Aromatic targeting colloid biochar as well as preparation method and application thereof

Abstract

The invention relates to aromatic targeting colloid biochar and a preparation method and application thereof, and the method comprises the following steps: taking cellulose-treated crop straws or saccharification residues as raw materials, and carrying out anaerobic pyrolysis to obtain an aromatic biochar template; performing low-temperature air thermal oxidation on the aromatized biochar template to obtain modified biochar; carrying out ball milling on the modified biochar to obtain aromatic targeting colloid biochar; the aromatic targeting colloid biochar is applied to targeted adsorption of polycyclic aromatic hydrocarbon in anionic surfactant leacheate. Compared with the prior art, on the basis that the stability and aromaticity of the hot air oxidation modified biochar are reserved, the biochar is endowed with colloidal characteristics, and efficient targeted adsorption of polycyclic aromatic hydrocarbon in the anionic surfactant leacheate is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of comprehensive utilization of abandoned crops and adsorption and removal of organic pollutants, and in particular to an aromatic targeted colloidal biochar and a preparation method and application thereof. Background Art

[0002] Lignocellulosic biomass mainly includes agricultural and forestry wastes, and crop straw is one of the most abundant renewable lignocellulosic raw materials in nature. The effective use of straw can not only achieve carbon emission reduction and reduce pollutant emissions (such as PM2.5), but also produce products with economic value. Therefore, researching and promoting efficient straw utilization technology is crucial for the green transformation and sustainable development of my country's agriculture.

[0003] Pyrolyzing straw into biochar can greatly reduce greenhouse gas emissions. Biochar can be used as a soil conditioner, adsorbent, livestock feed, etc., which is conducive to achieving negative carbon emissions from straw throughout its life cycle. At present, biochar is often used as an adsorbent and catalyst in the field of soil and water remediation. The pollution of polycyclic aromatic hydrocarbons in soil and groundwater poses a great threat to the ecological environment and human health. Surfactant leaching technology is usually used to repair contaminated sites, and then biochar is used to adsorb polycyclic aromatic hydrocarbons in the leaching solution to achieve the reuse of surfactants. However, almost all biochars will also adsorb anionic surfactants, resulting in low adsorption efficiency and increased remediation costs.

[0004] Due to the structural characteristics of lignocellulose-based biomass, biochar produced by pyrolysis cannot achieve the high specific surface area, surface functional group content and high stability of activated carbon. Although many biochar modification methods can enhance the adsorption of pollutants, such as acid-base modification, high temperature modification, metal impregnation modification and other methods can effectively improve the specific surface area and surface functional groups of biochar, these methods largely ignore the combination of functionality and stability of biochar. Functionality includes improving the adsorption of polycyclic aromatic hydrocarbons while avoiding the adsorption of surfactants. Low stability can cause the disintegration and fragmentation of biochar, the release of soluble substances, the loss of surface functional groups, and other consequences, which have an adverse effect on adsorption in soil and water environments.

[0005] Chinese patent CN202310948019.8 discloses a dual-effect modified biochar and its preparation method and application, which includes: using crop straw treated with cellulase or saccharification residue as raw materials, anaerobic pyrolysis to obtain biochar; low-temperature air thermal oxidation of biochar to obtain modified biochar. Compared with the prior art, this patent greatly reduces the amount of soluble release, effectively improves hydrophobicity, and thus improves the environmental friendliness and stability of biochar, as well as its ability to adsorb organic pollutants. Summary of the invention

[0006] The purpose of the present invention is to provide an aromatic targeted colloidal biochar and its preparation method and application. Based on the biochar in patent CN202310948019.8, the present invention adds a colloid modification method to obtain aromatic targeted colloidal biochar in order to address the functional and stability defects that basically exist in the above lignocellulose-based biochars. The present invention can impart colloidal properties to biochar while retaining the stability and aromaticity of hot air oxidation-modified biochar, thereby achieving efficient targeted adsorption of polycyclic aromatic hydrocarbons in anionic surfactant eluents. The present invention enables biochar to have targeted adsorption function and high stability, thereby improving the environmental friendliness of biochar.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A method for preparing aromatic targeted colloidal biochar, the specific steps are as follows:

[0009] S1, using cellulase-treated crop straw as raw material or saccharification residue as raw material, anaerobic pyrolysis to obtain an aromatized biochar template;

[0010] S2, subjecting the aromatized biochar template obtained in step S1 to low-temperature air thermal oxidation to obtain modified biochar;

[0011] S3. The modified biochar obtained in step S2 is colloidized to obtain aromatic targeted colloidal biochar.

