A method for leaching lithium from clay-type lithium ore using recyclable solid acid

Abstract

The present invention discloses a method for leaching lithium from clay-type lithium ore by using recyclable solid acid. The method involves successively crushing, grinding, and roasting and activating the clay-type lithium ore, followed by leaching with an oxalic acid solution. After low-temperature crystallization of the obtained leaching solution, solid-liquid separation is carried out. The solid is oxalic acid, and the liquid is a lithium-containing solution. Oxalic acid can be easily recovered after the leaching process, and both the lithium leaching rate and the oxalic acid recovery rate reach nearly 90%, which can significantly reduce the cost of lithium recovery.

Description

Technical Field

[0001] The present invention relates to a method for leaching lithium from clay-type lithium ores, in particular to a method for leaching lithium from clay-type lithium ores using a recyclable solid acid, and belongs to the technical field of lithium extraction. Background Art

[0002] Lithium (Li) is an important metal with very valuable applications and shows great industrial prospects in military and civilian advanced technologies. The widespread use of lithium-ion batteries in electric vehicles and electronic devices will lead to a rapid increase in the demand for lithium resources. Generally, the main types of natural lithium deposits are mainly distributed in pegmatites and brines. However, due to the depletion of pegmatite-type lithium ores and the high difficulty and cost of extracting and separating lithium from salt lake brines, conventional lithium ores (pegmatite-type and brine-type) cannot meet the explosive growth of lithium consumption.

[0003] Research shows that sedimentary lithium ores with huge lithium reserves may be potential lithium resources. Clay-type lithium ores have the advantage of large lithium reserves, while relatively few related extraction studies have been conducted. Extracting lithium from clay-type lithium ores is mainly through leaching with high-concentration inorganic acids (usually sulfuric acid or hydrochloric acid). Chinese Patent CN110042262A discloses a method for leaching lithium from low-grade sedimentary lithium ores, the core of which is to roast the raw ore at 500-750°C and then leach it in an acidic solution of 0.5-4.0 mol / L. Chinese Patent CN111575504A discloses a method for efficiently leaching lithium from lithium-containing clay rocks. The main steps are to first crush the raw ore to less than 2 mm, then mix it with concentrated sulfuric acid to form a slurry and heat-treat it at 150-210°C for 1-4 hours for ripening, and then leach the clinker with water at 80°C. Although these methods can achieve efficient leaching of lithium, high-concentration inorganic acids not only increase the corrosion risk of leaching equipment, but also introduce acid impurities into the subsequent deacidification and purification process, and a large amount of alkali is required to neutralize the excessive acid. Summary of the Invention

[0004] Aiming at the defects and deficiencies of the above-mentioned existing technologies, the purpose of the present invention is to provide a method for leaching lithium from clay-type lithium ores using a recyclable solid acid. This method uses an oxalic acid solution as a leaching agent, which can not only efficiently leach lithium elements from clay-type lithium ores, but also efficiently recover the oxalic acid leaching agent, reduce the leaching cost, and provide a new technical idea with low cost and environmental friendliness for the development and utilization of lithium resources.

[0005] To achieve the above technical purpose, the present invention provides a method for leaching lithium from clay-type lithium ores using a recyclable solid acid. In this method, the clay-type lithium ore is sequentially subjected to crushing, grinding, and roasting activation, and then leached with an oxalic acid solution. After the obtained leaching solution is subjected to low-temperature crystallization, solid-liquid separation is carried out. The solid is oxalic acid, and the liquid is a lithium-containing solution.

[0006] The key to the technical solution of the present invention is to use oxalic acid to achieve the leaching of lithium from clay-type lithium ores, which can achieve efficient leaching of lithium in clay-type lithium ores. Almost all of the excessive oxalic acid can be recycled and utilized, greatly reducing the leaching cost of lithium in clay-type lithium ores and reducing the generation of acidic waste liquid.

[0007] As a preferred solution, after the clay-type lithium ore is crushed and pulverized, the fineness is controlled such that the mass percentage content with a particle size less than 200 mesh is more than 85%. Grinding the clay-type lithium ore to an appropriate particle size is beneficial to improving the subsequent high-temperature activation and leaching efficiency.

