Iron-loaded dolomite composite material for efficiently removing alkaline organic dye

Abstract

The invention discloses an iron-loaded dolomite composite material for efficiently removing alkaline organic dye, which takes natural dolomite mineral as a main carrier, loads nanoscale ferrite magnetic particles, and introduces a silica sol template agent to construct a porous structure; the invention also relates to a preparation method and an application thereof in dye removal. By optimizing the iron source introduction and calcination process, ferrite magnetic components are uniformly distributed and stably combined in the material, and good magnetic response performance is formed; through mineral structure stability of dolomite and optimized iron load proportion control, the magnetic component is not easy to fall off and not agglomerate in multiple use, the adsorption activity is maintained, and after more than five times of adsorption-desorption cycles, the adsorption efficiency of the material is still maintained to be more than 90%.

Description

TECHNICAL FIELD

[0001] The present application relates to an iron-loaded dolomite composite material, in particular to an iron-loaded dolomite composite material for efficiently removing alkaline organic dyes. BACKGROUND

[0002] In the field of wastewater treatment, magnetic composite adsorbents as a new type of pollutant removal material have been widely used in water pollution control due to their good adsorption performance and convenient recovery characteristics. Especially for the removal of toxic dyes and antibiotic pollutants, magnetic adsorbents show great potential. Common magnetic composite adsorbents are usually composed of magnetic materials and adsorbents (such as activated carbon, iron oxide, silica gel, etc.), which can effectively remove dyes, heavy metal ions and other organic pollutants. Traditional preparation methods generally include synthesis of magnetic materials and loading of adsorbents, and common methods include co-precipitation, chemical precipitation, etc. However, these methods have certain limitations, such as long reaction time, complex operation, high material cost, etc.

[0003] The prior art uses a magnesium source, an iron source and citric acid to mix in a sol-gel system, and then obtains a magnetic composite adsorbent through drying, ignition and low-temperature calcination, etc. The obtained adsorbent has good magnetic and adsorption properties, can efficiently remove tetracycline and malachite green and other organic pollutants in water, and can be quickly recovered by magnetic field solid-liquid separation. However, the raw materials used in the prior art are mostly chemical reagents, such as pure iron source, magnesium source and citric acid as precursors, which have relatively high cost. And the structure of the material adsorbent is single, the specific surface area is low, and there is still a problem of insufficient removal efficiency for some high-concentration pollutants (such as dyes); the preparation method lacks means for structure regulation, and the pore is uncontrollable; although the material recycling ability is shown, the performance decays quickly during the recycling process, and the stability is insufficient. Therefore, there is an urgent need for an iron-loaded dolomite magnetic composite adsorbent material with adjustable structure, large specific surface area, high adsorption efficiency, cheap and easily available raw materials, and strong recyclability. SUMMARY

[0004] To solve the above technical problems, the present application provides an iron-loaded dolomite composite material for efficiently removing alkaline organic dyes, aiming to obtain an iron-loaded dolomite magnetic composite adsorbent material with adjustable structure, large specific surface area, high adsorption efficiency, cheap and easily available raw materials, and strong recyclability, so as to realize efficient removal of dye and antibiotic organic pollutants.

[0005] To achieve the above purpose, the technical scheme provided by the present application is as follows:

[0006] The iron-loaded dolomite composite material for efficiently removing basic organic dyes comprises a natural dolomite mineral as a main carrier, loaded with nano-sized ferrite magnetic particles, and a silica sol template agent for constructing a porous structure, thereby forming a composite adsorption material with the functions of magnetism, adsorption and structure adjustment.