[0012] Furthermore, in step S1, the crop straw is selected from any one or more of rice, wheat, barley or corn straw, and the lignin content is greater than 50%.

[0013] Furthermore, in step S1, the specific steps of treating the crop straw with cellulase are as follows:

[0014] S1-1, drying, coarsely grinding, and crushing the crop straw to obtain crop straw powder;

[0015] S1-2, adding cellulase to the crop straw powder, saccharifying to obtain the crop straw treated with cellulase.

[0016] Furthermore, in step S1-2, the material ratio of cellulase to crop straw powder is 2-300 FPU / g; the saccharification temperature is 40-60°C, the rotation speed is 50-200 r / min, and the time is 12-72 h.

[0017] Furthermore, in step S1, the anaerobic pyrolysis temperature is 500-600°C and the time is 2-3h.

[0018] Furthermore, in step S2, the air flow rate is 200-500 mL / min.

[0019] Furthermore, in step S2, the thermal oxidation temperature is 150-300° C. and the time is 20-60 min.

[0020] Step S1 and step S2 of the present invention are steps in patent CN202310948019.8, and step S3 is an innovative invention based on this.

[0021] Furthermore, in step S3, the specific steps of colloidizing the modified biochar are as follows:

[0022] S3-1, drying the modified biochar obtained in step S2 and then refrigerating it;

[0023] S3-2, ball milling the refrigerated modified biochar obtained in step S3-1;

[0024] S3-3, mixing the ball-milled modified biochar obtained in step S3-2 with a solvent to obtain a suspension;

[0025] S3-4, after filtering the suspension obtained in step S3-3 in the dark, drying the biochar remaining on the filter paper to obtain aromatic targeted colloidal biochar.

[0026] Furthermore, in step S3-1, the drying temperature is 25-45°C, the refrigeration temperature is -10-0°C, and the refrigeration time is 5-10 hours.

[0027] As a preferred technical solution, in step S3-1, the drying temperature is 25-30°C and the refrigeration time is 6-8h.

[0028] Furthermore, in step S3-2, the refrigerated modified biochar is ball-milled in a planetary ball mill, the ball milling beads in the planetary ball mill are 95% zirconium oxide with a size of 2-5 mm, the mass ratio of zirconium oxide beads to modified biochar is 150-300:1, the total working time of the planetary ball mill is 4-10 hours, and there is a rest time of 3-7 minutes every 15-20 minutes of work.

[0029] As a preferred technical solution, in step S3-2, the ball milling beads are 2 mm 95% zirconium oxide, the mass ratio of zirconium oxide beads to modified biochar is 200-250:1, and the total working time of the planetary ball mill is 6-8 hours.

[0030] Furthermore, in step S3-3, the solvent is pure water, and the concentration of the modified biochar in the suspension is 5-18 g / L.

[0031] As a preferred technical solution, in step S3-3, the concentration of the modified biochar suspension in the suspension is 10-15 g / L.

[0032] Furthermore, in step S3-4, the suspension obtained in step S3-3 is placed in an ultrasonic cleaning machine for cleaning for 10-50 minutes and then placed in a dark place.

[0033] As a preferred technical solution, in step S3-4, the cleaning time is 20-40 minutes.

[0034] Furthermore, in step S3-4, the light-proof standing time is 12-36 hours.

[0035] The filtration membrane used is a nylon membrane with a pore size of 100 nm.

[0036] The drying temperature is 25-45°C.

[0037] As a preferred technical solution, in step S3-4, the light-proof standing time is 24-30 hours.

[0038] Furthermore, in step S3, the aroma-targeted colloidal biochar is placed for more than one week. When the freshly prepared aroma-targeted colloidal biochar is used directly, its adsorption performance is unstable, but after being placed, its adsorption performance is relatively stable.

[0039] The present invention also provides an aromatic targeted colloidal biochar, wherein the amount of soluble released matter of the aromatic targeted colloidal biochar is 14.0-25.0 mg / L.

[0040] Furthermore, the concentrations of carboxyl, lactone and hydroxyl groups of the aromatic targeted colloidal biochar are 1.6-3.0 mM / g: 1.6-4.0 mM / g: 0.5-2.4 mM / g, and it has strong stability and adsorption effect.

