photo-Fenton Process Research Articles

Tetracycline removal via photo-Fenton processes using Fe-based metal-organic frameworks loaded with Bi2S3: Performance evaluation and insights into the charge-transfer mechanism

Combining photocatalytic technology with the Fenton system may help overcome these technologies’ limitations. Photo-Fenton catalysis is economical and eco-friendly. The Fe based heterogeneous photo-Fenton process appears to be a promising wastewater treatment technology. Herein, an Fe based metal–organic framework (MIL-101 (Fe)) was produced via hydrothermal processing. Subsequently, Bi2S3 was loaded onto the surface of MIL-101 (Fe) to form a composite catalyst. A type-II heterojunction was established between MIL-101 (Fe) and Bi2S3. The 10 % Bi2S3-loaded MIL-101 (Fe) (MBS-10) was effective in the photocatalytic degradation of tetracycline, particularly after H2O2 addition. This outcome was due to the enhanced generation of radical species through the photo-Fenton process. The MBS-10 photocatalyst promoted Fe (II)/Fe (III) cycling in the presence of H2O2 and under visible light irradiation. MBS-10 also showed a higher kinetic rate constant during the photocatalytic reaction compared to MIL-101 (Fe) and Bi2S3, suggesting enhanced activity through greater electron-hole separation. Furthermore, MBS-10 proved to be stable and reusable photocatalyst after four testing cycles. The charge-transfer mechanism was elucidated through radical scavenging experiments which demonstrated that superoxide and hydroxyl radicals are the major charge carriers. Therefore, the Bi2S3-MIL-101 (Fe) composite exhibits great potential for degrading tetracycline antibiotics.

DBD plasma assisted synthesis of Ce-MIL-88B(Fe) with electron-rich CUSs and mixed-valent bimetallic sites for enhanced photo-Fenton performance

Iron-based metal-organic frameworks (Fe-MOFs) are regarded as a kind of prospective catalysts for photo-Fenton process. However, high cost, rate-limiting Fe(III)/Fe(II) circulation and limited metal sites greatly restricted the application of Fe-MOFs in photo-Fenton system. Ce-MIL-88B(Fe) was synthesized with mixed-valent bimetallic sites and tunable coordinated unsaturated metal sites (CUSs) using dielectric barrier discharge (DBD) plasma with waste PET. The incorporation of Ce altered the structure and the electron aggregation, as well as induced structural defects. Ce substitution in Fe-MOFs induced the regulation of the ratio of Fe ions and formation of electron-rich CUSs, which were beneficial for the rapid adsorption and activation of H2O2, thus enhancing the photo-Fenton performance. The effect of reaction conditions on TC degradation was investigated by response surface methodology (RSM) combined with Box-Behnken design (BBD). This study demonstrates a new perspective on the construction of bimetallic MOFs for the photo-Fenton system.

Enhanced degradation of venlafaxine induced by Fe2O3/CeO2 heterostructures through the thermal transformation from type I to direct Z-scheme in heterogeneous photo-Fenton

Heterostructures based on Fe2O3/CeO2 were synthesized by coprecipitating iron and cerium salts, with 70 % and 50 % atomic percentage of iron, and heat treatment at 600 and 800 °C (Fe70Ce600, Fe50Ce600, Fe70Ce800, Fe50Ce800). The catalytic activity in the Fenton and photo-Fenton process was evaluated in the degradation of venlafaxine (VEN) using UV/Vis LEDs. Treatment at 800 °C promoted greater crystallinity, increased crystallite size, decreased specific area, and high absorption between 200 and 600 nm, and bandgap energy (Eg) between 1.6 and 3.0 eV were observed. The heat treatment promoted different mechanisms in heterostructure materials with type I (straddling) schemes for Fe70Ce600 and Fe50Ce600, type II for Fe50Ce800, and direct Z for Fe70Ce800 responsible for generating a higher concentration of HO• radicals, high oxidation-reduction power (Fe2+/Fe3+) and (Ce4+/Ce3+), greater effective separation of charge carriers, providing improved catalytic activity due to the synergy between heterogeneous photocatalysis and photo-Fenton processes. LC-MS/MS analysis identified 12 transformation products (TPs), involving hydroxylation reactions, demethylation, and loss of cyclohexanol. The transformation products TP2 and TP9 were exclusive to Fe70Ce800, confirming different mechanisms among the heterostructures.

