Iron-carbon composite material as well as preparation method and application thereof

Abstract

The invention provides an iron-carbon composite material and a preparation method and application thereof.The iron-carbon composite material is of a porous structure and is composed of micropores and / or mesopores with the pore diameter ranging from 1 nm to 5 nm and macropores with the pore diameter ranging from 100 nm to 10 [mu] m, or composed of mesopores with the average pore diameter ranging from 2 nm to 4 nm and macropores with the pore diameter ranging from 100 nm to 10 [mu] m, the specific surface area of the iron-carbon composite material is 200m < 2 > / g-300m < 2 > / g, and the existence forms of the iron element comprise FeO, Fe2O3, Fe3O4, Fe3C and Fe2C. The iron-carbon composite material prepared by the invention has both chemical adsorption and physical adsorption, and has high adsorption efficiency on sulfur-containing compounds in water. The iron-carbon composite material is wide in material source, simple in preparation process and low in development cost, large-scale production is easy to realize, and the iron-carbon composite material has great application potential in refining and chemical wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to an iron-carbon composite material, its preparation method, and its applications. Background Technology

[0002] Sulfur-containing wastewater mainly originates from the drainage of secondary processing units in oil refineries, such as catalytic cracking, catalytic pyrolysis, coking, and hydrocracking. This sulfur-containing wastewater is highly corrosive, causing corrosion to pipes and equipment, shortening equipment lifespan, and increasing maintenance costs for businesses. If sulfides are not effectively removed, the directly or indirectly discharged wastewater can cause serious harm to the ecological environment and human health.

[0003] Traditional methods for treating sulfur-containing wastewater in the refining and chemical industry include physical coagulation, chemical precipitation, and biological absorption. Physical coagulation involves adding coagulants to the wastewater, causing colloidal particles and fine suspended solids to destabilize, aggregate, and precipitate, thereby removing sulfides. However, this method has limited effectiveness against high concentrations of sulfides, requires large amounts of coagulants, resulting in high operating costs, and generates large amounts of sludge that require further treatment to prevent secondary pollution. Chemical precipitation utilizes the reaction of metal ions with sulfides to form insoluble precipitates, removing sulfides from wastewater. Commonly used precipitants include iron salts and zinc salts. This method is simple to operate, but the precipitates are small, making sludge-water separation difficult. Furthermore, high sulfide concentrations require large amounts of precipitants, increasing treatment costs. Biological absorption uses microorganisms to convert sulfides in wastewater into other forms of sulfur through biological metabolism. This method is often used as a further treatment step after physical and chemical treatment of high-sulfur wastewater. However, biological methods are mostly suitable for low-concentration sulfur-containing wastewater. For high-concentration sulfur-containing wastewater, the growth and metabolism of microorganisms may be inhibited, resulting in poor treatment effects. In addition, the tiny sulfur particles excreted by microorganisms are in a colloidal state in the water and are difficult to settle naturally.

[0004] Utilizing the high efficiency of physical adsorption and the specificity of chemical adsorption, the preparation of composite adsorbent materials is an effective strategy to improve sulfide removal efficiency. The formation of CO-Fe bonds between carbon materials and iron-containing oxides can effectively improve the stability and electron transfer efficiency of the composite material. However, some existing carbon materials, such as carbon nanotubes and graphene oxide, have complex preparation processes, high costs, and are difficult to scale up, limiting their application in the treatment of sulfur-containing wastewater.

[0005] Given the potential hazards of sulfides and the shortcomings of current technologies, it is necessary to develop new adsorbent materials with low cost and high adsorption efficiency to achieve efficient adsorption and removal of sulfides in wastewater, providing a new approach for the efficient treatment of sulfur-containing wastewater. Summary of the Invention

[0006] The purpose of this invention is to provide an iron-carbon composite material with good adsorption effect on sulfides in sulfur-containing wastewater and low preparation cost, as well as its preparation method and application.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] The first aspect of this invention provides a method for preparing an iron-carbon composite material, the method comprising:

[0009] (1) Porous cedar charcoal was obtained by calcining KOH-adsorbed cedar powder at 400-600℃ in a CO2 atmosphere.

[0010] (2) Porous cypress charcoal adsorbed with K2FeO4 was prepared using the aforementioned porous cypress charcoal and K2FeO4;

[0011] (3) The porous fir charcoal adsorbed with K2FeO4 is first calcined at 450-550℃ in a CO2 atmosphere, and then calcined at 650-750℃ to obtain the iron-carbon composite material.

