Metal oxide / polyphenol biochar adsorbent, preparation method and application

Abstract

The invention belongs to the field of water treatment, and discloses a metal oxide / polyphenol biochar adsorbent, a preparation method and application. The metal oxide / polyphenol biochar adsorbent is obtained by mixing metal salt, plant polyphenol and a protein auxiliary agent according to the mass ratio of (1 / 3-1): 1: (0.1-0.5), reacting and then carrying out high-temperature cracking. Plant polyphenol is used as a raw material, phenolic hydroxyl groups in the polyphenol are coordinated with metal ions, and the metal oxide / polyphenol biochar adsorbent is prepared through high-temperature cracking. In the prepared adsorbent, the rigid benzene ring structure of polyphenol increases the defect degree of the biochar surface, and meanwhile, due to the strong coordination effect of phenolic hydroxyl groups and metal ions, metal oxides are uniformly distributed in the adsorbent, so that the density of adsorption sites is greatly increased, and the removal effect on humus in a water body is remarkably improved; and the removal rate is up to 99% or above.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a metal oxide / polyphenol biochar adsorbent, a preparation method and an application thereof. Background Art

[0002] Dissolved organic pollutants in landfill leachate pose a serious threat to the environment and human health due to their wide range of sources, complex composition and diverse properties. These pollutants mainly originate from the biodegradation of solid organic waste in landfills, and include aromatic compounds, proteins, carbohydrates and aliphatic compounds with different functional groups. Due to the complex composition of leachate and the large differences due to factors such as region, landfill age and garbage source, these dissolved organic pollutants have the characteristics of high concentration, complex composition and difficulty in degradation, which greatly increases the difficulty of treatment.

[0003] Although traditional treatment methods such as biological treatment, membrane separation and advanced oxidation processes have their own advantages, they all face problems such as low efficiency, high cost or easy secondary pollution when treating such pollutants. In particular, these soluble organic pollutants are difficult to be effectively removed by conventional adsorbents due to their high water solubility, wide molecular weight distribution, large polarity differences, and the fact that some substances are difficult to biodegrade. For example, low molecular weight organic acids can easily penetrate traditional adsorption materials due to their high water solubility; and some specific organic pollutants such as phenolic compounds, although they can be partially adsorbed, are prone to desorption, affecting the stability of the treatment effect. In addition, the inorganic salt ions commonly present in the leachate will compete with organic pollutants for adsorption sites, further reducing the adsorption efficiency. Summary of the invention

[0004] The purpose of the present invention is to provide a metal oxide / polyphenol biochar adsorbent and a preparation method for efficiently removing complex and diverse soluble organic pollutants in landfill leachate, solving the problem that traditional treatment technologies are difficult to degrade these pollutants, and providing an economical, efficient and environmentally friendly solution for the treatment of landfill leachate.

[0005] To achieve the above object, the first technical solution adopted by the present invention is: The metal oxide / polyphenol biochar adsorbent is obtained by mixing metal salts, plant polyphenols and protein additives in a mass ratio of (1 / 3~1):1:(0.1~0.5) and then pyrolyzing them at high temperature.

[0006] Preferably, the protein adjuvant is an amino acid and / or a small molecule polypeptide.

[0007] Preferably, the pyrolysis is carried out at a temperature of 500-900° C. for 1-2 h in a nitrogen atmosphere.

[0008] Preferably, the metal salt includes any one or more of aluminum sulfate, aluminum chloride, zirconium sulfate, copper sulfate, cerium sulfate, and bismuth sulfate.

[0009] Preferably, the plant polyphenols include any one or more of bayberry tannin, wattle bark tannin, catechin, and tannic acid.

[0010] The second technical solution adopted by the present invention is: The preparation method of the metal oxide / polyphenol biochar adsorbent in the first technical solution comprises the following steps: After the metal salt solution and the plant polyphenol solution are evenly mixed, a protein additive is added and stirred evenly, the pH of the solution is adjusted to 7-8 to generate a precipitate, the precipitate is obtained by filtration, the precipitate is cracked at high temperature, cooled, washed and dried.

[0011] Preferably, the pyrolysis is carried out at a temperature of 500-900° C. for 1-2 h under a nitrogen atmosphere.

