Heterogeneous photo-Fenton Process Research Articles

Assessing the application of a biochar-supported iron oxide catalyst to the treatment of imidacloprid by photo-Fenton technologies

Emerging contaminants entail a great challenge to conventional treatment systems because they are not able to remove most of these bio-recalcitrant compounds. In particular, the presence of pesticides, such as imidacloprid, in the environment is a great hazard to soil microbiota, pollinating insects, and the aquatic environment. This research aims to enhance the treatment efficiency of advanced oxidation processes applied to the removal of bio-recalcitrant pollutants that are present in stormwater by assessing the application of a newly designed, economical, and efficient treatment alternative. Specifically, solar and LED (365 and 420 nm) heterogeneous photo-Fenton processes were carried out to remove a concentration of 5 mg·L−1 of imidacloprid, which was selected as the model pollutant that has been identified present in stormwater, using a magnetic iron oxides catalyst supported on pinewood waste biochar. The removal kinetics and mineralization of this contaminant were determined under the effect of the natural pH value of the solution and under a circumneutral pH environment, and heterogeneous and homogeneous catalytic contributions to the process were assessed. All these treatments achieved the successful efficient removal of the contaminant whether applying LED (UVA or visible blue) or solar radiation. The heterogeneous photo-Fenton treatment using a magnetic iron oxide catalyst supported on pinewood waste biochar totally removed imidacloprid after 10 minutes of oxidation at the initial natural pH value of the solution using 365 nm UVA LED radiation. Moreover, a 70% TOC removal was addressed after 60 minutes of treatment. The solar version of this heterogeneous photo-Fenton process removed the contaminant after 60 minutes of reaction, together to a TOC removal of the 60–65% after 120 minutes of treatment, including certain photolytic contribution; as well as it showed very efficient results under the effect of a circumneutral pH value. The assessed biochar-supported iron oxide catalyst was displayed as very stable under all the tested reaction conditions and its heterogeneous contribution to the process was confirmed superior to an exclusive homogeneous process.

Enhanced degradation of enoxacin using ferrihydrite-catalyzed heterogeneous photo-Fenton process

The ferrihydrite-catalyzed heterogeneous photo-Fenton reaction shows great potential for environmental remediation of fluoroquinolone (FQs) antibiotics. The degradation of enoxacin, a model of FQ antibiotics, was studied by a batch experiment and theoretical calculation. The results revealed that the degradation efficiency of enoxacin reached 89.7% at pH 3. The hydroxyl radical (∙OH) had a significant impact on the degradation process, with a cumulative concentration of 43.9 μmol L−1 at pH 3. Photogenerated holes and electrons participated in the generation of ∙OH. Eleven degradation products of enoxacin were identified, with the main degradation pathways being defluorination, quinolone ring and piperazine ring cleavage and oxidation. These findings indicate that the ferrihydrite-catalyzed photo-Fenton process is a valid way for treating water contaminated with FQ antibiotics.

HOFs structured CN template enables the dual regulation of Cu–O and Cu–N active sites in porous Cu-g-CN for synergistic photo-Fenton process

