Fe3O4 / CdS heterojunction material, preparation method thereof and application of Fe3O4 / CdS heterojunction material in uranium-containing wastewater treatment

Abstract

The invention belongs to the cross technical field of environment and metallurgical engineering, and particularly relates to a Fe3O4 / CdS heterojunction material, a preparation method thereof and application of the Fe3O4 / CdS heterojunction material in uranium-containing wastewater treatment. According to the method, firstly, a silicon component in the copper slag is selectively dissolved out through alkaline leaching, a fayalite structure is selectively decomposed, wrapped Fe3O4 magnetic particles are promoted to be exposed to the surface of the copper slag, the surface of Fe3O4 generated in situ is rich in redox sites which are equivalent to Fe2 + / Fe3 +, and the Fe3O4 generated in situ has the characteristics of being magnetic and easy to recover. In-situ generated Fe3O4 is creatively used for adsorbing Cd < 2 + > in cadmium-containing wastewater, then the Fe3O4 reacts with a sulfur source to generate CdS nano-particles, the CdS nano-particles are loaded on the surface of Fe3O4 through in-situ hydrothermal treatment, and the Fe3O4 / CdS heterojunction material is constructed.

Description

Technical Field

[0001] The present invention belongs to the cross-technical field of environment and metallurgical engineering, and particularly relates to an Fe3O4 / CdS heterojunction material and a preparation method thereof, and application thereof in the treatment of uranium-containing wastewater. Background Art

[0002] Copper slag, as a by-product of the copper smelting process, has an iron content of up to 25-40%. However, the iron in copper slag is mainly present in the form of fayalite (Fe2SiO4). The iron-silicon phase in fayalite is tightly interwoven and embedded in the lattice, making it impossible to achieve efficient separation of iron and silicon using traditional physical separation methods (magnetic separation and flotation), which seriously restricts the recycling of copper slag iron resources.

[0003] Existing methods for recovering copper slag and iron resources mainly include pyrometallurgy, wet acid leaching, and melt separation. The pyrometallurgy process uses carbon thermal reduction (>1400°C) or oxidative roasting (800-1200°C) to recycle copper slag and iron resources. Wet acid leaching can dissolve iron through acid leaching, thereby recyclable copper slag and iron resources. Melt separation uses fluxing agents such as CaO to adjust the alkalinity, thereby recyclable copper slag and iron resources.

[0004] However, none of the above methods can directionally regulate the iron oxide phase, and cannot obtain Fe3O4 active carriers with specific surface properties. Summary of the Invention

[0005] The purpose of the present invention is to provide a Fe3O4 / CdS heterojunction material and its preparation method and application in the treatment of uranium-containing wastewater. The preparation method provided by the present invention obtains an Fe3O4 active carrier, which gives the Fe3O4 surface rich ≡Fe 2+ / Fe 3+ Redox sites were formed, and Fe3O4 / CdS heterojunction materials were further prepared.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a Fe3O4 / CdS heterojunction material, comprising the following steps:

[0008] (1) copper slag is mixed with alkali and water to perform alkali treatment to obtain alkali-treated copper slag;

[0009] (2) The alkali-treated copper slag and cadmium-containing wastewater are mixed for adsorption and then subjected to a hydrothermal reaction with a sulfur source to obtain the Fe3O4 / CdS heterojunction material.

[0010] Preferably, the temperature of the alkali treatment is 70-130° C., and the holding time is 2-4 hours.

[0011] Preferably, the concentration of cadmium ions in the cadmium-containing wastewater is 30 to 1500 mg / L; the mass ratio of the alkali-treated copper slag to the cadmium-containing wastewater is 1:200 to 2600; and the molar ratio of cadmium ions in the cadmium-containing wastewater to sulfur ions in the sulfur source is 1:1 to 3.

[0012] Preferably, the adsorption temperature is 15-45° C., and the insulation time is 1-6 hours.

[0013] Preferably, the sulfur source includes one or more of H2S, Na2S, thiourea and thioacetamide.

[0014] Preferably, the method further comprises aging the obtained reaction solution (the reaction solution is obtained by mixing alkali-treated copper slag and cadmium-containing wastewater for adsorption and then adding a sulfur source) before the hydrothermal reaction.

