Method for leaching dolomite-type surrounding rock

Abstract

The invention discloses a leaching method of dolomite type surrounding rock. The method comprises the following steps: mixing dolomite type surrounding rock powder with the particle size of less than or equal to 150 meshes with a formic acid solution with the concentration of 1.5-4.5 mol / L to obtain dolomite type surrounding rock powder slurry; the dolomite type surrounding rock powder slurry is leached for 2-12 h under the condition that the temperature ranges from 60 DEG C to 100 DEG C, and a leached product is obtained; carrying out solid-liquid separation on the leaching product to obtain a leaching solution and leaching residues; wherein the liquid-solid ratio of the formic acid solution to the dolomite type surrounding rock powder is (5-9) mL: 1g; reacting the leachate with oxalic acid to obtain a reaction product; and carrying out solid-liquid separation on the reaction product to obtain a mixture of calcium oxalate and magnesium oxalate and a liquid product. According to the leaching method, selective leaching of calcium and magnesium in the dolomite type surrounding rock is achieved, rare earth and niobium elements are enriched, and follow-up recycling of rare earth and niobium resources in the dolomite type surrounding rock is facilitated; in addition, the recycling of formic acid in the production process is realized by recycling calcium and magnesium in the leachate.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for leaching dolomite type surrounding rock. BACKGROUND

[0002] Rare earth-niobium resources are irreplaceable "industrial vitamins" for high-tech industries, and play a key role in special alloys and superconducting materials. As a rare large iron-rare earth-niobium polymetallic coexisting deposit in the world, the Baiyunebo deposit has a large niobium reserve, but the niobium minerals are finely disseminated (about 20-80 μm), have multiple types (such as calcio-olivine, pyrochlore, niocalite, and niobite), and are closely associated with iron, rare earth, and fluorite, resulting in a low niobium grade and great difficulty in beneficiation and smelting, and thus the niobium resources have not been effectively utilized.

[0003] Rare earth and niobium in the Baiyunebo deposit are distributed in the iron ore, upper and lower panels of the iron ore body, and dolomite and slate independent of the iron ore body. Among them, the grade of rare earth (REO) and niobium (Nb2O5) in dolomite type surrounding rock can reach more than 2wt% and 0.05wt%, respectively, and the stockpiling scale is large, having a high recovery value.

[0004] Currently, the leaching technology for extracting rare earth-niobium mostly uses strong acid or strong base to decompose the minerals, which not only increases the subsequent separation cost, but also generates highly polluted wastewater. In addition, the conventional roasting process is prone to cause mineral inclusions or recrystallization of rare earth / niobium when facing low-grade ore types, resulting in a low leaching rate. Furthermore, the traditional leaching process focuses on the recovery of a single element, ignoring the synergistic extraction of calcium, magnesium, iron, and other elements in the rare earth residue, which is easy to cause resource waste. SUMMARY

[0005] Therefore, the purpose of the present application is to provide a leaching method for dolomite type surrounding rock, which can separate rare earth elements, niobium elements, and calcium elements and magnesium elements in dolomite type surrounding rock. Further, the method can enrich rare earth and niobium in the leaching residue, facilitating the subsequent beneficiation and smelting process to recover and utilize rare earth and niobium resources in dolomite type surrounding rock. Further, the method has a high calcium and magnesium leaching rate. Further, the method generates less industrial wastewater.

[0006] The present application achieves the above-mentioned purposes by the following technical method.

[0007] The present application provides a leaching method for dolomite type surrounding rock, comprising the following steps:

[0008] The leaching step includes: mixing dolomite type country rock powder with a particle size of less than or equal to 150 mesh with a formic acid solution with a concentration of 1.5-4.5 mol / L to obtain a dolomite type country rock powder slurry; leaching the dolomite type country rock powder slurry at a temperature of 60-100℃ for 2-12 h to obtain a leaching product; and solid-liquid separating the leaching product to obtain a leaching solution and a leaching residue; wherein the liquid-solid ratio of the formic acid solution to the dolomite type country rock powder is (5-9) mL:1 g.

