A supported br-mn02 catalyst, its preparation method and application

Abstract

The application relates to the technical field of advanced oxidation wastewater treatment, in particular to a supported Br-MnO2 catalyst and a preparation method and application thereof. The application modifies the electronic structure of MnO2 by Br doping, and combines a foamed nickel (NF) carrier and a thermoplastic polyurethane (TPU) binder to construct a supported composite catalyst which is stable in structure and rich in active sites. In the process of activating peroxymonosulfate (PMS) to degrade organic pollutants in printing and dyeing wastewater, the catalyst exhibits excellent catalytic performance and cycle stability. The prepared catalyst has simple process and controllable cost, and the effluent quality of the printing and dyeing wastewater treated by the catalyst can completely meet the reuse standard of the textile dyeing process, and there is no significant difference between the effluent and industrial water in key indexes such as color difference and K / S value, so the catalyst has a wide industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of advanced oxidation wastewater treatment technology, specifically to a supported Br-MnO2 catalyst, its preparation method, and its application. Background Technology

[0002] Dyeing and printing wastewater contains a large number of complex and recalcitrant organic pollutants, such as azo dyes, anthraquinone dyes, and triphenylmethane dyes, which are characterized by high color intensity, high COD content, and strong biotoxicity. Conventional biological treatment processes are insufficient to completely degrade them, and the effluent often fails to meet the water quality requirements for reuse in dyeing processes. Based on sulfate free radicals ( SO4 - Advanced oxidation technologies, such as persulfate (PMS), have shown potential in the deep treatment of dyeing and printing wastewater due to their strong oxidizing power and wide pH adaptability. PMS is a commonly used sulfate radical precursor, and its activation efficiency is highly dependent on catalyst performance.

[0003] Manganese dioxide (MnO2) is considered a promising heterogeneous PMS activation material due to its multivalent state characteristics, environmental friendliness, and low cost. However, the catalytic activity of MnO2 is limited, and the number of its surface active sites and reaction kinetics are insufficient to meet the requirements for efficient treatment. Furthermore, nano-sized MnO2 powder is prone to agglomeration and difficult to separate and recover during actual water treatment processes, and is easily lost in continuous flow processes, leading not only to decreased activity but also potential secondary pollution.

[0004] Therefore, controlling the electronic structure and surface properties of MnO2 through elemental doping to increase active sites and then firmly loading it onto a support to construct a structured catalyst is key to improving its catalytic performance and practicality. This is of great significance for promoting the application of PMS advanced oxidation technology in actual wastewater treatment. Summary of the Invention

[0005] This invention provides a supported Br-MnO2 catalyst, its preparation method, and its applications. By modifying the electronic structure of MnO2 with Br doping and combining it with a nickel foam (NF) support and a thermoplastic polyurethane (TPU) binder, a structurally stable supported composite catalyst with abundant active sites is constructed. This catalyst exhibits excellent catalytic performance and cycle stability during the degradation of organic pollutants in dyeing and printing wastewater by activated persulfate (PMS). The prepared catalyst is simple to process and cost-effective. The effluent quality of dyeing and printing wastewater after deep treatment with this catalyst fully meets the standards for reuse in textile dyeing processes, showing no significant difference from industrial water in key indicators such as color difference and K / S value, demonstrating broad industrial application prospects.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a supported Br-MnO2 catalyst, comprising: S1. Dissolve divalent manganese salt, persulfate and bromide in deionized water, perform hydrothermal reaction, separate, wash and dry, and calcine to obtain Br-MnO2 powder; the molar ratio of manganese in the divalent manganese salt, persulfate and bromine in potassium bromide is 1:1:(0.4~0.6); S2. The nickel foam substrate is dried after being acid-washed, alcohol-washed, and water-washed. S3. First, disperse the Br-MnO2 powder obtained in S1 in a polyurethane solution to obtain a Br-MnO2 / TPU mixed dispersion; then, impregnate the nickel foam obtained in S2 in the Br-MnO2 / TPU mixed solution, stir and remove it, and then centrifuge and dry it to obtain a supported Br-MnO2 catalyst.

[0007] This invention optimizes the electronic structure of manganese sites by introducing bromine to promote the transformation of γ-MnO2 to the highly active α phase. The weak electron-withdrawing properties of bromine lengthen the Mn-O bond, weaken its covalent nature, enhance the electron density of manganese sites, and increase the specific surface area, oxygen vacancy density, and Mn(III) content, thus improving the Mn-O2 electron density. g The increased orbital electron occupancy rate results in the catalyst exhibiting superior catalytic performance in the degradation of organic pollutants in dyeing and printing wastewater by activated persulfate (PMS).

