Preparation method of Al-UIO-66 bacterial cellulose beads and wastewater treatment method

Abstract

The invention relates to a preparation method of Al-UIO-66 at bacterial cellulose beads and a wastewater treatment method, and belongs to the technical field of sewage treatment, and the specific scheme is as follows: the preparation method of the Al-UIO-66 at bacterial cellulose beads comprises the following steps: step 1, uniformly mixing and dispersing purified and fermented bacterial cellulose and deionized water to obtain a bacterial cellulose dispersion liquid I; 2, adding a chemical cross-linking agent into the bacterial cellulose dispersion liquid I, heating to obtain a preliminarily cross-linked bacterial cellulose dispersion liquid II, and dropwise adding the bacterial cellulose dispersion liquid II into the secondary cross-linking liquid for cross-linking reaction; wherein the secondary cross-linking liquid comprises aluminum chloride, zirconium chloride and absolute ethyl alcohol; and step 3, putting a product obtained after the cross-linking reaction into a ligand solution of UIO-66, and synthesizing the Al-UIO-66 at bacterial cellulose beads in situ through a water bath hot method. The prepared Al-UIO-66 (at) bacterial cellulose beads can be used as an adsorbent to realize efficient removal of TCH in wastewater.

Description

Technical Field

[0001] The invention 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, and specifically relates to a preparation method of an Al-UIO-66@bacterial cellulose bead composite material that uses bacterial cellulose as a skeleton to in situ synthesize Al-UIO-66@bacterial cellulose beads, and a water treatment method that uses Al-UIO-66@bacterial cellulose beads to efficiently remove antibiotics in water at room temperature. Background Art

[0002] Antibiotics are mainly derived from secondary metabolites of microorganisms, but also include artificially synthesized substances with similar structures. They can inhibit or eliminate pathogenic microorganisms and are widely used in medical and aquaculture fields. Tetracycline antibiotics (TCs) are a class of widely used antibiotics. Since animals and plants have difficulty digesting and absorbing TCs, about 50-80% of TCs intake will be converted into more toxic metabolites and enter the soil and rivers through excrement, affecting the environment and human health.

[0003] Tetracycline hydrochloride (TCH) is a common TCs. Currently, the commonly used methods for removing TCH include adsorption, membrane technology, photocatalysis and biological methods. However, since biological, photocatalysis and membrane technology all have their own disadvantages, resulting in high treatment costs, adsorption is often the most widely used method in actual treatment. The mass transfer capacity and rate of the adsorbent can be achieved by increasing the adsorption sites and improving the porosity. Metal organic frameworks (MOFs) are a type of nano-adsorbent materials with large specific surface area and high porosity. The UIO-66 series is a very typical MOF. In order to improve the adsorption effect, metal doping is one of the strategies to improve the adsorption performance of MOF. Therefore, combining Al with the UIO-66 series to prepare bimetallic UIO-66 can effectively improve the adsorption effect. However, UIO-66 is a powdery solid with defects such as poor stability, easy aggregation and low biosafety, which greatly limits its application range. Bacterial cellulose is a polymer with a three-dimensional network structure and rich functional groups. Combining it with UIO-66 to prepare a composite material can improve the mechanical strength of the material while making up for the defects of UIO-66. However, the high degree of polymerization of bacterial cellulose leads to its low solubility in water, which increases the difficulty of preparing bacterial cellulose composite materials. In addition, in order to improve the specific surface area, permeability and hydraulic properties of adsorbents, spherical adsorbents have received more and more attention, but the preparation of UIO-66@bacterial cellulose beads currently has the disadvantages of complex process and poor adsorption effect. Therefore, it is urgent to improve the preparation process to improve the adsorption performance of this type of material. Summary of the invention

