Preparation method of cellulose-based material loaded cobalt-doped metal organic framework compound catalyst and application thereof in degrading pollutants

Abstract

The application discloses a preparation method and application of a cellulose-based material loaded cobalt-doped metal organic framework compound catalyst. The composite catalyst takes a cellulose-based material as a carrier, and is subjected to hydrothermal treatment together with an aqueous solution of ferric chloride hexahydrate and fumaric acid, so as to obtain a metal organic framework compound MIL-88A which is in-situ grown on the cellulose-based material, and then the MIL-88A is subjected to freeze drying. After the treatment, the obtained cellulose-based material loaded MIL-88A is added into a mixed aqueous solution of cobalt nitrate nonahydrate and urea, and is subjected to water bath treatment at 90 DEG C, and then the cellulose-based material loaded MIL-88A obtained after the treatment is subjected to freeze drying, so as to obtain the cellulose-based material loaded cobalt-doped MIL-88A catalyst. The prepared heterogeneous catalyst can efficiently degrade dyes by activating potassium monopersulfate. The catalyst is easy to recover, and can be used in an intermittent or continuous dye degradation process. In the continuous degradation of a dye rhodamine B, when the flow rate is 6 ml / h, the catalyst can still maintain high catalytic degradation activity for 72 h.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic pollutant degradation treatment, and relates to a preparation method of a cellulose-based material loaded with a cobalt-doped metal organic framework compound catalyst and application of the cellulose-based material in catalytic activation of potassium monopersulfate and efficient degradation of organic pollutants. BACKGROUND

[0002] Methylene blue is one of the most commonly used dyes in textile dyeing, and the discharge of dyeing and finishing wastewater containing methylene blue causes great damage to the aquatic environment. Some commonly used wastewater treatment methods, such as adsorption, chemical precipitation, etc., cannot completely remove methylene blue from water. The advanced oxidation technology based on sulfate radicals has excellent organic pollutant degradation capacity and has attracted more and more attention in recent years. As an oxidant, potassium monopersulfate (PMS) is easy to transport and has high solubility, and the generated sulfate radicals have a higher oxidation-reduction potential in the reaction process. The activation methods of potassium monopersulfate include thermal activation, ultraviolet activation and transition metal activation. Metal organic framework compounds containing transition metals have great potential as a heterogeneous activator of potassium monopersulfate due to their large specific surface area, rich active sites and other advantages. However, metal organic framework compounds are usually powdery, easy to aggregate, and not conducive to the recycling of catalysts. Therefore, a simple and effective method can be used to anchor metal organic framework compounds on a suitable carrier to prepare a heterogeneous catalyst.

[0003] The impregnated catalyst has uniform active site distribution and is easy to recover. More importantly, its insertion / removal can almost instantaneously turn on / off the reaction. The cellulose-based material made of cellulose fibers is an ideal substrate for preparing the impregnated catalyst, which has the advantages of low cost, high flexibility and biodegradability. On the one hand, metal ions can be loaded on the cellulose-based material by impregnation. On the other hand, the synergistic effect of different metals in metal organic framework compounds on catalytic performance provides a new idea for preparing a bimetallic catalyst for activating potassium monopersulfate. The present application uses an in-situ synthesis method to first load the iron-based metal organic framework compound MIL-88A on the cellulose-based material, and then dope cobalt in MIL-88A, which significantly improves the activation performance of the composite catalyst for potassium monopersulfate and can be used for continuous degradation of pollutants. SUMMARY

[0004] The purpose of this invention is to provide a simple method for preparing and applying a heterogeneous catalyst. The method employs an in-situ synthesis approach, first loading the iron-based metal-organic framework compound MIL-88A onto a cellulose-based material, and then doping MIL-88A with cobalt. The resulting cellulose-based material-supported cobalt-doped metal-organic framework catalyst (Co-M88A-CM) is then applied to activate potassium persulfate for the degradation of rhodamine B.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A cellulose-based material supported on a cobalt-doped metal-organic framework catalyst is prepared by the following method:

[0007] 1) Dissolve a certain amount of FeCl3·9H2O in deionized water and stir until homogeneous to obtain solution A. Dissolve a certain amount of fumaric acid in deionized water and stir until homogeneous to obtain solution B.

