A sludge-based granule, its method of preparation and use in wastewater treatment

Abstract

The present application provides a kind of sludge-based particles and its preparation method and application in wastewater treatment.The sludge-based particles of the present application include sludge-based carbon skeleton, iron species, manganese species and cerium species loaded or embedded in the sludge-based carbon skeleton, nitrogen-sulfur co-doped carbon layer and alginate-chitosan composite granulation layer, and the surface contains oxygen vacancy or defect oxygen site.The present application realizes cobalt-free, recyclable, and efficient activation of persulfate suitable for near-neutral complex municipal wastewater system, with high efficiency of antibiotic micropollutant deep removal, low risk of metal dissolution, strong water quality disturbance resistance, good reuse stability and excellent continuous operation adaptability, etc., and has good application prospect in the fields of municipal wastewater deep treatment, tail water upgrading, reclaimed water safety reuse and high-value utilization of municipal sludge.

Description

Technical Field

[0001] This invention relates to the field of urban wastewater treatment technology, and in particular to a sludge-based granule, its preparation method, and its application in wastewater treatment. Background Technology

[0002] Secondary effluent, tailwater, and pre-treated water for reuse in urban wastewater treatment plants often still contain a certain amount of recalcitrant organic micropollutants. Among them, antibiotics such as sulfonamides, quinolones, and tetracyclines have become key pollutants that need to be controlled in the field of advanced urban wastewater treatment due to their environmental persistence, biological activity, and potential risks of inducing the spread of resistance genes.

[0003] Existing persulfate-activated catalysts for urban wastewater treatment face several challenges in long-term applications. These include potential metal leaching during operation, leading to secondary pollution and ecological risks. Furthermore, their limited metal valence state cycling capacity and insufficient active site regeneration efficiency in near-neutral urban wastewater systems make it difficult to balance catalytic efficiency and operational stability. Additionally, existing catalysts are mostly used in powder form, making recovery difficult and potentially increasing the burden on subsequent solid-liquid separation, which is detrimental to fixed-bed, magnetic separation, or engineered continuous operation. Moreover, urban wastewater commonly contains coexisting components such as chloride ions, bicarbonate ions, nitrate ions, phosphates, and natural organic matter. These components may quench free radicals, compete for active sites, or affect oxidation pathways, thereby reducing the stability and adaptability of the catalytic system under complex water quality conditions. Finally, urban wastewater treatment plants generate large quantities of wastewater with high moisture content and high disposal costs. Traditional landfilling, incineration, or low-value utilization methods are insufficient to fully realize the high-value conversion of organic matter, inorganic minerals, and trace metal resources within this wastewater.

[0004] Therefore, it is necessary to provide a sludge-based particle, its preparation method, and its application, which uses municipal waste sludge or sludge carbon as a carbon source, is cobalt-free, multi-metal synergistic, heteroatom doped, and is suitable for engineering applications in urban wastewater treatment, in order to solve the above problems simultaneously. Summary of the Invention

[0005] The first aspect of the present invention provides sludge-based particles, comprising a sludge-based carbon skeleton, iron species, manganese species and cerium species loaded or embedded in the sludge-based carbon skeleton, a nitrogen-sulfur co-doped carbon layer and an alginate-chitosan composite granulation layer. The sludge-based granules are made by using municipal waste sludge or sludge carbon as a carbon source and iron salts, manganese salts, cerium salts, nitrogen- and sulfur-containing ligands and volatile pore-forming agents as modifying components, through oxygen-limited pyrolysis, dilute acid washing and compound granulation. Based on 100 parts of dry sludge or sludge carbon, the amount of iron added is 1.0 to 8.0 parts, the amount of manganese added is 0.2 to 5.0 parts, the amount of cerium added is 0.1 to 3.0 parts, the amount of nitrogen-sulfur ligands added is 5 to 25 parts, and the amount of volatile pore-forming agent added is 5 to 35 parts.

[0006] Preferably, the sludge-based particles have a dry particle size of 0.8~4.0 mm and a specific surface area of ​​100~250 m². 2 / g, with a saturation magnetization of 10~30 emu / g, can be collected and recycled under the action of an external magnetic field.

