Preparation method of al-uio-66@bacterial cellulose beads and wastewater treatment method

Abstract

The application relates to a preparation method of Al-UIO-66@ bacterial cellulose beads and a wastewater treatment method, and belongs to the technical field of sewage treatment. The specific scheme is as follows: a preparation method of Al-UIO-66@ bacterial cellulose beads comprises the following steps: step one, uniformly mixing and dispersing purified bacterial cellulose after fermentation and deionized water to obtain bacterial cellulose dispersion solution I; step two, adding a chemical crosslinking agent to the bacterial cellulose dispersion solution I and heating to obtain a preliminarily crosslinked bacterial cellulose dispersion solution II, and dropping the bacterial cellulose dispersion solution II into a secondary crosslinking solution for crosslinking reaction; wherein the secondary crosslinking solution comprises aluminum chloride, zirconium chloride and anhydrous ethanol; and step three, placing the product after the crosslinking reaction in a ligand solution of UIO-66, and in-situ synthesizing Al-UIO-66@ bacterial cellulose beads through a water bath heating method. The prepared Al-UIO-66@ bacterial cellulose beads can realize efficient removal of TCH in wastewater as an adsorbent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sewage treatment, and relates to a preparation method of Al-UIO-66@ bacterial cellulose beads and a wastewater treatment method, in particular to a preparation method of Al-UIO-66@ bacterial cellulose bead composite material synthesized in situ by using bacterial cellulose as a skeleton and a water treatment method for efficiently removing antibiotics in water at room temperature by using Al-UIO-66@ bacterial cellulose beads. BACKGROUND

[0002] Antibiotics are mainly derived from secondary metabolites of microorganisms, and also include artificially synthesized substances with similar structures. They can inhibit or eliminate pathogenic microorganisms and are widely used in medical and breeding fields. Tetracycline antibiotics (TCs) are a kind of widely used antibiotics. Since animals and plants are difficult to digest and absorb TCs, about 50-80% of the intake of TCs will be converted into more toxic metabolites and enter the soil and rivers through excrement, which has an impact on the environment and human health.

[0003] Tetracycline hydrochloride (TCH) is a common TCs. At present, the commonly used methods for removing TCH include adsorption method, membrane technology method, photocatalysis method and biological method, etc. However, the biological method, the photocatalysis method and the membrane technology method all have their own disadvantages, resulting in high treatment cost, so the adsorption method is often the most widely used method in actual treatment. The mass transfer capacity and rate of the adsorbent can be realized by increasing the adsorption sites and improving the porosity, and metal organic framework (MOF) is a kind of nano adsorption material with large specific surface area and high porosity, and UIO-66 series is a typical MOF. In order to improve the adsorption effect, metal doping is one of the strategies to improve the adsorption performance of MOF, so the preparation of bimetallic UIO-66 by combining Al with UIO-66 series can effectively improve the adsorption effect. However, UIO-66 is a powdery solid, which has defects such as poor stability, easy aggregation and low biological safety, which greatly limits its application range. Bacterial cellulose is a high molecular substance with a three-dimensional network structure and rich functional groups, and the preparation of a composite material by combining bacterial cellulose with UIO-66 can improve the mechanical strength of the material and make up for the defects of UIO-66, but the high degree of polymerization of bacterial cellulose leads to its low solubility in water, which increases the difficulty of preparing bacterial cellulose composite material. In addition, in order to improve the specific surface area, permeability and hydraulic performance of the adsorbent, spherical adsorbent has attracted more and more attention, but the preparation of UIO-66@ bacterial cellulose beads has the defects of complex process and poor adsorption effect, so it is urgent to improve the preparation process to improve the adsorption performance of this type of material. SUMMARY

[0004] In order to solve the problems of poor treatment effect of conventional treatment process of sewage treatment plant on antibiotics in influent such as pharmaceutical wastewater and aquaculture wastewater, complex preparation process of existing adsorbent and poor adsorption effect, the application provides a preparation method of Al-UIO-66@ bacterial cellulose beads and a wastewater treatment method, and specifically applies to a water treatment method for efficiently removing antibiotics in water by using Al-UIO-66@ bacterial cellulose beads. The Al-UIO-66 and the bacterial cellulose beads are uniformly compounded, high-efficiency adsorption treatment of TCH is realized, and an effective treatment method for high-efficiency adsorption of antibiotics in water is provided.

