Method for recycling co-associated low-grade valuable elements in lepidolite flotation concentrate through normal-pressure alkaline leaching method

Abstract

The invention discloses a method for recycling co-associated low-grade valuable elements in lepidolite flotation concentrate through a normal-pressure alkaline leaching method, and belongs to the technical field of recycling and recycling of lithium, rubidium and cesium resources. According to the method, valuable elements such as lithium, rubidium and cesium in the lepidolite flotation concentrate are recycled through a normal-pressure alkaline leaching method, and lithium, rubidium and cesium are green and high in efficient synergistic leaching rate. In order to solve the problems of resource waste, high energy consumption, secondary pollution to the environment and the like in the prior art, the invention provides a method for efficiently and synergistically recovering lithium, rubidium and cesium in lepidolite ore by utilizing high reaction activity provided by unconventional alkali. The technological process consumes less time, equipment operation is simple and safe, the synergistic recovery rate of lithium, rubidium and cesium is high, the impurity removal effect is good, secondary pollution is reduced, medium recycling of the follow-up process can be achieved, the follow-up flat lithium slag amount is sharply reduced, and the lithium slag amount generated by per ton of lepidolite ore is averagely reduced by 80%; and a new theoretical reference is provided for extraction of low-grade co-associated lithium-rubidium-cesium resources and reduction of resource waste in China.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium, rubidium and cesium resource recovery and recycling, and specifically relates to a method for recovering co-associated low-grade valuable elements in lepidolite flotation concentrate by utilizing a normal pressure alkali leaching method. Background Art

[0002] Lepidolite contains a variety of rare metal resources such as lithium, rubidium and cesium. Lithium, rubidium and cesium are important strategic metal resources. As "new energy" and "new materials", they are widely used in military and other fields. In addition, lepidolite has low mining costs and abundant domestic reserves. In order to meet the needs of high-tech industries for rare metals such as lithium, rubidium and cesium, how to efficiently and economically extract rare metals such as lithium, rubidium and cesium from lepidolite has become an increasingly prominent issue. Reasonable development and utilization of low-grade lithium, rubidium and cesium and other valuable elements co-existing in lepidolite can reduce resource waste, realize the rational utilization of resources, and take the path of green and sustainable development.

[0003] At present, the extraction of lithium, rubidium and cesium from lithium mica has extremely high economic value, but the current technical methods for the extraction and recovery of lithium, rubidium and cesium have a series of key technical bottlenecks, such as the difficulty of lithium, rubidium and cesium synergistic dissolution, the difficulty of purifying, enriching and separating rubidium and cesium solutions, and the inability to recycle resources, resulting in resource waste. In addition, the existing technology also has high energy consumption in the process flow, and the waste gas generated in the process harms the environment and conflicts with the current "dual carbon" goals. It is necessary to study more green and low-carbon processing technologies to achieve high-quality utilization of valuable elements such as lithium, rubidium and cesium in lithium mica ores.

[0004] Lithium, rubidium and cesium are mainly extracted and recovered from pegmatites and salt lake brine, but the rubidium and cesium content and concentration of salt lake brine are low and the current technology does not have the value of independent development and utilization. Pegmatites represented by spodumene and lepidolite have simple spodumene ore composition and high lithium grade, with Li2O grade reaching 6% to 8%, but the domestic reserves of spodumene minerals are not high and mainly rely on imports, and large-scale industrial production cannot be carried out. Although the lithium, rubidium and cesium grade of lepidolite is low, and the extraction process has the disadvantages of valuable components not being able to be used in high quality, resulting in waste of resources, the development cost of lepidolite is low and the reserves are large, and it has extremely high economic value. If valuable elements such as lithium, rubidium and cesium in lepidolite can be efficiently developed and utilized, it can not only greatly reduce production costs, but also ensure the supply of lithium, rubidium and cesium resources, support the development of emerging industries, and achieve sustainable development of resources.

