A method for efficiently degrading nitrophenol wastewater by using a ferrozinc bimetallic catalytic system and a catalyst recovery method
Patent Information
- Application Number
- CN202511035077.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-25
- Publication Date
- 2026-09-22
- Estimated Expiration
- 2045-07-25
AI Technical Summary
然而，铁腐蚀产物中过量铁氧化物的形成会覆盖在零价铁表面，导致其催化效能受限
[0017]1.本发明采用铁锌双金属催化体系降解硝基酚废水，不仅可以有效去除污染物，还可以克服铁腐蚀产物中，过量铁氧化物的形成覆盖在零价铁表面导致的催化效能受限的问题。铁锌双金属催化体系中，Zn2+的存在能够加速零价铁表面的电子转移，释放更多的Fe(II)，从而强化零价铁的反应效能。
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Figure CN120771873B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for the efficient degradation of nitrophenol wastewater using an iron-zinc bimetallic catalytic system and a catalyst recovery method. Background Technology
[0002] Nitrophenols have wide applications in many fields, such as in the synthesis of dyes, plasticizers, pesticides, herbicides, coatings, pharmaceuticals, explosives, and wood or leather preservatives. However, nitrophenols and their derivatives are generally highly toxic, carcinogenic, and bioaccumulative, and some nitrophenol pollutants have been listed as priority pollutants by the U.S. Environmental Protection Agency (USEPA). Direct discharge of wastewater containing nitrophenols and their derivatives into water bodies poses a threat to ecosystems and human health. Traditional biological wastewater treatment processes (such as activated sludge processes) are ineffective in treating these pollutants because the nitro groups in nitrophenols have electron adsorption properties, inhibiting the electrophilic attack of enzymes. However, the biotoxicity of aminophenols, the products of nitrophenol reduction, is significantly reduced. Therefore, it is necessary to develop a simple and efficient catalytic reduction method for nitrophenols.
[0003] Currently, zero-valent iron (ZVFe) is considered a promising method for reducing nitrophenolic compounds, as it is an economical, efficient, and environmentally friendly functional material for water treatment. However, the formation of excess iron oxides from iron corrosion products can coat the surface of ZVFe, limiting its catalytic efficiency. Adding co-catalyst metals (such as Cu, Sn, In, and Zn) to the reducing agent surface can enhance its reaction efficiency. However, finding an economical, efficient, and environmentally friendly co-catalyst to further improve the degradation efficiency of nitrophenolic compounds remains a challenge that urgently needs to be addressed. Summary of the Invention
[0004] The purpose of this invention is to address the aforementioned problems in the prior art and provide a method for the efficient degradation of nitrophenol wastewater using an iron-zinc bimetallic catalytic system, along with a catalyst recovery method. This method utilizes zero-valent iron as a reducing agent and zinc salt solution as a co-catalyst, thereby achieving efficient degradation of nitrophenol compounds. Taking p-nitrophenol as an example, 500 mg / L of p-nitrophenol can be completely degraded within one hour in the iron-zinc bimetallic catalytic system. This system significantly improves degradation efficiency by accelerating electron transfer.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0006] A method for efficiently degrading nitrophenol wastewater using an iron-zinc bimetallic catalytic system, the method comprising the following steps:
[0007] Step 1: Dissolve the zinc salt in pure water or deionized water to prepare a zinc salt solution, which serves as a co-catalyst.
[0008] Step 2: Mix the wastewater containing nitrophenol compounds with a zinc salt solution until homogeneous, then add zero-valent iron particles to form an iron-zinc bimetallic catalytic system. This system facilitates the catalytic reduction of nitrophenol compounds, thus treating the wastewater. The catalyst in the iron-zinc bimetallic catalytic system is zero-valent iron particles, and the co-catalyst is Zn. 2+ This forms zero-valent iron-Zn 2+ In a solid-liquid two-phase system, the iron-zinc bimetallic catalytic system gradually adsorbs zinc onto the surface of zero-valent iron during the degradation of nitrophenol, acting as a co-catalyst on the iron surface rather than being dispersed in the aqueous solution.
