Study On Recycling Of Titanium Dioxide From Red Mud Slag Leached By Sulfuric Acid

The recycling of secondary resources exerts profound influence on the resource problems facing the world today. Red mud is the solid waste produced in production process of alumina. It is discharged and piled in abundance. The abundant discharge and piling of red mud bring about enormous pressure to environment. At the same time, it is also a huge waste of resources. Red mud is rich in iron, aluminum, titanium and rare earth elements. To recover valued metals in red mud is of great significance for the comprehensive utilization of red mud.This paper summarizes research status of red mud at home and abroad. Then make a study on chemical composition, element occurrence state and particle size distribution of red mud slag generated by hydrochloric acid leaching. In addition, the author put forward the process flow of titanium dioxide recovered by leaching red mud.The results of chemical analysis showed that the main chemical components of red mud slag is silica(41.4%), iron oxide(14.21%), alumina(9.67%), titanium dioxide (5.78%), calcium oxide (5.67%) and so on. XRD analysis showed that the main phase of red mud slag is perovskite, titanium acid iron calcium, calcium ferrite, chloride aluminate calcium, tricalcium aluminate, aluminosilicate calcium, and aluminate calcium sodium etc. Particle size analysis indicated that compared with red mud, particle size of red mud slag increased markedly and the specific surface area of red mud slag reduced significantly.According to the theoretical analysis of sulfuric acid leaching of red mud slag, the main influencing factors in sulfuric acid leaching of titanium contain the leaching temperature, concentration of sulfuric acid, leaching time and liquid-to-solid rate. By the orthogonal experiment, the influencing factors of TiO2leaching rate in the sequencing order is:concentration, liquid-to-solid ratio, temperature, and time. The optimal conditions for acid leaching are as following:150DEG C for leaching temperature,9mol/L for sulfuric acid concentration,6:1for liquid-solid ratio. Under such conditions, the average leaching rate for TiO2is95.2%.In addition to titanium salt in sulfuric acid leaching solution, there is aluminum, iron sulfate and a small amount of silicic acid. Orthosilicate in leaching solution is removed by seeding-insulation in order to reduce the impact on extraction of iron. By three groups of single-factor test, the optimal decilication conditions are as following:150DEG C for decilication temperature, mass fraction of2%seed and desilication of6h. Under this condition, desilication rate for leaching solution reaches90.2%. After decilication of leaching solution, tributyl phosphate can be adopted to extract iron in sulfuric acid leaching solution mixed with a good amount of Cl". By means of test, the optimal conditions for extracting iron are as following:at room temperature (20degrees C), the phase ratio for O/A is1:1; the concentration of Cl-is4mol/L; under the condition that the organic phase TBP accounts for50%, the extraction rate for iron reaches96.8%; iron-recovery rate reaches95.3%, when the solution is extracted and neutralized by0.01mol/L hydrochloric acid.After the extraction of iron in leaching solution, ammonia water is added to adjust acidity of leaching solution and remove part of aluminum sulfate in leaching solution. Based on titanium hydrolysis experiments, the optimal hydrolysis conditions should be as following:2for F value of titanium solution,120min for hydrolysis time,100DEG C for hydrolysis temperature,1%for seed adding amount. Under these conditions, hydrolysis rate for titanium is92.7%.