Abstract:
The photodegradation under artificial and solar irradiation of Naproxen (NPX, induced by 3 iron (III) oxy (hydroxide) based semiconductors (Goethite) was studied in aqueous solution in heterogeneous phase. The phototransformation of the substrate was followed by spectrophotometry and HPLC in the different systems. Semiconductors including particulate Goethite (GO), nanoparticle (nGO) and nanocomposite montmorillonite - Goethite (MGO) were synthesized at laboratory, and characterized by different methods (RDX, BET, SEM, TEM ...). The results of the XRD show good crystallinity. In addition, SEM and TEM analysis revealed that the particle sizes of GO, nGO and MGO are: 5 μm, 37.64 nm and 45.79 nm respectively. The removal of NPX in the presence of GO, in the absence and in the presence of light, has shown that the NPX is eliminated by both processes with a faster rate in the presence of light and seems closely dependent on the PH. The optimization of important parameters in the photochemical process was also undertaken in order to quantify the reagents necessary for the completion of the reaction. The addition of activators such as hydrogen peroxide and oxalic acid in the NPX-GO mixture significantly improves the disappearance of the substrate. In a second part, the degradation of NPX by nGO was undertaken in a similar way comparing with GO. It appeared in the systems nGO-H2O2-UV and nGO- AOx-UV are more efficient than the corresponding simple system. Finally, the performance of the new MGO catalyst has been demonstrated in the degradation of NPX. In the absence of light, an interaction between NPX and MGO was found where 33% of NPX was eliminated for a quantity of MGO of 1 g / L. Under light irradiation, 96.5% of NPX was degraded after 5 hours. The Fe (II) formed exclusively in the mixture shows the photocatalytic dissolution of the MGO. The influence of some parameters has been treated. The degradation efficiency of NPX in mixture (NPX-MGO- H2O2, pH = 3) made it possible to improve the rate of degradation to 100% NPX in 60 minutes. The formation of iron (II) in the H2O2- containing mixture creates the Fenton process under these conditions. The hydroxyl radicals have been demonstrated by the use of 1% isopropanol. Illumination of this mixture significantly advanced the reaction with 100% substrate degradation in only 10 minutes. Several parameters affecting this process have been optimized: pH, MGO dosage and H2O2 concentration. Under solar irradiation, the results showed that 30 minutes were sufficient for complete degradation of NPX at free pH. The effect of pH and some cationic metals allows considering this low-cost process in the elimination of this kind of emerging pollutants.
