A red mud-based Prussian blue adsorbent and its preparation method and application

Abstract

The present invention discloses a red mud-based Prussian blue adsorbent, its preparation method, and application. The method comprises mixing red mud with an acid solution for an acid hydrolysis reaction, then dripping a potassium ferrocyanide solution into the system for a precipitation reaction, then dripping an alkaline solution to adjust the pH of the system to 7-9, stirring the reaction, and subjecting the resulting reaction product to solid-liquid separation to recover the solid. The adsorbent has good dispersibility and excellent adsorption properties, and can effectively adsorb and remove antibiotics from a solution system. Its preparation method is simple, low-cost, and suitable for industrial-scale production.

Description

Technical Field

[0001] The invention relates to an adsorbent, in particular to a red mud-based Prussian blue adsorbent, and also to a preparation method and application thereof, belonging to the technical fields of adsorption materials and chemical separation. Background Art

[0002] Red mud (RM) is a highly alkaline solid waste generated during the alumina extraction process. It is generally disposed of in piles, but due to its low utilization rate, it has posed a threat to the surrounding ecological environment. Therefore, the development of new red mud disposal methods is of great significance. Notably, studies have utilized the small particle size, certain porosity, and stable chemical composition of red mud to modify it for the adsorption and removal of heavy metal ions, non-metallic ions, and organic pollutants. However, in order to consume RM more quickly and treat different pollutants economically and efficiently, more types of red mud-based adsorbents with low cost and simple synthesis processes need to be developed.

[0003] Antibiotics have been used to treat human and animal diseases, and their consumption is increasing worldwide. As an emerging pollutant, antibiotics are persistent and cumulative, making them difficult to degrade. Antibiotics in natural water bodies can induce the production of drug-resistant bacteria or drug-resistant genes, posing a potential threat to the ecological environment and human health. A variety of technologies have been developed to treat antibiotic wastewater. Among them, adsorption has the advantages of simple operation, low operating cost, and environmental friendliness. It is considered to be the most commonly used and economical treatment method. However, the adsorbents currently developed are difficult to meet the needs of treating different pollutants. Therefore, exploring an economical and efficient adsorbent is of great significance for the treatment of antibiotic wastewater. Summary of the Invention

[0004] In response to the problems existing in the prior art, the first object of the present invention is to provide a red mud-based Prussian blue adsorbent that is not prone to agglomeration, has good adsorption performance, and can effectively adsorb and remove organic pollutants in solutions.

[0005] A second object of the present invention is to provide a method for preparing a red mud-based Prussian blue adsorbent, which is simple, low-cost, and suitable for industrial-scale production.

[0006] The third object of the present invention is to provide an application of a red mud-based Prussian blue adsorbent, which has a high removal efficiency when used to adsorb and remove antibiotics in a solution system.

[0007] In order to achieve the above technical objectives, the present invention provides a method for preparing a red mud-based Prussian blue adsorbent, which comprises mixing red mud with an acid solution for acid hydrolysis reaction, first adding a potassium ferrocyanide solution dropwise into the system for precipitation reaction, then adding an alkaline solution dropwise to adjust the pH of the system to 7-9 for stirring reaction, and performing solid-liquid separation on the obtained reaction product to recover the solid.

[0008] Among them, the main reaction principle involved is: 3K4[Fe(CN)6]+4FeCl3→Fe4[Fe(CN)6]3↓+12KCl. The hydroxide ions in the alkaline solution can fix the Si, Al and other components dissolved in the red mud in the form of hydroxides as the support matrix of the Prussian blue generated above, further improving the dispersibility of the Prussian blue. Controlling the pH of the system within a suitable range so that the hydroxide ions in the solution are within a suitable range is beneficial to improving the adsorption performance of the material. If the pH of the system is lower than 7, the amount of hydroxide ions is too small, which will cause waste of Si, Al and other ions in the solution and reduce the Prussian blue support matrix; if the pH of the system is greater than 9, the amount of hydroxide ions is too much, and the excess hydroxide will react with the generated Prussian blue to form iron hydroxide precipitate: Fe4[Fe(CN)6]3+12OH - =3Fe(CN)6 4- +4Fe(OH)3, thereby reducing the adsorption performance.