[0009] Further, in step 1, the concentration of the zinc salt solution is 0.25~1.5 mmol / L; the zinc salt is one of zinc nitrate, zinc sulfate or zinc chloride; the resistivity of the pure water is 1~5 MΩ·cm and the pH is 5.5~6.5.
[0010] Further, in step 2, the nitrophenol compound is one or more of p-nitrophenol, o-nitrophenol, or m-nitrophenol; the concentration of the nitrophenol compound in the wastewater containing the nitrophenol compound is 125~1000 mg / L.
[0011] Further, in step 3, the volume ratio of the wastewater containing nitrophenol compounds to the zinc salt solution is 800:1 to 400:3; the dosage of the zero-valent iron particles is 8 to 12 g / L.
[0012] Furthermore, in step 3, the zero-valent iron particles are particles with a mesh size between 250 and 200 after passing through a sieve.
[0013] Furthermore, in step 3, before mixing the wastewater containing the nitrophenol compound with the zinc salt solution, the initial pH of the wastewater needs to be adjusted to 3.0.
[0014] Furthermore, in step 3, the temperature of the catalytic reduction reaction is 20~30℃ and the time is 60min.
[0015] A method for recovering the catalyst obtained by the above method is characterized by: washing the catalyst three times with water after the reaction and drying it at 40°C for 4 hours under vacuum. Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis of the recovered catalyst material showed the presence of zinc on the surface of the zero-valent iron. X-ray diffraction (XRD) analysis showed diffraction peaks for zero-valent iron and magnetite (Fe3O4), but no diffraction peaks for the zinc crystal structure were found. X-ray photoelectron spectroscopy analysis indicated that zinc is divalent and exists in the Zn(II) form.
[0016] The advantages of this invention over the prior art are:
[0017] 1. This invention employs an iron-zinc bimetallic catalytic system to degrade nitrophenol wastewater. This not only effectively removes pollutants but also overcomes the problem of limited catalytic efficiency caused by the formation of excessive iron oxides covering the surface of zero-valent iron in iron corrosion products. In the iron-zinc bimetallic catalytic system, Zn... 2+ The presence of [something] can accelerate electron transfer on the surface of zero-valent iron, release more Fe(II), and thus enhance the reaction efficiency of zero-valent iron.
[0018] 2. This invention exhibits higher degradation efficiency compared to the zero-valent iron reduction system, with lower catalytic reaction costs and no secondary pollution. This invention utilizes zinc from zinc-containing wastewater generated in industries such as electroplating, metallurgy, and chemicals as a source of zinc salts, achieving the goal of "treating waste with waste," and has significant application prospects. This invention can be used for the treatment of nitrophenol-containing wastewater generated in industries such as military, chemical, dye, and pharmaceutical. Attached Figure Description
[0019] Figure 1 This is a comparison chart of the degradation efficiency of p-nitrophenol in Example 1 of the present invention;
[0020] Figure 2 This is a graph showing the change of Fe(II) content over time in the system of Example 1 of the present invention;
[0021] Figure 3 This is a comparison chart of the degradation efficiency of p-nitrophenol in Example 2 of the present invention;
[0022] Figure 4 This is a graph showing the change of Fe(II) content over time in the system of Example 2 of the present invention;
[0023] Figure 5 This is a comparison chart of the degradation efficiency of p-nitrophenol in Example 3 of the present invention;
[0024] Figure 6 Zn in Embodiment 4 of the present invention 2+ Concentration versus time graph;
[0025] Figure 7 This is a scanning electron microscope-energy dispersive spectroscopy (EDS) image of the catalyst after reaction in Example 4 of the present invention.
[0026] Figure 8 This is a fine XPS spectrum fitting diagram of the zinc element of the catalyst after the reaction in Example 4 of the present invention;
[0027] Figure 9 The image shows the XRD pattern of the catalyst after reaction in Example 4 of this invention. Detailed Implementation
[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.
