Method for preparing ceramsite by using molybdenum tailings

Abstract

The present disclosure relates to the technical field of ceramite preparation, and particularly relates to a method for preparing ceramite by using molybdenum tailings, which comprises the following steps: step one: uniformly dry mixing molybdenum tailings powder, cement, silicon powder, a cementing enhancer, a water-retaining agent and a pore stabilizer; step two: adding water, a water-reducing agent and a foaming agent to stir into a slurry; step three: preparing 3-30mm spheres from the slurry by using a sphere forming machine; step four: performing ladder curing on the spheres: first, curing in a 55-65 DEG C saturated steam environment for 1.5-3h, then transferring into a microwave field with a microwave frequency of 2.45GHz and a power of 700-900W for irradiation for 8-15min, and then placing in an atmosphere with a CO2 concentration of 15-30% for curing for 5-8h, thereby obtaining molybdenum tailings ceramite; wherein the foaming agent comprises an oxygen-releasing component which generates oxygen at 40-80 DEG C, and a molten coating component which can form a gas pore coating layer under microwave irradiation; and the pore stabilizer is inorganic nanoparticles with a particle size of not more than 100nm.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramsite preparation, and particularly relates to a method for preparing ceramsite by using molybdenum tailings. BACKGROUND

[0002] Molybdenum tailings are industrial wastes generated in the process of molybdenum mining and beneficiation, containing a large amount of silicate minerals, metal oxides and unextracted molybdenum resources. With the increase of molybdenum mining, the accumulation of molybdenum tailings is also rapidly increasing, not only occupying a large amount of land resources, but also possibly causing environmental pollution. The traditional treatment methods (such as direct stacking, sintering method, concrete admixture, etc.) generally have problems such as low resource utilization rate and insufficient added value, and it is difficult to realize large-scale resource utilization. At the same time, as a lightweight and high-strength building material, ceramsite often relies on high-energy-consumption processes or non-environmentally friendly materials (such as clay and industrial waste slag) in its preparation process, resulting in high production cost and unstable performance (such as low cylinder compressive strength and high water absorption). SUMMARY

[0003] In order to solve the problems in the related art, the present application provides a method for preparing ceramsite by using molybdenum tailings.

[0004] A method for preparing ceramsite by using molybdenum tailings is provided in the present application, comprising the following steps:

[0005] Step one: uniformly dry-mixing molybdenum tailings powder, cement, silicon powder, cementing enhancer, water-retaining agent and pore stabilizer;

[0006] Step two: adding water, water-reducing agent and foaming agent to stir into slurry;

[0007] Step three: preparing 3-30mm spheres from the slurry by a sphere forming machine;

[0008] Step four: performing ladder curing on the spheres: first, curing in a 55-65℃ saturated steam environment for 1.5-3h, then transferring into a microwave field with a microwave frequency of 2.45GHz and a power of 700-900W for irradiation for 8-15min, and then placing in an atmosphere with a CO2 concentration of 15-30% for curing for 5-8h, to obtain molybdenum tailings ceramsite.

[0009] The foaming agent comprises an oxygen-releasing component that generates oxygen at 40-80℃, and a melt-coating component that can form a pore-coating layer under microwave irradiation; and the pore stabilizer is inorganic nanoparticles with a particle size of no more than 100nm.

[0010] In the present disclosure, the foaming agent comprises an oxygen releasing component and a molten coating component. The oxygen releasing component releases oxygen in the steam curing stage to form initial bubbles; the molten coating component melts and wraps the bubbles under microwave irradiation to prevent them from breaking or merging, thereby forming a uniform and stable closed pore structure. This synergistic effect enables the ceramic cylinder to reach a compressive strength of about 7 MPa, while the water absorption rate is stable at 3.8%-5%.

[0011] In the present disclosure, the pore stabilizer uses inorganic nanoparticles (such as nano-hydroxyapatite) with a particle size of ≤100 nm. The small size characteristic of the nanoparticles can fill the connected gaps between micrometer-sized pores, reducing the water penetration path.

[0012] In the present disclosure, the low-temperature steam environment promotes the early hydration reaction of cement and silica powder, forming a dense gel network to provide skeletal support for subsequent microwave pore formation. Microwave irradiation causes the molten coating component to quickly melt and solidify, locking the bubble morphology and preventing pore collapse caused by high-temperature calcination. Thus, the traditional curing period is compressed from 28 days to 8 hours.

