CN113786849A

CN113786849A - FeOCl/GQDs composite transition metal catalyst, and preparation method and application thereof

Info

Publication number: CN113786849A
Application number: CN202111147699.0A
Authority: CN
Inventors: 郑红艾; 孙鑫; 蒋双燕; 朱美琳; 周垚; 王德睿; 范棪堃; 胡丽丽; 黄菁; 于静涵; 段剑平; 冒芮旻
Original assignee: Shanghai University of Electric Power
Current assignee: Shengdakang Jiangsu Power Technology Co ltd
Priority date: 2021-09-29
Filing date: 2021-09-29
Publication date: 2021-12-14
Anticipated expiration: 2041-09-29
Also published as: CN113786849B

Abstract

The invention relates to an iron oxychloride graphene quantum dot composite transition metal catalyst, and a preparation method and application thereof, wherein the preparation method specifically comprises the following steps: 1) adding urea and citric acid into water for dissolving, then carrying out hydrothermal reaction, cooling after the reaction is finished, and then sequentially carrying out dialysis and drying to obtain GQDs; 2) and (3) uniformly mixing iron salt and GQDs, sintering, cooling and taking out to obtain the oxyferric chloride graphene quantum dot composite transition metal catalyst. Compared with the prior art, the composite catalyst prepared by the invention has strong catalytic capability, high degradation rate and simple preparation, and can catalyze PMS to oxidize and remove various toxic and harmful refractory organic pollutants including dyes, medicines and endocrine disruptors.

Description

FeOCl/GQDs composite transition metal catalyst, and preparation method and application thereof

Technical Field

The invention relates to the technical field of inorganic catalyst preparation and advanced oxidation, in particular to an iron oxychloride graphene quantum dot composite transition metal catalyst and a preparation method and application thereof.

Background

During human activities, a large amount of wastewater containing organic pollutants is generated, and thus the global water pollution problem has attracted much attention.

Advanced oxidation technologies (SR-AOPs) based on sulfate radicals are a new type of technology developed in recent years for treating refractory organic pollutants, and the technology is widely proved to be capable of effectively removing the organic pollutants in water by activating PMS (monosulfate) or PS (persulfate) to generate sulfate radicals and hydroxyl radicals in the oxidation process. Compared with hydroxyl radicals, the sulfate radicals generated by SR-AOPs have wider pH adaptation range, longer half-life and higher oxidation-reduction potential (HO, E)₀＝2.8V；SO₄ ^2-·，E₀2.5-3.1V). Activation of PMS can generally be achieved using UV, heat, ultrasound and transition metal ions,among these activation methods, transition metals have been considered as effective and feasible activators due to their advantages of low cost, simple operation, etc. A plurality of previous researches show that the cobalt-based material has high PMS (PMS) activation efficiency, but leached cobalt ions have carcinogenicity. Iron ion is also an environmentally friendly and inexpensive activator and has been used to activate PMS, however, Fe³⁺Reduction to Fe²⁺The process of (a) is very slow, limits the overall reaction rate of the SR-AOPs system, and always requires the addition of an excessive amount of iron salt, resulting in increased costs. Therefore, an accelerated Fe was devised³⁺/Fe²⁺The recycled catalyst becomes one of the main solutions.

Iron oxychloride (FeOCl) has the advantages of high chemical stability, large theoretical energy, weak inter-layer van der waals interaction, and the like, and thus has attracted much attention in the fields of electrode materials, supercapacitors, catalysis, and the like. Since FeOCl has a special oxygen bridge structure, after appropriate modification, it transfers charge between the inserted compound and its inorganic matrix, thereby changing the chemical state of Fe (Fe) in FeOCl³⁺→Fe²⁺). About 25% Fe³⁺Can be reduced to Fe in situ²⁺Reaction proceeds but Fe in FeOCl²⁺Regeneration is still insufficient for its practical application. Thus, Fe is accelerated³⁺The reduction of (b) is very important to improve the catalytic activity.

Disclosure of Invention

The invention aims to provide an iron oxychloride graphene quantum dot composite transition metal catalyst, a preparation method and an application thereof, and solves the problems of low catalytic efficiency and large dosage in the existing transition metal catalyst.

The purpose of the invention is realized by the following technical scheme:

the preparation method of the oxyferric chloride graphene quantum dot composite transition metal catalyst specifically comprises the following steps:

1) adding urea and citric acid into water for dissolving, then carrying out hydrothermal reaction in a reaction kettle, cooling after the reaction is finished, sequentially carrying out dialysis to remove redundant ions, and finally drying to obtain GQDs (graphene quantum dots), wherein the Graphene Quantum Dots (GQDs) are new members of a carbon family, and are combined with the excellent characteristics of quantum dots and graphene, and have unique characteristics (such as high electron transfer capacity, large surface area, good chemical stability and good biocompatibility), compared with a method for preparing graphene quantum dots by electrochemical stripping and ultrasonic stripping, the hydrothermal reaction method adopted in the step is simple and efficient;

2) and uniformly mixing iron salt and GQDs, sintering, cooling, and taking out to obtain the FeOCl/GQDs composite transition metal catalyst.

