Preparation method and product of a quinone-rich biochar and its application in enhancing the iron-nitrogen cycle

Abstract

The present invention relates to the technical fields of biochar preparation and sewage denitrification, and particularly relates to a preparation method of quinone-rich biochar, a product thereof, and an application thereof in enhancing the iron-nitrogen cycle. The preparation method of the quinone-rich biochar of the present invention comprises the following steps: drying and pulverizing a biomass material and then pyrolyzing to obtain biochar; impregnating the biochar in an anthraquinone-2-sulfonic acid sodium solution, and then filtering, washing, and drying to obtain the quinone-rich biochar. The present invention provides a preparation method of quinone-rich biochar. The present invention uses the residues of the aquatic plant Iris pseudacorus as raw materials to produce biochar and quinone-rich biochar, providing a reference for the resource utilization of aquatic plant biomass. The present invention also provides a method for improving iron cycle-nitrogen conversion. The quinone-rich biochar of the present invention has a high content of quinone-based functional groups, and coupling with zero-valent iron can significantly improve the iron cycle-nitrogen conversion efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of biochar preparation and sewage denitrification, and particularly to a preparation method of quinone-rich biochar, a product thereof, and an application thereof in strengthening the iron-nitrogen cycle. Background Art

[0002] The secondary effluent of sewage treatment plants is an important nitrogen emission source. Although it can meet the first-class B or first-class A standards in the "Pollutant Discharge Standard for Municipal Sewage Treatment Plants" (18918-2002), the total nitrogen content in the secondary effluent is still much higher than the limit value of surface water class V. If it is discharged into the receiving water body without advanced denitrification treatment, it will pose a threat to the water ecological safety of the receiving water body. The nitrogen form in the secondary effluent of sewage plants is mainly nitrate nitrogen, and the concentration of biodegradable organic matter is low, which is the key and difficulty of advanced denitrification.

[0003] Zero-valent iron has attracted wide attention in the field of sewage advanced denitrification due to its strong reducibility, low cost, high safety, low sludge production, and the ability to use mechanical processing waste iron filings, iron sheets, iron shavings, etc. as raw materials to reduce nitrate nitrogen. Therefore, the iron autotrophic denitrification technology is a new type of green, environmentally friendly, and low-carbon denitrification technology.

[0004] However, the application of zero-valent iron-based materials for enhanced denitrification is often troubled by passivation phenomena, resulting in poor denitrification performance. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of quinone-rich biochar, a product thereof, and an application thereof in strengthening the iron-nitrogen cycle. The present invention grafts more quinone groups onto the surface of biochar through modification, and uses quinone-rich biochar to improve the electron transfer rate of the iron cycle-nitrogen conversion process and enhance the denitrification performance of the system.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a preparation method of quinone-rich biochar, comprising the following steps:

[0008] Drying and pulverizing the biomass material, and then pyrolyzing to obtain biochar;

[0009] Impregnating the biochar in anthraquinone-2-sulfonic acid sodium solution, then filtering, washing, and drying to obtain the quinone-rich biochar.

[0010] Another technical solution of the present invention is a quinone-rich biochar prepared according to the above preparation method.

[0011] Another technical solution of the present invention is the application of the above quinone-rich biochar in strengthening the iron-nitrogen cycle.

[0012] Fourth technical solution of the present invention: A method for improving iron cycle-nitrogen conversion. After uniformly mixing the above-mentioned quinone-rich biochar with zero-valent iron, it is added to the sewage containing nitrate nitrogen and ammonia nitrogen for denitrification.

[0013] The essence of iron cycle nitrogen conversion is electron transfer. Improving the electron transfer efficiency by optimizing the iron cycle process and thus promoting the transformation of nitrogen forms is the key to efficient denitrification. Biochar is a low-cost, environmentally friendly, and highly aromatic biomass resource product. Its surface contains redox-active groups such as quinone groups, which endow biochar with a large number of active sites and play an important role in the electron transfer during the iron cycle nitrogen conversion process. Based on this, grafting more quinone groups onto the biochar surface through functional group modification can effectively promote the iron cycle process and enhance the removal of total nitrogen in sewage.

[0014] The present invention discloses the following technical effects:

[0015] The present invention provides a preparation method of quinone-rich biochar. The present invention uses the residues of the aquatic plant Iris pseudacorus as raw materials to produce biochar and quinone-rich biochar, providing a reference for the resource utilization of aquatic plant biomass.

[0016] The present invention also provides a method for improving iron cycle-nitrogen conversion. The quinone-rich biochar of the present invention has a high content of quinone functional groups, and coupling with zero-valent iron can significantly improve the iron cycle-nitrogen conversion efficiency.

