Modified biochar, composition containing modified biochar and contaminated soil remediation method

Abstract

The invention provides modified biochar, a composition containing the modified biochar and a contaminated soil remediation method. The modified biochar is obtained by pyrolyzing corncobs and modifying the pyrolyzed corncobs with acid, and can adsorb harmful substances such as aromatic hydrocarbons and hydrocarbons in polluted soil, relieve soil alkalinity, improve soil enzyme activity, treat waste with waste, exert the value of the corncobs and realize recycling and harmless utilization of the corncobs. The composition provided by the invention comprises the modified charcoal and urea which have a synergistic effect, so that the enzyme activity of soil catalase and soil dehydrogenase in the soil is improved, the relative abundance of Alcanivorax in the soil is obviously increased, degradation of indigenous microorganisms in the soil on petroleum hydrocarbon is promoted, and the degradation rate of the indigenous microorganisms on the petroleum hydrocarbon is increased. The efficient remediation of the petroleum-polluted saline-alkali soil is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of petroleum - polluted soil remediation, and particularly relates to a modified biochar, a composition containing the same, and a method for remediating polluted soil. Background Art

[0003] Petroleum pollutants refer to harmful substances released during the processes of petroleum production, processing, transportation, and accidents such as oil spills, including carbon hydrocarbons, sulfides, long - chain hydrocarbons, long - chain hydrocarbon alcohols, etc. The presence of these substances in the soil will cause a series of harms to the soil environment: First, petroleum pollutants will reduce the oxygen content in the soil, affect the growth and activities of microorganisms in the soil, and hinder the growth and development of plants; Second, petroleum pollutants will also damage the biosphere of the soil, cause changes in the chemical structure of the soil, increase the soil C / N, and reduce the soil fertility; At the same time, petroleum - polluted soil is often accompanied by salinization; In addition, petroleum pollutants will also poison animals and plants in the soil, posing a potential threat to human health. Therefore, paying attention to and preventing the problem of petroleum pollutants affecting the soil environment is an important contribution to the human living environment. By improving the safety and environmental protection of petroleum production, processing, transportation, and management, adopting effective soil remediation technologies, and improving the environmental monitoring and assessment system, the harm of petroleum pollutants to the soil environment can be effectively reduced.

[0004] Currently, the methods for treating soil petroleum pollution mainly include physical methods, chemical methods, and biological methods. Physical methods include extraction and recovery, which are fast and efficient methods, but may produce a large amount of waste. Chemical methods use chemical reactions to remove petroleum pollutants, but may produce harmful by - products. Biological methods use the metabolic ability of microorganisms to treat pollutants, which is an environmentally friendly and low - cost method, but the treatment speed is slow.

[0005] At the same time, as a kind of agricultural waste with high yield and sufficient nutrients, the resource utilization of corncobs is often ignored. Farmers generally burn or discard corncobs, which not only pollutes the environment but also wastes a large number of opportunities for resource utilization. How to realize the resource utilization of corncobs is also a technical problem that urgently needs to be solved at present. Summary of the Invention

[0006] To solve the problems of slow treatment speed, accompanied by a large amount of waste and harmful pollutants in the existing methods for treating soil petroleum pollution, and the problem that it is difficult to effectively utilize corncob resources, the object of the present invention is to provide a method that can not only effectively utilize corncob resources but also efficiently remediate petroleum - polluted soil without generating a large amount of waste and harmful pollutants.

[0007] To achieve the above object, in the first aspect of the present invention, a method for preparing modified biochar is provided, which includes the following steps:

[0008] 1) Pyrolyze corncobs to obtain biochar;

[0009] 2) Immerse the biochar in phosphoric acid and dry it to obtain the modified biochar.

[0010] In a specific embodiment, the corncobs have an organic carbon content of 300 g / kg to 500 g / kg; and / or a total nitrogen content of 90 g / kg to 200 g / kg; and / or a total phosphorus content of 1 g / kg to 3 g / kg; and / or a pH of 6 to 7;

[0011] Preferably, the corncobs have an organic carbon content of 350 g / kg to 450 g / kg; and / or a total nitrogen content of 110 g / kg to 190 g / kg; and / or a pH of 6.1 to 6.7.

[0012] In a specific embodiment, the phosphoric acid is a 25 wt% aqueous phosphoric acid solution.

[0013] In a specific embodiment, in step 1), the pyrolysis conditions are pyrolysis at 550 °C for 60 min to 90 min; and / or

[0014] In step 2), the immersion duration is 24 h to 36 h;

[0015] Preferably, in step 1), the temperature is raised to 550 °C in a gradient manner for the pyrolysis; and / or

[0016] The rate of the gradient temperature increase is 10 °C / h; and / or

[0017] The pyrolysis is carried out in an anaerobic environment.

[0018] In a specific embodiment, in step 1), first dry the corncobs at 75 °C for 48 h, then crush them through a 30-mesh sieve, and then carry out the pyrolysis; and / or

[0019] After the pyrolysis, cool down to below 50 °C to obtain the biochar.

[0020] In a specific embodiment, in step 2), after immersing the biochar in the phosphoric acid, wash it with water, filter it by suction, and then carry out the drying;

[0021] Preferably, the drying conditions are drying at 75 °C for 24 h to 36 h.

[0022] The corncobs used in the present invention are from the corn variety named Zenong 558, which is cultivated by Shandong Zenong Seed Industry Co., Ltd.

[0023] The second aspect of the present invention provides a modified biochar prepared by the method described in the first aspect of the present invention.

[0024] In a specific embodiment, the organic carbon content of the modified biochar is 300 g / kg to 400 g / kg; and / or the total nitrogen content is 10 g / kg to 50 g / kg; and / or the total phosphorus content is 1 g / kg to 10 g / kg; and / or the pH is 5.5 to 6.5; and / or the specific surface area is 58 m 2 / g to 64 m 2 / g; and / or the average pore diameter is 14 nm to 16 nm;

[0025] Preferably, the organic carbon content of the modified biochar is 310 g / kg to 400 g / kg; and / or the total nitrogen content is 19 g / kg to 47 g / kg; and / or the total phosphorus content is 2 g / kg to 8 g / kg; and / or the pH is 5.5 to 6.2.