[0041] Furthermore, the specific surface area of ​​the aromatic targeted colloidal biochar is 250-400m 2 / g.

[0042] In addition, the present invention also provides an application of an aromatic targeted colloidal biochar, wherein the aromatic targeted colloidal biochar is used for targeted adsorption of polycyclic aromatic hydrocarbons in anionic surfactant eluent, and does not adsorb anionic surfactants.

[0043] Furthermore, the anionic surfactant includes rhamnolipid (RL) and sodium dodecyl sulfate (SDS), and the polycyclic aromatic hydrocarbons include naphthalene and phenanthrene.

[0044] The principle of the present invention is as follows:

[0045] The present invention provides a method for preparing aromatic targeted colloidal biochar, and the specific steps are as follows:

[0046] (1) Using crop straw treated with cellulase or saccharification residue (waste tailings in the process of producing bioethanol from crop straw) as raw materials, the biochar obtained by anaerobic pyrolysis is used as a precursor of modified biochar, and the lignin content is increased by cellulase treatment, which is beneficial to the establishment of an aromatic carbon structure, thereby obtaining an aromatic biochar;

[0047] (2) oxidizing the aromatized biochar with low-temperature hot air to obtain hot air oxidized biochar;

[0048] (3) The hot air oxidized biochar is colloided into an aromatic targeted colloidal biochar. Based on the first two steps, a biochar with a high aromatic structure and a high content of surface oxygen-containing functional groups is obtained. In the colloidation step of the present invention, the characteristics of the high aromatic structure and the high content of surface oxygen-containing functional groups are retained to a great extent, and the specific surface area is greatly improved. The high aromatic carbon structure is conducive to providing a strong carbon structure stability for the biochar after colloidation. For example, the concentration of soluble release of the aromatic targeted colloidal biochar is reduced by 92.64%, 40.75%, and 83.56% compared with ordinary biochar, modified biochar, and ordinary colloidal biochar, respectively. The oxygen-containing functional groups of the aromatic targeted colloidal biochar are greatly increased, and the carboxyl group, lactone group, and phenolic hydroxyl group are 2.15 times, 2.48 times, and 5.62 times of the modified biochar, respectively, and are 2.73 times, 3.81 times, and 1.79 times of the ordinary colloidal biochar. The high content of surface oxygen-containing functional groups is conducive to maintaining the colloidal stability of colloidal biochar. The removal rate of phenanthrene increased by 500.0% compared with modified biochar and 35.9% compared with ordinary colloidal biochar.

[0049] The present invention adds a colloidal modification method based on the low-temperature hot air oxidation modification of saccharification residue biochar, and achieves efficient targeted adsorption of polycyclic aromatic hydrocarbons in anionic surfactant eluents by greatly increasing the specific surface area and giving high aromatization and high content of oxygen-containing functional group biochar colloidal properties, while maintaining a low amount of soluble release, improving its environmental friendliness and stability, improving performance, and expanding the scope of application. Under the modification conditions of the present invention, completely different effects from the prior art can be achieved. The present invention has a positive effect on the country's biomass energy goals and environmental governance.

[0050] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0051] (1) Resource utilization of agricultural waste: The present invention uses discarded crop straw to prepare biochar, thus turning waste into treasure;

[0052] (2) Inheritance and developmental regulation of biochar carbon structure characteristics: The present invention aims to address the shortcomings of biochar produced by pyrolysis of lignocellulose-based biomass, which generally lacks high performance and stability. On the basis of hot air oxidation-modified biochar, the present invention performs colloidal modification, inherits and retains a large amount of aromatic carbon structure and high content of oxygen-containing functional groups, adds colloidal properties to the biochar, maintains high stability, and greatly increases the specific surface area.

[0053] (3) Adding targeted adsorption function to biochar: The present invention effectively increases the adsorption capacity of polycyclic aromatic hydrocarbons by colloidal modification, inheriting a large number of aromatic carbon structures and increasing the specific surface area; it gives biochar colloidal properties to achieve targeted adsorption of polycyclic aromatic hydrocarbons in the surfactant eluent, completely avoiding the adsorption of surfactants. In practical applications, it effectively increases the number of times the surfactant can be reused and improves the barrier properties to pollutants.