[0005] In order to achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0006] A preparation method of Al-UIO-66@ bacterial cellulose bead composite material, comprising the following steps:

[0007] Step one, purify the fermented blocky bacterial cellulose and mix it with deionized water, and use a food processor to disperse to obtain a bacterial cellulose dispersion liquid I;

[0008] Step two, add a chemical crosslinking agent to the bacterial cellulose dispersion liquid I and heat to obtain a preliminarily crosslinked bacterial cellulose dispersion liquid II, and at the same time, realize uniform dispersion of the flocculent bacterial cellulose in the bacterial cellulose dispersion liquid II; drop the bacterial cellulose dispersion liquid II into a secondary crosslinking liquid to perform crosslinking reaction to obtain bacterial cellulose beads, wherein the secondary crosslinking liquid comprises aluminum chloride, zirconium chloride and anhydrous ethanol, and the metal ions are uniformly attached to the bacterial cellulose skeleton by forming coordination bonds while crosslinking into balls;

[0009] Step three, place the bacterial cellulose beads in a ligand solution of UIO-66, and synthesize Al-UIO-66@ bacterial cellulose beads in situ by water bath heating method.

[0010] Further, in step one, the purification treatment step is: rinsing the fermented bacterial cellulose block with deionized water, then adding it to a 0.1-0.2M NaOH solution, stirring and boiling for 1-2h until it becomes white and translucent, then repeatedly rinsing the bacterial cellulose block with a 0.5-0.8% acetic acid solution and deionized water until the filtrate is neutral to obtain the purified bacterial cellulose block.

[0011] Further, in step one, the food processor parameters are 20000-22000r / min, and the operation time is 20-30min. The solid content of the bacterial cellulose dispersion liquid I is 0.6-0.7%, which is a suspension liquid containing flocculent substances.

[0012] Further, in step two, the added chemical crosslinking agent is selected as a 50% mass fraction glutaraldehyde solution, and the added amount is 5.3 mL per 100 mL of the bacterial cellulose dispersion solution I. Then the pH value of the bacterial cellulose dispersion solution I is adjusted to 7-8 using acid and alkali solutions, and the preliminary crosslinking is carried out under heating to obtain a uniformly dispersed flocculent bacterial cellulose dispersion solution II.

[0013] Further, in step two, the acid solution used for adjusting the pH value is a 20-30% mass fraction hydrochloric acid solution, the alkali solution used is a 1M sodium hydroxide solution, the heating temperature is 75-80°C, and the heating and stirring time is 40-50 min.

[0014] Further, in step two, the bacterial cellulose dispersion solution II is dropped into the secondary crosslinking solution using a needle tube, and the secondary crosslinking and the coordination process of Zr 4+ , Al 3+ are simultaneously carried out, and the formed bacterial cellulose beads are filtered out after 4-5 h, and subsequent material synthesis is carried out.

[0015] Further, in step two, the secondary crosslinking solution is a mixed solution of aluminum chloride, zirconium chloride and anhydrous ethanol, and the proportion is 6-7 mL of anhydrous ethanol, 1:1 molar ratio of aluminum chloride and zirconium chloride, and the total amount of substance of the aluminum chloride and the zirconium chloride is 2.047-4.094 mmol per 10 mL of deionized water.

[0016] Further, in step three, the ligand solution of UIO-66 includes a DMF solvent, a ligand and glacial acetic acid, the ligand is 2-hydroxyterephthalic acid (H2BDC) or 2-amino terephthalic acid (H2BDC-NH2), the content of the ligand is 2.0-3.0 mmol per 10 mL of DMF, and the amount of glacial acetic acid is 1 mL per 10 mL of DMF.