[0012] Preferably, the metal salt solution and the plant polyphenol solution are mixed uniformly at 20-30°C.

[0013] The third technical solution adopted by the present invention is: The first technical solution is the application of metal oxide / polyphenol biochar adsorbent in the adsorption of soluble organic pollutants in landfill leachate.

[0014] Preferably, the adsorption conditions are: normal pressure, initial pH of the adsorbed landfill leachate is 3-10, reaction temperature is 10-40°C, rotation speed is 100-250 rpm, and adsorbent dosage is 0.1-1.0 g / L.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The use of the protein additive in the present invention enhances the binding force between the polyphenols and the metal oxides, and significantly improves the adsorption effect on soluble organic pollutants in the landfill leachate.

[0016] The adsorbent of the invention has N-doping and MNC structure, which enhances the electron transfer ability and catalytic performance of the material and further improves the treatment efficiency. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] The first embodiment of the present invention provides a metal oxide / polyphenol biochar adsorbent, which is obtained by mixing a metal salt, a plant polyphenol and a protein additive in a mass ratio of (1 / 3~1):1:(0.1~0.5) and then pyrolyzing the mixture at high temperature.

[0019] The synergistic effect of the protein adjuvant (amino acid and small molecule polypeptide) and the high temperature cracking process in this embodiment gives the material obtained by the reaction of plant polyphenols with metal oxides an excellent physical structure. The phenolic hydroxyl groups of plant polyphenols form a strong coordination effect with metal ions, and the protein adjuvant as a "cross-linking agent" enhances the binding force between polyphenols and metal oxides, promotes them to be more tightly complexed, thereby preventing metal leakage. The high temperature cracking process promotes the formation of the biochar structure, so that it has a developed pore structure and a high specific surface area, providing a large number of adsorption sites. This structure allows soluble organic pollutants to be fixed on the surface of biochar by physical adsorption, and at the same time, the aromatic structure in the biochar can have a π-π stacking effect with the aromatic ring of the organic pollutant to enhance the adsorption capacity. In addition, the functional groups (such as hydroxyl groups and carboxyl groups) on the surface of metal oxide / polyphenol biochar can form hydrogen bonds, ion exchange or complexation with organic pollutants to achieve chemical adsorption, and the metal ions therein can also form surface complexes with certain functional groups in organic pollutants to further enhance the adsorption effect.

[0020] The chemical composition and structural characteristics of the adsorbent of this embodiment give it unique electronic properties and catalytic ability. Under high temperature pyrolysis conditions, the nitrogen element in the protein additive is doped into the carbon skeleton to form an N-doped carbon material, which not only enhances the electron transfer ability and adsorption performance, but also forms a metal-nitrogen-carbon (MNC) structure with metal and carbon. This structure plays an important role in catalytic and adsorption applications, and is beneficial to the oxidative degradation of certain organic pollutants. In addition, the formation of metal-polyphenol nanoparticles not only improves the structural stability, but also may promote the degradation of certain organic pollutants through catalysis, further improving the treatment efficiency of the material.

[0021] In addition, the benzene ring structure of polyphenols provides a large π bond, which can form a π-π stacking effect with many soluble organic matter in the landfill leachate, especially compounds containing aromatic ring structures. This interaction significantly enhances the adsorption capacity of the adsorbent for such organic pollutants. At the same time, the introduction of polyphenols changes the surface chemical properties of biochar. The presence of large π bonds increases the electron density on the surface of biochar and improves its ability to interact with organic pollutants.

[0022] In summary, the metal oxide / polyphenol biochar adsorbent forms a multi-level, multi-mechanism synergistic system through its optimized physical structure and unique chemical composition. This comprehensive performance improvement far exceeds the effect of using biochar, metal oxides or polyphenols alone, allowing the material to simultaneously cope with the complex and diverse dissolved organic pollutants in landfill leachate. Through the synergistic effect of multiple mechanisms such as physical adsorption, chemical adsorption, and catalytic degradation, the adsorbent achieves efficient and broad-spectrum removal of dissolved organic pollutants in landfill leachate, showing excellent performance and applicability. This innovative material design and preparation method not only provides strong technical support for the treatment of landfill leachate, but also opens up new ways for the efficient removal of environmental pollutants, showing great potential in the field of environmental governance.

