Search Results (54)

This study reports the synthesis, structural characterization, adsorption studies, nanoscale interaction, and photocatalytic application of pure and Fe-doped ZnS quantum dots for the degradation of the antibiotic cefalexin in aqueous solution. Nanoparticles were synthesized via the microwave-assisted method, and Fe doping was introduced at a 1% molar ratio. HRTEM images confirmed quasi-spherical morphology and high crystallinity, with particle sizes averaging 2.4 nm (pure) and 3.5 nm (doped). XRD analysis showed a consistent cubic ZnS structure. UV-vis spectra showed strong absorption at 316 nm for both samples, and PL measurements revealed emission quenching upon Fe doping. Photocatalytic tests under UV light demonstrated significantly higher degradation rates of 10 ppm cefalexin with Fe-doped ZnS, reaching near-complete removal within 90 min. Adsorption experiments revealed higher affinity and adsorption capacity of Fe-doped ZnS toward cefalexin compared to pure ZnS, as demonstrated by the Freundlich isotherm analyses, contributing significantly to enhanced photocatalytic degradation performance. High-resolution QTOF LC-MS analysis confirmed the breakdown of the β-lactam and thiazolidine rings of cefalexin and the formation of low-mass degradation products, including fragments at m/z 122.0371, 116.0937, and 318.2241. These findings provide strong evidence for the structural destruction of the antibiotic and validate the enhanced photocatalytic performance of Fe-doped ZnS. Full article

In this study, Bi₂MoO₆ nanoflowers with different molybdenum sources were in situ grown on the surface of g-C₃N₄ nanosheets (OCN) by a simple one-step solvothermal method. The effects of doping and different molybdenum sources on the photocatalytic degradation and bactericidal activity of Bi₂MoO₆/OCN were discussed. Among them, the solvothermal preparation of P-Bi₂MoO₆/OCN using phosphomolybdic acid as molybdenum source can make up for the shortcomings caused by the destruction of OCN structure by generating more lattice defects to promote charge separation and constructing Lewis acid/base sites to effectively improve the photocatalytic performance. In addition, by adding phosphoric acid to increase the P-doped content, more exposed alkaline active sites are induced on the surface of P-Bi₂MoO₆/OCN, as well as larger specific surface area and charge transfer efficiency, which further improve the photocatalytic performance. Finally, the optimized 16P-Bi₂MoO₆/OCN showed a degradation rate of 99.7% for 20 mg/L rhodamine B (RhB) within 80 min under visible light, and the antibacterial rates against E. coli, S. aureus and P. aeruginosa within 300 min were 99.58%, 98.20% and 97.48%, respectively. This study provides a reference for optimizing the synthesis of environmentally friendly, solar-responsive, photocatalytic sterilization materials from the perspective of preparation, raw materials and structure. Full article

The mining industry often relies on the natural degradation of tailings dams to break down cyanide in wastewater. However, this method has drawbacks, including high costs due to significant water demand and variable effectiveness dependent on environmental conditions, and it is a time-consuming process. To address this issue, this study focused on preparing, characterizing, and applying a ZnO-BiOI heterostructure for cyanide removal in water. The heterojunction was thoroughly characterized using techniques such as SEM-EDX, X-ray diffraction, nitrogen adsorption–desorption isotherms, photoluminescence, and XPS scans. The photocatalytic efficacy was evaluated by degrading CN⁻-containing solutions across varying photocatalyst masses, temperatures, and initial cyanide concentrations. The results showed that 5 mg of the heterostructure completely eliminated 40 ppm of cyanide in 35 min. Increasing the catalyst mass to 15 mg significantly reduced the time for the complete degradation of 40 ppm cyanide, while 25 mg of the photocatalyst achieved cyanide removal in 35 min. The optimal temperature was found to be 50 °C, with complete cyanide removal occurring in 20 min within the temperature range of 25 °C to 70 °C. Moreover, when the cyanide concentration ranged from 40 ppm to 100 ppm, 15 mg of heterojunction catalyst achieved a 97% destruction efficiency in removing a 100 ppm cyanide solution within 35 min. These results strongly indicate that the synthesized heterojunction has the potential to serve as an effective and efficient photocatalyst for cyanide degradation in process effluents and wastewater. Full article

