Method for preparing magnetic biochar adsorbent from red mud and peanut shells and application of magnetic biochar adsorbent

Abstract

The invention discloses a method for preparing a magnetic biochar adsorbent from red mud and peanut shells, and belongs to the field of solid waste resource utilization. The method comprises the following steps: (1) sequentially drying, grinding and sieving red mud to obtain pretreated red mud; sequentially washing, drying, grinding and sieving the peanut shells to obtain pretreated peanut shells; (2) mixing the pretreated red mud and peanut shells to obtain a mixed material; (3) performing pyrolysis treatment on the mixed material in a protective atmosphere to obtain a pyrolyzed material; and (4) sequentially washing, drying, grinding and sieving the pyrolysis material to obtain the magnetic biochar adsorbent. According to the method, the resource high-value utilization of the red mud and the peanut shell solid waste can be effectively realized by adopting a one-step pyrolysis method, the prepared magnetic biochar shows excellent Cu (II) wastewater treatment capacity, and the material can be quickly separated and recycled through an external magnetic field and has good cyclic regeneration performance.

Description

Technical Field

[0001] The invention relates to the field of solid waste resource utilization, and in particular to a method for preparing a magnetic biochar adsorbent from red mud and peanut shells and application thereof. Background Art

[0002] Red mud is a solid waste discharged during the production of alumina from bauxite, and its disposal has always been an important issue facing the industrial field. Traditional dry stockpiling not only occupies a large amount of land resources, but also poses a potential threat to the surrounding ecological environment due to its high alkalinity, fine particle size and the presence of various heavy metal components. At the same time, as a major peanut producer in the world, my country produces a large amount of peanut shell biomass waste every year. Except for some used as chemical raw materials, animal feed and organic fertilizers, most peanut shells are still treated by direct incineration, resulting in waste of resources and environmental pollution. Therefore, it is of great practical significance to develop an economically feasible and environmentally friendly resource utilization plan.

[0003] Cu(Ⅱ) is an essential trace element for the human body. When it accumulates excessively, it will bring serious burden to important organs such as the digestive system. Cu(Ⅱ) mainly comes from industries such as zinc plating and paint production. The annual discharge of wastewater containing Cu(Ⅱ) is huge, causing continuous pollution to the water environment, and it is urgent to adopt efficient and economical treatment technology. Among the existing treatment methods, adsorption method has become one of the most widely used heavy metal wastewater treatment technologies at home and abroad due to its advantages such as stable treatment effect and simple operation.

[0004] The Chinese invention patent with publication number CN112791696A discloses a magnetic Fe 3 O 4 / Biochar adsorbent and its application, which proposes to convert FeCl 2 ·4H 2 O, FeCl 3 6H 2 O is dispersed in an organic solvent, biochar and alkali solution are added, and the mixture is placed in a microwave environment for reaction to prepare magnetic biochar. However, due to the sustainability problem of microwaves, it is still in the laboratory stage and difficult to achieve large-scale application. The Chinese invention patent with publication number CN115138336A discloses a method for preparing a red mud-peanut shell-based composite material for acidic phosphorus-containing sewage treatment, and proposes to introduce the pretreated red mud and peanut shells into a dilute hydrochloric acid solution for acid treatment, and then obtain an adsorbent after drying, grinding, and high-temperature pyrolysis. Although this method has made certain progress in improving the porosity and adsorption performance of the material, it does not fully consider the strong alkalinity characteristics of red mud, and requires the consumption of a large amount of acidic reagents, which has certain limitations in terms of economy and environment. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a magnetic biochar adsorbent from red mud and peanut shells and application thereof.

[0006] The technical solution adopted by the present invention is:

[0007] A method for preparing a magnetic biochar adsorbent from red mud and peanut shells, comprising the following steps:

[0008] (1) drying, grinding and sieving red mud in sequence to obtain pretreated red mud; washing, drying, grinding and sieving peanut shells in sequence to obtain pretreated peanut shells;

[0009] (2) mixing the pretreated red mud and peanut shells to obtain a mixed material;

[0010] (3) placing the mixed material in a protective atmosphere for pyrolysis treatment to obtain a pyrolysis material;

[0011] (4) The pyrolysis material is washed, dried, ground and sieved in sequence to obtain a magnetic biochar adsorbent.

[0012] Preferably, in step (1), the red mud iron grade TFe shall not be less than 15%.

[0013] Preferably, in step (1), when the peanut shells are washed, the peanut shells are washed 2 to 3 times with deionized water.

[0014] Preferably, in step (1), the drying treatment temperature is 50 to 100° C., and the drying time is 6 to 24 hours.

[0015] Preferably, in step (1): during the sieving process, the sieve hole size is 100 to 325 meshes.

[0016] Preferably, in step (2), the mass ratio of red mud to peanut shells in the mixture is 1:1 to 3:1.

