Preparation method and application of iron-crosslinked sodium alginate modified bagasse biochar

Abstract

The invention relates to the technical field of adsorption materials, in particular to a preparation method and application of iron-crosslinked sodium alginate modified bagasse biochar, which comprises the following steps: respectively pretreating red mud and bagasse, and then mixing the pretreated product with melamine to obtain a mixed material; the mixed material is placed in a protective atmosphere for pyrolysis treatment, and modified bagasse biochar is obtained; mixing the modified bagasse charcoal with a sodium alginate solution, performing ultrasonic treatment, heating and stirring to obtain a blended solution; the preparation method comprises the following steps: mixing bagasse and sodium alginate in a mixed solution, dropwise adding the mixed solution into a ferric chloride solution for standing and cross-linking, and carrying out washing treatment, freeze drying and grinding to obtain sodium alginate modified bagasse biochar, the method adopts bagasse as a biochar raw material, and introduces a magnetic material, a nitrogen-containing substance and sodium alginate to modify the biochar function; the surface active sites of the prepared material are increased, the adsorption capacity on tetracycline hydrochloride is improved, and the resource high-value utilization of the red mud and bagasse solid waste is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorption materials, and particularly relates to a preparation method and application of iron-crosslinked sodium alginate modified bagasse biochar. Background Art

[0002] Tetracycline hydrochloride (TC-HCl) is one of the most commonly used antibiotics for treating human / animal infectious diseases, and has made great contributions to the prevention of human diseases and the promotion of the development of animal husbandry. However, due to the long-term accumulation and poor degradability of TC-HCl, the residual problem of TC-HCl in water bodies, especially in surface waters, is becoming increasingly serious. It is reported that while soluble TC-HCl accumulates in water, it may produce synergistic effects or binding reactions with other pollutants (such as pesticides, heavy metals, polycyclic aromatic hydrocarbons), posing a threat to human health through drinking water. In addition, TC-HCl in water may induce the generation of multi-drug resistant bacteria, reducing the therapeutic effect of drugs on human infectious diseases. Therefore, there is an urgent need to develop an efficient and low-cost method to remove TC-HCl from water bodies.

[0003] The biochar adsorption method is a simple and practical water treatment technology. As one of the sources for preparing biochar, bagasse is rich in cellulose, hemicellulose and lignin, and can be used to prepare biochar with excellent pore structure, large specific surface area and high adsorption capacity. In addition, bagasse biochar can introduce new functional groups by doping heteroatoms (such as N, S, B, O) to improve its adsorption performance. In particular, N doping has been proven to enhance the adsorption capacity of biochar by increasing surface functional groups, and can also improve the hydrophilicity and dispersibility of biochar. In addition, endowing biochar with magnetism can greatly improve the reusability of biochar and make it easy to recycle. However, the high-purity chemical reagent iron source means a high preparation cost for magnetic biochar. Red mud (RM) is an iron-rich alkaline solid waste discharged during the production of alumina from bauxite, and is a suitable and economical iron source.

[0004] Different polymers such as sodium alginate (SA), polyvinyl alcohol, chitosan, polyacrylamide, etc. can be used for the fixation of powdered biochar. Among them, sodium alginate (SA) is a biopolymer mainly extracted from kelp or seaweed. SA can form a water-insoluble network structure gel under the action of metal cations, and the abundant oxygen-containing functional groups (such as -COOH and -OH) on the molecular chain can provide a large number of adsorption sites. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method and application of iron-crosslinked sodium alginate modified bagasse biochar, aiming to propose a modified bagasse biochar adsorbent for efficiently adsorbing tetracycline hydrochloride by using bagasse and red mud as raw materials, introducing N atoms and sodium alginate, and pyrolyzing, so as to treat waste with waste and realize the resource utilization of waste.

