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The processes of Fe(III) activated persulfate (PS) and H 2 O 2 modified by catechin (CAT) had been shown to be effective in degrading contaminants. In this study, the performance, mechanism, degradation pathways and products toxicity of PS (Fe(III)/PS/CAT) and H 2 O 2 (Fe(III)/H 2 O 2 /CAT) systems were compared using atenolol (ATL) as a model contaminant. 91.0% of ATL degradation was reached after 60 min in H 2 O 2 system which was much higher than that in PS system (52.4%) under the same experimental condition. CAT could react directly with H 2 O 2 to produce small amounts of HO• and the degradation efficiency of ATL was proportional to CAT concentration in H 2 O 2 system. However, the optimal CAT concentration was 5 μM in PS system. The performance of H 2 O 2 system was more susceptible to pH than that of PS system. Quenching experiments were conducted indicating that SO 4 •- and HO• were produced in PS system while HO• and O 2 •- accounted for ATL degradation in H 2 O 2 system. Seven pathways with nine byproducts and eight pathways with twelve byproducts were put forward in PS and H 2 O 2 systems respectively. Toxicity experiments showed that the inhibition rates of luminescent bacteria were both decreased about 25% after 60 min reaction in two systems. Although the software simulation result showed few intermediate products of both systems were More toxic than ATL, but the amounts of them were 1–2 orders of magnitude lower than ATL. Moreover, the mineralization rates were 16.4% and 19.0% in PS and H 2 O 2 systems respectively. [Display omitted] • Comparative studies were done in Fe(III)/H 2 O 2 /CAT and Fe(III)/PS/CAT system. • The performance of ATL degradation was efficient in Fe(III)/H 2 O 2 /CAT system. • The ATL degradation rates were slightly affected by pH in Fe(III)/PS/CAT system. • Degradation pathways of ATL in two systems were proposed and compared. • Several byproducts showed less toxicity in two systems. [ABSTRACT FROM AUTHOR]

This paper outlines the synthesis and application of a sustainable composite for the photo-Fenton-like degradation of caffeine, bisphenol A, and simazine. The phase, morphology, optical and magnetic properties of the samples were evaluated by different characterization techniques. The composite of Fe 2.5 Co 0.3 Zn 0.2 O 4 and copper-chromium layered double hydroxide (CuCr-LDH) was determined to be the most favorable photocatalyst in the photo-Fenton-like process when compared with Fe 3 O 4 , Fe 2.5 Co 0.3 Zn 0.2 O 4 , CuCr-LDH, and Fe 3 O 4 /CuCr-LDH composite. Studying the efficiency of the photo-Fenton-like degradation process in the presence of the Fe 2.5 Co 0.3 Zn 0.2 O 4 /CuCr-LDH composite revealed a degradation rate constant of caffeine twice more than the sum of those obtained for the individual processes. This ascribes to the synergistic effect by which the photo-generated electron-hole from the catalyst and the efficient reduction of Fe3+, Cu2+, etc. during the photo-Fenton-like reaction is accelerated. Moreover, under the optimal condition and after 120 min of heterogenous photo-Fenton-like process at natural pH, > 90% of pollutants mixture was decomposed. The experiments fulfilled in near-real conditions demonstrated I) the high stability and magnetically recoverability of the photocatalyst and II) the proper degradation performance of the applied heterogenous photo-Fenton-process in the removal of pollutant mixture in different water bodies and in the presence of chloride and bicarbonate ions. [Display omitted] • Co 0.3 Zn 0.2 Fe 2.5 O 4 /CuCr-LDH composite as sustainable photocatalyst was synthesized. • Photo-Fenton-like process showed a synergetic effect in degradation of pollutants. • Under the optimal condition almost 90% of pollutants mixture was degraded. • 68% of TOC removal was observed for the pollutants mixture after 4 h of process. • Different water types and available inorganic ions showed a low inhibiting effect. [ABSTRACT FROM AUTHOR]

