Particle emission rates during electrostatic spray deposition of TiO₂ nanoparticle-based photoactive coating

Here, we studied the particle release rate during Electrostatic spray deposition of anatase-(TiO₂)-based photoactive coating onto tiles and wallpaper using a commercially available electrostatic spray device. Spraying was performed in a 20.3m³ test chamber while measuring concentrations of 5.6nm to 31μm-size particles and volatile organic compounds (VOC), as well as particle deposition onto room surfaces and on the spray gun user hand. The particle emission and deposition rates were quantified using aerosol mass balance modelling. The geometric mean particle number emission rate was 1.9×10¹⁰s^-1 and the mean mass emission rate was 381μgs^-1. The respirable mass emission-rate was 65% lower than observed for the entire measured size-range. The mass emission rates were linearly scalable (±ca. 20%) to the process duration. The particle deposition rates were up to 15h^-1 for <1μm-size and the deposited particles consisted of mainly TiO₂, TiO₂ mixed with Cl and/or Ag, TiO₂ particles coated with carbon, and Ag particles with size ranging from 60nm to ca. 5μm. As expected, no significant VOC emissions were observed as a result of spraying. Finally, we provide recommendations for exposure model parameterization.