Process for recovering iron and rare earth elements from high-weathering iron-containing rare earth ore

Abstract

The invention relates to the technical field of mineral separation of weathered iron-containing rare earth ores, and particularly discloses a process for recovering iron and rare earth elements from high-weathering iron-containing rare earth ores, which is characterized by comprising the following steps: S1, crushing raw ores of the high-weathering iron-containing rare earth ores, and then carrying out reduction roasting to obtain reduced roasted ores; s2, performing low-intensity magnetic separation on the reduced roasted ore to obtain magnetic concentrate and magnetic tailings, and performing magnetic concentration on the magnetic concentrate to obtain iron concentrate and concentrated tailings; s3, the magnetic tailings and the fine tailings are combined, then acid leaching impurity removal is carried out, and impurity-removed ores are obtained; s4, the impurity-removed ore is subjected to oxidizing roasting, then a leaching agent is added for rare earth leaching, and rare earth leaching liquid is obtained; and S5, NaHCO3 is added into the rare earth leachate to adjust the pH to 1.8-2, precipitation and impurity removal are conducted, then NaHCO3 continues to be added to adjust the pH to 7-8, rare earth precipitation is conducted, and rare earth carbonate is obtained. Mineral resources are utilized to the maximum extent through the processes of reduction roasting, leaching, alkali adjustment, precipitation and the like.

Description

Technical Field

[0001] The invention relates to the technical field of beneficiation of weathered iron-containing rare earth ores, in particular to a process for recovering iron and rare earth elements from highly weathered iron-containing rare earth ores. Background Art

[0002] Weathered iron-containing rare earth ores are a type of rare earth ores. The minerals are characterized by high iron content and high differentiation. Compared with hard rock rare earth ores, due to long-term weathering and erosion, the number of independent rare earth minerals in the minerals has decreased. Conventional mineral processing technology makes it difficult to effectively recover rare earths, but the occurrence of rare earth elements in the minerals is also different from that of ion-adsorbing rare earth minerals, which makes it difficult to recover rare earth elements. Among weathered iron-based rare earth minerals, iron elements show a high degree of weathering characteristics. The diversity of iron-containing mineral types makes it difficult to utilize the minerals. Among highly weathered minerals, magnetite generally accounts for a small proportion, and there are many mineral types such as hematite, limonite, specularite, and iron silicate. The complex mineral types are also a reason why this type of mineral is difficult to utilize. At the same time, due to the weathering of the minerals, some waste rocks are stripped off, which enriches the rare earth elements to a certain extent. The content of rare elements in this type of minerals is generally higher than that of weathered sedimentary rare earths, but the difficulty of utilization is also high.

[0003] In terms of the utilization technology of highly weathered iron-based rare earth resources, the rare earth minerals in the rare earth mining area contain a lot of iron but have not reached a highly weathered state, and the rare earths still exist in the form of minerals such as monazite or fluorocarbon cerium. At present, reduction roasting technology has been used in the removal of iron from ferromanganese ore and rare earth ores, and has a good effect in the recovery of iron resources. Since there are no independent rare earth minerals in weathered ores, or the rare earth minerals are embedded in extremely fine particles, it is difficult to recover rare earth minerals using conventional mineral processing methods. At the same time, the complex iron element has a great influence on the flotation of rare earths, making it difficult to utilize rare earth resources.

[0004] Among the current patents on comprehensive recovery of iron and rare earth elements from iron-based rare earth ores, some involve reduction roasting, but the overall process is quite different from the content of this patent, and the relevant patents do not mention that the minerals targeted are highly weathered ores; the following are three patents involving recovery of iron and rare earth elements from minerals: (1) Gao Peng, Yuan Shuai, Ning Jilai, et al. Process for recovery of niobium iron and rare earth from refractory ores based on suspended mineral phase transformation method. CN202211372790.7 [2024-09-20]. (2) She Xue Feng. A method for separating and producing rare earths from iron-containing rare earth ore: CN201710147998.1[P]. CN106916941A[2024-09-20]. (3) Wang Jingsong, Ding Yingui, Xue Qingguo, et al. A method for separating and enriching iron and rare earths in iron-containing rare earth ore. 2013[2024-09-20]. The above patents involve reduction roasting operations, but according to the description of the patent content, there are still many independent rare earth minerals in the minerals, and the minerals have certain selectivity.

