Preparation method and application of acid-modified high-temperature pyrolysis peanut shell-based biochar

Abstract

The present invention discloses a method for preparing acid-modified high-temperature cracking peanut shell-based biochar and its application, wherein the method for preparing acid-modified high-temperature cracking peanut shell-based biochar is as follows: washing peanut shells, drying and performing high-temperature cracking to obtain biochar; soaking the high-temperature cracking biochar with an acidic solution; freeze-drying the obtained solid, grinding and sieving, and obtaining acid-modified high-temperature cracking peanut shell-based biochar. The present invention adopts a high temperature of more than 700°C as the peak temperature for pyrolysis of peanut shell biomass, and the peak temperature residence time is as long as 5h, which is higher than the peak temperature for pyrolysis prepared by traditional biochar, and the residence time is longer, and the biochar after high-temperature cracking is acid-modified to strengthen the adsorption performance of peanut shell-based biochar, which can not only efficiently remove long-chain perfluorinated compounds, but also significantly improve the removal efficiency and adsorption performance of short-chain perfluorinated compounds in water environment, and can quickly and efficiently remove low-concentration PFAS in the environment, with very good environmental and social benefits.

Description

Technical Field

[0001] The present invention belongs to the technical field of biochar materials, and in particular relates to a method for preparing acid-modified high-temperature cracking peanut shell-based biochar and its application in removing new pollutants. Background Art

[0002] With the rapid development of industry and agriculture in recent years, more and more new pollutants have entered the water environment through sewage and wastewater discharge. Perfluorinated compounds (PFAS), as an important representative of new pollutants, have been widely detected in the water environment. With the increasingly stringent control and restrictions on long-chain PFAS such as PFOA and PFOS, the manufacture, use and discharge of short-chain perfluorinated compounds have gradually increased. At present, the sewage treatment process cannot completely remove long-chain PFAS by defluorination, and other short-chain PFAS by-products will be generated during the defluorination degradation process. In addition to sewage treatment plants containing high concentrations of short-chain PFAS, short-chain PFAS have been found in various water bodies such as oceans, rivers, lakes, and groundwater at different concentrations. Compared with long-chain homologs, short-chain PFAS such as PFBS and PFBA are also environmentally persistent, bioaccumulative, and biotoxic. In addition, short-chain PFAS also have higher solubility and fluidity. The study found that PFBS is the main PFAS pollutant in the groundwater under the Fuxin Fluoridation Park in China. The maximum concentration of PFBS increased from 0.87μg / L to 32.4μg / L between 2009 and 2019, which is much higher than the 3μg / L health risk value of PFBS in drinking water set by the Minnesota Department of Health. The spread and pollution caused by short-chain PFAS in the water environment will have a harmful impact on the ecology and threaten human health. Therefore, it is crucial to take effective measures to remove short-chain perfluorinated compounds in the water environment.

[0003] Adsorption is a common PFAS treatment method with advantages such as simple operation, low cost, and environmental friendliness. There are many materials that can be used as adsorbents to remove PFAS from water environments. However, due to the short chain length, strong hydrophilicity, and high water solubility of short-chain PFAS, it is difficult to adsorb and separate them from water. Currently, traditional long-chain PFAS adsorption materials such as activated carbon, biochar, hydrotalcite, and resins have very limited removal effects on short-chain PFAS and cannot meet actual application needs. Biochar refers to the carbon-rich product obtained after biomass is heat-treated in an oxygen-limited environment. The physical and chemical properties of biochar materials can be changed and the adsorption performance of the material can be improved by regulating the conditions such as the pyrolysis peak temperature, peak temperature residence time, and heating rate during the biochar preparation process. It is an ideal candidate material for short-chain PFAS adsorbents.

[0004] Therefore, finding and preparing adsorbent materials that can efficiently remove short-chain perfluorinated compounds at low concentrations in the environment is a current research hotspot. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a method for preparing acid-modified high-temperature pyrolysis peanut shell-based biochar, and the prepared biochar can efficiently remove short-chain perfluorinated compounds at low concentrations in the environment.