[0029] This embodiment describes a method for the efficient degradation of nitrophenol wastewater using an iron-zinc bimetallic catalytic system, the method comprising the following steps:
[0030] Step 1: Dissolve zinc salt in pure water to prepare a zinc salt solution, which will serve as a co-catalyst zinc salt solution;
[0031] The concentration of the zinc salt solution is 0.25–1.5 mmol / L. The zinc salt can be zinc nitrate, zinc sulfate, or zinc chloride. When the zinc salt solution dosage is 0.25, 0.50, 1.00, and 1.50 mmol / L, the degradation rates of p-nitrophenol (PNP) after 60 min of reaction are 93.09%, 99.99%, 91.64%, and 78.26%, respectively, all higher than those without added Zn. 2+ The iron reduction system.
[0032] Step 2: Mix nitrophenol wastewater and zinc salt solution at a volume ratio of 800:1 to 400:3 until homogeneous, then add zero-valent iron particles to form an iron-zinc bimetallic catalytic system for the catalytic reduction reaction of nitrophenol compounds; the temperature of the catalytic reduction reaction is 20 to 30°C and the time is 60 min.
[0033] In the iron-zinc bimetallic catalytic system, zero-valent iron serves as the catalyst, and the initial introduction of zinc as a co-catalyst is in the form of divalent ions, forming zero-valent iron-Zn. 2+ Solid-liquid two-phase system.
[0034] The dosage of the zero-valent iron particles is 8~12g / L, which can achieve a removal rate of over 95% for nitrophenol. Doses <8g / L or >12g / L reduce the removal rate of nitrophenol, with the removal rate only reaching about 85~88%.
[0035] The zero-valent iron particles are selected from those with a mesh size of 250-200 after sieving. Zero-valent iron particles with a mesh size of 250-200 have a large specific surface area, exposing more active sites to promote the degradation of nitrophenol, and are easily separated from the solution, overcoming the drawback of difficult separation due to agglomeration of nano-sized zero-valent iron particles. The synergistic effect of the iron-zinc bimetallic catalytic system can complete the rapid adsorption-electron transfer-reduction degradation process of nitrophenol within 60 minutes. Insufficient reaction time will lead to incomplete degradation of nitrophenol pollutants, while excessive time will increase treatment costs.
[0036] The optimal temperature range for removing nitrophenol is 20-30℃. Below 20℃, mass transfer in the reduction system deteriorates, hindering the reaction. Above 30℃, oxidation of iron particles intensifies, reducing the utilization rate of iron electron transfer. 20-30℃ is close to room temperature, saving energy and suitable for treating most industrial wastewater.
[0037] Furthermore, before mixing the nitrophenol wastewater and zinc nitrate solution, the initial pH of the nitrophenol solution needs to be adjusted to 3.0. Adjusting the initial pH of the nitrophenol wastewater to 3.0 can effectively prevent iron surface passivation, enhance particle activity, accelerate the corrosion of zero-valent iron, and facilitate the reduction process of nitrophenol.
[0038] In nitrophenol wastewater, the concentration of nitrophenol compounds is 125~1000 mg / L; the nitrophenol compounds are p-nitrophenol compounds, o-nitrophenol compounds, or m-nitrophenol compounds;
[0039] When using an iron-zinc bimetallic catalytic system for degradation, the removal rate of p-nitrophenol wastewater with a concentration of 125~1000 mg / L can reach over 85%. In particular, when the concentration of p-nitrophenol wastewater is in the range of 250~1000 mg / L, the removal rate can reach over 95%.
[0040] Step 3: After the reaction is complete, the catalyst material is recovered (i.e., zero-valent iron particles are recovered).
[0041] The catalyst material after the reaction exhibits the presence of zinc on its surface. The catalyst material is composed of zero-valent iron and magnetite (Fe3O4), and no zinc crystal structure was observed. The zinc in the catalyst material exists in the Zn(II) form.
[0042] In the following embodiments, zero-valent iron is used as a catalyst and zinc ions as a co-catalyst to achieve efficient degradation of nitrophenols. p-Nitrophenol is used as an example:
[0043] The preparation process of the p-nitrophenol solution is as follows: 0.25g, 0.5g, 1.0g, 1.5g, and 2.0g of p-nitrophenol powder are dissolved in 2L of pure water to form p-nitrophenol solutions with concentrations of 125mg / L, 250mg / L, 500mg / L, 750mg / L, and 1000mg / L, respectively.
