Use of sulfidized zero-valent manganese for the removal of tetracycline from water bodies
By using sulfide-modified zero-valent manganese (SZVMn) as an adsorbent, the problem of poor removal efficiency of zero-valent iron from tetracycline antibiotics in water was solved, achieving a highly efficient and stable tetracycline removal effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUANGZHOU UNIVERSITY
- Filing Date
- 2024-04-02
- Publication Date
- 2026-05-12
AI Technical Summary
In existing technologies, zero-valent metals such as zero-valent iron are not very effective in removing tetracycline antibiotics from water and have poor stability, making them difficult to apply effectively to wastewater treatment.
Sulfide-modified zero-valent manganese (SZVMn) was used as an adsorbent. By adding zero-valent manganese sulfide to the water, its surface activity was optimized and its stability was improved, which was then used to adsorb and remove tetracycline antibiotics.
Zero-valent manganese sulfide exhibits an adsorption rate of up to 96.20% for tetracycline under alkaline conditions, which is significantly better than that of unmodified zero-valent manganese. It is highly efficient, widely applicable, easy to operate, and has minimal impact on water quality.
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Figure CN118084125B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of environmental remediation technology, specifically relating to the application of zero-valent manganese sulfide in the removal of tetracycline antibiotics from wastewater. Background Technology
[0002] Tetracycline antibiotics, as broad-spectrum antibiotics, are widely used in clinical medicine and livestock and aquaculture. Tetracycline antibiotics share a common chemical matrix and mainly include tetracycline, chlortetracycline, oxytetracycline, demeclocycline, doxycycline, minocycline, and tigecycline. The excessive use, abuse, and improper disposal of antibiotics have led to their frequent detection in environmental water bodies and soil. Livestock farming and aquaculture are among the main sources of tetracycline pollution. These antibiotics are often added to animal feed to improve growth rates and prevent disease. With the expansion of livestock farming, large quantities of tetracycline antibiotics enter the animal's body, and some unabsorbed antibiotics enter the environment through animal excrement.
[0003] Methods for removing tetracycline antibiotics mainly include advanced oxidation, adsorption, coagulation, and microbial treatment. Traditional urban wastewater treatment methods primarily focus on removing suspended solids, organic matter, nitrogen, and phosphorus from wastewater, while their effectiveness in removing trace amounts of drugs and antibiotics is relatively limited.
[0004] Zero-valent metals have attracted widespread attention in environmental remediation and pollution control due to their strong reducing and adsorption properties, as well as their applicability to a variety of pollutants. While zero-valent metals exhibit good degradation and removal effects on antibiotics, unmodified zero-valent metals, such as zero-valent iron (ZVI), are prone to passivation, poor stability, and limited selectivity. Sulfidation treatment of zero-valent metals is an effective way to improve their performance, optimizing surface activity, preventing passivation, and enhancing stability. Currently, there is no known application of sulfided zero-valent manganese in the removal of tetracycline antibiotics from wastewater. Summary of the Invention
[0005] No studies have been reported on the treatment of tetracycline-containing antibiotic wastewater using zero-valent manganese (ZVMn) and its sulfide-modified form. This invention aims to investigate the removal effect of sulfide-modified zero-valent manganese (SZVMn) on tetracycline in water.
[0006] This invention provides the application of zero-valent manganese sulfide in the removal of tetracycline antibiotics from water bodies. The method involves adding zero-valent manganese sulfide to the water body at a dosage of 0.5–2.0 mg per milliliter of water.
[0007] The method for preparing zero-valent manganese sulfide is as follows: NaBH4 solution is injected into MnSO4·H2O solution at a rate of 10 mL·min. -1The mixture was stirred to obtain a ZVMn suspension; Na2S·9H2O solution was added to the prepared ZVMn suspension to synthesize zero-valent manganese sulfide; in the preparation method of zero-valent manganese sulfide, the S / Mn molar ratio was 1.0.