In the step 1), the hydrothermal temperature is 150-200 ℃, preferably 180 ℃, and the hydrothermal time is 3-5 h, preferably 4 h.

In the step 1), cooling to room temperature for dialysis, wherein the dialysis is carried out for 22-26 h, and water is replaced every 11-13 h.

Further, the dialysis was performed for 24 hours with water change every 12 hours.

In the step 1), the drying temperature is 70-90 ℃, preferably 80 ℃, and the drying time is 18-24 h.

In the step 1), the mass ratio of the urea to the citric acid is 1: 1.

In the step 1), the specification of the dialysis bag is MD44, and the molecular weight is 1000.

In the step 2), FeCl is adopted as the ferric salt₃·6H₂O。

In step 2), the FeCl₃·6H₂The mass ratio of O to GQDs is 2-40: 1, preferably 5: 1.

In the step 2), the sintering temperature is 230-270 ℃, the preferred sintering temperature is 250 ℃, the sintering time is 1.5-2.5 h, the preferred sintering time is 2h, and the temperature rising rate is 10 ℃ min^-1。

In the step 2), grinding the oxyferric chloride graphene quantum dot composite transition metal catalyst for later use.

According to the oxygroup ferric chloride graphene quantum dot composite transition metal catalyst prepared by the preparation method, the prepared oxygroup ferric chloride graphene quantum dot composite transition metal catalyst is similar to oxygroup ferric chloride and is of a sheet structure, the appearance of the oxygroup ferric chloride graphene quantum dot composite transition metal catalyst is not changed after the oxygroup ferric chloride graphene quantum dot composite transition metal catalyst is compounded with graphene quantum dots, a large specific surface level is still reserved, and catalytic reaction is facilitated.

The application of the oxyferric chloride graphene quantum dot composite transition metal catalyst in catalyzing degradation of organic pollutants in water by PMS specifically comprises the following steps: the method comprises the steps of adding the iron oxychloride graphene quantum dot composite transition metal catalyst and the PMS into water to be treated containing organic pollutants together to form a treatment system for treatment.

Specifically, the method comprises the following steps:

a) putting a certain volume of organic pollutant solution with certain concentration into a beaker, and adjusting the pH, the anion concentration and the humic acid concentration of the solution to the required concentrations before adding the catalyst;

b) adding the composite transition metal catalyst prepared by the invention into a beaker, adjusting the concentration of the composite transition metal catalyst, and fully stirring to ensure that the adsorption and the resolution are balanced;

c) adding an oxidant PMS into the beaker, and adjusting the concentration of the oxidant;

d) fully mixing and stirring until the organic pollutants are completely degraded.

In the treatment system, the concentration of the iron oxychloride graphene quantum dot composite transition metal catalyst is 0.1-0.5 g/L, the concentration of PMS is 0.1-0.5 mM, and the pH value is 3-11, preferably 3.0-9.35.

Stirring is carried out during the treatment process, and stirring reaction is carried out for 30 min.

The water to be treated also contains one or more of chloride ions, bicarbonate ions, dihydrogen phosphate ions or humic acid.

In the water to be treated, the concentration of the chloride ions is 0-100mM, and the influence of the chloride ions on the degradation effect of organic pollutants is small, so that the water to be treated can contain the chloride ions, and the content of the chloride ions is not limited.

The concentration of bicarbonate ion in the water to be treated is 0-10mM, preferably 0-2 mM. The higher the concentration of bicarbonate ions, the less effective the degradation of organic contaminants, so the concentration of bicarbonate ions is as low as possible during processing.

The concentration of dihydrogen phosphate ions in the water to be treated is 0-50mM, preferably 0-10mM, and more preferably 0-2 mM. The higher the concentration of the dihydrogen phosphate ions, the less the effect of degrading the organic contaminants, so the concentration of the dihydrogen phosphate ions is as low as possible.

In the water to be treated, the concentration of humic acid is 0-50mg/L, and the influence of humic acid on the degradation effect of organic pollutants is small, so that the water to be treated can contain humic acid, and the content of humic acid is not limited.

The organic pollutant comprises one or more of dye, endocrine disrupter, medicine or pesticide, such as rhodamine B, ATZ, BPA, OPP, Rifampin.