[0015] Preferably, the temperature of the hydrothermal reaction is 100-200° C., and the insulation time is 6-24 hours.

[0016] The present invention also provides a Fe3O4 / CdS heterojunction material obtained by the preparation method described in the above scheme, comprising Fe3O4 and CdS nanoparticles loaded on the surface of the Fe3O4; the Fe3O4 and CdS nanoparticles form a heterojunction.

[0017] Preferably, the mass ratio of the Fe3O4 to CdS nanoparticles is 1:1-5.

[0018] The present invention also provides the use of the Fe3O4 / CdS heterojunction material described in the above scheme in the treatment of uranium-containing wastewater.

[0019] The present invention provides a method for preparing Fe3O4 / CdS heterojunction material. The present invention first selectively dissolves the silicon component in the copper slag by alkali leaching, controls the leaching temperature and alkali dosage, and selectively decomposes the fayalite structure, so that the silicon element enters the liquid phase in the form of sodium silicate. At the same time, the wrapped Fe3O4 magnetic particles are exposed to the surface of the copper slag. The in-situ generated Fe3O4 is not only rich in ≡Fe 2+ / Fe 3+ The redox sites provide an ideal substrate for constructing heterojunction materials and also have magnetic properties that are easy to recycle. This invention innovatively uses in-situ generated Fe3O4 to adsorb Cd in cadmium-containing wastewater. 2+ , and then react with a sulfur source to generate CdS nanoparticles with narrow bandgap characteristics (~2.4eV). The CdS nanoparticles are loaded on the Fe3O4 surface through in situ hydrothermal treatment to construct a Fe3O4 / CdS heterojunction material, while solving the problem of high recombination rate of photogenerated carriers in CdS.

[0020] The present invention also provides a Fe3O4 / CdS heterojunction material obtained by the preparation method described in the above scheme. In the structure of the Fe3O4 / CdS heterojunction material of the present invention, the energy band matching of Fe3O4 and CdS can form a built-in electric field, effectively promoting the directional migration and separation of photogenerated electron-hole pairs, thereby improving the resistance to radioactive uranyl ions (UO2 2+ )'s photocatalytic reduction efficiency.

[0021] The present invention also provides the application of the Fe3O4 / CdS heterojunction material in the treatment of uranium-containing wastewater. The Fe3O4 / CdS heterojunction material provided by the present invention can be used as a visible light catalyst to treat radioactive uranyl ions (UO2 2+ ) has a high photocatalytic reduction efficiency, can achieve efficient conversion of hexavalent uranium ions U(VI) to insoluble tetravalent uranium ions U(IV), and achieve efficient purification of radioactive uranium-containing wastewater. The present invention breaks through the traditional solid waste and wastewater separation mode, and through the technical coupling of copper slag alkali leaching modification-cadmium resource recovery-heterostructure construction, the iron phase in the copper slag is directionally converted to generate magnetite, and then the cadmium in the cadmium-containing wastewater is recovered in the form of high-value-added CdS, forming a heterojunction material as a photocatalyst for the treatment of uranium-containing wastewater, providing a new idea for the coordinated treatment of heavy metal pollution. The present invention not only solves the dual environmental problems of copper slag solid waste storage and heavy metal wastewater pollution, but also significantly reduces costs through the "waste treatment with waste" strategy, providing an innovative solution for radioactive wastewater treatment with both environmental and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 4 is a process flow chart of the preparation method of the Fe3O4 / CdS heterojunction material of the present invention;

[0024] Figure 2 1 is the XRD pattern of the copper slag and the alkali-treated copper slag of Example 1;

[0025] Figure 3 This is an efficiency diagram of photocatalytic reduction of uranium (VI)-containing wastewater in Example 1;

[0026] Figure 4 This is the efficiency diagram of the photocatalytic reduction of uranium (VI)-containing wastewater in Example 2. DETAILED DESCRIPTION

[0027] The present invention provides a method for preparing a Fe3O4 / CdS heterojunction material, comprising the following steps:

[0028] (1) copper slag is mixed with alkali and water to perform alkali treatment to obtain alkali-treated copper slag;

[0029] (2) The alkali-treated copper slag and cadmium-containing wastewater are mixed for adsorption and then subjected to a hydrothermal reaction with a sulfur source to obtain the Fe3O4 / CdS heterojunction material.