[0008] This invention utilizes three-dimensional porous nickel foam as a carrier and employs a thermoplastic polyurethane (TPU) binder to load the Br-MnO2 active component onto the carrier surface, constructing a structurally stable supported composite catalyst rich in active sites. On one hand, the strong interfacial adhesion and film-forming properties of TPU effectively suppress the dissolution and detachment of the active component during the reaction process. On the other hand, the three-dimensional conductive nickel foam framework not only provides excellent mechanical support, but its interconnected porous structure and high conductivity also promote mass transfer and rapid electron transfer. The strong bonding of TPU and the conductive network of the nickel foam create a synergistic enhancement effect, jointly improving the catalyst's activation efficiency for persulfate and promoting the generation of a large number of reactive oxygen species, thereby achieving deep oxidation and efficient removal of organic pollutants in dyeing and printing wastewater.

[0009] Preferably, in S1, the divalent manganese salt is at least one of manganese sulfate, manganese nitrate, or manganese carbonate.

[0010] And / or, the persulfate is at least one of ammonium persulfate, potassium persulfate, or sodium persulfate.

[0011] And / or, the bromide is at least one of potassium bromide, ammonium bromide, or sodium bromide.

[0012] Preferably, in S1, the temperature of the hydrothermal reaction is 80~100℃.

[0013] And / or, the hydrothermal reaction time is 22 to 26 hours.

[0014] And / or, the calcination temperature is 250~350℃.

[0015] And / or, the calcination time is 1 to 3 hours.

[0016] Preferably, in S3, the polyurethane solution is a mixed solution of thermoplastic polyurethane and N,N-dimethylformamide.

[0017] Preferably, the concentration of the thermoplastic polyurethane is 0.3~0.7 g / L.

[0018] Preferably, in step S3, the concentration of Br-MnO2 powder in the Br-MnO2 / TPU mixed dispersion is 3~7 g / L.

[0019] Preferably, in step S3, the stirring time is 5 to 15 minutes.

[0020] And / or, the drying temperature is 90~110℃.

[0021] And / or, the drying time is 0.5 to 1.5 hours.

[0022] The present invention also provides a supported Br-MnO2 catalyst prepared by the above preparation method.

[0023] This invention also provides the application of a supported Br-MnO2 catalyst in activating persulfate for deep treatment of dyeing and printing wastewater and realizing its dyeing reuse.

[0024] Preferably, the application is as follows: the dyeing and printing wastewater is subjected to persulfate activation oxidation treatment under the action of the supported Br-MnO2 catalyst, and the treated effluent can be directly reused in the process of dyeing knitted cotton with reactive dyes.

[0025] Therefore, the present invention has the following beneficial effects: 1. This invention introduces bromine to promote the transformation of γ-MnO2 into the highly active α-phase, thereby optimizing the electronic structure of manganese sites, effectively enhancing the electron cloud density on the catalyst surface, and improving the accessibility of active sites and oxygen vacancy concentration. This invention promotes the activation efficiency of the catalyst for persulfate, stimulating the generation of a large number of sulfate free radicals, thus achieving efficient oxidative degradation of organic pollutants in dyeing and printing wastewater.

[0026] 2. This invention uses TPU binder to fix the powdered catalyst onto a highly conductive nickel foam with a large specific surface area. The strong adhesion of TPU and the conductive network of the nickel foam form a synergistic enhancement effect, jointly improving the activation efficiency of the catalyst for persulfate and promoting the generation of a large number of reactive oxygen species, thereby achieving deep oxidation and efficient removal of organic pollutants in dyeing and printing wastewater.

[0027] 3. This invention utilizes the prepared supported Br-MnO2 catalyst to activate PMS, constructing a highly efficient heterogeneous advanced oxidation system. This system can achieve deep degradation and decolorization of organic pollutants in dyeing and printing wastewater, and the treated effluent meets the standards for reuse in dyeing processes, allowing it to be directly used in subsequent production, thus realizing a resource-based closed loop of wastewater treatment and reuse.

[0028] 4. The preparation process of this invention is simple and the conditions are mild. The raw materials used are inexpensive and readily available, making it suitable for large-scale production. It has significant potential for industrial application and provides an economical and efficient technical solution for the deep treatment and reuse of dyeing and printing wastewater. Attached Figure Description

[0029] Figure 1 PXRD patterns of γ-MnO2 powders prepared in Example 1 and Comparative Examples 1-4 (a); PXRD patterns of γ-MnO2 catalysts prepared in Example 1 and Comparative Examples 4-6 (b).

[0030] Figure 2 FE-SEM images and EDS elemental mappings of γ-MnO2 powders prepared in Example 1 and Comparative Examples 1-4: γ-MnO2 (a, b); F-MnO2 (c, d); Cl-MnO2 (e, f); Br-MnO2 (g, h); I-MnO2 (i, j).

[0031] Figure 3 The N2 adsorption / desorption curves (a) and pore size distribution diagrams (b) of the γ-MnO2 powders prepared in Example 1 and Comparative Examples 1-4 are shown.

[0032] Figure 4 XPS spectra of γ-MnO2 powders prepared in Example 1 and Comparative Examples 1-4: Mn 2p (a); O 1s (b); Mn3s (c).

[0033] Figure 5 The solid EPR spectra of γ-MnO2 powders prepared in Example 1 and Comparative Examples 1-4 are shown.

