Method for complexing leaching of beryllium from lithium mica leaching residue

Abstract

This invention provides a method for complexing and leaching beryllium from lepidolite leaching residue. The lepidolite leaching residue is mixed with a sulfuric acid solution containing DTPA, and the pH is adjusted to 0.1-1.5, the DTPA concentration to 0.03-0.1 mol / L, and the solid-liquid ratio to 1g:8-15mL. The resulting slurry is ball-milled, and the exposed beryllium is in situ complexed by DTPA through mechanochemical processes to disrupt the mineral phase lock-in. After solid-liquid separation, a beryllium-containing filtrate and purified residue are obtained. This invention achieves a beryllium leaching rate of over 60%, effectively solving the problems of deep beryllium lock-in and deactivation of chelating agents under strong acid conditions. The process operates at room temperature and low energy consumption, showing promising prospects for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical beryllium extraction technology, specifically relating to a method for complexing leached beryllium from lepidolite leaching residue. Background Technology

[0002] The lithium extraction process from lepidolite generates a large amount of leaching residue, which is enriched with the highly toxic metal beryllium. If directly stockpiled or landfilled, beryllium will gradually leach and migrate into the soil and aquatic environment, posing a serious threat to ecosystems and human health. Therefore, deep beryllium removal treatment of lepidolite leaching residue to achieve its harmlessness and resource utilization has become an urgent environmental problem to be solved in the lithium smelting industry.

[0003] Existing technologies for treating beryllium-containing solid waste mainly include high-temperature roasting, solidification and stabilization, and conventional acid leaching. While high-temperature roasting can destroy the mineral structure, it is energy-intensive, requires demanding equipment, and is difficult to completely remove beryllium, easily causing secondary pollution. Solidification and stabilization only seals beryllium in the solidified body, failing to achieve complete removal, and long-term storage still poses environmental risks. Conventional acid leaching methods (such as direct sulfuric acid leaching) generally achieve beryllium leaching rates below 45% when treating lepidolite leaching residue. The reason for this is that the lepidolite leaching residue undergoes high-temperature, strong acid, or high-salt environments during lithium extraction, causing rearrangement and reconstruction of its original mineral structure. Beryllium is deeply locked within chemically stable aluminosilicate lattices or secondary precipitates such as calcium sulfate and calcium fluoride, with residual beryllium accounting for more than 50% of the total beryllium content. This unique secondary locking structure makes it difficult for conventional acid leaching to reach the beryllium sites, and simply increasing acidity or extending leaching time is ineffective. In addition, some studies have attempted to use mechanical activation pretreatment (such as ball milling followed by leaching), but the beryllium sites exposed by ball milling are very prone to secondary adsorption during subsequent leaching, or are mechanically encapsulated and carried away by the existing solid matrix such as calcium sulfate in the system, resulting in beryllium being locked again, and the leaching rate is still not ideal.

[0004] Therefore, how to achieve efficient and deep removal of beryllium from the leaching residue of lepidolite with deep locking characteristics, and avoid secondary adsorption and phase encapsulation of beryllium during the leaching process, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] Aiming to solve the technical problems of how to achieve efficient and deep removal of beryllium from lepidolite leaching residue with deep locking characteristics in the aforementioned commonly used technologies, and to avoid secondary adsorption and phase encapsulation of beryllium during the leaching process, this invention provides a method for complexing and leaching beryllium from lepidolite leaching residue, comprising the following steps: The leaching residue of lepidolite is mixed with a leaching agent to obtain a reaction slurry; the complexing agent includes diethylenetriaminepentaacetic acid; the leaching agent includes a complexing agent and an acid agent; The reaction slurry was sequentially ball-milled and separated into solid and liquid components to obtain a beryllium-containing filtrate and a purified residue.

[0006] Furthermore, the pH of the leaching agent is 0.1-1.5.

[0007] Furthermore, the pH of the leaching agent is 0.5-1.

[0008] Furthermore, the solid-liquid ratio of the lithium mica leaching residue to the leaching agent is 1g:8-15mL.