Compared with the prior art, the invention has the following beneficial effects:

the invention adopts a simple method to prepare a novel catalyst FeOCl/GQDs, Fe for the first time²⁺There is a gain effect for SR-AOPs, although there is about 25% Fe in FeOCl³⁺Can be reduced to Fe in situ²⁺Reaction is carried out but Fe²⁺Regeneration is still insufficient for practical use, and therefore, Fe is accelerated³⁺The reduction of (A) is very important for improving the catalytic activity, but the invention adopts FeOCl to be compounded with GQDs, and utilizes the high electron transfer capability of the GQDs to accelerate Fe³⁺Reduction to Fe²⁺And the PMS and the catalyst form a novel advanced oxidation technology system to efficiently degrade organic pollutants, synergize and improve the pollutant removal rate. The invention takes rhodamine B (RhB), bisphenol A (BPA), o-phenylphenol (OPP), Rifampicin (RIF) and Atrazine (ATZ) as catalytic degradation model pollutants to carry out degradation experiments, and the experimental results prove that the FeOCl/GQDs catalyst can efficiently and quickly degrade waste waterCompared with the traditional Fenton technology, the method can improve the degradation efficiency of the organic pollutants by a large extent, can also better degrade the organic pollutants in a wide pH range and a high salt concentration, and has a wider application range. The oxyferric chloride graphene quantum dot composite transition metal catalyst can provide theoretical reference for developing high-efficiency and promising advanced oxidation technology, and has good practical application prospect.

Drawings

Fig. 1 is an XRD crystal structure diagram of the iron oxychloride graphene quantum dot composite transition metal catalyst prepared in example 1;

FIG. 2 is an SEM topography of the FeOOH graphene quantum dot composite transition metal catalyst prepared in example 1;

fig. 3 is an XPS survey spectrum of the iron oxychloride graphene quantum dot composite transition metal catalyst prepared in example 1;

fig. 4 is a graph of the degradation effect of the iron oxychloride graphene quantum dot composite transition metal catalyst with different ratios and the iron oxychloride catalyzed PMS prepared in example 1 for degrading rhodamine B;

FIG. 5 is a diagram of the degradation effect of rhodamine B in different systems;

fig. 6 is a graph of the degradation effect of the iron oxychloride graphene quantum dot composite transition metal catalyst prepared in example 1 on the degradation of various organic pollutants by PMS under different concentrations;

fig. 7 is a graph showing the degradation effect of the oxyferric chloride graphene quantum dot composite transition metal catalyst prepared in example 1 on the degradation of rhodamine B under different PMS concentrations;

fig. 8 is a graph of the degradation effect of the iron oxychloride graphene quantum dot composite transition metal catalyst prepared in example 1 in catalyzing PMS to degrade rhodamine B at different concentrations;

fig. 9 is a graph of the degradation effect of the iron oxychloride graphene quantum dot composite transition metal catalyst prepared in example 1 on the degradation of rhodamine B by PMS at different phs;

fig. 10 is a graph of the degradation effect of the iron oxychloride graphene quantum dot composite transition metal catalyst prepared in example 1 on the degradation of rhodamine B by PMS under different chloride ion concentrations;

fig. 11 is a graph of the degradation effect of the iron oxychloride graphene quantum dot composite transition metal catalyst prepared in example 1 in catalyzing PMS to degrade rhodamine B at different bicarbonate concentrations;

fig. 12 is a graph of the degradation effect of the iron oxychloride graphene quantum dot composite transition metal catalyst prepared in example 1 in catalyzing PMS to degrade rhodamine B at different concentrations of dihydrogen phosphate;

fig. 13 is a graph of the degradation effect of the iron oxychloride graphene quantum dot composite transition metal catalyst prepared in example 1 on the degradation of rhodamine B by PMS under different humic acid concentrations;

fig. 14 is a graph of the degradation effect of the iron oxychloride graphene quantum dot composite transition metal catalyst prepared in example 1 in catalyzing PMS to degrade different pollutants.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The reagents in this example are all commercially available products.

1) adding urea and citric acid into water for dissolving, then carrying out hydrothermal reaction in a reaction kettle, cooling after the reaction is finished, sequentially dialyzing to remove redundant ions, and finally drying to obtain GQDs, wherein the hydrothermal temperature is 150-200 ℃, the hydrothermal time is 3-5 h, cooling to room temperature for dialysis, dialyzing for 22-26 h, changing water every 11-13 h, the drying temperature is 70-90 ℃, and the drying time is 18-24 h;

2) and uniformly mixing iron salt and GQDs, sintering, cooling, and taking out to obtain the oxyferric chloride graphene quantum dot composite transition metal catalyst, which is abbreviated as FeOCl/GQDs, and grinding for later use, wherein the sintering temperature is 230-270 ℃, and the sintering time is 1.5-2.5 h.

