Application of iron sulfide-based sludge carbon in coking wastewater treatment and preparation method of iron sulfide-based sludge carbon

Abstract

The invention relates to the technical field of industrial solid waste recycling and wastewater advanced oxidation treatment, in particular to application of iron sulfide-based sludge carbon in coking wastewater treatment and a preparation method of the iron sulfide-based sludge carbon. The method comprises the following steps: compounding iron-containing sludge and activated carbon through acid dissolution, modifying with sodium sulfide, calcining at a controlled temperature in an inert atmosphere, and post-treating with alkali liquor, so as to prepare the sludge carbon which is high in specific surface area and rich in sulfur-iron active sites. As a heterogeneous catalyst, the material can be used for activating peracetic acid generated by tetraacetylethylenediamine and sodium percarbonate in situ, degradation-resistant organic matters in coking wastewater are efficiently degraded, and the purpose of treating waste with waste is achieved. The method is simple in process and low in cost, the prepared catalyst is stable in performance, the COD removal rate of the coking wastewater at normal temperature and normal pressure reaches 81% or above and reaches up to 87.7%, and the method has remarkable environmental and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of industrial solid waste resource utilization and advanced wastewater oxidation treatment technology, specifically to the application of iron sulfide-based sludge char in coking wastewater treatment and its preparation method. Background Technology

[0002] Coke, a representative product of the traditional coal chemical industry, plays a vital role in the steel industry. The large amount of wastewater generated during the coking process contains phenols and polycyclic aromatic hydrocarbons (PAHs). S Heterocyclic compounds (pyridine, indole), cyanides, thiocyanates, etc., possess biotoxicity and persistence, making them difficult to completely degrade using conventional biological treatments. This portion of recalcitrant organic matter is treated using traditional anaerobic-aerobic combined processes (such as A / O, A...). 2 Coking wastewater often requires advanced treatment due to the difficulty in removing pollutants such as chlorine (O2), which can lead to COD exceeding standards. Currently, commonly used advanced treatment methods for coking wastewater include Fenton oxidation, ozone oxidation, and electrochemical oxidation. While the former is effective against some pollutants, it involves high reagent costs and may produce intermediate toxic products. Electrochemical oxidation, on the other hand, requires significant equipment investment and suffers from electrode passivation and high maintenance costs. Therefore, it is necessary to find efficient and low-cost alternative technologies for the advanced treatment of coking wastewater.

[0003] Peracetic acid (PAA) activation for wastewater treatment is a highly efficient advanced oxidation technology. It activates peracetic acid chemically or physically, generating highly oxidizing free radicals (such as hydroxyl radicals (·OH) and acetoxy radicals (CH3COO·), which can rapidly degrade recalcitrant organic matter, pathogenic microorganisms, and persistent pollutants in wastewater. Its core advantages lie in its strong oxidizing power, fast reaction rate, wide applicable pH range, and the fact that its decomposition products are water and acetic acid, making it significantly environmentally friendly. Importantly, its lower toxicity, higher selectivity, and lower O / O bond cleavage compared to persulfate and hydrogen peroxide make PAA a promising technology for the advanced treatment of coking wastewater. However, it is important to note that PAA has a strong pungent odor, is highly volatile, and is prone to explosion at low temperatures and concentrations exceeding 45%. It is also unstable and difficult to transport, and its concentration is limited by the need for continuous titration. Therefore, there is an urgent need to develop a new, low-cost catalyst to address these issues.

[0004] Iron-containing sludge, a byproduct of steel plant wastewater treatment, is typically disposed of as landfill waste. However, due to the large workload and high cost of sludge reprocessing, and the potential for secondary pollution from traditional landfilling methods, resource utilization has become an important research direction for dewatered sludge treatment and disposal. Currently, the resource utilization of dewatered sludge mainly involves the acid dissolution and reuse of iron salts and their use as building materials. However, this approach has low resource utilization rates and high costs, and its treatment and disposal remain urgent environmental problems to be solved.

