Search Results (48)

Due to its persistence and potential negative effects on ecosystems and human health, microplastic pollution in aquatic environments has become a major worldwide concern. Photocatalytic degradation is a sustainable manner to degrade microplastics to non-toxic by-products. In this review, comprehensive discussion focuses on the synergistic effects of various photocatalytic materials including TiO₂, ZnO, WO₃, graphene oxide, and metal–organic frameworks for producing heterojunctions and involving multidimensional nanostructures. Such mechanisms can include the generation of reactive oxygen species and polymer chain scission, which can lead to microplastic breakdown and mineralization. The advancements of material modifications in the (nano)structure of photocatalysts, doping, and heterojunction formation methods to promote UV and visible light-driven photocatalytic activity is discussed in this paper. Reactor designs, operational parameters, and scalability for practical applications are also reviewed. Photocatalytic systems have shown a lot of development but are hampered by shortcomings which include a lack of complete mineralization and production of intermediary secondary products; variability in performance due to the fluctuation in the intensity of solar light, limited UV light, and environmental conditions such as weather and the diurnal cycle. Future research involving multifunctional, environmentally benign photocatalytic techniques—e.g., doped composites or composite-based catalysts that involve adsorption, photocatalysis, and magnetic retrieval—are proposed to focus on the mechanism of utilizing light effectively and the environmental safety, which are necessary for successful operational and industrial-scale remediation. Full article

This study employs density functional theory (DFT) to investigate the electronic and optical properties of molybdenum (Mo) and chalcogen (S, Se, Te) co-doped anatase TiO₂. Two co-doping configurations were examined: Model 1, where the dopants are adjacent, and Model 2, where the dopants are farther apart. The incorporation of Mo into anatase TiO₂ resulted in a significant bandgap reduction, lowering it from 3.22 eV (pure TiO₂) to range of 2.52–0.68 eV, depending on the specific doping model. The introduction of Mo-4d states below the conduction band led to a shift in the Fermi level from the top of the valence band to the bottom of the conduction band, confirming the n-type doping characteristics of Mo in TiO₂. Chalcogen doping introduced isolated electronic states from Te-5p, S-3p, and Se-4p located above the valence band maximum, further reducing the bandgap. Among the examined configurations, Mo–S co-doping in Model 1 exhibited most optimal structural stability structure with the fewer impurity states, enhancing photocatalytic efficiency by reducing charge recombination. With the exception of Mo–Te co-doping, all co-doped systems demonstrated strong oxidation power under visible light, making Mo-S and Mo-Se co-doped TiO₂ promising candidates for oxidation-driven photocatalysis. However, their limited reduction ability suggests they may be less suitable for water-splitting applications. The study also revealed that dopant positioning significantly influences charge transfer and optoelectronic properties. Model 1 favored localized electron density and weaker magnetization, while Model 2 exhibited delocalized charge density and stronger magnetization. These findings underscore the critical role of dopant arrangement in optimizing TiO₂-based photocatalysts for solar energy applications. Full article

Microcystins (MCs) are produced by cyanobacteria blooms in eutrophic water and can cause acute and chronic toxicity and even mortality to animals and humans. Previous MC removal strategies concernedonly highly contaminated water, in which the concentration of the pollutant was considerably larger than that in the natural world. In this study, we developed a composite of TiO₂-coated magnetic carbon microtube (C-TiO₂-Fe₃O₄) and used it as a photocatalyst to efficiently remove microcystin-LR (MC-LR) from water under visible light from water. And the huge surface of the carbon microtube dramatically boosted the adsorbability and charge mobility, which lowered the recombination rate of electron–hole pairs, and hence systematically enhanced photocatalytic activity. The combination of adsorption and photodegradation endowed the composite with a better performance in the removal of trace amounts of MC-LR than the C-TiO₂. It was found that increasing the contact time and catalyst dosage, acidic environment, and lower initial MC-LR concentration had positive effects on MC-LR removal. The optimum reaction conditions of C-TiO₂-Fe₃O₄ was a reaction time of 12.68 min, a catalyst dosage of 0.39 g·L⁻¹, and a pH of 7.72. The C-TiO₂-Fe₃O₄ (surface area normalized apparent reaction rate constants K/S_BET = 1.2 × 10⁻⁴) presented a higher reaction rate than C-TiO₂ (K/S_BET = 8.4 × 10⁻⁵). Moreover, the stable removal capability of C-TiO₂-Fe₃O₄ was confirmed over multiple cycles. Finally, the ecological safety performance was also evaluated after visible light illumination. This work paves the way for the development of more efficient and easily separable purifiers for the removal of pollutants and toxins from contaminated water. Full article