TiO₂ used for photocatalytic water purification is most active in the form of nanoparticles (NP), but their use is fraught with difficulties in separation from solution or/and a tendency to agglomerate. The novel materials designed in this work circumvent these problems by immobilizing TiO₂ NPs on the surface of exfoliated clay minerals. A series of TiO₂/clay mineral composites were obtained using five different clay components: the Na-, CTA-, or H-form of montmorillonite (Mt) and Na- or CTA-form of laponite (Lap). The TiO₂ component was prepared using the inverse microemulsion method. The composites were characterized with X-ray diffraction, scanning/transmission electron microscopy/energy dispersive X-ray spectroscopy, FTIR spectroscopy, thermal analysis, and N₂ adsorption–desorption isotherms. It was shown that upon composite synthesis, the Mt interlayer became filled by a mixture of CTA⁺ and hydronium ions, regardless of the nature of the parent clay, while the structure of Lap underwent partial destruction. The composites displayed high specific surface area and uniform mesoporosity determined by the size of the TiO₂ nanoparticles. The best textural parameters were shown by composites containing clay components whose structure was partially destroyed; for instance, Ti/CTA-Lap had a specific surface area of 420 m²g⁻¹ and a pore volume of 0.653 cm³g⁻¹. The materials were tested in the photodegradation of methyl orange and humic acid upon UV irradiation. The photocatalytic activity could be correlated with the development of textural properties. In both reactions, the performance of the most photoactive composites surpassed that of the reference commercial P25 titania. Full article

Per- and polyfluoroalkyl substances (PFAS) are fluorinated and refractory pollutants that are ubiquitous in industrial wastewater. Photocatalytic destruction of such pollutants with catalysts such as TiO₂ and ZnO is an attractive avenue for removal of PFAS, but refined forms of such photocatalysts are expensive. This study, for the first time, utilized milled unrefined raw mineral ilmenite, coupled to UV-C irradiation to achieve mineralization of the two model PFAS compounds perfluorooctanoic acid (PFOA) and perfluoro octane sulfonic acid (PFOS). Results obtained using a bench-scale photocatalytic reactor system demonstrated rapid removal kinetics of PFAS compounds (>90% removal in less than 10 h) in environmentally-relevant concentrations (200–1000 ppb). Raw ilmenite was reused over three consecutive degradation cycles of PFAS, retaining >80% removal efficiency. Analysis of degradation products indicated defluorination and the presence of shorter-chain PFAS intermediates in the initial samples. End samples indicated the disappearance of short-chain PFAS intermediates and further accumulation of fluoride ions, suggesting that original PFAS compounds underwent mineralization due to an oxygen-radical-based photocatalytic destruction mechanism induced by TiO₂ present in ilmenite and UV irradiation. The outcome of this study implies that raw ilmenite coupled to UV-C is suitable for cost-effective reactor operation and efficient photocatalytic destruction of PFAS compounds. Full article

The increasing awareness of the importance of a clean and sustainable environment, coupled with the rapid growth of both population and technology, has instilled in people a strong inclination to address the issue of wastewater treatment. This global concern has prompted individuals to prioritize the proper management and purification of wastewater. Organic pollutants are very persistent and due to their destructive effects, it is necessary to remove them from wastewater. In the last decade, porous organic polymers (POPs) have garnered interest among researchers due to their effectiveness in removing various types of pollutants. Porous biopolymers seem to be suitable candidates among POPs. Sustainable consumption and environmental protection, as well as reducing the consumption of toxic chemicals, are the advantages of using biopolymers in the preparation of effective composites to remove pollutants. Composites containing porous biopolymers, like other POPs, can remove various pollutants through absorption, membrane filtration, or oxidative and photocatalytic effects. Although composites based on porous biopolymers shown relatively good performance in removing pollutants, their insufficient strength limits their performance. On the other hand, in comparison with other POPs, including covalent organic frameworks, they have weaker performance. Therefore, porous organic biopolymers are generally used in composites with other compounds. Therefore, it seems necessary to research the performance of these composites and investigate the reasons for using composite components. This review exhaustively investigates the recent progress in the use of composites containing porous biopolymers in the removal of organic pollutants in the form of adsorbents, membranes, catalysts, etc. Information regarding the mechanism, composite functionality, and the reasons for using each component in the construction of composites are discussed. The following provides a vision of future opportunities for the preparation of porous composites from biopolymers. Full article