[0005] In recent years, some technological explorations have emerged regarding the resource utilization of iron-containing sludge and its application in wastewater treatment. For example: Chinese patent document CN119263414B discloses a "multifunctional water treatment catalyst and its preparation method," which involves modifying sulfur powder and then combining it with an iron-carbon material prepared from iron-containing sludge, followed by foaming and granulation to obtain the catalyst. While this catalyst exhibits some denitrification and phosphorus removal capabilities, it primarily relies on the internal microbial community and catalytic synergy, and its effectiveness in treating poorly biodegradable coking wastewater is limited.

[0006] Chinese patent document CN118416889A discloses a “resource utilization treatment method for Fenton iron sludge and preparation of iron-containing biochar”. Iron-containing biochar is prepared by acid treatment, alkali treatment and high-temperature pyrolysis, which is expected to be used for wastewater treatment or soil remediation. However, the document does not disclose its specific application effects, especially its catalytic performance against recalcitrant organic matter.

[0007] Chinese patent document CN118341427 A discloses a "Preparation method of cobalt-iron-based hydrothermal carbon based on iron-containing sludge and its application." This material can degrade recalcitrant organic matter in water by activating persulfate, and has advantages such as large specific surface area and good catalytic performance. However, this method relies on persulfate as an oxidant, which poses a risk of introducing secondary sulfate pollution, and is limited by the stability and environmental adaptability of the oxidant itself.

[0008] Despite the aforementioned technological attempts, existing methods generally suffer from low catalytic efficiency, limited oxidant selection, complex material preparation, high cost, or the risk of secondary pollution when dealing with recalcitrant and highly toxic systems such as coking wastewater. In particular, the technology of using iron-containing sludge to prepare high-performance catalysts and coupling them with peracetic acid, an environmentally friendly oxidant, for the deep treatment of coking wastewater has not yet been reported.

[0009] Therefore, providing a method for preparing sulfur-modified iron-based sludge carbon, and using it to activate the peracetic acid generated in situ, thereby economically and efficiently improving the treatment effect of coking wastewater, is of great significance for promoting the advancement of water treatment technology and realizing the resource utilization of iron-containing sludge. Summary of the Invention

[0010] To overcome the shortcomings of existing technologies, this invention provides an application of iron-sulfurized sludge char in coking wastewater treatment and its preparation method. By utilizing sulfur-modified iron-based sludge char to activate peracetic acid for economical and efficient treatment of coking wastewater, this invention also realizes the resource utilization of iron-containing sludge, solving the problem of difficult treatment of recalcitrant organic matter in existing coking wastewater treatment processes.

[0011] To achieve the above objectives, the present invention employs the following technical solution: The preparation method of iron sulfide-based sludge char includes the following steps: Step 1: The iron-containing sludge and activated carbon are processed separately to obtain iron sludge powder and activated carbon powder.

[0012] Step 2: Add the iron mud powder and activated carbon powder obtained in Step 1 to the acidic solution in sequence and stir thoroughly to obtain an iron mud and carbon mixture.

[0013] Step 3: Adjust the iron peat mixture obtained in Step 2 to alkaline with an alkaline solution, add sodium sulfide, stir the mixture thoroughly, filter, dry, and grind to obtain the sulfur-modified iron peat precursor.

[0014] Step 4: The sulfur-modified iron peat precursor obtained in Step 3 is calcined, ground, alcohol washed, dried, alkali impregnated, filtered, and dried in an inert atmosphere to obtain sulfur-modified iron-based sludge peat.

[0015] Further, in step 1, the iron-containing sludge is iron-containing sludge from a steel plant, with an iron weight percentage of 30% to 35%; the activated carbon has a specific surface area of ​​1200 to 1400 m². 2 / g.

[0016] Furthermore, in step 1, the process includes drying, grinding, and sieving.

