Waste non-woven fabric derived efficient potassium persulfate catalyst for tail water treatment and preparation thereof

Abstract

The invention relates to the technical field of wastewater treatment, and discloses a waste non-woven fabric derived efficient potassium persulfate catalyst for tail water treatment and preparation thereof. According to the method, the waste non-woven fabric is converted into the sulfur-nitrogen co-doped hierarchical pore carbon material catalyst, so that high-value utilization of solid wastes is realized, and the environmental pressure caused by traditional landfill or incineration is effectively relieved. According to the catalyst, through core-shell structure design and surface functional group regulation and control, the activation efficiency of potassium persulfate is remarkably improved, organic pollutants difficult to treat in tail water can be efficiently degraded, and the defects that a traditional Fenton method is sensitive to pH, activated carbon is difficult to regenerate, and the efficiency of a biological method is low are overcome. The preparation process is simple and environment-friendly, precious metal or complex synthesis steps are not needed, the production cost is reduced, meanwhile, the catalyst is excellent in stability and can be recycled for multiple times, and secondary pollution is avoided. In addition, the technology is wide in applicability, can stably operate in a wide pH range, and provides an economical and efficient solution for advanced treatment of industrial tail water.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for tailwater treatment and its preparation. Background Technology

[0002] With the acceleration of industrialization, wastewater contains a large amount of organic pollutants and heavy metal ions. The advanced treatment of organic pollutants in wastewater is a challenge in the field of environmental engineering.

[0003] Traditional wastewater treatment methods, such as adsorption, biological methods, and Fenton oxidation, suffer from drawbacks such as low efficiency, high cost, and poor applicability. For example, Fenton oxidation relies on iron ions and is pH-limited, and activated carbon regeneration is difficult after adsorption. Biological methods have limited capacity to treat recalcitrant pollutants. Furthermore, waste non-woven fabrics, as common solid waste, have an underutilized carbon skeleton structure. Traditional treatment methods (landfill and incineration) not only waste resources but may also cause environmental pollution. Therefore, this paper proposes a high-efficiency potassium persulfate catalyst derived from waste non-woven fabrics for wastewater treatment and its preparation. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a highly efficient catalyst based on waste nonwoven fabric and its preparation method, thereby solving the problems of low efficiency and high cost in existing water treatment technologies. This catalyst can effectively remove pollutants from effluent, exhibiting excellent catalytic performance and economic efficiency.

[0005] In a first aspect, to achieve the above objectives, the present invention provides the following technical solution: a high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for wastewater treatment, wherein the catalyst is a sulfur-nitrogen co-doped hierarchical porous carbon material, comprising:

[0006] Microporous structure, with pore sizes of 0.5-2 nm, accounting for 30-50%;

[0007] Mesoporous structure, with a pore size of 2-10 nm, accounting for 40-60%;

[0008] Macroporous structure, with pore sizes of 10-50 nm, accounting for 10-20%;

[0009] Among them, sulfur is represented by CSC and - - It exists in the form of functional groups, with nitrogen in the form of pyridine nitrogen, pyrrole nitrogen and graphitic nitrogen, and sulfur and nitrogen atoms are distributed in a gradient in the carbon skeleton.

[0010] Preferably, the catalyst has functional groups formed on its surface, including carboxyl, hydroxyl and quinone groups, and the molar ratio of carboxyl, hydroxyl and quinone groups is 1:1.5-2.5:0.8-1.2.

[0011] Preferably, the catalyst has a core-shell structure, with the core being a highly graphitized carbon layer and the outer shell being an amorphous carbon layer rich in sulfur and nitrogen functional groups, and the thickness ratio of the core to the outer shell is 1:2 to 1:5.

[0012] Preferably, the sulfur-nitrogen-doped carbon material has a specific surface area of ​​500-800 m² / g, a pore size distribution of 0.5-50 nm, a sulfur content of 3-5 wt%, and a nitrogen content of 5-8 wt%.

[0013] Preferably, the surface functional groups comprise 40-50% carboxyl groups, 30-40% hydroxyl groups, and 20-30% quinone groups.

