Nonmetal grafted charcoal ozone catalyst and preparation method and application thereof

Abstract

The invention discloses a nonmetal grafted charcoal ozone catalyst as well as a preparation method and application thereof, and belongs to the field of environmental catalysis and water treatment. The catalyst takes granular biochar as a substrate, and a nitrogen-containing, boron-containing or nitrogen-boron co-grafted functional group is grafted on the surface of the granular biochar through a one-step roasting method. The preparation method comprises the following steps: granulating and pyrolyzing biomass to obtain granular biochar, mixing the granular biochar with a nitrogen-containing and / or boron-containing precursor, roasting at 500-700 DEG C in an inert atmosphere, cooling and washing to obtain the product. According to the invention, through introduction of elements N and B, especially a synergistic electronic effect generated by co-grafting of N and B, the polarizability and electron transfer capability of the surface of the biochar are remarkably enhanced, so that the catalytic activation efficiency on ozone is greatly improved, and when the biochar is used for degrading new pollutants such as tetracycline hydrochloride, the biochar shows catalytic activity far higher than that of original biochar. The catalyst has the advantages of cheap raw materials, simple preparation, good stability, no metal dissolution risk, and wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials and advanced oxidation technology, specifically relating to a non-metallic grafted biochar ozone catalyst, its preparation method and application, which is particularly suitable for removing recalcitrant new pollutants such as antibiotics from water bodies. Background Technology

[0002] Traditional water treatment processes have limited ability to remove new pollutants such as antibiotics, endocrine disruptors, and persistent organic pollutants.

[0003] Catalytic ozonation, as a highly efficient advanced oxidation process, utilizes catalysts to activate ozone, generating strong oxidizing species such as hydroxyl radicals (·OH), enabling deep mineralization of organic pollutants and showing promising prospects in drinking water and wastewater treatment. However, the large-scale application of this technology still faces bottlenecks: firstly, the raw material costs of commonly used catalysts (such as supported metal oxides) are relatively high; secondly, the catalytic performance is easily affected by factors such as water pH and coexisting ions, and its universality needs to be improved.

[0004] Biochar, as a widely available, low-cost, and environmentally friendly carbon material, is considered an ideal support for replacing or partially replacing noble metal / metal oxide catalysts. However, the catalytic activity of raw biochar for ozone is usually limited. Introducing non-metallic elements (such as N, B, and P) through doping or surface modification is an effective strategy to regulate its electronic structure and surface chemistry, thereby improving its catalytic performance. Existing research mostly focuses on single-element doping, while studies on constructing N and B co-grafted structures through specific processes to generate synergistic effects and significantly improve ozone catalytic performance are insufficient, and there is a lack of reports on simple and efficient preparation methods for shaped (particulate) catalysts.

[0005] Therefore, developing a non-metallic grafted biochar ozone catalyst that is inexpensive to produce, easy to prepare, highly catalytically active, and stable is of great value for promoting the practical application of catalytic ozonation technology in the field of new pollutant treatment. Summary of the Invention

[0006] To address the problems of high cost, limited water quality adaptability, and insufficient catalytic activity of existing ozone catalysts, this invention provides a non-metallic (N, B) grafted biochar ozone catalyst, its preparation method, and its applications. This invention aims to introduce specific functional groups containing nitrogen, boron, or a coexistence of nitrogen and boron onto the surface of granular biochar through a simple calcination grafting process, reconstructing its surface electronic structure and significantly improving its catalytic activation efficiency for ozone, thereby achieving efficient and stable removal of new pollutants.

[0007] Technical solution: To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a non-metallic grafted biochar ozone catalyst, characterized in that: the catalyst is granular, the matrix of which is biochar, and non-metallic functional groups are grafted onto the surface and internal pores of the biochar by chemical bonding; the non-metallic functional groups are nitrogen-containing functional groups, boron-containing functional groups, or nitrogen-boron co-grafted functional groups.

