Method for improving Fammox deamination efficiency based on Fe3O4-coated CF functional material

Abstract

The invention discloses a method for improving Fammox deamination efficiency based on a Fe3O4-coated CF functional material, which comprises the following steps of: firstly, generating a precursor solution on a modified carbon felt in situ by adopting a hydrothermal method and loading nano Fe3O4 to prepare the Fe3O4-coated CF functional material; the method comprises the following steps: adding ammonia nitrogen simulation wastewater and a Fe3O4-coated CF functional material into anaerobic sludge to complete Feammox sludge domestication, adding the Fe3O4-coated CF functional material into the domesticated Feammox sludge to construct a Feammox biological system coupled with the Fe3O4-coated CF functional material, adding ammonia nitrogen wastewater to be treated into the coupled system in a sequencing batch reaction mode, and continuously operating the system. According to the invention, a new approach for strengthening Feammox deamination is explored, and the method has relatively high practical significance for reducing the treatment cost of the ammonia-nitrogen wastewater and engineering application of Feammox.

Description

Technical Field

[0001] The invention belongs to the technical field of ammonia nitrogen wastewater treatment, and specifically relates to a method for improving Feammox deammoniation efficiency based on Fe3O4@CF functional material. Background Art

[0002] Anaerobic iron ammonia oxidation (Feammox) is an emerging biological deammoniation process, which is of great significance to the innovation of wastewater biological deammoniation technology. Theoretically, Feammox functional bacteria can directly oxidize ammonia nitrogen to produce nitrate nitrogen, nitrite nitrogen and nitrogen gas under anaerobic and autotrophic conditions, and reduce trivalent iron. Compared with traditional nitrification / denitrification, Feammox is expected to save the cost of aeration and organic substrate addition, thereby reducing energy loss and carbon emissions; at the same time, the Feammox biological process has a unique enzymatic mechanism, which can greatly reduce the production of greenhouse gas N2O, so it is a cleaner and more environmentally friendly biotechnology. Compared with anaerobic ammonia oxidation (Anammox) technology, Feammox also has the advantages of easy availability of electron acceptors and good resistance to adverse conditions. In addition, Feammox can also serve as a pretreatment unit for other biological processes to further optimize the denitrification framework. For example, the coupling of 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 the precursor unit of the Anammox process, oxidizing part of the ammonia nitrogen in the ammonia nitrogen wastewater into nitrite nitrogen, facilitating the stable operation of the latter.

[0003] Although Feammox has good prospects in the field of wastewater deammonification, its engineering application is still 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 deammonification 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 deammonification performance. However, there are few studies on the potential interspecies electron transfer between functional bacteria in Feammox. In recent years, more and more molecular-level studies have shown that the mutualism between electroactive iron-reducing bacteria and ammonia-oxidizing bacteria in the multi-bacteria Feammox system may be the main pathway for ammonia nitrogen conversion, which means that it is also possible to break through the efficiency bottleneck of Feammox by promoting interspecies electron transfer. In anaerobic digestion systems, conductive environmental functional materials have been widely shown to mediate interspecies electron transfer between acid-producing bacteria and methanogens, thereby improving methanogenesis. However, there are no reports on the use of conductive functional materials to strengthen the Feammox system. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for improving the deamination efficiency of Feammox based on Fe3O4@CF functional materials. The deamination efficiency of Feammox is improved by introducing Fe3O4@CF functional materials into the traditional Feammox system to promote the enrichment of relevant functional bacteria and mediate interspecies electron transfer, aiming to provide a more efficient and energy-saving technical reserve for the Feammox process.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for improving the deamination efficiency of Feammox based on Fe3O4@CF functional material, comprising the following steps:

[0007] Step 1) using a hydrothermal method to in-situ generate and load nano-Fe3O4 on a precursor solution on a modified carbon felt to prepare a Fe3O4@CF functional material;

[0008] Step 2) adding ammonia nitrogen simulated wastewater and the Fe3O4@CF functional material prepared in step 1) into the anaerobic sludge to complete the Feammox sludge domestication;

[0009] Step 3) Add the Fe3O4@CF functional material prepared in step 1) to the domesticated Feammox sludge to construct a 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 for reaction, and operate the system uninterruptedly.

