A green and efficient photocatalytic removal method of cyanide

Abstract

This invention relates to the field of cyanide removal technology, and discloses a green and efficient photocatalytic removal method for cyanide. The chemical formula of the high-entropy zinc ferrite described in this invention is (Co... 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 The high-entropy zinc ferrite supported on zinc foam described in this invention can photocatalytically degrade cyanide in water. The preparation method of the high-entropy zinc ferrite supported on zinc foam is as follows: High-entropy zinc ferrite (Co) is prepared by... 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 Fe2O4 and polyvinylidene fluoride are mixed evenly, and then N-methylpyrrolidone is added to form a glue solution. The glue solution is then loaded onto zinc foam to obtain zinc foam-loaded high-entropy zinc ferrite (Co). 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 Fe2O4. This invention is the first to discover that high-entropy zinc ferrite supported on zinc foam can photocatalytically degrade cyanide in water, and the degradation efficiency is very high, completely degrading cyanide in 3 hours. Furthermore, the high-entropy zinc ferrite supported on zinc foam can be reused 30 times.

Description

Technical Field

[0001] This invention relates to the field of cyanide decyanation technology, specifically to the photocatalytic degradation and removal of cyanide using zinc foam-supported high-entropy zinc ferrite. Background Technology

[0002] In the aluminum electrolysis industry, aluminum electrolysis cells require major overhauls after a period of use. The waste lining removed from the electrolysis cell during the overhaul is called electrolysis cell overhaul slag. Due to long-term corrosion from the electrolyte solution under high-temperature conditions, the overhaul slag after the cell is shut down contains soluble fluorides and cyanides (CN). - Cyanide is a highly toxic substance, 10 times more toxic than arsenic. It can seep into the soil and pollute groundwater, causing long-term ecological risks. Therefore, if cyanide is not removed from the slag from major repairs, it will cause fatal harm to the environment.

[0003] While the mainstream bleaching powder oxidation method can degrade cyanide, the generation of CaCO3 waste increases treatment costs by 30% and poses a risk of secondary pollution. The sulfur dioxide-air process (Inco process) is one of the most mature and widely used methods for treating industrial cyanide, but this method requires a continuous supply of sulfur dioxide gas, which introduces the risk of sulfur dioxide leakage and dispersion, potentially causing air pollution and safety hazards in the workplace. Furthermore, the storage, transportation, and dosing systems for sulfur dioxide require strict management, increasing operational complexity and safety costs.

[0004] Visible light photocatalysis is currently a preferred method for degrading pollutants. This technology uses clean, cost-free sunlight as the visible light source, adding a photocatalyst for degradation, directly converting cyanide ions into nitrogen (N2). This is undoubtedly a green and efficient method. The core of this technology lies in the selection of a highly active, recyclable catalyst. However, the currently mainstream commercial catalyst, TiO2, only responds to ultraviolet light and cannot be recycled. Using TiO2 as a photocatalyst to treat cyanide ions would increase costs. Therefore, the preparation of highly active, recyclable, and green visible light photocatalysts has significant commercial value. Summary of the Invention

[0005] To address the problems existing in the prior art, one of the objectives of this invention is to provide a method for preparing high-entropy zinc ferrite supported on zinc foam, the specific steps of which are as follows: (1) Fe(NO3) 3• 9H2O, Co(NO3) 2• 6H₂O, Ni(NO₃) 2• 6H₂O, Zn(NO₃) 2• 6H2O 、 Mg(NO3) 2• 6H₂O, Cu(NO₃) 2•After mixing 9H2O and glacial acetic acid evenly, calcination is performed to obtain the chemical formula (Co). 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 Powdered high-entropy zinc ferrite (Fe2O4).

[0006] (2) The chemical formula is (Co 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 Powdered high-entropy zinc ferrite (Fe2O4) is mixed evenly with polyvinylidene fluoride (PVDF), and then N-methylpyrrolidone is added to form a colloid. This colloid is then loaded onto zinc foam to obtain zinc foam-loaded high-entropy zinc ferrite (Co). 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 )Fe2O4.

