Iron-based hydrothermal carbon catalytic material as well as preparation method and application thereof

Abstract

The invention relates to a preparation method and application of an iron-based hydrothermal carbon catalytic material. The catalytic material takes reed biomass as a carbon-based carrier and ferric sulfate heptahydrate as an iron precursor. The iron-based hydrothermal carbon catalytic material is prepared through one-step acid etching, hydrothermal carbonization and metal doping, the preparation steps are simple, operation is convenient, and meanwhile generation of a furan ring product and doping of iron can be achieved. The obtained material is high in stability and can be repeatedly utilized. And the reed powder is easy to obtain and low in cost, so that the preparation cost is greatly reduced, and a new idea is provided for effectively solving the water eutrophication problem. The product has a good degradation effect on DCF in wastewater under the condition that a cocatalyst L-cysteine is added. According to the work, Fe < 3 + > is promoted to be converted into Fe < 2 + > through the combination of the reed biomass resource utilization product and the cocatalyst L-Cys, so that a new thought is provided for improving the catalytic reaction efficiency of a heterogeneous persulfate system, and a new method is provided for treating DCF in actual water.

Description

Technical Field

[0001] The present invention belongs to the technical fields of environmental functional materials and new water treatment technologies, and particularly relates to an iron-based hydrothermal carbon catalytic material, a preparation method thereof, and an application thereof in a water body polluted by non-steroidal anti-inflammatory drugs. Background Art

[0002] In recent years, environmental pollution problems caused by the abuse and unreasonable treatment of pharmaceutical products and personal care products (PPCPs) have begun to attract attention at home and abroad. More than 160 PPCPs have been detected in different water environments (surface water, groundwater, sewage treatment plants, sediments, etc.) in countries such as the United States, Europe, and China. As a typical type of PPCPs drugs, non-steroidal anti-inflammatory drugs (NSAIDs) have anti-inflammatory, analgesic, and antipyretic effects, and are clinically used for the treatment of diseases such as osteoarthritis and rheumatoid arthritis. They are one of the most widely used drug types globally. Diclofenac (DCF), as a commonly used non-steroidal anti-inflammatory drug (NSAIDs), has anti-inflammatory, analgesic, and antipyretic effects, and is clinically used for the treatment of diseases such as osteoarthritis and rheumatoid arthritis. It is one of the most widely used drug types globally and is also one of the PPCPs with relatively high detection levels in surface water and groundwater. Since traditional sewage treatment technologies cannot effectively treat excessive DCF, the remaining DCF is thus discharged into water bodies in large quantities. DCF exposed to the water environment for a long time will cause irreversible damage to aquatic organisms and produce a bioaccumulation effect, further endangering human health and safety and the stability of the ecological environment. Therefore, it is necessary to explore an economical and efficient method to degrade DCF in water.

[0003] Currently, the treatment technologies for DCF-polluted wastewater are relatively mature, mainly including adsorption method, membrane separation method, biological method, advanced oxidation method, etc. Persulfate (PS) advanced oxidation technology is a new type of advanced oxidation technology based on sulfate radicals (SO 4 • ), which has the characteristics of fast rate, thorough reaction, mild reaction conditions, etc., and is widely used in the treatment of organic wastewater, and is favored by domestic and foreign research scholars. Persulfate activation is the key and difficult point in this technology. Currently, common persulfate activation methods include thermal activation, alkali activation, ultraviolet activation, ultrasonic activation, and transition metal activation, etc. Among them, the transition metal activation method has a rapid reaction, simple operation, and does not require additional energy, and is one of the most commonly used methods for activating persulfate to degrade organic pollutants.

