Composite catalyst, its preparation method and application in sludge treatment

Abstract

This invention discloses a composite catalyst, its preparation method, and its application in sludge treatment, belonging to the field of sludge treatment and environmental protection technology. The invention synthesizes an iron-carbon nanocomposite catalyst using ferric nitrate nonahydrate, antibiotic bacterial residue, and melamine as precursors. The resulting catalyst can, on the one hand, activate ammonium persulfate to generate free radicals that disrupt the water-locking structure of the sludge, enhancing its hydrophobicity and thus improving dewatering efficiency. On the other hand, the Fe species in the composite catalyst activates ammonium persulfate to form Fe... 3+ Fe 3+ The hydrolysis generates ferric hydroxide colloids that can adsorb sludge particles, neutralize surface charges, thereby reducing interparticle repulsion, promoting floc aggregation, and enhancing dewatering efficiency. The advanced oxidation process of ammonium persulfate catalyzed by iron-carbon nanocomposite catalysts also achieves the removal of antibiotic resistance genes from sludge.

Description

Technical Field

[0001] This invention belongs to the field of sludge treatment and environmental protection technology, specifically relating to a composite catalyst, its preparation method, and its application in sludge treatment. Background Technology

[0002] Activated sludge technology is widely used in wastewater treatment plants worldwide to treat municipal wastewater, a process that generates large quantities of sewage sludge. Developing effective strategies to remove harmful contaminants from the sludge and improve its dewatering performance is a major challenge for the recycling of sewage sludge back to land. Among these harmful contaminants, antibiotic resistance genes (ARGs) are widely detectable in sewage sludge due to their rapid spread via mobile genetic elements (MGEs), which exacerbates the prevalence of antibiotic resistance. Therefore, controlling the release of resistance genes during sludge treatment is crucial.

[0003] Currently, the mainstream sludge dewatering technology is mainly mechanical dewatering. However, mechanical dewatering can only separate free water and some bound water, leaving a considerable amount of antibiotic resistance genes (ARGs) in the dewatered sludge cake. These resistance genes can rapidly spread in the soil environment after the sludge cake is applied to the land. Furthermore, resistance genes in the dewatering filtrate have a significant potential to spread into the aquatic environment through transformation processes. Therefore, it is necessary to develop novel, efficient, and low-cost sludge dewatering technologies that simultaneously remove antibiotic resistance genes from the sludge.

[0004] Antibiotic residue is a solid waste generated during the drug extraction process in antibiotic production. Its composition is complex, containing not only incompletely extracted antibiotics, metabolites, unused culture medium components, and bacterial residues, but also abundant nitrogen. Due to the presence of residual antibiotics and toxic substances, it is classified as hazardous waste. If not properly disposed of, the antibiotics may spread through soil and water, inducing drug-resistant bacteria and contaminating the food chain. At the same time, if nitrogen is not effectively treated, it may lead to environmental problems such as eutrophication of water bodies, threatening ecology and human health. Currently, it is mainly treated by incineration, fertilizer production, feed production, anaerobic digestion, pyrolysis, and physicochemical fertilizer production, but all of these methods face challenges such as cost, secondary pollution, or residual risks. Further research and development of safe, efficient, harmless, and resource-based technologies are needed. Summary of the Invention

[0005] The purpose of this invention is to provide a composite catalyst, its preparation method, and its application in sludge treatment. An iron-carbon nanocomposite catalyst is synthesized using ferric nitrate nonahydrate, antibiotic bacterial residue, and melamine as precursors. The resulting composite catalyst can, on the one hand, activate ammonium persulfate to generate free radicals that disrupt the water-locking structure of the sludge, enhancing its hydrophobicity and thus improving dewatering efficiency. On the other hand, the Fe species in the composite catalyst activates ammonium persulfate to form Fe... 3+ Fe3+ The hydrolysis generates ferric hydroxide colloids that can adsorb sludge particles, neutralize surface charges, thereby reducing interparticle repulsion, promoting floc aggregation, and enhancing dewatering efficiency. The advanced oxidation process of ammonium persulfate catalyzed by a composite catalyst also achieves the removal of antibiotic resistance genes from sludge.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] One of the technical solutions of this invention is to provide a method for preparing a composite catalyst, comprising the following steps:

[0008] Ferric nitrate nonahydrate, antibiotic bacterial residue, and melamine were added to hydrochloric acid ethanol, mechanically stirred, dried, and then calcined at 700-1100℃ under an inert atmosphere. The calcined product was acid-washed, dried, and ground to obtain the composite catalyst.