[0013] According to an embodiment of the present disclosure, the oxygen releasing component is at least one of sodium percarbonate and sodium perborate, and the molten coating component is at least one of zinc stearate and calcium stearate.

[0014] According to an embodiment of the present disclosure, the foaming agent comprises sodium percarbonate and zinc stearate; wherein the mass ratio of sodium percarbonate to zinc stearate is 3.5-4:1.5-2.

[0015] According to an embodiment of the present disclosure, the pore stabilizer is nano-hydroxyapatite or nanosilica, and the specific surface area of the pore stabilizer is not less than 150 m² / g.

[0016] According to an embodiment of the present disclosure, the pore stabilizer is nano-hydroxyapatite; wherein the particle size of the nano-hydroxyapatite is 10-40 nm, and the specific surface area is not less than 200 m² / g.

[0017] According to an embodiment of the present disclosure, the CO2 concentration in step four is 25-30%.

[0018] According to an embodiment of the present disclosure, the microwave field irradiation in step four is intermittent, with 800W irradiation for 2 minutes followed by 1 minute of stopping, and the cycle is repeated 5 times.

[0019] According to an embodiment of the present disclosure, the particle size of the spheres in step three is 3-10 mm, and 0.5-1% of carbon nanofibers based on the total weight of the raw materials is added in the dry mixing step in step two.

[0020] According to the embodiment of the present disclosure, the ball diameter in the step three is 20-30 mm, and the silane hydrophobic agent is sprayed on the surface of the ceramsite after the step four of ladder curing on the ball.

[0021] According to the embodiment of the present disclosure, by weight: 60-80 parts of molybdenum tailings powder, 10-20 parts of cement, 5-8 parts of silicon powder, 5-10 parts of cementitious reinforcing agent, 1-2 parts of water retaining agent, 2-4 parts of water reducing agent, 3-6 parts of foaming agent, 0.5-1 part of pore stabilizer, and 10-20 parts of water.

[0022] The technical effect provided by the embodiment of the present disclosure can include the following beneficial effects:

[0023] According to the technical scheme provided by the embodiment of the present disclosure, the method for preparing ceramsite from molybdenum tailings comprises the following steps: step one: uniformly dry mixing molybdenum tailings powder, cement, silicon powder, cementitious reinforcing agent, water retaining agent, and pore stabilizer; step two: adding water, water reducing agent, and foaming agent to stir into slurry; step three: preparing 3-30 mm ball through the slurry machine; step four: ladder curing on the ball: first curing in a 55-65℃ saturated steam environment for 1.5-3h, then transferring into a microwave field with a microwave frequency of 2.45GHz and a power of 700-900W for irradiation for 8-15min, and then placing in an atmosphere with a CO2concentration of 15-30% for curing for 5-8h, thereby obtaining molybdenum tailings ceramsite; wherein, the foaming agent comprises an oxygen releasing component that generates oxygen at 40-80℃, and a molten coating component that can form a gas pore coating layer under microwave irradiation; and the pore stabilizer is inorganic nanoparticles with a particle size of not more than 100nm. In the above technical scheme, the oxygen releasing component provides the power for bubble generation, and the molten coating component forms a physical barrier through microwave melting, and the combination of the two makes the gas pore distribution more uniform, thereby improving the strength and reducing the water absorption. Through the cascade effect of ladder curing, the problems of insufficient early hydration, poor gas pore stability, and low structure density are solved respectively, and the effects of shortening the curing period and improving the simple strength are finally achieved.

[0024] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present disclosure. DETAILED DESCRIPTION

[0025] The present application will be further illustrated by the following examples, but it should be understood that these specific examples will not limit the scope of the present application in any way. It should be noted that, unless otherwise specified, the raw materials used in the following examples are commercially available.

[0026] Example 1

[0027] Raw material ratio:

[0028] Take molybdenum tailings powder 60 parts (specific surface area 550 square meters per kilogram), cement 10 parts (type P.O 42.5), silicon powder 5 parts, redispersible latex powder 5 parts (gelling enhancer), methyl cellulose 1 part (water retaining agent), polycarboxylate superplasticizer 2 parts. Foaming agent consists of sodium percarbonate 2 parts and zinc stearate 1 part, pore stabilizer uses nano silicon dioxide 0.5 parts (specific surface area 180 square meters per gram), water 10 parts.

