Preparation method of poplar biochar for adsorbing antibiotics

Abstract

The present invention provides a method for preparing poplar biochar for adsorbing antibiotics, comprising: washing, drying, crushing, and sieving poplar wood to obtain biomass powder; immersing the biomass powder in an alkaline solution for activation, taking it out and drying it, and then heating it under vacuum conditions for carbonization; grinding and sieving the carbonized material, and washing it with acid and water in sequence to obtain poplar biochar. Magnetic poplar biochar is further prepared by co-precipitation. The poplar biochar and magnetic poplar biochar prepared by the present invention both have good adsorption effects on antibiotics in water, and the adsorption properties are changed after magnetic modification. The preparation method of the present invention is simple and feasible, and has the advantages of low cost and wide source, and has a good removal effect on tetracyclines and fluoroquinolones in water, and is suitable for remediation of antibiotic pollution in water bodies.

Description

Technical Field

[0001] The invention relates to the technical field of water adsorption materials, and in particular to a method for preparing poplar biochar for adsorbing antibiotics. Background Art

[0002] Antibiotics play an important role in daily life and are mostly used for antibacterial purposes. Among them, the most commonly used antibiotics are sulfonamides, tetracyclines, fluoroquinolones, macrolides and β-lactams. It is reported that TCs are the second most used antibiotics in the world. This is a group of broad-spectrum antibiotics that includes tetracycline, doxycycline, doxycycline and chlortetracycline. Fluoroquinolones FQs, such as ciprofloxacin, enrofloxacin, enrofloxacin and norfloxacin, are the most important class of antibacterial agents for the treatment of various bacterial infections. However, only a small part of the antibiotics used in humans and animals is metabolized or absorbed in the body. In addition, most antibiotics and their metabolites are excreted into the environment. Surveys show that the concentration of residual antibiotics in soil ranges from 10 -3 to 10 3 Concentrations of FQs range from 100 μg / kg to 200 μg / kg. In a few areas, FQs and TCs are the primary residues in cultivated land. Antibiotic residues have also been detected in various aquatic environments. Antibiotic surveys in major rivers and four marine areas revealed that TCs and FQs can be found in various water bodies. Ofloxacin, enrofloxacin, norfloxacin, and ciprofloxacin had the highest concentrations, reaching μg / L and μg / g in water and sediment, respectively.

[0003] Methods for removing antibiotics from water include advanced oxidation, adsorption, membrane technology, and coagulation-flocculation. Adsorption is a very effective technology for removing and treating pollutants. Due to its advantages such as simple operation, low cost, and high efficiency, it has received great attention. In recent years, the use of biomass to prepare cheap biochar has become an important treatment method for the adsorption of antibiotics in water. Different biomass raw materials have significant performance differences in the prepared biochar due to differences in their elemental content and microstructure. For example, there are large differences in the carbon content and microstructure of straw and wood biomass. Therefore, how to select a biomass that is suitable for efficient adsorption of antibiotics and has a simple preparation method among the many biomass raw materials is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing poplar biochar for adsorbing antibiotics. Poplar wood is used as raw material, and a biochar suitable for adsorbing antibiotics is obtained through activation and carbonization. Through magnetic modification, the biochar is given a magnetic separation function and its adsorption performance can be adjusted.

[0005] To achieve the above object, the present invention provides a method for preparing poplar biochar for adsorbing antibiotics, comprising:

[0006] S1. Crush and sieve the poplar wood to obtain a poplar wood biomass powder;

[0007] S2. The biomass powder is activated by immersing in an alkaline solution, removed and dried, and then heated and carbonized under vacuum conditions;

[0008] S3. The carbonized material is ground and sieved, and then washed sequentially with acid and water to obtain poplar biochar. Woody biomass is abundant, but due to its dense texture, it is generally not considered a suitable material for adsorption. However, the present invention has experimentally discovered that simple activation and carbonization of poplar wood exhibits excellent adsorption properties in the field of antibiotic adsorption, breaking with conventional thinking and providing an effective method for the preparation of simple and efficient antibiotic adsorption materials.

[0009] Furthermore, in step S2, the heating rate of the carbonization is 3-6°C / min, preferably 5°C; the carbonization temperature is 450-550°C, preferably 500°C; and the carbonization time is 1-4 hours, preferably 2-3 hours.

[0010] Furthermore, the alkaline solution is potassium hydroxide or sodium hydroxide aqueous solution.

[0011] Furthermore, the mass fraction of the alkaline solution is 20-35%, and the immersion activation time is 30-90 minutes. Alkaline activation promotes carbonization, increases the biochar porosity and the content of surface active groups, and facilitates uniform loading during subsequent magnetic modification. A KOH aqueous solution with a solubility of 4.11 mol / L is preferred.