[0014] Secondly, the preparation of a high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for wastewater treatment, as described in the first aspect, includes the following steps:

[0015] Step 1, sulfonation pretreatment: Mix the crushed waste nonwoven fabric with concentrated sulfuric acid at a mass ratio of 1:1.5-1:3, react at 90-120℃ for 6-12 hours, wash, dry and grind through a 100-200 mesh sieve to obtain the sulfonation precursor;

[0016] Step 2, nitrogen-doped calcination: The sulfonated precursor and urea are mixed at a mass ratio of 1:6 to 1:12, and calcined in stages under a nitrogen atmosphere.

[0017] First stage: Increase the temperature to 300-400℃ at a rate of 5-10℃ / min, and hold for 0.5-1 hour;

[0018] Second stage: Increase the temperature to 700-900℃ at 10-15℃ / min, hold for 1-2 hours, and cool to room temperature to obtain crude product;

[0019] Step 3, post-oxidation treatment: The crude product is treated in air or an oxygen-containing mixed gas (O2 volume fraction 5-20%) at 300-500℃ for 0.5-1 hour. After cooling, it is acid washed and dried to form surface hydroxyl, carboxyl and quinone functional groups, thus obtaining a core-shell structured sulfur and nitrogen-doped carbon material, and obtaining the catalyst.

[0020] Preferably, the segmented calcination process in step two is used to control the core-shell structure:

[0021] The first stage involves low-temperature calcination to form an amorphous carbon shell.

[0022] The second stage of high-temperature calcination promotes the graphitization of the core.

[0023] Preferably, the temperature of the oxidation post-treatment in step three is 400-450℃, and the treatment time is 1 hour, in order to control the ratio of surface hydroxyl groups, carboxyl groups, and quinone groups.

[0024] Preferably, the pickling in step three uses a 0.1-0.5 mol / L hydrochloric acid solution and the pickling time is 30-60 minutes to remove unreacted metal impurities and stabilize surface functional groups.

[0025] Preferably, in step one, the mass ratio of concentrated sulfuric acid to nonwoven fabric is 1:2, the reaction temperature is 100℃, and the reaction time is 10 hours.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention achieves high-value utilization of solid waste by converting waste nonwoven fabric into a sulfur- and nitrogen-co-doped hierarchical porous carbon catalyst, effectively alleviating the environmental pressure caused by traditional landfill or incineration. Through core-shell structure design and surface functional group regulation, this catalyst significantly improves the activation efficiency of potassium persulfate, enabling efficient degradation of recalcitrant organic pollutants in wastewater. It overcomes the shortcomings of traditional Fenton processes, such as pH sensitivity, difficulty in activated carbon regeneration, and low efficiency of biological methods. The preparation process is simple and environmentally friendly, requiring no precious metals or complex synthesis steps, thus reducing production costs. Simultaneously, the catalyst exhibits excellent stability and can be recycled multiple times, avoiding secondary pollution. Furthermore, this technology has wide applicability, operating stably over a wide pH range, providing an economical and efficient solution for the advanced treatment of industrial wastewater.

[0028] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the preparation process of a high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for wastewater treatment according to the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Please see Figure 1 The present invention relates to a high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for wastewater treatment and its preparation.

[0032] Example 1

[0033] Step 1: Sulfonation Pretreatment

[0034] Raw material processing: The waste non-woven fabric is mechanically crushed into 1-3 mm fragments to remove surface impurities.

[0035] Sulfonation reaction: Mix the shredded nonwoven fabric with 98% concentrated sulfuric acid at a mass ratio of 1:2 (nonwoven fabric: concentrated sulfuric acid) and place the mixture in a sealed reactor. Heat to 100℃ and maintain the temperature for 10 hours, stirring continuously (50 r / min) during the reaction.

[0036] Post-processing: After the reaction was completed, the mixture was cooled to room temperature and washed repeatedly with deionized water until the filtrate was neutral (pH=6.5-7.0). Then it was dried in an oven at 80℃ for 12 hours and ground through a 200-mesh sieve to obtain the sulfonated precursor.