[0026] The third aspect of the present invention provides a composition, which comprises a modified biochar and urea;

[0027] The modified biochar is the modified biochar prepared by the method described in the first aspect of the present invention or the modified biochar described in the second aspect of the present invention.

[0028] In a specific embodiment, the mass ratio of the modified biochar to urea is 1:1.

[0029] The fourth aspect of the present invention provides a method for remediating contaminated soil, which comprises the following steps:

[0030] Mix the composition with the contaminated soil to remediate the contaminated soil;

[0031] The composition is the composition described in the third aspect of the present invention;

[0032] Preferably, taking the mass of the contaminated soil as 100%, the dosage of the composition is 2 wt%;

[0033] Preferably, the remediation is carried out under the conditions of room temperature (25 °C), air humidity of 17%, and water content of the contaminated soil of 17.5%;

[0034] Preferably, the duration of the remediation is 80 days.

[0035] In a specific embodiment, during the remediation process, plowing is carried out every 7 days for oxygen supply.

[0036] Use of any one of the modified biochar prepared by the method according to the first aspect of the present invention, the modified biochar according to the second aspect of the present invention, the composition according to the third aspect of the present invention, and the contaminated soil remediation method according to the fourth aspect of the present invention in the remediation of petroleum-contaminated saline-alkali soil;

[0037] Preferably, the content of petroleum hydrocarbons in the petroleum-contaminated saline-alkali soil is not less than 4.5 g / kg; and / or

[0038] The pH value of the petroleum-contaminated saline-alkali soil is not less than 8;

[0039] Preferably, the content of petroleum hydrocarbons in the petroleum-contaminated saline-alkali soil is 4.5 g / kg to 5.1 g / kg; and / or

[0040] Among the petroleum hydrocarbons, the content of petroleum hydrocarbons from C 10 to C 40 is not less than 99 wt%.

[0041] Advantages of the present invention:

[0042] Aiming at the problems of slow treatment speed, a large amount of associated waste and harmful pollutants in the existing soil petroleum pollution treatment methods, and the problem of difficult effective utilization of corn cob resources, the present invention provides a modified biochar, a composition containing the same, and a contaminated soil remediation method. The modified biochar is obtained by acid modification after pyrolysis of corn cobs, has a porous structure, can adsorb harmful substances such as aromatic hydrocarbons and hydrocarbons in contaminated soil, can also alleviate soil alkalinity, improve soil enzyme activity, and effectively utilize corn cob resources, treating waste with waste, giving play to the value of corn cobs, and realizing the resource utilization and harmless treatment of corn cobs. The composition provided by the present invention includes the modified biochar and urea, and they synergistically enhance the effect, improve the enzyme activities of soil catalase and soil dehydrogenase in the soil, significantly increase the relative abundance of Alcanivorax in the soil, promote the degradation of petroleum hydrocarbons by indigenous microorganisms in the soil, and achieve efficient remediation of petroleum-contaminated saline-alkali soil: Using the composition provided by the present invention and adopting the contaminated soil remediation method provided by the present invention, the petroleum hydrocarbon degradation rate after 80 days of remediation of petroleum-contaminated saline-alkali soil is 74.36% to 79.07%; the petroleum hydrocarbons in the petroleum-contaminated saline-alkali soil are divided into C 10 to C 19 , C 20 to C 29 , C 30 to C 40 three categories of petroleum hydrocarbons. In the petroleum-contaminated saline-alkali soil remediated by the composition provided by the present invention after 80 days, the content of C 10 to C 19 is about 100 mg / kg, and the content of C 20 to C 29The content reaches about 300 mg / kg, C 30 to C 40 The content reaches about 550 mg / kg. Compared with the result of directly repairing for 80 days under the same environmental conditions without using the composition provided by the present invention, C 10 to C 19 , C 20 to C 29 , C 30 to C 40 The contents of three types of petroleum hydrocarbons are reduced by 81.8%, 85%, and 56.3% respectively. After 30 days and 60 days of repairing the petroleum-polluted saline-alkali soil with the composition provided by the present invention: the specific activities of soil dehydrogenase in the petroleum-polluted saline-alkali soil reach about 10.3 U / g and 11.5 U / g in sequence; the specific activities of soil catalase reach about 26.4 U / g and 31.3 U / g in sequence. In the petroleum-polluted saline-alkali soil after being repaired for 80 days with the composition provided by the present invention, the relative abundance of Alcanivorax is nearly 0.5. In summary, the modified biochar, the composition containing the same, and the method for repairing polluted soil provided by the present invention can achieve efficient repair of petroleum-polluted saline-alkali soil, and do not produce a large amount of waste and harmful pollutants. At the same time, the harmless utilization of corncob resources is realized, and it has broad application prospects. Description of the Drawings

[0043] Figure 1 It is the infrared spectrogram of the modified biochar prepared in Example 1;

[0044] Figure 2 It is the scanning electron microscope image of the modified biochar prepared in Example 1 with a magnification of 10,000 times;

[0045] Figure 3 It is the scanning electron microscope image of the modified biochar prepared in Example 1 with a magnification of 100,000 times;

[0046] Figure 4 It is the degradation rate of petroleum hydrocarbons at different repair stages in Example 1 and Comparative Examples 1 to 3;

[0047] Figure 5 It is the content of different petroleum hydrocarbon components in the petroleum-polluted saline-alkali soil after being repaired for 80 days in Example 1 and Comparative Examples 1 to 3;

[0048] Figure 6 It is the specific activity of soil dehydrogenase when the petroleum-polluted saline-alkali soil is repaired for 30 days and 60 days in Example 1 and Comparative Examples 1 to 3;

[0049] Figure 7 It is the specific activity of soil catalase when the petroleum-polluted saline-alkali soil is repaired for 30 days and 60 days in Example 1 and Comparative Examples 1 to 3;

[0050] Figure 8 , Figure 9 The relative abundances of various microbial genera in the soil after 80 days of remediation of petroleum - contaminated saline - alkali soil in Example 1 and Comparative Examples 1 to 3. Detailed implementation mode

[0051] The following further illustrates the present invention with reference to the embodiments. However, the embodiments of the present invention are only exemplary descriptions, and under no circumstances do they constitute a limitation to the present invention.

