CN117414829A

CN117414829A - Preparation method and application of municipal wastewater peat-based catalyst

Info

Publication number: CN117414829A
Application number: CN202311362538.2A
Authority: CN
Inventors: 楚英豪; 杨川樊; 方宁杰; 刘兆兵; 李晨曦
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2023-10-19
Filing date: 2023-10-19
Publication date: 2024-01-19
Anticipated expiration: 2043-10-19
Also published as: CN117414829B

Abstract

The invention discloses a preparation method and application of a municipal sludge peat-based catalyst, wherein the preparation method comprises the following steps of S1, drying municipal sludge, crushing and sieving to obtain a sample precursor; s2, adding a sample precursor and ferric trichloride into deionized water, performing hydrothermal reaction for 20 hours at 80-200 ℃ in a hydrothermal kettle, cooling, alternately washing with deionized water and absolute ethyl alcohol, and drying to obtain hydrothermal carbon; and S3, placing the hydrothermal carbon in a muffle furnace, and roasting for 1h at 200-400 ℃ to obtain the carbon-based catalyst. The carbon-based catalyst is used as an activator in the process of oxidative degradation of organic pollutants by persulfate, so that the oxidation efficiency of the persulfate can be improved. The carbon-based catalyst is prepared from municipal sludge serving as a raw material, so that the recycling utilization of municipal sludge is realized, and the problems that the effect of degrading pollutants in water by using persulfate is poor, heavy metals are dissolved out by activating metal compounds, secondary pollution is caused, the energy consumption is high by using pyrolytic biochar, the cost is high and the like are solved.

Description

Preparation method and application of municipal wastewater peat-based catalyst

Technical Field

The invention relates to the technical field of solid waste utilization, in particular to a preparation method and application of a municipal wastewater peat-based catalyst.

Background

Industrial organic wastewater such as medicines, printing and dyeing, papermaking and the like has large discharge amount and contains a large amount of nondegradable pollutants which can have long-term adverse effects on human health, for example, tetracycline is one of typical pollutants in the industrial organic wastewater, and the organic pollutants are major pollution sources which cause the destruction of water ecological environment and seriously affect the utilization of water resources. Among them, advanced oxidation technology is one of the effective means for treating the organic pollutants difficult to degrade, while advanced oxidation system based on persulfate is a class of advanced oxidation technology which is widely used and widely accepted at present due to the advantages of low cost, good effect and the like.

Persulfate is a sulfate complex that undergoes some degree of self-decomposition in water to form, among other characteristic free radicals that have high oxidizing properties and oxidize organic contaminants in water. In addition, the free radicals can react with water or dissolved oxygen to generate other free radicals such as hydroxyl free radicals, superoxide free radicals and the like, so as to accelerate the degradation of pollutants. However, the oxidation efficiency of persulfate itself is not high, and activation is needed, and currently common persulfates include peroxymonosulfate and peroxydisulfate, wherein peroxymonosulfate is more activated than peroxydisulfate. Common activating materials include metal oxides, transition metal activation, carbon-based material activation, and the like. The metal oxide is easy to dissolve out, so that secondary pollution is caused; transition metal activation is often a problem of high cost due to complex preparation process; and the pyrolysis biochar is adopted, so that the energy consumption requirement is high.

Municipal sludge is a precipitate substance generated in the water treatment process of an urban sewage treatment plant, contains a large amount of microorganisms and organic matters, contains rich nitrogen, potassium and other nutrient substances, and also contains excessive heavy metals, pathogenic microorganisms and the like. Municipal sludge has high sludge content and is difficult to dewater compared with industrial sludge. The disposal route of municipal sewage sludge generally comprises the following methods: land utilization, sanitary landfill, incineration treatment and the like. The purpose of sludge treatment is stabilization, reduction, harmlessness and recycling. The municipal sludge is used for preparing the carbon-based catalyst and is used as an activating material for oxidative degradation of organic matters by persulfate, so that the recycling utilization of the municipal sludge is realized.

Disclosure of Invention

Aiming at the problems that the heavy metal dissolution of the existing activated material is easy to cause secondary pollution, the pyrolysis biochar has higher requirement on energy consumption and the like, the invention provides a preparation method for preparing a carbon-based catalyst from municipal sludge. The method loads the transition metal on the carbon base, so that the problem of secondary pollution caused by heavy metal dissolution is avoided, and meanwhile, the method adopts a low-temperature heat treatment mode, so that the energy consumption and the cost are reduced.

The invention provides a preparation method of a carbon-based catalyst prepared from municipal sludge, which comprises the following specific steps:

s1, drying municipal sludge, crushing, and sieving with a 40-mesh sieve to obtain a sample precursor.