[0006] To achieve the above object, in a first aspect, the present invention provides a preparation method of iron-crosslinked sodium alginate modified bagasse biochar, comprising the following steps:

[0007] Obtain red mud and sugarcane, and pre-treat the red mud and bagasse respectively, and then mix the pretreated products with melamine to obtain a mixed material;

[0008] Pyrolyze the mixed material in a protective atmosphere to obtain modified bagasse biochar;

[0009] Mix the modified bagasse biochar with sodium alginate solution, perform ultrasonic treatment, heat and stir to obtain a blend solution;

[0010] Drop the blend solution into ferric chloride solution for static crosslinking, and through washing treatment, freeze-drying and grinding, obtain sodium alginate modified bagasse biochar.

[0011] Wherein, the pretreatment of the red mud includes drying, grinding and sieving, the pretreatment of the bagasse includes washing, drying, grinding and sieving, the drying temperature is 70 °C, the drying time is 48 h, when sieving, the sieve hole size is 120 mesh, and when performing the washing treatment, the bagasse is washed 2-3 times with ultrapure water.

[0012] Wherein, the mass ratio of bagasse, red mud and melamine in the mixed material is 1:0.5-1.5:1 and 1:1:0.5-1.5.

[0013] Wherein, the protective atmosphere is nitrogen, the heating rate during the pyrolysis treatment is 5 °C / min, the pyrolysis treatment temperature is 500-800 °C, and the pyrolysis treatment time is 2 h.

[0014] Wherein, the ultrasonic treatment time is 1 h, the heating temperature is 60 °C, and the stirring time is 2 h.

[0015] Wherein, the concentration of the ferric chloride solution is 1-9 g / 100 mL, the static crosslinking time is 24 h, when performing the washing treatment, it is washed 3-4 times with ethanol and ultrapure water respectively until the filtrate is clear and neutral, the freeze-drying temperature is -80 °C, and the time is 48 h.

[0016] In a second aspect, the present invention also provides an application of iron-crosslinked sodium alginate modified bagasse biochar, which is prepared by using the preparation method of iron-crosslinked sodium alginate modified bagasse biochar described in the first aspect as above, and is applied to treat tetracycline hydrochloride in water.

[0017] A preparation method of iron-crosslinked sodium alginate modified bagasse biochar of the present invention is as follows: obtain red mud and sugarcane, and perform pretreatment on the red mud and bagasse respectively, then mix the pretreated products with melamine to obtain a mixed material; place the mixed material in a protective atmosphere for pyrolysis treatment to obtain modified bagasse biochar; mix the modified bagasse biochar with a sodium alginate solution, perform ultrasonic treatment, heat and stir to obtain a blend solution; drop the blend solution into a ferric chloride solution for static crosslinking, and through washing treatment, freeze-drying and grinding, obtain sodium alginate modified bagasse biochar. This method uses bagasse as the biochar raw material, introduces magnetic materials, nitrogen-containing substances and sodium alginate to modify the functions of the biochar, increasing the number of surface active sites of the prepared material and enriching the types of functional groups; and this adsorbent material has magnetism, is easy to separate from the treated water, the material is more environmentally friendly, reduces the treatment cost, provides a new theory for the removal of tetracycline hydrochloride in wastewater, effectively improves the adsorption capacity for tetracycline hydrochloride, effectively realizes the resource utilization of red mud and bagasse solid waste with high value, treats waste with waste, and has good application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 FIGs. are the scanning electron microscope images of MRBC and SA@MRBC, where A and B are the SEM images of MRBC at different magnifications, and C and D are the SEM images of SA@MRBC at different magnifications.

[0020] Figure 2 FIGs. are the infrared spectra of MRBC and SA@MRBC.

[0021] Figure 3 FIG. is the adsorption performance diagram of SA@MRBC for TC-HCl at different times.

[0022] Figure 4 FIG. is the adsorption performance diagram of SA@MRBC for TC-HCl at different initial concentrations of TC-HCl.