[0005] Lithium, rubidium and cesium in lepidolite exist mainly in the form of oxides. At the same time, the mineral contains 2% to 4% F, which is easy to form insoluble fluorides and affect the leaching rate of lithium, rubidium and cesium. At present, the acid method, alkali method, salt method and pressure cooking method are mainly used to recover lithium, rubidium and cesium and other valuable elements. For example, Yubo Liu et al. used the acid method to determine the experimental parameters through thermodynamic calculation simulation, so that the extraction rates of Li, Rb and Cs reached 90.5%, 91.2% and 89.4% respectively, realizing the selective extraction of lithium, rubidium and cesium. ZHANG used the sulfuric acid method to make Li, Rb and Cs exist in the leachate in the form of soluble sulfate, and the synergistic leaching rate of Li, Rb and Cs reached more than 95%, but there are disadvantages such as difficulty in deep removal of impurities and serious equipment corrosion. MULWANDA et al. used the mixed alkali method to use NaOH and Ca(OH)2 as mixed leaching agents. After pressure leaching, water washing, precipitation separation and other processes, the final leaching rates of Li, Rb and Cs reached 94%, 96% and 90% respectively. Since the impure cations in the solution will produce co-precipitation phenomenon, which affects the purity of the valuable elements, and the concentrated alkali waste liquid is difficult to recycle. Guo Chunping et al. used the sulfate method to mix potassium sulfate, calcium sulfate and barium sulfate as mixed sulfates with lithium mica in a ratio of 1:1, and then calcined at 900℃ for dilute acid leaching. The lithium leaching rate was 92.2%. Although the leachate can directly precipitate 0-grade lithium carbonate, the barium in the mixed salt is similar to rubidium and cesium in nature and can only replace part of rubidium and cesium. Therefore, the leaching rates of rubidium and cesium only reached 61.5% and 63.8% respectively. YAN et al. and Qiu Shiyuan et al. respectively used lime milk pressure cooking method and salt pressure cooking method, both of which used high temperature and high pressure conditions to pressure cook and dissolve valuable elements such as lithium, rubidium and cesium. The process conditions were harsh and industrialization was limited. Jinliang Wanga et al. used mixed salt roasting method, mixed Na2SO4 and CaCl2 and used thermodynamic model to simulate and calculate the optimal reaction conditions. After roasting and filtering and separation, the extraction efficiencies of Li, Rb and Cs were 98.70%, 97.27% and 98.40% respectively. YAN et al. used mixed salt roasting method, and the leaching rates of Li, Rb and Cs were 94.8%, 93.5% and 90.1% respectively after processes such as normal temperature water immersion and five-stage countercurrent washing. The salt method has high extraction efficiency, but the process produces toxic and harmful gases, which conflicts with the current "dual carbon" goal. Therefore, it is necessary to develop more green and low-carbon technologies to achieve efficient and coordinated extraction and recovery of valuable elements in lithium mica.

[0006] Based on the above reasons, this application is filed. Summary of the invention

[0007] In view of the complex composition and stable structure of lithium mica flotation concentrate, it is difficult to dissolve rubidium, cesium and lithium simultaneously and efficiently. The existing pressure cooking method, sulfuric acid / salt roasting method and other co-existing lithium, rubidium and cesium resources have poor endowment, lithium, rubidium and cesium synergistic dissolution is difficult, lithium, rubidium and cesium solution purification, enrichment and separation are difficult, and environmental pollution is easy to cause a series of key technical bottlenecks. The present invention provides a method for recovering co-existing low-grade valuable elements in lithium mica flotation concentrate by using normal pressure alkaline leaching method, which solves or at least partially solves the above technical defects existing in the prior art: the present invention uses the high chemical reaction activity provided by sub-molten salt unconventional alkali to realize the phase transformation of lithium mica flotation concentrate under normal pressure and recover valuable elements such as lithium, rubidium and cesium therein, improve the utilization efficiency of associated rubidium and cesium resources, and realize efficient and green leaching of lithium, rubidium and cesium resources.

