A bio-abiotic hybrid material Ni / Fe LDH@C-AGS and its synthesis method and application

Abstract

The present invention discloses a bio-non-biological hybrid material Ni / Fe LDH@C-AGS and a synthesis method and application thereof, belonging to the technical field of anaerobic biological treatment of wastewater. First, an in-situ co-precipitation method is used to prepare a composite material Ni / Fe LDH@C with both biocompatibility and conductivity as a loading substrate. Then, electrostatic attraction is used to anchor Ni / Fe LDH@C on the surface of AGS to synthesize a stable bio-non-biological hybrid material Ni / Fe LDH@C-AGS. The hybrid material disclosed by the present invention has excellent specific surface area, catalytic performance and conductive performance. Under the synergistic effect of external voltage and a biological reaction system, the hybrid material can enable microorganisms to directly utilize electrons provided by an external electric field to electrochemically decompose non-conductive substances on the surface of AGS, thereby promoting the DIET process between LDH and microorganisms and improving the yield of CH4 in the anaerobic digestion process. The present invention also discloses a synthesis method of the hybrid material. Not only is the process simple and cost-effective, but the synthesized hybrid material can also maintain good stability during long-term operation.

Description

Technical Field

[0001] The present invention belongs to the technical field of anaerobic wastewater treatment, and specifically relates to a biological-abiotic hybrid material Ni / Fe LDH@C-AGS and a synthesis method and application thereof. Background Art

[0002] With the acceleration of global economic development and urbanization, energy and water resource crises have become critical issues facing global sustainable development. Anaerobic wastewater treatment technology, with its numerous advantages, including low investment, low energy consumption, recyclable biogas energy, high load capacity, low sludge production, and resistance to shock loads, has once again attracted the attention of environmentalists. Anaerobic biological treatment utilizes the metabolic properties of anaerobic microorganisms to decompose organic pollutants and produce methane gas. Because this technology does not require external energy, it uses organic matter as a hydrogen acceptor, reducing it to energy-valuable methane. This allows wastewater to be used as a valuable resource, providing both recycled water and methane energy, thereby changing its role as a carrier of environmental pollution.

[0003] The anaerobic digestion process consists of three stages. First, fermentative bacteria break down organic matter into organic acids or alcohols. Second, hydrogen-producing and acetogenic bacteria degrade it into acetic acid and H2 / CO2, and finally, methanogenic archaea convert it into CH4 and CO2. The essence of methanogenesis in anaerobic digestion is the bacterial breakdown of organic matter, providing substrate and electrons for methanogens, which then reduce CO2 to CH4. The rate of methanogenesis depends heavily on interspecies electron transfer (IET). Providing electron donors to methanogens in the form of electron carriers such as acetate and H2, ultimately reducing CO2 to CH4, is a key IET mechanism in anaerobic digestion. Recent research has demonstrated a more efficient IET mechanism: direct interspecies electron transfer (DIET), achieved by constructing a reaction interface between biological and non-biological electroactive materials. This improved electron transfer efficiency can significantly increase CH4 yield.

[0004] AGS is a unique microbial aggregate formed during anaerobic biological treatment. It is composed of microorganisms and high-molecular-weight natural polymers secreted into the extracellular environment. Compared to flocculent sludge, AGS exhibits strong settling ability, high metabolic activity, high sludge concentration, shock resistance, and strong load-bearing capacity. AGS is primarily composed of hydrolytic and fermentative bacteria, hydrogen-producing and acetogenic bacteria, and methanogenic bacteria. Because the surface of AGS is coated with a thick layer of EPS, which contains a large amount of non-conductive substances, the conductivity of AGS is several orders of magnitude lower than that of biofilms, significantly limiting the IET process. Furthermore, due to the compactness of the extracellular material of AGS, even the addition of conductive materials often fails to effectively promote the microbial DIET process.

[0005] LDH is a nanoscale hydrotalcite-like material with excellent biocompatibility, low toxicity, and efficient catalytic performance. Due to its unique chemical structure and positive surface charge, it can electrostatically attract and bind to the negatively charged surfaces of microorganisms. Combined with LDH's excellent biocompatibility and the electrical conductivity of carbon, if the complex can promote the DIET process of microorganisms, it could increase the yield of CH4 during anaerobic digestion, thereby improving the purity of CH4 in biogas. This could provide a technical solution for the energy utilization of CH4, a field in which research has yet to be reported.