[0009] Furthermore, the concentration of diethylenetriaminepentaacetic acid in the leaching agent is 0.03-0.1 mol / L.

[0010] Furthermore, the rotation speed during the ball milling process is 300-600 rpm, and the ball milling time is 0.5-5 hours.

[0011] Furthermore, the acid agent includes at least one of sulfuric acid and nitric acid.

[0012] Furthermore, the chemical composition of the lepidolite leaching residue, by mass percentage, includes: SO3 20-30%, CaO 20-30%, SiO2 15-25%, Al2O3 10-15%, F ≤5%, K2O ≤5%, Fe2O3 ≤5%, and Na2O ≤5%.

[0013] Furthermore, the residual beryllium in the lepidolite leaching residue accounts for more than 50% of the total beryllium content.

[0014] Furthermore, the beryllium leaching rate is greater than 60%.

[0015] Compared with the prior art, the present invention has at least the following advantages: This invention provides a method for complexing and leaching beryllium from lepidolite leaching residue. The method involves mixing the lepidolite leaching residue with a leaching agent containing diethylenetriaminepentaacetic acid (DTA) and then directly ball-milling it. The mechanical force generated during ball milling disrupts the physical locking structure of the aluminosilicate lattice and secondary solid phase in the lepidolite leaching residue, exposing the coated beryllium sites. Simultaneously, the strong complexing ability of DTA, even under strong acid conditions, is utilized to chelate and lock the beryllium ions in situ the moment they are exposed, effectively suppressing secondary adsorption of beryllium ions and preventing them from being encapsulated by existing components such as calcium sulfate. Compared to existing technologies, this invention has the following advantages: It breaks through the technical bottleneck that conventional acid leaching is difficult to destroy the secondary locking structure. The total leaching rate of beryllium can reach more than 60%. With further optimization of parameters, the beryllium leaching rate can be optimized to more than 85%, which is significantly better than conventional stirring acid leaching (<45%) or ball milling followed by leaching process. It achieves simultaneous and in-situ synergy between mechanical barrier breaking and chemical complexation stability, avoids secondary locking of beryllium, and solves the problems of re-adsorption and phase encapsulation caused by barrier breaking followed by leaching in traditional processes. The process is carried out at room temperature, without the need for high-temperature roasting or high-pressure equipment, resulting in low energy consumption, simple operation, and good industrial applicability. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Figure 1 The image shows the XRD pattern of the lithium mica residue processed in Example 1 of this invention.

[0018] Figure 2 This is a line graph showing the beryllium leaching rate at different DTPA concentrations in Example 2 of this invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0021] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of the invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to the methods, devices, and materials in the embodiments of the present invention.

[0022] This invention provides a method for complexing leached beryllium from lepidolite leaching residue, comprising the steps of: S1. The leaching residue of lithium mica is mixed with the leaching agent to obtain a reaction slurry; the complexing agent includes diethylenetriaminepentaacetic acid; the leaching agent includes a complexing agent and an acid.

[0023] In some embodiments, the lepidolite leaching residue can be prepared by, but is not limited to, the following methods: lepidolite ore is mixed with sodium and calcium-containing additives (such as one or more of sodium sulfate, calcium carbonate, or calcium chloride) in a certain proportion, and then roasted at a high temperature of 800-950°C to fully replace the lithium in the layered structure of lepidolite with sodium, potassium, calcium, etc., causing the interlayer structure to collapse; after the roasted product is leached with water or dilute acid to extract soluble lithium salts, the solid residue obtained by solid-liquid separation is the lepidolite leaching residue.

[0024] More specifically, during the aforementioned high-temperature roasting and water leaching lithium extraction process, the aluminosilicates in the lepidolite ore undergo significant structural rearrangement and partial vitrification, while simultaneously generating a large amount of secondary phases such as calcium sulfate (existing in the forms of dihydrate and hemihydrate), calcium fluoride, and anorthite. These secondary phases intertwine and encapsulate with the residual aluminosilicate lattice of the ore, deeply encapsulating beryllium within them, forming a highly stable physically / chemically locked structure. X-ray diffraction analysis revealed that the phase composition of the lepidolite leaching residue includes: calcium sulfate dihydrate, calcium sulfate hemihydrate, anorthite, calcium fluoride, muscovite, etc.