[0030] The process flow of the preparation method of the Fe3O4 / CdS heterojunction material of the present invention is as follows Figure 1 The present invention mixes copper slag with alkali and water for alkali treatment to obtain alkali-treated copper slag. In the present invention, the particle size of the copper slag can be 38 to 270 μm, specifically 50 μm, 80 μm, 120 μm, 150 μm, 200 μm or 250 μm.

[0031] In the present invention, the copper slag can be obtained by crushing, grinding and screening the original copper slag in sequence to obtain copper slag with a target particle size; the original copper slag can be the original copper slag produced by the copper smelting process; the main components of the original copper slag include magnetite, fayalite and quartz.

[0032] In the present invention, the alkali may be one or both of sodium hydroxide and potassium hydroxide.

[0033] In the present invention, the mass ratio of the copper slag to the alkali may be 1 to 5:1, specifically 2:1, 3:1 or 4:1.

[0034] In the present invention, the mass ratio of water to copper slag may be 1 to 5:1, specifically 2:1, 3:1 or 4:1.

[0035] In the present invention, the temperature of the alkali treatment can be 70 to 130° C., specifically 90° C. or 110° C., and the holding time can be 2 to 4 hours, specifically 3 hours. In the present invention, through the alkali treatment, fayalite reacts with the alkali to dissociate into Fe3O4 and SiO2, and the SiO2 further reacts with the alkali to dissolve into the liquid phase. Ultimately, the mineral phase structure of the alkali-treated copper slag retains only magnetite, and all other components enter the liquid phase.

[0036] In the present invention, the alkali treatment may be followed by solid-liquid separation of the obtained product system; the solid-liquid separation may be performed by filtration.

[0037] After obtaining the alkali-treated copper slag, the present invention mixes the alkali-treated copper slag with cadmium-containing wastewater for adsorption, and then hydrothermally reacts with a sulfur source to obtain the Fe3O4 / CdS heterojunction material. In the present invention, the cadmium-containing wastewater can be derived from the electroplating industry or the battery manufacturing industry; the concentration of cadmium ions in the cadmium-containing wastewater can be 30 to 1500 mg / L, specifically 50 mg / L, 100 mg / L, 150 mg / L, 300 mg / L, 500 mg / L, 700 mg / L, 1000 mg / L, or 1200 mg / L.

[0038] In the present invention, the mass ratio of the alkali-treated copper slag to the cadmium-containing wastewater can be 1:200-2600, specifically 1:500, 1:1000, 1:1500, 1:2000 or 1:2500.

[0039] In the present invention, the adsorption temperature can be 15 to 45° C., specifically 25° C. or 35° C., and the holding time can be 1 to 6 hours, specifically 2 hours, 3 hours, 4 hours, or 5 hours. The present invention adopts the above-mentioned adsorption conditions to ensure that adsorption equilibrium is achieved. After adsorption equilibrium, no separation is required. A sulfur source can be added to the adsorption equilibrium system to carry out a hydrothermal reaction.

[0040] In the present invention, the sulfur source may include one or more of H2S, Na2S, thiourea and thioacetamide; the sulfur source may be in the form of gas or aqueous solution, and the concentration of the aqueous solution may be 0.1 mol / L.

[0041] In the present invention, the molar ratio of cadmium ions in the cadmium-containing wastewater to sulfur ions in the sulfur source can be 1:1 to 3, specifically 1:2.

[0042] In the present invention, the hydrothermal reaction may further include aging the resulting reaction solution before the reaction. The aging time may be 1 to 24 hours, specifically 4 hours, 8 hours, 12 hours, 16 hours, or 20 hours. The aging may be performed under stirring. The aging process increases the size of the cadmium sulfide particles, thereby enhancing the photocatalytic performance of the Fe3O4 / CdS heterojunction material.

[0043] In the present invention, the temperature of the hydrothermal reaction can be 100-200° C., specifically 125° C., 150° C., or 170° C., and the holding time can be 6-24 hours, specifically 10 hours, 15 hours, or 20 hours. The present invention constructs a heterojunction structure through a hydrothermal reaction.

