Multiscale modeling for nanoscale surface composition of spray-dried powders: The effect of initial droplet size

ABSTRACT

The surface composition of spray-dried powders is influenced by spray drying conditions in a complex manner. Among them, precise control of the size of atomized droplets is most challenging and the droplet size affects the surface composition of dried powders. A multiscale approach that couples molecular-level packing interpretation with a continuum diffusion model was introduced recently to predict surface compositions of spray-dried monodisperse powders. In this work, the method is extended to take the droplet size distribution into account. Detailed sample calculations for the lactose–protein systems have demonstrated that not only the average size, but also the standard deviation of the size distribution of atomized droplets affect predictions significantly when the precursor solution contains a small amount of protein. Model predictions of the effects of droplet size on surface coverage of protein have been validated using published experimental data. Moreover, model-based analysis provides important insights into our understanding of the X-ray photoelectron spectroscopy measurement data on surface chemical composition.

KEYWORDS:

• Multiscale modeling
• particle size distribution
• spray drying
• surface composition
• XPS (X-ray photoelectron spectroscopy) measurement