[0006] Another object of the present invention is to provide the application of the acid-modified high-temperature cracking peanut shell-based biochar to remove new pollutants.

[0007] Technical solution: In order to achieve the above-mentioned purpose, the present invention provides a method for preparing acid-modified high-temperature pyrolysis peanut shell-based biochar, which specifically comprises the following steps:

[0008] (1) washing the peanut shells, drying them and then performing high temperature cracking;

[0009] (2) soaking the high temperature cracked biochar obtained in step (1) with an acidic solution, filtering and then soaking and washing the material;

[0010] (3) The obtained solid is placed in a refrigerator for freezing and then transferred to a vacuum freeze dryer for freeze drying, grinding and sieving to prepare acid-modified high-temperature pyrolysis peanut shell-based biochar.

[0011] Furthermore, the drying condition in step (1) is drying at 60° C. for 24 hours.

[0012] Furthermore, the high temperature cracking process in step (1) is as follows: the first stage is a heating stage, in which the temperature is raised to 700-900°C at a heating rate of 3-10°C / min; the second stage is a constant temperature stage, in which the high temperature of 700-900°C is maintained for 3-5 hours; and the third stage is a cooling stage, in which the temperature is cooled to room temperature.

[0013] Preferably, the high temperature cracking process in step (1) is as follows: the first stage is a heating stage, in which the temperature is raised to 800-900°C at a heating rate of 3-10°C / min; the second stage is a constant temperature stage, in which the high temperature of 800-900°C is maintained for 3-5 hours; and the third stage is a cooling stage, in which the temperature is cooled to room temperature.

[0014] Preferably, the specific setting procedure of the muffle furnace in step (1) is as follows: the first stage is a heating stage, in which the temperature is raised to 900°C at a heating rate of 5°C / min; the second stage is a constant temperature stage, in which the temperature is maintained at a high temperature of 900°C for 5 hours; and the third stage is a cooling stage, in which the temperature is cooled to room temperature.

[0015] Furthermore, the acidic solution in step (2) is any one of hydrochloric acid, sulfuric acid or phosphoric acid.

[0016] Preferably, the acidic solution in step (2) is hydrochloric acid.

[0017] Furthermore, in the step (2), the acidic solution is a hydrochloric acid solution with a concentration of 0.01 to 1 mol / L, and the soaking time is 8 to 12 hours.

[0018] Preferably, in step (2), the concentration of hydrochloric acid is 1 mol / L and the soaking time is 12 h.

[0019] Furthermore, in the step (2), after filtering, the material is rinsed and soaked in ultrapure water until it becomes neutral.

[0020] Furthermore, in the step (3), the product is stored in a refrigerator at -10 to -20°C for 24 to 36 hours and ground through a 80 to 100 mesh sieve.

[0021] Preferably, in step (3), the product is stored at -20°C for 24 hours and ground through a 100-mesh sieve.

[0022] Application of acid-modified high-temperature cracked peanut shell-based biochar prepared by the preparation method of the present invention in removing new pollutants.

[0023] The application process is specifically as follows: adding the acid-modified high-temperature cracked peanut shell-based biochar into a solution containing pollutants and oscillating the reaction at room temperature.

[0024] Furthermore, the pollutant is any one of perfluorobutanesulfonic acid (PFBS), perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA) or perfluorobutyric acid (PFBA).

[0025] Furthermore, the mass volume ratio of the acid-modified high-temperature cracked peanut shell-based biochar to the pollutants is 0.1 to 1 g:1L.

[0026] Furthermore, the concentration of the new pollutant is 1 μg / L to 75 mg / L.

[0027] The invention provides an acid-modified high-temperature cracking peanut shell-based biochar immobilized microorganism, which comprises the acid-modified high-temperature cracking peanut shell-based biochar.

[0028] Wherein, the immobilized microorganism is Pseudomonas aeruginosa adsorbed and colonized on biochar.

