Sustainable Harnessing of SiO2 Nanoparticles from Rice Husks: A Review of the Best Synthesis and Applications

Abstract

The extraction of silica particles from rice husks has been extensively studied. This review aims to present the most efficient approach to harnessing rice husk biomass and converting silica into high-value-added materials for direct applications to address current challenges like water purification. Rice husks, as a residue from agriculture, had been largely used as a source of power through direct incineration in major rice-producing countries. However, rice husks present an intriguing opportunity as a renewable source of SiO2, offering a low-cost adsorbent with a high surface area and ease of functionalization that can be transformed into diverse mesoporous silica structures or composites, enabling applications in catalysis, drug delivery, water treatment, etc. This dual potential of rice husks can be harnessed by combining bio-oil and syngas production through pyrolysis with the efficient extraction of SiO2, ensuring the comprehensive utilization of the biomass. This review not only highlights the immense potential of silica nanoparticles but also serves as a roadmap for future investigations, with the ultimate aim of harnessing the full capabilities of this renewable and sustainable resource, contributing to the circular economy by yielding valuable by-products.

Direct pseudomorphic transformation of silica from rice husk into organo-functionalized MCM-41

“…2 RH has attracted much attention in recent years as a source of biogenic silica nanoparticles. 3 Besides being a bio-based material, this silica is also a material of circular economy, as it is a by-product of agricultural activities that will gain much higher value thanks to its applications. The production of this bio-circular silica will be launched by the end of 2024 by Solvay in Europe (Livorno, Italy) as an alternative to silica nanoparticles coming from sand for the tires industry.…”

“…6–8 Various researchers have developed methods to reach high-purity silica from different sources of RH (see for example a recent review on the best synthesis to produce silica nanoparticles from RH and its applications). 3…”

A Comparative Study on Rice Husk, as Agricultural Waste, in the Production of Silica Nanoparticles via Different Methods

“…Rice husk is a prevalent agricultural by-product in many rice-producing regions worldwide [ 20 ]. Approximately 20 kg of rice husk waste is produced for every 100 kg of paddy grain processed into rice [ 21 ]. The International Grains Council (IGC) has released data that project global rice production to reach 511.3 million tons in 2023/24, resulting in the production of 102.3 million tons of rice husk waste.…”