Method for preparing calcium aluminum garnet and magnesium aluminum garnet from molybdenum ore tailings

Abstract

A method for preparing calcium aluminum garnet and magnesium aluminum garnet from molybdenum ore tailings belongs to the technical field of mining and metallurgy, the molybdenum ore tailings are used as raw materials, alumina-containing materials, magnesium oxide-containing materials and calcium oxide-containing materials are added to prepare spucite and spucite, proliferation and utilization of the molybdenum ore tailings are realized, the whole technological process is green and environment-friendly, and the method is suitable for industrial production. The garnet prepared by the method accords with the national secondary resource recycling strategy and has remarkable economic benefits and social and environmental benefits, the quality of the prepared garnet is good, and the method has positive effects on recovery of mining and metallurgy waste resources and artificial synthesis of natural mineral resources.

Description

Technical Field

[0001] The present invention belongs to the technical field of mining and metallurgy, and particularly relates to the recovery of resources from mining and metallurgical wastes. Specifically, it is a method for preparing calcium aluminum garnet and magnesium aluminum garnet from molybdenum ore tailings. Background Art

[0002] Molybdenum ore tailings refer to the waste of unextracted substances remaining after separating molybdenum from molybdenum ore. The composition of molybdenum ore tailings is complex and varies with regions. The main components are about 33.0 - 40.0% of SiO2, about 7.0 - 16.0% of CaO, about 6.5 - 9.0% of Al2O3, about 2.0 - 8.0% of MgO, about 7.0 - 11.0% of Fe2O3, about 0.2 - 1.4% of K2O, etc. The remaining content of metal Mo in molybdenum ore tailings is very low. Generally, its content is 0.01% - 0.5%, and the extraction is difficult and of little value. The current utilization methods of molybdenum ore tailings are mainly to produce bricks or fill mine pits, and the reuse of elements such as silicon, iron, calcium, and magnesium in them has not been effectively realized.

[0003] Garnet is a mineral resource with a wide range of uses. Due to its different chemical compositions, it has various colors and properties and is applied in the fields of industry, jewelry, decoration, etc. Garnet has a high hardness, with a Mohs hardness between 6.5 and 7.5, second only to diamond, corundum, etc., making garnet a high-quality abrasive material for grinding, polishing, and sandblasting. In the metal processing industry, it can polish various metal surfaces, remove impurities and defects, and improve the surface finish. For glass manufacturing, it can finely grind glass to produce optical lenses, glass handicrafts, etc. Garnet particles are uniform and chemically stable, and can be used as a water filtration medium to remove impurities such as suspended solids, sediment, and algae in water, and is widely used in swimming pool water treatment, industrial circulating water purification, and sewage treatment, etc., which can effectively purify water quality and ensure the normal operation of the water system. Garnet has bright and rich colors, commonly including red, orange, purple, etc., with high crystal transparency and good luster. After cutting and polishing, it can be made into necklaces, bracelets, earrings, rings and other jewelry. In particular, the red series of magnesium aluminum garnet and iron aluminum garnet, the orange series of manganese aluminum garnet, and the green series of calcium aluminum garnet are very popular among people and can also be used to make handicrafts and decorations. Some high-quality garnet crystals have high collection value.

[0004] However, most of the garnets currently in use are natural minerals, and artificial synthesis is rare because of their complex composition and difficulty in artificial manufacturing. Different combinations of elements in garnets form a series of isomorphous garnet groups with the general formula A3B2(SiO4)3, where A represents divalent elements (calcium, magnesium, iron, manganese, etc.), and B represents trivalent elements (aluminum, iron, chromium, titanium, vanadium, zirconium, etc.). Since the radii of trivalent cations are similar, isomorphous substitution is likely to occur between them. However, divalent oxygen ions are different. Because the radius of Ca is larger than that of Mg, Fe, Mn and other ions, it is difficult to undergo isomorphous substitution with them. Therefore, garnets are usually divided into two series: (1) aluminous series: common varieties include pyrope Mg3Al2(SiO4)3, almandine Fe3Al2(SiO4)3 and spessartine Mn3Al2(SiO4)3; (2) calcareous series: common varieties include grossular Ca3Al2(SiO4)3 and andradite Ca3Fe2(SiO4)3.