[0037] Step 2: Nitrogen-doped segmented calcination

[0038] Mixed precursor: The sulfonated precursor and urea are mixed uniformly at a mass ratio of 1:9 (claim 7) and placed in an alumina crucible.

[0039] Segmented calcination:

[0040] First stage (formation of amorphous shell): Under nitrogen protection, the temperature is increased to 350°C at 10°C / min and held for 1 hour (claim 8).

[0041] Second stage (graphitized core formation): Continue to increase the temperature to 800℃ at a rate of 15℃ / min and hold for 2 hours.

[0042] Cooling: Allow to cool naturally to 200°C, then introduce nitrogen gas to accelerate cooling to room temperature, yielding the crude product.

[0043] Structural features:

[0044] Core-shell structure: The core is a highly graphitized carbon layer (Raman ID / IG=1.3), and the outer shell is an amorphous carbon layer with a thickness ratio of 1:3.

[0045] Sulfur and nitrogen doping: Sulfur exists as CS bonds and -SO3⁻ (XPS analysis), while nitrogen is distributed as pyridine nitrogen (398.5 eV) and graphitic nitrogen (401.2 eV).

[0046] Step 3: Post-oxidation treatment and pickling

[0047] Oxidation treatment: The crude product is placed in a tube furnace and an oxygen-containing mixed gas (10% O2 volume fraction) is introduced and treated at 400°C for 1 hour.

[0048] Acid washing purification: Ultrasonic cleaning with 0.3 mol / L hydrochloric acid solution for 40 minutes (frequency 40 kHz) to remove unreacted metal salts and impurities.

[0049] Drying: After acid washing, the material was dried in a vacuum drying oven at 100°C for 8 hours to obtain the final catalyst.

[0050] High-temperature oxidation: In an oxidizing atmosphere of 300~500℃, the surface of carbon materials reacts with oxygen to generate oxygen-containing functional groups. For example:

[0051] Carboxyl group (-COOH): Carbon atoms at the edge of the carbon skeleton are oxidized into carboxylic acid groups;

[0052] Hydroxyl group (-OH): An unsaturated site on the carbon surface reacts with oxygen or water vapor to form a hydroxyl group;

[0053] Quinone group (C=O): Some carbon atoms in the aromatic ring structure are oxidized to the quinone structure.

[0054] Surface functional group regulation:

[0055] Functional group ratio: carboxyl (-COOH) 45%, hydroxyl (-OH) 35%, quinone (C=O) 20% (XPS quantitative analysis), molar ratio 1:1.8:1.0.

[0056] Multi-level porous structure: BET specific surface area 720 m² / g, micropores (0.5-2 nm) account for 35%, mesopores (2-10 nm) account for 55%, and macropores (10-50 nm) account for 10%.

[0057] Performance testing

[0058] The prepared catalyst was ground through a 200-mesh sieve, and the product was weighed according to a solid-liquid ratio of 0.5 g / L. It was then thoroughly mixed with 100 mL of a 30 mg / L organic pollutant solution (including, but not limited to, tetracycline hydrochloride, carbamazepine, and bisphenol A). The mixture was placed in a 25°C air bath shaker, and then 0.5 mM potassium persulfate was added and reacted for 30 min. The shaker speed was set to 150 r / min.

[0059] After the oxidation reaction was completed, the solution was filtered through a 0.22 μm PES filter to obtain a clear supernatant. The concentration of organic matter (including, but not limited to, tetracycline hydrochloride, carbamazepine, and bisphenol A) in the supernatant was determined by ultraviolet spectrophotometry or liquid chromatography, and the organic micropollutant removal rate of the product was calculated according to formula (1). The specific organic micropollutant removal rates were tetracycline hydrochloride, carbamazepine, and bisphenol A, respectively.

