A Fenton-assisted sludge single-atom promoter and preparation method thereof, and a Fenton-assisted method for treating wastewater

Abstract

The present invention provides a Fenton-promoting sludge single-atom co-catalyst and a preparation method thereof, as well as a Fenton-promoting method for treating wastewater. The preparation method of the Fenton-promoting sludge single-atom co-catalyst provided by the present invention comprises the following steps: a) drying and crushing sludge waste to obtain a precursor; b) co-pyrolyzing the precursor with a S-containing compound to obtain a modified carbon-based material; c) wetting the modified carbon-based material with a solvent, and wet-milling the ball-milled material to obtain a ball-milled material; d) chemically activating the ball-milled material with a sulfuric acid solution, and then performing solid-liquid separation to obtain sludge single-atom co-catalyst powder material and pickling wastewater, respectively. The co-catalyst provided by the present invention can solve the homogeneous Fenton technology (Fe 2+ / H2O2 and Fe 3+ / H2O2), improve the overall efficiency of the Fenton reaction, and increase the utilization efficiency of hydrogen peroxide and the mineralization degree of organic pollutants.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection, and in particular to a Fenton-assisted sludge single-atom catalyst and a preparation method thereof, as well as a Fenton-assisted wastewater treatment method. Background Art

[0002] Advanced oxidation technology (AOPs) is the mainstream method for treating toxic and difficult-to-degrade organic pollutants in the world. It plays an extremely important role in the fields of industrial wastewater treatment, urban sewage and drinking water deep treatment. The Fenton process, as the most widely used method in AOPs, plays an irreplaceable role in water treatment and water environment remediation. Its basic principle is to use Fe 2+ As a catalyst, under acidic conditions, activated hydrogen peroxide produces redox active species (ROS, mainly hydroxyl radical ·OH) with strong oxidizing properties, and degrades organic pollutants in water into small molecules or even completely mineralizes them through ·OH.

[0003] Since the Fenton technology is mainly based on ·OH to degrade pollutants, it has the advantages of strong oxidation ability, high degradation efficiency, wide application range of pollutants, no secondary pollution, simple operation, few interference factors, and high stability. 3+ Reduction back to Fe 2+ It is very slow and becomes the rate-limiting step of the entire Fenton reaction, so it is easy to form iron sludge, leading to catalyst poisoning. In order to ensure that there is sufficient Fe in the system 2+ To generate sufficient OH, a large excess of H 2 O 2 and catalysts are required, making the Fenton technology too expensive for large-scale application in wastewater treatment; in addition, the low efficiency of hydrogen peroxide utilization and the low degree of organic matter mineralization are also bottleneck problems in the actual application of the Fenton technology.

[0004] Many approaches have been developed to date to address one or more of the above limitations. The introduction of energy (e.g., UV, ultrasound, etc.) can improve the efficiency of the Fenton reaction, but this can create additional problems, such as harmful effects on human health and increased costs. Numerous studies have shown that the introduction of co-catalysts can improve the overall efficiency of the Fenton reaction and minimize Fe 2+ Among them, organic small molecule co-catalysts (such as quinone-hydroquinone analogs, phenolic acid, ascorbic acid, etc.) as iron chelators or reductants can effectively regulate Fe 2+Circulation, inhibiting the generation of iron sludge, and widening the pH, but the oxidation-induced self-degradation of organic co-catalysts makes them unrecyclable, easily causing secondary pollution, and the system has a low degree of mineralization. Therefore, the development of inorganic co-catalysts has more significant economic and environmental benefits. Zero-valent metals (ZVM) and metal sulfides are the two most representative materials. They can effectively promote iron circulation, but ZVM has the problem of easy oxidation and passivation (agglomeration), and metal sulfides will cause secondary pollution due to the dissolution of heavy metal ions and the generation of toxic gases. In addition, the metal sulfide-assisted Fenton system reported so far often requires light assistance, resulting in certain limitations in its practical application. It is reported that single-atom materials show unique advantages in catalytic interfacial reactions due to their highly dispersed active sites, unique electronic structure and excellent stability, but the research on the application of single-atom materials in Fenton is still in its infancy, and is limited by the preparation method and cost of single-atom catalysts. There are still many problems to be solved before industrial application. At present, there is still a lack of economical, efficient, green and practical industrial application scenarios for Fenton treatment. Summary of the invention

[0005] In view of this, the present invention provides a Fenton sludge single atom catalyst and a preparation method thereof, as well as a Fenton wastewater treatment method. The catalyst provided by the present invention can solve the problem of homogeneous Fenton technology (Fe 2+ / H 2 O 2 and Fe 3+ / H 2 O 2 ) The core bottleneck problem of iron cycle speed limitation in the process of production will be solved, the overall efficiency of the Fenton reaction will be improved, the formation of iron sludge will be reduced, the utilization efficiency of hydrogen peroxide and the mineralization degree of organic pollutants will be improved, the catalytic performance and long-term operation stability will be improved, and the cost will be reduced.

