Method for efficiently extracting barite single mineral from black mudstone rich in organic matters

Abstract

The invention relates to the technical field of mineral extraction, particularly discloses a method for efficiently extracting barite single mineral in black mudstone rich in organic matters, and solves the technical problems that micron-sized barite in black mudstone cannot be efficiently extracted in the prior art, lattice destruction / isotope fractionation of barite is easily caused in the extraction process, the purity and the recovery rate are low and the like. The purity of the extracted barite single mineral is larger than or equal to 99%, the recovery rate of fine-fraction barite is larger than or equal to 90%, crystal lattices are complete and free of damage, isotope fractionation and component change are avoided, and the high-precision geochemical test requirement can be met; meanwhile, the method is suitable for various sedimentary rocks such as marine / continental black mudstone, shale and siliceous mudstone, and the applicability is wide.

Description

Technical Field

[0001] The invention belongs to the field of mineral extraction technology, specifically relating to an efficient extraction method for micron-sized barite single minerals in organic-rich black mudstone, which is particularly suitable for extracting biogenic barite single minerals with a particle size of <10μm in black mudstone. Background Technology

[0002] Organically enriched black mudstone is an important carrier of oil and gas resources and key metal elements and minerals. Barite (BaSO4), a sulfate mineral widely developed in sedimentary basins, provides important evidence for inverting paleooceanic chemical conditions, diagenetic evolution, and hydrothermal activity through its major and trace element contents and isotopic composition of sulfur, strontium, oxygen, and barium. At the same time, barite in black mudstone can adsorb / encapsulate key metals such as Sr, Ga, and rare earth elements, forming "barite-key metal" associated minerals. In addition, it can also serve as an identification marker for high-quality source rocks and improve the reservoir properties of black mudstone, which is of great significance for shale oil and gas exploration and development and comprehensive mineral utilization.

[0003] Barite in black mudstone is mostly biogenic barite, characterized by small grain size (generally <10μm), low content, and close association with clay / quartz / carbonate / siliceous matter. This poses a significant challenge to its single-mineral extraction. Currently, there is no systematic extraction method for single barite from black mudstone, and related research and extraction techniques have many shortcomings, which can be divided into two categories:

[0004] Indirect research methods for barite in black mudstone include: ① Scanning electron microscopy combined with TIMA (Thermal Mineral Analysis) to analyze black mudstone samples. This method is time-consuming, has a low success rate, and cannot obtain actual single barite minerals; ② Testing the Ba content of the whole black mudstone rock and reconstructing the barite content from the data. This method can only obtain theoretical data and cannot obtain complete single barite mineral grains and morphology, thus failing to assess the genesis of barite and conduct subsequent geochemical tests.

[0005] Application of conventional mineral extraction methods: Methods for extracting barite from barite veins and drilling waste are applied to the extraction of barite from black mudstone. These methods mainly include physical sorting, strong acid dissolution, and calcination flotation. The core drawback is:

[0006] (1) Simple gravity separation or magnetic separation is difficult to effectively remove carbonates, silica and other minerals from black mudstone, and the symbiotic relationship between barite and clay minerals cannot be broken.

[0007] (2) Direct treatment with strong acids such as concentrated sulfuric acid can easily cause partial dissolution of barite and destruction of the crystal lattice, leading to isotope fractionation. The treated sample cannot meet the requirements of high-precision geochemical testing.

[0008] (3) The existing calcination process is designed for high-content, coarse-grained barite veins. The thermal stress generated by high-temperature calcination causes the barite to break out of the gangue. However, fine-grained barite in black mudstone is wrapped in clay minerals. High temperature will cause the clay minerals to sinter / vitrify, sealing the barite inside. Moreover, high-temperature reduction conditions will destroy the original structure of barite.

[0009] (4) The existing physical and chemical combined extraction process is a random combination and is not designed for the occurrence characteristics of black mudstone barite. It cannot separate fine-grained barite that is closely coexisting with clay / siliceous matter. The final extracted product has low purity and low recovery rate. The recovery rate of fine-grained barite is less than 50% and the purity is <90%.