[0008] 2) Soak the cellulose-based material in solution A for a period of time, then mix it with solution B. After ultrasonic mixing, transfer it to a hydrothermal reactor for reaction for a period of time. Place the resulting cellulose-based material in a freeze dryer for drying.

[0009] 3) Take a certain amount of urea, Co(NO3)2·6 H2O and deionized water and mix them evenly at room temperature. Add the dried cellulose-based material from step 2) to the mixed solution and heat it in a water bath for a certain time.

[0010] 4) Wash the cellulose-based material after water bath heating, place it in a freeze dryer, and the catalyst is obtained after drying.

[0011] In step 1), the composition ratio of solution A is 10 mmol FeCl3·9 H2O dissolved in every 25 mL of deionized water, and the composition ratio of solution B is 10 mmol fumaric acid dissolved in every 25 mL of deionized water.

[0012] In step 2), the soaking time is 5-12 hours, the hydrothermal reaction temperature is 60-120℃, the hydrothermal reaction time is 2-12 hours, the freeze-drying temperature is -56℃, and the freeze-drying time is 2-12 hours.

[0013] In step 3), the amounts of urea and Co(NO3)2·6 H2O used per 100 mL of deionized water are 55.6 mmol and 22.4 mmol, respectively. The water bath reaction is carried out at 90 °C and the heating time is 1-2 h.

[0014] In step 4), the cellulose-based material after the reaction is washed repeatedly with deionized water to remove excess urea, and the freeze-drying temperature is -56℃, and the freeze-drying time is 2-12h.

[0015] The application of the cellulose-based material-supported cobalt-doped metal-organic framework compound catalyst in the degradation of rhodamine B.

[0016] In the aforementioned application, the reaction substrate is a 20 mg / L Rhodamine B solution.

[0017] In the aforementioned application, during intermittent experiments, the amount of potassium persulfate reactant used was 40-120 mg / L.

[0018] In the aforementioned application, during intermittent experiments, the amount of the composite catalyst (Co-M88A-FP) used is 50-150 mg / L.

[0019] In the described application, the intermittent experiment used conventional water bath heating, with a reaction temperature of 25-45℃, a reaction time of 20 min, and a rotation speed of 100 rpm.

[0020] In the aforementioned application, during continuous experiments, the flow rate of the Rhodamine B and PMS mixed solution was controlled at 6-12 ml / h using a peristaltic pump, the reaction temperature was room temperature, and the continuous reaction time was 0-72 h.

[0021] The beneficial effects of this invention are:

[0022] This invention uses common cellulose-based materials as a carrier, and synthesizes iron-based metal-organic framework compounds in situ on the cellulose-based material via an impregnation method, followed by cobalt doping. The prepared heterogeneous catalyst efficiently activates potassium persulfate to generate active oxygen groups that degrade pollutants. Furthermore, this catalyst can be used in a filtration manner for long-term, continuous degradation of pollutants. Attached Figure Description

[0023] Figure 1 The X-ray diffraction (XRD) pattern of the prepared catalyst is shown.

[0024] Figure 2 This image shows a scanning electron microscope (SEM) image of the prepared catalyst.

[0025] Figure 3 Figure showing the effect of PMS and catalyst dosage on the batch degradation efficiency of Rhodamine B.

[0026] Figure 4 Figure showing the effect of flow rate on the continuous degradation of Rhodamine B Detailed Implementation

[0027] The specific experimental methods of the present invention will be described in detail below with reference to specific experimental examples. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0028] Experimental Case 1

[0029] The preparation steps of the filter paper-supported cobalt-doped metal-organic framework compound catalyst are as follows:

[0030] 10 mmol FeCl3·9H2O and 10 mmol fumaric acid were dissolved in 25 mL of deionized water, respectively, and named solution A and solution B. A filter paper with a diameter of 3 cm was soaked in solution A for 12 h, and then mixed with solution B by ultrasonication. The mixture was transferred to a 100 mL hydrothermal reactor and reacted at 80 °C for 2 h. After the reaction, the filter paper was rinsed three times with deionized water and dried in a freeze dryer for 4 h. 55.6 mmol urea and 22.4 mmol Co(NO3)2·6H2O were dissolved in 100 mL of deionized water and mixed thoroughly at room temperature. The freeze-dried filter paper was added to the mixed solution and heated in a water bath at 90 °C for 1 h. Finally, the obtained filter paper was washed with deionized water and freeze-dried to obtain the filter paper-supported cobalt-doped metal-organic framework compound catalyst.

