Preparation method and application of chitin modified magnesium oxide fluorine removal agent
Chitosan-modified magnesium oxide fluoride remover was prepared by sol-gel method, which solved the problems of high cost and poor effect of existing fluoride removal methods, and achieved efficient and stable fluoride ion removal effect, which is suitable for coking wastewater treatment.
Patent Information
- Application Number
- CN202511162276.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-19
- Publication Date
- 2025-11-07
AI Technical Summary
Existing defluorination methods are costly to operate and maintain, complex to operate, and may cause secondary pollution. Direct application of activated magnesium oxide has poor adsorption effect and is difficult to effectively remove fluoride ions from industrial fluoride-containing wastewater.
Chitosan-modified magnesium oxide defluorinating agent was prepared using the sol-gel method. By adjusting process parameters such as the ratio of magnesium nitrate to chitosan, calcination temperature and time, and stirring time, a chitosan-modified magnesium oxide defluorinating agent with good porosity and hydrogen bonding was prepared for use in coking wastewater treatment.
It improves the removal rate of fluoride ions in wastewater, is simple to operate, and produces a small and stable defluorinating agent that can effectively remove fluoride ions from wastewater and avoid secondary pollution.
Smart Images
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Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of wastewater treatment, and particularly relates to a preparation method and application of a chitin-modified magnesium oxide fluorine removal agent. BACKGROUND
[0002] Fluorine is the most active and the most electronegative non-metallic element discovered so far, and gaseous fluorine has particularly strong corrosiveness. Under normal conditions, fluorine cannot exist in a free state, but can have extremely strong chemical reactions with many substances to generate stable compounds. In recent years, industrial fluorine-containing "three wastes" have brought pollution to the society and caused serious harm to the environment. The influence has been generated worldwide. It is worth noting that the industrial production produces fluorine-containing wastewater, especially inorganic fluorine-containing wastewater. Even if the fluorine content of the treated effluent reaches the 10mg / L limit value specified in the "Integrated Wastewater Discharge Standard" (GB8979-1996), the discharge of this part of wastewater will still have a strong impact on the surface water and groundwater environment.
[0003] Traditional fluorine removal methods, such as adding lime to generate fluorine precipitate, adding iron ions to generate complex precipitate, and active alumina, have been widely studied. In addition, ion exchange, electrodialysis and reverse osmosis have also been used for the study of removing fluorine ions in drinking water. However, most of these methods have high operation and maintenance costs, produce secondary pollution (such as harmful sludge), and have complex operation procedures.
[0004] Active magnesium oxide shows good adsorption performance due to its structural characteristics such as large specific surface area and porosity. However, the adsorption effect of directly adding active magnesium oxide is poor and needs to be further improved, so it is necessary to further research and develop new fluorine removal materials to improve the fluorine removal effect. SUMMARY
[0005] In view of the above problems, the application provides a preparation method and application of a chitin-modified magnesium oxide fluorine removal agent.
[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows:
[0007] A preparation method of a chitin-modified magnesium oxide fluorine removal agent, the preparation method comprises the following steps: adding magnesium nitrate to deionized water, adding nitric acid to adjust pH, then adding chitin, stirring and dispersing, adding sodium hydroxide to adjust pH while stirring, continuing to stir, filtering, placing in a 105 DEG C oven for drying, and then calcining in a muffle furnace to obtain the chitin-modified magnesium oxide fluorine removal agent.
[0008] Further, the weight ratio of magnesium nitrate to chitin is 15:4-5.
[0009] Further, the calcination temperature is 350-370 DEG C.
[0010] Further, the calcination time is 2-3h.
[0011] Further, the stirring and dispersing time after adding chitin and before adding sodium hydroxide to adjust pH is 15-20min.
[0012] The stirring time after adding sodium hydroxide to adjust pH and before filtering is 20-24h.
[0013] Further, the final value of pH adjusted by adding nitric acid is 4-5.
[0014] The final value of pH adjusted by adding sodium hydroxide is 9.5-10.
[0015] Further, the weight-volume ratio of magnesium nitrate to water is 15g:60-80mL.
[0016] The application of a chitin-modified magnesium oxide fluoride removal agent, wherein the chitin-modified magnesium oxide fluoride removal agent is prepared by the above method.
[0017] The application is adding the chitin-modified magnesium oxide fluoride removal agent to coking wastewater, stirring and reacting, and filtering, thereby completing the coking wastewater treatment.
[0018] Further, the weight-volume ratio of the chitin-modified magnesium oxide fluoride removal agent to coking wastewater is 15-20g:1L.
[0019] Further, the stirring and reacting time is 1.5-2h.
