Preparation method of iron-molybdenum bimetallic MOF derived catalyst and application thereof in wastewater treatment

Abstract

The application relates to a preparation method of an iron-molybdenum bimetallic MOF derived catalyst and application of the iron-molybdenum bimetallic MOF derived catalyst in treatment of refractory organic wastewater by activated persulfate. The application is based on a transition metal activated persulfate (PDS) advanced oxidation process, and a magnetic recyclable iron-molybdenum bimetallic composite catalyst (Fe / Mo@C) is successfully prepared by a co-precipitation and calcination method. The Fe / Mo@C is a porous nanomaterial, has rich surface active sites, a large specific surface area, a simple synthesis process, superior performance, a wide pH action range, and has a good application prospect. In the present study, bisphenol A (BPA) is selected as a target pollutant, and the composite catalyst shows high reaction activity in removal of BPA, and 20mg / L BPA can be rapidly removed within 10min. The excellent performance is due to the synergistic effect of the molybdenum-iron bimetallic material, which accelerates Fe(II) / Fe(III), Mo(IV) / Mo(VI) double circulation, accelerates generation of SO4 · And ·OH by activation of PDS to rapidly further attack and decompose organic pollutants. The application provides a new idea for preparation of a new efficient catalyst and treatment of refractory organic pollutants by activated persulfate.

Description

Technical Field

[0001] This invention relates to a method for preparing an iron-molybdenum bimetallic MOF-derived catalyst and its application in the degradation of bisphenol A-containing wastewater by activated persulfate, belonging to the fields of environmental functional material preparation and treatment of recalcitrant organic wastewater. Background Technology

[0002] Bisphenol A (BPA) is widely used as an important raw material in industrial production. It enters the aquatic environment through wastewater and subsequently enters the soil, groundwater, and human body in various forms. Currently, varying levels of BPA have been detected in the environments of many countries and regions, highlighting the significant pollution problem. BPA is an endocrine disruptor that can induce tissue or organ proliferation and tumors, and can also affect the development of infants and young children, seriously threatening human health. Therefore, while actively seeking alternative raw materials for BPA, we also need to explore efficient methods for treating BPA in wastewater. Currently, several BPA treatment technologies exist, but these methods are significantly affected by water quality and have relatively low treatment efficiency. Further development of cost-effective and efficient treatment technologies is needed.

[0003] To activate persulfate sulfate free radicals (SO4) ·- Advanced oxidation processes (SR-AOPs) based on persulfate have become an emerging technology for treating recalcitrant organic compounds due to their high free radical redox potential, wide pH range, convenient storage, and long free radical lifetime. Currently, activation methods for persulfate mainly include heat treatment, microwave treatment, and transition metal ion catalysis. Transition metal activation processes have attracted much attention due to their mild reaction conditions, simple operation, and fast reaction rate. The activation of persulfate with transition metals to produce SO4 is a key technology. ·- Hydroxyl radicals (·OH) exhibit good treatment effects on recalcitrant organic matter. However, metal ions require subsequent treatment after the reaction, which not only increases operating costs but also increases heavy metal pollution in the effluent. Heterogeneous activated persulfate technology can effectively separate the catalyst from the active components, preventing metal ions from being introduced into the water. Therefore, current research both domestically and internationally is focusing on novel heterogeneous catalysts.

[0004] Iron-based catalysts are widely used in advanced sulfate radical oxidation processes due to their environmental friendliness, low cost, availability, and low toxicity. These catalysts mainly include zero-valent iron, iron oxides, and supported iron-based catalysts. However, pure iron-based catalysts have low activation efficiency for persulfate. Composite iron-based materials exhibit superior catalytic performance and stability, showing promising application prospects in the degradation of organic pollutants in water using activated persulfate. Molybdenum-based catalysts, such as MoO2 and MoS2, have been found to possess excellent performance in activating persulfate. Due to molybdenum's efficient electron transfer capability and the strong adsorption of persulfate and water by sulfur vacancies in MoS2, MoS2 can catalyze the production of SO4. ·- Molybdenum-based catalysts degrade organic pollutants through the reaction with ·OH. However, these catalysts are difficult to separate from water after use, and their residues pose certain risks to the environment and human health. Given these current challenges, there is an urgent need to develop a highly efficient catalyst that can effectively activate persulfate to treat recalcitrant organic pollutants and is easily separable. Improving catalytic activity and stability is a crucial problem that needs to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing an iron-molybdenum bimetallic MOF-derived catalyst, and provides its application in the treatment of bisphenol A-containing wastewater using activated persulfate.