[0023] In some preferred embodiments, the protein adjuvant is an amino acid and / or a small molecule polypeptide.

[0024] In some preferred embodiments, the pyrolysis is carried out at a temperature of 500-900° C. for 1-2 h in a nitrogen atmosphere.

[0025] In some preferred embodiments, the metal salt includes any one or more of aluminum sulfate, aluminum chloride, zirconium sulfate, copper sulfate, cerium sulfate, and bismuth sulfate.

[0026] In some preferred embodiments, the plant polyphenols include any one or more of bayberry tannin, wattle bark tannin, catechin, and tannic acid.

[0027] The second aspect of the present invention provides a method for preparing a metal oxide / polyphenol biochar adsorbent, comprising the following steps: mixing a metal salt solution and a plant polyphenol solution evenly, adding a protein additive and stirring evenly, adjusting the pH of the solution to 7-8 to generate a precipitate, filtering to obtain the precipitate, and high-temperature cracking the precipitate, cooling, washing, and drying.

[0028] In some preferred embodiments, the pyrolysis is carried out at a temperature of 500-900° C. for 1-2 h under a nitrogen atmosphere.

[0029] In some preferred embodiments, the metal salt solution and the plant polyphenol solution are uniformly mixed at 20-30°C.

[0030] The second aspect of the present invention provides the use of metal oxide / polyphenol biochar adsorbent in adsorbing soluble organic pollutants in landfill leachate.

[0031] In some preferred embodiments, the adsorption conditions are: normal pressure, initial pH of the adsorbed landfill leachate is 3-10, reaction temperature is 10-40°C, rotation speed is 100-250 rpm, and adsorbent dosage is 0.1-1.0 g / L.

[0032] It should be noted that the soluble organic pollutants in the landfill leachate in the embodiment of the present invention are obtained by filtering the landfill leachate with a 0.45 μm filter membrane. 0.45 μm is used to distinguish between soluble substances and suspended substances in water samples. Substances that pass through this filter membrane are considered soluble, while those retained by the filter membrane are considered suspended.

[0033] In order to make the scheme of the present invention clearer, the metal oxide / polyphenol biochar adsorbent, preparation method and performance are described in detail through multiple specific examples below.

[0034] Some of the preparations used in the following examples are as follows: Amino acids and small molecule peptides were purchased from TCI Chemicals Co., Ltd., bayberry tannin was purchased from Shanghai Koraman Reagent Co., Ltd., chinensis bark tannin was purchased from Hubei Xinghengye Technology Co., Ltd., tannic acid was purchased from Shandong Tianshili Biotechnology Co., Ltd., catechin was purchased from Jiangxi Huayuyuan Biotechnology Co., Ltd., and chemicals and reagents were purchased from Sigma-Aldrich.

[0035] Example 1 Metal oxide / polyphenol biochar adsorbent, the mass ratio of each raw material is metal salt: bayberry tannin: protein additive = 0.5:1: 0.5; among them, the metal salt is aluminum sulfate and aluminum chloride with a mass ratio of 3:2, and the protein additive is amino acid and small molecule polypeptide with a mass ratio of 1:1.

[0036] The preparation method of the metal oxide / polyphenol biochar adsorbent is: S11. The metal salt and bayberry tannin were mixed with deionized water to obtain a metal ion solution and a bayberry tannin solution; S12. The metal ion solution and the bayberry tannin solution were mixed evenly at 28°C, and the protein additive was slowly added dropwise. After continuing stirring for 10 minutes, the pH value of the solution was adjusted to 7. After filtering, the precipitate was washed with water to obtain metal-polyphenol nanoparticles. The metal-polyphenol nanoparticles were pyrolyzed at 750°C for 2 hours under a nitrogen atmosphere, cooled, washed and dried to obtain a metal oxide / polyphenol biochar adsorbent.