[0020] The preparation method and application of the chitin-modified magnesium oxide fluoride removal agent have the following beneficial effects:
[0021] The application uses a sol-gel method to prepare a new inorganic-organic hybrid composite adsorption material, and by adjusting specific process steps and parameters, the size, shape, structure and chemical properties of the new inorganic-organic hybrid composite adsorption material are controlled, thereby obtaining the chitin-modified magnesium oxide fluoride removal agent with good defluorination effect.
[0022] The chitin-modified magnesium oxide fluoride removal agent prepared by the application has a large number of pores, which is conducive to the occurrence of adsorption, and because the magnesium oxide is modified by chitin, hydrogen bonds can also be generated in the adsorption process, thereby further improving the removal rate of fluorine in wastewater; at the same time, the functional groups such as amino and hydroxyl groups contained in chitin can further interact with fluorine ions, thereby improving the adsorption effect.
[0023] The preparation method of the application is simple to operate, and the chitin-modified magnesium oxide fluoride removal agent prepared by the application has small and stable particle size, and can effectively remove fluorine ions in wastewater. DETAILED DESCRIPTION
[0024] The technical solutions in the embodiments of the present application are described clearly and completely below. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other manners different from those described herein, and those skilled in the art can make similar generalizations without departing from the spirit and scope of the present application, so the present application is not limited to the specific embodiments disclosed below.
[0025] Embodiment 1: Preparation method and application of chitin-modified magnesium oxide fluoride removal agent
[0026] The present embodiment is a preparation method and application of a chitin-modified magnesium oxide fluoride removal agent, which is specifically as follows:
[0027] I. Preparation method of chitin-modified magnesium oxide fluoride removal agent
[0028] 15 g of magnesium nitrate was weighed and added to 70 mL of deionized water, 10 wt% nitric acid aqueous solution was added to adjust the pH value to 4.5 (labeled as the first pH value adjustment), then 5 g of chitin was added, stirred and dispersed for 15 min, 20 wt% sodium hydroxide aqueous solution was added dropwise while stirring to adjust the pH value to 10 (labeled as the second pH value adjustment), and stirring was continued for 24 h, then filtration was performed, the product was placed in a 105℃ oven for drying, and then calcination was performed in a muffle furnace at 350℃ for 2.5 h to obtain the chitin-modified magnesium oxide fluoride removal agent.
[0029] II. Method for treating wastewater by using the above chitin-modified magnesium oxide fluoride removal agent
[0030] 1 L of biochemical secondary sedimentation effluent from a wastewater station of different coking plants (fluoride ion concentration of 106.3 mg / L, COD of 337 mg / L, and hardness of 256 mg / L) was taken, 20 g of chitin-modified magnesium oxide fluoride removal agent was added, stirring was performed for 1.5 h, filtration was performed, the supernatant was taken, and the fluoride ion concentration was detected. The fluoride ion concentration in the supernatant was 1.3 mg / L, the COD was 68 mg / L, the hardness was 46 mg / L, and the fluoride removal rate was 98.78%.
[0031] Embodiments 2-5: Preparation method and application of chitin-modified magnesium oxide fluoride removal agent
[0032] Embodiments 2-5 are each a preparation method and application of a chitin-modified magnesium oxide fluoride removal agent, which are basically the same as Embodiment 1, and the only difference is that some process parameters are different, and specific details are shown in Table 1:
[0033] Table 1: List of process parameters in Embodiments 2-5
[0034]
[0035]
[0036] The contents and results of other parts of Examples 2-5 are basically the same as those of Example 1, and are not described here again.
[0037] Process parameter investigation in the preparation of chitin-modified magnesium oxide fluoride removal agent in Example 6
[0038] In this example, the process conditions in the preparation of chitin-modified magnesium oxide fluoride removal agent in Example 1 are investigated. In the investigation, the preparation method of chitin-modified magnesium oxide fluoride removal agent is basically the same as that in Example 1, and the method for treating wastewater with the above chitin-modified magnesium oxide fluoride removal agent is also the same as that in Example 1.
[0039] I. Investigation of chitin dosage
[0040] In the preparation of fluoride removal agent by sol-gel method, the mass ratio of raw materials is related to the surface chemical properties and porosity of the fluoride removal agent. The adsorption performance of the fluoride removal agent prepared by different mass ratios of raw materials is also different. In order to investigate the mass ratio of raw materials, the preparation method of chitin-modified magnesium oxide fluoride removal agent in Example 1 is followed, only the amount of chitin is changed (i.e. the amount of chitin is 1 g, 2 g, 3 g, 4 g, 5 g, 6 g, and 7 g, respectively), and chitin-modified magnesium oxide fluoride removal agents corresponding to different amounts of chitin are prepared. Then, the same batch of biochemical secondary sedimentation effluent is treated with the corresponding chitin-modified magnesium oxide fluoride removal agent, and the treatment results are shown in Table 2.
