Method for enhancing microorganism driven iron reduction by super activated carbon

Abstract

The invention discloses a method for enhancing microorganism driven iron reduction by super activated carbon, which belongs to the technical field of advanced oxidation and biological co-treatment in environmental engineering, and comprises the following steps: (1) co-precipitation treatment: adding super activated carbon and polyaluminum chloride into a Fenton reaction stage, and standing for reaction to generate precipitate; (2) culturing a reducing bacteria solution, namely putting reducing bacteria into a liquid culture medium, culturing, collecting bacterial cultures through a refrigerated centrifugation method, adding the bacterial cultures into the sterilized broth, and culturing under an anaerobic condition to obtain the reducing bacteria solution; and (3) reduction treatment: adding the precipitate obtained in the step (1) into the reducing bacteria solution obtained in the step (2), carrying out oscillation reduction under an anaerobic condition, standing and precipitating, and then carrying out solid-liquid separation. According to the method, the sedimentation efficiency of the iron sludge can be remarkably improved, the reduction rate is obviously increased, accelerated treatment of the whole circulation process is facilitated, and the production cost is effectively reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of advanced oxidation and biological collaborative treatment in environmental engineering, and particularly relates to a method for super activated carbon enhanced microbial driven iron reduction. BACKGROUND

[0002] The circulating Bio-Fenton technology is a green and efficient wastewater treatment technology, which realizes iron ion recycling and avoids the generation of iron sludge solid waste by reducing Fe (III) iron sludge produced by Fenton reaction to Fe (II) by iron-reducing bacteria (such as decoloring shewanella MR-1). However, the existing technology has two core defects: (1) low iron sludge sedimentation efficiency: the Fe (III) colloidal particles produced by homogeneous Fenton are small, and it takes more than 8.3 hours to completely precipitate by adding polyaluminum chloride (PAC) flocculation, and the residual Fe (III) concentration in the supernatant is high (> 6 mg / L), which increases the load of the subsequent iron-reducing bacteria and affects the recycling efficiency; (2) slow Fe (III) reduction rate: when the iron-reducing bacteria MR-1 directly reduces Fe (III), the contact area between the bacteria and the iron is small, and the electron transfer efficiency is low, so the Fe (III) reduction rate is only 43% in 24 hours, which cannot meet the rapid iron supply demand of the circulating Bio-Fenton; and the bacteria have poor tolerance to environmental disturbance (such as H2O2 residue and pH fluctuation), which easily leads to reduction activity attenuation. SUMMARY

[0003] The purpose of the present application is to provide a method for super activated carbon enhanced microbial driven iron reduction, which aims to solve the above problems.

[0004] A method for super activated carbon enhanced microbial driven iron reduction, comprising the following steps: (1) synergistic precipitation treatment: Add super activated carbon and polyaluminum chloride to the Fenton reaction stage, and generate a precipitate after standing and reacting; (2) reduction bacteria liquid culture: Take the reduction bacteria and place it in a liquid culture medium, culture for 15-17 hours, collect the bacterial culture by freezing centrifugation, then add it to the sterilized broth, and culture the reduction bacteria liquid under anaerobic conditions; (3) reduction treatment: Add the precipitate obtained in step (1) to the reduction bacteria liquid obtained in step (2), and shake under anaerobic conditions for 20-26 hours, then perform solid-liquid separation after standing and precipitating.

[0005] Further, the addition amount of the super activated carbon and the polyaluminum chloride in step (1) is 0.5 g / L.

[0006] Furthermore, the preparation method of the super activated carbon is as follows: wheat bran, citric acid, and potassium hydroxide are mixed in a mass ratio of 1:1:3, stirred for 2 hours, dried at 105℃ for 12 hours, then activated at 700℃ for 2 hours by increasing the temperature at 5℃ / min. Finally, the resulting product is ground through a 200-mesh sieve. The super activated carbon prepared in this way has significantly improved physicochemical properties compared to traditional activated carbon, can accelerate electron transfer efficiency, and can effectively improve the tolerance of reducing bacteria.

[0007] Furthermore, during the static reaction described in step (1), the pH is adjusted to 8.5; the reaction time is 20-25 min.

