Biochar anaerobic digestion tracking method based on triple dye labeling

Abstract

The invention relates to a biochar anaerobic digestion tracking method based on triple dye labeling, and belongs to the technical field of biochar tracking. In order to solve the problem that a single dye is easy to mix with the background color of digestive juice, the invention provides a biochar anaerobic digestion tracking method based on triple dye labeling, which comprises the following steps: mixing methyl red, amaranth and erythrosine to prepare a triple mixed dye solution, and carrying out adsorption dyeing on biochar; the dyed biochar is subjected to vacuum freeze-drying treatment and then added into an anaerobic digestion system, anaerobic digestion is completed, digestion residues are collected and subjected to density gradient centrifugation, and after centrifugation, the biochar is layered and recycled according to different color bands. According to the invention, a multi-element dye binding mechanism improves the binding stability of the dye and the biochar, and the trigeminy dye has high specificity and can avoid background interference of digestive juice; and surface functional groups of the charcoal are not changed. According to the method, accurate tracking of the migration rule of the biochar in the anaerobic digestion system is realized, and data support is provided for an optimized feeding strategy of the biochar in anaerobic digestion.

Description

Technical Field

[0001] The present invention belongs to the technical field of biochar tracking, and in particular relates to a biochar anaerobic digestion tracking method based on triple dye labeling. Background Art

[0002] As a synergist in anaerobic digestion systems, tracking the behavior of biochar in complex digestion environments has always been a research challenge. Biochar anaerobic digestion tracking uses labeling and analytical methods to study the behavior, fate, and interactions of biochar with microorganisms within anaerobic digestion systems. The core purpose of this technology is to reveal how biochar influences and participates in various biochemical processes within anaerobic digestion, thereby providing a scientific basis for optimizing biochar properties and improving digestion system efficiency.

[0003] In complex anaerobic digestion systems, dynamic interactions exist between biochar and microbial communities, organic substrates, and other intermediate products. Tracking technology can reveal key questions such as how long biochar remains in the digestive system, where it accumulates in the system, which microbial communities preferentially colonize the biochar surface, and how the surface properties of biochar change during digestion. This information is crucial for understanding the enhancement mechanisms of biochar. In terms of environmental benefit assessment, biochar tracking technology can quantify its contribution to carbon fixation and emission reduction. Biochar itself is highly stable and degrades slowly, and its retention in the digestive system is equivalent to a form of carbon sequestration. Tracking technology can accurately assess the carbon sink effect of this process, providing data support for life cycle assessment.

[0004] Dye labeling is one of the important technical means to study the behavior of biochar in anaerobic digestion systems. By combining fluorescent dyes or isotope markers with biochar, researchers can use microscopic observation or spectral analysis to track the distribution, migration and transformation process of biochar. However, traditional single dyes are easily confused with the background color of the digestate, and there are problems such as large signal interference, single recognition dimension, and low centrifugal separation purity. Magnetic modified biochar combines magnetic materials with biochar to make the biochar magnetically responsive, which facilitates separation and enrichment in an external magnetic field. However, the change in the surface properties of biochar will affect its interaction with other components in the environment. Summary of the Invention

[0005] In order to solve the problems of large signal interference and single recognition dimension in the single dye labeling method, the present invention provides a biochar anaerobic digestion tracking method based on triple dye labeling.

[0006] The technical solution of the present invention:

[0007] The biochar anaerobic digestion tracking method based on triple dye labeling includes the following steps:

[0008] Step 1: Methyl red, amaranth and erythrosine are mixed to prepare a triple mixed dye solution, and the biochar is immersed in the triple mixed dye solution for adsorption dyeing;

[0009] Step 2: The dyed biochar is freeze-dried in a vacuum process and then added to an anaerobic digestion system to complete anaerobic digestion, and the digestion residue is collected;

[0010] Step 3: Perform density gradient centrifugation on the digestion residue collected in step 2. First, add a bromoform-ethanol mixture as the bottom layer in the centrifuge tube, then add NaI solution as the middle layer, and finally add the digestion residue as the top layer. After density gradient centrifugation, a clearly visible interface color band will be formed in the centrifuge tube, and the biochar can be recovered in layers according to different color bands.

[0011] Furthermore, the dye concentration of the triple mixed dye solution in step 1 is 150 mg / L, wherein the mass ratio of methyl red, amaranth and erythrosine is 1:1:1.

[0012] Furthermore, the mass volume ratio of the biochar in step 1 to the triple mixed dye solution is 1 g:100 mL.

[0013] Furthermore, the adsorption dyeing in step 1 is carried out at a constant temperature of 40° C. and oscillated for 24 hours to ensure that the dye adsorption amount is not less than 150 mg / g biochar.

[0014] Furthermore, the vacuum degree of the vacuum freeze-drying treatment in step 2 is ≤10Pa, the freezing stage is cooled to -196°C with liquid nitrogen, and the drying stage is heated to -50°C and maintained for 24 to 48 hours.

