Preparation of metal ion doped zinc ferrite and catalytic degradation application thereof

Abstract

The invention relates to the technical field of novel environment-friendly materials, and particularly discloses preparation and catalytic degradation application of metal ion doped zinc ferrite, metal ions are doped into zinc ferrite, and the catalytic performance and magnetism of pure-phase zinc ferrite are remarkably improved. The modified zinc ferrite has a very good catalytic effect on the catalytic reaction process of oxidizing agents such as persulfate, hydrogen peroxide and a Fenton reagent under the condition of no illumination, and has a very good catalytic effect on antibiotics and organic dyes (with the concentration of 1t; 100 mg / L) and the like, and the catalytic degradation rate gt of degradation-resistant organic pollutants is obtained; the magnetic separation efficiency is more than or equal to 95%, and the catalyst can be recycled for more than or equal to 20 times. The method can realize simple, convenient and green modification of zinc ferrite and high-effect degradation and removal of various organic pollutants, in addition, the metal ion doped zinc ferrite can efficiently magnetically separate and pit inorganic salts, is suitable for treating various industrial refractory enterprise sewage, is low in operation cost, reduces the cost and improves the efficiency, and meets the industrial production requirements.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly new materials technology, and in particular to the preparation of metal ion-doped zinc ferrite and its catalytic degradation application. Background Technology

[0002] The extensive use and discharge of antibiotics have polluted aquatic ecosystems, damaging the structure and function of aquatic organisms. Antibiotic degradation is difficult, and the lack of efficient treatment processes makes them more likely to remain in the ecosystem, polluting soil, water, and water sources. To protect human health and ecological safety, there is an urgent need to develop effective, economical, and energy-efficient green technologies to remove them from wastewater, achieving sustainable water resource utilization. Among existing technologies, advanced oxidation techniques (AOPs) using sulfate free radicals as the main active species stand out, and AOPs are considered the most effective method for oxidizing resistant organic compounds. PMS is an asymmetric oxidant with an equation-based redox potential of 1.82V, which generates sulfate free radicals through catalytic activation, thereby partially oxidizing some organic compounds. The nanostructured catalyst ZnFe2O4 has attracted widespread attention in the field of catalytic oxidation due to its low cost, magnetic recyclability, and high visible light absorption rate. However, pure-phase ZnFe2O4 showed a degradation rate of only 65.53% for Orange II under UV irradiation for 45 minutes (Borhan et al.).

[0003] (DOI:10.1016 / j.apsusc.2018.11.164), and the CN113426461B patent requires the addition of multiple modifiers (urea / F127) and relies on light, resulting in significant drug and energy consumption. In recent years, transition metals have been widely used to activate oxidants to generate free radicals to degrade organic compounds. The ZnFe2O4 structure contains tetrahedral (Zn) and octahedral (Fe) voids, and many metal ions can replace Zn2+ or Fe2+ positions to fill the spinel-type ferrite structure, thereby achieving the effect of regulating the physical properties of the material. Borhan et al. prepared Al3+-doped ZnFe2O4 powder using a sol-gel self-combustion method. Their results showed that the grain size and specific surface area of ​​the sample both influenced its photocatalytic performance. Under ultraviolet light irradiation, the photocatalytic degradation rate of orange rhododendron solution reached 65.53% after 45 minutes (DOI: 10.1016 / j.apsusc.2018.11.164). This preparation method is relatively complex, requires additional light for pollutant treatment, resulting in high energy consumption and poor performance. Patent CN113426461B discloses a method for preparing silver-doped polycrystalline zinc ferrite photocatalytic nanomaterials. This method uses multiple modifiers such as urea, ammonium fluoride, and an oxy-propoxy-ethoxy amphoteric triblock polymer (F127) during preparation, increasing reagent consumption. Furthermore, while this method improves the photocatalytic performance of zinc ferrite, it still requires additional light for subsequent applications, further increasing energy consumption. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and to propose a method for preparing metal ion-doped zinc ferrite and its catalytic degradation application.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The preparation of metal ion-doped zinc ferrite and its catalytic degradation application include the following steps:

[0007] Step 1: Weigh the raw materials according to the molar ratio of zinc salt to iron salt of 1:2, dissolve them in deionized water, and ultrasonically vibrate to form a homogeneous mixed solution;

[0008] Step 2: Add a transition metal salt to the solution from Step 1, with a doping ratio of 0.05 to 0.3 times the molar amount of zinc salt, and stir until completely dissolved; adjust the pH to 3-5, and stir at 200-400 r / min for 2-4 hours.

[0009] Step 3: Under vigorous stirring, gradually add alkaline solution to the solution obtained in step 2 to adjust the pH value of the solution to 11-13. After the precipitate is formed, continue stirring for 1-2 hours.

