Search Results (125)

Fe-doped BiOBr nanomaterials with varying Fe concentrations were synthesized using a solvothermal method. Paracetamol (APAP) was selected as the target pollutant to evaluate the visible-light-driven peroxydisulfate (PDS) activation performance of the prepared catalysts. Among all samples, 5% Fe-doped BiOBr (5% Fe-BOB) exhibited the highest catalytic efficiency, which can completely degrade APAP in 30 min under visible light irradiation. The degradation kinetics of APAP, PDS consumption, and the dominant reactive species in the 5% Fe-BOB/PDS/visible light system were systematically investigated. Results revealed that both photocatalyst dosage and PDS concentration significantly influenced activation efficiency. The primary active species responsible for APAP degradation were identified as photogenerated holes (h⁺) and singlet oxygen (¹O₂). Furthermore, cycling tests and control experiments confirmed that the 5% Fe-BOB/PDS/visible light system maintained high stability and effectively degraded APAP across a wide pH range. This work provides an efficient and stable photocatalytic system for pharmaceutical wastewater treatment through PDS-based advanced oxidation processes. Full article

This work shows a sustainable methodology for the synthesis of biogenic materials designed for the removal and photodegradation of rhodamine B (RhB), a highly dangerous environmental pollutant that induces reproductive toxicity. The classical synthesis of MCM-41-ordered mesoporous materials was modified using biocompatible rice husk as the silica template. Iron was incorporated and the so-prepared biogenic photocatalysts were characterized by X-ray diffraction, N₂ adsorption–desorption isotherms, transmission electron microscopy, diffuse reflectance UV-Vis, surface pH, cyclic voltammetry, and Fourier transform infrared spectral analysis of pyridine adsorption. The photocatalytic performance of the materials was evaluated following the removal by adsorption and the photon-driven degradation of RhB. The adsorption capacity and photocatalytic activity of the biogenic materials were correlated with their properties, including iron content, texture, surface content, and electrochemical properties. The best biogenic material boosted the degradation rates of RhB under UV irradiation up to 4.7 and 2.2 times greater than the direct photolysis and the benchmark semiconductor TiO₂-P25. It can be concluded that the use of rice husks for the synthesis of biogenic Fe-modified mesoporous materials is a promising strategy for wastewater treatment applications, particularly in the removal of highly toxic organic dyes. Full article

This study aims to demonstrate the feasibility of the use of chestnut waste as a green and circular material for developing iron-based photocatalysts for non-steroidal anti-inflammatory drug (NSAID) photodegradation. Four Fe-based catalysts and two pristine biochars were obtained upon a pyrolysis process at 500 and 700 °C and fully characterised. Due to the applied synthesis, iron is present in the form of isotropic grains of magnetite (Fe₃O₄), quite homogeneously dispersed onto the biochar. The textural properties of all the materials are mainly determined by the pyrolytic temperature, which results in macroporous materials at 500 °C and microporous ones at 700 °C. Fe-based catalysts were tested in Diclofenac (DFC) photodegradation. DFC removal was the result of both adsorption and photocatalytic reactions. Despite the good yield in DFC removal (80–100%), the formation of degradation by-products can partially invalidate the good effectiveness of this approach. However, the encouraging results of this study represent a step forward for the possible development of waste-derived biochar-based catalysts for in-field application. Full article

A polyoxometalate-based metal–organic complex with the ability to treat pollutants in water was obtained under hydrothermal conditions, namely [Ni(H₂L)(HL)₂](PMo₁₂O₄₀)·3H₃O·4H₂O (1) (H₂L = 4,4′-(1H,1′H-[2,2′-biimidazole]-1,1′-diyl)dibenzoicacid). Structural analysis reveals that the [Ni(H₂L)(HL)₂] units are interconnected into a 2D layer via hydrogen bonds between adjacent carboxyl groups and water molecules of crystallization. [PMo₁₂O₄₀]³⁻ anions are embedded within the larger pores of the layer and are connected to the adjacent layers through hydrogen bonds, ultimately expanding the structure into a 3D supramolecular architecture. The intermolecular interactions were studied via Hirshfeld surface (HS) analysis. Electrochemical performance tests reveal that 1 exhibits electrocatalytic activity toward the oxidation and reduction of diverse pollutants in water, including NO₂⁻, Cr(VI), BrO₃⁻, Fe(III), and ascorbic acid (AA). Additionally, it can also serve as an amperometric sensor for the detection of BrO₃⁻ and Cr(VI). Photocatalytic studies reveal that compound 1 functions as a bifunctional photocatalyst, which not only achieves efficient degradation of organic dyes but also demonstrates remarkable reduction efficiency for toxic Cr(VI). Compound 1 demonstrates significant potential for practical water remediation applications. Full article