[0017] The bacterial cellulose beads are placed in the ligand solution of UIO-66, and then poured into a 50 mL high-pressure kettle with a polytetrafluoroethylene lining, and kept in a 120°C oven for 24 h, and after natural cooling, the composite bacterial cellulose beads are filtered out, and washed with DMF and methanol multiple times to obtain a product, and the amount of DMF and methanol used for each washing is 10 mL; then the composite bacterial cellulose beads are washed with deionized water multiple times, and finally Al-UIO-66@bacterial cellulose beads with the function of efficiently removing antibiotics in water are obtained.

[0018] The yield of the Al-UIO-66@bacterial cellulose beads is calculated by the following method: 1 mL of the bacterial cellulose dispersion solution II obtained by titration crosslinking and water bath heating is filtered, the surface moisture is wiped dry, and then freeze-dried at -43°C for 12 h to completely remove the water therein, and then the dry weight is measured to obtain the material yield.

[0019] A water treatment method for efficiently removing antibiotics in water by using Al-UIO-66@ bacterial cellulose beads, for treating antibiotic pollutants in water bodies, the water treatment method is completed by the following steps:

[0020] Al-UIO-66@ bacterial cellulose bead composite material is synthesized by using bacterial cellulose as a skeleton to support Al-UIO-66; a certain amount of Al-UIO-66@ bacterial cellulose beads is put into a solution containing TCH, and under certain conditions, uniform shaking is continuously carried out, so that efficient removal of TCH can be achieved within a few hours.

[0021] The concentration of the used TCH solution is 30-50 mg / L, the pH of the solution is 4-7, and the dry weight of Al-UIO-66@ bacterial cellulose beads is 0.3-0.6 g / L. The TCH solution containing Al-UIO-66@ bacterial cellulose bead adsorbent is placed on a shaker for continuous uniform shaking for adsorption, and samples are taken at specific time points, filtered through a 0.22 mu m filter membrane, and then the remaining TCH content in the solution is determined by spectrophotometry.

[0022] The working parameters of the shaker are 350-360 rpm and 20-25 DEG C; the sampling specific time points are 0, 0.5, 1, 2, 3, 4, 5, 8, 12, 24, 36 and 48 hours after the start of adsorption; and the wavelength for spectrophotometry measurement is 357 nm.

[0023] Compared with the prior art, the beneficial effects of the present application are:

[0024] The application uses a bacterial cellulose material with good structure as a skeleton and grows Al-UIO-66 in situ to obtain a uniform composite material, and uses the material to achieve efficient removal of TCH in water. The Al-UIO-66@bacterial cellulose bead material with a dry base concentration of 0.6 g / L is used to adsorb 30 mL of TCH with a concentration of 30 mg / L, and 98.27% of the TCH can be removed in 4 hours. Compared with the treatment effect of the traditional activated sludge system, the removal rate of the material to TCH is 63.8% higher, indicating that the water treatment method can achieve efficient adsorption and removal of TCH. Compared with the same mass of pure bacterial cellulose block, the removal rate of the bacterial cellulose bead prepared in step two to TCH is increased by 60.44% in 4 hours, indicating that the spherical adsorbent has good adsorption effect. The Al-UIO-66@bacterial cellulose bead composite material with a dry base concentration of 0.35 g / L is used to adsorb 70 mL of TCH with a concentration of 50 mg / L, and the adsorption capacity can reach 150.19 mg / g. Compared with UIO-66@bacterial cellulose beads without Al doping, the doping of Al increases the adsorption capacity of the composite material to TCH by about 24.51%, indicating that the introduction of Al can significantly improve the adsorption performance of the material, and the combination of UIO-66 and bacterial cellulose also makes up for the disadvantage that UIO-66 powder is difficult to separate in water. The method is simple in operation and stable in synthesis, and can be applied to the treatment of flowing wastewater containing antibiotics in a fluidized bed process. Not only the uniform preparation of the composite material is realized, but also the production cost is reduced, and a series of environmental problems caused by the poor removal effect of antibiotic pollution in the inflow of the sewage treatment plant are solved, so the application prospect is wide. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 : Comparison chart of TCH removal rates of Al-UIO-66@bacterial cellulose beads, bacterial cellulose beads and step one bacterial cellulose blocks prepared in example 1;