Catalytic activity insight into sustainable Fe-hydroxyapatite application using an experimental design approach

Combining experimental design with advanced characterisation methods provides a valuable opportunity to deepen our understanding of catalytic processes and their underlying mechanisms. Here, a series of hydroxyapatite doped with Fe2+ at different molar loadings noted HAP-FeX% (X = 1; 5.5 and 10; Ca/Fe molar ratio) were elaborated using a one-pot synthesis method. Characterization of these catalysts by various techniques such as ICP, BET/BJH, TGA/DSC, XRD, Raman, UV–visible, TPD-NH3, SEM, and TEM revealed substantial Fe2+ oxidation during synthesis, inducing changes in the morphological and physical-chemical characteristics of HAP caused by Fe3+/Ca2+ substitution. Furthermore, the synthesis produced nanoparticles (approximately 0.30 nm in size) on the hydroxyapatite surface, resulting from the precipitation of Fe/O phases. The catalysts exhibited good catalytic performance in methylene blue (MB) degradation through the photo-Fenton process (95 %). The Ca/Fe molar ratio = 8.8 %, [H2O2] = 2.8 mmol L−1, and pH = 8.8 were optimized using the design of experiments (DOE) via response surface methodology (RSM). A mathematical model was developed to determine the influence of the Ca2+/Fe3+ substitution and the Fe/O phase on the catalytic activity. The results revealed the role of the Fe/O phase in the reaction initiation and the surface modification induced by Ca2+/Fe3+ substitution to facilitate the reaction chain.

Fuzzy optimization of the photo-Fenton process on o-toluidine degradation in the aspect wastewater treatment

Significant volumes of wastewater, particularly from the textile industry, pose environmental concerns due to the presence of hazardous substances such as ortho-toluidine (OT). The photo-Fenton process can be used to break down and remove this hazardous organic compound. Previous studies on the photo-Fenton process have focused on local optimization of operating variables without considering cost factors. The photo-Fenton process is studied in this paper with UVA irradiation, Fe2+ dosage, and H2O2 concentration considered as variables. The study uses fuzzy optimization in a multi-objective framework for making decisions to determine the optimal values of OT degradation with its corresponding cumulative uncertainty error (YA), and the total operating cost (CT), both of which are essential for assessing the techno-economic feasibility of the process. The Pareto front was generated from the objective functions to establish the boundary limits for YA and CT. The results show an overall satisfaction level of 71.81% for the objective functions, indicating a partially satisficing solution for maximizing OT degradation while minimizing operating cost. The optimum conditions of the variables require 85.70 W m−3 UVA irradiation, 0.5177 mM for Fe2+ dosage, and 7.85 mM for the H2O2 concentration. These conditions yielded an OT degradation value of 83.22% and a total operating cost of 768.61 USD·m−3. Comparison with previous literature showed an OT degradation efficiency that was 16.78% lower. However, this tradeoff in the process efficiency is offset by a total operating cost that is 2.28 times cheaper, emphasizing the cost-effectiveness of the fuzzy optimized solution.

