Preparation method of magnesium and zirconium modified acidified aluminum oxide fluorine adsorbent

Abstract

The invention discloses a preparation method of a magnesium and zirconium modified acidified aluminum oxide fluorine adsorbent, and relates to a preparation method of an aluminum oxide fluorine adsorbent. The invention aims to solve the technical problems of insufficient fluoride selectivity, limited adsorption capacity, weak anti-interference capability and poor regeneration performance of the existing activated aluminum oxide adsorbent. According to the invention, MgO and ZrOCl2. 8H2O are used as metal sources to modify parent aluminum oxide to form the active aluminum oxide fluorine adsorption material loaded with Mg-Zr bimetals, and abundant surface hydroxyl groups and Mg-Zr active sites synergistically enhance chemical-physical adsorption of F-. Through triple modification of bimetal and acidification, systematic optimization of the number of active sites, surface charge characteristics, a pore structure and an adsorption mechanism is realized, so that the material is endowed with high adsorption capacity, high selectivity and good coexisting ion interference resistance.

Description

Technical Field

[0001] This invention relates to a method for preparing an alumina fluorine adsorbent. Background Technology

[0002] Fluorine, as an important industrial raw material, is widely used in the lithium industry, metallurgy, and chemical industry. In lithium industry clusters, the recycling and treatment of lithium-containing waste such as lithium fluoride generates large amounts of fluoride-containing wastewater, of which fluoride (F...) is present. - If fluoride is discharged directly into industrial wastewater without effective treatment, it will not only cause water pollution and soil acidification, but also accumulate in the food chain, harming human health and posing a serious threat to the ecological environment and sustainable human development. Therefore, the efficient removal and pollution control of fluoride in industrial wastewater is a key link in practicing the concept of a circular economy, protecting natural resources, and reducing the environmental burden.

[0003] Currently, the main technologies for removing fluoride from water include adsorption, precipitation, and membrane separation. Among these, adsorption is widely used in the treatment of fluoride-containing wastewater due to its simple operation, low cost, and ease of resource recovery. Activated alumina, as a common adsorbent material, is a frequently chosen choice for fluoride adsorption treatment due to its large specific surface area and good chemical stability. However, traditional activated alumina adsorbents suffer from insufficient selectivity for fluorides, limited adsorption capacity, weak anti-interference ability, and poor regeneration performance, making it difficult to meet the demand for highly selective and efficient fluoride removal from complex industrial wastewater. Its treatment effect is further limited, especially in wastewater containing lithium waste and coexisting interfering ions such as Al, P, and S.

[0004] Therefore, how to develop novel activated alumina adsorbents with high adsorption capacity, high selectivity, good stability, and anti-interference ability through material modification and optimization to achieve efficient removal of fluorides from water has become a research hotspot and challenge in the field of fluoride pollution control. This invention addresses this need by proposing a method for preparing magnesium and zirconium-modified acidified alumina and its application in removing fluorides from water, aiming to overcome the shortcomings of existing adsorbent materials and provide technical support for the efficient treatment of industrial fluoride wastewater. Summary of the Invention

[0005] The present invention aims to address the technical problems of existing activated alumina adsorbents, such as insufficient selectivity for fluorides, limited adsorption capacity, weak anti-interference ability, and poor regeneration performance, and provides a method for preparing magnesium and zirconium modified acidified alumina fluoride adsorbent.

[0006] The preparation method of the magnesium and zirconium modified acidified alumina fluorine adsorbent of the present invention is carried out according to the following steps:

[0007] 1. Acid treatment of alumina: Add sulfuric acid solution to alumina, stir evenly, let stand for activation, and after activation, wash the acid-treated alumina with water to remove residual excess sulfuric acid; after washing, transfer the alumina to a hot air oven for drying until the moisture is completely evaporated.

[0008] II. Acid treatment of magnesium oxide: Mix magnesium oxide with distilled water to prepare a homogeneous mixture. During this process, magnesium oxide will react chemically with water, thereby causing a change in its surface structure and generating magnesium hydroxide. Then, under continuous stirring, sulfuric acid solution is slowly added dropwise to the homogeneous mixture. After the addition is completed, the mixture is allowed to stand to ensure that the reaction is complete. Finally, drying is performed.

