Preparation method and application of granular cobalt ion modified red mud based on microwave heat treatment

Abstract

The invention discloses a preparation method and application of granular cobalt ion modified red mud based on microwave heat treatment, and relates to the technical field of adsorption technology sewage treatment. Industrial solid waste red mud is used as a main raw material, and the granular porous cobalt aluminum silicate / red mud composite material is prepared through granulation, secondary microwave roasting and cobalt ion impregnation modification processes. The red mud is granulated, and after secondary microwave roasting and cobalt ion loading on the surface, the obtained composite material shows excellent adsorption capacity on organic dye in wastewater, is good in cycling stability, realizes efficient resource utilization of the red mud, and has the potential of low cost, environmental protection and industrial application.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment using adsorption technology, and in particular to a preparation method and application of granular cobalt ion-modified red mud based on microwave heat treatment. Background Art

[0002] With the rapid development of the metallurgical, mining, and chemical industries, industrial solid waste emissions continue to increase. Red mud, a highly alkaline solid waste generated during alumina production, accounts for over 100 million tons of this waste globally annually. The accumulation of large amounts of red mud not only consumes valuable land resources, but its high alkalinity and heavy metal content also contribute to soil and water pollution, posing a serious threat to the ecological environment.

[0003] Traditional red mud recycling technology relies primarily on high-temperature calcination, but this method suffers from drawbacks such as high energy consumption, uneven heating, and complex equipment, limiting its widespread application. Therefore, there is an urgent need to develop an efficient, environmentally friendly, and economically viable technology to achieve resource utilization and harmless treatment of red mud. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of granular cobalt ion modified red mud based on microwave heat treatment and its application, so as to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention is to provide a method for preparing granular cobalt ion-modified red mud based on microwave heat treatment, comprising the following steps:

[0007] (1) red mud, fly ash, pore former, binder and sulphoaluminate cement are mixed and granulated to obtain granulated red mud (GRM);

[0008] (2) subjecting the granular red mud to microwave roasting to obtain porous red mud particles;

[0009] (3) using the porous red mud particles to load cobalt ions to obtain a precursor;

[0010] (4) The precursor is subjected to a second microwave calcination to obtain the granular cobalt ion modified red mud, i.e., granular cobalt aluminum silicate / red mud composite material (CAS / GRM).

[0011] As a further preferred embodiment of the present invention, the temperatures of the first microwave roasting and the second microwave roasting are independently 723-823K.

[0012] As a further preferred embodiment of the present invention, in step (3), the porous red mud particles are immersed in a cobalt ion solution to load cobalt ions.

[0013] As a further preferred embodiment of the present invention, the cobalt ion solution is CoCl2·6H2O or Co(NO3)2 solution.

[0014] As a further preferred embodiment of the present invention, the concentration of Co in the cobalt ion solution is 0.1-0.2 mol / L.

[0015] As a further preference of the present invention, the soaking time is 24-48 hours.

[0016] As a further preferred embodiment of the present invention, the pore-forming agent is sodium bicarbonate; and / or the binder is carboxymethyl cellulose.

[0017] As a further preferred embodiment of the present invention, the mass ratio of the red mud, fly ash, pore former, binder and sulphoaluminate cement is (80-55):(5-30):5:5:5.

[0018] The present invention uses industrial solid waste red mud (RM) as the main raw material, replaces the traditional high-temperature solid-phase sintering method with microwave roasting technology, combines pore-forming agents and binders, and undergoes mixing, granulation, microwave roasting and cobalt ion impregnation modification processes to prepare granular porous cobalt aluminum silicate / red mud (CAS / GRM) composite materials.

[0019] Microwave heat treatment technology uses electromagnetic waves to stimulate molecular polarization within the material, achieving rapid and uniform heating. This technology combines both thermal and non-thermal effects, significantly improving the material's porosity and reaction efficiency. This invention uses microwave roasting technology to treat red mud, which not only improves recovery efficiency but also avoids the energy waste and secondary pollution associated with traditional calcination techniques. It also avoids the secondary pollution caused by traditional acid-base pretreatment, achieving a "waste-to-waste" approach. Through microwave roasting and the coordinated loading of cobalt ions, red mud is converted into a highly efficient adsorbent, providing a new approach for solid waste resource utilization and wastewater treatment.

