Utilization of Expanded Perlite as a Source of Silica for Synthesizing Wollastonite by Solid State Reaction

Abstract

Naturally occurring volcanic glass in the form of the expanded perlite consist of 72.59wt% silica was used as a starting material together with the calcined eggshell in order to explore the wollastonite formation via solid state reaction. The molar mixing ratios of CaO:SiO2 were carried out from 1:0.8 to 1:1.4, calcined in the range of 600 - 1100°C for 2 - 5 hours. The XRD results confirm the formation of wollastonite (CaSiO3) started at 800°C, and increasing of calcination temperature favoured the formation of gelehnite (Ca2Al2SiO7) associated with wollastonite. The morphology characterized by SEM clearly show tiny needle-like shape of primary wollastonite on the surface of agglomerate particles. The CaO:SiO2 ratio of 1:1.4 which calcined at 1100 °C for 2-5 hours was found to be the most appropriate molar ratio in the case of using the calcined eggshell and expanded perlite as starting materials.