[0009] 3. Mixing: The products dried in the above two steps are mixed and dissolved in distilled water, and aged under magnetic stirring. After aging, they are dried in a hot air oven. The mass of alumina in step one is equal to that of magnesium oxide in step two.

[0010] IV. Adding ZrOCl2: The dried sample obtained in step 3 and ZrOCL2·8H2O are mixed evenly in distilled water and aged for 24-25 hours under magnetic stirring. After aging, the product is washed with water, dried, and then crushed in a mortar and pestle to obtain a fine powder sample, which is the magnesium and zirconium modified acidified alumina fluorine adsorbent.

[0011] The mass ratio of ZrOCL2·8H2O to alumina in step one is 1:(2~2.5).

[0012] This invention uses MgO and ZrOCl2·8H2O as metal sources to modify the parent alumina, forming an active alumina fluorine adsorbent material supported on Mg-Zr bimetals. The adsorption process conforms to the Langmuir / Freundlich model and pseudo-second-order kinetics. The abundant surface hydroxyl groups and Mg-Zr active sites synergistically enhance the adsorption of fluorine. - Chemical-physical adsorption.

[0013] The adsorbent prepared in this invention exhibits excellent removal efficiency for fluoride ions. Its mechanism lies in the synergistic construction of a multi-layered enhanced adsorption system through Mg-Zr bimetallic co-doping and acidification modification. First, the Mg and Zr bimetals form multiple active sites on the alumina surface. XPS characterization confirms that Mg and Zr elements are successfully loaded and enriched on the material surface, with the addition of Zr 3d and Mg 2p characteristic peaks compared to the unmodified state, directly expanding the density of fluoride ion binding sites. Second, the bimetals exert a synergistic regulatory effect through electronic effects: the introduction of Mg optimizes the charge distribution on the material surface, enhancing the electrostatic attraction to fluoride ions; Zr increases the effective specific surface area by regulating the alumina crystal structure. Furthermore, acidification activates the alumina surface, generating abundant surface hydroxyl groups (-OH). These hydroxyl groups synergistically enhance the removal of fluoride ions through ion exchange and coordination with the Mg-Zr active sites. - Chemisorption, high fitting of pseudo-second-order kinetic model (R 2 The significantly higher values ​​(compared to the pseudo-first-order model) confirm that chemisorption is the dominant mechanism. Simultaneously, the adsorption behavior of the adsorbent material for fluoride ions conforms to the Langmuir and Freundlich models, indicating that the adsorption process exhibits characteristics of both single-layer chemisorption and multi-layer physisorption. This synergistic chemisorption mechanism enables the material to achieve highly selective targeted capture in complex water conditions while simultaneously enhancing its capacity and resistance to interference through physisorption. In summary, this invention achieves systematic optimization of the number of active sites, surface charge characteristics, pore structure, and adsorption mechanism through triple modification involving bimetallization and acidification, thereby endowing the material with high adsorption capacity, high selectivity, and good resistance to interference from coexisting ions. Attached Figure Description

[0014] Figure 1 X-ray diffraction pattern of magnesium and zirconium-modified acidified alumina fluorine adsorbent prepared for Experiment 1;

[0015] Figure 2 Scanning electron microscope image of the magnesium and zirconium modified acidified alumina fluorine adsorbent prepared for Experiment 1;

[0016] Figure 3 The isotherm model curve for Experiment 2;

[0017] Figure 4 The dynamic model curves for Experiment 3 are shown below;

[0018] Figure 5 This is a comparison diagram of the Freundlich and Langmuir isotherms from Example 1;

[0019] Figure 6 This is a comparison diagram of the pseudo-first-order and second-order dynamic models in Example 2;

[0020] Figure 7 XPS image of Example 3;

[0021] Figure 8 This is a comparison chart of the removal rates in the interference test of Example 4. Detailed Implementation

[0022] Specific Implementation Method 1: This implementation method is a preparation method of magnesium and zirconium modified acidified alumina fluorine adsorbent, specifically carried out according to the following steps:

[0023] 1. Acid treatment of alumina: Add sulfuric acid solution to alumina, stir evenly, let stand for activation, and after activation, wash the acid-treated alumina with water to remove residual excess sulfuric acid; after washing, transfer the alumina to a hot air oven for drying until the moisture is completely evaporated.

