Preparation of composite adsorbent and application of composite adsorbent in removal of tetracycline pollutants

Abstract

The invention relates to the technical field of wastewater treatment, in particular to preparation of a composite adsorbent and application of the composite adsorbent in removal of tetracycline pollutants. According to the Bi-doped HKUST-1 / SA-Cu composite hydrogel adsorbent (BixHKUST-1 / SA-Cu) provided by the invention, due to the introduction of Bi, the water stability of the material is enhanced, and meanwhile, additional adsorption sites are provided, so that the adsorption capacity on tetracycline pollutants is improved; a network structure formed by alginate enhances the mechanical strength of the material, and the adsorption performance is further improved through a Cu < 2 + > bond bridge effect; under the condition of 313K, the maximum adsorption capacity of BixHKUST-1 / SA-Cu to aureomycin (CTC) and oxytetracycline (OTC) reaches 2000mg g <-1 >, and the maximum adsorption capacity of BixHKUST-1 / SA-Cu is obviously superior to that of a traditional adsorbent; the material is easy to separate and recover, and the adsorption performance is still kept at a high level when the material is recycled for 10 times.

Description

Technical Field

[0001] The patent of this invention relates to the field of wastewater treatment technology, specifically to the preparation of a composite adsorbent and its application in the removal of tetracycline pollutants. Background Art

[0002] Tetracycline antibiotics (TCs) are an important class of antimicrobial drugs widely used in animal husbandry and medicine. However, due to the widespread use of tetracycline antibiotics and the limitations of wastewater treatment technology, these pollutants have entered the water environment in large quantities, posing a serious threat to ecosystems and human health. Due to the difficulty of TCs to degrade in water, their pollution has become an environmental issue of global concern. Currently, the mainstream methods for removing TCs from water bodies include contact electrocatalysis (CEC), photocatalysis, microbial degradation, advanced oxidation, and membrane filtration. However, these methods usually have problems such as complex operation, high cost, and secondary pollution. In contrast, adsorption is considered to be the most promising method for removing TCs due to its advantages of high efficiency, energy saving, environmental protection, and recyclability.

[0003] Currently, a variety of adsorbents have been used to remove tetracycline pollutants from water, including:

[0004] (1) Activated carbon: It has a large specific surface area, but its adsorption capacity is limited and the regeneration process is complicated.

[0005] (2) Carbon nanotubes and graphene materials: They have good adsorption capacity, but the synthesis cost is high and it is difficult to apply them on a large scale.

[0006] (3) Metal-organic framework materials (MOFs): Metal-organic frameworks (MOFs) are porous materials composed of metal ions and organic ligands. Due to their high specific surface area, highly adjustable pore structure and excellent adsorption capacity, they are widely used in the field of environmental management. For example, ZIF-8 and CAU-17 have strong adsorption capacity, but some MOFs have insufficient adsorption capacity in aqueous environments and poor stability, making them difficult to recycle for a long time. Chen's research group synthesized Zn-based metal-organic framework ZIF-8 at room temperature to simultaneously adsorb tetracycline and oxytetracycline in water, with the maximum adsorption capacity of 303.0 mg g -1 and 312.5 mg g -1 HKUST-1 (copper-benzenetricarboxylate metal-organic framework) is considered an ideal material for the adsorption and removal of tetracycline pollutants due to its high porosity and excellent chemical stability. Yu's team obtained HDC-350 (derivative porous carbon material) by carbonizing HKUST-1 at high temperature in an oxygen-free environment and applied it to the adsorption of tetracycline, with a maximum adsorption capacity of 136.88 mg g -1Wang's group synthesized Bi-based MOF CAU-17 through simple hydrothermal synthesis and applied it to the adsorption and photocatalysis of tetracycline, with a maximum adsorption capacity of 39.59 mg g -1 At the same time, its adsorption capacity can be improved by metal doping technology. Wang's group synthesized lanthanum-doped bimetallic Bi-MOF (La-CAU-17) to adsorb phosphate. Due to the incorporation of La, the adsorption capacity of the original CAU-17 (186.57 mg g -1 ), the maximum adsorption capacity of La-CAU-17 is as high as 216.07 mg g -1 .

[0007] (4) Copper alginate (SA-Cu) gel: It is a natural polymer adsorbent based on alginate. It can adsorb tetracycline pollutants through copper ion bridges, but its adsorption capacity is limited. Lin's group used copper ion solidified alginate to prepare copper alginate (SA-Cu) gel to adsorb tetracycline, and its maximum adsorption capacity was 53.26 mg g -1 On this basis, Rong's research group synthesized a double-layer polyvinyl alcohol-copper alginate aerogel composite material to adsorb tetracycline in water, which not only enhanced the mechanical properties of the material but also increased the adsorption capacity (231.43 mg g -1 ).