This work presents an overview of the reports on the bacterial cell photocatalytic destruction and mineralization process in the presence of TiO₂-based photocatalysts. The presented research included experiments conducted in air and water. Numerous works confirmed that a photocatalytic process with TiO₂ led to bacteria and their organic residues’ mineralization. Additionally, based on the obtained results, a possible two-stage mechanism of photocatalytic mineralization in the presence of TiO₂-based materials was proposed. To help future studies, challenges of photocatalytic microorganism mineralization are also proposed. There are some aspects that need to be addressed, such as the lack of standardization of conducted research or relatively small amount of research on photocatalytic microorganism mineralization. According to our best knowledge, in the available literature, no work regarding a summary of previous research on photocatalytic bacterial mineralization process was found. Full article

Micrometer-sized polycrystalline anatase particles are widely used in materials and life sciences, serving as essential components in photocatalytic materials. The ability to tailor their composition, shape, morphology, and functionality holds significant importance. In this study, we identified and examined the non-destructive route of Copper(II) implantation at the surface of polycrystalline TiO₂. The [Cu(en)(Im)₂]²⁺ complex ion demonstrated a remarkable affinity to concentrate and bind with the semiconductor’s surface, such as anatase, forming a surface-bound adduct: ≡TiO₂ + [Cu(en)(Im)₂]²⁺ → ≡TiO₂//[Cu(en)(Im)₂]²⁺. The misalignment of Fermi levels in TiO₂//[Cu(en)(Im)₂]²⁺ triggered electron transfer, leading to the reduction of the metal center, releasing Copper(I) in the process. Although less efficient, the released Copper(I) encountered a highly favorable environment, resulting in the formation of the surface complex TiO₂:Cu^II_sc. The implanted Cu(I) was converted back into Cu(II) due to re-oxidation by dissolved oxygen. The penetration of the metal ion into the surface level of the polycrystalline TiO₂ lattice was influenced by surface residual forces, making surface grafting of the Cu(II) ion inevitable due to surface chemistry. FTIR, UV–vis, Raman, XRD, EPR, and surface morphological (SEM, EDAX, and HRTEM) analyses identified the typical surface grafting of the Cu(II) cluster complex on the anatase surface matrix. Moreover, the XRD results also showed the formation of an impure phase. The TiO₂ polycrystalline materials, modified by the incorporation of copper complexes, demonstrated an enhanced visible-light photocatalytic capability in the degradation of Rhodamine B dye in aqueous solutions. This modification significantly improved the efficiency of the photocatalytic process, expanding the applicability of TiO₂ to visible light wavelengths. These studies open up the possibility of using copper complexes grafted on metal oxide surfaces for visible-light active photocatalytic applications. Moreover, this investigation not only showcases the improved visible-light photocatalytic behavior of copper-modified TiO₂ polycrystalline materials, but also underscores the broader implications of this improvement in the advancement of sustainable and efficient water treatment technologies. Full article

The use of heterogeneous photocatalysis in biologically contaminated water purification processes still requires the development of materials active in visible light, preferably in the form of thin films. Herein, we report nanotube structures made of TiO₂/Ag₂O/Au⁰, TiO₂/Ag₂O/PtO_x, TiO₂/Cu₂O/Au⁰, and TiO₂/Cu₂O/PtO_x obtained via one-step anodic oxidation of the titanium-based alloys (Ti₉₄Ag₅Au₁, Ti₉₄Cu₅Pt₁, Ti₉₄Cu₅Au₁, and Ti₉₄Ag₅Pt₁) possessing high visible light activity in the inactivation process of methicillin-susceptible S. aureus and other pathogenic bacteria—E. coli, Clostridium sp., and K. oxytoca. In the samples made from Ti-based alloys, metal/metal oxide nanoparticles were formed, which were located on the surface and inside the walls of the NTs. The obtained results showed that oxygen species produced at the surface of irradiated photocatalysts and the presence of copper and silver species in the photoactive layers both contributed to the inactivation of bacteria. Photocatalytic inactivation of E. coli, S. aureus, and Clostridium sp. was confirmed via TEM imaging of bacterium cell destruction and the detection of CO₂ as a result of bacteria cell mineralization for the most active sample. These results suggest that the membrane ruptures as a result of the attack of active oxygen species, and then, both the membrane and the contents are mineralized to CO₂. Full article

