Sulfurized zero-valent iron preparation method based on solid waste resource utilization

Abstract

The invention belongs to the technical field of solid waste resource utilization and environmental function material preparation, particularly relates to a method for preparing sulfurized zero-valent iron based on solid waste resource utilization, and relates to a novel method for converting industrial solid waste into an environmental function material. A solid waste-based sulfur source (solid waste ardealite and / or desulfurized gypsum) and iron-based solid waste (iron-containing copper smelting slag) are used as raw materials, the solid waste-based sulfurized zero-valent iron is synthesized in one step in a carbothermal reduction mode, the reaction temperature of carbothermal reduction is remarkably reduced due to the addition of the solid waste-based sulfur source, and the reaction time is shortened; and the sulfurized zero-valent iron prepared by doping the solid waste-based sulfur source can significantly enhance the degrading capability on fleroxacin, the reaction rate of the sulfurized zero-valent iron in degrading fleroxacin is increased, and a powerful technical support is provided for large-scale production and environmental application of the sulfurized zero-valent iron.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste resource utilization and environmental functional material preparation, and more specifically relates to a method for preparing zero-valent iron sulfide based on solid waste resource utilization. Background Art

[0002] Zero-valent iron (ZVI) (micronized and nanoscale) has attracted widespread attention in industrial catalysis and environmental remediation due to its efficient electron-donating capacity, strong reducing properties, and high reactivity. However, ZVI suffers from drawbacks such as poor electron selectivity, poor stability, short lifetime, easy aggregation, surface passivation, and high preparation cost.

[0003] Sulfurization can significantly improve the aggregation effect of ZVI, enhance its conductivity, hydrophobicity (electron selectivity), and stability (slowing down its reaction with oxygen), and reduce the passivation of ZVI caused by the accumulation of non-conductive corrosion products (iron oxides) on the surface. Therefore, sulfurization has become a feasible method to improve the life of ZVI.

[0004] The current preparation methods of zero-valent iron sulfide include adding sulfide (Na2S), dithionite (S2O4 2- ), thiosulfate (S2O3 2- ) and a two-step synthesis method by mechanically ball-milling zero-valent iron and sulfide or elemental sulfur. However, the two-step synthesis method of zero-valent iron sulfide based on liquid phase one-step synthesis and mechanical ball milling is still limited by high cost and dangerous preparation process (the reaction is too violent and produces a large amount of hydrogen).

[0005] Carbon thermal reduction of zero-valent iron has gradually attracted attention due to its advantages such as low cost and easy large-scale preparation. At present, the iron source for preparing zero-valent iron based on carbon thermal reduction is mainly soluble iron salts (such as ferrous sulfate, ferric chloride, etc.). A small number of studies have used minerals such as limonite, red mud, iron slag, and solid waste to prepare zero-valent iron through carbon thermal reduction. There are very few studies related to zero-valent iron sulfide based on the carbon thermal reduction process. The main focus is on the preparation of zero-valent iron sulfide using limonite as the iron source and sulfur (the main component is elemental sulfur) as the sulfur source. However, the large-scale preparation of zero-valent iron sulfide based on materials such as limonite and sulfur is still constrained by high costs. The present invention uses solid waste-based iron sources and solid waste-based sulfur sources to prepare zero-valent iron sulfide, which can provide an important technical reference for the economical, green, and large-scale preparation of zero-valent iron sulfide. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing zero-valent iron sulfide based on solid waste resource utilization, which relates to a new method for converting industrial solid waste into environmental functional materials. Solid waste-based sulfur source (solid waste phosphogypsum and / or desulfurized gypsum) and iron-based solid waste (iron-containing copper smelting slag) are used as raw materials to synthesize solid waste-based zero-valent iron sulfide in one step through carbothermal reduction. This solves the problems existing in the above-mentioned prior art and significantly reduces the temperature required for carbothermal reduction synthesis of zero-valent iron sulfide (S-ZVI), providing technical support for the large-scale production of zero-valent iron sulfide.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] One of the technical solutions of the present invention is to provide a method for preparing zero-valent iron sulfide based on solid waste resource utilization, comprising the following steps:

[0009] The zero-valent iron sulfide is synthesized in one step by carbothermal reduction using a solid waste-based sulfur source and an iron-based solid waste as reactants in the presence of a carbon source;

[0010] The solid waste-based sulfur source includes solid waste phosphogypsum and / or desulfurization gypsum.