[0009] The precipitation step includes: reacting the leaching solution with oxalic acid to obtain a reaction product.

[0010] The separation step includes: solid-liquid separating the reaction product to obtain a mixture of calcium oxalate and magnesium oxalate and a liquid product.

[0011] In the leaching step, the concentration of the formic acid solution is 1.5-4.5 mol / L, preferably, the concentration of the formic acid solution is 2-4 mol / L, and more preferably, the concentration of the formic acid solution is 3.2 mol / L. In this way, the rare earth and niobium elements can be retained in the leaching residue, and the magnesium and calcium elements can be leached into the leaching solution.

[0012] In the leaching step, the liquid-solid ratio of the formic acid solution to the dolomite type country rock powder is (5-9) mL:1 g, preferably (6-8) mL:1 g, and according to one specific embodiment of the present application, the liquid-solid ratio of the formic acid solution to the dolomite type country rock powder is 7 mL:1 g. In this way, the enrichment efficiency of the rare earth and niobium elements and the leaching rate of the calcium and magnesium elements can be improved.

[0013] In the leaching step, the leaching temperature of the leaching reaction is 60-100℃, preferably, the leaching temperature of the leaching reaction is 80-100℃, and more preferably, the leaching temperature of the leaching reaction is 95℃. In this way, the leaching reaction can be fully carried out.

[0014] In the leaching step, the leaching time of the leaching reaction is 2-12 h, preferably, the leaching time of the leaching reaction is 5-9 h, and more preferably, the leaching time of the leaching reaction is 6-8 h. In this way, the leaching reaction can be fully carried out.

[0015] In the leaching step, the leaching product is solid-liquid separated to obtain a leaching solution mainly containing calcium and magnesium elements and a leaching residue enriched with rare earth elements and niobium elements.

[0016] In the precipitation step, the leaching solution reacts with oxalic acid to obtain a reaction product.

[0017] In the separation step, the reaction product is solid-liquid separated by means of suction filtration to obtain a mixture of calcium oxalate and magnesium oxalate and a liquid product. The oxalic acid solution participating in the reaction is preferably anhydrous oxalic acid.

[0018] According to the leaching method of the present application, preferably, the leaching method further comprises the following steps:

[0019] Grinding step: grinding the dolomite type country rock to obtain dolomite type country rock powder.

[0020] In the present application, the particle size of the dolomite type country rock powder is preferably less than or equal to 200 mesh.

[0021] According to the leaching method of the present application, preferably, in the dolomite type country rock powder, the content of rare earth elements is 1-5wt%, the content of niobium elements is 0.01-0.5wt%, the content of calcium elements is 23-43wt%, and the content of magnesium elements is 9-14wt%; wherein the content of rare earth elements is calculated as REO, the content of niobium elements is calculated as Nb2O5, the content of calcium elements is calculated as CaO, and the content of magnesium elements is calculated as MgO.

[0022] In the dolomite type country rock powder, the content of rare earth elements can be 1-5wt%, preferably 2-3wt%; the content of niobium elements can be 0.01-0.5wt%, preferably 0.05-0.3wt%; the content of calcium elements can be 23-43wt%, preferably 25-33wt%; and the content of magnesium elements can be 9-14wt%, preferably 9-12wt%; wherein the content of rare earth elements is calculated as REO, the content of niobium elements is calculated as Nb2O5, the content of calcium elements is calculated as CaO, and the content of magnesium elements is calculated as MgO.

[0023] In some embodiments, in the dolomite type country rock powder, the content of rare earth elements is 2.03wt%, the content of niobium elements is 0.22wt%, the content of calcium elements is 27.66wt%, and the content of magnesium elements is 11.50wt%; wherein the content of rare earth elements is calculated as REO, the content of niobium elements is calculated as Nb2O5, the content of calcium elements is calculated as CaO, and the content of magnesium elements is calculated as MgO.

[0024] According to the leaching method of the present application, preferably, the loss on ignition of the dolomite type country rock powder is 30-45wt%. In some embodiments, the loss on ignition of the dolomite type country rock powder is 35-40wt%.