[0007] Preferably, the iron species include Fe3O4 and Fe. 0 Fe 2+ Coordination species and Fe 3+ At least one of the coordination species; the manganese species includes Mn 2+ Mn 3+ Mn 4+ At least one of oxides or coordination species; the cerium species includes Ce 3+ Ce 4+ At least one of oxides or coordination species.

[0008] Preferably, the nitrogen-sulfur co-doped carbon layer includes at least one of pyrrole nitrogen, graphitic nitrogen, thiophene sulfur, and sulfur oxide species; the surface of the sludge-based particles contains oxygen vacancies or defective oxygen sites.

[0009] Preferably, the iron salt is selected from at least one of ferric chloride, ferric nitrate, ferric sulfate, and ferric acetate; the manganese salt is selected from at least one of manganese acetate, manganese nitrate, manganese sulfate, and manganese chloride; the cerium salt is selected from at least one of cerium nitrate, cerium chloride, and cerium ammonium sulfate; the nitrogen-sulfur ligand is selected from at least one of thiourea, cysteine, and thioacetamide; and the volatile pore-forming agent is selected from at least one of ammonium bicarbonate, urea, and melamine.

[0010] A second aspect of the present invention provides a method for preparing the sludge-based granules, comprising the following steps: S1. Dry, crush and sieve municipal waste sludge or sludge char to obtain sludge-based raw material; S2. Add iron salt, manganese salt, cerium salt, nitrogen-sulfur ligand and volatile pore-forming agent to solvent, add the sludge-based raw material, stir, impregnate, age and dry to obtain metal-ligand modified sludge precursor; S3. The metal-ligand modified sludge precursor is placed in an oxygen-limited atmosphere and pyrolyzed at 500~800℃ for 0.5~4h to obtain iron-manganese-cerium-nitrogen-sulfur co-doped sludge-based magnetic carbon. S4. The iron-manganese-cerium-nitrogen-sulfur co-doped sludge-based magnetic carbon is washed with dilute acid and water until it is nearly neutral and then dried to obtain sludge-based catalytic powder. S5. The sludge-based catalytic powder is mixed with sodium alginate solution to form a slurry. The slurry is then added dropwise to a crosslinking solution containing calcium ions and chitosan to crosslink into granules. The granules are then washed and dried to obtain the sludge-based particles.

[0011] Preferably, in step S1, the municipal waste sludge is residual activated sludge from an urban wastewater treatment plant; the sludge carbon is obtained by pre-carbonizing municipal waste sludge at 300~500℃ under an oxygen-limited atmosphere for 0.5~2 h.

[0012] Preferably, in step S3, the oxygen-limiting atmosphere is nitrogen, argon, a nitrogen-carbon dioxide mixture, or an oxygen-deficient atmosphere with an oxygen content not exceeding 5% by volume; the heating rate is 2~10℃ / min.

[0013] Preferably, in step S4, the dilute acid washing is performed using a 0.01~0.5 mol / L hydrochloric acid, acetic acid, or citric acid solution for 5~120 min, followed by washing with deionized water until the pH of the washing solution is 6.5~7.5.

[0014] Preferably, in step S5, the mass concentration of sodium alginate solution is 1.0~4.0%, the mass concentration of chitosan is 0.1~1.5%, the mass concentration of calcium ions is 0.5~5.0%, and the cross-linking time is 0.5~12 h.

[0015] The third aspect of the present invention provides the application of the sludge-based particles in urban wastewater treatment, wherein the sludge-based particles are added to the secondary effluent or tailwater of an urban wastewater treatment plant containing antibiotic micropollutants, and persulfate is added for catalytic oxidation treatment.

[0016] Preferably, the antibiotic micropollutant includes at least one of sulfonamides, quinolones, and tetracyclines; the persulfate is a potassium persulfate compound salt, sodium persulfate, or ammonium persulfate; the treatment conditions are: sludge-based granular dosage 0.1~5.0 g / L, persulfate concentration 0.02~2.0 mmol / L, reaction time 5~120 min, pH 5.5~8.5, and the persulfate concentration is expressed as HSO5. - count.