Example 1

1. Preparation of composite transition metal catalyst

Adding 2mg of urea and 2mg of citric acid into water for dissolving, transferring the solution into a reaction kettle, carrying out hydrothermal treatment at 180 ℃ for 4 hours, cooling the solution to room temperature, dialyzing the solution for 24 hours by using a dialysis bag with the specification of MD44 and the molecular weight of 1000, changing water every 12 hours, and transferring the solution into an oven with the temperature of 80 ℃ for drying for 24 hours to obtain GQDs;

as shown in Table 1, 3g of FeCl was taken₃·6H₂Mixing O and 0-1.5 g GQDs (0 g, 1.5g, 0.6g, 0.3g, 0.15g, 0.075g), transferring into crucible, and heating in muffle furnace at 10 deg.C for min^-1The temperature rise rate is increased to 250 ℃, the mixture is sintered for 2 hours at the temperature, and after cooling, the iron oxychloride catalyst and five iron oxychloride graphene quantum dot composite transition metal catalysts which are in different proportions and are in a block shape are obtained, wherein the iron oxychloride catalyst and the five iron oxychloride graphene quantum dot composite transition metal catalysts are respectively named as FeOCl, FeOCl/GQDs/2, FeOCl/GQDs/5, FeOCl/GQDs/10, FeOCl/GQDs/20 and FeOCl/GQDs/40, and after grinding for standby application, the XRD crystal structure diagrams of FeOCl, GQDs and FeOCl/GQDs/5 are all shown in figure 1, and it can be seen that for the GQDs, the diffraction peaks at 26.5 degrees are well corresponding to (002) of graphite, and in the XRD diagrams of FeOCl and FeOCl/GQDs, the diffraction peaks at 11.1 degrees, 26.1 degrees and 35.5 degrees are respectively assigned to (010), (110) and (CPDS (J1005) crystal faces of FeOCl (J1005 No. 24-1005). The SEM topography of FeOCl/GQDs/5 is shown in FIG. 2 (the scale bar is 200nm), and the prepared composite catalyst is seen to be flaky. The XPS survey of FeOCl/GQDs/5 is shown in FIG. 3, and it can be seen that Fe, O, Cl and C are present in FeOCl/GQDs sample, and a small amount of N is due to the addition of urea when preparing GQDs sample.

TABLE 1

2. Composite transition metal catalysts with different proportions for catalyzing PMS to degrade organic pollutants

Preparing 20mg/L rhodamine B solution, respectively placing six 100ml portions in a beaker, not adjusting pH, not adding anions and humic acid, labeling the beaker, respectivelyAdding the five composite transition metal catalysts of FeOCl, FeOCl/GQDs/2, FeOCl/GQDs/5, FeOCl/GQDs/10, FeOCl/GQDs/20 and FeOCl/GQDs/40 prepared in the embodiment into a beaker in sequence to ensure that the concentration of the catalyst is 0.3g/L, and fully stirring to ensure that the adsorption and resolution are balanced; adding an oxidant PMS into the beaker to enable the concentration of the oxidant to be 0.3 mM; fully mixing and stirring (the calculation formula of the degradation rate is 1-C/C₀C represents the concentration of organic contaminants at a given time, C₀Initial organic contaminant concentration, the same applies below), the degradation rate is shown in table 2, and the degradation rate is shown in fig. 4.

As can be seen, when FeOCl/GQDs/5 is adopted, the degradation rate of rhodamine B is the highest, so that the FeOCl/GQDs/5 is adopted as the catalyst with the optimal proportion in the subsequent embodiment for researching the influence of other factors on the degradation effect.

TABLE 2

Name of composite transition metal catalyst	Degradation rate of rhodamine B at 30min
		FeOCl	46.11％
FeOCl/GQDs/2	93.63％
		FeOCl/GQDs/5	97.86％
FeOCl/GQDs/10	96.86％
		FeOCl/GQDs/20	83.11％
FeOCl/GQDs/40	82.16％

3. The degradation effect of the composite transition metal catalyst for catalyzing PMS to degrade organic pollutants is compared with that of other systems

Preparing 20mg/L rhodamine B solution, placing 100ml of the rhodamine B solution in a beaker, not adjusting the pH value, not adding anions and humic acid, and then adding 30mg of FeOCl/GQDs/5 into the beaker (the time for carrying out a plurality of experiments in the embodiment 1 is earlier than that for researching the degradation effect of different quality catalysts on the rhodamine B, the adding amount of 30mg of the catalyst is selected based on literature research), so that the concentration of the catalyst is 0.3g/L, and fully stirring the solution to ensure that the adsorption and the resolution are balanced; adding oxidant PMS into the beaker to make the oxidant concentration 0.3mM (several experiments in example 1 are carried out for a time earlier than the experiments for exploring the degradation effect of different concentrations of PMS on degrading rhodamine B, and the addition amount of 0.3mMPMS is the amount selected based on literature research); fully mixing and stirring (the calculation formula of the degradation rate is 1-C/C₀C represents the concentration of organic contaminants at a given time, C₀Initial organic contaminant concentration, the same applies below), the degradation rate is shown in table 3, and the degradation rate is shown in fig. 5. As can be seen, when only an oxidant or a catalyst exists, the degradation rate is lower than 10%, the degradation rate of FeOCl + PMS is 46.11%, and the degradation rate of FeOCl/GQDs/5+ PMS is 97.86%, which shows that the composite transition metal catalyst has a good effect of catalyzing PMS to degrade organic pollutants.