[0017] Further, in step 1, the drying is vacuum drying at 100-110℃ for 10-15 hours, the grinding is grinding with an agate mortar for 15-25 minutes, and the sieving is done using a 70-90 mesh sieve. In step 3, the stirring reaction is constant temperature stirring at 20-30℃ for 5-7 hours; the filtration is vacuum filtration; the drying is vacuum drying at 100-110℃ for 10-15 hours; and the grinding is grinding with an agate mortar for 15-25 minutes. In step 4, the grinding is grinding with an agate mortar for 15-25 minutes; the alcohol washing is ethanol washing; the drying is vacuum drying at 100-110℃ for 10-15 hours; and the filtration is vacuum filtration.

[0018] Preferably, the drying is carried out at 105°C for 12 hours, the grinding is carried out in an agate mortar for 20 minutes, the sieving is carried out using an 80-mesh sieve, and the stirring reaction is carried out at a constant temperature of 25°C for 6 hours.

[0019] Further, in step 2, the amount of iron sludge powder added is 20-25 g / L; the mass ratio of iron sludge powder to activated carbon powder added is 5-10:1; the acidic solution is hydrochloric acid; the acidic solution H +The molar ratio of iron in the iron mud powder to iron is 1~1.5:1; the stirring reaction is carried out at a constant temperature of 20~30℃ for 7~8h.

[0020] Furthermore, in step 3, the alkaline solution is sodium hydroxide and potassium hydroxide; the pH of the iron peat mixture is 9-11; and the molar ratio of sodium sulfide to iron in the iron powder is 0.17-0.25:1.

[0021] Furthermore, in step 4, the inert gas atmosphere calcination is calcination in a tube furnace under an inert gas atmosphere, wherein the inert gas is nitrogen, argon or helium, the inert gas flow rate is 0.3~0.5L / min, the calcination temperature is 600~800℃, the heating rate is 5~10℃ / min, and the calcination time is 120~150min.

[0022] Further, in step 4, the alkaline impregnation is the impregnation of iron-based sludge carbon with an alkaline solution; the alkaline solution is ammonia, sodium hydroxide, or potassium hydroxide; the mass concentration of the alkaline solution is 5% to 32%; and the alkaline impregnation time is 4 to 24 hours.

[0023] The iron sulfide-based sludge carbon prepared by the above method is used to treat coking wastewater, activate peracetic acid in coking wastewater, and degrade COD in waste coking wastewater.

[0024] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention achieves high-value resource utilization of iron-containing sludge and constructs a highly efficient and stable heterogeneous catalytic system. The invention combines iron-containing sludge from steel plants (Fe content 30%~35%) with high specific surface area activated carbon (1200~1400m²). 2 By combining iron (e.g., iron) with sodium sulfide and undergoing controlled-temperature calcination under an inert atmosphere, the iron in sludge is converted into highly dispersed iron sulfide / iron oxide species, which are then firmly loaded onto a sludge carbon carrier. This process not only achieves complete utilization of waste but also constructs a heterogeneous catalyst with carbon as the framework and iron sulfide as the active center. Compared to homogeneous Fenton systems or easily leached simple supported materials, this catalyst exhibits good stability, is less prone to iron ion dissolution, and avoids the generation of secondary sludge.

[0025] 2. The synergistic effect of sulfur modification and calcination significantly improves the specific surface area and the number of catalytic sites in the material. Simple iron-containing sludge pyrolysis carbon often has a limited specific surface area and underdeveloped pore structure. This invention introduces activated carbon as a pore-forming template and structural support, followed by sodium sulfide treatment under alkaline conditions, allowing sulfur to combine with iron species. During the subsequent inert atmosphere calcination at 600-800℃, sulfur escape and thermal reconstruction of the carbon matrix occur simultaneously, creating a large number of micropores and mesopores in situ. For example, the SWNC prepared in Examples 1-3 all have a specific surface area of ​​no less than 1200 m² / g. This large specific surface area not only provides abundant adsorption sites for pollutants, but more importantly, it greatly exposes the active sites of iron sulfide / iron oxide, laying the foundation for subsequent catalytic reactions.

