A comparative study on physio-mechanical properties of silica compacts fabricated using rice husk ash derived amorphous and crystalline silica

Recent Advances on Porous Siliceous Materials Derived from Waste

“…In particular, by increasing the heating rate, an increment of the SSA and pore volume of the remaining ashes occurred as far as a reduction in SiO 2 purity and brightness. Interestingly, a multi-step decomposition of rice husk and rice straw was observed during the laboratory studies to obtain high-purity SiO 2 with a low-carbon content and high SSA (>200 m 2 g −1 ) [ 102 , 103 ]. Specifically, the first stage corresponded to drying (50–200 °C) for the removal of physically bonded water, the second stage involved the burnout of volatile organic components with (200–340 °C), and the final stage was due to the degradation of carbonaceous phase cellulose and hemicellulose (340–500 °C).…”

“…This strategy guarantees the amorphous structure of SiO 2 since the operating temperature of the plant (600–800 °C) can be kept below the SiO 2 crystallization temperature [ 103 , 106 , 107 ]. However, even if this method can reach a productivity of 100 kg h −1 of raw rice husks, preserving the resulting SiO 2 from self-aggregation phenomena and maintaining high SSA (compared to the alkaline extraction method [ 108 ]), the further upscaling of this combustion process at the industrial level still presents some technological limitations, such as the need for time-consuming procedural sequences [ 109 , 110 , 111 ].…”