[0025] For example, the chemical composition of the lepidolite leaching residue, by mass percentage, includes: SO3 20-30%, CaO 20-30%, SiO2 15-25%, Al2O3 10-15%, F ≤5%, K2O ≤5%, Fe2O3 ≤5%, Na2O ≤5%.

[0026] For example, the chemical composition of the lepidolite leaching residue, by mass percentage, includes: SO3 25-28%, CaO 22-26%, SiO2 18-22%, Al2O3 10-15%, F ≤5%, K2O ≤5%, Fe2O3 ≤5%, Na2O ≤5%.

[0027] In other embodiments, to further characterize the occurrence forms of beryllium in the lepidolite leaching residue, the BCR (European Communities Bureau of Reference) continuous extraction method was used for analysis. This method divides heavy metals in solid waste into four components: weakly acid-extractable (exchangeable), reducible, oxidizable, and residual. The analysis results showed that the weakly acid-extractable beryllium accounted for less than 40% of the beryllium in the lepidolite leaching residue, the reducible beryllium accounted for approximately 9%, the oxidizable beryllium accounted for approximately 1%, while the residual beryllium accounted for more than 50% of the total beryllium content. The residual beryllium is firmly bound in the aluminosilicate lattice or the glassy secondary precipitate phase, and is extremely difficult to release under conventional acid leaching conditions.

[0028] For example, the proportion of weakly acid-extractable beryllium in the lepidolite leaching residue can be 30-50%, the proportion of reducible beryllium can be 5-15%, the proportion of oxidizable beryllium can be ≤5%, and the proportion of residual beryllium can be 40-60%.

[0029] It is worth noting that the occurrence characteristics of beryllium in the leaching residue of lepidolite are fundamentally different from those in the raw lepidolite ore. In the raw ore, beryllium is mainly dispersed in the mica lattice in an isomorphous form and can be partially extracted through conventional acid leaching or mechanical activation. However, the beryllium in the leaching residue has undergone high-temperature roasting, lattice rearrangement, and encapsulation by derived phases, resulting in significantly higher chemical stability and locking strength compared to the raw ore. Therefore, conventional leaching or mechanical pretreatment methods for the raw ore are insufficient to achieve deep removal of beryllium from the leaching residue.

[0030] Based on the unique locking characteristics of beryllium in lepidolite leaching residue, this invention proposes a deep beryllium descaling method with interconnected and synergistic effects. Specifically, this invention achieves beryllium extraction by organically combining the following key elements: First, the pH of the leaching system is precisely controlled to be 0.1-1.5. This strong acid environment can effectively dissolve acid-sensitive phases such as calcium fluoride and induce microscopic exfoliation and structural loosening of the solid matrix such as calcium sulfate, thus initially loosening the physical encapsulation of beryllium. On the other hand, it provides the necessary conditions for the application of the specific complexing agent DTPA of this invention—DTPA maintains strong complexing activity within this pH range, overcoming the defect of common chelating agents (such as EDTA) that are protonated and deactivated under strong acid.

[0031] Secondly, diethylenetriaminepentaacetic acid (DTPA) was selected as the exclusive complexing agent. DTPA can form a stable soluble complex even under strong acid conditions, achieving capture-lock-desorption the moment beryllium sites are exposed. Effective complexation is completed in a very short time, avoiding secondary lock-up of partially exposed beryllium. Its complexing ability is significantly superior to conventional chelating agents such as EDTA.