[0054] (4) The biochar of the present invention can maintain a low release concentration and eco-friendliness during application. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a graph showing the amount of soluble released substances of different biochars in Experimental Example 1 of the present invention;

[0056] Figure 2 This is a representative surface oxygen-containing functional group content diagram of different biochars in Experimental Example 2 of the present invention;

[0057] Figure 3 This is a diagram showing the removal efficiency of phenanthrene in the rhamnolipid eluate using different biochars in Experimental Example 3 of the present invention. DETAILED DESCRIPTION

[0058] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0059] Unless otherwise specified, the equipment used in the following examples are all conventional equipment in the art; the reagents used are all commercially available products or prepared by conventional methods in the art unless otherwise specified. Anything not described in detail in the following examples can be achieved by conventional experimental means in the art.

[0060] In conjunction with the accompanying drawings, some embodiments of the present invention are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0061] Embodiment 1:

[0062] This embodiment provides a method for preparing aromatic targeted colloidal biochar, and the specific steps are as follows:

[0063] (1) Preparation of aromatized biochar template:

[0064] 100 g of corn straw from Yancheng City, Jiangsu Province was taken, dried, coarsely ground, and pulverized to obtain crop straw powder. Cellulase was added to the crop straw powder. After treatment, the lignin content was 63%. An aromatized biochar template was obtained by anaerobic pyrolysis at 500°C for 2 h.

[0065] (2) Preparation of modified biochar:

[0066] 5.00 g of the aromatized biochar template prepared in step (1) was placed in a tubular furnace with an air flow rate of 300 mL / min and treated at 200° C. for 30 min to finally obtain 4.95 g of modified biochar.

[0067] (3) Preparation of aromatic targeted colloidal biochar:

[0068] The modified biochar prepared in step (2) was dried in a forced air drying oven at 25°C, and then refrigerated in a refrigerator at -4°C for 5 hours.

[0069] The refrigerated modified biochar was placed in a ball mill filled with 2 mm 95% zirconium oxide. The mass ratio of zirconium oxide beads to modified biochar was 200:1. The total working time of the ball mill was 8 h, with a rest time of 5 min after every 15 min of work.

[0070] Weigh a certain amount of ball-milled modified biochar to prepare a 12 g / L suspension, place it in an ultrasonic cleaner for 30 min, and keep the suspension away from light for 24 h. Siphon off the bottom sediment, filter the upper suspension with a nylon filter membrane with a pore size of 100 nm, and dry the filter membrane in a 25°C forced air drying oven. Use a medicine spoon to gently scrape the biochar on the dried filter paper to obtain aromatic targeted colloidal biochar.

[0071] Comparative Example 1:

[0072] This comparative example provides a common biochar, that is, biochar directly prepared by anaerobic pyrolysis of straw that has not been treated with enzymes at 500° C. for 2 h.

[0073] Comparative Example 2:

[0074] This comparative example provides a modified biochar, which is prepared by step (1) and step (2) in Example 1. The specific steps are as follows:

[0075] (1) Preparation of aromatized biochar template:

[0076] 100 g of corn straw from Yancheng City, Jiangsu Province was taken, dried, coarsely ground, and pulverized to obtain crop straw powder. Cellulase was added to the crop straw powder. After treatment, the lignin content was 63%. An aromatized biochar template was obtained by anaerobic pyrolysis at 500°C for 2 h.

[0077] (2) Preparation of modified biochar:

[0078] 5.00 g of the aromatized biochar template prepared in step (1) was placed in a tubular furnace with an air flow rate of 300 mL / min and treated at 200° C. for 30 min to finally obtain 4.95 g of modified biochar.

[0079] Comparative Example 3:

[0080] This comparative example provides a common colloidal biochar, that is, biochar directly prepared by anaerobic pyrolysis of straw without enzyme treatment at 500° C. for 2 h and then colloidized.

[0081] Test Example 1

[0082] This test example provides a test for the soluble release content of biochar, and the specific steps are as follows:

[0083] Weigh 0.03 g of the aromatic targeted colloidal biochar prepared in Example 1, the ordinary biochar prepared in Comparative Example 1, the modified biochar prepared in Comparative Example 2, or the ordinary colloidal biochar prepared in Comparative Example 3, put them into a 100 mL stoppered conical flask, add 60 mL of ultrapure water, and prepare a 0.5 g / L biochar solution;

[0084] The above biochar solution was placed in a constant temperature shaker at 30°C and 200 r / min for 1 hour, and then the total dissolved solids (TDS) of the sample was measured. All experiments were repeated three times, and the average value of the soluble release content was calculated.

