A method for preparing a molybdenum tailings cementitious material using a microwave method

Abstract

This invention belongs to the field of cement technology, specifically relating to a method for preparing molybdenum tailings cementitious composites using a microwave method. The specific steps of this method are as follows: Molybdenum tailings are ground together with other admixtures; water is added to the molybdenum tailings powder and stirred evenly to obtain a mixture; a microwave field is applied to the mixture and maintained for 10-40 minutes to obtain a composite material; the composite material is crushed and sieved to obtain the molybdenum tailings cementitious composite material prepared by the microwave method. This method uses molybdenum tailings as the main raw material, combined with natural minerals such as limestone and bauxite, to prepare a composite material with high activity. The operation is simple and does not require extensive new equipment or technology.

Description

Technical Field

[0001] This invention belongs to the field of cement technology, specifically relating to a method for preparing molybdenum tailings cement blends using a microwave method. Background Technology

[0002] my country has abundant molybdenum resources, but because molybdenum ore grades are usually low, the tailings yield is high during the extraction process. Molybdenum tailings account for 95% of the ore mined during beneficiation, and the vast majority of these are discharged as powdery tailings after beneficiation.

[0003] Molybdenum tailings, aside from trace amounts of valuable associated elements, are mainly composed of calcite and dolomite, with SiO2 being the primary component (approximately 80%). Other impurities are present in low concentrations, primarily metal oxides such as iron oxide, aluminum oxide, and potassium oxide. Metal mine tailings are both waste and a resource. Research on the comprehensive utilization of molybdenum tailings resources is beneficial for both waste recycling and regional environmental protection.

[0004] The amount of tailings discharged from molybdenum mines nationwide is enormous, and the stockpiles are even larger. Utilizing the high silica content in molybdenum tailings is a crucial direction for achieving resource-based treatment of molybdenum tailings. Numerous researchers have conducted exploratory studies on the application of molybdenum tailings in cement-based materials. Current technological explorations mainly focus on its use as coarse aggregate in cement (CN 202210711324.0) and in dry-mixed cement mortar (CN 202210560001.6). However, both of these methods utilize the alkali reactivity of quartz, potassium feldspar, and muscovite in molybdenum tailings by activating the pozzolanic activity. The autoclaving process allows the active SiO2 and Al2O3 in the prepared cement coarse aggregate to fully participate in the reaction and generate hydration products. Finely ground molybdenum tailings powder is then incorporated to form a reasonable particle framework, with the fine tailings particles filling the gaps. This process is complex, requiring pre-screening of the molybdenum tailings and incineration of large tailings particles to ensure the quality of the resulting coarse aggregate. Using molybdenum tailings to make dry-mixed mortar requires acid leaching of the screened molybdenum tailings powder with hydrochloric acid. Hydrofluoric acid is then added to the leaching solution, followed by the dropwise addition of ammonia to initiate the reaction. After the reaction, the mixture is aged, and the resulting aged product is filtered under reduced pressure, dried, and calcined to obtain molybdenum tailings silica powder. This method generates experimental wastewater requiring further treatment, such as hydrochloric acid, fluorosilicic acid, and ammonia, placing high environmental and equipment requirements on subsequent production, which is not conducive to large-scale promotion. Summary of the Invention

[0005] Based on the problems existing in the prior art, this invention aims to propose a method for preparing molybdenum tailings cementitious composites using a microwave method. This method employs microwave heating to thermally activate mineral phases such as quartz, potassium feldspar, and muscovite in the molybdenum tailings. Electrical energy is converted into microwaves by the magnetron of a microwave oven, which penetrate the molybdenum tailings at an oscillation frequency of 2450 MHz. When the microwaves are absorbed by the molybdenum tailings, the polar molecules within the tailings are attracted and oscillate rapidly at a rate of 2.45 billion times per second. This macroscopic manifestation of oscillation heats the molybdenum tailings.

[0006] The present invention adopts the following technical solution.

[0007] A method for preparing molybdenum tailings cementitious composite material using a microwave method, specifically including the following steps:

[0008] Step 1: Grind the molybdenum tailings together with other admixtures until finely ground;

[0009] Step 2: Add 3% water to the molybdenum tailings powder and stir evenly to obtain a mixture;

[0010] Step 3: Apply a microwave field to the mixture obtained in Step 2 and maintain it for 10-40 minutes to obtain the mixed material;

[0011] Step 4: Crush and screen the mixture obtained in Step 3 after microwave field treatment to obtain molybdenum tailings cement mixture prepared by microwave method.