[0017] Preferably, in step (3), the protective atmosphere is a nitrogen atmosphere. Of course, other inert atmospheres may also be used.

[0018] Preferably, in step (3): the heating rate during the pyrolysis treatment is 5 to 15°C / min, the pyrolysis treatment temperature is 600 to 800°C, and the pyrolysis treatment time is 1 to 3 hours.

[0019] Preferably, in step (4): during the washing treatment of the pyrolysis material, the pyrolysis material is washed 2 to 3 times with an organic solvent and deionized water respectively.

[0020] The magnetic biochar adsorbent prepared as above can be used in the adsorption and removal of Cu(II) in wastewater.

[0021] The principles and beneficial technical effects of the present invention are as follows:

[0022] The reactions involved in the mixture of red mud and peanut shells under nitrogen atmosphere are mainly as follows:

[0023] Peanut shell (biomass) → biochar + CO, H 2 , C X H X Other reducing gases;

[0024] Fe 2 O 3 +CO,H 2 , C X H X Reducing gases →Fe 3 O 4 +CO 2 +H 2 O;

[0025] During the pyrolysis treatment under protective atmosphere, peanut shells will produce H 2 ,CO,C X H X The reducing gases such as pyrolysis provide a reducing atmosphere for the transformation of Fe(III) to Fe(II), converting the iron minerals in red mud into strong magnetic minerals. At the same time, the water and reducing gases released during the pyrolysis process also provide abundant pores for biochar, significantly increasing its specific surface area, average pore volume, and average pore size, which can provide more adsorption sites for heavy metals.

[0026] The above magnetic biochar adsorbent and peanut shell biochar or magnetic Fe 3 O 4 The adsorption efficiency of Cu(Ⅱ) was significantly improved.

[0027] The present invention can adjust the saturation magnetization intensity and Cu(II) adsorption efficiency of magnetic biochar to target values ​​by adjusting the mass ratio of red mud and peanut shells. The reducing gas generated by the pyrolysis of peanut shells is used to reduce the goethite and hematite in the red mud into highly magnetic Fe 3 O 4 , no external iron source is required.

[0028] The present invention adopts a one-step pyrolysis method to effectively realize the resource-based high-value utilization of red mud and peanut shell solid waste. The prepared magnetic biochar exhibits excellent Cu(II) wastewater treatment capacity. The material can be quickly separated and recovered by an external magnetic field and has good recycling performance. This simple and efficient preparation process and excellent application performance have significant industrial promotion value and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A flow chart of the method for preparing magnetic biochar adsorbent from red mud and peanut shells of the present invention;

[0030] Figure 2 X-ray diffraction patterns of the magnetic biochar adsorbent and peanut shell biochar obtained in Example 1 and Comparative Example 1 of the present invention, respectively;

[0031] Figure 3 This is a graph showing the test results of the unit adsorption capacity of Cu(II) by the magnetic biochar adsorbent prepared in Examples 1 to 5 of the present invention. DETAILED DESCRIPTION

[0032] The present invention provides a method for preparing a magnetic biochar adsorbent from red mud and peanut shells, such as Figure 1 As shown, the method is carried out according to the following steps: drying, grinding and sieving red mud; washing, drying, grinding and sieving peanut shells; mixing the sieving red mud and peanut shells in proportion to obtain a mixed material; placing the mixed material in a protective atmosphere for pyrolysis treatment to obtain a pyrolysis material; washing, drying, grinding and sieving the pyrolysis material to obtain a magnetic biochar adsorbent. The present invention uses red mud and peanut shells as raw materials, and the preparation method is simple. The one-step pyrolysis method can effectively realize the resource-based high-value utilization of red mud and peanut shell solid wastes, and utilizes the reducing gas generated by the pyrolysis process of peanut shells to reduce the goethite and hematite in the red mud into highly magnetic Fe 3 O 4 The prepared magnetic biochar has a strong adsorption capacity for wastewater containing Cu(Ⅱ), can be quickly separated and recovered by an external magnetic field, can be reused, and is suitable for large-scale promotion and application.

[0033] The present invention will be further explained and illustrated below in conjunction with specific embodiments.

[0034] Embodiment 1:

[0035] Wash the peanut shells with deionized water for 2 to 3 times, and then place them and the red mud in a forced air drying oven at 50°C for 18 hours, grind and sieve to less than 100 mesh for later use.

[0036] The red mud and peanut shells were uniformly mixed in a mass ratio of 1.895:1 to obtain a mixed raw material.

[0037] The mixed raw materials were heated at a rate of 10.59 °C / min and a protective atmosphere (N 2 ) was pyrolyzed for 2.09 h to obtain a pyrolysis material.

