Search Results (4,062)

The immobilization of photocatalysts onto biodegradable polymeric supports has emerged as an effective strategy to overcome catalyst recovery limitations associated with conventional slurry photocatalytic systems. In this study, chitosan/TiO₂ composite beads with different chitosan properties and TiO₂ loadings were synthesized and evaluated for the photocatalytic removal of Reactive Black 5 (RB5), a recalcitrant azo dye commonly encountered in textile wastewater. The effects of chitosan molecular weight, degree of deacetylation, and crosslinking treatment on the structural characteristics and photocatalytic performance of the composite beads were systematically investigated. The synthesized composites were characterized through physical property measurements, point of zero charge (pH_pzc) determination, and FTIR analyses. Photocatalytic performance was evaluated under various operational conditions, including pH, catalyst dosage, initial dye concentration, and temperature. Among the prepared materials, the crosslinked chitosan/TiO₂ composite bead produced from chitosan with an 85% degree of deacetylation exhibited the highest mineralization efficiency, achieving 76.23% total organic carbon (TOC) removal. FTIR analyses performed before and after treatment indicated that RB5 removal occurred through the combined effects of adsorption and photocatalytic oxidation. The effects of operational parameters revealed that acidic conditions significantly enhanced RB5 removal, while increasing temperature improved reaction kinetics and overall degradation efficiency. Kinetic studies indicated that the photocatalytic degradation process was best described by the pseudo-first-order kinetic model, with correlation coefficients ranging from 0.9841 to 0.9976. Arrhenius analysis yielded an apparent activation energy of 11.76 kJ mol⁻¹, indicating a low energy barrier for the degradation process. The results demonstrate that crosslinked chitosan/TiO₂ composite beads are promising, environmentally friendly, and sustainable photocatalytic materials for the treatment of dye-containing wastewater and advanced water purification applications. Full article

SrTiO₃/Nb₂O₅ composite materials with 1 and 10 wt.% Nb₂O₅ were prepared by a sol–gel route and characterized by XRD, Raman spectroscopy, SEM, BET, UV-Vis DRS, photoluminescence, and dielectric spectroscopy. The photocatalytic activity was evaluated via degradation of rhodamine B and tetracycline under UV and visible light. The addition of Nb₂O₅ resulted in a significant reduction in specific surface area (from 22.7 to 3.1 m²/g), a narrowing of the optical band gap (from 3.22 to 2.49 eV), and a decrease in photoluminescence intensity. Despite these changes, the photocatalytic performance decreased with increasing Nb₂O₅ content. For rhodamine B degradation, the UV rate constant fell from 0.0136 min⁻¹ for pristine SrTiO₃ to 0.0035 min⁻¹ for SrTiO₃/10% Nb₂O₅. The lower activity is mainly ascribed to the loss of active sites, surface carbonate formation, and enhanced non-radiative recombination at interface defects, which suppress charge transfer to the surface. The results demonstrate that careful control of the composite microstructure is essential for achieving efficient photocatalysis, even when heterojunction formation is thermodynamically favorable. Full article

The photocatalytic degradation of Acid Orange 7 (AO7) in aqueous solution in the presence of exfoliated C₃N₄ (n-C₃N₄) as a photocatalyst was investigated under simulated solar light irradiation. The n-C₃N₄ photocatalyst was synthesized by polymerization of urea as a precursor and characterized by UV/Vis and FTIR spectroscopy, and transmission electron microscopy. Degradation products were identified by high-performance liquid chromatography with high-resolution mass spectrometry (LC–HRMS). It was found that AO7 undergoes a series of oxidation steps mediated by radicals generated during light absorption by n-C₃N₄, as well as through a photosensitization process initiated by light absorption by AO7. This results in decolorization and the formation of aromatic and aliphatic intermediates, which undergo further oxidation to simpler compounds. Full article

