A method for improving Feammox deammoniation efficiency based on Fe3O4@CF functional materials

Abstract

The application discloses a method for improving Feammox deamination efficiency based on Fe3O4@CF functional materials, which comprises the following steps: firstly, in-situ generating and loading nano Fe3O4 on modified carbon felt by using a hydrothermal method to prepare Fe3O4@CF functional materials; then, adding ammonia nitrogen simulated wastewater and Fe3O4@CF functional materials into anaerobic sludge, completing Feammox sludge domestication, adding the Fe3O4@CF functional materials into the domesticated Feammox sludge, constructing a Fe3O4@CF functional material coupled Feammox biological system, and finally adding ammonia nitrogen wastewater to be treated into the coupled system for reaction in a sequencing batch reaction mode, and the system can be operated continuously. The application explores a new way for strengthening Feammox deamination, and has high practical significance for reducing the treatment cost of ammonia nitrogen wastewater and engineering application of Feammox.

Description

Technical Field

[0001] This invention belongs to the field of ammonia nitrogen wastewater treatment technology, specifically relating to a method for improving Feammox ammonia removal efficiency based on Fe3O4@CF functional materials. Background Technology

[0002] Anaerobic iron ammonia oxidation (Feammox) is an emerging biological ammonia removal process with significant implications for the innovation of biological ammonia removal technology in wastewater. Theoretically, Feammox functional bacteria can directly oxidize ammonia nitrogen to nitrate nitrogen, nitrite nitrogen, and nitrogen gas under anaerobic and autotrophic conditions, while reducing ferric iron. Compared to traditional nitrification / denitrification, Feammox promises to save on aeration and organic substrate addition costs, thereby reducing energy consumption and carbon emissions. Simultaneously, the Feammox biological process possesses a unique enzymatic mechanism that can significantly reduce the generation of the greenhouse gas N2O, making it a cleaner and more environmentally friendly biotechnology. Compared to anaerobic ammonia oxidation (Anammox) technology, Feammox also has advantages such as readily available electron acceptors and good resistance to adverse conditions. Furthermore, Feammox can serve as a pretreatment unit for other biological processes, further optimizing the nitrogen removal framework. For example, the coupling of the Feammox / denitrification process can be used to treat iron-containing ammonia nitrogen wastewater, thereby eliminating the need for aeration in the aerobic nitrification step; similarly, Feammox can also replace short-cut nitrification as a pre-processing unit of the Anammox process to oxidize some of the ammonia nitrogen in the ammonia nitrogen wastewater into nitrite nitrogen, which facilitates the stable operation of the latter.

[0003] Despite the promising prospects of Feammox in wastewater ammonia removal, its engineering applications remain in the proof-of-concept stage. Early studies have shown that the limited electron transfer rate between microorganisms and iron sources is one of the main reasons for the low ammonia removal efficiency of Feammox. The addition of redox-active electron shuttles, such as AQDS (anthraquinone-2,6-disulfonate) and activated carbon, has been shown to mediate extracellular electron transfer between functional bacteria and iron minerals, thereby improving ammonia removal performance. However, potential interspecies electron transfer among Feammox functional bacteria has been poorly studied. In recent years, increasing molecular-level studies have indicated that the symbiotic relationship between electroactive iron-reducing bacteria and ammonia-oxidizing bacteria in multi-bacterial Feammox systems may be the main pathway for ammonia nitrogen conversion, meaning that promoting interspecies electron transfer could potentially overcome the efficiency bottleneck of Feammox. In anaerobic digestion systems, electrically conductive environmental functional materials have been widely demonstrated to mediate interspecies electron transfer between acid-producing and methanogenic bacteria, thereby improving methanogenesis performance. However, there are still few reports on using electrically conductive functional materials to enhance the Feammox system. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for improving the deammoniation efficiency of Feammox based on Fe3O4@CF functional materials. By introducing Fe3O4@CF functional materials into the traditional Feammox system, the deammoniation efficiency of Feammox is improved by promoting the enrichment of relevant functional bacteria and mediating interspecies electron transfer. This aims to provide a more efficient and energy-saving technological reserve for the Feammox process.