[0012] In an embodiment of the present invention, in step (2), the mass ratio of the porous fir charcoal to K2FeO4 is 1:(0.5-1), more preferably 1:(0.7-0.9).

[0013] In an embodiment of the present invention, in step (1), the KOH-adsorbed fir powder is heated to 400-600°C in a CO2 atmosphere at a heating rate of 1-10°C / min and held at 400-600°C for 1-3 hours to obtain the porous fir charcoal.

[0014] More preferably, in step (1), the temperature is increased to 400-600°C at a heating rate of 4-8°C / min.

[0015] More preferably, in step (1), the temperature is increased to 400-600°C at a heating rate of 4-6°C / min.

[0016] In an embodiment of the present invention, in step (2), the porous fir charcoal and K2FeO4 are stirred in water at 75-85°C until the moisture content is reduced by 80% to 90%, and then dried at 75-85°C to obtain the porous fir charcoal adsorbed with K2FeO4.

[0017] Furthermore, the stirring speed is 100-150 r / min, more preferably 110-130 r / min.

[0018] In an embodiment of the present invention, the mass ratio of KOH to cedar powder in the KOH-adsorbed cedar powder is 1:(0.8-1.2).

[0019] In an embodiment of the present invention, the method for preparing the KOH-adsorbed fir powder is as follows: fir powder and KOH are placed in ultrapure water and stirred at a speed of 180-200 r / min for 10-15 h at room temperature. The resulting mixture is allowed to stand and centrifuged, and the resulting solid is dried at 75-85℃ to obtain the KOH-adsorbed fir powder.

[0020] In an embodiment of the present invention, in step (3), the temperature is first raised to 450-550°C at a heating rate of 1-10°C / min and held at 450-550°C for 0.5-1.5h, and then raised to 650-750°C at a heating rate of 1-10°C / min and held at 650-750°C for 1-3h to obtain the iron-carbon composite material.

[0021] More preferably, in step (3), the heating rate is 4-8℃ / min, and even more preferably 4-6℃ / min.

[0022] In an embodiment of the present invention, step (3) further includes post-processing, which is as follows: the porous fir charcoal obtained by roasting is cooled to room temperature, washed with 0.05-0.15M HCl, then washed with deionized water until the eluent is neutral, and then dried and ground in a vacuum oven at 75-85℃.

[0023] A second aspect of the present invention provides an iron-carbon composite material, which is prepared by the above-described preparation method.

[0024] The iron-carbon composite material of the present invention has a porous structure, which consists of micropores and / or mesopores with a pore size range of 1-5 nm and macropores with a pore size range of 100 nm-10 μm, or consists of mesopores with an average pore size of 2-4 nm and macropores with a pore size range of 100 nm-10 μm. The specific surface area of ​​the iron-carbon composite material is 200 m². 2 / g-300m 2 / g, iron exists in the forms of FeO, Fe2O3, Fe3O4, Fe3C, and Fe2C, and Fe is present. 2+ Fe 3+ Mixed valence states, in amorphous particulate form, are loaded on the surface, channels, and under the carbon layer of biochar.

[0025] In some embodiments of the present invention, the porous structure of the iron-carbon composite material of the present invention consists of a microporous structure with a pore size range of 1-2 nm, a mesoporous structure with a pore size range of 2-5 nm, and a macroporous structure with a pore size range of 100 nm-10 μm, wherein some of the microporous structure and the mesoporous structure form a micro / mesoporous composite structure.

[0026] Preferably, the porous structure includes a microporous structure with a pore size range of 1-1.5 nm, a micro / mesoporous composite structure with a pore size range of 1.6-2.8 nm, and a macroporous structure with a pore size range of 200 nm-5 μm.

[0027] In some specific embodiments, the porous structure includes mesoporous structures with an average pore size of 2-3 nm and macroporous structures with an average pore size of 200 nm-5 μm.

[0028] In some specific embodiments, the specific surface area of ​​the iron-carbon composite material is 220 m². 2 / g-260m 2 / g, further preferably 230m 2 / g-260m 2 / g, further preferably 240m 2 / g-260m 2 / g, more preferably 250m 2 / g-260m 2 / g.

[0029] A third aspect of the present invention also provides the application of the above-mentioned iron-carbon composite material in the treatment of sulfur-containing wastewater.