[0026] 3. The prepared SWNC can efficiently and selectively activate peracetic acid, generating a variety of active species with strong targeting. This invention uses peracetic acid (PAA) as the oxidant, which has a lower OO bond energy and is more easily activated. The iron sulfide species (such as FeS) and zero-valent iron (partially generated during calcination) in SWNC can efficiently activate PAA through electron transfer. The mechanism includes not only the generation of highly active hydroxyl radicals (·OH) and acetoxy radicals (CH3COO·), but also the potential initiation of non-radical oxidation pathways through surface complexation. This synergistic effect of free radicals and non-free radicals gives it a specific attack capability against benzene rings and heterocyclic recalcitrant organic compounds (such as phenols, polycyclic aromatic hydrocarbons, and pyridines) with high electron cloud density abundant in coking wastewater. It exhibits high degradation efficiency and is not easily affected by coexisting inorganic ions in the water.

[0027] 4. The invention demonstrates excellent deep treatment effects in the treatment of coking wastewater, achieving a win-win situation for both environmental and economic benefits. Experimental data (see Example 4 in the specification) directly proves the technical effectiveness of this invention: under normal temperature conditions, with only the addition of SWNC catalyst and the in-situ generation of PAA, after 60 minutes of reaction, the COD removal rate of the actual coking wastewater anaerobic tank effluent reaches as high as 81.0%~87.7%. This effect significantly surpasses traditional biological treatment and many processes that require the addition of large amounts of chemical agents (such as the Fenton process) or rely on high-risk oxidants (such as the direct addition of high-concentration PAA). This invention successfully combines the two environmental challenges of "iron-containing sludge treatment" and "deep treatment of coking wastewater," achieving "waste treatment with waste." On the one hand, it completely eliminates the disposal costs and risks of iron-containing sludge, transforming it into high-value-added products; on the other hand, it provides a highly efficient, low-cost, and environmentally friendly deep treatment solution for coking wastewater, avoiding the risks of oxidant storage and transportation, and has outstanding industrial application potential.

[0028] In summary, this invention employs a composite system of "iron-containing sludge-activated carbon-sulfur" in terms of composition, and through multi-step synergistic regulation of "acid leaching-sulfur modification-inert atmosphere calcination-alkali impregnation" in terms of process, it ultimately achieves efficient activation of PAA and deep removal of refractory organic matter from coking wastewater in application. Attached Figure Description

[0029] Figure 1 Photograph of SWNC-1, an iron sulfide-based sludge carbon prepared in Example 1 of this invention. Detailed Implementation

[0030] This invention discloses the application of iron sulfide-based sludge char in coking wastewater treatment and its preparation method. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0031] The preparation method of iron sulfide-based sludge char includes the following steps: Step 1: Dry, grind and sieve the iron-containing sludge and activated carbon separately to obtain iron sludge powder and activated carbon powder.

[0032] Drying was carried out at 105℃ for 12 hours, grinding was carried out in an agate mortar for 20 minutes, and sieving was carried out using an 80-mesh sieve.

[0033] The iron-containing sludge is from a steel plant, with an iron content of 30%–35% by weight; the activated carbon has a specific surface area of ​​1200–1400 m². 2 / g.

[0034] Step 2: Add the iron mud powder and activated carbon powder obtained in Step 1 to the acidic solution in sequence and stir thoroughly to obtain an iron mud and carbon mixture.

[0035] The dosage of iron sludge powder is 20-25 g / L, the mass ratio of iron sludge powder to activated carbon powder is 5-10:1, the acidic solution is hydrochloric acid, and the acidic solution H... + The molar ratio of iron in the iron mud powder is 1~1.5:1, and the stirring reaction is carried out at a constant temperature of 20~30℃ for 7~8 hours.