[0009] As a preferred solution, the acid solution includes at least one of hydrochloric acid, sulfuric acid, and nitric acid. The more preferred acid solution is hydrochloric acid.

[0010] As a preferred solution, the liquid-to-solid ratio of the acid solution to the red mud is 60-120 mL:3-7 g, and more preferably 60-120 mL:3-7 g.

[0011] As a preferred solution, the concentration of the acid solution is 2 to 4 mol / L.

[0012] As a preferred solution, the conditions for the acid hydrolysis reaction are: temperature of 80-95° C. and time of 2-4 hours.

[0013] As a preferred solution, the molar ratio of potassium ferrocyanide in the potassium ferrocyanide solution to the iron element in the red mud is 2.5-3.5:4.

[0014] As a preferred solution, the concentration of the potassium ferrocyanide solution is 0.01 to 0.024 mol / L.

[0015] As a preferred solution, the potassium ferrocyanide solution is added at a rate of 3 to 7 mL / min. If the potassium ferrocyanide solution is added at a rate too high, the reaction may be too fast, causing the generated Prussian blue to aggregate severely, thereby affecting the adsorption performance of the material.

[0016] As a preferred solution, the precipitation reaction conditions are: room temperature, and time is 10 to 14 hours.

[0017] As a preferred solution, the alkaline solution includes at least one of ammonia water, sodium hydroxide solution, and potassium hydroxide solution.

[0018] As a preferred solution, the alkaline solution is aqueous ammonia.

[0019] As a preferred solution, the mass concentration of the ammonia water is 25%.

[0020] As a preferred solution, the alkaline solution is added at a rate of 3 to 7 mL / min. Too fast an alkaline solution addition rate can lead to the rapid formation of hydroxide precipitates with Prussian blue as the core, which in turn form inclusions and reduce the adsorption functional sites.

[0021] As a preferred solution, the stirring reaction conditions are: temperature is room temperature, and time is 2 to 6 hours.

[0022] The present invention also provides a red mud-based Prussian blue adsorbent, which is prepared by the above method.

[0023] The present invention also provides an application of a red mud-based Prussian blue adsorbent, which is used for adsorbing antibiotics in a solution system.

[0024] As a preferred solution, the antibiotic is tetracycline. The adsorbent has an excellent adsorption and removal effect on tetracycline.

[0025] As a preferred solution, the mass concentration of the adsorbent in the solution system is not less than 0.5 g / L.

[0026] As a preferred solution, the initial concentration of the antibiotic in the solution system is 5 to 30 ppm, more preferably 5 to 15 ppm.

[0027] As a preferred solution, the initial pH of the solution system is 4-7, the temperature of the solution system is 25-35° C. and the shaking speed is 160-240 rpm.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) Red mud was used for the first time to prepare RM-PB adsorbent, which has excellent adsorption properties and can effectively remove organic pollutants in water. In particular, it has a high adsorption and removal efficiency for antibiotics and has good application prospects.

[0030] (2) The preparation method is simple, the cost is low, the raw materials are widely available, and it is suitable for industrial-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 X-ray diffraction (XRD) patterns of RM-PB (red mud-based Prussian blue adsorbent) prepared in Example 1, RM (red mud), and PB (Prussian blue) prepared in Comparative Example 1.

[0032] Figure 2 Scanning electron microscope (SEM) images of RM-PB (b) and RM (a) prepared in Example 1 and PB (c) prepared in Comparative Example 1.

[0033] Figure 3 BET nitrogen adsorption-desorption curves of RM-PB (b) and RM (a) prepared in Example 1 and PB (c) prepared in Comparative Example 1.

[0034] Figure 4 This is a graph showing the change in the adsorption rate of tetracycline by RM-PB and RM prepared in Example 1 and PB prepared in Comparative Example 1 over time.

[0035] Figure 5 This is the tetracycline adsorption rate curve of RM-PB prepared in Example 1 at different addition amounts.

[0036] Figure 6 1 is the tetracycline adsorption rate curve of RM-PM prepared in Example 1 at different initial tetracycline concentrations.

