CN109647413B

CN109647413B - Supported metal catalyst for catalyzing persulfate to treat organic wastewater and preparation method thereof

Info

Publication number: CN109647413B
Application number: CN201811338034.6A
Authority: CN
Inventors: 陈朱琦; 周新全; 汪佳; 廖朱玮; 罗春光; 朱静怡; 罗梦伊
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2018-11-12
Filing date: 2018-11-12
Publication date: 2020-10-16
Anticipated expiration: 2038-11-12
Also published as: CN109647413A

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a supported metal catalyst for efficiently catalyzing persulfate to treat refractory organic wastewater and a preparation method thereof. The chemical formula of the compound is expressed as CuOMO @ Fe₃O₄Which is a transition metal oxide Fe₃O₄The carrier is loaded with metal oxide CuO and non-redox metal oxide MO on the surface of the carrier by a coprecipitation method, wherein M is non-redox metal. The catalyst can realize high-efficiency catalysis on PMS and effectively degrade various organic pollutants.

Description

Supported metal catalyst for catalyzing persulfate to treat organic wastewater and preparation method thereof

Technical Field

The invention belongs to the technical field of sewage treatment, and particularly relates to a supported metal catalyst for catalyzing persulfate to treat refractory organic wastewater and a preparation method thereof.

Background

With the continuous increase of the industrialization level of modern society, the effective treatment of various organic waste waters, especially waste waters containing organic pollutants which are difficult to degrade, is under increasing pressure. The advanced oxidation method can realize the rapid treatment of organic pollutants, has small secondary pollution and good economical efficiency, and has good application prospect.

The oxidant adopted in the advanced oxidation method system at present mainly comprises persulfate (PDS, PMS) and hydrogen peroxide. Among them, PMS has become a hot spot for various researches because it has an asymmetric structure and relatively low bond dissociation energy, making it more activated.

Based on the advanced oxidation technology of activated PMS, the adopted activating factors mainly comprise light, heat, ultraviolet rays, transition metals and the like. Among them, catalytic activation of PMS using a catalyst made of a transition metal is currently the most commonly used method. Among the wide variety of transition metal catalysts, supported transition metal catalysts have received much attention due to the ability to provide greater specific surface area and reduced metal leaching. Meanwhile, the bimetallic catalyst prepared by combining different metal characteristics is also an effective means for improving the catalytic performance of the catalyst. For example catalyst Mn_1.8Fe_1.2O₄And CuFeO₂All show more efficient catalytic performance than the respective single oxides when used as catalysts.

The preparation of the supported bimetallic catalyst is expected to further improve the catalytic performance of the catalyst by combining the advantages of the supported metal catalyst and the bimetallic catalyst. However, these catalysts still have some technical difficulties and research defects in application, mainly including: 1) in the catalytic system, the utilization rate of the oxidant PMS is not high, secondary pollution can be generated, 2) the catalyst carrier generally adopts non-redox metal oxide (Al)₂O₃Etc.) and non-metallic carriers (activated carbon, graphene, etc.), for supported catalysis with transition metals as carriersReagents are less studied, 3) the choice of metal components in bimetallic catalysts is often limited to the transition metal range, ignoring the role of non-redox metals.

Disclosure of Invention

Aiming at the defects or the improvement requirements of the prior art, the invention provides a supported metal catalyst for catalyzing persulfate to treat refractory organic wastewater and a preparation method thereof, and aims to use transition metal oxide Fe₃O₄The carrier is used for loading metal copper oxide CuO and non-redox metal oxide MO by a coprecipitation method, so that the persulfate is efficiently catalyzed, various organic pollutants are effectively degraded, and the technical problems that the utilization rate of an oxidant is low and secondary pollution is generated in the existing persulfate catalysis system are solved.

