Synthesis of Fe2O3/TiO2 monoliths for the enhanced degradation of industrial dye and pesticide via photo-Fenton catalysis

Novel MoS2/C3N5 composites with extended spectral response towards highly efficient photocatalytic abatement of hazardous pollutants

Carbon nitride materials are one of the potential candidates for photocatalytic application. The present work demonstrates the fabrication of C₃N₅ catalyst from a simple, low-cost, and easily available nitrogen-containing precursor, melamine. The facile and microwave mediated method was used to prepare novel MoS₂/C₃N₅ composites (referred to as MC) with varying weight ratios (1:1, 1:3, and 3:1). This work provided a novel strategy to improve photocatalytic activity and accordingly fabricated a potential material for effective removal of organic contaminants from water. XRD and FT-IR results affirms the cryatalinity and successful formation of the composites. The elemental composition/distribution was analysed via EDS and color mapping. The elemental oxidation state and successful charge migration in hetrostructure was confirmed by XPS findings. The catalyst's surface morphology indicates tiny MoS₂ nanopetals dispersed throughout C₃N₅ sheets, while BET studies revealed its high surface area (34.7 m²/g). The MC catalysts were highly active in visiblelight, with an energy band gap value of 2.01 eV and a lowered recombination of charges. Because of the strong synergistic relationship (2.19) in the hybrid, excellent activity for methylene blue (MB) dye (88.9%; 0.0157 min^-1) and fipronil (FIP) photodegradation (85.3%; 0.0175 min^-1) with MC (3:1) catalyst under visible-light irradiation was obtained. Investigations were carried out on the effect of catalyst quantity, pH, and effectual illumination area on photoactivity. Post-photocatalytic assessment verified the high re-useable character of the catalyst with a high degradation (63% (5 mg/L MB) and 54% (600 mg/L FIP)) after five cycles. The trapping investigations demonstrated that superoxide radicals and holes were intimately enrolled in the degradation activity. Remarkable removal rates of COD (68.4%) and TOC (53.1%) demonstrate excellent photocatalytic removal of practical wastewater even without any preliminary processes. The new study, when paired with previous research, demonstrates the real-world perspective of these novel MC composites for the elimination of refractory contaminants.

Hydrothermally improved natural manganese-containing catalytic materials to degrade 4-chlorophenol

Natural manganese-containing mineral (NMM) was used as a catalyst in heterogeneous catalytic ozonation for 4-chlorophenol (4-CP) degradation. The surface and structural properties of NMM were modified by the hydrothermal aging process and called H-NMM. The catalytic activity of NMM and H-NMM were evaluated for the catalytic ozonation process (COP). The synergistic effect of NMM and H-NMM in ozonation processes for 4-CP degradation under optimal conditions (pH of 7, 1 g/L of NMM and H-NMM, 0.85 mg/min of O₃, and 15 min of reaction time) was measured by 3.04 and 4.34, respectively. During the hydrothermal process, Mn⁴⁺ and Fe²⁺ were converted to Mn²⁺ and Fe³⁺, which caused better performance of the H-NMM than the NMM. During the catalytic ozonation process, Mn²⁺ is completely oxidized, which increases the production of Hydroxyl radical (•OH). The reactive oxygen species (ROS) generated in the system were identified using radical scavenging experiments. •OH, superoxide radical (•O₂^-), and singlet oxygen (¹O₂) represented the dominant reactive species for 4-CP degradation. The O₃/H-NMM process indicated a powerful ability in the mineralization of 4-CP (66.31% of TOC degradation). H-NMM exhibited excellent stability and reusability in consecutive catalytic cycles, and the NMM exhibited desirable performance. This study offers NMM and H-NMM as effective, stable, and competitive catalysts for hastening and enhancing the ozonation process to mitigate environmentally related pollutants of high concern.