[0044] The preparation process of the zinc nitrate solution used is as follows: 1.894g of zinc nitrate is dissolved in 50mL of pure water to form a 0.2mol / L zinc nitrate solution.
[0045] The zero-valent iron particles used were obtained by sieving micron-sized zero-valent iron particles and taking particles between 250 and 200 mesh for subsequent experiments.
[0046] The ethanol used was 99.5% anhydrous ethanol.
[0047] The acetic acid used was glacial acetic acid with a purity of 99.5%.
[0048] Pb used 2+ The preparation process is as follows: Dissolve 0.2399g of lead nitrate in 50mL of pure water to form a lead nitrate solution.
[0049] The purified water used was Wahaha brand purified water for laboratory use, with a resistivity of 1~5 MΩ·cm and a pH of 5.5~6.5.
[0050] Recovery of zero-valent iron: After the reaction is complete, the zero-valent iron particles are collected by filtration and washed three times with clean water.
[0051] Example 1:
[0052] 300 mL of 500 mg / L p-nitrophenol wastewater and 0.375 mL, 0.75 mL, 1.50 mL, and 2.25 mL of 0.2 mol / L zinc nitrate solution were poured into four different beakers and mixed thoroughly to obtain homogeneous mixtures. The beakers were placed in a constant temperature water bath and heated to 25°C. The initial pH of the p-nitrophenol solution was adjusted to 3.0. 3.0 g of zero-valent iron particles were added to each mixture, and the mixture was stirred at 400 rpm to initiate the p-nitrophenol degradation reaction. At 5, 10, 20, 30, 40, 50, and 60 min after the start of the reaction, 2 mL samples were immediately filtered through a 0.22 µm polytetrafluoroethylene (PTFE) membrane. The concentrations of p-nitrophenol and Fe(II) in the system were measured. The results are shown below. Figure 1 and Figure 2 As shown.
[0053] The method described in Example 1 of this invention can improve the removal efficiency of p-nitrophenol in water, such as... Figure 1 As shown, the removal efficiency of the method of the present invention is higher than that of the single zero-valent iron reduction system. At 25°C, the dosage of zero-valent iron in the iron-zinc reduction system is 3.0 g, and the Zn... 2+ At dosages of 0.25 mmol / L, 0.50 mmol / L, 1.00 mmol / L, and 1.50 mmol / L, after treating a 500 mg / L p-nitrophenol solution for 60 min, the removal rates of p-nitrophenol reached 93.09%, 99.98%, 91.64%, and 78.26%, respectively, all higher than the 76.88% of the zero-valent iron system alone. During the reaction, the ferrous ion concentration in the system increased with increasing Zn concentration. 2+ The increase with increasing dosage indicates the addition of Zn to the reduction system. 2+It facilitates the transfer of electrons from zero-valent iron for the reduction of p-nitrophenol.
[0054] Nitrophenol pollutants, such as p-nitrophenol, o-nitrophenol, and m-nitrophenol, have similar structures, all consisting of a benzene ring, a nitro group, and a hydroxyl group. The principle of the iron-zinc bimetallic catalytic system for degrading p-nitrophenol is that zero-valent iron reduces the nitro group (-NO2) in p-nitrophenol to an amino group (-NH2), while Zn... 2+ In the system, it acts as a co-catalyst, accelerating the reduction process of p-nitrophenol with zero-valent iron. Therefore, the iron-zinc bimetallic catalytic system is suitable for the removal of nitrophenol pollutants.
[0055] Example 2:
[0056] Five separate beakers were filled with 300 mL of p-nitrophenol solutions (125 mg / L, 250 mg / L, 500 mg / L, 750 mg / L, and 1000 mg / L) and 0.75 mL of 0.2 mol / L zinc nitrate solution, respectively, and mixed thoroughly to obtain homogeneous mixtures. The beakers were placed in a constant-temperature water bath and heated to 25°C. The initial pH of p-nitrophenol was adjusted to 3.0. 3.0 g of zero-valent iron particles were added to the mixture, and the mixture was stirred at 400 rpm to initiate the degradation reaction of p-nitrophenol. At 5, 10, 20, 30, 40, 50, and 60 min after the start of the reaction, 2 mL samples were immediately filtered through a 0.22 µm polytetrafluoroethylene (PTFE) membrane. The concentrations of p-nitrophenol and Fe(II) in the system were measured. The results are shown below. Figure 3 and Figure 4 As shown.
