A carbon-based composite material, a preparation method and application thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CENTRAL SOUTH UNIVERSITY OF FORESTRY AND TECHNOLOGY
- Filing Date
- 2024-02-27
- Publication Date
- 2026-06-26
Smart Images
Figure CN118239608B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of water treatment technology, specifically relating to a carbon-based composite material, its preparation method, and its application. Background Technology
[0002] With the development of industry and agriculture and the improvement of social standards, water pollution has become one of the world's most important ecological problems, such as heavy metal pollution and eutrophication caused by nitrogen and phosphorus. Currently, wastewater treatment technologies mainly include adsorption, chemical precipitation, and biological methods. Nitrogen and phosphorus wastewater is mainly treated through a combination of biological and chemical methods. Nitrogen removal relies on microorganisms to achieve ammonification-nitrification-denitrification-N2 conversion. Phosphorus removal can be achieved using activated sludge anaerobic-aerobic methods or by adding chemical agents such as aluminum salts and iron salts to combine with phosphorus in the wastewater to form chemical sludge precipitation. Adsorption methods are often used for the removal of heavy metals from wastewater due to their ease of operation, variety of adsorbents, low cost, high efficiency, and ease of treatment. Some studies have found that adsorbents can also be used for nitrogen and phosphorus removal from wastewater.
[0003] Biochar is a pyrolysis product of waste biological materials under oxygen-limited conditions. Due to its large specific surface area, abundant pore space, high surface energy, and readily available raw materials, as well as its simple preparation process, it is widely used as an adsorbent material in wastewater treatment. However, biochar itself has almost no ability to generate strong oxidizing substances such as hydroxyl radicals through advanced oxidation. The adsorption and desorption effects of raw biochar are limited, and the adsorbed waste biochar is difficult to separate from the aqueous phase. With the development of materials science, many scholars have turned their attention to the modification of biochar, attempting to improve its specific surface area, pore structure, and surface functional groups through physical or chemical activation, in order to obtain modified biochar materials with higher pollutant removal potential. Chinese invention patent CN107983300B discloses a manganese dioxide-modified biochar composite material and its preparation method. In this material, manganese dioxide modification of the biochar surface reduces the aggregation of biochar particles, thereby increasing the specific surface area of the biochar and improving the composite material's adsorption capacity for heavy metals. Chinese invention patent application CN117303491A discloses an iron / calcium oxide-loaded biochar and its application in wastewater treatment. The loading of iron and calcium increases the specific surface area and pore structure of the biochar, improving its adsorption capacity. Furthermore, the iron oxides can selectively adsorb phosphate ions in the water, while calcium ions combine with phosphate ions to form relatively stable calcium phosphate precipitates, achieving efficient phosphorus removal. Chinese invention patent CN106115938B discloses a magnetic biochar-loaded photosynthetic bacteria material. This material achieves strong adsorption and microbial degradation effects by gradually loading nano-iron oxides and photosynthetic bacteria onto the surface of the biochar, thereby improving its ability to degrade organic matter and remove nitrogen and phosphorus from wastewater.
[0004] However, the content and types of pollutants in urban sewage, such as antibiotics and persistent pollutants, are constantly increasing, leading to a gradual increase in the difficulty of sewage treatment. Microorganisms are unable to completely degrade pollutants, chemical agents are costly and prone to causing secondary pollution, and single treatment methods cannot meet the requirements for stable and compliant sewage discharge. Economical and efficient sewage treatment technologies remain the pursuit of technical personnel, and the innovative synthesis and application of biochar composite materials remain a research hotspot. Summary of the Invention
[0005] To address the shortcomings of existing wastewater treatment technologies, such as poor efficiency and high costs, one objective of this invention is to provide a carbon-based composite material. This material uses biochar as a matrix and is loaded with manganese oxides and magnesium oxides on its surface, exhibiting strong oxidizing and adsorption properties. A second objective is to provide a method for preparing the carbon-based composite material, using readily available raw materials and a simple method. A third objective is to provide the application of the carbon-based composite material in the treatment of nitrogen and phosphorus wastewater. The carbon-based composite material can synergistically oxidize and degrade nitrogen and phosphorus in wastewater with microorganisms, improving wastewater treatment efficiency. Furthermore, the carbon-based composite material is recyclable, making it economical and efficient.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] A carbon-based composite material includes a biochar matrix and manganese oxide and magnesium oxide supported on the surface of the biochar; the mass ratio of biochar to manganese oxide and magnesium oxide in the carbon-based composite material is 1:0.6-0.95:0.95-1.6; the specific surface area of the carbon-based composite material is 180-460 m². 2 / g, with a particle size of 6–18 nm.