[0036] Step 3: Adjust the iron peat mixture obtained in Step 2 to alkaline with an alkaline solution, add sodium sulfide, stir the mixture thoroughly, filter, dry, and grind to obtain the sulfur-modified iron peat precursor.

[0037] The alkaline solution consisted of sodium hydroxide and potassium hydroxide; the pH of the iron peat mixture was 9-11; the molar ratio of sodium sulfide to iron in the iron powder was 0.17-0.25:1; the stirring reaction was carried out at a constant temperature of 25℃ for 6 hours; the filtration was carried out under vacuum; the drying was carried out under vacuum at 105℃ for 12 hours; and the grinding was carried out using an agate mortar for 20 minutes.

[0038] Step 4: The sulfur-modified iron peat precursor obtained in Step 3 is calcined, ground, alcohol washed, dried, alkali impregnated, filtered, and dried in an inert atmosphere to obtain sulfur-modified iron-based sludge peat.

[0039] Inert gas atmosphere calcination is calcination in a tube furnace under an inert gas atmosphere, where the inert gas is nitrogen, argon, or helium, the inert gas flow rate is 0.3~0.5 L / min, the calcination temperature is 600~800℃, the heating rate is 5~10℃ / min, and the calcination time is 120~150 min.

[0040] Grinding was performed using an agate mortar for 20 minutes, alcohol washing was performed using ethanol, drying was performed under vacuum at 105℃ for 12 hours, and filtration was performed under vacuum.

[0041] Alkaline impregnation involves impregnating iron-based sludge carbon with an alkaline solution, which consists of ammonia, sodium hydroxide, and potassium hydroxide. The mass concentration of the alkaline solution is 5% to 32%, and the impregnation time is 4 to 24 hours.

[0042] The iron sulfide-based sludge carbon prepared by the above method is used to treat coking wastewater, activate peracetic acid in coking wastewater, and degrade COD in waste coking wastewater.

[0043] All materials and instruments used in the following examples are commercially available, and the raw materials are of analytical grade. Unless otherwise specified, the data obtained in the following examples are the average values ​​of three or more repeated experiments.

[0044] Example 1: Preparation and application of iron sulfide-based sludge char (SWNC-1) 1. Preparation process Step 1: Take Fenton iron sludge with an iron content of 30.72% and a specific surface area of ​​1250 m² from a steel plant. 2 / g of activated carbon was dried at 105℃ for 12h. After drying, it was ground in an agate mortar for 20min and sieved through an 80-mesh sieve to obtain iron mud powder and activated carbon powder. Step 2: Add 2.0g of iron sludge powder obtained in Step 1 and 0.25g of activated carbon powder obtained in Step 1 to 100mL of hydrochloric acid solution with a molar concentration of 0.12mol / L, and stir at 25℃ for 6h to obtain iron sludge and carbon mixture; Step 3: Add 10 mL of 32% sodium hydroxide solution to the iron peat mixture obtained in Step 2, add 0.055 g of sodium sulfide, and stir at 25°C for 6 h. The pH of the iron peat mixture is 9-11. After vacuum filtration, vacuum dry at 105°C for 12 h, and grind for 20 min to obtain the sulfur-modified iron peat precursor. Step 4: Transfer the sulfur-modified iron peat precursor obtained in Step 3 to a crucible and place it in a tube furnace. Under a nitrogen atmosphere with a gas flow rate of 0.5 L / min, heat the mixture to 600℃ at a heating rate of 5℃ / min, and calcine it at 600℃ for 150 min. After cooling, grind it into powder, wash it with alcohol, and then vacuum dry it at 105℃ for 12 h. Impregnate the dried iron-based peat with a 5% potassium hydroxide solution for 24 h, then vacuum filter it and vacuum dry it at 105℃ for 12 h to obtain sulfur-modified iron-based peat. Figure 1 As shown, it is named SWNC-1.