[0030] The fourth aspect of the present invention also provides a method for treating sulfur-containing wastewater, wherein the iron-carbon composite material is added to the sulfur-containing wastewater, the pH of the sulfur-containing wastewater is adjusted to 7-7.2, and the wastewater is shaken or stirred at 36-38°C for 1-5 hours.

[0031] More preferably, the mixture is shaken or stirred at 36-38℃ and 100-200 r / min for 2-4 hours.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] The iron-carbon composite material prepared by this invention exhibits both chemical and physical adsorption properties, demonstrating high adsorption efficiency for sulfur-containing compounds in water. The iron-carbon composite material of this invention has wide availability, a simple preparation process, low development costs, and is easily scalable for large-scale production, showing great application potential in the treatment of refining wastewater. Attached Figure Description

[0034] Figure 1 The microstructure diagrams of the iron-carbon composite material of Example 1 at different magnifications are shown.

[0035] Figure 2 The image shows the pore size distribution of the iron-carbon composite material in Example 1 (large pores are not shown).

[0036] Figure 3 This is a nitrogen adsorption curve of the iron-carbon composite material in Example 1;

[0037] Figure 4 This is the XPS full spectrum result of the iron-carbon composite material in Example 1;

[0038] Figure 5 The image shows the infrared test results of the iron-carbon composite material in Example 1.

[0039] Figure 6 The image shows the XRD results of the iron-carbon composite material in Example 1.

[0040] Figure 7 This is the XPS result of the Fe2p peak separation of the iron-carbon composite material in Example 1;

[0041] Figure 8 The image shows the microstructure of the iron-carbon composite material in Example 2. Detailed Implementation

[0042] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in this industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other. The implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually conditions in conventional experiments.

[0043] It should be noted that in this invention, "room temperature" refers to 25±5℃.

[0044] The cedar wood powder used in the following examples and comparative examples was prepared in-house. The preparation method was as follows: 30g of dried cedar wood was placed in a pulverizer and pulverized for 30 minutes. After washing with ultrapure water, it was dried in an 80℃ forced-air drying oven to obtain cedar wood powder for later use. Ultrapure water (>18.2MΩ) was produced using a Milli-Q pure water system (Bedford, MA, USA).

[0045] Example 1

[0046] This embodiment provides an iron-carbon composite material, the preparation method of which is as follows:

[0047] 1. Weigh 5g of cedar powder and 5g of KOH into 100mL of ultrapure water, and stir at 200r / min for 12h at room temperature to allow the cedar raw material to fully and uniformly adsorb KOH. After the mixture is allowed to stand and centrifuged, the resulting solid is placed in an 80℃ forced-air drying oven to dry and obtain cedar powder adsorbed with KOH.

[0048] 2. Place the KOH-adsorbed cedar powder in an alumina ceramic boat, transfer it to a tube furnace, purge with high-purity CO2 gas for 30 min to remove air interference in the tube, continue purging with high-purity CO2 gas, heat to 500℃ at a heating rate of 5℃ / min and hold for 2 h, cool to room temperature, wash the obtained material three times with ultrapure water to remove excess potassium salt, and obtain porous cedar charcoal.

[0049] 3. Weigh out K2FeO4 according to a mass ratio of porous fir charcoal to K2FeO4 of 1:0.8. Place the porous fir charcoal and K2FeO4 in ultrapure water, with the amount of water being 22 times the sum of the masses of the porous fir charcoal and K2FeO4. Stir at 120 r / min at 80℃ until most of the water in the beaker evaporates (evaporation until the water mass decreases by about 85%). Place the remaining material in the beaker in an 80℃ drying oven to dry, and obtain porous fir charcoal adsorbed with K2FeO4.

[0050] 4. The porous fir charcoal adsorbed with K2FeO4 was placed in an alumina ceramic boat and transferred to a tube furnace. High-purity CO2 gas was passed through the tube furnace to purge the air. High-purity CO2 gas was continued to be passed through the furnace, and the furnace was heated to 500℃ at a heating rate of 5℃ / min and held at 500℃ for 1 hour. Then, the furnace was heated to 700℃ at a heating rate of 5℃ / min and held at 700℃ for 2 hours. After cooling to room temperature, the furnace was washed with 0.1mol / L HCl and then washed with deionized water until the eluent was neutral to remove ash, uncrystallized material and unloaded metal salts. The washed material was dried and ground in an 80℃ vacuum oven (a small amount of agglomerates were present in the dried product, which were crushed by grinding) to obtain the iron-carbon composite material.