Removal of contaminants in paper dyeing wastewater by Fenton and photo-Fenton processes with biological treatment

Removal of contaminants in paper dyeing wastewater by Fenton and photo-Fenton processes with biological treatment

Photo-Fenton-like activity of Fe/ZnO structure applied as a heterogeneous catalyst for the methylene blue dye removal in aqueous matrices

This work developed efficient heterogeneous catalysts for the methylene blue (MB) dye degradation under photo-Fenton-like conditions. The material was modified to incorporate Fe(III) into ZnO, creating Fe/ZnO strucuture, and applied as heterogeneous catalysts at various pH levels. SEM analysis revealed an agglomerated and plate-like morphology of the synthesized catalysts. The enhanced structure facilitated a removal efficiency of 96.2% for MB dye when employing the photo-Fenton-based process using 5.0% Fe/ZnO catalyst. The high removal efficiency is attributed to the synergy between ≡Fe(III) and ≡Zn(II), which promotes the generation of photoradical species through the Fenton effect. Real water matrices served as a source of MB dye contamination, exhibiting minimal interference and achieving ∼100 % of removal. Scavenger studies indicate that •OH and e⁻ are the primary contributors to the high MB dye degradation efficiency. Additionally, the by-products formed after photo-Fenton process exhibit minimal toxicity towards Lactuca sativa L. No Fe(II) ions were leached at the end of the process. Eight cycles of degradation did not cause significant spectral changes in the FTIR analysis, as well as in the XRD patterns, indicating the material efficient and stable structure.

Advanced technological integration for swine wastewater: Enhancing treatment with photo-Fenton and electrocoagulation

The increase in pork consumption and its reputation as one of the best sources of protein has led to growth in this industry, however, its production generates a significant amount of swine wastewater (SWW). Conventional biological treatment methods are typically used to treat SWW. However, their applicability in small and medium sized enterprises (SMEs) in the swine industry is limited due to their high space requirements. Therefore, advanced oxidation processes (AOPs) such as photofenton (PF) and electrocoagulation (EC) represent a potential alternative for SWW treatment due to their lower space requirements. The aim of this study was to treat SWW by integrating the PF process followed by EC as a technological couple to optimize the removal efficiency of pollutants present in SWW. Experiments were conducted in a 2 L batch reactor, examining the effects of hydrogen peroxide (H2O2) concentration (0.5, 2.5, 5.0 g L−1) and current density (10, 50, 90 A m−2) on pH, organic matter, nutrients, and germination index (GI). The results showed that the optimum process conditions correspond to 2.6 g L−1 H2O2 and a current density of 41 A m−2. Under these conditions, an effluent is obtained with pH values of 7.8, TSS of 385 mg L−1, COD of 254 mg L−1, BOD5 of 139.8 mg L−1, TN of 190.4 mg L−1 and GI of 117 %. The results showed that the effluent complies with the Colombian standards. From a cost perspective, the use of Photo-Fenton to treat wastewater under these conditions would be US$ 0.7 per liter.

Hydrogen Peroxide Heterolytic Cleavage Induced Gas Phase Photo-Fenton Oxidation of Nitric Oxide.

Nitric oxide (NO) is one of the major air pollutants that may cause ecological imbalance and severe human disease. However, the removal of NO faces challenges of low efficiency, high energy consumption, and production of toxic NO2 byproducts. Herein, we report an efficient *OOH intermediate-involved NO oxidation route with high NO3- selectivity via a gas phase photo-Fenton system. Fe single atoms (Fe SAs)-anchored NH2-UiO-66(Zr) (Fe SAs@NU) was synthesized. The five-coordinated Fe SAs undergo a transient structure reconstitution during the photo-Fenton process, which enables a novel heterolytic cleavage pathway of H2O2 to derive specific ·OOH/·O2- radicals as reactive oxygen species. Therefore, a high NO (550 parts per billion) removal rate of 81% (NO3- selectivity up to 99%) is achieved under visible-light irradiation (>420 nm). This study provides new insight for the high-performance photo-Fenton process via a transient structure reconstitution pathway for the removal of gas phase NOx pollutants.

