MBBR (Moving Bed Biofilm Reactor) composite modified filler as well as preparation method and application thereof

Abstract

The invention discloses an MBBR (Moving Bed Biofilm Reactor) composite modified filler as well as a preparation method and application thereof, the MBBR composite modified filler comprises the following raw material components in parts by mass: 5-15 parts of elemental iron-carbon powder, 80-95 parts of a framework material, 5-10 parts of a corrosion inhibition carbon source and 3-5 parts of paraffin oil, wherein the corrosion inhibition carbon source comprises modified chitosan and starch, and the mass ratio of the modified chitosan to the starch is (1.5-4): 1; the modified chitosan comprises chitosan, 2-hydroxy-1, 4-naphthoquinone which is grafted on the chitosan through a-C = N-bond, and catechin which is grafted on the 2-hydroxy-1, 4-naphthoquinone. The iron-carbon micro-electrolysis technology is combined with the MBBR process, so that the biodegradability of the refractory wastewater is improved, and the wastewater treatment effect of the MBBR process is improved.

Description

Technical Field

[0001] The invention relates to an MBBR composite modified filler and a preparation method and application thereof, belonging to the technical field of sewage treatment. Background Art

[0002] The MBBR process works by adding a certain amount of suspended carriers to the reactor to increase the biomass and biodiversity in the reactor, thereby improving the reactor's treatment efficiency. The suspended carrier is the core component of the MBBR process, providing a habitat for the biofilm to attach and grow. The performance of the carrier directly affects the effectiveness of water treatment.

[0003] The principle of iron-carbon micro-electrolysis is to exploit the electrode potential difference between iron and carbon to form a closed circuit in an aqueous electrolyte solution, thereby forming countless microscopic primary cells and initiating electrochemical reactions. Iron-carbon micro-electrolysis can generate highly oxidatively active substances (O·), which degrade high-molecular-weight organic matter into small-molecule products through a series of organic reactions such as bond scission, addition, and electron transfer. Therefore, this technology is often widely used to treat high-concentration, refractory organic wastewater. However, the application cost of iron-carbon micro-electrolysis is relatively high when the water treatment volume is large, and the single MBBR process is also difficult to treat refractory organic wastewater. Summary of the Invention

[0004] The purpose of the present invention is to provide an MBBR composite modified filler and its preparation method and application, by combining iron-carbon micro-electrolysis technology with the MBBR process to improve the biodegradability of refractory wastewater, thereby improving the wastewater treatment effect of the MBBR process.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A MBBR composite modified filler, wherein the raw materials thereof include the following components, calculated by weight: 5-15 parts of elemental iron-carbon powder, 80-95 parts of skeleton material, 5-10 parts of corrosion-inhibiting carbon source, and 3-5 parts of paraffin oil; The corrosion inhibition carbon source includes modified chitosan and starch, and the mass ratio of modified chitosan to starch is (1.5-4):1; The modified chitosan comprises chitosan, 2-hydroxy-1,4-naphthoquinone grafted onto the chitosan via a -C=N- bond, and catechin grafted onto the 2-hydroxy-1,4-naphthoquinone.

[0006] Preferably, the mesh size of the elemental iron-carbon powder is ≤100, and the mass ratio of iron to carbon is 1:(2-5).

[0007] Preferably, the skeleton material is polyethylene or polypropylene.

[0008] Preferably, the preparation method of modified chitosan comprises the following steps: S1: Add 2-hydroxy-1,4-naphthoquinone solution dropwise to chitosan acid solution, adjust the pH to 4.5-5.5, shake in a water bath under light-proof conditions, pour the reaction solution into alcohol solution for precipitation, and then centrifuge, wash, and dry to obtain 2-hydroxy-1,4-naphthoquinone grafted chitosan; S2: Add EDC·HCl and NHS to the buffer solution containing catechins, and stir at room temperature for activation; then add 2-hydroxy-1,4-naphthoquinone-grafted chitosan to the activation solution, adjust the pH to 7-8, shake the reaction in a water bath in the dark, dialyze the reaction solution, and then freeze-dry.

[0009] Preferably, in step S1, the mass ratio of 2-hydroxy-1,4-naphthoquinone in the 2-hydroxy-1,4-naphthoquinone solution to chitosan in the chitosan acid solution is (1-3):(5-15).

[0010] Preferably, in step S1, the conditions for the water bath oscillation reaction are: 55-65° C., 100-200 rpm, and 5-8 h.

[0011] Preferably, in step S2, the mass ratio of catechin, EDC·HCl, NHS and 2-hydroxy-1,4-naphthoquinone grafted chitosan is: (1-3): (0.4-0.7): (0.2-0.5): (8-15).

[0012] Preferably, in step S2, the activation time is 20-50 min; The conditions for the water bath shaking reaction are: 65-85°C, 100-150 rpm, 3-5 h.