Photo-Fenton catalysis with strong oxidation potential and cyclic stability represents a promising technique for addressing the escalating environmental challenges. However, the photo-Fenton activity using Fe/Cu doped graphitic carbon nitride (g-CN) catalysts is significantly hindered by the limited reaction interface and non-tunable surface-active sites. Herein, we present a novel CN polymer type hydrogen bonded organic framework (CN-HOFs) template derived Cu-g-CN (Cu/CH-g-CN) based hybriding catalyst (CN-HOFs/Cu/CH-g-CN), which process greatly optimized surface features for high-performance photo-Fenton reaction with exceptional durability in a broad pH range of 3–11. Importantly, the distinctive porous structure of CN-HOFs template offers not only high specific surface area, but also the possibility to regulate Cu active sites. The coexistence of Cu–O and Cu–N active sites is identified by XPS, which facilitates the separation and migration of photogenerated charges, expediting the redox cycle. The synergistic photo-Fenton reaction boosted by the porous CN-HOFs structure and the dual Cu active sites (Cu–O and Cu–N) was verified by degradation activity of tetracycline. Under visible light irradiation at a concentration of 20 mg/L, the degradation efficiency reaches nearly 100% within 20 min, with exceptional cycling stability. Further investigations have revealed that the Cu–O active site is conducive to the adsorption of organic pollutants, while the Cu–N active site promotes electron transfer, accelerates the cyclic conversion of Cu+ and Cu2+. The dual copper active site is beneficial for the generation of hydroxyl radicals and the stable operation of the catalyst, resulting in significant photo-Fenton activity. This work underscores the importance of regulating the nanoscale morphology and electronic structure of photofunctional catalysts, not only to increase the active sites for photo-Fenton reactions but also to facilitate charge transfer and the cycling of active metal ions, thereby improving the sustainability of heterogeneous photo-Fenton process.

Hydrophobic microenvironment mediated photo-Fenton beads confining free radicals in vicinity of water-soluble contaminants for enhancing water purification

Heterogeneous photo-Fenton process can produce reactive oxygen species (ROS) on the catalysts surface; however, it will decay quickly in bulk solution, resulting in low utilization rate. Herein, we design a hydrophobic microenvironment mediated polymer beads (HMPBs) as an alternative platform to immobilize Fenton-like catalysts for efficiently confining ROS in hydrophilic area and improving mass transfer. Molecular dynamics simulation predicted that diffusion of reactants will slow down on mixed hydrophilic/hydrophobic interface so that the short-lived ROS can oxidize contaminants efficiently. Consequently, the optimal HMPBs exhibits remarkably increased degradation kinetic constants, which is about 4.4 and 1.5-fold improvement in comparison with single hydrophilic and hydrophobic beads, respectively. The continuous flow degradation system with packed column type is further developed to expanded its application for Fenton-like oxidation. Altogether, this work revealed the wettability effects on the Fenton chemstrity, manifesting a deeper understanding of ROS-based reaction behaviors on special wettability interface.

Heterogeneous photo-Fenton process with zerovalent iron nanoparticles for degradation of toluene in aqueous solution

Degradation of toluene by treatment with zerovalent iron nanoparticles and different H2O2 concentrations under UVA light has been analyzed at pH 3. The highest removal of toluene was found with 100 mg L−1 nZVI and 400 mg L−1 H2O2, but 100 and 200 mg L−1 of H2O2 were used in most experiments as the degradation rate was similar. Experiments with Fe(II) (10 and 1 mg L−1) were performed for comparison. Benzaldehyde and bibenzyl were found the main oxidation products. nZVI could be reused without loss of efficiency. A mechanism was proposed.

Solar heterogeneous photo-Fenton for complete inactivation of Escherichia coli and Salmonella typhimurium in secondary-treated wastewater effluent

In this work, complete elimination of Escherichia coli and Salmonella typhimurium was achieved in 120 min using a heterogeneous photo-Fenton process under sunlight at pH 6.5 in distilled water. A face-centered composite central design 22 with one categoric factor and three replicates at the central point was used to evaluate the effect of iron (III) oxide concentration (0.8–3.4 mg L−1), H2O2 (2–10 mg L−1), and the type of iron oxide phase (maghemite and hematite) on the inactivation of both bacteria. The results showed that the amount of catalyst, H2O2 concentration and their interaction were significant factors (p < 0.05) in the elimination of the microorganisms. Thus, under the best conditions (3.4 mg L−1 of iron (III) oxide and 10 mg L−1 of H2O2) in the experimental ranges, complete inactivation of E. coli and S. typhimurium was achieved (6-log reduction) in 120 min using the photo-Fenton treatment with both iron-oxide phases. Furthermore, the photocatalytic elimination of both bacteria by the photo-Fenton process using hematite and maghemite in secondary-treated wastewater effluent was performed obtaining slower inactivation rates (1.2–5.9 times) than in distilled water due to the matrix effect of the effluent from a wastewater treatment plant. Nevertheless, the process continued to be effective in the effluent, achieving complete bacterial elimination in 150 min using the hematite phase. Additionally, the SEM images of the bacterial cells showed that the heterogeneous photo-Fenton treatment generated permanent and irreversible cell damage, resulting in complete cell death.