Application of natural hematite as catalyst in heterogeneous photo-Fenton like process for 2,4-dichlorophenol degradation

This work investigates the degradation of 2,4-dichlorophenol (2,4-DCP) through the combination of hematite and UV light for the activation of sodium percarbonate (SPC) in a heterogeneous photo-Fenton like (HPF) process. The hematite was fully characterised and the effects of different reaction parameters such as pH, doses of hematite and SPC, 2,4-DCP initial concentration, and the presence of co-existing anions were investigated. Under the optimised conditions (pH = 3.0, [Hematite]0 = 300.0 mg L−1, [SPC]0 = 500.0 mg L−1), the degradation of 2,4-DCP (50.0 mg L−1) was 99.88 ± 0.05 %. Quenching experiments demonstrated the participation of 1O2, O2−, CO3−, and OH radicals in the degradation of 2,4-DCP, with the dominance of OH radicals (82.39 %). Furthermore, the degradation of 2,4-DCP was effectively retarded by the presence of Cl−, NO3−, CO32−, and PO43− anions in the solution. Overall, the HPF process with hematite can be proposed as an effective and promising approach for the degradation of 2,4-DCP from the waste stream and can be used for the decontamination of other organic compounds due to its stability and feasibility.

Photocatalytic efficacy of pyrite in the degradation of antiretroviral drugs: Biomphalaria glabrata as a bioindicator of toxic and genotoxic effects

Population growth and the increase in the consumption of different pharmaceuticals combined with the insufficiency in the removal of these compounds by conventional treatments have contributed to the increase in the detection of these contaminants in aquatic matrices. Aiming to contribute in solving this problem, this promoted the degradation of a mixture of the drugs lamivudine and zidovudine in different matrices (aqueous solution and synthetic effluent) using the heterogeneous photo-Fenton process applying pyrite as a catalyst and artificial solar radiation. At the end of the treatment, degradations greater than 99 % were found for zidovudine in both matrices studied, while for lamivudine, 97 % and 94 % degradations were obtained for aqueous solution and synthetic effluent, in that order. In the investigation of toxic effects using Biomphalaria glabrata molluscs, embryotoxicity tests showed embryonic lethality in 100 % of individuals for all samples. Acute toxicity tests on adult molluscs resulted in mortality rates of 100 % (aqueous solution after treatment) and 50 % (synthetic effluent after treatment). Thus, to investigate cellular changes, genotoxicity analyses were carried out, and different degrees of DNA damage were observed, however, the highest level of damage to this organism was not observed. Therefore, B. glabrata demonstrated to be sensitive to toxic effects at the concentrations present in the matrices studied, providing evidence to predict the ecotoxicological potential of samples when released into aquatic ecosystems.

Microstructure evolution and catalytic activity of AlCo1−xFeNiTiMox high entropy alloys fabricated by powder metallurgy route

This investigation presents the synthesis of equiatomic and non-equiatomic AlCo1−xFeNiTiMox (x = 0, 0.1, 0.25 and 1.0) high entropy alloys fabricated by mechanical alloying. Mo partially replaced Co. Classic thermodynamic calculations, such as mixing enthalpy (ΔHmix), configurational entropy (ΔSmix), the atomic size difference (δ), entropy to enthalpy ratio (Ω), electronegativity difference (△χ), and valence electron concentration (VEC) were used. Considering δ, Ω and VEC parameters, a BCC solid solution and an intermetallic phase can be predicted due to the partial replacement of Co by Mo. X-ray and electron diffraction of equiatomic HEA without Mo content revealed that after 35 h of milling, a Fe-type BCC lattice phase was formed in the alloy and two L21 phases, in addition to a minimal amount of FCC phase. As the Mo content increased, the Fe-type BCC phase was steadily replaced by the Mo-type BCC phase and the Fe-type FCC phase, and two L21 phases were also developed. When the 5 at% Mo-containing (x = 0.25) alloy was further milled for 80 h, the amount of phases remained almost the same; only the grain size was strongly reduced. The influence of the Mo addition on the properties of studied alloys was also confirmed in the decolourisation of Rhodamine B using a modified photo-Fenton process. The decolourisation efficiency within 20 min was 72% for AlCoFeNiTi and 87% for AlCo0.75FeNiTiMo0.25 using UV light with 365 nm wavelength.

