Photodegradation Of Anthracene Research Articles

Photodegradation of Polycyclic Aromatic Hydrocarbons Under Visible Light Using Modified g-C3N4 as Photocatalyst, Spectroscopic Studies

In this work, visible light was used for the photodegradation of polycyclic aromatic hydrocarbons (PAHs) using graphitic carbon nitride (g-C3N4) and it was modified as a photocatalyst. Modification of g-C3N4 was performed using SDS, MIL-101, and TiO2. The UV–Vis spectroscopy, XRD, and FTIR spectrometry were applied for characterization. The photodegradation of pyrene and anthracene was investigated using the photocatalyst. Results indicated that the modified photocatalytic has better photocatalytic properties than that unmodified due to the more surface area and better optical properties of the former. Results also revealed that the photodegradation efficiency significantly improved by using g-C3N4@TiO2 so that it degrades about 95% of the pyrene molecules within 12 h. While g-C3N4@ SDS and g-C3N4@ MIL-101 are degraded very low (below 10%) under the same circumstances. The LED lamp (8 W) was used as a source of radiation. Photodegradation of anthracene was also investigated; results revealed that the anthracene is degraded more quickly than the pyrene, so that after 6 h about 98% of anthracene is decomposed. The mechanism of photodegradation was discussed.

Photodegradation enhances the toxic effect of anthracene on skin

Anthracene, a polycyclic aromatic hydrocarbon (PAH), is a widespread environmental pollutant that poses potential risks to human health. Exposure to anthracene can result in various adverse health effects, including skin-related disorders. Photo exposure sufficiently removes the anthracene from the environment but also generates more degradation products which can be more toxic. The goal of this study was to assess the change in anthracene dermotoxicity caused by photodegradation and understand the mechanism of this change. In the present study, over 99.99% of anthracene was degraded within 24 h of sunlight exposure, while producing many intermediate products including 9,10-anthraquinone and phthalic acid. The anthracene products with different durations of photo exposure were applied to 2D and 3D human keratinocyte cultures. Although the non-degraded anthracene significantly delayed the cell migration, the cell viability and differentiation decreased dramatically in the presence of the photodegraded anthracene. Anthracene photodegradation products also altered the expression patterns of a number of inflammation-related genes in comparison to the control cells. Among these genes, il1a, il1b, il8, cxcl2, s100a9, and mmp1 were upregulated whereas the tlr4 and mmp3 were downregulated by the photodegraded anthracene. Topical deliveries of the photodegraded and non-degraded anthracene to the dorsal skin of hairless mice showed more toxic effects by the photodegraded anthracene. The 4-hour photodegradation products of anthracene thickened the epidermal layer, increased the dermal cellularity, and induced the upregulation of inflammatory markers, il1a, il1b, s100a9, and mmp1. In addition, it also prevented the production of a gap junction protein, Connexin-43. All the evidence suggested that photodegradation enhanced the toxicities of anthracene to the skin. The 4-hour photodegradation products of anthracene led to clinical signs similar to acute inflammatory skin diseases, such as atopic and contact dermatitis, eczema, and psoriasis. Therefore, the potential risk of skin irritation by anthracene should be also considered when an individual is exposed to PAHs, especially in environments with strong sunlight.

Synthesis of graphene nanosheets from coffee ground waste and its incorporation to mixed-phase TiO2 as photocatalyst in anthracene degradation

The increasing level of coffee consumption in Indonesia causes a significant amount of coffee ground waste as landfill, leading to serious environmental problems on account of phenol derivatives and acidic compounds as its constituents. Containing high carbon content, waste coffee ground is a favourable biomass candidate to be converted into carbon-based material, such as graphene nanosheet (GN). Having wide surface area, graphene derivatives can be used to modify surface of many materials, such as TiO2. The aim of this study is to synthesize graphene-modified TiO2 with a mixed anatase:rutile phase (9:1) and to analyse its photocatalytic activity towards the photodegradation of anthracene, in comparison with unmodified TiO2. UV-DRS analysis showed a significant decrease in the band gap of TiO2/GN-A (2.78 eV) compared with TiO2 (3.00 eV), leading to an increase in photocatalytic activity (Kt TiO2 = 7.26 × 10-4 min−1; Kt TiO2/GN-A = 3.43 × 10-3 min−1). All in all, the synthesized photocatalyst materials presented promising potential to be applied as photocatalysts in photodegradation of organic compounds.

