Abstract:
Our objectives in this thesis were to demonstrate the effectiveness of Goethite (GOE) in the
amoxicillin (AMX) photodegradation process under artificial and solar irradiation by different
systems, as well as the optimization of experimental parameters affecting the rate of the
degradation. Different analytical methods have been used in the characterization of AMX and
GOE. In the absence of light, the transformation of AMX was studied in different mixtures
(AMX-GOE, AMX-GOE-H2O2 and AMX-GOE-Carboxylic Acid). An interaction between
AMX and GOE was demonstrated; H2O2 significantly improved the degradation of AMX
while no effect was mentioned in the case of the presence of carboxylic acids. Under
irradiation and in the absence of GOE, AMX was found to be photolysed at 254 nm and
refractory to photolysis at 365 nm (monochromatic and polychromatic); this is due to the
overlap between the absorption spectrum of AMX and the light source.
The photodegradation of AMX by heterogeneous photocatalysis in the presence of GOE has
been studied. Results show that the photodegradation is dependent on several parameters such
as pH, substrate and catalyst concentration. The use of free radical inhibitors has shown that
the reaction mechanism is dominated by •OH radicals where oxygen plays an important role.
The addition of H2O2 to the solution improves the degradation of AMX and increases its rate
of mineralization in terms of chemical oxygen demand. The degradation is effected by the
contribution of the •OH radicals and also by oxidation on the surface of GOE. The AMXGOE-carboxylic acid system has been tested, among the used acids, oxalic acid was the only
one that showed a photo-activity. By comparing the degradation kinetics of AMX in natural
and artificial light in the three studied systems, it is found that the degradation rate is higher
under solar irradiation.