[0017] The quinone-rich biochar described in the present invention is easy to obtain raw materials, has a simple preparation method, low cost, and remarkable denitrification enhancement performance. Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is the functional group characterization diagram of the biochar and quinone-rich biochar prepared in Example 1 of the present invention;

[0020] Figure 2 It is the change diagram of ammonia nitrogen (a), nitrite nitrogen (b), nitrate nitrogen (c), and total nitrogen (d) in the solution with time after coupling the biochar and quinone-rich biochar prepared in Example 1 of the present invention with zero-valent iron;

[0021] Figure 3 It is the change diagram of ferrous iron (a) and total iron (b) in the solution with time after coupling the biochar and quinone-rich biochar provided in the embodiment of the present invention with zero-valent iron. Detailed Embodiments

[0022] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be construed as a limitation on the present invention, but rather as a more detailed description of certain aspects, features, and implementation schemes of the present invention.

[0023] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0025] Without departing from the scope or spirit of the present invention, various improvements and variations can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0026] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0027] The existing biochar technology has low efficiency in mediating the iron cycle-nitrogen transformation process. Therefore, in the present invention, quinone groups that play an electron transfer role are grafted onto biochar to solve the problem of limited electron transfer in the iron cycle-nitrogen transformation process and improve the denitrification efficiency of the system.

[0028] The first aspect of the present invention provides a method for preparing quinone-rich biochar, comprising the following steps:

[0029] Dry and crush the biomass material and then pyrolyze it to obtain biochar;

[0030] Immerse the biochar in a sodium anthraquinone-2-sulfonate solution, then filter, wash, and dry it to obtain the quinone-rich biochar.

[0031] In a preferred embodiment of the present invention, the biomass material is Iris pseudacorus.

[0032] In a preferred embodiment of the present invention, the drying temperature is 105 °C and the time is 6 h.

[0033] In a preferred embodiment of the present invention, the pyrolysis is specifically heating to 400 °C at a rate of 10 °C / min in a nitrogen atmosphere and holding for 2 hours.

[0034] In the present invention, if the pyrolysis temperature exceeds 400 °C, the content of quinone functional groups in the biochar will decrease, and if the pyrolysis temperature is lower than 400 °C, the raw material will not be completely carbonized; therefore, the pyrolysis temperature in the present invention is limited to 400 °C.

[0035] In a preferred embodiment of the present invention, during the pyrolysis process, the flow rate of nitrogen is 0.45 L / min.

[0036] In a preferred embodiment of the present invention, the drying temperature is 60 °C and the time is 24 h.

[0037] In a preferred embodiment of the present invention, the solvent of the sodium anthraquinone-2-sulfonate solution is ultrapure water; the concentration of the sodium anthraquinone-2-sulfonate solution is 3 mM.

[0038] In an embodiment of the present invention, the sodium anthraquinone-2-sulfonate (AQS) solution is prepared by dissolving sodium anthraquinone-2-sulfonate in ultrapure water.

[0039] In a preferred embodiment of the present invention, the impregnation is specifically stirring at a speed of 120 rpm for 2 hours first, and then standing for 72 hours.

[0040] The second aspect of the present invention provides a quinone-rich biochar prepared by the above preparation method.

[0041] The third aspect of the present invention provides an application of the above quinone-rich biochar in strengthening the iron-nitrogen cycle.

[0042] The fourth aspect of the present invention provides a method for improving iron cycle-nitrogen conversion, in which the above quinone-rich biochar is uniformly mixed with zero-valent iron and then added to sewage containing nitrate nitrogen and ammonia nitrogen for denitrification.

[0043] In a preferred embodiment of the present invention, the mass ratio of the quinone-rich biochar to the zero-valent iron is 1:(1 - 8).

[0044] The technical solutions of the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are all purchased from commercial channels or have been made public.

[0045] The technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0046] Example 1

[0047] (1) Preparation of biochar

[0048] Iris pseudacorus was used as the raw material for biochar preparation and collected from the constructed wetland system during the mature period. After being washed clean with deionized water and naturally air-dried, the Iris pseudacorus residues were cut into pieces of 3 - 5 cm in size, placed in an oven at 105 °C for 6 h of drying, crushed, and then sieved through a 100-mesh sieve to obtain Iris pseudacorus powder for standby.

[0049] The quartz boat filled with 200 g of Iris pseudacorus powder was placed in a tubular furnace, and nitrogen was introduced into the tubular furnace at a flow rate of 0.45 L / min to carry out pyrolysis under a nitrogen atmosphere. The pyrolysis temperature was set at 400 °C and kept constant for 2 hours, and the heating rate was controlled at 10 °C / min. After cooling to room temperature, biochar powder was obtained.

[0050] (2) Preparation of quinone-rich biochar

[0051] 1000 mL of 3 mM AQS solution was prepared and 50 g of the biochar powder prepared in step (1) was put into it. It was stirred at a speed of 120 rpm at room temperature for 2 h to make AQS fully contact with the biochar. After standing for 72 h, it was filtered. The biochar modified by AQS was subjected to vacuum filtration and washed with ultrapure water, and then placed in an oven at 60 °C for 24 h of drying to obtain quinone-rich biochar.