[0006] The present invention provides a method for preparing a Fenton-promoting sludge single-atom promoter, comprising the following steps:

[0007] a) drying and crushing the sludge waste to obtain a precursor;

[0008] b) co-pyrolyzing the precursor and the sulfur-containing compound to obtain a modified carbon-based material;

[0009] c) wetting the modified carbon-based material with a solvent and performing wet ball milling to obtain a ball mill material;

[0010] d) chemically activating the ball mill material with a sulfuric acid solution, and then performing solid-liquid separation to obtain sludge single-atom promoter powder material and acid-washing wastewater respectively.

[0011] Preferably, in step b), the sulfur-containing compound is sublimated sulfur and / or potassium thiocyanate.

[0012] Preferably, in step b), the mass ratio of the S-containing compound to the precursor is 1:(3-20).

[0013] Preferably, in step b), the co-pyrolysis temperature is 500-900° C. and the time is 1-5 h.

[0014] Preferably, in step c), the solvent is ethanol and / or methanol;

[0015] The ratio of the solvent to the modified carbon-based material is (0.4-3) mL: 1 g;

[0016] The rotation speed of the wet ball mill is 330-521 r / min, and the ball-to-material ratio is (1-16):4.

[0017] Preferably, in step d), the concentration of the sulfuric acid solution is 1.0 to 3.0 mol / L;

[0018] The dosage ratio of the sulfuric acid solution to the ball mill is (10-60) mL: 1 g.

[0019] Preferably, in step d), the temperature of the chemical activation is 20-60° C. and the time is 3-12 hours.

[0020] Preferably, after step d), the method further comprises:

[0021] e) mixing the sludge single atom promoter powder material, gypsum and water to obtain a viscous paste;

[0022] f) Extruding the viscous paste into shapes and drying them to obtain sludge single-atom promoter particles.

[0023] The present invention also provides a Fenton-promoting sludge single-atom catalyst prepared by the preparation method described in the above technical scheme.

[0024] The present invention also provides a Fenton-assisted wastewater treatment method, wherein the co-catalyst used is the Fenton-assisted sludge single-atom co-catalyst described in the above technical solution.

[0025] The preparation method of the Fenton-promoting sludge single-atom co-catalyst provided by the present invention comprises the following steps: firstly drying and crushing the sludge waste to obtain a precursor; then co-pyrolyzing the precursor with a S-containing compound to obtain a modified carbon-based material; then, wetting the modified carbon-based material with a solvent, and wet-milling the material to obtain a ball-milled material; finally, chemically activating the ball-milled material with a sulfuric acid solution, and then performing solid-liquid separation to obtain a sludge single-atom co-catalyst powder material and pickling wastewater, respectively. The present invention uses municipal sludge waste as a raw material to synthesize and prepare a high-performance, low-cost, and environmentally friendly Fe single-atom co-catalyst, which can solve the homogeneous Fenton technology (Fe 2+ / H 2 O 2 and Fe 3+ / H 2 O 2 ) The core bottleneck problem of the iron cycle speed limit, as well as the technical difficulties caused by the iron cycle speed limit, such as easy poisoning of catalysts, low utilization rate of hydrogen peroxide, and low degree of pollutant mineralization.

[0026] The test results show that the co-catalyst of the present invention can be used in the Fenton reaction system to effectively remove pollutants in wastewater and significantly improve the mineralization degree of pollutants in the Fenton system. Moreover, the decomposition efficiency of hydrogen peroxide can reach more than 94%. 2+ The regeneration rate can reach over 71%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0028] Figure 1 A schematic diagram of the present invention assisting Fenton in treating wastewater;

[0029] Figure 2 This is a scanning electron microscope (SEM) image of the sludge single-atom promoter obtained in Example 1;

[0030] Figure 3 This is a transmission electron microscope (TEM) image of the sludge single-atom promoter obtained in Example 1;

[0031] Figure 4 The high-resolution transmission electron micrograph of the sludge single-atom promoter obtained in Example 1 and the corresponding elemental analysis diagram;

[0032] Figure 5 This is a high-angle dark field scanning transmission electron microscopy image of the sludge single-atom promoter obtained in Example 1;

[0033] Figure 6 This is a schematic diagram of the appearance of the sludge single-atom promoter particles obtained in Example 2;

[0034] Figure 7 A comparison chart of the mineralization capacity of the sludge single atom-assisted Fenton technology and the homogeneous Fenton technology for treating phenol wastewater;

[0035] Figure 8 The treatment effect of the sludge single atom-assisted Fenton system of the present invention on high-concentration sodium benzoate using pickling wastewater as a catalyst and pH regulator;

