Abstract
Developing more sustainable and economical viable strategies to access high value-added products from alternative and less costly sources is currently a challenge in the chemical industry. Silica is among the most used chemicals and is widely used in many industrial applications such as toothpastes as a cleansing agent, rubber industry as a reinforcing agent, as an anticaking agent in cosmetics, in salts, and so on. This review summarizes alternative approaches for the synthesis of porous and hybrid silica as well as silica composites. So far, these phases are mostly synthesized from molecular silane precursors via hydrolytic sol–gel chemistry or via combustion processes of chlorosilanes, and therefore indirectly from quartz sand. However, quartz sand is a non-renewable resource, and the actual sand shortage becomes more and more problematic for various processes in the chemical industry. Indeed, quartz sand is the world’s second most consumed raw material after water and its availability has high impact on numerous production processes, e.g., in healthcare or in electronics. In the actual context of sand shortage, the elaboration of silica-based materials from alternative sources attracts more and more interest. This review article describes new ways to access silica-based materials from alternative sources such as biosourced and renewable feedstocks, waste electrical and electronic equipment or from fluorosilicic acid, a by-product of the phosphate industry. We show that silica must be considered as a valuable raw material and that alternative production processes from renewable resources as well as cyclic lifetime assessment and valuable recycling strategies of these materials should be considered in view of the elaboration of more sustainable and cyclic production processes. A comparative study between different sources will be given regarding the silica extraction methods, the types of silica, stability, and performance of the as-obtained nanosilica materials. Perspectives regarding the potential large-scale production of nanosilica and their hybrid or composite materials from these alternative sources will be also discussed.