A biochar-iron coupling filler, a preparation method and application thereof

Abstract

The present application relates to tail water nitrate purification technical field, especially to a kind of biochar iron chip coupling filler and its preparation method and application.The preparation method of the biochar iron chip coupling filler includes the following steps: after biochar and acid liquor are mixed, acidification treatment is carried out, and modified biochar is obtained after grinding;After ceramsite and adhesive are mixed, ceramsite covered with adhesive is obtained for standby;Modified biochar, iron chip, ceramsite covered with adhesive are mixed, and the biochar iron chip coupling filler is obtained after standing.The biochar iron chip coupling filler of the present application has two ways of chemical denitrification and biological denitrification to remove nitrate, and does not need additional organic matter, has good nitrate removal effect, and low operating cost.

Description

Technical Field

[0001] This invention relates to the field of nitrate purification technology for wastewater, and in particular to a biochar iron filings coupled packing material, its preparation method, and its application. Background Technology

[0002] The enrichment of nitrate nitrogen in water bodies is a growing concern in the environmental field. Nitrogen pollution leads to eutrophication, endangering human health and damaging ecosystems. The systematic management of nitrate nitrogen in secondary effluents and urban water flows remains a challenge. Furthermore, nitrate-contaminated wastewater and groundwater have low carbon-to-nitrogen ratios, resulting in insufficient carbon sources for denitrification reactions, and a lack of mature and cost-effective treatment technologies.

[0003] Existing technologies utilize exogenous organic sources such as thiosulfate, methanol, and acetic acid to maintain high nitrogen removal rates, but these result in secondary pollution from inorganic degradation products and organic residues. Therefore, autotrophic denitrification, which requires no additional carbon source, is more feasible for practical water treatment processes and minimizes secondary pollution.

[0004] Iron, an abundant element in nature, profoundly influences the geochemical cycle of nitrogen. Due to its strong reducing potential, iron has been extensively studied for its application in nitrate removal via chemical and biological pathways. Iron is also widely used as a material for nitrate removal. However, the application of iron in nitrate degradation is limited by the electron transfer rate, resulting in a relatively low rate of nitrate removal using iron.

[0005] Therefore, how to provide a method with high adsorption efficiency of nitrate nitrogen in water is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a biochar iron filings coupled filler, its preparation method and application, in order to overcome the defects of the existing technology.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing biochar iron filings coupled packing material, comprising the following steps:

[0009] (1) After mixing biochar with acid solution, the mixture is acidified and then ground to obtain modified biochar.

[0010] (2) After mixing the ceramsite with the adhesive, the ceramsite coated with the adhesive is prepared for use.

[0011] (3) Mix modified biochar, iron filings, and ceramsite covered with adhesive, and let stand to obtain biochar-iron filings coupled filler.

[0012] The steps (1) and (2) are not in any particular order.

[0013] Preferably, the solid-liquid ratio of biochar to acid solution is 1:2 to 4; the acid solution is a mixed solution of hydrochloric acid and nitric acid, with the concentration of nitric acid in the acid solution being 0.3 to 0.5 mol / L and the concentration of hydrochloric acid being 0.15 to 0.25 mol / L.

[0014] Preferably, the acidification treatment involves mixing biochar with acid and then shaking the mixture for 2 to 3 hours.

[0015] Preferably, the mass ratio of modified biochar to iron filings is 1:1.8 to 2.2;

[0016] The mass ratio of biochar to ceramsite is 0.8–1.2:50;

[0017] The mass ratio of adhesive to ceramsite is 0.8–1.2:20.

[0018] Preferably, the modified biochar has a particle size ≤ 18 mesh; the ceramsite has a particle size of 10–20 nm.

[0019] Preferably, the settling time in step (3) is 22 to 26 hours.

[0020] The present invention also provides a biochar iron filings coupled packing material prepared by the above preparation method.

[0021] The present invention also provides an application of biochar iron filings coupled packing for the removal of nitrates.

[0022] Preferably, biochar-iron-shavings coupled packing is used in denitrification reaction columns.

[0023] Preferably, the bottom of the denitrification reaction column is made of sunflower seed chips, and the upper part is made of biochar and iron filings coupled packing material; the volume ratio of sunflower seed chips to biochar and iron filings coupled packing material is 1:1.8 to 2.2.