[0006] Patent publication number CN114163085A discloses an anaerobic bioreactor that uses an electrochemical system to enhance methane production. The anaerobic bioreactor and an electrochemical system installed external to the anaerobic bioreactor accelerate the mass transfer rate between anaerobic digestion microorganisms, while enhancing the metabolic activity of the methanogenic microorganisms, improving effluent quality, and increasing methane production. However, due to the poor conductivity of wastewater, the electrochemical mass transfer efficiency is low, significantly increasing operating costs. Using only the disclosed reactor and electrochemical system electrochemical methods cannot achieve energy savings. Patent CN115925110A discloses a method for enhancing methane yield by anaerobic treatment of high-concentration acidic organic wastewater. It also discloses a method for enhancing anaerobic methane production in high-concentration acidic organic wastewater using a Cs-Fe3O4 microsphere composite material. However, this patent uses traditional granular sludge, and the disclosed Cs-Fe3O4 microsphere composite material is only suitable for "high-concentration," "acidic," and "organic wastewater." Summary of the Invention

[0007] The present invention introduces a biological-abiotic hybrid material Ni / Fe LDH@C-AGS and its synthesis method and application. The hybrid material not only has excellent specific surface area, catalytic performance and conductive properties, but also significantly improves the ability of AGS to convert organic matter in wastewater into CH4.

[0008] The technical solutions of the present invention are as follows:

[0009] One of the objectives of the present invention is to provide a method for synthesizing a biological-abiotic hybrid material Ni / Fe LDH@C-AGS. The synthesis method uses an in situ co-precipitation method to prepare Ni / Fe LDH@C as a loading substrate, and then uses electrostatic attraction to anchor Ni / Fe LDH@C on the surface of anaerobic granular sludge AGS to synthesize the biological-abiotic hybrid material Ni / Fe LDH@C-AGS.

[0010] Further, the following steps are included:

[0011] (1) Preparation of loaded substrate: Mix Ni(NO3)2·6H2O solution and Fe(NO3)3·9H2O solution to form mixed solution A, and mixed solution A and powdered activated carbon C to form suspension solution B. Suspension solution B is titrated to pH = 10.0 with NaOH. After stirring and reacting, wash with deionized water several times until neutral, and dry to obtain Ni / Fe LDH@C loaded substrate.

[0012] (2) Acclimation of anaerobic granular sludge AGS: The sludge containing AGS was cultivated using culture medium, and nitrogen was introduced for aeration until the dissolved oxygen content in the water was lower than 0.5 mg / L, and its pH was adjusted.

[0013] (3) Synthesis of Ni / Fe LDH@C-AGS: Taking advantage of the fact that the Ni / Fe LDH@C loading substrate carries a large amount of positive charge, Ni / Fe LDH@C is anchored on the surface of anaerobic granular sludge AGS by electrostatic attraction to synthesize the hybrid material Ni / Fe LDH@C-AGS.

[0014] Furthermore, the metal molar ratio of Ni(NO3)2·6H2O to Fe(NO3)3·9H2O in the mixed solution A is 3:1.

[0015] Furthermore, the powdered activated carbon C was obtained by soaking in a 30% hydrochloric acid solution for 24 hours and washing with deionized water multiple times, and the ratio of LDH formed in the suspension B to the powdered activated carbon C was 4:1.

[0016] Furthermore, the culture solution is composed of culture solution A and culture solution B, and the specific components are as follows:

[0017] Culture medium A: glucose 500 mg / L, ammonium chloride 32 mg / L, KH2PO4 20 mg / L, yeast fermentation product 100 mg / L, NaCl 50 mg / L, NaHCO3 75 mg / L, MgSO4·7H2O 25 mg / L, CaCl2 25 mg / L;

[0018] Culture medium B: CoCl2·6H2O 0.1 g / L, ZnCl20.13 g / L, CuSO4·5H2O 0.01 g / L, H3BO30.01 g / L, Na2MoO4·2H2O 0.025 g / L, NiCl2·6H2O 0.024 g / L, Na2WO4·2H2O 0.025g / L, MnCl2·4H2O 0.62g / L, EDTA·2Na 1.5g / L.

[0019] Furthermore, in step (3), the pH is adjusted to 6.8-7.2.

[0020] A second object of the present invention is to provide a biological-non-biological hybrid material Ni / Fe LDH@C-AGS.

[0021] The third object of the present invention is to provide an application of a biological-non-biological hybrid material Ni / Fe LDH@C-AGS.

[0022] Furthermore, the hybrid material can improve the yield of CH4 during anaerobic digestion under the synergistic effect of external voltage and biological reaction system.