[0036] Fig. 9 A comparison diagram of the hydrogen peroxide decomposition efficiency of the sludge single atom promoter-Fenton technology of the present invention and various existing Fenton-promoting technologies;

[0037] Fig.10 The sludge single atom promoter Fenton technology of the present invention is different from the existing various Fenton technologies. 2+ Regeneration rate comparison chart. DETAILED DESCRIPTION

[0038] The present invention provides a method for preparing a Fenton-promoting sludge single-atom promoter, comprising the following steps:

[0039] a) drying and crushing the sludge waste to obtain a precursor;

[0040] b) co-pyrolyzing the precursor and the sulfur-containing compound to obtain a modified carbon-based material;

[0041] c) wetting the modified carbon-based material with a solvent and performing wet ball milling to obtain a ball mill material;

[0042] d) chemically activating the ball mill material with a sulfuric acid solution, and then performing solid-liquid separation to obtain sludge single-atom promoter powder material and acid-washing wastewater respectively.

[0043] Regarding step a) :

[0044] a) Drying and crushing the sludge waste to obtain a precursor.

[0045] In the present invention, the sludge waste is the sludge waste generated by the sewage treatment plant. The present invention first collects the sludge waste generated by the sewage treatment plant and performs certain pretreatment. In the present invention, the pretreatment is drying and crushing. In the present invention, the drying is drying or natural air drying; wherein the drying temperature is preferably 60 to 105°C, specifically 60°C, 70°C, 80°C, 90°C, 100°C, 105°C. In the present invention, after drying, crushing is performed. The present invention has no special restrictions on the crushing method, which can be a conventional crushing method in the art. In the present invention, after the above-mentioned drying and crushing, it is preferably screened. In the present invention, the screening is preferably screened through a 10-mesh sieve. After the above treatment, a submillimeter dry sludge powder precursor is obtained.

[0046] Sludge treatment and disposal has always been a global problem in the field of water treatment. Realizing sludge reduction, harmlessness, resource utilization and comprehensive utilization is its development trend. However, the methods developed so far, such as landfill, agricultural utilization, incineration, and building material utilization, still have problems such as cost and environmental health risks. In general, there is an urgent need to develop a sludge upgrading strategy and application method with economic and environmental benefits. The present invention uses sludge as a raw material to prepare a catalyst promoter, which can reuse sludge waste and realize the resource utilization of waste sludge.

[0047] Regarding step b) :

[0048] b) co-pyrolyzing the precursor and a sulfur-containing compound to obtain a modified carbon-based material.

[0049] In the present invention, the S-containing compound is preferably sublimed sulfur and / or potassium thiocyanate. In the present invention, the mass ratio of the S-containing compound to the precursor is preferably 1:(3-20), specifically 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20.

[0050] In the present invention, the above step b) preferably includes: uniformly mixing the precursor and the S-containing compound, and then performing a co-pyrolysis treatment. In the present invention, the temperature of the co-pyrolysis is preferably 500-900°C, specifically 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C. In the present invention, the time of the co-pyrolysis is preferably 1-5h, specifically 1h, 2h, 3h, 4h, 5h. In step b) of the present invention, after the co-pyrolysis treatment, the precursor undergoes pyrolysis and carbonization, and S element doping occurs at the same time, thereby obtaining a modified carbon-based material.

[0051] Regarding step c) :

[0052] c) Wetting the modified carbon-based material with a solvent and performing wet ball milling to obtain a ball mill material.

[0053] In the present invention, the solvent is preferably ethanol and / or methanol. The present invention uses the above-mentioned solvent to remain stable during the ball milling process, and will not introduce solvent components into the ball milled material, while facilitating the removal of the solvent in subsequent steps. In the present invention, the amount ratio of the solvent to the modified carbon-based material is preferably (0.4-3) mL: 1g, that is, the amount of solvent is (0.4-3) mL / g modified carbon-based material, and the amount ratio can specifically be 0.4 mL: 1g, 1.0 mL: 1g, 1.5 mL: 1g, 2.0 mL: 1g, 2.5 mL: 1g, 3.0 mL: 1g.

[0054] In the present invention, the modified carbon-based material is wetted with the above-mentioned solvent and wet ball milled. In the present invention, the rotation speed of the wet ball mill is preferably 330-521r / min, specifically 330r / min, 350r / min, 400r / min, 450r / min, 500r / min, 520r / min, 521r / min. The ball milling time of the wet ball milling is preferably 2-12h, specifically 2h, 4h, 6h, 8h, 10h, 12h. The ball-to-material ratio of the wet ball milling is preferably (1-16):4, specifically 1:4, 4:4, 8:4, 12:4, 16:4. After the above-mentioned wet ball milling, a ball mill material is obtained. In step c) of the present invention, the distribution of each element in the material is optimized through wet ball milling, and the surface geometry and electronic properties of the material are regulated.

