Preparation of coagulated iron mud derived catalyst and application of coagulated iron mud derived catalyst in removal of antibiotics

Abstract

The invention relates to the technical field of advanced oxidative degradation of antibiotics, in particular to preparation and application of a coagulated iron mud derived catalyst. According to the method, by adjusting the pyrolysis temperature and the pyrolysis time and utilizing inherent transition metal iron in the coagulated iron sludge, structural regulation and control of the coagulated iron sludge derivative catalyst are achieved, the antibiotic removal performance is improved, and the removal rate of tetracycline within 16 min is 88%. The invention provides a method for preparing the catalyst by utilizing inherent metal of the coagulated iron sludge without adding other metal, and the method is a green, economical and sustainable coagulated iron sludge recycling strategy.

Description

Technical Field

[0001] The present invention belongs to the technical field of advanced oxidation water treatment, and particularly relates to a method for preparing a catalyst from solid waste coagulated iron sludge as a raw material and its application in activating persulfate to degrade tetracycline antibiotics in wastewater. Background Art

[0002] Antibiotics are new pollutants that are key controlled in China. Traditional biological, physical or chemical treatment technologies (such as activated sludge method, coagulation, adsorption, etc.) have limited removal effects on trace antibiotics and are prone to cause secondary pollution to the environment. Advanced oxidation technology uses in-situ generated reactive oxygen species (ROS) to directly mineralize antibiotics, which can achieve efficient and rapid degradation of antibiotics. At present, transition metal catalysts can activate oxidants to generate ROS, but traditional transition metal catalysts often need to add additional metal precursors to improve the activity of the catalyst, resulting in problems such as high preparation cost, low metal utilization rate, high metal leaching, and poor stability, which are not conducive to the efficient removal of antibiotics.

[0003] Coagulated iron sludge, as a solid waste inevitably generated in water treatment plants, contains a large amount of iron elements. Existing resource utilization technologies have problems such as low iron element utilization rate and low product added value, and there is an urgent need to develop a high-value utilization technology for coagulated iron sludge. Pyrolyzing and carbonizing coagulated iron sludge to prepare a catalyst not only does not require additional metal precursors to "turn waste into treasure" with iron elements, but also can prepare coagulated iron sludge into a series of biomass carbon materials with high added value. However, existing patents (such as CN112495423A) pyrolyze iron sludge at a fixed temperature (such as 400°C), without revealing the influence mechanism of temperature-time co-regulation on the catalyst structure, resulting in unstable catalyst activity. Therefore, developing a method for resource utilization of coagulated iron sludge to prepare a catalyst, which can efficiently utilize the inherent iron elements, is of great significance in the field of antibiotic pollution control. Summary of the Invention

[0004] To solve the deficiencies of the prior art, the purpose of the present invention is to provide a method for preparing a catalyst using the inherent metals in coagulated iron sludge without adding other metals additionally, which is used for persistently and efficiently removing antibiotics in water, thereby solving the dual problems of sludge resource utilization and antibiotic sewage treatment.

[0005] Specifically, the technical solution provided by the present invention is as follows:

[0006] In the first aspect of the present invention, a preparation method of a coagulated iron sludge-derived catalyst is provided, which specifically includes: drying the coagulated iron sludge to constant weight and then performing pyrolysis carbonization to obtain it.

[0007] The coagulated iron sludge contains a large amount of organic matter, mostly organic polymers with a relatively high carbon content, which can be used as a carbon source for catalyst synthesis. During the carbonization process, the coagulated iron sludge can thermally decompose to generate a large number of intermediate products, such as monomers and dimers, and undergo cross-linking cyclization reactions to form a carbon material framework. At the same time, the iron in the coagulated iron sludge is reduced and loaded on the carbon surface, enabling the in-situ upgrading of transition metal elements.

[0008] Preferably, the pyrolysis temperature is 500 - 900 °C, and the pyrolysis time is 30 min - 90 min.

[0009] More preferably, the pyrolysis temperature is 800 °C, and the pyrolysis time is 60 min.

[0010] The purpose of drying here is to remove the moisture in the coagulated iron sludge as much as possible to avoid affecting the temperature and time of the subsequent pyrolysis carbonization process. Therefore, a blast drying method is specifically used for operation, and the drying temperature and time can be based on the actual ability to dry to a constant weight.

[0011] In the second aspect of the present invention, there is provided an application of the coagulated iron sludge-derived catalyst described in the first aspect in the advanced oxidation degradation of antibiotics.