[0008] A method for preparing a carbon-based composite material includes the following steps:
[0009] Step 1: Dry the biomaterials and then grind them to obtain biomass;
[0010] Step 2: The biomass is stirred and mixed evenly with a low-valent manganese salt solution and a permanganate solution to obtain a sample solution; the ratio of biomass, low-valent manganese salt and permanganate in the sample solution is 200-500g:1.5-2.5mol:1-1.5mol; the sample solution is washed, filtered and freeze-dried to obtain Mn-loaded biomass;
[0011] Step 3: Mix and grind the Mn-loaded biomass with inorganic magnesium salt at a mass ratio of 1:1 to 1.6 to obtain sample powder. Pyrolyze the sample powder at 650 to 750°C for 2 to 2.5 hours under an inert atmosphere to obtain biochar loaded with Mn and Mg bimetals, i.e., the carbon-based composite material.
[0012] This invention utilizes a mixture of two Mn compounds with different valence states with biomass, successfully loading multiple valence states of Mn onto the biomass surface. The Mn-loaded biomass is then co-ground with Mg compounds and subjected to high-temperature pyrolysis. The biomass pyrolyzes into biochar with a high surface area and numerous hydrophilic groups. Mn and Mg replace some of the -OH and -CO functional groups in the biochar, forming Mn-O and Mg-O functional groups. Mn, Mg, and C are stably combined to form a carbon-based composite material. This material retains the high specific surface area and porous interface characteristics of biochar, while also being doped with abundant metals and functional groups. It can directly generate free radicals and possesses high oxidation performance. Simultaneously, the Mg-O functional group exhibits high adsorption capacity and selectivity for phosphates and enhances the limited heavy metal stabilization capacity of biochar.
[0013] Furthermore, in step 1, the biomaterial is successively subjected to natural drying and drying at 60-80℃, and then ground and sieved to obtain biomass with a particle size of 60-80 mesh; the biomaterial is plant-derived biomaterial, preferably wetland plants.
[0014] The source of biomass determines the proportion of major elements such as C, O, and N in biochar, and affects the types and numbers of functional groups on the biochar surface, as well as its surface chemical properties. In line with green and environmentally friendly principles, this invention selects harvested wetland plants as the biomass source, resulting in biochar with a surface rich in functional groups and porous structures.
[0015] Further, in step 2, the low-valent manganese salt is a divalent manganese salt, preferably at least one of manganese acetate, manganese sulfate, and manganese chloride, more preferably manganese acetate; the permanganate is at least one of potassium permanganate, lithium permanganate, and sodium permanganate, preferably potassium permanganate.
[0016] Furthermore, the stirring time in step 2 is 20–60 min, preferably 30–40 min.
[0017] Furthermore, in step 2, the ratio of biomass, low-valent manganese salt, and permanganate in the sample solution is 250–400 g: 1.7–2.1 mol: 1.1–1.3 mol.
[0018] Furthermore, in step 3, the inorganic magnesium salt is at least one of magnesium chloride, magnesium sulfate, and magnesium nitrate, preferably magnesium chloride.
[0019] Furthermore, in step 3, the pyrolysis temperature is 700℃ and the pyrolysis time is 2 hours.
