Aromatic Pollutants Research Articles

Non-stoichiometric magnetite as catalyst for the photocatalytic degradation of phenol and 2,6-dibromo-4-methylphenol - a new approach in water treatment.

Phenol and 2,6-dibromo-4-methylphenol (DBMP) were removed from aqueous solutions by ozonolysis and photocatalysis. The properties and structural features of the catalysts and the organic compounds are discussed, as well as their influence on the degradation reaction rates. The degradation efficiency in photocatalytic processes was higher for DBMP (98%) than for phenol (approximately 50%). This proves the high efficiency of magnetite in the photocatalytic degradation of halogenated aromatic pollutants. The particularly high degradation efficiency regarding halogen-containing DBMP molecules and the yield of bromide ions indicate that DBMP degradation follows a mixed reduction-oxidation mechanism. DBMP molecules interact with the magnetite surface, enabling them to react with the available electrons, and, as a result, bromide ions can be released. The results confirm that magnetite is an effective photocatalyst in the degradation of halogenated aromatic pollutants.

Molecular level insight into the different interaction intensity between microplastics and aromatic hydrocarbon in pure water and seawater

The interaction of MPs and aromatic hydrocarbons in seawater and pure water was examined using experimental measurements, molecular dynamics (MD) simulations, and density functional theory (DFT) calculations in light of the potential health risks posed by microplastic (MPs)-associated aromatic hydrocarbon pollutants. Isothermal studies and MD simulations suggested that MPs have a stronger affinity for aromatic hydrocarbons in seawater. To uncover the mechanism, MPs' surface characteristics and their intermolecular interactions with aromatic hydrocarbons were examined. According to the research, MPs in seawater have less compact structure, bigger pores, and a higher specific surface area, all of which contribute to more sorption sites. Analysis of the intermolecular interaction indicated that MPs have a greater ability for molecular interactions in seawater and the interaction energy between MPs and aromatic hydrocarbons in seawater is higher. Additionally, seawater cations may act as bridges, which also accelerate sorption in seawater. In summary, this study provides a molecular-level understanding of MPs-aromatic hydrocarbons interaction and demonstrates that the interaction is stronger in seawater.

Autocatalytic effect of in situ formed (hydro)quinone intermediates in Fenton and photo-Fenton degradation of non-phenolic aromatic pollutants and chemical kinetic modeling

While the electron-shuttling properties of (hydro)quinones can facilitate the redox cycling of iron species (Fe2+ and Fe3+), the impact of in situ formed (hydro)quinones from degradation of non-phenolic aromatic pollutants in Fenton-type processes has not been reported. This study investigated the catalytic effect of (hydro)quinone intermediates produced from degradation of p-arsanilic acid (p-ASA) and roxarsone (ROX) in Fenton and photo-Fenton processes, and its chemical kinetic modeling. The bimolecular rate constants of the reactions of OH with p-ASA and ROX were determined to be (2.79 ± 0.29) × 109 and (2.03 ± 0.07) × 109 M−1·s−1, respectively. However, ROX degraded faster than p-ASA in Fenton process under the same conditions, which was attributed to the greater catalytic effect of the in situ formed (hydro)quinone intermediates. p-Hydroquinone, p-benzoquinone, and 1,2,4-benzenetriol were identified among the oxidation intermediates of p-ASA, while 2-nitrohydroquinone, 2-nitrobenzoquinone, 1,2,4-benzenetriol, and 2-hydroxy-benzoquinone were found for ROX oxidation. The autocatalytic degradation of p-ASA and ROX in Fenton and photo-Fenton processes could be well described by a chemical kinetic model after accounting for the reactions of the (hydro)quinone intermediates. Both experimental and modeling results consistently showed that the redox cycling of iron promoted by the in situ formed (hydro)quinone intermediates was critical for the oxidation of p-ASA and ROX in Fenton process. Chemical kinetic modeling revealed that (hydro)quinone-related reactions and photo-reduction of Fe3+-complexes were responsible for producing the vast majority of OH that sustained the continuous degradation of p-ASA and ROX in photo-Fenton process with the presence of limited amount of Fe2+. The autocatalytic effect observed for phenylarsonic acid compounds and the chemical kinetic model developed in this study could guide the development of Fenton and solar photo-Fenton treatment for other non-phenolic aromatic pollutants.