[0020] In the present invention, microwaves have the characteristics of rapid and uniform heating, which can significantly accelerate the chemical reaction process. After the cobalt ions are loaded, the interaction between the cobalt ions and the hydroxyl groups on the red mud surface is strengthened by secondary microwave treatment, ensuring that the cobalt ions are evenly and stably distributed on the red mud surface, effectively promoting the formation of nanoparticle structure. After the red mud is selectively impregnated with cobalt ions, microwave heat treatment further activates the process, prompting the cobalt ions to form stable nanoparticles within the porous structure of the red mud. The subsequent microwave roasting process successfully achieved the loading of cobalt aluminum silicate on the surface of the red mud particles, and the CAS / GRM composite material finally prepared has excellent adsorption properties. This process not only shortens the preparation time, but also reduces energy consumption, greatly improving the overall performance of the material.

[0021] When preparing red mud-based granules, sulfoaluminate cement is added to increase granule strength, facilitating the composite's ability to absorb organic matter from wastewater and allow for multiple recycling. This significantly increases the material's lifespan and economic efficiency, providing strong support for large-scale industrial applications.

[0022] The present invention eliminates the need for traditional acid-base activation pretreatment of the red mud raw material during the preparation process, thus avoiding secondary environmental pollution caused by the waste acid-base solution generated by the acidification and alkali treatment. By converting industrial solid waste red mud into a composite material with high adsorption properties, this method truly realizes the resource utilization of waste, achieving the green environmental protection goal of turning waste into treasure and treating waste with waste, which is of great significance for promoting sustainable development.

[0023] The second technical solution of the present invention is to provide granular cobalt ion-modified red mud prepared by the above preparation method.

[0024] The granular cobalt ion-modified red mud prepared by the present invention has uniform pore size distribution and good compressive strength.

[0025] The third technical solution of the present invention: provides the application of the above-mentioned granular cobalt ion modified red mud in sewage treatment.

[0026] The fourth technical solution of the present invention: provides the application of the above-mentioned granular cobalt ion-modified red mud in dye adsorption and removal.

[0027] As a further preferred embodiment of the present invention, the dye is an organic dye, and more preferably Congo red.

[0028] The present invention discloses the following technical effects:

[0029] The present invention granulates red mud, and after secondary microwave roasting and surface loading of cobalt ions, the obtained composite material exhibits excellent adsorption capacity for organic dyes (such as Congo red) in wastewater and good cyclic stability.

[0030] The present invention realizes the efficient resource utilization of red mud and has the advantages of low cost, green environmental protection and industrial application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 0.15CAS / GRM in Example 3 RH 70 Macromorphology of the composite material.

[0033] Figure 2 1 is a comparison chart of the adsorption curves of the CAS / GRM composite materials in Examples 1-6.

[0034] Figure 3 1 is a comparison chart of the particle compressive strength of the CAS / GRM composite materials in Examples 1-6.

[0035] Figure 4 The porous GRM in Example 3 RH 70 particles and 0.15CAS / GRM RH Comparison of the adsorption effect of 70 composite materials on Congo red.

[0036] Figure 5 0.15CAS / GRM in Example 3 RH Comparison of solution color before and after adsorption of Congo red by 70 composite materials.

[0037] Figure 6 0.15CAS / GRM in Example 3 RH 70 Graph showing the recycling performance of composite materials adsorbing Congo red. DETAILED DESCRIPTION

[0038] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0040] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0041] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0042] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0043] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0044] The present invention provides a method for preparing granular cobalt ion-modified red mud based on microwave heat treatment, comprising the following steps:

[0045] Step 1: Raw material pretreatment: dry red mud, fly ash, and sulphoaluminate cement at 333-500K for 12-48h, grind for 15-40min, and then sieve with 250-150 mesh;

[0046] Step 2, mixing and granulating: red mud, fly ash, sodium bicarbonate, carboxymethyl cellulose, and sulfoaluminate cement are mixed in a mass ratio of (80-55):(5-30):5:5:5, ground for 15-40 minutes, and then granulated with water to obtain GRM with a particle size of 5-7 mm;

[0047] Step 3, microwave calcination: After the GRM is naturally dried for 12-48 hours, microwave calcination is performed at 723-823K for 10-20 minutes to obtain porous GRM particles;

[0048] Step 4, cobalt ion loading: immerse the porous GRM in 0.1-0.2 mol / L CoCl2·6H2O or Co(NO3)2 cobalt salt solution with a solid-liquid ratio of 1.0-10 g: 20-100 ml. After immersion for 24-48 hours, separate the solid and liquid, and dry at 333-500 K for 12-48 hours to obtain the CAS / GRM precursor.