[0024] II. Acid treatment of magnesium oxide: Mix magnesium oxide with distilled water to prepare a homogeneous mixture; then, under continuous stirring, slowly add sulfuric acid solution dropwise to the homogeneous mixture. After the addition is complete, keep it still to ensure that the reaction proceeds fully; finally, perform drying treatment.

[0025] 3. Mixing: The products dried in the above two steps are mixed and dissolved in distilled water, and aged under magnetic stirring. After aging, they are dried in a hot air oven. The mass of alumina in step one is equal to that of magnesium oxide in step two.

[0026] IV. Adding ZrOCl2: The dried sample obtained in step 3 and ZrOCL2·8H2O are mixed evenly in distilled water and aged for 24-25 hours under magnetic stirring. After aging, the product is washed with water, dried, and then crushed in a mortar and pestle to obtain a fine powder sample, which is the magnesium and zirconium modified acidified alumina fluorine adsorbent.

[0027] The mass ratio of ZrOCL2·8H2O to alumina in step one is 1:(2~2.5).

[0028] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the mass concentration of the sulfuric acid solution mentioned in step one is 95%~98%. Everything else is the same as in Specific Implementation Method One.

[0029] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the mass ratio of aluminum oxide to sulfuric acid solution in step 1 is 1g:(1mL~1.5mL). Everything else is the same as in Specific Implementation Method 1 or 2.

[0030] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: in step one, the device is allowed to stand for 30 minutes for activation. Everything else is the same as in Specific Implementation Methods One to Three.

[0031] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method Four in that the drying temperature in step one is 105℃. Everything else is the same as in Specific Implementation Method Four.

[0032] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Five in that the mass ratio of magnesium oxide to distilled water in step two is 1g:(5mL~6mL). Everything else is the same as in Specific Implementation Method Five.

[0033] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Six in that the mass concentration of the sulfuric acid solution mentioned in step two is 95%~98%. Everything else is the same as in Specific Implementation Method Six.

[0034] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Seven in that the mass ratio of magnesium oxide to sulfuric acid solution in step two is 1g:(1mL~1.5mL). Everything else is the same as in Specific Implementation Method Seven.

[0035] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Eight in that the step two involves letting it stand for 30 minutes. Everything else is the same as in Specific Implementation Method Eight.

[0036] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Method Nine in that the aging time in step three is 12 hours. Everything else is the same as in Specific Implementation Method Nine.

[0037] The invention was verified using the following experiments:

[0038] Experiment 1: This experiment demonstrates a method for preparing a magnesium and zirconium-modified acidified alumina fluorine adsorbent, specifically carried out according to the following steps:

[0039] 1. Acid treatment of alumina: Add 2 mL of sulfuric acid solution to 2 g of alumina, stir well, and let stand for 30 min for activation. After activation, wash the acid-treated alumina with water to remove excess residual sulfuric acid. After washing, transfer the alumina to a hot air oven for drying until the moisture is completely evaporated. The drying temperature is 105℃.

[0040] The sulfuric acid solution has a mass concentration of 98%.

[0041] II. Acid treatment of magnesium oxide: Mix 2g of magnesium oxide with 10mL of distilled water to prepare a homogeneous mixture; then, under continuous stirring, slowly add 2mL of sulfuric acid solution dropwise to the homogeneous mixture. After the addition is complete, let it stand for 30min to ensure that the reaction is complete; finally, perform drying treatment at a temperature of 105℃.

[0042] The sulfuric acid solution mentioned in step two has a mass concentration of 98%.

[0043] 3. Mixing: Mix the dried products from the above two steps together and dissolve them in 20 mL of distilled water. Aging is carried out for 12 h under magnetic stirring (300 rpm). After aging, dry in a hot air oven at 105 °C.

[0044] IV. Adding ZrOCl2: The dried sample obtained in step 3 and 1g of ZrOCL2·8H2O are mixed evenly in 20mL of distilled water and aged for 24h under magnetic stirring (300rpm). After aging, the product is washed with water and then dried at 105℃. It is then crushed in a mortar and pestle to obtain a fine powder sample, which is the magnesium and zirconium modified acidified alumina fluorine adsorbent.