Photocatalysis based on titanium dioxide (TiO₂) has become a promising method to remediate industrial and municipal effluents in an environmentally friendly manner. However, the efficiency of TiO₂ is hampered by problems such as rapid electron–hole recombination and limited solar spectrum absorption. Furthermore, the sensitization of TiO₂ through heterojunctions with other materials has gained attention. Vanadium, specifically in the form of ammonium vanadate ((NH₄)₂V₃O₈), has shown promise as a photocatalyst due to its ability to effectively absorb visible light. However, its use in photocatalysis remains limited. Herein, we present a novel synthesis method to produce lamellar (NH₄)₂V₃O₈ as a sensitizer in a supramolecular hybrid photocatalyst of TiO₂–stearic acid (SA), contributing to a deeper understanding of its structural and magnetic characteristics, expanding the range of visible light absorption, and improving the efficiency of photogenerated electron–hole separation. Materials, such as TiO₂–SA and (NH₄)₂V₃O₈, were synthesized and characterized. EPR studies of (NH₄)₂V₃O₈ demonstrated their orientation-dependent magnetic properties and, from measurements of the angular variation of g-values, suggest that the VO₂⁺ complexes are in axially distorted octahedral sites. The photocatalytic results indicate that the 2D/2D heterojunction layered TiO₂/vanadate at a ratio (1:0.050) removed 100% of the methylene blue, used as a model contaminant in this study. The study of the degradation mechanism of methylene blue emphasizes the role of reactive species such as hydroxyl radicals (^•OH) and superoxide ions (O₂^•−). These species are crucial for breaking down contaminant molecules, leading to their degradation. The band alignment between ammonium vanadate ((NH₄)₂V₃O₈) and TiO₂–SA, shows effective separation and charge transfer processes at their interface. Furthermore, the study confirms the chemical stability and recyclability of the TiO₂–SA/(NH₄)₂V₃O₈ photocatalyst, demonstrated that it could be used for multiple photocatalytic cycles without a significant loss of activity. This stability, combined with its ability to degrade organic pollutants under solar irradiation, means that the TiO₂–SA/(NH₄)₂V₃O₈ photocatalyst is a promising candidate for practical environmental remediation applications. Full article

Textile industry effluents contain several hazardous substances, such as dye-containing effluents, which pose environmental and aesthetic challenges. Presently, the microbial-based remediation process is in use. This study investigated the application of ferrous–ferric oxide (Fe₃O₄) nanoparticles, a readily formulated nanoadsorbent, to remove scattered dye molecules from industrial effluents. The ferrous–ferric oxide nanoparticles were prepared using a chemical co-precipitation method. The nanoparticles had 26.93 emu g⁻¹ magnetization, with sizes smaller than 20 nm, and possessed a highly purified cubic spinel crystallite structure. The catalytic activity of the iron oxide depended on the dose, photocatalytic enhancer, i.e., H₂O₂ level, pH of the reaction medium, and dye concentration. We optimized the Fenton-like reaction to work best using 1.0 g/L of ferrous–ferric oxide nanoparticles, 60 mM oxalic acid at pH 7.0, and 60 ppm of dye. Iron oxides act as photocatalysts, and oxalic acid generates electron–hole pairs. Consequently, higher amounts of super-radicals cause the rapid degradation of dye and pseudo-first-order reactions. Liquid chromatography–mass spectrometry (LC-MS) analysis revealed the ferrous–ferric oxide nanoparticles decolorized and destroyed Disperse Red 277 in 180 min under visible light. Hence, complete demineralization is observed using a photo-Fenton-like reaction within 3 h under visible light. These high-capacity, easy-to-separate next-generation adsorption systems are suggested to be suitable for industrial-scale use. Ferrous–ferric oxide nanoparticles with increased adsorption and magnetic properties could be utilized to clean environmental pollution. Full article