[0032] Furthermore, an integrated process of mixing and ball milling is employed, rather than a stepwise operation of ball milling followed by leaching. During high-energy ball milling, mechanochemical effects continuously disrupt the aluminosilicate lattice and glassy coating, constantly exposing new beryllium sites; simultaneously, pre-existing DTPA molecules in the solution immediately react with the exposed Beryllium sites. 2+ Complexation occurs, locking the substance into a soluble state and rapidly detaching it from the solid-phase interface. This instantaneous linkage of exposure-complexation-detachment effectively avoids the exposure of bare Be. 2+In an unprotected state, it is re-adsorbed by the slag matrix, and the surface passivation and physical encapsulation caused by the in-situ recrystallization of inherent components such as CaSO4 at the newly formed high-energy interface are blocked. This mechanism successfully overcomes the technical bottleneck of traditional processes where the active sites are covered and locked by residual / associated biomass phases again due to the time and space lag after barrier breaking and leaching.

[0033] Finally, controlling the ball milling time further enhanced the aforementioned synergistic effect. Extending the ball milling time allows for the continuous application of mechanical force, gradually unlocking beryllium in deeper crystal layers. For example, with a ball milling time of 2 hours, the leaching rate was 75.9%; with a ball milling time of 4 hours, the leaching rate was 88.5%, demonstrating the gradual and irreplaceable nature of mechanochemical action.

[0034] In summary, the four elements of this invention—precise pH control, DTPA-specific complexing agent, integrated ball milling process after mixing, and appropriate ball milling time—are interdependent and interconnected, and none can be omitted. The absence of any single element or a change in its order (such as ball milling before adding DTPA) will lead to a significant decrease in beryllium leaching rate, which fully demonstrates the integrity and non-obviousness of the technical solution of this invention.

[0035] In some embodiments, the pH of the leachate is 0.1-1.5.

[0036] In some preferred embodiments, the pH of the leaching agent is 0.5-1. Within this pH range, the beryllium leaching rate can reach over 70% (see Examples 1 and 5); the effect is optimal when pH=1, with a leaching rate of 75.9%; when the pH exceeds this range (e.g., 1.5), the leaching rate drops significantly to 62.0%.

[0037] In some embodiments, the solid-liquid ratio of the lepidolite leaching residue to the leaching agent is 1g:8-15mL.

[0038] In some embodiments, the concentration of diethylenetriaminepentaacetic acid in the leaching agent is 0.03-0.1 mol / L.

[0039] In some preferred embodiments, the concentration of diethylenetriaminepentaacetic acid in the leaching agent is 0.05-0.1 mol / L. Within this concentration range, the beryllium leaching rate can reach 75.9%-79.3% (see Examples 1 and 4), which is significantly better than 71.2% at 0.03 mol / L; and the increase in concentration tends to be gradual after further increasing to 0.1 mol / L, thus balancing economy and leaching effect.

[0040] In some embodiments, the acid agent includes at least one of sulfuric acid and nitric acid.

[0041] S2. The reaction slurry is sequentially ball-milled and separated into solid and liquid components to obtain a beryllium-containing filtrate and a purified residue.

[0042] It should be noted that the mixing in step S1 can be carried out in advance outside the ball mill jar or directly inside the ball mill jar.

[0043] Ball milling refers to the continuous process in which the grinding balls move within the mill jar after the ball mill is started, exerting mechanical and chemical effects such as shearing, impact, and friction on the material. It does not include the static mixing stage when the material is simply placed in the ball mill jar or before the ball mill is started. Even if the material is premixed outside the ball mill jar, the DTPA in the leaching agent may have weak surface contact with the beryllium on the surface of the leaching residue, but no significant complex leaching will be formed; the real exposure of beryllium sites and in-situ complex locking mainly occur after the ball milling process is started - the mechanical force continuously destroys the aluminosilicate lattice and exposes fresh beryllium sites in real time, and the DTPA immediately chelates and locks them.

[0044] Therefore, in the ball milling embodiment described in this invention, it should not be understood that the material has already completed the complexation reaction during the mixing stage and then ball milling is performed; rather, it should be understood that after the ball milling process is started, the mechanochemical action destroys the lattice and exposes the beryllium sites in real time, while DTPA causes in-situ complexation locking—that is, mixing is only a preparation for material contact, and ball milling is the key step in triggering the real-time exposure-in-situ complexation synergistic mechanism. This limitation of the operation sequence effectively avoids secondary adsorption or precipitation of beryllium due to premature exposure or surface contact before ball milling, thereby ensuring the efficient leaching of beryllium.

