Search Results (183)

The utility of nanostructured TiO₂ in the degradation of organic compounds and the disinfection of pathogenic microorganisms represents an important endeavor in photocatalysis. However, the low photocatalytic efficiency of TiO₂ remains challenging. Herein, we report a robust photocatalytic route to benzene removal rendered by enhancing its adsorption capacity via rationally designed mesoporous SiO₂-coated TiO₂ colloids. Specifically, amorphous, mesoporous SiO₂-coated TiO₂ nanoparticles (denoted T@S NPs) are produced via a precipitation-gel-hydrothermal approach, possessing an increased specific surface area over pristine TiO₂ NPs for improved adsorption of benzene. Notably, under UV irradiation, the degradation rate of benzene by T@S NPs reaches 89% within 30 min, representing a 3.1-fold increase over that achieved by pristine TiO₂. Moreover, a 99.5% degradation rate within 60 min is achieved and maintains a stable photocatalytic activity over five cycles. Surface coating of TiO₂ with amorphous SiO₂ imparts the T@S composite NPs nearly neutral characteristic due to the formation of Ti-O-Si bonds, while manifesting enhanced light harvesting, excellent stability, adhesion, and photocatalytic bacteriostatic effects. Our study underscores the potential of T@S composites for practical applications in photocatalysis over pristine counterparts. Full article

Microwave-assisted processing has shown tremendous promise in accelerating chemical reactions and reducing energy consumption through targeted dielectric heating. This study develops MOF-derived Mn-Co and Ce-Co oxide catalysts for energy-efficient benzene oxidation via microwave catalysis. The MnCo spinel oxides (particularly MnCo11-400) exhibit superior microwave absorption and catalytic activity due to enhanced oxygen mobility and tailored dielectric properties. Microwave irradiation enables rapid benzene mineralization over the MnCo11-400 catalyst, achieving 78% conversion at 30 W and complete conversion at 50 W, demonstrating exceptional energy efficiency at low power inputs. Microwaves significantly lower the reaction temperature compared to conventional thermal catalysis (ΔT = 100–250 °C). Stability tests confirm robustness over repeated power cycling (80% conversion retained after 3 × 1 h on/off cycles). Furthermore, an adsorption–microwave oxidation synergistic strategy is demonstrated: pre-adsorbed low-concentration benzene (1.15 mmol) at ambient temperature undergoes complete mineralization within 20 min under 30 W microwave irradiation. The intermittent microwave operation achieves equivalent benzene removal to continuous thermal processing while significantly reducing energy demand. This work establishes MOF-derived spinel oxides as high-performance microwave catalysts for low-temperature VOC abatement. Full article

This study provides an assessment of BTEX compounds—benzene, toluene, ethylbenzene, and xylene isomers—in urban precipitation collected in the city of Novi Sad, Republic of Serbia, during autumn and winter 2024, analyzed by gas chromatography-mass spectrometry (GC-MS). By combining chemical analysis with meteorological observations and HYSPLIT backward trajectory modeling, the study considers the mechanisms of BTEX removal from the atmosphere via wet scavenging and highlights the role of local weather conditions and long-range atmospheric transport in pollutant concentrations. During the early observation period (September to late November), average concentrations were 0.45 µg/L benzene, 3.45 µg/L ethylbenzene, 4.0 µg/L p-xylene, 2.31 µg/L o-xylene, and 1.32 µg/L toluene. These values sharply dropped to near-zero levels in December for benzene, ethylbenzene, and xylenes, while toluene persisted at 1.12 µg/L. A pronounced toluene spike exceeding 6 µg/L on 28 November was likely driven by transboundary air mass transport from Central Europe, as confirmed by trajectory modeling. The environmental risks posed by BTEX deposition, especially from toluene and xylenes, underline the need for regulatory frameworks to include precipitation as a pathway for pollutant deposition. It should be clarified that the identified risk primarily concerns aquatic organisms, due to the potential for BTEX infiltration into surface waters and subsequent ecotoxicological impacts. Incorporating such monitoring into EU policies can improve protection of air, water, and ecosystems. Full article