[0008] This invention investigates the effect of water pH on the adsorption of tetracycline by zero-valent manganese sulfide. The pH of the water in which zero-valent manganese sulfide adsorbs tetracycline is preferably 4–10. Especially under alkaline conditions, zero-valent manganese sulfide exhibits a high adsorption rate for tetracycline. More preferably, the pH of the water in which zero-valent manganese sulfide adsorbs tetracycline is 10.
[0009] This invention investigates the effect of water temperature on the adsorption of tetracycline by zero-valent manganese sulfide. The suitable water temperature for the adsorption of tetracycline by zero-valent manganese sulfide is 20–30°C. Specifically, the water temperature for the adsorption of tetracycline by zero-valent manganese sulfide is 25°C.
[0010] Furthermore, the present invention provides an adsorbent for removing tetracycline antibiotics from water. The adsorbent comprises the aforementioned zero-valent manganese sulfide.
[0011] This invention provides a preferred method for preparing the zero-valent manganese sulfide: NaBH4 solution is pumped into MnSO4·H2O solution using a peristaltic pump at a rate of approximately 10 mL / min. -1 The stirring speed was 500 rpm. After the inflow of MnSO4·H2O was complete, stirring continued for 30 min, followed by precipitation for 10 min. Similarly, SZVMn was synthesized by adding Na2S·9H2O solution to the prepared ZVMn suspension, reacting for 30 min, and then precipitating for 10 min. The above steps provide a theoretical S / Mn molar ratio of 1.0.
[0012] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:
[0013] The zero-valent manganese sulfide provided by this invention exhibits excellent adsorption effects on tetracycline antibiotics in water. When the tetracycline concentration is 5–200 mg / L, the reaction temperature is 25°C, and the initial pH is 10, the maximum adsorption capacity of zero-valent manganese sulfide for tetracycline is 127.0223 mg / g. Experiments have verified that the adsorption effect of zero-valent manganese sulfide on tetracycline is significantly higher than that of zero-valent manganese. The application of zero-valent manganese sulfide in the removal of tetracycline antibiotics from wastewater provided by this invention features high removal efficiency, wide applicability, simple operation, and minimal impact on water quality. Attached Figure Description
[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0015] Figure 1 The graph shows the adsorption efficiency of zero-valent manganese sulfide and zero-valent manganese for tetracycline under different pH conditions.
[0016] Figure 2 The graph shows the adsorption efficiency of tetracycline by zero-valent manganese sulfide at different temperatures.
[0017] Figure 3 The graph shows the adsorption efficiency of tetracycline by zero-valent manganese sulfide at different addition amounts.
[0018] Figure 4 This is a graph showing the adsorption efficiency of zero-valent manganese sulfide for tetracycline under the influence of different metal ions.
[0019] Figure 5 This is a scanning electron microscope image of zero-valent manganese sulfide before adsorption.
[0020] Figure 6 This is a scanning electron microscope image of zero-valent manganese sulfide after adsorption of tetracycline.
[0021] Figure 7 The image shows the XRD patterns of zero-valent manganese sulfide before and after the adsorption of tetracycline.
[0022] Figure 8 The image shows the FTIR spectra of zero-valent manganese sulfide before and after the adsorption of tetracycline.
[0023] Figure 9 Figure showing the kinetic fitting analysis results of the process of removing tetracycline from zero-valent manganese sulfide.
[0024] Figure 10 The figure shows the fitting results of the Langmuir and Freundlich isothermal adsorption models to the experimental data. Detailed Implementation
[0025] The technical solution of the present invention will be described below with reference to the embodiments. However, the present invention is not limited to the following embodiments.
[0026] Unless otherwise specified, the experimental and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.
[0027] Example 1
[0028] This embodiment describes the adsorption and removal performance of zero-valent manganese sulfide for tetracycline under different conditions. In this embodiment, the absorbance of tetracycline in the solution was measured using a UV spectrophotometer, and the adsorption rate and adsorption amount were calculated based on the measured tetracycline absorbance.