[0024] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The biochar iron filings coupled packing of the present invention removes nitrates through both chemical and biological denitrification pathways, without requiring additional organic matter, and has a good nitrate removal effect and low operating cost.

[0026] 2. Biochar in biochar-iron-shavings coupled packing can remove a portion of the nitrates in the water through physical adsorption.

[0027] 3. The manufacturing process of biochar iron filings coupled packing material is simple, the raw materials are readily available, and the overall cost is low. Attached Figure Description

[0028] Figure 1 The nitrate concentrations in the influent and effluent of the denitrification reaction columns prepared using the packing materials of Examples 2 and Comparative Examples 1-4 are shown.

[0029] Figure 2 The nitrogen changes of various forms of 2-MAPB prepared in Example 2. Detailed Implementation

[0030] This invention provides a method for preparing biochar iron filings coupled packing material, comprising the following steps:

[0031] (1) After mixing biochar with acid solution, the mixture is acidified and then ground to obtain modified biochar.

[0032] (2) After mixing the ceramsite with the adhesive, the ceramsite coated with the adhesive is prepared for use.

[0033] (3) Mix modified biochar, iron filings, and ceramsite covered with adhesive, and let stand to obtain biochar-iron filings coupled filler.

[0034] The steps (1) and (2) are not in any particular order.

[0035] In this invention, the solid-liquid ratio of biochar to acid solution is 1:2 to 4, preferably 1:2.5 to 3.5; the acid solution is a mixed solution of hydrochloric acid and nitric acid, wherein the concentration of nitric acid in the acid solution is 0.3 to 0.5 mol / L, preferably 0.35 to 0.45 mol / L, and the concentration of hydrochloric acid is 0.15 to 0.25 mol / L, preferably 0.18 to 0.22 mol / L.

[0036] In this invention, the acidification treatment involves mixing biochar with acid and then shaking the mixture. The acidification treatment time is 2-3 hours, preferably 2.2-2.6 hours, and more preferably 2.3-2.5 hours.

[0037] In this invention, the mass ratio of modified biochar to iron filings is 1:1.8 to 2.2, preferably 1:1.9 to 2.1;

[0038] The mass ratio of biochar to ceramsite is 0.8–1.2:50, preferably 0.9–1:50;

[0039] The mass ratio of adhesive to ceramsite is 0.8–1.2:20, preferably 0.9–1.1:20.

[0040] In this invention, the modified biochar has a particle size of ≤18 mesh, preferably ≤20 mesh; the ceramsite has a particle size of 10-20 nm, preferably 12-18 nm.

[0041] In this invention, the settling time in step (3) is 22 to 26 hours, preferably 25 to 25 hours.

[0042] The present invention also provides a biochar iron filings coupled packing material prepared by the above preparation method.

[0043] The present invention also provides an application of biochar iron filings coupled packing for the removal of nitrates.

[0044] In this invention, biochar iron filings coupled packing is used in denitrification reaction columns.

[0045] In this invention, the bottom of the denitrification reaction column is made of sunflower seed chips, and the upper part is made of biochar and iron filings coupled packing material; the volume ratio of sunflower seed chips to biochar and iron filings coupled packing material is 1:1.8 to 2.2, preferably 1:1.9 to 2.1.

[0046] In this invention, the sunflower seed chips can be replaced by other common water purification materials such as quartz sand and zeolite.

[0047] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0048] Example 1

[0049] (1) The biochar and acid solution were mixed at a solid-liquid ratio of 1:2 and shaken for 20 hours. Then the biochar was filtered out with deionized water and washed until the filtrate was colorless. The biochar was then taken out and ground with a ball mill until it passed through a 20-mesh sieve to obtain modified biochar. The acid solution was a mixed solution of hydrochloric acid and nitric acid, with a concentration of 0.3 mol / L for nitric acid and 0.15 mol / L for hydrochloric acid.

[0050] (2) Mix the ceramsite and phenolic resin at a mass ratio of 20:0.8, and then coat the surface of the ceramsite with adhesive evenly to obtain ceramsite covered with adhesive for later use.

[0051] (3) First, mix the modified biochar and iron filings, and then pour them into a drum mixer together with the ceramsite covered with adhesive. Set the speed to 80 r / min and the running time to 10 min. After the mixing is finished, place the prepared packing in a ventilated place and let it stand for 24 h to stabilize. The biochar and iron filings coupled packing is obtained, wherein the mass ratio of modified biochar to iron filings is 1:1.8 and the mass ratio of biochar to ceramsite is 0.8:50.