Chitin biochar as an effective and low-cost alternative for improving electron charge transfer of supported ZnFe2O4 during catalytic oxidation of high molar mass pollutants

In this work, a novel photocatalyst was prepared by supporting ZnFe2O4 onto chitin biochar. The novelty of this work lies in being the first report of ZnFe2O4 supported on biochar obtained from chitin residues, with a complete investigation of its efficiency carried out in two model pollutant molecules, namely ponceau and methylene blue dyes, using the mechanisms that rule heterogeneous photo-Fenton processes. Different ratios of biochar to metal oxide were tested, and it was observed that the electron/hole recombination rate decreased in the composite with equal amounts of each component, named Zn50B. The catalytic process for ponceau red and methylene blue degradation best fit the first-order kinetic model, with a degradation rate at least 26 times faster than the values reported in the literature, with complete removal after 15 and 60 min, respectively. According to radical scavenging experiments and quantum chemical calculations, the degradation mechanism behind Zn50B efficiency consists on the generation of highly oxidizing •OH(aq) and •O2-(aq) species, and its surface plays a minor role by attracting the studied molecules to near radical-generating active sites. Therefore, Zn50B composite is a promising novel photocatalyst, with proven high stability in up to 8 sequential recycles.

Flower-like magnetite nanoparticles with unfunctionalized surface as an efficient catalyst in photo-Fenton degradation of chemical dyes

Flower-like magnetite nanoflowers (Fe3O4 NFs) were synthesized in this study using a new, highly scalable, modified co-precipitation method. The heterogeneous photo-Fenton process was optimized for the degradation of Rhodamine B using sodium percarbonate as an alternative source of H2O2. The low dosage of NPs (0.6 mg/ml) can ensure the high Rhodamine B degradation of about 93.6% at pH 4 and sodium percarbonate concentration of 8.3 mg/ml. Studies confirm the high cyclic stability of Fe3O4 NFs and the possibility of using optimized reaction condition in the degradation of Lissamine Green B (97.3%) and Naphthol Green B (61.8%). Moreover, it was confirmed that O2̇− and HO∙ are the primary radicals oxidizing Rhodamine B, while the ultrafast Lissamine Green B degradation corresponds to their oxidation by O2̇−. Finally, surface functionalization was confirmed as one of the most critical parameters in designing catalysts for heterogeneous photo-Fenton processes. The study confirms that in the case of surface functionalization, the degradation of dyes is slowed down (reduction of active sites on the magnetite surface by the organic molecules). Accordingly, the ultrafine, spherical-shaped magnetite nanoparticles functionalized by thrietylene glycol were characterized by above 3 times lower catalytic activity than unfunctionalized Fe3O4 NFs.

Pd-Based Nanoparticles as Catalysts for Improved Removal of Florfenicol via Heterogeneous Fenton and Photo-Fenton(-like) Processes

In this work, Fe2O3-Ni, Fe2O3-Ni-Pd, MgO-Ni, and MgO-Ni-Pd nanoparticles were synthesized, characterized, and used for the degradation of florfenicol (FLO). The main goals were to compare the removal capacity of Fe2O3-Ni and MgO-Ni nanocatalysts and evaluate the effect of Pd incorporation on Fe2O3-Ni and MgO-Ni nanoparticles on the degradation of FLO by heterogeneous Fenton(-like) and photo-Fenton(-like) processes. The adsorption and degradation processes of FLO were assessed, determining that the latter process is the principal mechanism for FLO degradation. Through the heterogeneous photo-Fenton process, the antibiotic was 78 and 44% removed using the Fe2O3-Ni and MgO-Ni nanocatalyst, respectively, improving degradation by 22% when Pd is incorporated into both nanostructures. FLO degradation occurs because of the generation of hydroxyl and superoxide radical and holes in the interface and the Fenton reaction with Fe and Mg present in the nanoparticles. Finally, the main organic intermediates produced during the degradation were identified, allowing the proposal of a degradation pathway. Thus, heterogeneous Fenton(-like) and photo-Fenton(-like) processes using nanoparticles as solid phase catalysts are an excellent alternative to FLO degradation from water, especially considering the easy recovery of the nanoparticles through a simple separation process such as filtration.