[0004] Studies have shown that there are problems in the degradation of organic pollutants by transition metal ions activating persulfate, such as the secondary pollution of the environment caused by the residue or leaching of metal ions, the easy aggregation of transition metals and the susceptibility to pH. At present, transition metals are often dispersed and loaded on carbon-based carriers to improve the stability of the catalyst while enhancing its catalytic performance. Research shows that carbon-based carriers (such as graphene, carbon nanotubes, carbon nitride, etc.) have attracted much attention due to their large specific surface area, rich functional groups, and numerous pores, and are excellent carriers for preparing transition metal atom catalysts. However, the preparation costs of these materials are high, they are toxic to the environment, and it is difficult to prepare them on a large scale. Therefore, it is necessary to develop a carbon-based carrier with low cost and wide applicability. Hydrothermal carbon (HTCC) is a new type of carbon material prepared through the hydrothermal carbonization process, which has attracted extensive attention due to its advantages of environmental friendliness, energy conservation, low cost, wide source, and simple preparation method. Compared with most chemical processes, the raw materials used in the hydrothermal carbonization process are mostly biomass raw materials with thermal stability and low volatility, and usually use H 2 O as the reaction solvent. The hydrothermal carbonization process is carried out in a low-oxygen or oxygen-free low-temperature (100~300 o °C) closed environment. After the material stays in this environment for a period of time, a dehydration and decarboxylation reaction occurs to form hydrothermal carbon. Moreover, compared with organic solvents, water as a solvent can improve the selectivity and activity of the material. Hydrothermal carbon (HTCC) contains a large number of oxygen-containing functional groups on its surface, which can activate persulfate (PDS) to generate active substances such as OH• and SO 4 •− etc., and is an excellent carrier for transition metals. Reed contains a large amount of cellulose, which can be converted into glucose after hydrolysis. If an appropriate method is used to convert reed biomass into hydrothermal carbon materials and apply them to the field of degrading environmental pollutants, it will play an important role in alleviating the environmental pollution problem of reed biomass in water bodies and responding to the national strategy of high-value utilization of agricultural waste. However, after the hydrothermal reaction, cellulose continues to maintain its cellulose state and is difficult to be effectively converted into polyfuran products. Therefore, how to hydrolyze cellulose into glucose is an important challenge for the conversion of reed biomass into HTCC. Studies have shown that inorganic acids, organic acids, and solid acid catalysis technologies are commonly used in biomass hydrolysis. Therefore, this study intends to use the method of acid pretreatment to hydrolyze the cellulose in reed so that it can be effectively converted into polyfuran products. Preparing a carbon-supported metal catalyst (HTCC-Fe) using hydrothermally carbonized reed biomass as the transition metal Fe carrier is a new idea for the resource utilization of reed as abandoned biomass waste. It not only protects the ecological environment, solves the problem of waste disposal, but also improves its economic value, and is worthy of attention and research.

[0005] Although Fe 2+ and Fe 3+Ions, as transition metal ions, can all activate PDS to generate SO 4 •− , but the activation efficiency of Fe 3+ ions is much lower than that of Fe 2+ . Therefore, the more Fe 2+ ions there are in the system, the faster the degradation rate of the system. However, as the reaction time progresses, Fe 2+ will be oxidized to Fe 3+ after activating PDS, resulting in a decrease in the activation efficiency of PDS. To promote the activation of PDS, the research chose to add a co-catalyst L-cysteine (L-Cys) to the system, making Fe 3+ be reduced to Fe 2+ , ensuring the activation efficiency.

[0006] The present invention is expected to synthesize an iron-based hydrothermal carbon catalytic material with low cost and good catalytic performance through hydrothermal carbonization, acid etching, metal doping and other means, and at the same time add a co-catalyst to improve the activation efficiency, providing a promising technology for the treatment of DCF wastewater. Summary of the Invention

[0007] The technical problem to be solved by the present invention is: aiming at the technical problems existing in the prior art, to develop an iron-based hydrothermal carbon catalytic material with low cost and high removal efficiency for DCF-polluted water bodies in the environment.

[0008] A preparation method of an iron-based hydrothermal carbon catalytic material proposed by the present invention. Using the reed from Dongting Lake in Hunan as the hydrothermal carbon raw material and FeSO 4 ·7H 2 O as the metal precursor, an iron-based hydrothermal carbon catalytic material (HTCC-Fe) is prepared in one step. During the hydrothermal process, the addition of Fe can promote the decarboxylation reaction of lignocellulose, increase the content of lactone groups and phenolic hydroxyl groups, reduce the destruction of surface oxygen-containing functional groups at high temperature, and enhance the catalytic activity of the composite material. The oxygen-containing functional groups on the surface of the hydrothermal carbon can form complexes with Fe, inhibiting the leaching of Fe, and due to the presence of iron, the discrete polyfuran rings in HTCC are linked together, improving the stability of the material.

