Page 639 - Polymer-based Nanocomposites for Energy and Environmental Applications

590 Polymer-based Nanocomposites for Energy and Environmental Applications

scrap (often known as “prompt scrap”) and (ii) postconsumer recycling. The former
primarily involves recovering and reusing waste polymer resulting from processing
operations. Recyclability varies strongly between different methods and technologies
used for water treatment. Few options for polymer nanocomposite recycling are grind-
ing of the residues, retreating, chemical treatment, pyrolysis, incineration with energy
recovery, etc.
Recycling is a very useful determinant of environmental performance. The envi-
ronmental performance per cycle of usage may be improved by optimizing the extent
that nanocomposites can be recycled a number of times as product, material, or con-
stituent substances, with limited inputs into the recycling process. The recovery of the
polymer nanocomposites after water treatment is a crucial factor for economic feasi-
bility and proper disposal.

21.10 Toxicity of polymer nanocomposites

Polymer nanocomposites used for water treatment may pose a risk to humans, aquatic
and terrestrial organisms, and the environment. This may be caused by the potential
release of NPs into the environment or even from the matrix polymer phase. Although
there are significant developments on the use of polymer nanocomposites for water
treatment, until now, there are major gaps in our knowledge about the risks posed
by NPs and polymer matrix. The main biological factors regarding the potential toxic
effects of NPs are inflammation, acute toxicity, oxidative stress, DNA damage, cross-
ing, and damage to tissue barriers [78]. The possible adverse effects also depend on the
nature of the ultrafine particles released (pristine NPs or NPs combined with soot or
other ultrafine particles).
Only limited information is available in the literature regarding toxicological
effects of nanocomposites. At high doses, nano-ZnO was found to be toxic [79,80].
Al 2 O 3 particles of 20 nm induce an inflammatory reaction in rat lungs [79].Ag
NPs are toxic in living organisms at high concentrations [81] and chronic exposure
to silver has been reported to cause argyria and/or argyrosis in humans [82]. Shvedova
et al. [83] reported that single-wall carbon nanotubes (SWCNT) when introduced into
human keratinocytes reduce cellular viability, causing structural and morphological
modifications of the epithelial cells of bronchi. Radomski et al. [84]observed blood
platelet aggregation influenced by SWCNT and multiwall carbon nanotubes
(MWCNT). Although most of the polymer matrices in nanocomposites are nontoxic,
Ibarra et al. [85] evaluated the acute toxicity effects of NPs of polyaniline in different
dispersants on embryos and larvae of Rhinella arenarum.

21.11 Conclusions and future prospects

In a current scenario, there is a significant need for advanced water technologies to
ensure a high quality of water, eliminate chemical and biological pollutants, and inten-
sify industrial production processes of wastewater. In this regard, nanotechnology is