[0007] Preferably, in step (1) Fe(NO3) 3• 9H2O, Co(NO3) 2• 6H₂O, Ni(NO₃) 2• 6H₂O, Zn(NO₃) 2• 6H2O 、 Mg(NO3) 2• 6H₂O, Cu(NO₃) 2• The molar ratio of 9H2O is 10:1:1:1:1:1; the molar ratio of nitrate to acetate in the system is 0.9:1.

[0008] Preferably, the calcination temperature in step (1) is 600~800 degrees and the calcination time is 2~3 hours.

[0009] Preferably, the chemical formula in step (2) is (Co 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 The mass ratio of high-entropy zinc ferrite to polyvinylidene fluoride in Fe2O4 is 96~97:3~4.

[0010] The second objective of this invention is to provide a foamed zinc-supported high-entropy zinc ferrite (Co) 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2The application of Fe2O4 in the photocatalytic degradation of cyanide in water, specifically the following steps: adding zinc foam-loaded high-entropy zinc ferrite (Co) to water containing cyanide. 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 Fe2O4 (the amount of high-entropy zinc ferrite supported by zinc foam is not particularly required; if the degradation is incomplete, more can be added), and hydrogen peroxide is added. The reaction is carried out under sunlight or a xenon lamp for at least 3 hours.

[0011] Preferably, the volume ratio of water to hydrogen peroxide is 300:1.

[0012] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention is the first to discover high-entropy zinc ferrite (Co) supported by zinc foam. 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 This invention relates to a method for removing cyanide from water using Fe2O4 catalysis, which is characterized by being green and highly efficient.

[0013] (2) This invention, by rationally controlling the ratio of nitrate and acetate in the preparation system and simultaneously doping with five metals, involves multiple elements of different atomic sizes "crowding" each other's space, resulting in severe distortion and stress in the crystal structure, creating abundant active sites, making it easier to adsorb and activate reactants. This is one of the reasons for the high catalytic activity. The distorted crystal lattice makes the surface atoms irregularly arranged, making it easier to adsorb and activate reactants, promoting charge separation, and thus improving catalytic activity. This is the second reason for the high catalytic activity. This material is used to degrade and remove CN. - Under visible light irradiation, the degradation rate reaches 80% within 1 hour, and complete degradation occurs within 3 hours. - It is removed, and the amount of hydrogen peroxide used in the catalytic process can be reduced.

[0014] (3) Due to the high entropy of multi-element doping, atoms have difficulty migrating in the severely distorted lattice and the element diffusion rate is extremely slow. This makes the catalyst structure less likely to be destroyed and elements less likely to be precipitated in light, high temperature or harsh chemical environment, resulting in a longer lifespan. Therefore, the catalyst is very stable.

[0015] (4) Corrosion-resistant zinc foam is used as the substrate material for high-entropy zinc ferrite support. The high-temperature and corrosion-resistant "golden combination" PVDF and NNP are used as binders to achieve the three stabilities of the material: catalyst stability, binder stability, and support substrate material stability. Therefore, the catalytic activity of the material remains unchanged after 30 repeated uses. Using zinc foam to support powdered high-entropy zinc ferrite catalyst can effectively solve the practical problem that powdered catalyst is not easy to recover in water and cannot be reused, causing secondary pollution. Attached Figure Description

[0016] Figure 1 High-entropy zinc ferrite (Co 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 XRD of Fe2O4.

[0017] Figure 2 High-entropy zinc ferrite (Co 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 SEM of Fe2O4.

[0018] Figure 3 High-entropy zinc ferrite (Co 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 EDS of Fe2O4 Figure 4 The images show the appearance of zinc foam (A), zinc foam-loaded high-entropy zinc ferrite sample material (B), zinc foam-loaded high-entropy zinc ferrite sample material after one use (C), and zinc foam-loaded high-entropy zinc ferrite sample material after 30 cycles (D).

[0019] Figure 5 The UV spectra of CN- (cyanide) in the aluminum electrolysis overhaul slag after zinc foam (A), zinc foam-loaded high-entropy zinc ferrite (B), and zinc foam-loaded high-entropy zinc ferrite after 30 cycles (C) are shown.

[0020] Figure 6 XRD comparison of zinc foam and zinc foam-loaded high-entropy zinc ferrite before and after reaction.