[0052] Preparation of modified biochar and its composition, and implementation of the contaminated soil remediation method

[0053] The corncobs used in Examples 1 to 3 are from the corn variety named Zenong 558, which is cultivated by Shandong Zenong Seed Industry Co., Ltd.

[0054] In the present invention, the organic carbon content is measured by a TOC analyzer (SHIMADZU, TOC - L CPH); the total nitrogen content is measured by an elemental analyzer (Elementar, UNICUBE); the total phosphorus content is measured by the molybdenum antimony anti - spectrophotometry method; the specific surface area and average pore diameter are measured by a specific surface area and porosity analyzer (Micromeritics, ASAP 2020Plus).

[0055] Example 1

[0056] Preparation of modified biochar:

[0057] 1) Physical drying: Take 500 g of corncobs and place them in an oven, dry at 75 °C for 48 h for standby; in the dried corncobs, the organic carbon content is 400 g / kg, the total nitrogen content is 150 g / kg, the total phosphorus content is 2 g / kg, and the pH is 6.5;

[0058] 2) Crushing: Crush the corncobs dried in step 1) with a crusher and sieve through a 30 - mesh sieve for standby;

[0059] 3) Pyrolysis to prepare biochar: Take 100 g of the crushed and sieved corncobs in step 2) and place them in a quartz boat, wrap and seal them with aluminum foil and tin foil, then place them in a tube furnace for pyrolytic carbonization. Set the heating rate to 10 °C / min, the nitrogen flow rate to 30 mL / min, the pyrolysis temperature to 550 °C, and the retention time to 60 min. When the temperature slowly drops below 50 °C, obtain biochar and seal it in a serum bottle for storage and standby;

[0060] 4) Acid modification: Take 10 g of the biochar in step 3) in a 250 - mL Erlenmeyer flask, add 100 mL of 25 wt% phosphoric acid aqueous solution, oscillate on a shaker for 24 h. After the oscillation ends, repeatedly rinse with distilled water, filter by suction, and then put it into an oven and dry at 75 °C for 24 h to obtain modified biochar;

[0061] In the modified biochar, the organic carbon content is 310 g / kg, the total nitrogen content is 20 g / kg, the total phosphorus content is 2 g / kg, the pH is 5.5, the specific surface area is 62 m 2 / g, and the average pore diameter is 14 nm.

[0062] Preparation of the composition:

[0063] The modified biochar prepared in this example and urea are mixed evenly according to a mass ratio of 1:1 to obtain the composition.

[0064] Remediation of petroleum-polluted saline-alkali soil:

[0065] In this example, the petroleum-polluted saline-alkali soil to be remediated: the petroleum hydrocarbon content is approximately 4.5 g / kg, and the pH is approximately 9.0; the petroleum hydrocarbons are mainly composed of C 10 to C 40 components, and the mass of petroleum hydrocarbons from C 10 to C 40 accounts for 99.8% of the total mass of petroleum hydrocarbons in the petroleum-polluted saline-alkali soil;

[0066] Before soil remediation, the petroleum-polluted saline-alkali soil sample is crushed, ground evenly, and then sieved. The polluted soil below 10 mesh is collected for standby;

[0067] The composition prepared in this example is mixed evenly with the petroleum-polluted saline-alkali soil. The addition amount of the composition is 2 wt% of the mass of the petroleum-polluted saline-alkali soil, and the remediation is carried out under the conditions of a cultivation temperature of 25 °C, an air humidity of 17%, and a water content of the petroleum-polluted saline-alkali soil maintained at 17.5%; during the remediation period, plowing and oxygen supply are carried out once every 7 days, and the remediation is carried out for 80 days in total to complete the remediation of the petroleum-polluted saline-alkali soil.

[0068] Comparative Example 1

[0069] Remediation of petroleum-polluted saline-alkali soil:

[0070] In this comparative example, the petroleum-polluted saline-alkali soil to be remediated: the same as in Example 1;

[0071] Before soil remediation, the petroleum-polluted saline-alkali soil sample is crushed, ground evenly, and then sieved. The polluted soil below 10 mesh is collected for standby;

[0072] The modified biochar prepared in Example 1 is mixed evenly with the petroleum-polluted saline-alkali soil. The addition amount of the modified biochar is 1 wt% of the mass of the petroleum-polluted saline-alkali soil, and the remediation is carried out under the conditions of a cultivation temperature of 25 °C, an air humidity of 17%, and a water content of the petroleum-polluted saline-alkali soil maintained at 17.5%; during the remediation period, plowing and oxygen supply are carried out once every 7 days, and the remediation is carried out for 80 days in total to complete the remediation of the petroleum-polluted saline-alkali soil.

[0073] Comparative Example 2

[0074] Remediation of petroleum-polluted saline-alkali soil:

[0075] The petroleum-polluted saline-alkali soil to be remediated in this comparative example: the same as in Example 1;

[0076] Before soil remediation, the petroleum-polluted saline-alkali soil sample was crushed, ground evenly and then sieved, and the polluted soil below 10 mesh was collected for standby;

[0077] Urea was mixed evenly with the petroleum-polluted saline-alkali soil, and the addition amount of urea was 1 wt% of the mass of the petroleum-polluted saline-alkali soil. Remediation was carried out under the conditions of a cultivation temperature of 25 °C, an air humidity of 17%, and a water content of the petroleum-polluted saline-alkali soil maintained at 17.5%; during the remediation period, tillage and oxygen supply were carried out once every 7 days, and the remediation was completed after 80 days to complete the remediation of the petroleum-polluted saline-alkali soil.