[0034] Figure 6 The CV curve (a), LSV curve (b), Tafel polarization curve (c), and corrosion current change (d) of the γ-MnO2 powders prepared in Example 1 and Comparative Examples 1, 2, and 4 are shown.

[0035] Figure 7 The degradation of p-chlorophenol in the PMS system activated by the supported catalysts prepared in Example 1 and Comparative Examples 1-6 is shown in (a) and its pseudo-first-order rate constant k is shown in (b).

[0036] Figure 8 It is a self-assembling continuous flow reactor.

[0037] Figure 9 The degradation rate of phenol by the supported catalyst prepared in Example 1 during continuous operation of PMS activation.

[0038] Figure 10 This is a schematic diagram of the dyeing process. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0040]

Example

[0041] (2) Pretreatment of nickel foam: NF was cut into substrates of 100×200×1.5mm. First, it was sonicated in hydrochloric acid solution at pH = 2 for 5 minutes to remove the oxide layer formed by natural oxidation on the surface; then it was sonicated in anhydrous ethanol solution for 5 minutes to remove adsorbed organic pollutants on the surface; finally, it was sonicated in deionized water for 5 minutes to ensure the cleanliness of the NF substrate surface. After cleaning, the NF was placed in an 80℃ vacuum oven to dry overnight.

[0042] (3) Preparation of supported Br-MnO2 catalyst: First, 25 mg of thermoplastic polyurethane masterbatch was weighed and dissolved in 50 mL of DMF solvent to prepare a 0.5 g / L TPU solution. The Br-MnO2 powder catalyst (5 g / L) was uniformly dispersed in the TPU solution by ultrasonic dispersion to obtain a Br-MnO2 / TPU mixed solution. Then, the pretreated NF was immersed in the above mixed solution, stirred for 10 min, taken out, and slightly centrifuged to remove the dispersion on the surface of NF. It was then placed in a 100℃ oven and dried for 1 h to obtain the supported Br-MnO2 catalyst, denoted as BMNFT.

[0043] Comparative Example 1 This comparative example is basically the same as Example 1, except that: (1) potassium bromide in the precursor solution is replaced with an equal amount of potassium fluoride to obtain a black powder catalyst, denoted as F-MnO2; after treatment by (2) and (3), a supported F-MnO2 catalyst is obtained, denoted as FMNFT.

[0044] Comparative Example 2 This comparative example is basically the same as Example 1, except that: (1) potassium bromide in the precursor solution is replaced with an equal amount of potassium chloride to obtain a black powder catalyst, denoted as Cl-MnO2; after treatment by (2) and (3), a supported Cl-MnO2 catalyst is obtained, denoted as CMNFT.

[0045] Comparative Example 3 This comparative example is basically the same as Example 1, except that: (1) potassium bromide in the precursor solution is replaced with an equimolar amount of potassium iodide to obtain a black powder catalyst, labeled as I-MnO2; after treatment by (2) and (3), a supported I-MnO2 catalyst is obtained, denoted as IMNFT.

[0046] Comparative Example 4 This comparative example is basically the same as Example 1, except that: (1) no potassium halide salt is added to the precursor solution to obtain a black powder catalyst, denoted as γ-MnO2; after treatment by (2) and (3), a supported γ-MnO2 catalyst is obtained, denoted as MNFT.

[0047] Comparative Example 5 This comparative example is basically the same as Example 1, except that: (1) the molar amount of potassium bromide in the precursor solution is adjusted to 0.003 mol to obtain a black powder catalyst, denoted as Br-MnO2-0.1; after treatment by (2) and (3), a supported Br-MnO2 catalyst is obtained, denoted as BMNFT-0.1.

[0048] Comparative Example 6 This comparative example is basically the same as Example 1, except that: (1) the molar amount of potassium bromide in the precursor solution is adjusted to 0.024 mol to obtain a black powder catalyst, denoted as Br-MnO2-0.8; after treatment by (2) and (3), a supported Br-MnO2 catalyst is obtained, denoted as BMNFT-0.8.

[0049] [Performance Testing] Electrochemical performance testing: Cyclic voltammetry (CV), Tafel polarization, and linear sweep voltammetry (LSV) curves of the samples were measured using an E660 electrochemical workstation from Shanghai Chenhua Instrument Co., Ltd. 5 mg of catalyst powder, 0.5 mL of ethanol, and 50 μL of perfluorosulfonic acid resin solution were mixed and dispersed evenly. Then, 5.0 μL of the dispersion was pipetted onto a 5 mm glassy carbon electrode surface and allowed to air dry to obtain the working electrode. To verify the formation of complexes (PMS) on the surface of γ-MnO2 catalysts with different halogen doping... To investigate the role of phenol in pollutant degradation, a dual-chamber H-type electrolytic cell system was designed and constructed. The two chambers were filled with 50 mL of phenol solution (anode chamber) and 50 mL of PMS solution (cathode chamber), respectively, and connected by a salt bridge filled with agar-saturated KCl. Catalyst-coated Pt sheets were used as the working electrode (anode) and counter electrode (cathode), respectively, connected via a multimeter. After the reaction started, electrons flowed from the anode to the cathode through an external circuit. Samples were taken from the anode chamber at specific time points, filtered through a 0.22 μm filter membrane, and the phenol concentration was determined by HPLC to evaluate the PMS migration via the salt bridge. Indirect oxidation capacity of pollutants. Test conditions: saturated calomel reference electrode; electrolyte: 80 mL of 0.1 mol / L Na2SO4 solution; scan range: -1 to 1 V; scan rate: 0.01 V / s.

