The influence of persulfate addition for the degradation of micropollutants by ionizing radiation

Nowadays the removal of organic micropollutants is one of the major challenges of water and wastewater treatment plants. The objective of this study was to investigate the influence of persulfate addition on micropollutants degradation by ionizing radiation. In this system, the radicals SO4−/OH can be present simultaneously due to persulfate reaction with solvated electrons. Ibuprofen (IB), progesterone (Pg) and benzotriazole (BT) have been selected for this study. The degradation of micropollutants was followed at various radiation doses and under the influence of persulfate (S2O82−) addition at a fixed dose (30 Gy), in deionized and tap water. In deionized water the addition of 500 μM persulfate improved the degradation of BT, IB and Pg by 17%, 36% and 24% respectively and the removal of micropollutants was increased when the concentration of persulfate ions increased. No influence of the presence of persulfate ions was observed in tap water. Contrary to tap water experiments, the persulfate (500 μM) increases the elimination of BT slightly in the presence of bicarbonate ions. In the case of IB and Pg the influence of persulfate addition is significant even in the presence of bicarbonate ions which indicate that the bicarbonate ions do not completely inhibit the influence of persulfate addition in tap water. Even if the bicarbonate ions have an inhibitory effect on the irradiation system, it was suggested that the inhibition could be explained by the presence of nitrate ions, which would prevent the formation of sulfate radicals.