[0045] Figure 1 The X-ray diffraction (XRD) pattern of the magnesium and zirconium-modified acidified alumina fluorine adsorbent prepared in Experiment 1 is shown. The characteristic diffraction peaks belonging to the γ-Al₂O₃ support are clearly visible in the spectrum, indicating that the acidification and metal loading processes did not destroy the crystal framework structure of alumina, maintaining its structural stability as an adsorption matrix. Simultaneously, a weak characteristic ZrO₂ diffraction peak appears at approximately 30.2° 2θ, while a diffraction signal of MgO can be observed near approximately 42.9° 2θ, but with low peak intensity. This indicates that Mg and Zr species are mainly uniformly loaded on the alumina surface in a highly dispersed or amorphous state, which is consistent with XPS (…). Figure 7 The surface enrichment phenomenon revealed by the characterization is mutually corroborated. This highly dispersed loading morphology is conducive to the full exposure of active sites and avoids the aggregation and covering of active components, thereby ensuring the effective exertion of the Mg-Zr bimetallic synergistic effect and providing a structural basis for the material to achieve a high adsorption capacity of 93.57 mg / g.

[0046] Figure 2 Scanning electron microscope (SEM) images of the magnesium and zirconium-modified acidified alumina fluoride adsorbent prepared in Experiment 1 show that the modified adsorbent material exhibits an irregular nanoscale particle packing morphology, with particle sizes mainly concentrated in the range of 50-200 nm, forming abundant mesoporous structures between particles. The material has a high surface roughness, with numerous fine grains and lamellar structures visible, indicating that the active components of Mg and Zr have successfully adhered to and modified the alumina surface. This morphological feature significantly increases the specific surface area of ​​the material, providing ample contact and diffusion channels for fluoride ions. Simultaneously, moderate particle aggregation forms a three-dimensional porous network structure, ensuring both the accessibility of adsorption sites and enhancing the sedimentation and separation performance of the material in aqueous phase. This microstructure, together with the XRD results, reveals that the stepwise acidification-aging process of this invention achieves controllable growth and uniform anchoring of the active components on the carrier surface, which is the key structural guarantee for the material's high adsorption capacity and good practicality.

[0047] Experiment 2: This experiment is an adsorption isotherm test of fluoride ions on the magnesium and zirconium-modified acidified alumina fluoride adsorbent prepared in Experiment 1. The specific process is as follows:

[0048] For fluoride ion solutions (solute is sodium fluoride, solvent is deionized water) with concentrations of 50, 100, 200, 400, 600, 800, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, and 5000 mg / L, respectively, 20 mL was taken into centrifuge tubes, and 0.12 g of the fluoride adsorbent prepared in Experiment 1 was added. The tubes were then placed in a shaker for adsorption. After adsorption, the fluoride concentration in the solution was measured using a UV spectrophotometer. - The concentration of the adsorbent was used to calculate the effect of the adsorbent on F in solutions of different concentrations. - The amount of adsorption;

[0049] The reaction conditions using a shaker were 25°C, 24 hours, and 180 rpm.

[0050] The obtained data were fitted with Freundlich and Langmuir adsorption isotherms. Figure 3 The figure shows the isotherm model curves, with black dots representing actual test data and dashed lines representing the fitted isotherm curves. As shown, the Freundlich and Langmuir adsorption isotherm fitting results are both good, indicating that the adsorption process of this adsorbent material tends to exhibit both physical adsorption mechanisms on non-uniform surfaces and chemical adsorption.

[0051] Experiment 3: This experiment is an adsorption kinetics test of fluoride ions on the magnesium and zirconium-modified acidified alumina fluoride adsorbent prepared in Experiment 1. The specific experiment is as follows:

[0052] Measure 20 mL of fluoride ion solution (solute is sodium fluoride, solvent is deionized water, fluoride ion concentration is 5000 mg / L) and add it to a 50 mL centrifuge tube. Weigh 0.12 g of the adsorbent material prepared in Experiment 1 and add it to the centrifuge tube to disperse it evenly. Place the tube in a shaker and shake to perform adsorption. Take samples at regular intervals during the adsorption process. After adsorption is complete, use a UV spectrophotometer to test the fluoride concentration in the solution. - The concentration of the adsorbent was calculated, and the effect of the adsorbent on F at different time points was determined. - The amount of adsorption;

[0053] The sampling times are 0, 5, 10, 15, 20, 30, 40, 60, 80, 100, 150, 200, 300, 450, 500 and 600, all in minutes.