[0055] Regarding step d) :

[0056] d) chemically activating the ball mill material with a sulfuric acid solution, and then performing solid-liquid separation to obtain sludge single-atom promoter powder material and acid-washing wastewater respectively.

[0057] In the present invention, the concentration of the sulfuric acid solution is preferably 1.0 to 3.0 mol / L, specifically 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, or 3.0 mol / L.

[0058] In the present invention, the dosage ratio of the sulfuric acid solution to the ball mill is preferably (10-60) mL: 1 g, that is, the dosage of the sulfuric acid solution is (10-60) mL / g ball mill. The dosage ratio can specifically be 10 mL: 1 g, 20 mL: 1 g, 30 mL: 1 g, 40 mL: 1 g, 50 mL: 1 g, and 60 mL: 1 g.

[0059] In the present invention, the temperature of the chemical activation is preferably 20-60° C., specifically 20° C., 30° C., 40° C., 50° C., 60° C. The time of the chemical activation is preferably 3-12 h, specifically 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h.

[0060] In the present invention, after the above-mentioned chemical activation treatment, solid-liquid separation is carried out. The present invention has no special restrictions on the method of solid-liquid separation, and it can be any conventional separation method in the field, such as filtration. In the present invention, after solid-liquid separation, the obtained solid separator is preferably dried. The drying temperature is preferably 50-100°C. After the above treatment, sludge single atom promoter powder material and pickling wastewater are obtained respectively. Among them, the pickling wastewater can be used to assist in Fenton treatment of wastewater, as a catalyst in the Fenton reaction (Fe 3+ ) and pH regulator. In step d) of the present invention, metal nanoparticles and other impurities on the surface of the material are removed by acid washing and activation, the pore structure of the material is improved, the Fe single atom active sites are exposed, and the site activity is enhanced. The sludge single atom catalyst powder material obtained in step d) of the present invention is a multi-substrate (C-based, SiO 2 , Al 2 O 3 ) coexistence, N, P, S co-doped Fe single atom co-catalyst (Fe is coordinated by N), is a porous material with irregular structure.

[0061] In the present invention, after the above step d), it is preferred to further include:

[0062] e) mixing the sludge single atom promoter powder material, gypsum and water to obtain a viscous paste;

[0063] f) Extruding the viscous paste into shapes and drying them to obtain sludge single-atom promoter particles.

[0064] Regarding step e) :

[0065] In the present invention, the gypsum (CaSO 4 ) as a binder. The mass ratio of the sludge single atom promoter powder material to gypsum is preferably 5:(1-3), specifically 5:1, 5:1.5, 5:2, 5:2.5, 5:3. In the present invention, the water is preferably deionized water. In the present invention, the mass ratio of the water to the sludge single atom promoter powder material is preferably (0.5-4):5, specifically 0.5:5, 1:5, 1.5:5, 2:5, 2.5:5, 3:5, 4:5. In the present invention, the mixing operation process is preferably: first mix the sludge single atom promoter powder material and gypsum evenly, and then moisten them with water to obtain a paste with a certain viscosity.

[0066] Regarding step f) :

[0067] In the present invention, there is no special limitation on the extrusion molding method, and the sludge can be formed into round particles according to conventional operations in the art. After the extrusion molding, drying is performed. In the present invention, the drying temperature is preferably 60 to 80°C, specifically 60°C, 65°C, 70°C, 75°C, 80°C. After drying, solid-supported sludge single-atom promoter particles are obtained.

[0068] The present invention prepares the sludge single-atom promoter powder material through steps a) to d), and can further solidify and shape the sludge single-atom promoter powder material through steps e) to f) to obtain sludge single-atom promoter particles. Both types of products, whether promoter powder materials or promoter particles, can be used to treat wastewater using the Fenton technology and achieve good results.

[0069] The present invention also provides a Fenton-promoting sludge single atom promoter prepared by the preparation method described in the above technical solution. The Fenton-promoting sludge single atom promoter can be a sludge single atom promoter powder material or a sludge single atom promoter particle.

[0070] The present invention also provides a Fenton-assisted wastewater treatment method, wherein the co-catalyst used is the Fenton-assisted sludge single-atom co-catalyst described in the above technical solution. Figure 1 , Figure 1 This is a schematic diagram of the present invention assisting Fenton in treating wastewater.

[0071] In the present invention, in the method, the catalyst used is Fe 2+ and / or Fe 3+ , which can be provided by Fenton's reagent, or can come from pickling wastewater or other waste iron materials in the previous preparation process.

[0072] In the present invention, the method preferably specifically comprises: adding a promoter and an iron source to a Fenton reactor containing wastewater to be treated, stirring and dispersing, and then adding a hydrogen peroxide solution to the Fenton reactor and continuously stirring to obtain purified water. The promoter is the Fenton sludge single atom promoter described in the above technical solution.