[0050] Activated PMS degradation experiment: Prepare a phenol solution with a concentration of 20 mg / L (or a 1:1 (mass ratio) mixture of phenol and p-chlorophenol containing 20 mg / L phenol and 20 mg / L p-chlorophenol). Accurately weigh 10 mg of catalyst and add it to 50 mL of pollutant solution, sonicating for 30 min to ensure uniform dispersion. Then, add 0.5 mM PMS to initiate the reaction. Every 2 min, transfer 1 mL of the reaction solution sample and immediately filter it through a 0.22 μm pore size aqueous microporous filter. Quickly add 30 μL of 0.1 mol·L⁻¹ PMS to the filtrate. -1 The residual PMS and ROS were quenched in Na2S2O3 solution to terminate the continued oxidation. As a control experiment, the PMS system alone was used without a catalyst, while other experimental conditions remained consistent. The degradation rate of organic pollutants (1-C) was measured. t / C0) is calculated using the following formula: 1-Ct / C0=1-N t / N0 Where C t C0 is the concentration of phenol (and p-chlorophenol) solution at time t, in mg / L; C0 is the initial concentration of phenol (and p-chlorophenol) solution, in mg / L; N0 is the peak area of ​​the characteristic peak of phenol (and p-chlorophenol) solution at time t; N0 is the concentration of phenol (and p-chlorophenol) solution at time t. t The peak area represents the initial characteristic peak of phenol (and p-chlorophenol).

[0051] The removal performance of the catalyst for phenol under 10 h continuous operation: Phenol was selected as the model pollutant. Construction of a self-assembled continuous fixed-bed flow-through reactor: BMNFT catalyst was cut into several 20 mm diameter discs and filled into the reactor pipes. During the experiment, PMS was added to a 10 mg / L phenol solution on the left side, driven by a peristaltic pump, flowing upwards through the catalyst bed reactor at a flow rate of 1 rpm. The effluent after the reaction was collected from the upper outlet. To track the degradation of the pollutant during the reaction, samples were taken from the effluent at regular intervals, and the phenol concentration was immediately determined by HPLC.

[0052] Dyeing performance test of recycled dyeing wastewater after deep treatment: 500 mL of dyeing wastewater was treated with 10 mM PMS activated by 0.2 g / L catalyst for 120 min. The recycled water was directly used in the dyeing process of reactive dye (Kyoto Blue K-BF) and compared with the dyed fabric samples using tap water. The dyeing wastewater, knitted cotton fabric, reactive dye, and auxiliaries used in the experiment were all provided by Zhejiang Daneng Dyeing Co., Ltd. according to the company's main processing categories. The dyeing performance of recycled dyeing wastewater after deep treatment with different catalysts was evaluated by comparing the dyeing rate, color difference, and color depth of the dyed fabric samples. First, the cotton fabric was cut into 5×20 cm pieces, weighing approximately 2.25 g. The specific dyeing process is as follows: (1) Staining prescription Dye: 5 (owf) %; Sodium sulfate: 70 g / L; Soda ash: 20 g / L; Leveling agent: 1 g / L.

[0053] (2) Dyeing process flow like Figure 10 As shown.

[0054] (3) Soap washing prescription Soap flakes: 2g / L; Bath ratio: 1:20; Temperature: 98℃; Time: 10min.