[0085] Experimental results: Figure 1 As shown, the soluble release of ordinary biochar prepared in Comparative Example 1 is 45.23 mg / L; the soluble release of modified biochar prepared in Comparative Example 2 is 5.62 mg / L; the soluble release of ordinary colloidal biochar prepared in Comparative Example 3 is 20.25 mg / L; the soluble release of aromatic targeted colloidal biochar prepared in Example 1 is 3.33 mg / L, and its soluble release is greatly reduced, which is 92.64% less than that of ordinary biochar, 40.75% less than that of modified biochar, and 83.56% less than that of ordinary colloidal biochar.

[0086] Embodiment 2:

[0087] This embodiment provides a method for preparing aromatic targeted colloidal biochar, and the specific steps are as follows:

[0088] (1) Preparation of aromatized biochar template:

[0089] 100 g of corn straw from Yancheng City, Jiangsu Province was taken, dried, coarsely ground, and pulverized to obtain crop straw powder. Cellulase was added to the crop straw powder. After treatment, the lignin content was 63%. An aromatized biochar template was obtained by anaerobic pyrolysis at 500°C for 2 h.

[0090] (2) Preparation of modified biochar:

[0091] 5.00 g of the aromatized biochar template prepared in step (1) was placed in a tubular furnace with an air flow rate of 300 mL / min and treated at 200° C. for 30 min to finally obtain 4.95 g of modified biochar.

[0092] (3) Preparation of aromatic targeted colloidal biochar:

[0093] The modified biochar prepared in step (2) was dried in a forced air drying oven at 25°C, and then refrigerated in a refrigerator at -4°C for 10 hours.

[0094] The refrigerated modified biochar was placed in a ball mill filled with 2 mm 95% zirconium oxide. The mass ratio of zirconium oxide beads to modified biochar was 300:1. The total working time of the ball mill was 10 h, with a rest time of 5 min after every 15 min of work.

[0095] Weigh a certain amount of ball-milled modified biochar to prepare a suspension of 8 g / L, place it in an ultrasonic cleaner for 50 min, and keep the suspension away from light for 24 h. Siphon off the bottom sediment, filter the upper suspension with a nylon filter membrane with a pore size of 100 nm, and dry the filter membrane in a blast drying oven at 25°C. Use a medicine spoon to gently scrape the biochar on the dried filter paper to obtain aromatic targeted colloidal biochar.

[0096] Test Example 2

[0097] This test example provides a method for testing the surface oxygen-containing functional group content of biochar by Boehm titration method, and the specific steps are as follows:

[0098] Prepare 0.05 mol / L sodium bicarbonate (NaHCO3), sodium carbonate (Na2CO3) and sodium hydroxide (NaOH) solutions, and 0.02 mol / L hydrochloric acid (HCl) solution.

[0099] Use standard anhydrous sodium carbonate (Na2CO3) to calibrate the hydrochloric acid solution. Weigh a certain amount of anhydrous sodium carbonate and dissolve it in water. Add methyl orange as an indicator and titrate with hydrochloric acid until it turns orange-red to determine the concentration of the hydrochloric acid.

[0100] Use calibrated hydrochloric acid solution to calibrate NaHCO3, Na2CO3 and NaOH solutions respectively. Take a certain volume of alkaline solution, add bromocresol green-methyl red indicator, and titrate with hydrochloric acid until the color changes to determine the concentration of the alkaline solution.

[0101] Weigh about 0.1g of the dried sample (aromatic targeted colloidal biochar prepared in Example 2, modified biochar prepared in Comparative Example 2, and ordinary colloidal biochar prepared in Comparative Example 3) and put it into a polytetrafluoroethylene bottle, add 50mL 0.05mol / L NaHCO3, Na2CO3 and NaOH solution respectively, seal the bottle and shake it vigorously to prevent air from entering. The reaction was stirred and shaken in a numerically controlled vibrator for 24 hours, and the sample was manually shaken at least three times in the middle to prevent the sample from sticking to the wall and ensure that the reaction was complete. The solution after the reaction was filtered, 10mL of the filtrate was taken, bromocresol green-methyl red indicator was added, and the solution was titrated with standard hydrochloric acid solution until the solution changed from green to wine red, and the volume of hydrochloric acid consumed was recorded. According to the volume of hydrochloric acid consumed by titration, the amount of material consumed during the reaction of the material surface functional groups (such as carboxyl, lactone, phenolic hydroxyl) with NaHCO3, Na2CO3 and NaOH solution was calculated to determine the content of different acidic groups in the sample.