Hydrosphere pollution by organic pollutants of different nature (persistent dyes, phenols, herbicides, antibiotics, etc.) is one of the urgent ecological problems facing humankind these days. The task of water purification from such pollutants can be effectively solved with the help of modern photocatalytic technologies. This article is devoted to the study of photocatalytic properties of composite catalysts based on ZnO modified with plasmonic Ag nanoparticles. All materials were obtained by laser synthesis in liquid and differed by their silver content and preparation conditions, such as additional laser irradiation and/or annealing of produced powders. The prepared ZnO-Ag powders were investigated by electron microscopy, X-ray diffraction and UV-Vis spectroscopy. Photocatalytic tests were carried out with well- known test molecules in water (persistent dye rhodamine B, phenol and common antibiotic tetracycline) using LED light sources with wavelengths of 375 and 410 nm. The introduction of small concentrations (up to 1%) of plasmonic Ag nanoparticles is shown to increase the efficiency of the ZnO photocatalyst by expanding its spectral range. Both the preparation conditions and material composition were optimized to obtain composite photocatalysts with the highest efficiency. Finally, the operation mechanisms of the material with different distribution of silver are discussed. Full article

Metal oxide semiconductor-based photocatalysis and advanced oxidation processes (AOPs) are effective in treating various recalcitrant pollutants such as organic dyes present in industrial wastewater streams. AOPs rely on the highly reactive hydroxyl radicals (OH^•) that facilitate the non-selective destruction of most organic pollutants. Here, we present the novel synthesis of mesoporous FeTiO₃ catalyst via a simple, hard template-free, aqueous-solution-based hydrothermal synthesis method. The surfactant, tetradecyltrimethylammonium bromide (TTAB), was used as the structure-directing agent, the removal of which led to the formation of the mesoporous structure. The catalyst was characterized by thermo-gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Branauer–Emette–Teller analysis (BET), X-ray diffraction (XRD), and scanning electron microscope (SEM) techniques. The obtained catalyst has been studied for its photocatalytic application in the presence of H₂O₂ towards the degradation of organic dyes as representative pollutants, namely, rhodamine B (RhB) and methylene blue (MB) under direct solar light irradiation. The various characterizations confirm the formation of mesoporous FeTiO₃ with a pore size of ≈7.5 nm and a specific surface area of 65 ± 5 m²/g. The influence of H₂O₂ oxidant on the removal of the said dyes has also been studied at various concentrations in the presence of the synthesized catalyst to determine the optimum dosage of H₂O₂. The catalyst was efficient in the complete synergistic adsorption-led photo-Fenton-like removal of MB in just 30 min of irradiation time, while the 96% RhB was degraded in 240 min. Moreover, this catalyst has also shown potential for fluoride adsorption that reaches up to more than 50% in 90 min. Full article

This study demonstrates rapid photocatalytic oxidation of a benzene, toluene, ethylbenzene, and xylene (BTEX) mixture over TiO₂/volcanic glass. The assessment of the photocatalytic oxidation of BTEX was conducted under conditions simulating those found in indoor environments affected by aromatic hydrocarbon release. We show, under UV-A intensities of 15 mW/cm² and an air flow rate of 55 m³/h, that low ppmv levels of BTEX concentrations can be reduced to below detectable levels. Solid-phase microextraction technique was employed to monitor the levels of BTEX in the test chamber throughout the photocatalytic oxidation, lasting approximately 21 h. Destruction of BTEX from the gas phase was observed in the following sequence: o-xylene, ethylbenzene, toluene, and benzene. This study identified sequential degradation of BTEX, in combination with the stringent regulatory level set for benzene, resulted in the air quality hazard indexes (Total Hazard Index and Hazard Quotient) remaining relatively high during the process of photocatalytic oxidation. In the practical application of photocatalytic purification, it is crucial to account for the slower oxidation kinetics of benzene. This is of particular importance due to not only its extremely low exposure limits, but also due to the classification of benzene as a Group 1 carcinogenic compound by the International Agency for Research on Cancer (IARC). Our study underscores the importance of taking regulatory considerations into account when using photocatalytic purification technology. Full article