[0055] PXRD tests were performed on the γ-MnO2 powders prepared in Example 1 and Comparative Examples 1-6, and the results are as follows: Figure 1 As shown. By Figure 1(a) It can be seen that the PXRD pattern of γ-MnO2 shows the typical diffraction pattern of standard γ-MnO2 at 2θ=22.43°, 37.12° and 56.14°, indicating that the target crystal form was successfully prepared. After halogen doping modification, the PXRD patterns of Br-MnO2, F-MnO2, Cl-MnO2 and I-MnO2 all show new characteristic diffraction peaks at 2θ=12.78°, 18.10° and 28.84°, which correspond to the (110), (200) and (310) crystal planes of α-MnO2, respectively. This phenomenon confirms that the four halogen doping can effectively induce the crystal transformation of γ-MnO2 to α-MnO2. However, the degree of crystal transformation varies significantly depending on the halogen doping method: F-MnO2 and Cl-MnO2 spectra still retain characteristic peaks of the γ phase (such as the (301) crystal plane at 2θ = 22.43°), indicating that they are γ / α mixed-phase structures; while Comparative Example 3 shows characteristic diffraction peaks of the (201) and (210) crystal planes of Mn(IO3)2 at 2θ = 25.61° and 30.12°, indicating that I-MnO2 forms a mixed crystal phase of α-MnO2 and Mn(IO3)2 iodate. This phenomenon indicates that iodine doping not only induces crystal transformation but also accompanies the generation of iodate byproducts, which may interfere with the electronic structure regulation of Mn active sites. In contrast, Br-MnO2 shows that the γ phase diffraction peaks completely disappear, presenting a single α phase structure, indicating that the crystal phase transformation of γ-MnO2 to α-MnO2 guided by bromine doping is more significant than that of other halogen atoms. By adjusting the Br / Mn doping ratio ( Figure 1 (b) It was found that when Br / Mn = 0.1 (molar ratio), the crystal structure of Br-MnO2-0.1 was still dominated by the γ phase. With the increase of Br content, the intensity of the characteristic peak of the α phase (310) crystal plane was significantly enhanced, while the intensity of the characteristic peak of the γ phase decayed to the baseline level, eventually achieving a pure α phase transformation. The Br doping in Example 1 had a significantly better effect on promoting the phase transformation than other halogens. This efficient phase transformation not only led to a complete change in crystal form, but may also more effectively adjust the spatial arrangement and electronic environment of Mn active sites.

[0056] FE-SEM analysis was performed on the γ-MnO2 powders prepared in Example 1 and Comparative Examples 1-4, and the results are as follows: Figure 2 As shown in Table 1, γ-MnO2 exhibits a sea urchin-like structure with uniformly distributed nanorods on its surface. However, the growth of the sea urchin-like structure of γ-MnO2 crystals changed significantly after doping with different halogens ( Figure 2(c,e,g): Fluorine, chlorine, and bromine-doped samples retained their intact spherical structures, but the spherical size increased after fluorine doping, suggesting a significant improvement in SBET; the size of chlorine and bromine-doped samples did not change significantly, but the arrangement of nanorods on the surface became disordered, which may affect mass transfer and accessibility of active sites during activation; while iodine doping caused the spherical structure to collapse, transforming into a rough blocky structure formed by irregular nanoparticle stacking. Figure 2 (i)). The elemental mapping shows that Mn, O, and the corresponding halogen elements are uniformly distributed in γ-MnO2, spatially verifying the successful doping of halogen atoms. Figure 2 (b,d,f,h,j)). Further quantitative EDS analysis (Table 1) revealed that when the halogen addition ratio was (F,Cl,Br,I) / Mn=0.5, the halogen content on the γ-MnO2 surface varied, showing a trend of F / Mn (0.09) > I / Mn (0.01) > Br / Mn (0.0008) > Cl / Mn (0.0003). It is speculated that because fluorine atoms have the highest electronegativity and the smallest ionic radius, they easily combine with the active sites of Mn(III) / Mn(IV) through electrostatic or coordination interactions, thus having the highest doping substitution rate; iodine ions have the largest radius and are difficult to enter the Mn-O octahedral interstices, tending to exist in the form of surface adsorption or heterogeneous compounds, thus some are retained; chloride and bromide ions have moderate radii, but are both larger than oxygen ions, resulting in poor lattice matching with Mn and difficulty in effectively replacing oxygen. However, this trend in doping content is inconsistent with the subsequent observed trend in catalytic performance, indicating that the doping amount is not the key factor affecting catalytic activity, but rather the influence of halogen itself on the local electronic environment of manganese sites is the key factor determining catalytic activity.

[0057] Table 1. XPS, EDS, and EPR information of MnO2-based powders prepared in Example 1 and Comparative Examples 1-4

[0058] BET tests were performed on the MnO2-based powders prepared in Example 1 and Comparative Examples 1-4, and the results are as follows: Figure 3 As shown in Table 2, the MnO2-based powders prepared in Examples 1 and Comparative Examples 1-4 all exhibit typical Type IV isotherms with H3 hysteresis loops, indicating that they are all mesoporous structures. From the pore size distribution diagram (… Figure 3 (b) It can be seen that the pore sizes of both are mainly concentrated in the range of 20-50 nm, but different halogen-doped systems exhibit significant differences in pore structure. Br-MnO2, F-MnO2, and Cl-MnO2 show narrower and more concentrated pore size distributions, with pore volumes of (0.28-0.57 cm³). 3 / g) and specific surface area (50.17-76.38m²) 2 / g) compared to γ-MnO2 (0.24cm3 / g, 48.63m 2 The surface area and pore volume of I-MnO2 showed significant improvements, with the average pore size moderately increasing to 22.14-30.01 nm. This optimized pore structure is beneficial for reactant diffusion and exposure of active sites (Table 2). In contrast, the pore structure of I-MnO2 showed significant collapse, with the specific surface area and pore volume decreasing to 10.16 m². 2 / g and 0.07cm 3 / g, which is mainly attributed to the large size I - This leads to lattice distortion and pore blockage effects. Among them, Br-MnO2 exhibits the optimal pore structure, with a specific surface area of ​​76.38 m². 2 / g) and pore volume (0.57cm) 3 The concentrations of γ-MnO2 (g / g) are 1.57 times and 2.38 times that of γ-MnO2, respectively, which helps to improve the mass transfer efficiency of the active site reaction.