[0010] Furthermore, existing barite extraction technologies primarily target the flotation of barite ore and the recovery of drilling waste, such as microwave flotation based on infrared spectroscopy, flotation of low-grade barite using novel collectors, and separation of barite from shale gas drilling mud. These technologies target coarse-grained, high-content barite. In high-content, coarse-grained barite veins, barite is the main mineral, and its coarse-grained intercalation with surrounding minerals (such as quartz and calcite) allows for the extrusion of barite using the thermal stress generated during calcination, followed by recovery through flotation. Additionally, using a reducing agent under high-temperature calcination can convert barite into soluble barium sulfide, which is then chemically enriched into barite using calcium oxide. However, biogenic barite is typically micron-sized crystals (generally <10μm) encased in clay minerals. High temperatures cause the clay minerals to sinter / vitrify, sealing the barite within. Furthermore, high-temperature reducing conditions can damage the original structure of barite, compromising its integrity and original chemical signature. The barite in the black mudstone described in this application is significantly different from the fine-grained, low-content barite with complex symbiotic characteristics, and therefore cannot be directly applied.

[0011] Therefore, developing a single-mineral extraction method for barite that is specific to the occurrence characteristics of black mudstone, can extract micron-sized barite, is gentle and low-damage, and has high purity and high recovery rate has become an urgent need in the fields of sedimentary geochemistry and oil and gas geology research. Summary of the Invention

[0012] Purpose of the invention: The purpose of this invention is to overcome the shortcomings of the prior art and provide a highly efficient method for extracting barite from organic-rich black mudstone. This method solves the problems of existing technologies, such as the inability to extract fine-grained barite (<10μm) from black mudstone, the easy damage to the barite lattice / initiation of isotope fractionation during the extraction process, low purity and recovery rate, and poor process adaptability.

[0013] Technical Solution: To achieve the above objectives, this invention provides a method for the efficient extraction of barite, a single mineral, from organic-rich black mudstone. Targeting the characteristics of barite in black mudstone—particle size <10μm, close association with clay / siliceous matter, and low content—a directional adaptation process coupling physical sorting and mild chemical dissolution is designed. Simultaneously, the process parameters for each step are optimized. The specific steps are as follows:

[0014] 1) Sample pretreatment: Crush and grind the organic-rich black mudstone to 150-200 mesh, and sieve to remove coarse debris;

[0015] 2) High-temperature removal of organic matter: The rock powder obtained in step 1) is placed in a muffle furnace and calcined at 450-500°C for 10-12 hours, then cooled to room temperature;

[0016] 3) Removal of calcium carbonate impurities: Add 6 mol / L hydrochloric acid to the sample obtained in step 2), react at room temperature for 22-24 h, centrifuge and wash until the supernatant is neutral, and collect the solid residue;

[0017] 4) Separation of light minerals from heavy liquid: Add diiodomethane heavy liquid to the solid residue obtained in step 3), mix thoroughly, centrifuge, and collect the bottom barite concentrate; add deionized water to the concentrate, centrifuge, and wash three times to remove the heavy liquid.

[0018] 5) Directional dissolution of silicate minerals: First, add nitric acid to the sample obtained in step 4), and after the system stabilizes, add hydrofluoric acid and react at room temperature for 1-2 hours. Then, wash the sample three times with deionized water using the centrifugation washing method in step 4) and collect the solid phase.

[0019] 6) Purification of barite: Add 1 mol / L nitric acid solution of saturated aluminum chloride to the solid phase obtained in step 5), shake well, loosen the lid, and place in an oven at 75-80℃ for 1-1.5 h. After cooling, wash 3 times by centrifugation as in step 4).

[0020] 7) Separation of crystals by filter membrane: The solid residue obtained in step 6) is vacuum filtered through a 0.4 μm vacuum filter membrane. The filter membrane is placed in a labeled plastic petri dish with the lid loosened and left to dry at room temperature overnight.

[0021] 8) Lattice stabilization treatment: Place the dried sample obtained in step 7) in a crucible, calcine it in a muffle furnace at 700℃ for 0.8 to 1 hour, and allow it to cool naturally to room temperature to obtain barite single mineral with a purity ≥99%.

[0022] Furthermore, in step 3), the density of the diiodomethane heavy liquid is 2.8–3.2 g / cm³.

[0023] Further, add 20 mL of 0.8–1.0 mol / L nitric acid to the sample obtained in step 4), and after the system has stabilized, add 8–10 mL of 49% hydrofluoric acid.

[0024] Further, in step 5), 12-15 mL of 1 mol / L nitric acid solution of saturated aluminum chloride is added to the resulting solid phase.