[0008] However, the tetracycline adsorbents in the prior art have the following technical problems:

[0009] 1. Limited adsorption capacity: Traditional adsorbents (such as activated carbon, zeolite, etc.) have low adsorption capacity for tetracycline pollutants, making it difficult to achieve efficient removal.

[0010] 2. Poor water stability: Some MOF materials are easily decomposed or structurally collapsed in aqueous solutions, affecting their long-term application.

[0011] 3. Poor recyclability: Some adsorbents are difficult to recycle and reuse after use, which increases processing costs.

[0012] 4. Weak anti-interference ability: In complex water environments (such as those containing high concentrations of inorganic ions), the adsorption capacity of some adsorbents is significantly reduced.

[0013] Patent application number CN118059826A discloses a method for preparing Fe-MOF biochar composite adsorption materials. Biochar and Fe-MOF are composited, and the adsorption capacity of TC antibiotics is only 63.84 mg g -1 , and during the preparation process, due to the compounding of biochar, a higher cracking temperature is required, resulting in higher energy consumption.

[0014] The patent application with publication number CN115869924A discloses a defective zirconium-based metal-organic framework adsorbent and its preparation method. It uses sodium carboxylate and zirconium salt compounds as the main raw materials, and by adjusting the ratio of water and organic solvents, constructs a defective metal-organic framework, namely a defective Zr-MOF, to create mesopores and achieve high adsorption performance. However, the structural stability of the defective Zr-MOF needs to be improved.

[0015] Patent application publication number CN108201878A discloses a method for preparing a carbon dot-modified metal organic framework adsorption material and its application in water pollutant treatment. Although the resulting CDs-ZIF-67(Co) composite adsorption material has a high adsorption capacity and good stability for the antibiotic tetracycline pollutant in water bodies, carbon dots need to be introduced during the preparation process, and the steps in the carbon dot preparation process are complicated. Summary of the Invention

[0016] In order to solve the above technical problems, the purpose of the present invention is to provide a Bi-doped HKUST-1 / SA-Cu composite hydrogel adsorbent (Bi x HKUST-1 / SA-Cu), the introduction of Bi enhances the water stability of the material and provides additional adsorption sites, thereby improving the adsorption capacity of tetracycline pollutants; the network structure formed by alginate enhances the mechanical strength of the material and 2+ The bond bridge effect further improves the adsorption performance; at 313K, Bi x The maximum adsorption capacity of HKUST-1 / SA-Cu for chlortetracycline (CTC) and oxytetracycline (OTC) reached 2000 mg g -1 , which is significantly better than traditional adsorbents; the material is easy to separate and recycle, and its adsorption performance remains at a high level after being recycled 10 times.

[0017] The purpose of the present invention can be achieved through the following technical solutions:

[0018] In a first aspect, the present invention provides a method for preparing a composite adsorbent, comprising the following steps:

[0019] (1)Bi x Synthesis of HKUST-1: 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate and bismuth nitrate pentahydrate were dissolved in DMF and stirred, then heated to react, centrifuged, washed with DMF, vacuum dried and ground to obtain Bi x HKUST-1 powder;

[0020] (2)Bi x Synthesis of HKUST-1 / SA-Cu composite beads: Bi xHKUST-1 powder was mixed with sodium alginate powder and ground, then added to deionized water, heated and stirred to melt into a gel state, and air bubbles were removed by ultrasound to eliminate the air in the gel. The gel was then absorbed and added dropwise to the ionic solution to solidify it, thereby obtaining Bi x The HKUST-1 / SA-Cu composite beads were transferred to deionized water for soaking, and the deionized water was replaced every 8 hours.

[0021] Furthermore, in step (1), the molar ratio of 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate and bismuth nitrate pentahydrate is 14:(17-19):(1-3).

[0022] Furthermore, in step (1), the molar ratio of 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate and bismuth nitrate pentahydrate is 7:9:1.

[0023] Furthermore, in step (1), the temperature-raising reaction refers to reacting at 110° C. for 18 hours.

[0024] Furthermore, in step (1), the vacuum drying temperature is 70° C., and the vacuum drying time is 12 h.

[0025] Furthermore, in step (2), the Bi x The mass ratio of HKUST-1 powder to sodium alginate powder is 1:(1-3).

[0026] Furthermore, in step (2), the Bi x The mass ratio of HKUST-1 powder to sodium alginate powder was 1:1.

[0027] Furthermore, in step (2), the temperature of the heating and stirring is 85°C.

[0028] Furthermore, in step (2), the curing time is 24 hours.

[0029] In the second aspect, the present invention provides an application of an adsorbent prepared by the above preparation method, wherein the adsorbent is used to adsorb tetracycline pollutants in water, and the amount of the adsorbent is 0.1 g L -1 , the pH value of the water body is 4-8.