Sunshine and a pinch of tropical soils: A natural, low-cost photo-Fenton variation for safer water, assisted by H2O2 or percabonate

Clean water is essential for human survival, but access to safe drinking water remains a challenge in resource-limited regions. Herein, we explored a low-cost but effective solution for water potabilization using natural iron sources from soils along with sunlight to remove coliforms from water. We evaluated 30 soil samples from tropical regions and among them, we found that soils from Colombia and Cameroon with high clay content and low carbon levels were the most effective catalysts. Their combination with H2O2 enhanced the solar disinfection (SODIS) yield and induced a heterogeneous photo-Fenton process with secondary homogeneous contribution and/or photocatalytic action. We also found that storing soils in acidic conditions increased the concentration of soluble iron species, leading to enhanced E. coli removal due to homogeneous Fenton and Fenton-like processes. The addition of citrate as a ligand further improved the performance of the system, by facilitating the regeneration of dissolved iron, through metal chelation, thanks to the formation of photo-active complexes. Moreover, we explored the possibility of using sodium percarbonate as a substitute for H2O2 and found it to be a successful alternative, even over alkaline lake water samples. We discuss the mechanism behind the improved activity of sodium percarbonate and suggest that ferruginous soils, when combined with any form of H2O2, can induce the photo-Fenton process over a wide pH range and at low mg/L concentrations. Our study provides valuable insights into the potential of using natural iron sources to enhance solar disinfection, making clean water more accessible to communities in need.

Rapid removal of methylene blue by a heterogeneous photo-Fenton process using economical and simple-synthesized magnetite–zeolite composite

A hetero-Fenton zeolite-supported Fe3O4 catalyst was synthesized using a simple impregnation–precipitation method. The structure, morphology, and components of the catalyst were characterized using various analytical methods (XRD, SEM, and ICP-MS). Subsequently, the catalyst was used to degrade the azo dye methylene blue (MB), via a heterogeneous photo-Fenton process under UV irradiation in an aqueous solution. This study investigated the influence of different parameters on MB decolorization efficiency, such as the initial concentration of hydrogen peroxide, amount of catalyst, initial dye concentration, and reusability of the catalyst. The removal efficiency was nearly 100% within only 5 min with an initial concentration of methylene blue of 50 mg L−1 under the following experimental conditions: a pH solution of 3, a catalyst of 0.6 g L−1, an H2O2 concentration of 66 mg L−1, and a UV lamp power of 6 W. Moreover, the Fe3O4/zeolite A catalyst (Fe/ZA) showed good stability in the photo-Fenton degradation of methylene blue after four consecutive cycles, implying that the Fe/ZA catalyst could be a potential wastewater treatment option. Furthermore, the findings of the reaction kinetics study demonstrate that the kinetics of the dye removal reaction can be fitted using the Langmuir–Hinshelwood model for heterogeneous catalytic reactions.

