CN113979435A

CN113979435A - Biochar and application thereof in catalyzing sodium persulfate to degrade 4-chlorophenol

Info

Publication number: CN113979435A
Application number: CN202111359214.4A
Authority: CN
Inventors: 傅海燕; 金月正; 宋依晴; 柳炳辉; 郑渊茂; 高攀峰; 程前
Original assignee: Xiamen University of Technology
Current assignee: Xiamen University of Technology
Priority date: 2021-11-17
Filing date: 2021-11-17
Publication date: 2022-01-28

Abstract

The invention relates to biochar and application thereof in catalyzing sodium persulfate to degrade 4-chlorophenol, wherein the preparation method of the biochar comprises the following steps: obtaining the melon seed shells, crushing and sieving the melon seed shells, performing carbonization treatment at 400-1000 ℃ under a protective atmosphere, cooling and grinding the obtained carbonized products, adding an alkaline solution for soaking, performing primary heat treatment at a first temperature of 300-400 ℃, heating to a second temperature which is higher than the first temperature of 400-500 ℃, cooling, washing and drying. According to the invention, the unique thin-wall and parallel fibrous structure of the melon seed shells is utilized, the modification is carried out through secondary heat treatment, other elements do not need to be loaded, the obtained catalyst main body is the biochar, and the catalyst has the advantages of low processing cost, high catalytic efficiency and good application prospect.

Description

Biochar and application thereof in catalyzing sodium persulfate to degrade 4-chlorophenol

Technical Field

The invention relates to a preparation technology of a carbon material, in particular to biochar and application thereof in catalyzing sodium persulfate to degrade 4-chlorophenol.

Background

4-chlorophenol is a representative of chlorophenol-type contaminants in the environment, found in many industrial wastewaters of petrochemicals, dyes, paper and pharmaceuticals. Furthermore, the european union has listed 4-chlorophenol as one of the priority pollutants due to its toxicity, potential carcinogenicity, and mutagenicity to mammals and aquatic organisms. Therefore, the method has important significance in exploring a more environment-friendly and more efficient degradation and mineralization technology of the 4-chlorophenol in the water medium.

Advanced oxidation technology has made significant advances in wastewater treatment over the last several decades. Among them, sulfate-based AOPs (SR AOPs) have been extensively and intensively studied. Persulfates include Peroxodisulfate (PDS) and Peroxomonosulfate (PMS), with PDS being preferred over PMS due to its higher stability, longer service life and lower price. However, persulfate itself is difficult to directly react with organic pollutants, and needs to be activated to generate other active substances, such as sulfate radicals, hydroxyl groups, singlet oxygen and the like, so as to play a role in degrading pollutants. There are many activation methods, such as external energy (e.g., thermal activation, radiation activation) activation and activation using a catalyst (e.g., transition metal ions, metal oxides, metal-free carbon materials). These methods are not energy-efficient, heat activation is inconvenient to use, and methods requiring metal or metal oxide may even cause secondary pollution.

On the other hand, the carbon material is a green and efficient catalyst, and has the advantages of low cost, wide source and no risk of secondary pollution caused by metal leakage. Common carbon materials include activated carbon, reduced graphene oxide, carbon nanotubes, nanodiamonds, and biochar. Biochar in particular is considered to be a cheap material from a wide source. The biochar is a product obtained by utilizing biomass after heat treatment, and a specific porous structure of the biochar is usually used for adsorption reaction, but the physical adsorption acting force is limited, so that the problems that the biochar material cannot be recycled, the adsorbed product still needs to be treated, the reaction is insufficient and the like exist.

Further deep processing of carbon materials into activated carbon, reduction of graphene oxide, carbon nanotubes, nanodiamonds, etc. can improve their performance, but these carbon materials are relatively expensive and require raw materials. Therefore, based on the biochar itself, the search for a solution is a problem that people are constantly making efforts to research.

Most biochar prepared by the traditional method at present has undesirable product application effect, and needs additional treatment such as loading or doping of oxide particles of other active catalytic components (such as metal). For example, chinese patent CN 111921536 a discloses a novel catalytic adsorbent material prepared based on natural minerals and biomass, wherein biochar is used only as a carrier, and Fe and Mn are main catalytic elements. The biochar prepared by doping or loading the metal elements and the metal oxides has good performance, but has the risk of secondary leakage of metal ions, which increases the production cost.