[0006] This invention utilizes an advanced oxidation process for persulfate activated by transition metals to successfully prepare a magnetically recyclable iron-molybdenum bimetallic composite catalyst (Fe / Mo@C) via co-precipitation and calcination. Fe / Mo@C is a porous nanomaterial with abundant surface active sites, a large specific surface area, a simple synthesis process, and superior performance, showing promising application prospects. In this study, bisphenol A was selected as the primary target pollutant, and the composite catalyst exhibited high reactivity in the removal of bisphenol A. This excellent performance is attributed to the synergistic effect of the iron-molybdenum bimetallic catalyst, which accelerates the Fe(II) / Fe(III) and Mo(IV) / Mo(VI) dual cycles, promoting the rapid activation and generation of SO4. · The free radicals generated from - and ·OH further undergo redox reactions, promoting the degradation of organic pollutants. This result contributes to a deeper understanding of the BPA / SR-AOPs mechanism and provides a feasible technology for the effective degradation of recalcitrant organic matter in wastewater.

[0007] This invention is achieved through the following technical solution:

[0008] The preparation method of iron-molybdenum bimetallic MOF-derived catalyst and its application in wastewater treatment include the following steps:

[0009] (1) Dissolve molybdate and dimethylimidazole in deionized water in a certain proportion and stir to obtain mixed solution A. Dissolve zinc salt in deionized water and stir to obtain solution B. Dissolve ferrous salt in deionized water and stir to obtain solution C. After stirring for a certain time, mix the three solutions and continue stirring to react.

[0010] (2) The mixed solution obtained after the above reaction was centrifuged and washed several times, dried and ground at 25-80℃ to obtain the precursor. The precursor was placed in an inert gas atmosphere, heated to a certain temperature and calcined, and then cooled to room temperature to obtain a series of iron-molybdenum bimetallic MOF-derived catalysts that can be used to activate persulfate.

[0011] (3) Add the iron-molybdenum bimetallic MOF-derived catalyst to the recalcitrant organic wastewater, and add persulfate at the same time. After mixing evenly, react at 15-45℃ to degrade and remove the recalcitrant organic matter in the organic wastewater.

[0012] According to a preferred embodiment of the present invention, in step (1), the molybdate is ammonium molybdate tetrahydrate, ammonium molybdate heptahydrate, sodium molybdate dihydrate, etc., the zinc salt is zinc nitrate hexahydrate, zinc chloride hexahydrate, zinc sulfate heptahydrate, etc., and the ferrous salt is ferrous sulfate heptahydrate, ferrous chloride tetrahydrate, etc.

[0013] According to a preferred embodiment of the present invention, in step (1), molybdate and dimethylimidazole are dissolved in deionized water at a molar ratio of 1:(0-30), and the mixture is stirred for 0.5-2 hours to obtain a mixed solution A. A certain amount of zinc salt is dissolved in deionized water at a molar ratio of 1:1 for dimethylimidazole and zinc nitrate hexahydrate, and the mixture is stirred for 0.5-2 hours to obtain solution B. A certain amount of ferrous salt is dissolved in deionized water at a molar ratio of 1:(0-5) for ferric salt and molybdenum salt, and the mixture is stirred for 0.5-2 hours to obtain solution C. The three solutions are then mixed and reacted under magnetic stirring for 1-4 hours.

[0014] More preferably, the molar ratio of molybdate to dimethylimidazolium is 1:(0-2), and the molar ratio of iron salt to molybdate is 1:(0-1).

[0015] Further preferably, solution A is obtained by stirring and reacting for 1-1.5 hours, solution B is obtained by stirring and reacting for 1-1.5 hours, and solution C is obtained by stirring and reacting for 1-1.5 hours. The three solutions are then mixed and reacted under magnetic stirring for 2-3 hours.

[0016] According to a preferred embodiment of the present invention, in step (2), the mixed solution is centrifuged and washed 3-5 times with 80% ethanol aqueous solution and deionized water, dried and ground at 80°C to obtain the precursor. The precursor is calcined in a nitrogen atmosphere at a heating rate of 3°C / min to 500-900°C for 1-3 hours.

[0017] Further preferred, the calcination temperature is 800-850℃, and the calcination time is 1.5-2h.

[0018] According to a preferred embodiment of the present invention, the catalyst dosage in step (3) is 0.1 g / L; the persulfate is perdisulfate (PDS), and the dosage is 0-0.4 g / L; the organic wastewater is a simulated organic wastewater containing one or more of bisphenol A, phenol, sulfonamide, p-chlorophenol, benzoic acid, p-chlorophenol, p-nitrophenol, and p-hydroxyphenol; the catalytic degradation reaction temperature is 25°C; and the catalytic degradation reaction time is 30 min.