[0029] Preparation steps:

[0030] Step one: put molybdenum tailings powder, cement, silicon powder, redispersible latex powder, methyl cellulose, nano silicon dioxide into the mixer and dry mix for 3 minutes until uniform;

[0031] Step two: add water, superplasticizer, sodium percarbonate and zinc stearate, stir for 5 minutes to form a homogeneous slurry;

[0032] Step three: the slurry is rolled into 10mm diameter balls by the ball forming machine;

[0033] Step four: step-by-step curing:

[0034] 1. The balls are placed in a 55 degree Celsius saturated steam environment for 3 hours;

[0035] 2. Transfer to a microwave field with a frequency of 2.45 GHz and a power of 700 watts for continuous irradiation for 15 minutes;

[0036] 3. Move to a sealed cabin with a carbon dioxide concentration of 15% for 8 hours to obtain the ceramic product.

[0037] Example 2

[0038] Raw material ratio:

[0039] Molybdenum tailings powder 80 parts, cement 20 parts, silicon powder 8 parts, vinyl acetate copolymer powder 10 parts (gelling enhancer), hydroxypropyl methyl cellulose 2 parts (water retaining agent), naphthalene superplasticizer 4 parts. Foaming agent is sodium perborate 4 parts and calcium stearate 2 parts, pore stabilizer uses nano hydroxyapatite 1 part (specific surface area 220 square meters per gram), water 20 parts. Additional 0.8% of the total weight of carbon nanofibers is added.

[0040] Preparation steps:

[0041] Step one: dry mix all powders (including carbon nanofibers) for 4 minutes;

[0042] Step two: add water, superplasticizer, sodium perborate and calcium stearate, stir for 5 minutes to form a homogeneous slurry,

[0043] Step three: the slurry is rolled into 3mm diameter balls by the ball forming machine;

[0044] Step four: Staged curing:

[0045] 1. The ball is placed in a saturated steam environment at 65 degrees Celsius for 1.5 hours;

[0046] 2. The frequency is changed to 2.45 GHz, and the power is 800 watts. The microwave field is irradiated in an intermittent mode: 800 watts for 2 minutes, stop for 1 minute, cycle 5 times (total irradiation time 10 minutes);

[0047] 3. Move into a sealed cabin with a carbon dioxide concentration of 30% for 5 hours to obtain the ceramsite product.

[0048] Example 3

[0049] Raw material ratio:

[0050] Molybdenum tailings powder 70 parts, cement 15 parts, silicon powder 7 parts, acrylic glue powder 7 parts, carboxymethyl cellulose 1.5 parts, polycarboxylate superplasticizer 3 parts. Foaming agent is sodium percarbonate 3.5 parts and zinc stearate 1.8 parts, pore stabilizer uses nano hydroxyapatite 0.8 parts (particle size 30 nanometers, specific surface area 250 square meters per gram), water 15 parts.

[0051] Preparation steps:

[0052] Steps one to three are the same as example 1, and the ball diameter is 10 millimeters;

[0053] Step four: Staged curing:

[0054] 1. The ball is placed in a saturated steam environment at 60 degrees Celsius for 2 hours;

[0055] 2. The frequency is changed to 2.45 GHz, and the power is 800 watts. The microwave field is irradiated for 10 minutes;

[0056] 3. Move into a sealed cabin with a carbon dioxide concentration of 25% for 6 hours to obtain the ceramsite product.

[0057] Example 4

[0058] Raw material ratio and steps:

[0059] The same as example 3, but the ball diameter is 25 millimeters. After staged curing, a silane water-repellent agent is sprayed on the surface of the ceramsite (the amount is 0.3% of the weight of the ceramsite).

[0060] Example 5

[0061] Raw material ratio and steps:

[0062] The same as example 3, but the carbon dioxide concentration in step three of the staged curing is increased to 28%.

[0063] Example 6

[0064] Raw material ratio: except for the pore stabilizer replaced by nano-silica (specific surface area 200 square meters per gram), the rest is the same as example 3.

[0065] Step: the same as example 3.

[0066] Comparative example 1

[0067] Raw material ratio: the same as example 3, but delete the foaming agent, and replace it with mechanical foaming (inject air into the slurry).