[0023] Figure 5 FIG. is the flow chart of a preparation method of iron-crosslinked sodium alginate modified bagasse biochar provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] Please refer to Figures 1 to 5 , in a first aspect, the present invention provides a preparation method of iron-crosslinked sodium alginate modified bagasse biochar, comprising the following steps:

[0026] S1 Obtain red mud and sugarcane, and pre-treat the red mud and bagasse respectively, and then mix the pre-treated products with melamine to obtain a mixed material;

[0027] In an embodiment of the present invention, red mud and sugarcane are obtained, the red mud is dried, ground and sieved in sequence to obtain pre-treated red mud; the bagasse is washed, dried, ground and sieved in sequence to obtain pre-treated bagasse; the pre-treated red mud and bagasse are mixed with melamine to obtain a mixed material;

[0028] The mass ratio of bagasse, red mud and melamine in the mixed material is 1:0.5-1.5:1 and 1:1:0.5-1.5, and the best mixing ratio is 1:1:1. The drying temperature is 70 °C and the drying time is 48 h. When sieving, the sieve hole size is 120 mesh. When washing, the bagasse is washed 2-3 times with ultrapure water.

[0029] S2 Place the mixed material in a protective atmosphere for pyrolysis treatment to obtain modified bagasse biochar;

[0030] In an embodiment of the present invention, the protective atmosphere is nitrogen, the heating rate during the pyrolysis treatment is 5 °C / min, the pyrolysis treatment temperature is 500-800 °C, and the best pyrolysis treatment temperature is 700 °C. The pyrolysis treatment time is 2 h. The main reactions involved in the mixture of red mud and bagasse in a nitrogen atmosphere are as follows:

[0031] Bagasse (biomass) → Biochar + CO, H2, C X H X and other reducing gases;

[0032] Fe2O3 + CO, H2, C X H X and other reducing gases → Fe3O4 + CO2 + H2O;

[0033] In the pyrolysis treatment under a protective atmosphere, bagasse will produce H2, CO, C X H XReducing gases such as [specific gases] provide a reducing atmosphere for the transformation of Fe(III) to Fe(II), converting the iron minerals in red mud into strongly magnetic minerals. Meanwhile, the water and reducing gases released during the pyrolysis treatment also provide abundant pores for the biochar, significantly increasing its specific surface area, average pore volume, and average pore diameter, and providing more adsorption sites for antibiotics. Melamine provides N element. N doping can increase surface functional groups and improve the graphitization of biochar, which is beneficial to enhancing the adsorption capacity of biochar.

[0034] S3 Mix the modified bagasse biochar with sodium alginate solution, perform ultrasonic treatment, and heat and stir to obtain a blended solution.

[0035] In the embodiment of the present invention, first add 1 g of sodium alginate dissolved in 100 mL of ultrapure water, then add 1 g of modified bagasse biochar and mix. The ultrasonic treatment time is 1 h, the heating temperature is 60 °C, and the stirring time is 2 h.

[0036] S4 Drop the blended solution into ferric chloride solution for static cross-linking, and obtain sodium alginate-modified bagasse biochar through washing treatment, freeze-drying, and grinding.

[0037] In the embodiment of the present invention, the concentration of the ferric chloride solution is 1 - 9 g / 100 mL, and the optimal concentration is 5 g / 100 mL. The static cross-linking time is 24 h. During the washing treatment, wash 3 - 4 times with ethanol and ultrapure water respectively until the filtrate is clear and neutral. The freeze-drying temperature is -80 °C and the time is 48 h.

[0038] Sodium alginate (SA) is a natural polysaccharide with abundant carboxyl (-COOH) and hydroxyl (-OH) groups on its surface. However, sodium alginate is easily soluble in water and has poor mechanical properties, which limits its application in water treatment. In the present invention, a small amount of sodium alginate is cross-linked and deposited on the surface of modified bagasse biochar through cross-linking to prepare a sodium alginate-modified bagasse biochar adsorbent, and its adsorption performance for tetracycline hydrochloride is studied.