[0005] This invention is achieved through the following technical solution:

[0006] A method for improving the deammoniation efficiency of Feammox based on Fe3O4@CF functional materials includes the following steps:

[0007] Step 1) The precursor solution was generated in situ on modified carbon felt and nano-Fe3O4 was loaded using a hydrothermal method to prepare Fe3O4@CF functional material.

[0008] Step 2) Add ammonia nitrogen to simulated wastewater and the Fe3O4@CF functional material prepared in step 1) to the anaerobic sludge to complete the Feammox sludge acclimatization.

[0009] Step 3) Add the Fe3O4@CF functional material prepared in Step 1) to the acclimated Feammox sludge to construct the Fe3O4@CF functional material coupled Feammox biological system; then add the ammonia nitrogen wastewater to be treated into the Fe3O4@CF functional material coupled Feammox biological system in a sequencing batch reaction mode to carry out the reaction, and run the system continuously.

[0010] Preferably, the modified carbon felt in step 1) is prepared as follows:

[0011] The graphite carbon felt is cut into small pieces, washed and dried with acetone, then immersed in dilute nitric acid solution, and then washed with deionized water and ethanol until the washing water is neutral. After drying, it is ready for use.

[0012] Preferably, the precursor solution in step 1) is prepared as follows:

[0013] Weigh 0.8855g of FeCl3·6H2O and dissolve it in 30mL of deionized water. Add 0.5976g of sodium citrate and stir magnetically until homogeneous. Add 0.1642g of polyethylene glycol and continue stirring magnetically until homogeneous. Slowly add ammonia water to adjust the pH to 9.

[0014] Preferably, the specific preparation method of the Fe3O4@CF functional material in step 1) is as follows:

[0015] After mixing and stirring the modified carbon felt with the precursor solution, the mixture was transferred into a reaction vessel and placed in a forced-air drying oven to react at 200℃ for 8 hours. After the reaction was completed, the carbon felt loaded with nano-Fe3O4 was taken out, washed repeatedly with deionized water, and dried in a vacuum drying oven to obtain the Fe3O4@CF functional material.

[0016] Preferably, the specific steps of Feammox sludge acclimation in step 2) are as follows:

[0017] Simulated wastewater with an ammonia nitrogen concentration of 20 mg / L and Fe3O4@CF functional material were added to the anaerobic sludge for acclimatization. Specifically, 0.4 L of simulated wastewater and 120 mg of Fe3O4@CF functional material were added to each liter of simulated wastewater. After the ammonia nitrogen in the simulated wastewater was completely converted, the ammonia nitrogen concentration of the simulated wastewater was gradually increased to 40 mg / L and added to the anaerobic sludge to continue sludge acclimatization. The sludge acclimatization was completed after the effluent quality stabilized.

[0018] Preferably, the dosage of the Fe3O4@CF functional material in step 3) is 0.6–2.4 g / L.

[0019] Preferably, the dosage is 1.2 g / L.

[0020] Preferably, in step 3), the volume ratio of the ammonia nitrogen wastewater to be treated to the acclimated Feammox sludge is 3:1, and the ammonia nitrogen concentration in the ammonia nitrogen wastewater to be treated is ≤40mg / L.

[0021] Preferably, the specific steps of the uninterrupted operation system in step 3) are as follows:

[0022] The Fe3O4@CF functional material coupled with the Feammox biological system, which was added to the ammonia nitrogen wastewater to be treated, was placed in a constant temperature oscillator for mixing and reaction. The rotation speed was controlled at 170 r / min, the temperature was controlled at 30℃, and the reaction time was 84 h.

[0023] The beneficial effects of this invention are as follows:

[0024] (1) The method provided by this invention does not require complex reaction requirements and conditions. Only a small amount of easily prepared Fe3O4@CF functional material is needed to promote the conversion of ammonia nitrogen in the Feammox system. When the ammonia nitrogen concentration in the wastewater is below 40 mg / L, the ammonia nitrogen conversion rate can reach over 95% when Fe3O4@CF functional material is added to the Feammox biological system coupled with Fe3O4@CF functional material. This process does not require aeration or additional organic carbon source addition, thus reducing the wastewater treatment cost.

