[Efficiency and Kinetics of Triclosan Degradation in Aqueous Solution by UV/Sodium Persulfate]

UV activated sodium persulfate was employed to remove triclosan (TCS) in aqueous solution. The effects of several factors such as UV wavelength,UV₂₅₄ intensity,sodium persulfate dosage,pH value,and HA on TCS degradation were investigated. The second-order rate constants of free radicals (·OH, SO₄^·-) reacting with TCS and their contributions to TCS removal were determined,respectively. The dominant free radical was also identified. Furthermore, the TCS degradation efficiency in natural water by UV₂₅₄/SPS and UV₂₅₄/H₂O₂ was compared. Finally,the possible pathway and intermediate products of TCS degradation were analyzed with GC/MS. The results indicated that UV₂₅₄ activated sodium persulfate could effectively remove TCS. The removal rate of TCS could reach 98.15% within 100s under the conditions of UV wavelength of 254 nm,UV intensity of 11.5μW·cm^-2,sodium persulfate dosage of 1mmol·L^-1,and TCS initial concentration of 275 μg·L^-1. TCS degradation followed the pseudo-first-order kinetic model and the pseudo-first-order rate constant was determined to be 0.0392 s^-1. Pseudo-first-order rate constant for TCS degradation increased with the increase of UV₂₅₄ intensity(I)and sodium persulfate dosage within experiment ranges. The effect of UV wavelength on TCS removal was not notable. Neutral condition was detrimental to TCS degradation. TCS removal was inhibited in the presence of HA. The reaction rate constants for·OH and SO₄^·- reacting with TCS were 7.62×10⁹ L·mol^-1·s^-1 and 9.86×10⁹ L·mol^-1·s^-1,respectively. SO₄^·- was the dominant free radical and its contribution rate to TCS removal was 97.63% in UV₂₅₄/SPS system. The K value of UV₂₅₄/SPS was 4.13 times higher than that of UV₂₅₄/H₂O₂ process,which demonstrated that UV₂₅₄/SPS process could remove TCS more effectively than UV₂₅₄/H₂O₂. The main intermediate products found were 2,4-DCP and phenol in the degradation process of TCS in Milli-Q water by UV₂₅₄/SPS.