Heterogeneous photo-Fenton degradation of acid orange 7 activated by red mud biochar under visible light irradiation

The heterogeneous photo-Fenton process is an effective technology for degrading organic contaminants in wastewater, and Fe-based catalysts are recently preferred due to their low biotoxicity and geological abundance. Herein, we synthesized a Fe-containing red mud biochar (RMBC) via one-step co-pyrolysis of red mud and shaddock peel as a photo-Fenton catalyst to activate H2O2 and degrade an azo dye (acid orange 7, AO7). RMBC showed excellent AO7 removal capability with a decolorization efficiency of nearly 100% and a mineralization efficiency of 87% in the heterogeneous photo-Fenton process with visible light irradiation, which were kept stable in five successive reuses. RMBC provided Fe2+ for H2O2 activation, and the light irradiation facilitated the redox cycle of Fe2+/Fe3+ in the system to produce more reactive oxygen species (ROS, i.e., •OH) for AO7 degradation. Further investigation revealed that •OH was the predominant ROS responsible for AO7 degradation in the light-free condition, while more ROS were produced in the system with light irradiation, and 1O2 was the primary ROS in the photo-Fenton process for AO7 removal, followed by •OH and O2•-. This study provides insight into the interfacial mechanisms of RMBC as a photo-Fenton catalyst for treating non-degradable organic contaminants in water through advanced oxidation processes under visible light irradiation.

Photodegradation of acetaminophen and ibuprofen in iron supported in SBA-15 under UV irradiation

In this research, the photodegradation of Acetaminophen and (RS)-2-(4-isobutylphenyl)propanoic acid was evaluated by the heterogeneous photo-Fenton process using solid catalysts of iron nitrate (Fe(NO3)3) supported on mesoporous silica type SBA-15 under UV irradiation. This study began with the synthesis of the SBA-15 support and then by the preparation of the iron salt catalysts by means of the impregnation method at incipient volume and subsequently they were calcined. Afterwards, its chemical characterization, chemical composition, specific surface area and morphology were carried out by Scanning Electron Microscopy, and Scanning Transmission Electron Microscopy, Energy Dispersive Spectroscopy, Atomic Absorption Spectroscopy, X-ray Photoelectron Spectroscopy, Transmission Electron Microscopy, this result confirms the presence of iron incorporated in the support, low-angle X-ray diffractograms are observed to show a diffraction peak (100), which indicates that the material has a structure mesoporous similar to SBA-15, the textural characterization will be obtained from the adsorption–desorption isotherms of N2 at −196.15 °C, Infrared Spectroscopy with Fourier transform, Spectroscopy Ultraviolet Visible by Diffuse Reflectance it is observed that the samples of 2FeSBA-15 and 5FeSBA-15 present higher percentages of isolated species of Fe3+ and the photocatalytic study, determination of nitrates, it is observed that the 5FeSBA-15 catalyst in the presence of H2O2 was the best for drugs degradation, being 99 % for Acetaminophen and Ibuprofen at 60 and 40 min of reaction respectively. The study of radical inhibitors was carried out, observing that hydroxyl radicals are the most active species in the degradation of both drugs, variations were made in the effect of Fe loading, initial concentration, amount of catalyst, temperature, pH, amount of H2O2, in order to obtain the best reaction conditions, a number of five cycles were carried out with each of the drugs. This project will be possible research in the development of topics directed towards water treatment.

Solar disinfection of drinking water at alkaline pH, assisted by ashes of spices and herbs containing catalytic metals, in a novel “phyto-Fenton” process

In this manuscript, the improvement of solar disinfection (SODIS) for water treatment through the photo-Fenton reaction using iron replacements, namely calcined herbs and spices (thyme, cumin, cinnamon, ginger, and cocoa), naturally containing high content of metals. The bactericidal performance of SODIS, H2O2/light and solar photo-Fenton (light/H2O2/Fe2+) were assessed in pure and Lake Leman water. Sodium percarbonate (SPC) and ashes were successfully employed as substitutes of H2O2 and Fe2+, respectively. Low spices‘/herbs’ addition improved the H2O2/light process, especially when ginger, cumin, thyme, or cocoa were used, inducing effective heterogeneous photo-Fenton process even at alkaline pH. In ultrapure water, solar photo-Fenton with ashes was only slightly slower than the corresponding Fe2+-driven reaction, while in lake water total bacterial inactivation was achieved by cumin, thyme or ginger ashes. SPC enhanced SODIS performance, while the addition of ashes resulted in faster kinetics than light/SPC only. Overall, this work succeeded in converting the classic photo-Fenton process into a low-cost variant, the “phyto-Fenton” process, driven by the metals contained in the organic-free ashes and the H2O2 content of SPC.