[0038] The pyrolysis material was washed with ethanol and deionized water for 2 to 3 times, respectively, and then dried in a forced air drying oven at 70° C. for 10 h, ground and sieved to less than 100 mesh to obtain magnetic biochar.

[0039] Embodiment 2:

[0040] Wash the peanut shells with deionized water for 2 to 3 times, and then place them and the red mud in a forced air drying oven at 60°C for 12 hours, grind and sieve to less than 100 mesh for later use.

[0041] The red mud and peanut shells were uniformly mixed in a mass ratio of 1:1 to obtain a mixed raw material.

[0042] The mixed raw materials were heated at a rate of 10 °C / min and a protective atmosphere (N 2 ) for 2 h to obtain a pyrolysis material.

[0043] The pyrolysis material was washed with ethanol and deionized water for 2 to 3 times, respectively, and then dried in a forced air drying oven at 60° C. for 8 h, ground and sieved to less than 200 meshes to obtain magnetic biochar.

[0044] Embodiment 3:

[0045] Wash the peanut shells with deionized water for 2 to 3 times, and then place them and the red mud in a forced air drying oven at 100°C for 6 hours, grind and sieve to less than 200 mesh for later use.

[0046] The red mud and peanut shells were uniformly mixed in a mass ratio of 3:1 to obtain a mixed raw material.

[0047] The mixed raw materials were heated at a rate of 5 °C / min and a protective atmosphere (N 2 ) for 2 h to obtain a pyrolysis material.

[0048] The pyrolysis material was washed with ethanol and deionized water for 2 to 3 times, respectively, and then dried in a forced air drying oven at 70° C. for 8 h, ground and sieved to less than 200 meshes to obtain magnetic biochar.

[0049] Embodiment 4:

[0050] Wash the peanut shells with deionized water for 2 to 3 times, and then place them and the red mud in a forced air drying oven at 80°C for 10 hours, grind and sieve to less than 100 mesh for later use.

[0051] The red mud and peanut shells were uniformly mixed in a mass ratio of 2:1 to obtain a mixed raw material.

[0052] The mixed raw materials were heated at a rate of 10 °C / min and a protective atmosphere (N 2) for 3 h to obtain a pyrolysis material.

[0053] The pyrolysis material was washed with acetone and deionized water for 2 to 3 times, respectively, and then dried in a forced air drying oven at 50° C. for 18 h, ground and sieved to less than 100 mesh to obtain magnetic biochar.

[0054] Embodiment 5:

[0055] Wash the peanut shells with deionized water for 2 to 3 times, and then place them and the red mud in a forced air drying oven at 50°C for 24 hours, grind and sieve to less than 200 mesh for later use.

[0056] The red mud and peanut shells were uniformly mixed in a mass ratio of 2:1 to obtain a mixed raw material.

[0057] The mixed raw materials were heated at a rate of 15 °C / min and a protective atmosphere (N 2 ) for 2 h to obtain a pyrolysis material.

[0058] The pyrolysis material was washed with acetone and deionized water for 2 to 3 times, respectively, and then dried in a forced air drying oven at 70° C. for 8 h, ground and sieved to less than 200 mesh to obtain magnetic biochar.

[0059] Comparative Example 1:

[0060] Wash the peanut shells with deionized water for 2 to 3 times, and then dry them in a forced air drying oven at 60°C for 8 hours, grind them, sieve them to less than 100 mesh, and set them aside for use.

[0061] The sieved peanut shells were heated at a rate of 10 °C / min and a protective atmosphere of 700 °C (N 2 ) for 2 h to obtain a pyrolysis material.

[0062] The pyrolysis material was washed with ethanol and deionized water for 2 to 3 times, respectively, and then dried in a forced air drying oven at 70° C. for 8 h, ground and sieved to less than 200 meshes to obtain peanut shell biochar.

[0063] 1. Structural test of magnetic biochar adsorbent;

[0064] The magnetic biochar and peanut shell biochar prepared by the methods of Example 1 and Comparative Example 1 were subjected to X-ray diffraction analysis and specific surface area and pore size analysis, and the results are shown below.

[0065] (1) X-ray diffraction analysis results;

[0066] X-ray diffraction spectrum Figure 2 As shown. Figure 2It can be seen that there is no obvious diffraction peak in the peanut shell biochar, indicating that the biochar formed after pyrolysis is difficult to form a crystal structure, and the substances in the peanut shell biochar exist in an amorphous form. The magnetic biochar has strong diffraction peaks at 20.7°, 30.1°, 35.4°, 43.0°, 53.4°, 56.9°, and 62.5°. After analysis, it is Fe 3 O 4 The characteristic peaks of (PDF#19-0629) indicate that the iron-containing phase in the red mud is converted into magnetite during the pyrolysis process, which makes the adsorbent magnetic. After the adsorption is completed, the adsorbent can be recovered by applying an external magnetic field.