[0012] Furthermore, in step S1, the sieving is performed using a 200-mesh screen. Using small-particle biomass raw materials facilitates activation and carbonization, further improving the carbonization effect.

[0013] Furthermore, in step S3, the sieving is performed using a 200-mesh sieve; and the acid is 0.5-1.5 mol / L HCl, preferably 1 mol / L.

[0014] Furthermore, the preparation method further includes: mixing the poplar biochar obtained in step S3 with a solution of divalent and trivalent iron salts, then adding ammonia water dropwise in a nitrogen atmosphere for co-precipitation for 10-13 hours, washing and drying (preferably vacuum drying at 80°C for 12 hours) to obtain the magnetic poplar biochar. Under the action of ammonia water, the divalent and trivalent iron salts gradually form ferroferric oxide, which is loaded on the surface and pores of the biochar. Due to the excellent graphitized structure and high content of surface active groups of poplar biochar, it is conducive to the formation and adsorption of ferroferric oxide and can improve magnetic properties.

[0015] Furthermore, the divalent and trivalent iron salt solutions are (NH4)2Fe(SO4)2·6H2O and NH4Fe(SO4)2·12H2O aqueous solutions in a molar ratio of (0.8-1.3):2, preferably (1.1-1.2):2. Controlling the appropriate molar ratio facilitates the formation of a well-structured magnetic ferrosoferric oxide, thereby improving its magnetic separation performance. The ammonia concentration is 8 mol / L. The coprecipitation reaction temperature is preferably 50°C, and the reaction time is 12 hours.

[0016] Furthermore, the molar ratio of poplar biochar to iron from divalent and trivalent iron salts is 1g:(0.01-0.03)mol, preferably 1g:(0.02-0.026)mol. By controlling the amount of poplar biochar and iron, optimal magnetic biochar performance can be achieved. Magnetic modification not only imparts magnetic properties to biochar but also modulates its antibiotic adsorption properties.

[0017] The magnetic biochar prepared by the present invention has a large specific surface area (122.12m 2 / g), rich pore structure (total pore volume 0.46cm 3 / g), good magnetic properties (saturation magnetization 59.685emu / g.

[0018] Furthermore, the antibiotics include tetracycline (TC), doxycycline (DOX), and oxytetracycline (OTC), and the FQs are enrofloxacin (ENR), enoxacin (ENO), and norfloxacin (NOR).

[0019] The poplar biochar or magnetic poplar biochar prepared by the present invention was added to an aqueous solution containing TCs and FQs antibiotics at a concentration of 1-60 mg / L. An adsorption reaction was performed at a temperature of 25-45°C to detect the antibiotic content in the water. The magnetic poplar biochar showed a maximum adsorption capacity of 70.28-89.58 mg / g for tetracycline antibiotics (tetracycline, doxycycline, and oxytetracycline) in water, and a maximum adsorption capacity of 35.54-60.31 mg / g for fluoroquinolone antibiotics (enrofloxacin, enoxacin, and norfloxacin).

[0020] The beneficial effects of the present invention are as follows:

[0021] (1) The method for preparing poplar biochar for adsorbing antibiotics provided by the present invention uses poplar as raw material and obtains poplar biochar with good adsorption performance for antibiotics in water through simple activation and carbonization. The removal rate can reach up to 99.92%, which provides an effective way to prepare antibiotic adsorption materials.

[0022] (2) The present invention uses discarded poplar wood as raw material, which has the advantages of easy availability of raw materials and low cost, realizes waste recycling, and has environmental protection significance.

[0023] (3) The present invention obtains magnetic poplar biochar by coprecipitation modification of poplar biochar, which not only imparts magnetic separation function but also adjusts its adsorption properties. The prepared magnetic biochar has good adsorption properties for antibiotics. At 0.5 g / L of adsorbent, the maximum adsorption capacity for TC, DOC, and OTC can reach 70.28–89.58 mg / g, and the maximum adsorption capacity for ENR, ENO, and NOR can reach 35.54–60.31 mg / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is a diagram showing the magnetic separation effects of MPBC-2h, MPBC-8h, and MPBC-12h.

[0026] Figure 2 This is the SEM image of MPBC-12h.

[0027] Figure 3 This is the XRD pattern of MPBC-12h.

[0028] Figure 4 Nitrogen adsorption-desorption curve and pore size distribution diagram of MPBC-12h.

[0029] Figure 5 FT-IR spectra of PBC and MPBC-12h.