[0045] 2. Material characterization and performance testing The BET specific surface area of ​​SWNC-1, measured using a nitrogen adsorption-desorption analyzer, is 1280 m². 2 / g. X-ray diffraction (XRD) analysis showed obvious characteristic peaks of Fe3O4 and FeS crystal phases. X-ray fluorescence spectroscopy (XRF) determined the iron content to be 22.5% by mass.

[0046] Take 200 mL of coking wastewater sample (initial COD = 127.4 mg / L) into a 500 mL beaker, and simultaneously add tetraacetylethylenediamine (TAED) and sodium percarbonate (SPC) to make the initial concentration of both in the solution 10 mM (this is a typical precursor combination for in-situ PAA generation). Then, add 0.1 g / L (20 mg) of SWNC-1 catalyst. At room temperature (-25℃), continuously introduce air into the system using a micro-aeration pump (aeration rate of approximately 0.1 L / min), and magnetically stir the reaction for 60 min. After the reaction is complete, take a sample for filtration, and determine the COD value of the filtrate using the potassium dichromate method.

[0047] Results: After the reaction, the COD of the water sample decreased to 24.2 mg / L, and the COD removal rate reached 81.0%.

[0048] Example 2: Preparation and application of iron sulfide-based sludge char (SWNC-2) 1. Preparation process Step 1: Take Fenton iron sludge with an iron content of 33.46% and a specific surface area of ​​1300 m² from a steel plant. 2 / g of activated carbon was dried at 105℃ for 12h. After drying, it was ground in an agate mortar for 20min and sieved through an 80-mesh sieve to obtain iron mud powder and activated carbon powder. Step 2: Add 2.25g of iron mud powder obtained in Step 1 and 0.45g of activated carbon powder obtained in Step 1 to 100mL of hydrochloric acid solution with a molar concentration of 0.13mol / L, and stir at 25℃ for 6h to obtain iron mud and carbon mixture; Step 3: Add 15 mL of 32% sodium hydroxide solution to the iron peat mixture obtained in Step 2, add 0.098 g of sodium sulfide, and stir at 25°C for 6 h. The pH of the iron peat mixture is 9-11. After vacuum filtration, vacuum dry at 105°C for 12 h, and grind for 20 min to obtain the sulfur-modified iron peat precursor. Step 4: The sulfur-modified iron peat precursor obtained in Step 3 was transferred to a crucible and placed in a tube furnace. Under an argon atmosphere with a gas flow rate of 0.4 L / min, the temperature was increased to 800℃ at a heating rate of 10℃ / min, and calcined at 800℃ for 120 min. After cooling, it was ground into powder, washed with alcohol, and then vacuum dried at 105℃ for 12 h. The dried iron-based peat was then impregnated with a 32% sodium hydroxide solution for 4 h, vacuum filtered, and vacuum dried at 105℃ for 12 h to obtain sulfur-modified iron-based peat, named SWNC-2.

[0049] 2. Material characterization and performance testing The BET specific surface area of ​​SWNC-2 is 1350 m². 2 / g, XRD showed that its crystallinity was higher than that of SWNC-1, and the FeS phase characteristics were more obvious. XRF measured its iron content to be 24.8%.

[0050] Under the exact same reaction conditions as in Example 1 (initial COD of water sample = 141.9 mg / L), 0.1 g / L of SWNC-2 was added to carry out the catalytic reaction.

[0051] Results: After the reaction, the COD of the water sample decreased to 17.5 mg / L, and the COD removal rate reached 87.7%.