[0004] In order to solve the problems that conventional treatment processes of sewage treatment plants have poor treatment effects on antibiotics in water such as medical wastewater and aquaculture wastewater, the existing adsorbent preparation process is complicated and the adsorption effect is poor, the present invention provides a preparation method of Al-UIO-66@bacterial cellulose beads and a wastewater treatment method, which is specifically applied to a water treatment method for efficiently removing antibiotics in water using Al-UIO-66@bacterial cellulose beads. The method uniformly compounds Al-UIO-66 and bacterial cellulose beads, realizes efficient adsorption treatment of TCH, and provides an effective treatment means for efficiently adsorbing antibiotics in water.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing an Al-UIO-66@bacterial cellulose bead composite material comprises the following steps:

[0007] Step 1, purifying the fermented block bacterial cellulose and mixing it with deionized water, and dispersing it using a food processor to obtain a bacterial cellulose dispersion liquid I;

[0008] Step 2, adding a chemical crosslinking agent to the bacterial cellulose dispersion liquid I and heating it to obtain a preliminary crosslinked bacterial cellulose dispersion liquid II, while achieving uniform dispersion of flocculent bacterial cellulose in the bacterial cellulose dispersion liquid II; dropping the bacterial cellulose dispersion liquid II into a secondary crosslinking liquid for a crosslinking reaction to obtain bacterial cellulose beads, wherein the secondary crosslinking liquid includes aluminum chloride, zirconium chloride and anhydrous ethanol, and while crosslinking into balls, metal ions are uniformly attached to the bacterial cellulose skeleton by forming coordination bonds;

[0009] Step 3: Place the bacterial cellulose beads in the UIO-66 ligand solution and synthesize the Al-UIO-66@bacterial cellulose beads in situ by water bath thermal method.

[0010] Furthermore, in step one, the purification step is as follows: the fermented bacterial cellulose block is rinsed with deionized water, then added into a 0.1-0.2M NaOH solution, stirred and boiled for 1-2 hours, until it becomes white and translucent, and then the bacterial cellulose block is repeatedly rinsed with an acetic acid solution with a mass fraction of 0.5-0.8% and deionized water until the filtrate is neutral to obtain a purified bacterial cellulose block.

[0011] Furthermore, in step 1, the cooking machine parameter is 20000-22000 r / min, and the operation time is 20-30 min. The bacterial cellulose dispersion liquid I has a solid content of 0.6-0.7%, and is a suspended liquid containing flocculent substances.

[0012] Furthermore, in step 2, the added chemical crosslinking agent is a 50% glutaraldehyde solution, and the added amount is 5.3 mL per 100 mL of bacterial cellulose dispersion I. Then, the pH value of the bacterial cellulose dispersion I is adjusted to 7-8 using an acid-base solution, and preliminary crosslinking is performed under heating conditions to obtain a uniformly dispersed flocculent bacterial cellulose dispersion II.

[0013] Furthermore, in step 2, the acid solution used to adjust the pH is a hydrochloric acid solution with a mass fraction of 20-30%, the alkaline solution used is a 1M sodium hydroxide solution, the heating temperature is 75-80° C., and the heating and stirring are performed for 40-50 minutes.

[0014] Furthermore, in step 2, the bacterial cellulose dispersion II is dripped into the secondary crosslinking solution using a syringe to simultaneously perform secondary crosslinking and Zr 4+ 、Al 3+ After 4 to 5 hours of coordination process, the formed bacterial cellulose beads are filtered out for subsequent material synthesis.

[0015] Furthermore, in step 2, the secondary cross-linking liquid is a mixed solution of aluminum chloride, zirconium chloride and anhydrous ethanol, with a ratio of 6 to 7 mL of anhydrous ethanol and aluminum chloride and zirconium chloride in a molar ratio of 1:1 added to every 10 mL of deionized water, wherein the total amount of aluminum chloride and zirconium chloride is 2.047 to 4.094 mmol.