To achieve the above objects, according to one aspect of the present invention, there is provided a supported metal catalyst having a chemical formula expressed as CuOMO @ Fe₃O₄Which is a transition metal oxide Fe₃O₄The carrier is obtained by loading metal oxide CuO and non-redox metal oxide MO on the surface of the carrier through a coprecipitation method; m is a non-redox metal element having a valence of + 2.

Preferably, the non-redox metal element M is one of Ca, Mg and Zn.

Preferably, the molar ratio of metal oxide in the supported metal catalyst is CuO: MO: fe₃O₄＝1～2:15～20:2～4。

According to another aspect of the present invention, there is provided a method for preparing the supported metal catalyst, comprising the steps of:

(1) under the condition of stirring, in the presence of transition metal oxide Fe₃O₄Adding precursor solution of metal oxide CuO and non-redox metal oxide MO into the mixed system of the metal oxide CuO and the alkaline solution to perform coprecipitation reaction to obtain floccule; wherein M is a non-redox metal element;

(2) aging, solid-liquid separation, drying and calcining the floccule to obtain the metal catalyst;

wherein the metal oxide CuO, the non-redox metal oxide MO and the transition metal oxide Fe₃O₄The molar ratio of (A) to (B) is 1-2: 15-20: 2-4.

Preferably, the catalyst contains transition metal oxide Fe₃O₄And adding precursor solutions of metal oxide CuO and non-redox metal oxide MO into a mixed system of the metal oxide CuO and the alkaline solution in a dropwise manner.

Preferably, the aging time is not less than 24 hours.

Preferably, the calcining temperature is 400-600 ℃, and the calcining time is 4-6 h.

According to another aspect of the invention, the supported metal catalyst is applied to catalyzing persulfate to treat organic wastewater, wherein the persulfate is an oxidant, the pH of the organic wastewater is controlled to be 7-10, and the temperature of a catalytic system is controlled to be 25-30 ℃.

According to another aspect of the invention, a catalyst for catalyzing persulfate to treat organic wastewater is provided, which comprises the supported metal catalyst.

Preferably, the persulfate is a peroxymonosulfate.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

(1) the invention provides a transition metal oxide Fe₃O₄The supported composite metal catalyst is a carrier, and a metal oxide CuO and a non-redox metal oxide MO are supported on the surface of the carrier by a coprecipitation method. The active component in the catalyst is CuO, and the non-redox metal oxide MO is introduced, so that the redox characteristic and the surface pH value of the catalyst are changed, and the catalytic performance of the catalyst is improved.

(2) The supported composite metal catalyst provided by the invention can be used for catalyzing persulfate to treat refractory organic wastewater, and particularly shows a good catalytic effect when being used for catalyzing peroxymonosulfate. The peroxymonosulfate is used as an oxidant, and compared with peroxydisulfate and hydrogen peroxide, the peroxymonosulfate has an asymmetric structure and relatively low bond dissociation energy, so that the peroxymonosulfate is easier to activate. The peroxymonosulfate is used as an oxidant, and the using amount of the catalyst and the oxidant is small when the peroxymonosulfate is used; the catalytic degradation reaction condition is mild, the equipment is simple, and the investment is small; leaching of various metal ions contained in the catalyst in a solution is small; the reaction system has high utilization rate of oxidant PMS and small secondary pollution; the reaction is carried out under the condition of neutral alkali, and the application range is wide.

(3) The preparation method of the supported composite metal catalyst provided by the invention is simple, and Fe is used₃O₄The flocculant is used as a carrier and is obtained by coprecipitation in alkaline solution and then filtering and calcining.

(4) When the supported composite metal catalyst provided by the invention is used for catalyzing persulfate to treat organic wastewater, the catalytic activity is improved, so that compared with the existing catalyst, the supported composite metal catalyst provided by the invention achieves the same pollutant treatment effect, and the adding amount of the catalyst and the oxidant is greatly reduced.

Drawings

FIG. 1 is a schematic diagram of the preparation of a supported metal catalyst according to example 1 of the present invention.

FIG. 2 is CuOCaO @ Fe of example 2 of the present invention₃O₄PMS system radical quenching diagram.