Photo-Fenton catalyst Fe(III)@PCN-222 grafted on PVDF membrane for multitasking applications: Oil/water separation, aromatic pollutants degradation and bacterial inactivation

In this work, a novel PCN-222 metal−organic framework based multitasking membrane was developed for separation of emulsified oils as well as photo-Fenton degradation of refractory aromatic pollutants and inactivation of pathogenic bacteria in water. Fe(III)@PCN-222 nanorods were prepared via impregnation method and subjected to amino-modification, and then robustly anchored on polydopamine (PDA) decorated PVDF membrane via catechol-amine reaction. The as-prepared N-Fe(III)@PCN-222/PDA/PVDF composite membrane exhibited underwater superoleophobicity, and showed high separation efficiency (above 99.4 %) as well as relatively favorable permeation flux (874.9–1592.3 Lm−2h−1) in the separation of emulsified oils ranged from nanoscale to microscale from water. Meanwhile, the membrane serving as a recyclable photo-Fenton platform showed an extensive degradation capacity towards aromatic contaminants and high inactivation activity against bacteria under visible light. The grafted Fe(III) is used as an electron acceptor to promote the separation of photo-generated charge carriers, adjusted the band structure to shorten the bandgap value, and can be reduced to Fe(II) by photo-generated electrons as a Fenton-like catalyst. The photo-Fenton mechanism was studied in detail from the aspects of photoelectric properties, band structure and reactive oxygen species. This work could promote the application of PCN subclass MOFs based superwetting membrane as a recyclable platform for complex wastewater treatment.

Preparation of magnetic Fe3O4@PDA/CuS core-shell nanocomposite as a green photocatalyst

To solve the emerging aromatic organic pollutants in aqueous environment, in this study, the efficient recyclable core-shell structured photocatalyst Fe3O4@PDA/CuS was prepared by in situ reduction method. Firstly, Fe3O4 as cores were prepared to provide magnetic recovery. Through the self-polymerization of dopamine (DA), polydopamine (PDA) was coated on Fe3O4 as shells to protect Fe3O4 cores. Then, Cu2+ coordinated with PDA on the surface of Fe3O4@PDA and in situ reduced by Na2S to obtain core-shell structural Fe3O4@PDA/CuS with CuS uniformly growing on the PDA. CuS with a narrow band gap will endow Fe3O4 @PDA/CuS excellent photocatalytic performance for organic dyes degradation. The decomposition rate of methylene blue (MB) reached to 92.1 % within 180 min under visible light irradiation of Fe3O4@PDA/CuS as photocatalyst without any cocatalyst. When pH= 10, the decomposition rate of MB can reach to 92.7 % in 60 min, indicated Fe3O4@PDA/CuS was more suitable for use under alkaline conditions. The capture experiment determined that·OH was the main active substance. This also explained that under alkaline conditions, numerous OH- was conducive to the formation of ·OH, thus accelerated the degradation rate. And the decomposition rate of MB by Fe3O4@PDA/CuS can still reach 83.95 % after reused three times.

Dual-functional Mo2C quantum dots enriched N-doped graphitic carbon layers in advanced oxidation processes (AOPs)

Advanced oxidation processes (AOPs) are reckoned effective for removing persistent and recalcitrant pollutants by reactive oxygen species (ROSs), including hydroxyl radicals (•OH), sulfate radicals (SO4•-), and superoxide radicals (•O2-), as well as singlet oxygen (1O2). In this work, the Mo2C quantum dots enriched N-doped graphitic carbon layers (Mo2C QDs/NGCLs) were constructed via a facile two-step methodology. Interestingly, the Mo2C QDs/NGCLs acted as a highly efficient cocatalyst and/or catalyst simultaneously in AOPs, in particular visible-light-driven (VLD) Fenton and VLD PMS activation. In the hydroxyl radical-based AOPs (•OH-AOPs), it exhibited a remarkable removal efficiency for a range of aromatic organic pollutants, including rhodamine B (RhB) (99.9 %), phenol (90 %), benzophenone-3 (BZP) (83 %), methyl orange (MO) (58 %), methyl blue (MB) (89 %), ibuprofen (IBU) (100 %), and carbamazepine (CBZ) (50 %). Sulfate radicals-based AOPs (SR-AOPs) effectively degrade RhB (72 %), MO (83 %), IBU (70 %), and BZP (100 %). Thus, the present findings confirmed the potential of transition metal carbides for AOP applications and established a solid theoretical and technical basis for further research.