[0011] The main components of phosphogypsum and desulfurized gypsum are CaSO4·2H2O. The sulfate ions in them serve as a sulfur source, and Ca can be converted into CaO through the reaction, thereby reducing the temperature of the carbothermal reduction reaction to generate zero-valent iron and sulfided zero-valent iron, and improving the reaction efficiency.

[0012] Furthermore, the main component of the solid waste-based sulfur source is CaSO4·2H2O.

[0013] Furthermore, the iron-based solid waste includes iron-containing copper smelting slag.

[0014] Optionally, the iron-containing copper smelting slag is a product of copper ore smelting, the main component of which is Fe2SiO4, and the iron oxide content is 35-60wt%.

[0015] Furthermore, the carbon source includes anthracite and / or lignite.

[0016] Furthermore, the mass ratio of the iron-based solid waste, the carbon source and the solid waste-based sulfur source is (5-7):3:(0-2), and the amount of solid waste phosphogypsum is not 0.

[0017] Optionally, the mass ratio of the iron-based solid waste, the carbon source and the solid waste-based sulfur source is 6:3:1.

[0018] Furthermore, the carbon thermal reduction is carried out in an inert atmosphere at a temperature of 800-1200° C. for 60 minutes.

[0019] The second technical solution of the present invention is to provide a zero-valent iron sulfide based on the resource utilization of solid waste, wherein the zero-valent iron sulfide is prepared by the above-mentioned preparation method.

[0020] The third technical solution of the present invention is to provide an application of the above-mentioned zero-valent iron sulfide based on solid waste resource utilization in improving the reaction rate of degrading fleroxacin.

[0021] A fourth technical solution of the present invention provides a method for lowering the reaction temperature of zero-valent iron sulfide synthesized by carbothermal reduction, wherein the reaction temperature of zero-valent iron sulfide synthesized by carbothermal reduction is lowered by adding 0-20 wt% of a solid waste-based sulfur source as a sulfurization-modifying material to a carbothermal reduction reaction system, and the amount of solid waste phosphogypsum added is not zero.

[0022] The solid waste-based sulfur source includes solid waste phosphogypsum and / or desulfurized gypsum, the main component of which is CaSO4·2H2O.

[0023] The present invention discloses the following technical effects:

[0024] The present invention uses solid waste phosphogypsum and / or desulfurized gypsum as a sulfur source, and iron-based solid waste (iron-containing copper smelting slag) as an iron source. With the participation of a carbon source, zero-valent iron sulfide is synthesized in a one-step carbon thermal reduction. The addition of the limited sulfur source in the present invention significantly reduces the reaction temperature of the carbon thermal reduction. The zero-valent iron sulfide prepared by doping with solid waste phosphogypsum and / or desulfurized gypsum can significantly enhance the degradation ability of fleroxacin and increase the reaction rate of the zero-valent iron sulfide in degrading fleroxacin, providing strong technical support for the large-scale production of zero-valent iron sulfide and its environmental application.

[0025] The present invention uses solid waste materials to prepare zero-valent iron sulfide. Compared with existing methods for preparing zero-valent iron sulfide (existing reported zero-valent iron sulfide is mostly obtained by liquid-phase reduction or by ball milling zero-valent iron and sulfide, while the present invention uses high-temperature carbon thermal reduction), the raw materials are different, the preparation cost is lower, the preparation method is simpler, and it is more suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0027] Figure 1 This is the standard Gibbs free energy-temperature relationship diagram of the carbothermal reduction process involved in equations (1) to (4).

[0028] Figure 2 1 and 2 are XRD patterns of the iron-containing copper smelting slag, and the products obtained in Example 1 and Example 2.

[0029] Figure 3The XRD patterns of the products obtained in Example 3 and Comparative Example 1 are shown in FIG.

[0030] Figure 4 The degradation performance of the products obtained in Comparative Example 2, Example 1 and Example 2 on fleroxacin is shown.

[0031] Figure 5 is the degradation rate constant of fleroxacin by the products of Comparative Example 2 and Example 1.