This study investigates the emission characteristics and environmental impacts of pollutants from bagasse-fired biomass boilers through the integrated field monitoring of two sugarcane processing plants in Guangxi, China. Comprehensive analyses of flue gas components, including PM_2.5, NOx, CO, heavy metals, VOCs, HCl, and HF, revealed distinct physicochemical and emission profiles. Bagasse exhibited lower C, H, and S content but higher moisture (47~53%) and O (24~30%) levels compared to coal, reducing the calorific values (8.93~11.89 MJ/kg). Particulate matter removal efficiency exceeded 98% (water film dust collector) and 95% (bag filter), while NOx removal varied (10~56%) due to water solubility differences. Heavy metals (Cu, Cr, Ni, Pb) in fuel migrated to fly ash and flue gas, with Hg and Mn showing notable volatility. VOC speciation identified oxygenated compounds (OVOCs, 87%) as dominant in small boilers, while aromatics (60%) and alkenes (34%) prevailed in larger systems. Ozone formation potential (OFP: 3.34~4.39 mg/m³) and secondary organic aerosol formation potential (SOAFP: 0.33~1.9 mg/m³) highlighted aromatic hydrocarbons (e.g., benzene, xylene) as critical contributors to secondary pollution. Despite compliance with current emission standards (e.g., PM < 20 mg/m³), elevated CO (>1000 mg/m³) in large boilers indicated incomplete combustion. This work underscores the necessity of tailored control strategies for OVOCs, aromatics, and heavy metals, advocating for stricter fuel quality and clear emission standards to align biomass energy utilization with environmental sustainability goals. Full article

The first coalification jump (FCJ) has a significant effect on changes in the microstructural properties of coal and plays a crucial role in understanding the efficient utilization of low-rank coal. One lignite (QSY-2), two subbituminous (MHJ-10 and YCW-2), and three high-volatile A-grade bituminous coals (YX-12, JF-18, and HY-5) from the Ningdong coalfield were selected for research, avoiding the influence of regional geology. The evolution characteristics of the microstructures before and after the FCJ were investigated via spectroscopic experiments. The complex and unstable molecular structure of low-rank coal gradually decomposes and polymerizes at 350 °C. The aliphatic structure shows a V-shaped change trend as metamorphism increases. The inflection point is around an R_o of 0.6%. Demethylation and polymerization occur simultaneously during the FCJ. The reconnection of benzene substances with the aromatic ring increases the density of aromatic rings in the YCW-2 sample, significantly enhancing its aromaticity. The removal of oxygen-containing functional groups, especially methoxy and carbonyl groups, provides the possibility for the formation of CH₄ and CO₂ during the metamorphosis of lignite to subbituminous coal. Furthermore, high temperatures result in a loss of moisture content during the FCJ, which is the primary factor leading to a reduction in the hydroxyl content in coal. The selected samples are primarily composed of organic matter, with low levels of heteroatoms in the coal. It is preliminarily determined that coalification is not significantly affected. This study provides a theoretical foundation for investigating the molecular structure evolution of low-rank coal during the FCJ. Full article

This study aims to investigate the oxidative pyrolysis of biomass volatiles with a particular focus on the formation of liquid products. Furfural, hydroxyacetone, and 3,4-dimethoxybenzaldehyde were chosen as volatile model compounds. The impacts of the oxygen equivalence ratio (ER, 0–15%) and temperature (400–500 °C) on the product composition and distribution were examined using a two-stage quartz-tube reactor. The results showed that volatile pyrolysis was limited at the lower temperature of 400 °C even with oxygen introduction, while it could be significantly promoted at 500 °C as illustrated by the observed great decrease in the GC-MS peak areas of the volatile compounds especially under an oxidative atmosphere. For instance, the peak area of 3,4-dimethoxybenzaldehyde at 500 °C under an ER of 4% was only ~9% of that at 400 °C. Oxygen introduction enhanced the volatile decomposition with the formation of mainly permanent gases (although not given in the study) rather than liquid products, but distinct impacts were obtained for varied volatile compounds possibly due to their different chemical structures and autoignition temperatures. From the perspective of liquid product formation, furfural would undergo the cleavage of C-C/C-O bonds to form linear intermediates and subsequent aromatization to generate aromatics (benzene and benzofuran). The presence of oxygen could enhance the oxidative destruction of the C-C/C-O bonds and the removal of O from the molecules to form simple aromatics such as benzene, phenol, and toluene. Hydroxyacetone mainly underwent C-C/C-O cleavage that was further enhanced in the presence of oxygen; the resultant intermediates would recombine to generate acetoin and 2,3-pentanedione. A higher ER would directly oxidize the alcoholic hydroxyl group (-OH) into an aldehyde group (-CHO) to form methyl glyoxal, while 3,4-dimethoxybenzaldehyde mainly underwent cleavage and recombination of bonds connected with the benzene ring including aldehyde group (-CHO), C_Ar-O, C_Methoxy-O bonds, thus forming 1,2-dimethoxybenzene, toluene, and 3-hydroxybenzadehyde. This study provides more fundamental insights into the homogeneous oxidation of volatiles during the oxidative fast pyrolysis of biomass, facilitating the deployment of this technology. Full article