[0007] The preparation method of the iron-loaded dolomite composite material for efficiently removing basic organic dyes comprises the following steps:

[0008] (1) Preparation of precursor mixed slurry: white dolomite powder and silica sol are added into a beaker, mixed well, and then left to stand, so that the silica sol is uniformly distributed on the surface and in the pores of the white dolomite, thereby obtaining a precursor mixed slurry;

[0009] (2) Introduction of magnetic components: ferrous chloride tetrahydrate (FeCl2·4H2O) is added into the precursor mixed slurry obtained in step (1), and then ultrasonic stirring is performed to promote the adsorption and infiltration of iron ions on the surface of the white dolomite, thereby forming a uniformly distributed precursor system;

[0010] (3) Drying and molding: the precursor system obtained in step (2) is transferred into a polytetrafluoroethylene mold, and then dried to stabilize the molding;

[0011] (4) Pretreatment, grinding and calcination: the dried substance obtained in step (3) is ground, placed in a muffle furnace, and then calcined at 300-600°C for 2 h, which helps to form a ferrite magnetic structure, promotes the decomposition of part of the template, and enhances the stability of the skeleton; the calcined substance is soaked in an alkaline solution and stirred to selectively remove the silicon dioxide in the template agent, thereby exposing the porous structure;

[0012] (5) Washing and drying: the material obtained after stirring in step (4) is washed with deionized water until the washing liquid is neutral, and then dried in an oven, thereby obtaining the iron-loaded dolomite composite material for efficiently removing basic organic dyes.

[0013] Preferably, in step (1), 1-5 g of white dolomite powder and 1-5 mL of silica sol are added into a beaker and mixed well.

[0014] Preferably, in step (1), the white dolomite powder has a particle size of less than 200 mesh, and the standing time is 12 h.

[0015] Preferably, in step (2), the ultrasonic time is 30 min, and the amount of ferrous chloride tetrahydrate (FeCl2·4H2O) added in step (2) is 1%-10% of the mass of the white dolomite added in step (1).

[0016] Preferably, the drying in step (3) is performed at 80°C for 6 hours.

[0017] Preferably, the alkaline solution in step (4) is a 2 mol / L NaOH solution; the stirring is carried out at 60°C for 6 h; and in step (4), the solution is placed in a muffle furnace and calcined at 500°C for 2 h.

[0018] The application of iron-loaded dolomite composite materials for efficiently removing alkaline organic dyes, as described above, in dye removal.

[0019] Preferably, the dye is malachite green or methyl green; the dye concentration is 200 mg / L.

[0020] Preferably, 1 mg of the iron-loaded dolomite composite material for efficiently removing alkaline organic dyes is added to every 5 mL of dye.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) The material of this invention uses natural dolomite mineral as the main carrier and adopts the silica sol template method to construct a multi-level pore structure, which can control the porosity and pore size distribution and adjust the adaptability of the adsorbent to pollutants of different molecular sizes; and introduces highly dispersed magnetic ferrite nanoparticles, which significantly improves the specific surface area and effective adsorption sites of the material, thereby increasing the adsorption capacity of dyes such as methyl green and malachite green by about 30-50%, shortening the equilibrium time to less than 1 hour, and greatly improving the treatment efficiency.

[0023] (2) By optimizing the iron source introduction and calcination process, the present invention enables the ferrite magnetic components to be uniformly distributed and stably combined in the material, forming good magnetic response performance; by optimizing the mineral structure stability of dolomite and controlling the iron load ratio, the magnetic components are not easy to fall off or agglomerate during multiple uses, maintaining adsorption activity. After more than 5 adsorption-desorption cycles, the adsorption efficiency of the material is still maintained at more than 90%.

[0024] (3) This invention uses natural dolomite mineral as the main carrier to replace traditional expensive synthetic inorganic oxides; at the same time, it adopts a lower temperature (500℃) calcination process to avoid high temperature sintering and multi-step operation. The whole preparation process is green, low toxicity and has no waste liquid discharge problem, which is in line with the current development direction of environmental protection materials industry. Attached Figure Description

[0025] Figure 1 The present invention describes the removal rates of methyl green and malachite green at different times using an iron-loaded dolomite composite material for the efficient removal of alkaline organic dyes.

[0026] Figure 2This is a BET (Body Surface Area) diagram of dolomite before and after modification; where CaMg(CO3)2 represents dolomite before modification, and Fe / CaMg(CO3)2 represents dolomite after modification.

[0027] Figure 3 SEM-EDS image of the iron-supported dolomite composite material for efficiently removing alkaline organic dyes according to the present invention.

[0028] Figure 4 The thermogravimetric analysis (TGA) values ​​are for dolomite before and after modification; where CaMg(CO3)2 represents dolomite before modification, and Fe / CaMg(CO3)2 represents dolomite after modification.