Uterine decidual stromal cell-derived exosomes mediate the indirect effects of 1-nitropyrene on trophoblast biological behaviors

1-nitropyrene (1-NP) is representative nitropolycyclic aromatic hydrocarbon pollutant widely present in exhaust particles of internal combustion engine, which is known for its carcinogenicity and mutagenicity. Previous studies have demonstrated that 1-NP has reproductive toxicity, but the specific mechanism is unknown. In this study, Human decidual stromal cells (HDSCs) were treated by 1-NP, exosomes were extracted from the conditioned medium of HDSCs, which were then used to treat human chorionic trophoblast cells (HTR8/SVneo) for 24 h. The findings showed that human decidual stromal cell-derived exosomes (HDSC-EXOs) can promote the proliferation, migration, invasion and epithelial-mesenchymal transition (EMT; Vimentin and N-cadherin) of HTR8/SVneo by about 64%, 17%, 23%, 81% and 13%. The process of regulating the biological behaviors of embryonic trophoblast cells by maternal decidual stromal cells during pregnancy was simulated. Further investigations showed that HDSC-EXOs treatment activated the Wnt/β-catenin signaling pathway in HTR8/SVneo. Co-treatment by dickkopf-1 (DKK-1) significantly suppressed the activation of Wnt/β-catenin signaling pathway in HTR8/SVneo, and inhibited the proliferation, migration, invasion and EMT (N-cadherin and E-cadherin) of HTR8/SVneo by about 60%, 22%, 42%, 25%, 55% and 21%. These findings indicated that 1-NP exposure could induce the secretion of HDSC-EXOs from HDSCs, which in turn activate the Wnt/β-catenin signaling pathway and enhance the proliferation, migration, invasion and EMT of HTR8/SVneo.

In-situ SERS detection of aromatic amine pollutants in fire-fighting wastewater using low-cost flexible substrates

Surface-enhanced Raman scattering (SERS) technology has been widely used in the field of environmental pollutant detection due to its fast and intuitive characteristics and low water interference. Herein, a low-cost and flexible SERS substrate was fabricated by transferring gold nanoparticles (NPs) onto polydimethylsiloxane (AuNPs@PDMS) membranes, which enabled highly sensitive detection of aromatic amine pollutants in wastewater after fire suppression. Finite time domain-difference calculations confirmed that the uniformly distributed NP gap significantly enhanced the localized electromagnetic field. The AuNPs@PDMS substrate performed satisfactorily in testing for rhodamine 6G (R6G) with a detection limit (LOD) of 5.5 × 10−10 M. This substrate also demonstrated high reproducibility for detection of different concentrations of R6G and the relative standard deviation (RSD) was <7 %. These excellent SERS properties made AuNPs@PDMS a promising substrate in the detection of aniline and benzidine. Quantitative analysis of aniline and benzidine was achieved with LODs of 4.5 × 10−9 and 7.8 × 10−9 M, respectively. In addition, this substrate could be applied in rapid analysis of mixtures in wastewater after fire suppression using SERS without any complex pretreatments, displaying a great potential for rapid, high-sensitivity, and on-site detection of contaminants in fire-fighting sites.