[0052] Example 3: Preparation and application of iron sulfide-based sludge char (SWNC-3) 1. Preparation process Step 1: Take Fenton iron sludge with an iron content of 34.23% and a specific surface area of ​​1350 m² from a steel plant. 2 / g of activated carbon was dried at 105℃ for 12h. After drying, it was ground in an agate mortar for 20min and sieved through an 80-mesh sieve to obtain iron mud powder and activated carbon powder. Step 2: Add 2.5g of iron mud powder obtained in Step 1 and 0.25g of activated carbon powder obtained in Step 1 to 100mL of hydrochloric acid solution with a molar concentration of 0.11mol / L, and stir at 25℃ for 6h to obtain iron mud and carbon mixture; Step 3: Add 20 mL of 20% potassium hydroxide solution to the iron peat mixture obtained in Step 2, add 0.107 g of sodium sulfide, and stir at 25 °C for 6 h. The pH of the iron peat mixture is 9-11. After vacuum filtration, vacuum dry at 105 °C for 12 h, and grind for 20 min to obtain the sulfur-modified iron peat precursor. Step 4: The sulfur-modified iron peat precursor obtained in Step 3 was transferred to a crucible and placed in a tube furnace. Under a nitrogen atmosphere with a gas flow rate of 0.3 L / min, the temperature was increased to 700℃ at a heating rate of 10℃ / min, and calcined at 700℃ for 135 min. After cooling, it was ground into powder, washed with alcohol, and then vacuum dried at 105℃ for 12 h. The dried iron-based peat was impregnated with a 28% ammonia solution for 5 h, vacuum filtered, and then vacuum dried at 105℃ for 12 h to obtain sulfur-modified iron-based peat, named SWNC-3.

[0053] 2. Material characterization and performance testing The BET specific surface area of ​​SWNC-3 is 1310 m². 2 / g, with an iron content of 23.1% by mass.

[0054] Under the exact same reaction conditions as in Example 1 (initial COD of water sample = 144.1 mg / L), 0.1 g / L of SWNC-3 was added to carry out the catalytic reaction.

[0055] Results: After the reaction, the COD of the water sample decreased to 23.9 mg / L, and the COD removal rate reached 83.4%.

[0056] Comparative Example 1: Unsulfur-modified iron-based sludge carbon (WNC) The preparation process is basically the same as in Example 1, except that sodium sulfide is not added in step 3, while the remaining steps and parameters are exactly the same. The resulting material is labeled WNC.

[0057] Characterization showed that its specific surface area was 980 m². 2 / g, iron is mainly in the form of iron oxide.

[0058] Treating coking wastewater under the same application conditions (initial COD≈130mg / L).

[0059] Results: The COD removal rate was only 52.3%. Comparative analysis shows that sulfidation modification is a key step in significantly improving the catalytic activity of the material.

[0060] Comparative Example 2: Commercial Retail Iron Powder (ZVI) Purchase 100-mesh commercial zero-priced iron powder directly and treat coking wastewater (initial COD≈130mg / L) under the same application conditions.

[0061] Results: The COD removal rate was 48.7%, and the water became turbid after the reaction, indicating significant iron ion dissolution. Comparative analysis demonstrates that the supported heterogeneous catalyst prepared in this invention is superior to the homogeneous iron source in both activity and stability.

[0062] Comparative Example 3: Sodium percarbonate / TAED system only (without catalyst) Under the same reaction conditions as in Example 1, but without the addition of any catalyst.

[0063] Results: The COD removal rate was less than 15% after 60 minutes. This demonstrates that the in-situ generated PAA has very limited ability to oxidize organic matter in coking wastewater without activation by a highly efficient catalyst.

[0064] Summary of the effects of the examples The key wastewater treatment data from the above embodiments and comparative examples are summarized in the table below: Table 1 Key data on wastewater treatment in the examples and comparative examples Conclusion: The above examples and comparative data demonstrate that the method for preparing iron-sulfurized sludge-based char provided by this invention exhibits stability and repeatability. By controlling the raw material ratio, sulfidation process, and calcination parameters, a series of high-performance catalysts (SWNC-1 / 2 / 3) can be obtained. In applications of activated PAA for treating actual coking wastewater, these materials all demonstrate excellent and stable COD removal efficiency (81.0%~87.7%), significantly outperforming unsulfurized materials and traditional iron-based materials. This fully confirms that this invention successfully constructs a highly efficient heterogeneous catalytic system by combining "sulfur modification" with "high-temperature calcination," demonstrating clear technical effects and outstanding innovation.