[0015] Furthermore, the volume ratio of bromoform to ethanol in the bromoform-ethanol mixture in step 3 is 3:1, the density is 1.8 g / mL, the mass volume concentration of the NaI solution is 35%, and the density is 1.5 g / mL.

[0016] Furthermore, in step 3, the volume of the bromoform-ethanol mixture added accounts for 40% of the volume of the centrifuge tube, the volume of the NaI solution added accounts for 30% of the volume of the centrifuge tube, and the volume of the digestion residue added accounts for 30% of the volume of the centrifuge tube.

[0017] Furthermore, the density gradient centrifugation condition in step 3 is 4° C. and 4000 rpm for 20 min.

[0018] Furthermore, when the biochar is recovered by stratification according to different color bands after the density gradient centrifugation described in step 3, the upper aqueous phase containing organic impurities is directly discarded, and the middle purple biochar marked with amaranth, the pink biochar marked with erythrosine, and the lower orange biochar marked with methyl red are recovered.

[0019] Furthermore, the biochar recovered in step 3 was washed three times with distilled water to remove the residual density liquid, and then vacuum-dried at 40°C for 24 h before use in experimental analysis.

[0020] Beneficial effects of the present invention:

[0021] In the triple dye labeling method provided by the present invention, methyl red is embedded into the biochar mesopores through hydrogen bonding with -N=N- and carboxyl groups, and amaranth is embedded into the biochar mesopores through -SO3 - Electrostatic adsorption binds to the positively charged surface of activated carbon, and erythrosine is absorbed by I - It binds to the metal sites in the biochar ash through coordination bonds with metal ions. This multi-component binding mechanism improves the binding stability of the dye to the biochar, ensuring that the residual dye rate on the biochar is still over 90% after 60 days of anaerobic consumption at 37°C. At the same time, the characteristic peak separation of the triple dye ultraviolet spectrum is greater than 95%, which has high specificity and can avoid background interference from the digestive fluid. The triple dye labeling method of the present invention does not change the functional groups on the biochar surface. FTIR confirms that after triple dye labeling, the retention rate of carboxyl / phenolic hydroxyl groups on the biochar surface is greater than 85%.

[0022] The biochar anaerobic digestion tracking method based on triple dye labeling provided by the present invention realizes the precise tracking of the migration pattern of biochar in the anaerobic digestion system. At the same time, combined with the magnetic-free modification strategy, it shows significant advantages in precise separation, multi-type identification and recovery rate improvement, providing data support for the optimized dosing strategy of biochar in anaerobic digestion. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below with reference to the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the scope of protection of the present invention. The process equipment or devices not specifically noted in the following examples are all conventional equipment or devices in the art. Unless otherwise specified, the raw materials used in the examples of the present invention can be obtained commercially; unless otherwise specified, the technical means used in the examples of the present invention are all conventional means well known to those skilled in the art.

[0024] Example 1

[0025] This embodiment provides a method for tracking anaerobic digestion of biochar based on triple dye labeling, which specifically includes the following steps:

[0026] Step 1: Methyl red, amaranth and erythrosine are mixed in a mass ratio of 1:1:1 to prepare a triple mixed dye solution with a concentration of 150 mg / L, and biochar is immersed in the triple mixed dye solution at a mass volume ratio of 1 g:100 mL. The mixture is kept at a constant temperature of 40°C for 24 hours for adsorption dyeing to ensure that the dye adsorption amount is not less than 150 mg / g biochar.

[0027] Step 2: Place the dyed biochar in an environment with a vacuum degree of ≤10Pa for freeze-drying. Cool it to -196°C with liquid nitrogen during the freezing stage and heat it to -50°C for 24 hours during the drying stage to obtain dyed activated carbon until the moisture residue is <5%.

[0028] Dyed biochar was added to the anaerobic digestion system. The substrates for anaerobic digestion consisted of cow dung (TS 13.22%, VS 11.38%), corn stover (TS 92.34%, VS 77.83%), and dyed biochar (TS 88.34%). The biochar addition rate was 5%. Anaerobic digestion substrate formulation requirements included a total solids content (TS) of 8% and a VS loading rate of ≤4.01%. The anaerobic digestion temperature was 37°C, the pH range was 6.8-7.5, the hydraulic retention time (HRT) was 20 days, and the organic loading rate (OLR) was 3gVS / L / day.

[0029] After anaerobic digestion is completed, the digestion residue is collected.

[0030] Step 3: Perform density gradient centrifugation on the digestion residue collected in step 2.

[0031] A bromoform-ethanol mixture was prepared with a volume ratio of 3:1 between bromoform and ethanol, and the density was 1.8 g / mL. A NaI solution with a mass volume concentration of 35% was prepared, and the density was 1.5 g / mL.