[0005] The molybdenum ore tailings were analyzed by X-ray diffraction (XRD), as Figure 1 shown. Comparing the diffraction pattern with the standard pattern, the diffraction peak intensity of SiO2 is the highest, the characteristic peak is obvious, and the content is the highest. Secondly, the contents of Ca, Mg, Fe, Al and K elements are relatively high. Ca and Mg belong to the same family of elements, and Fe and Al are often associated with Si and O elements and are difficult to separate. Therefore, it is very difficult to recycle molybdenum ore tailings. On the other hand, considering that there is a certain degree of similarity in the types of elements between these elements and garnets, it has theoretically become possible to treat molybdenum ore tailings through certain chemical reaction measures, separate the unnecessary elemental components, and produce garnets with high added value. In the existing technology, there are some literatures discussing the treatment measures for natural minerals containing garnets, but most of them use shaking table flotation. After certain attempts, it is found that the quality of the garnet products obtained by these measures is poor, the yield is low, and the universality is poor, which is not applicable to molybdenum ore tailings. Summary of the Invention

[0006] In order to solve the deficiencies of the existing technology, the present invention proposes a method for preparing grossular and pyrope from molybdenum ore tailings. Using molybdenum ore tailings as raw materials to prepare grossular and pyrope, the purpose of increasing the utilization of various elements in the tailings is achieved.

[0007] The technical problems to be solved by the present invention are realized through the following technical solutions:

[0008] A method for preparing grossular and pyrope from molybdenum ore tailings, comprising the following steps:

[0009] S1: Oxidatively roast the pre-ground and dried molybdenum ore tailings in an air atmosphere to convert the iron minerals into Fe2O3, and then add a certain amount of biomass charcoal and reductively roast under oxygen-free conditions to convert Fe2O3 into Fe3O4, and magnetically separate Fe3O4 to obtain Material 1;

[0010] S2: Add the material containing alumina to Material 1, grind and homogenize to obtain Material 2, and then add the material containing calcium oxide to Material 2, grind and homogenize to obtain Material 31; or add the material containing magnesium oxide to Material 2, grind and homogenize to obtain Material 32;

[0011] S3: Heat and melt Material 31 or 32 in a furnace to obtain Material 41 or 42, soak it in water, and separate the kettle liquid to obtain a filtrate and a filter cake;

[0012] S4: Wash and dry the filter cake obtained in Step S3 to obtain calcium aluminum garnet or magnesium aluminum garnet, and the aluminum liquid is used to prepare potassium metaaluminate.

[0013] Among them, Material 31 and Material 41 are used for the preparation of calcium aluminum garnet, and Material 32 and Material 42 are used for the preparation of magnesium aluminum garnet.

[0014] The temperature of the oxidative roasting described in Step S1 is 600 - 800 °C, the roasting time is 1 - 3 h, the temperature of the reductive roasting is 400 - 700 °C, and the roasting time is 1 - 3 h.

[0015] The material containing calcium oxide described in Step S2 mainly consists of calcium carbonate, and any one or a mixture of calcite, limestone, marble, white marble, chalk, stalactite, and travertine is used, and calcite and limestone with low prices are preferably used.

[0016] The material containing magnesium oxide described in Step S2 mainly consists of magnesium carbonate, and magnesite and / or dolomite is used, and magnesite is preferably used.

[0017] The material containing alumina described in Step S2 mainly consists of Al2O3, and alumina, dehydrated aluminum hydroxide, and / or the material after denitrification and dechlorination of aluminum ash are used. Among them, the aluminum ash is the aluminum ash produced by electrolytic aluminum or the aluminum ash produced by aluminum-magnesium alloy, and alumina and dehydrated aluminum hydroxide are preferably used.