[0078] Comparative Example 3

[0079] Remediation of petroleum-polluted saline-alkali soil:

[0080] The petroleum-polluted saline-alkali soil to be remediated in this comparative example: the same as in Example 1;

[0081] Before soil remediation, the petroleum-polluted saline-alkali soil sample was crushed, ground evenly and then sieved, and the polluted soil below 10 mesh was collected for standby;

[0082] Without adding the composition prepared in Example 1, the same petroleum-polluted saline-alkali soil as in Example 1 was directly remediated under the conditions of a cultivation temperature of 25 °C, an air humidity of 17%, and a water content of the petroleum-polluted saline-alkali soil maintained at 17.5%; during the remediation period, tillage and oxygen supply were carried out once every 7 days, and the remediation was completed after 80 days to complete the remediation of the petroleum-polluted saline-alkali soil.

[0083] Example 2

[0084] Preparation of modified biochar:

[0085] 1) Physical drying: Take 500 g of corncobs and place them in an oven, dry them at 75 °C for 48 h for standby; in the dried corncobs, the organic carbon content is 450 g / kg, the total nitrogen content is 190 g / kg, the total phosphorus content is 3 g / kg, and the pH is 6.1;

[0086] 2) Crushing: Crush the corncobs dried in step 1) with a crusher and sieve them through a 30-mesh sieve for standby;

[0087] 3) Pyrolysis to prepare biochar: Take 100 g of the corn cobs sieved after crushing in step 2) and place them in a quartz boat. Wrap and seal them with aluminum foil and then put them in a tube furnace for pyrolytic carbonization. During the carbonization process, set the heating rate to 10 °C / min, the nitrogen flow rate to 30 mL / min, the pyrolysis temperature to 550 °C, and the retention time to 75 min. When the temperature slowly drops below 50 °C, biochar is obtained and stored in a serum bottle for later use after sealing;

[0088] 4) Acid modification: Take 10 g of the biochar from step 3) and put it into a 250 mL Erlenmeyer flask. Add 100 mL of 25 wt% phosphoric acid aqueous solution and oscillate on a shaker for 30 h. After the oscillation ends, rinse repeatedly with distilled water, filter by suction, and then put it into an oven and dry at 75 °C for 30 h to obtain the modified biochar;

[0089] In the modified biochar, the organic carbon content is 350 g / kg, the total nitrogen content is 47 g / kg, the total phosphorus content is 8 g / kg, the pH is 6.2, the specific surface area is 58 m 2 / g, and the average pore diameter is 15 nm.

[0090] Prepare the composition:

[0091] Mix the modified biochar prepared in this example and urea evenly according to a mass ratio of 1:1 to obtain the composition.

[0092] Remediation of petroleum-polluted saline-alkali soil:

[0093] The petroleum-polluted saline-alkali soil to be remediated in this example: The petroleum hydrocarbon content is approximately 5.1 g / kg and the pH is approximately 9.4; The petroleum hydrocarbons are mainly composed of C 10 to C 40 and the mass of petroleum hydrocarbons from C 10 to C 40 accounts for 99.8% of the total mass of petroleum hydrocarbons in the petroleum-polluted saline-alkali soil;

[0094] Before soil remediation, crush and grind the petroleum-polluted saline-alkali soil sample evenly and then sieve it. Collect the polluted soil below 10 mesh for later use;

[0095] Mix the composition prepared in this example evenly with the petroleum-polluted saline-alkali soil. The addition amount of the composition is 2 wt% of the mass of the petroleum-polluted saline-alkali soil. Carry out remediation under the conditions of a cultivation temperature of 25 °C, an air humidity of 17%, and a water content of the petroleum-polluted saline-alkali soil maintained at 17.5%; During the remediation period, turn over the soil and supply oxygen once every 7 days, and a total of 80 days of remediation is completed to complete the remediation of the petroleum-polluted saline-alkali soil.

[0096] Example 3

[0097] Prepare modified biochar:

[0098] 1) Physical drying: Take 500 g of corncobs and place them in an oven. Dry them at 75 °C for 48 h for later use. In the dried corncobs, the organic carbon content is 350 g / kg, the total nitrogen content is 110 g / kg, the total phosphorus content is 1 g / kg, and the pH is 6.7.

[0099] 2) Crushing: Crush the corncobs dried in step 1) with a crusher and sieve them through a 30-mesh sieve for later use.

[0100] 3) Pyrolysis to prepare biochar: Take 100 g of the crushed and sieved corncobs from step 2) and place them in a quartz boat. Wrap and seal them with aluminum foil and then put them in a tube furnace for pyrolytic carbonization. During the carbonization process, set the heating rate to 10 °C / min, the nitrogen flow rate to 30 mL / min, the pyrolysis temperature to 550 °C, and the retention time to 90 min. When the temperature slowly drops below 50 °C, biochar is obtained and stored in a serum bottle for later use.

[0101] 4) Acid modification: Take 10 g of the biochar from step 3) and put it in a 250 mL Erlenmeyer flask. Add 100 mL of 25 wt% phosphoric acid aqueous solution and shake it on a shaker for 36 h. After shaking, rinse it repeatedly with distilled water, filter it by suction, and then put it in an oven and dry it at 75 °C for 36 h to obtain modified biochar.

[0102] In the modified biochar, the organic carbon content is 400 g / kg, the total nitrogen content is 19 g / kg, the total phosphorus content is 5 g / kg, the pH is 5.9, the specific surface area is 64 m 2 / g, and the average pore diameter is 16 nm.

[0103] Prepare the composition:

[0104] Mix the modified biochar prepared in this example and urea evenly according to a mass ratio of 1:1 to obtain the composition.

[0105] Remediation of petroleum-polluted saline-alkali soil:

[0106] In this example, the petroleum-polluted saline-alkali soil to be remediated: The petroleum hydrocarbon content is about 4.8 g / kg, and the pH is about 8.8; The petroleum hydrocarbons are mainly composed of C 10 to C 40 , and the mass of petroleum hydrocarbons from C 10 to C 40 accounts for 99.8% of the total mass of petroleum hydrocarbons in the petroleum-polluted saline-alkali soil.