[0021] Figure 7 XRD pattern of the high-entropy zinc ferrite prepared in Comparative Example 1. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1 A method for preparing high-entropy zinc ferrite supported on zinc foam, the specific steps of which are as follows: (1) 11 mmol of Fe(NO3) 3• 9H₂O, 1.1 mmol of Co(NO₃) 2• 6H2O, 1.1 mmol Ni(NO3)26H2O, 1.1 mmol Zn(NO3)2 2• 6H2O 、 1.1 mmol of Mg(NO3) 2• 6H₂O, 1.1 mmol Cu(NO₃) 2• 9H₂O and 48.89 mmol of glacial acetic acid were mixed, with a molar ratio of nitrate to acetate of 0.9:1. The mixture was then calcined in a muffle furnace at 600 °C for 2 hours to obtain high-entropy zinc ferrite (Co). 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 Fe2O4, high-entropy zinc ferrite (Co) 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 XRD pattern of Fe2O4 as follows Figure 1 As shown in the figure, the material is a single spinel phase (compared with the standard colorimetric card (PDF#22-1012)). All diffraction peaks correspond perfectly to the standard diffraction peaks of the spinel structure. The peaks are sharp and the baselines are stable, indicating good crystallinity and the absence of impurities. This figure confirms the successful synthesis of the material with the chemical formula (Co). 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 (Fe2O4) high-entropy zinc ferrite; (Co) 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 SEM images of Fe2O4 are shown below. Figure 2As shown in the figure, at a scale of 10 μm, the overall coverage is uniform and layered. With increasing magnification, at a scale of 1 μm, localized agglomeration occurs. Further increasing the magnification, at a scale of 200 nm, spherical particles are clearly visible with well-defined boundaries, indicating good crystallinity. This is clearly the morphology of zinc ferrite, confirming the successful synthesis of high-entropy zinc ferrite. (Co) 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 EDS of Fe2O4 as follows Figure 3 As shown in the figure, the elements of the material are O, Fe, Zn, Co, Ni, Cu, and Mg. The O element is uniformly distributed, corresponding to the oxide phase. The Fe and Zn elements are uniformly distributed and overlap well, indicating the formation of a uniform zinc ferrite phase. The doping elements (Co, Ni, Cu, Mg) are uniformly distributed without obvious agglomeration or clustering, indicating that multi-element doping has been successfully achieved, forming a high-entropy solid.

[0024] (2) High-entropy zinc ferrite (Co 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 Fe₂O₄ and PVDF (polyvinylidene fluoride) were mixed at a mass ratio of 96:4, and then NMP (N-methylpyrrolidone) was added dropwise until a gel was formed. The gel was then coated onto zinc foam to obtain zinc foam-loaded high-entropy zinc ferrite (Co). 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 )Fe2O4.

[0025] Example 2 High-entropy zinc ferrite (Co) supported by zinc foam 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 The application of Fe2O4 in the degradation of cyanide in the overhaul slag of aluminum electrolysis industry involves the following specific steps: Add 300 mL of water to 100 g of aluminum electrolytic cell overhaul slag and stir thoroughly to fully dissolve the cyanide in the slag. Then add zinc foam-loaded high-entropy zinc ferrite (Co). 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2Fe2O4 was mixed with 1 ml of hydrogen peroxide, and the xenon lamp was turned on. Samples were taken every hour. A control group was set up for comparison, which consisted of zinc foam loaded with high-entropy zinc ferrite (Co). 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 Fe2O4 was replaced with zinc foam, and CN was detected using a cyanide colorimetric tube test kit (manufacturer: Luheng Biotechnology, detection range: 0.05-5 mg / L). - content.

[0026] from Figure 5 As can be seen in B, high-entropy zinc ferrite (Co) loaded with zinc foam is used. 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 After 1 hour of Fe2O4 catalytic light irradiation, CN - The degradation rate reached 80% after 3 hours and 99.5% after 1 hour of catalytic light irradiation with zinc foam. - The degradation rate reached 53%, and 72% after 3 hours.