[0012] Furthermore, in step 1, the mass percentage of molybdenum tailings is 70 to 100 parts, the mass percentage of limestone is 15 to 20 parts, and the mass percentage of granulated slag is 10 to 15 parts.

[0013] Furthermore, in step 3, the microwave used is an industrial microwave oven (ORW10S-3T model) manufactured by Nanjing Aorun Microwave Factory, with a microwave power of 1.33KW.

[0014] Furthermore, in steps 1 and 4, the grinding or sieving conditions are as follows: the residue on the 45-micron sieve is below 10%, and the residue on the 80-micron sieve is controlled below 1%.

[0015] Compared with the prior art, the present invention has the following beneficial effects.

[0016] 1. This method effectively recovers and utilizes high-silicon components such as quartz, potassium feldspar, and muscovite from molybdenum tailings, promoting the low-carbon and sustainable development of the cement industry.

[0017] 2. This method uses molybdenum tailings as the main raw material, combined with natural minerals such as limestone and bauxite, to prepare a composite material with high activity. It can be used as an auxiliary cementitious material to replace cement in concrete, saving energy, protecting the environment, and having high environmental and economic benefits.

[0018] 3. This method is simple to operate, does not require a large number of new equipment and technologies, only requires equipment that can apply microwave fields, and has strong applicability.

[0019] 4. This method also provides a new approach for the resource utilization of molybdenum tailings in my country, expands the resource recycling rate of molybdenum tailings, and can actively promote the sustainable development of the non-ferrous metals industry. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are implemented based on the technology of the present invention, and detailed implementation methods and specific operating procedures are provided to illustrate the inventiveness of the present invention. However, the scope of protection of the present invention is not limited to the following embodiments.

[0021] A method for preparing molybdenum tailings cementitious composite material using a microwave method, specifically including the following steps:

[0022] Step 1: Grind the molybdenum tailings together with other admixtures until finely ground;

[0023] Step 2: Add 3% water to the molybdenum tailings powder and stir evenly to obtain a mixture;

[0024] Step 3: Apply a microwave field to the mixture obtained in Step 2 and maintain it for 10-40 minutes to obtain the mixed material;

[0025] Step 4: Crush and screen the mixture obtained in Step 3 after microwave field treatment to obtain molybdenum tailings cement mixture prepared by microwave method.

[0026] Furthermore, in step 1, the mass percentage of molybdenum tailings is 70 to 100 parts, the mass percentage of limestone is 15 to 20 parts, and the mass percentage of granulated slag is 10 to 15 parts.

[0027] Furthermore, in step 3, the microwave used is an industrial microwave oven (ORW10S-3T model) manufactured by Nanjing Aorun Microwave Factory, with a microwave power of 1.33KW.

[0028] Furthermore, in steps 1 and 4, the grinding or sieving conditions are as follows: the residue on the 45-micron sieve is below 10%, and the residue on the 80-micron sieve is controlled below 1%.

[0029] Example 1.

[0030] Molybdenum tailings, limestone, and granulated slag were dried and crushed. The crushed material was then ground in a ball mill for 30 minutes to obtain fine raw material powder. A composite mixture was prepared from the raw materials according to the following weight proportions: 20 parts limestone, 10 parts granulated slag, and 70 parts molybdenum tailings. 3% water was added and the mixture was thoroughly mixed. The resulting sample was then microwave-activated for 30 minutes, followed by grinding for 45 minutes. The fineness met the requirements of 0.5% residue on an 80μm sieve and 4.2% residue on a 45μm sieve. The prepared activated composite molybdenum tailings powder was added to a reference cement for comparison, as shown in Table 1.

[0031] Table 1. Activity index of the sample from Example 1 and unactivated molybdenum tailings.

[0032]

[0033] The hydration activity of the composite activated molybdenum tailings powder was determined using a microcalorimeter. The results showed that the cementitious activity of the composite activated molybdenum tailings powder was significantly higher than that of the unactivated molybdenum tailings powder, with a cumulative hydration heat release of 331 J / g over 72 hours. Further testing using the autoclaving method (GB / T750) confirmed its stability was satisfactory.

[0034] Comparative Example 1.

[0035] The molybdenum tailings were dried and crushed, then ground in a ball mill for 30 minutes to obtain fine raw material powder. 3% water was added and thoroughly mixed. The resulting sample was then subjected to microwave thermal activation. The activated molybdenum tailings powder was added to a reference cement for comparison. The activity index of the prepared composite material is shown in Table 2.