TiO₂ mesoporous supports were obtained by the sol–gel method from different precursors (titaniumethoxide, isopropoxide, or butoxide) in the presence of nonionic, cationic, and anionic surfactants. Among these samples, those obtained from Ti isopropoxide, Brij58 w/o activated carbon (AC), were selected as supports. Photocatalysts were obtained by modifying these supports with Ag, Fe, and AgFe (each metal around 1% mass). The characterization results showed a stronger influence of titania precursors, surfactants, and AC on the texture and an insignificant effect on the crystalline structure and morphology of the obtained materials. X-ray photoelectron spectroscopy revealed the effects of AC and Fe on the Ag⁰ concentration and of Ag on Fe-reduced species. Based on this information, the results obtained by H₂-TPR, UV–Vis, Raman, and photoluminescence spectroscopy were explained. The performance of the photocatalysts was evaluated in the degradation of Congo Red (CR) and Crystal Violet (CV) dyes under UV and visible light. The Ag-TiO₂ sample exhibited the best activity in degrading CR at acidic pH and in degrading CV under basic conditions. In visible light, we observed the significant effects of the surface plasmon resonance, AC, Ag, and Fe on the activity in CR photodegradation. The proposed kinetics and mechanisms complete the study of the reactions. Full article

This review analyzes TiO₂-based coatings formed by the plasma electrolytic oxidation (PEO) process of titanium for the photocatalytic degradation of methyl orange (MO) under simulated solar irradiation conditions. PEO is recognized as a useful technique for creating oxide coatings on various metals, particularly titanium, to assist in the degradation of organic pollutants. TiO₂-based photocatalysts in the form of coatings are more practical than TiO₂-based photocatalysts in the form of powder because the photocatalyst does not need to be recycled and reused after wastewater degradation treatment, which is an expensive and time-consuming process. In addition, the main advantage of PEO in the synthesis of TiO₂-based photocatalysts is its short processing time (a few minutes), as it excludes the annealing step needed to convert the amorphous TiO₂ into a crystalline phase, a prerequisite for a possible photocatalytic application. Pure TiO₂ coatings formed by PEO have a low photocatalytic efficiency in the degradation of MO, which is due to the rapid recombination of the photo-generated electron/hole pairs. In this review, recent advances in the sensitization of TiO₂ with narrow band gap semiconductors (WO₃, SnO₂, CdS, Sb₂O₃, Bi₂O₃, and Al₂TiO₅), doping with rare earth ions (example Eu³⁺) and transition metals (Mn, Ni, Co, Fe) are summarized as an effective strategy to reduce the recombination of photo-generated electron/hole pairs and to improve the photocatalytic efficiency of TiO₂ coatings. Full article

The ever-increasing importance of sustainable environmental remediation calls for academics’ contribution to satisfy such a need. The 3R’s criteria of recover, recycle and reuse is designed to sustain the waste stream to produce a valuable product. In this regard, the circular economy looks to deliver banana peel waste as a photocatalyst for pharmaceutical effluent oxidation, which we investigated in this study. Banana peel waste is treated thermally and chemically then augmented with magnetite nanoparticles and labeled as ACBP-Fe₃O₄. The mixture is characterized through Scanning Electron Microscopy (SEM) and the composition of the composite material is attained by energy dispersive X-ray spectroscopy (EDX), and then introduced as a Fenton catalyst. The notable oxidation of tetracycline (TC), evaluated by TC removal and chemical Oxygen Demand (COD) oxidation tenancy, is achieved. The effectiveness of the operational parameters is also assessed and the most influenced parameters are optimized through numerical optimization based on a Response Surface Methodology (RSM) tool. The effects of initial pH value, ACBP-Fe₃O₄ and H₂O₂ concentrations on the oxidation efficiency of the Tetracycline were optimized at pH 6.6 and 350 mg/L and 43 g/L for H₂O₂ and ACBP-Fe₃O₄, respectively. Thermodynamics and kinetics were also studied and the experimental and model data revealed the reaction is spontaneous and exothermic in nature and follows the first-order reaction kinetics. Also, the thermodynamic results the reaction proceeds at a low energy barrier of 34.33 kJ mol⁻¹. Such a system introduces the role of engineers and academics for a sustainable world without a waste stream. Full article