[0009] Preferably, the volume fraction of concentrated hydrochloric acid in the hydrochloric acid ethanol is 2%; the ratio of the amount of ferric nitrate nonahydrate, antibiotic residue, melamine and hydrochloric acid ethanol is 0.1~1g:0.5~2g:1~3g:50~70mL.

[0010] The concentrated hydrochloric acid used in this invention is a commercially available concentrated hydrochloric acid reagent commonly used in the field (hydrochloric acid mass fraction of 36~38%).

[0011] Preferably, the mechanical stirring speed is 500~700 rpm and the stirring time is 3~8 hours.

[0012] Preferably, the drying temperature after mechanical stirring is 60°C, and the time is 12~24h.

[0013] Preferably, the heating rate of the high-temperature calcination is 2.5~8℃ / min, and the holding time is 2h.

[0014] Preferably, the pickling solution used is 6 mol / L hydrochloric acid.

[0015] Preferably, the drying temperature after pickling is 60°C and the time is 12 hours.

[0016] Preferably, the grinding is performed until the material passes through a 100-mesh sieve.

[0017] The second technical solution of the present invention is to provide a composite catalyst prepared according to the above-mentioned method for preparing composite catalysts.

[0018] The third technical solution of the present invention provides an application of the above-mentioned composite catalyst in sludge treatment, comprising the following steps:

[0019] The composite catalyst and ammonium persulfate solution are added to the sludge and stirred to achieve sludge dewatering and simultaneous removal of antibiotic resistance genes from the sludge.

[0020] Preferably, the amount of the composite catalyst added is 8-12% of the sludge mass; the concentration of the ammonium persulfate solution is 0.75-1.25 mol / L; and the amount of ammonium persulfate solution added is 0.1-0.3 mL / g sludge.

[0021] Preferably, the stirring rate of the stirring reaction is 100~300 rpm and the time is 20~60 min.

[0022] Preferably, the ammonium persulfate in the ammonium persulfate solution is obtained by electrolyzing an electrolyte containing ammonium sulfate and sulfuric acid.

[0023] More preferably, the concentrations of sodium sulfate and sulfuric acid in the electrolyte containing ammonium sulfate and sulfuric acid are both 0.5~1.25 mol / L; and the electrolysis current density is 0.5~1 A / m. 2 The voltage is 5~10V and the time is 4~6h.

[0024] The beneficial technical effects of the present invention are as follows:

[0025] 1. This invention uses extremely simple components and methods to achieve rapid dewatering of sludge, improves the dewatering capacity of sludge, and reduces the transportation pressure of sludge.

[0026] 2. This invention uses extremely simple components and methods to remove antibiotic resistance genes from sludge, significantly reducing environmental pressure.

[0027] 3. The sludge treatment method of the present invention can simultaneously achieve sludge dewatering and pollutant removal within 1 hour, reducing treatment time and cost.

[0028] 4. This invention achieves sludge dewatering and harmlessness while also realizing the high-value utilization of antibiotic bacterial residue, providing an innovative solution for developing an economical and efficient green catalytic material system. Attached Figure Description

[0029] Figure 1 The change in sludge moisture content before and after treatment in Example 1 is shown.

[0030] Figure 2 The change in sludge capillary suction time before and after treatment in Example 1 is shown.

[0031] Figure 3 The removal rate of antibiotic resistance genes in the sludge after treatment in Example 1 is shown.

[0032] Figure 4The changes in sludge capillary suction time after treatment in Examples 1, 2, 3, and 4 are shown.