[0018] The addition amount of the material containing alumina in Step S2 is 0.10 - 0.15 times the mass of the molybdenum ore tailings, the addition amount of the material containing calcium oxide is 0.45 - 0.55 times the mass of the molybdenum ore tailings, and the addition amount of the material containing magnesium oxide is 0.40 - 0.50 times the mass of the molybdenum ore tailings.

[0019] In step S3, the temperature for heating and smelting is 1000 - 1500 °C, and the smelting time is 1 - 5 h. Preferably, the smelting temperature is 1100 - 1300 °C, and the smelting time is 2 - 4 h.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) This application uses molybdenum ore tailings as raw materials, adds alumina, magnesia-containing materials, and calcium oxide-containing materials to prepare pyrope and grossular, realizing the value-added utilization of molybdenum ore tailings;

[0022] (2) In view of the composition characteristics of molybdenum ore tailings containing silicon dioxide, iron oxide, calcium oxide, alumina, and magnesia, this application ingeniously designs the process for preparing garnet. The process flow is short, without the use of acids and bases, and there is no discharge of "three wastes" during the whole production process. The production process is green and pollution-free, realizing the full utilization of elements such as silicon, iron, aluminum, calcium, and magnesium in molybdenum ore tailings;

[0023] (3) In the preparation process of this application, the roasting process separates iron elements, the washing process separates potassium elements, and the smelting process recovers silicon elements, which conforms to the national strategy of secondary resource recycling and utilization. The tailings are transformed into products such as garnet, magnetite, and potassium meta-aluminate, turning waste into treasure, and having significant economic, social, and environmental benefits.

[0024] Therefore, the present invention has novel ideas and ingenious designs, and has positive effects on both the recovery of mining and metallurgical waste resources and the artificial synthesis of natural mineral resources.

[0025] Description of the Drawings

[0026] Figure 1 It is the XRD diffraction pattern of molybdenum ore tailings;

[0027] Figure 2 It is the appearance diagram of the crude products of pyrope (left) and grossular (right) prepared by the method of this application;

[0028] Figure 3 It is the comparison diagram of the contents of the main components (CaO, Al2O3, SiO2) in the grossular prepared by the method of this application and natural garnet. Detailed Embodiments

[0029] In order to more clearly elaborate the technical solutions and implementation effects of the present invention, the following further details the method for preparing pyrope and grossular using molybdenum ore tailings of the present invention with specific embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0030] Example 1

[0031] A method for preparing calcium aluminum garnet and pyrope aluminum garnet from molybdenum ore tailings, comprising the following steps:

[0032] S1: Select a certain amount of molybdenum tailings, grind them in advance to make their particle size meet the requirements of subsequent processes, and then put them in an oven for drying. Place the dried molybdenum tailings in a muffle furnace and perform oxidation roasting in an air atmosphere. Set the oxidation roasting temperature to 600°C and the roasting time to 3h to fully convert the iron minerals therein into Fe2O3. After the oxidation roasting is completed, add an appropriate amount of biochar to it, transfer the material to a tubular furnace, and perform reduction roasting under the condition of isolating oxygen. Set the reduction roasting temperature to 400°C and the roasting time to 3h to convert Fe2O3 into Fe3O4. After the material is cooled, use magnetic separation equipment for magnetic separation to obtain Fe3O4, and the remaining material is marked as material 1.

[0033] S2: Weigh a certain mass of material 1, add alumina (alumina-containing material) according to 0.10 times the mass of molybdenum tailings, put it into a grinding device, grind and homogenize it thoroughly, and obtain material 2. Next, weigh material 2, add calcite (as calcium oxide-containing material) whose main component is calcium carbonate according to 0.45 times the mass of molybdenum tailings, grind and homogenize it again, and obtain material 31; in addition, weigh the same mass of material 2, add magnesite (as magnesium oxide-containing material) according to 0.40 times the mass of molybdenum tailings, grind and homogenize it, and obtain material 32.