[0030] The beneficial effects of this application are as follows:

[0031] (1) Bi of the present invention 0.1 HKUST-1 / SA-Cu beads utilize synergistic effects such as hydrogen bonds, interactions, and cationic bond bridges to improve adsorption performance and have a high adsorption capacity. The maximum adsorption capacity for CTC at 298 K is 588.24 mg g -1The maximum adsorption capacity of OTC is 476.19 mg g -1 The adsorption capacity is greatly affected by temperature. When the temperature reaches 313K (40℃), the maximum adsorption capacity of the material for both is 2000.00 mg g -1 , much higher than traditional adsorbents.

[0032] (2) Bi doping in the present invention improves the structural stability of the material, avoids the decomposition of MOF in water, and provides additional adsorption sites. 3+ and Cu 2+ The release complies with WHO standards.

[0033] (3) The present invention utilizes alginate to enhance the material's recyclability, forming a gel-like structure that facilitates recycling and reuse. It maintains a high adsorption capacity even after 10 cycles. It is suitable for a variety of water environments, including tap water and river water, and has strong ion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is Bi in Example 2 0.1 SEM image of HKUST-1 (a), Bi in Example 4 0.1 SEM image of HKUST-1 / SA-Cu composite beads after drying (b), HKUST-1 in Comparative Example 1, Bi 0.05 HKUST-1, Bi in Example 2 0.1 HKUST-1, Bi in Example 3 0.15 HKUST-1, Bi in Example 4 0.1 XRD patterns of HKUST-1 / SA-Cu composite beads (c), HKUST-1 in Comparative Example 1, Bi in Example 2 0.1 HKUST-1, Bi in Example 4 0.1 FTIR image of HKUST-1 / SA-Cu composite beads (d).

[0035] Figure 2 is Bi in Example 4 0.1 Optical photographs of HKUST-1 / SA-Cu complex beads (left) and their adsorption of CTC (middle) and OTC (right).

[0036] Figure 3 HKUST-1 in Comparative Example 1, Bi in Example 1 0.05 HKUST-1, Bi in Example 2 0.1 HKUST-1, Bi in Example 3 0.15Capacity comparison of HKUST-1 adsorbing CTC (a) and OTC (c), SA-Cu gel in comparative example 2, Bi in example 4 0.1 HKUST-1 / SA-Cu composite beads, Bi in Example 5 0.1 HKUST-1 / SA-Cu composite beads, Bi in Example 6 0.1 Capacity comparison of HKUST-1 / SA-Cu composite beads for adsorbing CTC (b) and OTC (d).

[0037] Figure 4 is Bi in Example 4 0.1 Comparison of the adsorption capacity of HKUST-1 / SA-Cu composite beads at different adsorbent dosages (a) and (b) of OTC, Bi in Example 4 0.1 Comparison of the adsorption capacity of CTC by HKUST-1 / SA-Cu composite beads at different pH values ​​(c) and (d) of OTC.

[0038] Figure 5 is Bi in Example 4 0.1 HKUST-1 / SA-Cu composite beads were condensed in 0.01 mol L -1 Comparison of the adsorption capacity of CTC and OTC by interfering ions and different water qualities.

[0039] Figure 6 is Bi in Example 4 0.1 Figure 2. Adsorption regeneration cycle experiment of HKUST-1 / SA-Cu composite beads. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0041] Example 1

[0042] Bi 0.05 Synthesis of HKUST-1

[0043] 3.5mmol of 1,3,5-benzenetricarboxylic acid (H3BTC), 4.75mmol of copper nitrate trihydrate (Cu(NO3)2·3H2O) and 0.25mmol of bismuth nitrate pentahydrate (Bi(NO3)2·5H2O) were dissolved in 40mL of analytical grade DMF and stirred for 1h. The above solution was transferred to a polytetrafluoroethylene container and reacted at 110℃ for 18h. After centrifugation, it was washed with an appropriate amount of N,N-dimethylformamide (DMF) to remove the unreacted precursor and the remaining guest, and then dried in a vacuum oven at 70℃ for 12h and ground to obtain Bi 0.05 HKUST-1.