[0008] As a preferred solution, the conditions for roasting activation are: the temperature is 400 - 600 °C, and the time is 1 - 3 h. During the high-temperature roasting process, the crystal form transformation of the lithium-bearing minerals in the clay-type lithium ore can be achieved, which is a prerequisite for achieving efficient lithium leaching.

[0009] As a preferred solution, the concentration of the oxalic acid solution is 2 - 12 mol / L. The concentration of the oxalic acid solution is further preferably 8 - 12 mol / L. The concentration of the oxalic acid solution has a relatively large impact on the leaching efficiency of lithium and the recovery rate of oxalic acid. When the concentration of the oxalic acid solution is within the range of 2 - 12 mol / L, the leaching rate of lithium remains above 75%. However, the recovery rate of oxalic acid is not ideal when the oxalic acid concentration is below 8 mol / L. Therefore, the preferred concentration of the oxalic acid solution is 8 - 12 mol / L.

[0010] As a preferred solution, the conditions for leaching are: the liquid-solid ratio is 3 - 5 L / 1 kg, the temperature is 80 - 100 °C, and the time is 1 - 3 h. Leaching under the preferred conditions can ensure efficient leaching of lithium.

[0011] As a preferred solution, the temperature for low-temperature crystallization is less than 5 °C. The further preferred temperature is 0 - 4 °C. Within this temperature range, oxalic acid can be efficiently crystallized out.

[0012] As a preferred solution, the leaching residue is washed with hot water, and the washing liquid is mixed with the leaching liquid and subjected to low-temperature crystallization. The hot water is water with a temperature higher than 40 °C, further preferably water with a temperature higher than 60 °C, and most preferably water with a temperature higher than 80 °C. It is only necessary to rinse the leaching residue with a small amount of hot water, mainly to wash the oxalic acid and the leached lithium ions adhered to the leaching residue by acid. The amount of washing water has little impact on the subsequent crystallization of oxalic acid.

[0013] The method for leaching lithium from clay-type lithium ores using a recyclable solid acid provided by the present invention includes the following steps:

[0014] (1) Crushing: Crushing and pulverizing the ore, and controlling the fineness such that the mass percentage content less than 200 mesh is above 85%;

[0015] (2) High-temperature roasting: Roast the crushed and ground clay-type lithium ore. The roasting temperature is 400 - 600 °C, and the heat preservation time is 1 - 3 h. If the roasting temperature is lower than 400 °C, the roasting is incomplete and the complete transformation of the mineral crystal form in the clay-type lithium ore cannot be achieved. If the roasting temperature is higher than 600 °C, lithium will enter the newly formed crystal form, which is not conducive to subsequent leaching.

[0016] (3) Oxalic acid leaching: Add an oxalic acid solution with a concentration of 2 - 12 mol / L to the ore powder treated in step (2). The liquid-solid ratio is 3 - 5 L / 1 kg. Heat it to 80 - 100 °C and carry out leaching for 1 - 3 h under stirring.

[0017] (4) Filtration and separation: After the reaction ends, carry out solid-liquid separation and collect the filter residue and filtrate.

[0018] (5) Low-temperature crystallization to recover oxalic acid: Wash the filter residue collected in step (4) with a small amount of hot water above 40 °C, mix it with the filtrate collected in step (4), and carry out crystallization at a low temperature below 5 °C. Carry out solid-liquid separation to recover oxalic acid and collect the lithium-containing solution.

[0019] Beneficial technical effects brought by the technical solution of the present invention compared with the prior art:

[0020] The technical solution of the present invention uses an oxalic acid solution to effectively leach lithium from clay-type lithium ore, and the lithium leaching rate is about 90%. Different from other methods for extracting lithium from lithium ore, the present invention uses oxalic acid as the leaching agent, and can efficiently recover the leaching agent by changing the solubility, greatly reducing the use cost of the leaching agent. Compared with the existing technology, it has the characteristics of low cost, high efficiency, environmental friendliness, and simple process. Brief Description of the Drawings

[0021] Figure 1 is the process flow chart for extracting lithium from clay-type lithium ore in the present invention.

[0022] Figure 2 is the XRD comparison chart of the original ore and the ore roasted at 500 °C; after the clay-type lithium ore is roasted at 500 °C, kaolinite in the original ore is transformed into metakaolinite, which is a prerequisite for its leaching.