An efficient, green, and magnetic recycling wastewater treatment technique enabled by ZnO/NiFe2O4/BiOBr 3D nanofibers photo-fenton process

A novel magnetic recycling ZnO/NiFe2O4/BiOBr 3D nanofibers photo-Fenton system was successfully prepared by parallel electrospinning combining with solvothermal method. ZnO/NiFe2O4 composite nanofibers was prepared via parallel electrospinning, then ZnO/NiFe2O4/BiOBr 3D nanofibers was obtained by solvothermal growth of BiOBr on electrospun ZnO/NiFe2O4 composite nanofibers. The composition, morphologies, structures and photocatalytic properties of ZnO/NiFe2O4/BiOBr 3D nanofibers were systematically tested and analyzed, and some meaningful results were obtained. The prepared ZnO/NiFe2O4/BiOBr 3D nanofibers, combined with H2O2, form a photo-Fenton system that exhibits excellent photocatalytic performance. When 0.05 mL of H2O2 is added to the photo-Fenton system, the degradation rate of organic dye Rhodamine B (RhB) reaches 99.61 % under light exposure for 10 min. Capture experiments and Electron Spin Resonance (ESR) measurements have confirmed that holes (h+) and hydroxyl radicals (·OH) are the primary active species that play a dominant role in the photocatalytic degradation of Rhodamine B (RhB). Furthermore, the ZnO/NiFe2O4/BiOBr 3D nanofibers have demonstrated exceptional photocatalytic degradation efficiency towards RhB, maintaining a degradation rate of over 95 % even after undergoing three recycling experiments. Significantly, this photo-Fenton system also has good magnetic properties, which can be separated from the treatment system under the applied magnetic field, avoiding secondary pollution of the treatment system, improving reuse rate and saving costs. This study provides valuable insights for the purposeful utilization of the photocatalytic materils.

Photo-Fenton Treatment under UV and Vis Light Reduces Pollution and Toxicity in Water from Madín Dam, Mexico

Water from Madín Dam in Mexico has been shown to contain a wide variety of pollutants such as drugs, pesticides, personal care products and compounds that are released into the environment as waste from production processes. In this work, the effect of the main process variables on the percentage of total organic carbon (TOC) removal in water samples from the Madín reservoir was studied by applying a photo-Fenton treatment catalyzed with iron-pillared clays. The catalyst was characterized by XRD, N2 physisorption, DRS and XPS. The sampling and characterization of the water from the Madín reservoir was carried out according to Mexican standards. The system for treatment tests was 0.1 L of reaction volume and a controlled temperature of 23–25 °C, and the reaction system was kept under constant stirring. After 4 h of treatment time under UV light, the TOC removal was 90%, and it was 60% under Vis light. The main ROS involved in the photo-Fenton process driven by UVC light were hydroxyl radicals, while hydroperoxyl radicals predominate in the Vis-light-driven process. Evidence of superoxide anion participation was not found. The toxicity of untreated and treated water was assessed on Danio rerio specimens, and it was observed to be reduced after the photo-Fenton treatment.

Production of pyrite-based catalysts supported on graphene oxide and zinc oxide to treat drug mixture via advanced oxidation processes.

Advanced oxidation processes (AOP) stood out as an efficient alternative for the treatment of organic contaminants. In this work, there were proposed syntheses of mixed catalysts of pyrite and graphene oxide and pyrite and zinc oxide to treat a mixture of the drugs atenolol and propranolol in aqueous solution through the photo-Fenton process with ultraviolet radiation. The efficiency of the methodologies used in the syntheses was confirmed through different characterization analyses. It was verified that the pyrite and zinc oxide catalyst led to the best contaminant degradation percentages with values equal to 88 and 84% for the groups monitored at the wavelengths (λ) of 217 and 281nm. The degradation kinetics presented a good fit to the kinetic model proposed by Chan and Chu (2003) with R2 equal to 0.99, indicating a pseudo-first-order degradation profile. Finally, toxicity tests were carried out with two types of seeds, watercress and cabbage, for the solution before and after treatment. The cabbage seeds showed a reduction in germination percentages for the samples after treatments, while no toxicity was observed for watercress ones. This highlights the importance of evaluating the implications caused by products in relation to different organisms representing the biota.

