Recent progress of wastes derived nano-silica: Synthesis, properties, and applications

Recently, nano-silica (NS) particles with their tailorable property had gained widespread attention due to their broad and emerging application areas, which included adsorption, biomedical, polymer filler, catalyst, and optical devices. Generally, NS particles were commercially prepared from expensive raw (alkoxysilane compounds) materials with complicated processes, which inspired researchers to seek alternatives. Meanwhile, the fast-economic growth had led to the generation of enormous wastes from the agricultural, industrial, municipality, and mining fields. In the past decade, significant progresses had been made on utilizing the waste ingredients with novel processing methodologies to synthesize the NS, resulted in better purity, porosity, control shape, size, and significant improvements in the extraction yields. This study presents a review of the recent advancements in NS's and silica aerogel synthesis using agricultural, industrial, municipality, and mining wastes. It is also focused on appliance technologies along with their process-dependent properties and suitable applications. This work will draw the attention of research and industries to the potential of silica-containing wastes as sustainable resources for NS's preparation. The future research directions and the challenges for the commercial application of NS are also presented. The waste to NS conversion is expected to solve the disposal problems and conserve natural resources.