LAUSR

Abstract The photo-catalytic degradation of methylene blue (MB) and reactive blue 21 (RB 21) dyes in aqueous medium was studied in dynamic mode using titanium dioxide (TiO2) immobilized on cellulosic fibers. Experiments were carried out under UV light irradiation as a function of a variety of operating conditions such as pH, initial dye concentration, feed flow rate, contact time, aeration, and presence of ethanol which acts as inhibitor of OH° reaction. The best photo-degradation yield of MB dye was obtained in basic medium, while that of RB 21 was reached in acid medium. The initial concentration of dyed solution and the photo-degradation efficiency are inversely proportional. Likewise, the feed flow rate and consequently the residence time in the dynamic photo-reactor significantly affect the performance of the process. Furthermore, the oxygen enrichment of the reaction medium improves the photo-catalytic degradation of both studied dyes. However, adding ethanol has a negative impact on the oxidation process by the produced hydroxyl radicals OH°. The study of the efficiency of the photo-catalyst, after cleaning, highlights its stability after repeated use.