In this work, the photo reactivity of ferric oxalate (Fe(III)-Ox) complex in atmospheric particles was investigated. Raman spectroscopy was used to explore the mechanism and kinetics of Fe(III)-Ox photolysis occurring at the aqueous/gas interface, inside the droplet and in bulk solution. Ferrous carbonate (FeCO 3) was detected indicating that carbonate ion (CO 3 2−) formed inside the droplets would compete with oxalate ligands for iron complexation. A higher concentration of photoproduct Fe(II)-Ox was observed at the surface and inside of the droplets than in bulk solution. In particular, Fe(III)-Ox on the droplet surface was quickly reduced with light and Fe(II)-Ox concentration gradually decreased with irradiation time. The evolution of Fe(II)-Ox concentration was similar inside the droplet and in bulk solution with a trend of first increasing and then gradually decreasing during irradiation time. Although FeCO 3 would hinder Fenton intermediate reaction, the photolysis rate of Fe(III)-Ox in droplets was almost two orders of magnitude times faster than that observed during bulk experiment. In general, the photolysis mechanism and kinetics of Fe(III)-Ox in aqueous/air interface, inside of droplet and bulk solution were distinct, and the production of oxide species from the atmospheric Fe(III)-Ox droplets was underestimated. The reaction mechanism diagram in the Fe(III)-Ox droplet. [Display omitted] • The photolysis rate of ferric oxalate for a droplet was approximately 100 times that in bulk solution. • Fast and intense photoreduction of ferric oxalate occurs at the aqueous/air interface of droplet. • For the first time, the formation of FeCO 3 in atmospheric droplets was reported. [ABSTRACT FROM AUTHOR]

[Display omitted] • S-scheme magnetite@copper-chromium- layered double hydroxide was synthesized. • SO 4 − and OH were produced by the highly active photocatalyst and PMS. • The catalyst preserved its stability after 5 cycles of the degradation process. • 70% of phthalate was degraded by the Vis-light/Composite/PMS process. • The S-scheme mechanism was proposed for the enhanced activity of photocatalyst. Herein, a stable and S-scheme Fe 3 O 4 @CuCr-LDH nanocomposite was synthesized and used for the photocatalytic degradation of diethyl phthalate (DEP) through the activation of peroxymonosulfate (PMS). In comparison with pure Fe 3 O 4, and LDH, the Fe 3 O 4 @CuCr-LDH nanocomposite demonstrated significantly enhanced photocatalytic activity due to its S-scheme charge-carrier migration mechanism. The prepared composite was also magnetically recoverable from the treated water which is favorable to avoid the production of secondary pollution. The integration of the composite and visible light showed the presence of a synergy factor of 14 for the degradation of diethyl phthalate. However, the photocatalytic performance of Fe 3 O 4 @CuCr-LDH was dependent on the different physicochemical parameters; wherein, the higher degradation efficiency was achieved using the solution pH of 8, the catalyst, DEP, and PMS concentrations of 1 g L−1, 20 mg L−1, and 8 mM, respectively. The high photocatalytic activity of the catalyst was maintained after 5 consecutive reaction runs and the stability of the material was proved by the XPS. Moreover, the ICP-AES analysis proved that the leaching of Fe, Cr, and Cu is lower than the standard concentration in the drinking water. Finally, the mineralization ability and the decreased toxicity of the treated solution of DEP were assessed. [ABSTRACT FROM AUTHOR]

The Fe(III)-S(IV) system used for advanced oxidation processes (AOPs) at acidic pH has just been proposed and demonstrated valid for very few contaminants in the last several years. In this work, we investigated the effect of ultraviolet A (UVA) radiation on the degradation efficiency of the Fe(III)/S(IV) system at near-neutral pH. Paracetamol (PARA) was selected as a model contaminant. The influencing factors, such as initial pH and Fe(III)/S(IV) molar ratio on chemical kinetics, and the mechanism of PARA degradation are investigated, with an emphasis on the determination of dominant oxidant species. Our results show that irradiation enhances the PARA degradation by accelerating the decrease of pH to acidic levels, and the optimal pH for the degradation of PARA in the Fe(III)/S(IV)/O2 system was around 4.0. At near-neutral pH, more than 60% of PARA was decomposed within 40 min under irradiation, whereas no significant degradation of PARA was observed using Fe(III)/S(IV) at pH 7.0 without irradiation. Mechanism investigation revealed that sulfate radical (SO4•‒) is the main oxidant species generated and responsible for the PARA degradation under these conditions. This finding may have promising implications in developing a new degradation process for dealing with wastewater at near-neutral pH by the Fe(III)/S(IV)/O2 system under UVA irradiation. [ABSTRACT FROM AUTHOR]

