Mnfe2o4 / biomass-based photo-fenton motor and preparation method and application thereof

Abstract

The application discloses a MnFe2O4 / biomass-based photo-Fenton motor and a preparation method and application thereof, and belongs to the photo-Fenton catalysis field.The preparation method specifically comprises the following steps: firstly, MnFe2O4 is in-situ synthesized on a biomass-based gel bead constructed by crosslinking through an extrusion method and a coprecipitation method 2+ Secondly, the gel bead is subjected to cutting treatment, so that the gel bead presents a hemispherical shape with an asymmetric surface structure, and self-driving performance is given to the gel bead.The MnFe2O4 / biomass-based photo-Fenton motor prepared by the application has a hemispherical asymmetric structure, the structure enables the motor to discharge air bubbles when reaching a gas-liquid interface, and self-driven movement of the motor is given, so that self-mixing with pollutants can be realized without external force stirring, and the motor can efficiently remove antibiotic pollutants in water, and the motor can also be magnetically recycled, so that the problems of traditional Fenton catalyst agglomeration and low mass transfer efficiency are solved.

Description

TECHNICAL FIELD

[0001] The application discloses a MnFe2O4 / biomass-based photo-Fenton motor and a preparation method thereof, and applies the same to removal of tetracycline hydrochloride in water, and belongs to the technical field of environmental protection. BACKGROUND

[0002] At present, the technologies for treating TCH wastewater include microbial degradation, adsorption, membrane separation and advanced oxidation processes (AOPs). Among them, AOPs has mild reaction conditions and strong oxidation capacity, and is a research hotspot in recent years. AOPs mainly include photo-Fenton oxidation method, electrochemical oxidation method, photocatalytic oxidation method and ozone oxidation method, wherein the Fenton oxidation method has the advantages of fast reaction rate, small secondary pollution and simple operation, MnFe2O4 is a transition metal oxide which can effectively adsorb and catalytically degrade pollutants in water, and has the characteristics of easy loading, magnetic recovery and simple synthesis, and is a suitable candidate for Fenton catalyst in AOPs reaction. However, the defect of easy agglomeration limits the catalytic efficiency, and the biomass-based material is a green and naturally degradable material, which can effectively inhibit the agglomeration of MnFe2O4 nanoparticles by loading MnFe2O4 on the biomass-based gel, and the functional groups on the surface and the high specific surface area structure are beneficial to adsorb more pollutants, thereby improving the catalytic effect.

[0003] Generally, MnFe2O4 / gel beads need to be stirred or shaken when applied to photo-Fenton technology to enhance the contact with pollutants, but mechanical external force can easily damage the structure of the gel. Macroscopic size (>100 μm) self-driven intelligent materials (mini-motor) refer to macroscopic systems that can spontaneously move or provide driving force for objects and make them move under external stimulation, which can convert other forms of energy into kinetic energy for autonomous movement. Compared with traditional materials, its movement performance can enhance mass transfer in fluid media by generating convection, which helps to overcome diffusion limitations, promote material and particle transport, and improve reaction rate. MnFe2O4 / gel beads can catalyze the decomposition of H2O2 to produce O2 bubbles during the photo-Fenton reaction process, and are expected to realize autonomous movement by floating-up and diving-up through buoyancy. However, this requires the bubbles to be attached to the gel in the water body and released after reaching the water surface, so as to regulate the buoyancy to realize self-driving, which requires the structure of the gel to be designed and regulated. SUMMARY

[0004] The application discloses a preparation method of a MnFe2O4 / biomass-based photo-Fenton motor and application thereof, and belongs to the photo-Fenton catalysis field.The MnFe2O4 / biomass-based photo-Fenton motor prepared by the application has an asymmetric structure, which enables the motor to discharge air bubbles when reaching a gas-liquid interface, realizes self-driving of the MnFe2O4 / gel bead through attachment and detachment of O2 bubbles on the gel, and endows the motor with autonomous movement of floating and diving; meanwhile, the motor shows high degradation performance on antibiotics in the self-driven movement process.The photo-Fenton motor can realize autonomous mixing with pollutants without a stirring device, can efficiently remove pollutants in water, and can be magnetically recycled, and thus has great potential in practical application.