TABLE 3

Example 2

1. Preparation of composite transition metal catalyst

The composite transition metal catalyst in this example was prepared in the same manner as in example 1.

2. Composite transition metal catalyst for catalyzing PMS to degrade organic pollutants

Preparing 20mg/L rhodamine B solution, placing five 100ml parts in a beaker, not adjusting the pH value, not adding anions and humic acid, then respectively adding 10mg, 20mg, 30mg, 40mg and 50mg of the composite transition metal catalyst prepared in the embodiment into the beaker, so that the concentrations of the composite transition metal catalyst are respectively 0.1g/L, 0.2g/L, 0.3g/L, 0.4g/L and 0.5g/L, and fully stirring to ensure that the adsorption and analysis are balanced; adding an oxidant PMS into the beaker to enable the concentration of the oxidant to be 0.2 mM; after the mixture is fully mixed and stirred, the degradation rate of the organic pollutants can reach above 90.30 percent, the degradation rate is shown in table 4, and the degradation rate is shown in fig. 6. When the catalyst concentration is 0.2g/L, the degradation rate reaches 98.63%, which is the best experimental group in the five experiments, so that the concentrations of the composite transition metal catalysts in examples 3-13 are all set to be 0.2 g/L.

TABLE 4

Concentration (g/L) of composite transition metal catalyst	0.1	0.2	0.3	0.4	0.5
						Degradation rate of rhodamine B at 30min	98.10％	98.63％	97.86％	95.55％	90.30％

Example 3

1. Preparation of composite transition metal catalyst

Preparing 20mg/L rhodamine B solution, placing five 100ml portions in a beaker, adding 20mg of the composite transition metal catalyst prepared in the embodiment into the beaker, enabling the concentration of the composite transition metal catalyst to be 0.2g/L, and fully stirring to enable adsorption and desorption to be balanced; adding oxidants PMS with different qualities into a beaker to ensure that the concentrations of the oxidants are 0.1mM, 0.2mM, 0.3mM, 0.4mM and 0.5mM respectively; the mixture was thoroughly mixed and stirred, and the degradation rate were as shown in Table 5 and FIG. 7, respectively. When the concentration of PMS is 0.1mM, the degradation rate is 76.14%; when the concentration of PMS is 0.5mM, the degradation rate is 98.50%; when the concentration of PMS is 0.2mM, the degradation rate reaches 98.63%, which is the best group of experiments in the five groups of experiments, so that the concentrations of the oxidants in examples 3-13 are all set to be 0.2 mM.

TABLE 5

Concentration of oxidizing agent (mM)	0.1	0.2	0.3	0.4	0.5
						Degradation rate of rhodamine B at 30min	76.14％	98.63％	98.35％	98.02％	98.50％

Example 4

1. Preparation of composite transition metal catalyst

Respectively preparing 10mg/L, 20mg/L, 50mg/L and 100mg/L rhodamine B solutions, respectively placing 100ml of the rhodamine B solutions in a beaker, adding 20mg of the composite transition metal catalyst prepared in the embodiment into the beaker to ensure that the concentration of the composite transition metal catalyst is 0.2g/L, and fully stirring to ensure that the adsorption and the desorption are balanced; adding an oxidant PMS into the beaker to enable the concentration of the oxidant to be 0.2 mM; the mixture was thoroughly mixed and stirred, the degradation rate was as shown in Table 6, and the degradation rate was as shown in FIG. 8. When the concentration of rhodamine B is 10mg/L, the degradation rate is 97.81 percent; when the concentration of rhodamine B is 20mg/L, the degradation rate is 98.63 percent; when the concentration of rhodamine B is 50mg/L, the degradation rate is 63.10 percent; when the concentration of rhodamine B is 100mg/L, the degradation rate is 9.82%. This result indicates that the concentration of the oxidizing agent and the concentration of the catalyst should be matched with the concentration of the degradation target, and that the amounts of the oxidizing agent and the catalyst should be increased in proportion to each other when the concentration of the degradation target is very high, so that the investigation experiments of other factors were conducted in each of examples 5 to 9 using a system in which the concentration of the catalyst was 0.2g/L, the concentration of the oxidizing agent was 0.2mM, and the concentration of rhodamine B was 20 mg/L.