[0010] Step 4: Adjust the pH of the solution obtained in Step 3 to 10-11, transfer it to a reaction vessel, and perform a hydrothermal reaction at 150℃~200℃ for 10-18 hours. After magnetic separation, the target product is obtained.

[0011] Step 5: The target product obtained in Step 4 is filtered, washed with water and ethanol, and vacuum dried to obtain a metal ion-doped zinc ferrite catalyst.

[0012] The obtained metal ion-doped zinc ferrite catalyst, under light-free conditions, can achieve highly efficient catalytic degradation of antibiotics or organic dyes in water by activating persulfate or persulfate / hydrogen peroxide. The catalytic degradation rate for recalcitrant organic pollutants such as antibiotics and organic dyes (concentration <100 mg / L) in water is >90%. Comparative Example 1 demonstrates that the degradation rate after doping (96.12%) is 3.37 times that of the undoped sample (28.5%), and the specific magnetization is >10 emu / g, allowing for magnetic separation and multiple recycling.

[0013] Preferably, the zinc salt is selected from zinc nitrate, zinc sulfate, zinc chloride, or zinc acetate.

[0014] Preferably, the iron salt is selected from ferric nitrate, ferric sulfate, or ferric chloride.

[0015] Preferably, the transition metal salt is one of copper, cobalt, or nickel salts, specifically including copper chloride, copper sulfate, cobalt nitrate, or nickel chloride.

[0016] Preferably, the alkaline solution in step 3 is a sodium hydroxide solution or ammonia water with a concentration of 1 to 4 mol / L.

[0017] Preferably, the hydrothermal reaction heating rate in step 4 is 3-5℃ / min, and the reaction is allowed to cool naturally to room temperature after completion.

[0018] Preferably, the catalyst has the general chemical formula MxZn1-xFe2O4, where M is Cu, Co or Ni, and x = 0.05 to 0.3.

[0019] The initial concentration of pollutants is 10–100 mg / L, the degradation rate is ≥90%, the catalyst can be recycled ≥20 times, and the magnetic separation efficiency is ≥95%.

[0020] Preferably, the application of the metal ion-doped zinc ferrite catalyst in the treatment of organic wastewater is suitable for complex water quality containing high concentrations of chloride ions, sulfate ions or phosphates, and requires no additional light or energy input.

[0021] Therefore, a catalyst and persulfate are added to the reaction tank, and a magnetic separation device is used for solid-liquid separation. The recovered catalyst is washed and recycled. This method can be applied to catalytic reaction processes using oxidants such as persulfate, hydrogen peroxide, and Fenton's reagent without the need for light, and can efficiently catalyze the degradation of recalcitrant organic pollutants such as antibiotics, organic dyes, and surfactants.

[0022] A wastewater treatment agent, obtained using the preparation method described above.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] 1. This invention employs a simple hydrothermal synthesis method and utilizes relatively few chemical reagents to dope and modify zinc ferrite, resulting in low energy consumption and minimal secondary pollution.

[0025] 2. M prepared by this invention x Zn 1-x The combination of Fe2O4 catalyst and persulfate advanced oxidation technology can effectively remove organic pollutants such as antibiotics without the need for light, with a degradation rate of ≥90%. This not only simplifies the catalytic process but also reduces energy consumption by more than 80%, and is suitable for complex water bodies where multiple ions coexist, which is beneficial for industrial production.

[0026] 3. The prepared metal ion-doped zinc ferrite catalyst has a specific magnetization of >10 emu / g, can be recovered through magnetic separation with a magnetic separation efficiency of ≥95%, and can be recycled ≥20 times. Attached Figure Description

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort. Attached Figure Description

[0029] Figure 1 XRD patterns (ZnFe2O4 vs Cu) 0.1 Zn 0.9 Fe2O4);

[0030] Figure 2 Hysteresis loop (saturation magnetization 25.7 emu / g);

[0031] Figure 3 Optimization curve of catalyst dosage (0.2 g / L is optimal);

[0032] Figure 4 Optimization curve of persulfate dosage (1 mmol / L is optimal);

[0033] Figure 5 The influence of coexisting ions (H2PO4) - (Most significant inhibition);

[0034] Figure 6 Cyclic experiment (degradation rate 71.06% after 5 cycles). Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0037] Example 1:

[0038] 1. Preparation of copper-doped zinc ferrite

[0039] Weigh 8 mmol Fe(NO3)3·9H2O and 3.6 mmol zinc acetate into a beaker containing 30 ml deionized water, sonicate, and stir thoroughly to form an ionic solution. Weigh 0.4 mmol CuSO4·anhydrous into the beaker and continue stirring thoroughly. Add 4 mol / L NaOH solution dropwise to the solution until pH = 13, and continue stirring after precipitate formation. Slowly transfer the solution to a polytetrafluoroethylene reactor and hydrothermally react at 180 °C for 12 h. The obtained product is filtered, washed with deionized water and anhydrous ethanol until neutral, and vacuum dried to obtain Cu. 0.1 Zn 0.9 Fe2O4.