[0030] Figure 6 This is the magnetic hysteresis curve of MPBC-12h.

[0031] Figure 7 This is the effect of time on the adsorption capacity of MPBC-12h.

[0032] Figure 8 The effect of initial concentration on the adsorption capacity of MPBC-12h

[0033] Figure 9 This is the effect of temperature on the adsorption capacity of MPBC-12h. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] Biomass selection

[0037] Biochar was prepared from three different biomass sources: bamboo powder, corn straw, and poplar wood. The raw materials were passed through a 200-mesh sieve, and 5g of powder was added to 10mL of a 30% KOH aqueous solution. The mixture was left to activate for 1h and then dried in a vacuum drying oven at 80°C for 3h. The activated biochar powder was placed in a vacuum tube furnace, heated to 500°C at a heating rate of 5°C / min, and pyrolyzed at 500°C for 2h. After cooling, the mixture was ground through a 200-mesh sieve, thoroughly washed with 1mol / L HCl, then washed with distilled water until neutral, and dried in a vacuum drying oven at 80°C for 12h to obtain bamboo powder biochar (BBC), corn straw biochar (CSBC), and poplar wood biochar (PBC), respectively.

[0038] 5 mg of each of the three biochars were added to 10 mL of a 2 ppm antibiotic solution. After vortexing for 5 minutes, the solution was filtered through a 0.22 μm water filter and measured using LC-MS / MS. The experiment was repeated three times. The removal rates are shown in Table 1. It can be seen that the present invention can effectively remove antibiotic solutions with a concentration of only 2 ppm. After removal, the remaining antibiotic concentration in the solution is less than 10 -2 ppm. It can be seen that the removal effect is excellent.

[0039] Table 1 Effect of different biochars on antibiotic removal rate

[0040]

[0041] Example 2

[0042] Preparation of magnetic poplar biochar

[0043] 4.84 g NH4Fe(SO4)2·12H2O and 1.96 g (NH4)2Fe(SO4)2·6H2O were ultrasonically dissolved (200 W, 40 kHz) in 100 mL of distilled water, 1 g PBC (poplar biochar) was added, and the mixture was stirred for 30 min in a nitrogen atmosphere. Then 10 mL of 8 mol / L ammonia water was added dropwise, and the mixture was stirred and heated at 50 °C for 2 h, 8 h, and 12 h, respectively. After cooling to room temperature, the obtained product was alternately washed with distilled water and ethanol until the supernatant was colorless, and then dried in a vacuum drying oven at 80 °C for 12 h to obtain magnetic poplar biochar MPBC-2h, MPBC-8h, and MPBC-12h, respectively.

[0044] 5 mg of MPBC-2h, MPBC-8h, and MPBC-12h were added to 5 mL of aqueous solution and separated using an external magnet. The separation effect was as follows: Figure 1 As shown, MPBC-12h has the best magnetic separation effect, and MPBC-12h was used in subsequent adsorption experiments.

[0045] like Figure 2 Shown is the SEM image of MPBC-12h, combined with Figure 3-6 This shows that the present invention successfully prepared magnetic biochar. Figure 4 It can be seen that the average pore diameter of biochar is about 25 nm.

[0046] Example 3

[0047] Effect of adsorption time

[0048] Prepare 20 mL of 2 mg / L antibiotic aqueous solution in a 50 mL centrifuge tube, then add 10 mg of MPBC. Oscillate at 180 rpm in a constant temperature oscillator at 25°C. Sampling is performed at 0, 10, 20, 30, 40, 50, 60, 120, 240, 360, and 540 min, respectively. The solution is first magnetically separated and then filtered through a 0.22 μm water filter membrane for determination by LC-MS / MS. The experiment is repeated three times.

[0049] Figure 7 is the effect of time on MPBC adsorption. Figure 7It can be seen that the adsorption of six antibiotics by MPBC shows a trend of first increasing and then gradually stabilizing with the increase of time. The total content of antibiotics relative to MPBC is 4 mg / g (removal rate 100%). It can be seen that the removal rates of six antibiotics by MPBC are basically above 87.5%, and basically reach saturated adsorption capacity at 100 minutes, indicating that the adsorption rate is fast. Among them, the adsorption capacity of TC, OTC and DOX is the highest, and the removal rate reaches 98%. It can be seen that the present invention also has a good removal effect on antibiotic aqueous solutions with a concentration of only 2 ppm, so that the remaining antibiotic concentration in the solution is only 10 -2 ppm.