[0025] Furthermore, this method is applicable to the extraction of barite single minerals from marine black mudstone, terrestrial black mudstone, shale, and siliceous mudstone. Purity detection: The purity of the samples was detected by scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS), and barite single minerals with a purity ≥99% and a fine-grain recovery rate ≥90% were finally obtained.

[0026] Beneficial effects:

[0027] 1) Highly targeted, achieving efficient extraction of fine-grained barite: This invention is specifically designed for biogenic barite with a particle size of <10μm in black mudstone, breaking through the technical bottleneck of existing technologies that cannot separate fine-grained barite from clay / siliceous symbiosis. The recovery rate of fine-grained barite is ≥90%, filling the technical gap in the extraction of fine-grained barite from black mudstone.

[0028] 2) Mild and low-damage treatment, preserving the original geochemical characteristics of barite: The entire process uses mild acid etching and low-temperature treatment, without the use of strong acids such as concentrated sulfuric acid, and without high-temperature sintering / reduction treatment. This avoids the destruction of barite crystal lattice, dissolution and loss, and isotope fractionation. The extracted barite crystal structure is complete and can meet the requirements of high-precision geochemical testing of sulfur, strontium, oxygen, barium isotopes and trace elements. This solves the core pain point of existing technologies that "processed samples cannot be used for high-precision testing".

[0029] 3) High purity and excellent process adaptability: Through a process sequence of targeted impurity removal + step-by-step purification, specific removal steps are designed for impurities such as organic matter, carbonates, light minerals, silicates, and clay in black mudstone. The process sequence is not a simple arrangement of existing technologies, but a targeted adaptation based on the occurrence characteristics of barite. The final extracted barite single mineral purity is ≥99%.

[0030] 4) High recovery rate and wide applicability: The 0.4μm filter membrane retains fine-grained minerals, avoiding the loss of fine-grained barite and ensuring the extraction efficiency of low-content samples; at the same time, it is applicable to a variety of sedimentary rocks such as marine / terrestrial black mudstone, shale, and siliceous mudstone, providing a reliable sample preparation method for sedimentary geochemistry, oil and gas geology, and exploration of key metal minerals.

[0031] 5) Simple operation and easy to industrialize: The equipment used in this invention is conventional laboratory equipment, the reagents are conventional chemical reagents, the process steps are clear, the parameters are controllable, and no complicated special equipment is required. It is suitable for small-batch sample processing in the laboratory, and can also be scaled up to achieve industrial-scale batch extraction. Attached Figure Description

[0032] Figure 1 SEM image of biogenic barite extracted from organic-rich black mudstone in the foreshore facies of this invention;

[0033] Figure 2 The elemental energy spectrum of biogenic barite from organic-rich black mudstone before extraction in this invention;

[0034] Figure 3 This is a SEM image of the single mineral extraction results of barite at 500x magnification in Example 1 of the present invention;

[0035] Figure 4 The elemental energy spectrum of the barite single mineral extraction results at 500 magnification in Example 1 of this invention;

[0036] Figure 5 This is a SEM image of the single mineral extraction results of barite at 5000 magnification in Example 1 of the present invention;

[0037] Figure 6 This is the elemental energy spectrum of the single mineral extraction results of barite at 5000 magnification in Example 1 of the present invention. Detailed Implementation

[0038] Current methods for extracting single-mineral particles of biogenic barite primarily employ a combination of physical sorting and chemical extraction. This method requires first removing carbonates and organic matter from mudstone samples, followed by repeated washing and sedimentation to initially enrich barite. Subsequently, isohyet centrifugation is used to analyze low-density minerals such as clay and quartz. A strong magnetic separator is then used to remove magnetic minerals, and finally, selection is performed under a microscope. This method involves the individual use of acid dissolution, calcination, and heavy liquid separation, but it cannot separate barite tightly associated with clay / siliceous materials in mudstone. Furthermore, the particle size of biogenic barite is often <10 μm, making microscopic selection even after enrichment extremely difficult.

[0039] To address the shortcomings and needs of existing technologies, this invention provides a method for the efficient extraction of barite, a single mineral, from organic-rich black mudstone. Targeting the characteristics of barite in black mudstone—particle size <10μm, close association with clay / siliceous matter, and low content—a directional adaptation process coupling physical sorting and mild chemical dissolution is designed, while optimizing the process parameters for each step. The specific steps are as follows:

[0040] 1) Sample pretreatment: Crush and grind the organic-rich black mudstone to 150-200 mesh, and pass it through a standard sieve to remove coarse debris to ensure uniform sample particle size, laying the foundation for subsequent step-by-step impurity removal; if the grinding particle size is greater than 200 mesh, fine barite particles are easily lost, and if it is less than 150 mesh, the symbiotic relationship between barite and clay minerals cannot be broken.

