Abstract
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•Integrating UV/TiO2/Persulfate was more efficient process in degrading Safranin O.•The combination of UV/TiO2 and UV/persulfate exhibited a synergistic effect.•Both OH and SO4− radicals contribute efficiently in the degradation of the dye.•Nitrate and carbonate enhanced the efficiency of integrated process.•The integrated process is more efficient in natural mineral waterThe integrated process is more efficient in natural mineral water.
In this work, the degradation of Safranin O (SO), a cationic dye pollutant, by integrating UV/TiO2/PPS treatment (PPS: potassium persulfate) was found to be more efficient than UV/TiO2 and UV/PPS individual binary systems. The complete removal of SO by the integrated system was achieved after only 25min, whereas 22, 39, 83 and 97% of SO remained in the solutions with UV/TiO2, UV/PPS, UV and PPS separated systems. Moreover, the combination of UV/TiO2 and UV/PPS exhibited a synergistic effect. A complete systematic study of SO removal by UV/TiO2/PPS system was carried out by assessing the effect of operating parameters, additives and several complex matrices. Chemical probes experiments showed that both OH and SO4− radicals contribute efficiently in the degradation of the dye by the UV/TiO2/PPS system. It was found that the degradation of the dye did not obey first-order kinetics law. The initial degradation rate increased significantly with the increase of initial dye and PPS concentrations, catalyst loading, liquid temperature and solution pH. Salts such as KNO3 and Na2CO3 enhanced notably the degradation of the dye probably by the formation of secondary radicals, such as CO3−, NO2 and NO3, which participate in the oxidation reactions. Humic acid, as natural organic matter, decreased the efficiency of the integrated process toward the removal of SO. The conversion yield of SO by the UV/TiO2/PPS process was improved when the experiments was performed in natural mineral water, making this process as a promising technique for treating contaminated real natural waters. However, the very high quantity of salts present in seawater alters the reaction of radicals with the dye molecules resulting in lower degradation rate.