Graphitic carbon nitrides (g-C₃N₄) and microorganisms could collaboratively enhance photocatalytic properties or facilitate environmental depollution through coupled photocatalytic and biological reactions, which prevented the destruction of photocatalytic stresses to ecological systems and resulted in a sustainable technology for water remediation in rivers and lakes. However, the roles of bio-substances as well as electronic interactions between inorganic and organic systems were still unclear. Herein, g-C₃N₄, nitrogen-deficient g-C₃N₄ (ND-g-C₃N₄), and fluorinated g-C₃N₄ (F-g-C₃N₄) were coated with representative bacteria, i.e., Escherichia coli MG 1655, and characterized using integrated spectroscopic techniques. Photocatalytic activities were then evaluated through nitrobenzene degradation performance in an aqueous solution under visible light illumination. Nano-photocatalysts were observed to be adsorbed onto bio-aggregates, and surface hydrophilicity was convinced to be determined in the toxicity of photocatalysts in dark environments. Layered structures of ND-g-C₃N₄ and F-g-C₃N₄ were revealed in XRD spectra, and surface coverage of the Luria–Bertani medium was eliminated during E. coli cultivation. Hetero-junctions between photocatalysts and bio-substances were indicated in XPS results. Red-shifts for g-C₃N₄ and F-g-C₃N₄ materials as well as a slight blue-shift for ND-g-C₃N₄ were demonstrated in UV-vis spectra, which might be attributed to the destruction of nitrogen defects on ND-g-C₃N₄. Owing to the attached bio-substances, nitrobenzene removal could reach twice that with pristine photocatalysts, and ROS quantitative analysis confirmed that hydroxyl radicals were the determined reactive species degrading nitrobenzene in the water solution. The observation of more OH species generation indicated that extracellular electron transfer of E. coli reduced electron–hole recombination and provided reduction sites during photocatalytic degradation of nitrobenzene. This work proved additional electron-transfer paths and reaction mechanisms in hybridized photocatalytic and biological processes, which indicated that bio-activities could be a great promoter of material modification and the incorporation between inorganic and organic systems successfully showed an eco-friendly and sustainable pathway to utilize photocatalysts in natural water. Full article

Cyanobacteria outbreaks are serious water pollution events, causing water crises around the world. Photocatalytic disinfection, as an effective approach, has been widely used to inhibit blue algae growth. In this study, a tiny reaction room containing a TiO₂ film was designed to fulfill in situ optical observation of the destruction process of a one-dimensional multicellular microorganism, Anabaena sp. PCC 7120, which is also a typical bacterial strain causing water blooms. It was found that the fragment number increased exponentially with the activation time. The fracture mechanics of the algae chains were hypothesized to be the combining functions of increased local tensile stress originated from the cell contracting as well as the oxidative attacks coming from reactive oxygen species (ROSs). It was assumed that the oxidative species were the root cause of cellular structure changes in and chain fractures of Anabaena sp. PCC 7120 in the photocatalytic inactivation activity. Full article

TiO₂ is one of the most promising heterogeneous photoredox catalysts employed in oxidative pollutant destruction, CO₂ reduction, water splitting, disinfection, solar cell design and organic synthesis. Due to the wide bandgap of TiO₂, visible light energy is not sufficient for its activation, and electron/hole pairs generated upon UV irradiation demonstrate limited selectivity for application in organic synthesis. Thus, the development of TiO₂-based catalytic systems activated by visible light is highly attractive. In the present work we demonstrate the generation of t-BuOO• radicals from tert-butylhydroperoxide catalyzed using commercially available unmodified TiO₂ under visible light. This finding was used for the highly selective CH-peroxidation of barbituric acids, which contrasts with the behavior of the known TiO₂/H₂O₂/UV photocatalytic system used for deep oxidation of organic pollutants. Full article