Bentonite beneficiation process analysis

Bentonite is a type of clay rock with montmorillonite as the main mineral component, and the montmorillonite content is usually 85% - 90%. Its unique crystal structure consists of two layers of silicon-oxygen tetrahedrons sandwiched by one layer of aluminum-oxygen octahedron, which gives bentonite many special properties. In addition, bentonite is often accompanied by other minerals such as illite and kaolinite.

In the field of bentonite beneficiation, wet beneficiation technology occupies an important position. This process is suitable for processing ores with a particle size of less than 5mm. The first step is to make it into a slurry of a specific concentration. Specifically, after the ore is pre-treated by crushing and grinding, water is added to make a slurry with a concentration of 25%. This concentration has been verified by a large number of practices to balance the fluidity of the slurry with the subsequent separation effect. After the slurry is made, it is separated with the help of a hydraulic separator and a centrifuge. The hydraulic separator uses the difference in centrifugal force on different particles when the slurry rotates at high speed to achieve separation. Coarse particles are discharged from the bottom sand outlet and can be used as raw materials for low value-added products such as building sand; fine particles flow out from the top overflow port and enter the centrifuge for further separation. The centrifuge uses strong centrifugal force to throw heavier and larger impurity particles to the cylinder wall and discharge them. High-quality bentonite particles are retained as the main component of the product and are used in industries with high performance requirements such as casting and oil drilling; the lighter part contains fine impurities and bentonite fine powder, which can be further processed as needed.

The heavy metaphosphate method is also an important mineral processing method. This method has requirements for the grade of the selected ore, and generally requires a montmorillonite content of not less than 50%. Sodium hexamethaphosphate is a key additive, and its dosage is accurately calculated according to the properties of the ore, usually 1-5kg is added for every 1000kg of ore. In terms of the operation process, the ore that meets the grade requirements is first crushed and ground to a particle size of less than 200 mesh, then placed in a stirring tank, and water and sodium hexametaphosphate are added and stirred for 30-60 minutes to allow the additives to fully contact and disperse with the ore particles, followed by classification with equipment, and finally the concentrate is filtered and dried to obtain the final product.

In addition to the above common methods, special or emerging processes also bring new ideas to the development of bentonite. Alkali treatment is a special process that uses alkaline substances to react with impurities to remove impurities and improve performance. Alkaline reagents such as sodium hydroxide and sodium carbonate are commonly used. During operation, bentonite powder is mixed with a certain concentration of alkaline solution in proportion and reacted under appropriate temperature and stirring conditions. If the concentration of sodium hydroxide solution is controlled at 5%-15%, the reaction temperature is maintained at 50-80℃, and stirring is performed for 1-3 hours, some aluminosilicate impurities and metal oxides can be dissolved to improve purity, and the montmorillonite crystal structure can also be changed to enhance expansion and adsorption.

Homogenizer treatment is an emerging process that can refine and homogenize bentonite slurry under high pressure and high shear force. The preliminarily treated slurry is input into the homogenizer, and the internal high-speed rotating parts generate strong shear force, refine the particles, make the composition distribution more uniform, and improve the stability and consistency of the product. After treatment, the bentonite particles are finer and more uniform, and can better play the performance advantages.

In summary, from the traditional wet beneficiation process and the heavy metaphosphate method to the special alkali treatment and the emerging homogenizer treatment, different beneficiation processes have their own characteristics and advantages. The rational use of these processes can effectively improve the quality and utilization rate of bentonite and meet various industrial needs.