Challenges in Groundwater Remediation with Iron Nanoparticles: Enabling Colloidal Stability - Nanotechnologies for Water Environment Applications - page 198

is known to remain strong even at high ionic strengths where the electrostatic double
layer becomes insignificant (Pincus, 1991; Biesheuvel, 2004; Saleh et al., 2008).
Electrosteric stabilization provides the best interparticle repulsion and, hence, the best
nZVI dispersion in groundwater.
8.3 Surface Modification with Amphiphilic Polysiloxane Graft
Copolymers
8.3.1 Hypothesis
Considering the requirements of an effective delivery system for nZVI,
functionalized amphiphilic polysiloxanes are an ideal class of polymers for the
application. Figure 8.1 provides a schematic representation of amphiphilic polysiloxane
graft copolymers (APGC) that could be easily synthesized and used for nZVI
modification. The hydrophobicity of the polysiloxane polymer backbone provides
protection of nZVI surfaces from excessive oxidation by creating a barrier to water
while also creating an affinity of the coated nanoparticles for the water/contaminant
interface, as illustrated schematically in Figure 8.2. Since polysiloxanes have a very low
glass transition temperature (-120°C) and are highly soluble in most hydrocarbons, they
will readily allow permeation of organic contaminants, such as trichloroethene, to the
Fe° nanoparticle surface providing fast, efficient contaminant remediation. Additionally,
the versatility of the hydrosilylation reaction used to produce the polymers will enable
tailoring of the chemical structure to enhance contaminant specificity.
Figure 8.1 A schematic representation of amphiphilic polysiloxane graft copolymers.