[0073] Wherein, before adding the catalyst and the iron source, the pH value of the wastewater to be treated in the Fenton reactor can be adjusted in advance. The present invention preferably adjusts the pH value to 2.5-4.0, specifically 2.5, 3.0, 3.5, 4.0. In the present invention, sulfuric acid and alkaline substances are preferably used to adjust the pH value. The alkaline substance is preferably a strong alkaline substance such as NaOH or KOH.

[0074] In the present invention, after adjusting the pH value, preferably under stirring conditions, a promoter and an iron source are added to the Fenton reactor. The promoter is preferably added in an amount of 0.2 to 1 g / L of wastewater, specifically 0.2 g / L of wastewater, 0.5 g / L of wastewater, or 1 g / L of wastewater. The iron source is used to provide the catalyst Fe 2+ and / or Fe 3+ , which can be an aqueous solution of ferric sulfate, the pickling wastewater mentioned above, or Fenton's reagent. The amount of the iron source is preferably such that Fe 2+ / Fe 3+ The concentration reaches 2 to 15 mg / L, specifically 2 mg / L, 3 mg / L, 4 mg / L, 5 mg / L, 6 mg / L, 7 mg / L, 8 mg / L, 9 mg / L, 10 mg / L, 11 mg / L, 12 mg / L, 13 mg / L, 14 mg / L, 15 mg / L. After the addition of the promoter and the iron source, the pH value of the system is adjusted as appropriate to maintain the pH value of the system at 2.5 to 4.0. For example, if the pH value of the system changes significantly due to the addition of the promoter and the iron source, the pH value is readjusted to return to the range of 2.5 to 4.0 after the addition of the materials; on the contrary, if the pH value of the system remains within the above pH range after the addition of the promoter and the iron source, there is no need to readjust and restore.

[0075] In the present invention, after the above treatment, a hydrogen peroxide solution is added to the system. The concentration of the hydrogen peroxide solution is not particularly limited, and it can be a commercial product with a concentration of 30%. The amount of the hydrogen peroxide solution used can be determined according to the concentration of hydrogen peroxide after addition, c(H 2 O 2 , mg / L) : COD concentration of wastewater to be treated (mg / L) is (0.5-2) : 1. After adding hydrogen peroxide solution, stirring is continued to purify the wastewater to obtain purified water.

[0076] The above-mentioned wastewater treatment method provided by the present invention is an efficient and low-carbon Fe single-atom assisted Fenton technology method, which not only has the characteristics of high catalytic efficiency, good stability, high hydrogen peroxide utilization rate, greatly reduced iron sludge generation and high degree of pollutant mineralization, but also realizes the comprehensive utilization of pickling wastewater. At the same time, the method is simple, and municipal sludge waste is upgraded and recycled, which has significant economic and environmental benefits. It is expected to become an important technical direction for the future development of Fenton technology and sludge resource treatment and disposal.

[0077] The preparation method of the Fenton-promoting sludge single-atom co-catalyst provided by the present invention comprises the following steps: firstly drying and crushing the sludge waste to obtain a precursor; then co-pyrolyzing the precursor with a S-containing compound to obtain a modified carbon-based material; then, wetting the modified carbon-based material with a solvent, and wet-milling the material to obtain a ball-milled material; finally, chemically activating the ball-milled material with a sulfuric acid solution, and then performing solid-liquid separation to obtain a sludge single-atom co-catalyst powder material and pickling wastewater, respectively. The present invention uses municipal sludge waste as a raw material to synthesize and prepare a high-performance, low-cost, and environmentally friendly Fe single-atom co-catalyst, which can solve the homogeneous Fenton technology (Fe 2+ / H 2 O 2 and Fe 3+ / H 2 O 2 ) The core bottleneck problem of the iron cycle speed limit in the process of wastewater treatment, as well as the technical difficulties caused by the iron cycle speed limit, such as easy poisoning of catalysts, low utilization rate of hydrogen peroxide, and low degree of mineralization of pollutants. In the Fenton-assisted wastewater treatment, the following problems can be solved specifically: (1) Effectively regulate the iron cycle and improve the overall efficiency of the Fenton reaction; (2) Effectively reduce the generation of iron sludge; (3) Effectively improve the utilization efficiency of hydrogen peroxide and the degree of mineralization of organic pollutants; (4) Further improve the catalytic performance and long-term operation stability on the basis of existing co-catalysts, reduce costs, so as to achieve practical industrial application scenarios; (5) Effectively reduce environmental emissions and secondary pollution during material preparation and application; (6) Realize the solidification and molding of powder materials, which is convenient for practical application; (7) Realize the upgrading and resource utilization of sludge waste, and provide an economical and green technical direction for the future resource utilization treatment and disposal of sludge.