[0027] High-entropy zinc ferrite (Co) loaded with zinc foam 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 After Fe2O4 was recycled 30 times, its photocatalytic performance was tested, and the CN content was measured after 3 hours. - The degradation rate is 99.7% ( Figure 5 C), when tested with a cyanide colorimetric tube test kit, no color was detected ( Figure 5 C), indicating that CN in aluminum electrolytic overhaul slag. - The concentration was below 0.05 mg / L, meeting the first-level standard for cyanide emissions, indicating that the high-entropy zinc ferrite (Co) foam supported on zinc prepared in this invention... 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 Fe2O4 can be reused.

[0028] After 3 hours of photocatalytic degradation using zinc foam, the color was still detectable using a cyanide colorimetric test kit, indicating that the photocatalytic degradation effect of zinc foam was not good. Figure 5 A).

[0029] Finally, zinc foam and zinc foam-loaded high-entropy zinc ferrite (Co) were added. 0.2 Ni 0.2 Zn0.2 Mg 0.2 Cu 0.2 Fe2O4, zinc foam-supported high-entropy zinc ferrite (Co) 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 Fe2O4 photocatalysis was used once, and after 30 days of photocatalysis, high-entropy zinc ferrite (Co) supported on zinc foam was obtained. 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 XRD comparison of Fe2O4 yielded the following results: Figure 6 As shown, from Figure 6 It can be seen that high-entropy zinc ferrite was successfully loaded onto zinc foam, and the system was stable. After 30 reactions, the peak intensities of each diffraction peak in the zinc ferrite phase did not decrease.

[0030] Comparative Example 1 In comparison, this comparative example differs from Example 1 in that the ratio of nitrate to acetate in the system is 1:1. The XRD pattern of the finally prepared high-entropy zinc ferrite is shown below. Figure 7 As shown, from Figure 7 As can be seen from the comparison of the prepared high-entropy zinc ferrite with the standard colorimetric card (PDF#22-1012), an impurity α-Fe2O3 phase appears (represented by the triangle symbol in the figure). Due to the appearance of the impurity phase, the catalytic performance of the prepared high-entropy zinc ferrite is reduced.

[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A green and efficient photocatalytic removal method for cyanide, characterized in that: The foam zinc loaded high-entropy zinc ferrite is put into a water body containing cyanide, and hydrogen peroxide is added for illumination, so as to remove cyanide in the water body, the chemical formula of the high-entropy zinc ferrite is (Co 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 )Fe2O4.

2. The green and efficient photocatalytic removal method for cyanide according to claim 1, characterized in that: The volume ratio of water to hydrogen peroxide is 300:

1.

3. The green and efficient photocatalytic removal method for cyanide according to claim 1, characterized in that: The specific steps for preparing the zinc foam-supported high-entropy zinc ferrite are as follows: (1) Fe (NO3) 3• 9H2O, Co (NO3) 2• 6H2O, Ni (NO3) 2• 6H2O, Zn (NO3) 2• 6H2O 、 Mg (NO3) 2• 6H2O, Cu (NO3) 2• 9H2O and glacial acetic acid are mixed uniformly and calcined to obtain high-entropy zinc ferrite with chemical formula (Co 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 ) Fe2O4. (2) The chemical formula is (Co 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 High-entropy zinc ferrite (Fe2O4) is mixed uniformly with polyvinylidene fluoride (PVDF), and then N-methylpyrrolidone is added to form a gel. This gel is then loaded onto zinc foam to obtain zinc foam-loaded high-entropy zinc ferrite (Co). 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 )Fe2O4.

4. The green and efficient photocatalytic removal method for cyanide according to claim 3, characterized in that: In step (1), Fe(NO3) 3• 9H2O, Co(NO3) 2• 6H₂O, Ni(NO₃) 2• 6H₂O, Zn(NO₃) 2• 6H2O 、 Mg(NO3) 2• 6H₂O, Cu(NO₃) 2• The molar ratio of 9H2O is 10:1:1:1:1:1; the molar ratio of nitrate to acetate in the system is 0.9:

1.

5. The green and efficient photocatalytic removal method for cyanide according to claim 3, characterized in that: In step (1), the calcination temperature is 600~800 degrees Celsius and the calcination time is 2~3 hours.

6. The green and efficient photocatalytic removal method for cyanide according to claim 3, characterized in that: The chemical formula in step (2) is (Co) 0.2 Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 The mass ratio of high-entropy zinc ferrite to polyvinylidene fluoride in Fe2O4 is 96~97:3~4.

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