[0067] (2) Specific surface area and pore size analysis results;

[0068] Table 1 shows the specific surface area and pore size data of peanut shell biochar and magnetic biochar;

[0069] Table 1

[0070] sample <![CDATA[Specific surface area / (m 2 / g)]]> <![CDATA[Average pore volume / (cm 3 / g)]]> Peanut Shell Biochar 125.18 0.099 Magnetic biochar 291.87 0.170

[0071] As can be seen from Table 1, the specific surface area of ​​biochar formed by direct pyrolysis of peanut shells is 125.18 m 2 / g, average pore volume is 0.099cm 3 / g. The specific surface area and average pore volume of magnetic biochar obtained by pyrolysis of red mud and peanut shells increased significantly to 291.87m 2 / g and 0.170cm 3 / g, indicating that the pyrolysis process not only gives biochar magnetic properties, but also the iron-containing phases and CO, H 2 , C X H X The reaction with reducing gases will increase the specific surface area and enrich the porosity, thereby improving the adsorption performance of Cu(Ⅱ).

[0072] 2. Performance testing;

[0073] Take 5 100mL conical flasks, add 50mL of 200mg / L Cu(Ⅱ) solution respectively, adjust the pH of Cu(Ⅱ) solution to 4 with 0.1mol / L HCl solution and 0.1mol / L NaOH solution, and then add 0.1g of magnetic biochar adsorbent obtained in Examples 1 to 5 respectively. Then place the conical flask in a 25℃ constant temperature shaker, react at a speed of 150r / min for 2h, and then measure the solubility of Cu(Ⅱ) in the solution after filtering through a 0.45μm filter membrane, and calculate the unit adsorption amount, and obtain the unit adsorption amount test results of the magnetic biochar adsorbent for Cu(Ⅱ) in Examples 1 to 5, as shown in FIG. Figure 3 shown.

[0074] from Figure 3 It can be seen that Example 1 has the best adsorption capacity for Cu(II), and the unit adsorption amounts of Cu(II) in Examples 1 to 5 are 95.86, 85.29, 80.7, 76.65, and 77.27 mg / g, respectively. It can be seen that the unit adsorption amount of Cu(II) by the magnetic biochar within 2 hours reaches more than 75 mg / g, showing excellent adsorption performance.

[0075] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing magnetic biochar adsorbent from red mud and peanut shells, characterized in that The following steps are involved: (1) drying, grinding and sieving red mud in sequence to obtain pretreated red mud; washing, drying, grinding and sieving peanut shells in sequence to obtain pretreated peanut shells; (2) mixing the pretreated red mud and peanut shells to obtain a mixed material; (3) placing the mixed material in a protective atmosphere for pyrolysis treatment to obtain a pyrolysis material; (4) The pyrolysis material is washed, dried, ground and sieved in sequence to obtain a magnetic biochar adsorbent.

2. The method for preparing magnetic biochar adsorbent from red mud and peanut shells according to claim 1, characterized in that: In step (1): the iron grade TFe of the red mud shall not be less than 15%.

3. The method for preparing magnetic biochar adsorbent from red mud and peanut shells according to claim 1, characterized in that: In step (1), when the peanut shells are washed, the peanut shells are washed 2 to 3 times with deionized water.

4. The method for preparing magnetic biochar adsorbent from red mud and peanut shells according to claim 1, characterized in that: In step (1): the temperature of the drying treatment is 50 to 100° C., and the drying time is 6 to 24 hours.

5. The method for preparing magnetic biochar adsorbent from red mud and peanut shells according to claim 1, characterized in that: In step (1): during the sieving process, the sieve hole size is 100 to 325 meshes.

6. The method for preparing magnetic biochar adsorbent from red mud and peanut shells according to claim 1, characterized in that: In step (2): the mass ratio of red mud to peanut shells in the mixed material is 1:1 to 3:

1.

7. The method for preparing magnetic biochar adsorbent from red mud and peanut shells according to claim 1, characterized in that: In step (3): the protective atmosphere is a nitrogen atmosphere.

8. The method for preparing magnetic biochar adsorbent from red mud and peanut shells according to claim 1, characterized in that: In step (3): the heating rate during the pyrolysis treatment is 5 to 15°C / min, the pyrolysis treatment temperature is 600 to 800°C, and the pyrolysis treatment time is 1 to 3h.

9. The method for preparing magnetic biochar adsorbent from red mud and peanut shells according to claim 1, characterized in that: In step (4): during the washing treatment of the pyrolysis material, the pyrolysis material is washed 2 to 3 times with an organic solvent and deionized water respectively.

10. Use of the magnetic biochar adsorbent prepared according to any one of claims 1 to 9 in the adsorption and removal of Cu(II) in wastewater.

Images