Efficient catalytic degradation of methylene blue by a novel Fe3+-TiO2@CGS three-dimensional photoelectric system

In this study, a novel three-dimensional photoelectric system was designed and constructed for the degradation of methylene blue (MB) via photocatalysis, electrocatalysis, and photoelectric catalysis. To this end, a Ti/RuO₂-IrO₂-SnO₂-CeO₂ electrode was prepared via a thermal oxidation coating method and used as a dimensionally-stable anode (DSA). The cathode was made of a titanium sheet with Fe³⁺-doped TiO₂ loaded on coal gasification slag (CGS) (Fe³⁺-TiO₂@CGS) as a photocatalyst. The factors affecting the degradation efficiency, such as the supporting electrolyte, current density, and initial pH were systematically investigated. The results revealed Fe³⁺-TiO₂@CGS three-dimensional photoelectric system exhibiting efficient synergistic performance of photocatalysis and electrocatalysis with a synergistic factor of 1.11. Photo-generated holes (h⁺) were generated by light irradiation and direct anodic oxidation. Furthermore, hydroxyl radicals (HO·) radicals were induced via other pathways. Such active species showed highly-oxidizing abilities, beneficial to the degradation of methylene blue (MB). The representative Fe³⁺-TiO₂@CGS three-dimensional photoelectric system showed super high degradation efficiency at pH 11 and current density of 18.76 mA cm^-2. Using NaCl as a supporting electrolyte, the degradation yield reached 99.98% after 60 min of photoelectrical treatment. Overall, the novel Fe³⁺-TiO₂@CGS three-dimensional photoelectrical system looks very promising for the highly efficient catalytic degradation of organic contaminants.

Sol-gel synthesis of TiO2 on Co3O4-coated sporopollenin exine microcapsules (SECs) and photocatalytic performance of new semiconductor heterojunction material

In this study, a new approach was developed to prepare mesoporous hybrid TiO₂/Co₃O₄ coated on Juglans sporopollenin exine microcapsules (SECs). TiO₂ was synthesized on Co₃O₄-coated SECs used as substrate, by sol-gel method. The obtained semiconductor/semiconductor hetero-junction hybrid materials were characterized with X-ray diffractometry (XRD), UV-Vis absorption spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), particle size distribution, specific surface area, and zeta potential measurements. Photocatalytic performances of hybrid materials were tested for Reactive Black 5 dye under both UV and visible light. Equilibrium pH of the solution containing 10 mg/L Reactive Black 5 dye and 0.1% wt/v TiO₂/Co₃O₄ was around 4.7. After irradiation in the solar box, more than 98% of the Reactive Black 5 was photocatalytically degraded within 60 min.

Heterostructured γ-Fe2O3/FeTiO3 magnetic nanocomposite: An efficient visible-light-driven photocatalyst for the degradation of organic dye

The catalyst recovery is the major concern in commercialization of photocatalysts for the industrial effluent treatment process. To overcome this major issue, Fe₂O₃ based magnetic photocatalytic heterostructure ɣ-Fe₂O₃/FeTiO₃ nanocomposite was synthesized by hydrothermal method. Fe₂O₃ is the cheapest visible active magnetic photocatalytic material, but it has the limitation of fast e^-/h + recombination. Titanium (Ti) was loaded on γ-Fe₂O₃ to overcome this issue. The loaded Ti has grown as FeTiO₃ on the surface of ɣ-Fe₂O₃ nanocrystals and emerged as heterostructure ɣ- Fe₂O₃/FeTiO₃ nanocomposites, which was confirmed by XRD and TEM results. The loading concentration of Ti on γ-Fe₂O₃ was optimized to achieve the maximum photocatalytic efficiency without compromising the magnetic property of γ-Fe₂O₃ to facilitate the magnetic separation. DRS-UV spectra revealed the strong visible light response of γ- Fe₂O₃/FeTiO₃ nanocomposite. The photocatalytic efficiencies of the synthesized materials were evaluated using methylene blue (MB) as a model pollutant under sunlight. The built-in electric field between p-n junction between FeTiO₃ and Fe₂O₃ and type II charge transfer mechanism extended the lifetime of the charge carriers at the heterojunction of γ- Fe₂O₃/FeTiO₃, which was confirmed by PL spectra. The vibrating sample magnetometer (VSM) study revealed the decreasing magnetization, coercivity (Hc), and retentivity (Mr) of γ-Fe₂O₃ with increasing concentration of Ti. 92% of the used-up 20 wt% Ti loaded γ-Fe₂O₃/FeTiO₃ magnetic nanocomposite was recovered from the treated wastewater using an electromagnet. Both magnetic properties and efficiency of the nanocomposite increased up to 20 wt% of Ti loading, beyond that decreased due to the increasing composition of antiferromagnetic FeTiO₃ and the increasing number of defect sites as recombination centers. Hence, 20 wt% loading of Ti was concluded as the optimum to enhance the efficiency and to retain the magnetic properties. This work aims the commercialization of magnetic photocatalytic materials for the industrial effluent treatment.