[0029] The method for preparing zero-valent manganese sulfide described in this embodiment is as follows: NaBH4 solution is pumped into MnSO4·H2O solution using a peristaltic pump at a rate of approximately 10 mL / min. -1 The stirring speed was 500 rpm. After the inflow of MnSO4·H2O was complete, stirring continued for 30 min, followed by precipitation for 10 min. Similarly, SZVMn was synthesized by adding Na2S·9H2O solution to the prepared ZVMn suspension, reacting for 30 min, and then precipitating for 10 min. The above steps provide a theoretical S / Mn molar ratio of 1.0. The obtained ZVMn and SZVMn were washed three times with anhydrous ethanol and then freeze-dried under vacuum at -228 K. The resulting products were sealed in self-sealing bags and stored in a desiccator for later use.
[0030] 1. Adsorption and removal experiments of tetracycline by zero-valent manganese and zero-valent manganese sulfide under different pH conditions
[0031] Solution pH plays a crucial role in the adsorption process by regulating the activity of ions in the solution and the charge properties of the adsorbent surface. This experiment investigated the adsorption and removal efficiency of zero-valent manganese and zero-valent manganese sulfide for tetracycline under different pH conditions at room temperature. Experimental results are shown below. Figure 1 .
[0032] Prepare a 250 mL tetracycline solution with a concentration of 10 mg / L, and divide it into 12 portions of 20 mL each. React on a shaker at 25 °C and 150 rpm for 30 min.
[0033] Treatment group 1 (Mn): The pH was adjusted to 2, 4, 6, 7, 8 and 10 with NaOH solution and dilute nitric acid respectively, and 0.02g of zero-valent manganese was weighed and added to the solutions of different pH values.
[0034] Treatment group 2 (s-Mn): The pH was adjusted to 2, 4, 6, 7, 8 and 10 respectively with NaOH solution and dilute nitric acid. 0.02g of zero-valent manganese sulfide was weighed and added to the solutions of different pH values.
[0035] like Figure 1As shown, the adsorption efficiency increases rapidly with increasing pH, then rises slowly. Furthermore, the adsorption rate of tetracycline by the sulfur-modified zero-valent manganese material is significantly higher than that of the unmodified zero-valent manganese. Under alkaline conditions, the adsorption and removal rate of tetracycline by the sulfur-modified zero-valent manganese material is higher. At pH 10, the adsorption and removal rate of tetracycline by sulfur-modified zero-valent manganese is 96.20%. Comparative experiments show that the adsorption rate of tetracycline by sulfur-modified zero-valent manganese is significantly higher than that of unmodified manganese, and the increase in adsorption rate is gradual as the pH changes from 8 to 10. Therefore, subsequent experiments will only explore the optimal removal rate of sulfur-modified zero-valent manganese under different conditions, and the reaction will be conducted in a solution at pH 10.
[0036] 2. Adsorption and removal experiments of tetracycline by zero-valent manganese sulfide at different temperatures
[0037] Prepare a 120 mL tetracycline solution with a concentration of 10 mg / L, and divide it into 5 portions of 20 mL each. Weigh 0.02 g of zero-valent manganese sulfide into each portion of the tetracycline solution and adjust the pH to 10. Place the solutions in a shaker at 20℃, 25℃, 30℃, 35℃, and 40℃ for 30 min at 150 rpm, respectively. The experimental results are shown below. Figure 2 .
[0038] like Figure 2 As shown, the adsorption efficiency of zero-valent manganese sulfide first increases and then decreases with increasing temperature, and the highest adsorption efficiency for tetracycline is observed at 25℃, reaching 96.20%. This indicates that adsorption equilibrium has been reached at 25℃. As the reaction temperature further increases, the thermal motion of molecules intensifies, leading to desorption of the adsorbate from the adsorbent surface, thereby reducing the adsorption efficiency.