[0023] Furthermore, the hybrid material enables microorganisms to directly utilize electrons provided by an external electric field to electrochemically decompose non-conductive substances on the surface of AGS, thereby promoting the DIET process between LDH and microorganisms and improving the CH4 yield of the anaerobic bioreactor.

[0024] Furthermore, the anaerobic bioreactor mainly includes a DC power supply, a plate, anaerobic granular sludge AGS, and a cylindrical reactor, wherein the material is an acrylic plate with an inner diameter of 10 cm, a height of 15 cm, and an effective volume of 1.0 L. The reactor plate is composed of a graphite plate, and the DC power supply applies a voltage of 1 V.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The bio-non-biological hybrid material Ni / Fe LDH@C-AGS synthesized by the present invention has the following advantages: (1) The present invention grows LDH in situ on the surface of acidified activated carbon powder through a co-precipitation synthesis method, so that the formation of LDH is spatially inhibited, and the obtained material has a larger specific surface area; (2) Unlike the traditional biofilm method, the present invention anchors Ni / Fe LDH@C on the surface of AGS by electrostatic attraction. The size of Ni / Fe LDH@C is much smaller than that of AGS and can quickly adhere to the surface of AGS to form a larger contact area; (3) By applying an external voltage of 1 V, the present invention enables the Ni / Fe LDH@C loaded on the surface of AGS to effectively decompose a large amount of non-conductive substances in the EPS outside AGS, thereby reducing IET resistance.

[0027] 2. Unlike the existing technology that only increases methane yield by adding composite materials, the present invention prepares a biological-non-biological hybrid material. The Ni / Fe LDH@C loading substrate in the hybrid material can serve as a nanowire between methanogenic archaea and hydrogen-producing and acetic acid-producing or fermentative bacteria, directly promoting DIET, thereby promoting the increase of CH4 production and improving the yield; and this hybrid material Ni / Fe LDH@C-AGS promotes the redox reaction under the action of an external electric field, so that the electrical activity of EPS outside AGS is regulated, wherein a large amount of non-conductive substances are oxidized and decomposed, reducing the resistance to electron transfer; the present invention accelerates the hydrogen circulation rate in the anaerobic bioreactor by exerting the synergistic effect of applied voltage and Ni / Fe LDH@C, promotes the transformation of the dominant archaeal species from acetate methanogens to hydrogen-type methanogens, consumes more CO2, and significantly reduces the CO2 concentration, thereby improving the methane production performance of methanogens and achieving an increase in CH4 purity.

[0028] 3. The synthesis method of the biological-non-biological hybrid material Ni / Fe LDH@C-AGS provided by the present invention is not only simple in steps, cost-effective, and environmentally friendly, but also the synthesized hybrid material has excellent specific surface area, catalytic performance and conductive properties, can maintain good stability during long-term operation, and significantly improves the ability of AGS to convert organic matter in wastewater into CH4. In addition, this patent can be applied to "low temperature and low turbidity" conditions, especially suitable for municipal sewage, which is of great significance for achieving the "carbon neutrality" goal of the wastewater treatment process, and provides new possibilities for sustainable energy and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Flow chart of the synthesis of the biological-non-biological hybrid material Ni / Fe LDH@C-AGS in Example 1 of the present invention;

[0030] Figure 2Schematic diagram of the structure of the Ni / Fe LDH@C-AGS anaerobic bioreactor of the biological-abiotic hybrid material in Example 2 of the present invention;

[0031] Figure 3 This is a graph showing changes in methane production in anaerobic bioreactors 1#, 2#, and 3# in performance test 1 of the present invention;

[0032] Figure 4 This is an analysis chart of EPS composition and concentration in anaerobic bioreactors 1#, 2#, and 3# in performance test 2 of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings and preferred embodiments. The given embodiments are only for illustrating the present invention, rather than for limiting the scope of the present invention.

[0034] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0035] The quantitative tests in the following examples were repeated three times, and the results were averaged.

[0036] The experimental methods in the following examples are conventional methods unless otherwise specified.

[0037] Example 1

[0038] This embodiment provides a method for synthesizing a biological-non-biological hybrid material Ni / Fe LDH@C-AGS. Figure 1 As shown, the following steps are included:

[0039] S1. Mix Ni(NO3)2·6H2O solution and Fe(NO3)3·9H2O solution in a metal molar ratio of 3:1 to form a mixed solution A, which is then mixed with powdered activated carbon C to form a suspension B. The ratio of LDH formed in the suspension B to the powdered activated carbon C is 4:1.