[0044] In the present invention, after the hydrothermal reaction, the obtained product system may be subjected to solid-liquid separation and then solid drying; the solid-liquid separation may be centrifugation and / or filtration.

[0045] The present invention also provides a Fe3O4 / CdS heterojunction material obtained by the preparation method described in the above scheme, comprising Fe3O4 and CdS nanoparticles loaded on the surface of the Fe3O4; the Fe3O4 and CdS nanoparticles form a heterojunction.

[0046] In the present invention, the mass ratio of the Fe3O4 to CdS nanoparticles may be 1:1 to 5, specifically 1:2, 1:3 or 1:4.

[0047] The present invention also provides the use of the Fe3O4 / CdS heterojunction material described in the above scheme in the treatment of uranium-containing wastewater.

[0048] In the present invention, the application method may include the following steps: adding the Fe3O4 / CdS heterojunction material to uranium-containing wastewater and performing a photocatalytic reduction reaction under light source conditions.

[0049] In the present invention, the concentration of uranyl ions in the uranium-containing wastewater may be 0.05 to 50 mg / L, specifically 1 mg / L or 10 mg / L.

[0050] In the present invention, the ratio of the mass of the Fe3O4 / CdS heterojunction material to the volume of the uranium-containing wastewater can be (0.1-0.5) g:1L, specifically 0.3 g:1L.

[0051] In the present invention, the light source may be visible light (xenon lamp) or a white LED lamp; the wavelength of the light source may be 400-750 nm; and the power of the light source may be 300 W.

[0052] In the present invention, the temperature of the photocatalytic reduction reaction may be 20-45° C., specifically 30° C., and the insulation time may be no less than 15 minutes, specifically 30 minutes or 60 minutes.

[0053] In order to further illustrate the present invention, the scheme of the present invention is described in detail below with reference to the accompanying drawings and embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0054] Example 1

[0055] (1) The original copper slag was crushed and ground through a sieve with an aperture of 74 μm to obtain copper slag. The copper slag was then mixed with a NaOH solution in a mass ratio of 1:3 for alkali treatment. The mass ratio of the NaOH solution solvent to the copper slag was 2:1. The alkali treatment temperature was 90°C and the holding time was 2 hours. The alkali-treated solution was filtered and dried to obtain a silicon-containing filtrate and an alkali-treated copper slag, respectively.

[0056] (2) According to the mass ratio of alkali-treated copper slag and CdS of 1:1, Fe3O4 / CdS heterojunction material was prepared:

[0057] 0.1 g of alkaline-treated copper slag was placed in 62 mL of cadmium-containing wastewater with a cadmium ion concentration of 1250.7 mg / L to obtain a premix. A sodium sulfide aqueous solution (0.1 mol / L) was then added to the premix to achieve a 1:1 molar ratio of Cd ions to S. After stirring and aging for 1 hour, the mixture was added to a hydrothermal reactor and hydrothermally reacted at 160°C for 12 hours. Following the hydrothermal reaction, the mixture was centrifuged, filtered, and dried overnight to obtain the Fe3O4 / CdS heterojunction material.

[0058] The Fe3O4 / CdS heterojunction material prepared in this embodiment was subjected to XRD analysis, and the results were as follows: Figure 2 As shown. Figure 2 It can be seen that the phase of the alkali-treated copper slag is transformed into magnetically separated Fe3O4, and no other impurities appear, which proves that the alkali treatment effectively transforms the phase of the copper slag and effectively realizes the separation of iron and silicon.

[0059] (3) The prepared Fe3O4 / CdS heterojunction material was added to uranium-containing wastewater for photocatalytic reduction reaction. The concentration of uranyl ions in the uranium-containing wastewater was 10 mg / L, the addition amount of Fe3O4 / CdS heterojunction material was 0.2 g / L, the light source was a 300W xenon lamp, the temperature of the photocatalytic reduction reaction was 25°C, and the time was 40 min. The results are as follows: Figure 3 shown.

[0060] according to Figure 3 It can be seen that after the photocatalytic reduction reaction, the removal rate of cadmium ions in cadmium-containing wastewater reached more than 99% within 40 minutes, achieving efficient photocatalytic removal of uranyl ions.