[0078] Compared with the prior art, the present invention has the following beneficial effects:

[0079] 1. The present invention has developed a new type of high-performance, low-cost, environmentally friendly Fe single-atom catalytic material using municipal sludge waste as raw materials. The method is simple, greatly reducing the cost of Fenton technology, and realizing the simultaneous resource utilization of carbon, silicon, nutrient elements (nitrogen, phosphorus), sulfur and low-content heavy metal elements in municipal sludge;

[0080] 2. The unique structure and catalytic mechanism of the sludge single-atom catalyst of the present invention enable it to have excellent Fenton-promoting performance. The regeneration rate of divalent iron and the utilization efficiency of hydrogen peroxide have reached the highest level reported so far, and the acidic pH application range of the traditional Fenton reaction has been effectively broadened. The mineralization degree of organic matter has been greatly improved, and it can be used to remove water pollutants efficiently, quickly and thoroughly. It has high catalytic stability, and the material can be reused, which greatly reduces the operating cost of the water treatment process;

[0081] 3. The application method of the sludge single-atom catalyst of the present invention comprehensively utilizes the pickling wastewater in the material preparation process and effectively recycles most of the components in the sludge, which can promote the further research, development and application of the entire technology to a certain extent;

[0082] 4. The sludge single atom-assisted Fenton technology of the present invention increases the possibility of practical application of single atom materials in the field of AOPs, and helps promote the development and industrialization of single atom science;

[0083] 5. The Fenton-assisted wastewater treatment technology of the present invention has high iron circulation efficiency and can effectively avoid the problem of catalyst poisoning and iron sludge generation in the Fenton reaction. 3+ Or other waste iron materials as catalysts, which solves the problem of the difficulty in preserving ferrous salts in Fenton reagents and can effectively reduce the cost of Fenton treatment technology;

[0084] 6. The sludge single-atom catalyst preparation method of the present invention is coupled with the powder material molding technology to solve the problem of catalyst recovery;

[0085] 7. The present invention uses the emerging single-atom science to effectively upgrade and utilize toxic and hazardous substances such as heavy metals that pose the greatest environmental risk in sludge, which has significant economic and environmental benefits;

[0086] 8. The present invention adopts pyrolysis carbonization process to prepare the catalytic material, which can better retain various resource elements in the sludge and produce less CO, NOx, SO 2 , HCl, heavy metals, dioxins and other toxic and harmful pollutants, with little secondary pollution;

[0087] 9. Upcycling of sludge waste into highly efficient single-atom catalysts can directly save a large amount of sludge disposal costs in sewage treatment plants, with significant economic benefits. It is also expected to replace traditional sludge disposal methods and reduce carbon emissions in the field;

[0088] 10. The waste sludge upgrading and resource utilization technology of the present invention is simple, has a high material yield, strong operability, significant effect, and obvious economy. It has broad industrial application prospects in the field of environmental pollution purification.

[0089] The test results show that the co-catalyst of the present invention can be used in the Fenton reaction system to effectively remove pollutants in wastewater and significantly improve the mineralization degree of pollutants in the Fenton system. Moreover, the decomposition efficiency of hydrogen peroxide can reach more than 94%. 2+ The regeneration rate can reach over 71%.

[0090] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0091] Example 1: Preparation of sludge single atom promoter powder material

[0092] 1. Sample preparation

[0093] a) Collect the sludge waste generated by the sewage treatment plant, dry it at 90°C, crush it, and pass it through a 10-mesh sieve to obtain a precursor.

[0094] b) The obtained precursor is evenly mixed with potassium thiocyanate (the mass ratio of potassium thiocyanate to the precursor is 1:10), and then co-pyrolysis treatment is performed at 700° C. for 3 h to obtain a modified carbon-based material.

[0095] c) The obtained modified carbon-based material was moistened with ethanol (the amount of ethanol was 2 mL / g of modified carbon-based material) and subjected to wet ball milling under the following conditions: rotation speed of 400 r / min, ball-to-material ratio of 4:1, and time of 8 h to obtain a ball-milled material.

[0096] d) placing the obtained ball mill material in a sulfuric acid solution (sulfuric acid solution concentration 2.0 mol / L, amount 40 mL / g ball mill material), activating at 25° C. for 8 h, then filtering and drying to obtain sludge single atom promoter powder material and acid washing wastewater, respectively.