[0054] The reaction conditions using a shaker were 25°C and 180 rpm.

[0055] The obtained data were fitted with pseudo-first-order and pseudo-second-order dynamics. Figure 4 The graph shows the dynamic model curves, where the black dots represent actual test data and the dashed lines represent the dynamic fitting curves. Figure 4 The fitting results show that the correlation coefficient (R0) of the pseudo-second-order dynamic model of the material is... 2 The value is significantly greater than the R of the pseudo-first-order dynamic model. 2 Furthermore, the pseudo-second-order model showed a higher overall fit to the experimental data. In conclusion, the adsorption process of the adsorbent prepared in Experiment 1 better conforms to the characteristics of the pseudo-second-order kinetic model, further revealing that its adsorption mechanism is dominated by chemisorption.

[0056] Comparative Example 1: This experiment differs from Experiment 1 in that step four is omitted, i.e., ZrOCl2 is not added.

[0057] Comparative Example 2: This experiment differs from Experiment 1 in that steps two and three are omitted, i.e., MgO is not added.

[0058] Example 1: To verify that the performance of magnesium and zirconium-modified acidified alumina fluorine adsorbent material is superior to that of parent alumina and single-metal-doped alumina materials, this experiment first systematically investigated the adsorption thermodynamic properties of four adsorbent materials (parent alumina, Mg-doped alumina in Comparative Example 1, Zr-doped alumina in Comparative Example 2, and Mg-Zr co-doped alumina in Experiment 1). The core principle is to characterize the material's adsorption capacity (e.g., the maximum adsorption amount fitted by the Langmuir model). Figure 5 (a, b, c, and d represent the parent alumina, Mg-doped alumina of Comparative Example 1, Zr-doped alumina of Comparative Example 2, and Mg-Zr co-doped alumina of Experiment 1, respectively.) The specific experiments were as follows: For fluoride ion solutions with concentrations of 50, 100, 200, 400, 600, 800, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, and 5000 mg / L, 20 mL was transferred to centrifuge tubes, and 0.12 g of the adsorbent material prepared in Experiment 1 was added to each. The tubes were then placed in a shaker for adsorption. After adsorption, the fluoride concentration in the solution was measured using a UV spectrophotometer. - The concentration of F was calculated, and the effect of the material on F in solutions of different concentrations was determined. -The adsorption capacity was measured; the reaction conditions using a shaker were 25℃, 24h, and 180rpm. Data showed that the maximum adsorption capacities of the four materials were 32.1, 63.34, 62.18, and 93.57 mg / g, respectively. Single metal doping (Mg or Zr) increased the alumina adsorption capacity by approximately 97.3%–99.8%, presumably due to the introduction of additional active sites by the doped metal. The maximum adsorption capacity of the Mg-Zr co-doped material prepared in Experiment 1 was approximately 47.7% and 50.5% higher than that of the Mg-doped and Zr-doped materials, respectively, demonstrating a significant synergistic performance enhancement effect. This synergistic effect can be attributed to the synergistic regulation of electronic effects by Mg and Zr: the introduction of Mg optimizes the distribution of surface charge, while Zr increases the effective specific surface area by regulating the alumina crystal structure. Together, they construct more highly active adsorption sites, effectively overcoming the performance bottleneck of single doping.