[0005] The application discloses a preparation method of a MnFe2O4 / biomass-based photo-Fenton motor, and specifically comprises the following steps.

[0006] S1: a natural high-molecular containing carboxyl is dispersed in deionized water, stirred at 25 DEG C for 30 minutes and ultrasonically treated for 10 minutes to uniformly disperse, and the obtained high-molecular dispersion liquid is slowly added drop by drop into a manganese salt solution by using a syringe to obtain Mn 2+ crosslinked biomass-based gel beads, and is left to stand for 4 hours to solidify;

[0007] S2: the biomass-based gel beads obtained in step S1 are washed and soaked in deionized water for 30 minutes to remove excess Mn 2+ , and then are soaked in a mixed solution of manganese salt and iron salt for 40 minutes, so that Fe 3+ ions and Mn 2+ ions are replaced into the gel interior, the molar ratio of Mn 2+ to Fe 3+ in the mixed solution of manganese salt and iron salt is 1:2;

[0008] S3: the mixture in step S2 is slowly warmed, and the pH is adjusted to 11-12 to react, and then is filtered and washed until the pH is 7 to obtain biomass-based gel beads;

[0009] S4: the biomass-based gel beads in step S3 are cut into hemispherical structures along the central axis by using a blade to form photo-Fenton motors with asymmetric surfaces, and the MnFe2O4 / biomass-based photo-Fenton motor is obtained.

[0010] The natural high-molecular containing carboxyl in step S1 is carboxymodified cellulose nanofiber, sodium alginate or sodium hyaluronate, etc.; the manganese salt is MnCl2 or Mn(NO3)2, and the mass fraction of the manganese salt solution is 0.5%-5%; the Mn 2+ crosslinked biomass-based gel beads have a diameter of 2mm to 4mm.

[0011] The solute in the mixed solution of the manganese salt and the iron salt in the step S2 is one of MnCl2·4H2O and FeCl3·6H2O, Mn(NO3)2·4H2O and Fe(NO3)3·9H2O, the molar concentration of Mn 2+ in the mixed solution is 10-80 mmol / L, wherein the molar ratio of Mn 2+ to Fe 3+ is 1:2.

[0012] In the step S3, the reaction temperature is 75-90℃.

[0013] In the step S4, the spherical gel beads are cut into hemispherical gel beads along the central axis.

[0014] A MnFe2O4 / biomass-based photo-Fenton motor is prepared by the preparation method.

[0015] The application of the MnFe2O4 / biomass-based photo-Fenton motor in the field of environmental protection technology uses the photo-Fenton motor to remove organic pollutants in the water environment.

[0016] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0017] 1. The MnFe2O4 / biomass-based photo-Fenton motor prepared by the present application has an asymmetric structure, which enables the motor to expel air bubbles when reaching the gas-liquid interface, giving it autonomous movement of floating and diving, enhancing the interaction frequency of the motor and pollutants in water, and showing high photo-Fenton degradation performance on antibiotics during movement.

[0018] 2. The MnFe2O4 / biomass-based photo-Fenton motor prepared by the present application uses biomass-based gel beads as a carrier for MnFe2O4 photo-Fenton catalyst material, which can avoid agglomeration of MnFe2O4 particles and also enable magnetic recovery. DETAILED DESCRIPTION

[0019] Figure 1 The digital photo and particle size distribution graph of the MnFe2O 4 / CNF gel beads in Example 2.

[0020] Figure 2 The XRD graph of the MnFe2O4 / CNF photo-Fenton motor (S-MFC50) and MnFe2O4 in Example 2.

[0021] Figure 3 The floating and diving movement photo of the MnFe2O4 / CNF photo-Fenton motor (S-MFC50) in Example 2.