[0050] Compared to the removal rates in Table 1, the adsorption efficiency of biochar for different types of antibiotics varies after magnetic modification. The removal rates for DOX and TC are significantly improved, indicating that the adsorption properties have changed after magnetic modification. Furthermore, in practical applications, the magnetism can be controlled to tailor the adsorption of antibiotics to meet specific needs, while also achieving efficient magnetic separation. Furthermore, the MPBC of the present invention contains approximately 60 wt% ferrosoferric oxide compared to PBC. In this case, even with the same adsorbent dosage, it can achieve an adsorption rate comparable to PBC. This demonstrates that the magnetic biochar of the present invention still possesses good adsorption properties, and the ferrosoferric oxide in MPBC has a promoting effect.

[0051] Example 4

[0052] Effect of initial antibiotic concentration

[0053] In a 50 mL centrifuge tube, 40 mL of antibiotic aqueous solution with concentrations of 1, 2, 5, 10, 20, 40, and 60 mg / L was prepared, and then 10 mg of MPBC was added thereto. The solution was shaken at 180 rpm in a constant temperature oscillator at 25°C. After 9 hours of shaking, samples were collected, magnetically separated, and then filtered through a 0.22 μm water filter membrane for determination by LC-MS / MS. The experiment was repeated three times.

[0054] Figure 8 is the effect of initial antibiotic concentration on MPBC adsorption. Figure 8 It can be seen that the adsorption capacity of MPBC for the six antibiotics first increases and then gradually stabilizes with the increase of initial concentration. Among them, the saturated adsorption capacity of OTC, TC and DOX is the highest.

[0055] Example 4

[0056] Effect of temperature

[0057] In a 50 mL centrifuge tube, 40 mL of antibiotic aqueous solution with concentrations of 1, 2, 5, 10, 20, 40, and 60 mg / L was prepared, and then 10 mg of MPBC was added thereto. The solution was shaken at 180 rpm in a constant temperature oscillator at 25°C, 35°C, and 45°C, respectively. After shaking for 9 hours, samples were collected, magnetically separated, and then filtered through a 0.22 μm water filter membrane for determination by LC-MS / MS. The experiment was repeated three times.

[0058] Figure 9 The effect of different temperatures on MPBC adsorption. Figure 9 The adsorption capacity of antibiotics by MPBC increased with increasing temperature. At 25°C, the maximum adsorption capacity of MPBC for the six antibiotics ranged from 35.54 to 73.32 mg / g; at 35°C, the maximum adsorption capacity ranged from 36.35 to 78.39 mg / g; and at 45°C, the maximum adsorption capacity ranged from 40.56 to 89.58 mg / g. The adsorption capacity for TC, OTC, and DOX was particularly high.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing poplar biochar for adsorbing antibiotics, characterized in that: include: S1. Crush and sieve the poplar wood to obtain a poplar wood biomass powder; S2. The biomass powder is activated by immersing in an alkaline solution, removed and dried, and then heated and carbonized under vacuum conditions; The heating rate of the carbonization is 3-6°C / min, the carbonization temperature is 450-550°C, and the carbonization time is 1-4h; S3. The carbonized material was ground and sieved, and washed with acid and water to obtain poplar biochar; The preparation method further comprises: mixing the poplar biochar obtained in step S3 with a divalent and trivalent iron salt solution, then dropwise adding ammonia water in a nitrogen atmosphere for co-precipitation for 10-13 hours, and washing and drying to obtain the magnetic poplar biochar; The divalent and trivalent iron salt solutions are (NH4)2Fe(SO4)2·6H2O and NH4Fe(SO4)2·12H2O aqueous solutions, with a molar ratio of (0.8-1.3):2; The mass molar ratio of the poplar biochar to the iron element in divalent and trivalent iron salts is 1g: (0.01-0.03)mol.

2. The method for preparing poplar biochar for adsorbing antibiotics according to claim 1, characterized in that: The alkaline solution is potassium hydroxide or sodium hydroxide aqueous solution.

3. The method for preparing poplar biochar for adsorbing antibiotics according to claim 1, characterized in that: The mass fraction of the alkaline solution is 20-35%, and the immersion activation time is 30-90 minutes.

4. The method for preparing poplar biochar for adsorbing antibiotics according to claim 1, characterized in that: In step S1, the sieving is performed using a 200-mesh sieve.

5. The method for preparing poplar biochar for adsorbing antibiotics according to claim 1, characterized in that: In step S3, the sieving is performed using a 200-mesh sieve; and the acid is 0.5-1.5 mol / L HCl.

6. The method for preparing poplar biochar for adsorbing antibiotics according to any one of claims 1 to 5, characterized in that: The antibiotics include tetracycline, doxycycline, oxytetracycline, enrofloxacin, enoxacin, and norfloxacin.

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