In this study, we report the synthesis of few-layer graphene via ultrasonic treatment of a graphite-benzene solution at room temperature. Raman spectroscopy revealed a significant reduction in the intensity ratio of the G and 2D peaks for samples subjected to 20 min of treatment, indicating a decrease in defect density and oxidation. Prolonged treatment times led to fragmentation of the graphene sheets, which facilitated restacking, as evidenced by Raman spectroscopy and microscopy. FTIR analysis confirmed the complete removal of the solvent from the extracted and dried graphene. Additionally, electron paramagnetic resonance (EPR) measurements indicated the presence of carbon-based magnetism in the synthesized samples, suggesting potential applications in spintronic devices. Our findings highlight the effectiveness of ultrasonic treatment for producing high-quality few-layer graphene with desirable structural and magnetic properties. Full article

Through the application of advanced membrane modification strategies, high-performance membranes have been developed to effectively remove organic contaminants such as toluene and xylene from wastewater. These membranes demonstrate superior antifouling resistance and long-term operational stability, offering a competitive advantage for semiconductor wastewater treatment. This study introduces a novel approach to membrane fabrication using polyvinylidene fluoride (PVDF), recognized for its cost-effectiveness and distinct antifouling properties in contaminant removal. To enhance the performance of the membrane, the solvent (DMA, DMF, NMP) that dissolves PVDF and the immersion time (30 min, 60 min, 90 min) at which phase separation occurs were identified. Additionally, the membranes were treated with polyvinyl alcohol (PVA) through multiple dip coatings to enhance their hydrophilicity before a comparative analysis was conducted. The resulting optimized membranes demonstrated high emulsion fluxes (4412 $\mathrm{L}{\mathrm{m}}^{-2}{\mathrm{h}}^{-1}{\mathrm{bar}}^{-1}$ for toluene) and achieved oil-removal efficiencies exceeding 90% when tested with various organic solvents, including toluene, cyclohexane, xylene, benzene, and chloroform. The resulting optimized membranes prove to be a reliable means of producing clean water and of efficiently separating organic contaminants from wastewater. Showcasing remarkable antifouling capabilities and suitability for repeated use without significant efficiency loss, this solution effectively addresses cost and fouling challenges, presenting it as a sustainable and efficient wastewater treatment method for the semiconductor industry. Full article

Ibuprofen (IBF), as a representative emerging contaminant, poses urgent environmental and ecological risks that demand efficient removal technologies. This study employed an O₃/H₂O₂ catalytic oxidation process to degrade IBF in aqueous systems and systematically investigated the effects of reactant ratios, pH, and reactive species on the degradation efficiency. The results demonstrated that O₃-dominated oxidation significantly outperformed H₂O₂ alone in IBF removal, with an optimal dosage ratio of c(O₃):c (H₂O₂) = 6:1 and a removal efficiency of 94.75% at pH > 7. Radical quenching experiments confirmed that •OH served as the dominant reactive species, the concentration and stability of which directly governed the degradation kinetics. Combined density functional theory (DFT) calculations and mass spectrometry analysis revealed that the benzene ring and carboxyl groups in IBF were vulnerable to radical attack, with degradation pathways involving hydroxylation, decarboxylation, and ring-opening reactions, yielding 13 intermediate products. The toxicity assessment indicated that over 70% of these intermediates exhibited low or negligible toxicity. Remarkably, IBF removal efficiencies exceeded 99.4% in real water matrices (raw, filtered, and finished water), validating the robust anti-interference capability of the O₃/H₂O₂ system. This process, characterized by high efficiency and low ecological risk, provides a feasible solution for eliminating trace emerging contaminants in advanced drinking water treatment. Full article