[0037] The conditions for the adsorption of soluble organic pollutants in landfill leachate by metal oxide / polyphenol biochar adsorbent are: normal pressure, initial wastewater pH 3~10, reaction temperature 10~40℃, rotation speed 100~250rmp, and adsorbent dosage 0.1~1.0g / L.

[0038] Example 2 Metal oxide / polyphenol biochar adsorbent, the mass ratio of each raw material is zirconium sulfate: chinquapin bark tannin: protein additive = 1 / 3:1: 0.5; wherein the protein additive is amino acid and small molecule polypeptide with a mass ratio of 2:1.

[0039] The preparation method of the metal oxide / polyphenol biochar adsorbent is: S11. The zirconium sulfate and nepal bark tannins were mixed with deionized water to obtain a zirconium sulfate solution and a nepal bark tannin solution; S12. The zirconium sulfate solution and the chinquapin bark tannin solution were mixed evenly at 20°C, and a protein additive was slowly added dropwise. After continuing stirring for 10 minutes, the pH value of the solution was adjusted to 7. After filtering, the precipitate was washed with water to obtain metal-polyphenol nanoparticles. The metal-polyphenol nanoparticles were pyrolyzed at 500°C for 1 hour under a nitrogen atmosphere, and then cooled, washed, and dried to obtain a metal oxide / polyphenol biochar adsorbent.

[0040] Example 3 Metal oxide / polyphenol biochar adsorbent, the mass ratio of each raw material is copper sulfate: catechin: protein additive = 1:1:0.1; among which, the protein additive is amino acid and small molecule polypeptide in a mass ratio of 1:2.

[0041] Preparation method of metal oxide / polyphenol biochar adsorbent: S11. The copper sulfate and catechin were mixed with deionized water to obtain a copper sulfate solution and a catechin solution; S12. The copper sulfate solution and the catechin solution were mixed evenly at 30°C, and the protein additive was slowly added dropwise. After continuing to stir for 10 minutes, the pH value of the solution was adjusted to 8. After filtering, the precipitate was washed with water to obtain metal-polyphenol nanoparticles. The metal-polyphenol nanoparticles were pyrolyzed at 900°C for 2 hours under a nitrogen atmosphere, and then cooled, washed and dried to obtain a metal oxide / polyphenol biochar adsorbent.

[0042] Example 4 Metal oxide / polyphenol biochar adsorbent, the mass ratio of each raw material is cerium sulfate: tannic acid: protein additive = 0.6:1:0.3; among which, the protein additive is amino acid and small molecule polypeptide with a mass ratio of 1:3.

[0043] Preparation method of metal oxide / polyphenol biochar adsorbent: S11. The cerium sulfate and tannic acid were mixed with deionized water to prepare a cerium sulfate solution and a tannic acid solution; S12. Evenly mix the cerium sulfate solution and the tannic acid solution at 22°C, slowly drop the protein additive, continue stirring for 10 minutes, and then adjust the pH value of the solution to 7; after filtering, wash the precipitate with water to obtain metal-polyphenol nanoparticles. The metal-polyphenol nanoparticles are pyrolyzed at 600°C for 1 hour under a nitrogen atmosphere, cooled, washed, and dried to obtain a metal oxide / polyphenol biochar adsorbent.

[0044] Example 5 Metal oxide / polyphenol biochar adsorbent, the mass ratio of each raw material is cerium sulfate: tannic acid: protein additive = 0.8:1:0.4; among which, the protein additive is amino acid and small molecule polypeptide with a mass ratio of 3:1.

[0045] Preparation method of metal oxide / polyphenol biochar adsorbent: S11. The cerium sulfate and tannic acid were mixed with deionized water to obtain a cerium sulfate solution and a tannic acid solution; S12. Evenly mix the cerium sulfate solution and the tannic acid solution at 26°C, slowly drop the protein additive, continue stirring for 10 minutes, and then adjust the pH value of the solution to 8; after filtering, wash the precipitate with water to obtain metal-polyphenol nanoparticles. The metal-polyphenol nanoparticles are pyrolyzed at 850°C for 1 hour under a nitrogen atmosphere, cooled, washed, and dried to obtain a metal oxide / polyphenol biochar adsorbent.