Heterogeneous Photo-Fenton Degradation of Azo Dyes over a Magnetite-Based Catalyst: Kinetic and Thermodynamic Studies

Textile wastewater containing dyes poses significant environmental hazards. Advanced oxidative processes, especially the heterogeneous photo-Fenton process, are effective in degrading a wide range of contaminants due to high conversion rates and ease of catalyst recovery. This study evaluates the heterogeneous photodegradation of the azo dyes Acid Red 18 (AR18), Acid Red 66 (AR66), and Orange 2 (OR2) using magnetite as a catalyst. The magnetic catalyst was synthesized via a hydrothermal process at 150 °C. Experiments were conducted at room temperature, investigating the effect of catalyst dosage, pH, and initial concentrations of H2O2 and AR18 dye. Kinetic and thermodynamic studies were performed at 25, 40, and 60 °C for the three azo dyes (AR18, AR66, and OR2) and the effect of the dye structures on the degradation efficiency was investigated. At 25 °C for 0.33 mmolL−1 of dye at pH 3.0, using 1.4 gL−1 of the catalyst and 60 mgL−1 of H2O2 under UV radiation of 16.7 mWcm−2, the catalyst showed 62.3% degradation for AR18, 79.6% for AR66, and 83.8% for OR2 in 180 min of reaction. The oxidation of azo dyes under these conditions is spontaneous and endothermic. The pseudo-first-order kinetic constants indicated a strong temperature dependence with an order of reactivity of the type OR2 > AR66 > AR18, which is associated with the molecular size, steric hindrance, aromatic conjugation, electrostatic repulsion, and nature of the acid–base interactions on the catalytic surface.

Sustainable Water Treatment: Harnessing Mining Waste as Catalysts for Sicomet Green Degradation

This paper presents a novel circular economy approach to water remediation that focuses on creating sustainable systems by utilizing mining waste from El-Ouenza, Tebessa, in the east of Algeria. Waste materials are employed as catalysts in Fenton and photo-Fenton processes. Two cases were studied: the conventional and the modified heterogeneous photo-Fenton at a pH of 3 and under modified pH conditions for degrading Sicomet Green food dye ZS120. Catalysts were characterized through various analyses. Catalyst performance and dye degradation were examined for raw and calcined waste at 500°C. Parameters like catalyst amount, sodium sulfite concentration, oxalic acid, and pH were optimized for both systems, with and without ligand. The first system achieved 91.5% mineralization using 0.15 g L-1 catalyst, pH of 3, and 0.45 mM Na2SO3 in 90 minutes under sunlight. The second reached 78.5% efficiency with variable conditions. Kinetic models demonstrated a first-order model for both photo-Fenton degradation and mineralization under sunlight. These findings guide eco-friendly dye degradation via mining waste-based catalysts in photo-Fenton systems, supporting sustainable wastewater treatment.

Ingenious development of bandgap engineered MIL-101(Fe) core-shell supported on SnO2/ZnO heterojunction and its photocatalytic activity towards azo dye degradation: Process optimization and mechanistic insight