[0022] Figure 4The movement speed of the MnFe2O4 / CNF photo-Fenton motor (S-MFC50) in Example 2 under different H2O2 concentrations.

[0023] Figure 5 The removal effect of tetracycline hydrochloride by the MnFe2O4 / CNF photo-Fenton motor (S-MFC50) in Example 2 under different pH conditions over time. DETAILED DESCRIPTION

[0024] The technical solutions of the present application are further described in detail below in combination with specific embodiments, but the protection scope of the present application is not limited thereto. It should be pointed out that the relevant technical personnel in the art can easily understand the structural design principles of the present application, and the technical personnel in the art can make any changes or modifications to the present application, but other examples obtained without creative labor are within the scope of protection of the present application.

[0025] Example 1

[0026] Step 1, disperse the carboxyl-modified cellulose nanofiber (CNF) in deionized water, stir at 25°C for 30 minutes and ultrasonic for 10 minutes to make it uniformly dispersed. The obtained CNF dispersion is slowly added dropwise to a 1wt% MnCl2 solution using a syringe, and Mn 2+ Crosslink the CNF gel beads and let stand for 4 hours to solidify.

[0027] Step 2, wash and soak the CNF gel beads obtained in step 1 in deionized water for 30 minutes to remove excess Mn 2+ , and then soak them in a mixed solution of MnCl2·4H2O and FeCl3·6H2O for 40 minutes, and Fe 3+ ions and Mn 2+ ions are replaced into the gel interior, wherein the molar ratio of Mn 2+ to Fe 3+ is 1:2, and the Mn 2+ ion concentration is 40mM.

[0028] Step 3, slowly warm the solution obtained in step 2 to 90°C while adjusting the pH to 11-12, and keep for 40 minutes, and then filter and wash to pH 7 to obtain CNF gel beads (MFC40).

[0029] Step 4, cut it along the central axis using a blade to obtain MnFe2O4 / CNF photo-Fenton motor (S-MFC40).

[0030] Example 2

[0031] Step 1, Carboxyl-modified cellulose nanofiber (CNF) was dispersed in deionized water, stirred at 25°C for 30 minutes and ultrasonicated for 10 minutes to disperse uniformly. The obtained CNF dispersion was slowly added dropwise to a 1 wt% MnCl2solution using a syringe, to obtain Mn 2+ Crosslink the CNF gel beads and let them cure for 4 hours.

[0032] Step 2, The CNF gel beads obtained in step 1 were washed and soaked in deionized water for 30 minutes to remove excess Mn 2+ , and then soaked in a mixed solution of MnCl2-4H2O and FeCl3-6H2O for 40 minutes, replacing Fe 3+ ions and Mn 2+ ions into the gel interior, with a molar ratio of Mn 2+ to Fe 3+ of 1:2 and a Mn 2+ ion concentration of 50 mM.

[0033] Step 3, The solution obtained in step 2 was slowly warmed to 90°C while adjusting the pH to 11-12, and kept for 40 minutes, and then filtered and washed to pH 7 to obtain CNF gel beads (MFC50).

[0034] Step 4, After cutting it in half along the central axis using a blade, MnFe2O4 / CNF photo-Fenton motor (S-MFC50) was obtained.

[0035] Example 3

[0036] Step 1, Carboxyl-modified cellulose nanofiber (CNF) was dispersed in deionized water, stirred at 25°C for 30 minutes and ultrasonicated for 10 minutes to disperse uniformly. The obtained CNF dispersion was slowly added dropwise to a 1 wt% MnCl2solution using a syringe, to obtain Mn 2+ Crosslink the CNF gel beads and let them cure for 4 hours.

[0037] Step 2, The CNF gel beads obtained in step 1 were washed and soaked in deionized water for 30 minutes to remove excess Mn 2+ , and then soaked in a mixed solution of MnCl2-4H2O and FeCl3-6H2O for 40 minutes, replacing Fe 3+ ions and Mn 2+ ions into the gel interior, with a molar ratio of Mn 2+ to Fe 3+ of 1:2 and a Mn 2+ ion concentration of 60 mM.