[0037] Figure 7 This is the tetracycline adsorption curve of RM-PB material prepared with different HCl addition amounts.

[0038] Figure 8 The tetracycline adsorption curve of RM-PB material prepared with different ammonia addition amounts. DETAILED DESCRIPTION

[0039] The following specific examples or implementation modes are intended to further illustrate the present invention rather than to limit the present invention.

[0040] The red mud of the present invention was purchased from an aluminum plant in Gongyi, Henan Province. It is Bayer red mud and contains phases such as hematite, quartz, gibbsite, sodalite and boehmite. The contents of Fe, Al, Si, Na and Ti are 25.94%, 11.96%, 7.07%, 6.21% and 2.89% respectively.

[0041] Example 1

[0042] The following is a method for preparing a red mud-based Prussian blue adsorbent, and the specific steps are as follows:

[0043] (1) Add 5 g of red mud to a conical flask containing 100 mL of 3 mol / L hydrochloric acid and shake at 90 °C for 3 h;

[0044] (2) After cooling to room temperature, add 75 mL of 0.0174 mol / L potassium ferrocyanide solution dropwise with stirring at a rate of 4 mL / min. Continue shaking and stirring for 12 h.

[0045] (3) Add 25 mL of ammonia water (mass concentration of 25%) dropwise while stirring (reaction solution pH = 8.0 ± 0.5, dropwise addition rate 4 mL / min, shake and stir for 3 h after addition;

[0046] (4) The solid obtained by centrifugation and washing was dried at 80°C overnight to obtain RM-PB material.

[0047] Comparative Example 1

[0048] The preparation process of PB material is as follows:

[0049] Prepare 100 mL of 0.016 mol FeCl3 solution (liquid A) and 75 mL of 0.012 mol potassium ferrocyanide solution (liquid B); add liquid B dropwise into liquid A while stirring at a rate of 4 ml / min; after the addition is completed, shake the reaction for 12 hours; centrifuge and wash the obtained solid, and dry it at 80°C overnight to obtain the PB material.

[0050] XRD test was performed on the adsorbent materials of Example 1 and Comparative Example 1. Figure 1 As shown, compared with the PDF standard card JCPDS 01-0239 of PB, the main phase of RM-PB prepared in Example 1 is Prussian blue, which is consistent with the PB sample in Comparative Example 1, indicating that the red mud-based Prussian blue material was successfully synthesized; in addition, hematite, quartz and boehmite phases were also detected in RM-PB.

[0051] The microstructures of the RM-PB adsorbent, red mud (RM) and PB material prepared in Example 1 were analyzed by scanning electron microscopy. Figure 2As shown in the figure, the SEM image shows that RM has irregular shapes, mainly large particles and blocks; RM-PB has no obvious blocks and good dispersion, mainly spherical particles; PB has serious agglomeration and coarse particles due to the lack of supporting matrix.

[0052] Figure 3 Figure 2 shows the BET nitrogen adsorption / desorption curves for pure RM, RM-PB prepared in Example 1, and PB prepared in Comparative Example 1. The figure shows that the N2 adsorption / desorption curves for RM and RM-PB conform to the IV isotherm, indicating that both have mesoporous structures. PB conforms to the type I(b) isotherm, and although it has the highest specific surface area, it has the smallest average pore size, making it a narrow mesoporous material. RM-PB has the smallest specific surface area, due to the generated PB partially blocking the pores in the support matrix. However, its average pore size is the largest, which facilitates the adsorption of organic pollutants.

[0053] Example 2

[0054] The following adsorbent materials are used in the tetracycline adsorption removal process, which includes the following steps:

[0055] (1) Pour 100 mL of a 5 ppm tetracycline solution with a pH of 5 into a 250 mL conical flask.

[0056] (2) 0.05 g of pure RM material, RM-PB prepared in Example 1, and PB material prepared in Comparative Example 1 were respectively added to a tetracycline solution and subjected to an adsorption test in a shaker at 200 rpm and a temperature of 30°C. The shaker speed was controlled at 200 rpm;

[0057] (3) Take 0.5 mL of the reaction solution every 5 to 60 minutes, centrifuge at high speed, and measure the tetracycline concentration in the supernatant using a UV-visible spectrophotometer at a wavelength of 275 nm.