[0013] The preparation method of any of the above-mentioned MBBR composite modified fillers is to mix elemental iron-carbon powder, skeleton material, corrosion-inhibiting carbon source and paraffin wax, granulate the mixture and then extrude the mixture into a pellet; the granulation and extrusion molding are carried out under nitrogen or inert atmosphere.

[0014] Application of any of the above-mentioned MBBR composite modified fillers in sewage treatment.

[0015] The beneficial effects of the present invention are: 1. 2-Hydroxy-1,4-naphthoquinone reacts with chitosan's amino groups through its quinone group to form a Schiff base bond (-C=N-). The carbon atom in the Schiff base bond, connected to the electronegative nitrogen atom, is positively charged, becoming a new electrophilic site. Simultaneously, the catechin grafted onto the naphthoquinone forms an intramolecular hydrogen bond between its phenolic hydroxyl group and the carbonyl oxygen of the naphthoquinone, further enhancing the electrophilicity of the naphthoquinone ring through electronic polarization. This strong electrophilicity, brought about by the naphthoquinone-catechin composite structure, completely dominates the material's properties, far exceeding the loss of chitosan's own amino group electrophilicity due to its participation in the reaction. This enhances the overall electrophilicity of the filler, making it more susceptible to adsorption of microorganisms with negative surface charge, and shortening biofilm formation time. 2. The aromatic ring structure of naphthoquinone can provide π electrons to form π-π interactions with proteins on the surface of microorganisms. At the same time, catechins can also promote the secretion of extracellular polymers (EPS) by microorganisms, accelerate biofilm cross-linking, and enhance biofilm stability. 3. The combination of iron-carbon micro-electrolysis and MBBR process improves the biodegradability of difficult-to-degrade wastewater, thereby improving the wastewater treatment effect of MBBR process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a physical picture of the MBBR filler prepared in Example 1; Figure 2 This is a comparison chart of the sedimentation performance of MBBR fillers prepared in Example 1 (left side) and Comparative Example 1 (right side). DETAILED DESCRIPTION

[0017] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0018] Example 1: This embodiment provides a preparation method of a MBBR composite modified filler, which is to grind elemental iron and carbon particles into powder and sieve them with a 100-mesh sieve, and then mix them in an iron-carbon mass ratio of 1:3.5; then take 10 parts by mass of elemental iron-carbon powder, 80 parts by mass of polyethylene, 7 parts by mass of corrosion-inhibiting carbon source (modified chitosan and starch are compounded in a mass ratio of 2:1) and 3 parts by mass of paraffin oil, put them into a blender and mix them thoroughly, and then put the mixture into a screw machine and hot-melt granulate them at a temperature of 160°C to obtain composite particles; then put the composite particles into an injection molding machine (the feeding section, plasticizing section, homogenizing section and nozzle temperature are set to 160°C, 180°C, 190°C, and 200°C, respectively), and cool them after extrusion molding by a mold, wherein granulation and extrusion molding are carried out under nitrogen or an inert atmosphere, and the physical picture of the obtained filler is as shown in the figure. Figure 1 shown.

[0019] Wherein, the preparation method of modified chitosan comprises the following steps: S1: Add 2-hydroxy-1,4-naphthoquinone solution (1.5 g 2-hydroxy-1,4-naphthoquinone + 50 mL anhydrous ethanol, sonicated at 40 kHz for 10 min) dropwise to chitosan acid solution (10 g chitosan + 200 mL 2% acetic acid solution, stirred at 40°C for 2 h). Adjust the pH to 5 (0.1 M NaOH solution). Incubate in a 60°C water bath with shaking (150 rpm) for 6 h in the dark. The reaction solution is then poured into 5 volumes of anhydrous ethanol for precipitation. The mixture is then centrifuged, washed, and dried to obtain 2-hydroxy-1,4-naphthoquinone-grafted chitosan. S2: Add EDC·HCl (0.6 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride) and NHS (0.36 g of N-hydroxysuccinimide) to a buffer solution containing catechin (2 g of catechin + 100 ml of PBS buffer). Activate the solution by stirring at room temperature for 30 minutes. Then, add 10 g of 2-hydroxy-1,4-naphthoquinone-grafted chitosan to the activated solution, adjust the pH to 7.5 (0.1 M HCl solution), and incubate in a 70°C water bath with shaking (120 rpm) for 4 hours in the dark. The reaction solution is then dialyzed (MW cutoff 3500 Da, using deionized water as the dialyzate, with six replacements over 48 hours) and freeze-dried (-30°C for 24 hours).

[0020] Comparative Example 1: basically the same as Example 1, except that the chitosan in the corrosion inhibition carbon source in Comparative Example 1 was not modified.