[0019] Technical features and advantages of the present invention:

[0020] (1) This invention prepares an iron-molybdenum bimetallic MOF-derived catalyst, Fe / Mo@C, by doping an iron-based catalyst with molybdenum. This catalyst has a rich porous structure, exposing more metal active sites compared to monometallic catalysts, resulting in higher catalytic efficiency. The obtained catalyst can efficiently activate persulfate at room temperature and has a wide applicable pH range, which is beneficial for industrial application. This invention provides a simpler and more efficient method and a more efficient catalyst for activating persulfate to treat recalcitrant organic pollutants, which has important practical significance for the treatment of recalcitrant organic wastewater and water environment protection.

[0021] (2) The iron-molybdenum bimetallic MOF-derived catalyst prepared in this invention can accelerate the Fe(II) / Fe(III) and Mo(IV) / Mo(VI) dual cycle through bimetallic synergistic effect, and accelerate the activation of PDS to generate SO4. ·- The ·OH radical further attacks organic pollutants, promoting their degradation. This invention provides a new approach to improving the activation efficiency of persulfate for the efficient treatment of recalcitrant organic pollutants.

[0022] (3) The iron-molybdenum bimetallic MOF-derived catalyst prepared in this invention exhibits strong interaction and binding forces between the two metals, inhibiting the dissolution of metal ions during use and mitigating environmental pressure and risks to biological health. This catalyst is magnetic and can be directly separated from water, regenerated, and recycled, thereby reducing catalyst manufacturing costs and the environmental damage caused by previously discarded catalysts. Attached Figure Description

[0023] Figure 1 The effect of catalysts prepared with different iron-molybdenum ratios on BPA removal rate.

[0024] Figure 2 The preferred catalyst is used to determine the removal rate of different recalcitrant pollutants.

[0025] Figure 3 The XRD patterns are for different catalysts.

[0026] Figure 4 These are morphology diagrams of different catalysts. Detailed Implementation

[0027] The present invention will be further described below with reference to embodiments, but the present invention is not limited thereto.

[0028] Example 1:

[0029] The preparation of the iron-molybdenum bimetallic MOF-derived catalyst and its application in the degradation of bisphenol A wastewater by activated persulfate include the following steps:

[0030] (1) Ammonium molybdate and dimethylimidazole were dissolved in 80.0 mL of deionized water at a ratio of 1:2 and stirred for 2 h to obtain mixed solution A. Zinc nitrate hexahydrate with the same molar amount as dimethylimidazole was dissolved in 80.0 mL of deionized water and stirred for 2 h to obtain solution B. Ferrous sulfate heptahydrate with the same molar amount as zinc nitrate hexahydrate was dissolved in 80.0 mL of deionized water and stirred for 2 h to obtain solution C. The three solutions were then mixed and stirred for another 3 h. The resulting mixed solution was centrifuged and washed 5 times with 80% ethanol aqueous solution and deionized water, dried and ground at 80 °C to obtain the precursor. The precursor was placed in a nitrogen atmosphere at 850 °C and calcined for 2 h to obtain an iron-molybdenum bimetallic MOF-derived catalyst with a molar ratio of Fe:Mo = 1:1, and named Fe1Mo1@C or Fe / Mo@C.

[0031] (2) Add the iron-molybdenum bimetallic MOF-derived catalyst to the recalcitrant organic wastewater at a dosage of 0.1 g / L, and add persulfate at a dosage of 0.4 g / L. After mixing evenly, stir and react at 25°C for 30 min to degrade and remove bisphenol A from the organic wastewater.

[0032] Example 2:

[0033] The application of bisphenol A degradation using iron-molybdenum bimetallic MOF-derived catalyst to activate persulfate is the same as described in Experimental Example 1, except that: Fe:Mo = 1:4 (molar ratio), and it is named Fe1Mo4@C.

[0034] Example 3:

[0035] The application of bisphenol A degradation using iron-molybdenum bimetallic MOF-derived catalyst to activate persulfate is the same as described in Experimental Example 1, except that: Fe:Mo = 1:2 (molar ratio), and it is named Fe1Mo2@C.

[0036] Example 4:

[0037] The application of bisphenol A degradation using iron-molybdenum bimetallic MOF-derived catalyst to activate persulfate is the same as described in Experimental Example 1, except that: Fe:Mo = 2:1 (molar ratio), and it is named Fe2Mo1@C.