Photo-Fenton processes activated by biodegradable Fe(III)–EDDS complexes have attracted huge attention from the scientific community, but the operative mechanism of the photo-activation of H2O2 in the presence of Fe(III)–EDDS has not been fully clarified yet. The application of the Fe(III)–EDDS complex in Fenton and photo-Fenton (mainly under UV-B light) processes, using 4-chlorophenol (4-CP) as a model pollutant was explored to give insights into the operative mechanism. Furthermore, the potential synergistic contribution of soybean peroxidase (SBP) was investigated, since it has been reported that upon irradiation of Fe(III)–EDDS the production of H2O2 can occur. SBP did not boost the 4-CP degradation, suggesting that the possibly produced H2O2 reacts immediately with the Fe(II) ion with a quick kinetics that does not allow the diffusion of H2O2 into the bulk of the solution (i.e., outside the solvent cage of the complex). So, a concerted mechanism in which the photochemically produced H2O2 and Fe(II) react inside the hydration sphere of the Fe(III)–EDDS complex is proposed. [ABSTRACT FROM AUTHOR]

The preparation of anodic TiO2 nanotube layers has been performed using electrochemical anodization of Ti foil for 4 h at different voltages (from 0 V to 80 V). In addition, a TiO2 thin layer has been also prepared using the sol–gel method. All the photocatalysts have been characterized by XRD, SEM, and DRS to investigate the crystalline phase composition, the surface morphology, and the optical properties, respectively. The performance of the photocatalyst has been assessed in versatile photocatalytic reactions including the reduction of N2O gas and the oxidation of aqueous sulfamethoxazole. Due to their high specific surface area and excellent charge carriers transport, anodic TiO2 nanotube layers have exhibited the highest N2O conversion rate (up to 10% after 22 h) and the highest degradation extent of sulfamethoxazole (about 65% after 4 h) under UVA light. The degradation mechanism of sulfamethoxazole has been investigated by analyzing its transformation products by LC-MS and the predominant role of hydroxyl radicals has been confirmed. Finally, the efficiency of the anodic TiO2 nanotube layer has been tested in real wastewater reaching up to 45% of sulfamethoxazole degradation after 4 h. [ABSTRACT FROM AUTHOR]

In the present work, the photo-Fenton-like process based on the use of the Fe 2.5 Co 0.3 Zn 0.2 O 4 /CuCr-LDH composite was applied for the removal of green algal cells. First, the biological activity of the composite was proved with the antibacterial tests against the S. aureus ; thereafter, it was used for the removal of Scenedesmus quadricauda algal cells under the photo-Fenton-like process. Interestingly, compared with the individual processes, the photo-Fenton-like process displayed a synergistic effect in the deactivation of green algal cells. The effect of various parameters such as the initial concentration of the algal cells, concentration of the hydrogen peroxide (HP), and the solution pH on the total algal. The maximuml was assessed. Maximum algal removal efficiency was obtained in the presence of the algal cell concentration of 3.5 × 109 cells mL−1, 0.1 g L−1 composite, and HP concentration of 10 mM. Furthermore, the microscopic and SEM images of the algal cells before and after the photo-Fenton-like process proved their appropriate destruction. The reduction of the chlorophyll content after 60 and 120 min of the process was observed revealing the destruction of the algal cell walls. Finally, the disintegration of the macromolecules in the algal cell walls was proved by the GC-MS technique. [Display omitted] • Effective removal of Scenedesmus quadricauda algal cells from contaminated water. • Antibacterial activity of the composite of Fe 2.5 Co 0.3 Zn 0.2 O 4 and CuCr-LDH. • Photo-Fenton-like degradation process showed maximum algal removal efficiency. • Microscopic and SEM images showed effective algal cell destructions. • GC-MS analysis revealed the destruction of algal cell walls to small molecules. [ABSTRACT FROM AUTHOR]

[Display omitted] • Promising degradation efficiency of pollutants in sewage treatment plant water. • Predominant non-radical pathway in PDS-containing systems. • Predominant sulfate radical pathway in PMS-containing systems. • SO 4 •−, •OH and 1O 2 were generated in both CuFe 2 O 4 -PDS/PMS systems. • Correlation between XPS and radical quenching investigations. Copper ferrites (CuFe 2 O 4) nanopowder was prepared via hydrothermal method followed by annealing at 500 °C, and XRD, SEM, XPS and UPS were employed for its characterization. CuFe 2 O 4 was tested for the catalytic degradation of bisphenol A (BPA) in the dark and under UVA light, both in the presence of peroxymonosulfate (PMS) or peroxydisulfate (PDS) as radical precursor under natural pH of 6.2. While the individual photo-induced processes i.e. , photocatalysis (using CuFe 2 O 4 alone) and photolysis of either PMS or PDS, exhibited limited efficiencies in BPA degradation, a significant increase of performance was observed by combining CuFe 2 O 4 and UVA light with either PMS or PDS with a synergy effect of 3.8 and 34.1, respectively. Under the optimal conditions, employing 0.5 g/L of nanopowder, the degradation constant of 25 µM BPA was 0.211 min−1 with 2 mM of PMS and 0.018 min−1 with 2 mM of PDS, and resulted in the complete degradation of BPA within less than 20 min. The activation mechanism of PMS and PDS using CuFe 2 O 4 was elucidated, revealing sulfate radicals as the primary reactive species in PMS-containing systems, whereas a predominantly non-radical pathway was observed in the presence of PDS. Indeed, advanced spectroscopic techniques indicated that surface copper played an important role in the non-radical pathway. Furthermore, the CuFe 2 O 4 /PMS/UVA system exhibited high performance in the degradation of different phenolic compounds including BPA, phenol and p-nitrophenol in real water matrices. These achievements were observed across different real water matrices with a particular emphasis on sewage treatment plant water. [ABSTRACT FROM AUTHOR]

