Process for extracting boron from high-salinity gray-brown salt lake clay

Abstract

The present application relates to the technical field of salt lake clay development, and particularly relates to a high-salinity gray-brown salt lake clay boron extraction process. The high-salinity gray-brown salt lake clay boron extraction process comprises the following steps: rough selection, water washing, drying, crushing and sieving of the high-salinity gray-brown salt lake clay, then fine particles are immersed in a leaching agent, and a leaching solution containing boron elements is obtained by filtration; wherein the leaching agent is prepared by compounding concentrated hydrochloric acid and low-mineralization water, the volume fraction of the concentrated hydrochloric acid is 20% to 50%, and the low-mineralization water is natural water in Mahai basin. The leaching agent is prepared by compounding the low-mineralization water in the basin and the hydrochloric acid, and the high-salinity gray-brown salt lake clay boron extraction process suitable for the Mahai area is proposed, so that the boron resources can be directly extracted from the salt lake clay.

Description

Technical Field

[0001] This invention relates to the field of salt lake clay development technology, and in particular to a boron extraction process for high-salinity grayish-brown salt lake clay. Background Technology

[0002] High-salinity saline lake clay refers to fine-grained clay layers deposited during the salt-forming stage (from brine concentration to salt precipitation) in the evolution of saline lakes. It is typically associated with evaporative salts (such as halite, potash, and borates), and its salt content is significantly higher than that of ordinary clay. Regions where this type of clay forms experience long-term annual evaporation rates far exceeding precipitation, leading to continuous concentration of surface / groundwater. Salt accumulates in the clay layer through capillary action. With continuous climate change, the clay minerals from the salt-forming period undergo illiteration and chloritization, ultimately resulting in the saline lake clay being situated in a high-salinity environment.

[0003] High-salinity saline lake clays are mainly concentrated in China's four major inland basins, exhibiting a "zonal arid zone distribution" characteristic. Among them, the clay minerals in the Qaidam Basin of Qinghai Province are mainly illite and chlorite, while also containing montmorillonite and kaolinite. The clay chemical composition is rich in K2O and MgO, and strategic metals such as boron, lithium, and rubidium are abnormally enriched. High-salinity saline lake clays are formed in high-salinity closed lake basin environments. Due to the unique chemical conditions of the saline lakes, they have a higher cation adsorption capacity and selectivity. Therefore, high-salinity saline lake clays show unique advantages in the extraction of valuable elements such as boron.

[0004] The Balunmahai area is located in the northwest of the Qaidam Basin in Qinghai Province. Its salt lake clay minerals mainly include kaolinite, illite, montmorillonite and chlorite. The area belongs to a typical inland arid climate zone, with annual evaporation far exceeding precipitation. These extreme climatic conditions cause surface water and groundwater to continuously concentrate as they converge into the lake basin, resulting in a continuous enrichment of dissolved salts. Shallow, high-salinity groundwater migrates upwards and evaporates under capillary action, causing salt to crystallize and precipitate in the vadose zone soil. Simultaneously, cohesive soils, due to stronger capillary action than sandy soils, are more prone to forming salt-enriched cohesive layers, resulting in rhythmic stratification in saline lake sedimentary profiles: the upper layer is an evaporative salt layer, which can be divided into clay with high halite content (referred to as halite-clay layer) and clay with high silt content (referred to as silt-clay layer); the lower layer consists of grayish-brown clay (shallow strata, oxidizing environment, containing brown minerals such as hematite) and grayish-green clay (deep strata, reducing environment, containing grayish-green minerals such as siderite), rich in illite and chlorite. Among these, the grayish-brown clay has relatively large reserves, with illite as the main clay mineral (rich in adsorbed boron, which can be extracted through acid leaching), making it a primary research target for boron extraction from high-salinity saline lake clay in the Mahai area.

[0005] Boron, with its unique chemical stability and high melting point, has become a key strategic material supporting modern science and technology and industrial development. Currently, the global boron supply relies on low-cost salt lake brine (accounting for more than 60%), but high-grade deposits are gradually being depleted. In the future, it is necessary to shift towards the extraction of low-grade brine and the development and utilization of resources such as salt lake clay to meet the continuous demand of emerging industries such as new energy and semiconductors.