[0102] Experimental results: Figure 2 As shown, the carboxyl, lactone and phenolic hydroxyl groups of the modified biochar prepared in Comparative Example 2 are 1.05, 1.16 and 0.21 mM / g respectively; the carboxyl, lactone and phenolic hydroxyl groups of the common colloidal biochar prepared in Comparative Example 3 are 0.828, 0.756 and 0.658 mM / g respectively; the carboxyl, lactone and phenolic hydroxyl groups of the aromatic targeted colloidal biochar prepared in Example 2 are 2.258, 2.88 and 1.18 mM / g respectively. The oxygen-containing functional groups of the aromatic targeted colloidal biochar are greatly improved, and the carboxyl, lactone and phenolic hydroxyl groups are 2.15 times, 2.48 times and 5.62 times of the modified biochar respectively, and 2.73 times, 3.81 times and 1.79 times of the common colloidal biochar.

[0103] Embodiment 3:

[0104] This embodiment provides a method for preparing aromatic targeted colloidal biochar, and the specific steps are as follows:

[0105] (1) Preparation of aromatized biochar template:

[0106] 100 g of corn straw from Yancheng City, Jiangsu Province was taken, dried, coarsely ground, and pulverized to obtain crop straw powder. Cellulase was added to the crop straw powder. After treatment, the lignin content was 63%. An aromatized biochar template was obtained by anaerobic pyrolysis at 500°C for 2 h.

[0107] (2) Preparation of modified biochar:

[0108] 5.00 g of the aromatized biochar template prepared in step (1) was placed in a tubular furnace with an air flow rate of 300 mL / min and treated at 200° C. for 30 min to finally obtain 4.95 g of modified biochar.

[0109] (3) Preparation of aromatic targeted colloidal biochar:

[0110] The modified biochar prepared in step (2) was dried in a forced air drying oven at 35°C, and then refrigerated in a refrigerator at -4°C for 7 hours.

[0111] The refrigerated modified biochar was placed in a milling jar filled with 2 mm 95% zirconium oxide balls. The mass ratio of zirconium oxide beads to modified biochar was 250:1. The total working time of the ball mill was 6 h, with a rest time of 5 min every 15 min of work.

[0112] Weigh a certain amount of ball-milled modified biochar to prepare a 10 g / L suspension, place it in an ultrasonic cleaner for 40 minutes, and keep the suspension away from light for 24 hours. Siphon off the bottom sediment, filter the upper suspension with a nylon filter membrane with a pore size of 100 nm, and dry the filter membrane in a 35°C forced air drying oven. Use a medicine spoon to gently scrape the biochar on the dried filter paper to obtain aromatic targeted colloidal biochar.

[0113] Test Example 3

[0114] This test example provides a test of the adsorption performance of biochar on polycyclic aromatic hydrocarbons in anionic surfactant eluent. The specific steps are as follows:

[0115] A common anionic surfactant rhamnolipid (RL) was used with a concentration of 20 g / L, and a certain amount of phenanthrene was added to the rhamnolipid solution to prepare a simulated eluent of 10 mg / L. 2.0 mg of biochar sample (aromatic targeted colloidal biochar prepared in Example 3, modified biochar prepared in Comparative Example 2, and ordinary colloidal biochar prepared in Comparative Example 3) was added to 10 mL of pure water and placed in an ultrasonic cleaner for 30 min to prepare a biochar suspension.

[0116] The eluent was mixed with the biochar suspension in a volume ratio of 1:1, placed in a constant temperature shaker at 25°C, and shaken at 150 r / min for 12 h. All experiments were repeated three times, and the average value of the adsorption of PAHs was calculated.