[0038] Step 3, the solution obtained in step 2 was slowly warmed to 90°C while adjusting the pH to 11-12 and keeping for 40 minutes, then filtered and washed to pH 7 to obtain CNF gel beads (MFC60).

[0039] Step 4, after cutting it along the central axis using a blade, MnFe2O4 / CNF photo-Fenton motor (S-MFC60) was obtained.

[0040] Example 4

[0041] Step 1, sodium alginate (SA) was dispersed in deionized water, stirred at 25°C for 30 minutes and ultrasonic for 10 minutes to make it uniformly dispersed. The obtained SA dispersion was slowly added dropwise to a 1wt% MnCl2 solution using a syringe, and Mn 2+ SA gel beads were crosslinked and cured for 4 hours.

[0042] Step 2, the SA gel beads obtained in step 1 were washed and soaked in deionized water for 30 minutes to remove excess Mn 2+ , then immersed in a mixed solution of MnCl2·4H2O and FeCl3·6H2O for 40 minutes, and Fe 3+ ions and Mn 2+ ions were replaced into the gel interior, where the molar ratio of Mn 2+ to Fe 3+ was 1:2, and the concentration of Mn 2+ ions was 50mM.

[0043] Step 3, the solution obtained in step 2 was slowly warmed to 90°C while adjusting the pH to 11-12 and keeping for 40 minutes, then filtered and washed to pH 7 to obtain SA gel beads (MFSA50).

[0044] Step 4, after cutting it along the central axis using a blade, MnFe2O4 / SA photo-Fenton motor (S-MFSA50) was obtained.

[0045] Example 5

[0046] Step 1, sodium alginate (SA) was dispersed in deionized water, stirred at 25°C for 30 minutes and ultrasonic for 10 minutes to make it uniformly dispersed. The obtained SA dispersion was slowly added dropwise to a 1wt% MnCl2 solution using a syringe, and Mn 2+ SA gel beads were crosslinked and cured for 4 hours.

[0047] Step 2, the SA gel beads obtained in step 1 were washed and soaked in deionized water for 30 minutes to remove excess Mn 2+, then immersed in a mixed solution of MnCl2-4H2O and FeCl3-6H2O for 40 min, and Fe 3+ ions and Mn 2+ ions were replaced into the interior of the gel, in which the molar ratio of Mn 2+ to Fe 3+ was 1:2, and the concentration of Mn 2+ ions was 50 mM.

[0048] Step 3, the solution obtained in Step 2 was slowly warmed to 90°C while adjusting the pH to 11-12, and maintained for 40 min, then filtered and washed to pH 7 to obtain NaHA gel beads (MFHA50).

[0049] Step 4, after cutting it along the central axis using a blade, MnFe2O4 / HA photo-Fenton motor (S-MFHA50) was obtained.

[0050] Figure 1 are digital photos of MnFe2O4 / CNF gel beads (MFC50) in Example 2 and particle size distribution diagram. It can be seen that MnFe2O 4 / CNF gel beads present dark brown-black color, and the MnFe2O 4 / CNF gel beads have a particle size distribution of 1.7 mm-3.7 mm, mainly concentrated around 2.5 mm, indicating that the synthesized MnFe2O 4 / CNF gel beads have a relatively uniform size.

[0051] Figure 2 are XRD patterns of MnFe2O4 / CNF photo-Fenton motor (S-MFC50) and MnFe2O4 in Example 2. In the XRD pattern of MnFe2O4, obvious diffraction peaks were observed at 29.65°, 34.94°, 42.67°, 56.06° and 61.65°, which correspond to (220), (311), (400), (511) and (440) planes, respectively, consistent with the XRD standard card of MnFe2O4 (JCPDS No. 10-0319).