[0016] Further, in step 3, the ligand solution of UIO-66 includes DMF solvent, ligand and glacial acetic acid, and the ligand is 2-hydroxyterephthalic acid (H 2 BDC) or 2-aminoterephthalic acid (H 2 BDC-NH 2 ), the ligand content 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 were placed in the UIO-66 ligand solution, then poured into a 50 mL polytetrafluoroethylene-lined autoclave and kept in a 120°C oven for 24 h. After natural cooling, the composite bacterial cellulose beads were filtered out and rinsed with DMF and methanol multiple times to obtain the product. The amount of DMF and methanol used for each rinse was 10 mL. The composite bacterial cellulose beads were then rinsed with deionized water multiple times to finally obtain Al-UIO-66@bacterial cellulose beads with the function of efficiently removing antibiotics in water.

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

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

[0020] Al-UIO-66@bacterial cellulose bead composite materials were synthesized by using bacterial cellulose as the skeleton to support Al-UIO-66; a certain amount of Al-UIO-66@bacterial cellulose beads were put into a solution containing TCH, and the solution was continuously shaken at a uniform speed under certain conditions, which could achieve efficient removal of TCH within a few hours.

[0021] The concentration of TCH solution used 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 and continuously shaken at a uniform speed for adsorption, and samples are taken at specific time points, filtered through a 0.22 μm filter membrane, and the remaining TCH content in the solution is determined by spectrophotometry.

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

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention uses a bacterial cellulose material with a good structure as a skeleton and in situ grows Al-UIO-66 therein to obtain a uniform composite material, and uses the material to achieve efficient removal of TCH in water. The present invention uses Al-UIO-66@bacterial cellulose beads with a dry basis concentration of 0.6 g / L to adsorb 30 mL of TCH with a concentration of 30 mg / L, which can remove 98.27% of TCH within 4 hours. Compared with the treatment effect of the traditional activated sludge system, the removal rate of TCH by this material 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 blocks, the bacterial cellulose beads prepared in step 2 have a 60.44% increase in the removal rate of TCH within 4 hours, indicating that the spherical adsorbent has good The adsorption effect of Al-UIO-66@bacterial cellulose beads with a dry basis concentration of 0.35g / L was used to adsorb 70mL of TCH with a concentration of 50mg / L, and its adsorption capacity could reach 150.19mg / g. Compared with the undoped Al UIO-66@bacterial cellulose beads, the doping of Al increased the adsorption capacity of the composite material for TCH by about 24.51%, indicating that the introduction of Al can significantly improve the adsorption performance of the material. At the same time, the combination of UIO-66 and bacterial cellulose also makes up for the disadvantage that UIO-66 powder is difficult to separate in water. This method is simple to operate and has stable synthesis. It can be used in fluidized bed and other processes to treat flowing wastewater containing antibiotics. It not only realizes the uniform preparation of composite materials and reduces production costs, but also solves a series of environmental problems caused by the poor removal of antibiotic pollution in water from sewage treatment plants. It has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0026] Figure 2 : Comparison of the adsorption capacity of TCH by 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) adsorption saturated Al-UIO-66@bacterial cellulose beads in Example 2. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] Embodiment 1:

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

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

[0032] 2. Take 15mL of 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, put it in an oil bath and stir it at 80℃ for 45min to obtain bacterial cellulose dispersion Ⅱ. Use a syringe to extract 2mL of cross-linked bacterial cellulose dispersion Ⅱ, drip it into the secondary cross-linking liquid at a speed of 3 seconds / drop, and filter it after standing cross-linking for 5h to obtain bacterial cellulose beads. Then, wash the filtered bacterial cellulose beads with deionized water and put them into the ligand solution of UIO-66, and keep them at 120℃ for 24h in an autoclave with polytetrafluoroethylene lining. After the reaction is completed, cool it naturally to room temperature and filter it. Rinse the filtered product with DMF and methanol three times, 10mL of DMF and methanol each time, and rinse it with a large amount of deionized water until the surface is neutral, and you can get Al-UIO-66@bacterial cellulose bead material. The secondary crosslinking solution was prepared by adding 6.67 mL of anhydrous ethanol, 0.273 g of aluminum chloride, and 0.477 g of zirconium chloride (the total amount of aluminum chloride and zirconium chloride was 4.094 mmol) to 10 mL of deionized water. The UIO-66 ligand solution was prepared by adding 2.047 mmol of H 2 BDC-NH 2 , mix the two evenly and then add 1mL of glacial acetic acid.