[0058] The results are as follows Figure 4 As shown, within 180 minutes, the adsorption rates of RM, RM-PB, and PB were 14.67%, 78.77%, and 14.13%, respectively. The three adsorptions reached equilibrium around 30 minutes. PB exhibited poor adsorption performance, similar to that of RM and far below that of RM-PB. This is attributed to its low crystallinity, agglomeration, and narrow mesopores. Compared to RM and PB, RM-PB exhibited significantly improved adsorption performance, which is attributed to the PB formed within RM-PB, its porous surface, and large pore size. This suggests that RM-PB, which is simple to synthesize and relatively inexpensive, has the potential for large-scale application.

[0059] Example 3

[0060] The method described in this embodiment is mainly carried out according to the following steps:

[0061] (1) Pour 100 mL of a 5 ppm tetracycline solution with a pH of 5 into a 250 mL conical flask.

[0062] (2) 0.02, 0.05, 0.08, 0.11, and 0.14 g of the RM-PB prepared in Example 1 were placed in five conical flasks containing tetracycline solution, and adsorption tests were carried out in a shaker at 200 rpm and 30°C;

[0063] (3) Take 0.5 mL of the reaction solution every 5 to 60 minutes, centrifuge at high speed, and measure the tetracycline concentration in the supernatant using a UV-visible spectrophotometer at a wavelength of 275 nm.

[0064] Conclusion: If Figure 5 As shown, the adsorption rate of tetracycline increased with increasing RM-PB concentration, with the fastest increase from 0.2 g / L to 0.5 g / L. At a concentration of 1.1 g / L, the adsorption rate rose to 85.62%. This indicates that RM-PB can effectively adsorb and remove tetracycline, and is expected to improve the utilization rate of red mud resources while treating antibiotic-contaminated wastewater.

[0065] Example 4

[0066] (1) Pour 100 mL of tetracycline solution with pH = 5 and concentrations of 5, 10, 15, 20, and 30 ppm into four 250 mL conical flasks;

[0067] (2) 0.05 g of RM-PB prepared in Example 1 was placed in a conical flask containing tetracycline solution and an adsorption test was carried out in a shaker at 200 rpm and 30°C;

[0068] (3) Take 0.5 mL of the reaction solution every 5 to 60 minutes, centrifuge at high speed, and measure the tetracycline concentration in the supernatant using a UV-visible spectrophotometer at a wavelength of 275 nm.

[0069] Conclusion: If Figure 6 As shown in Figure 3, the adsorption rate of tetracycline decreased with the increase of tetracycline concentration, but was still higher than that of RM and PB alone. This indicates that the adsorption performance of RM-PB is most significant in low-concentration tetracycline solution.

[0070] Comparative Example 2

[0071] The following is the preparation method of RM-PB adsorbent under different hydrochloric acid dosages. The specific steps are as follows:

[0072] (1) Add 5 g of red mud to two conical flasks containing 100 mL of 0.5 mol / L and 100 mL of 1.5 mol / L hydrochloric acid, respectively, and shake at 90 °C for 3 h;

[0073] (2) After cooling to room temperature, add 75 mL of 0.0174 mol / L potassium ferrocyanide solution dropwise with stirring at a rate of 4 mL / min. Continue shaking and stirring for 12 h.

[0074] (3) Add 25 mL of ammonia water (mass concentration of 25%) dropwise while stirring at a rate of 4 mL / min. After addition, shake and stir the mixture for 3 h.

[0075] (4) The solid obtained by centrifugation and washing was dried at 80°C overnight to obtain RM-PB materials with different hydrochloric acid concentrations.

[0076] (5) The prepared material was subjected to adsorption study of tetracycline according to the process in Example 2.

[0077] like Figure 7 As shown in the figure, with the increase of hydrochloric acid concentration, the adsorption equilibrium of tetracycline becomes faster and the adsorption rate is higher. This is because the lower hydrochloric acid concentration cannot dissolve the red mud and release more iron ions, so the generated Prussian blue decreases and the adsorption performance decreases.