Facile Synthesis of Hafnium Oxide Nanoparticle Decorated on Graphene Nanosheet and Its Photocatalytic Degradation of Organic Pollutants under UV-Light Irradiation

The HfO2 nanoparticles and the nanocomposites of HfO2-graphene (10, 30, and 50 wt%) were prepared via precipitation and simple mixing method. The XRD pattern confirmed the presence of monoclinic HfO2 and hexagonal graphene in the nanocomposite. Raman spectroscopy studies revealed the formation of HfO2-graphene nanocomposite. According to SEM and TEM images the HfO2, NPs are spherical, and their size is less than 10 nm, anchored on the surface of the graphene sheets. The EDX spectrum shows carbon, oxygen, and HfO2 and reveals the formation of the HfO2-graphene nanocomposite. The UV-vis absorption spectra show the optical properties of synthesized HfO2-graphene nanocomposite. The study examines the influence of different ratios of the addition of graphene on the photocatalytic activity of HfO2-graphene. It was found that the HfO2-graphene (50 wt%) 40 mg nanocomposite exhibits enhanced photocatalytic activity than the bare HfO2 towards the methylene blue photodegradation, an aromatic pollutant in water under UV light irradiation, which can be applied optimally for individually wastewater management system. The HfO2-graphene (50 wt%) photocatalyst degrades 81 ± 2% of tetracycline in 180 min, implying that tetracycline can be degraded more efficiently under UV light. The enhancement in photocatalytic activity under UV light illumination can be attributed to the effective separation of photogenerated electrons, inhibiting recombination in the HfO2-graphene composite.

A water-stable luminescent cadmium-thiazole metal-organic framework for detection of some anionic and aromatic pollutants

Luminescent Cd-MOF, [Cd (DPTTZ) (5-AIP)] (IUST-1) was used for detecting Cr2O72− anion and nitrobenzene (NB) in an aqueous solution. Cd-MOF was synthesized by the reaction of 5-Aminoisophthalic acid (5-AIP), 2, 5-di (pyridine-4-yl) thiazolo [5,4-d] thiazole (DPTTZ), and cadmium nitrate tetrahydrate, via the solvothermal method. The experimental results show that this compound represents significant fluorescence properties, which can be used as a fluorescence sensor for the detection of Cr2O72− anion and nitrobenzene (NB) in water. In addition, this Cd-MOF can perform selectively and sensitively toward these pollutants in presence of other interfering species, which is the main option of sensor materials. The quenching constant Ksv of Cr2O72−anion and NB are 3.314 × 104 ​M−1, 5.84 × 104 ​M−1 and the limit of detection values of Cr2O72−anion and NB are 2.6 × 10−6 ​M, 6.02 × 10−7 ​M, respectively. According to reusability studies, the luminescence property of IUST-1 didn't change significantly up to five cycles.

80 years later: Marine sediments still influenced by an old war ship

Historic shipwrecks form an anthropogenic landmark in marine environment, yet their influence on the local geochemistry and microbiology remains largely unexplored. In this study, sediment and steel hull samples were taken around the V-1302 John Mahn, a World War II shipwreck, at increasing distance from the wreck, in different directions. Polycyclic aromatic hydrocarbons (PAH’s), explosives, and heavy metal levels were determined and related to the microbial composition. Benz(a)anthracene and fluoranthene remain present at the mg kg-1 level, probably originating from the coal bunker. These PAH’s indicate that the wreck is still influencing the surrounding sediments however the effects are very dependent on which side of the wreck is being studied. Known PAH degrading taxa like Rhodobacteraceae and Chromatiaceae were more abundant in samples with high aromatic pollutant content. Moreover, sulphate reducing bacteria (such as Desulfobulbia), proven to be involved in steel corrosion, were found present in the biofilm. This study shows that even after 80 years, a historic shipwreck can still significantly steer the surrounding sediment chemistry and microbial ecology.

Preparations of cyclodextrin polymer and MgO jointly entrapped iron(III)-TAML catalysts for the removal of aromatic pollutants in water