Residual drug pollutants in water environments represent a severe risk to human health, so developing a cheap, environmentally friendly, and effective photocatalyst to deal with them has become a hot topic. Herein, a magnetically separable Fe₃O₄@TiO₂/g-C₃N₄ photocatalyst with a special heterojunction structure was fabricated, and its photocatalytic performance was assessed by degrading tetracycline (TC). Compared to Fe₃O₄@TiO₂, the synthesized Fe₃O₄@TiO₂/g-C₃N₄ exhibited superior TC degradation performance, which was primarily ascribed to the heterojunction formed between TiO₂ and g-C₃N₄ and its ability to enhance the visible light absorption capacity and reduce the photoinduced electron/hole recombination rate. Moreover, a free radical capture experiment further confirmed that ·O₂⁻ and h⁺ are the predominant components in the TC degradation reaction. Under UV–Vis irradiation, the TC degradation rate escalated to as high as 98% within 120 min. Moreover, Fe₃O₄@TiO₂/g-C₃N₄ was demonstrated to be easily recovered by magnetic separation without any notable loss even after five cycles, showing exceptional stability and reusability. These findings indicate that Fe₃O₄@TiO₂/g-C₃N₄ is a promising photocatalyst for environmental remediation that may provide a sustainable approach to degrading antibiotic pollutants in wastewater. Full article

Developing photocatalytic nanomaterials with unique physical and chemical features using low-cost and eco-friendly synthetic methods is highly desirable in wastewater treatment. In this work, the magnetically separable α-Fe₂O₃-CeO₂ nanocomposite (NC), with its respective metal oxides of α-Fe₂O₃ and CeO₂ nanoparticles, was synthesized using a combination of hexadecyltrimethylammonium bromide (CATB) and ascorbic acid via the hydrothermal method. To tune the band gap, the heterojunction nanocomposite of α-Fe₂O₃-CeO₂ was decorated with plasmonic Au nanoparticles (Au NPs). The various characterization methods, such as FTIR, UV-vis DRS, XRD, XPS, TEM, EDX, SEM, and PL, were used to determine the properties of the materials, including their morphology, elemental composition, optical properties, band gap energy, and crystalline phase. The nanocomposite of α-Fe₂O₃-CeO₂@Au was utilized to remove Rose Bengal (RB) dye from wastewater using a photocatalytic technique when exposed to visible light. A comprehensive investigation of the impact of the catalyst concentration and initial dye concentration was conducted to establish the optimal photodegradation conditions. The maximum photocatalytic efficiency of α-Fe₂O₃-CeO₂@Au (50 mg L⁻¹) for RB (20 ppm) dye removal was found to be 88.9% in 120 min under visible-light irradiation at a neutral pH of 7 and 30 °C. Various scavengers, such as benzoquinone (BQ; 0.5 mM), tert-butyl alcohol (TBA; 0.5 mM), and ethylenediaminetetraacetic acid (EDTA; 0.5 mM), were used to investigate the effects of different free radicals on the photocatalytic process. Furthermore, the reusability of the α-Fe₂O₃-CeO₂@Au photocatalyst has also been explored. Furthermore, the investigation of the potential mechanism demonstrated that the heterojunction formed between α-Fe₂O₃ and CeO₂, in combination with the presence of deposited Au NPs, led to an enhanced photocatalytic efficiency by effectively separating the photogenerated electron (e⁻)–hole (h⁺) pairs. Full article

The promising physical and chemical properties of components of magnetic polymers could enable extending their intelligent behaviors to material applications. Indeed, investigation into magnetic nanofillers to ensure their uniform dispersion within the polymer matrix remains a great challenge at present. In this work, polyvinyl alcohol-stabilized iron oxide nanoparticles (PVA@IONPs) were prepared using ultrasonic-assisted coprecipitation at room temperature. It is possible to produce PVA@IONPs with desirable shapes and sizes, which would enable the control of their hyperthermia and photocatalytic performance under an external magnetic field. The saturation magnetization of PVA@IONPs (45.08 emu g⁻¹) was enhanced to the level of IONPs (41.93 emu g⁻¹). The PVA@IONPs showed good photocatalytic and outstanding self-heating behavior. The hydrogen yield was 60 mmole min⁻¹ g⁻¹ for photocatalyst PVA@IONPs under visible light with magnetic force. In addition, the PVA@IONPs exhibited a higher specific absorption rate (SAR) than IONPs under the same magnetic field conditions. The PVA@IONPs displayed superior self-heating and photocatalytic performances, rendering them appropriate materials for biomedical and environmental applications. Full article