S2, adding the sample precursor and ferric trichloride into deionized water, transferring the mixture into a hydrothermal kettle, carrying out hydrothermal reaction for 20 hours at the temperature of 80-200 ℃, naturally cooling to room temperature, and then alternately washing and drying the mixture through deionized water and absolute ethyl alcohol to obtain the hydrothermal carbon.

And S3, placing the hydrothermal carbon in a muffle furnace, roasting for 1h at 200-400 ℃, and cooling to obtain the carbon-based catalyst.

Preferably, in step S2, the ratio of the mass of sludge to the mass of ferric trichloride is 1:0.1 to 1:20. the concentration of the sludge added into deionized water is 20g/L.

Preferably, in step S2, the temperature rising rate is 2-5 ℃/min, and the temperature of the hydrothermal reaction is 120 ℃.

Preferably, in step S3, the temperature rising rate is 1-5 ℃/min. The roasting atmosphere is air, and the roasting temperature is 350 ℃.

The carbon-based catalyst prepared by the method is used as an activator in the process of oxidative degradation of organic pollutants by persulfate, and can improve the oxidation efficiency of persulfate. Particularly, the active agent is used as an activator in the process of oxidative degradation of the tetracycline by the persulfate, so that the efficiency of oxidative degradation of the tetracycline by the persulfate can be remarkably improved. The application method comprises the following steps:

adding a peroxymonosulfate solution into the aqueous solution containing the tetracycline, uniformly mixing and stirring, then adding a carbon-based catalyst, and carrying out degradation reaction for 30min to realize the degradation of the tetracycline.

Compared with the prior art, the invention has the following advantages:

(1) The invention prepares the carbon-based catalyst by taking municipal sludge as one of raw materials, loads transition metal on the carbon to prepare the carbon-based catalyst, and solves the problem of secondary pollution caused by heavy metal dissolution generated by activation of metal compounds in the process of degrading pollutants in water by using persulfate.

(2) The preparation method of the invention adopts a low-temperature treatment mode, reduces energy consumption and cost, can obtain the high-performance carbon-based catalyst at 100-400 ℃, greatly reduces cost, avoids the problem of high energy consumption caused by pyrolysis of biochar, and is simple to operate in the preparation process.

(3) The invention prepares the carbon-based catalyst by taking municipal sludge as one of raw materials, thereby realizing the resource utilization of municipal sludge.

(4) The carbon-based catalyst prepared by the invention has excellent effect of activating persulfate, and the removal rate of tetracycline can reach 98.5% within 30 min.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Drawings

FIG. 1 is a graph showing the effect of carbon-based catalysts prepared in examples 1-5 at different calcination temperatures on the degradation of tetracycline solutions.

FIG. 2 is a graph of the degradation effect of a carbon-based catalyst prepared at different hydrothermal reaction temperatures on a tetracycline solution.

FIG. 3 is the effect of the catalysts prepared in example 1, comparative example 1 and comparative example 2 on the catalytic degradation of tetracycline.

Fig. 4 is an SEM image of a sludge precursor (SS), hydrothermal carbon (Fe/SSHC) of comparative example 1, and carbon-based catalyst (Fe/SSBC) of example 1.

Fig. 5 is an Fe 2p image of XPS of a sludge precursor (SS), hydrothermal carbon (Fe/SSHC) of comparative example 1, and carbon-based catalyst (Fe/SSBC) of example 1.

Detailed Description

The preferred embodiments of the present invention will be described below with reference to the accompanying drawings, it being understood that the preferred embodiments described herein are for illustration and explanation of the present invention only, and are not intended to limit the present invention.

Example 1

And (3) drying municipal sludge for 12 hours at 105 ℃, taking out, putting the municipal sludge into a crusher for crushing for 5 minutes, and sieving the sludge with a 40-mesh sieve to obtain a sludge precursor. 1g of a sludge precursor and 0.054g of ferric trichloride hexahydrate were weighed, dissolved in 50ml of deionized water, and stirred at a stirring rate of 300r/min for 30min to obtain a mixed solution. Transferring the mixed solution into a hydrothermal reaction kettle, heating to 120 ℃ at a heating rate of 3 ℃/min, and carrying out hydrothermal reaction for 20h. Naturally cooling to room temperature, then washing by deionized water and absolute ethyl alcohol alternately, and drying at 60 ℃ after full washing to obtain the hydrothermal carbon. And then placing the hydrothermal carbon into a crucible, placing the crucible into a muffle furnace for roasting, setting the heating rate of the muffle furnace to be 5 ℃/min, setting the roasting atmosphere to be air, setting the target temperature to be 350 ℃, and keeping the temperature for 2 hours, and naturally cooling to obtain the carbon-based catalyst.