[0029] Figure 5 These are infrared images of dolomite before and after modification; CaMg(CO3)2 represents dolomite before modification, and Fe / CaMg(CO3)2 represents dolomite after modification.

[0030] Figure 6 These are the XRD patterns of dolomite before and after modification; where CaMg(CO3)2 represents dolomite before modification, and Fe / CaMg(CO3)2 represents dolomite after modification.

[0031] Figure 7 This is a cyclic adsorption diagram of malachite green.

[0032] Figure 8 This is a cyclic adsorption diagram of methyl green. Detailed Implementation

[0033] The following is a detailed description of specific embodiments in conjunction with the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise specified, the raw materials and reagents used in the examples are commercially available. Dolomite was purchased from Baofeng Mining Co., Ltd.

[0034] Example 1

[0035] The preparation method of iron-supported dolomite composite material for efficiently removing alkaline organic dyes includes the following steps:

[0036] (1) Preparation of precursor mixed slurry: Take 5 g of dolomite powder (after pretreatment, the particle size is controlled below 200 mesh) and 4 mL of silica sol and add them to a beaker. Stir and mix thoroughly to form a uniform slurry. Let it stand for 12 h to obtain the precursor mixed slurry.

[0037] (2) Introduction of magnetic components: 0.5 g FeCl2·4H2O was added to the precursor mixture slurry obtained in step (1), and the mixture was stirred and sonicated for 30 min to form a uniformly distributed precursor system;

[0038] (3) Drying and molding: The precursor system obtained in step (2) is transferred to a polytetrafluoroethylene mold and dried at 80°C for 6 h;

[0039] (4) Pretreatment grinding and calcination: Grind the material obtained after drying in step (3), place it in a muffle furnace, and calcine it at 500℃ for 2 h. Soak the calcined material in 2 mol / L NaOH solution and stir it at 60℃ for 6 h.

[0040] (5) Washing and drying: The material obtained after stirring for 6 hours in step (4) was thoroughly washed with deionized water until the washing solution was neutral. Then, it was dried in a vacuum drying oven at 80°C for 6 hours to obtain an iron-loaded dolomite composite material that efficiently removes alkaline organic dyes. The obtained iron-loaded dolomite composite material was characterized by XRD and FT-IR. The XRD spectrum showed that the characteristic diffraction peaks of dolomite were still present, indicating that its crystal structure was not damaged during the loading process. The FT-IR spectrum showed new absorption peaks related to iron-oxygen bonds, while the characteristic vibration peaks of dolomite remained intact, confirming the successful loading of the iron component on the support. From the SEM image ( Figure 3 The sample exhibits a three-dimensional layered structure formed by lamellar stacking and folds, rather than a dense bulk. This loosely packed morphology provides the material with a large specific surface area and openness, which is beneficial for the exposure of reaction sites and mass transport.

[0041] Example 2

[0042] The preparation method of iron-supported dolomite composite material for efficiently removing alkaline organic dyes includes the following steps:

[0043] (1) Preparation of precursor mixed slurry: Take 2 g of dolomite powder (after pretreatment, the particle size is controlled below 200 mesh) and 1 mL of silica sol and add them to a beaker. Stir and mix thoroughly to form a uniform slurry. Let it stand for 12 h to obtain the precursor mixed slurry.

[0044] (2) Introduction of magnetic components: 0.02 g FeCl2·4H2O was added to the precursor mixture slurry obtained in step (1), and the mixture was stirred and sonicated for 30 min to form a uniformly distributed precursor system;

[0045] (3) Drying and molding: The precursor system obtained in step (2) is transferred to a polytetrafluoroethylene mold and dried at 80°C for 6 h;

[0046] (4) Pretreatment grinding and calcination: Grind the material obtained after drying in step (3), place it in a muffle furnace, and calcine it at 300℃ for 2 h. Soak the calcined material in 2 mol / L NaOH solution and stir it at 60℃ for 6 h.

[0047] (5) Washing and drying: The material obtained after stirring for 6 hours in step (4) is thoroughly washed with deionized water until the washing solution is neutral. Then, it is dried in a vacuum drying oven at 80°C for 6 hours to obtain an iron-loaded dolomite composite material that can efficiently remove alkaline organic dyes.