[0006] Traditional boron extraction processes can be categorized into four main types based on the boron resource type: Salt lake brine extraction primarily uses solar evaporation, naturally or artificially concentrating and precipitating borax (e.g., in Turkey and the Qaidam Basin of China), which is low-cost but dependent on climate conditions; low-concentration brine extraction uses solvent extraction (e.g., in the Zabuye Salt Lake in Tibet), but the process is complex. Volcanic rock extraction commonly uses water leaching to dissolve borosilicate or sodium borate (e.g., in the Mt. Fuji mining area of ​​Japan), which is simple but inefficient; high-grade mines supplement this with alkaline leaching to improve the leaching rate. In sedimentary rock extraction, sulfate ores undergo high-temperature pyrolysis (e.g., in the Aktobe mining area of ​​Kazakhstan) to produce boron oxides, which is energy-intensive; potassium magnesium salt ores are separated from boron minerals through flotation (e.g., in the lithium salt lakes of Peru). Hard rock extraction (e.g., granite) often uses acid leaching (sulfuric acid / hydrochloric acid), but this is costly and highly polluting. Traditional boron extraction processes generally suffer from low efficiency, high energy consumption, and heavy environmental burdens. For example, salt lake mining is limited by geographical and climatic conditions, volcanic rock mining requires processing low-grade raw materials, and hard rock extraction is costly. As resources gradually dwindle, the available high-quality salt lake brine resources can no longer meet future development needs. Developing new technologies and new resource sites is an urgent need for various industries.

[0007] The clay layers of the salt lakes in the Mahai area of ​​Qinghai Province contain considerable boron resources, making their effective utilization crucial. Despite these abundant reserves, extracting boron from the clay of the Mahai salt lakes in Qinghai remains a significant challenge. The clay composition of the salt lakes in this region is complex, and conventional filtration and precipitation methods consume large amounts of chemical reagents and are costly. Furthermore, there are few readily available technological advancements; traditional methods such as solar evaporation struggle to precisely control the boron extraction process, easily leading to the formation of low-grade mixed salt layers and resulting in low boron recovery rates. Summary of the Invention

[0008] The purpose of this invention is to address the aforementioned shortcomings of the prior art by proposing a boron extraction process from high-salinity gray-brown salt lake clay.

[0009] The present invention discloses a boron extraction process from high-salinity grayish-brown salt lake clay, comprising the following steps: coarsely selecting, washing, drying, crushing and sieving the high-salinity grayish-brown salt lake clay, then impregnating the fine particles in a leaching agent, and filtering to obtain a leachate containing boron; wherein the leaching agent is prepared by using concentrated hydrochloric acid and low-mineralized water, the volume fraction of concentrated hydrochloric acid being 20%~50%, and the low-mineralized water being natural water from the Mahai Basin.

[0010] Furthermore, the leaching temperature is 25℃~55℃.

[0011] Furthermore, the leaching temperature is 35℃~50℃.

[0012] Furthermore, the soaking time is 15 min to 60 min.

[0013] Furthermore, the soaking time is 35 min to 45 min.

[0014] Furthermore, the liquid-to-solid ratio of the leaching agent and the sedimentary gray-green salt lake clay is 3-6:1.

[0015] Furthermore, the leaching temperature is 25℃~55℃, the leaching time is 35min~45min, the liquid-solid ratio of the leaching agent and the sedimentary gray-green salt lake clay is 3-5:1, and the volume ratio of concentrated hydrochloric acid and low-mineralized water is 40%~50%.

[0016] Furthermore, stirring is used to assist impregnation under constant temperature conditions.

[0017] Furthermore, the particle size of the fine particles is less than 16 mesh.

[0018] In response to the challenges posed by freshwater scarcity and high salinity of salt lake clay in Qinghai Province, this invention proposes a highly efficient boron extraction process for high-salinity, grayish-brown salt lake clay. This process utilizes a mixture of hydrochloric acid and local low-mineralized water as the leaching agent, thereby reducing the Ca content in the low-mineralized water. 2+ Mg 2+ The addition of B can be combined with B 3+ An exchange process occurs; under the influence of ion exchange and permeation, the pore structure shifts from micropores to macropores and then decomposes back into micropores, altering the morphology of the mineral particles and resulting in a looser internal structure of the clay minerals, which facilitates the leaching of boron. During the leaching process, the crystal lattice structure of the clay minerals is disrupted by strong acids, and simultaneously, under the action of hydrochloric acid, H... + And other cations in low-mineralized water (such as Na) + (etc.) and B(OH)4 on the clay surface - Competitive exchange occurs, producing soluble boric acid (H3BO3) or borate ions (BO3). 3- This can effectively promote the leaching of boron and, when combined with anions in the leaching agent (such as Cl), can effectively promote the leaching of boron. - Boron can form a soluble complex with boric acid, thereby improving the stability of boron in solution, reducing re-adsorption or precipitation, and further improving the leaching rate of boron.

