Preparation method of quinone-rich biochar, product and application of quinone-rich biochar in strengthening iron-nitrogen cycle

Abstract

The invention relates to the technical field of biochar preparation and sewage denitrification, in particular to a preparation method of quinone-rich biochar, a product and application of the quinone-rich biochar in strengthening iron-nitrogen circulation. The preparation method of the quinone-rich biochar comprises the following steps: drying, crushing and pyrolyzing a biomass material to obtain biochar; the biochar is soaked in an anthraquinone-2-sodium sulfonate solution, then filtering, washing and drying are conducted, and the quinone-rich biochar is obtained. According to the preparation method of the quinone-rich biochar, the biochar and the quinone-rich biochar are prepared by using aquatic plant yellow acorus calamus residues as raw materials, and reference is provided for resource utilization of aquatic plant biomass. The invention further provides a method for improving iron circulation-nitrogen conversion, the quinone-rich biochar has high quinonyl functional group content, and the iron circulation-nitrogen conversion efficiency can be remarkably improved by coupling the quinone-rich biochar with zero-valent iron.

Description

Technical Field

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

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

[0003] Zero-valent iron has attracted wide attention in the field of deep denitrification of sewage due to its strong reducing properties, low price, high safety, low sludge production, and the fact that it can use iron filings, iron sheets, iron shavings and other mechanical processing waste as raw materials to reduce nitrate nitrogen. Therefore, 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 plagued by the passivation phenomenon, resulting in poor denitrification performance. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing quinone-rich biochar, a product and its application in strengthening the iron-nitrogen cycle. The present invention grafts more quinone groups onto the surface of biochar through modification, utilizes quinone-rich biochar to improve the electron transfer rate in the iron cycle-nitrogen conversion process, and improves 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 method for preparing quinone-rich biochar, comprising the following steps:

[0008] The biomass material is dried, crushed and then pyrolyzed to obtain biochar;

[0009] The biochar is immersed in an anthraquinone-2-sodium sulfonate solution, and then filtered, washed and dried to obtain the quinone-rich biochar.

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

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

[0012] A fourth technical solution of the present invention is a method for improving iron cycle-nitrogen conversion, wherein the above-mentioned quinone-rich biochar is evenly mixed with zero-valent iron and then added to sewage containing nitrate nitrogen and ammonia nitrogen for denitrification and denitrification.

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

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

[0015] The invention provides a method for preparing quinone-rich biochar. The invention utilizes the residues of aquatic plant Iris phellodendron as raw materials to produce biochar and quinone-rich biochar, providing a reference for 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 higher quinone functional group content, and coupling with zero-valent iron can significantly improve the iron cycle-nitrogen conversion efficiency.

[0017] The quinone-rich biochar raw material of the present invention is easy to obtain, the preparation method is simple, the cost is low, and the enhanced denitrification efficiency is significant. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 Characterization diagram of functional groups of biochar and quinone-rich biochar prepared in Example 1 of the present invention;

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

[0021] Figure 3 A graph showing the change over time of ferrous iron (a) and total iron (b) in the solution after coupling of the biochar and quinone-rich biochar provided in the embodiments of the present invention with zero-valent iron. DETAILED DESCRIPTION

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0023] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0024] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only 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 associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0025] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0026] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0027] Existing biochar technology is not efficient in mediating the iron cycle-nitrogen conversion process. Therefore, the present invention grafts quinone groups that play an electron transfer role onto biochar to solve the problem of limited electron transfer in the iron cycle-nitrogen conversion process and improve the system's denitrification efficiency.

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

[0029] The biomass material is dried, crushed and then pyrolyzed to obtain biochar;

[0030] The biochar is immersed in an anthraquinone-2-sodium sulfonate solution, and then filtered, washed and dried to obtain the quinone-rich biochar.

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

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

[0033] In a preferred embodiment of the present invention, the pyrolysis is specifically carried out by heating the material to 400° C. at a rate of 10° C. / min under a nitrogen atmosphere and keeping the temperature 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 carbonization of the raw materials will be incomplete; therefore, the present invention limits the pyrolysis temperature 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 drying time is 24 hours.

[0037] In a preferred embodiment of the present invention, the solvent of the anthraquinone-2-sodium sulfonate solution is ultrapure water; and the concentration of the anthraquinone-2-sodium 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 performed by stirring at a speed of 120 rpm for 2 hours and then standing for 72 hours.

[0040] A second aspect of the present invention provides quinone-rich biochar prepared according to the above-mentioned preparation method.