[0009] (1) The final catalytic material is prepared by the hydrothermal carbonization method, which specifically includes the following steps: Weigh 2 g of FeSO 4 ·7H 2 O and place it in a 1.9 mol·L −1 sulfuric acid solution, and stir well until dissolved; Then add 2 g of crushed reed powder and stir evenly to make the powder completely immersed in the solution, and let it stand for 24 h to obtain mixture A; Transfer the mixture A to a high-pressure reactor, heat it at a certain temperature (180 °C) for 9 h, and take it out after cooling. After vacuum filtration, wash it repeatedly with ethanol and deionized water three times each, and dry the material in a vacuum oven for 24 h, then take it out to obtain the iron-based hydrothermal carbon catalytic material B.

[0010] The prepared iron-based hydrothermal carbon catalytic material is characterized in that the catalytic material is prepared from reed biomass as a raw material to obtain a carbon-based support, and Fe is doped thereon.

[0011] During the above preparation process, the reed powder used all comes from Dongting Lake in Hunan.

[0012] In the above preparation method, the dilute sulfuric acid used has a volume fraction of 10%.

[0013] In the above preparation method, the Fe precursor FeSO 4 ·7H 2 O has a mass ratio to the mass of reed powder of 1:1.

[0014] Use the iron-based hydrothermal carbon catalytic material prepared by the method of the present invention to remove DCF in wastewater, and the DCF concentration is 20 mg / L.

[0015] Compared with the prior art, the advantages of the present invention are as follows: The hydrothermal carbon catalytic material of the present invention uses H 2 O as a reaction solvent, reacts in an anaerobic environment at low temperature, has higher activity, and contains a large number of oxygen-containing groups on the surface, which is more conducive to the activation of PDS.

[0016] The present invention uses Fe doping on the surface of the hydrothermal carbon material, which promotes the decarboxylation reaction of lignocellulose, increases the content of lactone groups and phenolic hydroxyl groups, reduces the destruction of surface oxygen-containing functional groups at high temperature, improves the catalytic activity of the composite material, and due to the presence of iron, the discrete polyfuran rings in HTCC are linked together, improving the stability of the material.

[0017] The present invention uses an acid etching method to make the material form a smooth spherical structure, and the glucose formed by acid treatment and hydrolysis of lignocellulose is more easily converted into polyfuran, which is more conducive to electron transfer.

[0018] The iron-based hydrothermal carbon catalytic material of the present invention is prepared by one-step hydrothermal carbonization, with simple steps and convenient operation.

[0019] The matrix material used in the present invention becomes a smooth hydrothermal carbon sphere after acid etching and hydrothermal treatment. This structure makes the functional groups closely combined together, which is conducive to electron transfer and further promotes the activation of PDS.

[0020] The iron-based hydrothermal carbon catalytic material of the present invention uses reed biochar as a carbon-based carrier to prepare a metal atom-doped hydrothermal carbon catalytic material, which can provide a new way for the resource utilization of waste reed biomass and effectively alleviate the pollution problem of reed biomass to the water environment.

[0021] The iron-based hydrothermal carbon catalytic material of the present invention has high reusability, reduces preparation costs and is economical and efficient.

