Nanosilica is a technologically important material with applications in the composites, catalysis, drug delivery and separations sectors. The high value silica exhibit well-defined particle sizes or mesoporosity for nanoparticles and for porous materials respectively. To achieve these attributes, current methods require uneconomical synthesis with high energy purification (e.g. calcination), leading to wastefulness, thus preventing their industrial implementation. Bioinspired silica, synthesised using biologically inspired organic “additives”, are greener alternatives to many existing silicas. In this presentation we will describe the discovery of new syntheses of high-value silicas that are economical and sustainable for manufacturing. The first part of the presentation will focus on the synthesis of monodisperse silica nanoparticles of sizes between 9-300 nm using bioinspired chemistry. Further, we will discuss the synthesis of mesoporous silica between 9-20 nm pores, with tightly disperse pores. We note that both syntheses occur at room temperature and neutral pH in water and within 5 minutes – this is a significant step-change compared to traditional Stöber or template syntheses. The second part of the presentation will describe the discovery that a change in 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. Once extracted, additives can be directly reused for further silica synthesis, creating new bioinspired silica from old reaction media. Process calculations indicate that our new method will reduce the carbon footprint of purification by 95-97% and reduce the additive usage by 95% through is reuse, thus significantly reducing both the cost and wastefulness. While very well characterised at lab-scale, this method has not achieved a translation to large-scale manufacturing. The final part of the presentation will include the experimental results on the effect of mixing on the synthesis, which provide fundamental insights on how mixing affects the bioinspired silica process and final silica product. Using this knowledge, we have been able to scale-up to produce hundreds of grams per day of high value nanosilicas without the need for specialist equipment, with very low energy usage and low waste produced, thus demonstrating the sustainability and scalability of the new technique.

Application of bioinspired green chemistry to design sustainable and scalable high value nanosilica

2019 Fall National Meeting

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