[0019]

[0020]

[0021] This invention uses a mixed solution of hydrochloric acid and low-mineralized water as a leaching agent: according to the experimental design, a specific amount of concentrated hydrochloric acid and low-mineralized water are weighed, and the hydrochloric acid is slowly added to the low-mineralized water to prepare the leaching agent used in the process. At the same time, the heat generated in the preparation process is used for subsequent leaching, which realizes full utilization of heat and can save a lot of resources. Attached Figure Description

[0022] Figure 1 A schematic diagram of the process flow of this invention; Figure 2 pH-I single-factor experiment on B 3+ The effect of simulated adsorption; Figure 3 Nuclear magnetic resonance T2 spectra: a. Freshwater column immersion; b. Pore distribution map of freshwater column immersion; c. Ion immersion column; d. Pore distribution map of ion immersion column; Figure 4 Pore ​​size distribution at different times: a. Freshwater immersion column; b. Ion immersion column. Detailed Implementation

[0023] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0024] Technical solution (1) Preparation of leaching samples First, large impurities such as gypsum are removed. Then, the high-salinity, grayish-brown salt lake clay is washed with water to remove salt and reduce its impact on the subsequent leaching process. The clay samples are then dried in a vacuum drying oven at a low temperature (50-60℃). Samples taken from different sampling points are then mixed to reduce variability between sampling points and improve sample representativeness. Subsequently, the samples are coarsely crushed with a crushing hammer, finely ground with a mortar and pestle, and finally passed through a 16-mesh sieve. The resulting clay is the sample used in the leaching experiment.

[0025] (2) Preparation of leaching agent To prepare the required concentration of hydrochloric acid and low-mineralization water leaching agent (taking a 20% concentrated hydrochloric acid leaching agent as an example): Take 4000 mL of low-mineralization water in a volumetric flask, and measure the solution temperature at this point as 25℃. Then, slowly add a total of 1000 mL of concentrated hydrochloric acid (37%) to the volumetric flask in multiple portions to obtain the leaching agent required for acid leaching. The solution temperature at this point is measured as 53℃. Since temperature promotes the leaching effect during the leaching process, the heat generated during the preparation of the leaching agent can be used for subsequent leaching, improving energy utilization and saving significant costs.

[0026] Table 1. Composition and content of low-mineralized water

[0027] According to the data in Tables 1 and 2, the boron content in the leaching solution decreased after adding hydrochloric acid to low-mineralized water to prepare a compound leaching agent, and the decrease trend was progressively greater with increasing hydrochloric acid concentration. This indicates that the addition of hydrochloric acid can effectively reduce the initial boron content in low-mineralized water, thereby reducing its interference with the subsequent leaching process.

[0028] Table 2. Composition and content of the solution after mixing hydrochloric acid and low-mineralization water

[0029] (3) Content detection: Based on the testing requirements, boron in the leachate and leaching residue were tested separately. The laboratory developed corresponding analytical method protocols according to the sample properties and the requirements of the "Geological and Mineral Resources Laboratory Testing Quality Management Standard (DZ / T 0130-2006)" (hereinafter referred to as the "Standard").

[0030] 1) Standards and methods for testing immersion solutions: Table 3. Analysis methods and standards for liquid samples

[0031] Brief flowchart of the analysis method: Accurately pipette 2.5 mL of the leachate sample into a 30 mL polytetrafluoroethylene crucible, heat it on a constant temperature hot plate to remove sulfuric acid, extract with HCl, and dilute to 100 mL in a volumetric flask. Plot a standard curve in 10% HCl medium using a mixed standard solution, determine B2O3 by ICP-MS, and automatically correct for matrix and spectral interferences by computer.