[0022] The iron-based hydrothermal carbon catalytic material of the present invention has a good removal effect on DCF, and can achieve efficient degradation when the material dosage and persulfate dosage are relatively low. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of scanning electron microscope of iron-based hydrothermal carbon catalytic material B (b) and reed-based hydrothermal carbon catalytic material C (a) of Example 1 of the present invention; Figure 2 It is the X-ray diffraction (XRD) spectrum of the iron-based hydrothermal carbon catalytic material B and the reed-based hydrothermal carbon catalytic material C of Example 1 of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Embodiment 1: (1) The catalytic material is prepared by a one-step hydrothermal carbonization method, which specifically includes the following steps: Weigh 2 g FeSO 4 7H 2 O at 1.9 mol·L −1 2 g of crushed reed powder was added to a sulfuric acid solution and stirred until dissolved. Then 2 g of crushed reed powder was added and stirred evenly so that the powder was completely immersed in the solution. The mixture was allowed to stand for 24 h to obtain a mixture A. The mixture A was then transferred to a high-pressure reactor and heated at a certain temperature (180 ° C) for 9 h. After cooling, it was taken out. After vacuum filtration, it was repeatedly washed with ethanol and deionized water for 3 times each. The material was dried in a vacuum oven for 24 h and finally ground to obtain an iron-based hydrothermal carbon catalytic material B.

[0026] As described above, reed-based hydrothermal carbon catalytic material C was synthesized by the same method without adding copper sulfate heptahydrate.

[0027] The electron microscope scanning of catalytic material B and catalytic material C is shown in Figure 1 shown. Figure 1It is shown that the appearances of the prepared catalytic materials B and C are both black and have a spherical structure with irregular arrangement. Tiny particles and flaky Fe particles are doped on the surface of catalytic material B. The X-ray diffraction (XRD) patterns of catalytic material B and catalytic material C are as shown in Figure 2 . The spectral structures of the two materials are basically the same. An obvious diffraction peak is detected at 26°, and this diffraction peak corresponds to the broad diffraction peak of the carbon (002) crystal plane

[81] , which means that the introduction of Fe does not destroy the structure of HTCC itself. In addition, diffraction peaks located at 33° and 36° are also detected in the XRD spectrum of catalytic material B, corresponding to the (104) and (110) of α-Fe 2 O 3 respectively. This preliminarily indicates the successful doping of Fe.

[0028] Example 2: The experiment of treating DCF in wastewater with the iron-based hydrothermal carbon catalytic material of the present invention includes the following steps: Take 100 mL of 20 mg·L −1 DCF solution in a beaker, and add 0.03 g of HTCC-Fe and 0.1 mM of L-Cys solution. Place the beaker on a magnetic stirrer and adsorb it in the dark box for 30 min at 25°C and 400 r / min. After 30 min, the material reaches the adsorption equilibrium, and then add 1 mM of PDS solution. Samples are taken at the 0th, 10th, 20th, and 30th min during the adsorption process. After adding PDS, samples are taken at the 5th, 10th, 20th, 40th, and 60th min. The sampling volume is 1 mL. After filtration, it is transferred to a colorimetric tube, and 1 mL of 0.1 mol·L −1 sodium thiosulfate solution is added, and then it is made up to 10 mL. Use a high performance liquid chromatograph to measure the absorbance at 276 nm. The content of L-Cys in the solution is measured by the DTNB method. The calculated degradation efficiency results are shown in Table 1:

[0029] Table 1: DCF degradation efficiency data under different Fe doping amounts As can be seen from Table 1, increasing the Fe doping amount (from 0.5 g to 2.0 g) can increase the removal efficiency of DCF from 65.0% to 84.0%. However, when the Fe dosage is further increased (from 2.0 g to 2.5 g), the removal rate of DCF rises from 84.0% to 85.7%. Considering that the improvement effect of excessive doped iron on the system is not significant and is contrary to the concept of green chemistry, it is decided to adopt 2.0 g of Fe doping amount as the optimal dosage after consideration.

[0030] Example 3: The experiment on the treatment of DCF in wastewater with the iron-based hydrothermal carbon catalytic material of the present invention includes the following steps: Take 100 mL of 20 mg·L −1 DCF solution in a beaker, and add 0.03 g of HTCC-Fe and 0.1 mM of L-Cys solution. Place the beaker on a magnetic stirrer, and under the conditions of 25°C and 400 r / min, adsorb in the dark box for 30 min. After 30 min, the material reaches the adsorption equilibrium, and then add 1 mM of PDS solution. Samples are taken at the 0th, 10th, 20th, and 30th min during the adsorption process. After adding PDS, samples are taken at the 5th, 10th, 20th, 40th, and 60th min. The sampling volume is 1 mL. After filtration, transfer it to a colorimetric tube, add 1 mL of 0.1 mol·L −1 sodium thiosulfate solution, and then make up the volume to 10 mL. Use a high-performance liquid chromatograph to measure the absorbance at 276 nm. The L-Cys content in the solution is measured by the DTNB method. The calculated degradation efficiency results are shown in Table 2:

[0031] Table 2: Degradation efficiency data of DCF in different systems As can be seen from Table 2, the removal rate of DCF in the single PDS system is 1.2%. After adding the catalytic material B and the co-catalyst L-Cys, the removal rate of DCF rises to 84.0%. It is higher than both the single catalytic material B and the catalytic material C without doped Fe atoms, which confirms that the catalytic material B plus the co-catalyst L-Cys has a better activation effect on PDS.

[0032] Example 4: The experiment on the treatment of DCF in wastewater with the iron-based hydrothermal carbon catalytic material of the present invention includes the following steps: Take 100 mL of 20 mg·L −1 DCF solution in a beaker, and add 0.03 g of HTCC-Fe and 0.1 mM of L-Cys solution. Place the beaker on a magnetic stirrer, and under the conditions of 25°C and 400 r / min, adsorb in the dark box for 30 min. After 30 min, the material reaches the adsorption equilibrium, and then add 1 mM of PDS solution. Samples are taken at the 0th, 10th, 20th, and 30th min during the adsorption process. After adding PDS, samples are taken at the 5th, 10th, 20th, 40th, and 60th min. The sampling volume is 1 mL. After filtration, transfer it to a colorimetric tube, add 1 mL of 0.1 mol·L −1 sodium thiosulfate solution, and then make up the volume to 10 mL. Use a high-performance liquid chromatograph to measure the absorbance at 276 nm. The L-Cys content in the solution is measured by the DTNB method. The calculated degradation efficiency results are shown in Table 3:

[0033] Table 3: Degradation efficiency data of DCF by catalytic material B with different dosages of L-Cys As can be seen from Table 3, with the increase of the L-Cys concentration, the degradation rate of DCF also increases. When the L-Cys concentration increases to 0.2 mM, the degradation rate of the system reaches the maximum value of 85.7%. However, when the L-Cys concentration rises to 0.3 mM and 0.4 mM, the degradation rate decreases to 75.8% and 74.3% respectively. This may be because although the high L-Cys concentration at the initial stage of the reaction accelerates the reduction of Fe 3+ , which enables the rapid activation of PDS, with the progress of the reaction time, the excessive L-Cys quenches the active species in the solution, affecting the degradation rate of the system.

[0034] Example 5: The test of treating DCF in wastewater with the iron-based hydrothermal carbon catalytic material of the present invention includes the following steps: Take 100 mL of 20 mg·L −1 DCF solution in a beaker, and add 0.03 g of HTCC-Fe and 0.1 mM L-Cys solution. Place the beaker on a magnetic stirrer, and adsorb for 30 min in the dark at 25°C and 400 r / min. After 30 min, the material reaches the adsorption equilibrium, and then add 1 mM PDS solution. Samples are taken at the 0th, 10th, 20th, and 30th min during the adsorption process. After adding PDS, samples are taken at the 5th, 10th, 20th, 40th, and 60th min. The sampling volume is 1 mL. After filtration, transfer it to a colorimetric tube, add 1 mL of 0.1 mol·L −1 sodium thiosulfate solution, and then make up the volume to 10 mL. Use a high-performance liquid chromatograph to measure the absorbance at 276 nm. The content of L-Cys in the solution is measured by the DTNB method. The calculated degradation efficiency results are shown in Table 4:

[0035] Table 4: Catalytic efficiency data of DCF by catalytic material B at different pH values As can be seen from Table 4, the degradation rate of the system for DCF has a weak correlation with pH. When the pH value is between 5 and 7, the degradation efficiency of the system is the best. Conditions that are too acidic or too alkaline will reduce the degradation rate of DCF. Generally speaking, the change of pH value does not have a great impact on the degradation rate of the system.