Iron(III)-tetra-amido-macrocyclic (Fe(III)-TAML) activators generally activate H2O2 to efficiently degrade electron-rich pollutants (e.g., phenols) in water under basic conditions, though Fe(III)-TAML is readily demetallized and inactivated under acidic or nearly neutral conditions. Fe(III)-TAML/H2O2 systems often display low reactivity toward electron-deficient pollutants (benzenes) widespread in water. Fe(III)-TAML catalysts with improved pH adaptations and substrate spectra are highly desirable. Herein, we proposed one-pot preparations of cyclodextrin polymer (CDP) and MgO jointly supported Fe(III)-TAML catalysts for the removal of various aromatic contaminants in water. The composite catalysts exhibited typical polymeric network structure of CDP, embedded with basic MgO/Mg(OH)2 particles and three different Fe(III)-TAML species. The composites repeatedly used for 3–4 times still activated H2O2 to completely remove 4-chlorophenol in water during initial pH 2.0–9.0 conditions or in the presence of main water constituents. Despite low Fe(III)-TAML loadings (0.03%–0.10%), these composites displayed great pH adaptations and diverse reactive regions toward organic compounds, compared to other supported catalysts containing 0.24%–1.27% Fe(III)-TAML. Column experiments demonstrated that the composite/H2O2 completely removed electron-rich 4-chlorophenol and electron-deficient benzenes in simulated groundwater. This study indicates that taking CDP as a support may open new prospects for the design of supported catalysts.

Influence of acid-base equilibria on the rate of the chemical reaction in the advanced oxidation processes: Coumarin derivatives and hydroxyl radical

The decomposition and chemical manipulation of stable aromatic pollutants into less toxic products is an important topic for wastewater management and natural water remediation. The mechanism of the Advanced Oxidation Process (AOPs) of 4,7-dihydroxycoumarin (4,7-DHC) and 7-hydroxycoumarin (7-HC), as examples of stable naturally-occurring industrially-important compounds, in the presence of hydroxyl radical (HO) in the aqueous solution has been analyzed using Electron Paramagnetic Resonance spectroscopy (EPR) and Quantum Mechanics-based test for Overall Free Radical Scavenging Activity (QM-ORSA). The effect of pH values of the medium on the investigated reaction mechanisms has been fully investigated. The rate constants were estimated by the conventional transition state theory (TST) and Eckart's method (ZCT_0). Estimated values of the overall rate constant (koverall) higher than >4.06 × 109 M−1 s−1 at all pH values showed that both compounds undergo a chemical transformation when exposed to HO. When pH increased in the range of 0–14, the koverall increased from 4.06 × 109 to 1.11 × 1010 (4.7-DHC) and 2.09 × 109 to 1.76 × 1010 M−1s−1 (7-HC). At physiological pH = 7.4 value, 7-HC was ∼1.5 times more prone to radical action, as shown by EPR and QM-ORSA, due to the dominant anionic form. Both compounds were more reactive towards HO than Trolox at this pH value. The ecotoxicity assessment of the starting compounds, intermediates and oxidation products indicated that the formed products show lower acute and chronic toxicity effects on aquatic organisms than starting compounds, which is a prerequisite for the development of novel AOPs procedures.

Biodegradation of Reactive Red 195 azo dye and Chlorpyrifos organophosphate along with simultaneous bioelectricity generation through bacterial and fungal based biocathode in microbial fuel cell

A laboratory-scale dual-chambered bioanode and biocathode based Microbial Fuel Cell (MFC) was employed in the biodegradation of a dye Reactive Red 195 (RR195) and pesticide chlorpyrifos using bacterial and fungal strains. UV-spectrophotometery and and fourier transform infrared (FTIR) data showed removal rates of almost; 100% for both dye (150 mg/L) and pesticide (50 mg/L) with 70 and 81% Chemical Oxygen Demand (COD) in 18 h and 48 h respectively. Bio-electrochemical degradation of said pollutants was also coupled with simultaneous generation of electricity. The maximal cell potential was recorded to be 635 and 706 mV in bacterial and fungal MFC systems with corresponding power densities of 224.01 and 276.9mWm−2 respectively. Electrochemical performance of MFC reactors in term of cyclic voltammetry (CV) and chronoamperometry (CA) showed maximum electron transfer of 122 and 27.35 mA (applied voltage of −1 to +1 V (CV)) and current densities of 13.8 and 10.66mAcm−2 (CA) in the cathodic compartment where degradation of pollutants accomplished. The reactor was also tested for the simultaneous biodegradation of RR 195 dye in real wastewater along with bioelectricity production. The overall COD and colour removal efficiency was 72 %, and 95 % with concurrent increase in TDS, EC and with a maximum power density output of 519.49 mWm−2. The outcomes of this study revealed that MFC technology is highly effective in the treatment of ecological hazardous aromatic pollutants such as dyes (i.e., RR 195) and pesticides (e.g., chlorpyrifos) and for harnessing energy.