[0052] Figure 3 is the self-driving process of MnFe2O4 / CNF photo-Fenton motor (S-MFC50) in Example 2. The motor was placed in the solution, and due to the action of gravity, the motor would dive to the bottom of the water. When H2O2 was added, the motor would quickly float to the water surface in a short time (14 s) ( Figure 3 (b-d)). After reaching the water surface, the motor stayed on the water surface for 2 s, then began to dive to the middle position of the water body ( Figure 3 (e-g)). After a short stay, it continued to float for the next cycle ( Figure 3(h).

[0053] Figure 4 The movement speed of the MnFe2O4 / CNF photo-Fenton motor (S-MFC50) in Example 2 at different H2O2 concentrations. As the H2O2 concentration increased from 0.08% to 0.16%, the upward speed increased from 7.5 mms -1 to 9.25 mms -1 , but its downward speed decreased from 12.0 mms -1 to 6.0 mms -1 . When the H2O2 concentration reached 0.24%, its upward speed (12.3 mms -1 ) was the maximum, and the downward speed was 6.8 mms -1 . As the H2O2 concentration further increased, both its upward and downward speeds decreased.

[0054] Figure 5 The removal effect of tetracycline hydrochloride by the MnFe2O4 / CNF photo-Fenton motor (S-MFC50) in Example 2 under different pH conditions over time. As can be seen from the figure, the motor showed the highest removal capacity at pH = 3, and could completely degrade a 20 mgL -1 concentration of tetracycline hydrochloride solution in 20 minutes, and then as the pH value increased, the degradation performance of the motor on tetracycline hydrochloride decreased significantly, with the degradation rates at pH 5 and 7 being 58.1% and 52.1%, respectively.

Claims

1. A method for preparing a MnFe204 / biomass-based photo-Fenton motor, characterized in that, The preparation method specifically comprises the following steps: S1: The natural high molecule containing carboxyl group was dispersed in deionized water, stirred at 25 °C for 30 minutes and ultrasonic for 10 minutes to make it uniformly dispersed, the obtained high molecule dispersion liquid was added dropwise to the manganese salt solution using a syringe, to obtain Mn 2+ crosslinked biomass-based gel beads, and left to stand for 4 hours to solidify; S2: The biomass based gel beads obtained in step S1 were washed and soaked in deionized water for 30 minutes to remove excess Mn 2+ After that, it was soaked in a mixed solution of manganese and iron salts for 40 minutes, Fe 3+ and Mn 2+ ions were replaced into the gel interior, the molar ratio of Mn 2+ and Fe 3+ in the mixed solution of manganese and iron salts was 1:2; S3: heating the mixture in step S2 while adjusting the pH to 11-12 to perform a reaction, and then filtering and washing to a pH of 7 to obtain biomass-based gel beads; S4: cutting the biomass-based gel beads in step S3 into hemispherical structures along the central axis using a blade to form a light Fenton motor with an asymmetric surface, thereby obtaining MnFe2O4 / biomass-based light Fenton motor.

2. The method of claim 1, wherein, In the step S1, the natural high molecular containing carboxyl is carboxymethylated cellulose nanofiber, sodium alginate or sodium hyaluronate; the manganese salt is MnCl2 or Mn(NO3)2, and the mass fraction of the manganese salt solution is 0.5% to 5%; the Mn 2+ The diameter of the crosslinked biomass-based gel beads is 2 to 4 millimeters.

3. The preparation method according to claim 1, characterized in that, The solute in the mixed solution of the manganese salt and the iron salt in the step S2 is one of MnCl2·4H2O and FeCl3·6H2O, Mn(NO3)2·4H2O and Fe(NO3)3·9H2O, the molar concentration of Mn 2+ in the mixed solution is 10-80 mmol / L, and the molar ratio of Mn 2+ to Fe 3+ is 1:

2.

4. The preparation method according to claim 1, characterized in that, In the step S3, the reaction temperature is 75-90 ℃.

5. The MnFe2O4 / biomass-based light Fenton motor prepared by the preparation method in any one of claims 1-4.

6. Use of the MnFe204 / biomass-based photo-Fenton motor according to claim 5 in the field of environmental protection technology, characterized in that, The light Fenton motor is used for removing organic pollutants in a water environment.

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