[0059] Example 2: Based on the thermodynamic properties, this experiment further investigated the adsorption kinetics characteristics of four materials (e.g., Figure 6 (a, b, c, and d represent the parent alumina, Mg-doped alumina of Comparative Example 1, Zr-doped alumina of Comparative Example 2, and Mg-Zr co-doped alumina of Experiment 1, respectively.) The focus was on the adsorption rate and equilibrium behavior. The specific experiment involved: 20 mL of a fluoride ion solution with a concentration of 2000 mg / L was added to a 50 mL centrifuge tube. 0.12 g of the adsorbent material prepared in Experiment 1 was weighed and added to an Erlenmeyer flask to disperse it evenly. The flask was then placed in a shaker for adsorption. Samples were taken at regular intervals during adsorption. After adsorption, the F ion concentration in the solution was measured using a UV spectrophotometer. - The concentrations of magnesium and zirconium-modified acidified alumina were calculated to determine their effects on F at different time points. - The adsorption capacity was measured; the sampling times were 0, 5, 10, 15, 20, 30, 40, 60, 80, 100, 150, 200, 300, 450, 500, and 600 minutes, respectively; the reaction conditions using a magnetic stirrer were 25°C and 180 rpm. The results showed that the adsorption rate curves of the four materials all exhibited a typical pattern of "rapid adsorption - slow equilibrium": although the initial adsorption rates differed (presumably related to differences in diffusion resistance on the material surface), the time to reach adsorption equilibrium was not significantly different for the four materials. This phenomenon can be explained at the material structure level: all four materials use alumina as a substrate to construct a framework structure. Similar substrate structures result in similar diffusion coefficients within the materials, leading to smaller differences in mass transfer resistance, ultimately manifesting as a convergence in equilibrium times. In summary, the Mg-Zr co-doped alumina prepared in Experiment 1 achieved a significant increase in adsorption capacity while maintaining comparable kinetic efficiency to the other three materials, further confirming its comprehensive adsorption performance advantages.

[0060] Example 3: X-ray photoelectron spectroscopy (XPS) was used to characterize the surface elemental composition of the materials before and after modification in Experiment 1 (alumina before modification, magnesium and zirconium-modified acidified alumina fluorine adsorbent after modification). The full spectrum results are as follows: Figure 7 As shown in the spectrum of the Al2O3 sample before modification, only characteristic peaks of O1s (binding energy around 550 eV) and Al2p (binding energy around 80 eV) appear, which completely correspond to the inherent elemental composition (Al, O) of Al2O3, reflecting the original surface elemental characteristics of the substrate. However, in the spectrum of the modified sample, in addition to retaining the original O1s and Al2p characteristic peaks of the substrate, new characteristic signal peaks of Zr3d (binding energy around 200 eV) and Mg2p appear. These two types of signals have no corresponding response in the spectrum before modification. According to the characterization principle of XPS, characteristic binding energy peaks are a direct indicator of the presence of elements on the sample surface. Therefore, the appearance of Zr and Mg characteristic peaks in the modified spectrum can preliminarily confirm that Mg and Zr elements have been successfully loaded onto the Al2O3 substrate surface through the modification process. The relative peak intensity of Al2p is lower after modification than before modification, while the newly added Mg2p and Zr3d peaks have obvious signal responses. Based on XPS's characteristic that "the detection depth is only a few nanometers from the surface", it can be inferred that Mg and Zr elements are mainly enriched in the surface region of Al2O3, rather than penetrating into the interior of the substrate (i.e., the loading process is mainly surface modification).

