Fig. 1 shows UV–vis-DAD and 1H-NMR spectra of the samples
obtained at the beginning, at two intermediate times and at the
end of the photodegradation process. Fig. 1a shows a decrease in
the absorbance values, which is much more pronounced in the
visible zone. From this figure it follows that when dyes are
removed, the species that absorb in the UV range remain in
solution, but from the shape of the spectrum the number and
type of substances that cause this signal cannot be deduced.