[0029] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0030] (1) The present invention uses a high temperature of more than 700°C as the peak temperature for pyrolysis of peanut shell biomass, and the peak temperature residence time is as long as 5 hours, which is higher than the peak temperature and residence time of traditional biochar preparation, and the biochar after high temperature pyrolysis is acid-modified to further enhance the adsorption performance of peanut shell-based biochar. The prepared acid-modified high temperature pyrolysis peanut shell-based biochar has a large specific surface area, rich pore structure, high aromaticity and stability, and a wide applicable pH range, which can achieve the purpose of removing PFAS from the water environment.

[0031] (2) Compared with the existing hydrotalcite, activated carbon or other biomass biochar and low-temperature peanut shell-based biochar adsorbents, the acid-modified high-temperature pyrolysis peanut shell-based biochar prepared by the present invention can efficiently remove the long-chain perfluorinated compound PFOS, while significantly improving the removal efficiency of the short-chain perfluorinated compound PFBS in the water environment, and the adsorption performance is also greatly improved. It can quickly and efficiently remove low-concentration PFAS in the environment, and the preparation process is simple, which is suitable for large-scale promotion.

[0032] (3) The adsorption material is prepared using agricultural waste peanut shells as raw materials, which converts easily decomposable organic carbon into stable fixed carbon, realizes the resource utilization of biomass, avoids environmental pollution caused by direct incineration of large amounts of peanut shells, and reduces carbon dioxide emissions, which has very good economic, environmental and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The figure is an analysis diagram of the removal effect of PFOS by Example 3, Comparative Example 1 and Comparative Example 3;

[0034] Figure 2 It is an analysis diagram of the removal effect of PFBS by Examples 1 to 5 and Comparative Examples 1 to 3;

[0035] Figure 3 The Langmuir adsorption isotherm fitting diagram of PFBS in Examples 1 to 3;

[0036] Figure 4 The Langmuir adsorption isotherm fitting diagram of Comparative Example 3 for PFBS;

[0037] Figure 5 It is an analysis diagram of the removal effect of PFBS under different pH conditions for Example 1, Example 2, Example 3 and Example 5;

[0038] Figure 6 It is an analysis diagram of the removal effect of PFBS by Example 3 and Comparative Example 3;

[0039] Figure 7 This is an analysis diagram of the removal effect of Example 3 and Example 6 on PFBS. DETAILED DESCRIPTION

[0040] The present invention will be further explained and illustrated below in conjunction with specific examples.

[0041] Example 1

[0042] A method for preparing acid-modified high-temperature pyrolysis peanut shell-based biochar comprises the following steps:

[0043] (1) Rinse the raw peanut shells purchased from the market with ultrapure water three times to remove surface impurities, dry them in an oven at 60°C for 24 h;

[0044] (2) Place the dried peanut shells in a sealed crucible, place it in a muffle furnace and heat it to 700° C. at a heating rate of 5° C. / min, maintain it at 700° C. for 5 h, and then take it out after cooling it to room temperature;

[0045] (3) The high temperature cracked peanut shell-based biochar was soaked in 1 mol / L hydrochloric acid for 12 h, filtered and rinsed with ultrapure water until neutral, the obtained solid was placed in a -20 °C refrigerator for 24 h and then transferred to a vacuum freeze dryer and frozen at -50 °C until completely dry, and then ground through a 100 mesh sieve to obtain acid-modified high temperature cracked peanut shell-based biochar.

[0046] Embodiment 2:

[0047] A method for preparing acid-modified high-temperature pyrolysis peanut shell-based biochar comprises the following steps:

[0048] The maximum pyrolysis temperature of 700° C. in step (2) of Example 1 was replaced with 800° C., and the other steps were the same as in Example 1 to obtain acid-modified high-temperature pyrolysis peanut shell-based biochar.

[0049] Embodiment 3:

[0050] A method for preparing acid-modified high-temperature pyrolysis peanut shell-based biochar comprises the following steps:

[0051] The maximum pyrolysis temperature of 700° C. in step (2) of Example 1 was replaced with 900° C., and the other steps were the same as in Example 1 to obtain acid-modified high-temperature pyrolysis peanut shell-based biochar.