[0012] Preferably, the coagulated iron sludge-derived catalyst and potassium persulfate are added to the tetracycline-containing wastewater; among them, the dosage of the coagulated iron sludge-derived catalyst is 0 - 0.04 g / L, the consumption of potassium persulfate is 0 - 0.4 g / L, and the concentration of tetracycline in the antibiotic wastewater is 20 mg / L.

[0013] More preferably, the dosage of the coagulated iron sludge-derived catalyst is 0.2 g / L, the consumption of potassium persulfate is 0.02 g / L, and the concentration of tetracycline in the antibiotic wastewater is 20 mg / L.

[0014] Under these conditions, the coagulated iron sludge-derived catalyst prepared in this application can achieve an 88% removal rate of tetracycline within 16 min.

[0015] The present invention realizes the structural regulation of the coagulated iron sludge-derived catalyst by adjusting the pyrolysis temperature and pyrolysis time, and utilizes the inherent transition metals in the coagulated iron sludge to improve the removal performance of antibiotics.

[0016] One or more embodiments of the present invention at least have the following benefits:

[0017] (1) The present invention uses coagulated iron sludge as a raw material to prepare a catalyst by utilizing the inherent transition metal elements in the coagulated iron sludge. The raw materials are easily available and the cost is low, and the potential upgrading of the inherent elements in the coagulated iron sludge can be realized.

[0018] (2) The present invention pyrolyzes and carbonizes coagulated iron sludge to obtain a catalyst with high performance. The preparation method adopted is simple and has low requirements for equipment.

[0019] (3) The present invention uses the coagulated iron sludge-derived catalyst to degrade and remove tetracycline in wastewater. Fe 0 serves as the main active site, and efficiently degrades tetracycline through free radical and non-free radical pathways, and exhibits good cycle stability. Description of the Drawings

[0020] Figures 1 to 4 is the TEM image of the catalyst obtained in Example 6;

[0021] Figure 5 is the XRD pattern of the catalyst obtained in Example 6;

[0022] Figure 6 is the influence of the catalyst dosage on the degradation of tetracycline in the system;

[0023] Figure 7 is the influence of the PMS consumption on the degradation of tetracycline in the system. Detailed Embodiments

[0024] The embodiments of the present invention involved in the following description are usually only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0025] In view of the fact that most existing catalysts need to add metal precursors, the present invention proposes a method for preparing a catalyst using the inherent transition metals in coagulated iron sludge and its application for removing antibiotics.

[0026] Example 1: This example provides a method for preparing a coagulated iron sludge-derived catalyst, and the specific method is as follows:

[0027] (1) Catalyst precursor: Take a certain coagulated iron sludge. There are no special restrictions on the sludge, that is, ordinary coagulated iron sludge actually generated; dry the coagulated iron sludge. The drying method is air drying or oven drying, and the oven drying method can be drying at 105 °C for 18 h until constant weight.

[0028] (2) Pyrolysis and carbonization: Pyrolyze the catalyst precursor. The pyrolysis temperature is 500 °C, and the pyrolysis time is 30 min. After cooling, grind for 5 min to obtain the coagulated iron sludge-derived catalyst.

[0029] Example 2: This example is basically the same as Example 1, and the difference is that: the pyrolysis temperature is 600 °C, and the pyrolysis time is 30 min.

[0030] Example 3: This example is basically the same as Example 1, except that the pyrolysis temperature is 700 °C and the pyrolysis time is 30 min.

[0031] Example 4: This example is basically the same as Example 1, except that the pyrolysis temperature is 800 °C and the pyrolysis time is 30 min.

[0032] Example 5: This example is basically the same as Example 1, except that the pyrolysis temperature is 900 °C and the pyrolysis time is 30 min.

[0033] Example 6: This example is basically the same as Example 1, except that the pyrolysis temperature is 800 °C and the pyrolysis time is 60 min.

[0034] Example 7: This example is basically the same as Example 1, except that the pyrolysis temperature is 800 °C and the pyrolysis time is 90 min.