[0026] Figure 2 : Comparison chart of TCH adsorption capacities of Al-UIO-66@bacterial cellulose beads and UIO-66@bacterial cellulose beads in example 2;

[0027] Figure 3 : (a) Al-UIO-66@bacterial cellulose beads in example 1, (b) Al-UIO-66@bacterial cellulose beads in example 2, (c) Al-UIO-66@bacterial cellulose beads saturated with adsorption in example 2. DETAILED DESCRIPTION

[0028] The technical solutions in the present application will be clearly and completely described below in combination with the drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0029] Embodiment 1

[0030] A preparation method of Al-UIO-66@bacterial cellulose beads and a method for efficiently removing antibiotics in wastewater by using the Al-UIO-66@bacterial cellulose beads, comprising the following steps:

[0031] I. Take the fermented bacterial cellulose block in 0.15M NaOH solution and stir-boil for 1h, and then wash it to neutral with 0.5% acetic acid solution and deionized water. Mix the treated bacterial cellulose block with deionized water and add it into a food processor, and disperse it at 20000r / min for 20min to obtain a bacterial cellulose dispersion I with a solid content of 0.66%.

[0032] II. Take 15mL of the bacterial cellulose dispersion I in a beaker, add 0.8mL of 50% glutaraldehyde solution, adjust the pH to 7.56 with 20-30% hydrochloric acid solution and 1M sodium hydroxide solution, and then put it into an oil bath at 80℃ and stir for 45min to obtain a bacterial cellulose dispersion II. Use a needle to extract 2mL of the crosslinked bacterial cellulose dispersion II, and then drop it into a secondary crosslinking solution at a speed of 3 seconds / drop, and then stand for crosslinking for 5h and filter to obtain bacterial cellulose beads. Then wash the filtered bacterial cellulose beads with deionized water and put them into a UIO-66 ligand solution, and then put them into a high-pressure kettle with a polytetrafluoroethylene liner and keep them at 120℃ for 24h. After the reaction is completed, naturally cool them to room temperature and filter, wash the filtered product with DMF and methanol three times, each time using 10mL of DMF and methanol, and then wash them with a large amount of deionized water until the surface is neutral, and then Al-UIO-66@bacterial cellulose beads material can be obtained. The secondary crosslinking solution is configured as follows: 10mL of deionized water is added with 6.67mL of anhydrous ethanol, 0.273g of aluminum chloride and 0.477g of zirconium chloride (the total amount of substance of aluminum chloride and zirconium chloride is 4.094mmol). The UIO-66 ligand solution is configured as follows: 2.047mmol of H2BDC-NH2 is added into 10mL of DMF, and then 1mL of glacial acetic acid is added after the mixture is uniformly mixed.

[0033] Three, 30 mL of TCH solution with a concentration of 30 mg / L was prepared, and the Al-UIO-66@ bacterial cellulose beads prepared in the above step were added, with a dry base concentration of 0.6 g / L, and the pH was adjusted to 4.01. The same amount of pure bacterial cellulose block and bacterial cellulose beads prepared in step two were subjected to comparative experiments under the above conditions. The samples were taken at 0, 0.5, 1, 2, 3 and 4 hours after the start of adsorption, and the TCH concentration in the solution was analyzed at 357 nm by spectrophotometry after filtration with a 0.22 μm filter, and the TCH content removed by each adsorbent and the corresponding adsorption capacity were calculated.