[0031] X-ray diffraction (with appendix) Figure 1 It is known that the metal-organic framework compound MIL-88A was first successfully synthesized using the catalyst Co-M88A-FP, and its characteristic peaks disappeared after cobalt doping. Furthermore, scanning electron microscopy (SEM) was used to confirm this. Figure 2 It is known that the morphology of the metal-organic framework compound MIL-88A is disrupted, and its structure becomes porous and amorphous.

[0032] Experimental Case 2

[0033] Rhodamine B (RhB) degradation experiments were conducted in beakers. A 20 mg / L RhB solution was prepared using water as the solvent. 100 mL of the 20 mg / L RhB solution was added to a 100 mL beaker, along with a certain amount of potassium persulfate (PMS) and a certain amount of cobalt-doped metal-organic framework catalyst supported on filter paper. The reaction was heated in a water bath at 25 °C for 20 min. The rotation speed was 100 rpm during the reaction. 5 mL of the reaction solution was filtered, and 1 mL of methanol was added to stop the reaction. Residual Rhodamine B was quantitatively analyzed using a UV-Vis spectrophotometer. The results showed that the degradation rate increased with increasing PMS and catalyst concentrations. Furthermore, at 100 mg / L PMS and 100 mg / L catalyst concentrations, 20 mg / L Rhodamine B could be completely degraded within 20 min (see attached image). Figure 3 )

[0034] Experimental Case 3

[0035] Rhodamine B (RhB) degradation experiments were conducted in Buchner funnels. 40 mg / L RhB solutions and 20 mg / L PMS solutions were prepared using water as the solvent. The RhB and PMS solutions were added to the funnel at a 1:1 volume ratio using a peristaltic pump at a flow rate of 6 ml / h or 12 ml / h. The funnel had a diameter of 3 cm and contained a complete filter paper loaded with a cobalt-doped metal-organic framework catalyst. The degradation reaction was carried out at room temperature for 72 h. The filtered liquid was collected hourly, and the residual RhB was quantitatively analyzed using a UV-Vis spectrophotometer. The results showed that at a flow rate of 6 mg / L, the filter paper could completely degrade 20 mg / L Rhodamine B even after 72 h of continuous use; at a flow rate of 12 mg / L, the degradation rate of 20 mg / L Rhodamine B remained around 80% after 72 h of continuous use (see attached figure). Figure 4 )

[0036] Finally, it should be noted that the above embodiments are only used to further illustrate the preparation method and application of a cellulose-based material supported cobalt-doped metal-organic framework compound catalyst of the present invention. However, the present invention is not limited to the embodiments. Any simple modifications to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. The application of a cellulose-based material-supported cobalt-doped metal-organic framework compound catalyst in the degradation of rhodamine B by activated potassium persulfate, characterized in that: In the batch experiment, the catalyst, potassium persulfate, and rhodamine B were added to a beaker to form a reaction system; the reaction temperature was 25-45℃, the stirring speed was 100 rpm, the reaction time was 20 min, and the concentration of the pollutant rhodamine B was 20 mg / L. In the continuous experiment, the catalyst, potassium persulfate, and rhodamine B were added to the Buchner funnel to form a reaction system; the reaction temperature was room temperature, the flow rate was 6-12 mL / h, the reaction time was 72 h, the concentration of the pollutant rhodamine B was 20 mg / L, and the concentration of potassium persulfate was 100 mg / L. The preparation method of the catalyst includes the following specific steps: 10 mmol FeCl3·9H2O and 10 mmol fumaric acid were dissolved in 25 mL of deionized water, and named solution A and solution B, respectively. A filter paper with a diameter of 3 cm was soaked in solution A for 12 h, and then mixed with solution B by ultrasonication. The mixture was transferred to a 100 mL hydrothermal reactor and reacted at 80 °C for 2 h. After the reaction, the filter paper was rinsed three times with deionized water and placed in a freeze dryer to dry for 4 h. 55.6 mmol urea and 22.4 mmol Co(NO3)2·6H2O were dissolved in 100 mL of deionized water and mixed evenly at room temperature. The freeze-dried filter paper was added to the mixed solution and heated at 90 °C in a water bath for 1 h. Finally, the obtained filter paper was washed with deionized water and freeze-dried to prepare the filter paper-supported cobalt-doped metal-organic framework compound catalyst.

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