[0059] Table 2. Pore structure information of MnO2-based powders prepared in Example 1 and Comparative Examples 1-4

[0060] XPS tests were performed on the MnO2-based powders prepared in Example 1 and Comparative Examples 1-4, and the results are as follows: Figure 4 As shown in Table 1. Mn2p 3 / 2 Peak fitting of XPS spectra ( Figure 4(a) indicates that the characteristic peaks of γ-MnO2 at 641.90 and 642.75 eV correspond to Mn(III) and Mn(IV) species, respectively. Halogen doping significantly alters the electronic structure of the manganese sites: fluorine doping leads to a positive shift of the Mn2p orbital binding energy by 0.69 eV, indicating that fluorine, with its strong electronegativity, reduces the electron cloud density of the manganese sites by forming Mn-F bonds, thereby enhancing the binding of Mn atoms to their valence electrons. Conversely, doping with the less electronegative chlorine, bromine, and iodine induces a negative shift in the binding energy (-0.34 eV, -0.11 eV, -0.73 eV, respectively), indicating that the weaker electronegativity of halogen atoms reduces their ability to attract electrons, increasing the electron density of the manganese sites. This leads to elongation of the Mn-O bond, reduced covalency, and a greater willingness to donate electrons to the -OO- bonds of PMS, weakening their bond energy and accelerating the adsorption and activation process of PMS. Table 1 shows that the molar ratio of Mn(III) to Mn(IV) in Br-MnO2 is 1.20, which is 14 times higher than that in γ-MnO2 and significantly higher than the 31.90%-110.50% of other halogen-doped samples. This indicates that Br doping greatly increases the Mn(III) content in γ-MnO2. The high Mn(III) content induces significant Jahn-Teller distortion, promoting the elongation of Mn-O bond lengths in the lattice and increasing the oxygen vacancy concentration in the crystal. These two factors synergistically optimize the coordination environment of manganese sites. High-resolution O 1s XPS spectra of γ-MnO2 (…) Figure 4 In (b), there are two types of characteristic peaks for oxygen: surface-adsorbed oxygen (O2) with a binding energy of 529.70 eV. ads ) and 531.65 eV of lattice oxygen (O latt ), the ratio of the two (O) ads / O latt The value is 0.36. After halogen doping, O ads / O latt The electronegativity of halogen atoms first increases and then decreases with decreasing electronegativity, at 0.41, 0.45, 0.48, and 0.33 respectively, reaching a maximum of 0.48 with Br doping, a 33% improvement compared to the undoped γ-MnO2 sample. Higher O ads The ratio is typically related to the oxygen vacancy structure, providing more surface adsorption sites for PMS and promoting PMS adsorption and activation efficiency. Therefore, Br doping promotes the generation of oxygen vacancies in γ-MnO2 and enhances O2 adsorption efficiency. ads The increased content enhanced the adsorption and activation capacity for PMS. (From...) Figure 4(c) Observations show that halogen doping increases the binding energy difference ΔE between the two Mn 3s peaks from 4.61 eV for γ-MnO2 to 4.66-4.70 eV, corresponding to an inverted volcano-shaped distribution of AOS values ​​(γ-MnO2: 3.74 > F-MnO2: 3.68 > Cl-MnO2: 3.66 > I-MnO2: 3.65 > Br-MnO2: 3.64). Among them, Br-MnO2 exhibits the lowest AOS (3.64) and the highest ΔE value (4.70), indicating that it has the most unpaired electrons. This trend is basically consistent with the variation law of the Mn(Ⅲ) / Mn(Ⅳ) ratio, combined with the O 1s spectrum. ads / O latt The data shows that bromine doping lengthens the Mn-O bond, weakens the covalent nature of the Mn-O bond, increases the Mn(III) content and oxygen vacancy density, and enhances the electron density of manganese sites.

[0061] EPR tests were performed on the MnO2-based powders prepared in Example 1 and Comparative Examples 1-4. The results were obtained by... Figure 5 As shown in Table 1, the volumetric spin concentrations of γ-MnO2, Br-MnO2, F-MnO2, Cl-MnO2, and I-MnO2 are 8.71e⁻¹. +10 8.93e +10 9.11e +10 10.04e +10 and 4.71e +10 Furthermore, the spin concentration exhibits a volcano-shaped distribution trend with decreasing electronegativity of halogen atoms, meaning that the spin concentration first increases and then decreases as halogen electronegativity decreases. Higher spin-polarized electron concentration corresponds to a higher oxygen vacancy content. Therefore, except for iodine doping, doping with other halogen atoms can increase the oxygen vacancy content of γ-MnO2. Among them, Br-MnO2 shows a 116% increase in spin concentration compared to γ-MnO2, indicating that it has the highest oxygen vacancy content. This finding confirms that Br-MnO2 forms the most abundant oxygen vacancy sites, which can serve as key reaction sites for PMS activation, thereby improving catalytic reaction efficiency.