[0034] According to the above method, the dry weight yield of the Al-UIO-66@ bacterial cellulose bead composite material corresponding to 1 mL of bacterial cellulose dispersion solution II was about 18.1 mg. After 4 hours of adsorption of 30 mL of TCH solution with a concentration of 30 mg / L under the above conditions, about 98.27% of TCH was removed. The removal rate of traditional activated sludge system for many common TCs is only 50-70%, and the removal effect of the material is improved by 63.8%. Compared with the same amount of pure bacterial cellulose block, the removal rate of the bacterial cellulose beads prepared in step two for 30 mL of TCH solution with a concentration of 30 mg / L within 4 hours is increased by 60.44%. Therefore, the adsorption material prepared according to the embodiment has good removal effect on antibiotic pollutants in water.

[0035] Example 2:

[0036] A preparation method of Al-UIO-66@ bacterial cellulose beads and a method for efficiently removing antibiotics in wastewater by using Al-UIO-66@ bacterial cellulose beads, comprising the following steps:

[0037] One, the fermented bacterial cellulose block was stirred and boiled in 0.15M NaOH solution for 1 hour, and then washed to neutral with 0.5% acetic acid solution and deionized water. The treated bacterial cellulose block was mixed with deionized water and added to a food processor to disperse at 20000 r / min for 20 min to obtain a bacterial cellulose dispersion solution I with a solid content of 0.66%.

[0038] II. Take 15 mL of the bacterial cellulose dispersion I, add 0.8 mL of 50% glutaraldehyde solution, use 20-30% hydrochloric acid solution and 1 M sodium hydroxide solution to adjust the pH to 7.42, and put it in an oil bath at 80°C for 45 min to obtain the bacterial cellulose dispersion II. Use a needle to extract 2 mL of the cross-linked bacterial cellulose dispersion II, and drop it into the secondary cross-linking solution at a speed of 3 seconds / drop. After standing for 4 h, filter to obtain the bacterial cellulose beads. Then wash the filtered bacterial cellulose beads with deionized water, and put them into the ligand solution of UIO-66 in a high-pressure kettle with a polytetrafluoroethylene liner at 120°C for 24 h. After the reaction, cool it to room temperature naturally and filter, wash the filtered product with DMF and methanol three times, each time using 10 mL of DMF and methanol, and wash with a large amount of deionized water until the surface is neutral, to obtain the Al-UIO-66@ bacterial cellulose bead material. The configuration of the secondary cross-linking solution: add 6.67 mL of anhydrous ethanol, 0.136 g of aluminum chloride and 0.238 g of zirconium chloride (2.047 mmol in total) to 10 mL of deionized water. The configuration of the UIO-66 ligand solution: add 2.958 mmol of H2BDC to 10 mL of DMF, mix well, and then add 1 mL of glacial acetic acid.

[0039] III. Prepare 70 mL of a TCH solution with a concentration of 50 mg / L, add the Al-UIO-66@ bacterial cellulose beads prepared in the above step, with a dry base concentration of 0.35 g / L, adjust the pH to 4.34, and continuously shake at 360 rpm and 25°C on a shaker. At the same time, perform a control experiment using the same amount of UIO-66@ bacterial cellulose beads (the preparation of UIO-66@ bacterial cellulose beads is the same as that of Al-UIO-66@ bacterial cellulose beads, except that the secondary cross-linking solution is different. The formula of the secondary cross-linking solution for preparing UIO-66@ bacterial cellulose beads is: add 6.67 mL of anhydrous ethanol and 0.477 g of zirconium chloride to 10 mL of deionized water). Take samples at 0, 0.5, 1, 2, 3, 4, 5, 8, 12, 24, 36 and 48 h after the start of adsorption, filter with a 0.22 μm filter membrane, and analyze the concentration of TCH in the solution at 357 nm by spectrophotometry, to calculate the TCH content removed by the adsorbent and the corresponding adsorption capacity.

