4. Conclusions
Silica in cogon grass was extracted and characterised in this study.
Based on the study, cogon grass contains relatively low concentration
of silica (2.9 ± 0.1 wt.%). Nevertheless, this grass is still a potential
source of silica due to the natural abundance of the grass. Based on
the 10 metric tons of cogon grass that can be cut down per hectare of
land, a conserve estimate on 500 million hectares of infested land will
provide 145 millionmetric tons of amorphous silica reserve. In addition,
based on the calculated kinetic parameters and LHV, the heat released
(10,648 kJ g−1) during decomposition may also be reused to sustain
the combustion of cogon grass, or be channelled to other applications
as a zero-cost fuel. The analysis performed in this work confirms that
the overall quality of amorphous silica obtained from cogon grass rivals
those extracted fromother sources and may be suitable for many applications.
However, the purity of silica obtained is highly dependent on
how well the minerals in cogon grass can be removed. The result
of acid leaching shows that effective removal of minerals can be
achieved via long leaching periods (120 min) and high acid concentration
(2 mol L−1).