[0020] Further, in step 3, the flow rate of the inert gas in the inert atmosphere is 150-250 mL / min, and the heating rate is 5-15 °C / min; preferably, the flow rate of the inert gas is 200 mL / min, and the heating rate is 10 °C / min.
[0021] Furthermore, the inert gas is one of argon and nitrogen, preferably argon.
[0022] The present invention also provides the application of the carbon-based composite material as described above in nitrogen- and phosphorus-containing organic wastewater, comprising the following steps:
[0023] S1, after treating nitrogen and phosphorus organic wastewater through grit removal, anoxic treatment, and anaerobic treatment, pretreated wastewater is obtained;
[0024] S2, add the microbial carbon source and the carbon-based composite material to the pretreated wastewater and stir to mix evenly to obtain a homogenized mixture; wherein, the amount of the carbon-based composite material added is 2-5 kg / ton of wastewater;
[0025] S3, after the homogenized mixture is aerated and oxidized, the carbon-based composite material is separated and recovered using a magnetic field. The remaining mixture is then denitrified and discharged in compliance with standards.
[0026] Furthermore, the pH value of the pretreated wastewater in step S1 is 5-9, and the suspended solids (SS) in the pretreated wastewater are ≤220mg / L, NH3-N ≤30mg / L, TN ≤40mg / L, TP ≤30mg / L, CODcr ≤300mg / L, and BOD5 ≤200mg / L.
[0027] Furthermore, in step S2, the stirring time is 2 to 3 hours.
[0028] Furthermore, in step S3, persulfate and / or periodate are added to the homogenized mixture before the aeration oxidation treatment.
[0029] Compared with existing technologies, the carbon-based composite material, its preparation method, and its application provided by this invention have the following beneficial effects:
[0030] 1. The carbon-based composite material prepared by the preparation method provided by the present invention has a multi-layer structure, a large specific surface area, and abundant pore structure, which can provide more reaction interfaces for microorganisms and sludge to attach.
[0031] 2. The carbon-based composite material provided by this invention has a surface loaded with variable-valence metal Mn, which can enhance the oxidation of organic matter in wastewater in multiple ways, including:
[0032] (1) The material can directly generate hydroxyl radicals and superoxide radicals. These radicals have strong oxidizing properties and can directly oxidize nitrogen and phosphorus organic matter in wastewater.
[0033] (2) The manganese on the multi-interface of the material has multiple valence states. When the manganese is oxidized by free radicals, higher valence states such as heptavalent and pentavalent manganese are obtained. Then, the higher valence manganese can further oxidize the nitrogen and phosphorus organic matter adsorbed on the surface of the material.
[0034] (3) The material has a rich interface, which can realize the synergistic effect of microorganisms and chemicals, improves the reaction efficiency at the interface, overcomes the defect of low reaction efficiency of nitrogen and phosphorus in water, and improves its degradation efficiency at the interface.
[0035] (4) In an aeration oxidation system containing periodate and persulfate, the free radicals generated at the multi-interface of the material can activate periodate and persulfate to generate periodate free radicals and sulfate free radicals, further enhancing the degradation efficiency of organic nitrogen and phosphorus.
[0036] 3. The carbon-based composite material provided by this invention also has a large amount of magnesium oxide loaded on its surface, which can realize the in-situ mineralization of inorganic phosphorus and form relatively stable magnesium phosphate minerals in the sludge, which provides convenience for the resource utilization of sludge to prepare magnesium ammonium phosphate organic fertilizer.
[0037] 4. The carbon-based composite material provided by this invention is magnetic and can be separated and recycled using a magnetic field in wastewater treatment processes. Attached Figure Description
[0038] Figure 1 This is a schematic diagram of the preparation process of carbon-based composite materials in one embodiment of the present invention.
[0039] Figure 2 The image shows the characterization spectrum of the carbon-based composite material in one embodiment of the present invention, where (a) is a Fourier transform infrared spectrum and (b-e) are XPS spectra.