[0039] 3. Adsorption and removal experiments of tetracycline by zero-valent manganese sulfide at different addition amounts
[0040] Prepare a 100 mL tetracycline solution with a concentration of 10 mg / L, and divide it into four 20 mL portions. Weigh out 0.01 g, 0.02 g, 0.04 g, 0.06 g, and 0.08 g of zero-valent manganese sulfide, respectively, and add them to the tetracycline solution. Adjust the pH of the solution to 10. React on a shaker at 25℃ and 150 rpm for 30 min. The experimental results are shown below. Figure 3 .
[0041] Zero-valent manganese sulfide exhibits good removal effects on antibiotic-like pollutants due to its inherent functional groups, active sites, and porous structure. For example... Figure 3As shown, the adsorption efficiency first increases and then decreases with the increase of zero-valent manganese sulfide dosage, reaching a maximum of 96.19% at a dosage of 1.0 g / L. The reason for the initial increase and subsequent decrease in adsorption efficiency in this experiment may be that when the dosage is too high, zero-valent manganese sulfide will aggregate to form large particles or clumps, thereby reducing the effective surface area and lowering the adsorption efficiency.
[0042] 4. Adsorption and Removal Experiments of Tetracycline by Zero-Valence Manganese Sulfide under the Influence of Different Metal Ions
[0043] Weigh 0.02 g of zero-valent manganese sulfide and add it to a 10 mg / L tetracycline solution. Add different metal ion solutions separately, adjust the pH of the solution to 10, and react in a shaker at 25℃ and 150 rpm for 30 min.
[0044] Polluted water bodies often have complex compositions and contain many other metal ions, which can affect the adsorption and removal efficiency of tetracycline. Therefore, this experiment focuses on Mg, a common metal ion in water bodies. 2+ Ca 2+ Na + Plasma was used to design and investigate the effect of different ions on the adsorption efficiency of S-Mn materials for tetracycline. Experimental results are shown below. Figure 4 .
[0045] like Figure 4 As shown, the adsorption efficiency remained high and consistent under the influence of different ions. While the adsorption efficiency of the S-Mn material for tetracycline decreased slightly with increasing concentrations of the three metal ions, the effect was not significant. The highest efficiency was observed at a metal ion concentration of 0.001 g / L, and the lowest at 0.1 g / L. The decrease in adsorption efficiency may be due to the metal ions and antibiotic molecules competing for the same adsorption sites as the metal ion concentration increases.
[0046] Example 2
[0047] This embodiment describes the characterization of the zero-valent manganese sulfide material prepared in Example 1 using characterization methods such as SEM, FTIR, and XRD, and analyzes its surface morphology, elemental composition, surface functional groups, and other morphological structures.
[0048] 1. SEM analysis of the material before and after adsorption
[0049] The morphology of zero-valent manganese sulfide (SZVMn) has a certain influence on its adsorption performance. To investigate the surface morphology changes of the prepared SZVMn before and after adsorption, a certain amount of powdered SZVMn material was dried and then orderly and uniformly coated on conductive adhesive. SEM analysis was performed on the material, and the results are shown below. Figure 5 and Figure 6 .
[0050] from Figure 5 and Figure 6 It can be seen that the composite material before the reaction is granular with a slightly rough surface and many large pores. After the reaction, the sulfurized zero-valent manganese material agglomerates into larger particles, and the pores become smaller. The sulfurization modification results in a complex multilayer structure. Other morphological aspects do not change significantly, indicating that the material is relatively stable. Due to the decrease in the percentage of O and the increase in the proportion of Mn, it is inferred that oxygen-containing functional groups participated in the adsorption reaction. The main elements of the SZVMn material are O and Mn, with O accounting for 78.42% and Mn accounting for 24.79%. The SZVMn ion surface is easily oxidized, and manganese oxides are easily coated on the inner manganese core, which is a common phenomenon in the synthesis of nano-zero-valent metal surfaces.
[0051] Combined with SEM images, it can be seen that there are many smaller particles aggregated together in different geometries on the surface of SZVMn. These observations can be attributed to the sulfurization modification and the resulting MnS precipitates.