[0033] 3. Prepare 30 mL of 30 mg / L TCH solution, add the Al-UIO-66@ bacterial cellulose beads prepared in the above step with a dry basis concentration of 0.6 g / L, adjust the pH to 4.01, and shake continuously and uniformly on a shaker at 360 rpm and 25°C. At the same time, the same amount of pure bacterial cellulose block and bacterial cellulose beads prepared in step 2 were subjected to comparative experiments under the above conditions, and samples were taken at 0, 0.5, 1, 2, 3 and 4 hours after the start of adsorption, respectively. After filtering with a 0.22 μm filter membrane, the concentration of TCH in the solution was analyzed by spectrophotometry at 357 nm, and then 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 Al-UIO-66@bacterial cellulose bead composite material prepared corresponding to 1mL bacterial cellulose dispersion II is about 18.1mg. Under the above conditions, 30mL of 30mg / L TCH solution can be adsorbed for 4h to remove about 98.27% of TCH, while the removal rate of many common TCs in the traditional activated sludge system is only 50-70%, and the removal effect of this material is improved by 63.8%; compared with the same mass of pure bacterial cellulose blocks, the removal rate of 30mL of 30mg / L TCH solution prepared in step 2 is increased by 60.44% within 4h. It can be seen that the adsorption material prepared according to this embodiment has a good removal effect on antibiotic pollutants in water.

[0035] Embodiment 2:

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

[0037] 1. Take the fermented bacterial cellulose block and stir and boil it in 0.15M NaOH solution for 1 hour, and rinse it with 0.5% acetic acid solution and deionized water until it is neutral. Mix the treated bacterial cellulose block with deionized water and add it into a food processor, and disperse it at 20000r / min for 20 minutes to obtain a bacterial cellulose dispersion I with a solid content of 0.66%.

[0038] 2. Take 15mL of bacterial cellulose dispersion Ⅰ in a beaker, add 0.8mL of 50% glutaraldehyde solution, adjust the pH to 7.42 with 20-30% hydrochloric acid solution and 1M sodium hydroxide solution, put it in an oil bath and stir it at 80℃ for 45min to obtain bacterial cellulose dispersion Ⅱ. Use a syringe to extract 2mL of cross-linked bacterial cellulose dispersion Ⅱ, drip it into the secondary cross-linking liquid at a speed of 3 seconds / drop, let it stand for 4h and filter it to obtain bacterial cellulose beads. Then, wash the filtered bacterial cellulose beads with deionized water and put them into the ligand solution of UIO-66, and keep them at 120℃ for 24h in an autoclave with polytetrafluoroethylene lining. After the reaction is completed, cool it naturally to room temperature and filter it. Rinse the filtered product with DMF and methanol three times, 10mL of DMF and methanol each time, and rinse it with a large amount of deionized water until the surface is neutral, and you can get Al-UIO-66@bacterial cellulose bead material. Preparation of secondary crosslinking solution: 6.67 mL of anhydrous ethanol, 0.136 g of aluminum chloride and 0.238 g of zirconium chloride (2.047 mmol in total) were added to 10 mL of deionized water. Preparation of UIO-66 ligand solution: 2.958 mmol of H 2 BDC, mix the two evenly and then add 1mL of glacial acetic acid.

