EDX showed that all particles were primarily composed of silicon- or aluminum-oxides. While the drying method involved in
sample preparation prevents direct observations of nanoparticles in situ, we expect based on the absence of isolated nanoparticles and the fact that they often appeared in clusters of varied sizes that, in their natural state, they represent a polydisperse mixture. This was true regardless of the sample pH, which was always between 6 and 8 for all sampling points on all occasions except for one event in the weir box (the slurries are significantly diluted by the time they reach the slurry
lift tank).