[0032] Figure 6 The contact angles of the products of Comparative Example 2, Example 1 and Example 2, wherein (a) is Comparative Example 2, (b) is 6.5:3:0.5 in Example 2, (c) is Example 1, (d) is 5.5:3:1.5 in Example 2, and (e) is 5:3:2 in Example 2.

[0033] Figure 7 The specific surface area results of the products of Example 1 and Comparative Example 2, wherein (a) is the adsorption-desorption curve of Comparative Example 2, (b) is the adsorption-desorption curve of Example 1, and (c) is the specific surface area of ​​the products of Example 1 and Comparative Example 2. DETAILED DESCRIPTION

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0036] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0037] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0038] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0039] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0040] The present invention uses solid waste phosphogypsum as a sulfur source and iron-containing copper smelting slag as an iron source. In the presence of a carbon source, the reactions involved in synthesizing sulfided zero-valent iron through carbothermal reduction in one step are shown in the following formulas (1) to (4).

[0041] CaSO4+C=CaO+SO2(g)+CO(g) (1)

[0042] Fe2SiO4+2C=2Fe+SiO2+2CO(g) (2)

[0043] Fe2SiO4+2C+CaSO4=2Fe+CaSiO3+SO2(g)+2CO(g) (3)

[0044] Fe2SiO4+5C+CaSO4=Fe+CaSiO3+FeS(g)+5CO(g) (4)

[0045] Among them, the standard Gibbs free energy-temperature relationship diagram of the carbothermal reduction process involved in formula (1)-formula (4) is as follows Figure 1 As shown, in the present invention, iron-containing copper smelting slag is used as the iron source, anthracite is used as the reducing agent, and solid waste phosphogypsum is used as the sulfur source to sulfide-modify zero-valent iron. At the same time, solid waste phosphogypsum also serves as a calcium source to reduce the reaction temperature required for the iron reduction reaction in the copper slag to form zero-valent iron.

[0046] Since copper slag can be carbon-thermally reduced to zero-valent iron (e.g. Figure 2 As shown), the present invention first proves that solid waste phosphogypsum can generate sulfide zero-valent iron at 1000°C through the embodiment, and then verifies whether zero-valent iron can be formed at 800°C through the reaction at 800°C. Figure 1 It can be seen that theoretically, zero-valent iron cannot be formed at 800℃ without adding phosphogypsum. In fact, when copper slag is roasted at 800℃ without adding phosphogypsum, no zero-valent iron is found ( Figure 3The present invention successfully reduces copper slag to zero-valent iron sulfide by adding 10% solid waste phosphogypsum and reacting at 800°C ( Figure 3 ), which shows that the addition of phosphogypsum can reduce the temperature required for the reaction and promote the conversion of copper slag to zero-valent iron.

[0047] The solid waste phosphogypsum involved in the specific embodiment of the present invention is provided by Hubei Xingxing Environmental Protection Technology Co., Ltd., and its composition is shown in Table 1; the iron-containing copper smelting slag involved is provided by Huili County Pengcheng Waste Slag Utilization Co., Ltd., and its composition is shown in Table 2. The main mineral phases are fayalite (Fe2SiO4) and a small amount of magnetite (Fe3O4), and the XRD is as follows Figure 2 shown.

[0048] Table 1

[0049]

[0050]

[0051] Table 2

[0052]

[0053] Example 1

[0054] The preparation steps of zero-valent iron sulfide based on solid waste resource utilization (solid waste-based zero-valent iron sulfide) include:

[0055] Iron-containing copper smelting slag, anthracite and solid waste phosphogypsum were passed through a 100-mesh sieve, mixed in a mass ratio of 6:3:1, placed in an alumina crucible, calcined at 1000°C in a tubular furnace under a nitrogen atmosphere for 60 minutes, and naturally cooled to obtain solid waste-based sulfide zero-valent iron.

[0056] Example 2

[0057] Compared with Example 1, the only difference is that the mass ratio of iron-containing copper smelting slag, anthracite and solid waste phosphogypsum is 6.5:3:0.5, 5.5:3:1.5 or 5:3:2.

[0058] Example 3

[0059] Compared with Example 1, the only difference is that the calcination temperature is 800°C.

[0060] Comparative Example 1

[0061] Compared with Example 3, the only difference is that no solid waste phosphogypsum is added, and the mass ratio of iron-containing copper smelting slag to anthracite is 7:3.

