Degradation of ibuprofen in water by FeII-NTA complex-activated persulfate with hydroxylamine at neutral pH

Abstract

The activation of potassium persulfate (KPS) by FeII-NTA complex has been investigated to degrade ibuprofen in aqueous solutions under neutral pH conditions. The results showed that ibuprofen degradation by FeII-NTA/KPS process was not successful due to the rapid oxidation of FeII-NTA complex by dissolved oxygen. However, an efficient degradation of ibuprofen was achieved by FeII-NTA/KPS process in the presence of hydroxylamine (HA). It was evident that the steady-state FeII concentration in FeII-NTA/HA/KPS process was much higher than that in FeII-NTA/KPS process because of the quick regeneration of FeII-NTA complex by HA. The suitable conditions for FeII-NTA/HA/KPS process were obtained at [FeII] = 0.1 mM, [NTA/Fe] = 1:1, [HA/Fe] = 20:1 and [KPS/Fe] = 30:1. The generation of sulfate radical (SO4−) and hydroxyl radical (OH) contributed to ∼80% of ibuprofen degradation, and ∼20% of ibuprofen degradation was resulted from other reactive species such as persulfate radical (S2O8−). FeII-NTA complex was more effective than FeII-EDDS and FeII-EDTA complexes in the activation of KPS, and moreover which was also capable of activating Oxone at neutral pH. A successful degradation of ibuprofen in lake water was achieved by FeII-NTA/HA/KPS process, while the rate of ibuprofen degradation in simulated groundwater was relatively slower because of the scavenging effects of HCO3− on SO4−/OH. The major intermediates in ibuprofen degradation were identified by LC-QTOF-MS analysis and the degradation pathways were proposed.