Maghemite nanoparticles (NPs) were successfully developed using phenolic-rich extracts (cyanidin) from Citrus reticulata peel residues. The 11 nm maghemite NPs, obtained at 3% w/v and at 353 K, presented the optimal synthesis conditions. To improve dye adsorption performance, the synergetic adsorption behavior between these 11 nm NPs and multiwall carbon nanotubes was demonstrated. Prior to the adsorption tests, the aging effect on NPs was carefully assessed using various analytical techniques, which clearly showed the magnetite–maghemite phase transition. However, this had no impact on the cyanidin coating or adsorption properties. A remarkable percentage removal of (93 ± 3)% for methylene blue and (84 ± 3)% for methylene green was achieved in short equilibrium times of 10 and 25 min, respectively, with an optimum pH value of 5.5. Reuse experiments revealed that 90% removal for both dyes was achieved between the second to seventh regeneration cycles. Organic loading during these cycles was effectively confirmed by X-ray photoelectron spectroscopy and magnetic measurements. Dye adsorption involves a two-step mechanism: (i) electrostatic adsorption by the negative surface groups of the adsorbent (isoelectric point of 5.2) and the dye cationic groups and (ii) π–π stacking interactions between the aromatic benzene rings of the dyes, the hexagonal skeleton of the multiwall carbon nanotubes, and the phenolic ring groups of the biosynthesized sample. These results suggest that the low-cost modified phenolic adsorbent can be successfully applied to dye removal from water with promising recycling properties. Full article

Advanced water treatment technologies must offer selective, efficient, and cost-effective contaminant removal. In this study, TPB-DMTP-COF-SH, prepared from 1,3,5-tris(4-aminophenyl)benzene (TPB) and 2,5-dimethoxyterephaldehyde (DMTP), was synthesized via a two-step method and applied for the adsorption of aluminum (Al³⁺), iron (Fe²⁺), and manganese (Mn²⁺) ions from water. Adsorption performance was influenced by pH, initial concentration, and contact time, with optimal pH values of 3 for Al³⁺, 8 for Fe²⁺, and 10 for Mn²⁺. The adsorption data followed the Langmuir isotherm model, yielding maximum capacities of 3.27 mg g⁻¹ (Al³⁺), 8.5 mg g⁻¹ (Fe²⁺), and 0.67 mg g⁻¹ (Mn²⁺). Kinetic studies indicated a pseudo-second-order mechanism, suggesting chemisorption as the dominant process. Equilibrium adsorption was reached at 15 min for Al³⁺ and Mn²⁺ and 20 min for Fe²⁺. As a proof of concept, we demonstrate that this thiol-functionalized COF not only effectively removes metals but also offers enhanced processability into composite beads and membranes, making it a strong candidate for real-world water treatment applications. These findings highlight TPB-DMTP-COF-SH as a promising and scalable solution for water purification. Full article

The transformation of organochlorine and organic impurities such as CCl₄, C₂H₂Cl₂, C₂HCl₃, C₂Cl₄, C₂H₂Cl₄, CH₄, C₃H₈, C₄H₁₀, and C₆H₆ in the content range of 10⁻²–10⁻⁶ wt.%, as well as BCl₃ impurities at the level of 3 × 10⁻² wt.%, was considered. A method has been developed for removing limiting impurities of carbon and boron during the process of the hydrogen reduction of silicon tetrachloride in a high-frequency arc gas discharge at atmospheric pressure. The thermodynamic and gas-dynamic analyses of the reduction process of silicon tetrachloride in hydrogen plasma, along with the behavior of organochlorine impurities, organic substances, and boron trichloride, was conducted. These analyses suggest that under equilibrium conditions, the conversion reactions of impurities result in the formation of silicon carbide and boron silicide. Potential chemical reactions for the conversion of the studied impurities into silicon carbide and boron silicide have been proposed. A new potential for plasma chemical processes has been identified, enabling the effective purification of chlorosilanes from both limiting and limited impurities. The results demonstrate the possibility of significantly reducing the concentrations of organochlorine and organic impurities, as well as boron trichloride, during the reduction of silicon tetrachloride in hydrogen plasma. The maximum conversion rates achieved included 99% for the organochlorine impurity CCl₄ to silicon carbide, 91% for benzene impurity to silicon carbide, and 86% for boron trichloride to boron silicide. Full article