[0052] 2. XRD analysis of the material before and after adsorption
[0053] To investigate the adsorption performance of SZVMn and the phase distribution before and after adsorption, X-ray diffraction was used to analyze the zero-valent manganese sulfide material. The analytical results are shown below. Figure 7 .
[0054] like Figure 7 As shown, the XRD characteristic peaks at 2θ = 24.610°, 27.626°, 29.256°, 36.162°, 46.317°, 52.157°, and 54.463° correspond to the (100), (002), (101), (102), (110), (103), and (112) crystal planes of γ-MnS, respectively. Even after tetracycline adsorption, the XRD characteristic peaks of γ-MnS were still observed in the reactants, indicating that the heavy metal ions were successfully adsorbed onto the SZVMn material.
[0055] 3. FTIR analysis of materials before and after adsorption
[0056] SZVMn and its FTIR spectrum after tetracycline adsorption are as follows Figure 8 As shown. At 3421cm -1 The peak obtained at this location belongs to a relatively weak hydrogen bond formed by the stretching vibration of the -OH group. At 1118 cm⁻¹ -1 The narrow band observed is caused by the bending vibration of Mn-OH, and this peak is considered to be a characteristic band of manganese oxides.
[0057] After adsorbing tetracycline, at 1114 cm -1The weakening of the peak at 1632 cm⁻¹ is likely due to the bonding of tetracycline with -OH groups, causing the Mn-OH group to transform into an M-OH group, indicating that surface complexation may have occurred. -1 The distinct peak at 981 cm⁻¹ is attributed to the bending vibration of the HOH, indicating the possible presence of physically adsorbed water. -1 The peak value is assigned to the SO vibration, indicating that zero-valent manganese sulfide is oxidized. (400–650 cm⁻¹) -1 The peaks obtained within the range represent the bending vibrations of Mn-O, further indicating that some manganese sulfide in the material is converted into manganese oxide.
[0058] Example 3
[0059] This embodiment conducts kinetic fitting analysis on the process of removing tetracycline by zero-valent manganese sulfide to explore the adsorption mechanism of tetracycline removal by zero-valent manganese sulfide.
[0060] 200 mL of tetracycline solution with an initial concentration of 25 mg / L was placed in a magnetic stirrer with constant temperature heating, maintaining pH = 10.0, stirring speed of 200 r / min, and adsorption reaction temperature of 25 °C. 0.2 g of zero-valent manganese sulfide was added, and 3 mL of the supernatant was collected at 0, 0.5 min, 1 min, 2 min, 5 min, 10 min, 15 min, 30 min, 60 min, 120 min, 240 min, 480 min, 720 min, and 1440 min, respectively, filtered into centrifuge tubes. The concentration of tetracycline in the supernatant was measured, and the adsorption rate and adsorption amount were calculated. Experimental results are shown below. Figure 9 .
[0061] (1) Pseudo-first-order kinetic equation: An equation established assuming that the adsorption process is controlled by the diffusion step, with the Lagergern equation used for related calculations:
[0062] q t =q e (1-exp(-K1t))
[0063] Where: q t q represents the adsorption amount at time t (mg / g); e K1 is the adsorption amount at adsorption equilibrium (mg / g); K2 is the pseudo-first-order adsorption rate constant (min). -1 ).
[0064] (2) Pseudo-second-order kinetic equation: This equation is established based on the assumption that the adsorption process is controlled by chemisorption. The adsorption rate is related to the electron transfer and ion exchange states of the adsorbent, belonging to a complex adsorption process. Therefore, the pseudo-second-order kinetic model is more realistic in describing the adsorption of heavy metals in the aquatic environment. Its relevant calculation expression is:
[0065] q t =qe 2 K2t / (1+q e K2t)
[0066] Where: q t q represents the adsorption amount at time t (mg / g); e K2 is the adsorption amount at adsorption equilibrium (mg / g); K2 is the pseudo-second-order adsorption rate constant (g·mg). -1 ·min -1 ).