[0044] Example 2

[0045] Bi 0.1 Synthesis of HKUST-1

[0046] 3.5mmol of 1,3,5-benzenetricarboxylic acid (H3BTC), 4.5mmol of copper nitrate trihydrate (Cu(NO3)2·3H2O) and 0.5mmol of bismuth nitrate pentahydrate (Bi(NO3)2·5H2O) were dissolved in 40mL of analytical grade DMF and stirred for 1h. The above solution was transferred to a polytetrafluoroethylene container and reacted at 110℃ for 18h. After centrifugation, it was washed with an appropriate amount of N,N-dimethylformamide (DMF) to remove the unreacted precursor and the remaining guest, and then dried in a vacuum oven at 70℃ for 12h. The Bi 0.1 HKUST-1. Bi 0.1 SEM images of HKUST-1 are shown in Figure 2. Figure 1 As shown in a, Bi 0.1 HKUST-1 has an octahedral structure without distortion, and its structure is consistent with the previously reported HKUST-1 organic framework (MOF) material structure, indicating that the incorporation of Bi does not change its crystal shape and has good crystallinity.

[0047] Example 3

[0048] Bi 0.15 Synthesis of HKUST-1

[0049] 3.5mmol of 1,3,5-benzenetricarboxylic acid (H3BTC), 4.25mmol of copper nitrate trihydrate (Cu(NO3)2·3H2O) and 0.75mmol of bismuth nitrate pentahydrate (Bi(NO3)2·5H2O) were dissolved in 40mL of analytical grade DMF and stirred for 1h. The above solution was transferred to a polytetrafluoroethylene container and reacted at 110℃ for 18h. After centrifugation, it was washed with an appropriate amount of N,N-dimethylformamide (DMF) to remove the unreacted precursor and the remaining guest, and then dried in a vacuum oven at 70℃ for 12h and ground to obtain Bi 0.15 HKUST-1.

[0050] Example 4

[0051] Bi 0.1 Synthesis of HKUST-1 / SA-Cu composite beads (Bi 0.1 The mass ratio of HKUST-1 to SA-Cu is 1:1)

[0052] 0.15 g of Bi prepared in Example 2 0.1 HKUST-1 powder and sodium alginate (SA) powder were mixed in a mass ratio of 1:1 and ground to make the mixture uniform. The mixture was then added to 10 mL of deionized water and stirred at 85 °C to melt into a gel state. The bubbles were then removed by ultrasound to eliminate the air in the gel. The gel was then drawn up with a 10 mL syringe (needle specification: 0.7×32TWLB) and added dropwise to a 2 wt% copper ion solution and cured for 24 h to obtain Bi 0.1 HKUST-1 / SA-Cu composite beads. Finally, the beads were transferred to 200 mL of deionized water and soaked for 24 hours for washing. The deionized water was replaced every 8 hours. 0.1 SEM images of HKUST-1 / SA-Cu composite beads are shown in Figure 2. Figure 1 As shown in b, it can be found that there are a large number of wrinkled porous structures on the surface, which provide sufficient adsorption sites for the adsorption of CTC and OTC. 0.1 Optical images of HKUST-1 / SA-Cu composite beads (left) and their adsorption of CTC (middle) and OTC (right) Figure 2 As shown, it can be seen that Bi 0.1 The HKUST-1 / SA-Cu composite beads have a sky blue spherical appearance. After adsorbing CTC, they turn yellow-green and after adsorbing OTC, they turn brown, indicating that antibiotics have been adsorbed on the surface of the beads, but the shape has not changed significantly.

[0053] Example 5

[0054] Bi 0.1 Synthesis of HKUST-1 / SA-Cu composite beads (Bi 0.1 The mass ratio of HKUST-1 to SA-Cu is 1:2)

[0055] 0.15 g of Bi prepared in Example 2 0.1 HKUST-1 powder and sodium alginate (SA) powder were mixed in a mass ratio of 1:2 and ground to make the mixture uniform. The mixture was then added to 10 mL of deionized water and stirred at 85 °C to melt into a gel state. The bubbles were then removed by ultrasound to eliminate the air in the gel. The gel was then drawn up with a 10 mL syringe (needle specification: 0.7×32TWLB) and added dropwise to a 2 wt% copper ion solution for curing for 24 h to obtain Bi 0.1Finally, the beads were transferred to 200 mL of deionized water and soaked for 24 hours for washing, with the deionized water replaced every 8 hours.

[0056] Example 6

[0057] Bi 0.1 Synthesis of HKUST-1 / SA-Cu composite beads (Bi 0.1 The mass ratio of HKUST-1 to SA-Cu is 1:3)

[0058] 0.15 g of Bi prepared in Example 2 0.1 HKUST-1 powder and sodium alginate (SA) powder were mixed in a mass ratio of 1:3 and ground to make the mixture uniform. The mixture was then added to 10 mL of deionized water and stirred at 85 °C to melt into a gel state. The bubbles were then removed by ultrasound to eliminate the air in the gel. The gel was then drawn up with a 10 mL syringe (needle specification: 0.7×32TWLB) and added dropwise to a 2 wt% copper ion solution for curing for 24 h to obtain Bi 0.1 Finally, the beads were transferred to 200 mL of deionized water and soaked for 24 hours for washing, with the deionized water replaced every 8 hours.