[0040] 2. Combined with persulfate catalytic degradation of 20 mg / L ciprofloxacin wastewater

[0041] 20 mg of ciprofloxacin was poured into a beaker, dissolved thoroughly in deionized water, and then transferred to a 1 L volumetric flask. The solution was then diluted to volume with deionized water, resulting in a concentration of 20 mg / L. 200 mL of the ciprofloxacin solution was added to 0.2 g / L of copper-doped zinc ferrite catalyst, followed by 1 mmol / L of potassium persulfate. The mixture was stirred thoroughly and placed in a constant-temperature shaking incubator. At regular intervals, a suitable amount of solution was taken and its absorbance was measured at 275 nm. The concentration of ciprofloxacin in the solution was calculated based on the ciprofloxacin standard curve. The degradation rate reached 96.12% after 30 minutes.

[0042] Example 2:

[0043] Copper-doped zinc ferrite was prepared using the same method and used to degrade tetracycline hydrochloride wastewater at a concentration of 25 mg / L. The effects of different catalyst dosages, persulfate dosages, and different water systems on the degradation of tetracycline hydrochloride by the catalyst were investigated to select the optimal solution.

[0044] See Figure 1 , Figure 1 ZnFe2O4 and Cu 0.1 Zn 0.9 XRD pattern of Fe2O4 sample. (The text abruptly ends here.) Figure 1 It can be seen that using Cu 2+ The characteristic diffraction peak positions of the sample prepared with ZnFe2O4 doping at a ratio of 0.1 are basically consistent with those of the standard card (PDF#22-1012), indicating that Cu 2+ Doping did not change the crystal structure of ZnFe2O4; it remains a spinel structure. However, Cu... 2+ The doping of Cu causes the main diffraction peak of the sample to shift towards higher angles at the 2θ value position. This is because Cu 2+ The radius (0.057nm) is greater than that of Zn. 2+ The radius (0.074 nm) is small, when Cu 2+ After entering the crystal lattice, lattice distortion occurs, causing a change in the lattice constant. The improved catalytic performance after zinc ferrite modification may be related to this.

[0045] Figure 2 It is ZnFe2O4 and Cu 0.1 Zn 0.9 The hysteresis loop diagram of the Fe2O4 sample measured at room temperature. As can be seen from the figure, Cu... 0.1 Zn 0.9 Fe₂O₄ exhibits significant ferromagnetism at room temperature, with a maximum magnetization saturation of 25.7 emu / g, meeting the requirements for effective magnetic separation (the slanted line represents ZnFe₂O₄, and the curved line represents Cu). 0.1 Zn 0.9 Fe2O4). Furthermore, due to Cu 2+ The addition of Cu 0.1 Zn 0.9 Fe2O4 exhibits significantly enhanced magnetic properties compared to ZnFe2O4.

[0046] Figure 3 , 4 5 are Cu 0.1 Zn 0.9 The graphs show the Fe2O4 sample dosage, persulfate concentration, and catalytic degradation curves under different systems. Experiments were conducted by varying the amounts of catalyst and oxidant, revealing that at pH 7, 0.2 g / L Cu... 0.1 Zn 0.9Fe₂O₄ and 1 mmol / L persulfate showed the best catalytic effect, reaching up to 96.12%. Furthermore, coexisting anion experiments indicated that in Cu… 0.1 Zn 0.9 In the Fe2O4 / PMS system, 2 mmol / L CO3 was added 2- SO4 2- H2PO 4- and Cl - The degradation rates of TC (tetracycline hydrochloride) reached 90.13%, 94.9%, 84.54%, and 92.99%, respectively. H2PO 4- The significant effect is likely due to its quenching effect on the generated ROS.

[0047] Figure 6 Cu 0.1 Zn 0.9 Experimental diagram of Fe2O4 recycling. The diagram shows that Cu... 0.1 Zn 0.9 Fe2O4 exhibits good reusability and stability, with TC degradation still reaching 71.06% after 5 consecutive cycles.