[0039] In the second aspect, the present invention also provides an application of iron-crosslinked sodium alginate-modified bagasse biochar, which is prepared by using the preparation method of iron-crosslinked sodium alginate-modified bagasse biochar described in the first aspect as above and is applied to treat tetracycline hydrochloride in water.

[0040] The present invention has the following beneficial effects: Using bagasse as the raw material of biochar, introducing red mud, melamine and sodium alginate to modify the biochar function, increasing the surface active sites of the prepared iron-crosslinked sodium alginate modified bagasse biochar and enriching the types of functional groups; and the adsorbent material has magnetism, is easy to separate from the treated water, is more environmentally friendly, reduces the treatment cost, and provides a new theory for the removal of tetracycline hydrochloride from wastewater.

[0041] To better understand the technical solution, the following embodiments are provided for further illustration:

[0042] Example 1

[0043] The bagasse was washed 2 - 3 times with ultrapure water, and then placed in a blast drying oven with red mud at 70 °C for 48 h, ground and sieved to 120 mesh for later use. According to the mass ratio of melamine:red mud:bagasse of 1:1:1, they were uniformly mixed to obtain a mixed material. An appropriate amount of the mixed material (where the mass of bagasse was 0.5 g) was weighed and put into a nickel boat, and the nickel boat was placed in a tubular furnace. It was heated at 5 °C / min under a nitrogen atmosphere and pyrolyzed at 700 °C for 2 h. After the pyrolysis was completed, it was cooled to room temperature to obtain modified bagasse biochar, marked as MRBC.

[0044] Example 2

[0045] 0.5 g of sodium alginate (SA) was completely dissolved in 50 mL of ultrapure water at 60 °C. Then, 0.5 g of the MRBC prepared in Example 1 was added to the SA solution, ultrasonically treated for 1 h and magnetically stirred for 2 h to obtain a uniformly dispersed blend. 2.5 g of ferric chloride was dissolved in 50 ml of ultrapure water, and the blend was added dropwise to the ferric chloride solution with a 0.5 ml disposable plastic dropper, and the dropping rate was controlled during the dropping process; after the dropping was completed, it was left to crosslink at room temperature for 24 h. After that, the precipitate and the solution were separated by suction filtration, and washed 3 times each with ethanol and ultrapure water until the filtrate was clear and neutral; finally, the black precipitate was freeze-dried at -80 °C for 48 h, taken out, ground and sieved through a 60-mesh sieve to obtain iron-crosslinked sodium alginate modified bagasse biochar, marked as SA@MRBC.

[0046] Structure test of iron-crosslinked sodium alginate modified bagasse biochar;

[0047] The MRBC and SA@MRBC prepared by the methods of Example 1 and Example 2 were subjected to specific surface area and pore size (BET), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) analysis, and the results are shown as follows.

[0048] (1) Specific surface area and pore size analysis;

[0049] The adsorption performance of biochar is related to its specific surface area, pore volume, and average pore diameter. The more developed the specific surface area and pore structure are, the better the adsorption performance of biochar. The specific surface area, pore volume, and average pore diameter of MRBC and SA@MRBC were measured by a specific surface area and pore size analyzer.

[0050] Table 1 shows the data measured by BET. It can be obtained that the specific surface area of MRBC is 79.968 m 2 / g, the pore volume is 0.088 cm 3 / g, and the average pore diameter is 4.417 nm. After loading sodium alginate on the basis of MRBC, the specific surface area of SA@MRBC increased to 84.657 m 2 / g, the pore volume reached 0.298 cm 3 / g, and the average pore diameter reached 14.057 nm. Therefore, the loading of sodium alginate can increase the contact opportunity between the adsorbent and TC-HCl, and then improve the adsorption performance of the adsorbent.