[0107] Before soil remediation, crush and grind the petroleum-polluted saline-alkali soil sample evenly and then sieve it. Collect the polluted soil below 10 mesh for later use.

[0108] The composition prepared in this example was mixed evenly with petroleum-polluted saline-alkali soil. The addition amount of the composition was 2 wt% of the mass of the petroleum-polluted saline-alkali soil. The remediation was carried out under the conditions of a cultivation temperature of 25 °C, an air humidity of 17%, and a water content of the petroleum-polluted saline-alkali soil maintained at 17.5%. During the remediation, plowing and oxygen supply were carried out once every 7 days, and the remediation was completed in 80 days to complete the remediation of the petroleum-polluted saline-alkali soil.

[0109] Structural Characterization and Morphology Observation of Modified Biochar

[0110] A. Structural Characterization of Modified Biochar

[0111] The infrared spectra of the modified biochars prepared in Examples 1 to 3 were measured using a Fourier transform infrared spectrometer. Here, the infrared spectrum of the modified biochar prepared in Example 1 was taken as an example for analysis.

[0112] Figure 1 is the infrared spectrum diagram of the modified biochar prepared in Example 1, which shows the characteristic peaks of three surface groups, -OH, -C=C, and -CN, proving that the surface of the modified biochar prepared in Example 1 is connected with -OH, -C=C, and -CN groups.

[0113] The infrared spectra of the modified biochars prepared in Example 2 and Example 3 are similar to Figure 1 and both have the characteristic peaks of three surface groups, -OH, -C=C, and -CN, proving that the surfaces of the modified biochars prepared in Example 2 and Example 3 are also connected with -OH, -C=C, and -CN groups.

[0114] B. Morphology Observation

[0115] The morphologies of the modified biochars prepared in Examples 1 to 3 were observed using a scanning electron microscope. Here, the modified biochar prepared in Example 1 was taken as an example for detailed description.

[0116] Figure 2 、 Figure 3 are the scanning electron microscope images of the modified biochar prepared in Example 1 at different magnifications. Among them, Figure 2 has a magnification of 10,000 times, Figure 3 has a magnification of 100,000 times. From Figure 2 、 Figure 3 , it can be seen that there are many pores on the surface of the modified biochar, and this porous structure is beneficial to improving its adsorption performance.

[0117] The modified biochars prepared in Example 2 and Example 3 can both observe a porous structure similar to that shown in Figure 2 、 Figure 3 under the scanning electron microscope and also have good adsorption performance.

[0118] Evaluation of the Remediation Effect of the Composition on Petroleum-Contaminated Saline-Alkali Soil

[0119] ⅰ Determination of the degradation rate of petroleum hydrocarbons and the content of petroleum hydrocarbons in the petroleum-contaminated saline-alkali soil after remediation

[0120] According to the regulations in the standard HJ 1021-2019 "Determination of Petroleum Hydrocarbons (C 10 to C 40 ) in Soil and Sediments - Gas Chromatography Method":

[0121] a. Determine the content of petroleum hydrocarbons in the petroleum-contaminated saline-alkali soil after 80 days of remediation in Examples 1 to 3 and Comparative Examples 1 to 3. Combine with the initial content of petroleum hydrocarbons in the petroleum-contaminated saline-alkali soil before remediation in each example and comparative example, and calculate the degradation rate of petroleum hydrocarbons in Examples 1 to 3 and Comparative Examples 1 to 3;

[0122] b. Determine the content of different petroleum hydrocarbon components in the remediated petroleum-contaminated soil in Example 1 and Comparative Examples 1 to 3;

[0123] The degradation rates of petroleum hydrocarbons in Examples 1 to 3 and Comparative Examples 1 to 3 after 80 days of remediation are shown in Table 1. The degradation rates of petroleum hydrocarbons at different remediation stages within 80 days of remediation in Example 1 and Comparative Examples 1 to 3 are shown in Figure 4 , and the content of different petroleum hydrocarbon components in the petroleum-contaminated saline-alkali soil after 80 days of remediation in Example 1 and Comparative Examples 1 to 3 is shown in Figure 5 .

[0124] Table 1. Degradation rates of petroleum hydrocarbons in Examples 1 to 3 and Comparative Examples 1 to 3 after 80 days of remediation

[0125] Serial number <![CDATA[C 10 to C 40 Petroleum hydrocarbon degradation rate / %]]> Example 1 79.07 Example 2 74.36 Example 3 77.18 Comparative example 1 57.24 Comparative example 2 50.18 Comparative example 3 13.42

[0126] The data in Table 1 show that the degradation rates of petroleum hydrocarbons in Examples 1 to 3 for the remediation of petroleum-contaminated saline-alkali soil after 80 days are 74.36% to 79.07%, and the average degradation rate of petroleum hydrocarbons is 76.87%, which is greater than 75%. This indicates that the modified biochar, the composition containing the modified biochar, and the contaminated soil remediation method prepared in Examples 1 to 3 have good remediation effects on petroleum-contaminated saline-alkali soil.

