Atmospheric occurrences and bioavailability health risk of PAHs and their derivatives surrounding a non-ferrous metal smelting plant.

Non-ferrous metal smelting emits large amounts of organic compounds into the atmosphere. Herein, 20 parent polycyclic aromatic hydrocarbons (PPAHs), 9 nitrated PAHs (NPAHs), 14 chlorinated PAHs (ClPAHs), and 6 alkylated PAHs (APAHs) in atmospheric samples from a typical non-ferrous metal smelting plant (NMSP) and residential areas were detected. In NMSP, benzo[a]pyrene, dibenz[a,h]anthracene, 6-nitrochrysene, 9-chlorofluorene, and 1-methylfluorene were the predominant compounds in the particulate phase, while phenanthrene constituted 57.3% in the gaseous phase. The concentration of PAHs in residential areas around NMSP was 1.8 times higher than that in the control area. Additionally, there was a significant negative correlation between the concentration and the distance from the NMSP. In terms of health risks, although the skin penetration coefficient of PM2.5 is smaller than that of the gaseous phase, dermal absorption of PM2.5 posed a greater threat to the population, the incremental lifetime cancer risk (ILCR) of NMSP was 1.8 × 10-4. After considering bioavailability, BILCR decreased by 1-2 orders of magnitude in different regions, and dermal absorption decreased more than inhalation intake. Nevertheless, the dermal absorption of PM2.5 in NMSP still presents a probable carcinogenic risk. This study provides a necessary reference for the subsequent control of NMSP contamination.

Occurrence of BTX and PAHs in underground drinking water of coking contaminated sites: Linkage with altitude and health risk assessment by boiling-modified models.

The safety of underground drinking water has received widespread attention. However, few studies have focused on the occurrence and health risks of pollutants in underground drinking water of coking contaminated sites. In this study, the distribution characteristics, sources, and human health risks of benzene, toluene, xylene (BTX) and polycyclic aromatic hydrocarbons (PAHs) in underground drinking water from a typical coking contaminated site in Shanxi of China were investigated. The average concentrations of BTX and PAHs in coking plant (CP) were 5.1 and 4.8 times higher than those in residential area (RA), respectively. Toluene and Benzene were the main BTX, while Acenaphthene, Fluorene, and Pyrene were the main PAHs. Concentrations of BTX/PAHs were negatively correlated with altitude, revealing altitude might be an important geological factor influencing spatial distribution of BTX/PAHs. PMF model demonstrated that the BTX/PAHs pollution in RA mainly originated from coking industrial activities. Health risk assessments were conducted by a modified US EPA-based model, in which environmental concentrations were replaced by residual concentrations after boiling. Residual ratios of different BTX/PAHs were determined by boiling experiments to be 9.4-93.8 %. The average total carcinogenic risks after boiling were decreased from 2.6 × 10-6 to 1.4 × 10-6 for adults, and from 4.3 × 10-6 to 2.1 × 10-6 for children, suggesting boiling was an effective strategy to reduce the carcinogenic risks from BTX/PAHs, especially for ingestion pathway. Monte Carlo simulation results matched well with the calculated results, suggesting the uncertainty was acceptable and the risk assessment results were reliable. This study provided useful information for revealing the spatial distribution of BTX/PAHs in underground drinking water of coking contaminated sites, understanding their linkage with altitude, and also helped to more accurately evaluate the health risks by using the newly established boiling-modified models.

Atmospheric VOCs in an industrial coking facility and the surrounding area: Characteristics, spatial distribution and source apportionment.