[0051] The iron-carbon composite material of this embodiment has a rich pore structure, consisting of microporous structures with a pore size range of 1.09-1.35 nm, micro / mesoporous composite structures with a pore size range of 1.71-2.73 nm, and macroporous structures with a pore size range of 200 nm-5 μm. Figure 1 , Figure 2 ), with a specific surface area of ​​254 m². 2 / g(according to) Figure 3 The nitrogen adsorption curve shown is obtained through BET model calculation, mainly including Fe, C, and O. Figure 4 The surface contains oxygen-containing functional groups such as -OH, -COOH, -C=O, -COC-, and -Fe-O. Figure 5 Iron exists in the forms of FeO, Fe2O3, Fe3O4, Fe3C, and Fe2C. Figure 6 Fe is present. 2+ Fe 3+ Mixed valence state ( Figure 7), in amorphous particulate form, loaded on the surface, channels, and under the carbon layer of biochar ( Figure 1 ).

[0052] Example 2

[0053] This embodiment provides another iron-carbon composite material, prepared using a method basically the same as in Example 1, except that step 3 is slightly different. Except for changing the mass ratio of porous fir charcoal to K2FeO4 in step 3 to 1:0.9, all other operations are the same as in Example 1. The resulting iron-carbon composite material has a rich pore structure. Figure 8 It consists of a mesoporous structure with an average pore size of 2.51 nm and a macroporous structure with a pore size range of 200 nm to 5 μm, and has a specific surface area of ​​227 m². 2 / g, iron exists in the forms of FeO, Fe2O3, Fe3O4, Fe3C, and Fe2C, and Fe is present. 2+ Fe 3+ Mixed valence states, in amorphous particulate form, are loaded on the surface, channels, and under the carbon layer of biochar.

[0054] Example 3

[0055] This embodiment provides another iron-carbon composite material, the preparation method of which is basically the same as that of Example 1, except that step 4 is slightly different. Except for shortening the holding time at 700℃ for 2 hours in step 4 to 1 hour, the rest of the operation is the same as in Example 1. The obtained iron-carbon composite material has a rich pore structure, consisting of mesoporous structures with an average pore size of about 2.09 nm and macroporous structures with a pore size range of 200 nm-5 μm, and a specific surface area of ​​241 m². 2 / g, iron exists in the forms of FeO, Fe2O3, Fe3O4, Fe3C, and Fe2C, and Fe is present. 2+ Fe 3+ Mixed valence states, in amorphous particulate form, are loaded on the surface, channels, and under the carbon layer of biochar.

[0056] Comparative Example 1

[0057] This comparative example provides another iron-carbon composite material, the preparation method of which is basically the same as that of Example 1, except that the high-purity CO2 gas in steps 1 and 3 is replaced with high-purity N2 gas, and all other operations are the same as those in Example 1.

[0058] Comparative Example 2

[0059] This comparative example provides another iron-carbon composite material, the preparation method of which is basically the same as that of Example 1. The only difference is that in step 4, heating to 500°C at a heating rate of 5°C / min and holding at 500°C for 1 hour, and then continuing to heat to 700°C at a heating rate of 5°C / min and holding at 700°C for 2 hours, is replaced by heating to 500°C at a heating rate of 5°C / min and holding at 500°C for 3 hours. All other operations are the same as in Example 1.

[0060] Comparative Example 3

[0061] This comparative example provides another iron-carbon composite material, the preparation method of which is basically the same as that of Example 1. The only difference is that in step 4, heating to 500°C at a heating rate of 5°C / min and holding at 500°C for 1 hour, and then continuing to heat to 700°C at a heating rate of 5°C / min and holding at 700°C for 2 hours, is replaced by heating to 900°C at a heating rate of 5°C / min and holding for 2 hours. All other operations are the same as in Example 1.

[0062] A sulfide solution was prepared using Na2S·9H2O to simulate sulfur-containing wastewater. Sulfide adsorption experiments were conducted using iron-carbon composite materials from the above examples and comparative examples, respectively, according to the following methods:

[0063] 1. Weigh 100 mg of Na2S·9H2O solid and mix it with 100 mL of water to prepare a sulfide solution. Use a syringe to draw 0.05 mL of the sulfide solution to test the sulfide content in the solution before treatment.