[0127] Figure 4 shows the degradation rates of petroleum hydrocarbons at different remediation stages within 80 days of remediation in Example 1 and Comparative Examples 1 to 3. From Figure 4It can be seen that as the number of repair days increases, the degradation rates of petroleum hydrocarbons in the petroleum-contaminated saline-alkali soil of Example 1 and Comparative Examples 1 to 3 gradually increase. Among them, the growth rates of the petroleum hydrocarbon degradation rates of Example 1 and Comparative Examples 1 and 2 are relatively fast, the growth rate of the petroleum hydrocarbon degradation rate of Comparative Example 3 is the slowest, and the petroleum hydrocarbon degradation rate is the lowest. Further, the growth rate of the petroleum hydrocarbon degradation rate of Example 1 is the fastest with the increase of repair time, and the petroleum hydrocarbon degradation rate is significantly higher than that of Comparative Examples 1 and 2. Combining Table 1, it can be known that when the repair time reaches 80 days, the petroleum hydrocarbon degradation rate of Example 1 is 79.07%, and the petroleum degradation rates of Comparative Examples 1 to 3 are 57.24%, 50.18%, and 13.42% in sequence. From the formula, when repairing the petroleum-contaminated saline-alkali soil, Example 1 added the composition including modified biochar and urea provided by the present invention, while Comparative Examples 1 and 2 only had modified biochar or urea respectively. The petroleum hydrocarbon degradation rates of Comparative Examples 1 and 2 are relatively low, and the petroleum hydrocarbon degradation rate of Comparative Example 1 is slightly higher than that of Comparative Example 2, indicating that the modified biochar prepared by the present invention has a slightly better repair effect on the petroleum-contaminated saline-alkali soil than urea; the modified biochar and urea in the composition synergistically enhance the effect, realizing the efficient degradation of petroleum hydrocarbons and effectively repairing the petroleum-contaminated saline-alkali soil.

[0128] Figure 5 shows the contents of different petroleum hydrocarbon components in the petroleum-contaminated saline-alkali soil after 80 days of repair in Example 1 and Comparative Examples 1 to 3. In the figure, the petroleum hydrocarbons from C 10 to C 40 are divided into three categories of petroleum hydrocarbons: C 10 to C 19 , C 20 to C 29 , C 30 to C 40 . The specific contents of various petroleum hydrocarbons in the petroleum-contaminated saline-alkali soil after 80 days of repair in Comparative Example 3 without adding modified biochar and urea are about 550 mg / kg for C 10 to C 19 , about 2000 mg / kg for C 20 to C 29 , and about 1260 mg / kg for C 30 to C 40 , all of which are higher than those in Example 1 and Comparative Examples 1 and 2. Example 1 added the composition containing modified biochar and urea, and the contents of various levels of petroleum hydrocarbons in the petroleum-contaminated saline-alkali soil after its repair are the lowest, specifically about 100 mg / kg for C 10 to C 19 , about 300 mg / kg for C 20 to C 29 , and about 550 mg / kg for C 30 to C 40 . Compared with Comparative Example 3, for C10 to C 19 、C 20 to C 29 、C 30 to C 40 The contents of three types of petroleum hydrocarbons decreased by 81.8%, 85%, and 56.3% respectively; in Comparative Example 1, only modified biochar was added, and the contents of various levels of petroleum hydrocarbons in the petroleum-contaminated saline-alkali soil after remediation were slightly lower than those in Comparative Example 2 where only urea was added. It shows that the modified biochar prepared in the present invention has a better remediation effect on petroleum-contaminated saline-alkali soil than urea; in the composition, the modified biochar and urea prepared in the present invention have synergistic effects and have an excellent remediation effect on petroleum-contaminated saline-alkali soil.

[0129] ⅱ. Evaluation of the promoting effect of the composition on the degradation of petroleum hydrocarbons by indigenous microorganisms in petroleum-contaminated saline-alkali soil

[0130] c. Determination of the activities of soil dehydrogenase and soil catalase in petroleum-contaminated saline-alkali soil at different remediation time periods

[0131] Using the soil catalase (S-CAT) activity detection kit (specification: 50T / 24S) and soil dehydrogenase (S-DHA) activity detection kit (specification: 50T / 24S) produced by Beijing Solarbio Science & Technology Co., Ltd., the activities of soil catalase and soil dehydrogenase in petroleum-contaminated saline-alkali soil were measured respectively according to the instructions of the kits during the remediation process of Examples 1 and Comparative Examples 1 to 3 at 30 days and 60 days of remediation time. The enzyme activity values were calculated according to the formulas in the kit instructions. The wavelengths for the specific activity determination of soil catalase and soil dehydrogenase were 240 nm and 485 nm respectively. The definition of the unit of soil catalase activity is that 1 μmol of H2O2 is catalyzed to degrade per gram of air-dried soil sample per day as one enzyme activity unit; the definition of the unit of soil dehydrogenase activity is that at 37 °C, 1 μg of TF is catalyzed to be produced per gram of air-dried soil sample per day as one enzyme activity unit; the experimental data were analyzed and plotted using spreadsheets and SPSS Base Ver.19.0 statistical software. The specific results are shown in Figure 6 、 Figure 7 。