Challenges and effectiveness of nanotechnology-based photocatalysis for pesticides-contaminated water: A review

Pesticides have been frequently used in agricultural fields. Due to the expeditious utilization of pesticides, their excessive usage has negative impacts on the natural environment and human health. This review discusses the successful implications of nanotechnology-based photocatalysis for the removal of environmental pesticide contaminants. Notably, various nanomaterials, including TiO₂, ZnO, Fe₂O₃, nanoscale zero-valent iron, nanocomposite-based materials, have been proposed and have played a progressively essential role in wastewater treatment. In addition, a detailed review of the crucial reaction condition factors, including water matrix, pH, light source, temperature, flow rate (retention time), initial concentration of pesticides, a dosage of photocatalyst, and radical scavengers, is also highlighted. Additionally, the degradation pathway of pesticide mineralization is also elucidated. Finally, the challenges of technologies and the future of nanotechnology-based photocatalysis toward the photo-degradation of pesticides are thoroughly discussed. It is expected that those innovative extraordinary photocatalysts will significantly enhance the performance of pesticides degradation in the coming years.

Green Synthesis and Investigation of Surface Effects of α-Fe2O3@TiO2 Nanocomposites by Impedance Spectroscopy

Nanocomposites based on iron oxide/titanium oxide nanoparticles were prepared by employing green synthesis, which involved phytochemical-mediated reduction using ginger extract. XRD confirmed the composite formation, while scanning electron microscopy (SEM), dynamic light scattering (DLS), and energy-dispersive X-ray spectroscopy (EDX) was employed to investigate the particle size, particle morphology, and elemental analysis. SEM indicated the formation of particles with non-uniform shape and size distribution, while EDX confirmed the presence of Fe, Ti and oxygen in their elemental state. The surface effects were investigated by Fourier transform infrared radiation (FTIR) and impedance spectroscopy (IS) at room temperature. IS confirmed the co-existence of grains and grain boundaries. Thus, FTIR and IS analysis helped establish a correlation between enhanced surface activity and the synthesis route adopted. It was established that the surface activity was sensitive to the synthesis route adopted. The sample density, variation in grain size, and electrical resistivity were linked with surface defects, and these defects were related to temperature. The disorder and defects created trap centers at the sample's surface, leading to adsorption of CO₂ from the environment.

Coal mining pyritic waste in Fenton-like processes: Raw and purified catalysts in Reactive Blue 21 dye discoloration

Raw pyritic waste (RPW) from South Brazilian coal deposits and pure pyritic waste (PPW) were used as catalysts for organic dyes discoloration. Samples were characterized for their chemical, morphological, and structural properties. There was a significant content of Fe and S in both samples from the presence of iron sulfide. The average particle size is 10.9 μm for RPW and 7.4 μm for PPW, demonstrating that the beneficiation process could remove the larger quartz particles, interfered in the distribution, and average particle size. Smaller particle sizes promoted a larger surface area for the PPW. The influence of the pyritic waste in dosage, H₂O₂ concentration, and pH was evaluated, obtaining discoloration values above 95% for 0.5 g/L of pyritic waste, 2 g/L of H₂O_2, and pH 4.3 for both pyritic wastes. The degradation kinetics of the Reactive Blue 21 using the raw pyritic waste obtained a dye concentration removal above 93% in 90 min, with an iron release of 5.4 mg/L into the solution. Using PPW, the dye concentration removal was over 92% in 40 min, with the iron release of 15.5 mg/L into the solution. Discoloration rate for the PPW sample is 7 times greater than the rate obtained for RPW, indicating a faster decay rate for the purified sample. A decrease in discoloration efficiency is observed for PPW after 6 cycles of use, due to the higher concentration of iron leached into the medium. From the results, it was concluded that the raw pyritic waste has excellent potential for use as a catalyst for Fenton reaction, especially for dye-containing water discoloration, thus demonstrating the excellent applicability potential of pyritc waste in the degradation of organic pollutants in wastewater.