[0034] S3: Put material 31 and material 32 into a furnace for heating and smelting. Set the smelting temperature to 1000°C and the smelting time to 5 hours to obtain material 4. After material 4 is cooled, put it into water for water immersion to dissolve the soluble substances therein. Then separate it through solid-liquid separation equipment to obtain filtrate and filter cake.

[0035] S4: Wash the filter cake obtained in step 3 to remove impurities remaining on the surface, and then put it into an oven for drying to finally obtain calcium aluminum garnet and magnesium aluminum garnet. The obtained filtrate is further processed for preparing potassium aluminate.

[0036] Example 2

[0037] A method for preparing calcium aluminum garnet and pyrope aluminum garnet from molybdenum ore tailings, comprising the following steps:

[0038] S1: Take another batch of molybdenum tailings and repeat the grinding and drying operation. Oxidative roasting is carried out in a muffle furnace under air atmosphere, the temperature is set to 800℃, and the roasting time is 1h to realize the conversion of iron minerals into Fe2O3. Then add biochar and carry out reduction roasting in a tubular furnace isolated from oxygen, the temperature is 700℃, and the time is 1h to convert Fe2O3 into Fe3O4, and Fe3O4 is separated by magnetic separation to obtain material 1.

[0039] S2: For material 1, add aluminum hydroxide dehydrated material (material containing alumina) according to 0.15 times the mass of molybdenum ore tailings, and grind and homogenize to obtain material 2. For material 2, add limestone (material containing calcium oxide) according to 0.55 times the mass of molybdenum ore tailings, and grind and homogenize to obtain material 31; meanwhile, add magnesite (material containing magnesium oxide) according to 0.50 times the mass of molybdenum ore tailings to material 2, and grind and homogenize to obtain material 32.

[0040] S3: Put material 31 and material 32 into a furnace, raise the smelting temperature to 1500 °C, and control the smelting time at 1 h to obtain material 4. After water leaching of material 4, perform solid-liquid separation to obtain a filtrate and a filter cake.

[0041] S4: Wash and dry the filter cake to obtain calcium aluminum garnet and magnesium aluminum garnet; the filtrate is used to prepare potassium meta-aluminate.

[0042] Example 3

[0043] A method for preparing calcium aluminum garnet and magnesium aluminum garnet from molybdenum ore tailings, comprising the following steps:

[0044] S1: Weigh an appropriate amount of molybdenum ore tailings, grind and dry them, then perform oxidative roasting at 700 °C for 2 h in an air atmosphere, then add biomass carbon, and perform reduction roasting at 500 °C for 2 h under oxygen-free conditions, and magnetically separate Fe3O4 to obtain material 1.

[0045] S2: Add the material (material containing alumina) after denitrification and dechlorination of aluminum ash according to 0.12 times the mass of molybdenum ore tailings to material 1, and grind and homogenize to obtain material 2. Then, add calcite (material containing calcium oxide) according to 0.50 times the mass of molybdenum ore tailings and magnesite (material containing magnesium oxide) according to 0.45 times the mass of molybdenum ore tailings to material 2 respectively, and grind and homogenize them separately to obtain material 31 and material 32.

[0046] S3: Place material 31 and material 32 in a furnace, select a smelting temperature of 1200 °C and a smelting time of 3 h to obtain material 4. After water leaching of material 4, perform solid-liquid separation, and collect the filtrate and the filter cake.

[0047] S4: Wash and dry the filter cake to obtain calcium aluminum garnet and magnesium aluminum garnet; the filtrate is used to prepare potassium meta-aluminate.

[0048] Example 4

[0049] Verify the crude products of calcium aluminum garnet and magnesium aluminum garnet obtained in Examples 1-3 (as Figure 2 shown).

