A new application of copper slag-based FeC2O4 / SiO2 composite photocatalyst

Abstract

The invention discloses a novel use of a copper slag-based FeC2O4 / SiO2 composite photocatalyst and its application in the photocatalytic degradation of chlortetracycline hydrochloride. The copper slag-based FeC2O4 / SiO2 composite photocatalyst is prepared by ball-milling and sieving smelting copper slag, adding the smelting copper slag to a 0.6-0.8 mol / L oxalic acid solution for acid leaching, adjusting the pH of the acid leaching solution to 4-10, stirring and reacting at 80-100°C, separating the solid and the liquid, and drying the solid. When the copper slag-based FeC2O4 / SiO2 composite photocatalyst is used to remove chlortetracycline hydrochloride, the degradation rate can reach 90%, and the copper slag-based FeC2O4 / SiO2 composite photocatalyst can effectively reduce the harm caused by organic pollutants to the environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and in particular relates to a preparation method and application of a copper slag-based FeC2O4 / SiO2 composite photocatalyst. Background Art

[0002] With the rapid development of modern industrial production technology, environmental pollution problems are becoming increasingly serious. More and more organic wastewater is discharged into the natural environment, seriously damaging the ecosystem and threatening human health. Antibiotics, as one of the typical organic pollutants, mainly come from antibiotic industrial wastewater, human antibiotics and veterinary antibiotics. These include: (1) wastewater containing a variety of difficult-to-degrade biotoxic substances and high-concentration active antibiotics generated during the preparation process; (2) antibiotics used by the human body are excreted in organic form without being fully absorbed; (3) antibiotics used for disease prevention and feed additives in livestock, poultry and aquaculture may enter the water environment in the form of prototype drugs. Antibiotics that enter the natural environment or remain in water bodies through different pathways may have adverse effects on the human body through various pathways: (1) they are toxic to lower organisms and affect higher organisms through the transmission effect of the food chain, destroying the ecosystem; (2) they can cause pathogenic microorganisms to develop drug resistance, posing a potential risk to human health; (3) antibiotics and their derivatives remain in water and food, and are enriched for a long time through the food chain, causing potential impacts on human health. Therefore, how to effectively treat antibiotic wastewater is an environmental problem that needs to be solved urgently.

[0003] Photocatalytic technology is considered a promising water treatment method due to its mild reaction conditions, low energy consumption, and eco-friendliness. However, the photoreaction performance of photocatalytic materials is often influenced by factors such as specific surface area (SSA), band gap energy, and surface morphology. Low surface area and poor adsorption properties hinder their effective capture of pollutant molecules. Large band gaps, limited visible light absorption range, and rapid photocarrier recombination also restrict their application in photocatalysis. Therefore, the key to this technology lies in designing photocatalysts with strong catalytic activity and highly dispersed and exposed catalytic active sites. To this end, various strategies have been explored to enhance their photocatalytic performance, including element doping, morphology optimization, heterostructure formation, and composites with other semiconductor materials. However, the simple construction of composite materials with larger surface area, superior surface morphology, and improved photoelectrochemical performance remains a significant challenge.

[0004] SiO2, due to its large band gap and limited absorption of short-wave ultraviolet light, is not an effective photocatalyst on its own. However, its excellent adsorption properties, thermal and mechanical stability, low cost, and optical transparency make it suitable as a carrier or composite component for improving photocatalytic performance. Therefore, the combination of SiO2 with various photocatalysts can improve the photocatalytic performance of the catalysts through various means, including enhancing the adsorption of specific pollutants, maintaining the catalytic activity of the photocatalyst, promoting photoelectron transfer, and improving the catalyst's refractive index to optimize the utilization of incident light.

[0005] Common iron oxides, such as hematite, magmasite, and magnetite, are often used in photo-Fenton technology to treat organic wastewater due to their excellent Fenton-like catalytic and semiconductor photocatalytic properties. When combined with SiO2 in the form of loads, coatings, or spherical shells, the materials also exhibit significantly enhanced catalytic activity, reusability, and acid and alkali resistance. However, these materials face several challenges in their preparation and application: First, both Fenton-like and photo-Fenton technologies cannot avoid the use of unstable and biotoxic hydrogen peroxide or other highly oxidizing substances as oxidants; second, when combined with silicon, expensive and moisture-sensitive external alkyl silicon oxides are usually required as the silicon source. In addition, iron oxide has poor visible light absorption properties and can be replaced by other iron-based catalysts with better visible light absorption properties.