[0052] Example 2

[0053] (1) The biochar and acid solution were mixed at a solid-liquid ratio of 1:3 and shaken for 24 hours. Then the biochar was filtered out with deionized water and washed until the filtrate was colorless. The biochar was then taken out and ground with a ball mill until it passed through an 18-mesh sieve to obtain modified biochar. The acid solution was a mixed solution of hydrochloric acid and nitric acid, with a concentration of 0.4 mol / L for nitric acid and 0.2 mol / L for hydrochloric acid.

[0054] (2) Mix the ceramsite and phenolic resin at a mass ratio of 20:1, and then coat the surface of the ceramsite with adhesive evenly to obtain ceramsite covered with adhesive for later use.

[0055] (3) First, mix the modified biochar and iron filings, and then pour them into a drum mixer together with the ceramsite covered with adhesive. Set the speed to 80 r / min and the running time to 10 min. After the mixing is finished, place the prepared packing in a ventilated place and let it stand for 24 h to stabilize. The biochar and iron filings coupled packing is obtained, wherein the mass ratio of modified biochar to iron filings is 1:2 and the mass ratio of biochar to ceramsite is 1:50.

[0056] Example 3

[0057] (1) The biochar and acid solution were mixed at a solid-liquid ratio of 1:4 and shaken for 28 hours. Then the biochar was filtered out with deionized water and washed until the filtrate was colorless. The biochar was then taken out and ground with a ball mill until it passed through an 18-mesh sieve to obtain modified biochar. The acid solution was a mixed solution of hydrochloric acid and nitric acid, with a concentration of 0.5 mol / L for nitric acid and 0.25 mol / L for hydrochloric acid.

[0058] (2) Mix the ceramsite and phenolic resin at a mass ratio of 20:1.2, and then coat the surface of the ceramsite with adhesive evenly to obtain ceramsite covered with adhesive for later use.

[0059] (3) First, mix the modified biochar and iron filings, and then pour them into a drum mixer together with the ceramsite covered with adhesive. Set the speed to 80 r / min and the running time to 10 min. After the mixing is finished, place the prepared packing in a ventilated place and let it stand for 24 h to stabilize. The biochar and iron filings coupled packing is obtained, wherein the mass ratio of modified biochar to iron filings is 1:2.2 and the mass ratio of biochar to ceramsite is 1.2:50.

[0060] Comparative Example 1

[0061] The difference between Comparative Example 1 and Example 2 is that iron filings were not added to the prepared filler.

[0062] Comparative Example 2

[0063] The difference between Comparative Example 2 and Example 2 is that the mass ratio of iron filings to modified biochar is 1:1.

[0064] Comparative Example 3

[0065] The difference between Comparative Example 3 and Example 2 is that modified biochar was not added to the prepared filler.

[0066] Comparative Example 4

[0067] The difference between Comparative Example 4 and Example 2 is that the biochar used is unmodified biochar.

[0068] Test case

[0069] A cylindrical PVC pipe with a height of 60cm and a diameter of 16cm is used as the main body of the denitrification reactor. One end is sealed with a PVC pipe cap and waterproof glue, and holes are drilled at 10cm and 40cm in height of the column for water outlet and inlet.

[0070] Wash the sunflower seed pieces with deionized water and place them at the bottom of the reaction column. Then fill the column with biochar iron filings coupling packing material, with a volume ratio of sunflower seed pieces to biochar iron filings coupling packing material of 1:2.

[0071] The packing materials prepared in Example 2 and Comparative Examples 1-4 were used in denitrification reaction columns. Example 2 was designated as 2-MAPB, Comparative Example 1 as C-MAPB, Comparative Example 2 as 1-MAPB, Comparative Example 3 as M-MAPB, and Comparative Example 4 as 2-MCPB.

[0072] A 137-day flow experiment (influent configuration shown in Table 1) was conducted to determine the various forms of nitrogen in the water. The determination methods followed national standard methods (total nitrogen HJ 636-2012, nitrate nitrogen HJ / T 346-2007). The experiment was conducted in three phases, with water configurations for each phase shown in Table 1. Figure 1 .like Figure 1 As shown, each denitrification reactor exhibited a certain denitrification potential throughout the three stages, and 2-MAPB demonstrated consistent and effective denitrification capacity under different operating conditions. During 137 days of continuous operation, 2-MAPB achieved maximum NO3... - The removal rate of -N was 97.6±1.25%, achieving basic removal of nitrates.

