High‐purity amorphous silica from rice husk: Preparation and characterization

Abstract

Amorphous silica has a wide range of applications in chemical, biological and environmental sectors. In this work, we studied the preparation of amorphous silica from rice husk, an abundant silica-rich agricultural waste in Vietnam. We investigated and compared two methods of preparation: (1) via selective removal of alkaline and alkaline-earth oxides from rice husk ash to yield amorphous silica; and (2) via selective precipitation of silica from aqueous solutions which had been prepared by dissolving rice husk ask in NaOH solutions. The obtained silica was characterized by using XRD, EDX, SEM and BET techniques. The results show that the best obtained silica is a white amorphous and porous powder with high purity of SiO 2 , in the form of aggregates of 50nm-sized primary particles, and a specific surface area of 186 m 2 /g. The SiO 2 recovery is around 8.3 (g) per 100 (g) rice husk. Moreover, in the context of the present work, method (1) can be a more straightforward route for the preparation of amorphous silica in terms of silica's purity, porousity and amorphousness. In contrast, method (2) is shown for a lower grade of silica purity which could be due to strong adsorption of ions from the solution onto the amorphous SiO 2 precipitate during precipitation process. The obtained silica has promising applications as adsorbents, fillers and fertilizers.

Green synthesis and characterization of UKMRC-8 rice husk-derived mesoporous silica nanoparticle for agricultural application

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Preparation of green film with improved physicochemical properties and enhanced antimicrobial activity using ingredients from cassava peel, bamboo leaf and rosemary leaf

“…However, other researchers reported relatively lower yield; 18–20% SNPs from rice husk ( Setyawan et al., 2019 ). This variation is expected and might be due to the environmental conditions where the plants grow like other natural products ( Ngoc et al., 2018 ).…”

Green Route Synthesis of Amorphous Silica from Oil Palm Decanter Cake: From Literature Review to Experiments

“…The OPDCA at 600C was chosen to be treated with 140 mL of 5M NaOH solution. Subsequently, a broad diffraction peak at 2θ=22° confirmed that the crystalline silica has transformed into an amorphous form after being treated with an alkaline solvent, which is represented by the bellshaped peak observed in the spectrum (Bakar et al, 2016;Mosisa et al, 2019;Ngoc et al, 2018). No sharp peak was observed on the diffraction pattern, which strongly proved that the crystalline silica has not been exhibited (Anuar et al, 2018).…”