[0025] According to the leaching method of the present application, preferably, the leaching step and the precipitation step are carried out under stirring, and the stirring device has a rotation speed of 100-400rpm, further preferably, the stirring device has a rotation speed of 200-300rpm, for example, the rotation speed can be 300rpm.

[0026] According to the leaching method of the present application, preferably, in the leaching residue, the content of rare earth elements is 5-25wt%, and the content of niobium elements is 0.3-2.5wt%; wherein the content of rare earth elements is calculated as REO, and the content of niobium elements is calculated as Nb2O5.

[0027] In the present application, the content of rare earth elements in the leaching residue can be 5-25wt%, preferably 8-16wt%; the content of niobium elements can be 0.3-2.5wt%, preferably 0.8-1.5wt%; wherein the rare earth elements are calculated as REO, and the niobium elements are calculated as Nb2O5.

[0028] In some embodiments, the content of rare earth elements in the leaching residue is 8.88wt%, and the content of niobium elements is 1.02wt%; wherein the rare earth elements are calculated as REO, and the niobium elements are calculated as Nb2O5.

[0029] In the present application, the content of REO and Nb2O5 in the leaching residue is 4-5 times of the content of the corresponding elements in dolomite type country rock.

[0030] According to the leaching method of the present application, preferably, the amount of oxalic acid used is 1-1.5 times of the theoretical molar amount; the theoretical molar amount of oxalic acid is calculated by the following formula:

[0031] The theoretical molar amount of oxalic acid = the amount of substance of calcium elements contained in the leaching solution + the amount of substance of magnesium elements contained in the leaching solution.

[0032] In some embodiments, the amount of oxalic acid used is 1 times of the theoretical molar amount; in other embodiments, the amount of oxalic acid used is 1.2 times of the theoretical molar amount; in still other embodiments, the amount of oxalic acid used is 1.5 times of the theoretical molar amount.

[0033] The present application precipitates calcium and magnesium elements in the leaching solution with an appropriate amount of oxalic acid, which can not only precipitate calcium and magnesium sufficiently, but also the obtained liquid product can be reused in the leaching step, reducing the generation of waste water.

[0034] According to the leaching method of the present application, preferably, the leaching solution is reacted with oxalic acid at 15-40℃ for 0.5-6h.

[0035] In the present application, the reaction temperature of the leaching solution with oxalic acid is 15-40℃, preferably 20-30℃, more preferably 20-25℃; the reaction time of the leaching solution with oxalic acid is 0.5-6h, preferably 0.5-5h, more preferably 2-5h.

[0036] According to the leaching method of the present application, preferably, the precipitation step further comprises the following steps: drying the solid product obtained by solid-liquid separation of the reaction product at 80-100℃ for 0.5-4h to obtain a mixture of calcium oxalate and magnesium oxalate; the liquid product obtained in the precipitation step is returned to the leaching step as raw material to leach dolomite type country rock powder.

[0037] In the precipitation step of the present application, the drying temperature of the solid product is 80-100℃, preferably 90-100℃. The drying time of the solid product is 0.5-4h, preferably 2-3h.

[0038] According to the leaching method of the present application, the leaching rate of calcium is ≥60wt%, and the leaching rate of magnesium is ≥70wt%;

[0039] The leaching rate of calcium is calculated by the following formula:

[0040] The leaching rate of calcium is calculated by the following formula:

[0041] The leaching rate of magnesium is calculated by the following formula:

[0042] The leaching rate of magnesium is calculated by the following formula:

[0043] In the present application, the leaching rate of calcium is ≥60wt%, preferably ≥70wt%, and further preferably ≥75wt%; the leaching rate of magnesium is ≥70wt%, preferably ≥75wt%. According to some embodiments of the present application, the leaching rate of calcium is ≥80wt%, and the leaching rate of magnesium is ≥75wt%.