[0040] S2. Titrate the suspension B to pH 10.0 using 1 M NaOH, stir and react at 80°C for 24 h. After the reaction, wash with deionized water several times until neutral, and dry at 70°C to obtain a Ni / Fe LDH@C loaded substrate.

[0041] S3. A sludge containing AGS at a concentration of 3 g MLVSS / L was acclimated and cultured using culture medium, and then aerated with nitrogen until the dissolved oxygen content in the water was less than 0.5 mg / L. The pH was adjusted to 7.0 with 0.1 M HCl and NaOH. The culture medium consisted of culture medium A and culture medium B. The specific components were as follows:

[0042] Culture medium A: glucose 500 mg / L, ammonium chloride 32 mg / L, KH2PO4 20 mg / L, yeast fermentation product 100 mg / L, NaCl 50 mg / L, NaHCO3 75 mg / L, MgSO4·7H2O 25 mg / L, CaCl2 25 mg / L;

[0043] Culture medium B: CoCl2·6H2O 0.1 g / L, ZnCl2 0.13 g / L, CuSO4·5H2O 0.01 g / L, H3BO3 0.01 g / L, Na2MoO4·2H2O 0.025 g / L, NiCl2·6H2O 0.024 g / L, Na2WO4·2H2O 0.025 g / L, MnCl2·4H2O 0.62 g / L, EDTA·2Na 1.5 g / L;

[0044] S4. Taking advantage of the fact that the Ni / Fe LDH@C loading substrate carries a large amount of positive charge, Ni / FeLDH@C was anchored on the surface of anaerobic granular sludge AGS through electrostatic attraction to synthesize the hybrid material Ni / Fe LDH@C-AGS.

[0045] This synthesis method can also adjust the pH of the sludge containing AGS to other values ​​between 6.8 and 7.2 according to the actual situation during the synthesis process.

[0046] Example 2

[0047] This embodiment provides an application of a biological-non-biological hybrid material Ni / Fe LDH@C-AGS, including the following steps:

[0048] S1, set as Figure 2 The anaerobic bioreactor shown has an inner diameter of 10 cm, a height of 15 cm, an effective volume of 1.0 L, is made of acrylic plates, and the plates are composed of graphite plates;

[0049] S2, adding the biological-abiotic hybrid material Ni / FeLDH@C-AGS synthesized in Example 1 to the anaerobic bioreactor;

[0050] S3. At room temperature of 20°C, a voltage of 1 V was applied to the anaerobic bioreactor through a DC power supply to detect the COD removal rate and CH4 production in the anaerobic bioreactor.

[0051] Performance Testing

[0052] 1. COD removal rate and CH4 production test

[0053] S1, set three groups such as Figure 2 The anaerobic bioreactors shown are numbered 1#, 2# and 3#;

[0054] S2, anaerobic bioreactor No. 1 used only AGS and served as the control group; anaerobic bioreactor No. 2 used AGS and applied a voltage of 1 V; anaerobic bioreactor No. 3 used Ni / Fe LDH@C-AGS and applied a voltage of 1 V;

[0055] S3. At room temperature of 25 ℃, the COD removal rate and CH4 production during long-term operation of the anaerobic bioreactor were investigated.

[0056] 2. EPS composition and concentration test

[0057] S1, set three groups such as Figure 2 The anaerobic bioreactors shown are numbered 1#, 2# and 3#;

[0058] S2, anaerobic bioreactor No. 1 used only AGS and served as the control group; anaerobic bioreactor No. 2 used AGS and applied a voltage of 1 V; anaerobic bioreactor No. 3 used Ni / Fe LDH@C-AGS and applied a voltage of 1 V;

[0059] S3. At room temperature of 23 ℃, the protein and polysaccharide contents during long-term operation of the reactor were investigated.

[0060] Experimental results:

[0061] 1. Inspecting the COD removal rate in performance test 1, the COD removal rates in 1#, 2#, and 3# anaerobic bioreactors were 85%, 89%, and 93% respectively; inspecting the CH4 production in 1#, 2#, and 3# anaerobic bioreactors, the results are as follows: Figure 3 As shown in the figure, compared with the control group 1# reactor, the CH4 production of the 2# experimental group with a voltage of 1V and the 3# experimental group with a voltage of 1V and the addition of Ni / Fe LDH@C increased by 20% and 80%, respectively, indicating that Ni / Fe LDH@C-AGS has an excellent effect in promoting CH4 production from AGS.

