Abstract:
This work is a contribution to the elimination of three pharmaceutical compounds
from different therapeutic classes: carbamazepine (anti-epileptic), diclofenac (antiinflammatory) and venlafaxine (anti-depressor) by photochemical pathways in homogeneous
and heterogeneous aqueous environment under simulated sunlight.
In this study, we investigated the degradation of diclofenac and venlafaxine
in homogeneous medium in the presence of persulfate ion activated by ferrous iron and light.
The results have enabled us to deduce a very important efficiency of S2O82- /Fe2+/UV system
to degrade these molecules in aqueous media. The complete disappearance of venlafaxine is
reachedafter 45 minutes of irradiation and for a molar ratio Fe2+/S2O82- equal to 1/16 and a
death rate of 86% in the case of diclofenac for a ratio of 1/1 after 180 minutes of irradiation.
In heterogeneous phase, the disappearance of three molecules was performed
in aqueous suspensions containing the single bismuth oxychloride and doped with silver
chloride (BiOCl/AgCl) and bismuth molybdates (BiOCl/Bi2MoO6). The three types
of BiOCl showed a very high adsorption efficiency in the case of diclofenac (about 4.17 mg
adsorbed per g of BiOCl). However, the adsorption of the other two compounds revealed to
be negligible. The results of the photocatalytic degradation have shown very clearly that
bismuth oxychlorides contribute greatly to the elimination of selected pharmaceutical
pollutants. In the case of carbamazepine, the best rate of disappearance is obtained in the
presence of BiOCl/AgCl, while venlafaxine degrades very quickly in the presence of BiOCl.
Identification of carbamazepine transformation products were used to determine
the main routes of transformations such as hydroxylation reactions, epoxidation ring
contraction and hydroxylation on the aromatic ring. For venlafaxine, formation
of hydroxylated derivatives, desmethylvenlafaxine (ODV) and products resulting from the
oxidation of a CH3 group of ether function were observed.
The use of bismuth oxychlorides in the presence of the simulated sunlight
in the degradation of carbamazepine and venlafaxine detected in natural waters showed a very
high efficiency, which suggests the use of such systems in the treatment of wastewaters.