[0067] like Figure 9 As shown, the two dynamic models are similar in degree, but the quasi-second-order dynamic model (R... 2 =0.94955) compared to the quasi-first-order dynamic model (R 2 =0.88543) has a high degree of agreement and is more suitable for describing reactions. Furthermore, due to... Figure 9 The trend shows that the adsorption capacity of zero-valent manganese sulfide for tetracycline increases rapidly within the first 5 minutes of the reaction. This may be because in the early stage of the reaction, there are enough active sites on the surface of the adsorbent to quickly adsorb tetracycline. Subsequently, when the reaction time reaches 60 minutes, the adsorption capacity tends to stabilize, the growth trend slows down, and it slowly approaches the adsorption limit to reach adsorption equilibrium.
[0068] Example 4
[0069] This embodiment investigates the adsorption mechanism of tetracycline removal by zero-valent manganese sulfide through isothermal adsorption fitting and thermodynamic analysis.
[0070] 20 mL of tetracycline solutions with initial concentrations of 5 mg / L, 10 mg / L, 25 mg / L, 50 mg / L, 100 mg / L, and 200 mg / L were placed in a magnetic stirrer with a constant temperature heating system. The pH was maintained at 10.0, the stirring speed at 200 rpm, and the adsorption reaction temperature at 25 °C. 0.02 g of zero-valent manganese sulfide was added. After the adsorption reaction lasted 30 min, 5 mL of the supernatant was filtered into a 10 mL centrifuge tube. The concentration of thallium in the supernatant was measured, and the adsorption rate and adsorption amount were calculated. Experimental results are shown below. Figure 10 The Langmuir and Freundlich isothermal adsorption models were selected to fit the experimental data, and the fitting parameters are shown in Table 1.
[0071] Table 1. Isothermal adsorption fitting parameters of tetracycline for zero-valent manganese sulfide
[0072]
[0073] As shown in Table 1, Figure 10As shown, both the Langmuir and Freundlich adsorption isotherm models have high correlation coefficients, but the correlation coefficient R of the Langmuir adsorption isotherm model is lower. 2 The correlation coefficient (R²) is 0.9976, which is greater than the correlation coefficient (R²) of the Freundlich adsorption isotherm model. 2 (The value is 0.9665). It can be seen that the Langmuir model describes the adsorption process of tetracycline by zero-valent manganese sulfide more accurately than the Freundlich model. Furthermore, according to the Langmuir model, the maximum adsorption capacity of tetracycline by zero-valent manganese sulfide is 127.0223 mg / g. From the 1 / n value in the table, it can be seen that the adsorption reaction of tetracycline by the adsorbent proceeds easily, and the adsorption effect is high. From... Figure 10 It can be observed that when the tetracycline concentration is low (<75 mg / L), the adsorption capacity increases rapidly. As the concentration increases, the active sites of the adsorbent are gradually occupied, and the growth of adsorption capacity slows down.
[0074] As described above, the basic principles, main features, and advantages of the present invention have been well described. The above embodiments and specifications are merely descriptions of preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope defined by the present invention.
Claims
1. The application of zero-valent manganese sulfide in the removal of tetracycline from water bodies, characterized in that, Add zero-valent manganese sulfide to the water body at a dosage of 0.5~2.0 mg per milliliter of water. The method for preparing the zero-valent manganese sulfide is as follows: NaBH4 solution is dissolved at 10 mL / min... -1 The solution was injected into MnSO4·H2O at a certain rate and stirred to obtain a ZVMn suspension; Na2S·9H2O solution was added to the prepared ZVMn suspension to synthesize zero-valent manganese sulfide; in the preparation method of zero-valent manganese sulfide, the S / Mn molar ratio was 1.
0. The water in which zero-valent manganese sulfide adsorbs tetracycline has a pH of 10 and a temperature of 25°C.
2. An adsorbent for removing tetracycline antibiotics from water, characterized in that, The adsorbent comprises zero-valent manganese sulfide as described in claim 1.