Functionalized Magnetic Nanomaterials in Agricultural Applications

The development of functional nanomaterials exhibiting cost-effectiveness, biocompatibility and biodegradability in the form of nanoadditives, nanofertilizers, nanosensors, nanopesticides and herbicides, etc., has attracted considerable attention in the field of agriculture. Such nanomaterials have demonstrated the ability to increase crop production, enable the efficient and targeted delivery of agrochemicals and nutrients, enhance plant resistance to various stress factors and act as nanosensors for the detection of various pollutants, plant diseases and insufficient plant nutrition. Among others, functional magnetic nanomaterials based on iron, iron oxide, cobalt, cobalt and nickel ferrite nanoparticles, etc., are currently being investigated in agricultural applications due to their unique and tunable magnetic properties, the existing versatility with regard to their (bio)functionalization, and in some cases, their inherent ability to increase crop yield. This review article provides an up-to-date appraisal of functionalized magnetic nanomaterials being explored in the agricultural sector.

Optimal degradation of organophosphorus pesticide at low levels in water using fenton and photo-fenton processes and identification of by-products by GC-MS/MS

This study aiming to determine the optimal conditions to degrade an organophosphate pesticide diazinon (DZN) at low levels concentrations (μg.mL^-1) and to identify the by-products generated. The degradation processes utilized were the Fenton and photo-Fenton. The iron concentration [Fe²⁺], the hydrogen peroxide concentrations [H₂O₂], and the solution pH are the investigated parameters. The Doehlert three-parameter experimental design was applied to model and optimize both degradation processes. The mathematical models suggested were assessed and validated by application of analysis of variances ANOVA. In the case of Fenton process, the greatest yield of degradation (79%) was obtained at [Fe²⁺] = 35 mg.L^-1 (0.63 mmol.L^-1), [H₂O₂] = 423 mg.L^-1 (12.44 mmol.L^-1), and pH = 5.0. In photo-Fenton process, the maximum yield of degradation (96%) was obtained under the conditions of [Fe²⁺] = 29 mg.L^-1 (0.52 mmol.L^-1), [H₂O₂] = 258 mg.L^-1 (7.59 mmol.L^-1) and pH = 4.6. QuEChERS (quick, easy, cheap, effective, rugged, and safe), as extraction technique, and GC-MS/MS (gas chromatography coupled with triple quadrupole mass spectrometry) were used to identify the by-products degradation of DZN. The identified compounds are diazoxon, triethyl phosphate, triethyl thiophosphate, 2-isopropyl-5-ethyl-6-methylpyrimidine-4-ol, 2-isopropyl-6-methylpyrimidine-4-ol (IMP) and hydroxydiazinon. Three possible pathways for diazinon degradation have been suggested and the hydroxylation, oxidation and hydrolysis are likely probable degradation mechanisms.

Low cost effective heterogeneous photo-Fenton catalyst from drinking water treatment residuals for reactive blue 19 degradation: Preparation and characterization