Industrial coking facilities are an important emission source for volatile organic compounds (VOCs). This study analyzed the atmospheric VOC characteristics within an industrial coking facility and its surrounding environment. Average concentrations of total VOCs (TVOCs) in the surrounding residential activity areas (R1 and R2), the coking facility (CF) and the control area (CA) were determined to be 138.5, 47.8, 550.0, and 15.0 µg/m3, respectively. The cold drum process and coking and quenching areas within the coking facility were identified as the main polluting processes. The spatial variation in VOCs composition was analyzed, showing that VOCs in the coking facility and surrounding areas were mainly dominated by aromatic compounds such as BTX (benzene, toluene, and xylenes) and naphthalene, with concentrations being negatively correlated with the distance from the coking facility (p < 0.01). The sources of VOCs in different functional areas across the monitoring area were analyzed, finding that coking emissions accounted for 73.5%, 33.3% and 27.7% of TVOCs in CF, R1 and R2, respectively. These results demonstrated that coking emissions had a significant impact on VOC concentrations in the areas surrounding coking facility. This study evaluates the spatial variation in exposure to VOCs, providing important information for the influence of VOCs concentration posed by coking facility to surrounding residents and the development of strategies for VOC abatement.

Atmospheric occurrences and health risk assessment of polycyclic aromatic hydrocarbons and their derivatives in a typical coking facility and surrounding areas.

Coking facilities release large quantities of polycyclic aromatic hydrocarbons (PAHs) and their derivatives into the ambient air. Here we examined the profiles, spatial distributions, and potential sources of atmospheric PAHs and their derivatives in an industrial coking plant and its surrounding environment (gaseous and particulate). The mean concentrations of PAHs, nitrated PAHs (NPAHs), chlorinated PAHs (ClPAHs), and brominated PAHs (BrPAHs) in the air of the coking facility were 923, 23.8, 16.7 and 4.25 ng m-³, respectively, 1-2 orders of magnitude higher than those in the surrounding area and the control area. Linear regressions between contaminant concentrations and distance from the coking facility suggested that the concentrations of PAHs (r2 = 0.82, p < 0.05), NPAHs (r2 = 0.77, p < 0.01), and BrPAHs (r2 = 0.62, p < 0.01) were negatively correlated with distance. Additionally, the particle-bound fractions of PAHs and their derivatives were significantly correlated with their molecular weights (p < 0.01). Based on the calculation of the gas/particle partitioning coefficients (log KP) for PAHs and their derivatives and the corresponding subcooled liquid vapor pressures (log PL), the slope values for PAHs, NPAHs, ClPAHs, and BrPAHs ranged from -1 to -0.6, indicating that deposition of PAHs and their derivatives occurred through both adsorption and absorption. Five emissions sources were identified by positive matrix factorization (PMF), including coking emissions, oil pollution, industrial and combustion sources, secondary formation, and traffic emissions, with coking emissions accounting for more than 50% of total emissions. Furthermore, the results of the health risks assessment suggested that atmospheric PAHs and their derivatives in the coke plant and surrounding area negatively impacted human health.

Distribution characteristics, air-water exchange, ozone formation potential and health risk assessments of VOCs emitted from typical coking wastewater treatment process.

Coking industry has been considered as important source of volatile organic compounds (VOCs) emissions. However, few studies have emphasized the occurrence and adverse effects of VOCs from coking wastewater treatment processes. In this research, pollution profiles of both air and water phase VOCs in a typical coking wastewater treatment plant were investigated in terms of distribution characteristics, air-water exchange, ozone formation potential (OFP) and associated human health risks. Thirty VOCs were detected in the air phase, in which benzene and naphthalene were found to be the major VOCs with total contribution of 87.81 %. Nineteen VOCs were detected in the water phase, in which benzene, naphthalene and toluene contribute most to total VOCs with total contribution of 75.1 %. The regulating tank (RT) was the major source of VOCs, and the emission rate of total VOCs from all unites was 2711.03 g/d with annual emission of 0.99 t. The emission factor was estimated to be 1.36 g VOCs/m3 wastewater. The air-water exchange was assessed using the Fugacity model, and water-to-air volatilization was predominant based on the net flux of air-water exchange. OFP evaluated by emission factor indicated that the total OFP in RT was the highest (1.52 g O3/m3 wastewater), and toluene contributed 41.8 % of the total OFP, followed by naphthalene accounting for 38.7 % The total carcinogenic risks were in the range of 8.60 × 10-6 to 2.18 × 10-3, in which the RT exceeded the significant risk threshold (>1 × 10-4). The non-carcinogenic risks of hazard quotient value in RT also exceeded the risk threshold (>1), and naphthalene was the major contributor accounting for 79.02 %. These results not only provided comprehensive knowledge on pollution profiles and environmental risks of VOCs during coking wastewater treatment processes, but also facilitated the implement of VOCs regulation and occupational health protection strategies in coking industries.

