Dissolution Behavior Of Titanium And Rare Earth Elements In Perovskite Scale

Scarring in alumina production has always been one of the difficult problems restricting the development of alumina industry.Perovskite scarring occurs largely in the inner wall of the high pressure dissolution heating presser,which has the characteristics of high titanium,high rare earth elements and low impurities.In this paper,perovskite scar of a representative alumina enterprise in Guizhou is selected as the research object.Based on its mineralistics,the dissolution behavior of titanium and rare earth elements in the sulfuric acid system is studied to explore its dissolution mechanism,providing theoretical basis for the recovery and utilization of perovskite scar and optimization of the high-pressure dissolution process of alumina production.Mineralogy study of perovskite scar shows that the main chemical components in perovskite scar are TiO₂,CaO,Fe₂O₃,Na₂O,SiO₂ and Al₂O₃ in order of content,among which the TiO₂ content is 33.23% and Ca O content is 29.38%.There are mainly Ce,La,Nd,Pr and Sm rare earths,mainly light rare earths,with a total content of up to 5369.50 PPM.The main physical phases of perovskite scarring are perovskite,hematite and sodium aluminosilicate slag,and the scarring structure is hematite,microcrystalline calcium titanate,cryptic calcium titanate and sodium aluminosilicate slag.Titanium mainly occurs in microcrystalline calcium titanate and cryptocrystalline calcium titanate laminae.Rare earth occurs in the form of similar isoforms in the edge clasts of perovskite,calcium titanate gel and aluminosilicate sodium potassium crystals.The dissolution experiment of perovskite scar in sulfuric acid system shows that the separation of rare earth and titanium can be realized by two dissolution method.Compared with secondary dissolution,in the primary dissolution with low temperature?80??and low acid concentration?2 mol/L?,the dissolution rate of rare earth could reach 78.0%,and the dissolution temperature had the greatest influence on the dissolution rate of rare earth.In the secondary dissolution of titanium at high temperature?180??and high acid concentration?11 mol/L?,the dissolution rate of titanium could reach 94.4%,and the dissolution temperature had the greatest influence on the dissolution rate.Perovskite scarring dissolution mechanism analysis showed that a dissolution reaction,hematite,rare earth and sodium aluminum silicon slag spontaneous reaction under the system of dilute sulphuric acid,sodium aluminum silicon slag,dissolution of the perovskite rare earth element,in addition with the increase of temperature,a small amount of perovskite clastic react with dilute sulphuric acid,generated a half water calcium sulfate precipitation and unreacted perovskite residues in slag.In the secondary dissolution reaction,at high temperature and sulfuric acid concentration of perovskite,calcium sulfate hemihydrate and perovskite are converted into calcium sulfate crystals,and a large amount of titanium in perovskite is dissolved,resulting in calcium sulfate precipitation remaining in the secondary dissolution slag.