Abstract:
A thermo-chemical treatment method was used to produce biogenic amorphous silica
from South African sugarcane and maize residues. Different fractions of South African sugarcane
(leaves, pith, and fiber) were processed for silica production. The biomass samples were leached
with either 7 wt% citric acid or 7 wt% sulfuric acid at 353 K for 2 h prior to being rinsed, dried and
combusted using a four-step program ranging from room temperature to 873 K in a furnace. The
characterization of the pre-treated biomass samples was conducted using thermogravimetric analysis
(TG/DTA), X-ray fluorescence analysis (XRF) and elemental analysis (CHN), while the final products
were characterized by XRF, X-ray diffraction (XRD), elemental analysis, nitrogen physisorption and
scanning electron microscopy (SEM). Citric acid pre-treatment proved to be an attractive alternative
to mineral acids. Amorphous biogenic silica was produced from sugarcane leaves in good quality
(0.1 wt% residual carbon and up to 99.3 wt% silica content). The produced biogenic silica also had
great textural properties such as a surface area of up to 323 m2 g
−1
, average pore diameter of 5.0 nm,
and a pore volume of 0.41 cm3 g
−1
.