[0008] Furthermore, the reducing bacteria mentioned in step (2) are Fe(III) reducing bacteria; the liquid culture medium includes the following components in corresponding amounts: 8-12 g / L sodium chloride, 3-6 g / L yeast extract, and 8-12 g / L tryptone.

[0009] Furthermore, the anaerobic conditions described in step (2) are a nitrogen environment.

[0010] Furthermore, after the precipitate mentioned in step (3) is added to the reducing bacterial solution, nitrogen gas is continuously introduced to remove dissolved oxygen.

[0011] Furthermore, the nitrogen gas is introduced for 1-1.2 hours.

[0012] Furthermore, the temperature during the oscillation reduction described in step (3) is controlled at 36-37℃; the stirring speed during this period is 180-200 rpm.

[0013] The beneficial effects of this invention are: The overall method of this invention is simple. First, super-activated carbon adsorbs Fe(III) colloidal particles through its tiered pores. Simultaneously, polyaluminum chloride acts as an adsorption bridging agent to trap and aggregate the super-activated carbon-Fe(III) complex, achieving rapid precipitation with a precipitation efficiency of 99.5%. Then, the complex is added to the reducing bacterial solution. Super-activated carbon acts as an electron shuttle, absorbing electrons from the reducing bacteria and transferring them to Fe(III), while simultaneously increasing the bacteria-iron contact area and enhancing the reduction rate. After 24 hours, the Fe(III) reduction rate reaches over 80%. Furthermore, the addition of super-activated carbon improves the reducing bacteria's tolerance to H2O2. When the H2O2 concentration is ≤ 2 mmol / L, the bacterial activity can recover rapidly, facilitating subsequent repeated recycling. This method significantly improves the settling efficiency of iron sludge and significantly accelerates the reduction rate, facilitating faster overall recycling processes, effectively reducing production costs, and increasing reaction efficiency. Attached Figure Description

[0014] Figure 1 The image shown is a SEM image from the process corresponding to the test in Embodiment 2 of the present invention. Figure 2 The images shown are AFM morphology diagrams and surface spot change diagrams from the process corresponding to Example 2 of this invention. Figure 3 The graph shows the adsorption test data of Fe(III) on the super activated carbon corresponding to Example 1 and the activated carbon corresponding to Comparative Example 1. Detailed Implementation

[0015] The specific embodiments of the present invention will be further described in detail with reference to the accompanying drawings, examples, and comparative examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0016] Example 1: A method for enhancing microbial-driven iron reduction with super activated carbon, comprising the following steps: (1) Co-precipitation treatment: Super activated carbon and polyaluminum chloride were added to the Fenton reaction stage, both at a concentration of 0.5 g / L. The pH was adjusted to 8.5 and the mixture was allowed to stand for 20 min to form a precipitate. (2) Culture of reducing bacterial solution: Fe(III) reducing bacteria were placed in liquid culture medium and cultured for 15 h. The bacterial culture was collected by freezing centrifugation and then added to sterilized broth. The culture was then placed under nitrogen anaerobic conditions to obtain reducing bacterial solution. (3) Reduction process: Add the precipitate obtained in step (1) to the reducing bacterial solution obtained in step (2), continuously purge with nitrogen for 1 hour to remove dissolved oxygen, and then shake and reduce under anaerobic conditions for 20 hours. The temperature during shaking and reduction is controlled at 36℃. The stirring speed during this period is 180 rpm. After settling, solid-liquid separation can be performed.

[0017] The preparation method of super activated carbon is as follows: wheat bran, citric acid and potassium hydroxide are mixed in a mass ratio of 1:1:3, stirred for 2 h, dried at 105℃ for 12 h, then activated at 700℃ for 2 h at a rate of 5℃ / min, and finally the product is ground through a 200-mesh sieve.

[0018] The liquid culture medium contains the following components in the following proportions: 8 g / L sodium chloride, 3 g / L yeast extract, and 8 g / L tryptone.

