Alkali-Hydrothermal Synthesis of Acicular Tobermorite Using Natural Mineral K-Feldspar Powder

摘要

This research reports a new economical method of preparing acicular tobermorite as well as high-valuable KOH obtained. Acicular tobermorite was hydrothermally synthesized at 180 similar to 250 degrees C for 4 similar to 8 h using the K-feldspar powder and CaO chemical firstly while the filtrate could be used to prepare KOH. The K-feldspar powder used is from Luonan county of Shaanxi province in China. The XRD analysis indicated that the main phase is microcline with the content of 91%. The chemical analysis showed that the main chemical components of the K-feldspar powder are SiO2 64.53%, Al2O3 16.70% and K2O 14.75% in mass. The micrographs of the synthesized samples at the condition of different water/solid ratios, hydrothermal treated temperature and time were investigated. It is concluded that the well-crystallized tobermorite was formed with the acicular shape when the synthesized parameters were as follows. nCa/n(Si+Al) = 0.83, Water/Solid(in mass) = 20, T = 250 degrees C and t = 8h. The synthesized well-crystalline tobermorite sample was characterized by the use of chemical analysis, powder X-ray diffraction and scanning electron microscope. It is shown that the synthesized sample is acicular with the diameter of around 0.2 similar to 0.5 mu m.