Modelling the octanol-air partition coefficient of aromatic pollutants based on the solvation free energy and the dimer effect

In this study, generalized predictive models were developed to estimate KOA of four kinds of aromatic pollutants based on the calculated solvation free energy and taking the dimer effect into account. Uncorrected log KOA values, which were directly estimated from the calculated solvation free energy of individual molecules, underestimated experimental values, and the deviation increased with increasing log KOA. Dimers were found to greatly affect the apparent KOA values of these aromatic pollutants, which were driven by π-π interactions. London dispersion and exchange-repulsion terms were identified to be dominant components of the underlying π-π interactions. It is interesting to find that the π-π interactions of polybrominated diphenyl ethers correlate with not only the molecular polarizability but also the size of opposing aromatic surfaces, which leads to a different trend of π-π interactions from other aromatic pollutants. A universal quantitative structure-activity relationship model was developed to estimate the proportion of dimers based on five molecular structural descriptors relevant to the π-π interactions. After calibration with the dimer effect, estimations of log KOA were consistent with experimental values. Therefore, the dimer effect should be taken into consideration when investigating the partition behavior of aromatic pollutants, and the solvation free energy model could be an alternative method for the prediction of KOA.

CoFe2O4 functionalized PVDF membrane for synchronous oil/water separation and peroxomonosulfate activation toward aromatic pollutants degradation

Effective synchronous removal of water-immiscible oils and water-miscible refractory aromatic pollutants from wastewater is of great significance for water remediation. In this work, a low-cost and easy-prepared composite membrane was fabricated by vacuum assisted assembling of CoFe2O4 and tannic acid on polyvinylidene fluoride (PVDF) substrate. The CoFe2O4 functionalized PVDF membrane (CoFe2O4@PVDF) exhibited in-air superamphiphilic and underwater superoleophobic surface wettability. The resultant membrane displayed relatively favorable permeation flux (811.5 to 1837.5 Lm−2h−1) and high separation efficiency (above 99 %) in the separation of a series of emulsified oils ranged from nanoscale to microscale from water. Meanwhile, the as-fabricated CoFe2O4@PVDF membrane coupled with peroxymonosulfate (PMS) exhibited an extensive oxidizing capacity and high degradation efficiency towards aromatic contaminants with desired mineralization ability. More importantly, considering that the fabricated CoFe2O4@PVDF membrane possessed special super-wettability as well as PMS activation-based catalytic ability, it also applied in the treatment of simulated complex wastewater. The process achieved effectively synchronous oil/water separation and PMS activation toward pollutants degradation. Besides, in five cyclic continuous “degradation-separation” tests, the recovered CoFe2O4@PVDF membrane after PMS-based degradation in each cycle could separate oil/water emulsions as usual. It exhibited almost complete oil rejection and flux recovery property under multicycle filtration, demonstrating its excellent durability and stability. This flexible integration of PMS-based AOP catalytic capability and super-wettability into a composite membrane can provide inspiration for effective complicated wastewater rehabilitation.

Semi-interpenetrating Network-Coated Silica Gel Based on Green Resources for the Efficient Adsorption of Aromatic Pollutants from Waters

In the framework of the development of green analytical chemistry, a silica gel (SG) coated with a semi-penetrating network based on the partially biosourced poly(ethersulfone) is studied for a greener extraction process of aromatic organic pollutants. An optimized composition of the semi-penetrating network (80% of the linear polymer (LP): isosorbide-based poly(ethersulfone) and 20% cross-linking agent (XP) type bismaleimide) leads to a total adsorption of the selected aromatic pollutants, whatever their hydrophilicity. Adsorption characteristic, kinetics and isotherms of the SG-semi-INP LP80/XP20 for p-hydroxybenzoic acid and for toluic acid were studied. Langmuir model led to a better fitting of the adsorption isotherms; the adsorption of toluic acid is easier than that of p-hydroxybenzoic acid. 1/n values of benzoic acid was lower for SG-semi-INP LP80/XP20 compared to biochar and to cross-linked methacrylate resin, showing a higher adsorption efficiency.