The coordination chemistry of “salen-type” Schiff bases with the uranyl ion, trans-{U^VIO₂}²⁺, attracts the interest of several inorganic chemistry groups worldwide for a variety of reasons. The full synthetic investigation of the {UO₂}²⁺/H₂L reaction system, where H₂L is bis(2-hydroxyacetophenone)ethylenediamine, has provided access to complexes [UO₂(L)(EtOH)] (1) and [UO₂(L)(DMF)] (2) in moderate to good yields. The molecular structures of the two complexes are similar. The U^VI atoms are bonded to five oxygen and two nitrogen atoms in a distorted pentagonal bipyramidal geometry. The two uranyl oxo(or oxido) atoms occupy the axial positions, and the {O=U=O}²⁺ moiety is almost linear. The equatorial donor atoms are the two oxygens and the two nitrogens from the tetradentate chelating (1.1111 using Harris notation) L²⁻ ligand, and the oxygen atom of the coordinated solvent molecule. H-bonded dimers of 1 exist in its crystal structure. The complexes were fully studied in the solid state by IR, Raman, UV/Vis (diffuse reflectance) and emission spectroscopies, and the data are discussed in terms of the known structural data of the complexes and the coordination modes of the ligands. The structures of the complexes persist in solution as evidenced by NMR (¹H, ¹³C{¹H}) and UV/Vis spectroscopies, as well as by molar conductivity data. Complexes 1 and 2 exhibit moderate photocatalytic activity towards the degradation of the model organic dye methylene blue under continuous UV irradiation in aqueous media. The reaction kinetics were fitted using the Langmuir-Hinshelwood pseudo-first-order model. Combined IR and powder X-ray diffraction data show that the photocatalyst 1 remains unchanged after the photocatalytic experiment, whereas 2 undergoes DMF leaching. Based on literature reports, a simplified single-electron transfer mechanism has been proposed for the photocatalytic activity. Full article

Photocatalytic fuel cells (PFCs) integrate photocatalysis with fuel cell technology to enable simultaneous wastewater treatment and energy recovery. This review examines recent advances in PFC cathode materials, focusing on design strategies, reduction mechanisms, and applications. The cathode governs electron transfer and interfacial reactions, including oxygen reduction (4e⁻ or 2e⁻ pathways), direct pollutant electroreduction, and oxidant activation for radical generation. Cathodic materials including transition metal oxides/sulfides, carbon-based materials, metal–organic frameworks and their derivatives, are systematically summarized, evaluating their respective activities, stabilities and costs. Rational design via heterojunction engineering, defect modulation, and composite construction enables tunable reaction pathways and enhanced performance. Furthermore, representative applications are reviewed, with particular attention to the effective degradation of organic pollutants, and reduction of heavy metals and radionuclides in PFCs. Future efforts should prioritize long-term stability, scalable fabrication, and multi-functional cathode integration. Full article

The contamination of water bodies with organic pollutants has emerged as one of the most pressing environmental and public health challenges of the modern era. The continuous discharge of dyes, pesticides, agricultural runoff, and pharmaceutical residues into the aquatic ecosystem degrades water quality. Long-term exposure to these organic pollutants poses a severe risk to human and aquatic life. ZnO and TiO₂ have emerged as promising photocatalysts, particularly for degrading organic waste in wastewater. However, their photocatalytic activity is limited to the UV region due to their wide band gaps. To improve nanoparticle efficiency, polydopamine (PDA) is incorporated as a modifying agent. PDA-modified ZnO and TiO₂ nanocomposites exhibit enhanced photocatalytic activity in the degradation of various organic pollutants under visible light, compared with their unmodified counterparts. Furthermore, they exhibit improved antibacterial activity against a variety of waterborne pathogens; this is advantageous as wastewater contains both chemical pollutants and microorganisms. Thus, the combined photocatalytic and antibacterial properties of PDA-modified ZnO and TiO₂ make them promising materials for next-generation wastewater treatment. Full article