[0041] 2) High-temperature removal of organic matter: The rock powder is heated to 450℃-500℃. This is because the organic matter in the mudstone sample begins to decompose at 300℃ and is completely decomposed at 450℃. Barite undergoes a solid-phase reaction with hematite at 1190℃ under normal pressure. Therefore, this temperature condition ensures complete combustion of organic matter, preventing organic matter from encapsulating the barite and causing subsequent acid dissolution / sorting to be ineffective, and it conforms to the normal operating temperature range of most muffle furnaces. In addition, organic-rich mudstone often contains sulfides, which undergo oxidative decomposition at 500-600℃, producing SO2 or SO3. These gases may have a weak reaction with the surface of barite; this problem can be avoided at 450℃-500℃.

[0042] 3) Removal of calcium carbonate: Add 6 mol / L hydrochloric acid, react for 24 hours, and centrifuge until neutral. First sort, then remove impurities: First remove carbonate impurities to avoid their reaction with the heavy liquid affecting the density sorting effect, thus achieving preliminary enrichment of barite.

[0043] 4) Heavy Liquid Separation of Clay and Quartz: Using a heavy liquid such as diiodomethane with a density of 2.8–3.2 g / cm³, and taking advantage of the high density of biogenic barite (4.3–4.7 g / cm³), barite is separated from lighter minerals (such as clay / quartz with a density of 2.2–2.7 g / cm³) in mudstone by centrifugation in the heavy liquid. This achieves efficient heavy liquid centrifugation, with barite enriched at the bottom layer and lighter minerals separated. Deionized water is then added, and the mixture is centrifuged at 2500 rpm for 10 minutes, repeated three times to remove the heavy liquid.

[0044] 5) Removal of silicates, including barite: First, add 20 mL of 1 mol / L nitric acid to the treated mud sample. After the reaction stabilizes, add 10 mL of 49% hydrofluoric acid. The nitric acid is added first to oxidize the silicon on the mineral surface to form a thin layer of silica. The hydrofluoric acid then reacts with the silica generated by the nitric acid oxidation to produce soluble fluorosilicic acid, thereby removing the silicate minerals. Rinse three times with deionized water as described in step 4).

[0045] 6) Removing other impurities and purifying barite: Add approximately 15 mL of saturated aluminum chloride (in 1 mol / L nitric acid solvent) to the sample tube. Saturated aluminum chloride exists in the solution as Al³⁺. Al³⁺ can destroy the structure of clay minerals, allowing K, Na, Ca, Si, etc. in the clay minerals to enter the solution, while barite is enriched as a solid residue. The 1 mol / L nitric acid solvent can prevent Al³⁺ from hydrolyzing and forming a precipitate, ensuring that Al³⁺ functions as free ions or complexed ions. Shake well, loosen the cap, and place in an 80°C oven to react for 1 hour. After removal, add deionized water and rinse three times according to the method in step four, then cool to room temperature.

[0046] 7) Filtration of Mineral Crystals: Solid residue is filtered using a 0.4μm vacuum filter membrane. The membrane is placed in a labeled plastic petri dish, loosened, and allowed to dry overnight. The technical principle and necessity of using a 0.4μm filter membrane are as follows: The main grain size of biogenic barite in black mudstone is 1–10μm, with a large number of particles concentrated in 2–5μm. The 0.4μm pore size is much smaller than the smallest grain size of barite, which can retain 100% of all fine barite crystals, completely avoiding the loss of fine particles with the filtrate and ensuring a fine particle recovery rate of ≥90%. Filter membranes larger than 0.4 μm allow micron-sized barite to pass through directly, causing the recovery rate to drop from ≥90% to <30%, resulting in extraction failure. Filter membranes smaller than 0.4 μm, such as 0.22 μm and smaller, cause filtration to stop and the filtrate to be unable to pass through. This is because residual nano-sized clay fragments, silicate colloids, and aluminum hydroxide precipitates in the sample can instantly block pores of 0.22 μm and smaller. At the same time, excessively small pore sizes can extend filtration time from a few minutes to several hours. Prolonged exposure of the sample can easily adsorb impurities from the air and cause weak hydrolysis, damaging the purity of the barite surface.