[0045] In some embodiments, the rotation speed during the ball milling process is 300-600 rpm, and the ball milling time is 0.5-5 hours.

[0046] In some preferred embodiments, the ball milling time can be 3-5 hours. When the ball milling time is 3 hours, the leaching rate can reach 77.9%, and extending it to 4 hours can further increase it to 88.5% (see Example 2), achieving deep removal of beryllium; there is still room for improvement in the leaching rate when the milling time is extended to 5 hours, but considering both efficiency and energy consumption, 4 hours is preferred.

[0047] In some embodiments, the beryllium leaching rate is greater than 60%. Specifically, the above leaching effect can be achieved when the process parameters are controlled within the following ranges: the initial pH value of the leaching agent is 0.1-1.5, the DTPA concentration is 0.03-0.1 mol / L, the solid-liquid ratio is 1g:8-15 mL, the ball milling speed is 300-600 rpm, and the ball milling time is 0.5-4 hours; an integrated mixing and ball milling process is adopted.

[0048] In some embodiments, the beryllium leaching rate is greater than 70%. Specifically, the above leaching effect can be achieved when the process parameters are controlled within the following ranges: the initial pH value of the leaching agent is 0.5-1, the DTPA concentration is 0.03-0.1 mol / L, the solid-liquid ratio is 1g:8-15 mL, the ball milling speed is 300-600 rpm, and the ball milling time is 0.5-4 hours; an integrated mixing and ball milling process is adopted.

[0049] To facilitate a further understanding of the present invention by those skilled in the art, the following examples are provided: Example 1 S1. Take the leaching residue from lepidolite.

[0050] The XRF chemical composition of the lepidolite leaching residue, by mass percentage, includes: SO3 26.8%, CaO 24.1%, SiO2 19.9%, Al2O3 12.6%, F 3.9%, K2O 3.8%, Fe2O3 3.5%, and Na2O 2.7%. XRD analysis revealed that the main phases are calcium sulfate dihydrate, calcium sulfate hemihydrate, anorthite, calcium fluoride, and muscovite, etc. Figure 1 The image shows the XRD pattern of lithium mica residue.

[0051] The distribution of beryllium in lepidolite leaching residue was detected using the BCR continuous extraction method: weakly acid-extractable beryllium accounted for 40%, reducible beryllium accounted for 9%, oxidizable beryllium accounted for about 1%, and residual beryllium accounted for 50% of the total beryllium content.

[0052] Prepare a 0.05 mol / L DTPA sulfuric acid solution (leaching agent) and adjust the initial pH of the system to 1.0. Mix the lithium slag with this solution at a solid-liquid ratio of 1 g: 10 mL to obtain a reaction slurry.

[0053] S2. Place the reaction slurry in a planetary ball mill and ball mill it at 500 rpm at room temperature for 2 hours. After the reaction is completed, centrifuge to separate the beryllium-containing filtrate and purified residue.

[0054] Experimental results: The measured beryllium leaching rate was 75.9%.

[0055] Example 2 Compared to Example 1, the remaining steps in this example remain unchanged, except that the ball milling time in step S1 is adjusted to 4 hours.

[0056] Experimental results: The measured beryllium leaching rate was 88.5%. This example demonstrates that sustained mechanical activation can further unlock the matrix lock-in deep within the crystal lattice.

[0057] Analysis example 1 To investigate the effect of ball milling time on beryllium leaching rate, this analytical example, based on Example 1, kept other process conditions unchanged (DTPA concentration 0.05 mol / L, initial pH=1.0, solid-liquid ratio 1g:10 mL, ball milling speed 500 rpm), only the ball milling time was set to 0.5 hours, 1 hour, 2 hours, 3 hours, and 4 hours, and the beryllium leaching rate was measured at each time.