[0048] Example 3

[0049] The preparation method of iron-supported dolomite composite material for efficiently removing alkaline organic dyes includes the following steps:

[0050] (1) Preparation of precursor mixed slurry: Take 1 g of dolomite powder (after pretreatment, the particle size is controlled below 200 mesh) and 5 mL of silica sol and add them to a beaker. Stir and mix thoroughly to form a uniform slurry. Let it stand for 12 h to obtain the precursor mixed slurry.

[0051] (2) Introduction of magnetic components: 0.06 g FeCl2·4H2O was added to the precursor mixture slurry obtained in step (1), and the mixture was stirred and sonicated for 30 min to form a uniformly distributed precursor system;

[0052] (3) Drying and molding: The precursor system obtained in step (2) is transferred to a polytetrafluoroethylene mold and dried at 80°C for 6 h;

[0053] (4) Pretreatment grinding and calcination: Grind the material obtained after drying in step (3), place it in a muffle furnace, and calcine it at 600℃ for 2 h. Soak the calcined material in 2 mol / L NaOH solution and stir it at 60℃ for 6 h.

[0054] (5) Washing and drying: The material obtained after stirring for 6 hours in step (4) is thoroughly washed with deionized water until the washing solution is neutral. Then, it is dried in a vacuum drying oven at 80°C for 6 hours to obtain an iron-loaded dolomite composite material that can efficiently remove alkaline organic dyes.

[0055] Application Example 1

[0056] The iron-supported dolomite composite material for efficiently removing basic organic dyes prepared in Example 1 was used to remove malachite green and methylene blue dyes.

[0057] 20 mg of the iron-supported dolomite composite material for efficiently removing basic organic dyes prepared in Example 1 was added to 100 mL of a 200 mg / L dye solution (the dye was commercially available solid dye malachite green or methylene blue prepared with deionized water). The mixture was magnetically stirred in a 40 °C water bath for 60 min. Every 5 min during the experiment, a certain volume of solution was taken out, centrifuged, and the residual dye concentration was measured using a UV-Vis spectrophotometer. The removal rate at each time point was calculated, and plotted. Figure 1 The removal kinetics curve is shown.

[0058] After filtering the iron-loaded dolomite composite material used in Application Example 1 for the efficient removal of alkaline organic dyes, all solid materials were vacuum dried at 80°C for 6 hours, then calcined at -300°C for 1 hour before reuse; this constitutes one cycle. The composite material from Application Example 1 was repeatedly dried and calcined before being reused to remove malachite green and methylene blue dyes, respectively, for a total of 5 cycles. The removal effect was as follows: Figure 7 , 8 As shown.

[0059] Figure 2 The nitrogen adsorption-desorption isotherms and pore size distribution diagrams are shown for the dolomite before modification (i.e., dolomite purchased from Baofeng Mining Co., Ltd.) and the iron-supported dolomite composite material prepared in Example 1. Both groups of samples were tested using a surface area and pore structure analyzer (BET method). High-purity nitrogen was introduced at 77 K, and the adsorption-desorption curves were recorded with relative pressure (P / P0) as the abscissa. The pore size distribution was calculated using the BJH method.

[0060] Depend on Figure 2 It can be seen that the unmodified dolomite has almost no significant pore structure and a low specific surface area; while the iron-supported dolomite composite exhibits obvious type IV isotherms and H3 hysteresis loops, indicating that it possesses both microporous and mesoporous characteristics. Further calculations show that the specific surface area of ​​this composite is approximately 47 times that of the original dolomite. This micro / mesoporous synergistic structure significantly improves the specific surface area and porosity of the material, providing favorable conditions for the exposure of active sites and the mass transfer and diffusion of dye molecules, thus laying the structural foundation for its efficient removal of basic organic dyes.