[0047] 8) Place the crucible in a muffle furnace and ignite at 700°C for 1 hour to remove residual organic matter, decompose secondary mineral deposits generated during chemical treatment, stabilize the barite lattice, and after cooling, transfer the sample to a labeled aluminum foil bag and weigh and record the weight. The technical principle and necessity of choosing 700°C and ignition for 1 hour in this step are as follows:

[0048] (1) Thorough removal of residual organic matter: After the sample has undergone chemical treatment and room temperature drying, it may still adsorb trace amounts of organic residues, reagent residues or volatile impurities. 700℃ can achieve complete oxidative decomposition of residual organic matter, ensuring that the sample is free of organic pollution and avoiding interference with subsequent high-precision geochemical tests. Complete decomposition of secondary mineral deposits generated by chemical treatment: The steps of nitric acid and fluorine acid dissolution and aluminum chloride purification will generate trace amounts of fluoride salts, aluminum hydroxyl compounds, silicate colloids and adsorbed soluble salts on the surface of barite. The above-mentioned secondary mineral phases can be fully decomposed, volatilized or transformed into easily elutable components at 600–700℃, thereby ensuring that the surface of barite crystals is clean and free of secondary phase coverage. (2) Mild annealing to stabilize the barite crystal structure: After chemical dissolution, centrifugation, filtration and other processes, barite will generate weak lattice stress and surface defects. 700℃ is a mild annealing temperature, which can effectively eliminate lattice stress, repair crystal surface defects, stabilize crystal structure, and avoid signal drift, fractionation or data fluctuation in high-precision tests such as LA-MC-ICP-MS. The temperature is safe and does not damage barite or produce isotopic fractionation of barite (BaSO4). (3) Avoid clay mineral sintering / vitrification and prevent secondary encapsulation. Temperatures above 800℃ can easily cause trace amounts of residual clay in the sample to sinter and vitrify, re-encapsulate barite crystals, introduce impurities and reduce purity. 700℃ can effectively avoid clay sintering and does not produce new inclusions or impurity phases while removing impurities.

[0049] The rationale for calcination at 1 hour is that maintaining a constant temperature for 1 hour ensures uniform heating of small batches of samples within the muffle furnace, completely removing residual organic matter and secondary minerals, and achieving sufficient lattice stability. Less than 30 minutes results in incomplete impurity removal and unrelieved lattice stress; exceeding 2 hours offers no additional gain and may induce thermal diffusion of trace impurities, reducing sample surface purity and experimental efficiency. Therefore, calcination at 700℃ for 1 hour is the optimal condition for achieving the triple goals of impurity removal, purification, and lattice stability.

[0050] 9) Observe the sample using a scanning electron microscope to detect its purity / cleanliness.

[0051] To further illustrate the technical solution and implementation effect of the present invention, this invention is described in detail using marine organic-rich black mudstone (sample JY-15-2, whole-rock organic matter content 3.1997%, whole-rock barium content 1601ppm, biogenic barite grain size 5-8μm) as an example. This embodiment is only used to explain the present invention and is not intended to limit the present invention.

[0052] Example 1

[0053] Sample pretreatment: The JY-15-2 marine black mudstone sample was crushed, ground to 180 mesh with an agate mortar, sieved to remove coarse debris, and 100g of the ground sample was taken for later use.

[0054] High-temperature removal of organic matter: The sample was placed in a porcelain crucible and calcined in a muffle furnace at 480°C for 11 hours. After cooling to room temperature, the organic matter content was found to be 0.058%, and the organic matter removal rate was 98.19%.

[0055] Removal of calcium carbonate impurities: Add 200 mL of 6 mol / L hydrochloric acid to the sample, stir and react at room temperature for 23 h, centrifuge at 3000 r / min for 5 min, pour out the supernatant, add deionized water to wash and centrifuge, repeat until the pH of the supernatant is 7, and collect the solid residue.

[0056] Separation of light minerals from heavy liquid: Add 300 mL of diiodomethane heavy liquid with a density of 3.0 g / cm³ to the solid residue, stir and mix well, centrifuge, and collect the bottom enrichment; add deionized water, centrifuge at 2500 r / min for 9 min, and wash 3 times to remove the heavy liquid;

[0057] Directional dissolution of silicate minerals: Add 20 mL of 0.9 mol / L nitric acid, stir for 30 min until the system is stable, add 9 mL of 49% hydrofluoric acid, stir at room temperature for 1.5 h, and centrifuge and wash 3 times as in step 4);

[0058] Purifying barite: Add 15 mL of a mixed solution of saturated aluminum chloride and 1 mol / L nitric acid, shake well, loosen the lid, and place in a 78℃ oven to react for 1.2 h. After cooling, centrifuge and wash 3 times as per step 4).

