Investigating the stability of aromatic carboxylic acids in hydrated magnesium sulfate under UV irradiation to assist detection of organics on Mars

The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument onboard the Mars 2020 Perseverance rover detected so far some of the most intense fluorescence signals in association with sulfates analyzing abraded patches of rocks at Jezero crater, Mars. To assess the plausibility of an organic origin of these signals, it is key to understand if organics can survive exposure to ambient Martian UV after exposure by the Perseverance abrasion tool and prior to analysis by SHERLOC. In this work, we investigated the stability of organo-sulfate assemblages under Martian-like UV irradiation and we observed that the spectroscopic features of phthalic and mellitic acid embedded into hydrated magnesium sulfate do not change for UV exposures corresponding to at least 48 Martian sols and, thus, should still be detectable in fluorescence when the SHERLOC analysis takes place, thanks to the photoprotective properties of magnesium sulfate. In addition, different photoproduct bands diagnostic of the parent carboxylic acid molecules could be observed. The photoprotective behavior of hydrated magnesium sulfate corroborates the hypothesis that sulfates might have played a key role in the preservation of organics on Mars, and that the fluorescence signals detected by SHERLOC in association with sulfates could potentially arise from organic compounds.

Photocatalytic Degradation of Naproxen: Intermediates and Total Reaction Mechanism

Photochemical and photocatalytic oxidation of naproxen (NPX) with UV-A light and commercial TiO2 under constant flow of oxygen have been investigated. Adsorption experiments indicated that 90% of the solute remained in the solution. Combined chemical analysis of samples on the photochemical degradation indicated that NPX in an aqueous solution (20 ppm) is efficiently transformed into other species but only 18% of the reactant is mineralized into CO2 and water after three hours of reaction. Performing the photocatalytic oxidation in the presence of TiO2, more than 80% of the organic compounds are mineralized by reactive oxidation species (ROS) within four hours of reaction. Analysis of reaction mixtures by a combination of analytical techniques indicated that naproxen is transformed into several aromatic naphthalene derivatives. These latter compounds are eventually transformed into polyhydroxylated aromatic compounds that are strongly adsorbed onto the TiO2 surface and are quickly oxidized into low-molecular-weight acids by an electron transfer mechanism. Based on this and previous studies on NPX photocatalytic oxidation, a unified and complete degradation mechanism is presented.

Synthesis and Photocatalytic Activity of Novel Polycyclopentadithiophene

A novel π-conjugated polymer based on cyclopentadithiophene (CPDT) and poly(4,4']-(((4Hcyclopenta[2,1-b:3,4-b']dithiophene-4,4-diyl)bis(ethane-2,1-diyl))bis(oxy))bis(4-oxobutanoic acid)) (PCPDT-CO2H) was prepared as a sparingly soluble material. The generation of hydroxyl radicals from PCPDT-CO2H in water was confirmed by using coumarin as a hydroxyl radical indicator. Furthermore, PCPDT-CO2H was found to catalyze the oxidative hydroxylation of arylboronic acid and the oxidation of benzaldehyde, indicating that PCPDT-CO2H can be a promising candidate for metal-free and 100% organic heterogeneous photocatalysts.

Acute and Subchronic Oral Toxicity of Anthraquinone in Sprague Dawley Rats

Objective: This study was conducted to evaluate the acute and subchronic toxicity of anthraquinone. An acute toxicity test was performed in female Sprague Dawley (SD) rats, and the oral median lethal dose (LD50) of anthraquinone was estimated to be >5000 mg/kg body weight (BW). In the subchronic study, groups of 10 male and 10 female rats were dosed with anthraquinone by gavage at 0, 1.36, 5.44, 21.76, and 174.08 mg/kg BW, 7 days/week for 90 days followed by a recovery period of 28 days. No appreciable toxic-related changes were observed in the 1.36 mg/kg BW group. When the animals received 5.44 mg/kg BW or more of anthraquinone, hyaline droplet accumulation in the renal tubules was observed in both the male and female rats, and anemia was observed in the females. When the anthraquinone dose reached 174.08 mg/kg BW, mild hepatocellular hypertrophy around the central vein of the hepatic lobule and hypothyroidism were observed in the female rats. During the recovery period, changes in clinical symptoms and parameters were considerably alleviated. Based on the results of this study, the no observed adverse effect level (NOAEL) for anthraquinone in rats was set at 1.36 mg/kg BW, and the lowest observed adverse effect level (LOAEL) was 5.44 mg/kg BW.