[0049] Step 5, secondary microwave calcination: calcining the precursor at 723-823 K for 15-30 min to obtain a CAS / GRM composite material.

[0050] The present invention will be further described in detail below with reference to the embodiments.

[0051] Example 1

[0052] A method for preparing granular cobalt ion-modified red mud based on microwave heat treatment, comprising the following steps:

[0053] Step 1: Raw material pretreatment: Red mud, fly ash, and rapid-hardening sulphoaluminate cement were dried at 333K for 12 h, ground for 30 min, and then sieved with 200 mesh;

[0054] Step 2: Mixing and granulating: Red mud, fly ash, sodium bicarbonate, carboxymethyl cellulose and fast-hardening sulphoaluminate cement are mixed in a mass ratio of 80:5:5:5:5, grind for 30 minutes, and then add water to granulate to obtain GRM with a particle size of 5-7 mm. RH 80;

[0055] Step 3, microwave roasting: GRM RH After natural drying for 12 h, the porous GRM was prepared by microwave calcination at 773 K for 20 min. RH 80 pellets;

[0056] Step 4, Cobalt ion loading: Porous GRM RH 80 was immersed in 0.15 mol / L CoCl2·6H2O solution with a solid-liquid ratio of 1.0 g:20 mL. After immersion for 24 h, the solid and liquid were separated and dried at 333 K for 12 h to obtain CAS / GRM precursor;

[0057] Step 5, secondary microwave calcination: CAS / GRM precursor was microwave calcined at 773K for 20min to obtain CAS / GRM composite material, which was marked as (0.15CAS / GRM RH 80).

[0058] Example 2

[0059] A method for preparing granular cobalt ion-modified red mud based on microwave heat treatment, comprising the following steps:

[0060] Step 1: Raw material pretreatment: Red mud, fly ash, and rapid-hardening sulphoaluminate cement were dried at 333K for 12 h, ground for 30 min, and then sieved with 200 mesh;

[0061] Step 2: Mixing and granulating: Red mud, fly ash, sodium bicarbonate, carboxymethyl cellulose and fast-hardening sulphoaluminate cement are mixed in a mass ratio of 75:10:5:5:5, grind for 30 minutes, and then add water to granulate to obtain GRM with a particle size of 5-7 mm. RH 75;

[0062] Step 3, microwave roasting: GRM RH After natural drying at 75 for 12 h, the porous GRM was prepared by microwave calcination at 773 K for 20 min. RH 75 pellets;

[0063] Step 4, Cobalt ion loading: Porous GRM RH75 was immersed in 0.15 mol / L CoCl2·6H2O solution with a solid-liquid ratio of 1.0 g:20 mL. After immersion for 24 h, the solid and liquid were separated and dried at 333 K for 12 h to obtain the CAS / GRM precursor.

[0064] Step 5, secondary microwave calcination: The precursor was microwave calcined at 773K for 20 min to obtain a CAS / GRM composite material, which was labeled as (0.15CAS / GRM RH 75).

[0065] Example 3

[0066] A method for preparing granular cobalt ion-modified red mud based on microwave heat treatment, comprising the following steps:

[0067] Step 1: Raw material pretreatment: Red mud, fly ash, and rapid-hardening sulphoaluminate cement were dried at 333K for 12 h, ground for 30 min, and then sieved with 200 mesh;

[0068] Step 2: Mixing and granulating: Red mud, fly ash, sodium bicarbonate, carboxymethyl cellulose and fast-hardening sulphoaluminate cement are mixed in a mass ratio of 70:15:5:5:5, grind for 30 minutes, and then add water to granulate to obtain GRM with a particle size of 5-7 mm. RH 70;

[0069] Step 3, microwave roasting: GRM RH After natural drying at 70 °C for 12 h, the porous GRM was prepared by microwave calcination at 773 K for 20 min. RH 70 pellets;

[0070] Step 4, Cobalt ion loading: Porous GRM RH 70 was immersed in 0.15 mol / L CoCl2·6H2O solution with a solid-liquid ratio of 1.0 g:20 ml. After immersion for 24 h, the solid and liquid were separated and dried at 333 K for 12 h to obtain CAS / GRM precursor;

[0071] Step 5, secondary microwave calcination: The precursor was microwave calcined at 773K for 20 min to obtain a CAS / GRM composite material, which was labeled as (0.15CAS / GRM RH 70).