[0040] Figure 3 The following is a graph showing the degradation effect of different materials MV, PI, Mn / Mg@MV, and Mn / Mg@MV-PI on TPhP in one embodiment of the present invention, wherein (a) is a graph showing the degradation effect of different materials on TPhP; (b) is a graph showing the pseudo-first-order kinetic fitting results of different materials; and (c) is a graph showing the recycling effect of Mn / Mg@MV.
[0041] Figure 4 The image shows the removal effect of different materials MV, Mg@MV, Mn / Mg@MV, and Mn / Mg@MV-PI on residual inorganic phosphorus in one embodiment of the present invention. Detailed Implementation
[0042] The present invention will be described in detail below with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art, and the reagents and instruments used in the embodiments are available through conventional channels.
[0043] Example 1: Preparation and Characterization of Carbon-Based Composite Materials
[0044] 1.1 Preparation of carbon-based composite materials
[0045] Myriophyllum verticillatum was collected from a wetland park. After collection, it was washed several times with deionized water, air-dried naturally, and then dried in an oven at 60℃ for 24 hours. The dried Myriophyllum verticillatum was then pulverized into powder and passed through a 70-mesh sieve. A 0.15 mol / L manganese acetate solution and a 0.1 mol / L potassium permanganate solution were prepared. 2 g of Myriophyllum verticillatum powder was mixed with 100 mL of 0.15 mol / L manganese acetate solution and stirred continuously. Then, 100 mL of 0.1 mol / L potassium permanganate solution was slowly added to the solution, and the mixture was stirred continuously for 30 min. The resulting sample solution was washed, filtered, and freeze-dried to obtain Mn-loaded Myriophyllum verticillatum powder. The Mn-loaded Myriophyllum verticillatum powder was mixed with MgCl2 at a mass ratio of 1:1 and ground. The mixture was then pyrolyzed in a tube furnace at 700℃ for 2 h under an Ar atmosphere, with a heating rate of 10℃ / min and an Ar flow rate of 200 mL / min. A biochar loaded with Mn and Mg bimetals (modified biochar Mn / Mg@MV) was obtained, namely the carbon-based composite material.
[0046] The obtained carbon-based composite material has a biochar to manganese oxide and magnesium oxide mass ratio of 1:0.6-0.95:0.95-1.6; the specific surface area of the carbon-based composite material is 180-460 m². 2 / g, with a particle size of 6–18 nm.
[0047] As a comparison, the present invention also prepared unmodified biochar (MV) and biochar loaded only with metallic magnesium (Mg@MV) by pyrolysis at 700°C for 2 hours under Ar atmosphere.
[0048] 1.2 Characterization of carbon-based composite materials
[0049] The surface functional groups of the above-mentioned biochar materials (MV, Mn / Mg@MV) were identified by Fourier transform infrared spectroscopy (FTIR, Thermo Scientific Nicolet iS20).
[0050] Identification structure such as Figure 2As shown in (a), the surface of unmodified MV (Myriophyllum verticillata biochar) is also rich in functional groups. The peaks in the figure correspond to the stretching vibrations of different functional groups (OH groups correspond to the peak centered at 3430 cm⁻¹, aromatic CO bonds (~1048 cm⁻¹), aromatic C=C (~1420 cm⁻¹), and carbonyl C=O (~1631 cm⁻¹)). These organic functional groups provide strong support for the surface modification of biochar. The surface functional groups of modified biochar Mn / Mg@MV have changed significantly, but the aromatic functional groups C=C (~1420 cm⁻¹), C=O (~1631 cm⁻¹), and CO (~1048 cm⁻¹) are still retained. The aromatic structures can act as π-electron donors, achieving the removal of target organic pollutants in most cases through π-π electron donor-acceptor (EDA) interactions, and exhibiting a synergistic effect. On the other hand, compared with MV, the CO peak intensity of Mn / Mg@MV is weakened, while the peak representing the metal oxides at Mn-O and Mg-O (482 cm-1) is significantly enhanced, proving that the deposition of metal elements Mn and Mg is successful. The significant shift of the -OH peak further illustrates this point, in which Mn and Mg replace some of the -OH and -CO functional groups and form Mn-O and Mg-O functional groups. This indicates that manganese and magnesium are not simply loaded on the surface of biochar, but are combined by stable chemical bonds.
