Catalytic Photodegradation of Rhodamine B in the Presence of Natural Iron Oxide and Oxalic Acid under Artificial and Sunlight Radiation

Natural iron oxide was used as catalyst for a heterogeneous photo-Fenton-like process and it was characterized by X-ray diffraction, X-ray fluorescence, Raman spectroscopy, scanning electron microscopy and N-2 adsorption volumetry measurement. Natural iron oxide consists mainly of hematite (76 %). Rhodamine B was mineralized by iron oxide/oxalic acid/UV system, involving creation of dissolved Fe-oxalate and adsorption of Fe-oxalate on the iron oxide surface. The effects of the initial concentration of oxalic acid and pH value, amount of natural iron oxide and concentration of dye, temperature and sunlight irradiation on the kinetics of photodegradation of rhodamine B were investigated. Excellent degradation rate was achieved with 5 mmol.L-1 of oxalic acid at a pH around 2-4. During the process, the formation of Fe2+, H2O2 and the pH of the solution were strongly dependent on the initial concentration of oxalic acid. Use of t-butanol (2.0 %) confirms that hydroxyl radicals are the entities responsible for the rhodamine B photodegradation. The use of the natural iron oxide as a catalyst in wastewater treatment is very interesting; because it is an abundant mineral and easy to separate from the solution in the end of treatment.