Disclosure of Invention

The invention aims to overcome the problems in the existing preparation of biochar, and provides a preparation method of biochar.

Biochar common in the prior art, such as sludge biochar, straw biochar, pine needle biochar, bamboo biochar and peanut shell biochar, has been applied to persulfate advanced oxidation technology, but the performance is still not ideal, additional treatment is required, such as loading or doping of other active catalytic components (such as metal or metal oxide particles), and the risk of secondary leakage of metal ions exists. The shell of melon seeds is generally treated as waste, and a few melon seeds are used as plant fertilizers, so that the biological carbonization capacity of the melon seeds is ignored. The shell material of the melon seeds contains a large amount of cellulose, is easy to carbonize and modify, and the melon seeds as the sunflower seeds peel not only contain nutrient components such as nitrogen, phosphorus and potassium, but also contain some microelements such as iron, copper and zinc, and can provide stronger catalysis for the biochar.

The specific scheme is as follows:

a preparation method of biochar comprises the steps of obtaining melon seed shells, crushing and sieving the melon seed shells, carrying out carbonization treatment at 400-1000 ℃ under protective atmosphere, cooling and grinding the obtained carbonized products, adding an alkaline solution for soaking, carrying out primary heat treatment at a first temperature of 300-400 ℃, then heating to a second temperature which is higher than the first temperature of 400-500 ℃, cooling, washing and drying to obtain the biochar.

Furthermore, the particle size of the crushed and sieved melon seed shells is less than or equal to 150 mu m; the carbonization treatment adopts nitrogen or inert gas atmosphere, and the temperature of the carbonization treatment is 700-850 ℃.

Further, the alkaline solution is KOH aqueous solution, and the concentration is 0.1-5 mol/L; adding alkaline solution, soaking for 1-2h, and performing first heat treatment.

Further, the first heat treatment is carried out at a rate of 1-5 ℃/min to 350-.

The invention also protects the preparation method of the biochar and the biochar prepared by the method, wherein the particle size of the biochar is 10-50 mu m, and the specific surface area is 300-350m²The volume of the micro pores is 0.1-0.3 ml/g.

The invention also protects the application of the biochar in catalyzing the sodium persulfate to degrade the 4-chlorophenol.

The invention also provides a sewage treatment method containing 4-chlorophenol, which comprises the steps of putting the biochar into sewage, adding sodium persulfate, wherein the adding amount of the biochar is 0.1-0.3g/L, the adding amount of the sodium persulfate is 0.5-1g/L, and reacting at room temperature for 30-120 min.

Further, the mass concentration of the 4-chlorophenol in the sewage is 1-100 mg/L.

Further, the mass concentration of 4-chlorophenol in the sewage is 1-50mg/L, the addition amount of the biochar is 0.1-0.3g/L, the addition amount of sodium persulfate is 0.5-3g/L, the reaction is carried out at room temperature for 120min, and the removal rate of 4-chlorophenol is more than or equal to 99.0%.

Has the advantages that:

in the invention, the shell of the melon seeds is carbonized, the carbonized material is modified, the alkali activation is added, and the two heat treatments are carried out, wherein the primary pore channel is formed at a low temperature in the first heat treatment, the second heating temperature is 400 ℃ higher than the first heating temperature, and 500 ℃, the internal structure of the product is changed by utilizing the temperature difference of the two heating treatments, rich gaps are formed, the adsorption capacity of the product is improved, and the sodium persulfate is catalyzed to degrade the 4-chlorophenol.

The invention also provides a method for treating sewage containing 4-chlorophenol, which comprises the steps of degrading 4-chlorophenol at room temperature, utilizing the physical adsorption effect of the biochar and the catalysis of persulfate by the biochar by using the biochar as an adsorbent and a catalyst, generating a large amount of free radicals in water, and utilizing the free radicals to carry out advanced oxidation to directly degrade pollutants into nontoxic and harmless H₂O and CO₂。

In a word, the invention utilizes the unique thin-wall parallel fibrous structure of the melon seed shell, and the specific surface area and the porosity of the biochar are increased through alkali treatment and secondary heat treatment modification, so that the biochar has good adsorption and catalytic performance, other elements do not need to be loaded, the obtained catalyst main body is the biochar, the processing cost is low, the catalytic efficiency is high, and the 120min4-CP catalytic degradation efficiency reaches 99.19 percent. Provides a new way and a new method for degrading the 4-CP-containing wastewater, and has better application prospect.