Efficient Catalytic Combustion of Cyclohexane over PdAg/Fe2O3 Catalysts under Low-Temperature Conditions: Establishing the Degradation Mechanism Using PTR-TOF-MS and in Situ DRIFTS.

Cyclohexane, a typical volatile organic compound (VOC), poses high risks to the environment and humans. Herein, synthesized PdAg/Fe2O3 catalysts exhibited exceptional catalytic performance for cyclohexane combustion at lower temperatures (50% mineralization temperature (T50) of 199 °C, 90% mineralization temperature (T90) of 315 °C) than Pd/Fe2O3 (T50 of 262 °C, T90 of 335 °C) and Fe2O3 (T50 of 305 °C, T90 of 360 °C). In addition, PdAg/Fe2O3 displayed enhanced stability by alloying Ag with Pd. The redox and acidity of the PdAg/Fe2O3 were studied by XPS, H2-TPR, and NH3-TPD. In situ diffuse reflectance infrared Fourier transform spectroscopy and proton-transfer-reaction time-of-flight mass spectrometry were applied to identify the intermediates formed on the catalyst surface and in the tail gas during oxidation, respectively. Results suggested that loading PdAg onto Fe2O3 significantly enhanced the adsorption and activation of oxygen and cyclohexane, oxidative dehydrogenation of cyclohexane to benzene, and catalytic cracking of cyclohexane to olefins at low temperatures. This in-depth study will benefit the design and application of efficient catalysts for the effective combustion of VOCs at low temperatures.

Complete mineralization of phenolic compounds in visible-light-driven photocatalytic ozonation with single-crystal WO3 nanosheets: Performance and mechanism investigation.

Complete mineralization of phenolic compounds into CO2 and H2O is desirable for removing them in wastewater, but it is challenging due to the generated recalcitrant intermediates, which requires highly effective advanced oxidation process with proper catalysts. Herein, we found that single-crystal WO3 nanosheets (NSs)-based photocatalytic ozonation (PCO) can realize complete mineralization of phenols (phenol and 2-chlorophenol) under visible light irradiation. Almost 100% mineralization ratio of phenols was achieved through WO3 NSs-based PCO system within short time. By comparing their performances with those of polycrystalline WO3 nanoparticles, detecting and analyzing the intermediates, identifying the dominant radicals and conducting some electrochemical characterizations, the origin of superior catalytic activity of WO3 NSs was uncovered, the mineralization pathways and the overall mechanism were proposed. The excellent PCO performance of WO3 NSs was contributed to their nanosheet morphology with single-crystal microstructure and good dispersion, which can provide continuous interior channels for the photogenerated charge transport from the bulk to surface of WO3 NSs and enough active sites for the surface reactions triggered by these charges. This work puts forwards new ideas to design highly active photocatalysts for PCO and helps deepen understanding of the catalytic mechanism of PCO.

In situ growth of well-aligned Ni-MOF nanosheets on nickel foam for enhanced photocatalytic degradation of typical volatile organic compounds.