[0050] 1. Test purpose

[0051] Accurately verify the composition, structure, and properties of the calcium aluminum garnet and magnesium aluminum garnet prepared from molybdenum ore tailings, determine whether they meet the expected product standards, and evaluate the reliability and stability of the preparation process.

[0052] 2. Test samples

[0053] Randomly select 10 groups of calcium aluminum garnet and 10 groups of magnesium aluminum garnet samples from the products prepared in different batches in the specific implementation manner. The weight of each group of samples is not less than 5 g to ensure the representativeness of the samples.

[0054] 3. Test methods and indicators

[0055] 3.1 Composition analysis

[0056] (1) X-ray fluorescence spectrometer (XRF) analysis: Grind the sample into powder, pass it through a 200-mesh sieve, and press it into a thin slice. Use XRF to measure the contents of main elements such as calcium (Ca), magnesium (Mg), aluminum (Al), and silicon (Si) in the sample. Each sample is measured 3 times and the average value is taken. Compare the theoretical proportion of each element in the theoretical chemical formulas Ca3Al2(SiO4)3 and Mg3Al2(SiO4)3, and calculate the deviation between the measured value and the theoretical value. The deviation calculation formula is

[0057] After measurement, in calcium aluminum garnet, the deviation of the measured value of calcium element from the theoretical value is within ±5%, the deviation of aluminum element is within ±4%, and the deviation of silicon element is within ±3%, as Figure 3 shown; in magnesium aluminum garnet, the deviation of the measured value of magnesium element from the theoretical value is within ±5%, the deviation of aluminum element is within ±4%, and the deviation of silicon element is within ±3%. It is considered that the composition meets the requirements.

[0058] (2) Electron probe microanalysis (EPMA): Select a representative sample area and use EPMA to analyze the micro-area composition and observe the element distribution. The judgment standard for detecting the element distribution uniformity is: in different micro-areas, the content fluctuation range of each main element (calcium, magnesium, aluminum, silicon) does not exceed ±5% of the average value, and the element ratio is consistent with the overall XRF analysis result, indicating good composition uniformity.

[0059] 3.2 Structure identification

[0060] (1) X-ray diffractometer (XRD) analysis: Make the sample into a powder diffraction sample and test it on the XRD. The scanning range is 10° - 80°, and the scanning speed is 4° / min. Compare the obtained diffraction pattern with the patterns of calcium aluminum garnet and magnesium aluminum garnet in the standard cards of the International Center for Diffraction Data (ICDD). If the matching degrees of the main diffraction peaks of calcium aluminum garnet and magnesium aluminum garnet with the standard patterns reach over 96% and 97% respectively, it can be preliminarily judged that the crystal structure is correct.

[0061] (2) Transmission electron microscope (TEM) observation: The sample was made into a thin slice with a thickness of about 100 - 200 nm and placed under the TEM to observe the microstructure. The typical garnet crystal structure could be clearly seen, and the number of lattice defects did not exceed 5 per square micrometer, and the area ratio of the impurity phase did not exceed 2%, indicating that the crystal structure was good.

[0062] 3.3 Physical property tests

[0063] (1) Density measurement: The density of the sample was measured by the drainage method. First, the mass m of the sample was weighed accurately to 0.001 g, and then the sample was slowly placed into a density bottle filled with water, and the volume V of the drained water was measured accurately to 0.01 mL. The density of the sample was calculated according to the formula ρ = m / V. Each sample was measured 5 times, and the average value was taken. The average value of the density measurement of calcium aluminum garnet was between 3.52 - 3.58 g / cm 3 and the average value of the density measurement of magnesium aluminum garnet was between 3.63 - 3.75 g / cm 3 which was in line with the respective standard density ranges, and the density was qualified.

[0064] (2) Hardness test: The hardness of the sample was tested using a Vickers hardness tester with a loading load of 500 g and a holding time of 15 s. Five points were measured at different positions of the sample, and the average value was taken. The average value of the Vickers hardness measurement of calcium aluminum garnet was between 650 - 750 HV, and the average value of the Vickers hardness measurement of magnesium aluminum garnet was between 700 - 800 HV. After conversion to Mohs hardness, it was within the corresponding range, and the hardness met the requirements.