TABLE 6

Concentration of rhodamine B solution (mg/L)	10	20	50	100
					Degradation rate of rhodamine B at 30min	97.81％	98.63％	62.97％	9.82％

Example 5

1. Preparation of composite transition metal catalyst

Preparing 20mg/L rhodamine B solution, placing five 100ml portions into a beaker, adjusting the pH value to 3.00, 5.02, 7.00, 9.35 and 11.00 respectively by using 0.1M sulfuric acid and 0.1M sodium hydroxide, adding 20mg of the composite transition metal catalyst prepared in the embodiment into the beaker, enabling the concentration of the composite transition metal catalyst to be 0.2g/L, and fully stirring to enable the adsorption and analysis to be balanced; adding an oxidant PMS into the beaker to enable the concentration of the oxidant to be 0.2 mM; the mixture was thoroughly mixed and stirred, the degradation rate was as shown in Table 7, and the degradation rate was as shown in FIG. 9. The degradation efficiency of rhodamine B can be kept above 97.20 percent within a wide pH range of 3.0 to 9.35; when the pH value of the solution exceeds 11, the degradation efficiency of rhodamine B is reduced to 84.00 percent. This result indicates that the pH adaptation range of the composite transition metal catalyst and the oxidation system composed of the composite transition metal catalyst is very wide, so that the pH is not specially adjusted in other research experiments.

TABLE 7

pH	3.00	5.02	7.00	9.35	11.00
						Degradation rate of rhodamine B at 30min	99.18％	96.74％	97.81％	97.91％	84.00％

Example 6

1. Preparation of composite transition metal catalyst

Preparing 20mg/L rhodamine B solution, putting six 100ml parts into a beaker, adding a sodium chloride solution with a certain concentration into the beaker to ensure that the chloride ion concentration is 0mM, 2mM, 5mM, 10mM, 50mM and 100mM in sequence, adding 20mg of the composite transition metal catalyst prepared in the embodiment into the beaker to ensure that the concentration of the composite transition metal catalyst is 0.2g/L, and fully stirring to ensure that the adsorption and analysis are balanced; adding an oxidant PMS into the beaker to enable the concentration of the oxidant to be 0.2 mM; the mixture was thoroughly mixed and stirred, the degradation rate was as shown in Table 8, and the degradation rate was as shown in FIG. 10. In the chloride ion concentration range of 0-100mM, the degradation efficiency of the prepared composite transition metal catalyst for catalyzing PMS to degrade rhodamine B is only slightly reduced, but the degradation efficiency is all above 97.30%, which indicates that the composite transition metal catalyst can be suitable for high chloride ion concentration. This result indicates that the composite transition metal catalyst of the present invention and the oxidation system having the composition have a very wide range of applicable chloride ion concentrations, and therefore, it is not necessary to specifically adjust the chloride ion concentration in other research experiments, and thus, it is not necessary to adjust the chloride ion concentration of the treatment object in advance in the actual application.

TABLE 8

Chloride ion concentration (mM)	0	2	5	10	50	100
							Degradation rate of rhodamine B at 30min	98.63％	98.91％	98.92％	97.61％	95.57％	95.18％

Example 7

1. Preparation of composite transition metal catalyst

Preparing 20mg/L rhodamine B solution, putting four 100ml parts into a beaker, adding a sodium bicarbonate solution with a certain concentration into the beaker to ensure that the concentration of bicarbonate ions is 0mM, 2mM, 5mM and 10mM in sequence, adding 20mg of the composite transition metal catalyst into the beaker to ensure that the concentration of the composite transition metal catalyst is 0.2g/L, and fully stirring to ensure that the adsorption and the resolution are balanced; adding an oxidant PMS into the beaker to enable the concentration of the oxidant to be 0.2 mM; the mixture was thoroughly mixed and stirred, and the degradation rate were as shown in Table 9 and FIG. 11, respectively. In the range of bicarbonate ion concentration of 0-10mM, the degradation efficiency of the prepared composite transition metal catalyst for catalyzing PMS to degrade rhodamine B is obviously reduced, and when the bicarbonate ion concentration is 10mM, the degradation efficiency is only 10.30%. This result indicates that the applicable range of the bicarbonate ion concentration of the composite transition metal catalyst and the oxidation system of the composition of the present invention is narrow, and thus the concentration of the bicarbonate ion in the object to be treated should be reduced as much as possible in order to enhance the degradation effect in practical use.

TABLE 9

Bicarbonate ion concentration (mM)	0	2	5	10
					Degradation rate of rhodamine B at 30min	98.63％	91.08％	30.16％	10.30％

Example 8

1. Preparation of composite transition metal catalyst

Preparing 20mg/L rhodamine B solution, placing five 100ml portions in a beaker, adding sodium dihydrogen phosphate solution with certain concentration into the beaker to ensure that the concentration of dihydrogen phosphate ions is 0mM, 2mM, 5mM, 10mM and 50mM in sequence, adding 20mg of the composite transition metal catalyst into the beaker to ensure that the concentration of the composite transition metal catalyst is 0.2g/L, and fully stirring to ensure that adsorption and desorption are balanced; adding an oxidant PMS into the beaker to enable the concentration of the oxidant to be 0.2 mM; the mixture was thoroughly mixed and stirred, the degradation rate was as shown in Table 10, and the degradation rate was as shown in FIG. 12. In the range of 0-50mM of monobasic phosphate ion concentration, the degradation efficiency of the prepared composite transition metal catalyst for catalyzing PMS to degrade rhodamine B is obviously reduced, and when the concentration of monobasic phosphate ion is 50mM, the degradation efficiency is only 27.60%. This result indicates that the applicable range of the dihydrogen phosphate ion concentration of the composite transition metal catalyst and the oxidation system of the present invention is narrow, and thus the concentration of the dihydrogen phosphate ion in the object to be treated should be reduced as much as possible in order to improve the degradation effect in practical use.

