Abstract:
The photodegradation of two pharmaceuticals (PP), paracetamol (PC) and aspirin (ASP), induced
by an iron (III) oxyhydroxide (Goethite) was studied in aqueous solution in heterogeneous phase.
The phototransformation of the substrates was followed by spectrophotometry and HPLC in
various mixtures namely: PP-Goethite, PP-Goethite-H2O2 and PP-Goethite-carboxylic acid.
In absence of light both substrates showed different behavior with regard to Goethite in aqueous
solution. Indeed, no interaction was observed in the case of the PC whereas a particular reaction
was highlighted in the case of the ASP.
Under irradiation, photodegradation of PP induced by Goethite shows slow kinetics and is
dependent on several parameters such as pH, substrate concentration and catalyst. Fe (II) formed
exclusively in the ASP-Goethite mixture shows the photocatalytic dissolution of Goethite.
The mechanistic study reveals that hydroxyl radicals are not involved in the photocatalytic process
of PC, however they govern on the photodegradation mechanism of ASP.
The addition of hydrogen peroxide in the PP-Goethite mixture improves significantly the rate of
disappearance of the substrates following a large production of ●OH radicals generated by a
heterogeneous photo Fenton reaction. Different parameters have been studied, the effect of pH, as
well as the concentration of H2O2.
The addition of carboxylic acid to the PP-Goethite system has also been studied and shows that
oxalic acid has the most important photoactivity following the involvement of the heterogeneous
like-Fenton process resulting from the photoreductive dissolution of the complex surface formed
between Fe (III) of Goethite and oxalic acid.
The following of the mineralization shows that the life of intermediates reaction is much greater
than the starting product.
In order to verify the feasibility of the photochemical process in the environment, the same systems
were studied under solar irradiation. The results show that such systems operate with kinetics of
the same order as those observed in artificial irradiations. These results provide some knowledge
about the fate of PP in the aquatic environment as well as the photocatalytic treatment with oxy
(hydroxides) of Fe (III). These results are very promising for the application of this system under
pH conditions close to those met in the environment.