Exploitation of highly efficient catalysts for photocatalytic degradation of volatile organic compounds (VOCs) under visible light irradiation is highly desirable yet challenging. Herein, well-aligned 2D Ni-MOF nanosheet arrays vertically grown on porous nickel foam (Ni-MOF/NF) without lateral stacking were successfully prepared via a facile in situ solvothermal strategy. In this process, Ni foam could serve as both a skeleton to vertically support the Ni-MOF nanosheets and a self-sacrificial template to afford Ni ions for MOF growth. The Ni-MOF/NF nanosheet arrays with highly exposed active sites and light harvesting centres as well as fast mass and e- transport channels exhibited excellent photocatalytic oxidation activity and mineralization efficiency to typical VOCs emitted from the paint spray industry, which was almost impossible for their three-dimensional (3D) bulk Ni-MOF counterparts. A mineralization efficiency of 86.6% could be achieved at 98.1% of ethyl acetate removal. The related degradation mechanism and possible reaction pathways were also attempted based on the electron paramagnetic resonance (EPR) and online Time-of-Flight Mass Spectrometer (PTR-ToF-MS) results.

PdAg Nanoparticles within Core-Shell Structured Zeolitic Imidazolate Framework as a Dual Catalyst for Formic Acid-based Hydrogen Storage/Production.

Formic acid (FA; HCOOH) is one of the most promising candidates for the storage of hydrogen (H2). Herein, we report a H2 storage/production system based on the hydrogenation of CO2 and dehydrogenation of FA, using a nanostructured heterogeneous catalyst. Pd1Ag2 nanoparticles with an average size of 2.8 nm were encapsulated within a zeolitic imidazolate framework (ZIF-8) having a core-shell structure (ZIF-8@Pd1Ag2@ZIF-8). This composite displayed high activity and stability during both the hydrogenation of CO2 to produce FA and the dehydrogenation of FA into H2 and CO2. This improved performance is attributed to the use of ultrafine Pd1Ag2 nanoparticles as well as the spatial regulation of the nanoparticles within the reaction field. This study suggests a new strategy for controlling the spatial distribution of metal nanoparticles within MOFs so as to fine-tune the catalytic activity and selectivity of ZIF-8@metal nanoparticles@ZIF-8 catalysts.

Single-site and nano-confined photocatalysts designed in porous materials for environmental uses and solar fuels.

Silica-based micro-, meso-, macro-porous materials offer attractive routes for designing single-site photocatalysts, supporting semiconducting nanoparticles, anchoring light-responsive metal complexes, and encapsulating metal nanoparticles to drive photochemical reactions by taking advantage of their large surface area, controllable pore channels, remarkable transparency to UV/vis and tailorable physicochemical surface characteristics. This review mainly focuses on the fascinating photocatalytic properties of silica-supported Ti catalysts from single-site catalysts to nanoparticles, their surface-chemistry engineering, such as the hydrophobic modification and synthesis of thin films, and the fabrication of nanocatalysts including morphology controlled plasmonic nanostructures with localized surface plasmon resonance. The hybridization of visible-light responsive metal complexes with porous materials for the construction of functional inorganic-organic supramolecular photocatalysts is also included. In addition, the latest progress in the application of MOFs as excellent hosts for designing photocatalytic systems is described.

Design of Single-Site Photocatalysts by Using Metal-Organic Frameworks as a Matrix.

Single-site photocatalysts generally display excellent photocatalytic activity and considerably high stability compared with homogeneous catalytic systems. A rational structural design of single-site photocatalysts with isolated, uniform, and spatially separated active sites in a given solid is of prime importance to achieve high photocatalytic activity. Intense attention has been focused on the design and fabrication of single-site photocatalysts by using porous materials as a platform. Metal-organic frameworks (MOFs) have great potential in the design and fabrication of single-site photocatalysts due to their remarkable porosity, ultrahigh surface area, extraordinary tailorability, and significant diversity. MOFs can provide an abundant number of binding sites to anchor active sites, which results in a significant enhancement in photocatalytic performance. In this focus review, the development of single-site MOF photocatalysts that perform important and challenging chemical redox reactions, such as photocatalytic H2 production, photocatalytic CO2 conversion, and organic transformations, is summarized thoroughly. Successful strategies for the construction of single-site MOF photocatalysts are summarized and major challenges in their practical applications are noted.

Palladium Nanoparticles Supported on Titanium-Doped Graphitic Carbon Nitride for Formic Acid Dehydrogenation.