Effect of carboxyl and hydroxyl groups attached to the benzene ring on the photodegradation of polycyclic aromatic hydrocarbons in ice.

The effect of carboxyl and hydroxyl groups attached to the benzene ring on the photodegradation of anthracene (Ant) and pyrene (Pyr) in ice was investigated. The present study aims to explore the inhibition mechanism of five dissolved organic matter (DOM) model compounds' materials such as benzoic acid, o-hydroxybenzoic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, and 3-phenyl propionic acid on the degradation of Ant and Pyr in ice. The photodegradation rate of Ant and Pyr were 50.33 and 37.44% in ice, with the photodegradation rate of Ant being greater than that of Pyr. The five DOM model compounds inhibited the photolysis of Ant and Pyr, and the influence mechanism on the photodegradation of Ant and Pyr depended upon the types and positions of functional groups on the benzene. Among them, the structure in which the carboxyl group was directly connected to the benzene ring and carboxyl was located at the ortho position of a hydroxy group had a strong inhibitory effect on the photodegradation of Ant and Pyr. Light-screening effects and quenching effects were the main inhibiting mechanism, and the binding ability of DOM model compounds material and PAHs is dominantly correlated with its inhibiting effect.

Indirect photodegradation of anthracene and pyrene induced by dissolved organic matter derived reactive species in ice

The influences of dissolved organic matter (DOM) derived reactive species (RS), including singlet oxygen (1O2), hydroxyl radical (•OH) and triplet excited state DOM (3DOM*) on the photodegradation kinetics of polycyclic aromatic hydrocarbons (PAHs) in ice, as well as the spectroscopic changes of PAHs in ice caused by DOM-induced photodegradation were investigated. Anthracene (Ant) and pyrene (Pyr) were chosen as model compounds in this study. The minimum contributions of RS generated from the four DOM to the photodegradation of Ant and Pyr were higher than 20.0 %. •OH contributed more to the photodegradation of Ant and Pyr than 3DOM*. When PAHs coexisted with DOM, direct photodegradation and indirect photodegradation via reaction with 3DOM* seem to have no effect on aliphatic C−C functional groups corresponding to the peak at 1450 cm−1; Photodegradation pathways other than reaction with •OH resulted into the production of C−O functional groups corresponding to the peak at 1113 cm−1; the production of C═O functional groups corresponding to the peak at 1567 cm−1 and the elimination of amide-2 functional groups corresponding to the peak at 1567 cm−1 were attributed to direct photodegradation and indirect photodegradation via reaction with 1O2 and •OH. The fluorescence intensity decreases of Ant when coexisted with DOM were mainly attributed to its direct photodegradation, whereas indirect photodegradation induced by DOM contributed more to fluorescence intensity decreases of Pyr than direct photodegradation.

New Insights into the Phototoxicity of Anthracene-Based Chromophores: The Chloride Salt Effect†.