While silver halides (AgX) are promising visible-light photocatalysts for water remediation, their practical deployment is severely hindered by intrinsic photocorrosion, rapid charge recombination, and macroscopic recovery challenges. Here, we demonstrate a monolithic AgX/biomass carbon aerogel composite platform, constructed by anchoring AgX nanocrystals in situ onto a 3D hierarchical carbon skeleton. The carbon network not only suppresses nanoparticle aggregation but also plays contrasting optical roles: amplifying the intrinsic visible-light absorption of AgBr while endowing the otherwise UV-confined AgCl with substantial visible-light response. Consequently, the optimal 30 wt% AgBr/CA composite achieves a 95.68% methylene blue degradation efficiency within 60 min—outperforming pristine AgBr by 2.6-fold—while establishing robust activity against two additional, structurally distinct pollutants: rhodamine B and the colorless antibiotic ciprofloxacin. Notably, the free-standing monolith retains exceptional activity over six consecutive cycles. Mechanistic investigations reveal that the carbon aerogel functions as an electron-accepting reservoir, which accelerates interfacial charge separation and steers electron flow toward superoxide radical generation. Notably, XRD and XPS analyses confirm that no detectable metallic Ag⁰ is present in the as-prepared composites. This work establishes a sustainable and scalable architectural paradigm for designing highly efficient, stable, and easily recyclable photocatalytic systems. Full article

Synthetic azo dyes are the largest class of industrial colorants having widespread application in textile, food, cosmetic, and pharmaceutical industries. Moreover, they are persistent and toxic, threatening aquatic environments as well as human health. Disperse red 1 (DR1), a mono-azo dye belonging to the disperse dye group and widely used in polyester dyeing, cosmetics, and other applications, is of particular concern due to its mutagenic potential and resistance to conventional treatment processes. The present study investigated an integrated DR1 removal strategy using thermotolerant Bacillus licheniformis Tol1 as well as its EPS-stabilized biogenic silver nanoparticles (AgNPs). With a maximum tolerable concentration of 0.5 g L⁻¹, B. licheniformis Tol1 showed a maximum decolorization of 70.86% (0.2 g L⁻¹, 55 °C). However, response surface methodology (RSM) based on the Box–Behnken design showed an actual decolorization efficiency of 73.13%. The artificial neural network (ANN) model predicted an accuracy of R² = 0.9933, confirming the robustness and reliability of the experimental findings. To enhance dye removal efficiency, Tol1 EPS-stabilized AgNPs were synthesized via a green method and characterized using UV-Vis, SEM-EDAX, TEM, AFM, FTIR, DLS and zeta potential. Characterization of AgNP confirmed the formation of spherical stable AgNPs with an average size of 19.99 ± 0.38 nm, indicating polydisperse colloids nature with moderate electrostatic stability. A sunlight/H₂O₂-assisted process (photocatalytic experiments) demonstrated DR1 decolorization (80.72 ± 1.72% within 5 h under sunlight) following pseudo-first-order kinetics (k = 0.271 h⁻¹). Furthermore, FTIR analysis confirmed the degradation of the chemical structure of DR1 through the disappearance of the characteristic azo (–N=N–) bond, indicating cleavage of the dye molecule. Overall, the present study provides a dual biological–nanotechnological approach for DR1 decolorization using single bacteria as well as its polysaccharide-stabilized AgNP, a sustainable eco-friendly future approach. However, further studies on complete mineralization, transformation products, toxicity evaluation, detailed catalyst reusability, and silver (Ag) leaching are needed to facilitate the practical implementation for wastewater treatment. Full article

Engineered nanomaterials have been increasingly proposed for the treatment of contaminated soils. Nevertheless, most available evidence has been obtained in water, artificial substrates or short-term laboratory experiments, and performance in real soil is substantially more variable. This review examines nanoscale zero-valent iron, photocatalytic metal oxides, carbon-based nanomaterials, and supported or hybrid formulations, with particular attention to the soil properties and contaminant characteristics that control their mobility, transformation, reactivity, and persistence. Nano-enabled treatments can decrease the mobility of arsenic, chromium, lead, and other potentially toxic elements and can promote the degradation of selected pesticides and hydrocarbons. However, opposite responses have also been reported, including mobilisation of non-target elements, nanoparticle aggregation and passivation, effects on microbial communities and plants, contaminant rebound, and potential transport beyond the treated zone. Environmental assessment should therefore consider both the target contaminant and the applied or transformed nanomaterial, together with ecological and occupational exposure pathways. Current evidence does not support nanoremediation as a general replacement for conventional technologies. Its main value lies in its use as a site-specific component of integrated remediation strategies selected according to soil properties, contaminant behaviour, treatment scale, cost, life-cycle impacts, and future land use. European field experience remains limited, particularly in unsaturated soils, and no harmonised EU-wide authorisation procedure specifically for soil nanoremediation currently exists. Wider implementation will require realistic field trials, long-term monitoring, safer and recoverable formulations, transparent regulatory assessment, and evaluation of soil functions and ecosystem-service recovery. A site-specific decision framework is proposed to support material selection, risk–benefit evaluation, and responsible implementation. Full article