FIG. 3 is CuOCaO @ Fe of example 2 of the present invention₃O₄PMS system EPR identification diagram.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention provides a supported metal catalyst for treating organic wastewater, the chemical formula of which is expressed as CuOMO @ Fe₃O₄Which is a transition metal oxideFe₃O₄The carrier is loaded with metal oxide CuO and non-redox metal oxide MO on the surface of the carrier by a coprecipitation method, wherein M is a non-redox metal element, and M is positive divalent. The specific method is to mix CuO and Cu (NO) which is the precursor of MO₃)₂And M (NO)₃)₂Is added dropwise to the solution containing Fe₃O₄And Na₂CO₃In the alkaline solution of (2), CuCO is formed around the carrier₃And MCO₃Then filtering and calcining the flocculated body to obtain CuCO₃And MCO₃In the form of CuO and MO and Fe carrier₃O₄Are combined together. Through XPS analysis, the active component in the supported metal catalyst is determined to be CuO.

In some embodiments, the non-redox metal M is one of Ca, Mg, and Zn.

In some embodiments, the molar ratio of metal oxide in the supported metal catalyst is CuO: MO: fe₃O₄＝1～2:15～20:2～4。

The preparation method of the supported metal catalyst comprises the following steps:

(1) under the condition of stirring, in the presence of transition metal oxide Fe₃O₄Adding precursor solution of metal oxide CuO and non-redox metal oxide MO into the mixed system of the metal oxide CuO and the alkaline solution, wherein M is non-redox metal, and carrying out coprecipitation reaction to obtain floccule; the precursor solutions of the metal oxide CuO and the non-redox metal oxide MO may be salt solutions of the metal element Cu and the non-redox metal M, such as nitrates, chlorides, sulfates, etc.

(2) Aging the floccule for more than 24 hours, carrying out solid-liquid separation, drying and calcining to obtain the metal catalyst;

In some preferred embodiments, in the presence of transition metal oxide Fe₃O₄Mixed with alkaline solutionThe precursor solution of metal oxide CuO and non-redox metal oxide MO is added by stirring and dripping. The stirring and dropping way ensures that the metal oxide CuO and the non-redox metal oxide MO can be more uniformly deposited on the carrier Fe₃O₄A surface.

In some embodiments, the calcination temperature is 4 to 6 hours and the calcination time is 400 to 600 ℃.

The supported metal catalyst provided by the invention is a catalyst for catalyzing persulfate to treat refractory organic wastewater, and can be used for catalyzing persulfate to treat organic wastewater, peroxymonosulfate or peroxydisulfate is used as an oxidant when in use, the pH value of the organic wastewater is controlled to be 7-10, and the catalytic degradation efficiency is high when the temperature of a catalytic system is controlled to be 25-30 ℃. In a preferred embodiment, the catalyst, PMS and organic wastewater are mixed and stirred for reaction, and the reaction is finished when PMS is consumed. Wherein, CuOMO @ Fe₃O₄As a catalyst, the molar ratio of metal oxides is CuO: MO: fe₃O₄(1-2: 15-20: 2-4) in an amount of 0.05g/L, PS (peroxydisulfate) or PMS (peroxymonosulfate) as an oxidizing agent, and at an initial concentration of 0.5 mM/L. The preferred oxidant is PMS.