Humidity induces the formation of radicals and enhances photodegradation of chlorinated-PAHs on Fe(III)-montmorillonite

Chlorinated-PAHs (ClPAHs) are widely detected in the soil surface and atmospheric particles. However, the underlying mechanisms of their photodegradation are not well understood. In the present study, the formation of radicals on ClPAHs-contaminated clay minerals was quantitatively monitored via electron paramagnetic resonance (EPR) spectroscopy, and the impact of relative humidity (RH) was systematically explored. ClPAHs removal (> 75%) was attributed to electron transfer and •OH attack. The degradation easiness of ClPAHs follows: 2-ClNAP >2-ClANT >9-ClPHE >1-ClPYR. Light irradiation significantly improved the generation of reactive oxygen species (ROS, such as •OH and •O₂^-), and further generate a series of hydroxylated products of ClPAHs. Persistent free radicals (PFRs) were only detected on clay minerals contaminated with 2-ClANT and 1-ClPYR. RH 10-80%, the concentration of •OH and •O₂^- increased by 1.07 and 62.79 times respectively, which facilitated transformation of PFRs and ClPAHs degradation. The results of quantum chemical calculations indicate that the initial reaction of ClPAHs photodegradation is mediated by the substitution of •OH for chlorine groups. The present work implies that higher humidity may decrease the generation of PFRs on clay minerals and help mitigate the threats of PFRs and ClPAHs to human health.

Different metabolic pathways involved in anthracene biodegradation by Brevibacillus, Pseudomonas and Methylocystis Species

Background

Polycyclic aromatic hydrocarbons (PAHs) such as anthracene are one of the most toxic contaminants to our environment. Microbial biodegradation of these xenobiotics is a cost-effective technological solution. The present study aimed to recover some bacterial isolates from Beni-Suef Governorate in Egypt with high capabilities of anthracene biodegradation. The selected isolates were molecularly characterized by 16S rRNA gene sequencing, the degree of anthracene biodegradation was monitored using optical density (OD) and high-performance liquid chromatography (HPLC), PCR amplification of some selected genes encoding biodegradation of PAHs was monitored, and gas chromatography–mass spectrometry (GC–MS) analysis was applied for detecting the resulted metabolites.

Result

Three bacterial isolates were studied, the 16s rRNA sequences of the isolates showed homology of the first isolate to Brevibacillus sp. (94.58 %), the second isolates showed homology to Pseudomonas sp. (94.53%) and the third isolate showed homology to Methylocystis sp. (99.61 %), all isolates showed the ability to degrade anthracene. PCR amplification of some selected genes encoding biodegradation of PAHs revealed the presence of many biodegrading genes in the selected strains. Gas chromatography-mass spectrometry (GC–MS) analysis of the metabolites resulted from anthracene biodegradation in the present study suggested that more than one biodegradation pathway was followed by the selected isolates.

Conclusions

The selected strains could represent a potential bioremediation tool in solving the PAHs problem in the Egyptian environment with a clean and cost-effective technique.

Graphical Abstract

Combined fluorescent measurements, parallel factor analysis and GC-mass spectrometry in evaluating the photodegradation of PAHS in freshwater systems

To better understand the transformation and photochemical fate of PAHs in aquatic environments, a custom-designed closed-circuit recirculation photodegradation system, combined with inline semi-continuous fluorescence and absorbance measurements, as well as modelling of excitation-emission (EEM) measurements with parallel factor analysis (PARAFAC), and GC-MS analysis, were combined to create a robust tool for holistically assessing the photodegradation of individual PAHs, their mixtures and photoproduct formation. Selected compounds included in the US EPA priority list, representing 2- to 6-ring compounds, were monitored individually and in mixtures, during 24 h photodegradation experiments. Experiments were conducted in solutions simulating ideal (ultrapure water) and environmentally relevant conditions (1.00 mg L^-1 Suwannee River Natural Organic Matter (SRNOM)). The fluorescence, primary PARAFAC components and quantification data obtained by GC-MS, indicated that the decline in parent molecule concentration occurred rapidly within 200 min. The degradation rates of parent PAHs increased with aromaticity (6-ring ≫ 2-ring PAHs) and followed pseudo-first order degradation kinetics. The presence and transformation of degradation products, were captured by PARAFAC. NOM influenced the diversity of photoproducts. From the GC-MS results, photoproducts were only detected in Ant, BAnt and the PAH mixture solutions, but optical property analyses indicated that diverse changes occurred with all PAHs. Spectrometric and chromatographic data demonstrated that parent PAHs and photoproducts co-existed at various stages, which is significant for freshwater systems contaminated with these compounds if photoproducts have higher-toxic potential. These results may be used to model the hazard-potential associated with PAHs present in freshwater systems and understanding the mechanisms that govern their environmental fate.