[0051] This invention also utilizes XPS spectroscopy (Thermo Scientific K-Alpha) to study ( Figure 2 (be) to further understand the changes in the chemical composition and surface state of the modified biochar Mn / Mg@MV.
[0052] Figure 2 (b) The XPS-Survey diagram shows that the peaks at 285.39, 532.22, 643.12 and 1304.45 eV correspond to C1s, O 1s, Mn 2p and Mg 2p, respectively. This indicates that the Mn and Mg bimetals were successfully loaded on the surface of biochar, ensuring that the carbon-based composite material could fully exert its unique role in the subsequent degradation of organophosphorus compounds. Figure 2 (c) shows the high-resolution spectral peaks of Mn 2p, with the three Mn substances located at 645.03, 642.86, and 641.56 eV, corresponding to Mn(IV), Mn(III), and Mn(II), respectively. The 647.87 eV peak is classified as a metal satellite peak. Clearly, the biochar surface is uniformly doped with abundant Mn elements in different valence states, which may play an important role in the activation of the oxidant. The fine spectra of O 1s and C 1s are shown below. Figure 2 As shown in de. Figure 2 The peak at C1s 286.6 eV in (d) and Figure 2 (e) The peak at 533.47 eV for O at 1s confirms the presence of COC functional groups on the surface of the carbon-based composite material, which corroborates the FTIR detection results. The peaks at 288.85 eV for C at 1s and 534.83 eV for O at 1s confirm the presence of CO=O groups on the material surface, i.e., the presence of -COOH groups. The peak at 531.91 eV for O confirms the presence of C=O groups on the material surface, while the peak at 530.29 eV confirms the presence of Mn-O bonds. All the above results indicate that the surface of the carbon-based composite material Mn / Mg@MV has abundant reactive groups. The CO=O groups can well explain the dehydration and decarboxylation reactions of biochar at high temperatures, and their content is not higher than that of COC groups, which indirectly confirms the abundant oxygen content on the Mn / Mg@MV surface.
[0053] Example 2: Verification of Organophosphorus Degradation and Inorganic Phosphorus Removal in Carbon-Based Composite Materials
[0054] This embodiment uses triphenyl phosphate (TPhP) as the degradation target to investigate the degradation capacity of Mn / Mg@MV for organophosphates and the removal capacity for residual inorganic phosphorus. Triphenyl phosphate (TPhP), as a typical type of organophosphate (OPE), is widely used as a flame retardant in textiles, cable insulation, plastics, and paints. In recent years, it has been frequently detected in various environments such as air, water, and sediments, and has attracted widespread attention due to its environmental persistence, accumulation, and residual toxicity.
[0055] Among the technologies for treating TPhP wastewater, the advanced oxidation process (AOP) is recognized as one of the choices because of its complete degradation and the fact that most of the degradation products are non-toxic. Studies have found that persulfate oxidation system and periodate (PI) can achieve better degradation efficiency in TPhP treatment.
[0056] This invention investigates the degradation capacity of unmodified biochar MV, PI (sodium periodate) alone, Mn / Mg@MV alone, and Mn / Mg@MV-PI system for TPhP through batch experiments, as well as the removal capacity of unmodified biochar MV, Mg@MV loaded with only Mg, Mn / Mg@MV alone, and Mn / Mg@MV-PI system for residual inorganic phosphorus.
[0057] 2.1 TPhP Degradation Experiment
[0058] Unmodified biochar MV and Mn / Mg@MV were prepared according to the method in Example 1. Triphenyl phosphate (TPhP) and sodium periodate (PI) were purchased from Shanghai McLean Biochemical Co., Ltd., and high-performance liquid chromatography-grade acetonitrile was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. All TPhP degradation experiments were conducted in 150 mL Erlenmeyer flasks at a constant temperature of 25 °C in an incubator with a shaker speed of 180 rpm. 0.1 mol / L HCl or NaOH was prepared in advance to adjust the pH of the reaction solution.
