In the production process of titanium dioxide, if impurities are not completely removed, when high temperature calcination is used, many impurity elements such as iron, manganese, vanadium, lead, chromium, cobalt, cerium copper, cadmium, nickel, molybdenum, etc. exist in the state of oxides. These colored oxides show various hues, so that the hue of the entire titanium dioxide is affected and not pure white, which greatly affects the quality of the product. Therefore, various methods must be used to remove impurities.
1 beneficiation to remove impurities
To remove impurities, we must first beneficiate. Because any ilmenite is generally mixed with a lot of gangue and other minerals that are symbiotic, associated, and compound. Beneficiation is the use of different physical and chemical properties of minerals, using various effective methods to separate ilmenite from them. For example, the gravity beneficiation of a shaking table can remove most of the gangue in the cast iron ore, and then use a magnetic separator for magnetic separation to allow the minerals to pass through the magnetic field. Because ilmenite has high permeability and can be attracted by magnets, it cannot be absorbed by itself. Iron, a paramagnetic mineral that can be magnetized and demagnetized, can be attracted to magnetic disks, and other non-ilmenites with low permeability cannot be attracted to magnetic disks to be separated.
2 In addition to insoluble impurities
Titanium dioxide produced by sulfuric acid method is turbid and unclear titanium liquid obtained by acid leaching. Its insoluble impurities are mainly mechanical impurities with larger particles and colloidal impurities with smaller particles. Mechanical impurities are unreacted ilmenite minerals, which are in a coarsely dispersed state and are easy to precipitate; colloidal impurities are mainly aluminosilicates, etc., due to their small particles, which adsorb H and carry the same positive charge. The charges repel each other, and it is difficult for the colloidal particles to get close to larger particles and settle down, so they have higher stability. The solution is to use a negatively charged modified polyacrylamide colloid for electrical neutralization, so that the colloidal particles can aggregate and settle for removal. However, due to the incomplete sedimentation of the colloid, after the filtration of ferrous sulfate, there is still some filtration and exists in the titanium liquid. It is necessary to use a plate and frame filter press with charcoal powder as a filter aid to perform filtration until the filtrate is detected The clarity is qualified.