[0059] Comparative Example 1

[0060] Synthesis of HKUST-1

[0061] 3.5 mmol of 1,3,5-benzenetricarboxylic acid (H3BTC) and 5 mmol of copper nitrate trihydrate (Cu(NO3)2·3H2O) were dissolved in 100 mL of analytical-grade DMF and stirred for 1 h. The solution was transferred to a polytetrafluoroethylene container and reacted at 110°C for 18 h. After centrifugation, the unreacted precursor and remaining guest were removed by washing with an appropriate amount of N,N-dimethylformamide (DMF). The product was then dried in a vacuum oven at 70°C for 12 h and ground to obtain HKUST-1.

[0062] HKUST-1 in Comparative Example 1, Bi in Example 1 0.05 HKUST-1, Bi in Example 2 0.1 HKUST-1, Bi in Example 3 0.15 HKUST-1, Bi in Example 4 0.1 The XRD patterns of HKUST-1 / SA-Cu composite beads are shown in Figure 2. Figure 1As shown in c, it can be seen that the XRD spectrum of HKUST-1 is consistent with the literature. The incorporation of Bi produces a new peak, which is attributed to Bi MOF (CAU-17). With the increase of Bi incorporation, the peak intensity of CAU-17 increases, while the intensity of HKUST-1 gradually decreases. In addition, after the Bi ions are exchanged with the Cu ions in HKUST-1, the slight disorder of the lattice and the new cations cause the HKUST-1 peak to shift to a high angle, proving that Bi is successfully coordinated with the carboxylic acid ligand in BTC. Strong Bi-O chemical bonds form strong secondary structures, which make Bi 0.1 The hydrolysis stability of HKUST-1MOF is enhanced. 0.1 HKUST-1, Bi in Example 4 0.1 FTIR images of HKUST-1 / SA-Cu composite beads are shown in Figure 2. Figure 1 As shown in d, it can be seen that compared with HKUST-1 and Bi 0.1 The infrared spectrum of HKUST-1 shows that after doping with Bi, a peak at 728 cm -1 The presence of Bi-O coordination vibration bond indicates that Bi is successfully coordinated with BTC, and this peak is closely related to the 730cm-1 peak of Cu-O bond (HKUST-1). -1 The peaks overlap; the infrared spectra of the two curves also confirm that the material is successfully synthesized, and the results match those of XRD. 0.1 After HKUST-1 is composited with SA-Cu, Bi 0.1 The characteristic peaks of HKUST-1 still exist, but the intensity is reduced, which may be due to the encapsulation of SA-Cu ( Figure 1 The peak intensity of SA-Cu in d is low). In addition, after the composite, the peaks at 1434 cm-1, 1623 cm-1 and 1381 cm-1 -1 The characteristic peak at Bi 0.1 1443 cm-1, 1641 cm-1 and 1373 cm-1 of HKUST-1 -1 The characteristic peak shift at is obvious, which can be inferred that an interaction force is formed between alginate and MOF.

[0063] Comparative Example 2

[0064] Synthesis of SA-Cu gel

[0065] 0.3 g of sodium alginate (SA) powder was added to 10 mL of deionized water and stirred at 85°C until it melted into a gel. Air bubbles were then removed by ultrasound to eliminate the air trapped within the gel. The gel was then aspirated using a 10 mL syringe (needle size: 0.7×32 TWLB) and added dropwise to a 2 wt% copper ion solution for 24 hours to cure, yielding a SA-Cu gel. Finally, the gel was transferred to 200 mL of deionized water and soaked for 24 hours for washing, with the deionized water replaced every 8 hours.

[0066] Adsorption performance test:

[0067] CTC adsorption test: Bi prepared in Example 4 0.1 HKUST-1 / SA-Cu composite beads were used as adsorbents. 100 mL of CTC (50 mg / L) was added to 250 mL conical flasks, sealed, and placed at 25 °C with a rotation speed of 120 r min. -1 The mixture was shaken in a constant temperature shaker in the dark for 10 h. After the adsorption process, the absorbance of the CTC solution at a wavelength of 280 nm before and after adsorption was measured by ultraviolet spectrophotometry (UV-vis) to calculate the CTC concentration and adsorption amount in the solution after adsorption.

[0068] OTC adsorption test: Bi prepared in Example 4 0.1 HKUST-1 / SA-Cu composite beads were used as adsorbents. 100 mL of OTC (40 mg / L) was added to 250 mL conical flasks, sealed, and placed at 25 °C with a rotation speed of 120 r min. -1 The mixture was shaken in a constant temperature shaker in the dark for 9 h. After the adsorption process, the absorbance of the CTC solution before and after adsorption at a wavelength of 365 nm was measured by ultraviolet spectrophotometry (UV-vis) to calculate the OTC concentration and adsorption amount in the solution after adsorption.

