Degradação de Substâncias de Relevância Ambiental por ...

Abstract
Firstly, the degradation of the insecticides Thiamethoxam, Imidacloprid and
Methomyl in aqueous solutions by a number of processes was studied. It was verified
that although the UV radiation was highly efficient in promoting the degradation of
Thiamethoxam, the combined systems, i. e. UV/catalyst and UV/US/catalyst (catalyst =
Fe2O3 or Fe3O4), showed to be much less efficient. Other systems, i. e. Feº, Feº/Fe3O4,
and Feº/Fe3O4/H2O2, were also able to cause the degradation of the insecticides
Thiamethoxam and Imidacloprid in acidic aqueous solution (pH = 2). In addition, the
experimental data revealed that the Feº/Fe3O4 and Feº/Fe3O4/H2O2 systems lead to the
reduction and oxidation of both insecticides, respectively. Finally, the insecticide
Methomyl reached 100% of degradation when submitted to the UV radiation.
The degradation of prototype food dyes by a number of oxidative processes was
also investigated. The UV/H2O2, O3, and NaClO systems were able to promote a quick
and intense discoloration of the aqueous solutions of such dyes.
The analyses of TOC (total organic carbon) revealed that the degradation
processes were not able to promote a complete mineralization of pesticides and dyes.
The degradation products formed under such assorted conditions were characterized via
electrospray ionization mass (and tandem mass) spectrometry, which thus demonstrated
to be a suitable technique to monitor degradation processes in aqueous solution.
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