[0132] Figure 6It reflects the specific activities of soil dehydrogenase in the petroleum-polluted saline-alkali soil after 30 days and 60 days of remediation in Example 1 and Comparative Examples 1 to 3. It can be seen that within the period from 30 days to 60 days of remediation, the specific activities of soil dehydrogenase in the petroleum-polluted saline-alkali soil increased in Comparative Example 3, Comparative Example 2, and Example 1, while the specific activity of soil dehydrogenase in the petroleum-polluted saline-alkali soil decreased in Comparative Example 1 within the period from 30 days to 60 days of remediation. At the remediation time of 30 days: the specific activity of soil dehydrogenase in the petroleum-polluted saline-alkali soil remediated by Comparative Example 3 was the lowest, approximately 7.1 U / g; the specific activity of soil dehydrogenase in the petroleum-polluted saline-alkali soil remediated by Example 1 was the highest, approximately 10.3 U / g; the specific activities of soil dehydrogenase in the petroleum-polluted saline-alkali soil remediated by Comparative Examples 1 and 2 were approximately 9.1 U / g and 8.5 U / g in sequence, higher than that of Comparative Example 3 but lower than that of Example 1; there was a significant difference in the specific activity of soil dehydrogenase in the petroleum-polluted saline-alkali soil remediated by Example 1 and that in the petroleum-polluted saline-alkali soil remediated by Comparative Example 3; there were significant differences in the specific activities of soil dehydrogenase in the petroleum-polluted saline-alkali soil remediated by Comparative Examples 1 and 2 compared with those in Comparative Example 3 and Example 1, but there was no significant difference between Comparative Example 1 and Comparative Example 2. At the remediation time of 60 days: the specific activity of soil dehydrogenase in the petroleum-polluted saline-alkali soil remediated by Comparative Example 3 was still the lowest, approximately 7.7 U / g; the specific activity of soil dehydrogenase in the petroleum-polluted saline-alkali soil remediated by Example 1 was still the highest, approximately 11.5 U / g; the specific activity of soil dehydrogenase in the petroleum-polluted saline-alkali soil remediated by Comparative Example 1 was approximately 8.3 U / g, and there was no significant difference from that of Comparative Example 3; the specific activity of soil dehydrogenase in the petroleum-polluted saline-alkali soil remediated by Comparative Example 2 was approximately 9.8 U / g, higher than those of Comparative Examples 1 and 3 but lower than that of Example 1, and there were significant differences with Example 1, Comparative Example 1, and Comparative Example 3. It shows that urea alone, modified biochar alone, and the composition composed of urea and modified biochar can all improve the activity of soil dehydrogenase in the petroleum-polluted saline-alkali soil, and the performance of urea alone and modified biochar alone in improving the activity of soil dehydrogenase is quite similar in the short-term remediation stage. When the remediation time reaches 60 days, the performance of urea alone in improving the activity of soil dehydrogenase is slightly higher than that of modified biochar alone; while the performance of the composition obtained by compounding urea and modified biochar in improving the activity of soil dehydrogenase is significantly higher, and it does not decrease with the extension of the remediation time. Urea and modified biochar have a synergistic effect, can greatly improve the activity of soil dehydrogenase in the petroleum-polluted saline-alkali soil, accelerate the degradation of petroleum hydrocarbons by soil dehydrogenase, and ultimately improve the remediation efficiency of the petroleum-polluted saline-alkali soil.

[0133] Figure 7It reflects the specific activities of soil catalase in the petroleum-contaminated saline-alkali soil after 30 days and 60 days of remediation in Example 1 and Comparative Examples 1 to 3. It can be seen that the specific activities of soil catalase in the petroleum-contaminated saline-alkali soil increased from 30 days to 60 days of remediation in Example 1 and Comparative Examples 1 to 3. At the remediation time of 30 days: the specific activity of soil catalase in the petroleum-contaminated saline-alkali soil remediated by Comparative Example 3 was the lowest, about 20.2 U / g; the specific activity of soil catalase in the petroleum-contaminated saline-alkali soil remediated by Example 1 was the highest, about 26.4 U / g; the specific activities of soil catalase in the petroleum-contaminated saline-alkali soil remediated by Comparative Examples 1 and 2 were about 23.8 U / g and 23.2 U / g in sequence, higher than that of Comparative Example 3 but lower than that of Example 1; there was a significant difference in the specific activity of soil catalase between the petroleum-contaminated saline-alkali soil remediated by Example 1 and that remediated by Comparative Example 3; there were significant differences in the specific activities of soil catalase in the petroleum-contaminated saline-alkali soil remediated by Comparative Examples 1 and 2 compared with those in Comparative Example 3 and Example 1, but there was no significant difference between Comparative Example 1 and Comparative Example 2. At the remediation time of 60 days: the specific activity of soil catalase in the petroleum-contaminated saline-alkali soil remediated by Comparative Example 3 was still the lowest, about 22.6 U / g; the specific activity of soil catalase in the petroleum-contaminated saline-alkali soil remediated by Example 1 was still the highest, about 31.3 U / g; the specific activity of soil catalase in the petroleum-contaminated saline-alkali soil remediated by Comparative Example 1 was about 28.5 U / g, higher than those of Comparative Examples 2 and 3 but lower than that of Example 1, and there were significant differences with Example 1, Comparative Examples 2 and 3; the specific activity of soil catalase in the petroleum-contaminated saline-alkali soil remediated by Comparative Example 2 was about 25.1 U / g, and there was no significant difference with Comparative Example 3. It shows that urea alone, modified biochar alone, and the composition composed of urea and modified biochar can all improve the activity of soil catalase in the petroleum-contaminated saline-alkali soil, and the performance of urea alone and modified biochar alone in improving the dehydrogenase activity is comparable in the short-term remediation stage (30 days of remediation). When the remediation time reaches 60 days, the performance of modified biochar alone in improving the soil catalase activity is slightly higher than that of urea alone; while the composition obtained by compounding urea and modified biochar has significantly higher performance in improving the soil catalase activity, and it does not decrease with the extension of the remediation time. Urea and modified biochar have synergistic effects, can greatly improve the activity of soil catalase in the petroleum-contaminated saline-alkali soil, accelerate the degradation of petroleum hydrocarbons by soil catalase, and ultimately improve the remediation efficiency of the petroleum-contaminated saline-alkali soil.

[0134] d. Determination of the relative abundances of various soil microorganisms in the petroleum-contaminated saline-alkali soil after 80 days of remediation

[0135] First, genomic DNA was extracted from the petroleum-contaminated saline-alkali soil after 80 days of remediation in Example 1 and Comparative Examples 1 to 3 respectively. After concentration identification, specific DNA fragments of bacteria and fungi in the remediated petroleum-contaminated saline-alkali soil were PCR amplified. After the obtained PCR products were separated and purified, they were sent to Shenzhen Microecology Company for gene sequencing under low-temperature conditions. The sequences obtained by sequencing were annotated, analyzed and identified using the RDP Classifier online tool provided by the Ribosomal Database Project (RDP) website to obtain the relative abundance data at the microbial genus level, as shown specifically in Figure 8 , Figure 9 .