[0057] The method described in Example 2 of this invention showed good removal effects on different concentrations of p-nitrophenol in water. Figure 3 As shown, when the initial concentrations of p-nitrophenol were 125 mg / L, 250 mg / L, 500 mg / L, 750 mg / L, and 1000 mg / L, the degradation rates of the pollutants were 88.97%, 97.23%, 97.18%, 97.28%, and 95.70%, respectively, indicating that the iron-zinc bimetallic catalytic system had good removal efficiency for p-nitrophenol solutions of different concentrations. The changes in ferrous ion concentration during the reaction are shown in the figure. Figure 4 As shown, with increasing concentrations of p-nitrophenol, it leads to severe corrosion of zero-valent iron, which in turn promotes the reduction of p-nitrophenol.
[0058] In summary, this invention sequentially dissolves p-nitrophenol and zinc nitrate in pure water to form p-nitrophenol solution and zinc nitrate solution, respectively; then, after adjusting the initial pH of the p-nitrophenol solution, it is mixed with the zinc nitrate solution, and then zero-valent iron particles are added to catalytically degrade the p-nitrophenol.
[0059] Example 3:
[0060] To address the complex composition of actual wastewater, this embodiment adds coexisting pollutants ethanol, acetic acid, and Pb. 2+ To investigate the effect of ethanol, acetic acid, and lead nitrate solution on the degradation efficiency of p-nitrophenol, three beakers containing 300 mL of 500 mg / L p-nitrophenol were added respectively and mixed thoroughly. Ethanol, acetic acid, and lead nitrate solution were then added. 2+ The concentration was added according to the actual molar ratio of ethanol to p-nitrophenol in the water body. The actual molar ratio of ethanol:acetic acid:nitrophenol in nitrophenol production wastewater was 37.99:7.58:1, Pb 2+ The maximum concentration is 5 mg / L. In this example, ethanol, acetic acid, and Pb... 2+ The added amounts were 136.3 mmol / L, 27.2 mmol / L, and 5 mg / L, respectively. The beakers were placed in a constant-temperature water bath and heated to 25°C. The initial pH of p-nitrophenol was adjusted to 3.0, and 0.75 mL of 0.2 mol / L zinc nitrate solution was added. Then, 3.0 g of zero-valent iron particles were added sequentially to the mixture, and the mixture was stirred at 400 rpm to degrade the p-nitrophenol. At 5, 10, 20, 30, 40, 50, and 60 min after the start of the reaction, 1 mL samples were taken and immediately filtered through a 0.22 µm polytetrafluoroethylene (PTFE) membrane. The p-nitrophenol concentration was measured, and the results are as follows: Figure 5 As shown.
[0061] The method described in Example 3 of this invention has shown good results in removing p-nitrophenol from actual water bodies in the presence of coexisting pollutants. For example... Figure 5 As shown, during the degradation of p-nitrophenol in the iron-zinc bimetallic catalytic system, ethanol, acetic acid, and Pb were added respectively. 2+ Afterwards, the degradation rate of p-nitrophenol remained above 99.8%, confirming that the system has a highly efficient removal capacity for p-nitrophenol in complex aquatic environments.