The invention uses transition metal oxide Fe₃O₄As a carrier, loading a metal oxide CuO and a non-redox metal oxide MO on the surface of the carrier by a coprecipitation method to prepare a loaded composite metal catalyst CuOMO @ Fe₃O₄. Unlike current research, carbon materials (rGO, AC, ACF) and non-transition metal substances (Al) are often utilized₂O₃MgAl-LDH) as carrier, catalyst CuOMO @ Fe₃O₄Using transition metal oxides Fe₃O₄As a carrier. And is different from the current research that two or more transition metal oxides (Mn) are often used_1.8Fe_1.2O₄、CuFeO₂、CuCo@MnO₂) As a research object, the influence of the interaction among different transition metals on the performance of catalytically activated persulfate, particularly peroxymonosulfate is revealed, and the catalyst CuOMO @ Fe₃O₄Introduction of non-oxidative reductionThe active component of the original metal oxide MO in the supported metal catalyst is CuO, the introduction of the non-redox metal oxide MO changes the redox property and the surface pH value of the catalyst, and the carrier Fe₃O₄The presence of (b) promotes the reduction of the active ingredient CuO. The catalytic degradation pathway includes a free radical pathway (OH, SO)₄ ^·-) And a non-radical pathway (¹O₂) Wherein¹O₂Is the main active ingredient.

The following are examples:

example 1

Catalyst CuOMO @ Fe in the invention₃O₄The synthesis steps are as follows:

(1) in a 500ML beaker, 200ML of deionized water was added followed by 40mM Na₂CO₃And 0.5gFe₃O₄And fully stirring.

(2) Another 500ML beaker was charged with 200ML deionized water, followed by 1.5mM and 20mM Cu (NO) respectively₃)₂·3H₂O and M (NO)₃)₂·yH₂And O, fully stirring to completely dissolve the compound.

(3) The mixture of Na and₂CO₃and Fe₃O₄The solution is put into a 60 ℃ constant temperature magnetic stirrer to be stirred continuously at a proper rotating speed, and simultaneously, Cu (NO) is contained in the solution within 60min₃)₂·3H₂O and M (NO)₃)₂·yH₂Dropwise adding Na-containing solution into O₂CO₃And Fe₃O₄The pH of the solution (2M NaOH solution for pH adjustment) was kept at about 10 ± 0.02 throughout the process.

(4) After the solution is dripped, the obtained white suspension is kept stand and aged for 24h at room temperature, then is repeatedly filtered by deionized water and washed to ensure that the pH value of the remained precipitate is nearly neutral, and is placed in a 100ml porcelain crucible, and is put in an oven at 80 ℃ for overnight drying, the obtained white solid is ground into powder and is put in a muffle furnace at 500 ℃ for calcining for 5 h.

Wherein the catalyst CuOMO @ Fe obtained₃O₄Metal oxide CuO in the alloy, non-oxidizedReduced metal oxide MO and transition metal oxide Fe₃O₄Is 1.5:20:2, where M may be any one or more of Ca, Mg and Zn.

Example 2

0.00125g of catalyst CuOCaO @ Fe is added into the prepared reaction liquid (I), (II) or (III)25ML respectively₃O₄And 0.0125mM PMS, placing the mixed solution in a magnetic constant-temperature water bath kettle at the temperature of 30 ℃ for reaction for 1h, and after the reaction is finished, sampling and analyzing, wherein the results are shown in Table 1. The reaction liquid (I) was a p-acetamidophenol solution with a concentration of 30ppm, the reaction liquid (II) was a tetrachlorophenol solution with a concentration of 40ppm, and the reaction liquid (III) was a phenol solution with a concentration of 10 ppm.

With catalyst CuOCaO @ Fe₃O₄For example, for CuOCaO @ Fe₃O₄the/PMS system was subjected to a free radical quenching experiment and an EPR experiment. FIG. 2 is a free radical quenching diagram demonstrating OH, SO₄ ^·-Does not contribute much to the degradation of the substrate (paracetamol), and a singlet oxygen (¹O₂) Contributes greatly to the degradation of the substrate. The EPR profile of FIG. 3 further demonstrates¹O₂Is present.

Example 2

0.00125g of catalyst CuOMgO @ Fe is added into 25ML of prepared reaction liquid (I), (II) or (III)₃O₄And 0.0125mM PMS, placing the mixed solution in a magnetic constant-temperature water bath kettle at the temperature of 30 ℃ for reaction for 1h, and after the reaction is finished, sampling and analyzing, wherein the results are shown in Table 1. The reaction liquid (I) was a p-acetamidophenol solution with a concentration of 30ppm, the reaction liquid (II) was a tetrachlorophenol solution with a concentration of 40ppm, and the reaction liquid (III) was a phenol solution with a concentration of 10 ppm.