[0044] The present application enriches rare earth and niobium elements in dolomite-type country rock in leaching residue, significantly improves the grade of rare earth and niobium in rocks, and facilitates the subsequent recovery and utilization of rare earth and niobium resources in dolomite-type country rock by using beneficiation process. In addition, the present application selectively leaches calcium and magnesium elements by formic acid, improves the utilization rate of rock resources, realizes the recycling of formic acid in the production process, avoids the generation of high-pollution wastewater, and ensures a high leaching rate of calcium and magnesium. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 The XRD spectrum of the calcium oxalate and magnesium oxalate mixture in Example 1. DETAILED DESCRIPTION

[0046] The present application will be further described below in conjunction with specific examples, but the scope of protection of the present application is not limited thereto.

[0047] The content of each element in the following examples is calculated as its oxide.

[0048] The test method and calculation formula are described below:

[0049] Test method:

[0050] The dolomite-type country rock and leaching residue are tested by XRF full-element test.

[0051] The leachate was subjected to full element testing by ICP-OES.

[0052] Calculation formula:

[0053] Calcium leaching rate = (mass of calcium contained in leachate / mass of calcium contained in dolomite type country rock) x 100%.

[0054] Magnesium leaching rate = (mass of magnesium contained in leachate / mass of magnesium contained in dolomite type country rock) x 100%.

[0055] Purity of mixture of calcium oxalate and magnesium oxalate = (mass of calcium oxalate and magnesium oxalate in mixture / mass of mixture) x 100%.

[0056] The raw materials are described as follows:

[0057] The dolomite type country rock comes from the dolomite type country rock containing rare earth and niobium outside the Baiyunebo iron ore body.

[0058] Example 1

[0059] (1) The dolomite type country rock was ground, and the powder with particle size below 200 mesh was screened to obtain dolomite type country rock powder. The partial element composition and content of the dolomite type country rock are shown in Table 1. The loss on ignition of the dolomite type country rock was 38.46 wt%.

[0060] Table 1

[0061] Element Class SiO2 CaO Al2O3 MgO Na2O K2O Fe2O3 TiO2 Content (wt%) 2.32 27.66 0.36 11.50 0.36 0.05 12.30 0.79 Element Class ZnO BaO MnO SO3 SrO [Nb2O5] REO P2O5 Content (wt%) 0.04 0.85 2.00 0.66 0.21 0.22 2.03 0.17

[0062] (2) The dolomite type country rock powder was mixed with formic acid solution with a concentration of 3.2 mol / L to obtain dolomite type country rock powder slurry. In the dolomite type country rock powder slurry, the liquid-solid ratio of formic acid solution to dolomite type country rock powder was 7 mL:1 g. The dolomite type country rock powder slurry was leached under the conditions of stirring and temperature of 95℃ for 6 h to obtain a leaching product. The stirring speed of the stirring device for stirring the dolomite type country rock powder slurry was 300 rpm. The leaching product was subjected to solid-liquid separation to obtain leachate and leaching residue. The partial element composition and content of the obtained leachate and leaching residue are shown in Table 2. The loss on ignition of the leaching residue was 15.59 wt%.

[0063] Table 2

[0064]

[0065] (3) After adding anhydrous oxalic acid into the leaching solution, the reaction product was obtained by stirring at 25℃ and 300rpm for 2h and then standing for 3h. The amount of anhydrous oxalic acid was 1 times of the theoretical molar amount. The theoretical molar amount of anhydrous oxalic acid = the amount of substance of calcium element contained in the leaching solution + the amount of substance of magnesium element contained in the leaching solution.

[0066] The reaction product was suction filtered to obtain solid product and liquid product. The solid product was dried in an oven at 100℃ for 3h to obtain a mixture of calcium oxalate and magnesium oxalate. The liquid product could be returned to the dolomite type country rock powder in the leaching step as raw material to be recycled.

[0067] The XRD spectrum of the mixture of calcium oxalate and magnesium oxalate is shown in Figure 1

[0068] The leaching rate of calcium and magnesium, and the purity of the mixture of calcium oxalate and magnesium oxalate are shown in Table 3.

[0069] Table 3

[0070]

[0071] As shown in Tables 1 and 2, the present application can effectively enrich the rare earth elements and niobium elements in the dolomite type country rock, and the contents of REO and Nb2O5 enriched in the leaching residue are about 4.4 and 4.6 times of the original rock, respectively.