[0032] 2) Standards and methods for testing leaching residue: Table 4. Analytical methods and standards for solid samples

[0033] Brief flowchart of the analysis method: Weigh 0.1000 g of sample, add 0.1000 g of buffer, grind evenly in a mortar, load into the electrode, use germanium as internal standard, and perform AC vertical polarity spectroscopy on the electrode. Use a CCD-I type powder solid sample arc emission spectrometer with automatic background removal to determine boron.

[0034] Leaching conditions (factors) Boron was extracted from halite clay, silty clay, grayish-brown clay, and grayish-green clay using a prepared leaching agent. An orthogonal experiment was conducted, selecting four factors: leaching temperature, leaching time, concentrated hydrochloric acid volume fraction, and liquid-to-solid ratio. Each factor had four levels, resulting in sixteen orthogonal experiments. The factor levels are shown in Table 5. The leaching products were analyzed, the leaching rate was calculated, and the optimal experimental ratio was selected. The liquid-to-solid ratio represents the ratio of the leachate volume to the clay sample mass; for example, 3:1 means leaching 100g of sample with 300 mL of leachate.

[0035] Table 5. Factor Level Table for Orthogonal Experiment

[0036] Leaching Experiment Procedure like Figure 1 As shown, accurately weigh 100.00 g of dry clay sample into a 1 L beaker; add the leaching agent to the beaker while stirring; place the beaker in a heated ultrasonic cleaner, set the temperature and time conditions, and turn on the top-mounted stirrer to perform stirring and leaching. After the reaction is complete, immediately remove the beaker and use a circulating water vacuum pump to filter the leached suspension to obtain the leaching solution and leaching residue.

[0037] Leaching rate calculation:

[0038] To ensure accurate leaching rate calculation, the initial boron content in the compound leaching agent used was deducted from the boron content of the leachate.

[0039] Investigation of the leaching mechanism Based on the types and characteristics of clay minerals in the clay layer, experiments such as adsorption simulation and column leaching were conducted to understand the adsorption and migration mechanism of boron in clay minerals and to better explain the leaching mechanism of boron during acid leaching.

[0040] The clay minerals in the Balunma Sea salt lake mainly include kaolinite, illite, montmorillonite, and chlorite. These clay minerals differ in crystal structure, chemical composition, specific surface area, interlayer spacing, and mineral charge, resulting in variations in their adsorption capacity and mechanisms. Therefore, these four minerals were used to conduct adsorption simulations to comprehensively evaluate the boron leaching mechanism in the clay minerals.

[0041] like Figure 2 As shown, when the pH value increases from 4 to 7, the B³ of clay minerals... + The adsorption capacity fluctuated within the range of 2.4-2.7 mg / g, showing no significant trend. When the pH value was greater than 7, the B³ of illite and kaolinite... +The adsorption capacity reached its maximum at pH=8; while the adsorption capacity of kaolinite showed a linear increasing trend after pH>8, and the adsorption capacity of chlorite decreased. Overall, clay minerals have a greater affinity for B³. + The adsorption mainly occurs in a weakly alkaline environment (pH 7~8), indicating that this condition is favorable for the adsorption reaction.

[0042] Under lower ionic strength conditions, as the pH increases from 4 to 7, the B³ of clay minerals... + The adsorption capacity fluctuated within the range of 120–180 μg / g, but showed an overall upward trend. This is contrary to the adsorption behavior under acidic conditions, indicating that an acidic environment is unfavorable for B³. + The adsorption of H. The reason for this may be that: with the adsorption of H... + As the concentration increases, a large amount of H + Adsorbed by negatively charged clay minerals, and with B³ + Competitive adsorption occurs, leading to some of the already adsorbed B³ + It is desorbed into the solution.

[0043] To investigate the changes in the pore structure of clay, two groups of clay samples were subjected to column immersion tests: one group used samples containing Ca²⁺. + / Mg² + One group used a solution as the leachate, while the other group used deionized water as a control.

[0044] like Figure 3 As shown in (a) and (b), clay samples subjected to column leaching with deionized water (fresh water) rapidly reached saturation within 0.5 hours of leaching initiation. During this process, a rapid increase in the T2 spectrum curve and its corresponding relaxation time envelope area was observed. This is mainly due to the significant changes in the pore structure caused by the water absorption and swelling of the clay in the early stages of leaching (no obvious ion exchange reaction has yet occurred at this stage). Subsequently, the T2 spectrum curves at each time point basically no longer shifted, indicating that steady-state seepage was formed after the clay reached saturation, and a relatively fixed microchannel structure was established internally, with the pore structure tending to stabilize.