[0036] Table 2. Activity index of Comparative Example 1 sample and unactivated molybdenum tailings.

[0037]

[0038] Table 2 shows a comparison of the activity indices of the microwave-activated molybdenum tailings composite material prepared in Comparative Example 1. As can be seen from the table, the activity of the molybdenum tailings after microwave thermal activation is significantly improved. Compared to unactivated molybdenum tailings, it can act as an auxiliary cementitious material during cement hydration, generating hydration products and contributing positively to the development of strength in the later stages. The main principle of microwave activation is that by using microwave heating, the orientation of polar molecules such as water in the molybdenum tailings changes with the microwave field. The interaction between adjacent molecules generates frictional heat, raising the sample temperature and thus thermally activating the molybdenum tailings.

[0039] Comparative Example 2.

[0040] Molybdenum tailings and limestone were dried and crushed, then ground in a ball mill for 30 minutes to obtain fine raw material powder. A composite mixture was prepared by adding 15 parts limestone and 85 parts molybdenum tailings by weight, along with 3% water, and ensuring thorough mixing. The resulting sample was then subjected to microwave thermal activation. The activated composite molybdenum tailings powder was added to a reference cement for comparison, as shown in Table 3.

[0041] Table 3. Activity index of Comparative Example 2 sample and unactivated molybdenum tailings.

[0042]

[0043] Table 3 is a comparison table of the activity index of microwave-activated molybdenum tailings composite materials prepared in Comparative Example 2. As can be seen from the table, the activity of molybdenum tailings after microwave thermal activation with limestone is also significantly improved. Compared with the uncalcified molybdenum tailings, the activity of molybdenum tailings after microwave thermal activation with limestone is significantly improved. The activity of molybdenum tailings after microwave thermal activation with limestone is ...

[0044] The hydration activity of the composite activated molybdenum tailings powder was determined using a microcalorimeter. The results showed that the cementitious activity of the composite activated molybdenum tailings powder was significantly higher than that of the unactivated molybdenum tailings powder, with a cumulative hydration heat release of 323 J / g over 72 hours.

[0045] Comparative Example 3.

[0046] Molybdenum tailings and granulated slag were dried and crushed, then ground in a ball mill for 30 minutes to obtain fine raw material powder. The raw materials were then mixed according to the following weight proportions to prepare a composite mixture: 25 parts granulated slag, 75 parts molybdenum tailings, with 3% water added and thoroughly mixed. The resulting sample was then subjected to microwave thermal activation. The activated composite molybdenum tailings powder was added to a reference cement for comparison, as shown in Table 4.

[0047] Table 4. Activity index of Comparative Example 3 sample and unactivated molybdenum tailings.

[0048]

[0049] Table 4 is a comparison table of the activity index of microwave-activated molybdenum tailings composite material prepared in Comparative Example 3. As can be seen from the table, the activity of molybdenum tailings after microwave thermal activation with added granulated slag is also improved to a certain extent. Compared with the molybdenum tailings with added limestone, the activity of molybdenum tailings is slightly reduced during cement hydration. The activation mechanism is the same as in Example 1.

[0050] The hydration activity of the composite activated molybdenum tailings powder was determined using a microcalorimeter. The results showed that the cementitious activity of the composite activated molybdenum tailings powder was significantly higher than that of the unactivated molybdenum tailings powder, with a cumulative hydration heat release of 293 J / g over 72 hours.

Claims

1. A method for preparing a molybdenum tailings cementitious material by a microwave method, characterized by, Specifically, the steps include the following: Step 1: Grind the molybdenum tailings together with other admixtures to obtain molybdenum tailings powder; Step 2: Add 3% water to the molybdenum tailings powder and stir evenly to obtain a mixture; Step 3: Apply a microwave field to the mixture obtained in Step 2 and maintain it for 10-40 minutes to obtain the mixed material; Step 4: Crush and sieve the mixture obtained in Step 3 after microwave field treatment to obtain molybdenum tailings cement mixture prepared by microwave method; In step 1, the molybdenum tailings are 70 parts by weight, the limestone is 20 parts by weight, and the granulated slag is 10 parts by weight.

2. The method for preparing molybdenum tailings cementitious admixture using microwave method according to claim 1, characterized in that, In step 3, the microwave power is 1.33KW.

3. The method for preparing molybdenum tailings cementitious admixture using microwave method according to claim 1, characterized in that, In steps 1 and 4, the grinding or sieving conditions are as follows: the residue on the 45-micron sieve is below 10%, and the residue on the 80-micron sieve is controlled below 1%.

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