[0019] Example 2: A method for enhancing microbial-driven iron reduction with super activated carbon, comprising the following steps: (1) Co-precipitation treatment: Super activated carbon and polyaluminum chloride were added to the Fenton reaction stage, both at a concentration of 0.5 g / L. The pH was adjusted to 8.5 and the mixture was allowed to stand for 20 min to form a precipitate. (2) Culture of reducing bacterial solution: Fe(III) reducing bacteria were placed in liquid culture medium and cultured for 16 h. The bacterial culture was collected by freezing centrifugation and then added to sterilized broth. The culture was then placed under nitrogen anaerobic conditions to obtain reducing bacterial solution. (3) Reduction process: Add the precipitate obtained in step (1) to the reducing bacterial solution obtained in step (2), continuously purge with nitrogen for 1 hour to remove dissolved oxygen, and then shake and reduce under anaerobic conditions for 24 hours. The temperature during shaking and reduction is controlled at 37°C. The stirring speed during this period is 180 rpm. After settling, solid-liquid separation can be performed.

[0020] The preparation method of super activated carbon is as follows: wheat bran, citric acid and potassium hydroxide are mixed in a mass ratio of 1:1:3, stirred for 2 h, dried at 105℃ for 12 h, then activated at 700℃ for 2 h at a rate of 5℃ / min, and finally the product is ground through a 200-mesh sieve.

[0021] The liquid culture medium contains the following components in the following proportions: 10 g / L sodium chloride, 5 g / L yeast extract, and 10 g / L tryptone.

[0022] Example 3: A method for enhancing microbial-driven iron reduction with super activated carbon, comprising the following steps: (1) Co-precipitation treatment: Super activated carbon and polyaluminum chloride were added to the Fenton reaction stage, both at a concentration of 0.5 g / L. The pH was adjusted to 8.5 and the mixture was allowed to stand for 25 minutes to react before a precipitate was formed. (2) Culture of reducing bacterial solution: Fe(III) reducing bacteria were placed in liquid culture medium and cultured for 17 h. The bacterial culture was collected by freezing centrifugation and then added to sterilized broth. The culture was then placed under nitrogen anaerobic conditions to obtain the reducing bacterial solution. (3) Reduction process: Add the precipitate obtained in step (1) to the reducing bacterial solution obtained in step (2), continuously purge with nitrogen for 1.2 h to remove dissolved oxygen, and then shake and reduce under anaerobic conditions for 26 h. The temperature during shaking and reduction is controlled at 37℃. The stirring speed during this period is 200 rpm. After settling, solid-liquid separation can be performed.

[0023] The preparation method of super activated carbon is as follows: wheat bran, citric acid and potassium hydroxide are mixed in a mass ratio of 1:1:3, stirred for 2 h, dried at 105℃ for 12 h, then activated at 700℃ for 2 h at a rate of 5℃ / min, and finally the product is ground through a 200-mesh sieve.

[0024] The liquid culture medium contains the following components in the following proportions: 12 g / L sodium chloride, 6 g / L yeast extract, and 12 g / L tryptone.

[0025] To further verify the effectiveness of the present invention, the process of Example 2 was used for specific experimental testing. Specifically, in the Fenton reaction stage, 100 mL of 100 mg / L SMZ (sulfamethoxazole) solution was added to a 250 mL reaction vessel, the pH was adjusted to 4.0, 0.15 g / L FeSO4 and 4 mmol / L H2O2 were added, and the reaction was carried out at 25°C with shaking for 60 min to generate Fe(III) iron sludge. Subsequently, it was treated according to steps such as co-precipitation. The Fe(III) reducing bacteria used was Shewanella decolorationis MR-1, which was obtained from the Institute of Microbiology, Chinese Academy of Sciences. Finally, after the Fe(III) reduction was completed, the pH was adjusted to 4.0 and allowed to stand for a period of time. After the iron sludge precipitated, the reducing bacterial solution was taken out, centrifuged at freeze, and then stored in a -20°C refrigerator for reuse. The supernatant could be used for homogeneous Fenton reaction.