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

[0042] A fourth aspect of the present invention provides a method for improving iron cycle-nitrogen conversion, wherein the above-mentioned quinone-rich biochar is evenly mixed with zero-valent iron and then added to sewage containing nitrate nitrogen and ammonia nitrogen for denitrification and 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 described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0045] The technical solutions provided by the present invention are described in detail below in conjunction with the 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] As the raw material for biochar preparation, Iris calamus was collected from the artificial wetland system at the mature stage. After being washed with deionized water and naturally air-dried, the Iris calamus residue was cut into 3-5 cm pieces and placed in an oven at 105°C for 6 hours. After being crushed, it was passed through a 100-mesh sieve to obtain Iris calamus powder for later use;

[0049] A quartz boat containing 200 g of yellow calamus powder was placed in a tube furnace, and nitrogen was introduced into the tube furnace at a flow rate of 0.45 L / min to perform pyrolysis under nitrogen atmosphere. The pyrolysis temperature was set to 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] Prepare 1000 mL of 3 mM AQS solution, add 50 g of the biochar powder prepared in step (1), and stir at 120 rpm for 2 h at room temperature to allow AQS to fully contact the biochar. After standing for 72 h, filter, vacuum filter the AQS-modified biochar, wash with ultrapure water, and then dry in a 60 ° C oven for 24 h to obtain quinone-rich biochar.

[0052] The biochar prepared in step (1) and the quinone-rich biochar prepared in step (2) of this example were characterized. Figure 1 Shown by: Figure 1 It can be seen that the quinone-modified biochar can graft more quinone functional groups compared with the original biochar.

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

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

[0055] Use a 500mL blue-cap bottle as a reactor, add 100mL of activated sludge, and add 400mL of the above-prepared simulated sewage treatment plant tail water. The final sludge concentration in the system is 2000mg / L.

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

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

[0058] Figure 2 The changes of ammonia nitrogen (a), nitrite nitrogen (b), nitrate nitrogen (c) and total nitrogen (d) in the system with time after adding iron-biochar and iron-quinone-rich biochar coupling materials at different mass ratios are shown. 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 systems. The system with a mass ratio of 4:1 for iron-quinone-rich biochar has the lowest nitrite nitrogen concentration. As the reaction time progresses, the nitrate nitrogen concentration of the seven reaction systems gradually decreases, and the enhanced denitrification efficiency of quinone-rich biochar is better. At about 18h, the denitrification process of the 4:1 iron-quinone-rich biochar and 8:1 iron-quinone-rich biochar systems is basically completed, among which the system with a mass ratio of 4:1 for iron-quinone-rich biochar has the best denitrification and denitrification performance. The total nitrogen removal rule is basically the same as the nitrate nitrogen removal rule.

[0059] Figure 3 The results show that the ferrous iron (a) and total iron (b) in the system change over time when the iron-biochar and iron-quinone-rich biochar coupling materials are added in different mass ratios. The results show that the iron-quinone-rich biochar has a higher ferrous ion concentration than the iron-biochar group, and the system with an iron-quinone-rich biochar addition mass ratio of 4:1 has a higher total iron and ferrous iron content.

[0060] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing quinone-rich biochar, characterized in that: The following steps are involved: 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.

2. The method for preparing quinone-rich biochar according to claim 1, characterized in that: The biomass material is Iris pumila.

3. The method for preparing quinone-rich biochar according to claim 1, characterized in that: The pyrolysis is specifically carried out in a nitrogen atmosphere by heating the temperature to 400° C. at a rate of 10° C. / min and keeping the temperature for 2 hours.

4. The method for preparing quinone-rich biochar according to claim 1, characterized in that: The solvent of the anthraquinone-2-sodium sulfonate solution is water; the concentration of the anthraquinone-2-sodium sulfonate solution is 3 mM.

5. The method for preparing quinone-rich biochar according to claim 1, characterized in that: The immersion is specifically performed by stirring at a speed of 120 rpm for 2 hours and then standing for 72 hours.

6. Quinone-rich biochar prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the quinone-rich biochar as claimed in claim 6 in strengthening the iron-nitrogen cycle.

8. A method for improving iron cycle-nitrogen conversion, characterized in that: The quinone-rich biochar described in claim 6 is evenly mixed with zero-valent iron and then added to the sewage containing nitrate nitrogen and ammonia nitrogen.

9. The method for improving iron cycle-nitrogen conversion according to claim 8, characterized in that: The mass ratio of the quinone-rich biochar to the zero-valent iron is 1:(1-8).

Images