[0005] Overall, there is currently no mature utilization technology for weathered iron and rare earth ores. It is difficult to separate weathered iron minerals from rare earth minerals by flotation and magnetic separation. This patent proposes a beneficiation process for this type of mineral to recover iron and rare earth elements, providing a reference for the utilization of this type of minerals. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a process for recovering iron and rare earth elements from highly weathered iron-containing rare earth ores, so as to at least achieve a higher recovery rate of iron and rare earth elements.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] A process for recovering iron and rare earth elements from highly weathered iron-containing rare earth ores comprises the following steps:

[0009] S1: crushing the raw ore of highly weathered iron-containing rare earth ore, and then reducing and roasting it to obtain a reduced roasted ore;

[0010] S2: performing weak magnetic separation on the reduced roasted ore to obtain magnetic concentrate and magnetic tailings, and performing magnetic concentration on the magnetic concentrate to obtain iron concentrate and concentrated tailings;

[0011] S3: combining the magnetic tailings and the concentrated tailings, and then performing acid leaching to remove impurities to obtain a cleaned ore;

[0012] S4: oxidizing and roasting the impurity-removed ore, and then adding a leaching agent to leach rare earths to obtain a rare earth leaching solution;

[0013] S5: adding NaHCO3 to the rare earth leaching solution to adjust the pH to 1.8-2, performing precipitation and impurity removal, and then continuing to add NaHCO3 to adjust the pH to 7-8, performing rare earth precipitation, and obtaining rare earth carbonate.

[0014] Furthermore, the highly weathered iron-containing rare earth ore is selected from weathered rare earth ores in the Bayan Obo area, Uganda in Africa, Lufeng / Nujiang area in Yunnan, and Cape area in South Africa.

[0015] Furthermore, in step S1, the particle size of the highly weathered iron-containing rare earth ore is controlled to be below 0.5 mm after the crushing.

[0016] Furthermore, in step S1, the temperature of the reduction roasting is 500-550°C, the reducing atmosphere is a mixed gas of N2 and CO, the volume ratio of N2 and CO is 5-10:3, and the total gas flow rate is 1 L / min.

[0017] It is worth noting that the non-magnetic iron minerals are reduced to magnetic minerals using reducing gases such as CO or H2. The reactions that occur during roasting are as follows:

[0018] 3Fe2O3+CO——2Fe3O4+CO2↑ Hematite transformation 1

[0019] Fe2O3·nH2O+CO——Fe3O4+CO2↑+nH2O↑ Limonite transformation 2

[0020] FeCO3——FeO+CO2↑ Siderite decomposition 3

[0021] 6FeO(OH)+CO——2Fe3O4+CO2↑+3H2O↑ Goethite transformation 4

[0022] Under the influence of high-temperature reducing gas atmosphere, iron-containing minerals such as hematite, limonite, siderite, and goethite will decompose or transform into magnetic iron minerals, thus realizing the transformation of iron minerals. Reduction roasting can achieve the reorganization of iron ore to a certain extent, but not all iron ores can be transformed. For example, some iron elements in iron phosphate, iron silicate, and clay-like minerals will not be transformed, so further enrichment of iron elements is required.

[0023] Furthermore, in step S2, the weak magnetic separation is dry magnetic separation, and the magnetic field strength is 1500-2000 Oersted.

[0024] Furthermore, in step S2, the magnetic separation is wet magnetic separation, and the magnetic field strength is 1000-1200 Oersted.

[0025] It is worth noting that the present invention uses a combination of dry and wet magnetic separation to separate iron-containing minerals. After reduction roasting, due to the high temperature of the mineral, it is not possible to directly grind the ore. The dry magnetic separator performs preliminary separation on the roasted minerals. After separation, the coarse concentrate enters the mill for re-grinding. The grinding fineness is -325 mesh 75-80%. It enters the weak magnetic separation operation and then undergoes magnetic separation to obtain the magnetic separation concentrate. Since the mineral is a strongly weathered ore, even after reduction roasting, the embedded state in the mineral is still relatively complex, and it is difficult to obtain qualified iron minerals through one magnetic separation, so a process of dry magnetic roughing + wet magnetic selection is designed. Under this process, the grade of the iron concentrate is between 58-62%, which meets the requirements of the iron concentrate.