Four different catalysts from drinking water treatment residuals (DWTR) were prepared via impregnation in the iron nitrate, calcined at different temperatures ranged from 200°C to 500°C, and tested for the reactive blue 19 oxidation using the heterogeneous photo-Fenton, under UVA light source. XRD and XPS results revealed that iron nature was found under a ferric oxide form (Fe³⁺ ) similar to the magnetite. Calcination temperature results showed a significant effect on the activity of the catalysts. RB19 and TOC removals were 99% and 79%, respectively, with the best catalyst that calcined at 500°C in optimal conditions as follows: initial pH solution = 3, 10 mM of H₂ O₂ dosage, 0.5 g/L of catalyst loading, reaction temperature 35°C, and I_UVA  = 3.55 MW/cm² for 50 mg/L of RB19. The reusability of the catalyst after three cycles showed complete removal of RB19 and 65% TOC removal. PRACTITIONER POINTS: Synthetized heterogeneous photo-Fenton catalyst from drinking water treatment residuals for the photo Fenton oxidation. The calcination temperatures plays a crucial role in catalyst photocatalytic activity. Degradation of reactive blue 19 with Fe/DWTR-500 in presence of H₂ O₂ . The Fe/DWTR-500 catalyst exhibited the best photocatalytic activity. Reusability studies of Fe/DWTR-500 and the kinetics of reactive blue 19 degradation were investigated.

Fabrication, characterization, and application of ternary magnetic recyclable Bi2WO6/BiOI@Fe3O4 composite for photodegradation of tetracycline in aqueous solutions

We aim at fabricating a ternary magnetic recyclable Bi₂WO₆/BiOI@Fe₃O₄ composite that could be applied for photodegradation of tetracycline (TC) from synthetic wastewater. To identify any changes with respect to the composite's morphology and crystal structure properties, ΧRD, FTIR, FESEM-EDS, PL and VSM analyses are carried out. The effects of Fe₃O₄ loading ratio on the Bi₂WO₆/BiOI for TC photodegradation are evaluated, while operational parameters such as pH, reaction time, TC concentration, and photocatalyst's dose are optimized. Removal mechanisms of the TC by the composite and its photodegradation pathways are elaborated. With respect to its performance, under the same optimized conditions (1 g/L of dose; 5 mg/L of TC; pH 7; 3 h of reaction time), the Bi₂WO₆/BiOI@5%Fe₃O₄ composite has the highest TC removal (97%), as compared to the Bi₂WO₆ (63%). After being saturated, the spent photocatalyst could be magnetically separated from solution for subsequent use. In spite of three consecutive cycles with 71% of efficiency, the spent composite still has reasonable photocatalytic activities for reuse. Overall, this suggests that the composite is a promising photocatalyst for TC removal from aqueous solutions.

Enhanced photo catalytic degradation of methyl orange using p–n Co3O4-TiO2 hetero-junction as catalyst

Photo catalytic degradation of pollutants is one of the techniques used for treatment of dye contaminated wastewater. TiO2 has attracted much attention as photo catalyst for treatment of contaminated water. In this study, the photo catalytic performance of TiO2 has been enhanced by formation of p–n Co3O4-TiO2 hetero-junction. The p–n Co3O4-TiO2 hetero-junction was prepared by wet incipient impregnation method and characterized by various techniques. The photo catalytic activity of prepared composite was evaluated by photo degradation of methyl orange. The as prepared Co3O4-TiO2 composite was found as effective catalyst than Co3O4 and TiO2. The higher photo catalytic activity was attributed to p–n junction formed between Co3O4 and TiO2. The degradation data was analyzed according to Eley–Rideal mechanism in terms of 1st and 2nd order kinetics.

A Novel Reduced Graphene Oxide-Attapulgite (RGO-ATP) Supported Fe2O3 Catalyst for Heterogeneous Fenton-like Oxidation of Ciprofloxacin: Degradation Mechanism and Pathway

Ciprofloxacin, a third-generation fluoroquinolones (FQs) antibiotic, is observed to increasingly pollute the environment. In this study, a three-dimensional reduced graphene oxide-attapulgite-based catalyst Fe2O3/RGO-ATP was prepared and used to analyze the degradation of ciprofloxacin in a heterogeneous Fenton reaction. The heterogeneous catalyst Fe2O3/RGO-ATP was prepared by a one-step hydrothermal method, and the samples were characterized using BET(Brunauer-Emmett-Teller) surface area, Raman spectroscopy, X-ray diffraction (XRD), Fourier infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The effect of reaction time, temperature, pH, initial concentration, H2O2 dosage and reuse time on the degradation of ciprofloxacin by the catalyst Fe2O3/RGO-ATP was investigated. The optimum conditions of degradation of ciprofloxacin are observed to be 60 °C, pH 5, H2O2 concentration of 2.9724 mmol/L, and initial ciprofloxacin concentration of 50 mg/L. The catalyst could be reused several times with a decline in catalytic capacity. Fourier-transform ion cyclotron resonance mass spectrometer (FT) was also employed to study the degradation products of ciprofloxacin in the aqueous solution. The results show that the heterogeneous catalyst Fe2O3/RGO-ATP possessed an excellent ability for the catalytic degradation of ciprofloxacin. Direct hydroxyl oxidation is noted to be the main pathway of degradation of ciprofloxacin, and no defluorination reaction is observed during the degradation process.