[0059] Crystal separation by filter membrane: Solid residue was vacuum filtered using a 0.4 μm vacuum filter membrane. The filter membrane was then placed in a plastic petri dish with the lid loose and allowed to dry overnight at room temperature.

[0060] Lattice stabilization treatment: Place the dried sample in a crucible, ignite at 700℃ for 50 min, and then allow it to cool naturally to room temperature;

[0061] Purity testing: SEM-EDS analysis showed that the purity of barite in the sample was 99.5%, the recovery rate of fine-grained barite was 92.3%, the crystal lattice was intact, and there was no isotope fractionation.

[0062] Biogenic barite found authigenic in organic-rich black mudstone provides important information on paleooceanic chemistry and paleoproductivity evolution through its elemental and isotopic composition, and also serves as an indicator of high-quality hydrocarbon source rocks. Biogenic barite often occurs authigenic within silicate minerals, specifically appearing as irregular elliptical, dumbbell-shaped, or aggregates of these shapes, with diameters generally below 10 μm. Furthermore, due to barium being a trace element, it remains difficult to detect even under an electron microscope. Figure 1 Even if biogenic barite is found, micro-elemental analysis will be difficult because its mineral diameter is smaller than that of a typical laser beam, causing interference from surrounding silicate minerals in the test results. Figure 2 After the barite extraction in Example 1, a large amount of barite was observed to be distributed independently. The crystals were elliptical and dumbbell-shaped, without breakage or damage, and had smooth surfaces and intact lattices. There were no silicate, clay, or other minerals encapsulating the crystals. Figure 3 , Figure 5 This indicates that the selected temperature and acid treatment results did not damage the barite. Furthermore, during energy dispersive spectroscopy (EDS) testing, the silicon peak was largely eliminated, and the proportion of barite elemental peaks was ≥99%. Figure 4 , Figure 6 This indicates that the combination of nitric acid and hydrofluoric acid effectively removes silicate minerals from the surrounding rock, preventing interference from surrounding rock elements during subsequent micro-area elemental and isotopic analyses.

[0063] High-temperature removal of organic matter: Comparative example 1

[0064] The muffle furnace calcination temperature in the high-temperature organic matter removal step was adjusted to 350℃. The organic matter content of the whole rock of the JY-15-2 marine black mudstone sample was tested to be 0.6855%, and the organic matter removal rate was 78.6%.

[0065] High-temperature removal of organic matter (comparative example 2)

[0066] The muffle furnace calcination temperature in the high-temperature organic matter removal step was adjusted to 400℃. The organic matter content of the whole rock of the JY-15-2 marine black mudstone sample was tested to be 0.1910%, and the organic matter removal rate was 94%.

[0067] Example 2

[0068] Sample pretreatment: Grind the terrestrial black mudstone sample to 150 mesh and take 100g for later use;

[0069] High-temperature removal of organic matter: Incineration at 450℃ for 12 hours resulted in an organic matter removal rate of 97.95%.

[0070] Removal of calcium carbonate impurities: React with 6 mol / L hydrochloric acid at room temperature for 24 h, then wash until neutral;

[0071] Separation of light minerals from heavy liquid: Diiodomethane heavy liquid density 2.8 g / cm³, centrifuged at 2500 r / min for 10 min, washed 3 times;

[0072] Targeted dissolution of silicate minerals: 20 mL 1.0 mol / L nitric acid + 8 mL 49% hydrofluoric acid, react at room temperature for 2 h;

[0073] Purification of barite: 12 mL of saturated aluminum chloride in 1 mol / L nitric acid solution, reacted in an oven at 75℃ for 1 h;

[0074] Crystal separation by membrane filtration: 0.4μm membrane filtration, followed by drying at room temperature;

[0075] Lattice stabilization treatment: calcination at 700℃ for 1 hour;

[0076] Purity test: Barite purity 99.2%, fine particle recovery rate 90.5%, and intact crystal structure.