[0026] Furthermore, in step S3, the acid leaching and impurity removal is performed by eluting and spraying with a strong acid.

[0027] Furthermore, the strong acid is 15-20% sulfuric acid.

[0028] Furthermore, the impurity removal liquid removed by acid leaching is recycled and centrally processed when the number of cycles reaches a certain level.

[0029] It is worth noting that the main purpose of circulating leaching and impurity removal is to remove phosphorus in minerals. If phosphorus is not removed, rare earth phosphate precipitation will be produced during the subsequent rare earth leaching process. Phosphates in minerals are generally soluble in strong acids, but acid solutions with too high a concentration will cause great damage to mineral components. After adding sulfuric acid, the phosphates in the minerals have the following balance:

[0030] Ca2(PO4)2——3Ca 2+ +2PO4 3- ksp=2.07*10 -33 5

[0031] FePO4·2H2O——Fe 3+ +PO4 3- +2H2O ksp=9.91*10 -16 6

[0032] Fe3(PO4) 2 ——3Fe 2+ +2PΟ4 3- ksp=1*10 -36 7

[0033] RePO4——Re 3+ +4PO4 3- ksp=10 -11 -10 -12 8

[0034] Calcium phosphate is the main component of apatite and a common carrier mineral of phosphorus. Among the above-mentioned minerals, it is precipitated under normal conditions, but soluble in strong acid. According to the solubility product constant, it can be seen that ferrous phosphate has a slightly better solubility. It can be inferred that during the strong acid elution process, the mineral system undergoes the following reactions:

[0035] (1) Phosphorus-containing minerals are partially dissolved in the strong acid solution, and iron elements are also partially dissolved into the solution.

[0036] (2) As the number of eluent circulations increases, the phosphorus content in the circulating fluid gradually increases, and the ferrous phosphate content in the solution also gradually accumulates.

[0037] (3) After the circulating liquid accumulates to a certain extent, the divalent iron is converted into trivalent iron by heating, and iron phosphate precipitation is obtained.

[0038] (4) After replenishing the acid, continue the elution operation.

[0039] In the above process, the pH value of the eluent is controlled between 0.5-1, that is, the sulfuric acid concentration is between 15-20%. At this pH value, the phosphorus removal effect can be guaranteed and the loss of rare earth is also relatively small.

[0040] Furthermore, in step S4, the oxidative calcination temperature is 600-700° C., and the calcination time is 40-60 min.

[0041] Further, in step S4, the leaching agent includes sulfuric acid, preferably 10% sulfuric acid

[0042] And / or, the leaching temperature of the rare earth leaching is room temperature and the leaching time is 2-3 hours.

[0043] It is worth noting that in the present invention, after being roasted at 600-700°C, the rare earth elements in the mineral can be leached out by sulfuric acid. A sulfuric acid solution with a concentration of 8-10% is used in the rare earth leaching to reduce the rare earth precipitation caused by the residual phosphorus element in the mineral. The leaching is carried out at room temperature for 2-3 hours, and a leachate and a leachate residue are obtained after the leaching, wherein the pH value of the leachate is between 1-1.5.

[0044] Furthermore, in step S5, after the rare earth precipitation, filtering and drying are performed.

[0045] It is worth noting that the gradient alkali adjustment in step S5 is to gradually reduce the precipitation of the leaching solution using NaHCO3, and the reduction process is mainly divided into the following three parts:

[0046] (1) Use NaHCO3 to adjust the pH to 2-2.2, and yellow sodium iron vanadium precipitate will be generated in the solution, which can be removed by filtration.

[0047] (2) The pH is adjusted to 5-5.2 using NaHCO3, and most of the metal ions in the solution are precipitated in the form of hydroxides or carbonates and removed by filtration.

[0048] (3) Using NaHCO3, the pH is adjusted to 7-8, which is the rare earth precipitation range, to obtain rare earth carbonate products.

[0049] Furthermore, in step S2, the magnetic concentrate needs to be ground, and the grinding fineness is -325 mesh 80%.

