(382f) Modeling Aggregation and Size Distribution of Nanoparticles with Monte Carlo Simulation

The size distribution of the nanoparticles and their aggregates is crucial for predictions of the fate and transport of nanoparticles in the environment. Both diffusion and interaction of nanoparticles with solid surfaces (including sedimentation), as well as living organisms are affected by the size of the particles. In order to obtain the nanoparticle size distribution over the expected ranges of water chemistry and nanoparticle properties, predictive models are needed to assess the aggregation tendency of nanoparticles. In the present work, a constant-number kinetic Monte Carlo based model was developed to predict the aggregation rate and size distribution of nanoparticles. Model performance was evaluated using experimental dynamic light scattering (DLS) measurements of the evolution of nanoparticle size distribution under varying conditions (e.g., pH, ionic strength, size distribution of the primary nanoparticles, and nanoparticle surface charge). The modeling approach followed the "particles in a box" simulation method while allowing for particle sedimentation. The likelihood of nanoparticle aggregation was determined, based on the classical DLVO theory, via calculation of the aggregation probability of nanoparticle pairs, with the particle number density dynamically adjusted to ensure mass conservation. Model performance compared favorably with DLS data demonstrating the potential of the present modeling approach for use in environmental analysis of the transport and fate of nanoparticles.