The resource utilization of eutrophic cyanobacterial biomass provides a sustainable route for developing biochar-based catalytic materials for dye wastewater treatment. Herein, eutrophic cyanobacteria from Dianchi Lake, Kunming, were used as raw materials to prepare functional catalytic materials via pyrolysis-modification. A trimetallic photocatalyst, CuFeZnXBC₄₀₀ (XBC = cyanobacterial biochar), was fabricated for methylene blue (MB) degradation without hydrogen peroxide or other external oxidants. The samples were characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), liquid chromatography–mass spectrometry (LC–MS), and three-dimensional fluorescence spectroscopy. At an initial MB concentration of 100 mg/L and pH 11, under UV irradiation, CuFeZnXBC₄₀₀ achieved nearly 99% MB removal within 60 min and retained over 90% activity after eight cycles. Transient photocurrent measurements and quenching experiments indicated that photogenerated holes (h⁺) were the dominant oxidative species, while superoxide radicals (·O₂⁻) contributed to the reaction and hydroxyl radicals (·OH) played a limited role. LC–MS analysis supported the chemical transformation of MB, and three possible degradation pathways were proposed. The development of CuFeZnXBC400 provides a new biochar-based material and a potential strategy for cyanobacterial biomass utilization and organic dye wastewater treatment. Full article

Conventional food packaging cannot actively regulate spoilage-related molecules such as ethylene and volatile organic compounds that accumulate inside sealed packages. Smart adsorption based nanocatalysts (SABNs) integrate adsorptive scaffolds, catalytic centers, and stimuli responsive triggers to progressively remove these spoilage markers. This review establishes a unified three pillar framework and critically examines how adsorption, catalytic degradation, and regeneration cycles are proposed to function under food-relevant conditions. Across major food categories, reported photocatalytic systems achieve ethylene removal efficiencies of 50% to 90% and extend shelf life by 1 to 5 days under controlled light and temperature. However, performance declines sharply under the dark, humid, and refrigerated conditions typical of real supply chains. A systematic evidence level grading of twelve representative SABN systems reveals that the majority cluster at levels L³ and L⁴, while none has yet reached level L⁵, which requires both standardized migration testing and sensory evaluation. Key barriers, including nanoparticle migration, fragmented regulation, scalability, and life-cycle impacts, are assessed. By introducing explicit inclusion/exclusion criteria and a six-level evidence grading framework, this review maps critical gaps in migration data and cold-chain validation and outlines a staged roadmap toward regulation-ready active packaging technologies. Full article

Antibiotic contamination of water, particularly by tetracycline (TC), requires effective and sustainable treatment strategies. In this study, CoFe₂O₄ nanoparticles were synthesized using lime juice as a natural stabilizing agent and combined with ZnO to obtain a ZnO/CoFe₂O₄ nanocomposite for visible-light-driven TC degradation. Complementary characterization confirmed the coexistence of ZnO and CoFe₂O₄ without detectable secondary phases, with predominantly spherical and irregular particles. The composite exhibited ferromagnetic behavior, suggesting potential magnetic recovery, and showed broader visible-light absorption and a reduced band gap of 3.05 eV compared with 3.23 eV for ZnO. Although its specific surface area and pore volume were lower than those of CoFe₂O₄, the nanocomposite displayed the highest photocatalytic performance. Under the optimized conditions of pH 6, 20 mg L⁻¹ TC, and 1 g L⁻¹ catalyst, 96.8% degradation was achieved after 120 min, with a pseudo-first-order rate constant of 0.029 min⁻¹. The degradation efficiency remained 88.3% after five cycles. Scavenger experiments identified photogenerated holes (h⁺) and hydroxyl radicals (·OH) as the dominant reactive species. The improved photocatalytic activity may be associated with interfacial interactions between ZnO and CoFe₂O₄, suggesting that the green-synthesized nanocomposite has potential as a visible-light photocatalyst for TC degradation under the investigated conditions. Full article

