TiO_2选择性富集的物理化学行为

Physical Chemistry Behavior of Enrichment Selectivity of TiO_2 in Perovskite

创造合适的物理化学条件 ,可使富钛还原性熔渣体系 (CaO- SiO2- TiOx- MgO- Al2O3)中的钛组分在化学位梯度的驱使下 ,选择性地富集于钙钛矿相中 ,从而便于分离与提取 .促进钛组分选择性富集的物理化学成因可归结为 :将熔渣在高温下氧化 ,可使渣中低价钛转变为四价钛而增加 TiO2活度 ;此外 ,提高熔渣碱度可增加渣中 CaO活度 ,这些均增强了钙钛矿析出反应 TiO2＋ CaO = CaTiO3(s)的热力学趋势 ,促使渣中的 TiO2尽可能与 CaO结合生成钙钛矿并随之析出 .实验结果表明 ,将碱度调整在 1.3的熔渣彻底氧化 ,可使其中 80％左右的 TiO2富集于钙钛矿相中 ,其富集程度相对于调质与氧化前增加约一倍 .

For a Ti-enriched reductive slag system of CaO-SiO2-TiO-MgO-Al2O3, creating an optimum physical chemistry condition will selectively enrich TiO2 in perovskite at the drive of its chemical potential during slag's cooling. To investigate this physical chemistry behavior, two approaches were carried out. One was by oxidizing the slag at high temperatures and another was by adjusting the slag basicity. The physical chemical mechanism of selective enrichment was as following: Oxidization of molten slag could change multivalent Ti compounds into TiO2 and increase the activity of TiO2 within the slag. TiO2 combined with CaO in the slag forming perovskite. The oxidation not only changed the compositions and structures of the slag phases but also caused majority of TiO2 migrating into perovskite. The increment of perovskite precipitated by oxidization could go up to 30% to 40% of the precipitation in its original slag. It was found that raising the slag basicity could increase the activity of CaO in the slag that facilitated the selective precipitation of perovskite as well. Both approaches could promote the forward reaction of perovskite precipitation, TiO2 + CaO = CaTiO3 (s), if slag basicity was adjusted up to 1.3 and this slag was oxidized sufficiently, about 80% amount of TiO2 in slag could be collected in the form of perovskite.