[0008] In order to achieve the above-mentioned purpose of the present invention, the technical solution adopted by the present invention is as follows:

[0009] A method for recovering co-associated low-grade valuable elements in lepidolite flotation concentrate by using an atmospheric pressure alkali leaching method, the method specifically comprising the following steps:

[0010] S1, roasting the lepidolite flotation concentrate;

[0011] S2, adding an alkaline medium to the calcined lithium mica flotation concentrate, placing the resulting mixed reactant in a normal pressure reaction vessel, heating to 120° C. to 300° C. for constant temperature reaction for 1 to 10 hours;

[0012] S3, washing the product obtained after the reaction in S2, and performing solid-liquid separation to obtain a leachate and a leach residue;

[0013] S4, adjusting the pH value of the leachate obtained in S3 to 7.5-10, filtering and removing impurities, heating the leachate after impurity removal to 50°C-100°C, adding a precipitant, and continuing the constant temperature reaction until no crystals are precipitated; filtering to obtain a valuable element crystal precipitate and a filtrate;

[0014] S5, evaporating and concentrating the filtrate in S4, and then repeating steps S1-S4 to extract the valuable elements for the second time, and repeating the cycle.

[0015] Furthermore, in the above technical solution, the valuable element is specifically at least one of lithium, rubidium, cesium and the like.

[0016] Furthermore, in the above technical solution, the calcination temperature in step S1 is 800-1000° C., and the calcination time is 1-6 hours.

[0017] Furthermore, in the above technical solution, the alkaline medium in step S2 is an alkaline water mixed solution, which is composed of alkaline substances and deionized water. The mass concentration of the alkaline medium is 50%-80%.

[0018] Furthermore, in the above technical solution, the mass ratio of the lepidolite flotation concentrate to the alkaline medium in step S2 is 1:1-5.

[0019] Furthermore, in the above technical solution, the alkaline substance is one or more of sodium hydroxide, potassium hydroxide, aluminum hydroxide, sodium peroxide, and calcium hydroxide.

[0020] Furthermore, in the above technical solution, hydrochloric acid, sulfuric acid, oxalic acid or nitric acid is added in step S4 to adjust the pH value.

[0021] Furthermore, in the above technical solution, the precipitant in step S4 is at least one of a sodium carbonate solution or a sodium bicarbonate solution.

[0022] Furthermore, in the above technical solution, the mass concentration of the sodium carbonate solution or sodium bicarbonate solution is 30%-50%.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention adopts a normal pressure alkaline leaching method to recover valuable elements such as lithium, rubidium and cesium in lithium mica flotation concentrate, and the lithium, rubidium and cesium are green and highly efficient in synergistic leaching rate. In view of the problems of resource waste, high energy consumption and secondary pollution of the environment caused by the prior art, a method for realizing efficient synergistic recovery of lithium, rubidium and cesium in lithium mica flotation concentrate by using high reaction activity provided by unconventional alkaline media is provided. The process flow of the present invention is less time-consuming, the equipment operation is simple and safe, the synergistic recovery rate of lithium, rubidium and cesium is high, the impurity removal effect is good and secondary pollution is reduced, the medium recycling of subsequent processes can be realized, and the amount of subsequent lithium slag is sharply reduced. The average amount of lithium slag produced per ton of lithium mica ore is reduced by 80%, which provides a new theoretical reference for the extraction of low-grade co-existing lithium, rubidium and cesium resources in my country and the reduction of resource waste.