[0035] Among them, by comparing the coagulated iron sludge catalysts obtained in Examples 1-7, a pyrolysis temperature of 800 °C and a pyrolysis time of 60 min were preferably selected. Further, the catalyst obtained in Example 6 was analyzed by HR-TEM ( Figures 1 to 4 ) and XRD patterns ( Figure 5 ). TEM and HR-TEM images showed that iron elements were uniformly dispersed and well encapsulated in the carbon layer; the lattice fringe spacings of 0.206 nm, 0.250 nm, and 0.297 nm corresponded to Fe 0 (110), FeO(111), and Fe3O4(220), respectively. The results of the XRD patterns showed that the diffraction peak at 2θ of 30.18° corresponded to the (220) crystal plane of Fe3O4 (JCPDS NO.19-0629); the diffraction peaks at 2θ of 36.16° and 41.98° corresponded to the (111) and (200) crystal planes of FeO (JCPDS NO.06-0615)

[148] ; the strong peak at 2θ of 44.58° and the peak at 64.94° were the (110) and (200) crystal planes of Fe 0 (JCPDS NO.06-0696), respectively. The above results showed that due to the increase in the carbonization temperature, iron hydroxide in the sludge was reduced to Fe3O4 and FeO, and further reduced to Fe 0 at 800 °C.

[0036] This finding clarified that the main catalytic active site of the coagulated iron sludge-derived catalyst during application was Fe 0 , and tetracycline could be degraded through free radical and non-free radical pathways. Based on the above findings, the application efficiency of the prepared catalyst was measured.

[0037] Application Example 1: For the catalyst obtained in Example 6, the degradation of tetracycline wastewater was carried out. 0 - 0.04 g / L of the coagulated iron sludge-derived catalyst and 0.2 g / L of potassium monopersulfate triplesalt (PMS) were respectively added to a 20 mg / L tetracycline (TC) solution. The dosage of the catalyst was 0 g / L, 0.005 g / L, 0.01 g / L, 0.02 g / L, 0.03 g / L, 0.04 g / L. The reaction solution was taken every 5 minutes, and the concentration of TC was measured at a wavelength of 358 nm using an ultraviolet-visible spectrophotometer. The results are as Figure 6 shown.

[0038] Due to the direct oxidation of PMS, without adding a catalyst, the degradation rate of TC can reach 42% within 30 minutes. As the dosage of the catalyst increased to 0.02 g / L, the degradation rate of TC reached 88% within only 16 minutes. When the dosage of the catalyst continued to increase (>0.02 g / L), the degradation efficiency of TC decreased.

[0039] Application Example 2: This example is basically the same as Application Example 1, except that: the dosage of the coagulated iron sludge was 0.02 g / L, and the consumption of PMA was 0 g / L, 0.025 g / L, 0.05 g / L, 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L.

[0040] The results are as Figure 7 shown. In the case of not adding PMS, due to the adsorption capacity of the catalyst, the removal rate of TC within 30 minutes was only 6.5%. Due to the sufficient contact between PMS and the catalyst, when the concentration of PMS increased to 0.3 g / L, the removal rate of TC reached 92%. When the concentration of PMS further increased to 0.4 g / L, the degradation efficiency of TC decreased.

[0041] Taking into account the environmental and economic benefits of the catalyst, 0.02 g / L was selected as the optimal dosage of the catalyst, and 0.2 g / L was selected as the optimal consumption of PMS.

Claims

1. A method for preparing a coagulated iron mud-derived catalyst, characterized in that: The following steps are involved: S1 dries a certain concrete iron mud to obtain a catalyst precursor; S2 pyrolyzes the above precursor to obtain a coagulated iron sludge derived catalyst.

2. The preparation method according to claim 1, characterized in that: In S1, the drying is air drying or oven drying, and the drying method can be drying at 105° C. for 18 hours to constant weight.

3. The preparation method according to claim 1, characterized in that: In S2, the pyrolysis temperature is 500-900°C, and the pyrolysis time is 30 min-90 min.

4. The preparation method according to any one of claims 1 to 3, wherein a coagulated iron mud-derived catalyst is obtained.

5. The catalyst obtained according to claim 4, characterized in that The pyrolysis temperature is 800°C and the pyrolysis time is 60 min to obtain Fe 0 Concrete iron sludge derived catalyst with main catalytic active sites.

6. The method for removing antibiotics using a coagulated iron mud-derived catalyst according to claim 5, characterized in that: The following steps are involved: S3 is configured with 20 mg / L tetracycline wastewater; S4 coagulated iron sludge derived catalyst and potassium persulfate are added to the wastewater containing tetracycline to achieve the degradation and removal of tetracycline.

7. The method for removing antibiotics using a coagulated iron sludge-derived catalyst according to claim 6, characterized in that: In the S4, the dosage of the coagulated iron mud derived catalyst is 0-0.04 g / L, and the consumption of potassium persulfate is 0-0.4 g / L.

8. The use according to claim 7, characterized in that: The 0.02 g / L is the optimal dosage of the coagulated iron sludge derived catalyst, and 0.2 g / L is the optimal consumption of PMS.

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