[0006] Copper smelting slag (CS) is a hazardous industrial solid waste produced during the copper smelting process. It is mainly composed of fayalite (FeSiO4), magnetite (Fe3O4) and other metals (such as Al, Mg, Ca, etc.). If it is not effectively treated, it will not only cause waste of resources but also seriously damage the natural environment. Summary of the Invention

[0007] In response to the problems existing in the prior art, the present invention provides a new use of a copper slag-based FeC2O4 / SiO2 composite photocatalyst and its application in the photocatalytic degradation of chlortetracycline hydrochloride. The copper slag-based FeC2O4 / SiO2 composite photocatalyst uses smelting copper slag as the main raw material to prepare a slag-based FeC2O4 compound by an acid leaching method, and in situ composites amorphous SiO2 with a porous structure by a sol-gel method to construct a catalyst with high adsorption and photocatalytic properties. The catalyst is applied to the photocatalytic efficient degradation of chlortetracycline hydrochloride (CTC), solving the problems of small specific surface area, limited light absorption capacity and easy recombination of photogenerated electron-hole pairs of slag-based FeC2O4.

[0008] The slag-based FeC2O4 / SiO2 composite photocatalyst of the present invention is prepared by ball-milling copper smelting slag, adding the smelting copper slag to a 0.6-0.8 mol / L oxalic acid solution for acid leaching, adjusting the pH of the acid leaching solution to 4-10, stirring the reaction at 80-100°C, separating the solid and the liquid, and drying the solid to obtain the copper slag-based FeC2O4 / SiO2 composite photocatalyst. The specific surface area of ​​the composite photocatalyst is 123-124 m 2 / g, pore volume is 0.20~0.21cm 3 / g, the average pore size is 6-7nm, and the smelting copper slag is crushed and passed through a 200-mesh sieve, with the sieve residue less than 5%.

[0009] In the above method, 3-5 mol / L sodium hydroxide solution is used to adjust the pH.

[0010] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0011] 1. The present invention uses oxalic acid leaching to prepare slag-based FeC2O4 from copper smelting slag, and in situ grows amorphous SiO2 with a porous structure through a sol-gel method to construct a slag-based FeC2O4 / SiO2 composite photocatalyst with adsorption and photocatalytic properties. In this process, not only can the iron ions be combined with oxalate ions to form a main photocatalyst after release and be fully utilized, but the silicic acid released by dissolution is also dehydrated and condensed during the modification process to form porous amorphous SiO2 that combines with FeC2O4, thereby improving the catalyst performance and achieving efficient utilization of the iron-silicon dual components.

[0012] 2. During the preparation process of the composite material of the present invention, the amorphous SiO2 in situ composited using the sol-gel method has a porous structure, which makes the slag-based FeC2O4 / SiO2 composite photocatalyst have an increased specific surface area. By enriching organic pollutants in wastewater on the catalyst surface, the concentration of pollutants in the surface solution near the catalyst is increased, making the generated active free radicals, superoxide radicals, more likely to combine with CTC molecules, achieving the purpose of accelerating degradation and improving degradation efficiency.

[0013] 3. In the slag-based FeC2O4 / SiO2 composite photocatalyst, amorphous SiO2 grows on the surface of the slag-based FeC2O4 through Si-O-Fe bonds. The presence of these Si-O-Fe bonds can accelerate the transfer of photogenerated electrons, promote the separation and transfer of photogenerated carriers, increase electron utilization, and enhance photocatalytic activity.

[0014] 4. The porous amorphous SiO2 in the slag-based FeC2O4 / SiO2 composite photocatalyst increases the specific surface area while providing more pore structures that allow light to scatter, thereby improving light capture efficiency.

