Photocatalytic Degradation of Rhodamine Dyes with Nano-$TiO_2$

The photocatalytic degradation of various Rhodamine dyes with different functional groups, namely, Rhodamine\ud $B(C_{28}H_{31}ClN_2O_3)$, Rhodamine $6G (C_{28}H_{31}ClN_2O_3)$, Rhodamine Blue $(C_{28}H_{32}N_2O_3)$, and Rhodamine 6G perchlorate $(C_{28}H_{31}ClN_2O_7)$ was investigated under UV irradiation. The kinetics of degradation was determined in the presence of two catalysts: commercial Degussa P-25 and $TiO_2$ synthesized by the combustion solution method. The effect of organic solvents (ethanol and acetonitrile) and metal ions $(Cu^{2+}, Fe^{3+}, Zn^{2+}, and \hspace{2mm}Al^{3+})$ 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 $Cu^{2+}$ on the rate of photodegradation. It was shown that the degradation rate reduces primarily because of a decrease in electron concentration