Frontiers of Chemical Science and Engineering
Interactions between nano-TiO
1. Department of Civil and Environmental Engineering, University of Delaware, Newark, DE 19716, USA.2. Department of Chemical Engineering, Taiwan University of Science and Technology, Taipei, Taiwan, China
Nano-sized titanium dioxide (nano-TiO ) has wide industrial applications and therefore considerable chances of exposure are created for human beings and ecosystems. To better understand the interactions between nano-TiO and aquatic organisms, we first studied TiO uptake by algae exemplified by were exposed to nano-TiO in a series of concentrations and at various pH. TiO uptake was quantified using a sedimentation curve analysis technique. After exposure of algae to TiO , the variation of zeta potential was measured and the morphology of algae-TiO aggregate was observed with scanning electron microscopy and the optical microscopy. The steady-state TiO uptake was found to be pH-dependent and the isotherms can be described well by Freundlich model. TiO deposited on algal surfaces causes the shift of pH of TiO -covered algae from that of algae toward that of TiO . The attraction between TiO -covered algal cells induces the agglomeration of algae and TiO and thus the formation of algae-TiO aggregates in the size of 12 to 50 μm. The 2-D fractal dimension of the aggregates is pH-dependent and ranges from 1.31 to 1.67. The theoretical analysis of the Gibbs energy of interaction indicates that both TiO uptake by algae and the formation of algae-TiO aggregate are influenced by the interaction between TiO particles.