[0008] Furthermore, the nitrogen-containing functional groups are mainly pyridine nitrogen and pyrrole nitrogen; the boron-containing functional groups exist in the form of BC bonds and BO bonds; the nitrogen-boron co-branched functional groups form a heterocyclic structure containing C, N, and B elements and oxygen-containing functional groups.

[0009] Furthermore, the biochar is made from crop straw through crushing, granulation, and pyrolysis, and the particle diameter is preferably 0.2-1.0 cm, more preferably about 0.5 cm.

[0010] Secondly, the present invention provides a method for preparing the non-metallic grafted biochar ozone catalyst, characterized by comprising the following steps: S1. Preparation of granular biochar: After crushing the biomass raw material, granulate it and pyrolyze it at 400-800℃ for 0.5-3 hours under an inert atmosphere to obtain granular raw biochar; S2. Non-metallic grafting modification: The granular raw biochar is uniformly mixed with a solution or solid containing a non-metallic precursor, and then calcined under a programmed temperature rise under an inert atmosphere to allow non-metallic elements to enter the carbon skeleton of the biochar and complete the grafting reaction. S3. Post-processing: The calcined product is cooled to room temperature, washed, and dried to obtain the non-metallic grafted biochar ozone catalyst.

[0011] Further, in step S2, the non-metallic precursor includes: Nitrogen-containing precursors: selected from one or more of ethylenediamine, dicyandiamide, gelatin, and urea; Boron-containing precursors: selected from one or more of boric acid, borax (sodium tetraborate), sodium perborate, and ammonium metaborate; or, a mixture of nitrogen-containing and boron-containing precursors.

[0012] Further, in step S2, the mass ratio of the biochar to the non-metallic precursor is 100:1 to 100:20.

[0013] Furthermore, in step S2, the final temperature of the programmed heating calcination is 500-700℃, and the holding time is 15-60 minutes.

[0014] Thirdly, the present invention provides the application of the non-metallic grafted biochar ozone catalyst in the catalytic ozonation removal of organic pollutants in water.

[0015] Furthermore, the organic pollutant is an antibiotic, an endocrine disruptor, or a persistent organic pollutant, preferably tetracycline hydrochloride.

[0016] Furthermore, the method of application is as follows: the catalyst is added to the wastewater containing ozone to be treated, and a catalytic ozone oxidation reaction is carried out under the conditions of pH value of 3-10 and catalyst dosage of 0.02-1 g / L.

[0017] The beneficial effects of this invention are: Compared with the prior art, the present invention has the following significant advantages: 1. Low cost and green raw materials: Biochar substrate is prepared using abundant agricultural waste (straw) as raw material, and the precursor is a common chemical, which greatly reduces the cost of catalysts and is in line with the concept of green and sustainable development.

[0018] 2. High catalytic activity: The grafting of N and B elements, especially the co-grafting of N and B, significantly alters the electron distribution on the biochar surface. N grafting introduces electron-rich regions, while B grafting introduces electron-deficient centers. Together, they generate a strong polarization effect, reshaping the electron cloud density and greatly reducing the energy barrier for ozone activation, thus providing abundant catalytic active sites. Examples show that the first-order reaction kinetic constant of the N-boron co-grafted catalyst is 11.2 times that of the original biochar system.

[0019] 3. Good stability and wide applicability: Non-metallic elements are firmly bonded to the carbon skeleton through high-temperature calcination in the form of chemical bonds, making them less prone to loss and resulting in a long catalyst life. The catalytic performance remains stable within a wide pH range (3-10), making it more adaptable to complex water qualities.

[0020] 4. Simple process and easy to scale up: The preparation method adopts a one-step mixing and calcination method, which has a short process, simple operation, and no need for complex equipment, making it particularly suitable for the large-scale production of shaped granular catalysts.