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

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

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

[0013] 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 it magnetically; add 0.1642 g of polyethylene glycol and continue to stir it magnetically; slowly add ammonia water dropwise to adjust the pH to 9 to obtain the product.

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

[0015] The modified carbon felt and the precursor solution were mixed and stirred, and then all were transferred into a reactor, placed in a forced air drying oven and reacted at 200°C for 8 hours; after the reaction, the carbon felt loaded with nano-Fe3O4 was taken out, repeatedly washed with deionized water, and placed in a vacuum drying oven to obtain the Fe3O4@CF functional material.

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

[0017] Simulated wastewater with an ammonia nitrogen concentration of 20 mg / L and Fe3O4@CF functional materials were added to anaerobic sludge for domestication, wherein 0.4 L of simulated wastewater was added to each liter of anaerobic sludge, and 120 mg of Fe3O4@CF functional materials 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 domestication. After the effluent quality was stabilized, the sludge domestication was completed.

[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 ≤40 mg / 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 ammonia nitrogen wastewater to be treated was placed in a constant temperature oscillator for mixed reaction, wherein the speed was controlled at 170 r / min, the temperature was controlled at 30°C, and the reaction time was 84 h.

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

[0024] (1) The method provided by the present invention does not require complicated reaction requirements and conditions. Only a small amount of easily prepared Fe3O4@CF functional materials can be added 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 Fe3O4@CF functional material is added to the Fe3O4@CF functional material coupled Feammox biological system, and the ammonia nitrogen conversion rate can reach more than 95%. This process does not require aeration and additional organic carbon source addition, which reduces the cost of wastewater treatment.

[0025] (2) Based on the principle of mutual deammoniation of functional bacteria in the multi-bacteria Feammox system, the present invention adds Fe3O4@CF functional materials 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 between functional bacteria. At the same time, the nano-Fe3O4 in the functional material can serve as an additional electron acceptor for the Feammox reaction, further promoting the conversion of ammonia nitrogen; in addition, the carbon felt used to load Fe3O4 can provide an attachment carrier for microorganisms, increase the bacterial cell density, and enhance the system's resistance to adverse conditions. The present invention explores a new way to enhance Feammox deammoniation, which has a high practical significance for reducing the cost of ammonia nitrogen wastewater treatment and the engineering application of Feammox. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a diagram showing the ammonia nitrogen conversion effect of different systems in Example 1;

[0027] Figure 2 This is a diagram of the ammonia nitrogen conversion effect at different Fe3O4@CF functional material dosages in Example 2. DETAILED DESCRIPTION

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

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

[0030] Example 1

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

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

[0033] (1) Preparation of modified carbon felt

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

[0035] (2) Preparation of precursor solution

[0036] 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; add 0.1642 g of polyethylene glycol and continue to stir magnetically for 20 min; slowly add ammonia water dropwise to adjust the pH to 9, stir for 20 min, and the product is obtained.

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

[0038] The modified carbon felt and the precursor solution were mixed and stirred for 30 minutes, then all were transferred into a reactor and placed in a forced air drying oven to react at 200°C for 8 hours. After the reaction was completed, the carbon felt loaded with nano-Fe3O4 was taken out, repeatedly washed with deionized water, and placed in a vacuum drying oven at 60°C for 12 hours to obtain Fe3O4@CF functional material.

[0039] 2. Construction of Fe3O4@CF functional material coupled with Feammox biological system

[0040] (1) Simulated wastewater with an ammonia nitrogen concentration of 20 mg / L and Fe3O4@CF functional materials were added to anaerobic sludge for acclimation, wherein 0.4 L of simulated wastewater and 120 mg of Fe3O4@CF functional materials were added per liter of anaerobic sludge. 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 for further sludge acclimation. After the effluent quality was stabilized, the sludge acclimation was completed.