[0078] Comparative Example 3

[0079] The following is the preparation method of RM-PB adsorbent with different ammonia addition amounts. The specific steps are as follows:

[0080] (1) Add 5 g of red mud to two Erlenmeyer flasks containing 100 mL of 3 mol / L hydrochloric acid, and shake at 90 °C for 3 h;

[0081] (2) After cooling to room temperature, add 75 mL of 0.0174 mol / L potassium ferrocyanide solution dropwise with stirring at a rate of 4 mL / min. Continue shaking and stirring for 12 h.

[0082] (3) Add 5 mL (too little, pH = 1) and 40 mL (excess, pH = 13) of ammonia water (mass concentration of 25%) dropwise while stirring at a rate of 4 mL / min. After addition, shake and stir the mixture for 3 h.

[0083] (4) The solid obtained by centrifugation and washing was dried at 80°C overnight to obtain RM-PB material to which 5 mL and 40 mL of ammonia water were added.

[0084] (5) The prepared material was subjected to adsorption study of tetracycline according to the process in Example 2.

[0085] like Figure 8As shown in the figure, adding too little or too much ammonia is not conducive to the adsorption and removal of tetracycline; when 5 mL of ammonia is added, due to the generation of less supporting carriers, the generated Prussian blue agglomerates with each other, reducing the exposure of adsorption sites and thus decreasing the adsorption performance; when 40 mL of ammonia is added, the excess alkali reacts with the generated Prussian blue to form a strong iron oxide precipitate, which causes the adsorption sites to decrease sharply and irreversibly, resulting in the worst adsorption capacity.

Claims

1. A method for preparing a red mud-based Prussian blue adsorbent, characterized in that: After mixing red mud with an acid solution for acid hydrolysis, potassium ferrocyanide solution is first added dropwise to the system for precipitation reaction, and then an alkaline solution is added dropwise to adjust the pH of the system to 7-9 for stirring reaction, and the obtained reaction product is subjected to solid-liquid separation to recover the solid to obtain; The liquid-to-solid ratio of the acid solution to the red mud is 60-120 mL:3-7 g; The concentration of the acid solution is 2-4 mol / L.

2. The method for preparing a red mud-based Prussian blue adsorbent according to claim 1, wherein: The acid solution includes at least one of hydrochloric acid, sulfuric acid, and nitric acid.

3. The method for preparing a red mud-based Prussian blue adsorbent according to claim 1 or 2, characterized in that: The conditions of the acid hydrolysis reaction are: temperature of 80-95° C. and time of 2-4 hours.

4. The method for preparing a red mud-based Prussian blue adsorbent according to claim 1, wherein: The molar ratio of potassium ferrocyanide in the potassium ferrocyanide solution to iron in the red mud is 2.5-3.5:4; The concentration of the potassium ferrocyanide solution is 0.01-0.024 mol / L; The dropping speed of the potassium ferrocyanide solution is 3-7 mL / min.

5. The method for preparing a red mud-based Prussian blue adsorbent according to claim 1 or 4, characterized in that: The conditions of the precipitation reaction are: room temperature and time of 10 to 14 hours.

6. The method for preparing a red mud-based Prussian blue adsorbent according to claim 1, wherein: The alkaline solution includes at least one of aqueous ammonia, sodium hydroxide solution, and potassium hydroxide solution; The dropping speed of the alkaline solution is 3-7 mL / min.

7. The method for preparing a red mud-based Prussian blue adsorbent according to claim 1 or 6, characterized in that: The stirring reaction conditions are: room temperature, and time is 2 to 6 hours.

8. A red mud-based Prussian blue adsorbent, characterized in that: Prepared by the method according to any one of claims 1 to 7.

9. The use of a red mud-based Prussian blue adsorbent according to claim 8, characterized in that: Used to adsorb antibiotics in solution systems.

10. The use of a red mud-based Prussian blue adsorbent according to claim 9, characterized in that: The antibiotic is tetracycline; The mass concentration of the adsorbent in the solution system is not less than 0.5 g / L; The initial concentration of the antibiotic in the solution system is 5 to 30 ppm; The initial pH of the solution system is 4-7, and the temperature of the solution system is 25-35°C.

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