In this study, Fe₃O₄@SiO₂@TiO₂ (FS-FT (0 g)) photocatalysts, featuring a magnetic core–shell structure, and Fe-doped Fe₃O₄@SiO₂@Fe-TiO₂ (FS-FT (x g)) photocatalysts, were fabricated via the sol–gel method. Structural and compositional analyses of the processed samples were systematically conducted through X-ray diffraction (XRD), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), surface-sensitive X-ray photoelectron spectroscopy (XPS), and optical property assessment via UV-Vis diffuse reflectance spectroscopy (UV-DRS). The results show that TiO₂ on the outer layer of FS-FT (0 g) and FS-FT (x g) has an anatase structure, and that Fe is doped into FS-FT (x g). The photodegradation of methyl orange (MO) using FS-FT (0 g) and FS-FT (x g) with various Fe doping levels was evaluated in both pure MO (C₀ = 10 mg/L) and MO-Na₂SO₄-blended solutions. Under irradiation with high-pressure mercury lamps, the removal rates of MO using FS-FT (0 g) and FS-FT (0.36 g) in pure MO solution reached 90.25% and 99% at 25 min, respectively, which indicates that FS-FT (0.36 g) can enhance photocatalytic performance. The removal rates of MO using FS-FT (0 g) and FS-FT (0.36 g) in MO-Na₂SO₄-blended solution (C₀ = 10 mg/L, C_Na2SO4 = 12.5 g/L) reached 92.38% and 97.16% at 25 min, respectively. The removal rate of MO using FS-FT (0.36 g) decreased in MO-Na₂SO₄-blended solution in the previous 25 min, which indicates that Na₂SO₄ can inhibit degradation using FS-FT (0.36 g). The degradation experiments of MO-Na₂SO₄-blended solutions with different concentrations of Na₂SO₄ using FS-FT (0.36 g) showed that as the concentration of Na₂SO₄ increases, the inhibitory effect becomes more pronounced. Recovery and recycling experiments confirmed that the photocatalyst exhibited robust degradation performance over multiple cycles. Kinetic analysis of the photocatalytic data, based on a first-order model, was conducted to explore the underlying degradation principles. Full article

The development of heterostructures incorporating photocatalysts optimized for visible-light activity represents a major breakthrough in the field of environmental remediation research, offering innovative and sustainable solutions for environmental purification. This study explores the photocatalytic capabilities of a SnFe₂O₄/g-C₃N₄ heterojunction nanocomposite, successfully synthesized from graphitic carbon nitride (g-C₃N₄) and tin ferrate (SnFe₂O₄) and applied to the degradation of the cationic dye brilliant cresyl blue (BCB) in an aqueous solution. These two components are particularly attractive due to their low cost and ease of fabrication. Various characterization techniques, including XRD, FTIR, SEM, and TEM, were used to confirm the successful integration of SnFe₂O₄ and g-C₃N₄ phases in the synthesized catalysts. The photocatalytic and photo-Fenton-like activity of the heterojunction composites was evaluated by the degradation of brilliant cresyl blue under visible LED illumination. Compared to the pure components SnFe₂O₄ and g-C₃N₄, the SnFe₂O₄/g-C₃N₄ nanocomposite demonstrated a superior photocatalytic performance. Furthermore, the photo-Fenton-like performance of the composites is much higher than the photocatalytic performances. The significant improvement in photo-Fenton activity is attributed to the synergistic effect between SnFe₂O₄ and g-C₃N₄, as well as the efficient separation of photoexcited electron/hole pairs. The recyclability of the SnFe₂O₄/g-C₃N₄ composite toward BCB photo-Fenton like degradation was also shown. This study aimed to assess the modeling and optimization of photo-Fenton-like removal BCB using the SnFe₂O₄/g-C₃N₄ nanomaterial. The main parameters (photocatalyst dose, initial dye concentration, H₂O₂ volume, and reaction time) affecting this system were modeled by two approaches: a response surface methodology (RSM) based on a Box–Behnken design and artificial neural network (ANN). A comparison was made between the predictive accuracy of RSM for brilliant cresyl blue (BCB) removal and that of the artificial neural network (ANN) approach. Both methodologies provided satisfactory and comparable predictions, achieving R² values of 0.97 for RSM and 0.99 for ANN. Full article