Example 2

The preparation was the same as in example 1, the only difference being that the calcination temperature was 200 ℃.

Example 3

The preparation was carried out as in example 1, the only difference being that the calcination temperature was 250 ℃.

Example 4

The preparation was identical to example 1, except that the calcination temperature was 300 ℃.

Example 5

The preparation was carried out as in example 1, the only difference being that the calcination temperature was 400 ℃.

The carbon-based catalysts prepared in examples 1-5 were used in catalytic tetracycline degradation experiments. The catalytic performance of the municipal sludge catalyst provided by the invention is tested by taking a tetracycline solution with the concentration of 100mg/L as a degradation object. 5mg of a carbon-based catalyst is put into 50mL of tetracycline solution, 100ul of peroxymonosulfate with the concentration of 20mmol is added after adsorption for 30min under dark condition, 2mL of tetracycline reaction solution is collected every 5min, solid-liquid separation is realized by using a 0.45um filter membrane, and the absorbance of the tetracycline solution before and after the reaction is measured at 360 nm. FIG. 1 is a graph showing the effect of carbon-based catalysts prepared in examples 1-5 at different calcination temperatures on the degradation of tetracycline solutions. As can be seen from fig. 1, the degradation effect of the catalyst prepared by combining different low-temperature roasting temperatures is different under the premise of keeping the low-temperature hydrothermal condition constant, and when the roasting temperature is 350 ℃, the prepared catalyst has the best effect and the removal rate of the tetracycline is 98.5% in 30 min.

Example 6

On the basis of the example 1, the respective temperatures of the hydrothermal reaction were changed to 25, 40, 80, 160 and 200 ℃, and other conditions were unchanged, so as to prepare a carbon-based catalyst. And carrying out a catalytic degradation tetracycline experiment on the carbon-based catalyst prepared at different hydrothermal reaction temperatures. The tetracycline solution with the concentration of 100mg/L is taken as a degradation object. 5mg of a carbon-based catalyst is put into 50mL of tetracycline solution, 100ul of peroxymonosulfate with the concentration of 20mmol is added after adsorption for 30min under dark condition, 2mL of tetracycline reaction solution is collected every 5min, solid-liquid separation is realized by using a 0.45um filter membrane, and the absorbance of the tetracycline solution before and after the reaction is measured at 360 nm. FIG. 2 is a graph of the degradation effect of a carbon-based catalyst prepared at different hydrothermal reaction temperatures on a tetracycline solution. As can be seen from fig. 2, on the premise of keeping the low-temperature roasting temperature constant, different low-temperature hydrothermal reaction temperatures have a significant effect on the performance of the catalyst, and the prepared catalyst has the best effect when the hydrothermal reaction temperature is 120 ℃.

Comparative example 1

And (3) drying municipal sludge for 12 hours at 105 ℃, taking out, putting the municipal sludge into a crusher for crushing for 5 minutes, and sieving the sludge with a 40-mesh sieve to obtain a sludge precursor. 1g of a sludge precursor and 0.054g of ferric trichloride hexahydrate were weighed, dissolved in 50ml of deionized water, and stirred at a stirring rate of 300r/min for 30min to obtain a mixed solution. Transferring the mixed solution into a hydrothermal reaction kettle, heating to 120 ℃ at a heating rate of 3 ℃/min, and carrying out hydrothermal reaction for 20h. Naturally cooling to room temperature, then washing alternately by deionized water and absolute ethyl alcohol, and drying at 60 ℃ after full washing to obtain the catalyst.

Comparative example 2

And (3) drying municipal sludge for 12 hours at 105 ℃, taking out, putting the municipal sludge into a crusher for crushing for 5 minutes, and sieving the sludge with a 40-mesh sieve to obtain a sludge precursor. 1g of sludge precursor and 0.054g of ferric trichloride hexahydrate are weighed, the sludge precursor and the ferric trichloride are put into a mortar for grinding and uniformly mixed, then the mixture is put into a muffle furnace for roasting, the temperature rise rate of the muffle furnace is set to be 5 ℃/min, the roasting atmosphere is air, the target temperature is 350 ℃, the holding time is 2h, and the catalyst is obtained after natural cooling.

Comparative example 3

Weighing 0.054g of ferric trichloride hexahydrate, grinding the ferric trichloride in a mortar, uniformly mixing, then placing the mixture into a muffle furnace for roasting, setting the heating rate of the muffle furnace to be 5 ℃/min, setting the roasting atmosphere to be air, setting the target temperature to be 350 ℃, keeping the temperature for 2 hours, and naturally cooling to obtain the catalyst.