[0077] Example 3

[0078] Sample pretreatment: Grind the siliceous black mudstone sample to 200 mesh and take 100g for later use;

[0079] High-temperature removal of organic matter: Incineration at 500℃ for 10 hours resulted in an organic matter removal rate of 98.32%.

[0080] Removal of calcium carbonate impurities: React with 6 mol / L hydrochloric acid at room temperature for 22 h, then wash until neutral;

[0081] Separation of light minerals from heavy liquid: Diiodomethane heavy liquid density 3.2 g / cm³, centrifuged at 2500 r / min for 8 min, washed 3 times;

[0082] Targeted dissolution of silicate minerals: 20 mL 0.8 mol / L nitric acid + 10 mL 49% hydrofluoric acid, react at room temperature for 1 h;

[0083] Purification of barite: 15 mL of saturated aluminum chloride in 1 mol / L nitric acid solution, reacted in an oven at 75℃ for 1.5 h;

[0084] Crystal separation by membrane filtration: 0.4μm membrane filtration, followed by drying at room temperature;

[0085] Lattice stabilization treatment: calcination at 700℃ for 45 min;

[0086] Purity test: Barite purity 99.3%, fine particle recovery rate 91.8%, and intact crystal structure.

[0087] This invention targets the occurrence characteristics of biogenic barite in organic-rich black mudstone. Through process design, principle control, and parameter optimization, it achieves efficient extraction of barite as a single mineral. Compared with existing technologies, it has the following significant technical benefits, and these benefits are mutually supportive and synergistic: The method of this invention is simple to operate, low in cost, and highly applicable. It can be promoted and applied in small-batch extraction in the laboratory and industrial-scale production, providing a reliable sample preparation method for sedimentary geochemistry, oil and gas geology, and exploration of key metal minerals.

[0088] Although the present invention has been illustrated and described with reference to preferred embodiments, those skilled in the art should understand that various changes and modifications can be made to the present invention without departing from the scope defined by the claims.

Claims

1. A method for efficient extraction of barite, a single mineral, from organic-rich black mudstone, characterized in that, Includes the following steps: 1) Sample pretreatment: Crush and grind the organic-rich black mudstone to 150-200 mesh, and sieve to remove coarse debris; 2) High-temperature removal of organic matter: The rock powder obtained in step 1) is placed in a muffle furnace and calcined at 450-500°C for 10-12 hours, then cooled to room temperature; 3) Removal of calcium carbonate impurities: Add 6 mol / L hydrochloric acid to the sample obtained in step 2), react at room temperature for 22-24 h, centrifuge and wash until the supernatant is neutral, and collect the solid residue; 4) Separation of light minerals from heavy liquid: Add diiodomethane heavy liquid to the solid residue obtained in step 3), mix thoroughly, centrifuge, and collect the bottom barite concentrate; add deionized water to the concentrate, centrifuge, and wash three times to remove the heavy liquid. 5) Directional dissolution of silicate minerals: First, add nitric acid to the sample obtained in step 4), and after the system stabilizes, add hydrofluoric acid and react at room temperature for 1-2 hours. Then, wash the sample three times with deionized water using the centrifugation washing method in step 4) and collect the solid phase. 6) Purification of barite: Add 1 mol / L nitric acid solution of saturated aluminum chloride to the solid phase obtained in step 5), shake well, loosen the lid, and place in an oven at 75-80℃ for 1-1.5 h. After cooling, wash 3 times by centrifugation as in step 4). 7) Separation of crystals by filter membrane: The solid residue obtained in step 6) is vacuum filtered through a 0.4 μm vacuum filter membrane. The filter membrane is placed in a labeled plastic petri dish with the lid loosened and left to dry at room temperature overnight. 8) Lattice stabilization treatment: Place the dried sample obtained in step 7) in a crucible, calcine it in a muffle furnace at 700℃ for 0.8 to 1 hour, and allow it to cool naturally to room temperature to obtain barite single mineral with a purity ≥99%.

2. The method according to claim 1, characterized in that, In step 4), the density of the diiodomethane heavy liquid is 2.8–3.2 g / cm³.

3. The method according to claim 1, characterized in that, Add 20 mL of 0.8–1.0 mol / L nitric acid to the sample obtained in step 4), and after the system has stabilized, add 8–10 mL of 49% hydrofluoric acid.

4. The method according to claim 1, characterized in that, Step 5) Add 12-15 mL of 1 mol / L nitric acid solution of saturated aluminum chloride to the obtained solid phase.

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