[0065] In summary, it can be seen from Examples 1 - 3 that the method of the present invention can effectively use molybdenum ore tailings to prepare calcium aluminum garnet and magnesium aluminum garnet, and can effectively prepare calcium aluminum garnet and magnesium aluminum garnet under different process parameter conditions. It can be seen from Example 4 that the calcium aluminum garnet and magnesium aluminum garnet prepared in Examples 1 - 3 have element compositions, crystal structures and physical properties similar to those of natural mineral resources, and are closer to the theoretical values, that is, they are purer and have less impurity content. Therefore, the preparation method of the present invention effectively realizes the value-added utilization of molybdenum ore tailings, and the entire process flow is green and environmentally friendly, meeting the national strategy for the recycling of secondary resources, and having significant economic and social environmental benefits. In actual production, the process parameters can be optimized and adjusted according to the specific composition and production requirements of molybdenum ore tailings to achieve the best production effect.

Claims

1. A method for preparing calcium aluminum garnet and pyrope aluminum garnet from molybdenum ore tailings, characterized in that: The following steps are involved: S1: The molybdenum tailings that have been ground and dried in advance are oxidatively roasted in an air atmosphere to convert the iron minerals into Fe2O3, and then a certain amount of biochar is added and reduction roasted under oxygen-free conditions to convert Fe2O3 into Fe3O4, and Fe3O4 is separated by magnetic separation to obtain material 1; S2: adding a material containing aluminum oxide to material 1, grinding and homogenizing to obtain material 2, adding a material containing calcium oxide to material 2, grinding and homogenizing to obtain material 31; or adding a material containing magnesium oxide to material 2, grinding and homogenizing to obtain material 32; S3: placing material 31 or 32 in a furnace for heating and smelting to obtain material 41 or 42, soaking it in water, and performing solid-liquid separation to obtain filtrate and filter cake; S4: washing and drying the filter cake obtained in step S3 to obtain calcium aluminum garnet or pyrope aluminum garnet, and the filtrate is used to prepare potassium aluminate; Among them, material 31 and material 41 are used for the preparation of calcium aluminum garnet, and material 32 and material 42 are used for the preparation of magnesia aluminum garnet.

2. The method according to claim 1, characterized in that: The temperature of the oxidation roasting in step S1 is 600-800° C., and the roasting time is 1-3 hours. The temperature of the reduction roasting is 400-700° C., and the roasting time is 1-3 hours.

3. The method according to claim 1, characterized in that: The calcium oxide-containing material in step S2 is mainly composed of calcium carbonate, which is any one of calcite, limestone, marble, white marble, chalk, stalactite, and travertine, or a mixture of several of them.

4. The method according to claim 1, characterized in that: The magnesium oxide-containing material in step S2 is mainly composed of magnesium carbonate, which is magnesite and / or dolomite.

5. The method according to claim 1, characterized in that: The alumina-containing material in step S2 is mainly composed of Al2O3, and is made of alumina, aluminum hydroxide dehydrated material and / or aluminum ash denitrified and dechlorinated material.

6. The method according to claim 3, 4 or 5, characterized in that: In step S2, the amount of the material containing aluminum oxide added is 0.10-0.15 times the mass of the molybdenum ore tailings, the amount of the material containing calcium oxide added is 0.45-0.55 times the mass of the molybdenum ore tailings, and the amount of the material containing magnesium oxide added is 0.40-0.50 times the mass of the molybdenum ore tailings.

7. The method according to claim 1, characterized in that: The heating and smelting temperature in step S3 is 1000-1500° C., and the smelting time is 1-5 hours.

8. The method according to claim 7, characterized in that: The melting temperature is 1100-1300°C and the melting time is 2-4h.

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