[0025] (2) The unconventional alkaline medium used in the present invention (the unconventional medium is a medium whose alkali concentration is different from that of an alkaline solution. When the alkali concentration is higher than 50%, the medium is a sub-molten salt medium, which is an intermediate medium between a solution and a molten salt and has a higher reaction activity) has a higher reaction activity and activity coefficient, and a high-concentration alkaline medium with an alkali concentration greater than 50% is used to reduce the wrapping on the surface of lithium fluoride, so that the reaction can continue. The active oxygen component present in large quantities in the unconventional alkaline medium of the present invention is the core of its high chemical reaction activity. The active oxygen in the medium can undergo homogeneous substitution at the O on the surface of the mineral, causing lattice distortion and gradually destroying the mineral structure, thereby achieving the leaching of useful elements in the mineral particles. Compared with the traditional pressure cooking method and the acid / alkali / salt method, the high chemical reaction provided by the unconventional alkaline medium makes the alkaline medium more advantageous in terms of thermodynamics and kinetics. In addition, the unconventional alkaline medium can be recycled to reduce resource waste, and the process is green and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 The present invention is a process flow chart of a method for recovering co-associated low-grade valuable elements in lepidolite flotation concentrate by using normal pressure alkali leaching method. DETAILED DESCRIPTION

[0028] The present invention proposes to use a sub-molten salt method to recover valuable elements such as lithium, rubidium, cesium, etc. in lepidolite flotation concentrate, in order to reduce energy consumption, improve the recovery rate of valuable elements, and realize green, low-carbon, and efficient leaching of valuable elements such as lithium, rubidium, cesium, etc. in lepidolite flotation concentrate.

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0031] Example 1

[0032] The source of the lithium mica flotation concentrate in this embodiment is as follows: from the tantalum-niobium mine in Yichun, Jiangxi Province, wherein the contents of lithium, rubidium, and cesium oxides Li2O, Rb2O, and Cs2O are 2.88%, 0.55%, and 0.051%, respectively. The lithium mica ore is sorted and pre-enriched to obtain the lithium mica flotation concentrate; wherein:

[0033] The separation and pre-enrichment treatment is specifically as follows: a pre-desliming-flotation combined process is adopted, the lithium mica ore is ground to 15-18um and then pre-deslimed by a hydrocyclone, and then a flotation process is adopted, hydrogen fluoride (200g / t) is added according to the amount of minerals to activate the mineral surface, after activating for 20 minutes, caustic soda (10Kg / t) is added to treat the mineral surface, and then an oleic acid collector is added to float the lithium mica to obtain a lithium mica flotation concentrate.

[0034] A method for recovering co-associated low-grade valuable elements in lepidolite flotation concentrate by using normal pressure alkali leaching in this embodiment comprises the following steps:

[0035] S1, take the above-mentioned lithium mica flotation concentrate and put it into a muffle furnace for high-temperature roasting at 900°C for 2h, then take 10g of the roasted lithium mica concentrate, add it into a sodium hydroxide sub-molten salt alkaline medium made of 15g of sodium hydroxide and 10ml of deionized water, mix well, and place it in a normal pressure reaction vessel, and react at 190°C for 5h to obtain a reaction product;

[0036] S2, washing the reaction product obtained in S1 with tap water until the volume is 600 ml, suction filtering and fixing the volume to 1000 ml to obtain alkaline leachate and leach residue;

[0037] S3, add 30wt% hydrochloric acid solution to the alkaline leachate obtained in S2 to adjust the pH to 8.5, filter and remove impurities, heat the leachate after impurity removal to 60°C, add 2.5ml of 50% Na2CO3 solution (precipitant), continue to react at a constant temperature of 60°C for 1h until crystals are completely precipitated; filter to obtain a carbonate crystal precipitate and a filtrate;

[0038] S4, after evaporating and concentrating the filtrate, sequentially carry out steps S1, S2, and S2 to perform secondary extraction of valuable elements of lithium, rubidium, and cesium.

[0039] Example 2

[0040] The sources of the lithium mica flotation concentrate in this embodiment are as follows: the content of lithium mica ore at a certain place, wherein the contents of lithium rubidium cesium oxides Li2O, Rb2O, and Cs2O are 3.27%, 1.02%, and 0.08%, respectively.