[0045] like Figure 3 As shown in (c) and (d), within the first hour of leaching, the clay ore gradually reached saturation under the action of CaCl2 and MgCl2 leaching solutions. The buoyancy of water altered the mineral particle distribution, leading to a significant increase in the envelope area of ​​the T2 spectrum curve, indicating a marked increase in the number of pores. As leaching continued for the last 3 hours of the saturation period, the envelope area of ​​the T2 spectrum curve did not change significantly, indicating that the number of pores in the saturated soil sample remained relatively stable. However, during this stage, Ca²⁺… + Mg² + With B³ in the clay mineral lattice +Ion exchange occurs, altering the morphology of mineral particles and causing the T2 spectrum curve of ion leaching clay minerals to gradually shift to the right, with a decrease in the transverse relaxation time span. This indicates a transformation in the internal pore structure of the sample from large pores to medium and small pores, resulting in a change in pore distribution characteristics. The size of the pore radius within clay minerals is primarily controlled by their microstructure. The better the connectivity of the pore structure, the larger the pore radius typically is. Based on the classification criteria for pore radius and actual test results, pores can be divided into the following five categories: 0-0.1 μm are micropores, >0.1-0.16 μm are small pores, >0.16-0.25 μm are mesopores, >0.25-1 μm are macropores, and >1 μm are ultramacropores. Figure 4 As shown in (a) and (b), during freshwater column leaching and ion column leaching, although they were in different leaching stages, the internal pores of the clay were mainly small and medium pores, with medium pores accounting for the largest proportion and large pores accounting for a smaller proportion.

[0046] Using Ca² + Mg² + During the leaching of the solution, in the initial stage of leaching, as the clay sample gradually reaches saturation, Ca²⁺… + Mg² + With B in clay minerals 3+ An ion exchange reaction occurs. This reaction disrupts the van der Waals forces between large clay particles, causing them to break down into smaller particles, thus increasing the number of small particles. Correspondingly, the number of micropores and mesopores increases, while the number of macropores decreases significantly. In the later stages of leaching, microparticles migrate under the influence of water flow and enter the micropores, resulting in a significant reduction in the number of pores with a radius greater than 1 μm. When B... 3+ After the exchange reaction is completed, under the action of a stable seepage field, the pore morphology and its distribution tend to stabilize.

[0047] Column immersion experiments show that, under the bidirectional coupling of the seepage field and the chemical field, Ca, with its larger ionic radius, 2+ Mg 2+ With B in clay minerals 3+ Exchange occurs, altering the morphology of the mineral particles and resulting in a looser internal structure of the clay minerals, which is beneficial for B during the leaching process. 3+ The migration indicates the addition of Ca 2+ Mg 2+ It is beneficial for the leaching of boron.

[0048] Examples and Comparative Examples To compare the leaching effects of different solvents, three solvents were selected: low-mineralized water, hydrochloric acid plus low-mineralized water, and hydrochloric acid plus fresh water. High-salinity grayish-brown salt lake clay from the Mahai area was used as the research object for leaching experiments to investigate the influence of the solvent on the final leaching effect of the boron extraction process. The results are as follows: where L represents low-mineralized water, D represents fresh water, SY represents halite layer clay, FS represents silty sand layer clay, HH represents grayish-brown clay, HL represents grayish-green clay, and C represents hydrochloric acid. For example, L-HH-C represents a series of orthogonal experiments related to the leaching of grayish-brown clay using hydrochloric acid and low-mineralized water as solvents.

[0049] Case 1: Table 6. Orthogonal experimental results of water-soluble grayish-brown clay with low mineralization

[0050] Table 6 shows that the leaching effect of the 16 orthogonal experiments was poor. B in the leaching residue... 3+ The average content was 194.66 μg / g, while the extract contained B. 3+ The average content was only 10.07 μg / mL. It is noteworthy that the extract contained B... 3+ The content was even slightly lower than the initial value in low-mineralized water. This indicates that low-mineralized water alone cannot effectively disrupt the clay mineral structure, thus making it difficult to leach boron. Simultaneously, some boron is likely adsorbed by the leaching residue, which also contributes to the low boron content in the leachate. 3+ A key reason for the low content.