[0052] Embodiment 4:

[0053] A method for preparing acid-modified high-temperature pyrolysis peanut shell-based biochar comprises the following steps:

[0054] The maximum pyrolysis temperature of 700° C. in step (2) of Example 1 was changed to 900° C., and the high temperature holding time of 5 h was changed to 3 h. The other steps were the same as those in Example 1 to obtain acid-modified high-temperature pyrolysis peanut shell-based biochar.

[0055] Embodiment 5:

[0056] A method for preparing acid-modified high-temperature pyrolysis peanut shell-based biochar comprises the following steps:

[0057] The maximum pyrolysis temperature of 700° C. in step (2) of Example 1 was replaced with 900° C., and the 1 mol / L hydrochloric acid in step (3) was replaced with 0.01 mol / L hydrochloric acid. The other steps were the same as in Example 1 to obtain acid-modified high-temperature pyrolysis peanut shell-based biochar.

[0058] Embodiment 6:

[0059] A method for preparing acid-modified high-temperature cracking peanut shell-based biochar immobilized microorganisms comprises the following steps:

[0060] (1) Preparation of LB medium: Weigh 3.0 g of beef extract, 5.0 g of peptone, and 5.0 g of sodium chloride and dissolve them in 1 L of ultrapure water. Use 1 mol / L hydrochloric acid or sodium hydroxide solution to adjust the pH value of the medium to 7.0. Place the medium in an autoclave and sterilize it at 121°C for 20 min. After cooling to room temperature, take it out for use.

[0061] (2) Solid culture medium: Weigh 3.0 g of beef extract, 5.0 g of peptone, 5.0 g of sodium chloride, and 20 g of agar powder and dissolve them in 1 L of ultrapure water. Use 1 mol / L hydrochloric acid or sodium hydroxide solution to adjust the pH value of the culture medium to 7.0. Place the culture medium in an autoclave and sterilize it at 121°C for 20 min. Remove the culture medium from the autoclave while there is still residual heat.

[0062] (3) Pseudomonas aeruginosa was purchased from the China Center for Type Microorganism Collection (strain accession number: CCTCC AB93066). The purchased bacteria were inoculated on a solid culture medium and activated at 37°C. After obvious colonies grew, a single colony was taken from the solid culture medium and placed in a sterile LB culture medium, and cultured at 37°C and 150 rpm for 16 h; 1 mL of the bacterial solution was placed in 50 mL of new sterile LB culture medium and cultured at 150 rpm for 16 h (the sterile LB culture medium contained 200 μg / L, 500 μg / L, 1 mg / L, 2 mg / L and 5 mg / L of PFBS, respectively), and then 1 mL was taken and inoculated into 50 mL of new sterile culture medium containing the above concentrations of PFBS, and cultured at 37°C and 150 rpm for 16 h; the culture medium containing different concentrations of PFBS was cultured three times in a sterile LB culture medium according to this step, and bacteria with a certain PFBS tolerance were obtained.

[0063] (4) The bacteria acclimated in step (3) were inoculated onto new solid culture media and cultured at 37°C. After obvious colonies grew, a single colony (containing 5 mg / L PFBS) was taken from the solid culture media and placed in sterile LB culture media. The culture was shaken at 37°C and 150 rpm for 20 h. The bacterial suspension was then washed three times by centrifugation with sterile ultrapure water and resuspended in sterile ultrapure water to obtain a bacterial suspension of acclimated bacteria. The bacterial concentration was about 3.6×10 10 CFU / mL, stored in a 4℃ refrigerator for later use.

[0064] (5) Weigh 2 g of the acid-modified high-temperature pyrolysis peanut shell-based biochar prepared in Example 3 and add it to a conical flask, then add 200 mL of the bacterial suspension obtained in step (4), and culture it at 27°C and 150 rpm for 24 h to allow the bacteria to adsorb and colonize on the biochar. Use 0.2 mol / L PBS phosphate buffer (pH 7.0) to rinse off the free bacteria, then use sterile water for centrifugation and wash three times, and finally re-suspend it in 50 mL of ultrapure water to obtain the acid-pyrolysis biochar immobilized microbial suspension, which is placed in a -4°C refrigerator for later use. The mass of the obtained acid-pyrolysis biochar immobilized microorganism after freeze-drying is the dry weight.