[0025] (2) This invention is based on the principle of synergistic deammoniation by functional bacteria in the Feammox system. It incorporates Fe3O4@CF functional material with good electrical conductivity to promote the enrichment of electroactive functional bacteria and enhances the deammoniation performance of the Feammox system by mediating interspecies electron transfer among functional bacteria. Simultaneously, the nano-Fe3O4 in the functional material can act as an additional electron acceptor in the Feammox reaction, further promoting ammonia nitrogen conversion. Furthermore, the carbon felt used to load Fe3O4 can provide an attachment carrier for microorganisms, increasing bacterial cell density and enhancing the system's resistance to adverse conditions. This invention explores a new approach to enhance Feammox deammoniation, which has significant practical implications for reducing the cost of ammonia nitrogen wastewater treatment and for the engineering applications of Feammox. Attached Figure Description

[0026] Figure 1 The graph shows the ammonia nitrogen conversion effect of different systems in Example 1;

[0027] Figure 2 The graph shows the ammonia nitrogen conversion effect under different dosages of Fe3O4@CF functional materials in Example 2. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0029] Unless otherwise specified, the technical means used in the following embodiments are all conventional means well known to those skilled in the art, and the experimental methods without specific conditions are all conventional methods in the art.

[0030] Example 1

[0031] A method for improving the deammoniation efficiency of Feammox based on Fe3O4@CF functional materials, the specific steps of which are as follows:

[0032] 1. Preparation of Fe3O4@CF functional materials

[0033] (1) Preparation of modified carbon felt

[0034] Commercial carbon felt (CF) was cut into 1cm×1cm pieces, washed with acetone for 30min, and dried at 60℃ for 12h. The carbon felt was then immersed in 5% (v / v) dilute nitric acid solution and stirred at 80℃ for 3h. The treated carbon felt was then washed with deionized water and ethanol until the wash water was neutral, and dried at 60℃ for 12h before use.

[0035] (2) Preparation of precursor solution

[0036] Weigh 0.8855g of FeCl3·6H2O and dissolve it in 30mL of deionized water. Add 0.5976g of sodium citrate and stir magnetically until homogeneous. Add 0.1642g of polyethylene glycol and continue stirring magnetically for 20min. Slowly add ammonia water to adjust the pH to 9 and stir for 20min to obtain the final product.

[0037] (3) Preparation of Fe3O4@CF functional materials

[0038] After mixing and stirring the modified carbon felt with the precursor solution for 30 minutes, the mixture was transferred into a reaction vessel and placed in a forced-air drying oven at 200℃ for 8 hours. After the reaction was completed, the carbon felt loaded with nano-Fe3O4 was taken out, washed repeatedly with deionized water, and dried in a vacuum drying oven at 60℃ for 12 hours to obtain Fe3O4@CF functional material.

[0039] 2. Construction of Fe3O4@CF functional materials coupled with Feammox biological systems

[0040] (1) Simulated wastewater with an ammonia nitrogen concentration of 20 mg / L and Fe3O4@CF functional material were added to the anaerobic sludge for acclimatization. Specifically, 0.4 L of simulated wastewater was added per liter of anaerobic sludge, and 120 mg of Fe3O4@CF functional material was added per liter of simulated wastewater. After the ammonia nitrogen in the simulated wastewater was completely converted, the ammonia nitrogen concentration of the simulated wastewater was gradually increased to 40 mg / L and added to the anaerobic sludge to continue sludge acclimatization. The sludge acclimatization was completed after the effluent quality stabilized.

[0041] (2) Add Fe3O4@CF functional material to the acclimated sludge, and then add the ammonia nitrogen simulated wastewater to the coupled system in a sequencing batch reaction mode for reaction, as follows:

[0042] Add 75 mL of simulated wastewater with an ammonia nitrogen concentration of 40 mg / L to a 120 mL anaerobic serum bottle, purge the wastewater with high-purity nitrogen to remove residual oxygen until an anaerobic state is reached, then add 25 mL of acclimated Feammox sludge and 120 mg of Fe3O4@CF functional material, seal the conical flask, and label it as the Fe3O4@CF coupled Feammox biological system (coupled system).

[0043] At the same time, following the same steps as above, a Feammox biological control system without the addition of Fe3O4@CF functional material was set up.

[0044] 3. Place the two systems described above in a constant-temperature shaker to allow for a full reaction, controlling the rotation speed at 170 r / min and the temperature at 30℃. During the reaction cycle, at the set sampling time points, after flocculation and sedimentation, the water sample is filtered through a 0.22 μm filter membrane, and then the ammonia nitrogen content is determined by Nessler's reagent spectrophotometry at a wavelength of 420 nm.