[0097] 2. Sample characterization

[0098] The characterization results of the obtained samples can be found in Figure 2-5 ,in, Figure 2 This is a scanning electron microscope (SEM) image of the sludge single-atom promoter obtained in Example 1. Figure 3 This is a transmission electron microscope (TEM) image of the sludge single-atom catalyst obtained in Example 1. It can be seen that the powder material has an irregular structure, the size is in the nanometer to micrometer level, and there are abundant microporous and mesoporous structures on the surface of the material. Figure 4 This is a high-resolution transmission electron micrograph of the sludge single-atom co-catalyst obtained in Example 1 and the corresponding elemental analysis diagram. It can be seen that the sludge single-atom co-catalyst is a structure in which multiple substrates and multiple coordinated heteroatoms coexist. Figure 5 This is a high-angle dark field scanning transmission electron microscopy image of the sludge single-atom co-catalyst obtained in Example 1. It can be seen that the active metal is dispersed in single atoms.

[0099] Example 2: Preparation of sludge single atom promoter particles

[0100] 1. Sample preparation

[0101] S1. The sludge single-atom promoter powder material obtained in Example 1 and gypsum are mixed at a mass ratio of 10:3, and then moistened with deionized water (the mass ratio of water to the sludge single-atom promoter powder material is 2:5) to obtain a paste with a certain viscosity.

[0102] S2. The obtained paste is extruded and then dried at 70° C. for 12 h to obtain solid-supported sludge single-atom promoter particles.

[0103] 2. Sample characterization

[0104] The appearance of the obtained sample is as Figure 6 As shown, Figure 6 This is a schematic diagram of the appearance of the sludge single-atom promoter particles obtained in Example 2.

[0105] Example 3: Sludge single atom catalyst used to assist Fenton technology in treating phenol wastewater

[0106] The sludge single atom promoter powder material obtained in Example 1 was added to 40 mL of a solution for removing phenol (solution pH = 3, phenol concentration in the solution was 20 mg / L), with a dosage of 0.5 g / L, and ultrasonically dispersed. Subsequently, 40 μL of ferric sulfate mother solution was added dropwise to the solution to make the Fe in the solution 3+ The concentration reached 3 mg / L. Stirring was carried out at 700 rpm for 20 min to establish the adsorption-desorption equilibrium of pollutants. Then 24 μL of hydrogen peroxide solution (concentration 30%) was added to the solution. The stirring speed was maintained at 700 rpm. Results The Fenton-assisted system could achieve 100% removal of phenol within 8 min.

[0107] See also Figure 7 , Figure 7 The figure is a comparison of the mineralization capacity of the sludge single atom-assisted Fenton technology and the homogeneous Fenton technology in treating phenol wastewater; it can be seen from the figure that the sludge single atom promoter significantly enhances the mineralization capacity of the Fenton reaction for pollutants. The Fenton system can achieve 51.2% TOC removal in phenol wastewater within 60 minutes, while as a control, the homogeneous Fe 3+ / H 2 O 2 The TOC removal rate of the system is only 2.8%, and the homogeneous Fe 2+ / H 2 O 2 The system was only able to remove 13.2%.

[0108] Example 4: Application of comprehensive utilization of pickling wastewater

[0109] The sludge single atom promoter powder material obtained in Example 1 was added to a solution with sodium benzoate (BA) as the removal object (the concentration of sodium benzoate in the solution was 100 mg / L), and the addition amount was 0.5 g / L. 2.2 mL of the sulfuric acid pickling wastewater collected in Example 1 was added to the solution to make Fe in the solution 3+ The concentration reached 3 mg / L, and the solution pH was adjusted to 3 with NaOH, and ultrasonic dispersion was performed. Stirring was performed at 700 rpm for 20 min to establish the adsorption-desorption equilibrium of pollutants. Then 24 μL of hydrogen peroxide solution (concentration 30%) was added to the solution. The stirring speed was maintained at 700 rpm.

[0110] See also Figure 8 , Figure 8 The treatment effect of the sludge single atom Fenton system of the present invention on high concentration sodium benzoate using pickling wastewater as catalyst and pH regulator; it can be seen from the figure that single pickling wastewater (i.e. blank test without adding promoter) cannot activate hydrogen peroxide to remove sodium benzoate, while the Fenton system can achieve 99.2% removal of 100 mg / L sodium benzoate within 25 minutes, which is similar to the treatment effect of using chemical pure reagents to provide Fe 3+ The activity is consistent with that of acid regulator.

[0111] Example 5: Application of sludge single atom catalyst to assist Fenton technology in treating actual wastewater

[0112] The sludge single atom promoter obtained in Example 1 was added to 40 mL of actual wastewater (industrial wastewater, effluent from the secondary sedimentation tank after homogeneous Fenton pretreatment and biological treatment) with a pH of 3 and a removal target of 265 mg / LCOD. The dosage was 0.5 g / L and ultrasonically dispersed. Then 40 μL of ferric sulfate mother solution was added dropwise to the solution to make the Fe in the solution 3+ The concentration reached 3 mg / L. Stir at 700 rpm for 20 min to establish the adsorption-desorption equilibrium of pollutants. Then 48 μL of hydrogen peroxide solution (concentration 30%) was added to the solution. The stirring speed was maintained at 700 rpm. Within 60 min, the Fenton-assisted system could achieve 72.9% COD removal in wastewater, and at the same time, the decomposition rate of hydrogen peroxide reached 99.5%.