[0046] Comparative Example 1 Compared with Example 1, the only difference is that no protein additive is added to the adsorbent raw material, and the other raw materials and preparation method are the same as those in Example 1.

[0047] Comparative Example 2 Compared with Example 1, the only difference is that high temperature cracking is eliminated during the preparation of the adsorbent, and the raw materials and other preparation steps are the same as those in Example 1.

[0048] Comparative Example 3 Compared with Example 1, the only difference is that no protein additive is used in the adsorbent raw material, and high-temperature pyrolysis is not used in the preparation method. The remaining principles and preparation methods are the same as those in Example 1.

[0049] Test example The following performance tests were performed on the adsorbents prepared in the above examples and comparative examples: 1. Determine the specific surface area: grind the sample to less than 200 mesh, dry it at 105°C for 24 hours, cool it to room temperature and store it in a desiccator, turn on the fully automatic specific surface area and porosity analyzer, check the nitrogen and helium gas cylinders to ensure that there is enough gas, accurately weigh 0.2g of the sample, put the sample into the sample tube, install the sample tube on the analyzer, set the degassing temperature to 300°C, the degassing time to 4 hours, and evacuate to 10 -3 Pa, set the adsorption temperature to liquid nitrogen temperature (-196°C), select 6 to 8 relative pressure points for measurement, wait for adsorption equilibrium (about 10 to 15 min / point), use the instrument software to perform BET calculations, and obtain the specific surface area (m 2 / g).

[0050] 2. Determination of Al 3+Concentration: Prepare 0, 0.2, 0.4, 0.6, 0.8, 1.0 mg / L Al 3+ Standard solution, add indicator and buffer solution to each standard solution, measure the absorbance at 545nm wavelength with a spectrophotometer, and plot Al 3+ Concentration-absorbance standard curve. Take appropriate amount of filtrate from the preparation of adsorbent in Examples and Comparative Examples 1-3, dilute to the measurement range if necessary, add indicator and buffer solution, shake well, let stand for 5 minutes to allow the color to fully develop, measure the sample absorbance at a wavelength of 545nm using a spectrophotometer, and calculate the Al content in the sample according to the standard curve. 3+ concentration.

[0051] 3. Experiment on removal of soluble organic pollutants: Fresh leachate samples were collected from landfills, filtered with a 0.45 μm filter membrane to remove suspended matter, and the original TOC was determined. 0.5 g of the adsorbent of the embodiment group and the control group was added to 1 L of the sample, and the sample was shaken in a constant temperature oscillator at 25°C and 150 rpm for 24 h. The TOC was determined after filtration.

[0052] The experimental results are shown in Table 1.

[0053] Table 1 Specific surface area and removal effect of adsorbents in the example group and control group .

[0054] The specific surface area and removal effect of the adsorbents in the embodiment group and the control group are shown in Table 1. The specific surface area of ​​the embodiment group (1-5) ranges from 412.5 to 529.8 m² / g, which is generally higher than that of the control group. Among them, the specific surface area of ​​embodiment 3 is the highest, reaching 529.8 m² / g. The specific surface area of ​​comparative example 1 (488.6 m² / g) is comparable to that of the embodiment group, while the specific surface areas of comparative examples 2 and 3 are significantly lower, only 97.8 and 101.3 m² / g, respectively. This shows that the high temperature cracking process plays a key role in increasing the specific surface area of ​​the material.

[0055] Only Example 1, Comparative Examples 1, 2, and 3 provide Al³⁺ concentration data. Example 1 has the lowest Al³⁺ concentration (0.018 mg / L), indicating that it has the best metal ion fixation effect. Comparative Examples 1 and 3 have significantly higher Al³⁺ concentrations (0.156 and 0.198 mg / L, respectively), indicating that the addition of protein additives will promote the fixation of metal ions, and protein additives as "cross-linking agents" can enhance the binding force between polyphenols and metal oxides.

