Abstract Summary (Max 250 words)
Porous nanosilica particles are widely used in various applications due to their high surface area and tunable surface properties. Bio-inspired silica (BIS) synthesis offers a sustainable route for producing such materials under ambient conditions. In this process, a solution of sodium silicate is mixed with acidic medium (liquid, like HCl, or gaseous, like CO2). This causes precipitation, an intrinsically fast reaction, rendering the process sensitive to transport processes like micromixing and mass transfer. Previous studies have demonstrated influence of bulk pH, precursor concentration, and reactor configuration on critical properties of BIS. In this work, we investigate influence of micromixing (for liquid acidic streams) and mass transfer (with gaseous CO₂) on pH control, yield, and productivity for continuous synthesis of BIS particles. The synthesis was carried out using three fluidic devices – pinch tube, fluidic oscillator, and vortex-based cavitation device (VD), covering a wide range of micromixing times. We observed that surface area and particle size are strongly dependent on micromixing-controlled acidification rates for the HCl-based synthesis route. In addition, the effect of bubble size for the CO2-mediated silica synthesis is investigated by introducing VD for generation of fine bubbles. Enhanced gas-liquid mass transfer and reduced bubble size lead to smoother pH evolution and measurable changes in product properties, highlighting the importance of interfacial area as a design variable. Overall, this work establishes micromixing and mass transfer as tunable levers for controlling BIS characteristics and provides rational framework for designing scalable, continuous synthesis processes.