[0040] According to the above method, the dry weight yield of the Al-UIO-66@ bacterial cellulose bead composite material corresponding to 1 mL of bacterial cellulose dispersion solution II is about 24.3 mg, the dry weight yield of the UIO-66@ bacterial cellulose bead prepared from 1 mL of bacterial cellulose dispersion solution II is about 32.1 mg, and the adsorption capacity of the Al-UIO-66@ bacterial cellulose bead after 48 h of adsorption of a 70 mL TCH solution with a concentration of 50 mg / L can reach 150.19 mg / g. Compared with the UIO-66@ bacterial cellulose bead, the adsorption capacity of the composite material doped with Al for TCH is increased by about 24.51%. It can be seen that the material prepared according to the present embodiment has good removal effect on antibiotic pollutants in water.

[0041] In addition, it should be understood that although the present specification is described in terms of embodiments, each embodiment does not necessarily contain only one independent technical solution, and the description of the specification is only for the sake of clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A method for preparing Al-UIO-66@bacterial cellulose beads, characterized in that, The method comprises the following steps: Step one, purify the fermented bacterial cellulose and mix it with deionized water to obtain a bacterial cellulose dispersion I; Step two, add a chemical crosslinking agent to the bacterial cellulose dispersion I and heat to obtain a preliminary crosslinked bacterial cellulose dispersion II, and then drop the bacterial cellulose dispersion II into a secondary crosslinking solution to perform a crosslinking reaction to obtain bacterial cellulose beads; the secondary crosslinking solution comprises aluminum chloride, zirconium chloride and anhydrous ethanol; the chemical crosslinking agent is a 50% glutaraldehyde solution, and the volume ratio of the chemical crosslinking agent to the bacterial cellulose dispersion I is 5.3:100; the secondary crosslinking solution is prepared by adding 6-7 mL of anhydrous ethanol, 1:1 molar ratio of aluminum chloride and zirconium chloride into 10 mL of deionized water, and the total amount of aluminum chloride and zirconium chloride is 2.047-4.094 mmol; Step three, place the bacterial cellulose beads in a ligand solution of UIO-66, and in-situ synthesize Al-UIO-66@ bacterial cellulose beads by a water bath heating method; the ligand solution of UIO-66 comprises a DMF solvent, a ligand and glacial acetic acid, the ligand is 2-hydroxyterephthalic acid or 2-amino terephthalic acid, and the content of the ligand is 2.0-3.0 mmol per 10 mL of DMF, and the amount of glacial acetic acid is 1 mL per 10 mL of DMF.

2. The method of claim 1, wherein: In step one, the purification treatment is as follows: rinse the fermented bacterial cellulose block with deionized water, then add it to a 0.1-0.2 M NaOH solution, stir and boil until it becomes white and translucent, and then repeatedly rinse the bacterial cellulose block with a 0.5-0.8% acetic acid solution and deionized water until the filtrate is neutral.

3. The method of claim 1, wherein: In step one, the solid content of the bacterial cellulose dispersion I is 0.6-0.7%.

4. The method of claim 1, wherein: In step two, after adding the chemical crosslinking agent to the bacterial cellulose dispersion I, adjust the pH to 7-8 using an acid-base solution, and then heat to obtain the preliminary crosslinked bacterial cellulose dispersion II; the heating temperature is 75-80 ℃, and the heating time is 40-50 min.

5. The method of claim 1, wherein: In step three, the temperature of the water bath heating method is 120 ℃, and the time is 24 h.

6. A wastewater treatment method using the Al-UIO-66@bacterial cellulose beads prepared by the method of any one of claims 1-5, characterized in that: Put the Al-UIO-66@ bacterial cellulose beads into a solution containing TCH and shake to remove TCH.

7. The wastewater treatment method according to claim 6, characterized by: The concentration of TCH in the solution containing TCH is 30-50 mg / L, the pH of the solution is 4-7, and the dry weight of the Al-UIO-66@ bacterial cellulose beads is 0.3-0.6 g / L.

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