[0051] Table 1

[0052]

[0053] (2) Scanning electron microscopy analysis;

[0054] The microtopography of MRBC and SA@MRBC was analyzed by scanning electron microscopy to compare the changes in their microtopography.

[0055] The morphology and structure of MRBC were observed by scanning electron microscopy. The results are shown in Figure 1 (A, B). In the SEM images, unevenly distributed irregular blocks and pore structures distributed at the surface defects of the material can be seen. The irregular blocks are red mud particles covering the surface of the biochar, and the pore structures maintain the original shape of the biochar. The morphology and structure of SA@MRBC were observed by scanning electron microscopy. The results are shown in Figure 1 (C, D). In the SEM images, pore structures with larger pore diameters can be seen, and flocculent substances appear on the surface, which may be sodium alginate polysaccharides.

[0056] (3) Fourier transform infrared spectroscopy analysis;

[0057] Using a Fourier transform infrared spectrometer, samples were prepared by the KBr solid pressing method, and MRBC and SA@MRBC were characterized. The scanning wavenumber was 4000 - 400 cm -1 Wavenumber. The samples were qualitatively analyzed by plotting FT-IR spectra to analyze the functional groups present and determine whether the target substance was introduced.

[0058] The FT-IR spectral results are shown in Figure 2 . As shown by Figure 2(a) It can be seen that in the FT-IR spectrum of MRBC, the peaks at 3440 cm -1 , 1622 cm -1 and 1021 cm -1 are caused by the stretching vibrations of -OH, C=N and C-O respectively. In addition, a weak peak appears at 575 cm -1 , which is attributed to the Fe-O group. The above results indicate that there are nitrogen-containing functional groups and Fe-O groups on the surface of MRBC, which shows that the N atoms in melamine are successfully doped, and the Fe in red mud exists in the form of oxidation state in MRBC. From Figure 2 (b) It can be seen that in the FT-IR spectrum of SA@MRBC, the peaks at 3427 cm -1 , 1605 cm -1 , 1060 cm -1 and 578 cm -1 are caused by the stretching vibrations of -OH, C=N, C-O and Fe-O respectively. In addition, an absorption peak appears at 1417 cm -1 , which is attributed to the -COOH group of sodium alginate, indicating the successful loading of sodium alginate.

[0059] 2. Performance test of iron-crosslinked sodium alginate modified bagasse biochar;

[0060] (1) Study on the adsorption performance of SA@MRBC at different times;

[0061] To compare the adsorption performance effect of SA@MRBC prepared by the present invention on TC-HCl at different times, 10 portions of 0.02 g of SA@MRBC prepared in Example 2 were weighed and placed in 10 mL of TC-HCl solution with a concentration of 50 mg / L, and then placed in a constant temperature oscillator and shaken at 30 °C and 200 r / min for 2 min, 4 min, 6 min, 8 min, 10 min, 20 min, 30 min, 40 min, 60 min, 120 min respectively. After the reaction, the samples were filtered and sampled for adsorption performance determination.

[0062] The adsorption performance results are as Figure 3As shown in the figure, within 2 - 120 min, the adsorption rate and adsorption capacity of SA@MRBC for TC-HCl both first increase and then level off. This is because in the initial stage of adsorption, there are sufficient surface functional groups and more pores on the surface of SA@MRBC, which can provide enough active sites. TC-HCl can easily adsorb on the surface and then enter through the pores. As the adsorption time increases, TC-HCl occupies most of the surface adsorption active sites, and the particles diffuse inward and then fill the pore channels. Therefore, the adsorption rate and adsorption capacity of TC-HCl gradually increase and then tend to level off. At 120 min, the adsorption capacity of SA@MRBC for TC-HCl is 24.51 mg / g, and the adsorption rate is 98%.