[0073] C-MAPB exhibits denitrification potential under high nitrate influent conditions, which may be attributed to the biochar's adsorption capacity for nitrate ions. Similar to the other three iron-containing reactors, the nitrogen removal load of M-MAPB did not increase with increasing nitrate concentration, indicating that the nitrogen removal potential of iron-only M-MAPB is inhibited in high nitrate environments. Figure 2As shown, by observing the changes in nitrogen speciation in 2-MAPB, a hybrid denitrification process combining chemical and biological denitrification exists in the denitrification reactor. Throughout the experimental phase, the maximum nitrate removal rate of 2-MAPB was 99.26%. Simultaneously, a high ammonia formation rate was observed under a long HRT, indicating that the chemical denitrification reaction requires a minimum HRT of more than 12 hours to fully interact. Comparing the nitrate removal rates of 2-MAPB in the first and second stages, the denitrification performance of 2-MAPB was least affected.

[0074] Furthermore, compared to 2-MAPB, the denitrification reaction column prepared with 2-MCPB can increase the nitrogen removal load. This is because acid modification enhances the electron transfer capacity of biochar, thereby accelerating the electron transfer from mZVI to nitrate, which is precisely the rate-limiting factor in the chemical denitrification pathway. In addition, 2-MAPB exhibits stronger nitrate removal capacity than 1-MAPB in stages 1 and 2, indicating that a 2:1 iron-carbon mixture ratio has the best nitrate removal effect. Regardless of the presence or absence of iron filings, C-MAPB shows weak denitrification capacity in stages 2 and 3 (48–137 days), indicating that mixed denitrification mainly occurs in the presence of iron. Overall, 2-MAPB exhibits the best denitrification performance.

[0075] Table 1. Test inlet water configuration

[0076]

[0077] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An application of a biochar-iron-shavings coupled packing material, characterized in that, Used to remove nitrates; The preparation method of the biochar iron filings coupled packing includes the following steps: (1) After mixing biochar with acid solution, the mixture is acidified and then ground to obtain modified biochar. (2) After mixing the ceramsite with the adhesive, the ceramsite coated with the adhesive is prepared for use. (3) Mix modified biochar and iron filings, then add ceramsite covered with adhesive, and let stand to obtain biochar-iron filings coupled filler. The steps (1) and (2) are not in any particular order; The acid solution is a mixed solution of hydrochloric acid and nitric acid, with the concentration of nitric acid in the acid solution being 0.3–0.5 mol / L and the concentration of hydrochloric acid being 0.15–0.25 mol / L; The mass ratio of modified biochar to iron filings is 1:1.8 to 2.

2.

2. The application of the biochar-iron-shavings coupled packing material according to claim 1, characterized in that, The solid-liquid ratio of biochar to acid solution is 1:2 to 4.

3. The application of the biochar-iron filings coupled packing material according to claim 1 or 2, characterized in that, The acidification process involves mixing biochar with acid and then shaking the mixture for 2-3 hours.

4. The application of the biochar-iron-shavings coupled packing material according to claim 1, characterized in that, The mass ratio of biochar to ceramsite is 0.8–1.2:50; The mass ratio of adhesive to ceramsite is 0.8–1.2:

20.

5. The application of the biochar-iron filings coupled packing material according to claim 1, characterized in that, The modified biochar has a particle size ≤ 18 mesh; the ceramsite has a particle size of 10–20 nm.

6. The application of the biochar-iron-shavings coupled packing material according to claim 1, characterized in that, The settling time in step (3) is 22 to 26 hours.

7. The application of the biochar-iron-shavings coupled packing material according to claim 1, characterized in that, Biochar and iron filings coupled packing material is used in denitrification reaction columns.

8. The application of the biochar iron filings coupled packing material according to claim 7, characterized in that, The bottom of the denitrification reaction column is made of sunflower seed chips, and the top is made of biochar and iron filings coupled packing material; the volume ratio of sunflower seed chips to biochar and iron filings coupled packing material is 1:1.8 to 2.2.

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