Modified biochar material, preparation method thereof and application of modified biochar material in treatment of soil pollution

Abstract

The invention discloses a modified biochar material, a preparation method thereof and application of the modified biochar material in treatment of soil pollution, and the preparation method comprises the following steps: carbonizing melon vines or bean vines to obtain biochar; stirring biochar and concentrated nitric acid in an ice bath, then adding distilled water, carrying out heat-preservation stirring, then adding the mixture into an ammonium persulfate solution, and carrying out heat-preservation stirring again, so as to obtain first modified biochar; adding biochar into a calcium solution or an iron solution, and then adding a sodium selenite solution for reaction to obtain second modified biochar; dispersing the first modified biochar and the second modified biochar in distilled water, and adding sodium tetrapolypropylene benzene sulfonate and carboxymethyl cellulose for reaction to obtain the modified biochar material. The biochar material has good physical / chemical stability, can specifically adsorb heavy metals including cadmium, lead and arsenic, greatly improves the adsorption performance on heavy metal ions, improves the adsorption capacity and the adsorption efficiency, and is suitable for heavy metal pollution treatment of mine soil.

Description

Technical Field

[0001] The present invention relates to the technical field of soil pollution treatment, and particularly relates to a modified biochar material, a preparation method thereof, and an application thereof in treating soil pollution. Background Art

[0002] The prevention and control of mine soil pollution refers to technical measures for controlling or reducing the environmental pollution of soil caused by mining operations. After the pollutants generated by mining operations enter the soil body, through processes such as physical and mechanical absorption, retention, colloidal physical and chemical adsorption, chemical precipitation, and biological absorption of suspended pollutants by the soil body, they continuously accumulate in the soil. When reaching a certain amount, it causes deterioration of the soil composition, structure, properties, and functions. Heavy metals are difficult to degrade in the soil, have strong accumulativity and biological toxicity. They can be absorbed by plants and transmitted through the food chain, ultimately endangering human health and causing various diseases.

[0003] Biochar is a new type of environmental functional material. Biochar is a class of insoluble, stable, highly aromatic, carbon-rich solid substances produced by high-temperature pyrolysis of biological residues under anaerobic conditions. It has a developed pore structure, a large specific surface area, a large number of functional groups and negative charges on the surface, has a strong adsorption effect on heavy metal ions, can be used as a good adsorption material, and shows certain potential in soil pollution treatment. However, in actual mine soil treatment, the polluted area of mine soil is large, the treatment cost is high, and the soil pollution factors in mines are complex. There are not only heavy metal pollution, but also organic matter pollution, acid-base pollution, and even pollution containing some radioactive elements. Under various complex pollution factors in mines, the ability of traditional biochar to treat soil heavy metals is very limited.

[0004] Therefore, exploring the modification treatment of biochar to improve its stable adsorption, fixation, and degradation ability of soil heavy metal pollutants has important practical significance for the treatment of mine soil pollution. Summary of the Invention

[0005] In view of the above deficiencies, the present invention provides a modified biochar material, a preparation method thereof, and an application thereof in treating soil pollution. The biochar material of the present invention has good physical / chemical stability, can specifically adsorb heavy metals including cadmium, lead, and arsenic, greatly improves the adsorption performance of heavy metal ions, and the adsorption capacity and adsorption efficiency are improved. It is suitable for the treatment of heavy metal pollution in large-area mine soil. The specific technical solutions are as follows:

[0006] A preparation method of a modified biochar material includes the following steps:

[0007] S1. Preparation of biochar: Dry and crush melon vines or bean vines and then screen them. Then carry out high-temperature carbonization, take them out after natural cooling to room temperature to obtain biochar, and set it aside;

[0008] S2. Preparation of the first modified biochar: Take a certain amount of biochar, stir the biochar and concentrated nitric acid in an ice bath, react at 0 - 3 °C for 3 - 6 h to obtain a first reaction solution; heat the first reaction solution, add distilled water and keep stirring while maintaining the temperature, then add it to an ammonium persulfate solution and keep stirring while maintaining the temperature again to obtain a second reaction solution; filter the obtained second reaction solution, wash the filter residue alternately with ethanol and water, and dry it to obtain the first modified biochar;