[0068] Comparative example 2

[0069] Raw material ratio: except for the pore stabilizer replaced by equal amount of micron-sized calcium carbonate (particle size 5 microns), the rest is the same as example 3.

[0070] Step: the same as example 3.

[0071] Comparative example 3

[0072] Raw material ratio: the same as example 3.

[0073] Step: step curing replaced by normal temperature film curing, the rest of the steps are the same as example 3.

[0074] Comparative example 4

[0075] Raw material ratio: except for the amount of molybdenum tailings powder replaced by 50 parts, the rest is the same as example 3.

[0076] Step: the same as example 3.

[0077] Comparative example 5

[0078] Raw material ratio: the same as example 3.

[0079] Step: step four replaced by air curing, the rest of the steps are the same as example 3.

[0080] Comparative example 6

[0081] Raw material ratio: the same as example 2.

[0082] Step: microwave irradiation replaced by continuous 800 watt irradiation for 15 minutes, the rest of the steps are the same as example 2.

[0083] Performance test method

[0084] Cylinder pressure strength test: take 10 ceramsite and soak in water for 1 hour, wipe off the surface moisture; lay the ceramsite flat between the pressure test machine pressure plate, load at a rate of 500 newtons per second; record the maximum pressure value (kilonewton) at the moment of ceramsite breaking, divided by the pressure bearing area (square centimeter), converted to megapascal.

[0085] 1-hour water absorption test: weigh the mass of dry ceramsite (M0); immerse it in clean water for 1 hour, take it out, wipe off the water droplets on the surface with a wet cloth, and weigh the saturated surface dry mass (M1); water absorption rate = [(M1-M0) / M0]×100%.

[0086] Pore ​​uniformity test: The ceramsite was split open and the cross section was treated with gold spraying; 500x micrographs were taken using a scanning electron microscope (3 fields of view per sample); 100 pore diameters were counted using image analysis software and the standard deviation was calculated.

[0087] Curing cycle record: the total time from the completion of pelletizing to the time when the expanded clay reaches cylinder pressure strength ≥ 3.5 MPa.

[0088] The test results of cylinder pressure strength, 1-hour water absorption rate, pore size standard deviation and curing period of the above Examples 1-6 and Comparative Examples 1-6 are shown in the following table:

[0089]

[0090] From the above data, it can be seen that the cylinder pressure strength of Example 3 reached 7.9 MPa, the water absorption rate was stable at 4.1%, and the pore size standard deviation was only 0.09 mm, with the best overall performance. By optimizing the ratio of sodium percarbonate to zinc stearate (3.5:1.8) and introducing nano-hydroxyapatite to stabilize the pore structure, a dual improvement in mechanical properties and durability was achieved. In further verification, Example 5 increased the carbon dioxide concentration to 28%, breaking through 8.2 MPa in the cylinder pressure strength and reducing the pore size standard deviation to 0.08 mm, demonstrating the gain effect of carbonization strengthening on the ceramsite shell. In addition, the curing period of all examples was controlled at 8 hours, which is significantly shorter than the traditional 28-day process. The 3mm ultrafine ceramsite prepared in Example 2 achieved a strength of 7.1 MPa and a water absorption rate of 4.8%, with a pore size standard deviation of 0.14 mm, meeting the requirements for high-strength concrete. The 25mm ceramsite prepared in Example 4, after hydrophobic treatment, reduced its water absorption rate to 3.8%, had a pore size standard deviation of 0.1 mm, and a cylinder compressive strength of 7.7 MPa, meeting the requirements of anti-seepage projects. Both performance levels exceeded industry standards (cylinder compressive strength ≥ 3.5 MPa, water absorption ≤ 10%), demonstrating the universal applicability of this solution across a wide range of particle sizes.