[0069] 1. Adsorption capacity test: the concentration was 50 mg L -1 The CTC solution and the concentration were 40 mg L -1 OTC solution, adsorbent dosage: 0.1 g L -1 The adsorption time of CTC solution is 10h, the adsorption time of OTC solution is 9h, pH is set to 6, temperature is 298K, and the HKUST-1 in comparative example 1 and the Bi in example 1 are tested respectively. 0.05 HKUST-1, Bi in Example 2 0.1 HKUST-1, Bi in Example 3 0.15 The comparison of HKUST-1 adsorption capacity of CTC and OTC is shown in the figure below. Figure 3As shown in a and 3c, it can be seen that doping with Bi ions will increase the adsorption capacity of HKUST-1 for CTC and OTC. When Bi ions are doped and the Bi:Cu ratio increases from 0.05:0.95 to 0.10:0.90, Bi x The adsorption capacity of HKUST-1 increases. This is because the incorporation of metallic Bi occupies some of the Cu sites, which improves the water stability of the material and gives full play to the adsorption effect of the Cu active sites. However, when the Bi:Cu ratio increases to 0.15:0.85, the adsorption capacity decreases, which may be due to the increase in the molar content of Bi, which occupies the Cu adsorption sites. Therefore, the Bi:Cu ratio is 0.10:0.90, that is, Bi 0.1 HKUST-1 material has the highest adsorption capacity. SA-Cu gel in Example 2, Bi 0.1 HKUST-1 / SA-Cu composite beads, Bi in Example 5 0.1 HKUST-1 / SA-Cu composite beads, Bi in Example 6 0.1 The comparison of the adsorption capacity of CTC and OTC by HKUST-1 / SA-Cu composite beads is shown in the figure. Figure 3 As shown in b and 3d, it can be seen that when Bi 0.1 When HKUST-1 and SA-Cu were composited at a mass ratio of 1:1, the adsorption capacity reached the maximum, and the adsorption capacity of CTC and OTC reached 294.3 mg g -1 and 264.8 mg g -1 , and are higher than Bi before compounding 0.1 HKUST-1 and SA-Cu. It is worth noting that attempts were made to prepare Bi 0.1 The composite material with a mass ratio of HKUST-1 to SA-Cu of 2:1 failed to be encapsulated successfully, resulting in material rupture.

[0070] 2. Adsorption regeneration cycle experiment: Bi prepared in Example 4 0.1 HKUST-1 / SA-Cu composite beads were used as adsorbents and the concentration was 50 mg L -1 The CTC solution and the concentration were 40 mg L -1 OTC solution, adsorbent dosage: 0.1gL -1 The adsorption time of CTC solution was 10 h, and that of OTC solution was 9 h. The pH was set to 6 and the temperature was 298 K. After each adsorption, desorption was performed, i.e., the adsorbed material was first immersed in a hydrochloric acid solution with a pH of 4.5, and then placed in a sealed shock box at 35°C for desorption for 2 h. Finally, it was washed three times with 300 mL of water, and then the next adsorption operation was continued. The cycle was repeated to obtain the Bi in Example 4. 0.1Adsorption regeneration cycle experiment of HKUST-1 / SA-Cu composite beads Figure 6 As shown, it can be seen that Bi 0.1 The initial adsorption capacity of HKUST-1 / SA-Cu was very high. With the increase of adsorption cycles, the adsorption capacity decreased. However, it still had a high adsorption performance (close to 100 mg g) after 10 cycles. -1 ), indicating Bi 0.1 HKUST-1 / SA-Cu beads have practical value in the adsorption and removal of CTC and OTC in wastewater treatment.

[0071] Adsorption parameter test

[0072] 1. Adsorbent dosage test: the concentration is 50 mg L -1 The CTC solution and the concentration were 40 mg L -1 The adsorption time of OTC solution, CTC solution was 10h, and OTC solution was 9h. The pH was set to 6 and the temperature was 298K. The Bi prepared in Example 4 was 0.1 HKUST-1 / SA-Cu composite beads were used to adsorb CTC solution and OTC solution with different adsorbent dosages, respectively. 0.1 The comparison of the adsorption capacity of HKUST-1 / SA-Cu composite beads for CTC and OTC at different adsorbent dosages is shown in the figure. Figure 4 As shown in Figures 4a and 4b, it can be seen that with the increase of adsorbent dosage, more and more adsorption sites are available, thereby improving the removal efficiency of CTC and OTC. However, due to the aggregation of adsorbent particles, the actual adsorption capacity decreases with the increase of adsorbent dosage.