[0041] Table 2: Investigation results of chitin dosage
[0042]
[0043]
[0044] As can be seen from Table 2, as the amount of chitin used to prepare the chitin-modified magnesium oxide fluoride removal agent increases, the fluoride removal rate of the chitin-modified magnesium oxide fluoride removal agent for wastewater has been significantly improved, but when the amount of chitin exceeds a certain amount, the fluoride removal rate for wastewater will decrease. This may be due to the fact that when the amount of chitin is too low, the modification effect on magnesium oxide is poor, resulting in low fluoride removal effect; when the amount of chitin is too high, the adsorption pore size of the prepared chitin-modified magnesium oxide fluoride removal agent becomes smaller, resulting in poor adsorption effect, and thus leading to a decrease in the fluoride removal rate for wastewater.
[0045] II. Investigation of calcination temperature
[0046] The calcination temperature is related to the surface chemical properties and porosity of the fluoride removal agent, and the adsorption performance of the fluoride removal agent is different under different calcination temperatures. In order to save energy consumption, the optimal calcination temperature is investigated. The chitin modified magnesium oxide fluoride removal agent is prepared according to the preparation method of the chitin modified magnesium oxide fluoride removal agent in Example 1, only the calcination temperature is changed (i.e. the calcination temperature is 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, respectively), the chitin modified magnesium oxide fluoride removal agent corresponding to different calcination temperatures is prepared, and the same batch of biochemical secondary sediment effluent is treated by using the corresponding chitin modified magnesium oxide fluoride removal agent, and the treatment results are shown in Table 3.
[0047] Table 3 Investigation results of calcination temperature
[0048]
[0049] As can be seen from Table 3, within 350°C, with the increase of the calcination temperature, the fluoride removal rate increases slightly, but when the temperature is 350°C, the fluoride removal rate increases suddenly and reaches the peak, and the fluoride removal rate is 98.78%, and when the temperature is more than 400°C, the fluoride removal rate shows a significant decrease. This may be due to the fact that when the calcination temperature is too low, the magnesium hydroxide in the system cannot be decomposed to form magnesium oxide, and the adsorption effect cannot be achieved, and when the calcination temperature is more than 400°C, the chitin is decomposed in large amount, and the modification effect is obviously poor. Therefore, from the aspects of saving energy consumption and ensuring the fluoride removal effect, the optimal calcination temperature is 350-370°C.
[0050] III. Investigation of calcination time
[0051] In order to save the energy consumption in the preparation process of the fluoride removal agent, the optimal calcination time of the fluoride removal agent needs to be investigated. The chitin modified magnesium oxide fluoride removal agent is prepared according to the preparation method of the chitin modified magnesium oxide fluoride removal agent in Example 1, only the calcination time is changed (i.e. the calcination time is 1h, 2h, 3h, 4h, respectively), the chitin modified magnesium oxide fluoride removal agent corresponding to different calcination times is prepared, and the same batch of biochemical secondary sediment effluent is treated by using the corresponding chitin modified magnesium oxide fluoride removal agent, and the treatment results are shown in Table 4.
[0052] Table 4 Investigation results of calcination time
[0053]
[0054] As shown in Table 4, within 2h, the fluorine removal rate increases from 54.94% to 98.49% with the prolongation of the calcination time, showing a significant upward trend; but when the calcination time is prolonged to 3h, the fluorine removal rate does not increase significantly, and when the calcination time is further prolonged to 4h, the fluorine removal rate shows a certain degree of decrease. This may be due to the fact that when the calcination time is too short, the magnesium hydroxide cannot be completely converted into magnesium oxide, and when the calcination time is too long, the amount of chitin decomposition increases significantly, resulting in poor fluorine removal effect of the prepared fluorine removal agent.
[0055] Process parameter investigation of the wastewater treatment process by using the chitin modified magnesium oxide fluorine removal agent of Example 7
[0056] In this example, the process conditions in the wastewater treatment process by using the chitin modified magnesium oxide fluorine removal agent of Example 1 are investigated. In the investigation, the wastewater is treated by using the chitin modified magnesium oxide fluorine removal agent prepared in Example 1, and the wastewater treatment method is basically the same as that in Example 1.
[0057] I. Investigation of the fluorine removal agent dosage
[0058] The same batch of biochemical secondary sedimentation effluent is taken, and the chitin modified magnesium oxide fluorine removal agent prepared in Example 1 is used to investigate the influence of different dosages of the chitin modified magnesium oxide fluorine removal agent on the wastewater treatment effect (i.e. only the dosage of the chitin modified magnesium oxide fluorine removal agent in the wastewater treatment process of Example 1 is changed, and other conditions remain unchanged), wherein the dosages of the chitin modified magnesium oxide fluorine removal agent are 5g, 10g, 15g, 20g and 25g respectively, and the treatment results are shown in Table 5.
