Synthesis of White Mineral Trioxide Aggregate (WMTA) Using Silica from Rice Husk Ash and CaCO<sub>3</sub> from Limestone

Abstract

White mineral trioxide aggregate (WMTA) was successfully synthesized using silica from rice husk ash (RHA) and precipitate calcium carbonate (PCC) from limestone. Silica was synthesized from rice husk ash by the sol-gel method with the help of a strong base NaOH to obtain sodium silicate solution. In contrast, PCC in the calcite structure was extracted from limestone by a carbonation method. The limestone powder sample was calcined at 900 °C for 3 hours, dissolved in 0.8 M nitric acid solution, and was followed by carbonation for 60 minutes. The synthesis of WMTA was carried out by mixing silica, PCC, bismuth oxide, aluminum oxide, NH3 solution catalysts and treating the mixture thermally at 950 °C for 3 hours. Products were characterized by Fourtier-Transform Infrared (FTIR) spectroscopy, X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). The results showed that the RHA silica had an amorphous phase that peaked at 2θ= 22°, but the background intensity was irregular. The PCC obtained through isolation from limestone is predominantly calcite structure. WMTA has been successfully synthesized by thermal treatment at 950 °C using NH3 solution catalyst, as evidenced by the presence of tricalcium silicate (C3S), dicalcium silicate (C2S), tricalcium aluminate (C3A), and Bi2O3.