[0060] Ƞ=( - )÷ ×100% (1)

[0061] In the formula, (mg / L) represents the initial pollutant concentration, i.e., the measured concentration of organic pollutants in the tailwater before the reaction. (mg / L) represents the final pollutant concentration, i.e., the measured concentration of organic pollutants after the reaction. The test results are shown in Table 1 below.

[0062] Table 1

[0063] Types of pollutants Initial concentration (mg / L) Final concentration (mg / L) Removal rate (%) Tetracycline hydrochloride 30 3.9 87.0 Carbamazepine 30 4.5 85.0 Bisphenol A 30 3.0 90.0

[0064] Example 2

[0065] The effect of different urea ratios on catalyst performance;

[0066] The method of Example 1 is used, except that the mixing ratio of the sulfonated precursor and urea in step two is 1:6.

[0067] Test results:

[0068] The removal rate of bisphenol A was 85%, the removal rate of tetracycline hydrochloride was 78%, and the removal rate of carbamazepine was 82%.

[0069] Example 3

[0070] The effect of different calcination temperatures on catalyst performance;

[0071] The method of Example 1 was used, except that the calcination temperature in the second stage of step two was 700℃. Test results:

[0072] The removal rates were 92% for tetracycline hydrochloride, 88% for carbamazepine, and 90% for bisphenol A.

[0073] Comparative Example 1

[0074] Comparative experiments with low sulfonation ratios;

[0075] The method of Example 1 is used, except that the mass ratio of waste nonwoven fabric to concentrated sulfuric acid in step one is 1:1.

[0076] Test results:

[0077] The overall removal rate of organic pollutants was 55%.

[0078] Comparative Example 2

[0079] Comparative experiment with moderate sulfonation ratio;

[0080] The method of Example 1 is used, except that the mass ratio of waste nonwoven fabric to concentrated sulfuric acid in step one is 1:1.5.

[0081] Test results:

[0082] The overall removal rate of organic pollutants was 68%.

[0083] Comparative Example 3

[0084] Comparative experiment to optimize sulfonation ratio

[0085] The method of Example 1 is used, except that the mass ratio of waste nonwoven fabric to concentrated sulfuric acid in step one is 1:2.

[0086] Test results:

[0087] The overall removal rate of organic pollutants was 85%.

[0088] Comparative Example 4

[0089] Comparative experiment with high sulfonation ratio

[0090] The method of Example 1 was used, except that the mass ratio of waste nonwoven fabric to concentrated sulfuric acid in step one was 1:2.5. Test results: The total removal rate of organic pollutants was 72%.

[0091] Summarize:

[0092] Examples 1-3 and Comparative Examples 1-4 systematically verified the catalyst preparation process and performance optimization. Example 1 used a sulfonation ratio of 1:2, a urea ratio of 1:9, staged calcination (350℃ / 800℃), and post-oxidation treatment to prepare a core-shell structured sulfur-nitrogen-doped carbon material. Its hierarchical pore distribution (35% micropores, 55% mesopores, 10% macropores) and surface functional groups (carboxyl:hydroxy:quinone = 1:1.8:1.0) showed significant synergistic effects, achieving removal rates of 87%, 85%, and 90% for tetracycline hydrochloride, carbamazepine, and bisphenol A, respectively. Examples 2 (urea ratio 1:6) and 3 (calcination temperature 700℃) showed that reducing the urea ratio led to a decrease in the bisphenol A removal rate to 85%, while low-temperature calcination increased the tetracycline hydrochloride removal rate to 92%. In Comparative Examples 1-4, when the sulfonation ratio increased from 1:1 to 1:2.5, the total removal rate increased from 55% to 85% (1:2 was optimal). However, an excessively high ratio (1:2.5) caused pore structure collapse due to over-sulfonation, resulting in a removal rate drop to 72%. In summary, this technology, through precise control of the sulfonation ratio, calcination process, and functional group distribution, achieves efficient resource recovery and deep removal of pollutants from waste nonwoven fabrics, combining low cost, high activity, and environmental friendliness.