[0063] (2) Study on the adsorption performance of SA@MRBC at different initial concentrations;

[0064] To compare the adsorption performance of SA@MRBC prepared by the present invention for TC-HCl at different initial concentrations of TC-HCl solutions, 13 portions of 0.02 g of SA@MRBC prepared in Example 2 were weighed and placed into 10 mL of TC-HCl solutions with concentrations of 30 mg / L, 50 mg / L, 80 mg / L, 100 mg / L, 200 mg / L, 300 mg / L, 400 mg / L, 500 mg / L, 600 mg / L, 700 mg / L, 800 mg / L, 900 mg / L, and 1000 mg / L in sequence, and then placed in a thermostatic oscillator and shaken at 30 °C and 200 r / min for 120 min. After the reaction ended, the samples were filtered and sampled for adsorption performance determination.

[0065] The results of the adsorption performance are as Figure 4 shown. The adsorption capacity of SA@MRBC for TC-HCl increases with the increase of the initial concentration. This is because the increase in the concentration gradient improves the mass transfer of molecules from the bulk of the solution to the surface of SA@MRBC. However, with the increase of the concentration, the adsorption rate of SA@MRBC for TC-HCl decreases, which may be due to the lack of sufficient binding sites on SA@MRBC for adsorption.

[0066] The above-disclosed is only the preferred embodiment of the preparation method and application of an iron-crosslinked sodium alginate modified bagasse biochar of the present invention. Of course, the scope of the rights of the present invention cannot be limited by this. Those of ordinary skill in the art can understand all or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. A preparation method of iron-crosslinked sodium alginate modified bagasse biochar, characterized in that, It includes the following steps: Obtain red mud and sugarcane, and pre-treat the red mud and sugarcane bagasse respectively. Then mix the pre-treated products with melamine to obtain a mixed material; Place the mixed material in a protective atmosphere for pyrolysis treatment to obtain modified bagasse biochar; Mix the modified bagasse biochar with sodium alginate solution, perform ultrasonic treatment, heat and stir to obtain a blend solution; Drop the blend solution into ferric chloride solution for static cross-linking, and through washing treatment, freeze-drying and grinding, obtain sodium alginate-modified bagasse biochar.

2. The preparation method of the iron-crosslinked sodium alginate modified bagasse biochar according to claim 1, wherein ； The pre-treatment of the red mud includes drying, grinding and sieving. The pre-treatment of the sugarcane bagasse includes washing, drying, grinding and sieving. The drying temperature is 70 °C and the drying time is 48 h. When sieving, the sieve hole size is 120 mesh. When performing the washing treatment, wash the sugarcane bagasse with ultrapure water 2-3 times.

3. The preparation method of the iron-crosslinked sodium alginate modified bagasse biochar according to claim 1, characterized in that ； The mass ratio of sugarcane bagasse, red mud and melamine in the mixed material is 1:0.5-1.5:1 and 1:1:0.5-1.

5.

4. The preparation method of the iron-crosslinked sodium alginate modified bagasse biochar according to claim 1, wherein ； The protective atmosphere is nitrogen. The heating rate during the pyrolysis treatment is 5 °C / min, the pyrolysis treatment temperature is 500-800 °C, and the pyrolysis treatment time is 2 h.

5. The preparation method of the iron-crosslinked sodium alginate modified bagasse biochar according to claim 1, wherein ； The ultrasonic treatment time is 1 h, the heating temperature is 60 °C, and the stirring time is 2 h.

6. The preparation method of the iron-crosslinked sodium alginate modified bagasse biochar according to claim 1, It is characterized in that; The concentration of the ferric chloride solution is 1-9 g / 100 mL, the static cross-linking time is 24 h. When performing the washing treatment, wash 3-4 times with ethanol and ultrapure water respectively until the filtrate is clear and neutral. The freeze-drying temperature is -80 °C and the time is 48 h.

7. An application of iron-crosslinked sodium alginate-modified bagasse biochar, which is prepared by using the preparation method of iron-crosslinked sodium alginate-modified bagasse biochar according to any one of claims 1-6, and is applied to treat tetracycline hydrochloride in water.

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