In this study, we employed nano zero-valent iron catalysts supported on graphitized carbon (GC-nZVI) catalyst to efficiently degrade BPA under circumneutral pH conditions in both dark and UVA radiation. The GC-nZVI catalyst was characterized using specific techniques (XPS, FTIR, BET, etc.), and was used to activate both PS and PMS in solution. Although no significant BPA degradation constant (k BPA) was determined using PS/PMS or GC-nZVI alone, a significant synergistic effect was observed in the system. Under dark conditions, k BPA increased from 0.01 min−1 to 0.17 when PS was used, both in the dark and under UVA. Notably, when PMS was present in the system, the improvement was even higher with k BPA reaching 0.18 and 0.26 min−1 under dark and UVA conditions, respectively. To further support the synergistic effect, it was found that 80% of mineralization was achieved within 2 h of UVA exposure. Chemical quenching experiments were conducted using selective probes and kinetic modelling showed that the activation of PS/PMS produced sulfate radicals (SO 4 •−), hydroxyl radicals (•OH) and ferryl ions (FeIVO2+) in both systems. Additionally, GC-nZVI/PMS system demonstrated good stability in recycling experiments, with up to 70% of BPA still being degraded after 3 cycled in 1 h under UVA. In conclusion, the degradation efficiencies of GC-nZVI/PMS and GC-nZVI/PS systems under dark and UVA radiation were assessed for three different EDCs (BPA, E2, and EE2) in both tap and sewage treatment plant waters. This study has demonstrated that the highly efficient GC-nZVI/PS/UVA or GC-nZVI/PMS/UVA system has significant potential for application in different water matrix, and our findings provide insights into the design of heterogeneous Fenton-like and photo-Fenton-like catalysts. [Display omitted] • GC-nZVI with PS and PMS systems is able to degrade and mineralize BPA in water. • The steady-state concentration of reactive species such as HO.•, SO 4 •- and FeVIO2+ is determined • The main degradation products of BPA are characterized. • Efficient BPA, E2 and EE2 degradation was obtained using GC-nZVI + PMS under UVA. • 60% of EDCs degradation in Tap and STP waters was reached after 90 min. [ABSTRACT FROM AUTHOR]

• The recovered magnetite served as the iron source for photo-Fenton reactions. • Iron of the recovered magnetite was stabilized using citrate as a chelating agent. • Decomposition of the Ferric-citrate complex did not provide harmful by-products. • 77% of carbamazepine was degraded during the adopted photo-Fenton process. • The performance of the recycled magnetite was stable in five successive cycles. Herein, the recycled magnetite obtained from industrial ferrous scrap was used as an eco-friendly, sustainable iron source in the photo-Fenton degradation of carbamazepine (CBZ), an emerging contaminant in the aqueous environment. Citrate was used as a robust chelating agent to trap and stabilize the iron required for the Fenton reaction. The results proved the formation of the Fe(III)-citrate complex, followed by the reduction of iron to Fe(II) and the formation of harmless molecules such as malonate under UV radiation. The adopted photo-Fenton process in the presence of magnetite (0.3 g/L), H 2 O 2 (0.5 mM), and citrate (0.1 mM) led to about 77 % degradation of CBZ. Then, degradation efficiency was improved to 99 % by increasing the prior contact time between citrate and magnetite. In addition, 1 mM of citrate and 2 mM of H 2 O 2 were found to be the optimal values for the degradation of CBZ under the adopted photo-Fenton process. Eventually, the experiments illustrated that the recycled magnetite could be used in the photo-Fenton process in five successive cycles without losing its efficiency. [ABSTRACT FROM AUTHOR]

