[0033] The temperature of the vacuum drying oven is 20-90 °C, and the drying time is 12-24 h. Example 1

[0034] 0.5-5.0 g of hexamethylenetetramine is mixed with a soluble metal salt and dissolved with a solvent with an ethanol / water ratio of 1:1, and the solution is placed in a polytetrafluoroethylene high-pressure reaction kettle for hydrothermal reaction. Example 2

[0035] 0.5-5.0 g of hexamethylenetetramine is mixed with a soluble metal salt and dissolved with a solvent with an ethanol / water ratio of 0:1, and the solution is placed in a polytetrafluoroethylene high-pressure reaction kettle for hydrothermal reaction. Example 3

[0036] 0.5-5.0 g of hexamethylenetetramine is mixed with a soluble metal salt and dissolved with a solvent with an ethanol / water ratio of 1:0, and the solution is placed in a polytetrafluoroethylene high-pressure reaction kettle for hydrothermal reaction. Example 4

[0037] 0.4-0.5 g of hexamethylenetetramine is mixed with a soluble metal salt and dissolved with a solvent with an ethanol / water ratio of 1:0, and the solution is placed in a polytetrafluoroethylene high-pressure reaction kettle for hydrothermal reaction. Example 5

[0038] 0.9-1.0 g of hexamethylenetetramine is mixed with a soluble metal salt and dissolved with a solvent with an ethanol / water ratio of 1:0, and the solution is placed in a polytetrafluoroethylene high-pressure reaction kettle for hydrothermal reaction. Example 6

[0039] 1.4-1.5 g of hexamethylenetetramine is mixed with a soluble metal salt and dissolved with a solvent with an ethanol / water ratio of 1:0, and the solution is placed in a polytetrafluoroethylene high-pressure reaction kettle for hydrothermal reaction. Example 7

[0040] 1.9-2.0 g of hexamethylenetetramine is mixed with a soluble metal salt and dissolved with a solvent with an ethanol / water ratio of 1:0, and the solution is placed in a polytetrafluoroethylene high-pressure reaction kettle for hydrothermal reaction. Example 8

[0041] 0.1-5.0 g of LDH, 0.1-0.4 g of a soluble cobalt salt is dispersed in deionized water, 0.1-5.0 g of a reducing agent is added, and the water bath is heated in a water bath. Example 9

[0042] Disperse 0.1-5.0 g LDH and 0.5-0.8 g soluble cobalt salt in deionized water, add 0.1-5.0 g reducing agent, and heat in a water bath.

[0043] Example 10

[0044] 0.1-5.0 g LDH and 0.9-1.2 g soluble cobalt salt are dispersed in deionized water, and 0.1-5.0 g reducing agent is added. The mixture is then heated in a water bath.

[0045] Example 11

[0046] 0.02 g Co SA -LDH was added to 100 mL of a 20 mg / L solution of TC, RhB, or MB, followed by 10–100 μL of 0.5 mol / L PMS to initiate the catalytic reaction. After the addition of PMS, 100% of TC, RhB, or MB was removed within 5 min.

[0047] Example 12

[0048] 0.02 g Co SA -LDH was added to 100 mL of a 20 mg / L BPA solution, followed by 10-100 μL of 0.5 mol / L PMS to initiate the catalytic reaction. After the addition of PMS, over 90% of the BPA was removed within 5 minutes.

Claims

1. Use of a CoSA-LDH monatomic water treatment catalyst with high Co atomic loading for removing organic pollutants in water, characterized in that, With potassium hydrogen peroxymonosulfate as an oxidant, with CoSA-LDH as a catalyst, with dyes, antibiotics, and phenols as target pollutants, a water treatment application system is established, The controllable preparation method of the catalyst uses LDH as a single-atom Co carrier, and by adjusting the adding amount of hexamethylene tetramine in the LDH preparation process and the ratio of water and ethanol in the solvent, LDH with specific oxygen vacancy content and specific morphology can be controllably synthesized; the controllable preparation method of the CoSA-LDH single-atom water treatment catalyst specifically includes the following preparation process: First, LDH is prepared by a hydrothermal method; that is, 0.1-5.0 g of soluble metal salt and 0.5-5.0 g of hexamethylene tetramine are dissolved in 10-300 mL of ethanol / water and uniformly mixed, the ratio of the ethanol / water is 1:1, 0:1 or 1:0, the mixed solution is placed in a polytetrafluoroethylene high-pressure reaction kettle for hydrothermal reaction, and finally, after washing and drying, LDH is obtained; then, single-atom Co is loaded on the LDH by a solvothermal method; that is, 0.1-5.0 g of the carrier is dispersed in deionized water, then 0.1-5.0 g of soluble cobalt salt is added and stirred for 1-5 h; then, 0.1-5.0 g of a reducing agent is added, and the solution is placed in a water bath for heating and stirring, and finally, after washing and drying, the CoSA-LDH single-atom catalyst is obtained; In the process of preparing LDH by the hydrothermal method, the hydrothermal temperature is 100-500 DEG C, and the hydrothermal time is 1-24 h; in the process of loading single-atom Co on the LDH by the solvothermal method, the water bath heating temperature is 40-100 DEG C, and the water bath heating time is 1-10 h.

Images