[0033] Figure 5 The changes in sludge capillary suction time after treatment in Examples 1, 5, 6, 7, and 8 are shown. Detailed Implementation

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0035] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0036] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0038] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0039] Unless otherwise specified, "room temperature" in this invention refers to a temperature of 20±10℃.

[0040] The sludge used in this embodiment of the invention was taken from Jinan City, Shandong Province, and other raw materials were all conventional commercially available products.

[0041] Example 1

[0042] A method for dewatering sludge and simultaneously removing antibiotic resistance genes from sludge:

[0043] (1) Using a solution containing 0.75 mol / L ammonium sulfate and 0.75 mol / L sulfuric acid as the electrolyte, electrolysis was carried out in an electrolytic cell with platinum as the anode and graphite as the cathode, at a current density of 1 A / m 2Electrolysis was performed at 10V for 4 hours, followed by filtration, washing with ice water three times, and vacuum drying at 55℃ to obtain white ammonium persulfate crystals.

[0044] (2) 0.5g Fe(NO3)3·9H2O, 1g antibiotic residue and 2g melamine were added to 60mL hydrochloric acid ethanol (containing 2 vol.% concentrated hydrochloric acid). The mixture was mechanically stirred at 500rpm for 6h and then dried at 60℃ for 12h. Then, under an argon atmosphere, the temperature was raised to 900℃ at a heating rate of 5℃ / min and calcined for 2h. The calcined product was washed with 6mol / L hydrochloric acid solution and then dried at 60℃ for 12h. The product was ground and passed through a 100-mesh sieve to obtain the composite catalyst.

[0045] (3) Dissolve the pure ammonium persulfate crystals obtained in step (1) in water to prepare a 0.75 mol / L ammonium persulfate solution.

[0046] (4) Add 1g of the composite catalyst obtained in step (2) and 2mL of the ammonium persulfate solution obtained in step (3) to 10g of sludge, stir at 200rpm for 40min at room temperature to complete the sludge dewatering and removal of antibiotic resistance genes.

[0047] The moisture content of the sludge treated in Example 1 was measured, with the sludge before treatment serving as a control. The results are shown in [Figure 1]. Figure 1 .

[0048] Depend on Figure 1 It can be seen that after treatment according to the method of Example 1, the water content of the sludge decreased by 29.95 wt.%, indicating that the system can achieve rapid dewatering of sludge.

[0049] The capillary suction time (CST) of the sludge treated in Example 1 was measured, with the sludge before treatment serving as a control. The results are shown in [Figure 1]. Figure 2 .

[0050] Depend on Figure 2 It can be seen that after treatment with ammonium persulfate activated by composite catalyst, the capillary suction time of sludge decreased by 13 seconds, indicating that the method provided by the present invention has a good dewatering effect on sludge.

[0051] The concentration of antibiotic resistance genes in the sludge treated in Example 1 was measured, with the sludge before treatment serving as a control. The results are shown in [Figure 1]. Figure 3 .

[0052] Depend on Figure 3As can be seen, after treatment according to the method of Example 1, more than 99% of the β-lactam (blaTEM) resistance genes in the sludge were removed, 97.4% of the tetracycline (tetracycline A) resistance genes were eliminated, and 85.9% of the sulfonamide (sulfuric acid) resistance genes were eliminated. The resistance gene genetic element (intI 1) was also removed by 67.3%, indicating that the method provided by this invention can efficiently remove multiple antibiotic resistance genes from sludge and effectively reduce the spread of resistance genes.

[0053] Example 2

[0054] The only difference from Example 1 is that:

[0055] In step (3), the concentration of the ammonium persulfate aqueous solution is 0 mol / L, and the other dosages and operations are exactly the same as in Example 1.

[0056] Example 3

[0057] The only difference from Example 1 is that:

[0058] In step (3), the concentration of ammonium persulfate aqueous solution is 0.3 mol / L, and the other dosages and operations are exactly the same as in Example 1.

[0059] Example 4

[0060] The only difference from Example 1 is that:

[0061] In step (3), the concentration of ammonium persulfate aqueous solution is 1.25 mol / L, and the other dosages and operations are exactly the same as in Example 1.

