Effect of concentration on extraction of silica from rice husk, rice husk ash and imperata cylindrica via acid leaching treatment / Noratiqah Syahirah Mohd Zarib

Rice Husk and Imperata cylindrical (Cl) are natural agriculture waste and abundantly
waste that can be used as an effectively resources for production of silica (SiO2). Silica
can be apply as an additive for the manufacture of plastics and rubber; as a strengthening
filler for concrete and other construction composites. The purpose of this study is to
find an alternative way to extract the silica from the natural fibres which are Rice Husk
and Imperata cylindrica via acid leaching treatment, due to silica as a raw material that
can be contribute in industrial. Acid leaching treatment are carried out to extract the
silica and remove metallic impurities in Rice Husk and Imperata cylindrica. Besides,
the parameters such as concentration of acids and leaching time using organic and
inorganic acid leaching method are also analysed. In this research, the extraction of
silica from RH and Imperata cylindrica are done via acid leaching treatment using
organic and inorganic reagent known as hydrochloric acid (HCL) and citric acid
(C6H8O7). The scope of this research are to analyse the effect of acid treatment, the
effect of extraction on stirring time and different solvent used to the yield of silica
produced. The performance of this research is covered on several testing which are
scanning electron microscopy (SEM)/Energy Dispersive X-ray (EDX) analysis, X-ray
diffraction (XRD) spectroscopy analysis and Thermogravimetric Analysis (TGA) and
for mechanical properties are Impact testing (ASTM D256) and Tapped Density
(ASTM D7481-09) to analyse the samples. As a conclusion, results proved that silica
can be extracted from all natural fibres uses; RH and Imperata cylindrica using
concentration of 1.0 M of HCL acid at 90 minutes of stirring time compared with 0.1
M and 0.5 M. The purity of silica extracted for RH is more than 90% however for
Imperata cylindrica is more than 80%. All test and analysis results showed that 1.0 M
of treated RHA has the highest purity of silica content, crystalline in phase, highest
thermal stability, and impact strength and density rather than RH and Imperata
cylindrica.