Unraveling the causes underlying polycyclic aromatic hydrocarbon phototoxicity is an essential step in understanding the harmful effects of these compounds in nature. Toward this end, we have studied the DNA interactions and photochemistry of N1-(anthracen-9-ylmethyl)ethane-1,2-diaminium dichloride in the presence and absence of NaF, KF, NaCl, KCl, NaBr, KBr, NaI, and KI (350 nm hν, pH 7.0). Exposing pUC19 plasmid to UV light in solutions containing 400 mM KCl formed significantly more direct strand breaks in DNA compared to no-salt control reactions. In contrast, NaCl increased DNA damage moderately, while the sodium(I) and potassium(I) fluoride, bromide, and iodide salts generally inhibited cleavage (I- > Br- > F-). A halide anion-induced heavy-atom effect was indicated by monitoring anthracene photodegradation and by employing the hydroxyl radical (•OH) probe hydroxyphenyl fluorescein (HPF). These studies revealed that among no-salt controls and the eight halide salts, only NaCl and KCl enabled the anthracene to photosensitize the production of high levels of DNA-damaging reactive oxygen species (ROS). Pre-irradiation of N1-(anthracen-9-ylmethyl)ethane-1,2-diaminium dichloride at 350 nm increased the amounts of chloride salt-induced •OH detected by HPF in subsequent anthracene photoactivation experiments. Taking into consideration that •OH and other highly reactive ROS are extremely short-lived, this result suggests that the pre-irradiation step might lead to the formation of oxidized anthracene photoproducts that are exceedingly redox-active. The fluorometric probes HPF and Singlet Oxygen Sensor Green revealed that KCl concentrations ranging from 150 to 400 mM and from 100 to 400 mM, respectively, enhanced N1-(anthracen-9-ylmethyl)ethane-1,2-diaminium dichloride photosensitized •OH and singlet oxygen (1O2) production over no-salt controls. Considering the relatively high levels of Na+, K+, and Cl- ions that exist in the environment and in living organisms, our findings may be relevant to the phototoxic effects exhibited by anthracenes and other polycyclic hydrocarbons in vivo.

Synthesis and characterization of Ni-doped TiO2 activated carbon nanocomposite for the photocatalytic degradation of anthracene

Nickel-doped titanium dioxide nanoparticles (NDT) deposited on pine cone activated carbon (PAC) have been successfully synthesized by a hydrothermal method. The as synthesized nanocomposite was characterized by X-ray diffraction pattern (XRD), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron (XPS), Fourier transform infrared (FT-IR), UV–visible diffuse reflectance spectra (UV–vis DRS), Photoluminescence (PL), BET surface area, and pHzpc. The characterization results of the prepared nanocomposite revealed that Ni-TiO2 was loaded on the surface of PAC, and had a higher surface area and narrower bandgap than TiO2 nanoparticles. The visible-light photocatalytic activity of the Ni-TiO2@C nanocomposite towards anthracene degradation was found to be 99.9% in 50 mins leading to end products of (1E, 3Z)-hexa-1,3,5-trien-1-ol (1a; m/z = 96), and (1E, 3E)-penta-1,3-dien-1-ol. The synthesized Ni-TiO2@C nanocomposite exhibited a better photocatalytic activity towards the photocatalytic degradation of anthracene as compared to the TiO2 nanomaterial (22.5%) and TiO2/activated carbon nanocomposite (31%) under similar conditions. The photodegradation of anthracene followed the pseudo first-order rate kinetics. The Ni-TiO2@C nanocomposite had excellent regeneration properties till the fifth cycle of use during which it degraded around 73% anthracene.

Solar light mediated anthracene abatement in aerated aqueous media using a thermoplastic nanocomposite photocatalyst.

Polycyclic aromatic hydrocarbons (PAHs) are the most widespread xenobiotic pollutants in water and their abatement usually involves expensive and energy-consuming treatments. In this work, anthracene (AN) was selected as the recalcitrant model of PAHs and its solar light-stimulated heterogeneous photocatalytic abatement in aerated aqueous media was investigated using a new TiO2 derived thermoplastic nanocomposite in thin film form. The results were also compared with the benchmark TiO2 photocatalyst in slurry form. Finally, the possible contribution of reactive intermediates such as hydroxyl radical, AN radical cation and singlet oxygen, was investigated by using a hydroxyl radical trap and laser flash photolysis. Based on the obtained results, a feasible mechanism for AN photodegradation, which involves hydroxyl radical as the key oxidizing species is proposed.

