The effect of electrolytes on the aggregation kinetics of titanium dioxide nanoparticle aggregates
- 409 Downloads
Metal oxide nanoparticles (NPs) are receiving increasing attention due to their increased industrial production and potential hazardous effect. The process of aggregation plays a key role in the fate of NPs in the environment and the resultant health risk. The aggregation of commercial titanium dioxide NP powder (25 nm) was investigated with various environmentally relevant solution chemistries containing different concentrations of monovalent (Na+, K+) and divalent (Ca2+) electrolytes. Titanium dioxide particle size increased with the increase in ion concentration. The stability of titanium dioxide also depended on the ionic composition. Titanium dioxide aggregated to a higher degree in the presence of divalent cations than monovalent ones. The attachment efficiency of NPs was constructed through aggregation kinetics data, from which the critical coagulation concentrations for the various electrolytes are determined (80, 19, and 1 meq/L for Na+, K+, and Ca2+, respectively). Our results suggest that titanium dioxide NP powders are relatively unstable in water and could easily be removed by adding multivalent cations so hazardous potentials decrease in aquatic environment.
KeywordsNanoparticle Titanium dioxide Cation Attachment efficiency Ionic strength
The authors thank Environmental Protection Administration (EPA), Taiwan for the financial support under Contract No. EPA-97-U1U1-02-104. The authors would also send their gratitude to Prof. Shian-chee Wu, Prof. Ruey-an Doong, Dr. Gwo-Dong Roam (Taiwan EPA), and Desiree L. Plata (Duke U. in USA) for their valuable comments on this study.
- Elimelech M, Gregory J, Jia X, Williams RA (1998) Particle deposition and aggregation—measurement, modelling and simulation. Elsevier, AmsterdamGoogle Scholar
- Hiemenz P, Rajagopalan R (1997) Principles of colloid and surface chemistry. Marcel Dekker, New YorkGoogle Scholar
- Phenrat T, Saleh N, Sirk K, Kim H-J, Tilton R, Lowry G (2008) Stabilization of aqueous nanoscale zerovalent iron dispersions by anionic polyelectrolytes: adsorbed anionic polyelectrolyte layer properties and their effect on aggregation and sedimentation. J Nanopart Res 10(5):795–814CrossRefGoogle Scholar
- Research L (2008) Sizing nanotechnology’s value chain. New YorkGoogle Scholar
- Shih Y-h, Tso C-p (2012) Aggregation and disaggregation of three selected metal oxide nanoparticle powders in water. Coll Surf A (In review)Google Scholar