[0017] Preferably, the persulfate is based on the UV of urban sewage. 254 Alternatively, COD can be administered in tiers: When UV 254 ≤0.10 cm -1 Or, when COD ≤ 30 mg / L, the concentration of persulfate added should be 0.05~0.20 mmol / L; When 0.10 cm -1 <UV 254 ≤0.20 cm -1 Or, when 30 mg / L < COD ≤ 60 mg / L, the concentration of persulfate added should be 0.20~0.50 mmol / L; When UV 254 >0.20 cm -1 Or, when COD > 60 mg / L, the concentration of persulfate added should be 0.50~1.00 mmol / L; When the UV of the target water quality 254 When COD and COD belong to different levels, the dosage corresponding to the higher concentration level shall be used; When the total concentration of the target antibiotic is known, the molar ratio of persulfate to the total amount of the target antibiotic is (50~2000):1.

[0018] Preferably, after the reaction is completed, the sludge-based particles are recovered by magnetic separation, screening, sedimentation, or fixed bed retention; the recovered sludge-based particles are washed with water and reused at least 5 times, and the target antibiotic removal rate is maintained at more than 80% of the initial removal rate.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention uses municipal waste sludge or sludge carbon as a carbon source to prepare sludge-based particles, which transform the organic matter, inorganic ash and some trace elements in the sludge into a porous carbon-inorganic composite framework during oxygen-limited pyrolysis. This provides a structural basis for loading of metal active components, heteroatom doping and pollutant adsorption, which can reduce the raw material cost of catalytic materials and improve the level of sludge resource utilization.

[0020] This invention employs a cobalt-free multi-metal synergistic catalytic system of iron, manganese, and cerium, reducing the risk of cobalt leaching. Iron, manganese, and cerium species form oxides, zero-valent species, or coordinated species within the catalytic particles. Synergistic electron transfer occurs between the multivalent metals, promoting persulfate activation and active site regeneration, thereby improving the degradation efficiency of antibiotic micropollutants under near-neutral conditions.

[0021] This invention introduces nitrogen- and sulfur-containing ligands, which, after pyrolysis, form nitrogen- and sulfur co-doping sites such as pyrrole nitrogen, graphitic nitrogen, thiophene sulfur, and sulfur oxides in the sludge-based carbon skeleton. These sites may also be accompanied by the formation of defect sites or oxygen vacancies, thereby regulating the electron distribution of the carbon skeleton, improving the adsorption and electron transfer capacity of persulfate on the particle surface, and potentially promoting multi-pathway oxidation processes. This invention exhibits better adaptability and operational stability in complex urban wastewater containing coexisting components such as chloride ions, bicarbonate ions, nitrate ions, phosphates, and natural organic matter.

[0022] This invention removes unstable or easily soluble metal components through dilute acid washing, optimizes the exposure of active sites on the particle surface, and reduces the risk of leaching of metals such as iron, manganese, and cerium during operation, thereby improving the safety of treated water and the stability of the catalytic material for repeated use. By using alginate-chitosan composite granulation, this invention fixes sludge-based catalytic powder into millimeter-sized particles, improving the material's mechanical stability, hydrophilicity, resistance to leaching, and ease of recovery. It is suitable for magnetic separation, screening, sedimentation, or continuous operation in fixed beds.

[0023] The sludge-based granules provided by this invention can activate persulfate within a near-neutral pH range of 5.5 to 8.5, making them suitable for common water quality conditions in secondary effluent, tailwater, and pre-treatment water for reclaimed water reuse in urban wastewater treatment plants. They require no significant adjustment of the water's pH and operate under mild conditions. They can be customized according to the UV index of urban wastewater. 254 Alternatively, the dosage of persulfate can be tiered according to the COD level to match the organic load of the influent, which helps to improve the utilization efficiency of oxidant, reduce operating costs, and enhance the controllability of actual engineering operation. Detailed Implementation

[0024] The urban wastewater used in the examples is secondary effluent from an urban wastewater treatment plant. To ensure comparability between different treatment groups, in some examples, a target antibiotic was added to the urban wastewater as a challenge simulated pollutant. This added concentration was used to evaluate the removal capacity of the catalytic system and does not represent the actual environmental concentration of the antibiotic in the urban wastewater.