[0026] Then, the morphology of the super activated carbon and polyaluminum chloride loaded with MR-1 bacteria in the above experiment was observed by SEM scanning, as shown in the attached figure. Figure 1 As shown in the attached figure; and AFM morphology scanning observation and surface point change test were also performed on it, as detailed in the attached figure. Figure 2 As shown in the figure. The precipitation efficiency of the method of the present invention was finally measured to be 99.5%, and the Fe(III) reduction rate was more than 80% after 24 h, which is 1.86 times that of the traditional process without activated carbon (maximum 43%); proving that it has significant reduction efficiency.

[0027] To further compare the advantages of the super activated carbon prepared by this invention, the process for the super activated carbon in Example 1 was modified as Comparative Example 1. Specifically, only wheat bran was used as the raw material. The wheat bran was dried at 105°C for 12 hours, then activated at 700°C at a rate of 5°C / min for 2 hours. Finally, the resulting product was ground through a 200-mesh sieve. Commercially available activated carbon was also used as Comparative Example 2. Performance tests were then conducted on the super activated carbon from Example 1, the activated carbon from Comparative Example 1, and the activated carbon from Comparative Example 2, as shown in Table 1 below. Table 1 ; In addition, the activated carbon from Example 1 and Comparative Example 1 were subjected to Fe(III) adsorption tests, and the specific results are shown in the appendix. Figure 3 As shown.

[0028] Combining Table 1 and Appendix Figure 3 It can be seen that the super activated carbon prepared by the method of the present invention has significantly improved physicochemical properties, thereby enhancing the effect of microbial-driven iron reduction.

[0029] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for enhancing microbial-driven iron reduction with super activated carbon, characterized in that, Includes the following steps: (1) Co-precipitation treatment: Super activated carbon and polyaluminum chloride were added to the Fenton reaction stage, and a precipitate was formed after the reaction was allowed to stand. (2) Culture of reducing bacterial solution: The reducing bacteria were placed in a liquid culture medium and cultured for 15-17 h. The bacterial culture was then collected by freezing centrifugation and added to sterilized broth. The culture was then placed under anaerobic conditions to obtain the reducing bacterial solution. (3) Reduction process: Add the precipitate obtained in step (1) to the reducing bacterial solution obtained in step (2), shake and reduce under anaerobic conditions for 20-26 h, let it stand to precipitate, and then perform solid-liquid separation.

2. The method for enhancing microbial-driven iron reduction with super activated carbon according to claim 1, characterized in that, The amount of super activated carbon and polyaluminum chloride added in step (1) is 0.5 g / L.

3. The method for enhancing microbial-driven iron reduction with super activated carbon according to claim 1, characterized in that, The preparation method of the super activated carbon is as follows: wheat bran, citric acid and potassium hydroxide are mixed in a mass ratio of 1:1:3, stirred for 2 h and then dried at 105℃ for 12 h. Then, the temperature is increased to 700℃ at 5℃ / min and activated for 2 h. Finally, the obtained product is ground through a 200-mesh sieve.

4. A method for enhancing microbial-driven iron reduction with super activated carbon according to claim 1, characterized in that, During the static reaction described in step (1), the pH was adjusted to 8.5; the reaction time was 20-25 min.

5. A method for enhancing microbial-driven iron reduction with super activated carbon according to claim 1, characterized in that, The reducing bacteria mentioned in step (2) are Fe(III) reducing bacteria; the liquid culture medium includes the following components in corresponding amounts: 8-12 g / L sodium chloride, 3-6 g / L yeast extract, and 8-12 g / L tryptone.

6. The method for enhancing microbial-driven iron reduction with super activated carbon according to claim 1, characterized in that, The anaerobic conditions described in step (2) are a nitrogen environment.

7. The method for enhancing microbial-driven iron reduction with super activated carbon according to claim 1, characterized in that, After the precipitate mentioned in step (3) is added to the reducing bacterial solution, nitrogen gas is continuously introduced to remove dissolved oxygen.

8. A method for enhancing microbial-driven iron reduction with super activated carbon according to claim 7, characterized in that, The nitrogen gas is introduced for 1-1.2 hours.

9. A method for enhancing microbial-driven iron reduction with super activated carbon according to claim 1, characterized in that, The temperature control during the oscillation reduction in step (3) is 36-37℃; the stirring speed during this period is 180-200 rpm.

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