[0038] Example 5:

[0039] The application of bisphenol A degradation using iron-molybdenum bimetallic MOF-derived catalyst to activate persulfate is the same as described in Experimental Example 1, except that: Fe:Mo = 5:1 (molar ratio), and it is named Fe5Mo1@C.

[0040] Example 6:

[0041] The application of bisphenol A degradation using iron-molybdenum bimetallic MOF-derived catalyst to activate persulfate is the same as described in Experimental Example 1, except that: Fe:Mo = 8:1 (molar ratio), and it is named Fe8Mo1@C.

[0042] Example 7:

[0043] The application of bisphenol A degradation using iron-molybdenum bimetallic MOF-derived catalyst to activate persulfate is the same as described in Experimental Example 1, except that: Fe:Mo = 10:1 (molar ratio), and it is named Fe 10 Mo1@C.

[0044] Example 8:

[0045] The application of bisphenol A degradation using iron-molybdenum bimetallic MOF-derived catalyst to activate persulfate is the same as described in Experimental Example 1, except that: Fe:Mo = 1:0 (molar ratio, no Mo), and it is named Fe@C.

[0046] Example 9:

[0047] The application of bisphenol A degradation using iron-molybdenum bimetallic MOF-derived catalyst to activate persulfate is the same as described in Experimental Example 1, except that: Fe:Mo = 0:1 (molar ratio, no Fe), and it is named Mo@C.

[0048] Experimental example:

[0049] Organic matter degradation experiment

[0050] Degradation methods: The application of iron-molybdenum bimetallic MOF-derived catalysts in the activation of persulfate degradation of organic wastewater, with specific application methods as follows:

[0051] Prepare 20.0 mg / L bisphenol A solution and solutions of other typical organic pollutants. Take 50.0 mL of bisphenol A solution in a beaker, add 0.005 g (0.1 g / L) of catalyst (Experimental Examples 1-8) and 0.02 g (0.4 g / L) of PDS, and react in a 25℃ constant temperature magnetically stirred water bath. Take 1.0 mL of the reacted solution at different reaction time points, filter the sample through a 0.22 μm filter membrane into a sample vial for analysis, and then analyze the sample using a Shimadzu high-performance liquid chromatograph (HPLC-2030). Repeat all degradation experiments, and the results are expressed as average values. Apply the optimized catalyst to the degradation process of different pollutants. Take 50.0 mL of other typical organic pollutant solutions in a beaker, add 0.005 g (0.1 g / L) of catalyst (Experimental Example 1) and 0.02 g (0.4 g / L) of PDS, and react in a 25℃ constant temperature magnetically stirred water bath. Take samples for analysis.

[0052] Test results:

[0053] (1) The effect of MOF-derived catalysts with different iron-molybdenum ratios on the activation of persulfate degradation of BPA is shown in the figure. Figure 1 As shown.

[0054] from Figure 1 It can be seen that the degradation efficiency after 10 min is basically the same as that after 30 min, indicating that the reaction basically reaches equilibrium within 10 min. Comparison with the pure iron-based catalyst prepared without molybdenum shows that doping with an appropriate amount of molybdenum can significantly improve the efficiency of bisphenol A degradation by activated persulfate. The degradation efficiency of bisphenol A by the pure iron-based catalyst within 30 min is 50%, while after doping with an appropriate amount of molybdenum (Fe:Mo = 1:1), the degradation efficiency of bisphenol A within 30 min is 100%. However, the continuous increase in molybdenum content inhibits the catalyst's effect; when Fe:Mo = 1:4, the degradation efficiency of bisphenol A within 30 min is 97.9%. Considering both catalyst preparation cost and degradation efficiency, Fe:Mo = 1:1 was selected as the optimal catalyst for subsequent experiments.

[0055] (2) The removal efficiency of the preferred catalyst (Fe:Mo = 1:1) for different recalcitrant organic pollutants is as follows: Figure 2 As shown.

[0056] from Figure 2 It can be seen that the selected catalyst has high removal efficiency and fast removal rate for most organic pollutants (such as bisphenol A and phenol). Most of the target pollutants can be removed in the first 5 minutes of reaction, and the reaction basically reaches equilibrium after 10 minutes. At a reaction time of 10 minutes, the removal rates for bisphenol A, phenol, and sulfonamides are 100%, 80.0%, and 60.3%, respectively, and the removal rates remain basically unchanged thereafter.