[0072] Example 4

[0073] A method for preparing granular cobalt ion-modified red mud based on microwave heat treatment, comprising the following steps:

[0074] Step 1: Raw material pretreatment: Red mud, fly ash, and rapid-hardening sulphoaluminate cement were dried at 333K for 12 h, ground for 30 min, and then sieved with 200 mesh;

[0075] Step 2: Mixing and granulating: Red mud, fly ash, sodium bicarbonate, carboxymethyl cellulose and fast-hardening sulphoaluminate cement are mixed in a mass ratio of 65:20:5:5:5, grind for 30 minutes, and then add water to granulate to obtain GRM with a particle size of 5-7 mm. RH 65;

[0076] Step 3, microwave roasting: GRM RH After natural drying for 12 h, the porous GRM was prepared by microwave calcination at 773 K for 20 min. RH 65 pellets;

[0077] Step 4, Cobalt ion loading: Porous GRM RH 65 was immersed in 0.15 mol / L CoCl2·6H2O solution with a solid-liquid ratio of 1.0 g:20 ml. After immersion for 24 h, the solid and liquid were separated and dried at 333 K for 12 h to obtain the CAS / GRM precursor.

[0078] Step 5, secondary microwave calcination: The precursor was microwave calcined at 773K for 20 min to obtain a CAS / GRM composite material, which was labeled as (0.15CAS / GRM RH 65);

[0079] Example 5

[0080] A method for preparing granular cobalt ion-modified red mud based on microwave heat treatment, comprising the following steps:

[0081] Step 1: Raw material pretreatment: Red mud, fly ash, and rapid-hardening sulphoaluminate cement were dried at 333K for 12 h, ground for 30 min, and then sieved with 200 mesh;

[0082] Step 2: Mixing and granulating: Red mud, fly ash, sodium bicarbonate, carboxymethyl cellulose and fast-hardening sulphoaluminate cement are mixed in a mass ratio of 60:25:5:5:5, grind for 30 minutes, and then add water to granulate to obtain GRM with a particle size of 5-7 mm. RH 60;

[0083] Step 3, microwave roasting: GRM RH After natural drying for 12 h, the porous GRM was prepared by microwave calcination at 773 K for 20 min. RH 60 pellets;

[0084] Step 4, Cobalt ion loading: Porous GRM RH 60 was immersed in 0.15 mol / L CoCl2·6H2O solution with a solid-liquid ratio of 1.0 g:20 ml. After immersion for 24 h, the solid and liquid were separated and dried at 333 K for 12 h to obtain CAS / GRM precursor;

[0085] Step 5, secondary microwave calcination: The precursor was microwave calcined at 773K for 20 min to obtain a CAS / GRM composite material, which was labeled as (0.15CAS / GRM RH 60).

[0086] Example 6

[0087] A method for preparing granular cobalt ion-modified red mud based on microwave heat treatment, comprising the following steps:

[0088] Step 1: Raw material pretreatment: Red mud, fly ash, and rapid-hardening sulphoaluminate cement were dried at 333K for 12 h, ground for 30 min, and then sieved with 200 mesh;

[0089] Step 2: Mixing and granulating: Red mud, fly ash, sodium bicarbonate, carboxymethyl cellulose and fast-hardening sulphoaluminate cement are mixed in a mass ratio of 55:30:5:5:5, grind for 30 minutes, and then add water to granulate to obtain GRM with a particle size of 5-7 mm. RH 55;

[0090] Step 3, microwave roasting: GRM RH After natural drying for 12 h, the porous GRM was prepared by microwave calcination at 773 K for 20 min. RH 55 particles;

[0091] Step 4, Cobalt ion loading: Porous GRM RH 55 was immersed in 0.15 mol / L CoCl2·6H2O solution with a solid-liquid ratio of 1.0 g:20 ml. After immersion for 24 h, the solid and liquid were separated and dried at 333 K for 12 h to obtain the CAS / GRM precursor.

[0092] Step 5, secondary microwave calcination: The precursor was microwave calcined at 773K for 20 min to obtain a CAS / GRM composite material, which was labeled as (0.15CAS / GRM RH 55).