[0062] The capillary suction time of the sludge after treatment in Examples 1, 2, 3, and 4 was measured, with the sludge before treatment serving as a control. The results are shown in the figure. Figure 4 .

[0063] like Figure 4 As shown, the capillary suction time of sludge first increases and then decreases with the increase of ammonium persulfate concentration. This is because a lower ammonium persulfate concentration will destroy the stability of the original sludge flocs, produce more fine particles, increase the viscosity of the filtrate and the filtration resistance, and lead to an increase in CST; while a higher ammonium persulfate concentration will increase the hydrophobicity of the sludge, making it easier to aggregate and form dense flocs, thus improving dewatering performance.

[0064] Example 5

[0065] The only difference from Example 1 is that:

[0066] In step (4), the amount of composite catalyst added is 0g, and the remaining amounts and operations are exactly the same as in Example 1.

[0067] Example 6

[0068] The only difference from Example 1 is that:

[0069] In step (4), the amount of composite catalyst added is 0.4g, and the remaining amounts and operations are exactly the same as in Example 1.

[0070] Example 7

[0071] The only difference from Example 1 is that:

[0072] In step (4), the amount of composite catalyst added is 0.8g, and the remaining amounts and operations are exactly the same as in Example 1.

[0073] Example 8

[0074] The only difference from Example 1 is that:

[0075] In step (4), the amount of composite catalyst added is 1.2g, and the remaining amounts and operations are exactly the same as in Example 1.

[0076] The capillary suction time of the sludge after treatment in Examples 1, 5, 6, 7, and 8 was measured, with the sludge before treatment serving as a control. The results are shown in the figure. Figure 5 .

[0077] like Figure 5 As shown, the capillary suction time of sludge initially decreases and then increases with the increase of the composite catalyst mass. This is because excessive catalytic material can lead to over-hardening of the sludge, clogging the filter paper pores and causing the CST to rise.

[0078] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. The application of a composite catalyst in sludge treatment, characterized in that, Includes the following steps: The composite catalyst and ammonium persulfate solution were added to the sludge and stirred to achieve sludge dewatering and simultaneous removal of antibiotic resistance genes from the sludge. The preparation steps of the composite catalyst include: Ferric nitrate nonahydrate, antibiotic bacterial residue, and melamine were added to hydrochloric acid ethanol, mechanically stirred, dried, and then calcined at a high temperature of 700~1100℃ under an inert atmosphere. The calcined product was acid washed, dried, and ground to obtain the composite catalyst. The volume fraction of concentrated hydrochloric acid in the hydrochloric acid ethanol is 2%; the ratio of the amount of ferric nitrate nonahydrate, antibiotic residue, melamine and hydrochloric acid ethanol is 0.1~1g:0.5~2g:1~3g:50~70mL.

2. The application according to claim 1, characterized in that, The amount of the composite catalyst added is 8-12% of the sludge mass; the concentration of the ammonium persulfate solution is 0.75-1.25 mol / L; and the amount of ammonium persulfate solution added is 0.1-0.3 mL / g sludge.

3. The application according to claim 1, characterized in that, The stirring rate of the stirring reaction is 100~300 rpm, and the time is 20~60 min.

4. The application according to claim 1, characterized in that, The ammonium persulfate in the ammonium persulfate solution is obtained by electrolyzing an electrolyte containing ammonium sulfate and sulfuric acid.

5. The application according to claim 1, characterized in that, The mechanical stirring speed is 500~700 rpm, and the time is 3~8 h; and / or, the drying temperature after mechanical stirring is 60℃, and the time is 12~24 h; and / or, the heating rate of the high-temperature calcination is 2.5~8℃ / min, and the holding time is 2 h.

6. The application according to claim 1, characterized in that, The pickling process uses 6 mol / L hydrochloric acid; and / or, the drying temperature after pickling is 60°C and the time is 12 hours; and / or, the grinding process involves grinding until the material passes through a 100-mesh sieve.

Images