Pd nanoparticles (NPs) supported on Ti-doped graphitic carbon nitride (g-C3 N4 ) were synthesized by a deposition-precipitation route and a subsequent reduction with NaBH4 . The features of the NPs were studied by XRD, TEM, FTIR, XPS, EXAFS and N2 -physisorption measurements. It was found that the NPs had an average size of 2.9 nm and presented a high dispersion on the surface of Ti-doped g-C3 N4 . Compared to Pd loaded on pristine g-C3 N4 , the Pd NPs supported on Ti-doped g-C3 N4 exhibited a high catalytic activity in formic acid dehydrogenation in water at room temperature. The enhanced activity could be attributed to the small Pd NPs size, as well as the strong interaction between Pd NPs and Ti-doped g-C3 N4 .

Non-Noble-Metal Nanoparticle Supported on Metal-Organic Framework as an Efficient and Durable Catalyst for Promoting H2 Production from Ammonia Borane under Visible Light Irradiation.

In this work, we propose a straightforward method to enhance the catalytic activity of AB dehydrogenation by using non-noble-metal nanoparticle supported on chromium-based metal-organic framework (MIL-101). It was demonstrated to be effective for hydrogen generation from ammonia borane under assistance of visible light irradiation as a noble-metal-free catalyst. The catalytic activity of metal nanoparticles supported on MIL-101 under visible light irradiation is remarkably higher than that without light irradiation. The TOFs of Cu/MIL-101, Co/MIL-101, and Ni/MIL-101 are 1693, 1571, and 3238 h(-1), respectively. The enhanced activity of catalysts can be primarily attributed to the cooperative promoting effects from both non-noble-metal nanoparticles and photoactive metal-organic framework in activating the ammonia borane molecule and strong ability in the photocatalytic production of hydroxyl radicals, superoxide anions, and electron-rich non-noble-metal nanoparticle. This work sheds light on the exploration of active non-noble metals supported on photoactive porous materials for achieving high catalytic activity of various redox reactions under visible light irradiation.

Room-Temperature and Aqueous-Phase Synthesis of Plasmonic Molybdenum Oxide Nanoparticles for Visible-Light-Enhanced Hydrogen Generation.

A straightforward aqueous synthesis of MoO3-x nanoparticles at room temperature was developed by using (NH4 )6 Mo7 O24 ⋅4 H2 O and MoCl5 as precursors in the absence of reductants, inert gas, and organic solvents. SEM and TEM images indicate the as-prepared products are nanoparticles with diameters of 90-180 nm. The diffuse reflectance UV-visible-near-IR spectra of the samples indicate localized surface plasmon resonance (LSPR) properties generated by the introduction of oxygen vacancies. Owing to its strong plasmonic absorption in the visible-light and near-infrared region, such nanostructures exhibit an enhancement of activity toward visible-light catalytic hydrogen generation. MoO3-x nanoparticles synthesized with a molar ratio of Mo(VI) /Mo(V) 1:1 show the highest yield of H2 evolution. The cycling catalytic performance has been investigated to indicate the structural and chemical stability of the as-prepared plasmonic MoO3-x nanoparticles, which reveals its potential application in visible-light catalytic hydrogen production.

Hydrogen Doped Metal Oxide Semiconductors with Exceptional and Tunable Localized Surface Plasmon Resonances.

Heavily doped semiconductors have recently emerged as a remarkable class of plasmonic alternative to conventional noble metals; however, controlled manipulation of their surface plasmon bands toward short wavelengths, especially in the visible light spectrum, still remains a challenge. Here we demonstrate that hydrogen doped given MoO3 and WO3 via a facile H-spillover approach, namely, hydrogen bronzes, exhibit strong localized surface plasmon resonances in the visible light region. Through variation of their stoichiometric compositions, tunable plasmon resonances could be observed in a wide range, which hinge upon the reduction temperatures, metal species, the nature and the size of metal oxide supports in the synthetic H2 reduction process as well as oxidation treatment in the postsynthetic process. Density functional theory calculations unravel that the intercalation of hydrogen atoms into the given host structures yields appreciable delocalized electrons, enabling their plasmonic properties. The plasmonic hybrids show potentials in heterogeneous catalysis, in which visible light irradiation enhanced catalytic performance toward p-nitrophenol reduction relative to dark condition. Our findings provide direct evidence for achieving plasmon resonances in hydrogen doped metal oxide semiconductors, and may allow large-scale applications with low-price and earth-abundant elements.