[0062] Comparative Example 2

[0063] Compared with Example 1, the only difference is that the mass ratio of iron-containing copper smelting slag, anthracite and solid waste phosphogypsum is 7:3:0, and the product is unsulfurized zero-valent iron.

[0064] Test example

[0065] Figure 2 The following are XRD patterns of the iron-containing copper smelting slag, the products obtained in Comparative Example 2, Example 1, and Example 2. As can be seen from the figure, the primary mineral phases of the iron-containing copper smelting slag are fayalite (Fe2SiO4) and a small amount of magnetite (Fe3O4). After being mixed with solid waste phosphogypsum and anthracite and calcined in a tube furnace at 1000°C in the absence of oxygen for 60 minutes, the original fayalite phase of the iron-containing copper smelting slag disappears and is transformed into zero-valent iron, ferrous austenite, pyrrhotite, and calcium silicate, indicating the formation of zero-valent iron sulfide. Compared to the group without solid waste phosphogypsum (the 7:3:0 group in Comparative Example 2), the addition of solid waste phosphogypsum facilitates the reduction of fayalite and magnetite in the copper slag and the formation of zero-valent elemental iron. This is primarily due to the fact that the addition of solid waste phosphogypsum reduces the reaction temperature required for the conversion of the copper slag to zero-valent iron.

[0066] Figure 3 The following are XRD patterns of the products obtained in Example 3 and Comparative Example 1. In the figure, 10% Gypsum-800° is Example 3, and 0% Gypsum-800° is Comparative Example 1. As can be seen from the figure, the XRD pattern of the product after oxygen-free calcination of a mixture of iron-containing copper smelting slag, solid waste phosphogypsum, and anthracite at 800°C shows that the primary mineral phases of the product are zero-valent iron and fayalite, indicating that a carbothermal reduction reaction occurred in the iron-containing copper smelting slag, but the reaction extent was low, with some fayalite reduced to zero-valent iron. In Comparative Example 1, since no solid waste phosphogypsum was added, no zero-valent iron was produced in the product, demonstrating that the addition of solid waste phosphogypsum in the present invention can lower the reaction temperature.

[0067] The products obtained in Comparative Example 2, Example 1, and Example 2 were used to activate molecular oxygen to degrade the new pollutant fleroxacin. The specific steps included adding 0.01 g of zero-valent iron sulfide (0.5 g / L) to 20 mL of a 10 mg / L fleroxacin solution to trigger the reaction, removing 1 mL of sample at preset time intervals, completely filtering with a 0.22 μm nylon filter membrane, adding 0.1 mL of methanol to quench the reaction, and then determining the residual fleroxacin concentration in the solution using a high-performance liquid chromatograph.

[0068] Figure 4The degradation performance of the products obtained from Comparative Example 2, Example 1, and Example 2 for fleroxacin is shown in the figure. As can be seen from the figure, the unsulfurized zero-valent iron (Comparative Example 2) only degraded 48% of fleroxacin within 120 minutes. Zero-valent iron prepared by adding different proportions of solid waste phosphogypsum significantly enhanced its ability to degrade fleroxacin, primarily due to the sulfurization modification of the zero-valent iron by the introduction of solid waste phosphogypsum. Sulfurized zero-valent iron prepared with 10% solid waste phosphogypsum exhibited the best fleroxacin degradation efficiency, reaching 82% within 120 minutes.

[0069] Figure 5 is the degradation rate constant of fleroxacin by the products of Comparative Example 2 and Example 1. As can be seen from the figure, the degradation rate of fleroxacin by the sulfide zero-valent iron (Example 1) prepared by adding 10% solid waste phosphogypsum is (0.0097min -1 ) is the case where no solid waste phosphogypsum is added (Comparative Example 2) (0.0032min -1 ), indicating that the addition of an appropriate amount of solid waste phosphogypsum to prepare sulfided zero-valent iron can significantly enhance the environmental functionality of carbon thermally reduced zero-valent iron, and improve the aggregation, electron selectivity, stability, surface passivation layer and electron transport properties of zero-valent iron.