Water pollution is a pressing global concern, exacerbated by industrial effluents containing hazardous azo-dyes such as Trypan blue (TB) and Methyl orange (MO), which contaminate water bodies and threaten ecosystems. The scarcity of pure water intensifies the urgency to develop effective remediation strategies to tackle the toxic dye pollutants. In the present work, an attempt has been made to fabricate and utilize a novel ternary MOF-based SnO2/ZnO@MIL-101(Fe) photocatalyst for the removal of TB and MO dyes from an aqueous medium. The photocatalyst was characterized using various analytical techniques, like XRD, FTIR, UV–vis DRS, PL, SEM, TEM, and XPS, which provide insights into the composites’ crystal structure, morphology, and optical properties, which are crucial for understanding their photocatalytic behavior. The photocatalytic performance of the heterojunction was investigated under various reaction parameters such as catalyst dosage, initial concentration of dyes, and light irradiation time. The results demonstrated the superior performance of the SnO2/ZnO@MIL-101(Fe) composites in degrading the mono-azo and di-azo dyes under visible light irradiation via a photo-fenton process. The maximum degradation efficiency of 97.44 % and 98.8 % were obtained for TB and MO within 30 and 55 min, respectively. Furthermore, the change in the total organic carbon (TOC) was monitored to verify the degree of mineralization of the azo dyes. The extremely high dye degradation activity and TOC removal can be attributed to the formation of a suitable heterojunction interface between the components of the photocatalyst, leading to effective charge carrier transport and the generation of active radicals. Finally, based on the radical scavenging experiments, ESR, and VB-XPS analysis, a plausible mechanism for the photodegradation process was derived. This research contributes to the advancement of sustainable water treatment technologies by providing insights into the design, fabrication, and utilization of novel composites for efficient remediation of dye-contaminated wastewater.

Catalytic activity of Nb-doped α-Fe2O3—Heterojunction structure, ferrimagnet-like character, and high activity

Photocatalytic activity of α-Fe2O3 under visible light had been studied intensively. Rapid electron-hole recombination is the main drawback of α-Fe2O3 and the photocatalytic activity can be enhanced by transition metal doping and heterojunction structure. In the present study, α-Fe2O3 doped with various amounts of Nb were synthesized using a simple sol–gel method, and further characterization and catalytic activity were investigated. PXRD, TEM-EDS and Mössbauer measurement showed the formation of weak-ferromagnetic Nb-doped α-Fe2O3 and FeNbO4, where heterojunction structure was suggested. UV–vis spectrum showed a broad absorption in visible-light regions with a narrow band gap between 2.27 and 2.97 eV. Photo-Fenton reaction using α-Fe2O3 to decompose methylene blue (MB) was conducted to evaluate the catalytic activity. Nb-doped sample showed a significant improvement compared with pure α-Fe2O3. PXRD and Mössbauer spectroscopy revealed the α-Fe2O3 and FeNbO4 phases, which were attached to a magnet due to the ferrimagentic character of Nb-doped α-Fe2O3. The high catalytic activity with k value 7.1 * 10−2/min was obtained for 7.4Nb600. Higher catalytic activity was also observed for 20Nb600 and 40Nb600, which were driven by higher surface area, Nb substitution and heterojunction structure. Mechanistic analysis revealed that the primary reaction of MB decomposition is the Photo-Fenton process.

Photodegradation of tylosin tartrate by advanced oxidation processes.

Tylosin tartrate, a macrolide antibiotic, is one of a class of emerging contaminants that have been detected in natural bodies of water since they are not easily removed by conventional treatment processes. In this study, the direct and indirect photodegradation of tylosin tartrate was analyzed to understand the role of reactive oxygen species and organic matter that may be present in surface waters. While direct photolysis caused negligible degradation (k = (9.4 ± 1.8) × 10-5s-1), the addition of 0.4M hydrogen peroxide (k = (2.18 ± 0.01) × 10-4s-1) or usage of the photo-Fenton process (k = (2.96 ± 0.02) × 10-4s-1) resulted in greater degradation. The degradation was maximized by combining tylosin tartrate with an experimentally determined optimal concentration of humic acid (15mg/L), which readily produced singlet oxygen and increased the overall degradation (k = 1.31 ± 0.05) × 10-3s-1) by means of indirect photolysis. Absolute pseudo-first-order bimolecular reaction rate constants for tylosin tartrate were measured with singlet oxygen [(4.7936 ± 0.0001) × 105M-1s-1] and hydroxyl radical [(5.2693 ± 0.0002) × 109M-1s-1] using competition kinetics, and when combined with data on concentration of the reactive oxygen species, showed that the hydroxyl radical makes a contribution to the degradation that is approximately eleven orders of magnitude greater than singlet oxygen.