The increasing presence of persistent pollutants in industrial wastewater underscores the shortcomings of conventional treatment methods, prompting the adoption of advanced oxidation processes (AOPs) for sustainable water remediation. This review examines the development of AOPs, focusing on their ability to produce hydroxyl radicals and reactive oxygen species (ROS) to mineralize complex pollutants. Homogeneous systems such as Fenton’s reagent show high degradation efficiency. However, challenges like pH sensitivity, catalyst recovery issues, sludge generation, and energy-intensive operations limit their scalability. Heterogeneous catalysts, such as TiO₂-based photocatalysts and Fe₃O₄ composites, offer improved pH adaptability, visible-light activation, and recyclability. Emerging innovations like ultraviolet light emitting diode (UV-LED)-driven systems, plasma-assisted oxidation, and artificial intelligence (AI)-enhanced hybrid reactors demonstrate progress in energy efficiency and process optimization. Nevertheless, key challenges remain, including secondary byproduct formation, mass transfer constraints, and economic feasibility for large-scale applications. Integrating AOPs with membrane filtration or biological treatments enhances treatment synergy, while advances in materials science and computational modeling refine catalyst design and reaction mechanisms. Addressing barriers in energy use, catalyst durability, and practical adaptability requires multidisciplinary collaboration. This review highlights AOPs as pivotal solutions for water security amid growing environmental pollution, urging targeted research to bridge gaps between laboratory success and real-world implementation. Full article

In this study, the catalytic performance of the Fenton sludge iron-based biochar catalyst (Fe@BC700), generated during the Fenton process, was investigated regarding its role in oxidizing 2,4-dichlorophenol (2,4-DCP) and As(III) from aqueous solutions in peroxymonosulfate (PMS), peroxydisulfate (PDS), and hydrogen peroxide (H₂O₂) systems. The characteristics of the as-prepared catalyst, operational parameters of H₂O₂/UV/Fe@BC700, PDS/UV/Fe@BC700, and PMS/UV/Fe@BC700 systems, and the kinetics of 2,4-DCP degradation were evaluated. Fe@BC700 exhibited excellent capabilities for activating persulfate and an outstanding oxidant performance as a heterogeneous photocatalyst under UV irradiation. Among the tested systems, PMS/UV/Fe@BC700 showed the highest oxidation capabilities for both 2,4-DCP and As(III) within 40 min. The total organic carbon (TOC) removal efficiency for 2,4-DCP was up to 95.9% in the PMS/UV/Fe@BC700 system. The presence of free radicals in the PMS/PDS system included ·OH, SO₄^·−, and ·O₂⁻, which were facilitated by both UV irradiation and the catalyst. The by-products generated during the PMS/UV/Fe@BC700 treatment were identified via LC-MS analysis, which showed that catalytic degradation substantially reduced the chronic and acute toxicity of 2,4-DCP intermediates. The present study demonstrates that the iron-based biochar derived from Fenton sludge exhibited remarkable persulfate activation capabilities and was highly effective in removing 2,4-DCP and As(III). Full article

Metal vanadates are a developing group of semiconducting metal oxide materials that are gaining increasing attention due to their great redox potential, effective separation of photogenerated electron–hole pairs, and tunability of structural and physicochemical properties. Their rational design as effective photocatalysts can find use in various applications, including energy conversion/storage and environmental remediation. In particular, one of the viable ways to address energy-related issues can be through the sustainable production of hydrogen (H₂), a clean fuel produced by photocatalysis using metal vanadates. However, the rapid recombination of photogenerated electron–hole pairs limits their practical use as effective photocatalysts, and thus, many efforts have been devoted to optimizing metal vanadates to enhance their efficiency. Herein, we provide a comprehensive review that deals with the recent development strategies of metal (Ni, Fe, Zn, Ag, In, Bi, rare earth, etc.) vanadates with the working mechanisms. Their synthesis, doping, cocatalyst loading, heterojunction creation, and carbon loading are also reviewed for photocatalytic H₂ production. The challenges that metal vanadate-based photocatalysts have been facing are also discussed along with their significant potential for environmentally friendly and sustainable clean fuel production. Full article