Drawings

In order to illustrate the technical solution of the present invention more clearly, the drawings will be briefly described below, and it is apparent that the drawings in the following description relate only to some embodiments of the present invention and are not intended to limit the present invention.

FIG. 1 is an XRD (X-ray diffraction) characterization diagram of a biochar material provided by one embodiment of the invention;

FIG. 2 is a scanning electron microscope image of a biochar material provided by an embodiment of the invention;

FIG. 3 is a transmission electron microscope image of a biochar material provided by an embodiment of the invention;

FIG. 4 is a graph of biochar catalytic efficiency for different materials provided by an embodiment of the invention;

FIG. 5 is a graph illustrating the effect of different catalyst dosages provided by one embodiment of the present invention;

fig. 6 is a graph illustrating the effect of different PDS dosing amounts provided by an embodiment of the present invention.

Detailed Description

Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein. The examples do not specify particular techniques or conditions, and are performed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available. In the following examples, "%" means weight percent, unless otherwise specified.

Example 1

The method for preparing the melon seed shell biochar comprises the following steps: separating the hull and pulp of sunflower seed, drying the hull at 80 deg.C for 72 hr, grinding into powder, and sieving with 100 mesh sieve. Then, the powder was carbonized in a quartz tube furnace at 400 ℃, 600 ℃ and 800 ℃ for 2 hours in a nitrogen atmosphere. The carbonized product was ground and immersed in KOH solution in a nickel crucible for 2h, then raised to 350 ℃ at a rate of 5 ℃/min and activated at this temperature for 2h, followed by slow pyrolysis at a rate of 30 ℃/min to 800 ℃ for 2 h. After cooling to room temperature, thoroughly washing the final product with 0.1mol/L HCl and deionized water, finally drying at 80 ℃ for 24 hours, grinding to obtain the melon seed shell charcoal powder, and respectively recording the biochar obtained at different carbonization temperatures as: BC-400, BC-600 and BC-800.

Charcoal was prepared from general Wood chips by the above method and was designated as Wood Biochar.

XRD analysis was performed on biochar BC-400, BC-600, and BC-800, and the results are shown in FIG. 1. As can be seen from figure 1, no obvious peak appears in XRD spectrums of BC-400, BC-600 and BC-800, which indicates that all amorphous biochar is prepared at three temperatures.

The biochar BC-800 was characterized by (2) SEM and TEM, and the results are shown in FIGS. 2 and 3. As can be seen from FIG. 2, the biochar is in granular distribution, the grain diameter is about 10-50 μm, a large number of micropores are densely distributed on the surface of the biochar, and the specific surface area is 321.17m²The volume of the micropores was 0.11 ml/g. As can be seen from FIG. 3, the pore diameter of the biochar micropores is about 200 nm.

Example 2

The method for preparing the melon seed shell biochar comprises the following steps: separating the hull and pulp of sunflower seed, drying the hull at 80 deg.C for 72 hr, grinding into powder, and sieving with 100 mesh sieve. Thereafter, the powder was carbonized in a quartz tube furnace at 1000 ℃ for 2 hours under a nitrogen atmosphere. The carbonized product is ground and immersed in 1mol/L KOH solution in a nickel crucible for 2h, then is heated to 350 ℃ at the speed of 3 ℃/min and is activated at the temperature for 2h, and then is slowly pyrolyzed for 2h at the speed of 20 ℃/min to 750 ℃. After cooling to room temperature, the final product was washed thoroughly with 0.1mol/L HCl and deionized water, and finally dried at 80 ℃ for 24 hours to obtain the melon seed shell charcoal powder after grinding.

Example 3

The method for preparing the melon seed shell biochar comprises the following steps: separating the hull and pulp of sunflower seed, drying the hull at 80 deg.C for 72 hr, grinding into powder, and sieving with 100 mesh sieve. Thereafter, the powder was carbonized in a quartz tube furnace at 1000 ℃ for 2 hours under a nitrogen atmosphere. The carbonized product was ground and immersed in a 1mol/L KOH solution in a nickel crucible for 2h, then raised to 370 ℃ at a rate of 3 ℃/min and activated at this temperature for 2h, followed by slow pyrolysis at a rate of 20 ℃/min to 800 ℃ for 2 h. After cooling to room temperature, the final product was washed thoroughly with 0.1mol/L HCl and deionized water, and finally dried at 80 ℃ for 24 hours to obtain the melon seed shell charcoal powder after grinding.