Example 3

Respectively adding 0.00125g of catalyst CuOZnO @ Fe into the prepared reaction liquid (I), (II) or (III)25ML₃O₄And 0.0125mM PMS, placing the mixed solution in a magnetic constant-temperature water bath kettle at the temperature of 30 ℃ for reaction for 1h, and after the reaction is finished, sampling and analyzing, wherein the results are shown in Table 1. The reaction liquid (I) was a p-acetamidophenol solution having a concentration of 30ppm, and the reaction liquid (II) was a p-acetamidophenol solution having a concentration of 30ppm40ppm of tetrachlorophenol solution, and the reaction liquid (III) was a phenol solution having a concentration of 10 ppm.

TABLE 1

From Table 1, the catalyst CuOMO @ Fe can be seen₃O₄Through the catalytic activation of PMS, the method has higher extraction efficiency for different organic pollutants.

Example 4

25ML of the prepared reaction liquid (I) is added with the catalyst CuOMO @ Fe₃O₄The addition amounts of (A) and (B) are respectively 0.001g, 0.00125g, 0.0025g and 0.005g, then 0.0125mM PMS is added, the mixture is put into a magnetic constant-temperature water bath kettle at the temperature of 30 ℃ for reaction for 1h, and after the reaction is finished, sampling analysis is carried out, and the results are shown in Table 2. The reaction liquid (I) was a p-acetamidophenol solution having a concentration of 30 ppm.

TABLE 2

From Table 2, it can be seen that the value of CuOMO @ Fe₃O₄In PMS system, when the adding amount of the catalyst reaches 0.05g/L, the acetaminophen can be completely converted under the experimental conditions.

Example 5

25ML of the prepared reaction liquid (I) is changed to the dosage of PMS to be 0.01mM, 0.0125mM, 0.025mM and 0.05mM respectively, and then 0.00125g of catalyst CuOMO @ Fe is added₃O₄The mixed solution was placed in a magnetic thermostatic water bath at 30 ℃ for 1 hour, and after the reaction, sampling and analysis were performed, and the results are shown in table 3. The reaction liquid (I) was a p-acetamidophenol solution having a concentration of 30 ppm.

TABLE 3

From Table 3, it can be seen that the measured value is CuOMO @ Fe₃O₄In the PMS system, the optimum dosage of oxidant PMS is 0.5mM/L, in which case the complete conversion of paracetamol can be achieved under the experimental conditions.

Example 6

Respectively adding 0.00125g of catalyst CuOMO @ Fe into 25ML prepared reaction liquid (I)₃O₄And 0.0125mM PMS, respectively placing the mixed solution in magnetic constant temperature water bath pots with different temperatures for reaction for 1h, wherein the temperature gradient is 20 ℃, 30 ℃ and 40 ℃, after the reaction is finished, sampling and analyzing, and the result is shown in Table 4. The reaction liquid (I) was a p-acetamidophenol solution having a concentration of 30 ppm.

TABLE 4

From Table 4, it can be seen that the value of CuOMO @ Fe₃O₄In PMS system, when the reaction temperature reaches 30 ℃, the acetaminophen can be completely converted under the experimental conditions.

Example 7

Respectively adding 0.00125g of catalyst CuOMO @ Fe into 25ML prepared reaction liquid (I)₃O₄And 0.0125mM PMS, using 1M/L HNO₃And 1M/L of HaOH is used for adjusting the pH of the reaction solution to be 3, 5, 7, 9 and 11 respectively, then the mixed solution is placed in a magnetic constant-temperature water bath kettle at the temperature of 30 ℃ for reaction for 1 hour, and after the reaction is finished, a sample is taken for analysis, and the result is shown in Table 5. The reaction liquid (I) was a p-acetamidophenol solution having a concentration of 30 ppm.