[0015] 5. The slag-based FeC2O4 / SiO2 composite photocatalyst with high adsorption and photocatalytic properties can achieve a degradation rate of 90% when used to remove chlortetracycline hydrochloride, which can effectively reduce the harm caused by organic pollutants to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The acid leaching product of Example 2 (FOD / Si L ) and pH4 copper slag-based FeC2O4 / SiO2 photocatalyst (FOD / Si H )’s XRD pattern;

[0017] Figure 2 The product after acid leaching in Example 2 (FOD / Si L )

[0018] Figure 3 pH 4 copper slag based FeC2O4 / SiO2 photocatalyst (FOD / Si H ) SEM images;

[0019] Figure 4 The acid leaching product of Example 2 (FOD / Si L ) (a) and pH 4 copper slag-based FeC2O4 / SiO2 photocatalyst (FOD / Si H ) (b) N2 adsorption-desorption curve;

[0020] Figure 5 The acid leaching product of Example 2 (FOD / Si L ) and pH4 copper slag-based FeC2O4 / SiO2 photocatalyst (FOD / Si H )’s UV-visible diffuse reflectance pattern;

[0021] Figure 6 The acid leaching product of Example 2 (FOD / Si L ) and pH4 copper slag-based FeC2O4 / SiO2 photocatalyst (FOD / Si H )’s photoluminescence spectrum;

[0022] Figure 7 The commercially available ferrous oxalate (FOD) and the acid leaching product of Example 2 (FOD / Si L ), pH4 copper slag based FeC2O4 / SiO2 (FOD / Si H ) The degradation effect of composite photocatalyst on chlortetracycline hydrochloride (CTC). DETAILED DESCRIPTION

[0023] In order to better understand the specific contents of the present invention, the present invention is described in detail through the following specific examples, but the protection scope of the present invention is not limited to the following contents.

[0024] Example 1: Preparation of copper slag-based photocatalyst

[0025] The smelting copper slag was ball-milled and passed through a 200-mesh sieve with a sieve residue of less than 5%. 5 g of copper slag powder was added to 100 mL of 0.75 mol / L oxalic acid solution. The mixture was magnetically stirred at room temperature for 2 h. The suspension was then placed on a magnetic stirrer and vigorously stirred at 90°C for 3 h. The suspension was centrifuged at 10,000 rpm for 10 min, and the solid was dried in an oven at 60°C for 12 h to obtain a copper slag-based photocatalyst.

[0026] Example 2: Preparation of copper slag-based FeC2O4 / SiO2 photocatalyst

[0027] The copper slag was ball-milled and passed through a 200-mesh sieve with a sieve residue of less than 5%. 5 g of copper slag powder was added to 100 mL of 0.75 mol / L oxalic acid solution and reacted with magnetic stirring at room temperature for 2 h (the product FOD / Si L ), 4 mol / L NaOH solution was added to adjust the pH to 2, 4, 6, 8, and 10 respectively; the suspension after pH adjustment was placed on a magnetic stirrer and vigorously stirred at 90 ° C for 3 h, centrifuged at 10000 rpm for 10 min, and the solid was dried in an oven at 60 ° C for 12 h to obtain copper slag-based FeC2O4 / SiO2 photocatalyst (FOD / Si H );

[0028] The characterization and analysis of the copper slag-based FeC2O4 / SiO2 photocatalyst and the acid leaching product prepared at pH 4 are as follows:

[0029] The crystal structure of copper slag-based FeC2O4 / SiO2 photocatalyst (pH 4) is as follows Figure 1 As shown in the figure, it can be seen that the main component of the product obtained after oxalic acid leaching is β-FeC2O4. After the amorphous SiO2 with a porous structure is in situ grown by the sol-gel method, β-FeC2O4 is transformed into α-FeC2O4 with a more stable structure. No diffraction peak of SiO2 appears in the composite material, indicating that amorphous SiO2 is generated.

[0030] The macroscopic morphology of copper slag-based FeC2O4 / SiO2 photocatalyst (pH 4) is shown in Figure 4. Figure 2 、 3As can be seen in the figure, as FeC2O4 crystals grow, amorphous SiO2 forms on the surface of the tubular FeC2O4, forming a unique composite structure. This formation can be simply explained by the fact that during the pH adjustment and heating process, while FeC2O4 self-assembles into hollow tubular structures, silicic acid gradually dehydrates and condenses to form amorphous SiO2. These two reactions occur simultaneously, forming an interpenetrating structure. This unique structure and surface morphology significantly increases the specific surface area and adsorption capacity of the catalyst, enhancing its light-harvesting ability.