[0009] S3. Preparation of the second modified biochar: Take a certain amount of biochar, add it to a calcium solution or an iron solution, adjust the pH to 11 - 13, mix and let it stand, then add a sodium selenite solution, perform ultrasonic treatment, then heat and stir at 80 - 90 °C, dry it, and then wash it with distilled water until the pH = 7 to obtain the second modified biochar;

[0010] S4. Preparation of the modified biochar material: Disperse the first modified biochar and the second modified biochar in distilled water, mix evenly to obtain a dispersion liquid, add sodium tetrapropylene benzene sulfonate (ABS) and carboxymethyl cellulose to the dispersion liquid, stir evenly, and dry it to obtain the modified biochar material.

[0011] Preferably, in the step S2, the reaction steps of the second reaction solution are specifically to add distilled water, keep stirring at 50 - 60 °C for 30 min - 1 h, and then add it to the ammonium persulfate solution and raise the temperature to 70 - 80 °C and keep stirring for 3 - 6 h.

[0012] Preferably, in the step S2, the concentration of the concentrated nitric acid is 4 - 7 mol / L, and the mass ratio of the concentrated nitric acid to the biochar is 10 - 20:1; the concentration of the ammonium persulfate solution is 10 - 30%, and the mass ratio of the ammonium persulfate solution to the biochar is 30 - 50:1.

[0013] Preferably, in the step S3, the concentration of calcium ions or iron ions in the calcium solution or the iron solution is 0.1 - 2 mol / L, and the concentration of the biochar in the calcium solution or the iron solution is 10 - 20 g / L.

[0014] Preferably, in the step S4, the mass ratio of the first modified biochar, the second modified biochar, and distilled water is 1.5 - 2:1:10 - 15.

[0015] Preferably, in the step S4, the stirring temperature is 40 - 60 °C, and the stirring time is 1 - 3 h.

[0016] Preferably, in the step S4, the mass ratio of the dispersion liquid, sodium tetrapropylene benzene sulfonate (ABS), and carboxymethyl cellulose is 15 - 20:1 - 3:0.5 - 1.

[0017] Preferably, in the step S3, the mass ratio of the second modified biochar to sodium selenite is 2-3:0.5-1.

[0018] The present invention provides a modified biochar material, which is characterized in that it is prepared by the above-mentioned preparation method.

[0019] The present invention also provides an application of the modified biochar material as described above in the treatment of mine heavy metal contaminated soil.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. The material prepared by the preparation method of the modified biochar material provided by the present invention has good physical / chemical stability. Through dual modification treatment of functional oxidation and loading of calcium, iron and selenium active components, a variety of oxygen-containing functional groups (carboxyl group, carbonyl group, phenolic functional group) are introduced onto the biochar surface, and rich modification and decoration are carried out. The biochar is oxidized and functionalized with concentrated nitric acid and ammonium persulfate to obtain the first modified biochar, which endows the biochar with rich heavy metal anchoring active sites, and also has a stronger interaction with sodium tetrapolypropylene benzene sulfonate (ABS) and carboxymethyl cellulose, making its adsorption properties more stable; the second modified biochar also provides many pores that are uneven and exist in the form of small particle aggregates with rough morphology, has a larger specific surface area and more prominent microporous structure, can load iron and calcium ions in its micropores, and can also replace the iron and calcium ions in its micropores with heavy metal ions including cadmium (Cd), lead (Pb) and arsenic (As), reducing the content of cadmium (Cd), lead (Pb) and arsenic (As) in the soil. The combination of dual modification not only greatly improves the adsorption performance of the material for heavy metal ions, enhances the adsorption capacity and adsorption efficiency, but also stably exerts its adsorption effect under the complex pollution factors of mines with organic pollution, acid-base pollution and radioactive element pollution, and is applicable to the treatment of heavy metal pollution in large areas of mine soil.