Watch 10

Dihydrogen phosphate ion concentration (mM)	0	2	5	10	50
						Degradation rate of rhodamine B at 30min	98.63％	81.92％	67.09％	61.14％	27.60％

Example 9

1. Preparation of composite transition metal catalyst

Preparing 20mg/L rhodamine B solution, placing 100ml of the rhodamine B solution in a beaker, adding a HA solution with a certain concentration into the beaker to ensure that the HA concentration is 0mg/L, 2mg/L, 5mg/L, 10mg/L and 50mg/L in sequence, adding 20mg of the composite transition metal catalyst into the beaker to ensure that the concentration of the composite transition metal catalyst is 0.2g/L, and fully stirring to ensure that the adsorption and the desorption are balanced; adding an oxidant PMS into the beaker to enable the concentration of the oxidant to be 0.2 mM; the mixture was thoroughly mixed and stirred, and the degradation rate were as shown in Table 11 and FIG. 13, respectively. When the HA concentration is in the range of 0-50mg/L, the degradation efficiency of the prepared composite transition metal catalyst for catalyzing PMS to degrade rhodamine B is not obviously reduced, and when the phosphorus HA concentration is 50mM, the degradation efficiency is 27.60%, which indicates that the composite transition metal catalyst can be suitable for high HA concentration. This result indicates that the HA concentration of the composite transition metal catalyst and the oxidation system having the composition according to the present invention is very suitable for a wide range of HA concentrations, and therefore, in other research experiments, the HA concentration is not particularly adjusted, and thus, it is not necessary to adjust the HA concentration of the treatment object in advance in the actual application.

TABLE 11

HA concentration (mg/L)	0	2	5	10	50
						Degradation rate of rhodamine B at 30min	98.63％	99.08％	97.06％	96.61％	96.94％

Example 10

Preparing 20mg/L ATZ (atrazine) solution, placing 100ml into a beaker, not adjusting the pH value, not adding anions and humic acid, then adding 20mg of the composite transition metal catalyst (namely FeOCl/GQDs/5) prepared in the embodiment into the beaker to ensure that the concentration of the composite transition metal catalyst is 0.2g/L, and fully stirring to ensure that the adsorption and desorption are balanced; adding an oxidant PMS into the beaker to enable the concentration of the oxidant to be 0.2 mM; the mixture was thoroughly mixed and stirred, and the final degradation rate reached 82.10%, as shown in FIG. 14.

Example 11

Preparing 20mg/L BPA (bisphenol A) solution, taking 100ml, placing in a beaker, not adjusting the pH value, not adding anions and humic acid, then adding 20mg of the composite transition metal catalyst (namely FeOCl/GQDs/5) prepared in the embodiment into the beaker, so that the concentration of the composite transition metal catalyst is 0.2g/L, and fully stirring to ensure that the adsorption and desorption are balanced; adding an oxidant PMS into the beaker to enable the concentration of the oxidant to be 0.2 mM; the mixture was thoroughly mixed and stirred, and the final degradation rate reached 96.75%, as shown in FIG. 14.

Example 12

Preparing 20mg/L OPP solution, placing 100ml OPP solution in a beaker, not adjusting the pH value, not adding anions and humic acid, then adding 20mg of the composite transition metal catalyst (namely FeOCl/GQDs/5) prepared in the embodiment into the beaker to ensure that the concentration of the composite transition metal catalyst is 0.2g/L, and fully stirring to ensure that the adsorption and desorption are balanced; adding an oxidant PMS into the beaker to enable the concentration of the oxidant to be 0.2 mM; the mixture was thoroughly mixed and stirred, and the final degradation rate reached 82.51%, as shown in FIG. 14.

Example 13

Preparing 50mg/L Rifampin solution, placing 100ml of Rifampin solution in a beaker, not adjusting the pH value, not adding anions and humic acid, then adding 20mg of the composite transition metal catalyst (namely FeOCl/GQDs/5) prepared in the embodiment into the beaker, so that the concentration of the composite transition metal catalyst is 0.2g/L, and fully stirring to ensure that the adsorption and desorption are balanced; adding an oxidant PMS into the beaker to enable the concentration of the oxidant to be 0.2 mM; the mixture was thoroughly mixed and stirred, and the final degradation rate reached 81.07%, as shown in FIG. 14.