[0059] Group 1 (MV): First, 20 μM TPhP solution and a certain dose of MV (0.75 g / L) were placed in an Erlenmeyer flask and mixed thoroughly by shaking. The pH of the mixture was adjusted to 5. At predetermined time intervals, 0.5 mL of water sample was taken, and 0.5 mL of methanol was added for rapid decomposition. The residual concentration of TPhP was then quantitatively determined by high performance liquid chromatography (HPLC, Agilent 1200, Agilent Technologies). The reaction time was 150 min.
[0060] Group 2 (Mn / Mg@MV): Replace the material in Group 1 with Mn / Mg@MV, and keep the rest of the steps and dosages the same.
[0061] Group 3 (PI): Replace the material in Group 1 with 2mM sodium periodate PI, and keep the rest of the steps and dosages the same.
[0062] Group 4 (Mn / Mg@MV-PI): Replace the material in Group 1 with Mn / Mg@MV, mix thoroughly, and then add 2 mM PI to initiate the reaction. The remaining steps and amounts are the same.
[0063] The mobile phase in the high-performance liquid chromatography (HPLC) method is deionized water and acetonitrile 35:65 (V:V), the flow rate is 1 mL / min, and the wavelength of the UV-Vis spectrophotometer is 210 nm.
[0064] 2.2 TPhP Degradation Results
[0065] The results are as follows Figure 3 As shown in (a), under a reaction time of 150 minutes, Mn / Mg@MV-PI improves the degradation efficiency by 68.25% compared to Mn / Mg@MV alone, achieving a removal efficiency of 93.34%. This indicates that Mn / Mg@MV can effectively activate the oxidant PI, generating more free radicals and other oxidizing substances, thereby effectively degrading TPhP. In contrast, MV only removed 14.09% of TPhP under the same conditions, while PI alone could degrade 30.80% of TPhP. This is because PI also has a certain ability to generate free radicals, which can degrade certain pollutants.
[0066] Meanwhile, the removal process of TPhP in different systems was studied using pseudo-first-order reaction kinetics. Figure 3 (b) shows the fitting results of the pseudo-first-order reaction kinetic model. It can be seen that the PI, Mn / Mg@MV, and Mn / Mg@MV-PI systems used for TPhP degradation have high Ri values. 2 The values were 0.9259, 0.9540, and 0.9961, respectively, while the reaction system using MV alone to remove TPhP may be more appropriately classified as an adsorption reaction process. It can be seen that the Mn / Mg@MV-PI system (k = 0.0172 min) -1 The k value under ( ) is lower than that of the Mn / Mg@MV system (k = 0.0016 min) -1 The concentration was nearly 10 times higher. The results indicate that the Mn / Mg@MV-PI system can significantly enhance the degradation effect of MV on TPhP, and can effectively degrade TPhP.
[0067] 2.3 Reusability of Mn / Mg@MV
[0068] Group 2 in section 2.1 was repeated for 4 cycles, and the residual concentration of TPhP was measured at the end of each cycle. The results are as follows: Figure 3 As shown in (c), after four cycles, Mn / Mg@MV was still able to degrade 75.16% of TPhP within 150 minutes. This indicates that the stability of the functional group structure in the FTIR analysis of Example 1 and the valence state transition of Mn in the XPS analysis are the main factors contributing to the good reusability stability of Mn / Mg@MV. On the other hand, the decrease in the catalytic performance of Mn / Mg@MV is attributed to the filling of the biochar pores, depletion of active sites, and a decrease in specific surface area, leading to a decline in adsorption capacity. The results demonstrate that the Mn / Mg@MV prepared in this invention exhibits good reusability stability.
