CHARACTERISTICS OF WOLLASTONITE SYNTHESIZED FROM RICE HUSK AND RICE STRAW

Abstract

In this work, two types of paddy wastes i.e. rice husk and rice straw have been used as silica (SiO2) sources to synthesize CaSiO3. Precursor, the husk and the straw were burnt at 950  °C for 1 h to obtain the ash. Some characterization were done to investigate properties of the rice husk ash (RHA) and rice straw ash (RSA) such as XRD, XRF, FTIR and heavy metal element analyses. RHA and RSA contain about 89.50 and 79.0 wt. % of crystalline silica in the cristobalite phase, respectively. The CaSiO3 was synthesized using RHA and RSA mixed with CaO separately with SiO2:CaO molar ratio of 55:45. The prepared sample was autoclaved, sintered at 950 °C and followed by characterization using XRD and FTIR analyses. For heavy metal elemental study, metal panel that included As, Cd, Hg and Pb were selected and both precursor, RHA and RSA had fulfilled the requirement of ASTM F1538-03 standard specification. XRD results show that a single phase β-CaSiO3 was obtained after 8 h of autoclaving and sintering at 950 °C but different sintering time, which is 2 h for RHA and 3 h for RSA. The different in sintering time was due to the silica content in RHA and RSA. Results obtained from the study show that RHA and RSA can act as a precursor for wollastonite but required different synthesizing parameters.