TiO 2 nanotube (TNT) layers are prepared via electrochemical anodization of Ti foil in ethylene glycol-based electrolyte containing fluoride ions. Using spin-coating of Fe(III) precursor solutions of different concentrations (10 µM to 10 mM), iron surface-modified TNT (Fe-TNT) layers are formed after annealing at 450 °C for 2 h in air. The Fe-TNT layers are comprehensively characterized by XRD, SEM, DRS and XPS. To identify and assess the contribution of photocatalysis and Fenton-based processes that are simultaneously triggered by Fe-TNT layers, degradation of caffeine is investigated in the dark and under UVA with and without the presence of 500 µM H 2 O 2. It has been found that in the presence of H 2 O 2 under UVA, 100 µM Fe-TNT can degrade 67 % of caffeine after 3 h, of which 4 % is from photolysis, 23.5 % from photocatalysis and 39.5 % from Fenton-based processes. It is important to note that Fenton-based reactions are due to the iron leaching, while the main reactive oxygen species are identified as hydroxyl radicals. In addition, the main degradation by-products are identified by LC-MS and IC-MS techniques, thus leading to the proposal of different degradation pathways of caffeine. To sum up, the research's findings provide novel insights into the concept of photochemical versatility, which is only obliquely explored in the corpus of previous research. [Display omitted] • Fe modified TiO 2 nanotube layers trigger simultaneous processes. • Contribution of photocatalysis, Fenton and photolysis is assessed for the first time. • Fenton process is dependent to iron leaching from Fe-TiO 2. • Efficient degradation of caffeine under UVA in the presence of H 2 O 2. • Degradation pathway of caffeine is proposed using LC-MS and IC-MS data. [ABSTRACT FROM AUTHOR]

The crucial role of manganese(III) species in the oxidative and catalytic reactivity of manganese oxides have been widely reported. However, the direct activation of radical precursors by Mn(III) oxides is still a matter of discussion. In this work, the ability of Mn(III)-bearing oxide (Mn 2 O 3) for activation of peroxydisulfate (PS) and peroxymonosulfate (PMS) was evaluated and compared using caffeine (CAF) as a model pollutant. Complete CAF removal was achieved with 5 mM of PS or PMS after 8 h of reaction time, whereas 48% of mineralization was obtained after 70 h of reaction when PMS was used as oxidant. Electron paramagnetic resonance spin trapping (EPR) and radical scavenging experiments showed that the sulfate radical (SO 4 •–) was the dominant radical in the Mn 2 O 3 /PMS system. In comparison, a non-radical mechanism such as Mn 2 O 3 surface-activated PS promoted the removal of CAF in the system of Mn 2 O 3 /PS. Liquid chromatography coupled to mass spectrometry analyses enabled the detection of main degradation products and the proposition of the CAF degradation pathways. Investigations in the real sewage treatment plant water showed that the decrease of CAF removal observed in wastewater as compared to pure water can be alleviated by increasing the Mn 2 O 3 dosage. These findings highlight the great ability of Mn-species in PS or PMS activation in different water matrices, which have important implications for the development of novel wastewater treatment technologies. [Display omitted] • Mn 2 O 3 with PS and PMS systems are able to degrade and mineralize caffeine in water. • The CAF degradation mechanism via radical and non-radical pathways is elucidated. • Mn 2 O 3 /PMS system is found to be more efficient for caffeine degradation in STPW. • Mn(III)-based AOPs can be considered as promising and efficient water treatments. [ABSTRACT FROM AUTHOR]

The key role of trivalent manganese (Mn(III)) species in promoting sulfate radical-based advanced oxidation processes (SR-AOPs) has recently attracted increasing attention. This review provides a comprehensive summary of Mn(III) (oxyhydr)oxide-based catalysts used to activate peroxymonosulfate (PMS) and peroxydisulfate (PDS) in water. The crystal structures of different Mn(III) (oxyhydr)oxides (such as α-Mn2O3, γ-MnOOH, and Mn3O4) are first introduced. Then the impact of the catalyst structure and composition on the activation mechanisms are discussed, as well as the effects of solution pH and inorganic ions. In the Mn(III) (oxyhydr)oxide activated SR-AOPs systems, the activation mechanisms of PMS and PDS are different. For example, both radical (such as sulfate and hydroxyl radical) and non-radical (singlet oxygen) were generated by Mn(III) (oxyhydr)oxide activated PMS. In comparison, the activation of PDS by α-Mn2O3 and γ-MnOOH preferred to form the singlet oxygen and catalyst surface activated complex to remove the organic pollutants. Finally, research gaps are discussed to suggest future directions in context of applying radical-based advanced oxidation in wastewater treatment processes. [ABSTRACT FROM AUTHOR]