Photocatalytic Degradation of Rhodamine Dyes with Nano-TiO₂

The photocatalytic degradation of various Rhodamine dyes with different functional groups, namely, Rhodamine B (C28H31ClN2O3), Rhodamine 6G (C28H31ClN2O3), Rhodamine Blue (C28H32N2O3), and Rhodamine 6G perchlorate (C28H31ClN2O7) was investigated under UV irradiation. The kinetics of degradation was determined in the presence of two catalysts: commercial Degussa P-25 and TiO2 synthesized by the combustion solution method. The effect of organic solvents (ethanol and acetonitrile) and metal ions (Cu2+, Fe3+, Zn2+, and Al3+) on the photodegradation of Rhodamine B was investigated. The presence of solvents and metal ions significantly reduced the degradation rate. A detailed Langmuir−Hinshelwood kinetic model was developed to explain the effect of Cu2+ on the rate of photodegradation. It was shown that the degradation rate reduces primarily because of a decrease in electron concentration.