The effect of the catalysts prepared in example 1, comparative example 2 and comparative example 3 on the catalytic degradation of tetracycline is shown in fig. 3. The experimental method for catalytic degradation of tetracycline is the same as above. As can be seen from fig. 3, the catalyst prepared by separately performing low-temperature hydrothermal reaction or separately performing low-temperature roasting on the sludge precursor has a certain promotion effect on the tetracycline degradation system of the peroxymonosulfate, but the promotion effect is not obvious. The carbon-based catalyst prepared by combining low-temperature hydrothermal reaction and low-temperature roasting has the best effect in catalyzing a persulfate-degraded tetracycline system, and is obviously superior to a catalyst prepared by singly using low-temperature hydrothermal reaction or singly performing low-temperature roasting. In addition, the catalyst prepared by roasting the iron alone at a low temperature has a general effect of catalyzing the degradation of tetracycline by the peroxymonosulfate, because the iron can react with certain oxygen-containing functional groups in the sludge to form Fe-O functional groups in the preparation method of the invention, and active sites for promoting the degradation of the peroxymonosulfate are generated.

Fig. 4 is an SEM image of a sludge precursor (SS), hydrothermal carbon (Fe/SSHC) of comparative example 1, and carbon-based catalyst (Fe/SSBC) of example 1. From the figure, the sludge and ferric trichloride are subjected to co-hydrothermal reaction, so that iron can be successfully loaded on the surface of the carbon material, and the hydrothermal carbon exposed to air at the low temperature of 350 ℃ can further diffuse the iron, so that the surface of the whole carbon-based material is covered by the iron element.

Fig. 5 is an Fe 2p image of XPS of a sludge precursor (SS), hydrothermal carbon (Fe/SSHC) of comparative example 1, and carbon-based catalyst (Fe/SSBC) of example 1. The information in the figure shows that Fe-O functional groups are generated on the surface of the hydrothermal carbon in the hydrothermal reaction stage, and the surface of the carbon-based catalyst prepared by burning the hydrothermal carbon at the low temperature of 350 ℃ obviously contains higher peak intensity of the Fe-O functional groups, which shows that the low temperature burning at the temperature of 350 ℃ can improve the content of Fe-O in a sample and has positive influence on improving the tetracycline degradation effect.

The present invention is not limited to the above-mentioned embodiments, but is intended to be limited to the following embodiments, and any modifications, equivalents and modifications can be made to the above-mentioned embodiments without departing from the scope of the invention.

Claims

1. A preparation method of a municipal wastewater peat-based catalyst is characterized by comprising the following steps:

s1, drying municipal sludge, crushing and sieving to obtain a sample precursor;

s2, adding a sample precursor and ferric trichloride into deionized water, transferring the mixture into a hydrothermal kettle, carrying out hydrothermal reaction for 20 hours at the temperature of 80-200 ℃, naturally cooling to room temperature, and then alternately washing the mixture by using deionized water and absolute ethyl alcohol, and drying the mixture to obtain hydrothermal carbon;

2. The process for preparing a municipal sludge-based catalyst as claimed in claim 1, wherein in step S1, the sludge is crushed and passed through a 40 mesh screen.

3. The method for preparing a municipal sludge peat-based catalyst according to claim 1, wherein in step S2, the ratio of the mass of sludge to the mass of ferric trichloride is 1:0.1 to 1:20.

4. the method for preparing municipal sludge-based catalyst according to claim 3, wherein in step S2, the concentration of the sludge added to deionized water is 20g/L.

5. The method for preparing municipal sludge peat-based catalyst according to claim 4, wherein in step S2, the heating rate is 2-5 ℃/min and the hydrothermal reaction temperature is 120 ℃.

6. The method for preparing a municipal sludge peat-based catalyst according to claim 1, wherein in step S3, the heating rate is 1-5 ℃/min.

7. The method of preparing a municipal sludge peat-based catalyst according to claim 6, wherein in step S3, the roasting atmosphere is air and the roasting temperature is 350 ℃.

8. A municipal sludge peat-based catalyst, characterized by being produced by the method for producing a municipal sludge peat-based catalyst according to any one of claims 1-6.

9. The use of the municipal sludge peat-based catalyst as claimed in claim 8, wherein the char-based catalyst is used as an activator in the oxidative degradation of organic pollutants by persulfates, to increase the oxidation efficiency of persulfates.

10. The use of the municipal sludge peat-based catalyst according to claim 9, wherein the char-based catalyst is used as an activator in the oxidative degradation of tetracycline by persulfates, the method of use being as follows: