3.3.3. Kinetics of OPP and monuron disappearance
The photodegradation kinetics of OPP and monuron adsorbed by Fe(III)-montmorillonite complexes are presented in Fig. 7. The presence of iron related to montmorillonite has a negative effect on the degradation speed of OPP and monuron.
Table 4 illustrates the kinetics and the half lives of these experiences. As shown in Table 5 the half-life times of OPP photodegradation were 2 h 3 min and 4 h 18 min for K-montmorillonite and Fe(III)-montmorillonite, respectively. For monuron, degradation is completed after 43 and 78 hours K-M and Fe-M, respectively. The slow degradation can be explained by the consumption of the rays luminous by Fe3+, these ions cause a competition with the pesticides molecules.
In aqueous medium Mestanko (2004) has observed that degradation speed of monuron photo induced by Fe III was
accelerated and its strongly dependent on Fe(OH2+) concentration.