Synthesis and Evaluation of Rice Husk-Derived Silica: A Mini Review

Abstract

Rice husk silica (RHS) has emerged as a sustainable and high-value material derived from rice husk ash (RHA), an abundant agricultural by-product. With rice husk accounting for nearly 20% of global paddy production, its transformation into silica offers a compelling solution to waste management and resource efficiency. Rice husk (RH) is rich in silicon dioxide and can be synthesized through various techniques including acid-leaching, controlled calcination, alkaline extraction, hydrothermal processing, and emerging green methods such as microbial leaching and pyrolysis-integrated recovery. These approaches yield amorphous silica with high surface area, thermal stability, and functional surface chemistry, making it suitable for diverse applications. Evaluation of RHS reveals its unique physical and chemical properties such as high porosity, modifiable surface groups, and structural resilience, which support its use in industrial sectors like cement, rubber, and ceramics, as well as in environmental remediation and advanced technologies including drug delivery, energy storage, and carbon capture. Environmentally, RHS production reduces reliance on mined quartz, lowers carbon emissions, and supports circular economy models. Industrially, it offers a cost-effective alternative with scalable potential. Despite challenges in purity control, scalability, and market integration, RHS continues to gain traction as a versatile material for sustainable innovation.