[0136] Figure 8 which reflects the relative abundances of Alcanivorax, Lactobacillus, Luteimonas, Staphylococus, Bacillus and Pantoea in the soil after 80 days of remediation of petroleum-contaminated saline-alkali soil in Example 1 and Comparative Examples 1 to 3; Figure 9 which reflects the relative abundances of Pseudogymnoascus, Mortierella, Cephalotrichum, Trichoderma, Saccharomyces and Aspergillus in the soil after 80 days of remediation of petroleum-contaminated saline-alkali soil in Example 1 and Comparative Examples 1 to 3. Combining Figure 8 , Figure 9As can be seen, in the petroleum-contaminated saline-alkali soil after 80 days of remediation in Example 1, the relative abundance of Alcanivorax is nearly 0.5, which is the highest relative abundance and shows significant differences from Comparative Examples 1 to 3. Secondly, the relative abundance of Pseudogymnoascus is relatively high, specifically about 0.25. In the petroleum-contaminated saline-alkali soil after 80 days of remediation in Comparative Example 1, the relative abundance of Alcanivorax is about 0.075; in the petroleum-contaminated saline-alkali soil after 80 days of remediation in Comparative Example 2, the relative abundance of Alcanivorax is about 0.37; in the petroleum-contaminated saline-alkali soil after 80 days of remediation in Comparative Example 3, the relative abundance of Alcanivorax is about 0.07, showing no significant difference from Comparative Example 1. In the petroleum-contaminated saline-alkali soil after 80 days of remediation in Example 1 and Comparative Examples 1 to 3, the relative abundance of Alcanivorax in the soil after remediation in Example 1 is the highest, and it is higher than the sum of the relative abundances of Alcanivorax in Comparative Example 1 and Comparative Example 2, demonstrating that in the composition provided by the present invention, the modified biochar and urea have synergistic effects, which is beneficial to increasing the relative abundance of Alcanivorax in the soil, and thus helps to degrade petroleum hydrocarbons in the petroleum-contaminated saline-alkali soil, achieving efficient remediation of the petroleum-contaminated saline-alkali soil.

[0137] Based on the above determination results of the petroleum hydrocarbon degradation rate, the petroleum hydrocarbon content in the petroleum-contaminated saline-alkali soil after remediation, the activities of soil dehydrogenase and soil catalase in the petroleum-contaminated saline-alkali soil at different remediation time periods, and the relative abundances of various soil microorganisms in the petroleum-contaminated saline-alkali soil after 80 days of remediation, it can be known that by using the composition containing modified biochar and urea provided by the present invention and adopting the contaminated soil remediation method provided by the present invention, the petroleum-contaminated saline-alkali soil can be efficiently remediated, without generating redundant harmful substances or pollutants, and providing a suitable environment for indigenous microorganisms in the soil, increasing the activities of soil dehydrogenase and soil catalase in the soil, significantly increasing the relative abundance of Alcanivorax in the soil, and promoting the degradation of petroleum hydrocarbons by indigenous microorganisms. At the same time, it also solves the problem of the disposal of agricultural waste corn cobs, rationally utilizes the corn cob resources, treats waste with waste, fully exerts the value of corn cobs, and achieves the purpose of the present invention.

[0138] Although the present invention has been described with reference to specific embodiments, those skilled in the art should understand that various changes can be made without departing from the true spirit and scope of the present invention. In addition, various changes can be made to the subject matter, spirit and scope of the present invention to adapt to specific situations, materials, material compositions and methods. All such changes are included within the scope of the claims of the present invention.

Claims

1. A method for preparing modified biochar, which comprises the following steps: 1) Pyrolyze corncobs to obtain biochar; 2) Immerse the biochar in phosphoric acid and dry it to obtain the modified biochar.

2. The method according to claim 1, wherein The organic carbon content of the corncobs is 300 g / kg to 500 g / kg; and / or the total nitrogen content is 90 g / kg to 200 g / kg; and / or the total phosphorus content is 1 g / kg to 3 g / kg; and / or the pH is 6 to 7.

3. The method according to claim 1 or 2, characterized in that, The phosphoric acid is a 25 wt% aqueous phosphoric acid solution.

4. The method according to any one of claims 1 to 3, characterized in that, In step 1), the pyrolysis conditions are pyrolysis at 550 °C for 60 min to 90 min; and / or In step 2), the soaking duration is 24 h to 36 h; Preferably, in step 1), the temperature is raised to 550 °C in a gradient manner for the pyrolysis; and / or The rate of the gradient temperature increase is 10 °C / h; and / or The pyrolysis is carried out in an anaerobic environment.

5. A modified biochar prepared by the method according to any one of claims 1 to 4.

6. The modified biochar according to claim 5, characterized in that, The organic carbon content of the modified biochar is 300 g / kg to 400 g / kg; and / or the total nitrogen content is 10 g / kg to 50 g / kg; and / or the total phosphorus content is 1 g / kg to 10 g / kg; and / or the pH is 5.5 to 6.5; and / or the specific surface area is 58 m 2 / g to 64 m 2 / g; and / or the average pore diameter is 14 nm to 16 nm.

7. A composition, which comprises modified biochar and urea; The modified biochar is the modified biochar prepared by the method according to any one of claims 1 to 4 or the modified biochar according to claim 5 or 6.

8. The composition according to claim 7, characterized in that, The mass ratio of the modified biochar to urea is 1:

1.

9. A method for remediating contaminated soil, which comprises the following steps: Mix the composition and the contaminated soil to remediate the contaminated soil; The composition is the composition according to claim 7 or 8; Preferably, based on the mass of the contaminated soil being 100%, the dosage of the composition is 2 wt%; Preferably, the remediation is carried out under the conditions of room temperature, an air humidity of 17%, and a water content of the contaminated soil of 17.5%; Preferably, the duration of the remediation is 80 days.

10. The application of any one of the modified biochar prepared by the method according to any one of claims 1 to 4, the modified biochar according to claim 5 or 6, the composition according to claim 7 or 8, and the method for remediating contaminated soil according to claim 9 in the remediation of petroleum-contaminated saline-alkali soil; Preferably, the content of petroleum hydrocarbons in the petroleum-contaminated saline-alkali soil is not less than 4.5 g / kg; and / or the pH value of the petroleum-contaminated saline-alkali soil is not less than 8; Preferably, in the petroleum hydrocarbon, the content of petroleum hydrocarbon with carbon number from 10 to 40 is not less than 99 wt%.

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