[0093] Example 7

[0094] A method for preparing granular cobalt ion-modified red mud based on microwave heat treatment, comprising the following steps:

[0095] Step 1: Raw material pretreatment: Red mud, fly ash, and rapid-hardening sulphoaluminate cement were dried at 333K for 12 h, ground for 30 min, and then sieved with 200 mesh;

[0096] Step 2: Mixing and granulating: Red mud, fly ash, sodium bicarbonate, carboxymethyl cellulose and fast-hardening sulphoaluminate cement are mixed in a mass ratio of 70:15:5:5:5, grind for 30 minutes, and then add water to granulate to obtain GRM with a particle size of 5-7 mm. RH 70;

[0097] Step 3, microwave roasting: GRM RH After natural drying at 70 °C for 12 h, the porous GRM was prepared by microwave calcination at 773 K for 20 min. RH 70 pellets;

[0098] Step 4, Cobalt ion loading: Porous GRM RH 70 was immersed in 0.2 mol / L CoCl2·6H2O solution with a solid-liquid ratio of 1.0 g:20 ml. After immersion for 24 h, the solid and liquid were separated and dried at 333 K for 12 h to obtain CAS / GRM precursor;

[0099] Step 5, secondary microwave calcination: The precursor was microwave calcined at 773K for 20 min to obtain a CAS / GRM composite material, which was labeled as (0.2CAS / GRM RH 70).

[0100] Example 8

[0101] A method for preparing granular cobalt ion-modified red mud based on microwave heat treatment, comprising the following steps:

[0102] Step 1: Raw material pretreatment: Red mud, fly ash, and rapid-hardening sulphoaluminate cement were dried at 333K for 12 h, ground for 30 min, and then sieved with 200 mesh;

[0103] Step 2: Mixing and granulating: Red mud, fly ash, sodium bicarbonate, carboxymethyl cellulose and fast-hardening sulphoaluminate cement are mixed in a mass ratio of 70:15:5:5:5, grind for 30 minutes, and then add water to granulate to obtain GRM with a particle size of 5-7 mm. RH 70;

[0104] Step 3, microwave roasting: GRM RH After natural drying at 70 °C for 12 h, the porous GRM was prepared by microwave calcination at 773 K for 20 min. RH 70 pellets;

[0105] Step 4, Cobalt ion loading: Porous GRM RH 70 was immersed in 0.1 mol / L CoCl2·6H2O solution with a solid-liquid ratio of 1.0 g:20 ml. After immersion for 24 h, the solid and liquid were separated and dried at 333 K for 12 h to obtain CAS / GRM precursor;

[0106] Step 5, secondary microwave calcination: The precursor was microwave calcined at 773K for 20 min to obtain a CAS / GRM composite material, which was labeled as (0.1CAS / GRM RH 70).

[0107] Example 9

[0108] A method for preparing granular cobalt ion-modified red mud based on microwave heat treatment, comprising the following steps:

[0109] Step 1, raw material pretreatment: red mud, fly ash, and low-alkali sulphoaluminate cement were dried at 333K for 12 h, ground for 30 min, and then sieved with 200 mesh;

[0110] Step 2: Mixing and granulation: Red mud, fly ash, sodium bicarbonate, carboxymethyl cellulose and low-alkali sulphoaluminate cement are mixed in a mass ratio of 70:15:5:5:5, grind for 30 minutes, and then add water to granulate to obtain GRM with a particle size of 5-7 mm. LA 70;

[0111] Step 3, microwave roasting: GRM LA After natural drying at 70 °C for 12 h, the porous GRM was prepared by microwave calcination at 773 K for 20 min. LA 70 pellets;

[0112] Step 4, Cobalt ion loading: Porous GRM LA 70 was immersed in 0.15 mol / L CoCl2·6H2O solution with a solid-liquid ratio of 1.0 g:20 ml. After immersion for 24 h, the solid and liquid were separated and dried at 333 K for 12 h to obtain CAS / GRM precursor;

[0113] Step 5, secondary microwave calcination: The precursor was microwave calcined at 773K for 20 min to obtain a CAS / GRM composite material (0.15CAS / GRM LA 70).