[0073] 2. Adsorption pH value test: the concentration was 50 mg L -1 The CTC solution and the concentration were 40 mg L -1 OTC solution, the Bi prepared in Example 4 0.1 HKUST-1 / SA-Cu composite beads were prepared using 0.1 g L -1 The adsorbent dosage was 10 hours for the CTC solution and 9 hours for the OTC solution. The temperature was 298K. The Bi in Example 4 was tested. 0.1 The comparison of the adsorption capacity of CTC and OTC of HKUST-1 / SA-Cu composite beads at different pH values ​​is shown in the figure. Figure 4 As shown in Figures c and 4d, it can be seen that the adsorption amount is large when the solution pH is 4 to 8. The adsorption amount is the largest at pH 6. The zeta potential results show that the surface is positively charged at this time, generating electrostatic attraction with the oxygen anions in CTC and OTC.

[0074] 3. Test on the influence of different water qualities on adsorption performance: Bi prepared in Example 4 0.1 The HKUST-1 / SA-Cu composite beads were adsorbed at a concentration of 50 mg L -1 CTC solution and a concentration of 40 mg L -1 OTC solution, pH = 6, temperature 298K, 0.1g L -1 The adsorbent dosage and adsorption time were 10 h for CTC solution and 9 h for OTC solution, respectively. The water quality of CTC solution and OTC solution was 0.01 mol L -1 Interfering ions (Na + , K + 、Cl - 、SO4 2+ ) and different water qualities (deionized water, tap water, water from the Xiangjiang River in Changsha, Hunan), the Bi in Example 4 was obtained 0.1 HKUST-1 / SA-Cu complex beads were condensed in 0.01 mol L -1 The comparison of interfering ions and different water qualities on the adsorption capacity of CTC and OTC is shown in the figure below. Figure 5 As shown, it can be seen that the ion pairs Bi 0.1 The adsorption capacity of HKUST-1 / SA-Cu was affected little. By changing the water quality source, deionized water, tap water and Xiangjiang River water (taken from the Changsha section of Xiangjiang River in Hunan) were mixed into solutions for adsorption. It was found that the change of water quality had little effect on the adsorption capacity. 0.1 HKUST-1 / SA-Cu can be used for the adsorption and removal of pollutants in actual water bodies.

[0075] In Bi 0.1 During the adsorption of CTC or OTC by HKUST-1 / SA-Cu, no Bi ions were detected in the solution. Therefore, their release can be ignored. 2+ The release concentration was 0.1503 mg L -1 and 0.1581 mg L -1 , which is significantly lower than the maximum permissible concentration of copper in drinking water specified by WHO (2 mg L -1 ), indicating that Cu 2+ The release also meets the standards.

[0076] Bi 0.1 The fitting results of the adsorption kinetic curves of CTC and OTC on HKUST-1 / SA-Cu are shown in Tables 1 and 2, respectively. 0.1 Correlation coefficient R of the pseudo-second-order model of HKUST-1 / SA-Cu 2Higher than the correlation coefficient of pseudo-first-order kinetic model. At the same time, the theoretical q obtained from the linear plot of pseudo-second-order model e With the experimental q exp The values ​​are closer, which indicates that the adsorption process conforms to the pseudo-second-order kinetic model.

[0077] Table 1|Bi 0.1 Adsorption kinetic parameters of CTC with different initial concentrations on HKUST-1 / SA-Cu

[0078]

[0079] Table 2Bi 0.1 Adsorption kinetic parameters of HKUST-1 / SA-Cu for OTC with different initial concentrations

[0080]

[0081] Bi 0.1 The adsorption isotherm fitting results of HKUST-1 / SA-Cu on CTC and OTC are shown in Table 3 and Table 4, respectively. It can be seen that at each temperature, Bi 0.1 The correlation coefficient (R 2 ) are both higher than the correlation coefficient of Freundlich isotherm (R 2 ) is high, indicating that the adsorption process is more consistent with the Langmuir adsorption isotherm model and is a monolayer adsorption process; Bi 0.1 The maximum adsorption capacities of HKUST-1 / SA-Cu for CTC and OTC at 298 K were 588.24 mg g -1 and 476.19 mg g -1 , the adsorption capacity at 313K (40℃) is 2000.00 mg g -1 At the same time, R L The values ​​are all between 0 and 1, and the n values ​​are all greater than 1 and some are greater than 2, indicating that the adsorption process is favorable.