[0041] (2) Adding Fe3O4@CF functional material to the acclimated sludge, and then adding ammonia nitrogen simulated wastewater into the coupling 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 into a 120 mL anaerobic serum bottle, fill it with high-purity nitrogen to exhaust the residual oxygen in the wastewater to an anaerobic state, then add 25 mL of domesticated Feammox sludge and 120 mg of Fe3O4@CF functional material, seal the conical bottle, and record it as 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 adding Fe3O4@CF functional material was set up.

[0044] 3. The above two systems were placed in a constant temperature oscillator for full reaction, with the speed controlled at 170 r / min and the temperature at 30°C. During the reaction period, at the set sampling time point, the water sample was flocculated and precipitated, then filtered with 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.

[0045] 4. Experimental results

[0046] The results are as follows Figure 1 As shown in the figure, in the Feammox biological control system, since the ionic iron source FeCl3·6H2O has a high solubility, it is beneficial for microorganisms to obtain it as an electron acceptor. Therefore, a significant conversion of ammonia nitrogen was observed at the beginning of the reaction. As the reaction progressed, the iron source was exhausted, and the degradation of ammonia nitrogen was not significant in the later stage. The removal rate of ammonia nitrogen reached 47.6% at the end of the reaction. In the coupled system, thanks to the slow release of the iron source by the Fe3O4@CF functional material, ammonia nitrogen was degraded in large quantities at the beginning of the reaction. As the reaction continued, ammonia nitrogen steadily decreased. After 84 hours of reaction, the ammonia nitrogen removal rate reached 95.9%. It is worth noting that the coupled system showed a faster ammonia nitrogen degradation trend than the Feammox biological control system at the beginning of the reaction, which proves the promotion effect of the Fe3O4@CF functional material on the Feammox rate.

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

[0048] Example 2

[0049] In this example, a coupling system with different dosages of Fe3O4@CF functional materials was constructed to evaluate the effect of the dosage of Fe3O4@CF functional materials on the deammoniation performance of the Feammox system, as follows:

[0050] (1) According to the method of Example 1, a Fe3O4@CF coupled Feammox biological system (coupled system) was constructed with the dosage of Fe3O4@CF functional material being 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 oscillator for full reaction, with the speed controlled at 170 r / min, the temperature at 30°C, and the reaction time set to 84 h. During the reaction period, at the set sampling time point, the water sample was flocculated and precipitated, then filtered with 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 in the figure, when the dosage of Fe3O4@CF functional material is 0.6g / L, the electron transfer between functional bacteria in the Feammox system is enhanced, and the ammonia nitrogen oxidation rate is improved. However, due to the limited amount of loaded nano-Fe3O4, the iron source in the system is insufficient to support the degradation of more ammonia nitrogen. At the end of the reaction, the ammonia nitrogen removal rate reaches 78.9%. When the dosage of Fe3O4@CF functional material is increased to 1.2g / L, the ammonia nitrogen degradation rate is significantly improved, and the functional material provides sufficient additional iron source, so that at the end of the Feammox reaction, the ammonia nitrogen removal rate reaches 95.9%. When the dosage of Fe3O4@CF functional material is increased to 1.8g / L and 2.4g / L, a slight increase in the ammonia nitrogen degradation rate is observed, and at the end of the reaction, the ammonia nitrogen removal rate exceeds 95%. On the one hand, the nano-Fe3O4 and carbon felt in the functional materials have good biocompatibility and are widely used in bioprocessing. Therefore, the large-scale addition of functional materials does not have an excessive inhibitory effect on microbial activity, so that the coupled system still maintains a stable and efficient ammonia nitrogen degradation effect; but on the other hand, the strengthening effect of Fe3O4@CF functional materials on the Feammox system is not linear, which may be attributed to the limited biological density in the system and the limited utilization ability of Feammox bacteria for functional materials.

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

[0054] The embodiments described above are only some embodiments of the present invention, rather than all embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. The scope of protection of the present invention shall be subject to the scope required by the claims. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work shall fall within the scope of protection of the present invention.