Claims

1. A high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for wastewater treatment, characterized in that, The catalyst is a sulfur-nitrogen co-doped hierarchical porous carbon material, comprising: Microporous structure, with pore sizes of 0.5-2 nm, accounting for 30-50%; Mesoporous structure, with a pore size of 2-10 nm, accounting for 40-60%; Macroporous structure, with pore sizes of 10-50 nm, accounting for 10-20%; Among them, sulfur is represented by CSC and - - It exists in the form of functional groups, with nitrogen in the form of pyridine nitrogen, pyrrole nitrogen and graphitic nitrogen, and sulfur and nitrogen atoms are distributed in a gradient in the carbon skeleton.

2. The high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for wastewater treatment according to claim 1, characterized in that, The catalyst has functional groups formed on its surface, including carboxyl, hydroxyl and quinone groups, with a molar ratio of 1:1.5-2.5:0.8-1.

2.

3. The high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for wastewater treatment according to claim 1, characterized in that, The catalyst has a core-shell structure, with a core of highly graphitized carbon layers and an outer shell of amorphous carbon layers rich in sulfur and nitrogen functional groups, and the thickness ratio of the core to the outer shell is 1:2 to 1:

5.

4. The high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for wastewater treatment according to claim 1, characterized in that, The sulfur-nitrogen-doped carbon material has a specific surface area of ​​500-800 m² / g, a pore size distribution of 0.5-50 nm, a sulfur content of 3-5 wt%, and a nitrogen content of 5-8 wt%.

5. The high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for wastewater treatment according to claim 1, characterized in that, In the surface functional groups, carboxyl groups account for 40-50% of the total functional groups, hydroxyl groups account for 30-40%, and quinone groups account for 20-30%.

6. A high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for wastewater treatment, characterized in that, The preparation of the high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for tailwater treatment as described in claims 1-5 includes the following steps: Step 1, sulfonation pretreatment: Mix the crushed waste nonwoven fabric with concentrated sulfuric acid at a mass ratio of 1:1.5-1:3, react at 90-120℃ for 6-12 hours, wash, dry and grind through a 100-200 mesh sieve to obtain the sulfonation precursor; Step 2, nitrogen-doped calcination: The sulfonated precursor and urea are mixed at a mass ratio of 1:6 to 1:12, and calcined in stages under a nitrogen atmosphere. First stage: Increase the temperature to 300-400℃ at a rate of 5-10℃ / min, and hold for 0.5-1 hour; Second stage: Increase the temperature to 700-900℃ at 10-15℃ / min, hold for 1-2 hours, and cool to room temperature to obtain crude product; Step 3, post-oxidation treatment: The crude product is treated in air or an oxygen-containing mixed gas (O2 volume fraction 5-20%) at 300-500℃ for 0.5-1 hour. After cooling, it is acid washed and dried to form surface hydroxyl, carboxyl and quinone functional groups, thus obtaining a core-shell structured sulfur and nitrogen-doped carbon material, and obtaining the catalyst.

7. The preparation of the high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for tailwater treatment according to claim 6, characterized in that, The segmented calcination process in step two is used to control the core-shell structure: The first stage involves low-temperature calcination to form an amorphous carbon shell. The second stage of high-temperature calcination promotes the graphitization of the core.

8. The preparation of the high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for tailwater treatment according to claim 6, characterized in that, In step three, the oxidation post-treatment temperature is 400-450℃ and the treatment time is 1 hour, in order to control the ratio of surface hydroxyl groups, carboxyl groups and quinone groups.

9. The preparation of the high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for tailwater treatment according to claim 6, characterized in that, The pickling in step three uses a 0.1-0.5 mol / L hydrochloric acid solution and the pickling time is 30-60 minutes to remove unreacted metal impurities and stabilize surface functional groups.

10. The preparation of the high-efficiency potassium persulfate catalyst derived from waste nonwoven fabric for tailwater treatment according to claim 6, characterized in that, In step one, the mass ratio of concentrated sulfuric acid to nonwoven fabric is 1:2, the reaction temperature is 100℃, and the reaction time is 10 hours.

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