Progress in the development and application of cutting-edge barite minerals

China's traditional barite industry is mainly to produce low value-added primary products, including the production of oil, natural gas drilling mud weighting agents and bismuth-containing chemical products, and the production process has a greater pollution to the environment. In order to increase the added value of barite minerals, low-grade barite minerals can be purified and processed by physical and chemical methods to have new functions and uses, and the utilization value of barite minerals can be improved to realize resources. The efficient use of the new non-metallic mineral resources processing in China provides a new way of thinking.

With the depletion of high-quality, single-type barite ore, most of the barite ore in China is currently low in quality, closely associated with other metal ore and non-metal ore, directly affecting its industrial use value. The barite weighting agent used for drilling mud generally requires a fineness of -0.056 mm or more, a density of >4.2 g/cm ³ , a grade of >95%, and a soluble salt content of <1%. Rubber, paper grade barite packing usually requires> 98%, CaO content <0.36%, and allowed containing magnesium oxide, lead and other harmful components. Barite for different purposes has different requirements for the purity, whiteness and impurity content of barite.

Physical purification

The physical purification methods of barite mainly include: hand selection, reselection, and magnetic separation. The main basis for hand selection is the difference in color and density of barite and associated ore. After the ore is coarsely crushed, the barite mineral and the gangue mineral can be effectively dissociated, and the block-shaped barite can be selected by hand. For example, the Pancun Mine in Xiangzhou, Guangxi, can obtain rich ore with a particle size of 30-150 mm and a BaSO ₄ content of >92% by hand selection . The hand selection method is simple and convenient, has low dependence on equipment, and has low cost, but has high requirements on ore and low production efficiency, and is extremely wasteful of resources. Re-election is based on the difference in density between barite and associated minerals. The ore is crushed and ground to a certain size to enter the re-election equipment for sorting to remove the gangue. The content of barium sulphate after re-election of Hunan Hengnan barite mine is over 92%. After re-election of hand-selected tailings, re-election concentrate with barium sulfate content of 84.50% can be obtained. Magnetic separation is the method of selecting the magnetic force by using the difference in magnetic properties between different ores. To remove some of the main magnetic iron oxide having magnetic properties, such as mineral siderite, typically used in conjunction with re-election, to reduce the iron content in barite concentrate.

Chemical purification
Flotation purification
With the continuous development and utilization of high-grade and easy-to-select barite ore, it is urgent to increase the research and development of low-grade barite ore. Barite is often closely associated with minerals such as fluorite , calcite , and quartz . The grade is low, the size of the inlay is fine, and the composition is complex. It is difficult to separate it effectively by the traditional re-election process. Flotation can be adapted to barite of various complex inlay types, thus becoming the main method for the selection of barite at this stage. Collector is the key to determine whether barite minerals can be effectively separated. Commonly used collectors can be divided into three types according to the adsorption form: 1 anion collector based on chemisorption; 2 cations based on physical adsorption. Collector; 3 amphiphilic collector between the two. According to the separation process of barite and fluorite, it can be divided into two types: one is to inhibit the barite flotation fluorite; the other is to inhibit the fluorite flotation barite. Yu Futao et al used sodium oleate as the fluorite collector, YZ-4 tantalum glue and water glass, aluminum sulfate group cooperative inhibitor, inhibited the barite flotation fluorite, and finally obtained the CaF ₂ grade of 96.81%, the recovery rate 92.44% of fluorite concentrate and BaSO ₄ grade 91.36%, recovery rate of 86.75% barite concentrate, the efficient separation of fluorite and barite. Li Mingfeng used sodium dodecyl sulfate as collector, sodium silicate and citric acid as fluorite inhibitor, and adopted the scheme of inhibiting fluorite flotation barite. The final grade of BaSO ₄ was 93.28%, and the recovery rate was 94.06. % barite concentrate.

Calcination purification
The mineral calcination process is characterized by thermal dissociation into a simpler composition of minerals or minerals undergoing crystal transformation, from one solid phase pyrolysis to another physical phase of solid phase and gas phase. Since the barite mineral is mixed with impurities such as Fe ₂ O ₃ , TiO ₂ and organic matter during the bed formation process , these impurities may cause the barite to become gray, green and blue, thereby affecting the purity and whiteness of the barite. , seriously reducing the use value of barite. Calcination can volatilize organic matter, and calcination and impurity removal are mainly suitable for removing impurities capable of endothermic decomposition or volatilization at high temperatures. Lei Shaomin et al. calcined the barite ore powder with sulfuric acid at 850 ° C for 2 h, the whiteness can be increased from 88.19% to 90.64%; after calcination at 950 ° C for 2 h, the whiteness can reach 93.5%.