[0069] 2.4 Removal of Inorganic Phosphorus After TPhP Degradation Experiment
[0070] Because of the potential environmental hazards of inorganic phosphates in TPhP degradation residues, this invention also investigated the removal capabilities of unmodified biochar MV, Mg@MV loaded with only Mg, Mn / Mg@MV alone, and the Mn / Mg@MV-PI system for residual inorganic phosphorus. The total phosphorus values of simulated TPhP wastewater before and after the reaction of each system were measured, and then the total phosphorus removal rates were compared. The results are as follows: Figure 4As shown, the total phosphorus removal rate of the Mn / Mg@MV-PI system is only 34.13%. This low rate is likely due to incomplete TPhP degradation, possibly indicating the presence of a large amount of TPhP degradation intermediates. Compared to the 3.85% phosphorus removal rate of MV, the total phosphorus removal rate of the Mn / Mg@MV-PI system is 30.28% higher. The total phosphorus removal rate of the Mn / Mg@MV system is also significantly higher than that of MV and Mg@MV, suggesting that magnesium doping can effectively and specifically remove orthophosphate. The results indicate that Mn / Mg@MV can effectively remove residual inorganic phosphorus, and its removal effect is even better when used in conjunction with an oxidant.
[0071] In summary, the carbon-based composite material Mn / Mg@MV provided by this invention retains the characteristics of biochar while also possessing the ability to generate strong oxidizing substances such as hydroxyl radicals through advanced oxidation, effectively degrading oxidized organic nitrogen and phosphorus. On the other hand, Mn / Mg@MV can activate oxidants, and the oxidation system formed by its combination with oxidants such as PI has high organic phosphorus degradation efficiency and residual inorganic phosphorus removal capacity. Furthermore, Mn / Mg@MV is simple to prepare and has excellent reusability, making it a reliable material for nitrogen and phosphorus wastewater treatment.
[0072] Example 3: Application of carbon-based composite materials in nitrogen and phosphorus wastewater treatment
[0073] One ton of municipal sewage was collected from a certain area. The sewage was then subjected to pretreatment sequentially through a coarse screen, a sewage lift pump station, a fine screen, a vortex grit chamber, an anoxic treatment, and an anaerobic treatment to obtain pretreated wastewater. Using conventional testing methods in this field, the pretreated wastewater was found to contain 210 mg / L CODcr, 150 mg / L BOD5, 60 mg / L suspended solids (SS), 20 mg / L NH3-N, 25 mg / L TN, 5 mg / L TP, and a pH of 6.
[0074] Subsequent treatment using a modified MSBR process: Before aeration oxidation, based on the total organic matter content, biodegradability, nitrogen and phosphorus content, persistent pollutant content, and water temperature of the pretreated wastewater, 4.5 kg of carbon-based composite material (preparation method consistent with Example 1) and 1 kg of glucose (as carbon source) are added to each ton of pretreated wastewater. The mixture is stirred for 1 hour to ensure thorough mixing, allowing the carbon-based composite material, microorganisms, and organic matter in the wastewater to adhere uniformly. The reactants are concentrated at the interface of the carbon-based composite material or sludge particles, resulting in a homogenized mixture. The homogenized mixture is then discharged into an aeration reaction tank for aeration oxidation treatment. After repeated aeration, the carbon-based composite material is recovered by sedimentation using magnetic field separation. The carbon-based composite material that still retains its magnetic properties is retained in the aeration reaction tank for reuse. The remaining mixture is discharged into a denitrification tank for denitrification to convert nitrate in the wastewater into nitrogen. The sludge is recycled or disposed of as a resource. The effluent is disinfected and tested to meet standards before being discharged. In this embodiment, the TP content of a suitable amount of effluent was measured to be less than 0.4 mg / L, which means that the TP removal rate of municipal sewage in this embodiment is greater than 92%.
[0075] The above embodiments should be understood as being used only to illustrate the present invention more clearly, and not to limit the scope of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art fall within the scope defined by the appended claims.