[0065] Comparative Example 1:

[0066] A method for preparing acid-modified peanut shell-based biochar comprises the following steps:

[0067] The maximum pyrolysis temperature of 700° C. in step (2) of Example 1 was replaced with 600° C., and the other steps were the same as those of Example 1 to obtain acid-modified peanut shell-based biochar.

[0068] Comparative Example 2:

[0069] The purchased commercial peach pit biochar (manufacturer: Lingshou County Jiaqi Mineral Products Processing Plant, item number: jq) was directly reacted with new pollutants to detect the new pollutant removal performance test.

[0070] Comparative Example 3:

[0071] A method for preparing magnesium-iron hydrotalcite material comprises the following steps:

[0072] (1) Accurately weigh 0.15 mol of magnesium chloride hexahydrate and 0.07 mol of ferric chloride hexahydrate into a beaker, add 200 mL of ultrapure water, stir until dissolved, then slowly add 10 mol / L sodium hydroxide to the beaker to adjust the pH of the solution to 10.5, and continue stirring at 25°C for 2 h.

[0073] (2) The suspension was aged in a water bath at 65°C for 6 h, then allowed to stand at 25°C for 12 h, centrifuged at 3000 rpm for 15 min, the supernatant was discarded, ultrapure water was added, and the centrifugation was repeated three times until the supernatant was neutral.

[0074] (3) The obtained solid precipitate was placed in a -20°C refrigerator and frozen for 24 hours, then transferred to a vacuum freeze dryer and frozen at -50°C until completely dry, and then ground through a 100-mesh sieve to obtain magnesium-iron hydrotalcite.

[0075] Performance Test:

[0076] (1) The specific surface area, pore volume and average pore diameter of Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 are shown in Table 1. The short-term carbon fixation characteristics of Example 1, Example 2 and Example 3 are shown in Table 2.

[0077] Table 1

[0078]

[0079] Table 2

[0080]

[0081] It can be seen from Table 1 and Table 2 that the adsorption performance of the adsorbent is closely related to its specific surface area and pore structure. The acid-modified high-temperature pyrolysis peanut shell-based biochar prepared in Example 1, Example 2 and Example 3 has a large specific surface area and rich pore structure. Affected by the pyrolysis peak temperature, the specific surface area and total pore volume of the sample show an upward trend with the increase of the peak temperature. Compared with the acid-modified peanut shell-based biochar of Comparative Example 1 and the commercial peach kernel biochar of Comparative Example 2, the specific surface area, total pore volume, micropore specific surface area and micropore volume of Example 3 are significantly increased, and the average pore size is reduced, indicating that there are more pores close to micropores in the total pores, and the larger the pores that can play a role, the larger the contact area between the pollutants and the material, and the more effective adsorption sites that the material can provide, so it is more conducive to the adsorption of pollutants to the surface of Example 3. At the same time, using peanut shells as raw materials to prepare Examples 1, 2 and 3 is equivalent to reducing emissions by 6.12 to 6.75 Mt·a in the short term. -1 of carbon dioxide, which has very good environmental benefits.

[0082] (2) The purchased new pollutant PFOS standard (CAS No. 1763-23-1, DR. Ehrenstorfer, Germany) was dissolved in 1L ultrapure water to prepare a mother liquor, and then the mother liquor was diluted to an initial concentration of 500μg / L PFOS solution. 25mL of an initial concentration of 500μg / L PFOS solution was added to a 50mL centrifuge tube, and then 25mg of adsorbent material was added (there were 3 adsorbent materials, namely Example 3, Comparative Example 1 and Comparative Example 3, and only 1 adsorbent material was added to each centrifuge tube, totaling 3 groups). All samples were subjected to constant temperature oscillation reaction at 25°C and 150rpm for 30min. After centrifugation, the supernatant was filtered through a 0.22μm PES filter membrane (aqueous phase needle filter, PALL PES filter membrane, German MEMBRANA imported filter membrane, Nanjing Taipurui Instrument Equipment Co., Ltd.). Each group of experiments was repeated 3 times, the PFOS concentration after the reaction was detected, and the removal rate was calculated. The results are as follows: Figure 1 As shown. Among them, the removal rate calculation formula is as follows:

[0083]

[0084] Where, R is the removal rate, %; c0 is the initial concentration of new pollutants in the solution, mg / L; c t — is the concentration of new pollutants in the solution at time t, mg / L.

[0085] Depend on Figure 1 It can be seen that the acid-modified peanut shell-based biochar in Comparative Example 1 and the magnesium-iron hydrotalcite in Comparative Example 3 show good removal effects on PFOS, and the removal rates can reach 97.52% and 97.63% respectively within 30 minutes; the acid-modified high-temperature cracking peanut shell-based biochar in Example 3 has a removal rate of almost 100% for PFOS, which can quickly and completely remove PFOS in the solution. Compared with Comparative Examples 1 and 3, Example 3 has a better removal effect on PFOS.

[0086] (3) The purchased PFBS standard (CAS No. 375-73-5, DR. Ehrenstorfer, Germany) was dissolved in 1L ultrapure water to prepare a mother liquor, and then the mother liquor was diluted to an initial concentration of 500μg / L PFBS solution. 25mL of an initial concentration of 500μg / L PFBS solution was added to a 50mL centrifuge tube, and then 10mg of adsorbent material was added (a total of 8 adsorbent materials, namely Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2 and Comparative Example 3, only one adsorbent material was added to each centrifuge tube, a total of 8 groups), and the reaction was carried out at 25°C and 150rpm under constant temperature oscillation for 48h. After centrifugation, the supernatant was filtered through a 0.22μm PES filter membrane. Each group of experiments was repeated 3 times, the PFBS concentration after the reaction was detected, and the PFBS removal rate of different adsorbent materials was calculated. The test results are shown in the figure. Figure 2 shown.

[0087] Depend on Figure 2 It can be seen that Example 3 has the highest removal rate for PFBS, reaching 99.95%, followed by Example 2 (99.64%) > Example 5 (97.99%) > Example 4 (89.37%) > Example 1 (52.17%) > Comparative Example 1 (25.82) > Comparative Example 3 (17.54%). Comparative Example 2 has the lowest removal rate for PFBS, only 3.32%. It can be seen that the pyrolysis peak temperature, peak temperature residence time and acid modification in the preparation of peanut shell-based biochar have a great influence on the effect of biochar on the adsorption and removal of short-chain perfluorinated compounds PFBS. Overall, the removal effect of PFBS by acid-modified high-temperature cracking peanut shell biochar in Example 3 is far better than that of acid-modified peanut shell-based biochar in Comparative Example 1, commercial peach kernel biochar purchased in Comparative Example 2, and magnesium iron hydrotalcite in Comparative Example 3.

[0088] (4) 25 mL of PFBS solution with initial concentrations of 0.5 mg / L, 1 mg / L, 2 mg / L, 5 mg / L, 10 mg / L, 25 mg / L, 50 mg / L and 70 mg / L was added to each of 50 mL centrifuge tubes, and 10 mg of adsorbent material was added to each of 8 centrifuge tubes (there were 3 adsorbent materials, namely Example 1, Example 2 and Example 3, and only 1 adsorbent material was added to each centrifuge tube, for a total of 24 groups); 25 mL of PFBS solution with initial concentrations of 5 μg / L, 25 μg / L, 50 μg / L, 100 μg / L, 200 μg / L, 500 μg / L and 1.2 mg / L was added to each of 50 mL centrifuge tubes, and 10 mg of Comparative Example 3 was added to each centrifuge tube, for a total of 7 groups; all samples were subjected to constant temperature oscillation reaction at 25°C and 150 rpm for 48 h, and the supernatant was centrifuged and filtered through 0.22 μm PES filter membrane, each group of experiments were repeated 3 times, and the PFBS concentration after dilution was detected by instrument, and the Langmuir adsorption isotherm equation was fitted. The Langmuir adsorption isotherm fitting results of Example 1, Example 2 and Example 3 for PFBS are shown as follows: Figure 3 The Langmuir adsorption isotherm fitting results of comparative example 3 for PFBS are as follows Figure 4 shown.