[0051] Case 2: Table 7. Results of orthogonal experiments on the dissolution of gray-brown clay by hydrochloric acid and fresh water.

[0052] Table 7 shows the results of an orthogonal experiment using hydrochloric acid and fresh water as the leaching solvent. The data shows that B in the leaching residue 3+ The average content was 95.34 μg / g, while the extract contained B. 3+ The average content was 62.72 μg / mL, with the highest boron leaching rate at around 79%. Eight groups had leaching rates above 75%, with an average leaching rate of 73.54%. Comparison with Case 1 and Case 2 revealed that the addition of acid significantly enhanced the boron leaching effect, indicating that hydrochloric acid can release H₂O. + Disrupting the crystal structure of clay minerals allows boron to be released from silicates, aluminates, or other minerals and enter the solution as borate ions, thereby increasing the leaching rate.

[0053] Case 3: Table 8. Results of orthogonal experiments on hydrochloric acid + low-mineralization water-soluble gray-brown clay

[0054] Table 8 shows the orthogonal experimental results of using a leaching agent formulated with hydrochloric acid and low-mineralized water (leaching rate has been reduced by the initial B of the leaching agent). 3+ Value). Data shows that B in the leaching residue 3+ The average content was 33.17 μg / g, while the extract contained B. 3+ The average boron content was 79.55 μg / mL, with a maximum boron leaching rate of 93.26% and an average leaching rate of 88.25% (13 experimental groups achieved over 85%). Comparing Case 1 and Case 2, the residual boron content in this compound system was significantly reduced, and the overall leaching effect was significantly improved, indicating that more boron was extracted into the leachate. The mechanism is presumably related to the Ca²⁺ content in the low-mineralized water. + Mg² + It undergoes ion exchange with boron in minerals, altering the particle morphology of the ore and making its internal structure looser and more porous. Under seepage, this facilitates the migration of boron (such as borate ions) into the solution, thereby allowing it to react with H+ in hydrochloric acid. + The destructive effect creates a synergistic effect, while the anions (such as Cl) in it... - By forming a soluble complex with boric acid, boron can be stabilized in solution, thereby reducing re-adsorption or precipitation. Through the synergistic effect of multiple factors, efficient leaching of boron is promoted.

[0055] The data comparisons in the above cases reveal the significant impact of different leaching agents and leaching conditions on the boron leaching rate. Case 3, using hydrochloric acid and low-mineralized water as the leaching agent, demonstrates superior performance in terms of leaching efficiency, economy, and energy consumption, meeting production requirements. Therefore, based on this approach, orthogonal experiments were conducted on different layers of saline lake clay using hydrochloric acid and low-mineralized water as the leaching agent to systematically study the influence of this leaching agent on the boron leaching effect in clay from different layers.

[0056] An Investigation into the Leaching Effect of Hydrochloric Acid with Low-Mineralization Water-Based Leaching Agent on Different Clays The leaching effects of halite layer clay, silty clay, and gray-green clay were studied and compared with the leaching results of gray-brown clay experimental group to explore the leaching effect of compound leaching agent on different clays.

[0057] Case 4: Table 9. Results of orthogonal experiments on halite layer clay

[0058] Table 9 shows the orthogonal experimental results of leaching halite clay using a compound solvent of hydrochloric acid and low-mineralized water (leaching rate has been reduced by the initial B of the solvent). 3+Value). Data shows that B in the leaching residue 3+ The average content was 94.70 μg / g, while the extract contained B. 3+ The average content was 61.56 μg / mL, with a maximum boron leaching rate of 71.47% and an average leaching rate of 62.78%. This indicates that changes in leaching conditions have a limited impact on the leaching effect for halite clay. It is speculated that this may be because the halite clay contains a high amount of other salt minerals, which hinder boron leaching, making effective leaching difficult using hydrochloric acid and low-mineralized water.

[0059] Case 5: Table 10. Results of orthogonal experiments on silty clay layers

[0060] Table 10 shows the orthogonal experimental results of leaching silty clay layers using a compound solvent of hydrochloric acid and low-mineralization water (leaching rate has been reduced by the initial B of the solvent). 3+ Value). Data shows that B in the leaching residue 3+ The average content was 105.63 μg / g, while the extract contained B. 3+ The average content was 55.99 μg / mL, with a maximum boron leaching rate of 65.57% and an average leaching rate of 59.39%. This indicates that, similar to halite layers, the high content of silt and evaporite minerals in the clay layer hinders boron leaching. Therefore, the method of using hydrochloric acid and low-mineralized water is not suitable for extracting boron from silty clay layers.

