Role of Surface Area, Primary Particle Size, and Crystal Phase on Titanium Dioxide Nanoparticle Dispersion Properties

Characterizing nanoparticle dispersions and understanding the effect of parameters that alter dispersion properties are important for both environmental applications and toxicity investigations. The role of particle surface area, primary particle size, and crystal phase on TiO2 nanoparticle dispersion properties is reported. Hydrodynamic size, zeta potential, and isoelectric point (IEP) of ten laboratory synthesized TiO2 samples, and one commercial Degussa TiO2 sample (P25) dispersed in different solutions were characterized. Solution ionic strength and pH affect titania dispersion properties. The effect of monovalent (NaCl) and divalent (MgCl2) inert electrolytes on dispersion properties was quantified through their contribution to ionic strength. Increasing titania particle surface area resulted in a decrease in solution pH. At fixed pH, increasing the particle surface area enhanced the collision frequency between particles and led to a higher degree of agglomeration. In addition to the synthesis method, TiO2 isoelectric point was found to be dependent on particle size. As anatase TiO2 primary particle size increased from 6 nm to 104 nm, its IEP decreased from 6.0 to 3.8 that also results in changes in dispersion zeta potential and hydrodynamic size. In contrast to particle size, TiO2 nanoparticle IEP was found to be insensitive to particle crystal structure

Nutrient dynamics in shallow lakes: effects of changes in loading and role of sediment-water interactions.

The transport and cycling of nutrients through the various pools in water, soil and sediment is controlling the long term and short term productivity of water bodies. An understanding of the size of these pools and the fluxes between them is essential for the assessment of the usefulness of management measures resulting in reduced external input and the anticipated resilience of the system towards changes in trophic character. Large pools, such as phosphorus in surficial sediments and nitrate in groundwater have a potential for prolonged stimulation of productivity. Diffuse sources, fluxes towards sinks, competition between biota and adsorbents for sparse nutrients, feedback mechanisms, non-linearities and shifts among prevailing processes are discussed