Example 4

The method for preparing the melon seed shell biochar comprises the following steps: separating the hull and pulp of sunflower seed, drying the hull at 80 deg.C for 72 hr, grinding into powder, and sieving with 100 mesh sieve. Thereafter, the powder was carbonized in a quartz tube furnace at 1000 ℃ for 2 hours under a nitrogen atmosphere. The carbonized product is ground and immersed in 1mol/L KOH solution in a nickel crucible for 2h, then is heated to 380 ℃ at the speed of 5 ℃/min and is activated at the temperature for 2h, and then is slowly pyrolyzed for 2h at the speed of 20 ℃/min to 850 ℃. After cooling to room temperature, the final product was washed thoroughly with 0.1mol/L HCl and deionized water, and finally dried at 80 ℃ for 24 hours to obtain the melon seed shell charcoal powder after grinding.

Example 5

In order to verify the effect of the melon seed shell biochar on catalyzing persulfate, a simulation experiment is carried out in a beaker, 50ml of prepared 50 mg/L4-chlorophenol solution (hereinafter referred to as 4-CP) is taken, and the pH value is adjusted to 5 by hydrochloric acid. 0.01g (biochar addition equivalent to 0.2g/L) of the BC-400, BC-600, BC-800 biochar prepared in example 1 was added, respectively.

And (3) placing the beaker on a magnetic stirrer for stirring, and carrying out adsorption reaction for 60min at room temperature to ensure that the biochar material reaches adsorption balance. Then 0.025g (0.5g/L) of sodium persulfate Powder (PDS) was added for 120 min. For determining the progress of the adsorption and catalytic reactions, adsorption phases and catalystsThe reaction stage was sampled every 15 min. Sampling, detecting by a liquid chromatograph, and recording the initial concentration of the C, 4-chlorophenol as C₀Calculating C/C₀And drawing a degradation curve.

As a control, a simulation experiment was performed according to the above method using charcoal Wood Biochar prepared in example 1 and RGO (ultra pure graphene oxide, suzhou carbofeng graphene technologies ltd).

The result is shown in fig. 4, and it can be seen from fig. 4 that the efficiency of degrading 4-CP by PDS catalyzed by BC-800 biochar material is significantly improved, the degradation efficiency is the highest, the 120min4-CP degradation rate reaches 99.19%, compared with other structural materials, the BC-800 biochar material has the largest first-order reaction kinetic constant, the fastest reaction rate, and the catalytic effect and the adsorption effect superior to those of wood biochar and graphene materials.

Meanwhile, as can be seen from fig. 4, the biochar prepared by common wood chips according to the same preparation method has a weak catalytic effect. The graphene can promote the 4-CP degradation, but the degradation effect is not as good as that of the melon seed shell biochar prepared by the invention.

Example 6

On the basis of example 5, the influence of different dosages of biochar on the degradation effect was studied, and the degradation curves were drawn according to the method of example 5 with dosages of 0, 0.1g/L, 0.2g/L and 0.3g/L, respectively, as shown in FIG. 5.

As can be seen from FIG. 5, the reaction efficiency and rate are improved with the increase of the adding amount of the biochar material, and when the adding amount of the biochar material is 0.3g/L, the 4-chlorophenol solution can be degraded by 92.58% within 15min at room temperature, so that the biochar material has an excellent degradation effect.

Meanwhile, as can be seen from fig. 5, when no biochar is added and only PDS is added, the concentration of 4-chlorophenol has no obvious change, which indicates that under the condition of a simulation experiment performed at room temperature, only PDS directly acts on 4-chlorophenol, and almost no degradation effect exists.

Example 7

On the basis of example 5, the influence of different amounts of PDS on the degradation effect was studied, and the degradation curves were plotted according to the method of example 5 with the dosages of 0.5g/L, 1g/L, 2g/L and 3g/L, respectively, as shown in FIG. 6.