[0041] S1. Separate and pre-enrich the lepidolite ore to obtain lepidolite flotation concentrate; wherein:

[0042] The separation and pre-enrichment treatment is specifically as follows: determine to adopt a pre-desliming-flotation combined process, grind the lithium mica ore to 15-18um and then perform pre-desliming treatment in a hydrocyclone, then adopt a flotation process, add Ca(OCl)2 (200g / t) to activate the mineral surface according to the amount of minerals, activate for 15 minutes, wash and add caustic soda (10Kg / t) to treat the mineral surface, and then add oleic acid collector to float the lithium mica to obtain a lithium mica flotation concentrate.

[0043] A method for recovering co-associated low-grade valuable elements in lepidolite flotation concentrate by using normal pressure alkali leaching in this embodiment comprises the following steps:

[0044] The lithium mica flotation concentrate is placed in a muffle furnace for high-temperature roasting at 600° C. for 4 h, and then 15 g of the roasted lithium mica concentrate is added with an alkaline medium prepared by 10 g of sodium hydroxide, 10 g of potassium hydroxide and 10 g of deionized water, mixed evenly, and placed in a normal pressure reaction vessel, reacted at 220° C. for 7 h to obtain a reaction product;

[0045] S2, washing the reaction product obtained in S1 with deionized water until the volume is 200 ml, suction filtering and fixing the volume to 500 ml to obtain an alkaline leachate and leach residue;

[0046] S3, adding 40% nitric acid solution by mass to the alkaline leachate obtained in S2 to adjust the pH to 8, filtering to remove impurities, heating the leachate after impurity removal to 50° C., adding 1.5 ml of 60% Na2CO3 solution (precipitant), and continuing to react at a constant temperature of 50° C. for 2 h until crystals are completely precipitated; filtering to obtain a carbonate crystal precipitate and a filtrate;

[0047] S4, after evaporating and concentrating the filtrate, sequentially carry out steps S1, S2, and S3 to perform secondary extraction of valuable elements of lithium, rubidium, and cesium.

[0048] Example 3

[0049] The sources of the lithium mica flotation concentrate of the present embodiment are as follows:

[0050] The concentrate comes from a mineral processing plant in Jiangxi Province, in which the contents of lithium rubidium cesium oxides Li2O, Rb2O, and Cs2O are 2.86%, 1.75%, and 0.36% respectively.

[0051] S1. Separate and pre-enrich the lepidolite ore in sequence to obtain lepidolite flotation concentrate and tailings; wherein:

[0052] The separation and pre-enrichment treatment is specifically as follows: determine to adopt a pre-desliming-flotation combined process, grind the lithium mica ore to 15-18um and then perform pre-desliming treatment in a hydrocyclone, then adopt a flotation process, add sodium silicate (200g / t) to activate the mineral surface according to the mineral content, activate for 25 minutes, wash and add hydrochloric acid (10Kg / t) to treat the mineral surface, adjust the pulp pH: 3-9, and then add oleic acid collector to float the lithium mica to obtain the lithium mica flotation concentrate.

[0053] A method for recovering co-associated low-grade valuable elements in lepidolite flotation concentrate by using normal pressure alkali leaching in this embodiment comprises the following steps:

[0054] The lithium mica flotation concentrate is placed in a muffle furnace for high temperature roasting at 850°C for 3 hours. 5 g of the roasted lithium mica flotation concentrate is added with an alkaline medium prepared from 20 g of sodium hydroxide, 1 g of aluminum hydroxide and 15 g of deionized water, mixed evenly, and placed in a normal pressure reaction vessel for reaction at 180°C for 5 hours to obtain a reaction product;

[0055] S2, washing the reaction product obtained in S1 with deionized water until the volume is 600 ml, suction filtering and fixing the volume to 1000 ml to obtain alkaline leachate and leach residue;