[0022] 2. The applicant found that the introduction of sodium tetrapolypropylene benzene sulfonate (ABS) and carboxymethyl cellulose endows the material with good stability, making the biochar material not affected by the complex environment of organic pollution, excessive acid or excessive alkali, enabling it to more effectively adsorb heavy metals in the soil and making the biochar material have a stable binding and adsorption effect.

[0023] 3. During the crop harvest season, melon and bean vines are usually abandoned or burned, causing waste of resources and environmental pollution. Using them as biochar raw materials has great potential. The present invention utilizes common biological wastes such as melon and bean vines, which has the characteristics of environmental protection and low cost; and the reagents used are all non-toxic and will not cause pollution to the environment. Moreover, the biochar material can be directly added to the soil environment contaminated by the heavy metals without other additional conditions, which is convenient and easy to operate. Detailed Embodiments

[0024] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the protection scope of the present invention is not limited by the specific embodiments. Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0025] Example 1

[0026] A preparation method of a modified biochar material in this example includes the following steps:

[0027] S1. Preparation of biochar: Dry the watermelon vines and then crush them through a 100-mesh sieve, and then perform high-temperature carbonization at 800 °C. After naturally cooling to room temperature, take it out to obtain biochar for standby;

[0028] S2. Preparation of the first modified biochar: Stir the biochar and 5 mol / L concentrated nitric acid with a mass 10 times that of the biochar in an ice bath and react at 0 °C for 3 h to obtain the first reaction solution; Heat the first reaction solution, add distilled water and keep it warm and stirred at 50 °C for 30 min, then add an ammonium persulfate solution with a mass 30 times that of the biochar and raise the temperature to 80 °C and keep it warm and stirred for 3 h to obtain the second reaction solution; Filter the second reaction solution, and wash the filter residue alternately with ethanol and water, and then dry it to obtain the first modified biochar;

[0029] S3. Preparation of the second modified biochar: Add the biochar to a 0.5 mol / L ferric chloride solution, and the concentration of the biochar in the ferric chloride solution is 12 g / L. Use ammonia water to adjust the pH to 11, mix and let it stand, then add sodium selenite solution, perform ultrasonic treatment at 500 W for 1 h, then heat and stir at 80 °C for 4 h, dry it, and then wash it with distilled water until the pH = 7 to obtain the second modified biochar; The mass ratio of the second modified biochar to sodium selenite is 2:0.5.

[0030] S4. Preparation of the modified biochar material: Disperse the first modified biochar and the second modified biochar in distilled water. The mass ratio of the first modified biochar, the second modified biochar, and distilled water is 1.5:1:10, mix evenly to obtain a dispersion liquid. Add sodium dodecyl benzene sulfonate (ABS) and carboxymethyl cellulose to the dispersion liquid. The mass ratio of the dispersion liquid, sodium dodecyl benzene sulfonate (ABS), and carboxymethyl cellulose is 15:1:0.5, stir at 50 °C for 1 h, and dry it to obtain the modified biochar material.

[0031] Example 2

[0032] A preparation method of a modified biochar material in this embodiment includes the following steps:

[0033] S1. Preparation of biochar: Dry and crush watermelon vines, sieve them through a 100-mesh sieve, then carry out high-temperature carbonization at 800 °C, take them out after natural cooling to room temperature to obtain biochar for standby;

[0034] S2. Preparation of the first modified biochar: Stir biochar and concentrated nitric acid with a concentration of 7 mol / L and a mass 15 times that of the biochar in an ice bath, react at 0 °C for 6 h to obtain a first reaction solution; Heat the first reaction solution, add distilled water, keep it warm and stir at 60 °C for 1 h, then add an ammonium persulfate solution with a mass 40 times that of the biochar, raise the temperature to 80 °C, keep it warm and stir for 3 h to obtain a second reaction solution; Filter the obtained second reaction solution, wash the filter residue alternately with ethanol and water, and dry it to obtain the first modified biochar;

