Abstract
This work evaluated the photocatalytic activity of suspended TiO2, and TiO2-coated glass Raschig rings with respect to degradation of estrogens estrone (E1), 17β-estradiol (E2), and 17α-ethinylestradiol (EE2) in aqueous solutions and wastewater effluent samples. Gas chromatography/tandem mass spectrometry (GC-MS/MS) studies were carried out to identify degradation products for EE2. TiO2 suspensions allowed degradation rates higher than 90% for all studied estrogens in 30 min for an artificial (ultraviolet A) UVA-assisted process and aqueous solution. Immobilized TiO2 showed less favorable degradation kinetics, requiring ca. 60 min to achieve almost complete estrogen degradation. Some derivatized degradation products were identified for the first time by GC-MS/MS applying ultraviolet C (UVC) photolysis and TiO2/UVA photocatalysis. A degradation route was suggested for EE2 in UVC photolysis and TiO2/UVA processes. In the degradation of pretreated sewage samples, the immobilized TiO2 was more efficient than free TiO2, allowing ca. 85% removal of E2 and EE2 in 60 min.
Highlights
In the last twenty years, the high degradation capacity of advanced oxidative processes (AOPs) toward recalcitrant chemical species, including emergent contaminants such as estrogens, has been widely demonstrated.[1,2,3] In the context of AOPs, considerable emphasis should be given to TiO2mediated heterogeneous photocatalysis because of the excellent results achieved in environmental remediation.[4]the need for separation systems[5] and the restricted penetration of ultraviolet (UV) light in suspended photocatalyst systems offsets its well-known benefits and reduce its potential applicability to wastewater treatment.[6]
The results demonstrated low degradation capacity of the TiO2 photocatalysis in wastewater effluent (WWE) samples, which was due to the presence of organic and inorganic hydroxyl radical (HO) scavengers.[15]
Under the experimental conditions used in this and our previous work,[24] degradation by ultraviolet C (UVC) photolysis is very significant for E1, allowing almost complete removal of the estrogens studied in exposure times lower than 10 min (Figure 1)
Summary
The need for separation systems[5] and the restricted penetration of ultraviolet (UV) light in suspended photocatalyst systems offsets its well-known benefits and reduce its potential applicability to wastewater treatment.[6] In addition, recent studies have demonstrated significant cytotoxic effects of nanosized anatase TiO2.7. The use of immobilized photocatalysts has been proposed as a method to overcome these difficulties since 1993.5 Immobilization involves the use of inert supports, such as glass,[8,9] activated carbon,[10,11] silica-based materials,[12,13] and polymeric materials.[14]. As highlighted by Carbonaro et al.,[15] many studies have demonstrated the high degradation efficiency of TiO2 toward organic micropollutants under ideal laboratory conditions.[15] there are relatively few studies concerning photocatalyst performance in more complex matrices, such as wastewater effluent.[16,17,18]
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