[0025] Detection methods: Sulfamethoxazole, ciprofloxacin, and tetracycline were determined by high performance liquid chromatography or liquid chromatography-mass spectrometry; UV 254 The concentrations of Fe, Mn, and Ce leaching were determined by ultraviolet spectrophotometry; the concentrations of Fe, Mn, and Ce leaching were determined by inductively coupled plasma atomic emission spectrometry or inductively coupled plasma mass spectrometry; the turbidity of the effluent was determined by a turbidimeter; and the material recovery rate was calculated as the ratio of the mass of the recovered and dried material to the mass of the added material.

[0026] Example 1 (1) Preparation of sludge-based granules: Excess sludge from a municipal wastewater treatment plant was dried at 105℃ to constant weight, pulverized, and passed through an 80-mesh sieve to obtain dry-based sludge powder. 10.0 g of the dry-based sludge powder was weighed and added to 150 mL of deionized water, and stirred for 30 min. Then, 2.5 g of FeCl3·6H2O, 1.2 g of Mn(CH3COO)2·4H2O, 0.6 g of Ce(NO3)3·6H2O, 1.5 g of thiourea, and 2.0 g of ammonium bicarbonate were added, and stirring continued for 6 h, followed by aging for 12 h. The resulting mixture was dried at 80℃ to obtain a metal-ligand modified sludge precursor. All metal additions were calculated by elemental mass.

[0027] The above precursor was placed in a tube furnace and heated to 650℃ at a rate of 5℃ / min under a nitrogen atmosphere, held at that temperature for 2 h, and then naturally cooled to room temperature to obtain a crude product of iron-manganese-cerium-nitrogen-sulfur co-doped sludge-based magnetic carbon. The crude product was added to a 0.1 mol / L hydrochloric acid solution and washed with shaking for 30 min at a solid-liquid ratio of 1 g:50 mL. Then, it was washed with deionized water until the pH of the washing solution reached 7.0, and dried at 80℃ for 12 h to obtain sludge-based catalyst powder.

[0028] 4.0 g of sludge-based catalyst powder was weighed and added to 100 mL of 2.0 wt% sodium alginate solution, and stirred to form a homogeneous slurry. The slurry was then added dropwise via a peristaltic pump to a crosslinking solution containing 2.0 wt% CaCl2 and 0.5 wt% chitosan (the chitosan was pre-dissolved in 2.0 wt% acetic acid solution, and the pH was adjusted to 4.5). Crosslinking was carried out for 4 h, the particles were collected by filtration, washed three times with deionized water, and dried at 40 °C to obtain sludge-based iron, manganese, cerium, nitrogen, and sulfur co-doped particles. The obtained particles had a dry particle size of 2.0 ± 0.5 mm, exhibited magnetic responsiveness, and could be aggregated and recovered under the action of an external magnetic field.

[0029] (2) Urban wastewater treatment experiment: The secondary effluent from the municipal wastewater treatment plant was used as the treatment target, with initial water quality of: pH 7.3, UV... 254 It is 0.162cm -1 Sulfamethoxazole, ciprofloxacin, and tetracycline were added to the water sample as target antibiotic micropollutants, with an initial concentration of 200 μg / L for each.

[0030] Add 100 mL of water sample to a 250 mL Erlenmeyer flask, add 0.5 g / L of the particles from step (1), and add 0.30 mmol / L of persulfate. React at 25℃ and 150 r / min for 60 min. After the reaction, recover the particles by magnetic separation, and take the supernatant to detect the concentration of the target pollutant and UV. 254 And the concentration of metal leaching.

[0031] Example 2 The difference from Example 1 is that the carbon source is sludge char prepared by pre-carbonizing municipal waste sludge at 400°C under nitrogen atmosphere for 1 h, and the amount of sludge char is 10.0 g.

[0032] Example 3 The difference from Example 1 is that the urban wastewater treatment method is changed from intermittent reaction to fixed-bed continuous flow reaction. The sludge-based iron, manganese, cerium, nitrogen, and sulfur co-doped particles from Example 1 are packed into an plexiglass fixed-bed column to a height of 30 cm. The influent is secondary effluent from an urban wastewater treatment plant, the initial concentration of the target antibiotics is 100 μg / L, and the empty bed contact time is 30 min.