[0050] Furthermore, in step S2, the magnetic separation tailings need to be ground, and the grinding fineness is -325 mesh 60-70%.

[0051] The beneficial effects of the present invention are:

[0052] The present invention proposes a combined smelting process to recover iron and rare earth elements from minerals. The iron-containing minerals in the minerals are further integrated through reduction roasting and converted into magnetic iron minerals, and the separation of iron and rare earths is achieved through magnetic separation. The magnetic separation tailings are pre-cleaned to remove part of the iron and phosphorus elements, and then the overall activity of the rare earth elements is changed through oxidative roasting, and the rare earth is leached through sulfuric acid leaching. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a simplified process flow diagram of the present invention. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0055] The samples of highly weathered iron-containing rare earth ores used in the following examples are as follows: Rare earth ore samples from Uganda, Africa. The ore samples are earthy red in color, muddy to fine gravel, with occasional particles of +5 mm. The main elemental components of the minerals are shown in the following table:

[0056] Table 1

[0057] element MgO <![CDATA[Al2O3]]> <![CDATA[SiO2]]> <![CDATA[P2O5]]> <![CDATA[SO3]]> <![CDATA[K2O]]> CaO TiO PbO content 0.5 4.77 8.49 1.87 2.74 0.14 0.9 1.25 0.011 element MnO <![CDATA[Fe2O3]]> ZnO <![CDATA[Nb2O5]]> SrO BaO ZrO2 MoO3 REO content 3.44 64.549 0.49 0.57 0.07 6.69 0.08 0.06 1.41

[0058] Iron accounts for the highest proportion of minerals. Iron minerals are highly weathered and closely associated with other gangue and rare earth elements. In order to achieve the effective utilization of rare earths, it is necessary to prioritize the separation of iron and rare earths.

[0059] Example 1 Comparison of reduction roasting and direct magnetic separation test

[0060] Take 2 groups of ore samples, 200g each, and the first group is subjected to reduction roasting. The roasting conditions are CO 700ml / min, N2 300ml / min, roasting temperature 500℃, and roasting time 10min. After roasting, the roughing concentrate is ground to -325 mesh 80% by a dry magnetic separator, and magnetic separation is performed by a magnetic suspension tube. The second group directly grinds the mineral to -325 mesh 80%, and performs magnetic separation tests on magnetic separation tubes to obtain magnetic separation concentrates and tailings. The magnetic separation results are shown in Table 2:

[0061] Table 2

[0062]

[0063] It can be seen from the results that due to severe mineral weathering, the proportion of magnetite minerals is low and the direct magnetic separation index is poor. It can be seen that the effect of reducing roasting on increasing the iron ore index is significant.

[0064] Example 2 Acid leaching and impurity removal experiment

[0065] The medium ore of the first group in Example 1 was ground to -325 mesh 70% and mixed with the tailings. Four ore samples, 20 grams each, were taken and leached with 40 ml of 15% sulfuric acid solution. The leaching time was 10, 20, 30, and 40 minutes respectively. The leachate was analyzed and the endpoint pH was recorded. The test results are shown in Table 3:

[0066] Table 3

[0067]

[0068] It can be seen from the test results that when the leaching time is 10 minutes, the P ion content in the solution has reached a relatively high state. When the leaching time reaches 40 minutes, the P content decreases instead. It is speculated that due to the long leaching time, the pH value of the iron-containing mineral solution is reduced, resulting in the formation of phosphate precipitation and the reduction of the P content of the solution. It can be seen that the overall leaching time of the mineral should not be too long, so the impurity removal method of leaching operation is adopted.

[0069] Combined with the conditions in Example 1, 1 kg of raw ore was prepared for sample preparation, and a leached residue sample was prepared for rare earth leaching test.

[0070] Example 3 Oxidative roasting and rare earth leaching

[0071] Take 20g of slag samples from four embodiments 2 respectively, place them in porcelain boats respectively, and carry out oxidation roasting in a muffle furnace at 500°C, 600°C, 700°C, and 800°C respectively. The roasting time is 40min. Place the roasted mineral in 30ml of 10% sulfuric acid solution and stir for leaching for 60min. Filter and measure the rare earth content in the filtrate. The measurement results are shown in Table 4:

[0072] Table 4

[0073]

[0074] It can be seen that when the roasting temperature is in the range of 600-700, the leaching effect of rare earth is better, and the leaching rate reaches 56%. After the leaching is completed, the pH value of the solution is 1.3. Impurities such as phosphorus and iron exist. The solution needs to be decontaminated before precipitating the rare earth.

