Removal of iron in rice husk via oxalic acid leaching process

Rice husk (RH), an agricultural waste which has been used as an alternative source for silica (SiO₂). In order to produce high purity amorphous SiO₂ from RH, acid leaching pre-treatment was required to remove the metallic impurities, followed by calcination at 800 °C to obtain the ashes. This research was studied about using oxalic acid as the leaching agent to remove iron (Fe) content in RH. The experimental parameters used in this study were acid concentration, reaction temperature, and leaching time. Based on the chemical composition analysis, the highest SiO₂ content of 99.30% and the lowest Fe₂O₃ content of 0.43% were to be found in RHA which had treated under optimum parameters of 1.0 M of oxalic acid concentration, 90 °C of reaction temperature and 3 hours of leaching time. In addition, the particles of TRHA were observed with a tubular porous structure and irregular shape due to the leaching effect. Phase analysis by x-ray diffraction show that the amorphous SiO₂ was confirmed as a broad diffused peak. It's been found in the 2θ angle range of 18° to 30° with no crystalline peak observed. (paper)