OXYDATION DE DEUX COLORANTS PHARMACEUTIQUES PAR PHOTOLYSE ET PHOTOCATALYSE DANS UN REACTEUR SOLAIRE EN ABSENCE ET EN PRESENCE DES CATALYSEURS ET DES ADDITIFS

Abstract

In this study, we investigated two innovative systems, Solar-L/chlorine/TiO2, and Solar-L/ TiO2/KPS/ Fe2+, with the aim of treating two synthetic dyes, Rhodamine B (RhB) and Carmoisine Supra (CS). The Solar-L/chlorine system revealed the degradation process of Rhodamine B (RhB) in a highly alkaline environment (pH 11) using Solar-L and chlorine. It became evident that neither solar light alone nor chlorination resulted in degradation. However, the Solar-L/chlorine process proved effective, achieving complete removal in just 30 minutes with the use of 103μM ClO−. Furthermore, this process significantly reduced COT, with an 60% decrease after 120 minutes and an 80% reduction after 240 minutes. Our findings suggest that •OH/O•− species and reactive chlorine species (ERC) played a role in the degradation process. Process performance improved with decreasing initial dye concentration and increasing temperature. The addition of TiO2 to the Solar-L/chlorine system improved RhB degradation efficiency by more than 30%. It was found that neither adsorption (onto TiO2) nor Solar-L/TiO2 photolysis contributed to dye removal in the Solar-L/chlorine/TiO2 system. Instead, the enhancement in this system was linked to hypochlorite's involvement in the photocatalytic reaction on the catalyst's surface. A comprehensive discussion of TiO2's effect was conducted based on the physicochemical properties of RhB and TiO2 concerning solution pH. The second system, Solar-L/TiO2/KPS/ Fe2+, explored the degradation of the pharmaceutical dye Carmoisine Supra (CS) using a combination of four processes: Solar-L, TiO2, KPS, and Fe2+.The primary results indicate negligible degradation in the absence of UV-visible irradiation for the KPS, TiO2, and Fe2+processes. However, a significant improvement was observed when they were combined with the Solar-L process. The CS degradation rate increased with the quantity of TiO2, the optimal quantity was 1 g/L, and it was proportional to the initial CS concentration. An acidic pH (4) favored CS degradation, while the addition of S2O82- ions at an optimal concentration of 0.65 g/L accelerated the process. The presence of Fe2+ ions activated the decomposition of S2O82‾ into SO4‾● and H2O2 into HO● and OH‾, enhancing CS degradation. Additionally, the presence of radical scavengers, such as Phenol and Propanol-2, confirmed their role in the photocatalytic degradation of CS. It is worth noting that CS degradation was less effective in mineral and seawater compared to distilled water.