[0072] As shown in Tables 1-3, the method of the present application can enrich the rare earth and niobium in the dolomite type country rock in the leaching residue, and leach the calcium and magnesium into the leaching solution, thereby separating the rare earth, niobium from the calcium and magnesium, and having a high leaching rate of calcium and magnesium. The leaching solution is precipitated by oxalic acid to form a mixture of calcium oxalate and magnesium oxalate, and the obtained mixture has a high purity.

[0073] The present application is not limited to the above-mentioned embodiments, and any modification, improvement and replacement conceived by those skilled in the art without departing from the essential content of the present application falls within the scope of the present application.​

Claims

1. A leaching method for dolomite-type surrounding rock, characterized in that: The steps include: Leaching step: mixing dolomite-type surrounding rock powder with a particle size of less than or equal to 150 mesh with a formic acid solution with a concentration of 1.5 to 4.5 mol / L to obtain a dolomite-type surrounding rock powder slurry; leaching the dolomite-type surrounding rock powder slurry at a temperature of 60 to 100° C. for 2 to 12 hours to obtain a leaching product; separating the leaching product into a solid-liquid state to obtain a leachate and a leaching residue; wherein the liquid-solid ratio of the formic acid solution to the dolomite-type surrounding rock powder is (5 to 9) mL:1 g; Precipitation step: reacting the leachate with oxalic acid to obtain a reaction product; Separation step: separating the reaction product into solid and liquid to obtain a mixture of calcium oxalate and magnesium oxalate and a liquid product.

2. The leaching method according to claim 1, wherein Also includes the following steps: Grinding step: Grinding the dolomite surrounding rock to obtain dolomite surrounding rock powder.

3. The leaching method according to claim 1, wherein The dolomite-type surrounding rock powder has a rare earth element content of 1 to 5 wt%, a niobium element content of 0.01 to 0.5 wt%, a calcium element content of 23 to 43 wt%, and a magnesium element content of 9 to 14 wt%. The rare earth elements are calculated as REO, the niobium element is calculated as Nb2O5, the calcium element is calculated as CaO, and the magnesium element is calculated as MgO.

4. The leaching method according to claim 1, wherein The ignition loss rate of the dolomite surrounding rock powder is 30-45wt%.

5. The leaching method according to claim 1, wherein The leaching step and the precipitation step are carried out under stirring conditions, and the rotation speed of the stirring device is 100-400 rpm.

6. The leaching method according to claim 1, wherein The content of rare earth elements in the leaching residue is 5-25wt%, and the content of niobium is 0.3-2.5wt%. The rare earth elements are calculated as REO, and the niobium is calculated as Nb2O5.

7. The leaching method according to claim 1, wherein The amount of oxalic acid used is 1 to 1.5 times the theoretical molar amount; the theoretical molar amount of oxalic acid is calculated using the following formula: The theoretical molar dosage of oxalic acid = the amount of calcium element contained in the leachate + the amount of magnesium element contained in the leachate.

8. The leaching method according to claim 1, wherein The leachate is reacted with oxalic acid at 15-40°C for 0.5-6h.

9. The leaching method according to claim 1, wherein The following steps are also included: drying the solid product obtained by solid-liquid separation of the reaction product at 80-100° C. for 0.5-4 hours to obtain a mixture of calcium oxalate and magnesium oxalate; The liquid product is returned to the leaching step as a raw material to leach dolomite-type surrounding rock powder.

10. The leaching method according to claim 1, wherein The leaching rate of calcium is ≥60wt%, and the leaching rate of magnesium is ≥70wt%; The calcium leaching rate is calculated using the following formula: Calcium leaching rate = (the mass of calcium contained in the leachate / the mass of calcium contained in the dolomite-type surrounding rock) × 100%; The leaching rate of magnesium is calculated using the following formula: Magnesium leaching rate = (mass of magnesium contained in the leachate / mass of magnesium contained in the dolomite-type surrounding rock) × 100%.

Images