[0033] Persulfate according to influent UV 254 Tiered application: When UV 254 ≤0.10 cm -1 At that time, the concentration of persulfate added was 0.15 mmol / L; when 0.10 cm -1 <UV 254 ≤0.20 cm -1 At that time, the concentration of persulfate added was 0.30 mmol / L; when UV 254 >0.20 cm -1 At that time, the concentration of persulfate added was 0.60 mmol / L. During continuous operation, samples were taken periodically to detect the concentration of the target pollutant and UV. 254 The turbidity of the effluent and the material retention status.

[0034] Comparative Example 1 The difference from Example 1 is that Ce(NO3)3·6H2O is not added during the preparation process.

[0035] Comparative Example 2 The difference from Example 1 is that thiourea is not added during the preparation process.

[0036] Comparative Example 3 The difference from Example 1 is that: the alginate-chitosan composite granulation is not carried out in the preparation process, and the sludge-based catalytic powder after dilute acid washing is directly used for urban sewage treatment.

[0037] Comparative Example 4 The difference from Example 1 is that no dilute acid washing treatment is performed during the preparation process. That is, after pyrolysis, the product is washed with water and dried, and then directly granulated into alginate-chitosan composites.

[0038] Comparative Example 5 The difference from Example 1 is that no sludge-based granules were added in the urban sewage treatment experiment; only 0.30 mmol / L persulfate was added.

[0039] Comparative Example 6 The difference from Example 1 is that persulfate was not added in the urban sewage treatment experiment, but only 0.5 g / L of the sludge-based granules from Example 1 was added.

[0040] Table 1 Comparison of treatment effects (n=3, mean ± standard deviation)

[0041] Table 2. Stability results for repeated use and continuous operation (n=3, mean ± standard deviation)

[0042] Note: Examples 1, 3, and 4 are results of recycling and reuse; Example 3 is the result of fixed-bed continuous treatment of secondary effluent from an urban wastewater treatment plant, with an empty bed contact time of 30 min and sulfate treatment according to the influent UV. 254 The material is added in stages. The material recovery rate or retention rate is the proportion of the mass of material obtained after magnetic separation, sieving, or fixed-bed retention after the reaction is completed to the mass of the added material.

[0043] Example 4 To evaluate the adaptability of sludge-based magnetic catalytic particles in complex urban wastewater, a coexistence component interference experiment was conducted using sludge-based iron-manganese-cerium-nitrogen-sulfur co-doped particles from Example 1. The experimental water samples, target antibiotic types and initial concentrations, catalytic particle dosage, persulfate concentration, reaction temperature, rotation speed, and reaction time were all the same as in Example 1. Cl was added to the water samples... - HCO3 - NO3 - PO4 3- The treatment group containing humic acid, without any interfering substances, served as the blank control group.

[0044] Table 3. Effect of coexisting components on antibiotic removal efficiency (n=3, mean ± standard deviation)

[0045] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A sludge-based granule, characterized in that, It includes a sludge-based carbon skeleton, iron species, manganese species and cerium species loaded or embedded in the sludge-based carbon skeleton, a nitrogen-sulfur co-doped carbon layer and an alginate-chitosan composite granulation layer, wherein the particle surface or exposed pore surface contains oxygen vacancies or defective oxygen sites. The sludge-based granules are made by using municipal waste sludge or sludge carbon as a carbon source and iron salts, manganese salts, cerium salts, nitrogen- and sulfur-containing ligands and volatile pore-forming agents as modifying components, through oxygen-limited pyrolysis, dilute acid washing and compound granulation. Based on 100 parts by weight of dry sludge or sludge carbon, the amount of iron added is 1.0 to 8.0 parts, the amount of manganese added is 0.2 to 5.0 parts, the amount of cerium added is 0.1 to 3.0 parts, the amount of nitrogen-sulfur ligands added is 5 to 25 parts, and the amount of volatile pore-forming agent added is 5 to 35 parts. The amounts of iron, manganese and cerium added are all based on the mass of the corresponding elements.

2. The sludge-based granules according to claim 1, characterized in that, The sludge-based granules have a dry particle size of 0.8–4.0 mm and a specific surface area of ​​100–250 m². 2 / g, with a saturation magnetization of 10~30 emu / g.