[0021] The MBBR fillers prepared in Example 1 and Comparative Example 1 were applied to the treatment of landfill leachate. The leachate had complex components and poor biodegradability, with influent COD and ammonia nitrogen levels of 1715 mg / L and 169 mg / L, respectively. A control experiment was conducted under the conditions of a suspended sludge concentration of 3500 mg / L (negative surface charge of microorganisms in the sludge), a residence time of 6 hours, a filler filling ratio of 30%, and dissolved oxygen of 3 mg / L in the MBBR process. The effluent COD, ammonia nitrogen, sludge SVI value, and biofilm formation time of the control group of MBBR fillers before and after modification are shown in Table 1. The results show that the modified filler significantly improves the removal of effluent pollutants, significantly improves the sludge settling performance, and shortens the biofilm formation time of the filler. Figure 2 These are the sedimentation diagrams of the MBBR fillers prepared using Example 1 (left) and Comparative Example 1 (right) after stable operation. The sludge SV30 values are 29% (left) and 38% (right), respectively. It can be seen that the MBBR composite modified filler effectively improves the sludge sedimentation effect.

[0022] Table 1

[0023] After the MBBR filler biofilm is formed, the MBBR filler loaded with activated sludge is taken daily and placed in a beaker with water until the filler is submerged. The filler is then placed in an ultrasonic machine and ultrasonically treated at the same frequency (50KHz) for 2 hours. After the completion, the sludge removed from the beaker during the ultrasonic process is filtered and the mass of the removed sludge is measured to evaluate the sludge load on the filler surface. The results are shown in Table 2. After ultrasonic treatment, the amount of sludge removed from the modified MBBR filler is significantly greater than that removed from the unmodified filler, indicating that the modified filler has a greater sludge load on the surface, indicating that the modified MBBR filler is more conducive to microbial loading. The sludge removal rate can also reflect (the greater the removal rate, the greater the load before ultrasonic treatment). The sludge load on the unmodified filler decreases to a certain extent over time, while the sludge load on the modified filler does not decrease, indicating that the stability of the biofilm on the modified filler surface is improved.

[0024] Table 2

[0025] The above is only a preferred embodiment of the patent of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the patent of the present invention. These improvements and modifications should also be regarded as the scope of protection of the patent of the present invention.

Claims

1. A MBBR composite modified filler, characterized in that, The raw materials include the following components by weight: 5-15 parts of elemental iron-carbon powder, 80-95 parts of skeleton material, 5-10 parts of corrosion-inhibiting carbon source and 3-5 parts of paraffin oil; The corrosion inhibition carbon source includes modified chitosan and starch, and the mass ratio of modified chitosan to starch is (1.5-4):1; The modified chitosan comprises chitosan, 2-hydroxy-1,4-naphthoquinone grafted onto the chitosan via a -C=N- bond, and catechin grafted onto the 2-hydroxy-1,4-naphthoquinone.

2. The MBBR composite modified filler according to claim 1, characterized in that The mesh number of the elemental iron-carbon powder is ≤100, and the mass ratio of iron to carbon is 1:(2-5).

3. The MBBR composite modified filler according to claim 1, characterized in that The skeleton material is polyethylene or polypropylene.

4. The MBBR composite modified filler according to claim 1, characterized in that The preparation method of modified chitosan comprises the following steps: S1: Add 2-hydroxy-1,4-naphthoquinone solution dropwise to chitosan acid solution, adjust the pH to 4.5-5.5, shake in a water bath under light-proof conditions, pour the reaction solution into alcohol solution for precipitation, and then centrifuge, wash, and dry to obtain 2-hydroxy-1,4-naphthoquinone grafted chitosan; S2: Add EDC·HCl and NHS to the buffer solution containing catechins, and stir at room temperature for activation; then add 2-hydroxy-1,4-naphthoquinone-grafted chitosan to the activation solution, adjust the pH to 7-8, shake the reaction in a water bath in the dark, dialyze the reaction solution, and then freeze-dry.

5. The MBBR composite modified filler according to claim 4, characterized in that In step S1, the mass ratio of 2-hydroxy-1,4-naphthoquinone in the 2-hydroxy-1,4-naphthoquinone solution to chitosan in the chitosan acid solution is (1-3):(5-15).

6. The MBBR composite modified filler according to claim 4, characterized in that In step S1, the conditions for the water bath oscillation reaction are: 55-65° C., 100-200 rpm, 5-8 h.

7. The MBBR composite modified filler according to claim 4, characterized in that In step S2, the mass ratio of catechin, EDC·HCl, NHS and 2-hydroxy-1,4-naphthoquinone grafted chitosan is: (1-3): (0.4-0.7): (0.2-0.5): (8-15).

8. The MBBR composite modified filler according to claim 4, characterized in that In step S2, the activation time is 20-50 min; The conditions for the water bath shaking reaction are: 65-85°C, 100-150 rpm, 3-5 h.

9. The method for preparing the MBBR composite modified filler according to any one of claims 1 to 8, characterized in that: The method comprises mixing elemental iron-carbon powder, skeleton material, corrosion-inhibiting carbon source and paraffin wax, granulating the mixture, and then extruding the mixture into a granule. The granulation and extrusion molding are performed under nitrogen or inert atmosphere.

10. Use of the MBBR composite modified filler according to any one of claims 1 to 8 in sewage treatment.

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