[0061] from Figure 4It can be seen that the unmodified dolomite exhibits significant weight loss around ~700 °C, corresponding to the decomposition of CaMg(CO3)2; while the iron-supported dolomite composite material for efficiently removing alkaline organic dyes prepared in Example 1 of this invention has a slightly earlier decomposition initiation temperature and a higher residual mass. This indicates that the introduction of Fe / CaMg(CO3)2 promotes the decarbonation reaction of carbonates and forms a stable Fe-O-Ca / Mg bond structure at the interface, thereby altering the thermal decomposition pathway. This result further confirms the existence of significant chemical interfacial interactions in the composite material, rather than just physical mixing.

[0062] Figure 5 and Figure 6 Infrared and XRD scanning analysis was performed using dolomite and the iron-supported dolomite composite material obtained in Example 1, which efficiently removes alkaline organic dyes. Figure 5 FT-IR and Figure 6 XRD analysis revealed that iron was successfully loaded onto the dolomite surface: the characteristic peaks of dolomite shifted, and Fe-O absorption peaks appeared. Simultaneously, new diffraction peaks of iron oxides appeared in the XRD and were dispersed, indicating the formation of a structurally stable iron-dolomite composite material. This loaded structure effectively increased the active sites of the material and improved its adsorption / catalytic performance, demonstrating significant beneficial effects.

[0063] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. An iron-supported dolomite composite material for efficiently removing alkaline organic dyes, characterized in that: Using natural dolomite mineral as the main carrier, nanoscale ferrite magnetic particles are loaded and silica sol template agent is introduced to construct a porous structure, forming a composite adsorbent material with magnetic properties, adsorption properties and structural controllability. The material has a three-dimensional layered structure, exhibiting a synergistic structure of micropores and mesopores, and has a high specific surface area and uniformly distributed nanoscale magnetic particles.

2. The preparation method of the iron-supported dolomite composite material for efficiently removing alkaline organic dyes according to claim 1, characterized in that: The operation includes the following steps: (1) Preparation of precursor mixture slurry: Take dolomite powder and silica sol, stir and mix, let stand, and obtain precursor mixture slurry; (2) Introduction of magnetic components: Ferrous chloride is added to the precursor mixture obtained in step (1), and stirring is continued to form a precursor system; (3) Drying and molding: Transfer the precursor system obtained in step (2) into the mold and dry it; (4) Pretreatment grinding and calcination: Grind the material obtained after drying in step (3), calcine it at 300-600℃ for 2 h, and soak the calcined material in an alkaline solution and stir. (5) Washing and drying: Wash and dry the material obtained after stirring in step (4) to obtain an iron-loaded dolomite composite material that can effectively remove alkaline organic dyes.

3. The preparation method of the iron-supported dolomite composite material for efficiently removing alkaline organic dyes according to claim 2, characterized in that: In step (1), take 1-5 g of dolomite powder and 1-5 mL of silica sol and stir to mix.

4. The preparation method of the iron-supported dolomite composite material for efficiently removing alkaline organic dyes according to claim 2, characterized in that: The dolomite powder mentioned in step (1) has a particle size of less than 200 mesh; the standing time is 12 h.

5. The preparation method of the iron-supported dolomite composite material for efficiently removing alkaline organic dyes according to claim 2, characterized in that: The ultrasound time in step (2) is 30 min; the amount of ferrous chloride added in step (2) is 1%-10% of the mass of dolomite added in step (1).

6. The preparation method of the iron-supported dolomite composite material for efficiently removing alkaline organic dyes according to claim 2, characterized in that: The drying process described in step (3) is drying at 80°C for 6 hours.

7. The preparation method of the iron-supported dolomite composite material for efficiently removing alkaline organic dyes according to claim 2, characterized in that: The alkaline solution mentioned in step (4) is a 2 mol / L NaOH solution; the stirring is carried out at 60℃ for 6 h; and the calcination is carried out at 500℃ for 2 h in step (4).

8. The application of the iron-loaded dolomite composite material for efficiently removing alkaline organic dyes as described in claim 1 or the iron-loaded dolomite composite material for efficiently removing alkaline organic dyes prepared by any method of claims 2-7 in dye removal.

9. The application according to claim 9, characterized in that: The dye is malachite green or methyl green; the concentration of the dye is 200 mg / L.

10. The application according to claim 9, characterized in that: Add 1 mg of the iron-loaded dolomite composite material for efficiently removing alkaline organic dyes to every 5 mL of dye.

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