[0113] At the same time, compared with the existing Fenton-assisted technologies (i.e., MoS 2 , WS 2 , Mo, FeP, Mn-CNH as co-catalysts according to the process of Example 5) were compared in terms of hydrogen peroxide decomposition efficiency. The results are shown in Fig. 9 , Fig. 9This is a comparison chart of the hydrogen peroxide decomposition efficiency of the sludge single atom co-catalyst assisted Fenton technology of the present invention and various existing assisted Fenton technologies. It can be seen that the sludge single atom co-catalyst of the present invention can effectively improve the hydrogen peroxide decomposition efficiency.

[0114] In addition, the process of Example 5 was followed, except that the removal target was a 20 mg / L sodium benzoate solution and the amount of hydrogen peroxide solution added was 24 μL. 2 、P25、WO 3 、ZnS、MoO 2 , Mn-CNH as co-catalyst) were compared in terms of iron cycle efficiency. Fig.10 , Fig.10 The sludge single atom promoter Fenton technology of the present invention is different from the existing various Fenton technologies. 2+ Regeneration rate comparison chart, where Fe 2+ The regeneration rate is equal to the Fe in the system after 30 minutes of reaction. 2+ Concentration / Total iron concentration (3mg / L, the total iron added initially is 3mg / L Fe 3+ ), it can be seen that the sludge single atom promoter of the present invention can effectively increase Fe 2+ The regeneration rate can reach 71.1%.

[0115] Example 6: Application of the sludge single atom-assisted Fenton system in treating actual wastewater using acid wash wastewater

[0116] The sludge single atom promoter obtained in Example 1 was added to the actual wastewater (industrial wastewater, effluent from the secondary sedimentation tank after homogeneous Fenton pretreatment and biological treatment) with a COD removal target of 265 mg / L, and the dosage was 0.5 g / L. 2.2 mL of the sulfuric acid pickling wastewater collected in Example 1 was added to the solution to make the Fe 3+ The concentration reached 3 mg / L, and the solution pH was adjusted to 3 with NaOH, and ultrasonic dispersion was performed. Stirring was performed at 700 rpm for 20 min to establish the adsorption-desorption equilibrium of pollutants. Then 48 μL of hydrogen peroxide solution (concentration 30%) was added to the solution. The stirring speed was maintained at 700 rpm. Within 60 min, the Fenton-assisted system could achieve 83.5% COD removal in wastewater, and at the same time, the decomposition rate of hydrogen peroxide reached 94.9%.

[0117] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for treating wastewater by assisting Fenton, characterized in that: The co-catalyst used is a Fenton sludge single atom co-catalyst; The method for preparing the Fenton-promoting sludge single-atom promoter comprises the following steps: a) drying and crushing the sludge waste to obtain a precursor; b) co-pyrolyzing the precursor and a sulfur-containing compound to obtain a modified carbon-based material; the sulfur-containing compound is sublimated sulfur and / or potassium thiocyanate, and the mass ratio of the sulfur-containing compound to the precursor is 1:(10-20); c) wetting the modified carbon-based material with a solvent and performing wet ball milling to obtain a ball mill material; the solvent is ethanol and / or methanol; d) chemically activating the ball mill with a sulfuric acid solution, and then performing solid-liquid separation to obtain sludge single-atom catalyst powder material and pickling wastewater respectively; the temperature of the chemical activation is 20-40° C., and the time is 8-12 hours; the concentration of the sulfuric acid solution is 1.0-2.0 mol / L; and the amount ratio of the sulfuric acid solution to the ball mill is (40-60) mL: 1 g; The sludge single-atom co-catalyst powder material has an irregular structure and a size ranging from nanometers to micrometers. The surface of the material has abundant microporous and mesoporous structures, a structure in which multiple substrates and multiple coordinated heteroatoms coexist, and active metals are dispersed in single atoms.

2. The method according to claim 1, characterized in that In step b), the co-pyrolysis temperature is 500-900° C. and the time is 1-5 hours.

3. The method according to claim 1, characterized in that In step c), The ratio of the solvent to the modified carbon-based material is (0.4-3) mL: 1 g; The rotation speed of the wet ball mill is 330-521 r / min, and the ball-to-material ratio is (1-16):

4.

4. The method according to claim 1, characterized in that: After step d), the method further comprises: e) mixing the sludge single atom promoter powder material, gypsum and water to obtain a viscous paste; f) Extruding the viscous paste into shapes and drying them to obtain sludge single-atom promoter particles.

Images