[0057] (3) The XRD patterns of catalysts Fe / Mo@C, Fe@C and Mo@C are as follows: Figure 3 As shown.

[0058] The crystal structure of the composite Fe / Mo@C was identified by XRD pattern and was basically consistent with the Fe2MoC standard card (PDF#17-0911). The Fe@C single iron-based catalyst without molybdenum doping was consistent with the Fe3C standard card (PDF#35-0772). The composite catalyst retained some characteristic peaks of Fe@C and Mo@C, and at the same time formed new characteristic peaks such as 39.6° (340) and 43.3° (305), indicating that the composite catalyst was successfully prepared and a new structure was formed by doping molybdenum on the basis of the iron-based catalyst.

[0059] (4) The morphology and structure of catalysts Fe / Mo@C and Fe@C are as follows: Figure 4 As shown.

[0060] Transmission electron microscopy images of synthesized Fe / Mo@C and Fe@C are shown below. Figure 4 As shown in figures a and b, distinct Fe2MoC(340) and Fe3C(211) lattices can be observed, indicating the successful formation of Fe2MoC. Furthermore, the Fe2MoC is surrounded by a carbon layer, and the resulting carbon-coated metal nanomaterials can effectively slow down the dissolution of metal ions, thus mitigating environmental impact.

Claims

1. Use of an iron-molybdenum bimetallic MOF-derived catalyst in wastewater treatment, characterized in that, The steps include: (1) Dissolve molybdate and dimethyl imidazole in deionized water in a certain proportion, stir to obtain mixed solution A, dissolve zinc salt in deionized water to obtain solution B, dissolve ferrous salt in deionized water to obtain solution C, mix the three solutions after stirring for a certain time, continue to stir and react, the molar ratio of ferrous salt to molybdate is 1:(1-4), (2) The mixed solution obtained after the above reaction is washed several times by centrifugation, dried at 25-80℃, and ground to obtain a precursor, which is calcined in an inert gas atmosphere at a certain temperature, then cooled to room temperature to obtain a series of iron-molybdenum bimetallic MOF derived catalysts for activating persulfate, (3) Add the iron-molybdenum bimetallic MOF derived catalyst to the refractory organic wastewater, add persulfate at the same time, mix uniformly, and react at 15-45℃ to remove bisphenol A in the organic wastewater.

2. Use according to claim 1, characterized in that, In step (1), the molybdate is ammonium molybdate tetrahydrate, ammonium molybdate heptahydrate, and sodium molybdate dihydrate, the zinc salt is zinc nitrate hexahydrate, zinc chloride hexahydrate, and zinc sulfate heptahydrate, and the ferrous salt is ferrous sulfate heptahydrate and ferrous chloride tetrahydrate.

3. Use according to claim 1, characterized in that, In step (1), the molybdate and dimethyl imidazole are dissolved in deionized water in a molar ratio of 1:(2-30), stirred for 0.5-2h to obtain mixed solution A, a certain amount of zinc salt is dissolved in deionized water in a molar ratio of dimethyl imidazole to zinc salt of 1:1, stirred for 0.5-2h to obtain solution B, and a certain amount of ferrous salt is dissolved in deionized water in a molar ratio of ferrous salt to molybdate of 1:(1-4), stirred for 0.5-2h to obtain solution C, then the three solutions are mixed and reacted for 1-4h under magnetic stirring.

4. Use according to claim 3, characterized in that, The molar ratio of molybdate to dimethyl imidazole is 1:2, the stirring reaction time is 1-1.5h to obtain solution A, the molar ratio of dimethyl imidazole to zinc salt is 1:1, the stirring reaction time is 1-1.5h to obtain solution B, the molar ratio of ferrous salt to molybdate is 1:1, the stirring reaction time is 1-1.5h to obtain solution C, and the three solutions are mixed and reacted for 2-3h under magnetic stirring.

5. The use according to claim 1, characterized in that, In step (2), the mixed solution is washed 3-5 times by centrifugation with 80% ethanol aqueous solution and deionized water, dried at 80℃, and ground to obtain a precursor, which is calcined at a heating rate of 3℃ / min to 500-900℃ for 1-3h in a nitrogen atmosphere.

6. Use according to claim 5, characterized in that, The calcination temperature is 800-850℃, and the calcination time is 1.5-2h.

7. Use according to claim 1, characterized in that, In step (3), the catalyst dosage is 0.1g / L; the persulfate is peroxodisulfate (PDS), the dosage is 0.4g / L; the catalytic degradation reaction temperature is 25℃, and the catalytic degradation reaction time is 30min.

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