[0056] The TOC concentration of the leachate of all samples before treatment was 1120 mg / L. The TOC concentration of the example groups (1~5) after treatment ranged from 54.63 to 99.82 mg / L, and the removal rate reached 91.09% to 95.12%, showing excellent organic matter removal ability. Among them, the treatment effect of Example 1 was the best, and the TOC was reduced to 54.63 mg / L. The treatment effect of the comparative examples was significantly poorer, especially for Comparative Examples 2 and 3, where the TOC concentration after treatment was still as high as 403.89 mg / L and 584.39 mg / L, and the removal rate was only 63.94% and 47.82%. Although the treatment effect of Comparative Example 1 (311.74 mg / L) was better than that of Comparative Examples 2 and 3, it was still significantly lower than that of the example group.

[0057] Comprehensive analysis leads to the following conclusions: (1) The addition of protein additives is crucial to material performance. The lack of protein additives (Comparative Examples 1 and 3) will affect the binding effect between polyphenols and metal oxides, thereby affecting the removal effect of organic matter. (2) The high-temperature pyrolysis process also has an important influence on material performance. The specific surface area and organic matter removal effect of the sample without high-temperature pyrolysis (Comparative Example 2) are greatly reduced. (3) The synergistic effect of protein additives and high-temperature pyrolysis process (Example Group) can significantly increase the specific surface area of ​​the material, enhance the binding force between polyphenols and metal oxides, and greatly improve the removal effect of organic matter. (4) In the Example Group, different preparation conditions (such as metal salt type, plant polyphenol type, reaction temperature, high-temperature pyrolysis temperature, etc.) will affect the material performance, resulting in differences in specific surface area and organic matter removal effect. (5) Example 1 shows the best comprehensive performance, with high specific surface area, low metal ion leakage and the best organic matter removal effect, which may be related to its specific preparation conditions (such as the use of aluminum sulfate / aluminum chloride, bayberry tannin, 750℃ high-temperature pyrolysis, etc.).

[0058] In conclusion, this study demonstrated that the performance of metal oxide / polyphenol biochar adsorbents can be significantly improved by optimizing the raw material composition and preparation process, especially by introducing protein adjuvants and high-temperature pyrolysis steps, providing a highly efficient adsorbent for the treatment of high-concentration organic pollutants such as landfill leachate.

[0059] Finally, it should be noted that: Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. Metal oxide / polyphenol biochar adsorbent, characterized in that: The product is obtained by mixing metal salt, plant polyphenol and protein additive in a mass ratio of (1 / 3~1):1:(0.1~0.5) and then undergoing high-temperature cracking.

2. The metal oxide / polyphenol biochar adsorbent according to claim 1, characterized in that: The protein additive is amino acid and / or small molecule polypeptide.

3. The metal oxide / polyphenol biochar adsorbent according to claim 1, characterized in that: High temperature cracking at 500~900℃ under nitrogen atmosphere for 1~2h.

4. The metal oxide / polyphenol biochar adsorbent according to claim 1, characterized in that: The metal salt includes any one or more of aluminum sulfate, aluminum chloride, zirconium sulfate, copper sulfate, cerium sulfate, and bismuth sulfate.

5. The metal oxide / polyphenol biochar adsorbent according to claim 1, characterized in that: The plant polyphenols include any one or more of bayberry tannin, wattle bark tannin, catechin and tannic acid.

6. The method for preparing the metal oxide / polyphenol biochar adsorbent according to any one of claims 1 to 5, characterized in that: The following steps are involved: After the metal salt solution and the plant polyphenol solution are evenly mixed, a protein additive is added and stirred evenly, the pH of the solution is adjusted to 7-8 to generate a precipitate, the precipitate is obtained by filtration, the precipitate is cracked at high temperature, cooled, washed and dried.

7. The preparation method according to claim 6, characterized in that: Pyrolysis was carried out at 500~900℃ for 1~2h under nitrogen atmosphere.

8. The preparation method according to claim 6, characterized in that: The metal salt solution and the plant polyphenol solution are mixed evenly at 20-30°C.

9. Use of the metal oxide / polyphenol biochar adsorbent as claimed in any one of claims 1 to 5 in adsorbing soluble organic pollutants in landfill leachate.

10. The use according to claim 9, characterized in that The adsorption conditions are: normal pressure, initial pH of the adsorbed landfill leachate is 3~10, reaction temperature is 10~40℃, rotation speed is 100~250rmp, and adsorbent dosage is 0.1~1.0g / L.