D. Fabbri et al. / Journal of Photochemistry and Photobiology A: Chemistry 213 (2010) 14–22
21
In both cases, the release of nitrogen as ammonium ions was
favoured. It is particularly marked in the case of AV7, due to the
as it is known that tertiary and quaternary amino groups are mainly
transformed into ammonium ions [33]. Conversely, as far as the
degradation of the initial azo-dye was achieved, the formation of
N2 was evidenced [34,35]. It could justify the lack in nitrogen min-
eralization observed for AV7.
4. Conclusions
Acid Violet 7 and Acid Green 25 were degraded in aqueous solu-
tion using titanium dioxide as photocatalyst. The results from this
study had shown that TiO2 mediated photocatalytic degradation
was a suitable treatment to achieve not only the bleaching, but
also the complete mineralization of the investigated dyes. Along
with the dyes degradation, several intermediate compounds were
formed during the degradation process. This study confirmed that
LC–MS technique demonstrates to be a powerful tool to moni-
tor pollutants and their related degradation compounds, even at
trace level. The combined used of HPLC/MS and GC/MS allowed
the identification of diverse intermediates formed at the earlier
reaction steps, that involved detachment of one (or two) sul-
phonic group, hydroxylation, and further breakage of the dyes
molecule.
Fig. 5. Structure for the intermediate compounds at m/z 407 and 480.
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