[0058] Experimental results showed that the beryllium leaching rate was 72.7% when the ball milling time was 0.5 hours; it increased to 73.2% after 1 hour; 75.9% after 2 hours; 77.9% after 3 hours; and further increased to 88.5% after 4 hours. The overall trend showed that the beryllium leaching rate continuously increased with the extension of the ball milling time, but the relationship was not a simple linear one: the increase in leaching rate was slow in the 0-3 hour stage; and the increase was significant after 3 hours.

[0059] This result demonstrates that beryllium in lepidolite leaching residue is deeply locked within the aluminosilicate lattice and glass phase. In the initial stage of mechanochemical action (0-3 hours), the surface and shallow locked structures are primarily disrupted. When the ball milling time accumulates to over 3 hours, it triggers large-scale dissociation and disintegration of the lattice, resulting in a concentrated exposure of a large amount of deeply locked beryllium within 1 hour. This beryllium is then promptly complexed and locked by DTPA, leading to a significant increase in leaching rate at 4 hours. This gradual-to-sharp leaching pattern fully illustrates that the real-time exposure-in-situ complexation synergistic mechanism of this invention has a cumulative triggering effect under continuous mechanical force and can achieve a sharp increase in beryllium release after exceeding the critical time. Therefore, appropriately extending the ball milling time to 4 hours can achieve a beryllium removal effect far exceeding that of conventional leaching, realizing the deep harmless treatment of lithium residue.

[0060] Example 3 Compared to Example 1, the remaining steps in this example remain unchanged, except that the concentration of DTPA in the leaching agent in step S1 is changed to 0.03 mol / L.

[0061] Experimental results: The measured beryllium leaching rate was 71.18%.

[0062] Example 4 Compared to Example 1, the remaining steps in this example remain unchanged, except that the concentration of DTPA in the leaching agent in step S1 is changed to 0.1 mol / L.

[0063] Experimental results: The measured beryllium leaching rate was 79.3%.

[0064] Analysis example 2 To investigate the effect of DTPA concentration on beryllium leaching rate, this analytical example, based on Example 1, kept other process conditions unchanged (initial pH = 1.0, solid-liquid ratio 1 g: 10 mL, ball milling speed 500 rpm, ball milling time 2 hours), except that the DTPA concentration of the leaching agent in step S1 was set to 0.01 mol / L, 0.03 mol / L, 0.05 mol / L, 0.07 mol / L, and 0.10 mol / L, respectively, and the beryllium leaching rate at each concentration was measured. The results are as follows: Figure 2 As shown.

[0065] Experimental results show that when the DTPA concentration is 0.01 mol / L, the beryllium leaching rate is only 49.8% (significantly low); when the concentration is increased to 0.03 mol / L, the leaching rate jumps to 71.2%, a very significant increase; further increasing the concentration to 0.05 mol / L, the leaching rate reaches 75.9%; increasing the concentration to 0.07 mol / L, the leaching rate is 77.8%; and reaching 0.10 mol / L, the leaching rate is 79.3%. The overall trend shows that as the DTPA concentration increases from 0.01 mol / L to 0.03 mol / L, the beryllium leaching rate increases dramatically; while in the range of 0.03-0.10 mol / L, the leaching rate increases gradually with increasing concentration, without any obvious plateau or decrease.

[0066] This result demonstrates that a certain DTPA concentration (approximately 0.03 mol / L) is required to effectively capture transiently exposed beryllium ions in a strong acid ball milling system, achieving in-situ locking. Below this threshold, the complexing agent is relatively insufficient, and some exposed beryllium fails to be complexed in time, resulting in secondary adsorption or encapsulation, leading to a low leaching rate. When the concentration exceeds 0.03 mol / L, further increasing the DTPA concentration has limited effect on improving the leaching rate. Considering both economy and leaching effect, the optimal concentration is 0.05 mol / L.

[0067] Example 5 Compared to Example 1, the remaining steps in this example remain unchanged, except that the pH of the leaching agent in step S1 is changed to 0.5.

[0068] Experimental results: The measured beryllium leaching rate was 70.7%.

[0069] Example 6 Compared to Example 1, the remaining steps in this example remain unchanged, except that the pH of the leaching agent in step S1 is changed to 1.5.

