Progress in purification technology of barite and preparation process of active barite

With high-quality, single-type barite mines are depleted, the vast majority of China's current low-barite ore grade, ore and other metals, non-metallic mineral closely associated, directly affects their usefulness in industry. The barite weighting agent used for drilling mud generally requires a fineness of -0 056 mm or more, a density of >42 g3, a grade of >95%, and a soluble salt content of <1%. Rubber, paper grade barite packing usually requires> 98%, CaO content <036% 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.

1 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 BaSO4 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.

2 chemical purification

2.1 Purification by flotation

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 a fluorite collector, YZ-4 tantalum glue and water glass, aluminum sulfate group cooperative inhibitor, inhibited barite flotation fluorite, and finally obtained a CaF2 grade of 96.81%, the recovery rate 92.44% of fluorite concentrate and BaSO4 grade 91.36%, recovery rate of 86.75% barite concentrate, the efficient separation of fluorite and barite. Li Mingfeng [5] used sodium dodecyl sulfate as collector, sodium silicate and citric acid as fluorite inhibitor, and adopted the scheme of inhibiting fluorite flotation barite, finally obtaining BaSO4 grade of 93.28%, recovery rate. It is 94.06% barite concentrate.

2.2 Calcination and 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 Fe2O3, TiO2, organic matter and other impurities 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, and seriously reducing the weight. The use value of spar. 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%.

2.3 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 reduces the Fe3+ to Fe2+ by adding a reducing agent to dissolve it, thereby achieving impurity removal and whitening, and improving the mineral content. the goal of.

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 Fe2+, can remove the main coloring matter Fe3+ 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.

2 Preparation of active barite

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.

2.1 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 [8] 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.

2.2 Mechanical chemical 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.

2.3 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.