[0114] Example 10

[0115] A method for preparing granular cobalt ion-modified red mud based on microwave heat treatment, comprising the following steps:

[0116] Step 1, raw material pretreatment: red mud, fly ash, and fly ash sulphoaluminate cement were dried at 333K for 12h, ground for 30min, and then sieved with 200 mesh;

[0117] Step 2: Mixing and granulating: Red mud, fly ash, sodium bicarbonate, carboxymethyl cellulose and fly ash sulphoaluminate cement were mixed in a mass ratio of 70:15:5:5:5, ground for 30 minutes and then granulated with water to obtain GRM with a particle size of 5-7 mm. FA 70;

[0118] Step 3, microwave roasting: GRM FA After natural drying at 70 °C for 12 h, the porous GRM was prepared by microwave calcination at 773 K for 20 min. FA 70 pellets;

[0119] Step 4, Cobalt ion loading: Porous GRM FA 70 was immersed in 0.15 mol / L CoCl2·6H2O solution with a solid-liquid ratio of 1.0 g:20 ml. After immersion for 24 h, the solid and liquid were separated and dried at 333 K for 12 h to obtain CAS / GRM precursor;

[0120] Step 5, secondary microwave calcination: The precursor was microwave calcined at 773K for 20 min to obtain a CAS / GRM composite material marked as (0.15CAS / GRM FA 70).

[0121] Comparative Example 1

[0122] The only difference from Example 3 is that the CoCl2·6H2O solution is replaced by ZnCl2 of equal concentration.

[0123] The results showed that the maximum adsorption capacity of the material for 200 mg / L Congo red solution was about 28.49 mg / g, which was lower than that of Example 3 (0.15 CAS / GRM RH 70) as shown in 32.12 mg / g. Further analysis revealed that Zn 2+ During the loading process, particles tend to agglomerate and it is difficult to form a Co-like 2+ The stable complexation or oxidation structure of the adsorbent leads to pore blockage and a reduction in effective adsorption sites, thereby affecting the overall adsorption efficiency and material structure stability.

[0124] Comparative Example 2

[0125] The only difference from Example 3 is that the microwave calcination in step 3 is replaced by high-temperature solid-phase sintering. The steps are as follows:

[0126] Step 3, GRM RH After granulation, the porous GRM was obtained by calcining in a box furnace (773K, 120min). RH 70.

[0127] The remaining steps are the same as in Example 3.

[0128] The results showed that its maximum adsorption capacity for a 200mg / L Congo red solution was approximately 31.6mg / g. Because the traditional heating process involves the phenomenon of "surface sintering first and internal incomplete sintering," it inhibits pore formation and shrinks the pore structure within the material, thereby reducing its adsorption performance. This indicates that the thermal and non-thermal effects of microwaves are more beneficial for constructing porous structures.

[0129] Comparative Example 3

[0130] The only difference from Example 3 is that the secondary microwave roasting in step 5 is replaced by high-temperature solid-phase sintering. The steps are as follows:

[0131] Step 5: calcining the precursor in a box furnace (773K, 120min) to obtain a CAS / GRM composite material.

[0132] The remaining steps are the same as in Example 3.

[0133] The results showed that the maximum adsorption capacity of the material for a 200mg / L Congo red solution was approximately 24.8mg / g, which was approximately 22.8% lower than that of the material obtained by microwave calcination. The material exhibited structural cracks during the adsorption process, and its reproducible performance deteriorated, demonstrating that microwave calcination is superior to traditional high-temperature solid-phase methods in enhancing crystallinity and skeleton strength.

[0134] Comparative Example 4

[0135] The only difference from Example 3 is that the sulphoaluminate cement is replaced by starch of equal mass.

[0136] The results showed that the maximum adsorption capacity of the material for 200 mg / L Congo red solution was higher than that of 0.15 CAS / GRM in Example 3. RH 70%; Meanwhile, the granular material developed surface cracks during the adsorption process, and some particles broke apart, exhibiting poor mechanical strength and structural integrity. In contrast, sulphoaluminate cement reacts with components such as red mud and fly ash in a short period of time to form a stable structure, significantly improving the mechanical strength of the particles. It plays a key role in structural support and molding reinforcement in the CAS / GRM composite material constructed in this invention.

[0137] Figure 1 0.15CAS / GRM prepared in Example 3 RH Macroscopic morphology of the 70 composite material. The material is granular, demonstrating good recyclability. Furthermore, the particles are evenly distributed between 5 and 7 mm in size, and exhibit a noticeable roughness on the surface, which facilitates dye adsorption.