[0070] Figure 6 The contact angles of the products from Comparative Example 2, Example 1, and Example 2 are shown, where (a) represents Comparative Example 2, (b) represents the 6.5:3:0.5 ratio in Example 2, (c) represents Example 1, (d) represents the 5.5:3:1.5 ratio in Example 2, and (e) represents the 5:3:2 ratio in Example 2. As can be seen from the figure, the contact angle of unsulfurized zero-valent iron prepared without phosphogypsum is 73.1°, indicating its hydrophilicity and its tendency to react with water, consuming a large amount of electrons and producing hydrogen. With increasing phosphogypsum content, the contact angle of sulfided zero-valent iron first increases continuously and then decreases, indicating that sulfurization modification can significantly improve the hydrophobicity of zero-valent iron, reduce side reactions with water, and enhance the electron selectivity, stability, and long-term effectiveness of zero-valent iron.

[0071] Figure 7 The specific surface area results of the products of Example 1 and Comparative Example 2 are shown, where (a) is the adsorption-desorption curve of Comparative Example 2, (b) is the adsorption-desorption curve of Example 1, and (c) is the specific surface area of ​​the products of Example 1 and Comparative Example 2. The specific surface area of ​​unsulfurized zero-valent iron is 40.48 cm 2 / g, and the specific surface area of ​​zero-valent iron sulfide is 83.55 cm 2 / g, indicating that sulfurization modification significantly increases the specific surface area of ​​zero-valent iron. This is mainly because the ferrous sulfide generated by sulfurization modification inhibits the aggregation of zero-valent iron and improves its dispersion, thereby achieving an increase in the specific surface area and surface active sites.

[0072] In general, the sulfur required for vulcanization is a divalent sulfur ion, while the sulfur in phosphogypsum is sulfate, which is hexavalent. Therefore, adding solid waste phosphogypsum may not necessarily achieve the vulcanization of the material. Before the present invention was proposed, there was no report on using solid waste phosphogypsum as a vulcanization precursor. Using phosphogypsum as a sulfur source is one of the core innovations of the present invention. In the present invention, solid waste phosphogypsum can, on the one hand, serve as a sulfur source, and on the other hand, it can reduce the energy barrier and the required reaction temperature (such as the temperature) of the carbon thermal reduction of copper slag to form sulfided zero-valent iron (zero-valent iron). Figure 1 shown in the simulation).

[0073] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0074] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing zero-valent iron sulfide based on solid waste resource utilization, characterized in that the steps include: The zero-valent iron sulfide is synthesized in one step by carbothermal reduction using a solid waste-based sulfur source and an iron-based solid waste as reactants in the presence of a carbon source; The solid waste-based sulfur source includes solid waste phosphogypsum and / or desulfurization gypsum.

2. The preparation method according to claim 1, wherein The main component of the solid waste-based sulfur source is CaSO4·2H2O.

3. The preparation method according to claim 1, wherein The iron-based solid waste includes iron-containing copper smelting slag.

4. The preparation method according to claim 1, wherein The carbon source includes anthracite and / or lignite.

5. The preparation method according to claim 1, wherein The mass ratio of iron-based solid waste, carbon source and solid waste-based sulfur source is (5-7):3:(0-2), and the amount of solid waste phosphogypsum is not zero.

6. The preparation method according to claim 5, wherein The mass ratio of the iron-based solid waste, the carbon source and the solid waste-based sulfur source is 6:3:

1.

7. The preparation method according to claim 1, wherein The carbon thermal reduction is carried out in an inert atmosphere at a temperature of 800-1200° C. for 60 minutes.

8. A zero-valent iron sulfide based on solid waste resource utilization, characterized in that: The zero-valent iron sulfide is prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the zero-valent iron sulfide based on solid waste resource utilization according to claim 8 in improving the reaction rate of degrading fleroxacin.

10. A method for reducing the reaction temperature of carbon thermal reduction synthesis of zero-valent iron sulfide, characterized in that: By adding 0-20 wt% of a solid waste-based sulfur source as a sulfurization modification material to a carbothermic reduction reaction system, and the amount of solid waste phosphogypsum added is not zero, the reaction temperature of the carbothermic reduction synthesis of sulfided zero-valent iron is reduced; The solid waste-based sulfur source includes solid waste phosphogypsum and / or desulfurized gypsum, the main component of which is CaSO4·2H2O.

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