[0039] 3. Prepare 70 mL of 50 mg / L TCH solution, add the Al-UIO-66@bacterial cellulose beads prepared in the above step, the dry basis concentration of which is 0.35 g / L, adjust the pH to 4.34, and shake continuously and uniformly on a shaker at 360 rpm and 25°C. At the same time, add the same amount of UIO-66@bacterial cellulose beads (the preparation of UIO-66@bacterial cellulose beads is different from the secondary cross-linking solution used to prepare Al-UIO-66@bacterial cellulose beads, and the rest of the steps are the same The formula of the secondary cross-linking solution for preparing UIO-66@bacterial cellulose beads is as follows: 6.67 mL of anhydrous ethanol and 0.477 g of zirconium chloride are added to 10 mL of deionized water. A control experiment was carried out according to the above conditions, and samples were taken at 0, 0.5, 1, 2, 3, 4, 5, 8, 12, 24, 36 and 48 hours after the start of adsorption. After filtering with a 0.22 μm filter membrane, the concentration of TCH in the solution was analyzed by spectrophotometry at 357 nm, and then the TCH content removed by the adsorbent and the corresponding adsorption capacity were calculated.

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

[0041] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing Al-UIO-66@ bacterial cellulose beads, characterized in that: The following steps are involved: Step 1, purifying the fermented bacterial cellulose and mixing it with deionized water to uniformly disperse it to obtain bacterial cellulose dispersion liquid I; Step 2, adding a chemical crosslinking agent to the bacterial cellulose dispersion I and heating it to obtain a preliminary crosslinked bacterial cellulose dispersion II, and dropping the bacterial cellulose dispersion II into a secondary crosslinking liquid to perform a crosslinking reaction to obtain bacterial cellulose beads; wherein the secondary crosslinking liquid includes aluminum chloride, zirconium chloride and anhydrous ethanol; Step 3: Place the bacterial cellulose beads in the UIO-66 ligand solution and synthesize the Al-UIO-66@bacterial cellulose beads in situ by water bath thermal method.

2. The method according to claim 1, characterized in that: In step 1, the purification process is as follows: the fermented bacterial cellulose block is rinsed with deionized water, then added into a 0.1-0.2M NaOH solution, stirred and boiled until it becomes white and translucent, and then the bacterial cellulose block is repeatedly rinsed with a 0.5-0.8% mass fraction acetic acid solution and deionized water until the filtrate is neutral.

3. The method according to claim 1, characterized in that: In step 1, the solid content of the bacterial cellulose dispersion I is 0.6-0.7%.

4. The method according to claim 1 or 3, characterized in that: In step 2, the chemical cross-linking agent is selected as a glutaraldehyde solution with a mass fraction of 50%, and the volume ratio of the chemical cross-linking agent to the bacterial cellulose dispersion liquid I is 5.3:

100.

5. The method according to claim 1, characterized in that: In step 2, a chemical crosslinking agent is added to the bacterial cellulose dispersion I, and then the pH is adjusted to 7-8 using an acid-base solution, and then heated to obtain a preliminary crosslinked bacterial cellulose dispersion II, the heating temperature is 75-80° C., and the time is 40-50 min.

6. The method according to claim 1, characterized in that: In step 2, the secondary cross-linking liquid is prepared by adding 6 to 7 mL of anhydrous ethanol, aluminum chloride and zirconium chloride in a molar ratio of 1:1 to every 10 mL of deionized water, and the total amount of aluminum chloride and zirconium chloride is 2.047 to 4.094 mmol.

7. The method according to claim 1, characterized in that: In step 3, the ligand solution of UIO-66 includes DMF solvent, ligand and glacial acetic acid, the ligand is 2-hydroxyterephthalic acid or 2-aminoterephthalic acid, the ligand content 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.

8. The method according to claim 1, characterized in that: In step 3, the temperature of the water bath heating method is 120°C and the time is 24 hours.

9. A method for treating wastewater using Al-UIO-66@ bacterial cellulose beads prepared by the method described in any one of claims 1 to 8, characterized in that: Al-UIO-66@bacterial cellulose beads were placed in a solution containing TCH and shaken to remove TCH.

10. The wastewater treatment method according to claim 9, characterized in that: 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 usage of Al-UIO-66@bacterial cellulose beads is 0.3-0.6 g / L.

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