As can be seen from FIG. 6, reaction efficiency and rate are improved with the increase of the amount of the added PDS, but the increase of the amount of the added PDS has no obvious influence on the efficiency and the rate compared with biochar, which further shows that the biochar has a catalytic effect, the amount of the PDS reaches a sufficient level in a simulation experiment when the amount of the added biochar is 0.5g/L, and only when the amount of the biochar is increased, the adsorption effect is remarkable, and simultaneously, the PDS is promoted to react to generate a large amount of free radicals, and the free radicals have high oxidation activity, so that the 4-chlorophenol is efficiently degraded.

Comparative example 1

Referring to example 1, a control biochar was prepared by: separating the hull and pulp of sunflower seed, drying the hull at 80 deg.C for 72 hr, grinding into powder, and sieving with 100 mesh sieve. Thereafter, the powder was carbonized in a quartz tube furnace at 800 ℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the final product was washed thoroughly with 0.1mol/L HCl and deionized water and finally dried at 80 ℃ for 24 hours to obtain control charcoal powder 1 after grinding.

A simulation experiment was performed according to the method of example 5, and it was found that 4-CP degradation rate at 120min was 20.35% at a dose of 0.2g/L of charcoal powder 1 at room temperature.

Comparative example 2

Referring to example 1, a control biochar was prepared by: separating the hull and pulp of sunflower seed, drying the hull at 80 deg.C for 72 hr, grinding into powder, and sieving with 100 mesh sieve. Thereafter, the powder was carbonized in a quartz tube furnace at 800 ℃ for 2 hours under a nitrogen atmosphere. The carbonized product was ground and immersed in KOH solution in a nickel crucible for 2h, then raised to 350 ℃ at a rate of 5 ℃/min and activated at this temperature for 2h, followed by slow pyrolysis at a rate of 30 ℃/min to 500 ℃ for 2 h. After cooling to room temperature, the final product was washed thoroughly with 0.1mol/L HCl and deionized water and finally dried at 80 ℃ for 24 hours to give control charcoal powder 2 after grinding.

A simulation experiment was performed according to the method of example 5, and it was found that 4-CP degradation rate at 120min was 25.68% at a dosage of 0.2g/L of charcoal powder 1 at room temperature.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. A preparation method of biochar is characterized by comprising the following steps: comprises the steps of obtaining melon seed shells, crushing and sieving the melon seed shells, carbonizing at 400-1000 ℃ under protective atmosphere, cooling and grinding the obtained carbonized products, adding alkaline solution for soaking, performing primary heat treatment at a first temperature of 300-400 ℃, heating to a second temperature which is higher than the first temperature of 400-500 ℃, cooling, washing and drying to obtain the biochar.

2. The method for preparing biochar according to claim 1, wherein: the particle size of the crushed and sieved melon seed shells is less than or equal to 150 mu m; the carbonization treatment adopts nitrogen or inert gas atmosphere, and the temperature of the carbonization treatment is 700-850 ℃.

3. The method for preparing biochar according to claim 1, wherein: the alkaline solution is KOH aqueous solution, and the concentration is 0.1-5 mol/L; adding alkaline solution, soaking for 1-2h, and performing first heat treatment.

4. The method for preparing biochar according to claim 1, wherein: the first heat treatment is carried out at the speed of 1-5 ℃/min to 350-.

5. The biochar according to any one of claims 1 to 4, which is prepared by a method comprising: the particle diameter of the biochar is 10-50 mu m, and the specific surface area is 300-350m²The volume of the micro pores is 0.1-0.3 ml/g.

6. Use of the biochar of claim 5 to catalyze the degradation of 4-chlorophenol by sodium persulfate.

7. A method for treating sewage containing 4-chlorophenol is characterized by comprising the following steps: the biochar of claim 5 is adopted, the biochar is thrown into sewage, then sodium persulfate is added, the addition amount of the biochar is 0.1-0.3g/L, the addition amount of the sodium persulfate is 0.5-1g/L, and the reaction is carried out for 30-120min at room temperature.

8. The method for treating 4-chlorophenol-containing sewage according to claim 7, wherein: the mass concentration of the 4-chlorophenol in the sewage is 1-100 mg/L.

9. The method for treating 4-chlorophenol-containing sewage according to claim 8, wherein: the mass concentration of 4-chlorophenol in the sewage is 1-50mg/L, the addition amount of biochar is 0.1-0.3g/L, the addition amount of sodium persulfate is 0.5-3g/L, the reaction is carried out at room temperature for 120min, and the removal rate of 4-chlorophenol is more than or equal to 99.0%.