[0031] The specific surface area and pore size distribution of the material were characterized by nitrogen isothermal adsorption-desorption curves. Figure 4 The pore structure of the product after acid leaching is mainly composed of mesopores with a pore diameter of about 14.0 nm, and its specific surface area is only 34.7 m 2 / g; while the specific surface area of ​​pH4 copper slag-based FeC2O4 / SiO2 photocatalyst is 123.7 m 2 / g, which is 3.6 times larger. The larger specific surface area is conducive to the adsorption reaction and provides more active reaction sites for the catalytic reaction.

[0032] The optical properties of the prepared catalyst were studied using UV-visible diffuse reflectance. Figure 5 As can be seen from the figure, the acid-leached product has good light absorption capacity in the wavelength range below 420 nm, but has low absorption in the visible light range (>420 nm). When SiO2 is in situ compounded in the reaction suspension, the visible light absorption capacity of the copper slag-based FeC2O4 / SiO2 photocatalyst is significantly improved, indicating that the compounding of SiO2 can effectively enhance the visible light absorption capacity of the acid-leached product.

[0033] Photoluminescence spectroscopy (PL) was used to characterize the separation efficiency of photogenerated electrons and holes in the copper slag-based FeC2O4 / SiO2 photocatalyst. The higher the separation efficiency, the weaker the PL emission peak intensity. Figure 6 ,from Figure 6 The acid-leached product exhibits a strong emission peak at 460 nm, indicating a rapid recombination rate for photogenerated electrons and holes. When the acid-leached product is in situ composited with amorphous SiO2, the copper slag-based FeC2O4 / SiO2 photocatalyst exhibits the highest photogenerated electron-hole separation efficiency. This is likely due to the unique structure formed by the porous amorphous SiO2 and FeC2O4, which accelerates electron transport and improves the separation efficiency of photogenerated electrons and holes.

[0034] Example 3: Application of the catalyst prepared in the above example in photocatalytic degradation of chlortetracycline hydrochloride

[0035] The acid leaching product prepared in Example 2, the catalyst prepared in Examples 1 and 2, and commercially available ferrous oxalate were used in a photocatalytic reaction to remove chlortetracycline hydrochloride (CTC). The catalyst was added at a dosage of 0.8 g / L in a chlortetracycline hydrochloride solution of 50 mg / L at pH 4 for 2 h. The results of the acid leaching product and the copper slag-based FeC2O4 / SiO2 photocatalyst (pH 4) were shown in FIG. Figure 7 ,from Figure 7 It can be seen that the degradation rate of chlortetracycline hydrochloride by copper slag-based FeC2O4 / SiO2 photocatalyst (pH 4) is 90.96%, while when the acid leaching product is used as catalyst, the degradation rate of chlortetracycline hydrochloride is 60.06%.

[0036] At the same time, commercially available ferrous oxalate was used as a catalyst and the treatment conditions were the same as above. The results showed that the degradation rate of chlortetracycline hydrochloride was 40.34%;

[0037] The degradation rate of the catalyst prepared in Example 1 was 67.82%;

[0038] The degradation rate of chlortetracycline hydrochloride by copper slag-based FeC2O4 / SiO2 photocatalyst (pH 2) was 55.39%; the degradation rate of chlortetracycline hydrochloride by copper slag-based FeC2O4 / SiO2 photocatalyst (pH 6) was 89.62%; the degradation rate of chlortetracycline hydrochloride by copper slag-based FeC2O4 / SiO2 photocatalyst (pH 8) was 89.57%; and the degradation rate of chlortetracycline hydrochloride by copper slag-based FeC2O4 / SiO2 photocatalyst (pH 10) was 88.41%.

Claims

1. Application of a copper slag-based FeC2O4 / SiO2 composite photocatalyst in the photocatalytic degradation of chlortetracycline hydrochloride; The copper slag-based FeC2O4 / SiO2 composite photocatalyst is prepared by ball-milling and sieving the smelting copper slag, adding the smelting copper slag to a 0.6-0.8 mol / L oxalic acid solution for acid leaching, adjusting the pH of the acid leaching solution to 4-10 with a 3-5 mol / L sodium hydroxide solution, stirring and reacting at 80-100°C, separating the solid and the liquid, and drying the solid.

2. The use according to claim 1, characterized in that: The copper slag is crushed and passed through a 200-mesh sieve, and the sieve residue is less than 5% by mass.

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