Examples 1 to 9 and examples 10 to 13 show that the system composed of the composite transition metal catalyst and PMS prepared by the invention can be used for treating and degrading various organic pollutants including dyes, endocrine disruptors, medicines or pesticides, and has excellent degradation effect.

Comparative example 1

Preparing 20mg/L rhodamine B solution, placing 100ml of the rhodamine B solution in a beaker, not adjusting the pH, not adding anions and humic acid, and then adding an oxidant PMS into the beaker to enable the concentration of the oxidant to be 0.3 mM; the materials are fully mixed and stirred, the degradation rate is shown in table 3, the degradation rate is shown in figure 5, and the degradation rate of rhodamine B is 4.30% under the condition, namely the rhodamine B is not degraded basically.

Comparative example 2

Preparing 20mg/L rhodamine B solution, placing 100ml of the rhodamine B solution in a beaker, not adjusting the pH value, not adding anions and humic acid, then adding FeOCl/GQDs/530mg prepared in the embodiment into the beaker, so that the concentration of the composite transition metal catalyst is 0.3g/L, and fully stirring to ensure that the adsorption and desorption are balanced; the materials are fully mixed and stirred, the degradation rate is shown in table 3, the degradation rate is shown in figure 5, and under the condition, the degradation rate of rhodamine B is 8.38 percent, namely the rhodamine B is not degraded basically.

Comparative example 3

Preparing 20mg/L rhodamine B solution, placing 100ml of the rhodamine B solution in a beaker, not adjusting the pH value, not adding anions and humic acid, then adding 30mg of FeOCl into the beaker to ensure that the concentration of the FeOCl is 0.3g/L, and fully stirring to ensure that the adsorption and desorption are balanced; adding an oxidant PMS into the beaker to enable the concentration of the oxidant to be 0.3 mM; the materials are fully mixed and stirred, the degradation rate is shown in table 3, the degradation rate is shown in fig. 5, and it can be seen that under the condition, the degradation rate of rhodamine B is 46.11%, namely rhodamine B can be degraded, but the degradation rate is slow, the degradation effect is poor, and the degradation rate is only 46.11%.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. The preparation method of the oxyferric chloride graphene quantum dot composite transition metal catalyst is characterized by specifically comprising the following steps of:

1) adding urea and citric acid into water for dissolving, then carrying out hydrothermal reaction, cooling after the reaction is finished, and then sequentially carrying out dialysis and drying to obtain GQDs;

2) and (3) uniformly mixing iron salt and GQDs, sintering, cooling and taking out to obtain the oxyferric chloride graphene quantum dot composite transition metal catalyst.

2. The preparation method of the iron oxychloride graphene quantum dot composite transition metal catalyst according to claim 1, wherein in the step 1), the hydrothermal temperature is 150-200 ℃ and the hydrothermal time is 3-5 h;

in the step 1), cooling to room temperature for dialysis, wherein the dialysis is carried out for 22-26 h, and water is replaced every 11-13 h;

in the step 1), the drying temperature is 70-90 ℃, and the drying time is 18-24 h.

3. The preparation method of the iron oxychloride graphene quantum dot composite transition metal catalyst according to claim 1, wherein in the step 1), the mass ratio of urea to citric acid is 1: 1;

4. The method for preparing the oxyferric chloride graphene quantum dot composite transition metal catalyst according to claim 1, wherein in the step 2), the ferric salt is FeCl₃·6H₂O；

In step 2), the FeCl₃·6H₂The mass ratio of O to GQDs is 2-40: 1.

5. The preparation method of the iron oxychloride graphene quantum dot composite transition metal catalyst according to claim 1, wherein in the step 2), the sintering temperature is 230-270 ℃, and the sintering time is 1.5-2.5 h.

6. An iron oxychloride graphene quantum dot composite transition metal catalyst prepared by the preparation method of any one of claims 1 to 5.

7. The application of the iron oxychloride graphene quantum dot composite transition metal catalyst as claimed in claim 6 in catalyzing degradation of organic pollutants in water by PMS is characterized by comprising the following specific steps: the method comprises the steps of adding the iron oxychloride graphene quantum dot composite transition metal catalyst and the PMS into water to be treated containing organic pollutants together to form a treatment system for treatment.

8. The preparation method of the oxyferric chloride graphene quantum dot composite transition metal catalyst according to claim 7, wherein the concentration of organic pollutants in the water to be treated is 10-100 mg/L;

the organic contaminants include one or more of dyes, endocrine disruptors, drugs or pesticides.

9. The method according to claim 7, wherein the concentration of the transition metal complex catalyst is 0.1-0.5 g/L, the concentration of PMS is 0.1-0.5 mM, and the pH is 3-11.

10. The preparation method of the oxyferric chloride graphene quantum dot composite transition metal catalyst according to claim 7, wherein the water to be treated further contains one or more of chloride ions, bicarbonate ions, dihydrogen phosphate ions or humic acid.