[0059] Table 5 Investigation results of the fluorine removal agent dosage
[0060]
[0061] As shown in Table 5, when the fluorine removal agent dosage increases from 5g to 15g / L, the fluorine removal rate increases significantly, which is because within a certain range, the adsorption rate depends on the number of active sites, and with the increase of the fluorine removal agent dosage, the total amount of the active sites on the surface of the fluorine removal agent increases, which is beneficial to the adsorption of fluorine; when the fluorine removal agent dosage increases from 15g to 20g, the removal rate increases slowly, which may be due to the diffusion effect of the adsorbate in the interior of the fluorine removal agent particles. Then, when the dosage of the fluorine removal agent is further increased, the fluorine removal rate tends to be balanced, which is because most of the fluorine ions in the solution have been removed at this time, and the increase of the adsorption amount mainly depends on the mass transfer driving force. If the solid-liquid ratio is further increased, the effect of improving the fluorine removal rate is not obvious. Therefore, the dosage of the fluorine removal agent is selected to be 15-20g in the present application.
[0062] II. Investigation of the reaction time
[0063] Take the same batch of biochemical after two sediment effluent, using the chitin modified magnesium oxide fluorine removal agent prepared in example 1, respectively investigate the effect of reaction time on wastewater treatment (i.e. only change the stirring reaction time in the wastewater treatment process of example 1, other conditions remain unchanged), wherein the different stirring reaction time is 0.5h, 1h, 1.5, 2h, 2.5h, the treatment results are shown in table 6.
[0064] Table 6 reaction time investigation results
[0065]
[0066] It can be seen from table 6 that the adsorption time is within 1h, the adsorption amount per unit time increases significantly, that is, the adsorption rate is larger; 1-1.5h, the adsorption rate decreases significantly; and the adsorption amount reaches the maximum at 1.5h, and then the adsorption amount tends to balance, the adsorption and desorption rate reaches dynamic balance. This is because the adsorption process is sequential, the first stage (within 1.5h) is surface adsorption, the adsorbate reaches the surface of the fluorine removal agent and is adsorbed by interacting with the surface active site, the second stage (1-1.5h) the adsorbate can diffuse in the pores of the fluorine removal agent particles, and may interact with the pore wall surface and be adsorbed during the diffusion process. The adsorption rate changes from fast to slow, and finally tends to balance, at this time the adsorption amount is maximum. And the adsorption amount reaches the maximum at 1.5g. Therefore, the reaction time selected by the present application is 1.5-2h.
[0067] Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.
Claims
1. A method for preparing a chitosan-modified magnesium oxide defluorinating agent, characterized in that, The preparation method is adding magnesium nitrate into water, adding nitric acid to adjust pH, then adding chitin, stirring and dispersing, adding sodium hydroxide to adjust pH while stirring, continuing stirring, filtering, drying, calcining, and then the chitin modified magnesium oxide defluorination agent is obtained.
2. The method for producing a chitin-modified magnesium oxide defluorination agent according to claim 1, characterized by, The weight ratio of magnesium nitrate to chitin is 15:4-5.
3. The method for producing a chitin-modified magnesium oxide defluorination agent according to claim 1 or 2, characterized by, The calcining temperature is 350-370℃.
4. The method for producing a chitin-modified magnesium oxide defluorination agent according to claim 1 or 2, characterized by, The calcining time is 2-3h.
5. The method for producing a chitin-modified magnesium oxide defluorination agent according to claim 1 or 2, characterized by, The stirring and dispersing time after adding chitin and before adding sodium hydroxide to adjust pH is 15-20min. The continuing stirring time after adding sodium hydroxide to adjust pH and before filtering is 20-24h.
6. The method for producing a chitin-modified magnesium oxide defluorination agent according to claim 1 or 2, characterized by, The final value of pH adjusted by adding nitric acid is 4-5. The final value of pH adjusted by adding sodium hydroxide is 9.5-10.
7. The method for producing the chitin-modified magnesium oxide defluorination agent according to claim 1 or 2, characterized by, The weight to volume ratio of magnesium nitrate to water is 15g:60-80mL.
8. Use of a chitin-modified magnesium oxide fluoride removing agent, characterized by, The chitin modified magnesium oxide defluorination agent is prepared by the preparation method of any one of claims 1-7. The application is adding the chitin modified magnesium oxide defluorination agent into coking wastewater, stirring and reacting, and filtering, and then the coking wastewater treatment is completed.
9. Use of the chitin-modified magnesium oxide defluorination agent according to claim 8, characterized by, The weight to volume ratio of the amount of chitin modified magnesium oxide defluorination agent to coking wastewater is 15-20g:1L.
10. The use of the chitin-modified magnesium oxide defluorination agent according to claim 8 or 9, characterized by, The stirring and reacting time is more than 1.5h.