How Silica Impurity Is Removed?
The purification of silica sand is mainly manifested in the effective removal of impurities containing iron and aluminum. According to the impurity components of silica and the occurrence state of inclusions on the surface of silica, the purification process is mainly divided into scrubbing, magnetic separation, flotation, acid leaching, etc.
1. Silica scrub purification
Mechanical scrubbing is a process of removing the thin film iron and other impurities on the surface of the ore particles through the frictional collision between the equipment and the silica ore particles. Silica scrubbing pulp concentration between 50-60% can obtain a good purification effect.
B. Stick scrubbing
The rod friction scrubbing process can strengthen the scrubbing effect, and change the particle size of silica minerals, which provides a mineralogy basis for further selection of silica.
C. Medicated scrubbing
The electric repulsion between the silica and the surface of the impurity mineral particles is increased by adding a drug, and the separation effect between the mineral particles is enhanced.
D. Ultrasonic scrubbing
The secondary iron film is the main reason that the silica sand iron is too high and difficult to purify. The process utilizes ultrasonic waves to remove the secondary iron film and impurities on the silica surface to achieve impurity removal and purification.
2. Silica magnetic separation and purification
Magnetic separation and purification of silica can effectively remove magnetic minerals. Magnetic separation purification includes two methods: dry and wet. In dry magnetic separation, the greater the silica with the magnetic field strength, the higher the impurity detachment rate. The effect of silica is directly related to the number of magnetic separations and the strength of the magnetic field. The more magnetic separation times, the lower the iron content of the concentrate. Most of the iron-containing impurities can be removed under a specific magnetic field strength, but the increase of the magnetic field strength has little effect on the iron removal rate. In addition, the finer the silica particles, the better the iron removal effect.
3. Silica flotation purification
A. Feldspar mineral impurity removal
Silica and feldspar have similarities in physical properties, structure, and chemical composition, and they can be effectively separated by flotation. The conventional flotation process is divided into three categories: “fluorine and acid”, “fluorine-free and acid” and “fluorine-free acid-free”.
Fluorine and acid: silica-feldspar flotation separation was carried out in an acidic pH environment with a hydrofluoric acid activator and cationic collector. The flotation effect is good and the index is stable.
Fluorine-free and acid: the damage to the environment caused by fluoride ions is avoided, but the strong acid liquid in the flotation process will corrode the mineral processing equipment to a certain extent.
Fluorine-free and acid-free: Under the condition of natural pH, through reasonable allocation, anions and cations are used as collectors to preferentially flotation impurity minerals.
B. Mica mineral removal
The basic charge mechanism of mica is the same as that of feldspar, so in the process of feldspar impurity removal on silica, a large amount of mica ore is removed by flotation along with feldspar. E-8 collector can also be used, and flotation is carried out by using the charge characteristics of mica lattice. In the slurry of pH 2-3, the silica hardly floats, so that the mica impurities are floated out.
The purification process of silica should be determined according to the occurrence state of impurity minerals in raw minerals, beneficiation costs and the use and requirements of finished concentrates.