Measurement of ethanol concentration for monitoring the solvent exchange during the alcogel preparation

A crucial and time-consuming stage in aerogel production is the solvent exchange process for alcogel formation. This process involves multiple steps, exposing the hydrogel to ethanol solutions with increasing concentration until the equilibrium in each step. Currently, the determination of contact time between phases (hydrogel and liquid solution) is either arbitrary or based on prior studies. However, considering the unique physicochemical characteristics of each system, as well as the solid-liquid interactions and the liquid diffusion within the matrix, the required time may vary. Monitoring this step can lead to a reduction in the time needed for alcogel production and the optimization of the entire process. The refractive index serves as a tool to assess ethanol concentration in the liquid solution over time, providing immediate information about the status of the solvent exchange. Alongside, differential scanning calorimetry can be employed to evaluate ethanol content in the alcogel (solid phase), confirming the attainment of equilibrium between phases.

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  This research introduces a technique for monitoring solvent exchange.
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  Refractive index measurement of the liquid solvent offers immediate concentration information into the status of the solvent exchange.
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  Differential scanning calorimetry is applicable for measuring the ethanol content within the alcogel and validating refractive index findings.