3.6.2. Loss of A254
The breakdown of NOM by VUV irradiation was modelled
using first order parallel kinetics by Thomson et al. [11], and was
attributed to the action of the hydroxyl radicals (produced by radiation
at 185 nm) superimposed on the conjugated bond cleavage
induced by radiation at 254 nm, since the VUV lamp used produces
radiation at both wavelengths.
The results of the present study were modelled using the same
equation (Eq. (2)) for parallel kinetics used by Thomson et al. [11]:
C(t) =
C1 exp−k1t +
C2 exp−k2t +
Cr (2)
where C1 corresponds to the absorbance, concentration or colour
of the fast reacting species, C2 corresponds to these parameters for the slow reacting species and Cr denotes these parameters for the
remaining (or refractory) material. The values calculated for each
of these variables and the rate constants are given in Table 3.