(177g) The Application of Green Chemistry to Enable Sustainable Manufacture of Bioinspired Nanosilica

Porous silica is a technologically important material with applications in the polymer-composites, catalysis, drug delivery and separations sectors, with an estimated market value of $3.6 billion per annum. Bioinspired silica, synthesised using biologically inspired organic “additives”, are greener alternatives to many existing silicas. However, bioinspired (and other templated) silicas require high energy purification e.g. high-temperature calcination, leading to material and energy wastefulness, and preventing their industrial implementation. Although alternatives to calcination have been reported, e.g. solvent extraction, they are at least as energy intensive as calcination so are unsustainable on a larger scale.

Using recently developed molecular dynamics force-fields for amorphous silica surfaces, we have investigated the extraction of additives from silica surfaces for the first time. We discovered that pH can be used to controllably extract additives from silica hybrids without the need for any further energetic driving force, unlike the traditional mesoporous silicas. Unlike other purification methods, modification of silica surface chemistry through partial extraction was possible, thus creating a wide range of tailored silicas directly. Furthermore, with the ability to directly modify silica surface chemistry rather than using separate purification and functionalisation steps, we have been able to eliminate a synthesis step from the production of silica entirely. Once extracted, additives can be directly reused for further silica synthesis, creating new bioinspired silica from old reaction media. We have therefore been able to scale-up to produce hundreds of grams per day without the need for specialist equipment, demonstrating the improved scalability of the new technique. Process calculations indicate that extraction and additive reuse can reduce the energy requirements of purification by over 90% compared to conventional purification methods, while the room temperature reaction can reduce the energy requirement by 90%, thus significantly reducing both the cost and wastefulness. Therefore, by applying green chemistry principles to the synthesis and purification of bioinspired silica we have developed a cleaner, cheaper, and readily scalable method for silica production, a significant technological advance. We show that this method provides an effective “lab to market” route in applications ranging from environmental remediation to drug delivery.