In this work, Fe³⁺- and Co²⁺-doped ZnO NPs (zinc oxide nanoparticles), Zn_0.9Fe_xCo_0.1−xO, with a hexagonal wurtzite phase (single-phase), were synthesized via a co-precipitation technique where the phase purity and elemental composition were confirmed by XRD and EDX, respectively. Due to the substitution of Fe by Co, the cell parameters ($a$ and c) were increased, alongside which a slight shift to higher diffracted angles appeared. FTIR was carried out to confirm the insertion of both the Fe³⁺ and Co²⁺ dopants into the ZnO hexagonal phase. Based on the experimental results, different numerical techniques were used to determine the optical gap and refractive index for the ZnO NP-doped samples, and when the concentration of Fe³⁺ ions was increased, the band gap value of ZnO decreased from 3.36 eV to 3.29 eV, accompanied by a decrease in the Urbach energy, while the refractive index increased. The doped ZnO NPs were later found to be effective UV photocatalysts which demonstrated a maximum reduction (84%) of methylene blue (MB) in a neutral environment for X = 0.05. The correlation between the Fe³⁺ concentration, structure, optical parameters, and photocatalytic efficacy is explained in detail. Full article

The titanium dioxide (TiO₂) photocatalyst is an important semiconducting material that exhibits environmental purification functions when exposed to light. Elemental doping of TiO₂ is considered an important strategy to improve its photocatalytic activity. Herein, we have achieved the low-temperature, atmospheric-pressure synthesis of anatase TiO₂ particles with doping of 3d metals (Fe, Co, Ni and Cu) based on the liquid phase deposition technique. All products prepared by adding 3d metals were found to consist of TiO₂ crystals in the anatase phase with a fine protruding structure of about 40 nm on the surface, as was the case without the addition of metal ions. Iron and copper were observed to be incorporated at higher concentrations than cobalt and nickel, with an elemental addition of up to 4 at% and 1 at%, respectively, when 10 mM iron and copper nitrate were applied. Such doping efficiency could be explained by the difference in ionic radius and chemical stability. A narrowing of the optical band gap with doping elements was also observed, and it was found that optical sensitivity could be imparted down to the visible-light region of 2.4 eV (Fe: 4 at% addition). Furthermore, the 3d metal-doped TiO₂ demonstrated in this study was shown to exhibit photocatalytic methane degradation activity. The amount of methane degradation per unit area of the microparticles was twice as great when iron and copper were added, compared to the undoped counterpart. It has been demonstrated that the strategy of doping TiO₂ with 3d metal ions by low-temperature synthesis methods is effective in enhancing carrier dynamics and introducing surface active sites, thus increasing methane degradation activity. Full article

In pursuit of overcoming Fenton oxidation limitations in wastewater treatment, an introduction of a heterogeneous photocatalyst was developed. In this regard, the current work introduces ZnO nanocrystals that were successfully prepared via a thermal decomposition technique and then capped with oleic acid (OA). The synthesized ZnO-OA and the pristine ZnO were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FE-SEM). Then, the study introduces the application of such materials in advanced oxidation processes, i.e., a Fenton reaction to treat dye-containing wastewater. Synthetic wastewater that was prepared using Reactive Blue 4 (RB4) was used as a simulated textile wastewater effluent. Fenton’s oxidation was applied, and the system parameters were assessed using the modified Fenton’s system. The synthesized samples of ZnO were characterized by a recognized wurtzite hexagonal structure. The surface modification of ZnO with oleic acid (OA) resulted in an increase in crystallite size, lattice parameters, and cell volume. These modifications were linked to the efficient capping of ZnO nanoparticles by OA, which further improved the dispersion of the nanoparticles, as demonstrated through SEM imaging. The optimum conditions of ZnO- and ZnO-OA-synthesized modified Fenton composites showed 400 mg/L and 40 mg/L for H₂O₂ and the catalyst, respectively, at pH 3.0, and within 90 min under UV irradiation the maximal dye oxidation reached 93%. The catalytic performance at its optimal circumstances was in accordance with a pseudo-second-order kinetics model for both ZnO-OA- and the pristine ZnO-based Fenton’s systems. The thermodynamic parameters, including the enthalpy (ΔH′), the entropy (ΔS′), and Gibbs free energy (ΔG′) of activations, were also checked, and their values settled that both ZnO and ZnO-OA Fenton systems are non-spontaneous in nature. Furthermore, the reaction signified for processing at a low energy barrier condition (10.38 and 31.38 kJ/mol for ZnO-OA- and the pristine ZnO-based Fenton reactions, respectively). Full article