Fate and Transport of Nanomaterials in Aquatic Environments - Nanotechnologies for Water Environment Applications - page 536

demonstrate that nCeo transport and retention in water-saturated sand is strongly
dependent on electrolyte conditions and that release of deposited nCeo requires
substantial changes in surface charge, consistent with retention in a primary energy
minimum (Li et al., 2008).
Although the aforementioned studies have advanced our knowledge on NMs
stability and aggregation kinetics, existing information seems to indicate that there are
no satisfactory models to explain stability of NMs, particularly the deposition rate and
the aggregation attachment efficiency (a in eq. 15.89). Although the DLVO theory
suggests that particle attachment under unfavorable conditions should be a strong
function of particle size and ionic strength, the experimental evidence does not support
these predictions (Chen et al., 2006; Lecoanet et al., 2004; Mylon et al., 2004;
Kretzschmar and Sticher, 1997). Furthermore, models on the basis of the DLVO theory
typically describe changes of the balance between electrostatic and van der Waals forces
over length scales of many nanometers. Similarly, solvation forces and steric
interactions that affect particle stability may be important over length scales that are
much larger than NP dimensions. Therefore, extensions and modifications of current
theory may be needed to describe the stability of some smaller NMs (Lecoanet et al.,
15.5.2 Surface Functionalization and/or Modification of NMs
Surface functionalization and modification of NMs (/NMs) with unique
functional chemicals or polymers would greatly extend potential for new applications of
For example, water-soluble /CNTs may lead to a better cytoplasmic
translocation, a dramatic reduction in toxic effects, and more efficient binding, untaken
and internalization within or by cells (Kostarelos et al., 2007). /-NMs may have much
higher adsorption capacity or removal efficiency for different contaminants. NPs (e.g.,
RNIP) modified with novel polymers may target DNAPL/water interface more
efficiently (Saleh et al., 2005), have much higher stability or can be delivered /separated
much efficiently (Rosen, 2002; Ditsch et al., 2005), not to mention the huge potential of
/NMs in other areas (e.g., material science, information technology, energy, electronic
technology, etc.) (Booker and Boysen, 2005). In this section, some aspects related to
the environmental applications of/-NMs are briefly discussed.
The effectiveness NPs for groundwater remediation depends upon the effective
delivery of the NPs to the water/contaminate interface without flocculation and severe
oxidation. Stability of NPs can be enhanced using surfactants or other chemicals to
modify the surface of NMs (Rosen, 2002). Control over aggregation has been
demonstrated to be possible. Currently, a popular method for controlling aggregation is
to confine NMs within nano- or micro-scale structures to obtain monodispersed NPs of
well-defined size and shape (Ponder et al., 2000; Fugetsu et al., 2004). Coating the