[0061] Example 4: This experiment is an interference experiment, and the interfering ion is Cl. - NO3 2- SO4 2- HCO3 - and CO3 2- Each time, one ion was selected to coexist with fluoride ions for interference experiments. The initial concentration of fluoride ions was 2000 mg / L. 0.12 g of the adsorbent material prepared in Experiment 1 was added, and the mixture was placed in a shaker for adsorption. After adsorption, the concentration of fluoride ions in the solution was measured using a UV spectrophotometer. - The concentration of F was calculated to determine the effect of different concentrations of interfering ions on the material. - The adsorption capacity; the reaction conditions using a shaker were 25℃, 24h, 180rpm. The effect of coexisting ions on the fluoride removal rate (%) is as follows: Figure 8 As shown in the figure, the vertical axis represents the removal rate of fluoride ions. This graph indicates that Cl... - and NO3 2- It has the least impact on fluoride removal. Meanwhile, SO4 2- The effects are relatively mild, while HCO3 - and CO3 2-The removal of fluoride is significantly affected. Increased adsorption competition at the same active site is a common reason for the reduced defluorination efficiency caused by all coexisting ions. However, the degree of reduction in fluoride removal efficiency varies and is influenced by changes in the initial pH of the wastewater caused by externally added coexisting ions. Cl in the wastewater... - and NO3 2- The introduction of these ions changed the pH of the aqueous solution from 5.8 to 6.6 ± 0.2. Therefore, these ions may cause a slight increase in the degree of deprotonation on the adsorbent surface, thereby slightly reducing the electrostatic attraction of fluoride ions. SO4 2- The introduction of [a substance] changes the pH of the solution to 7.2 ± 0.3, potentially leading to a relatively higher degree of deprotonation. Therefore, its effect on fluoride removal is moderate, but higher than that on chloride and nitrate ions. HCO3- - and CO3 2- The introduction of these ions raised the pH of the solution to 8.7±0.3 and 11.8±0.3, respectively. These ions may increase the degree of deprotonation to the point that the adsorbent surface may become electronegative. In other words, these ions may cause the electrostatic attraction of fluoride ions to turn into electrostatic repulsion. As mentioned earlier, electrostatic repulsion leads to a decrease in fluoride removal efficiency. Therefore, HCO3- - and CO3 2- It has a major impact on defluorination efficiency.

Claims

1. A process for the preparation of a magnesium and zirconium modified acidified alumina fluoride adsorbent characterized in that The preparation method is carried out according to the following steps: I. Acid treatment of alumina: add sulfuric acid solution to alumina, stir uniformly, activate by standing, and after activation, wash the acid-treated alumina to remove excess sulfuric acid; the washed alumina is transferred to a hot air oven for drying treatment until the water is completely evaporated; II. Acid treatment of magnesium oxide: mix magnesium oxide with distilled water to prepare a uniform mixture; then slowly add sulfuric acid solution to the uniform mixture under continuous stirring, and keep standing after the addition is completed to ensure that the reaction is fully carried out; finally, dry treatment is carried out; III. Mixing: mix the dried products of the above two steps together and dissolve in distilled water, age under magnetic stirring, and dry in a hot air oven after aging; the mass of alumina in step I is equal to that of magnesium oxide in step II; IV. Add ZrOCl2: uniformly mix the dry sample obtained from step III and ZrOCL2·8H2O in distilled water, age for 24-25h under magnetic stirring, wash the product with water after aging, dry, and then crush in a mortar to obtain a fine powder sample, which is a magnesium and zirconium modified acidified alumina fluoride adsorbent; The mass ratio of ZrOCL2·8H2O to alumina in step I is 1:(2-2.5).

2. A process for the preparation of a magnesium and zirconium modified acidified alumina fluoride adsorbent according to claim 1, characterized in that The mass concentration of the sulfuric acid solution in step I is 95%-98%.

3. The process for preparing a magnesium and zirconium modified acidified alumina fluoride adsorbent according to claim 1, characterized in that The mass of alumina in step I to the volume of sulfuric acid solution is 1g:(1mL-1.5mL).

4. The process for preparing a magnesium and zirconium modified acidified alumina fluoride adsorbent according to claim 1, characterized in that In step I, stand for 30min for activation.

5. The method of making a magnesium and zirconium modified acidified alumina fluoride adsorbent of claim 1, characterized by The drying temperature in step I is 105℃.

6. The process for preparing a magnesium and zirconium modified acidified alumina fluoride adsorbent according to claim 1, characterized in that The mass of magnesium oxide in step II to the volume of distilled water is 1g:(5mL-6mL).

7. The process for preparing a magnesium and zirconium modified acidified alumina fluoride adsorbent according to claim 1, characterized in that The mass concentration of the sulfuric acid solution in step II is 95%-98%.

8. The method for preparing a magnesium and zirconium-modified acidified alumina fluorine adsorbent according to claim 1, characterized in that... The mass of magnesium oxide in step II to the volume of sulfuric acid solution is 1g:(1mL-1.5mL).

9. The process for preparing a magnesium and zirconium modified acidified alumina fluoride adsorbent according to claim 1, characterized in that In step II, stand for 30min.

10. The method for preparing a magnesium and zirconium-modified acidified alumina fluorine adsorbent according to claim 1, characterized in that... In step III, age for 12h.

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