[0035] S3. Preparation of the second modified biochar: Add biochar to a 2 mol / L calcium chloride solution, the concentration of the second modified biochar in the calcium chloride solution is 20 g / L, adjust the pH to 12 with ammonia water, add sodium selenite solution after mixing and standing, carry out ultrasonic treatment at 500 W for 1 h, then heat and stir at 90 °C for 4 h, dry it, and then wash it with distilled water until the pH = 7 to obtain the second modified biochar; The mass ratio of the second modified biochar to sodium selenite is 3:1.

[0036] S4. Preparation of the modified biochar material: Disperse the first modified biochar and the second modified biochar in distilled water, the mass ratio of the first modified biochar, the second modified biochar to distilled water is 2:1:15, mix evenly to obtain a dispersion liquid, add sodium tetrapropylene benzene sulfonate (ABS) and carboxymethyl cellulose to the dispersion liquid, the mass ratio of the dispersion liquid to sodium tetrapropylene benzene sulfonate (ABS) and carboxymethyl cellulose is 20:3:1, stir at 60 °C for 1 h, and dry it to obtain the modified biochar material.

[0037] Example 3

[0038] A preparation method of a modified biochar material in this embodiment includes the following steps:

[0039] S1. Preparation of biochar: Dry and crush mung bean vines, sieve them through a 100-mesh sieve, then carry out high-temperature carbonization at 800 °C, take them out after natural cooling to room temperature to obtain biochar for standby;

[0040] S2. Preparation of the first modified biochar: Stir the biochar and 4 mol / L concentrated nitric acid with a mass 20 times that of the biochar in an ice bath, and react at 0 °C for 3 h to obtain the first reaction solution; Heat the first reaction solution, add distilled water, keep it warm and stir at 55 °C for 1.50 min, then add an ammonium persulfate solution with a mass 30 times that of the biochar, raise the temperature to 80 °C, keep it warm and stir for 3 h to obtain the second reaction solution; Wash the obtained second reaction solution alternately with ethanol and water, and dry it to obtain the first modified biochar;

[0041] S3. Preparation of the second modified biochar: Add the biochar into a 0.5 mol / L ferric chloride solution, the concentration of the second modified biochar in the ferric chloride solution is 12 g / L, adjust the pH to 11 with ammonia water, add sodium selenite solution after mixing and standing still, perform ultrasonic treatment at 500 W, then heat and stir at 80 °C for 4 h, dry it, and then wash it with distilled water until the pH = 7 to obtain the second modified biochar; The mass ratio of the second modified biochar to sodium selenite is 2:0.5.

[0042] S4. Preparation of the modified biochar material: Disperse the first modified biochar and the second modified biochar in distilled water, and the mass ratio of the first modified biochar, the second modified biochar and distilled water is 1.5:1:10. Mix them evenly to obtain a dispersion liquid. Add sodium tetrapropylene benzene sulfonate (ABS) and carboxymethyl cellulose to the dispersion liquid, and the mass ratio of the dispersion liquid, sodium tetrapropylene benzene sulfonate (ABS) and carboxymethyl cellulose is 15:1:0.5. Stir at 50 °C for 1 h, and dry it to obtain the modified biochar material.

[0043] Comparative Example 1

[0044] This comparative example does not contain the first modified biochar, and the remaining preparation methods are the same as those in Example 1.

[0045] Comparative Example 2

[0046] This comparative example does not contain the second modified biochar, and the remaining preparation methods are the same as those in Example 1.

[0047] Comparative Example 3

[0048] The preparation method of the first modified biochar in this comparative example is: Stir the biochar and 5 mol / L concentrated nitric acid with a mass 10 times that of the biochar at 50 °C for 5 h, then wash it alternately with ethanol and water, and dry it to obtain the first modified biochar. The remaining preparation methods are the same as those in Example 1.