Direct Observation of Anthracene Clusters at Ice Surfaces.

Heterogeneous processes can control atmospheric composition. Snow and ice present important, but poorly understood, reaction media that can greatly alter the composition of air in the cryosphere in polar and temperate regions. Atmospheric scientists struggle to reconcile model predictions with field observations in snow-covered regions due in part to experimental challenges associated with monitoring reactions at air-ice interfaces, and debate regarding reaction kinetics and mechanisms has persisted for over a decade. In this work, we use wavelength-resolved fluorescence microscopy to determine the distribution and chemical speciation of the pollutant anthracene at environmentally relevant frozen surfaces. Our results indicate that anthracene adsorbs to frozen surfaces in monomeric form, but that following lateral diffusion, molecules ultimately reside within brine channels at saltwater ice surfaces, and in micron-sized clusters at freshwater ice surfaces; emission profiles indicate extensive self-association. We also measure anthracene photodegradation kinetics in aqueous solution and artificial snow prepared from frozen freshwater and saltwater solutions. Our results suggest that anthracene─and likely other aromatic pollutants─undergo bimolecular photodegradation at the surface of freshwater ice and sea ice, but not at the surface of frozen organic matter. These results will improve predictions of pollutant fate and exposure risk in the cryosphere. The techniques used can be applied to numerous surfaces within and beyond the atmospheric sciences.

Application of concrete modified with TiO2 to reduce anthracene concentration

In this study, samples of fine-grained concrete with the additive T1O2 microparticles were made. The photocatalytic properties of TiO2 for the decomposition of anthracene in solutions under UV irradiation were studied. To evaluate the efficiency of photodegradation, the method of luminescence analysis was used. For improving the quality of the analyzed solutions, model surfaces were made based on chitosan with the addition of TiO2. According to the results of the experiments, it was found that the degree of photodegradation of anthracene in solutions using solid chitosan-TiO2 matrices reaches 74% after 60 minutes under UV irradiation. The conducted studies confirm the feasibility of using chitosan-TiO2 matrices as model surfaces for studying the photocatalytic properties of TiO2 for the oxidation of anthracene.

Ag/TiO2 photocatalyst immobilized onto modified natural fibers for photodegradation of anthracene

This study reports the application of immobilized Ag/TiO2 onto coconut and sisal fibers to anthracene degradation via the UV–vis radiation. The fibers were previously treated with hot water and CTAB to clean their impurities surfaces. Immobilizations of Ag/TiO2 to the fibers were performed by anchorage of the catalysts via the post-synthesis method. The materials were characterized using AAS, TGA, XRD, UV–vis DRS, FTIR, STEM, EDS, and XPS analysis. FTIR and XPS results indicated the presence of hydroxyl groups and different silver species (Ago, Ag+, and Ag2+) on the catalyst surface. Immobilized Ag/TiO2 exhibited higher activity as compared to suspended Ag/TiO2 and TiO2. Ag/TiO2 immobilized on fibers treated with CTAB promoted the full anthracene photodegradation within 2 h at 40 °C. The results demonstrated that sisal and coconut fibers could be used as a support for Ag/TiO2.

Dissolved organic matter-mediated photodegradation of anthracene and pyrene in water

Toxicity and transformation process of polycyclic aromatic hydrocarbons (PAHs) is strongly depended on the interaction between PAHs and dissolved organic matters (DOM). In this study, a 125W high-pressure mercury lamp was used to simulate the sunlight experiment to explore the inhibition mechanism of four dissolved organic matters (SRFA, LHA, ESHA, UMRN) on the degradation of anthracene and pyrene in water environment. Results indicated that the photodegradation was the main degradation approach of PAHs, which accorded with the first-order reaction kinetics equation. The extent of degradation of anthracene and pyrene was 36% and 24%, respectively. DOM influence mechanism on PAHs varies depending upon its source. SRFA, LHA and ESHA inhibit the photolysis of anthracene, however, except for SRFA, the other three DOM inhibit the photolysis of pyrene. Fluorescence quenching mechanism is the main inhibiting mechanism, and the binding ability of DOM and PAHs is dominantly correlated with its inhibiting effect. FTIR spectroscopies and UV–Visible were used to analyze the main structural changes of DOM binding PAHs. Generally, the stretching vibration of N–H and C–O of polysaccharide carboxylic acid was the key to affect its binding with anthracene and C–O–C in aliphatic ring participated in the complexation of DOM and pyrene.