[0061] Case Six: Table 11 Results of orthogonal experiments on gray-green clay

[0062] Table 11 shows the orthogonal experimental results of leaching gray-green clay using a compound solvent of hydrochloric acid and low-mineralized water (leaching rate has been reduced by the initial B of the solvent). 3+ Value). Data shows that B in the leaching residue 3+ The average content was 91.52 μg / g, while the extract contained B. 3+ The average content was 40.44 μg / mL, with a maximum boron leaching rate of 54.81% and an average leaching rate of 47.75%. For the gray-green clay, the overall leaching effect was poor. Changes in leaching conditions could effectively affect the leaching effect, presumably because the organic matter in the gray-green clay interfered with the leaching process. Special treatment may be required before leaching; leaching with hydrochloric acid and low-mineralized water alone was not ideal.

[0063] Comparative analysis of leaching conditions for different types of high-salinity saline lake clay in the Mahai area revealed that, under consistent experimental conditions such as leaching temperature, leaching time, and liquid-solid ratio, the leaching effect of boron was significantly improved in the group using both low-salinity water and hydrochloric acid compared to the groups using fresh water and hydrochloric acid. Furthermore, compared to clay layers, the leaching effect of using a compound leaching agent of hydrochloric acid and low-salinity water in grayish-brown clay was significantly better. Therefore, a compound leaching agent of hydrochloric acid and low-salinity water can be used as an effective leaching agent to improve the leaching effect of boron in high-salinity grayish-brown saline lake clay in the Mahai area.

[0064] In summary, this patent explored the extraction effects and conditions of boron from clay layers at different strata through orthogonal leaching experiments, and innovatively proposed an extraction process and corresponding parameters for boron from high-salinity grayish-brown saline lake clay in the Mahai Basin of Qinghai Province. Furthermore, the exothermic reaction during the preparation of the leaching agent can be used in subsequent leaching processes, achieving full utilization of energy. Therefore, this process meets the dual needs of industrial production and environmental protection in the Mahai Basin and can be applied locally.

[0065] For any points not covered above, existing technologies shall apply.

[0066] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A boron extraction process from high-salinity grayish-brown salt lake clay, characterized in that, The process includes the following steps: coarsely selecting, washing, drying, crushing and sieving high-salinity gray-brown salt lake clay, then impregnating the fine particles in a leaching agent and filtering to obtain a leachate containing boron; wherein the leaching agent is prepared by mixing concentrated hydrochloric acid and low-mineralized water, with the volume fraction of concentrated hydrochloric acid being 20%~50% and the low-mineralized water being natural water from the Mahai Basin.

2. The boron extraction process from high-salinity grayish-brown salt lake clay as described in claim 1, characterized in that, Leaching temperature: 25℃~55℃.

3. The boron extraction process from high-salinity grayish-brown salt lake clay as described in claim 1, characterized in that, Leaching temperature: 35℃~50℃.

4. The boron extraction process from high-salinity grayish-brown salt lake clay as described in claim 1, characterized in that, Soaking time: 15 min to 60 min.

5. The boron extraction process from high-salinity grayish-brown salt lake clay as described in claim 1, characterized in that, Soaking time: 35-45 minutes.

6. The boron extraction process from high-salinity grayish-brown salt lake clay as described in claim 1, characterized in that, The liquid-solid ratio of the leaching agent to the sedimentary gray-green salt lake clay is 3-6:

1.

7. The boron extraction process from high-salinity grayish-brown salt lake clay as described in claim 1, characterized in that, Leaching temperature: 25℃~55℃, immersion time: 35min~45min, liquid-solid ratio of leaching agent to sedimentary gray-green salt lake clay: 3-5:1, volume ratio of concentrated hydrochloric acid to low-mineralized water: 40%~50%.

8. The boron extraction process from high-salinity grayish-brown salt lake clay as described in claim 1, characterized in that, Stirring is used to assist impregnation under constant temperature conditions.

9. The boron extraction process from high-salinity grayish-brown salt lake clay as described in claim 1, characterized in that, The particle size of the fine particles is less than 16 mesh.

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