[0065] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing iron sulfide-based sludge char, characterized in that, Includes the following steps: Step 1: The iron-containing sludge and activated carbon are processed separately to obtain iron sludge powder and activated carbon powder; Step 2: Add the iron mud powder and activated carbon powder obtained in Step 1 to the acidic solution in sequence and stir thoroughly to react, so as to obtain an iron mud and carbon mixture. Step 3: After adjusting the iron peat mixture obtained in Step 2 to alkaline with an alkaline solution, add sodium sulfide, stir the reaction thoroughly, filter, dry, and grind to obtain sulfur-modified iron peat precursor. Step 4: The sulfur-modified iron peat precursor obtained in Step 3 is calcined, ground, alcohol washed, dried, alkali impregnated, filtered, and dried in an inert atmosphere to obtain sulfur-modified iron-based sludge peat.

2. The method for preparing iron sulfide-based sludge char according to claim 1, characterized in that, In step 1, the iron-containing sludge is iron-containing sludge from a steel plant, with an iron content of 30% to 35% by weight; the activated carbon has a specific surface area of ​​1200 to 1400 m². 2 / g.

3. The method for preparing iron sulfide-based sludge char according to claim 1, characterized in that, In step 1, The process includes drying, grinding, and sieving.

4. The method for preparing iron sulfide-based sludge char according to claim 1 or 3, characterized in that, In step 1, the drying is vacuum drying at 100~110℃ for 10~15h, the grinding is grinding with an agate mortar for 15~25min, and the sieving is using a 70~90 mesh sieve. In step 3, the stirring reaction is carried out at a constant temperature of 20-30°C for 5-7 hours; the filtration is carried out under vacuum; the drying is carried out under vacuum at 100-110°C for 10-15 hours; and the grinding is carried out using an agate mortar and pestle for 15-25 minutes. In step 4, the grinding is performed using an agate mortar and pestle for 15-25 minutes; the alcohol washing is performed using ethanol; the drying is performed under vacuum at 100-110°C for 10-15 hours; and the filtration is performed under vacuum.

5. The method for preparing iron sulfide-based sludge carbon according to claim 1, characterized in that, In step 2, the amount of iron mud powder added is 20~25g / L; the mass ratio of iron mud powder to activated carbon powder added is 5~10:1; the acidic solution is hydrochloric acid; the molar ratio of H+ in the acidic solution to iron in the iron mud powder is 1~1.5:1; the stirring reaction is carried out at a constant temperature of 20~30℃ for 7~8h.

6. The method for preparing iron sulfide-based sludge carbon according to claim 1, characterized in that, In step 3, the alkaline solution is sodium hydroxide and potassium hydroxide; the pH of the iron peat mixture is 9-11; and the molar ratio of sodium sulfide to iron in the iron powder is 0.17-0.25:

1.

7. The method for preparing iron sulfide-based sludge char according to claim 1, characterized in that, In step 4, the inert gas atmosphere calcination is carried out in a tube furnace under an inert gas atmosphere. The inert gas is nitrogen, argon, or helium. The inert gas flow rate is 0.3~0.5 L / min. The calcination temperature is 600~800℃, the heating rate is 5~10℃ / min, and the calcination time is 120~150 min.

8. The method for preparing iron sulfide-based sludge carbon according to claim 1, characterized in that, In step 4, the alkaline impregnation involves impregnating iron-based sludge carbon with an alkaline solution; the alkaline solution is ammonia, sodium hydroxide, or potassium hydroxide; the mass concentration of the alkaline solution is 5%–32%; and the alkaline impregnation time is 4–24 hours.

9. An application of the iron sulfide-based sludge carbon prepared according to claim 1, characterized in that, It is used to treat coking wastewater, activate peracetic acid in coking wastewater, and degrade COD in waste coking wastewater.

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