Claims
1. A carbon-based composite material, characterized in that, The carbon-based composite material comprises a biochar matrix, manganese oxide and magnesium oxide supported on the surface of the biochar; the mass ratio of biochar to manganese oxide and magnesium oxide in the carbon-based composite material is 1:0.6~0.95:0.95~1.6; the specific surface area of the carbon-based composite material is 180~460 m2 / g, and the particle size is 6~18nm. The method for preparing the carbon-based composite material includes the following steps: Step 1: Dry and grind the biomaterial to obtain biomass; Step 2: Mix the biomass with a low-valent manganese salt solution and a permanganate solution to obtain a sample solution; the ratio of biomass, low-valent manganese salt, and permanganate in the sample solution is 200~500 g: 1.5~2.5 mol: 1~1.5 mol; wash, filter, and freeze-dry the sample solution to obtain Mn-loaded biomass; Step 3: Mix and grind the Mn-loaded biomass with inorganic magnesium salt at a mass ratio of 1:1~1.6 to obtain sample powder; pyrolyze the sample powder at 650-750℃ for 2~2.5 h under an inert atmosphere to obtain biochar loaded with Mn and Mg bimetals, i.e., the carbon-based composite material; In step 2, the low-valent manganese salt is a divalent manganese salt; In step 3, the inorganic magnesium salt is at least one of magnesium chloride, magnesium sulfate, and magnesium nitrate. Mn and Mg replace some of the -OH and -CO functional groups in biochar, forming Mn-O and Mg-O functional groups. Mn, Mg, and C are stably combined to form carbon-based composite materials.
2. The carbon-based composite material according to claim 1, characterized in that, In step 1, the biomaterial is successively dried naturally, then dried at 60-80℃, and then ground and sieved to obtain biomass with a particle size of 60-80 mesh; the biomaterial is plant-derived biomaterial.
3. The carbon-based composite material according to claim 1, characterized in that, The biological material is wetland plant.
4. The carbon-based composite material according to claim 1, characterized in that, In step 2, the low-valent manganese salt is at least one of manganese acetate, manganese sulfate, and manganese chloride; the permanganate is at least one of potassium permanganate, lithium permanganate, and sodium permanganate.
5. The carbon-based composite material according to claim 1, characterized in that, The stirring time in step 2 is 20-60 min; the ratio of biomass, low-valent manganese salt and permanganate in the sample solution is 250-400 g: 1.7-2.1 mol: 1.1-1.3 mol.
6. The carbon-based composite material according to claim 1, characterized in that, The inert gas in the inert atmosphere has a flow rate of 150~250 mL / min and a heating rate of 5~15℃ / min; the inert gas is either argon or nitrogen.
7. The carbon-based composite material according to claim 6, characterized in that, The inert gas is argon.
8. The application of the carbon-based composite material according to any one of claims 1-7 in nitrogen-phosphorus organic wastewater, characterized in that, Includes the following steps: S1, after treating nitrogen and phosphorus organic wastewater through grit removal, anoxic treatment, and anaerobic treatment, pretreated wastewater is obtained; S2, add microbial carbon source and carbon-based composite material to pretreated wastewater and stir to obtain homogenized mixture; wherein, the amount of carbon-based composite material added is 2~5 kg / ton of wastewater; S3, after aeration and oxidation treatment of the homogenized mixture, the carbon-based composite material is separated and recovered by magnetic field, and the remaining mixture is discharged after denitrification treatment to meet the standards.
9. The application according to claim 8, characterized in that, The pH value of the pretreated wastewater in step S1 is 5~9, and the suspended solids (SS) in the pretreated wastewater are <220 mg / L, NH3-N <30 mg / L, TN <40 mg / L, TP <30 mg / L, CODcr <300 mg / L, and BOD5 <200 mg / L.
10. The application according to claim 8, characterized in that, In step S2, the stirring time is 2-3 hours.
11. The application according to claim 8, characterized in that, In step S3, persulfate and / or periodate are added to the homogenized mixture before the aeration oxidation treatment.