[0091] In Comparative Example 1, after the oxygen-releasing component was omitted, the cylinder pressure strength dropped sharply to 3.2 MPa, the water absorption rate soared to 12.5%, and the pore size standard deviation expanded to 0.41 mm, demonstrating the crucial role of the oxygen-releasing function in the foaming agent in structural stability. In Comparative Example 2, micron-sized calcium carbonate was used in place of the nanopore stabilizer. The pore size standard deviation increased to 0.33 mm, the cylinder pressure strength decreased to 4.5 MPa, and the water absorption rate rose to 9.8%, demonstrating the role of nanoparticles in regulating pore uniformity. In Comparative Example 3, after switching to room temperature curing, despite the same components, the cylinder pressure strength was only 4.0 MPa, the curing period was extended to 28 days, the water absorption rate was 8.7%, and the pore size standard deviation was 0.28 mm. This demonstrates that the three-step curing process (steam activation, microwave pore setting, and carbonization strengthening) is the key to this performance breakthrough. In Comparative Example 4, after reducing the molybdenum tailings powder dosage to 50 parts per million, the cylinder pressure strength was only 4.9 MPa, the water absorption rate exceeded 10.2%, and the pore size standard deviation was 0.22 mm, confirming the rigid constraint of the lower limit of the component ratio. In Comparative Example 6, due to local overheating caused by continuous microwaves, the pore size standard deviation increased to 0.26 mm, the cylinder pressure strength decreased to 6.1 MPa, and the water absorption rate was 6.9%, which in turn confirmed the necessity of intermittent operation for structural uniformity.

[0092] The above description is merely a preferred embodiment of the present disclosure and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the invention herein is not limited to technical solutions formed by specific combinations of the aforementioned technical features. It also encompasses other technical solutions formed by any combination of the aforementioned technical features or their equivalents, without departing from the inventive concept. For example, a technical solution formed by replacing the aforementioned features with (but not limited to) technical features with similar functions disclosed in this disclosure.

Claims

1. A method for preparing ceramsite using molybdenum tailings, characterized in that: The following steps are involved: Step 1: dry-mixing molybdenum tailings powder, cement, silica fume, gelling agent, water-retaining agent, and pore stabilizer; the gelling agent is redispersible latex powder; Step 2: Add water, water reducing agent and foaming agent and stir into slurry; Step 3: The slurry is prepared into 3-30mm spheres by a spheroidizer; Step 4: Perform step-by-step curing on the spheres: first, cure them in a saturated steam environment at 55-65°C for 1.5-3 hours to decompose the oxygen-releasing components and generate bubbles. Then, irradiate them in a microwave field with a microwave frequency of 2.45GHz and a power of 700-900W for 8-15 minutes to melt the molten coating components and wrap the bubbles. Then, cure them in an atmosphere with a CO2 concentration of 15-30% for 5-8 hours to obtain molybdenum tailings ceramsite. The foaming agent comprises an oxygen-releasing component that decomposes at 40-80°C to generate oxygen, and a molten coating component that can melt under microwave irradiation to form a pore coating layer; the pore stabilizer is an inorganic nanoparticle with a particle size of no more than 100 nm; The oxygen-releasing component is at least one of sodium percarbonate and sodium perborate, and the melt-coating component is at least one of zinc stearate and calcium stearate.

2. The method according to claim 1, characterized in that The foaming agent includes sodium percarbonate and zinc stearate; wherein the mass ratio of the sodium percarbonate to the zinc stearate is 3.5-4:1.5-2.

3. The method according to claim 1, characterized in that The pore stabilizer is nano-hydroxyapatite or nano-silicon dioxide, and the specific surface area of ​​the pore stabilizer is not less than 150m² / g.

4. The method according to claim 3, characterized in that The pore stabilizer is nano-hydroxyapatite; wherein the particle size of the nano-hydroxyapatite is 10-40nm and the specific surface area is not less than 200m² / g.

5. The method according to claim 1, wherein The CO2 concentration in step 4 is 25-30%.

6. The method according to claim 1, characterized in that In the step 4, the microwave field irradiation is performed intermittently, irradiating at 800 W for 2 minutes and then stopping for 1 minute, and the cycle is repeated 5 times.

7. The method according to claim 1, characterized in that The particle size of the spheres in step three is 3-10 mm, and 0.5-1% of the total weight of the raw materials is added to the dry mixing step in step two.

8. The method according to claim 1, characterized in that In the step 3, the particle size of the spheres is 20-30 mm, and in the step 4, a silane water repellent is sprayed on the surface of the ceramsite after the spheres are subjected to step curing.

9. The method according to claim 1, characterized in that In parts by weight: 60-80 parts of molybdenum tailings powder, 10-20 parts of cement, 5-8 parts of silicon powder, 5-10 parts of gelling agent, 1-2 parts of water retaining agent, 2-4 parts of water reducing agent, 3-6 parts of foaming agent, 0.5-1 part of pore stabilizer, and 10-20 parts of water.

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