[0021] 5. Environmentally friendly: The catalyst does not contain heavy metals, avoiding the risk of secondary pollution caused by the leaching of metal ions during operation. Attached Figure Description

[0022] Figure 1 Scanning electron microscope (SEM) images of the nitrogen-boron co-grafted biochar ozone catalyst prepared according to embodiments of the present invention show its rough and porous particle surface morphology.

[0023] Figure 2 A comparison of first-order kinetic fitting curves for the ozonochemical degradation of tetracycline hydrochloride using different catalysts. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Based on the embodiments in this application, other similar embodiments obtained by those skilled in the art without creative effort should all fall within the scope of protection of this application.

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited thereto.

[0026] Example 1: Preparation of nitrogen-grafted biochar ozone catalyst Take 100 grams of spherical straw biochar granules with a diameter of 0.5 cm (obtained by pyrolysis of crushed and granulated straw at 600℃ for 1 hour in nitrogen). Dissolve 5 grams of dicyandiamide in an appropriate amount of deionized water to prepare a solution. Spray this solution evenly onto the surface of the biochar granules for impregnation and adsorption. Dry the loaded granules at 80℃.

[0027] The dried particles were placed in a tube furnace and heated to 600°C at a rate of 5°C / min under a nitrogen atmosphere, and then calcined at this temperature for 45 minutes. After the reaction was completed, the particles were allowed to cool naturally to room temperature, washed three times with deionized water, and dried at 105°C for 12 hours to obtain the nitrogen-grafted biochar ozone catalyst (denoted as N-BC).

[0028] Example 2: Preparation of Boron-Grafted Biochar Ozone Catalyst The preparation process is the same as in Example 1, except that the nitrogen-containing precursor dicyandiamide is replaced with an equal mass of boric acid (H3BO3) to obtain a boron-grafted biochar ozone catalyst (denoted as B-BC).

[0029] Example 3: Preparation of nitrogen-boron co-grafted biochar ozone catalyst The preparation process is the same as in Example 1, except that the nitrogen-containing precursor dicyandiamide is replaced with an equal mass of ammonium metaborate (NH4B2O4) to obtain a nitrogen-boron co-grafted biochar ozone catalyst (denoted as NB-BC).

[0030] Comparative example: Primitive biochar (BC) The spherical straw biochar pellets described in Example 1 were used without any modification.

[0031] Catalytic performance test experiment Catalytic ozonation experiments were conducted in a 2 L glass reactor. A porous titanium plate ozone aerator was installed at the bottom of the reactor. 2 L of simulated wastewater containing 100 mg / L tetracycline hydrochloride (TC) was prepared, and the initial pH was adjusted to 7.0 ± 0.1 using NaOH or H2SO4 solution.

[0032] Add 0.2 g (i.e., 0.1 g / L) of the catalyst prepared in the examples or comparative examples to the reactor. Turn on mechanical stirring and pre-adsorb for 30 minutes without ozone to reach adsorption equilibrium.

[0033] After adsorption equilibrium was reached, the ozone generator was turned on, and an ozone-oxygen mixture (ozone concentration approximately 20 mg / L) was introduced into the reactor at a rate of 0.3 g / h, while timing was started simultaneously. Samples were taken at 5, 10, 15, 20, and 30 min of reaction, and a small amount of Na₂S₂O₃ solution was immediately added to quench any residual ozone. After filtration through a 0.22 μm filter membrane, the concentration of total chlorine (TC) in the filtrate was determined by high-performance liquid chromatography (HPLC).

[0034] According to ln(C0 / C_t) = k_{obs} Calculate the pseudo-first-order kinetic constant k_{obs}, where C0 is the initial concentration after adsorption equilibrium and C_t is the concentration at time t.

[0035] Test Results Figure 2 The kinetic curves of the decomposition TC for different catalyst systems are presented. The calculated results of the pseudo-first-order reaction kinetic constant k_{obs} for each catalyst system are shown in the table below: Catalyst system k_{obs} (min -1 Multiples relative to the original BC O3alone (catalyst-free) 0.021 - BC + O30.038 1.0 (Baseline) N-BC + O30.214 5.6 B-BC + O30.240 6.3 NB-BC + O30.425 11.2 The results show that: 1. Ozone oxidation alone is slow in removing TC.