[0052] The biochar prepared in step (1) of this example and the quinone-rich biochar prepared in step (2) were characterized, and the results are as Figure 1 shown: It can be seen from Figure 1 that the biochar after quinone group modification can graft more quinone functional groups compared with the original biochar.

[0053] The effects of the biochar and quinone-rich biochar prepared in Example 1 applied to the iron cycle-nitrogen conversion process were verified as follows:

[0054] The test water was simulated sewage treatment plant effluent (the preparation method of simulated sewage treatment plant effluent: in the laboratory, using tap water as the raw water, potassium nitrate and ammonium chloride were added to it to prepare simulated sewage treatment plant effluent with nitrate nitrogen and ammonia nitrogen concentrations of 10.32 ± 2.28 mg / L and 4.18 ± 1.42 mg / L respectively). The main pollutants in the influent were nitrate nitrogen and ammonia nitrogen. The nitrate nitrogen concentration in the influent was measured to be 10.32 ± 2.28 mg / L, and the ammonia nitrogen concentration was 4.18 ± 1.42 mg / L.

[0055] Using a 500 mL blue-capped bottle as the reactor, 100 mL of activated sludge was added, and 400 mL of the above-prepared simulated sewage treatment plant effluent was added. The sludge concentration in the final system was 2000 mg / L;

[0056] Zero-valent iron (2.0 g, using iron shavings from mechanical processing waste, with a length of 2 - 3 cm) was respectively mixed evenly with the quinone-rich biochar prepared in Example 1 (2.0 g, 0.5 g, 0.25 g). The mass ratios of iron to quinone-rich biochar were 1:1, 4:1, and 8:1 respectively. At the same time, the iron-biochar experimental groups were set according to the same ratio above, and a blank control group was set. Each experiment was set with three parallels;

[0057] The evenly mixed iron-biochar and iron-quinone-rich biochar were put into a porous nylon mesh bag, placed in the blue-capped bottle, and cultured in a shaker at 25 °C at a rate of 120 rpm; Water samples were collected at 0 h, 3 h, 9 h, 18 h, 36 h, 54 h, and 72 h after the start of the reaction to measure the changes in the concentrations of nitrate nitrogen, nitrite nitrogen, ammonia nitrogen, total nitrogen, total iron, and ferrous iron.

[0058] Figure 2 It shows the changes of ammonia nitrogen (a), nitrite nitrogen (b), nitrate nitrogen (c), and total nitrogen (d) in the system with the addition of iron-biochar and iron-quinone-rich biochar coupling materials at different mass ratios over time. The results show that both iron-biochar and iron-quinone-rich biochar have high removal efficiency for ammonia nitrogen, and there is no significant difference among the seven groups of systems. The system with an iron-quinone-rich biochar mass ratio of 4:1 has the lowest nitrite nitrogen concentration. As the reaction time progresses, the nitrate nitrogen concentrations in the seven reaction systems all gradually decrease. The quinone-rich biochar has better enhanced denitrification efficiency. At about 18 h, the denitrification process in the 4:1 iron-quinone-rich biochar and 8:1 iron-quinone-rich biochar systems is basically completed. Among them, the system with an iron-quinone-rich biochar dosing mass ratio of 4:1 has the optimal denitrification and nitrogen removal performance. The total nitrogen removal pattern is basically the same as the nitrate nitrogen removal pattern.

[0059] Figure 3 It shows the changes of ferrous iron (a) and total iron (b) in the system with the addition of iron-biochar and iron-quinone-rich biochar coupling materials at different mass ratios over time. The results show that the iron-quinone-rich biochar group has a higher ferrous ion concentration than the iron-biochar group. Among them, the system with an iron-quinone-rich biochar dosing mass ratio of 4:1 has higher total iron and ferrous iron contents.

[0060] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for improving iron cycle-nitrogen conversion, characterized in that: The quinone-rich biochar and zero-valent iron are mixed evenly and then added to the sewage containing nitrate nitrogen and ammonia nitrogen; the mass ratio of the quinone-rich biochar to the zero-valent iron is 1:4; the amount of the zero-valent iron added to the sewage is 2g of zero-valent iron per 400mL of sewage; The zero-valent iron is iron shavings from mechanical processing waste; The method for preparing the quinone-rich biochar comprises the following steps: The biomass material is dried, crushed and then pyrolyzed to obtain biochar; The biochar is immersed in an anthraquinone-2-sodium sulfonate solution, and then filtered, washed, and dried to obtain the quinone-rich biochar; The biomass material is Iris pumila; The pyrolysis is specifically carried out by heating to 400°C at a rate of 10°C / min under a nitrogen atmosphere and keeping the temperature for 2 hours; The solvent of the anthraquinone-2-sodium sulfonate solution is water; the concentration of the anthraquinone-2-sodium sulfonate solution is 3 mM; The immersion is specifically performed by stirring at a speed of 120 rpm for 2 hours and then standing for 72 hours.

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