Photolysis of a mixture of anthracene and benzo[a]pyrene at ultra-trace levels in natural water with disinfection purposes

The photodegradation of anthracene (AN) and benzo[a]pyrene (BaP), two priority polycyclic aromatic hydrocarbons (PAHs), was examined at ultra-trace levels in surface water to elucidate their behaviour under several irradiance values and types of radiation. The emitting flux and the spectrum of the lamps were found to develop a crucial role in AN and BaP degradation since removal efficiencies of the target contaminants higher than 99% were found after 15 min of irradiation under an ultraviolet C (UVC) irradiance of 0.63 mW/cm2, corresponding to a fluence of 560.25 mJ/cm2. On the other hand, although ultraviolet A (UVA) lamps exhibited a higher irradiance compared to that of UVC lamps, they were not efficient for degrading the target PAHs. The removal kinetic studies corroborated these findings, being the AN elimination rate in surface water higher than that in deionized water at optimal operating conditions. Disinfection potential was also measured. A rapid microbial load inactivation, in terms of total coliforms naturally contained in the water matrix studied, was evidenced within 15 min of treatment for the fluence referred. However, after 24 hr in the dark, a regrowth was observed. Additionally, photolysis products more toxic than the parent compounds were found, which were not removed even by extending the treatment time. In this regard, it can be concluded that the individual action of UVC light for removing AN and BaP with disinfection purposes is not an efficient treatment; therefore, the use of radiation in combination with other kinds of treatments is required.

Synthesis and characterization of n-ZnO/p-MnO nanocomposites for the photocatalytic degradation of anthracene

n-ZnO/p-MnO nanocomposites with different percentages of manganese (0.5%, 1.1%, and 2.25%) with a semiconducting junction were prepared. Changes in Flat band potential (Efb) for ZnO due the different amounts of MnO was observed, meanwhile same donor density (Nd) was held in all materials. From chronoamperometric experiments under on-off illuminated conditions a transient time constant (τ), related to the electron transport in the electrodes were calculated, where higher values are observed in materials with high amounts of MnO. Photodegradation studies of anthracene in an ethanol:water (1:1, pH 12) solution were performed, showing that anthraquinone is the main product with no photodegrading of ethanol. The results suggest that the junction n-ZnO/p-MnO and materials with high transient time constant (τ), enhance the photocatalytic degradation. The best photocatalytic performance for the photodegradation of anthracene was obtained with the nanocomposite n-ZnO /p-MnO(Mn=2.25%).

The Role of Iron Oxide on the Photodegradation of Polycyclic Aromatic Hydrocarbons: Characterization and Toxicity

ABSTRACTLaboratory experiments were conducted to study the photocatalytic capability of amorphous α-Fe2O3 to degrade polycyclic aromatic hydrocarbons (PAHs). Solutions containing 16 US EPA priority PAHs were spiked with Fe2O3 and incubated in a climate chamber at stable conditions of temperature (20°C) and light (9.6 W·m−2) for 28 days. In addition, samples without Fe2O3 were also incubated. PAHs levels were monitored by means of GC–MS, and their toxicity was assessed using Microtox® bioassay. Fe2O3 had a significant photocatalytic effect on fluorene, phenanthrene, and benzo(a)pyrene, the photodegradation rate of the latter being 71% and 50% in presence and absence of Fe2O3, respectively. On the other hand, photolysis was significantly higher than photocatalysis for benzo(a)anthracene and dibenzo(ah)anthracene. Photodegradation of anthracene was notably the same regardless of Fe2O3 presence. Remaining PAHs were not photodegraded, neither with, nor without Fe2O3. These results indicated that, in some cases, Fe2O3 might act as a shield for PAHs by hindering their photodegradation. Other factors, such as the chemical structure of the Fe2O3, and also the absence of the soil matrix components (i.e., humic acid, other metals oxides, and texture) could also play a role. Photodegradation trends were supported by changes of EC50 values, suggesting the formation of more bioavailable or toxic PAHs by-products when Fe2O3 and light were present.