[0062] 2. Inspect the EPS composition and concentration in performance test 2. The results are as follows Figure 4 As shown in the figure, the protein content of EPS in 1#, 2# and 3# anaerobic bioreactors were 52.5 mg / L, 21.5 mg / L and 17.0 mg / L, respectively, and the polysaccharide content were 16.6 mg / L, 11.5 mg / L and 8.2 mg / L, respectively.

[0063] The protein and polysaccharide contents in the experimental group were much lower than those in the control group. The experimental results showed that more EPS was decomposed under the action of Ni / FeLDH@C-AGS in conjunction with external voltage, thereby reducing the resistance of IET. The use of this biological-abiotic hybrid material Ni / Fe LDH@C-AGS is conducive to the interfacial interaction between microorganisms and LDH, building a better DIET bridge and achieving an increase in CH4 production.

[0064] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. Application of a biological-non-biological hybrid material Ni / Fe LDH@C-AGS, characterized in that: The hybrid material enables microorganisms to directly utilize the electrons provided by the external electric field to electrochemically decompose non-conductive substances on the surface of AGS, promote the DIET process between LDH and microorganisms, and improve the CH4 yield of the anaerobic bioreactor; The hybrid material is prepared by in-situ co-precipitation method. Ni / Fe LDH@C is used as a loading substrate, and then Ni / Fe LDH@C is anchored on the surface of anaerobic granular sludge AGS by electrostatic attraction to synthesize the biological-abiotic hybrid material Ni / Fe LDH@C-AGS. The following steps are involved: (1) Preparation of the loaded substrate: Ni(NO3)2·6H2O solution and Fe(NO3)3·9H2O solution were mixed to form a mixed solution A, and the mixed solution A was mixed with powdered activated carbon C to form a suspension solution B. The suspension solution B was titrated with NaOH to pH = 10.

0. After stirring, the suspension was washed with deionized water several times until neutral, and dried to obtain the Ni / Fe LDH@C loaded substrate; (2) Acclimation of anaerobic granular sludge AGS: The sludge containing AGS was cultivated using culture medium, and nitrogen was introduced for aeration until the dissolved oxygen content in the water was less than 0.5 mg / L, and its pH was adjusted; (3) Synthesis of Ni / Fe LDH@C-AGS: Taking advantage of the fact that the Ni / Fe LDH@C loading substrate carries a large amount of positive charge, Ni / Fe LDH@C is anchored on the surface of anaerobic granular sludge AGS by electrostatic attraction to synthesize the hybrid material Ni / Fe LDH@C-AGS.

2. The use of the biological-non-biological hybrid material Ni / Fe LDH@C-AGS as claimed in claim 1, characterized in that: The anaerobic bioreactor includes a DC power supply, a plate, anaerobic granular sludge AGS, and a cylindrical reactor. The material is an acrylic plate with an inner diameter of 10 cm, a height of 15 cm, and an effective volume of 1.0 L. The reactor plate is composed of a graphite plate, and the DC power supply applies a voltage of 1 V.

3. The use of the biological-non-biological hybrid material Ni / Fe LDH@C-AGS as claimed in claim 1, characterized in that: The metal molar ratio of Ni(NO3)2·6H2O to Fe(NO3)3·9H2O in the mixed solution A is 3:

1.

4. The use of the biological-non-biological hybrid material Ni / Fe LDH@C-AGS as claimed in claim 1, characterized in that: The powdered activated carbon C was obtained by soaking in a 30% hydrochloric acid solution for 24 hours and washing with deionized water multiple times. The ratio of LDH formed in the suspension B to the powdered activated carbon C was 4:

1.

5. The use of the biological-non-biological hybrid material Ni / Fe LDH@C-AGS as claimed in claim 1, characterized in that: The culture solution is composed of culture solution A and culture solution B, and the specific components are as follows: Culture medium A: glucose 500 mg / L, ammonium chloride 32 mg / L, KH2PO4 20 mg / L, yeast fermentation product 100 mg / L, NaCl 50 mg / L, NaHCO3 75 mg / L, MgSO4·7H2O 25 mg / L, CaCl2 25 mg / L; Culture medium B: CoCl2·6H2O 0.1 g / L, ZnCl2 0.13 g / L, CuSO4·5H2O 0.01 g / L, H3BO3 0.01g / L, Na2MoO4·2H2O 0.025 g / L, NiCl2·6H2O 0.024 g / L, Na2WO4·2H2O 0.025 g / L, MnCl2·4H2O 0.62g / L, EDTA·2Na 1.5g / L.

6. The use of the biological-non-biological hybrid material Ni / Fe LDH@C-AGS as claimed in claim 1, characterized in that: In the step (2), the pH is adjusted to 6.8-7.2.

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