[0045] 4. Experimental Results

[0046] The results are as follows Figure 1 As shown, in the Feammox biological control system, the high solubility of the ionic iron source FeCl3·6H2O facilitates its use as an electron acceptor by microorganisms, resulting in significant ammonia nitrogen conversion in the early stages of the reaction. However, as the iron source was depleted, ammonia nitrogen degradation became less significant in the later stages, with a removal rate of 47.6% at the end of the reaction. In the coupled system, thanks to the slow-release iron source effect of the Fe3O4@CF functional material, ammonia nitrogen was significantly degraded in the early stages of the reaction. As the reaction continued, ammonia nitrogen steadily decreased, reaching a removal rate of 95.9% after 84 hours. Notably, the coupled system exhibited a faster ammonia nitrogen degradation trend than the Feammox biological control system in the early stages of the reaction, demonstrating the promoting effect of the Fe3O4@CF functional material on the Feammox rate.

[0047] The above results indicate that the addition of Fe3O4@CF functional materials can significantly promote the deammoniation effect of the Feammox system. The principle is as follows: on the one hand, the nano-Fe3O4 loaded on the functional materials provides additional electron acceptors for microorganisms during the reaction process, further promoting the oxidation of ammonia nitrogen; on the other hand, the highly conductive Fe3O4@CF functional materials can promote the enrichment of Feammox functional bacteria such as electroactive iron-reducing bacteria and ammonia-oxidizing bacteria, and mediate electron transfer in the synergistic process of functional bacteria, thereby improving the degradation efficiency of ammonia nitrogen.

[0048] Example 2

[0049] This embodiment evaluates the effect of Fe3O4@CF functional material dosage on the deammoniation performance of the Feammox system by constructing coupled systems with different Fe3O4@CF functional material dosages, as detailed below:

[0050] (1) Fe3O4@CF coupled Feammox biological systems (coupled systems) were constructed according to the method of Example 1 with Fe3O4@CF functional material dosages of 0.6 g / L, 1.2 g / L, 1.8 g / L and 2.4 g / L respectively.

[0051] (2) The above four systems were placed in a constant temperature shaker for full reaction, with the rotation speed controlled at 170 r / min, the temperature at 30℃, and the reaction time set at 84 h. During the reaction period, at the set sampling time points, the water sample was flocculated and precipitated, then filtered through a 0.22 μm filter membrane, and then the ammonia nitrogen content was determined by Nessler's reagent spectrophotometry at a wavelength of 420 nm.

[0052] The results are as follows Figure 2As shown, when the dosage of Fe3O4@CF functional material was 0.6 g / L, electron transfer between functional bacteria in the Feammox system was enhanced, and the ammonia nitrogen oxidation rate increased. However, due to the limited amount of nano-Fe3O4 loaded, the iron source in the system was insufficient to support further ammonia nitrogen degradation, and the ammonia nitrogen removal rate reached 78.9% at the end of the reaction. When the dosage of Fe3O4@CF functional material was increased to 1.2 g / L, the ammonia nitrogen degradation rate was significantly improved, and the functional material provided sufficient additional iron source, resulting in an ammonia nitrogen removal rate of 95.9% at the end of the Feammox reaction. When the dosage of Fe3O4@CF functional material was increased to 1.8 g / L and 2.4 g / L, a slight increase in the ammonia nitrogen degradation rate was observed, and the ammonia nitrogen removal rate exceeded 95% at the end of the reaction. On the one hand, both nano-Fe3O4 and carbon felt in the functional materials have good biocompatibility and are widely used in bioprocesses. Therefore, the large-scale addition of functional materials did not have an excessively high inhibitory effect on microbial activity, so the coupled system still maintained a stable and efficient ammonia nitrogen degradation effect. On the other hand, the strengthening effect of Fe3O4@CF functional materials on the Feammox system is not linear. This may be attributed to the limited biological density in the system and the limited utilization ability of Feammox bacteria of functional materials.

[0053] The above results indicate that Fe3O4@CF functional materials have bio-friendly properties, and that a small amount (1.2 g / L) can significantly improve the deammoniation performance of the Feammox system, which is of great significance for the engineering application of Feammox technology.