[0062] The electrochemical performance of the MnO2-based powders prepared in Example 1 and Comparative Examples 1, 2, and 4 was tested, and the results were obtained by... Figure 6 As shown, compared with γ-MnO2, the redox peak responses of halogen-doped γ-MnO2 are enhanced. Br-MnO2 exhibits two distinct oxidation and reduction peaks, corresponding to the stepwise reduction processes of Mn(Ⅳ)→Mn(Ⅲ) (0.95V) and Mn(Ⅲ)→Mn(Ⅱ) (0.57V), and the stepwise oxidation processes of Mn(Ⅲ)→Mn(Ⅳ) (0.75V) and Mn(Ⅱ)→Mn(Ⅲ) (-0.23V), respectively. Further analysis revealed the peak potential difference (ΔE) of the Mn(Ⅳ) / Mn(Ⅲ) redox pair. P1=0.20V) is significantly smaller than Mn(Ⅲ) / Mn(Ⅱ) for (ΔE) P2 =0.80V), indicating that Mn(Ⅳ) formation is more likely to occur on the catalyst surface. The reversible electron transfer cycle of Mn(Ⅲ). LSV testing further confirms that Br-MnO2 has the highest current density response ( Figure 6 (b) suggests its optimal electronic conductivity. Tafel polarization analysis ( Figure 6 (c,d) quantitatively revealed the difference in electron transfer efficiency: the corrosion current of γ-MnO2 was 8.97 × 10⁻⁶. -8 A; After halogen doping, the corrosion current of F-MnO2 decreased to 8.14 × 10⁻⁶. -8 A, while the corrosion current of Cl-MnO2 and Br-MnO2 increased to 1.16 × 10⁻⁶. -7 A and 2.18×10 -7 A represents 0.91 times, 1.29 times, and 2.43 times the baseline value of γ-MnO2, respectively. These findings collectively confirm that halogen doping has different effects on the redox cycle kinetics and interfacial charge transfer efficiency of Mn(Ⅳ) / Mn(Ⅲ), with Br doping significantly improving the electron transfer capability during PMS activation.

[0063] The supported catalysts prepared in Example 1 and Comparative Examples 1-6 were subjected to PMS activation degradation experiments for phenol. The results were obtained by... Figure 7 As shown. After NF was loaded with γ-MnO2 and doped with four different halogen atoms, except for Comparative Example 3, Examples 1 and Comparative Examples 1-2 could completely degrade phenol within 10 min. The k-values ​​showed a trend of first increasing and then decreasing with decreasing electronegativity of the halogen atoms: when fluorine (electronegativity 3.98), chlorine (electronegativity 3.16), bromine (electronegativity 2.96), and iodine (electronegativity 2.66) were doped, their k-values ​​were 0.3646, 0.4548, 0.4666, and 0.0189 min, respectively. -1 Among them, Example 1 showed the best catalytic activity, with k values ​​increasing by 27.98%, 2.59%, and 2368% compared to Comparative Examples 1-3, respectively, and by 74.23% compared to the unmodified catalyst in Comparative Example 4. Specifically, when the Br doping concentration increased from 0.1 to 0.8, the k value first increased and then decreased, indicating that a suitable bromine doping concentration is beneficial for PMS activation.

[0064] To further investigate the catalytic behavior of the catalyst in the complex pollution system, the synergistic degradation effect of the catalysts in Example 1 and Comparative Examples 1-6 on the mixed solution of phenol and p-chlorophenol was tested. The results are shown in Table 3. During the co-degradation process, the two pollutants exhibited significant competitive adsorption at the active sites of the catalyst and competitive consumption of reactive oxygen species. Since phenol is an electron donor and p-chlorophenol is an electron withdrawer, they have opposite electronic effects and inhibit each other in the reaction. This leads to the catalyst typically preferentially degrading one pollutant, making it difficult to achieve simultaneous and efficient removal of both under the same reaction conditions. As shown in Table 3, Example 1 exhibited the best performance in this system, achieving near-complete degradation of phenol and simultaneous 100% removal of p-chlorophenol within 10 minutes, demonstrating excellent broad-spectrum synergistic degradation capability. Comparing catalysts modified with different halogens reveals that: fluorine doping (Comparative Example 1) performed poorly, attributed to the excessive alteration of electron distribution on the catalyst surface by the extremely strong electronegativity of fluorine, which is detrimental to the adsorption of pollutants or further oxidation of intermediate products; chlorine doping (Comparative Example 2) showed lower degradation rates than Example 1, due to its strong electronegativity and poorer regulation of catalytic active sites; iodine doping (Comparative Example 3) performed the worst, as the excessively large radius of iodide ions severely damaged the MnO2 crystal structure, and byproducts such as iodates may be generated during the reaction, interfering with the electronic structure regulation of manganese active sites. Comparing the degradation effects of catalysts with different bromine doping amounts (Example 1 and Comparative Examples 5-6) shows that more bromine doping is not necessarily better. Appropriate bromine doping (Example 1, Br / Mn=0.5) not only promotes a complete and ordered crystal transformation but also effectively adjusts the spatial arrangement and electronic environment of Mn active sites, thereby significantly improving its activation ability for PMS; while excessively low (Comparative Example 5) or excessively high (Comparative Example 6) bromine doping amounts lead to insufficient or covered active sites, thus reducing catalytic efficiency. By precisely controlling the amount of bromine doping, the utilization efficiency of free radicals can be effectively balanced in a competitive degradation system, ultimately achieving efficient synergistic removal of phenol and p-chlorophenol in complex systems.