A magnetite chlorodeoxycellulose/ferroferric oxide (CDC@Fe₃O₄) heterogeneous photocatalyst was synthesised via treated and modified cotton in two steps. The designed nanocomposites were characterised by FTIR, TGA, XRD, SEM, and VSM analyses. The Fenton-photocatalytic decomposition efficiency of the synthesised magnetic catalyst was evaluated under visible sunlight using Methyl Orange (MO) as a model organic pollutant. The impacts of several degradation parameters, including the light source, catalyst load, irradiation temperature, oxidant dose, and pH of the dye aqueous solution and its corresponding concentration on the Fenton photodegradation performance, were methodically investigated. The (CDC@Fe₃O₄) heterogeneous catalyst showed a remarkable MO removal rate of 97.9% at 10 min under visible-light irradiation. (CDC@Fe₃O₄) nanomaterials were also used in a heterogeneous catalytic optimised protocol for a multicomponent reaction procedure to obtain nine tetra-substituted imidazole derivatives. The green protocol afforded imidazole derivatives in 30 min with good yields (91–97%) at room temperature and under ultrasound irradiation. Generally, a synthesised recyclable heterogeneous nano-catalyst is a good example and is suitable for wastewater treatment and organic synthesis. Full article

The major challenge of hydrogen production via photocatalytic water-splitting is to utilize active photocatalysts that respond to a wide range of visible light. In this work, hybrid nanostructures purposed to combine the tunable magnetic behavior of soft/semi-hard magnetic particles have shown advantageous photoactivity. A series of photocatalysts based on ferrite nanoparticles, magnetite nanoparticles (MNPs), cobalt ferrite nanoparticles (CFNPs), magnetite nanoparticles coated on cobalt ferrite nanoparticles (MNPs @ CFNPs), and cobalt ferrite nanoparticles coated on magnetite nanoparticles (CFNPs @ MNPs) were prepared. The size, morphology, magnetic properties, and optical activity of the prepared nanoparticles were characterized using multiple techniques. CFNPs @ MNPs had the largest particle size (~14 nm), while CFNPs had the smallest (~8 nm). The saturation magnetization of CFNPs @ MNPs was the highest at 55.45 emu g⁻¹. The hydrogen yield was 60, 26, 3.8, and 93 mmole min⁻¹ g⁻¹ for MNPs, CFNPs, MNPs @ CFNPs, and CFNPs @ MNPs. CFNPs @ MNPs displayed a superior photocatalytic performance for hydrogen production under the magnetic force as appropriate materials for water-splitting processing. Full article

In this study, magnetic CuFe₂O₄, MgFe₂O₄, and ZnFe₂O₄ nanosphere photocatalysts were prepared by the sol–gel method at 300 °C, 400 °C, and 500 °C, respectively (named as CF300, CF400, CF500, MF300, MF400, MF500, ZF300, ZF400, and ZF500). The characterization by X-ray diffraction (XRD) revealed that the optimal calcination temperature was 400 °C. Then, CF400, MF400, and ZF400 were used to treat high-concentration ammonia nitrogen wastewater (HCAW, 1000 mg/L) at different pH levels. The result showed that the optimal pH for CF400, MF400 and ZF400 to degrade HCAW was 9.0, and CF400 required a shorter illumination time (80 min) than MF400 and ZF400 (120 min) to completely remove ammonia nitrogen from HCAW. However, CF400 was unstable and decomposed, and a blue substance was observed during the magnetic recovery experiment. The recovery rate of ZF400 (66.7%) was higher than MF400 (53.2%) with no decomposition phenomenon, and the ammonia nitrogen removal rate of ZF400 remained above 90% after five cycles. Additionally, the ammonia nitrogen removal rate of ZF400 could reach 80.2% when the ammonia nitrogen concentration was as high as 5000 mg/L. Therefore, compared with CF400 and MF400, ZF400 was more suitable for treating HCAW. Full article

The development of photocatalysts with a wide spectral response and effective carrier separation capability is essential for the green degradation of tetracycline hydrochloride. In this study, a magnetic recyclable Z-scheme ZnO/ZnFe₂O₄ heterojunction (ZZF) was successfully constructed via the solid phase method, using MIL-88A(Fe)@Zn as the precursor. An appropriate band gap width and Z-scheme charge transfer mechanism provide ZZF with excellent visible light absorption performance, efficient charge separation, and a strong redox ability. Under visible light irradiation, the degradation efficiency of tetracycline hydrochloride for the optimal sample can reach 86.3% within 75 min in deionized water and 92.9% within 60 min in tap water, exhibiting superior stability and reusability after five cycles. Moreover, the catalyst in the water can be conveniently recovered by magnetic force. After visible light irradiation for 70 min, the temperature of the reaction system increased by 21.9 °C. Its degradation constant (35.53 × 10⁻³ min⁻¹) increased to 5.1 times that at room temperature (6.95 × 10⁻³ min⁻¹). Using thermal energy enhances the kinetic driving force of the reactants and facilitates carrier migration, meaning that more charge is available for the production of •O₂⁻ and •OH. This study provides a potential candidate for the efficient degradation of tetracycline hydrochloride by combining thermal catalysis with a photocatalytic heterojunction. Full article