[0032] First, add 40% bromoform-ethanol mixture accounting for the volume of the centrifuge tube as the bottom layer, then slowly add 30% NaI solution accounting for the volume of the centrifuge tube as the middle layer, and finally add 30% digestion residue accounting for the volume of the centrifuge tube as the top layer. Under 4°C conditions, after centrifugation at 4000rpm for 20 minutes, a clearly visible interface color band will be formed in the centrifuge tube. When recovering biochar in layers according to different color bands, the upper aqueous phase containing organic impurities is directly discarded, and the middle layer purple biochar marked with amaranth red, the pink biochar marked with erythrosine and the lower layer orange biochar marked with methyl red are recovered.

[0033] The biochar recovered in step 3 was washed three times with distilled water to remove the residual density liquid and vacuum dried at 40°C for 24 h.

[0034] The recovered activated carbon was characterized by SEM analysis of surface dye distribution and UV spectroscopy for quantitative recovery (methyl red 420nm / amaranth 520nm / erythrosine 530nm). Testing showed that the biochar recovery rate of this example was 89.3%, a 16.7% increase compared to the 76.5% recovery rate of the magnetic separation method; the separation purity was 92.7%, a 35.8% increase compared to the 68.2% separation purity of the magnetic separation method; and surface functional group retention was >90%. Compared to the 28% loss of surface carboxyl groups by the magnetic separation method, the surface property retention of this example was improved by over 220%. The cost of the triple-dye-labeled biochar anaerobic digestion tracking method provided in this example was only 105 yuan / ton, a 67.2% decrease compared to the 320 yuan / ton cost of the magnetic separation method.

Claims

1. A biochar anaerobic digestion tracking method based on triple dye labeling, characterized in that: The steps include: Step 1: Methyl red, amaranth and erythrosine are mixed to prepare a triple mixed dye solution, and the biochar is immersed in the triple mixed dye solution for adsorption dyeing; Step 2: The dyed biochar is freeze-dried in a vacuum process and then added to an anaerobic digestion system to complete anaerobic digestion, and the digestion residue is collected; Step 3: Perform density gradient centrifugation on the digestion residue collected in step 2. First, add a bromoform-ethanol mixture as the bottom layer in the centrifuge tube, then add NaI solution as the middle layer, and finally add the digestion residue as the top layer. After density gradient centrifugation, a clearly visible interface color band will be formed in the centrifuge tube, and the biochar can be recovered in layers according to different color bands.

2. The method for tracking anaerobic digestion of biochar based on triple dye labeling according to claim 1, characterized in that: The dye concentration of the triple mixed dye solution in step 1 is 150 mg / L, wherein the mass ratio of methyl red, amaranth and erythrosine is 1:1:

1.

3. The method for tracking anaerobic digestion of biochar based on triple dye labeling according to claim 1, characterized in that: The mass volume ratio of the biochar and the triple mixed dye solution in step 1 is 1g:100mL.

4. The method for tracking anaerobic digestion of biochar based on triple dye labeling according to claim 1, characterized in that: The adsorption dyeing in step 1 is carried out by constant temperature shaking at 40° C. for 24 h to ensure that the dye adsorption amount is not less than 150 mg / g biochar.

5. The method for tracking anaerobic digestion of biochar based on triple dye labeling according to claim 1, characterized in that: The vacuum degree of the vacuum freeze-drying treatment in step 2 is ≤10Pa, and the temperature is cooled to -196°C with liquid nitrogen during the freezing stage, and the temperature is raised to -50°C and maintained for 24 to 48 hours during the drying stage.

6. The method for tracking anaerobic digestion of biochar based on triple dye labeling according to claim 1, characterized in that: The volume ratio of bromoform to ethanol in the bromoform-ethanol mixture of step 3 is 3:1, the density is 1.8 g / mL, the mass volume concentration of the NaI solution is 35%, and the density is 1.5 g / mL.

7. The method for tracking anaerobic digestion of biochar based on triple dye labeling according to claim 1, characterized in that: In step 3, the volume of the bromoform-ethanol mixture added accounts for 40% of the volume of the centrifuge tube, the volume of the NaI solution added accounts for 30% of the volume of the centrifuge tube, and the volume of the digestion residue added accounts for 30% of the volume of the centrifuge tube.

8. The method for tracking anaerobic digestion of biochar based on triple dye labeling according to claim 1, characterized in that: The density gradient centrifugation conditions in step 3 are 4°C and 4000 rpm for 20 min.

9. The method for tracking anaerobic digestion of biochar based on triple dye labeling according to claim 1, characterized in that: When recovering biochar by different color bands after density gradient centrifugation in step 3, the upper aqueous phase containing organic impurities is directly discarded, and the middle purple biochar marked with amaranth, the pink biochar marked with erythrosine, and the upper orange biochar marked with methyl red are recovered.

10. The method for tracking anaerobic digestion of biochar based on triple dye labeling according to claim 1, characterized in that: The biochar recovered in step 3 was washed three times with distilled water to remove the residual density liquid and vacuum dried at 40 °C for 24 h before use in experimental analysis.