[0036] Example 6: The experiment of treating DCF in wastewater with the iron-based hydrothermal carbon catalytic material of the present invention includes the following steps: Take 100 mL of 20 mg·L −1 DCF solution in a beaker, and add 0.03 g of HTCC-Fe and 0.1 mM of L-Cys solution. Place the beaker on a magnetic stirrer and adsorb it in the dark box for 30 min at 25 °C and 400 r / min. After 30 min, the material reaches the adsorption equilibrium, and then add 1 mM of PDS solution. Sampling is carried out at the 0th, 10th, 20th, and 30th min during the adsorption process. After adding PDS, sampling is carried out at the 5th, 10th, 20th, 40th, and 60th min. The sampling volume is 1 mL. After filtration, transfer it to a colorimetric tube, add 1 mL of 0.1 mol·L −1 sodium thiosulfate solution, and then make up the volume to 10 mL. Use a high-performance liquid chromatograph to measure the absorbance at 276 nm. The content of L-Cys in the solution is measured by the DTNB method. The calculated degradation efficiency results are shown in Table 5:

[0037] Table 5: Catalytic efficiency data of catalytic material B for DCF under different interfering anions As can be seen from Table 5, Cl − has little effect on the catalytic activity, and the removal rate is hardly affected. While CO 3 − , NO 3 − and HCO 3 − show inhibitory effects to varying degrees respectively. Generally speaking, the HTCC-Fe 2 / PDS / L-Cys system shows strong anti-anion interference ability.

[0038] The above is only the preferred implementation mode of the present invention. The protection scope of the present invention is not limited to the above-mentioned embodiments. All process schemes that have no substantial difference from the concept of the present invention are within the protection scope of the present invention.

Claims

1. An iron-based hydrothermal carbon catalytic material, characterized in that The catalytic material uses reed biomass as a carbon-based carrier and copper sulfate heptahydrate as an iron-doped precursor, and is prepared by one-step acid etching, hydrothermal carbonization and iron doping.

2. A method for preparing the iron-based hydrothermal carbon catalytic material as claimed in claim 1, comprising the following steps: (1) Hydrolyzing cellulose in reed biomass by acid etching, specifically comprising the following steps: Weigh 2g FeSO4·7H2O and place it in 1.9 mol·L −1 of sulfuric acid solution and stir thoroughly until dissolved; Then add 2 g of crushed reed powder and stir evenly to make the powder completely immersed in the solution, and let it stand for 24 h to obtain mixture A; (2) The final composite material is obtained by high-temperature hydrothermal carbonization, which specifically includes the following steps: The mixture A was transferred to a high-pressure reactor, heated at a certain temperature (180°C) for 9 h, and then taken out after cooling. After vacuum filtration, it was repeatedly washed with ethanol and deionized water for 3 times each, and the material was dried in a vacuum oven for 24 h, and then taken out to obtain the iron-based hydrothermal carbon catalytic material B.

3. The preparation method of the iron-based hydrothermal carbon catalytic material according to claim 2 is prepared by one-step hydrothermal carbonization, which has simple steps and convenient operation, and can simultaneously achieve the generation of furan ring products and iron doping.

4. The method for preparing an iron-based hydrothermal carbon catalytic material according to claim 2, wherein in step (1), the mass ratio of the Fe precursor FeSO4·7H2O to the reed powder is 1:

1.

5. The method for preparing an iron-based hydrothermal carbon catalytic material according to claim 2, wherein in step (1), the sulfuric acid used is dilute sulfuric acid with a volume fraction of 10%.

6. Use of an iron-based hydrothermal carbon catalytic material, characterized in that: The iron-based hydrothermal carbon catalytic material according to claim 1 is used to remove diclofenac in wastewater, and the concentration of diclofenac is 20 mg / L.

7. The use of the iron-based hydrothermal carbon catalytic material according to claim 6, characterized in that: When the material is used to treat diclofenac wastewater under the condition of adding the co-catalyst L-cysteine ​​(L-Cys), the amount of L-Cys used in the wastewater treatment system is 0.2mM and the amount of PDS used is 1mM.

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