[0054] The embodiments described above are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. The scope of protection of the present invention is determined by the scope claimed in the claims. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for improving Feammox deamination efficiency based on Fe3O4@CF functional materials, characterized in that, Includes the following steps: Step 1) Fe3O4@CF functional material is prepared by in-situ generating and loading nano-Fe3O4 onto modified carbon felt using a hydrothermal method; the preparation method of the modified carbon felt is as follows: The graphite carbon felt is cut into small pieces, washed and dried with acetone, then immersed in dilute nitric acid solution, and then washed with deionized water and ethanol until the washing water is neutral. After drying, it is ready for use. Step 2) Add ammonia nitrogen to simulated wastewater and the Fe3O4@CF functional material prepared in step 1) to the anaerobic sludge to complete the Feammox sludge acclimatization. Step 3) Add the Fe3O4@CF functional material prepared in Step 1) to the acclimated Feammox sludge to construct the Fe3O4@CF functional material coupled Feammox biological system; then add the ammonia nitrogen wastewater to be treated into the Fe3O4@CF functional material coupled Feammox biological system in a sequencing batch reaction mode to carry out the reaction, and run the system continuously.

2. The method for improving Feammox deamination efficiency based on Fe3O4@CF functional material according to claim 1, characterized in that, Step 1) The preparation method of the precursor solution is as follows: Weigh 0.8855 g of FeCl3•6H2O and dissolve it in 30 mL of deionized water. Add 0.5976 g of sodium citrate and stir magnetically until homogeneous. Add 0.1642 g of polyethylene glycol and continue stirring magnetically until homogeneous. Slowly add ammonia water to adjust the pH to 9. 3.The method of improving Feammox deamination efficiency based on Fe 3O 4@CF functional material according to claim 1, characterized in that, The specific preparation method of the Fe3O4@CF functional material in step 1) is as follows: After mixing and stirring the modified carbon felt with the precursor solution, the mixture was transferred into a reaction vessel and placed in a forced-air drying oven to react at 200℃ for 8 h. After the reaction was completed, the carbon felt loaded with nano-Fe3O4 was taken out, washed repeatedly with deionized water, and dried in a vacuum drying oven to obtain the Fe3O4@CF functional material.

4. The method for improving Feammox deamination efficiency based on Fe3O4@CF functional material according to claim 1, characterized in that, Step 2) The specific steps of Feammox sludge acclimatization are as follows: Simulated wastewater with an ammonia nitrogen concentration of 20 mg / L and Fe3O4@CF functional material were added to the anaerobic sludge for acclimatization. Specifically, 0.4 L of simulated wastewater and 120 mg of Fe3O4@CF functional material were added to each liter of simulated wastewater. After the ammonia nitrogen in the simulated wastewater was completely converted, the ammonia nitrogen concentration of the simulated wastewater was gradually increased to 40 mg / L and added to the anaerobic sludge to continue sludge acclimatization. The sludge acclimatization was completed after the effluent quality stabilized.

5. The method for improving Feammox deamination efficiency based on Fe3O4@CF functional material according to claim 1, characterized in that, Step 3) The dosage of the Fe3O4@CF functional material is 0.6~2.4 g / L.

6. The method for improving Feammox deamination efficiency based on Fe3O4@CF functional material according to claim 5, characterized in that, The dosage is 1.2 g / L.

7. The method for improving Feammox deammoniation efficiency based on Fe3O4@CF functional materials according to claim 1, characterized in that, Step 3) The volume ratio of the ammonia nitrogen wastewater to be treated to the acclimated Feammox sludge is 3:1, and the ammonia nitrogen concentration in the ammonia nitrogen wastewater to be treated is ≤40 mg / L.

8. A method for improving Feammox deammoniation efficiency based on Fe3O4@CF functional materials according to claim 1, characterized in that, Step 3) The specific steps of the uninterrupted operation system are as follows: The Fe3O4@CF functional material coupled with the Feammox biological system, which was added to the ammonia nitrogen wastewater to be treated, was placed in a constant-temperature oscillator for mixing and reaction. The rotation speed was controlled at 170 r / min, the temperature was controlled at 30℃, and the reaction time was 84 h.

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