[0064] 2. Weigh 0.05g of iron-carbon composite material and add it to a stoppered conical flask containing the above sulfide solution. Adjust the pH of the solution to 7.13 with concentrated hydrochloric acid. Then place the conical flask in a constant temperature shaker (shaking rate of 150r / min) and shake at 37℃ for 3h. After standing, use a syringe to draw 0.05mL of the supernatant to test the sulfide content in the treated solution.

[0065] The sulfide content in the solution before and after the reaction was determined by methylene blue spectrophotometry (GB / T 16489-1996) at a detection wavelength of 665 nm. Based on the sulfide content in the solution before and after treatment, the adsorption capacity of a unit of iron-carbon composite material for sulfides in water was calculated, and the results are shown in Table 1.

[0066] Table 1

[0067] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 584.7 mg / g 479.0 mg / g 407.0 mg / g 318.0 mg / g 367.2 mg / g 198.6 mg / g

[0068] According to the results in Table 1, the iron-carbon composite material can adsorb sulfides in water. The adsorption effect of the iron-carbon composite material prepared under different conditions on sulfides is significantly different. Among them, the iron-carbon composite materials in Examples 1-3 have a significantly better adsorption effect on sulfides, and the iron-carbon composite material in Example 1 has the best effect.

[0069] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing an iron-carbon composite material, characterized in that, The preparation method includes: (1) Porous cedar charcoal was obtained by calcining KOH-adsorbed cedar powder at 400-600℃ in a CO2 atmosphere. (2) Porous cypress charcoal adsorbed with K2FeO4 was prepared using the aforementioned porous cypress charcoal and K2FeO4; (3) The porous fir charcoal adsorbed with K2FeO4 is first calcined at 450-550℃ in a CO2 atmosphere, and then calcined at 650-750℃ to obtain the iron-carbon composite material.

2. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the porous fir charcoal to K2FeO4 is 1:(0.5-1).

3. The preparation method according to claim 1, characterized in that, In step (1), the KOH-adsorbed cedar powder is heated to 400-600℃ in a CO2 atmosphere at a heating rate of 1-10℃ / min and held at 400-600℃ for 1-3h to obtain the porous cedar charcoal.

4. The preparation method according to claim 1, characterized in that, In step (2), the porous fir charcoal and K2FeO4 are stirred in water at 75-85℃ until most of the water evaporates, and then dried at 75-85℃ to obtain the porous fir charcoal adsorbed with K2FeO4.

5. The preparation method according to claim 1, characterized in that, The mass ratio of KOH to cedar powder in the KOH-adsorbed cedar powder is 1:(0.8-1.2); And / or, the method for preparing the KOH-adsorbed fir powder is as follows: place fir powder and KOH in ultrapure water, stir at 180-200 r / min for 10-15 h at room temperature, let the resulting mixture stand and centrifuge, and dry the resulting solid at 75-85℃ to obtain the KOH-adsorbed fir powder.

6. The preparation method according to claim 1, characterized in that, In step (3), the temperature is first raised to 450-550℃ at a heating rate of 1-10℃ / min and held at 450-550℃ for 0.5-1.5h, and then raised to 650-750℃ at a heating rate of 1-10℃ / min and held at 650-750℃ for 1-3h to obtain the iron-carbon composite material.

7. The preparation method according to claim 1, characterized in that, Step (3) further includes post-processing, which involves cooling the calcined porous fir charcoal to room temperature, washing it first with 0.05-0.15M HCl, then washing it with deionized water until the eluent is neutral, and then vacuum drying and grinding it at 75-85℃.

8. An iron-carbon composite material, characterized in that, The iron-carbon composite material is prepared by the preparation method according to any one of claims 1 to 7.

9. The iron-carbon composite material according to claim 8, characterized in that, The iron-carbon composite material has a porous structure, which consists of micropores and / or mesopores with a pore size range of 1-5 nm and macropores with a pore size range of 100 nm-10 μm, or consists of mesopores with an average pore size of 2-4 nm and macropores with a pore size range of 100 nm-10 μm. The specific surface area of ​​the iron-carbon composite material is 200 m². 2 / g-300m 2 / g, the iron element exists in the forms of FeO, Fe2O3, Fe3O4, Fe3C and Fe2C.

10. The application of the iron-carbon composite material as described in claim 8 or 9 in the treatment of sulfur-containing wastewater.

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