[0082] Table 3Bi 0.1 Adsorption isotherm parameters of CTC adsorption on HKUST-1 / SA-Cu

[0083]

[0084] Table 4Bi 0.1 Adsorption isotherm parameters of OTC adsorption on HKUST-1 / SA-Cu

[0085]

[0086] Bi 0.1 The thermodynamic fitting curves of CTC adsorption on HKUST-1 / SA-Cu at different temperatures are shown in Tables 5 and 6, respectively. It can be seen that the ΔG o are all negative, and the negative value increases with increasing temperature, indicating that the adsorption process of the adsorbent on CTC and OTC solutions is a spontaneous process, and is more favorable at high temperatures. o A positive value indicates that the adsorption is an endothermic process. o The positive value reflects that the affinity of the adsorbent for CTC and OTC is enhanced during the adsorption period, which may be due to the increase in disorder of the solid-liquid interface after adsorption and the continuous release of water molecules.

[0087] Table 5Bi 0.1 Thermodynamic parameters of CTC adsorption on HKUST-1 / SA-Cu at different temperatures

[0088]

[0089] Table 6Bi 0.1 Thermodynamic parameters of OTC adsorption on HKUST-1 / SA-Cu at different temperatures

[0090]

[0091] In summary, the present invention introduces Bi into HKUST-1 and composites it with copper alginate to prepare Bi with good mechanical properties and easy separation and recovery. x HKUST-1 / SA-Cu composite adsorbent is used to adsorb and remove CTC and OTC in aqueous solution. When the Bi:Cu molar ratio is 0.1:0.9, Bi 0.1 When the mass ratio of HKUST-1 to SA-Cu is 1:1, the adsorption capacity is the largest. 0.1 The adsorption process is uniform monolayer adsorption, mainly chemical adsorption, and the maximum adsorption capacity of CTC at 298K is 588.24mg g -1 The maximum adsorption capacity of OTC is 476.19 mgg -1 The adsorption capacity is greatly affected by temperature. When the temperature reaches 313K, the maximum adsorption capacity of the material for both is 2000.00 mg g -1 。Bi 0.1 The adsorption mechanism of CTC and OTC by HKUST-1 / SA-Cu beads is basically the same, including hydrogen bonding, π-π stacking, cationic bond bridge, n-πEDA interaction, hydrophobic interaction and π-πEDA interaction. Ionic strength, water quality test and adsorption regeneration test show that Bi0.1 HKUST-1 / SA-Cu beads have good practical performance. 0.1 HKUST-1 / SA-Cu beads are a promising tetracycline adsorbent and can be used for the treatment of CTC, OTC-containing pharmaceutical wastewater and medical wastewater.

[0092] The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A method for preparing a composite adsorbent, characterized in that: The following steps are involved: (1)Bi x Synthesis of HKUST-1: 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate and bismuth nitrate pentahydrate were dissolved in DMF and stirred, then heated to react, centrifuged, washed with DMF, vacuum dried and ground to obtain Bi x HKUST-1 powder; (2)Bi x Synthesis of HKUST-1 / SA-Cu composite beads: Bi x HKUST-1 powder was mixed with sodium alginate powder and ground, then added to deionized water, heated and stirred to melt into a gel state, and air bubbles were removed by ultrasound to eliminate the air in the gel. The gel was then absorbed and added dropwise to the ionic solution to solidify it, thereby obtaining Bi x The HKUST-1 / SA-Cu composite beads were transferred to deionized water for soaking, and the deionized water was replaced every 8 hours.

2. The method for preparing a composite adsorbent according to claim 1, characterized in that: In step (1), the molar ratio of 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate and bismuth nitrate pentahydrate is 14:(17-19):(1-3).

3. The method for preparing a composite adsorbent according to claim 2, characterized in that: In step (1), the molar ratio of 1,3,5-benzenetricarboxylic acid, copper nitrate trihydrate and bismuth nitrate pentahydrate is 7:9:

1.

4. The method for preparing a composite adsorbent according to claim 1, characterized in that: In step (1), the temperature-raising reaction refers to the reaction at 110° C. for 18 hours.

5. The method for preparing a composite adsorbent according to claim 1, characterized in that: In step (1), the vacuum drying temperature is 70° C., and the vacuum drying time is 12 h.

6. The method for preparing a composite adsorbent according to claim 1, characterized in that: In step (2), the Bi x The mass ratio of HKUST-1 powder to sodium alginate powder is 1:(1-3).

7. The method for preparing a composite adsorbent according to claim 6, characterized in that: In step (2), the Bi x The mass ratio of HKUST-1 powder to sodium alginate powder was 1:

1.

8. The method for preparing a composite adsorbent according to claim 1, characterized in that: In step (2), the temperature of the heating and stirring is 85°C.

9. The method for preparing a composite adsorbent according to claim 1, characterized in that: In step (2), the curing time is 24 hours.

10. Use of an adsorbent prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The adsorbent is used to adsorb tetracycline pollutants in water bodies, and the amount of the adsorbent is 0.1 g L -1 , the pH value of the water body is 4-8.

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