Airborne viral transmission necessitates effective indoor air purification strategies. Conventional methods often face operational challenges, including potential secondary aerosolization and performance degradation under high-humidity conditions. This study evaluates a hybrid control system integrating a multi-walled carbon nanotube (MWCNT) field-emission plasma with a UV-LED/TiO₂ photocatalyst to continuously inactivate airborne bacteriophages. The system’s performance was assessed under varying applied voltages and relative humidity (RH) levels. The kinetic results demonstrated that the hybrid configuration yields a synergistic inactivation effect compared to the isolated plasma or photocatalytic treatments. Based on the kinetic enhancement, it is hypothesized that trace ozone generated by the plasma discharge serves as an electron acceptor on the UV-illuminated TiO₂ surface, thereby mitigating electron–hole recombination and enhancing the generation of hydroxyl radicals (·OH). Furthermore, the hybrid system exhibited operational resilience under high-moisture conditions, maintaining a robust active inactivation constant (k_a = 0.190 min⁻¹) at 70% RH without statistical degradation. This stability indicates that the continuous field emission effectively utilizes ambient moisture for secondary radical generation rather than being quenched by water condensation. Ultimately, this hybrid technology presents a continuous and adaptable engineering control measure for mitigating airborne pathogens in enclosed occupational environments, including those in high-humidity climates. Full article

The rapid increase in antibiotic resistance has driven growing interest in advanced photocatalytic materials for the effective removal of antibiotic pollutants from wastewater systems. Among these materials, graphitic carbon nitride (g-C₃N₄), a metal-free polymeric semiconductor, has emerged as a sustainable and efficient photocatalyst due to its strong visible-light activity, excellent chemical stability, and tunable electronic properties. This review presents a comprehensive overview of recent advances in the synthesis of g-C₃N₄-based materials for peroxymonosulfate (PMS)-assisted visible-light-driven photocatalytic degradation of antibiotics. The antibiotics discussed in this review include tetracycline, ciprofloxacin, levofloxacin, sulfamethoxazole, sulfamethazine, doxycycline, oxytetracycline, and moxifloxacin, along with other pharmaceutical contaminants. The fundamental degradation mechanisms, including the generation of reactive oxygen species (ROS), PMS activation pathways, and interfacial charge-transfer processes, are systematically discussed. Furthermore, this review addresses factors influencing photocatalytic performance, including photocatalyst dosage, solution pH, temperature, pollutant concentration, and light intensity. Finally, the current challenges and future perspectives for the practical application of g-C₃N₄-based materials in wastewater treatment are highlighted. Full article

In this study, a simple, cost-effective, and eco-friendly approach was developed for the synthesis of AgNPs using white (Muscat Ottonel, WGPE) and red (Cabernet Sauvignon, RGPE) grape pomace extracts. The AgNPs were characterized by SEM, AFM, DLS, UV–Vis, FTIR, and XPS techniques. Their formation was initially indicated by a color change from colorless to dark brown and confirmed by the appearance of an SPR peak at 445 nm. The AgNPs are predominantly spherical with varied sizes. FTIR and XPS analyses indicated the presence of oxygen- and nitrogen-containing functional groups on the nanoparticle surface, suggesting their involvement in the reduction of Ag⁺ ions and the stabilization of the synthesized AgNPs. The biological activity of AgNPs was assessed through wheat (Triticum aestivum L.) seed priming experiments. Treatment with 25 mg/L AgNPs (WGPE) significantly enhanced seedling growth and chlorophyll content, whereas exposure to 100 mg/L AgNPs (RGPE) induced oxidative stress and negatively affected growth parameters. Furthermore, the photocatalytic activity of both AgNPs was evaluated against MB degradation under visible light irradiation. AgNPs (WGPE) showed superior photocatalytic efficiency, achieving up to 77% dye removal within 240 min and a constant rate nearly three times higher than that of AgNPs (RGPE). The photodegradation process was mainly driven by ^•OH radicals. Our results highlight the potential of biosynthesized AgNPs for agricultural applications and wastewater remediation. Full article