Table 1. As reported by previous works [24], the kinetic study
of the photochemical decomposition using UV radiation follows
pseudo-first-order kinetics in which the k value is determined by
the following expression:
ln
C0
C = kt (1)
where C0 represents the initial concentration of the organic
compound and C represents the concentration of the organic
compound as a function of time, t. The term ln(C0/C) was plotted
versus reaction time and the k value. The k value for formaldehyde
and methanol degradation in each condition is determined
as shown in Table 1.
From this work, it is obvious that the UV/H2O2 system
enhanced the photooxidation of formaldehyde and methanol.
Two effects of H2O2 addition can be clearly seen; first, the
enhanced effect of the combination of UV and H2O2 in comparison
to the single photodegradation by UV radiation and second
the positive influence of the H2O2 initial concentration on the
degradation of both formaldehyde and methanol. In UV/H2O2,
hydroxyl radicals are formed according to Eq. (2) [7]:
H2O2 + hν→ 2OH• (2)
The increasing of the initial H2O2 amount causes the increasing
of the disappearance rate of both organic compounds. This
trend is confirmed with the evaluation of the pseudo-first-order
rate constant, k, and the percentage removal in each condition,
which are also depicted in Table 1.