[0023] Figure 3 is the effect diagram of leaching and recovery with oxalic acid at different concentrations. Specific Embodiments

[0024] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0025] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the range.

[0026] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention.

[0027] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention's specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of this application are merely exemplary.

[0028] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0029] Unless otherwise specified, the "parts" described in the present invention are all calculated by mass parts.

[0030] Example 1

[0031] The clay-type lithium ore is pulverized and crushed, and pulverized by a crusher until the fineness of more than 85% of the ore is less than 200 mesh. It is calcined at 500 °C, cooled to room temperature after holding for 2 hours. Add an oxalic acid solution with a molar concentration of 8 mol / L at a ratio of 1 g:5 mL, mix evenly, and heat to 90 °C on a constant temperature water bath oscillator. Leaching is carried out for 1 hour under stirring conditions, and solid-liquid separation is carried out while it is hot, and the filter residue and filtrate are collected. The collected filter residue is rinsed with a small amount of hot water at 80 °C, mixed with the collected filtrate, and low-temperature crystallized at 4 °C, and solid-liquid separation is carried out to recover oxalic acid and collect the lithium-containing solution. The lithium leaching rate is 89.12%, and the oxalic acid recovery rate is 88.12%.

[0032] Control experimental group 1

[0033] Compared with Example 1, the only difference is that the concentration of the oxalic acid solution is replaced with 2 mol / L, 4 mol / L, 6 mol / L, 10 mol / L, and 12 mol / L respectively. The lithium leaching rate and oxalic acid recovery rate are as Figure 3 shown. From Figure 3It can be seen that when the concentration of the oxalic acid solution is 2 mol / L, the leaching rate of lithium can reach over 76%. Moreover, as the concentration of oxalic acid increases, the leaching rate of lithium gradually increases. When the concentration of oxalic acid increases to 8 mol / L, the further increase in the leaching rate of lithium is not obvious. However, the recovery rate of oxalic acid is not ideal when the concentration of oxalic acid is lower than 8 mol / L. Therefore, it can be seen that the optimal concentration range of the oxalic acid solution is 8 - 12 mol / L, which can not only maintain a high leaching rate of lithium but also obtain a high recovery rate of oxalic acid.

[0034] Control experimental group 2

[0035] Compared with Example 1, the only difference is that different roasting temperatures (unroasted, 300 °C, 400 °C, 600 °C, 700 °C) are adopted, and the final obtained lithium leaching rate and oxalic acid recovery rate are shown in Table 1.

[0036]

[0037] According to Table 1, it can be seen that the roasting activation process of clay-type lithium ore has an obvious influence on the leaching rate of lithium, but almost no influence on the recovery rate of oxalic acid. When the roasting temperature is above 400 °C, the phase transformation of the refractory clay-type lithium ore can be realized, which is beneficial to the leaching of oxalic acid. When the temperature is higher than 600 °C, the clay-type lithium ore will transform into a phase that is difficult to be leached, which is not conducive to the leaching of oxalic acid.

Claims

1. A method for leaching lithium from clay-type lithium ore using recyclable solid acid, characterized in that: The clay-type lithium ore is crushed, ground, and roasted for activation, and then leached with oxalic acid solution. The obtained leachate is crystallized at low temperature and then the solid and liquid are separated. The solid is oxalic acid and the liquid is a lithium-containing solution. The calcination activation conditions are: temperature of 400-600°C and time of 1-3h; The concentration of the oxalic acid solution is 8-12 mol / L.

2. The method for recovering lithium from clay-type lithium ore with solid acid leaching according to claim 1, characterized in that: The clay-type lithium ore is crushed and ground to a fineness that is controlled to be less than 200 mesh, with a mass percentage content of more than 85%.

3. The method for recovering lithium from clay-type lithium ore using solid acid leaching according to claim 1, wherein: The leaching conditions are: liquid-solid ratio of 3-5 L / 1 kg, temperature of 80-100° C., and time of 1-3 h.

4. The method for recovering lithium from clay-type lithium ore with solid acid leaching according to claim 1, characterized in that: The temperature of the low-temperature crystallization is less than 5°C.

5. The method for recovering lithium from clay-type lithium ore with solid acid leaching according to claim 1, characterized in that: The leaching residue obtained by the leaching is washed with hot water, and the washing liquid is mixed with the leaching liquid and subjected to low-temperature crystallization.

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