The textile industry consumes large volumes of freshwater, producing enormous wastewater containing chemicals from dyeing and bathing, but also microplastics concentrations that have not been deeply studied. Liquid wastes from the synthetic and natural textile manufacturers were treated with a new disruptive technology (Adiabatic Sonic Evaporation and Crystallization, ASEC), which completely removed contaminants from water, providing distilled water and crystallized solids. The current study presents the characterization of the industrial residues and the obtained by-products: microplastics and organic matter contained in the solid residue were analyzed and characterized through chromatography. The results of the analyses displayed that compounds such as benzene, benzoic acid and 2,4-dymethyl-1-heptene were found in the synthetic industry water samples as degraded compounds of polyester and polypropylene. Meanwhile, the natural industry water also contained polyester, nylon and PMM polymer. After the depuration of samples, microplastics were completely retained in the solid phase, together with the organic matter (sulfate and surfactants) resulting on clean water. This is the first study focused on the study of microplastics generated by the textile industry and their prevention by removing them as solid waste. Full article

Photocatalytic coatings incorporating nano-TiO₂ have emerged as effective solutions for air purification, utilizing solar radiation to degrade airborne pollutants. However, the long-term stability of such coatings, particularly those based on organic binders, remains a concern due to their susceptibility to photocatalytic-driven degradation. This study investigates the effects of low-intensity UV-A irradiation (1–10 W/m²) on acrylic-based photocatalytic coatings’ structural integrity and air purification performance. The findings reveal that significant binder decomposition occurs even under low irradiation conditions—comparable to natural sunlight exposure in Northern and Central Europe during autumn and winter. The surface porosity increased from 2.28% to 9.09% due to polymer degradation, exposing more nano-TiO₂ particles and enhancing NO removal efficiency from approximately 120 µg/hm² to 360 µg/hm² under UV-A irradiation (1 W/m²). However, this process also resulted in benzene emissions reaching approximately five ppb, raising concerns about secondary pollution and the potential release of nano-TiO₂ due to polymer matrix disintegration. These findings highlight the need for optimized coating formulations that balance photocatalytic efficiency with long-term material stability, mitigating the environmental and health risks associated with secondary pollutant emissions. Full article

A group of silica-based supports with varying Al/Si ratios (S−x) was synthesized using the sol–gel method, followed by a chlorosulfonic acid modification to produce supported sulfonic acids (SA−x). The S−x and SA−x materials, along with their adsorption products, were characterized via techniques such as FTIR, BET, and HPLC-MS. The analysis revealed that the sulfonic acid groups in the SA−x materials existed in two anchoring states: the covalently bonded (CB) state [SiOx–O]^ɗ−–SO₃H^ɗ+ and the ion-paired (IP) state AlO_y⁺:OSO₃H⁻. The sulfonation reactivity of the CB-state sulfonic acid was enhanced, whereas that of the IP-state counterpart was diminished. The incorporation of a minor quantity of aluminum ions (x = 0.1) markedly enhanced the adsorption efficiency of SAs for o-xylene, extending the reaction temperature range to 110–190 °C and increasing the breakthrough adsorption capacity (Q_B) to 946.1 mg g⁻¹. However, excessive aluminum ion incorporation was detrimental to the adsorption performance of SAs for o-xylene. SA−0.1 showed superior adsorptive capabilities and excellent recyclability, maintaining its performance over four consecutive adsorption/regeneration cycles with only a minor decrease of 4.5%. These findings suggest that SAs prepared with a minor amount of aluminum ions have significant potential for application as adsorbents for the removal of benzene series pollutants. Full article