Degradation of Rhodamine B in Wastewater through UV Radiation at Wavelengths of 207, 222, and 254 nm

The photolytic and photocatalytic degradation rates of Rhodamine B (RhB) in wastewater were investigated and compared through irradiation with UV light of three wavelengths (207 nm, 222 nm, and 254 nm). UV light of all three wavelengths exhibited good RhB degradation capability under both acidic and alkaline conditions. When UV light energy is about 690 J, the RhB degradation rate is the highest (78.93%) under UV 222 nm, followed by that under UV 207 nm (70.44%) and UV 254 nm (25.17%). At each wavelength, the reaction kinetics of RhB was investigated with and without the addition of H2O2. The degradation rate of RhB was found to increase at the presence of H2O2. Photolysis mechanisms under the three UV light wavelengths were proposed based on the electrospray ionization mass spectra results, which indicated that RhB underwent different degradation pathways at different UV wavelengths. This study could help enhance understanding of the capability of the UV light of 207, 222, and 254 nm to degrade water pollutants.