[0089] Depend on Figure 3 and 4It can be seen that: Example 1, Example 2 and Example 3 are acid-modified high-temperature pyrolysis peanut shell-based biochars prepared under different pyrolysis peak temperature conditions, and the removal effects on PFBS are quite different. Within a certain concentration range, the higher the initial PFBS concentration, the greater the adsorption amount. However, due to the limitation of the maximum adsorption amount, the adsorption amount does not increase all the time. R of Langmuir model fitting of PFBS adsorption in Example 1, Example 2, Example 3 and Comparative Example 3 2 The maximum adsorption capacity of Example 3 is 150 times that of Comparative Example 3, which is very different, and has the best adsorption effect on PFBS removal.

[0090] (5) Use hydrochloric acid or sodium hydroxide to adjust the pH value of the PFBS solution, and finally prepare a solution with a pH of 3, 7 and 11, respectively, and an initial PFBS concentration of 500μg / L. Add 25mL of PFBS solution with a pH of 3, 7 and 11 to each 50mL centrifuge tube, and then add 10mg of adsorption material (there are 4 adsorption materials in total, namely Example 1, Example 2, Example 3 and Example 5, only one adsorption material is added to each centrifuge tube, a total of 12 groups). All samples are subjected to constant temperature oscillation reaction at 25°C and 150rpm for 30min. After centrifugation, the supernatant is filtered through a 0.22μm PES filter membrane. Each group of experiments is repeated 3 times, and the PFBS concentration after the reaction is detected by an instrument, and the removal efficiency is calculated. The removal rates of PFBS under different pH conditions for Example 1, Example 2, Example 3 and Example 5 are as follows: Figure 5 shown.

[0091] Depend on Figure 5 It can be seen that as the initial pH value of the solution increases, the removal rates of PFBS in Example 1, Example 2, Example 3 and Example 5 show a decreasing trend, and the removal rates are lowest at a pH of 11, which are 7.37%, 19.92%, 74.77% and 18.99% respectively. Among them, the removal rate of PFBS in Example 3 is least affected by pH, the applicable pH range is higher, and the removal effect is better.

[0092] (6) To further explore the removal effect of Example 3 and Comparative Example 3 on short-chain perfluorinated compounds under low concentration conditions in the environment, 25 mL of PFBS solution with initial concentrations of 1 μg / L, 20 μg / L and 100 μg / L were added to 50 mL centrifuge tubes, and then 10 mg of adsorbent material was added (there were 2 adsorbent materials, namely Example 3 and Comparative Example 3, and only 1 adsorbent material was added to each centrifuge tube, for a total of 6 groups). All samples were subjected to constant temperature oscillation reaction at 25°C and 150 rpm for 48 h. After centrifugation, the supernatant was filtered through a 0.22 μm PES filter membrane. Each group of experiments was repeated 3 times, the PFBS concentration after the reaction was detected, and the removal efficiency was calculated. The results are as follows: Figure 6 shown.

[0093] Depend on Figure 6 It can be seen that the removal rate of PFBS by hydrotalcite in Comparative Example 3 is between 39.95% and 78.18%, which can remove PFBS in the solution, but the effect is limited; while the acid-modified high-temperature cracking peanut shell-based biochar in Example 3 has a PFBS removal rate of almost 100%, which can efficiently remove low-concentration short-chain perfluorinated compounds in the environment and has broad application prospects.