Complete removal of endocrine disrupting compound and toxic dye by visible light active porous g-C3N4/H-ZSM-5 nanocomposite

Photocatalytic degradation of toxic pollutants is an efficient technique to completely remove the toxic pollutants from water bodies. In the present investigation, photocatalytic degradation of pollutants was studied over porous g-C₃N₄/H-ZSM-5 nanocomposite under visible light irradiation. The composite g-C₃N₄/H-ZSM-5 was synthesized by mixing an aqueous solution of H-ZSM-5 zeolite (increases surface area and provides active sites for degradation) with melamine (precursor of g-C₃N₄) for 10-12 h followed by calcinations at 550 °C. The photocatalyst was characterized by XRD, BET, HRTEM, FESEM, EDS and elemental mapping analysis. These techniques confirmed that, g-C₃N₄/H-ZSM-5 composite have layered and porous structure with uniform distribution of g-C₃N₄ on H-ZSM-5 surface. The BET N₂ adsorption-desorption analysis verified that the catalyst has high surface area (∼175 m²/g) having mesopores and micropores. The prepared catalyst was then used for the photodegradation of a model dye, Methylene Blue (MB) and an endocrine disrupting compound, Fipronil (FIP). Effects of various parameters such as pH, catalyst dose and scavengers were also studied. The % photocatalytic degradation of MB and FIP were around ∼92% and ∼84% with a high rate constants of 0.00997 and 0.00875 min^-1, respectively. From the scavenger study, OH (hydroxyl radical) and radical was found to be the major reactive species for MB and FIP degradation. From these studies it is revealed that, the catalyst is visible active, easy to prepare and an efficient photocatalyst for toxic pollutant degradation.

Highly improved photocatalytic degradation of rhodamine B over Bi2Ga4-x Fe x O9 solid solutions under visible light irradiation

In this work, Bi2Ga4-x Fe x O9 (0 ≤ x ≤ 1.2) solid solutions were prepared via the traditional high-temperature solid-state reaction. The Le Bail fitting on the powder X-ray diffraction patterns shows that these solid solutions were successfully synthesized. Scanning electron microscopy showed that the Bi2Ga3.2Fe0.8O9 sample was composed of sub-micron particle crystallites. Energy dispersive spectroscopy analysis and X-ray photoelectron spectroscopy were used to identify that the Fe element is trivalent when doping into the crystal structure. Ultraviolet-visible diffused reflectance spectra suggested that the bandgap of Bi2Ga3.2Fe0.8O9 is narrower than that of the undoped Bi2Ga4O9 sample. Three strategies, including Fe3+ doping, addition of H2O2, and loading of the cocatalyst, were utilized to improve the photocatalytic degradation activity. The optimum photocatalytic performance was obtained over 2.5 wt% Cu/Bi2Ga3.2Fe0.8O9 sample in 20 ppm RhB aqueous solution (containing 1.5 mL H2O2) under visible light irradiation. Its photodegradation rate is 8.0 times that of Bi2Ga4O9 containing 0.5 mL H2O2. The 2.5 wt% Cu/Bi2Ga3.2Fe0.8O9 photocatalyst remained stable and active even after four cycles. Also, its photocatalytic conversion efficiency for RhB was nearly 100%, which was achieved in 3 hours. The photocatalytic mechanism indicated that ·OH and h+ played an important role in the photocatalytic degradation reaction.