[0048] Comparative Example 1: Degradation of ciprofloxacin by undoped ZnFe2O4 under the same conditions (degradation rate <30% after 30 min)

[0049] Pure-phase ZnFe2O4 (Cu-free) was prepared using the same process as in Example 1. 2+ Doping):

[0050] Degradation of 50 mg / L ciprofloxacin: 0.2 g / L catalyst + 1 mmol / L PMS, pH = 7, 30 min, degradation rate only 28.5% (HPLC-MS detection). Figure 3 (dashed line comparison curve), however, the addition of 10 mM ethanol (·OH / SO4· - After the quencher was applied, the degradation rate dropped to 5.2%, indicating insufficient free radical generation. No characteristic signal of DMPO-SO4·- was detected (g = 2.005), indicating weak PMS activation ability. Therefore, pure-phase ZnFe2O4 has low electron transfer efficiency (XPS showed Fe...). 2+ / Fe 3+ With a ratio of only 0.33, it is unable to effectively activate PMS to generate free radicals.

[0051] Comparative Example 2: Revealing the Problem of Co Leaching

[0052] A commercially available Co3O4 catalyst (Sigma-Aldrich, particle size 50 nm) was selected according to the requirements of Example 2.

[0053] Ciprofloxacin was degraded under the same conditions (0.2 g / L catalyst + 1 mmol / L PMS), and the cobalt ion concentration in the liquid phase was measured by ICP-OES after the reaction. The initial degradation rate was 91.3% (30 min), with cobalt leaching reaching as high as 2.8 mg / L (5.6 times exceeding the limit of GB 8978-1996 standard). After the third use, the degradation rate plummeted to 52% (loss of active sites). Therefore, Co... 3+ / Co 2+ In the redox cycle, insufficient oxygen vacancies in the lattice lead to the dissolution of Co ions (XPS confirmed Co). 2+ (Percentage > 40%)

[0054] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A metal ion-doped zinc ferrite catalyst, characterized in that, The general chemical formula of the catalyst is M x Zn 1- x Fe2O4, where M is Cu, Co or Ni, and x = 0.05 to 0.

3.

2. A method for preparing a metal ion-doped zinc ferrite catalyst, characterized in that, Includes the following steps: Step 1: Weigh the raw materials according to the molar ratio of zinc salt to iron salt of 1:2, dissolve them in deionized water, and ultrasonically vibrate to form a homogeneous mixed solution to obtain the mixed solution; Step 2: Add a transition metal salt to the mixed solution from Step 1, with a doping ratio of 0.05 to 0.3 times the molar amount of zinc salt, and stir until completely dissolved; adjust the pH and stir the reaction to obtain a reaction solution; Step 3: Under vigorous stirring, gradually add alkaline solution to the reaction solution obtained in step 2 to adjust the pH value of the solution. After the precipitate is formed, continue stirring to obtain the precipitate solution. Step 4: Adjust the pH value of the precipitate solution obtained in Step 3, transfer it to the reaction vessel, carry out hydrothermal reaction, and obtain the target product after magnetic separation; Step 5: The target product obtained in Step 4 is filtered, washed with water and ethanol, and vacuum dried to obtain a metal ion-doped zinc ferrite catalyst.

3. The method for preparing a metal ion-doped zinc ferrite catalyst according to claim 2, characterized in that, The zinc salt is selected from one of zinc nitrate, zinc sulfate, zinc chloride, or zinc acetate.

4. The method for preparing a metal ion-doped zinc ferrite catalyst according to claim 2, characterized in that, The iron salt is selected from one of ferric nitrate, ferric sulfate, or ferric chloride.

5. The method for preparing a metal ion-doped zinc ferrite catalyst according to claim 2, characterized in that, The transition metal salt is one of copper, cobalt, or nickel salts, specifically including copper chloride, copper sulfate, cobalt nitrate, or nickel chloride.

6. The method for preparing a metal ion-doped zinc ferrite catalyst according to claim 2, characterized in that, The alkaline solution mentioned in step 3 is a sodium hydroxide solution or ammonia water.

7. The method for preparing a metal ion-doped zinc ferrite catalyst according to claim 2, characterized in that, In step 4, the hydrothermal reaction heating rate is 3-5℃ / min, and the reaction is allowed to cool naturally to room temperature after completion.

8. The method for preparing a metal ion-doped zinc ferrite catalyst according to claim 2, characterized in that, The general chemical formula of the catalyst is M x Zn 1-x Fe2O4, where M is Cu, Co or Ni, and x = 0.05 to 0.

3.

9. The application of the metal ion-doped zinc ferrite catalyst according to any one of claims 1-8 in the treatment of organic compound wastewater, characterized in that: Suitable for complex water quality containing high concentrations of chloride ions, sulfate ions, or phosphates.

10. A wastewater treatment agent, characterized in that, Obtained using the preparation method described in any one of claims 1-8.

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