[0094] (7) Add 25 mL of PFBS solution with an initial concentration of 500 μg / L to a 50 mL conical flask, and then add 2.5 mg of material (there are 2 materials, namely Example 3 and Example 6, where Example 6 refers to the dry weight. Only one material is added to each conical flask, totaling 2 groups). Seal with a microbial breathable sealing membrane, and react at 27°C and 150 rpm for 3 days, 24 days and 100 days. After centrifugation, take the supernatant and filter it through a 0.22 μm PES filter membrane. Repeat each test 3 times. Detect the PFBS concentration and fluoride ion concentration after the reaction, and calculate the PFBS removal rate of different materials. Test results Figure 7 shown.

[0095] Depend on Figure 7It can be seen that after 3 days of reaction, the removal rate of PFBS in Example 3 was 92.61%, and the removal rate of PFBS in Example 6 was about 93.39%; when the reaction lasted for 24 days, the removal rate of Example 3 dropped to 92.38%, and the removal rate of Example 6 increased to 96.18%. It shows that as the reaction time increases, after Example 3 reaches adsorption saturation, part of the PFBS adsorbed on the surface of biochar will desorb and return to the solution, resulting in a decrease in the removal rate; the removal rate of PFBS in Example 6 gradually increases as the reaction time increases, and is higher than that in Example 3. Fluoride ion detection was performed on the solution after 100 days of reaction, and it was found that fluoride ions were detected in the solution after adding Example 6, while fluoride ions were not detected in the solution after adding Example 3, indicating that the microorganisms in the biochar-immobilized microbial composite material in Example 6 have a certain degradation effect on PFBS. Compared with Example 3, in Example 6, when the biochar adsorption reaches saturation, the microorganisms can continuously utilize the PFBS on the biochar after saturated adsorption, restore the biochar adsorption capacity, improve the PFBS removal effect, and at the same time achieve defluorination and degradation of PFBS, destroying the structure of PFBS.

Claims

1. Application of acid-modified high-temperature pyrolysis peanut shell-based biochar in removing short-chain perfluorinated compounds at low concentrations in the environment, characterized in that: The method for preparing acid-modified high-temperature pyrolysis peanut shell-based biochar comprises the following steps: (1) Washing peanut shells, drying them, and then pyrolyzing them at high temperature to obtain biochar; (2) soaking the high temperature cracked biochar obtained in step (1) in an acidic solution, filtering and then soaking and washing the material until it is neutral; (3) freeze-drying the obtained solid, grinding and sieving, and preparing acid-modified high-temperature pyrolysis peanut shell-based biochar; The high temperature cracking process in step (1) is as follows: the first stage is a heating stage, in which the temperature is raised to 800-900°C at a heating rate of 3-10°C / min; the second stage is a constant temperature stage, in which the temperature is maintained at 800-900°C for 3-5 hours; the third stage is a cooling stage, in which the temperature is cooled to room temperature; In step (2), the concentration of the acid solution is 0.01 to 1 mol / L, and the soaking time is 8 to 12 h.

2. The application according to claim 1, characterized in that: The acidic solution in step (2) is any one of hydrochloric acid, sulfuric acid or phosphoric acid.

3. The application according to claim 1, characterized in that: Short-chain perfluorinated compounds are any of perfluorobutanesulfonic acid (PFBS), perfluorooctanesulfonic acid (PFOS), perfluorobutyric acid (PFBA) or perfluorooctanoic acid (PFOA).

4. The use according to claim 1, characterized in that: The mass volume ratio of acid-modified high-temperature pyrolysis peanut shell-based biochar and short-chain perfluorinated compounds is 0.1 g ~ 1 g: 1 L.

5. The use according to claim 1, characterized in that: The concentration of short-chain perfluorinated compounds ranged from 1 μg / L to 75 mg / L.

6. An acid-modified high-temperature cracking peanut shell-based biochar immobilized microorganism, characterized in that: It comprises the acid-modified high-temperature cracked peanut shell-based biochar as described in claim 1.

7. The acid-modified high-temperature pyrolysis peanut shell-based biochar immobilized microorganism according to claim 6, characterized in that: The immobilized microorganism is the adsorption and colonization of Pseudomonas aeruginosa on acid-modified high-temperature cracked peanut shell-based biochar.

Images