[0062] Example 4:
[0063] A 300 mL solution of 500 mg / L p-nitrophenol and a 0.75 mL solution of 0.2 mol / L zinc nitrate were sequentially added to a beaker and mixed thoroughly to obtain a homogeneous mixture. The beaker was placed in a constant temperature water bath and heated to 25°C. The initial pH of the p-nitrophenol solution was adjusted to 3.0. 3.0 g of zero-valent iron particles were added to the mixture, and the mixture was stirred at 400 rpm to initiate the p-nitrophenol degradation reaction. At 5, 10, 20, 30, 40, 50, and 60 min after the start of the reaction, 2 mL samples were immediately transferred and filtered through a 0.22 µm polytetrafluoroethylene (PTFE) membrane. The zinc concentration in the solution was measured, and the results are as follows: Figure 6 As shown in the figure. After reacting for 60 min, the catalyst material was collected, washed three times with water, and dried at 40 °C under vacuum for 4 hours for characterization and analysis. The results are as follows. Figures 7-9 As shown.
[0064] The collected and recovered materials from the degradation of p-nitrophenol using the iron-zinc bimetallic catalytic system were characterized and analyzed. Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) revealed the presence of zinc on the iron surface, indicating that zinc was adsorbed onto the zero-valent iron surface during the degradation of p-nitrophenol, rather than being dispersed in the solution. The zinc concentration was less than 0.5 mg / L after 20 min of reaction and less than 0.1 mg / L after 60 min, further confirming that zinc was not dispersed in the solution. During the degradation of p-nitrophenol using the iron-zinc bimetallic catalytic system, zinc first adsorbs onto the zero-valent iron surface, accelerating electron transfer and causing the zero-valent iron to release more electrons to convert to Fe(II). Simultaneously, electrons are transferred to p-nitrophenol, reducing it to p-aminophenol and completing the degradation process.
[0065] X-ray photoelectron spectroscopy analysis of the zinc speciation in the post-reaction catalyst showed that zinc exists in the divalent state, specifically as Zn(II). X-ray diffraction (XRD) analysis of the post-reaction catalyst revealed diffraction peaks for zero-valent iron at 2θ = 44.6°, 65.0°, and 82.3°, and diffraction peaks for Fe3O4 at 2θ = 30.1°, 35.5°, and 43.2°. No diffraction peaks indicating the zinc crystal structure were found, indicating that the post-reaction catalyst is composed of zero-valent iron and magnetite (Fe3O4), and the absence of a zinc crystal structure confirms that zinc exists in an ionic state and did not undergo speciation during the degradation of p-nitrophenol.
Claims
1. A method for efficiently degrading nitrophenol wastewater using an iron-zinc bimetallic catalytic system, characterized in that: The method includes the following steps: Step 1: Dissolve the zinc salt in pure water or deionized water to prepare a zinc salt solution; the concentration of the zinc salt solution is 0.25~1.5 mmol / L; the zinc salt is one of zinc nitrate, zinc sulfate or zinc chloride; Step 2: Mix the wastewater containing nitrophenol compounds with a zinc salt solution until homogeneous, then add zero-valent iron particles to form an iron-zinc bimetallic catalytic system to carry out the catalytic reduction reaction of nitrophenol compounds, thereby treating the wastewater. The zero-valent iron particles are 250-200 mesh particles after sieving. Before mixing the wastewater containing nitrophenol compounds with the zinc salt solution, the initial pH of the wastewater needs to be adjusted to 3.
0. The temperature of the catalytic reduction reaction is 20-30℃, and the time is 60 min. The volume ratio of the wastewater containing nitrophenol compounds to the zinc salt solution is 800:1-400:
3. The dosage of the zero-valent iron particles is 8-12 g / L.
2. The method for efficiently degrading nitrophenol wastewater using the iron-zinc bimetallic catalytic system according to claim 1, characterized in that: In step 1, the resistivity of the pure water is 1~5 MΩ·cm and the pH is 5.5~6.
5.
3. The method for efficiently degrading nitrophenol wastewater using the iron-zinc bimetallic catalytic system according to claim 1, characterized in that: In step 2, the nitrophenol compound is one or more of p-nitrophenol, o-nitrophenol, or m-nitrophenol; the concentration of the nitrophenol compound in the wastewater containing the nitrophenol compound is 125~1000 mg / L.
4. The method for efficiently degrading nitrophenol wastewater using the iron-zinc bimetallic catalytic system according to claim 1, characterized in that: The method further includes: washing the reacted catalyst three times with water and drying it at 40°C for 4 hours under vacuum.