Claims

1. A Fe-based 3 O 4 @CF functional materials improve the deamination efficiency of Feammox, It is characterized in that The following steps are involved: Step 1) The precursor solution is in situ generated on the modified carbon felt by a hydrothermal method and nano-Fe is loaded 3 O 4 , prepare Fe 3 O 4 @CF functional materials; Step 2) Adding ammonia nitrogen simulated wastewater and the Fe prepared in step 1) to the anaerobic sludge 3 O 4 @CF functional materials, complete Feammox sludge domestication; Step 3) Adding the Fe prepared in step 1) to the domesticated Feammox sludge 3 O 4 @CF functional materials, building Fe 3 O 4 @CF functional material coupled with Feammox biological system; then the ammonia nitrogen wastewater to be treated is added with the Fe in a sequencing batch reaction mode. 3 O 4 @CF functional materials are coupled to the Feammox biological system to react and the system can be operated uninterruptedly.

2. A Fe-based method according to claim 1 3 O 4 @CF functional materials improve the deamination efficiency of Feammox, It is characterized in that The preparation method of the modified carbon felt in step 1) is as follows: The graphite carbon felt is cut into small pieces, washed with acetone and dried, and then immersed in a dilute nitric acid solution. The treated carbon felt is then washed with deionized water and ethanol until the washing water is neutral, and then dried for later use.

3. A Fe-based method according to claim 1 3 O 4 @CF functional materials improve the deamination efficiency of Feammox, It is characterized in that The preparation method of the precursor solution in step 1) is as follows: Weigh 0.8855 g of FeCl 3 6H 2 O was dissolved in 30 mL of deionized water, 0.5976 g of sodium citrate was added and magnetic stirring was performed to uniformly mix; 0.1642 g of polyethylene glycol was added and magnetic stirring was continued to uniformly mix; ammonia water was slowly added dropwise to adjust the pH to 9 to obtain the product.

4. A Fe-based method according to claim 1 3 O 4 @CF functional materials improve the deamination efficiency of Feammox, It is characterized in that Step 1) Fe 3 O 4 The specific preparation method of @CF functional material is as follows: the modified carbon felt and the precursor solution are mixed and stirred, and then all are transferred into the reaction kettle, placed in a blast drying oven at 200°C for 8 hours; after the reaction, the nano-Fe 3 O 4 The carbon felt is taken out, washed repeatedly with deionized water, and dried in a vacuum drying oven to obtain the Fe 3 O 4 @CF functional materials.

5. A Fe-based method according to claim 1 3 O 4 @CF functional materials improve the deamination efficiency of Feammox, It is characterized in that Step 2) The specific steps of Feammox sludge domestication are as follows: The simulated wastewater with ammonia nitrogen concentration of 20 mg / L and Fe 3 O 4 @CF functional materials were added to anaerobic sludge for acclimatization, wherein 0.4L simulated wastewater was added per liter of anaerobic sludge, and 120mg Fe was added per liter of simulated wastewater. 3 O 4 @CF functional materials; After the ammonia nitrogen in the simulated wastewater is completely converted, the ammonia nitrogen concentration of the simulated wastewater is gradually increased to 40 mg / L and added to the anaerobic sludge to continue sludge domestication. After the effluent quality is stabilized, the sludge domestication is completed.

6. A Fe-based method according to claim 1 3 O 4 @CF functional materials improve the deamination efficiency of Feammox, It is characterized in that Step 3) Fe 3 O 4 @The dosage of CF functional material is 0.6~2.4g / L.

7. A Fe-based method according to claim 6 3 O 4 @CF functional materials improve the deamination efficiency of Feammox, It is characterized in that The dosage is 1.2 g / L.

8. A Fe-based method according to claim 1 3 O 4 @CF functional materials improve the deamination efficiency of Feammox, It is 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.

9. A Fe-based method according to claim 1 3 O 4 @CF functional materials improve the deamination efficiency of Feammox, It is characterized in that Step 3) The specific steps of the uninterrupted operation system are as follows: The Fe 3 O 4 @CF functional material coupled with Feammox biological system was placed in a constant temperature oscillator for mixed reaction, wherein the speed was controlled at 170r / min, the temperature was controlled at 30°C, and the reaction time was 84h.

Images