[0070] Experimental results: The measured beryllium leaching rate was 62.0%.

[0071] Analysis example 3 To investigate the effect of initial pH on beryllium leaching rate, this analytical example, based on Example 1, kept other process conditions unchanged (DTPA concentration 0.05 mol / L, solid-liquid ratio 1g:10 mL, ball milling speed 500 rpm, ball milling time 2 hours), only the initial pH of the leaching agent in step S1 was adjusted to 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 4.0, respectively, and the beryllium leaching rate under each pH condition was measured.

[0072] Experimental results show that: at an initial pH of 0.5, the beryllium leaching rate was 70.7%; at pH 1.0, the leaching rate reached its highest value of 75.9%; at pH 1.5, the leaching rate decreased to 62.0%; at pH 2.0, the leaching rate dropped to 39.3%; at pH 3.0, the leaching rate was 24.9%; and at pH 4.0, the leaching rate was only about 14.7%. The overall trend shows that the beryllium leaching rate is optimal (≥70%) within the pH range of 0.5-1.0; when pH > 1.0, the leaching rate begins to decrease, and the decreasing trend is extremely steep in the pH range of 1.0-2.0; when pH ≥ 3.0, the leaching rate is significantly low, and at pH 4.0, it is only about 14.7%.

[0073] This result demonstrates that the DTPA strong acid complexing system described in this invention is highly sensitive to pH. Under extremely low pH conditions (0.5-1.0), on the one hand, sulfuric acid can effectively dissolve acid-sensitive phases such as calcium fluoride and promote the loosening of secondary solid phase structures such as calcium sulfate, thus initially destroying the surface structure of aluminosilicates; on the other hand, DTPA retains excellent complexing activity within this pH range and can promptly capture beryllium ions exposed by mechanical forces.

[0074] Comparative Example 1 Compared to Example 1, all other conditions remain the same in this comparative example, except that the addition of DTPA in step S1 is removed.

[0075] Experimental results: The measured beryllium leaching rate was 44.4%. This demonstrates the necessity of DTPA in-situ complexation locking for improving the leaching rate.

[0076] Comparative Example 2 Compared to Example 1, all other conditions in this comparative example remain unchanged, except that ball milling in S2 is replaced with conventional mechanical stirring (500 rpm). The duration remains the same.

[0077] Experimental results: The measured beryllium leaching rate was only 41.6%. This proves that simple chemical mass transfer is insufficient to overcome physical matrix lock-in, and that mechanochemical effects play a decisive role.

[0078] Comparative Example 3 Compared to Example 1, all other conditions in this comparative example remain unchanged, except that equimolar amounts of DTPA are replaced with equimolar amounts of EDTA.

[0079] Experimental results: The beryllium leaching rate was measured to be 48.5%. This demonstrates that DTPA exhibits superior stability and compatibility in strong acid systems.

[0080] Comparative Example 4 Compared to Comparative Example 1, all other conditions in this comparative example remain unchanged, except that the sulfuric acid used in Comparative Example 1 is replaced with an equal amount of H+. + Nitric acid of a certain concentration.

[0081] Experimental results: The leaching rate was measured to be only 44.6%. This proves that the sulfuric acid medium has the best destructive effect on the mineral phase structure involved in this invention.

[0082] Comparative Example 5 Compared to Example 1, all other conditions remained the same in this comparative example, except that DTPA was replaced with an equimolar amount of citric acid.

[0083] Experimental results: The measured beryllium leaching rate was 67.8%.

[0084] Comparative Example 6 Compared to Example 1, all other conditions remained the same in this comparative example, except that DTPA was replaced with an equimolar amount of oxalic acid.

[0085] Experimental results: The measured beryllium leaching rate was 61.6%.

[0086] Comparative Example 7 The difference between this comparative example and Example 1 is that it adopts a step-by-step operation of first ball milling and activation, and then adding leaching agent and stirring for leaching, rather than the integrated process of mixing and ball milling of the present invention.