[0075] According to the optimal conditions, 200g of ore sample was tested, and the leaching solution obtained from the test was used for rare earth impurity removal and precipitation experiments.

[0076] Example 4 Rare earth precipitation experiment

[0077] Take 500ml of the leachate in Example 3 and carry out the impurity removal and precipitation operation; the rare earth precipitation and impurity removal scheme adopts a two-stage impurity removal operation. In the first step, NaHCO3 is used to adjust the pH value of the solution to 2-2.2, and the solution is heated to 85 degrees to obtain a yellow sodium iron vanadium precipitate (precipitate 1), and impurities are removed by filtration. Then NaHCO3 is used to adjust the pH of the solution to 5-5.2 to obtain a metal impurity ion precipitate (precipitate 2), and impurities are removed by filtration. NaHCO3 is then added to adjust the pH to 7-8 to obtain a rare earth precipitate, which is filtered to obtain a rare earth precipitate product (precipitate 3). The content of each element in the product is shown in Table 5.

[0078] Table 5

[0079]

[0080] The carbonate product obtained by gradient alkali adjustment and impurity removal meets the grade requirements of rare earth separation. In all operations, the recovery rate of rare earth in magnetic separation operation is 81.5%; the loss of rare earth in leaching and impurity removal operation is about 3%; the leaching rate in rare earth leaching is 62.74%; the loss of rare earth in impurity removal operation is about 2%; it can be concluded that the overall recovery rate of rare earth is about 48.6%.

[0081] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A process for recovering iron and rare earth elements from highly weathered iron-containing rare earth ores, characterized in that: The following steps are involved: S1: crushing the raw ore of highly weathered iron-containing rare earth ore, and then reducing and roasting it to obtain a reduced roasted ore; S2: performing weak magnetic separation on the reduced roasted ore to obtain magnetic concentrate and magnetic tailings, and performing magnetic concentration on the magnetic concentrate to obtain iron concentrate and concentrated tailings; S3: combining the magnetic tailings and the concentrated tailings, and then performing acid leaching to remove impurities to obtain a cleaned ore; S4: oxidizing and roasting the impurity-removed ore, and then adding a leaching agent to leach rare earths to obtain a rare earth leaching solution; S5: adding NaHCO3 to the rare earth leaching solution to adjust the pH to 1.8-2, performing precipitation and impurity removal, and then continuing to add NaHCO3 to adjust the pH to 7-8, performing rare earth precipitation, and obtaining rare earth carbonate.

2. The process according to claim 1, characterized in that: In step S1, the particle size of the highly weathered iron-containing rare earth ore is controlled to be below 0.5 mm through the crushing.

3. The process according to claim 1, characterized in that: In step S1, the temperature of the reduction roasting is 500-550°C, the reducing atmosphere is a mixed gas of N2 and CO, and the volume ratio of N2 to CO is 5-10:

3.

4. The process according to claim 1, characterized in that: In step S2, the weak magnetic separation is dry magnetic separation, and the magnetic field strength is 1500-2000 Oersted.

5. The process according to claim 1, characterized in that: In step S2, the magnetic separation is wet magnetic separation, and the magnetic field strength is 1000-1200 Oersted.

6. The process according to claim 1, characterized in that: In step S3, the acid leaching and impurity removal is performed by rinsing and spraying with a strong acid.

7. The process according to claim 1, characterized in that: In step S4, the oxidative calcination temperature is 600-700° C., and the calcination time is 40-60 min.

8. The process according to claim 1, characterized in that: In step S4, the leaching agent includes sulfuric acid; And / or, the leaching temperature of the rare earth leaching is room temperature and the leaching time is 2-3 hours.

9. The process according to claim 1, characterized in that In step S2, the magnetic concentrate needs to be ground, and the grinding fineness is -325 mesh 80%.

10. The process according to claim 1, characterized in that: In step S2, the magnetic separation tailings also need to be ground, and the grinding fineness is -325 mesh 60-70%.

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