Cassava Starch Pearls as a Desiccant for Drying Ethanol

The fuel ethanol industry uses corn grits packed in fixed bed adsorption towers to dry hydrous ethanol vapors in an energy efficient manner. Spherical micropearl cassava starch exhibit a higher adsorption capacity than corn grits of the same size and may be a viable replacement for ground corn. Adsorption equilibrium curves, BET surface area measurements, and SEM images provide an explanation for the enhanced performance of cassava micropearls based on particle architecture and the surface area available to water molecules. The SEM images show that the micropearls form a core–shell structure with pregel starch acting as the scaffold that holds starch granules in an outer layer. This layer determines the BET surface area and the measured equilibrium adsorption capacity. The core–shell microstructure results in a shortened diffusion path-length and enhanced adsorption rates. These microstructural and operational characteristics provide a template for microfabrication of enhanced capacity starch based spherical adsorbents that could replace ground corn for the drying of ethanol.