[0065] Table 3 Performance of the supported catalysts prepared in Examples 1 and Comparative Examples 1-6 in activating PMS and simultaneously degrading phenol and p-chlorophenol

[0066] Employing self-assembled continuous flow reactors (such as...) Figure 8 As shown in the figure, the phenol removal performance of Example 1 was investigated under 10h continuous operation conditions, and the results are as follows. Figure 9 As shown, after 10 hours of continuous operation, the phenol removal rate of the BMNFT / PMS system remained stable at 100%, fully demonstrating the excellent stability and anti-deactivation ability of the catalytic system during long-term operation.

[0067] The monochlorotriazine type monoazo reactive dye, Jingren Blue K-BF, was selected. Using tap water as a benchmark, the dyeing performance of recycled dyeing wastewater treated with different catalysts was evaluated. The results are shown in Table 4. Table 4 shows that the recycled water treated in Example 1 had the closest dyeing rate (80.65%), color difference (CIE DE 0.46), and color depth (K / S 22.60) to the tap water benchmark (81.20%, K / S 23.79). Comparing the dyeing performance of recycled dyeing wastewater treated in Example 1 and Comparative Examples 1-4, it can be found that Br can effectively modulate the MnO2 lattice and active sites, promoting the complete degradation of organic matter; while Comparative Example 3 severely damaged the catalyst structure, resulting in a significant decrease in the dyeing performance of the treated water (e.g., a dyeing rate of only 60.32%). Therefore, after deep processing in Example 1, high-quality recycled water that meets the requirements of high-standard dyeing processes can be produced, providing a reliable technical solution with clear industrialization potential for solving the core problem of water resource recycling in the printing and dyeing industry.

[0068] Table 4 Comparison of dyeing performance of reclaimed water and tap water after treatment in Examples 1 and Comparative Examples 1-6

Claims

1. A method for preparing a supported Br-MnO2 catalyst, characterized in that, include: S1. Dissolve divalent manganese salt, persulfate and bromide in deionized water, perform hydrothermal reaction, separate, wash and dry, and calcine to obtain Br-MnO2 powder; the molar ratio of manganese in the divalent manganese salt, persulfate and bromine in potassium bromide is 1:1:(0.4~0.6); S2. The nickel foam substrate is dried after being acid-washed, alcohol-washed, and water-washed. S3. First, disperse the Br-MnO2 powder obtained in S1 in a polyurethane solution to obtain a Br-MnO2 / TPU mixed dispersion; then, impregnate the nickel foam obtained in S2 in the Br-MnO2 / TPU mixed solution, stir and remove it, and then centrifuge and dry it to obtain a supported Br-MnO2 catalyst.

2. The preparation method according to claim 1, characterized in that, In S1, the divalent manganese salt is at least one of manganese sulfate, manganese nitrate, or manganese carbonate; And / or, the persulfate is at least one of ammonium persulfate, potassium persulfate, or sodium persulfate; And / or, the bromide is at least one of potassium bromide, ammonium bromide, or sodium bromide.

3. The preparation method according to claim 1, characterized in that, In S1, the temperature of the hydrothermal reaction is 80~100℃; And / or, the hydrothermal reaction takes 22 to 26 hours; And / or, the calcination temperature is 250~350℃; And / or, the calcination time is 1 to 3 hours.

4. The preparation method according to claim 1, characterized in that, In S3, the polyurethane solution is a mixed solution of thermoplastic polyurethane and N,N-dimethylformamide; Preferably, the concentration of the thermoplastic polyurethane is 0.3~0.7 g / L.

5. The preparation method according to claim 1, characterized in that, In S3, the concentration of Br-MnO2 powder in the Br-MnO2 / TPU mixed dispersion is 3~7 g / L.

6. The preparation method according to claim 1, characterized in that, In S3, the stirring time is 5 to 15 minutes; And / or, the drying temperature is 90~110℃; And / or, the drying time is 0.5 to 1.5 hours.

7. The supported Br-MnO2 catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the supported Br-MnO2 catalyst as described in claim 7 in activating persulfate for deep treatment of dyeing and printing wastewater and realizing its dyeing reuse.

9. The application as described in claim 8, characterized in that, The application is as follows: dyeing and printing wastewater is subjected to persulfate activation oxidation treatment under the action of the supported Br-MnO2 catalyst, and the treated effluent can be directly reused in the process of dyeing knitted cotton with reactive dyes.

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