Visible-Light Activation of Persulfate or H2O2 by Fe2O3/TiO2 Immobilized on Glass Support for Photocatalytic Removal of Amoxicillin: Mechanism, Transformation Products, and Toxicity Assessment

Abstract

Fe2O3/TiO2 nanocomposites were fabricated via a facile impregnation/calcination technique employing different amounts iron (III) nitrate onto commercial TiO2 (P25 Aeroxide). The as-prepared Fe2O3/TiO2 nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDXS), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller analysis (BET), electron impedance spectroscopy (EIS), photoluminescence spectroscopy (PL), and diffuse reflectance spectroscopy (DRS). As a result, 5% (w/w) Fe2O3/TiO2 achieved the highest photocatalytic activity in the slurry system and was successfully immobilized on glass support. Photocatalytic activity under visible-light irradiation was assessed by treating pharmaceutical amoxicillin (AMX) in the presence and absence of additional oxidants: hydrogen peroxide (H2O2) and persulfate salts (PS). The influence of pH and PS concentration on AMX conversion rate was established by means of statistical planning and response surface modeling. Results revealed optimum conditions of [S2O82−] = 1.873 mM and pH = 4.808; these were also utilized in presence of H2O2 instead of PS in long-term tests. The fastest AMX conversion possessing a zero-order rate constant of 1.51 × 10−7 M·min−1 was achieved with the photocatalysis + PS system. The AMX conversion pathway was established, and the evolution/conversion of formed intermediates was correlated with the changes in toxicity toward Vibrio fischeri. Reactive oxygen species (ROS) scavenging was also utilized to investigate the AMX conversion mechanism, revealing the major contribution of photogenerated h+ in all processes.

Structural Features Promoting Photocatalytic Degradation of Contaminants of Emerging Concern: Insights into Degradation Mechanism Employing QSA/PR Modeling

“…The photocatalytic degradation of organics can occur via one of two mechanisms: (i) direct, occurring at the photocatalyst surface by photogenerated holes ( h + ) and electrons ( e − ); and (ii) indirect, occurring in the bulk by ROS, primarily HO• and O 2 • − , generated as products of reactions of HO − (as water dissociates) and O 2 (dissolved) with photogenerated h + and e − , respectively (Equations (2) and (3)) [ 9 , 10 , 15 ]. In this study, we focus only on the indirect degradation by ROS, and in that purpose, experiments with dimethyl sulfoxide (DMSO) and benzoquinone (BQ) as effective scavenging agents for HO• and O 2 • − , respectively (Equations (4) and (5)), were performed [ 16 , 28 ]. …”

“…On the other hand, the structure of organics would dictate whether degradation undergo preferably oxidation or reduction mechanism. These mechanisms occur simultaneously, but not to the same extent, and consequently, pathways and formed transformation products of organics would differ, affecting the overall quality of treated water in terms of toxicity and biodegradability [ 16 , 17 , 18 ]. Hence, Chen et al [ 19 ] investigated the kinetics of photocatalytic degradation of aliphatic carboxylic acids by UV/TiO 2 ; the results revealed that the degradation mechanism and its efficiency depend on structural features of studied aliphatics, particularly the number of carboxylic groups—more -COOH groups would yield higher degradation rate.…”

An Overview of Environmental Catalysis Mediated by Hydrogen Peroxide

“…For this reason, many efforts have been made to overcome these issues through metal and non-metal doping, surface modification, and fabrication of composites with other materials. Iron and/or H 2 O 2 assistance is a popular strategy in the literature [135][136][137]; here, two significant examples of the combination of titania with iron, H 2 O 2 and ultrasound to start different Fenton-like processes are reported in Table 1, entries 14 and 15. More detailed information on the modulation titania band gap, surface reactivity, charge transfer, and stability, among other properties, has been extensively reported in ad hoc reviews [138][139][140][141][142].…”

Enhancing Visible-Light Photocatalysis with Pd(II) Porphyrin-Based TiO2 Hybrid Nanomaterials: Preparation, Characterization, ROS Generation, and Photocatalytic Activity

“…For this reason, it is widely used in biomedical research but also in environmental applications, e.g., as a catalyst in air or water purification [24][25][26][27][28]. It is also used in self-cleaning surfaces, in CO 2 reduction [29,30], in H 2 generation [31], and in the catalytic decomposition of harmful organic compounds [32][33][34][35]. The development of nanomaterials has allowed for the improvement of their properties, including the increase in the absorbing material's band gap in the ultraviolet range.…”