3. The sludge-based granules according to claim 1, characterized in that, The iron species include Fe3O4 and Fe. 0 Fe 2+ Coordination species and Fe 3+ At least one of the coordination species; the manganese species includes Mn 2+ Mn 3+ Mn 4+ At least one of oxides or coordination species; the cerium species includes Ce 3+ Ce 4+ The nitrogen-sulfur co-doped carbon layer comprises at least one of pyrrole nitrogen, graphitic nitrogen, thiophene sulfur, and sulfur oxide species; the iron salt is selected from at least one of ferric chloride, ferric nitrate, ferric sulfate, and ferric acetate; the manganese salt is selected from at least one of manganese acetate, manganese nitrate, manganese sulfate, and manganese chloride; the cerium salt is selected from at least one of cerium nitrate, cerium chloride, and cerium ammonium sulfate; the nitrogen-sulfur ligand is selected from at least one of thiourea, cysteine, and thioacetamide; and the volatile pore-forming agent is selected from at least one of ammonium bicarbonate, urea, and melamine.

4. The method for preparing sludge-based granules according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Dry, crush and sieve municipal waste sludge or sludge char to obtain sludge-based raw material; S2. Add iron salt, manganese salt, cerium salt, nitrogen-sulfur ligand and volatile pore-forming agent to solvent, add the sludge-based raw material, stir, impregnate, age and dry to obtain metal-ligand modified sludge precursor; S3. The metal-ligand modified sludge precursor is pyrolyzed in an oxygen-limited atmosphere to obtain iron-manganese-cerium-nitrogen-sulfur co-doped sludge-based magnetic carbon. S4. The iron-manganese-cerium-nitrogen-sulfur co-doped sludge-based magnetic carbon is washed with dilute acid and water until it is nearly neutral and then dried to obtain sludge-based catalytic powder. S5. The sludge-based catalytic powder is mixed with sodium alginate solution to form a slurry. The slurry is then added dropwise to a crosslinking solution containing calcium ions and chitosan to crosslink into granules. The granules are then washed and dried to obtain the sludge-based particles.

5. The preparation method according to claim 4, characterized in that, In step S1, the municipal waste sludge is the residual activated sludge from an urban wastewater treatment plant; the sludge carbon is obtained by pre-carbonizing the municipal waste sludge at 300~500℃ under an oxygen-limited atmosphere for 0.5~2 h.

6. The preparation method according to claim 4, characterized in that, In step S3, the oxygen-limiting atmosphere is nitrogen, argon, a nitrogen-carbon dioxide mixture, or an oxygen-deficient atmosphere with an oxygen content not exceeding 5% by volume; the heating rate is 2~10℃ / min, the pyrolysis temperature is 500~800℃, and the pyrolysis time is 0.5~4 h.

7. An application of sludge-based granules in urban wastewater treatment, characterized in that, The sludge-based particles are the sludge-based particles according to any one of claims 1 to 3 or the sludge-based particles prepared by the method according to any one of claims 4 to 6. The application method is as follows: the sludge-based particles are added to the secondary effluent or tailwater of an urban wastewater treatment plant containing antibiotic micropollutants, and persulfate is added for catalytic oxidation treatment.

8. The application according to claim 7, characterized in that, The treatment conditions are as follows: sludge-based granule dosage 0.1~5.0 g / L, persulfate concentration 0.02~2.0 mmol / L, reaction time 5~120 min, pH 5.5~8.

5.

9. The application according to claim 7, characterized in that, The antibiotic microcontaminants include at least one of sulfonamides, quinolones, and tetracyclines; the persulfate is a potassium persulfate complex salt, sodium persulfate, or ammonium persulfate.

10. The application according to claim 8, characterized in that, The persulfate is based on the UV of urban sewage. 254 Alternatively, COD can be administered in tiers: When UV 254 ≤0.10 cm -1 Or, when COD ≤ 30 mg / L, the concentration of persulfate added should be 0.05~0.20 mmol / L; When 0.10 cm -1 <UV 254 ≤0.20 cm -1 Or, when 30 mg / L < COD ≤ 60 mg / L, the concentration of persulfate added should be 0.20~0.50 mmol / L; When UV 254 >0.20 cm -1 Or, when COD > 60 mg / L, the concentration of persulfate added should be 0.50~1.00 mmol / L; When the total concentration of the target antibiotic is known, the molar ratio of persulfate to the total amount of the target antibiotic is (50~2000):1.

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