Ultra-sensitive solid-phase Microextraction-Gas Chromatography-Mass spectrometry determination of polycyclic aromatic hydrocarbons in snow samples using a deep cavity BenzoQxCavitand.

A very sensitive and selective solid-phase microextraction-gas chromatography-mass spectrometry method based on the use of a deep cavity BenzoQxCavitand as innovative coating was developed and validated for the simultaneous determination of the 16 US-EPA priority pollutants polycyclic aromatic hydrocarbons (PAHs) in snow samples at ultra-trace levels. The presence of a 8.3Å deep hydrophobic cavity allowed the engulfment of all the 16 PAHs, providing enhanced selectivity also in presence of interfering aromatic pollutants at high concentration levels. Validation proved the reliability of the method for the determination of the investigated compounds achieving detection limits in the 0.03-0.30ng/L range, good precision, with relative standard deviations <18% and recovery rates in the 90.8(±2.1)%-109.6(±1.0)%. The detection of low-molecular weight PAHs in snow samples from Antarctica and Alps confirms the widespread occurrence of these compounds, thus assessing the impact of anthropogenic activities onto the environment.

Surface and Trapping Energies as Predictors for the Photocatalytic Degradation of Aromatic Organic Pollutants

In this study, anatase samples enclosed by the majority of three different crystal facets {0 0 1}, {1 0 0}, and {1 0 1} were successfully synthesized. These materials were further studied toward photocatalytic degradation of phenol and toluene as model organic pollutants in water and gas phases. The obtained results were analyzed concerning their surface structure, reaction type, and surface development. Moreover, the regression model was created to find the correlation between the possible predictors and the photodegradation rate constants (k). From the studied factors, the trapping energy of charge carriers at the surface was found to be the most significant one, exponentially affecting the observed k. This resulted in the overall per-surface activity between the samples being in the order {1 0 1} > {1 0 0} > {0 0 1}. Further introduction of the surface energy (Esurf) to the regression model and the number of possible trapping centers per number of pollutant’s molecules (ntrap·n–1) improved the model accuracy, simultaneously showing the dependence on the reaction type. In the case of phenol photocatalytic degradation, the best accuracy was observed for the model including Esurf ·(ntrap·n–1)1/2 relation, while for the toluene degradation, it included Esurf2 and the S·n–1 ratio, where S is the simple surface area. Concerning different surface features which influence photocatalytic performance and are commonly discussed in the literature, the results presented in this study suggest that trapping is of particular importance.

Detection of BaP in seawater based on multi-walled carbon nanotubes composites immunosenor.

Benzo(a)pyrene, as the main polycyclic aromatic hydrocarbon pollutant in marine oil spill pollution, has negative effects on marine ecology and human health. A facile and sensitive method of rapid benzo(a)pyrene detection in seawater is essential for marine conservation. In this paper, a novel immunosensor is fabricated using a multi-walled carbon nanotubes-chitosan composite loaded with benzo(a)pyrene antibody. This immunosensor is based on a biosensing assay mechanism that uses multi-walled carbon nanotubes-chitosan composites as conductive mediators to enhance electron transfer kinetics. Then, potassium ferricyanide was used as an electrochemical probe to produce an electrochemical signal for the voltammetric behavior investigation of the immune response by differential pulse voltammetry. Under optimal experimental conditions, the peak current change was inversely proportional to the benzo(a)pyrene concentration in the range of 0.5 ng⋅ml−1 and 80 ng⋅ml−1 with a detection limit of 0.27 ng⋅ml−1. The immunosensor was successfully applied to assay BaP in seawater, and the recovery was between 96.6 and 100%, which exhibited a novel, sensitive and interference-resistant analytical method for real-time water environment monitoring. The results demonstrate that the proposed immunosensor has a great potential for application in the monitoring of seawater.