[0117] Experimental results: Figure 3 As shown, after reaching adsorption equilibrium, the removal efficiency of the modified biochar prepared in Comparative Example 2 is 16.5%, and the removal efficiency of the common colloidal biochar prepared in Comparative Example 3 is 72.8%; the removal efficiency of the aromatic targeted colloidal biochar prepared in Example 3 for phenanthrene is 99.0%; its removal efficiency has increased significantly, increasing by 500.0% compared with the modified biochar and 35.9% compared with the common colloidal biochar. The adsorption amounts of rhamnolipids by modified biochar, common colloidal biochar, and aromatic targeted colloidal biochar are 12, 0, and 0 mg / g, respectively.

[0118] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing aromatic targeted colloidal biochar, characterized in that: The specific steps are as follows: S1, using cellulase-treated crop straw as raw material or saccharification residue as raw material, anaerobic pyrolysis to obtain an aromatized biochar template; S2, subjecting the aromatized biochar template obtained in step S1 to low-temperature air thermal oxidation to obtain modified biochar; S3. The modified biochar obtained in step S2 is colloidized to obtain aromatic targeted colloidal biochar.

2. The method for preparing an aromatic targeted colloidal biochar according to claim 1, characterized in that: In step S1, the crop straw is selected from any one or more of rice, wheat, barley or corn straw, and the lignin content is more than 50%; The anaerobic pyrolysis temperature is 500-600℃ and the time is 2-3h.

3. The method for preparing an aromatic targeted colloidal biochar according to claim 1, characterized in that: In step S2, the air flow rate is 200-500 mL / min, the thermal oxidation temperature is 150-300° C., and the time is 20-60 min.

4. The method for preparing an aromatic targeted colloidal biochar according to claim 1, characterized in that: In step S3, the specific steps of colloidizing the modified biochar are as follows: S3-1, drying the modified biochar obtained in step S2 and then refrigerating it; S3-2, ball milling the refrigerated modified biochar obtained in step S3-1; S3-3, mixing the ball-milled modified biochar obtained in step S3-2 with a solvent to obtain a suspension; S3-4, after filtering the suspension obtained in step S3-3 in the dark, drying the biochar remaining on the filter paper to obtain aromatic targeted colloidal biochar.

5. The method for preparing an aromatic targeted colloidal biochar according to claim 4, characterized in that: In step S3-1, the drying temperature is 25-45°C, the refrigeration temperature is -10-0°C, and the refrigeration time is 5-10h; In step S3-2, the refrigerated modified biochar is ball-milled in a planetary ball mill, the ball milling beads in the planetary ball mill are 95% zirconium oxide with a size of 2-5 mm, the mass ratio of zirconium oxide beads to modified biochar is 150-300:1, the total working time of the planetary ball mill is 4-10 hours, and the rest time is 3-7 minutes after every 15-20 minutes of working; In step S3-3, the solvent is pure water, and the concentration of modified biochar in the suspension is 5-18 g / L; In step S3-4, the suspension obtained in step S3-3 is placed in an ultrasonic cleaning machine for cleaning for 10-50 minutes and then placed in a dark place. The dark-proof standing time is 12-36 hours. The filtration membrane used is a nylon membrane with a pore size of 100 nm. The drying temperature is 25-45°C.

6. The method for preparing an aromatic targeted colloidal biochar according to claim 1, characterized in that: In step S3, the aromatic targeted colloidal biochar is placed for a period of more than one week.

7. An aromatic targeted colloidal biochar, characterized in that: The amount of soluble release of the aromatic targeted colloidal biochar prepared by the method as described in any one of claims 1 to 6 is 14.0-25.0 mg / L.

8. The aromatic targeted colloidal biochar according to claim 7, characterized in that: The concentration ratio of the carboxyl group, the lactone group, and the hydroxyl group of the aromatic targeted colloidal biochar is 1.6-3.0 mM / g: 1.6-4.0 mM / g: 0.5-2.4 mM / g; The specific surface area of ​​the aromatic targeted colloidal biochar is 250-400m 2 / g.

9. An application of the aromatic targeted colloidal biochar as claimed in claim 7, characterized in that: The aromatic targeted colloidal biochar is used for targeted adsorption of polycyclic aromatic hydrocarbons in anionic surfactant eluent, and does not adsorb anionic surfactants.

10. The use of an aromatic targeted colloidal biochar according to claim 9, characterized in that: The anionic surfactants include rhamnolipid and sodium dodecyl sulfate, and the polycyclic aromatic hydrocarbons include naphthalene and phenanthrene.

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