Leaching purification
Leaching purification is mainly used to remove carbon and colored impurities in barite. Their presence affects the whiteness and application prospects of barite concentrates. The main methods for removing these impurities are: acid leaching, oxidation-reduction, and organic acid complexing. The acid leaching method utilizes an acid to react with an impurity metal or a metal oxide in a mineral to form a compound soluble in water or a dilute acid, which is washed and filtered to remove the soluble matter, thereby achieving purification. After Lei Shaoming et al. leached a certain barite mine in Hubei through concentrated sulfuric acid, the whiteness of barite powder can be increased from 84.10% to 88.60%. The oxidation-reduction method firstly adds an oxidizing agent to dissolve the metal compound accompanying the mineral, and oxidizes the coloring organic matter in the barite, and then adds a reducing agent to reduce Fe ³⁺ to Fe ²⁺ to dissolve it, thereby achieving impurity removal and whitening. And improve the purpose of mineral items. Organic acid complexing method is to add organic acids such as EDTA, ascorbic acid, citric acid, oxalic acid, etc. during the iron removal process. These acids can dissolve iron oxides and form complexes to achieve a good iron removal effect. Li Xueqin and others in the sulfuric acid (1.6mol / L) acid leached barite, adding oxalic acid complex dissolved Fe ²⁺ , can remove the main coloring matter Fe ³⁺ in the ore .
After the basic purification, the barite can meet the requirements of producing primary strontium salt, but some fine and specialized products are still unable to be produced, and it is also dependent on imports. Further exploration of the development of barite is needed.

Barite is an inorganic non-metallic mineral. If it is used as a filler in organic materials, it can improve certain properties of organic materials, broaden the application range of barite, and increase its added economic value. However, there are significant differences in the physical and chemical structure and properties between natural barite and organic materials. The difference in surface properties between the two causes the barite ore as a filler to be effectively dispersed in the organic material, making it difficult to exert barite. The excellent properties of the particles and affect the mechanical properties of the composite. Therefore, the surface modification of barite ore powder purposefully changes the original physical and chemical properties of the powder surface, improves the dispersibility and affinity of the polymer material, and has a wider application prospect.

Surface coating modification
The surface coating modification refers to the physical or chemical method to form a stable and uniform coating layer on the surface of the barite particles by physical or chemical methods, thereby achieving the purpose of modifying the surface of the powder. Xiao Qin et al. used a chemical method to modify the surface of barite with an anionic surfactant sodium lauryl sulfate. The results show that the surface of the modified barite powder is hydrophilic and oleophobic, which improves its dispersibility and affinity in organic materials.

Mechanochemical modification
Mechanochemical modification refers to the process of superfine pulverization of minerals and activation of the surface properties of powders. In this process, due to the smaller particle size, the crystal structure, solubility, chemical adsorption and reactivity change significantly, which is beneficial to other minerals. Adsorption of matter. The main factors affecting the surface modification effect of mechanochemicals are the type of pulverizing equipment, the mode of mechanical action, the pulverizing environment, the type of grinding aid and dispersant, the action time of mechanical force, and the crystal structure of the powder material.

High energy surface modification
High-energy surface modification refers to the use of ultraviolet light, infrared light, plasma irradiation, corona discharge and electron binding to generate huge energy and surface modification of the powder. Due to the current complexity of this technology, high cost and poor process control, there are not many applications at this stage.

Activated barite filled polymer material
After modification, the barite enhances the compatibility and affinity with the organic polymer and improves its dispersibility, making it a fine filler with higher added value and better performance. In recent years, the development of activated barite-filled polymer composites has been very rapid. This is due to the addition of activated barite, which reduces the shrinkage of plastic products, improves dimensional stability, improves stiffness, and reduces costs. Chen Youshuang and other methods used stearic acid to modify the barite by organic activation. The barite/natural rubber (NR) composites were prepared by direct blending. The results show that barite has obvious reinforcing effect on NR. When the activated barite content is 30%, a composite material excellent in tensile strength, elongation at break, and abrasion resistance can be obtained. Chen Youshuang et al. used different coupling agents to modify the surface of barite. The barite/rubber (NR) composites were prepared by direct blending. The results showed that the barite content was 20 after modification with stearic acid. The tensile properties, hardness and wear resistance of the rubber composite are best at % to 30%. After activation, barite has excellent reinforcing effect and ideal processing characteristics, which can replace carbon black to realize its application in rubber. Wang Wei et al. used stearic acid and silane coupling agent to modify the barite powder. The hydrophobicity of the modified barite mineral was improved obviously, and the application test showed that the modified ultrafine powder in a copper-plate paper, paint coating and precipitated barium sulfate may be substituted.