Reactive dye degradation using Fe3+ modified membranes obtained from cigarette filters

The use of solid waste as a support material for catalysts used in heterogeneous photo-Fenton processes is promising. Hence, the process becomes environmentally sustainable and can be applied as a new alternative for wastewater treatment. In this study, a membrane was synthesized for the first time using cigarette filters with Fe3+ ions immobilized modified membranes of the cigarette filters (MMCF-Fe). The principal purpose was to evaluate the photocatalytic capacity of the MMCF-Fe as a catalyst in the heterogeneous photo- Fenton processes for the degradation of Reactive Black 5 (RB-5, tetrasodium;4-amino-5-hydroxy-3,6-bis[[4-(2 sulfonatooxyethylsulfonyl)phenyl] diazenyl]naphthalene-2,7-disulfonate) dye at neutral pH. The AAS, UV–Vis-DRS, SEM-EDS, and FTIR techniques were utilized to characterize the material. The experimental conditions for the photo-Fenton process were optimized by a 23 factorial design. The best conditions for these studies were pH 7.0, 40 mg L−1 of H2O2 concentration, and 5 % Fe3+ (w/w) amount, enabling 72.7 ± 0.5 % degradation of the Reactive Black 5 dye in 60 min. The results of the photo-Fenton process showed that under optimal conditions, intermediate compounds were removed, such as aromatic amines and phenol. These studies showed that the membrane with immobilized Fe is promising for application in the degradation of textile dyes and is environmentally sustainable, providing the use of a solid residue to produce films.

Heterogeneous photo-Fenton process over magnetically recoverable MnFe2O4/MXene hierarchical heterostructure for boosted degradation of tetracycline

Heterogeneous photo-Fenton technology is a kind of technology based on the in-situ generation of highly active and oxidized free radicals that can degrade most of the organic pollutants. As for the study, MnFe2O4/MXene (Ti3C2Tx) composites were obtained from a simple calcination strategy for photo-Fenton degradation of tetracycline (TC). The results of the characterization exhibit that MXene nanosheets could uniformly dispersed MnFe2O4 nanoparticles, which both improved the utilization rate of visible light over MnFe2O4 and effectively alleviate the agglomeration of MnFe2O4 nanoparticles as a support. The optimal sample (MT-10) displays the outstanding degradation efficiency (93.8%) of TC under the conditions of TC concentration (10 mg/L), catalyst dosage (100 mg/L), H2O2 dose (0.4 mL) and pH value (pH = 3). In addition, the as-prepared MnFe2O4/MXene composite also shows good cycle stability, magnetic recovery, and low biotoxicity. These findings expand the scope of MXene in synthesizing and designing efficient and stable composite material in environmental remediation field.

Fabrication of efficient, magnetic graphene oxide nanocomposite for the enhanced photodegradation of organic dyes under visible light

This study reports magnetic graphene oxide composite microspheres (MGO) were firstly synthesized via one step miniemulsion polymerization. α-FeOOH rods were then loaded onto MGO via a facile hydrothermal method to prepare α-FeOOH@MGO, which was served as the photocatalyst for the Fenton reaction. Subsequently, the properties of the resulting α-FeOOH@MGO were characterized by FT-IR, XRD, SEM, VSM and UV-vis DRS analysis methods. The influence of various parameters was investigated, such as dye type, dye concentration, H2O2 dosage, catalysts dosage and pH of MO solution during heterogeneous photo-Fenton processes. Under visible light irradiation, the degradation rate of MO, MB and CR could reach 99.96%, 98.47% and 99.97% in 40 min, respectively. Six cycle experiments confirmed that the α-FeOOH@MGO possessed a satisfied stability and recycling ability. In addition, the photocatalytic reaction mechanism was also revealed by the Mott-Schottky plot, band structure and trapping experiments of active species.