[0087] The specific steps are as follows: Take the same lepidolite leaching residue as in Example 1, without adding any leaching agent, and place it directly in a planetary ball mill. Dry grind it at 500 rpm for 2 hours to obtain ball-milled activated residue.

[0088] The obtained ball milling activated residue was mixed with a sulfuric acid solution containing DTPA, wherein the concentration of DTPA was 0.05 mol / L. The initial pH of the system was adjusted to 1.0 with sulfuric acid, and the solid-liquid ratio was 1g:10 mL. The mixture was leached for 2 hours under conventional mechanical stirring conditions (500 rpm, room temperature).

[0089] After the reaction was completed, centrifugation was performed to obtain filtrate and purified residue, and the beryllium content in the filtrate was determined.

[0090] Experimental results: The beryllium leaching rate was only 64.5% (significantly lower than 75.9% in Example 1).

[0091] This comparative example demonstrates that although ball milling alone can partially disrupt the mineral structure and expose certain beryllium sites, the lack of real-time in-situ protection from DTPA during the milling process leads to several problems. First, the exposed beryllium ions are easily re-adsorbed onto the highly active fresh mineral surface. Second, the inherent components in the system, such as CaSO4, readily recrystallize in situ at the newly formed high-energy interface, causing rapid surface passivation and physical encapsulation of the mineral surface, resulting in the re-covering and locking of beryllium sites. Therefore, even with the subsequent addition of a strong acid solution of DTPA, the leaching agent cannot effectively contact and disrupt this encapsulation layer due to physical barriers and significant mass transfer resistance, making it impossible to re-complex and leach the re-fixed beryllium.

[0092] Comparative Example 8 Compared to Comparative Example 7, the other conditions in this comparative example remained unchanged, except that dry grinding was replaced with wet grinding with water at a solid-liquid ratio of 1g:5mL.

[0093] Experimental results: The beryllium leaching rate was only 64.45%.

[0094] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A process for complexing leaching of beryllium from lithium mica leaching residue, characterized in that, Including the following steps: The leaching residue of lepidolite is mixed with a leaching agent to obtain a reaction slurry; the leaching agent includes a complexing agent and an acid agent; the complexing agent includes diethylenetriaminepentaacetic acid; The reaction slurry was sequentially ball-milled and separated into solid and liquid components to obtain a beryllium-containing filtrate and a purified residue.

2. The process for complexing leaching of beryllium from lithium mica leaching residue as claimed in claim 1 wherein, The pH of the leaching agent is 0.1-1.

5.

3. The process for complexing leaching of beryllium from lithium mica leaching residue as claimed in claim 1 wherein, The pH of the leaching agent is 0.5-1.

4. The method for complexing beryllium from lepidolite leaching residue according to claim 1, characterized in that, The solid-liquid ratio of the lepidolite leaching residue to the leaching agent is 1g:8-15mL.

5. The method for complexing beryllium from lepidolite leaching residue according to claim 1, characterized in that, The concentration of diethylenetriaminepentaacetic acid in the leaching agent is 0.03-0.1 mol / L.

6. The method for complexing beryllium from lepidolite leaching residue according to claim 1, characterized in that, The ball milling process involves a rotation speed of 300-600 rpm and a milling time of 0.5-5 hours.

7. The method for complexing beryllium from lepidolite leaching residue according to claim 1, characterized in that, The acid agent includes at least one of sulfuric acid and nitric acid.

8. The method for complexing beryllium from lepidolite leaching residue according to claim 1, characterized in that, The chemical composition of the lepidolite leaching residue, by mass percentage, includes: SO3 20-30%, CaO 20-30%, SiO2 15-25%, Al2O3 10-15%, F ≤5%, K2O ≤5%, Fe2O3 ≤5%, and Na2O ≤5%.

9. The method for complexing beryllium from lepidolite leaching residue according to claim 1, characterized in that, The residual beryllium in the lepidolite leaching residue accounts for more than 50% of the total beryllium content.

10. The method for complexing beryllium from lepidolite leaching residue according to any one of claims 1-9, characterized in that, The beryllium leaching rate is greater than 60%.

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