Effects of oil dispersants on photodegradation of parent and alkylated anthracene in seawater

This study investigated effects of three model oil dispersants on photodegradation of two model PAHs (anthracene and 9,10-dimethyanthracene (9,10-DMA)) under simulated sunlight. All three dispersants, i.e. Corexit EC9500A, Corexit EC9527A and SPC 1000, promoted the photolysis rate of 9,10-DMA, following the order of Corexit EC9500A > Corexit EC9527A > SPC 1000. The photodegradation rate was well interpreted by a two-stage, first-order kinetic law with a faster initial photolysis rate in the presence of the dispersants. Span 80, Tween 85 and kerosene were found as the key dispersant components, of which Span 80 and Tween 85 promoted the photodegradation by boosting absorbance of solar irradiation while kerosene by dispersing more PAHs in the upper layer of the water column. Dissolved oxygen (DO) inhibited photolysis of anthracene regardless of dispersant resulting from quenching the excited states of the PAH, while DO facilitated photolysis of 9,10-DMA due to the formation singlet oxygen (1O2) radicals in the presence of oil dispersants. The other ROS, i.e. •O2− and •OH, played a negligible role on the photodegradation of anthracene and 9,10-DMA. Fluorescence analysis showed that more anthracene was associated with dispersant than 9,10-DMA, which favored the direct transfer of energy to anthracene, while energy is more likely transferred to oxygen to form 1O2 in the case of 9,10-DMA. Direct photolysis dominated the photodegradation of anthracene and 9,10-DMA. Both direct ionization of anthracene and the electron transfer from excited 9,10-DMA to oxygen can lead to formation of the corresponding PAH radical cations. Overall, the oil dispersants accelerated the photolysis rates of the PAHs without altering the degradation pathway. The findings are useful for understanding photochemical weathering of dispersed oil components in the environment.

Photocatalytic efficiency of iron oxide nanoparticles for the degradation of priority pollutant anthracene

The present work demonstrates an efficient and cost effective methodology for the synthesis of iron oxide nanoparticles without the assistance of any capping agent. Two different forms of iron oxide nanoparticles, namely, goethite (α-FeOOH) and magnetite (Fe3O4) were synthesized and characterized through X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The XRD spectra were found concordant with JCPDS-ICDD data. The crystallite sizes for goethite and magnetite were found to be 9.85 and 14.13 nm, respectively. The mean particle sizes estimated via SEM analysis were 32.23 and 63.27 nm, respectively. Energy-dispersive X-ray (EDX) spectroscopy was used to estimate the elemental composition of the synthesized nanoparticles (NPs). The NPs were further used for the degradation of anthracene in the presence of UV light. The decay profiles of anthracene,a polycyclic aromatic hydrocarbon listed as a priority pollutant by United States Environmental Protection Agency (USEPA), were investigated with different forms of iron oxides NPs under UV irradiation at ambient temperature. Both forms of iron oxides were efficient for the photodegradation of anthracene. The decay profiles in both the cases followed the first-order kinetics. The half-lives for anthracene degradation were 3.21 and 4.39 h with α-FeOOH and Fe3O4, respectively. The results reveal that the photocatalytic activity of magnetite is low as compared to goethite.