Buriti biomass as catalysts based on activated carbon/Fe3O4 for ciprofloxacin removal by heterogeneous photo-Fenton process

In this study, activated carbon (AC) from Buriti biomass decorated with magnetite (Fe3O4) nanoparticles was produced as a new material to be applied in ciprofloxacin (CIP) removal using photo-Fenton-based process. All materials (identified as AC1, AC3 e AC4) were initially carbonized with H2SO4 at 100 °C for 24 h in an activating agent/biomass ratio of 0.85. Subsequently, AC3 and AC4 materials suffered a new heat treatment at 300 °C (AC3) and 400 °C (AC4) respectively, resulting in materials of low porosity. The Fe3O4 nanoparticles were produced by co-precipitation method and the catalysts were identified as AC1/F, AC3/F and AC4/F. The materials were characterized by TGA-DSC, MEV-EDS, porosimeter, FT-IR and point of zero charge (pHPZC). To evaluate the catalytic performance of the ACs/F in the removal of CIP as an emerging pollutant, a study using heterogeneous photo-Fenton process at pH 2.0, 7.0 and 10 was performed. It was found that the AC4/F catalyst at pH 2.0 was the most efficient material, achieving 100 % of CIP removal, monitored by UV–Vis. The pathway mechanism observed seems to be highly dependent on the greater interaction capacity of H2O2 and less dependent on the CIP adsorption with the hybrid surface catalyst, i.e. AC and Fe3O4. The total organic carbon (TOC) study for the AC4/F catalyst at pH 2.0 showed 71.8 % of CIP mineralization and residual iron content below the levels set by the Brazilian Environmental Legislation (15 mg L−1).

High-activity and excellent-reusability γ-Fe2O3/SiO2 coating on TC4 titanium alloy by plasma electrolytic oxidation for enhanced photo-Fenton degradation.

The immobilized coatings as a kind of promising Fenton-like catalysts with excellent performance and reusability for the efficient degradation of antibiotics and phenol under solar light irradiation is investigated. Herein, the porous γ-Fe2O3/SiO2 immobilized ceramic coating on TC4 titanium alloy as photo-Fenton catalyst was prepared via plasma electrolytic oxidation technology. The as-obtained immobilized coating manifested a remarkable catalytic activity that the removal efficiencies of phenol and various antibiotics could reach more than 92% within 90min, and presented excellent reusability after six runs in phenol removal. The high activity and excellent reusability of γ-Fe2O3 were attributed to the synergistic effect of multiple pathways to jointly produce abundant •OH, and the combination of γ-Fe2O3 and SiO2 in the coating could effectively reduce iron leaching during the heterogeneous photo-Fenton process, respectively. This work provides a novel strategy for the synthesis of high-performance photo-Fenton catalysts to dispose of wastewater in the future.

Regulating electron distribution of Fe/Ni-N4P2 single sites for efficient photo-Fenton process

Regulating local electron density by introducing single-atom is an effective strategy to improve the activity of heterogeneous photo-Fenton processes. Here N, P coordinated Fe and Ni single-atom catalysts on carbon nitrides (CN-FeNi-P) were prepared to activate H2O2 for contaminant mineralization under visible light irradiation. The as-prepared CN-FeNi-P presented a higher moxifloxacin degradation activity in photo-Fenton system, which was up to 3.7 times that of pristine CN, meanwhile, its TOC removal reached to 95.9 % in 60 min. Based on density functional theory calculations, the Ni single-atoms serve as the optimal reactive sites to produce •OH. The strong interaction between Fe and Ni single-atoms by P-bridging and the modulated local electron structure after introducing P into coordination environment can lower •OH formation energy. This study provides new doping strategies to design single-atom catalysts and expands the family of the Fenton-like system for advanced oxidation technologies.