[0056] S3, add 30% nitric acid solution by mass to the alkaline leachate obtained in S2 to adjust the pH to 8.5, remove impurities after filtering, heat the leachate after impurity removal to 80°C, add 1 ml of 30% Na2CO3 solution (precipitant), continue to react at a constant temperature of 80°C for 1 hour until crystals are completely precipitated; filter to obtain a carbonate crystal precipitate and a filtrate;

[0057] S4, after evaporating and concentrating the filtrate, sequentially carry out steps S1, S2, and S3 to perform secondary extraction of valuable elements of lithium, rubidium, and cesium.

[0058] The precipitates of valuable elements such as lithium, rubidium and cesium obtained in Examples 1-3 were analyzed, and the results are shown in Table 1.

[0059] Table 1 Product quality of lithium rubidium cesium precipitate

[0060]

[0061] As can be seen from Table 1, the invention patent examples 1-3 listed this time appropriately adjust the implementation scheme within the scope of this patent, and the quality and total content of the obtained lithium rubidium cesium precipitate are both above 90%. The lithium rubidium cesium and other valuable elements obtained by using the same implementation scheme of this patent in implementation case 1 are the best, and the synergistic recovery rate of valuable elements such as lithium rubidium cesium is high. At the same time, the process flow of the present invention is simple, the process is green and low-carbon, and the recycling of sub-molten salt medium is realized, which reduces resource waste, and finally realizes the green and efficient extraction of low-grade lithium rubidium cesium co-produced with lithium mica.

[0062] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment of the embodiment appropriately changed within the scope of the invention. Although the preferred embodiments of the present invention have been described, once those skilled in the art know the basic creative concept, they can make additional changes and modifications to these embodiments. Therefore, the attached claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0063] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for recovering co-associated low-grade valuable elements in lepidolite flotation concentrate by using normal pressure alkali leaching, characterized in that: The method specifically comprises the following steps: The method specifically comprises the following steps: S1, roasting the lepidolite flotation concentrate; S2, adding an alkaline medium to the calcined lithium mica flotation concentrate, placing the resulting mixed reactant in a normal pressure reaction vessel, heating to 120° C. to 300° C. for constant temperature reaction for 1 to 10 hours; S3, washing the product obtained after the reaction in S2, and performing solid-liquid separation to obtain a leachate and a leach residue; S4, adjusting the pH value of the leachate obtained in S3 to 7.5-10, filtering and removing impurities, heating the leachate after impurity removal to 50°C-100°C, adding a precipitant, and continuing the constant temperature reaction until no crystals are precipitated; filtering to obtain a valuable element crystal precipitate and a filtrate; S5, evaporating and concentrating the filtrate in S4, and then repeating steps S1-S4 to extract the valuable elements for the second time, and repeating the cycle.

2. The method according to claim 1, characterized in that: The valuable element is specifically at least one of lithium, rubidium and cesium.

3. The method according to claim 1, characterized in that: The calcination temperature in step S1 is 800-1000° C., and the calcination time is 1-6 hours.

4. The method according to claim 1, characterized in that: The alkaline medium in step S2 is an alkaline-water mixed solution, and the mass concentration of the alkaline medium is 50%-80%.

5. The method according to claim 1, characterized in that: The mass ratio of the lepidolite to the alkaline medium in step S2 is 1:1-5.

6. The method according to claim 1, characterized in that: The alkaline substance is one or more of sodium hydroxide, potassium hydroxide, aluminum hydroxide, sodium peroxide, and calcium hydroxide.

7. The method according to claim 1, characterized in that: In step S4, hydrochloric acid, sulfuric acid, oxalic acid or nitric acid is added to adjust the pH value.

8. The method according to claim 1, characterized in that: The precipitant in step S4 is at least one of a sodium carbonate solution or a sodium bicarbonate solution.

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