Effect of phenolic compounds on photodegradation of anthracene and benzo[a]anthracene in media of different polarity

Abstract The photodegradation of anthracene (Ant) and benz[a]anthracene (BaA) were studied in air-equilibrated hexane, methanol and pure water solutions in the absence and presence of phenolic compounds (4-methylcatechol, guaiacol and syringol). In the absence of phenolic compound, the pseudo first-order degradation rate constants of Ant and BaA increased with the polarity of solvent, demonstrating the influence of solvent effects on the photoreactivity. The differences can be attributed to factors such as the proton donating potential of the solvent, and the formation potentials of PAH radical cation and hydroxyl radical in solvent. In the presence of phenolic compound, Ant and BaA photodegradation rates were accelerated in hexane and methanol while inhibited in water solutions. Photodegradation kinetics of the phenolic compounds were also measured; and visible colored products were observed in all three solvents. The observed accelerations of Ant and BaA photodecay in the presence of the phenolic compounds can be explained by energy transfer from the phenolic compound to PAH, phenolic hydrogen abstraction by excited PAH and more reactive radical formation from the phenolic compound. However, the inhibition effects of Ant and BaA photodecay in water were more influenced by the quenching of photo-produced reactive oxygen species (ROS) by the phenolic compound and/or its photoproducts. The results indicate that the photodegradation of PAHs will be highly dependent on the aerosol water content. i.e., the chemical composition of the environmental aerosols.

Direct observation of the photodegradation of anthracene and pyrene adsorbed onto mangrove leaves.

An established synchronous fluorimetry method was used for in situ investigation of the photodegradation of pyrene (PYR) and anthracene (ANT) adsorbed onto fresh leaves of the seedlings of two mangrove species, Aegiceras corniculatum (L.) Blanco (Ac) and Kandelia obovata (Ko) in multicomponent mixtures (mixture of the ANT and PYR). Experimental results indicated that photodegradation was the main transformation pathway for both ANT and PYR in multicomponent mixtures. The amount of the PAHs volatilizing from the leaf surfaces and entering the inner leaf tissues was negligible. Over a certain period of irradiation time, the photodegradation of both PYR and ANT adsorbed onto the leaves of Ac and Ko followed first-order kinetics, with faster rates being observed on Ac leaves. In addition, the photodegradation rate of PYR on the leaves of the mangrove species in multicomponent mixtures was much slower than that of adsorbed ANT. Compared with the PAHs adsorbed as single component, the photodegradation rate of ANT adsorbed in multicomponent mixtures was slower, while that of PYR was faster. Moreover, the photodegradation of PYR and ANT dissolved in water in multicomponent mixtures was investigated for comparison. The photodegradation rate on leaves was much slower than in water. Therefore, the physical-chemical properties of the substrate may strongly influence the photodegradation rate of adsorbed PAHs.

Photodegradation of Anthracene and Benzo[a]anthracene in Polar and Apolar Media: New Pathways of Photodegradation

The photochemical reactions of anthracene and benzo[a]anthracene polycyclic aromatic hydrocarbons (PAHs) in polar and apolar solvents (cyclohexane and water/acetonitrile) were studied using spectroscopic and chromatographic techniques. These homogenous photolysis experiments are used as simplified models to compare PAHs photochemistry in water and oil (or oil films). Moreover, these processes were to some extent used as model in literature in order to study those occurring on particulate matter and aerosol surfaces. In both media, new photochemical reaction products were found. Generally, the reaction rate in the polar medium is faster than that in the apolar medium, and the photodegradation quantum yields increase with increasing polarity of the medium. HPLC-absorption/emission analysis confirmed the literature reports that mainly oxygenated photoproducts, such as PAH-hydroxides, were formed. The novelty of this article is that GC-MS data revealed the presence of new photoproducts that have not yet been described. This simplified model system allowed us to characterize the product distribution, thus simplifying the interpretation of the photodegradation mechanism. The identification of new photofragmentation paths, originating by irradiation of primary PAH photoproducts, may suggest an innovative way of remediation triggered by light.