Making radiation-proof concrete
With the increasing use of various radioisotopes, how to effectively shield radioactive rays, safely dispose of toxic and radioactive waste, protect workers from harm, and reduce environmental pollution have become urgent problems to be solved at this stage. Cement concrete is the most widely used radiation protection material at present, but generally cement concrete is often difficult to meet the specified requirements, and barite radiation-proof concrete is a kind of aggregate with barite as the main material, and the apparent density reaches 3500kg/m ³ or more. Special concrete suitable for the development of nuclear technology, which can increase the shielding ability of X and γ rays by increasing the apparent density and compactness of concrete, and can effectively weaken neutron rays by increasing the content of crystal water in concrete, and barite Aggregate has a wide distribution and low price, and has a good application prospect.
Yanziying made barite concrete mixture with barite as aggregate, and found that the water consumption and water-cement ratio have a linear effect on the concrete. The water consumption is less than 240kg/m ³ and the water-cement ratio is >0.45. When the sand ratio is 36%, the pebbles and ordinary sand have a great influence on the performance of the barite radiation-proof concrete. Gao Yuxin et al. used a "cement + barite powder" cementitious material system, using high-density barite and heavy crystal sand, using high admixture dosage and low water consumption, successfully developed an apparent density of >3600kg/m ³ , and Barite anti-radiation concrete with good workability and mechanical properties meeting design requirements. Xing Wei and other studies have found that the addition of an appropriate amount of barite powder in high alumina cement not only improves the early strength of high alumina cement, but also inhibits the strength of high alumina cement in the late stage.

Making conductive coatings
As a kind of functional pigment, conductive pigment is widely used in non-metal parts of aerospace, electronics, automotive and other industries, making it conductive, anti-static, screen electromagnetic waves and other functions. Conventional conductive pigments include carbon black, graphite , silver , copper, aluminum, etc., but these pigments have certain defects and are limited in application. Conductive graphite and the like are dark black, single color, oil resistance, poor adhesion and poor decorative effect. Although the metal powder conductive pigment has good conductivity, it has poor corrosion resistance, is expensive, interferes with radio waves, and has little use value. The conductive pigments of the light-colored metal oxide series well fill the defects of the above two types of conductive pigments, and have a wide range of development and application prospects.

Yang Huaming et al found that barite-based composite conductive powders for high performance conductive coatings show excellent overall performance and can greatly reduce the cost of preparation. When the conductive powder is used in an amount of 20% to 45%, the resistivity of the prepared acrylic conductive coating is only 10 Ω·cm; the conductive powder is used for the conductive coating to achieve a significant shielding effect (35 to 40 dB) for electromagnetic waves having a frequency of 100 MHz. The network structure of the conductive powder in the conductive coating and good dispersion are the key to ensure the conductivity of the conductive coating. Zhang Guangye et al. added a solution of SnCl ₄ /SbCl ₃ (about 3.4%) to the barite suspension at a pH of 1.5 to 2.0 and a temperature of 50 ° C for 30 min. After standing, filtering, washing, Drying, grinding, and calcination at a temperature of 550 to 750 ° C for 10 min can obtain a white conductive pigment having a low electrical resistivity.

Preparation of barium ferrite magnetic material
M-type barium ferrite is widely used in perpendicular magnetic recording, magnetic and magneto-optical devices, microwave devices and electromagnetic shielding materials due to its high saturation magnetization and magnetic anisotropy field and excellent chemical stability. One of the microwave absorbers. Hessien et al. calcined a mixture of hematite and barite ore at 1200 ° C for 20 h without adding carbon to obtain BaFe ₁₂ O ₁₉ . The coercivity of this sample is significantly lower than that of the pure material, but the specific saturation magnetization of the two is almost close. At present, barium salts and iron salts are generally used to prepare barium ferrite by physical and chemical methods.

Barite is widely used in petroleum, chemical, construction and other basic industries in China. At present, barite is mainly used in China to produce primary strontium salt, and fine bismuth chemical products need to be imported. China's in-depth research on barite and other aspects needs to be strengthened. We must persist in innovation and strengthen cross-cooperation research on mineral properties, mineral processing, material property processing and related fields and disciplines, and focus on the development of barite in fine The application of chemical, functional, and composite technologies provides a new way for high value-added development and application, which is of great significance for China to make full use of non-metallic minerals.

The future development trend of barite is mainly as follows: (1) development of high-purity, ultra-fine refining and compounding technology, focusing on the development of high-purity strontium salts and bismuth citrate; (2) modification of barite to enable coatings , plastics, paper industry, etc. to provide dispersive seasoning; (3) development of next-generation magnetic material barium ferrite; (4) development of auxiliary bismuth salt fine chemicals; (5) use of nano-barite to prepare high-performance composite material.