Advanced Microscopy of Inorganic Colloids Sampled From Consecutive Stages of RO Filtration

Understanding the phenomena governing silica scaling in reverse osmosis (RO) relies on properly characterising the water matrix. One of the challenges to characterising water samples is the presence of inorganic nanoparticles, which are difficult to detect and analyse. In this work we develop a straightforward approach for nanoparticle trapping, detection, visualisation and elemental analysis by means of electron microscopy. The new approach is applied to characterise samples from three consecutive stages of RO in a water treatment facility. Transmission electron microscopy grids are employed with and without carbon films, to capture nanoparticles. We find that film coated traps are more effective in collecting colloids, and the colloids collected are of similar size. For the waters tested, the nanoparticles are rich in silica and the number of particulates increases with the advancement of the RO process.