[0061] Example 2

[0062] (1) The raw copper slag was crushed and ground through a 74 μm sieve to obtain copper slag. The copper slag was then mixed with a NaOH solution in a mass ratio of 1:3 for alkali treatment. The mass ratio of the NaOH solution solvent to the copper slag was 2:1. The alkali treatment temperature was 130°C and the holding time was 3 hours. The alkali-treated solution was filtered and dried to obtain a silicon-containing filtrate and an alkali-treated copper slag, respectively.

[0063] (2) Fe3O4 / CdS heterojunction material was prepared according to the mass ratio of alkali-treated copper slag and CdS of 1:5:

[0064] 0.1g of alkaline-treated copper slag was placed in 260mL of cadmium-containing wastewater with a cadmium ion concentration of 1497.4mg / L to obtain a premix. A sodium sulfide aqueous solution (0.1mol / L) was then added to the premix to achieve a 1:1 molar ratio of Cd ions to S. After stirring and aging for 1 hour, the mixture was added to a hydrothermal reactor and hydrothermally reacted at 190°C for 12 hours. Following the hydrothermal reaction, the mixture was centrifuged, filtered, and dried overnight to obtain the Fe3O4 / CdS heterojunction material.

[0065] (3) The prepared Fe3O4 / CdS heterojunction material was added to uranium-containing wastewater for photocatalytic reduction reaction. The concentration of uranyl ions in the uranium-containing wastewater was 10 mg / L, the addition amount of Fe3O4 / CdS heterojunction material was 0.1 g / L, the light source was a 300W xenon lamp, the temperature of the photocatalytic reduction reaction was 25°C, and the time was 20 min. The results are as follows: Figure 4 shown.

[0066] according to Figure 4 It can be seen that after the photocatalytic reduction reaction, the removal rate of cadmium ions in cadmium-containing wastewater reaches more than 99% within 20 minutes, realizing efficient photocatalytic removal of uranyl ions.

[0067] It can be seen from the above examples that the preparation method provided by the present invention successfully constructs a Fe3O4 / CdS heterojunction using copper slag and cadmium-containing wastewater. The obtained Fe3O4 / CdS heterojunction material has good photocatalytic performance and can efficiently catalyze the removal of uranyl ions in uranium-containing wastewater.

[0068] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a Fe3O4 / CdS heterojunction material, characterized in that: The following steps are involved: (1) copper slag is mixed with alkali and water to perform alkali treatment to obtain alkali-treated copper slag; (2) The alkali-treated copper slag and cadmium-containing wastewater are mixed for adsorption and then subjected to a hydrothermal reaction with a sulfur source to obtain the Fe3O4 / CdS heterojunction material.

2. The preparation method according to claim 1, characterized in that The temperature of the alkali treatment is 70-130° C., and the insulation time is 2-4 hours.

3. The preparation method according to claim 1, characterized in that The concentration of cadmium ions in the cadmium-containing wastewater is 30 to 1500 mg / L; The mass ratio of the alkali-treated copper slag to the cadmium-containing wastewater is 1:200-2600; The molar ratio of cadmium ions in the cadmium-containing wastewater to sulfur ions in the sulfur source is 1:1-3.

4. The preparation method according to claim 1 or 3, characterized in that The adsorption temperature is 15-45° C., and the insulation time is 1-6 hours.

5. The preparation method according to claim 1 or 3, characterized in that The sulfur source includes one or more of H2S, Na2S, thiourea and thioacetamide.

6. The preparation method according to claim 1, characterized in that The method further comprises aging the obtained reaction solution before the hydrothermal reaction.

7. The preparation method according to claim 1 or 6, characterized in that The temperature of the hydrothermal reaction is 100-200° C., and the insulation time is 6-24 hours.

8. The Fe3O4 / CdS heterojunction material obtained by the preparation method according to any one of claims 1 to 7, comprising Fe3O4 and CdS nanoparticles loaded on the surface of the Fe3O4, wherein the Fe3O4 and CdS nanoparticles form a heterojunction.

9. The Fe3O4 / CdS heterojunction material according to claim 8, characterized in that: The mass ratio of the Fe3O4 to CdS nanoparticles is 1:1-5.

10. Use of the Fe3O4 / CdS heterojunction material according to any one of claims 8 to 9 in the treatment of uranium-containing wastewater.

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