In this study, a novel Fe₃O₄/Ag₃PO₄/g-C₃N₄ magnetic composite photocatalyst was successfully synthesized, tailored specifically for the visible light-driven photocatalytic degradation of sulfonamide antibiotics, more precisely, sulfamethazine (SMZ). To analyze the fabricated samples, characterization techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), photoluminescence spectroscopy (PL), and UV-vis diffuse reflectance spectra (UV-vis) were systematically employed. The composite showcased efficient visible-light absorption and charge separation, with its peak photocatalytic performance recorded at a solution pH value of 6.0. Significantly, the Fe₃O₄/Ag₃PO₄/g-C₃N₄ magnetic composite photocatalyst displayed excellent stability and recyclability, consistently maintaining a high degradation efficiency of over 97% even after five consecutive cycles. Further experimentation with radical scavengers confirmed a significant decrease in photocatalytic activity, establishing that superoxide radicals (•O₂⁻) and photo-generated holes (h⁺) are the primary active species during the degradation of SMZ. Overall, it provides a crucial understanding regarding the photocatalytic decomposition of sulfonamide antibiotics using magnetic composite photocatalysts. It also emphasizes the promising potential of the Fe₃O₄/Ag₃PO₄/g-C₃N₄ composite for tangible applications in environmental remediation. Full article

One of the main challenges is using an effective photocatalyst that responds to a broad range of visible light for hydrogen production during water splitting. Series types of photocatalysts based on magnetic ferrite nanostructure were fabricated via a two-step co-precipitation technique. Precisely, four types of magnetic structures: magnetite nanoparticles (MNPs), zinc cobalt ferrite nanoparticles (ZCFNPs), hybrid magnetite/zinc cobalt ferrite nanoparticles (MNPs @ ZCFNPs), and hybrid zinc cobalt ferrite/magnetite nanoparticles (ZCFNPs @ MNPs) were used to fabricate magnetic photocatalysts. The characterizations of the fabricated magnetic photocatalysts were investigated via TEM, zeta potential, XRD, VSM, and UV–VIS spectroscopy. ZCFNPs @ MNPs showed the smallest particle with size ≈11 nm. The magnetization value of ZCFNPs @ MNPs (59.3 emu/g) was improved compared to the MNPs (41.93 emu/g). The produced hydrogen levels via photocatalyst were 60, 10, 24, and 1.4 mmole min⁻¹ g⁻¹ for MNPs, ZCFNPs, MNPs @ ZCFNPs, and ZCFNPs @ MNPs, respectively, under visible light with magnetic force. MNPs displayed outstanding performance as magnetic photocatalysts for the water-splitting process. Full article

Nanocomposites of polyaniline (PANI)/Fe_2.85Ni_0.15O₄ (PFN) were successfully prepared using the co-precipitation method combined with an in-situ polymerization process. The FN and PFN nanocatalysts were characterized using various methods for the photocatalytic degradation of Rhodamine B (RhB). The XRD, Raman, TEM, and DTA-DTG analyses suggest that the FN nanoparticles (NPs) were effectively coated by PANI and that there were interactions between FN and PANI. Magnetic measurements indicated that PFN nanocomposites exhibited good superparamagnetic behavior and high saturation magnetization (39.5–57.6 emu/g), which are suitable for separating photocatalysts from solution for reuse. Adsorption-desorption analysis showed that the specific surface area of PFN was higher than that of FN. The UV-vis absorption spectra of FN and PFN nanocomposites exhibited strong absorption of visible light, attributed to the doping of Ni, which resulted in the reduction of the band-gap energy (E_g) of Fe₃O₄ to 2.4 eV. PFN nanocomposites with different mass ratios of PANI demonstrated superior photocatalytic activity compared to FN NPs. Furthermore, it was observed that PFN with a 10% mass ratio of PANI exhibited the highest RhB degradation efficiency, achieving a rate of approximately 98% after 300 min of irradiation. Finally, the possible photocatalytic degradation mechanisms of the PFN nanocomposites on RhB were discussed. PFN photocatalysts with good photocatalytic activity, inexpensive materials, and easy preparation could be potential candidates for wastewater purification applications. Full article