TABLE 5

From Table 5, it can be seen that the value of CuOMO @ Fe₃O₄In a PMS system, when the pH of the reaction system is 7-9, the acetaminophen can be completely converted under experimental conditions.

Comparative example 1

Adding 0.0125mM PMS and 0.0 mM PMS into the prepared reaction liquid (I), (II) or (III)25ML respectively0125g catalyst CuOMO @ Fe₃O₄Or CuO @ Fe₃O₄The mixed solution was placed in a magnetic thermostatic water bath at 30 ℃ for 1 hour, and after the reaction, sampling and analysis were performed, and the results are shown in table 6. The reaction liquid (I) was a p-acetamidophenol solution with a concentration of 30ppm, the reaction liquid (II) was a tetrachlorophenol solution with a concentration of 40ppm, and the reaction liquid (III) was a phenol solution with a concentration of 10 ppm.

TABLE 6

It can be seen from Table 6 that in the catalyst CuO @ Fe₃O₄The non-redox metal oxide MO is introduced into the catalyst, so that the catalytic activity of the catalyst on PMS can be obviously improved, and the degradation effect on a substrate is improved.

Comparative example 2

The results of comparing the supported metal catalyst provided by the invention with the existing catalysts in the aspect of catalyzing and degrading organic matters are shown in Table 7.

TABLE 7

The catalyst CuO @ Fe is used₃O₄The non-redox metal oxide MO is introduced to enhance the Cu in the CuO as an active component²⁺/Cu⁺Which facilitates electron transfer between the oxidant persulfate and the catalyst. Furthermore, the introduction of MO can enhance the alkalinity of the surface of the catalyst, and the catalyst is helped to adsorb the peroxymonosulfate of the oxidant. Through the above functions, the catalyst CuOMO @ Fe is realized₃O₄High-efficiency catalysis to peroxymonosulfate.

As can be seen from Table 7, the catalyst CuOMO @ Fe used in the present invention₃O₄Catalytic peroxymonosulfate treatmentCompared with other catalyst systems, when the catalyst is adopted in the organic wastewater, the dosage of the catalyst and the oxidant in the reaction system is smaller, but the substrate conversion speed is higher, and the catalytic conversion is more efficient.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. The application of the supported metal catalyst is characterized in that the supported metal catalyst is used for catalyzing persulfate to treat organic wastewater, wherein the persulfate is an oxidant, the pH of the organic wastewater is controlled to be 7-10, and the temperature of a catalytic system is controlled to be 25-30 ℃;

the chemical formula of the supported metal catalyst is expressed as CuOMO @ Fe₃O₄Which is a transition metal oxide Fe₃O₄The carrier is obtained by loading metal oxide CuO and non-redox metal oxide MO on the surface of the carrier through a coprecipitation method, wherein M is a non-redox metal element with a valence of + 2; the non-redox metal element M is one of Ca and Mg;

(1) under the condition of stirring, in the presence of transition metal oxide Fe₃O₄Adding metal oxide CuO and a precursor solution of the non-redox metal oxide MO into a mixed system of the metal oxide CuO and the alkaline solution to perform coprecipitation reaction to obtain floccules;

(2) aging, solid-liquid separation, drying and calcining the floccule to obtain the supported metal catalyst;

2. Use according to claim 1, wherein the persulfate salt is a peroxymonosulfate salt.

3. Use according to claim 1, characterised in that the transition metal oxide Fe is present₃O₄And adding precursor solutions of metal oxide CuO and non-redox metal oxide MO into a mixed system of the metal oxide CuO and the alkaline solution in a dropwise manner.

4. The use of claim 1, wherein step (2) is carried out for an aging time of not less than 24 hours.

5. The use of claim 1, wherein the calcining temperature in the step (2) is 400-600 ℃ and the calcining time is 4-6 h.