Nanotechnology for domestic water purification - Nanotechnology in Eco-efficient Construction - page 367

16.4.2 Dendrimers

Dendrons are dendritic wedges that comprise one type of functionality
(such as chemical bonding) at their core and another at the periphery. To
obtain a dendrimer structure, several dendrons are reacted with a multi-
functional core to yield a dendrimer. Using different synthetic strategies,
over 100 compositionally different dendrimer families have been synthe-
sized and over 1000 differentiated chemical surface modifi cations have
been reported (Bosman et al. , 1999; Fischer and Vögtle, 1999; Tomalia and
Majoros, 2003). One such dendrimer structure is shown in Fig. 16.2 (Jang
et al. , 2009).
Dendritic polymers exhibit many features that make them particularly
attractive as functional materials for water purifi cation. These 'soft' nanopar-
ticles, with sizes in the range of 1-20 nm, can be used as high capacity and
recyclable water soluble ligands for toxic metal ions, radionuclide and inor-
ganic anions (Ottaviani et al. , 2000). The environmental applications of
dendrimers were fi rst explored by Diallo et al. (2005). They reported the
effective removal of copper from water via different generations of
poly(amidoamine) (PAMAM) dendrimers. Later, Diallo et al. (2005) studied
the feasibility of using dendrimer improved ultrafi ltration to recover Cu
(II) from aqueous solution. The dendrimer-Cu (II) complexes can be effi -
ciently separated from aqueous solutions by ultrafi ltration. Dendritic poly-
mers can also be used as (i) recyclable unimolecular micelles for recovering
organic solutes from water (Arkas et al. , 2003) and (ii) scaffolds and tem-
plates for the preparation of redox and catalytically active nanoparticles.
Dendritic polymers have also been used successfully as delivery vehicles or
scaffolds for antimicrobial agents such as Ag (I) and quaternary ammonium
chlorides (Balogh et al. , 2001).
PAMAM-based silver complexes and nanocomposites have proved to be
effective antimicrobial agents in vitro . Rether and Schuster (2003) made a
water-soluble benzoylthiourea modifi ed ethylenediamine core-polyamido-
amine dendrimer for the selective removal and enrichment of toxicologi-
cally relevant heavy metal ions. They studied complexation of Co (II), Cu
(II), Hg (II), Ni (II), Pb (II) and Zn (II) by the dendrimer ligand and using
the polymer-supported ultrafi ltration process.
One of the novel systems for encapsulating organic pollutants is cross-
linked dendritic derivatives. In the research carried out by Arkas et al.
(2005) for the preparation of ultra pure water, the amino groups of poly-
propyleneimine dendrimer and hyperbranched polyethylene imine were
interacted under extremely mild conditions with 3-(triethoxysilyl) propyl
isocyanate. They produced porous ceramic fi lters and employed these den-
dritic systems for water purifi cation. In this experimental work, the concen-
tration of polycyclic aromatic compounds in water was reduced to a few

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