[0049] Comparative Example 4

[0050] The preparation method of the second modified biochar in this comparative example is as follows: Add biochar into 0.5 mol / L ferric chloride solution, and the concentration of the second modified biochar in the ferric chloride solution is 12 g / L. Adjust the pH to 11 using ammonia water, then heat and stir at 80 °C for 4 h, dry, and then wash with distilled water until the pH = 7 to obtain the second modified biochar.

[0051] Comparative Example 5

[0052] The preparation method of the biochar material in this comparative example is as follows: Directly mix the first modified biochar and the second modified biochar evenly at a ratio of 1.5:1. The remaining preparation methods are the same as those in Example 1.

[0053] The applicant conducted tests in a certain mining area in Nandan County, Hechi City, Guangxi Zhuang Autonomous Region. The pH value of the soil in the test area was 4 - 4.5, which was acidic soil. The detected heavy metals were mainly cadmium (Cd), lead (Pb), and arsenic (As). Among them, the cadmium content was 5.62 mg / kg, the lead content was 79.8 mg / kg, and the arsenic content was 36.9 mg / kg, all of which exceeded the standards.

[0054] The biochar materials prepared by the preparation methods of Examples 1 - 2 and Comparative Examples 1 - 5 of the present invention were tested. The test was divided into 7 groups, and the test area of each group was 50 m 2 , and the soil was plowed to a depth of 40 cm. The biochar material was mixed evenly with the plowed soil at a rate of 0.5 kg / m 2 . The removal rates of cadmium, lead, and arsenic in the soil were detected after 90 d and 180 d respectively. The test results are shown in Table 1 and Table 2 below.

[0055] Table 1 Removal rates of cadmium, lead, and arsenic in the soil detected after 90 d

[0056] Group Cadmium removal rate (%) Lead removal rate (%) Arsenic removal rate (%) Example 1 53.2 50.6 60.2 Example 2 54.9 51.5 61.9 Example 3 54.5 51.3 61.0 Comparative Example 1 39.2 35.7 50.8 Comparative Example 2 41.1 36.3 45.4 Comparative Example 3 44.5 40.6 41.0 Comparative Example 4 42.8 39.2 49.2 Comparative Example 5 47.1 44.3 53.9

[0057] Table 2 Removal rates of cadmium, lead, and arsenic in the soil detected after 180 d

[0058]

[0059]

[0060] The biochar materials prepared by the preparation methods of Example 1 and Comparative Example 5 were tested. 0.2 g of each biochar sample was taken and mixed with a solution containing 50 mg / L cadmium and 20 mg / L rhodamine B dye, and shaken intermittently at room temperature. The shaking interval was 6 hours each time, and the shaking time was 1 min each time. The removal effects after 96 h are shown in Table 3 below.

[0061] Table 3

[0062] Group Cadmium removal rate (%) Rhodamine B removal rate (%) Example 1 45.9 61.2 Comparative Example 3 36.8 40.5 Comparative Example 5 30.8 29.3

[0063] As can be seen from the above table, the biochar material of Example 1 of the present invention can still achieve good adsorption effect under the interference factors of organic matter, and at the same time has a certain removal rate for organic matter.

[0064] In summary, the material prepared by the preparation method of the modified biochar material provided by the present invention has good physical / chemical stability. Through dual modification treatments of functional oxidation and loading of calcium, iron and selenium active components, a variety of oxygen-containing functional groups (carboxyl group, carbonyl group, phenolic functional group) are introduced on the biochar surface, and rich modification and decoration are carried out. Moreover, many pores exist in the form of uneven and rough small particle aggregates adhering to each other. These unique adsorption pore structures are beneficial to the targeted adsorption of heavy metals including cadmium (Cd), lead (Pb) and arsenic (As), greatly improving the adsorption performance of the material for heavy metal ions, enhancing the adsorption capacity and adsorption efficiency, and being applicable to the treatment of heavy metal pollution in large-area mine soils. The introduction of tetrapropylene benzene sulfonate (ABS) and carboxymethyl cellulose endows the material with good stability, enabling the biochar material not to be affected by the complex environment of organic matter pollution, excessive acidity or alkalinity, making it more effectively adsorb heavy metals in the soil and having a stable binding and adsorption effect.

