Degradation of Safranin O by thermally activated persulfate in the presence of mineral and organic additives: impact of environmental matrices

This work explores the degradation of Safranin O (SO), an organic dye pollutant, in water by thermally activated persulfate (PS). The effect of operating parameters, i.e., PS and SO initial concentrations (100-2,000 mg L-1 for PS and 3-100 mg L-1 for SO), temperature (20 degrees C-70 degrees C) and initial solution pH (3-13) on the degradation rate of the dye was investigated. Additionally; the effect of several mineral (NaCl, K2SO4, NaHCO3 and FeSO4) and organic (humic acids [HAs] and surfactant) additives on the oxidation of SO was clarified. Besides, the efficiency of the heat-activated PS to remove SO from real environmental matrices such as natural mineral water and seawater was proven. The obtained results showed that SO (10 mg L-1) was completely removed after similar to 1 h of treatment at 50 degrees C with 2,000 mg L-1 of PS. The chemical probes experiments showed that SO4 center dot- was the main species involved in the degradation of SO. The degradation rate of the dye increased significantly with increasing PS and SO initial concentrations, liquid temperature and initial solution pH. While K2SO4 has no impact on the degradation kinetics of SO, NaCl slightly inhibited it and a relatively more inhibition was observed with NaHCO3. However, the presence of FeSO4 drastically enhanced the degradation of the dye. The presence of HA decreased the efficiency of the heat/PS process toward the elimination of SO and the inhibition degree was much markedly at high HA concentrations. Unexpectedly, sodium dodecyl sulfate anionic surfactant enhanced the degradation rate of the dye at the initial stage of the treatment. The degradation of SO slightly decreased in mineral water and seawater compared with that observed in deionized water, making heat/PS treatment a promising technique for treating contaminated environmental samples.