[0138] The CAS / GRM composite materials prepared in Examples 1-6 were used for sewage purification. Six portions of 50 mL of a 200 mg / L Congo red solution were prepared, and 0.3 g of the CAS / GRM composite material was placed in 50 mL of the above Congo red solution. A magnetic stirring test was performed in the dark. The adsorption time was 3 hours, with samples taken every 10 minutes for the first hour and every 30 minutes for the next 2 hours, with 3 mL of sample taken each time. The samples were centrifuged after sampling, and the adsorption was tested using a UV-visible spectrophotometer to determine the amount of Congo red that the adsorbent could adsorb.

[0139] Figure 2 This is the adsorption performance spectrum of the CAS / GRM composite material prepared in Examples 1-6 of the present invention. The data shows that after 3 hours of adsorption, the spectral intensity decreases significantly. Of particular note, when the red mud doping level reaches 70%, the composite material's adsorption rate for Congo red increases significantly, fully demonstrating the synthesized material's significant adsorption capacity for Congo red.

[0140] Figure 3 The following chart compares the compressive strength of the CAS / GRM composite particles in Examples 1-6. The results show that when the red mud content reaches 70%, the material exhibits relatively high compressive strength. Variations in red mud content affect the composite's pore structure, including pore number, pore size, and specific surface area, and thus its adsorption performance and mechanical stability. Therefore, the adsorbent must possess both good adsorption performance and sufficient mechanical strength to ensure structural integrity during the adsorption process and facilitate subsequent recycling.

[0141] Figure 4 The porous GRM in Example 3 RH 70 particles with 0.15CAS / GRM RH The results showed that the adsorption of Congo red by 0.15 mol L -1 GRM modified by CoCl2·6H2O solution impregnation and microwave calcination RH 70, its adsorption capacity for CR was significantly enhanced, and the adsorption capacity within 3 h was about GRM RH 70. This result shows that the GRM RH The in-situ loading of CAS nanostructures on the surface of 70 can effectively improve the removal efficiency of organic pollutants such as CR and realize high value-added utilization of red mud.

[0142] Figure 5 0.15CAS / GRM prepared in Example 3 RH A comparison of the solution colors of the 70 composite material before and after adsorption of Congo red. The solution was light red before adsorption, but after three hours of adsorption, it became nearly colorless and transparent. This significant change further demonstrates the excellent adsorption of Congo red by the prepared material. Furthermore, the granular adsorbent enables efficient solid-liquid separation and is easily recyclable.

[0143] Figure 6 0.15CAS / GRM in Example 3 RHThe cyclic performance diagram of the 70 composite material adsorbing Congo red. The results show that after one cycle, the adsorbent can remove 94.5% of CR. After 4 adsorption-desorption cycles, the CR removal rate decreased, but still had a good effect, indicating that 0.15CAS / GRM RH 70 has excellent CR removal efficiency and good reusability.

[0144] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing granular cobalt ion-modified red mud based on microwave heat treatment, characterized in that: The following steps are involved: (1) mixing red mud, fly ash, a pore former, a binder and sulphoaluminate cement, and granulating to obtain granular red mud; (2) subjecting the granular red mud to microwave roasting to obtain porous red mud particles; (3) loading cobalt ions onto the porous red mud particles to obtain a precursor; (4) The precursor is subjected to a second microwave roasting to obtain the granular cobalt ion modified red mud.

2. The preparation method according to claim 1, characterized in that The temperatures of the first microwave roasting and the second microwave roasting are independently 723-823K.

3. The preparation method according to claim 1, characterized in that In step (3), the porous red mud particles are immersed in a cobalt ion solution to load cobalt ions.

4. The preparation method according to claim 3, characterized in that The cobalt ion solution is CoCl2·6H2O or Co(NO3)2 solution.

5. The preparation method according to claim 3, characterized in that In the cobalt ion solution, the Co concentration is 0.1-0.2 mol / L.

6. The preparation method according to claim 1, characterized in that The pore-forming agent is sodium bicarbonate; and / or the binder is carboxymethyl cellulose.

7. The preparation method according to claim 1, characterized in that The mass ratio of the red mud, fly ash, pore former, binder and sulphoaluminate cement is (80-55):(5-30):5:5:

5.

8. Granular cobalt ion-modified red mud prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the granular cobalt ion modified red mud as claimed in claim 8 in sewage treatment.

10. Use of the granular cobalt ion modified red mud according to claim 8 in dye adsorption removal.

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