[0065] The foregoing description of specific exemplary embodiments of the present invention is for purposes of illustration and exemplification. These descriptions are not intended to limit the present invention to the precise forms disclosed, and obviously, many changes and variations are possible in light of the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical applications, so that those skilled in the art can implement and utilize various different exemplary embodiments of the present invention as well as various different selections and changes. The scope of the present invention is intended to be defined by the claims and their equivalents.

Claims

1. A preparation method of a modified biochar material, characterized in that, It includes the following steps: S1. Preparation of biochar: Dry and crush the melon vines or bean vines, then sieve them, and then carry out high-temperature carbonization to obtain biochar for standby; S2. Preparation of the first modified biochar: Take a certain amount of biochar, stir the biochar and concentrated nitric acid in an ice bath, react at 0-3°C for 3-6 h to obtain a first reaction solution; Heat the first reaction solution, add distilled water and keep stirring, and then add it to the ammonium persulfate solution and keep stirring again to obtain a second reaction solution; Filter the obtained second reaction solution, wash the filter residue alternately with ethanol and water, and dry it to obtain the first modified biochar; S3. Preparation of the second modified biochar: Take a certain amount of biochar, add it to a calcium solution or an iron solution, adjust the pH to 11-13, mix and let stand, then add a sodium selenite solution, carry out ultrasonic treatment, then heat and stir, dry, and then wash with distilled water until the pH = 7 to obtain the second modified biochar; S4. Preparation of the modified biochar material: Disperse the first modified biochar and the second modified biochar in distilled water, mix evenly to obtain a dispersion liquid, add sodium tetrapolypropylene benzene sulfonate and carboxymethyl cellulose to the dispersion liquid, stir evenly, and dry to obtain the modified biochar material.

2. The preparation method of a modified biochar material according to claim 1, characterized in that, In the step S2, the reaction steps of the second reaction solution are specifically to add distilled water and keep stirring at 50-60°C for 30 min-1 h, and then add it to the ammonium persulfate solution and heat up to 70-80°C and keep stirring for 3-6 h.

3. The preparation method of a modified biochar material according to claim 1, characterized in that, In the step S2, the concentration of the concentrated nitric acid is 4-7 mol / L, and the mass ratio of the concentrated nitric acid solution to the biochar is 10-20:1; the concentration of the ammonium persulfate solution is 10-30%, and the mass ratio of the ammonium persulfate solution to the biochar is 30-50:

1.

4. The preparation method of a modified biochar according to claim 1, characterized in that, In the step S3, the concentration of calcium ions or iron ions in the calcium solution or the iron solution is 0.1-2 mol / L, and the concentration of the biochar in the calcium solution or the iron solution is 10-20 g / L.

5. The preparation method of a modified biochar according to claim 1, wherein In the step S4, the mass ratio of the first modified biochar, the second modified biochar and distilled water is 1.5-2:1:10-15.

6. The preparation method of a modified biochar according to claim 1, characterized in that, In the step S4, the stirring temperature is 40-60°C, and the stirring time is 1-3 h.

7. The preparation method of a modified biochar according to claim 1, characterized in that, In the step S4, the mass ratio of the dispersion liquid, sodium tetrapolypropylene benzene sulfonate and carboxymethyl cellulose is 15-20:1-3:0.5-1.

8. The preparation method of a modified biochar according to claim 1, wherein, In the step S3, the mass ratio of the second modified biochar to sodium selenite is 2-3:0.5-1.

9. A modified biochar material, characterized in that, Prepared by the preparation method according to any one of claims 1-8.

10. Application of a modified biochar material as claimed in claim 9 in the treatment of mine heavy metal contaminated soil.

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