Removal of Titanium Dioxide Nanoparticles in a Monovalent Electrolyte via Conventional Water Treatment Methods
Authors:Christine Brown, Ryan Honda, Stacey Nwagbara
Mentor:Sharon Walker, Associate Professor of Chemical/Environmental Engineering, University of California, Riverside
Titanium Dioxide (TiO2) is a type of nanoparticle (NP) that is ubiquitous in many industrial and common household applications. These nanoparticles range from 1-100 nanometers. Growth in its use is causing researchers to look into the long term effects of exposure to TiO2. Studies on mice have shown NP to be cancerous in large amounts. Currently, there’s no set guideline as to how much humans can safely consume. Nanoparticles may end up in our drinking water from various sources of commercial waste or domestic waste water. This experimental study focuses on the removal of TiO2 from a monovalent solution (KCl). This is conducted via jar tests on a micro scale level. The first step is coagulation where a coagulant (Al2(SO4)3, aka alum) is added to destabilize the NP. The next 30 minute step, flocculation, allows for NP to aggregate and from flocs. The final step, sedimentation, which is one hour, allows for the flocs to settle out of solution. Samples are extracted from the jars after each step and undergo characterization studies (zeta potential and dynamic light scattering). The average particle size and charge were 1.2 microns and 30 mV, respectively. Up to date, this study has shown between 70-80% removal of TiO2 in the KCl solutions after the final treatment stage (sedimentation) with a 100 mg/L concentration of NP and a 50 mg/L alum dose. However, at the lower (more environmentally relevant) TiO2 concentrations, removal was notably lower, ranging between 0 - 15% in both KCl solutions.