Microwave-antenna induced in situ synthesis of Cu nanowire threaded ZIF-8 with enhanced catalytic activity in H2 production.

A microwave-antenna strategy was developed for the in situ synthesis of Cu nanowire (CuNW) threaded ZIF-8. The CuNWs acted as microwave-antennas to generate surface "super hot" dots. The high temperature of "super hot" dots induced adsorption and coordination of metal ions and organic ligands, followed by in situ assembly and crystal-growth along the CuNWs. This catalyst exhibited high activity and stability in H2 production via NH3BH3 hydrolysis owing to the synergetic effect. The CuNWs supplied a rapid electron transfer channel while ZIF-8 assembled on the CuNWs offered a large capacity for adsorbing reactants and channels for rapidly transferring H(-)/H(+) ions toward Cu active sites. Other one-dimensional threaded MOFs, including CuNW threaded MOF-5 and UIO-66, or carbon nanotube threaded ZIF-8 and ZIF-67 could also be prepared using the microwave-antenna strategy.

Hierarchical Nanostructured WO3 with Biomimetic Proton Channels and Mixed Ionic-Electronic Conductivity for Electrochemical Energy Storage.

Protein channels in biologic systems can effectively transport ions such as proton (H(+)), sodium (Na(+)), and calcium (Ca(+)) ions. However, none of such channels is able to conduct electrons. Inspired by the biologic proton channels, we report a novel hierarchical nanostructured hydrous hexagonal WO3 (h-WO3) which can conduct both protons and electrons. This mixed protonic-electronic conductor (MPEC) can be synthesized by a facile single-step hydrothermal reaction at low temperature, which results in a three-dimensional nanostructure self-assembled from h-WO3 nanorods. Such a unique h-WO3 contains biomimetic proton channels where single-file water chains embedded within the electron-conducting matrix, which is critical for fast electrokinetics. The mixed conductivities, high redox capacitance, and structural robustness afford the h-WO3 with unprecedented electrochemical performance, including high capacitance, fast charge/discharge capability, and very long cycling life (>50,000 cycles without capacitance decay), thus providing a new platform for a broad range of applications.

Amine-functionalized MIL-101(Cr) with imbedded platinum nanoparticles as a durable photocatalyst for hydrogen production from water.

The incorporation of Pt nanoparticles into a highly stable and porous amine-functionalized MIL-101(Cr) was performed for construction of a visible light driven H2 evolution system with high activity and strong stability.

Synthesis of ultralong copper nanowires for high-performance transparent electrodes.

Cu nanowires hold great promise for the fabrication of low-cost transparent electrodes. However, their current synthesis is mainly performed in aqueous media with poor nanowire dispersibility. We report herein the novel synthesis of ultralong single-crystalline Cu nanowires with excellent dispersibility, providing an excellent candidate material for high-performance transparent electrode fabrication.

Microwave-induced synthesis of porous single-crystal-like TiO2 with excellent lithium storage properties.

Porous anatase TiO(2) single crystal architectures with large specific surface area and remarkable crystalline phase-stability were fabricated via a green microwave-assisted process. Ionic liquid was chosen as both an essential structure-directing agent for the formation of the {001} facets exposed TiO(2) and an etching agent source for selective erosion of the exposed {001} facets, leading to robust porous framework with exposed {101} facets. These porous anatase single crystals were thermally stable up to 800 °C, indicating excellent structure stability. The product showed stable cyclability at high current rate, better reversibility, and high Coulumbic efficiency of 100% for lithium storage.