[0036] 2. Primitive biochar (BC) has some catalytic effect on ozone, but the effect is limited.

[0037] 3. After non-metallic grafting modification, the activity of the catalyst was significantly improved. The k_{obs} of N-BC and B-BC reached 5.6 and 6.3 times that of BC, respectively, proving that single-element grafting is effective.

[0038] 4. The nitrogen-boron co-grafted catalyst (NB-BC) exhibits the best performance, with a k_{obs} value as high as 0.425 min. -1This is 11.2 times that of the original BC system and significantly higher than that of the single-branched catalyst. This strongly demonstrates the synergistic effect of N and B co-branching, which greatly enhances the electron polarization and transfer capabilities of the catalyst surface, thereby significantly improving the catalytic activation efficiency of ozone.

[0039] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Those skilled in the art can modify or substitute the foregoing embodiments without departing from the spirit and scope of the present invention. All such modifications or substitutions should be included within the protection scope defined by the claims of the present invention. Optionally, specific examples in this embodiment can refer to the examples described in the above embodiments, and will not be repeated here.

[0040] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0041] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0042] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A non-metallic grafted biochar ozone catalyst, characterized in that: The catalyst is granular, and its matrix is ​​biochar. Non-metallic functional groups are chemically bonded to the surface and internal pores of the biochar. The non-metallic functional groups are nitrogen-containing functional groups, boron-containing functional groups, or nitrogen-boron co-branched functional groups.

2. The non-metallic grafted biochar ozone catalyst according to claim 1, characterized in that: The nitrogen-containing functional groups include pyridine nitrogen and / or pyrrole nitrogen; the boron-containing functional groups include BC bonds and / or BO bonds; the nitrogen-boron co-branched functional groups form a heterocyclic structure containing C, N, and B elements.

3. The non-metallic grafted biochar ozone catalyst according to claim 1 or 2, characterized in that: The biochar is produced by pyrolysis of crop straw and has a particle diameter of 0.2-1.0 cm.

4. A method for preparing a non-metallic grafted biochar ozone catalyst as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Preparation of granular biochar: After crushing and granulating the biomass raw material, it is pyrolyzed under an inert atmosphere to obtain raw granular biochar; S2. Non-metallic grafting modification: The original granular biochar is mixed with a non-metallic precursor and calcined under an inert atmosphere to allow non-metallic elements to enter the carbon skeleton of the biochar. S3. Post-processing: Cool, wash and dry the calcined product to obtain the catalyst.

5. The preparation method according to claim 4, characterized in that: In step S2, the non-metallic precursor is selected from nitrogen-containing precursors, boron-containing precursors, or a mixture of nitrogen-containing and boron-containing precursors; the nitrogen-containing precursor is selected from at least one of ethylenediamine, dicyandiamide, gelatin, and urea; and the boron-containing precursor is selected from at least one of boric acid, potassium borate, sodium perborate, and ammonium metaborate.

6. The preparation method according to claim 4, characterized in that: In step S2, the mass ratio of the original granular biochar to the non-metallic precursor is 100:1 to 100:

20.

7. The preparation method according to claim 4, characterized in that: In step S2, the roasting temperature is 500-700℃, and the constant temperature time is 15-60 minutes.

8. The preparation method according to claim 4, characterized in that: In step S1, the pyrolysis temperature is 400-800℃ and the time is 0.5-3 hours.

9. The application of a non-metallic grafted biochar ozone catalyst as described in any one of claims 1-3 in the catalytic ozonation removal of organic pollutants from water.

10. The application according to claim 9, characterized in that: The organic pollutant is an antibiotic; the application conditions are: catalyst dosage 0.02-1 g / L, wastewater pH 3-10.

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