Time-Related Alteration of Aqueous-Phase Anthracene and Phenanthrene Photoproducts in the Presence of TiO2 Nanoparticles

Polycyclic aromatic hydrocarbons (PAHs) and titanium dioxide (TiO₂) nanoparticles (NPs) are photoactive environmental pollutants that can contaminate aquatic environments. Aqueous-phase interactions between PAHs and TiO₂-NPs are of interest due to their emerging environmental relevance, particularly with the deliberate application of TiO₂-NPs to remediate pollution events (e.g., oil spills). Our objective was to investigate anthracene (ANT) and phenanthrene (PHE) photoproduct formation and transformation following ultraviolet A (UVA) irradiation in the presence and absence of TiO₂-NPs. ANT and PHE solutions were prepared alone or in combination with TiO₂-NPs, UVA-irradiated, and either exposed to larval zebrafish or collected for chemical analyses of diverse hydroxylated PAHs (OHPAHs) and oxygenated PAHs (OPAHs). The expression profiles of genes encoding for enzymes involved in PAH metabolism showed PAH-specific and time-dependent inductions that demonstrated changes in PAH and photoproduct bioavailability in the presence of TiO₂-NPs. Chemical analyses of PAH/NP solutions in the absence of zebrafish larvae identified diverse photoproducts of differing size and ring arrangements, which suggested photodissociation, recombination, and ring re-arrangements of PAHs occurred either during or following UVA irradiation. Both ANT and PHE solutions showed heightened oxidative potential following irradiation, but TiO₂-NP-related increases in oxidative potential were PAH-specific. The exploitation of multiple analytical methods provided novel insights into distinct PAH photoactivity, TiO₂-NP influence on photoproduct formation in a PAH-specific manner, and the significant role time plays in photochemical processes.

Persistent Free Radicals from Low-Molecular-Weight Organic Compounds Enhance Cross-Coupling Reactions and Toxicity of Anthracene on Amorphous Silica Surfaces under Light

Polycyclic aromatic hydrocarbon (PAH) contamination has raised great environmental concerns, while the effects of low-molecular-weight organic compounds (LMWOCs) on PAH photodegradation at amorphous silica (AS)/air interfaces have been largely ignored. In this study, the phototransformation of anthracene (ANT) at amorphous silica (AS)/air interfaces was investigated with the addition of LMWOCs. ANT removal was attributed to ^•OH attacking and the energy transfer process via ³ANT*. Light irradiation induced the fractured ≡SiO^• or ≡Si^• generation on AS surfaces, which could react with absorbed H₂O and O₂ to generate ^•OH and further yield a series of hydroxylated products of ANT. The presence of citric acid and oxalic acid improved ^•OH generation and enhanced ANT removal by 1.0- and 2.2-fold, respectively. For comparison, the presence of catechol and hydroquinone significantly decreased ANT removal and produced coupling products. The results of density functional theory calculations suggest that persistent free radicals (PFRs) on AS surfaces from catechol or hydroquinone after ^•OH attacking prefer to cross-couple with ANT via C-C bonding rather than self-couple. Dianthrone and cross-coupling products might possess higher ecotoxicity, while hydroxylated products were less ecotoxic than their parent compounds based on Ecological Structure Activity Relationships (ECOSAR) estimation. The results of this study revealed the potential ecotoxicity of PAH-adsorbed particulates coexisting with LMWOCs and also provided a new insight into PAH transformation through PFR pathways.

Reactivity-directed analysis - a novel approach for the identification of toxic organic electrophiles in drinking water

Drinking water consumption results in exposure to complex mixtures of organic chemicals, including natural and anthropogenic chemicals and compounds formed during drinking water treatment such as disinfection by-products. The complexity of drinking water contaminant mixtures has hindered efforts to assess associated health impacts. Existing approaches focus primarily on individual chemicals and/or the evaluation of mixtures, without providing information about the chemicals causing the toxic effect. Thus, there is a need for the development of novel strategies to evaluate chemical mixtures and provide insights into the species responsible for the observed toxic effects. This critical review introduces the application of a novel approach called Reactivity-Directed Analysis (RDA) to assess and identify organic electrophiles, the largest group of known environmental toxicants. In contrast to existing in vivo and in vitro approaches, RDA utilizes in chemico methodologies that investigate the reaction of organic electrophiles with nucleophilic biomolecules, including proteins and DNA. This review summarizes the existing knowledge about the presence of electrophiles in drinking water, with a particular focus on their formation in oxidative treatment systems with ozone, advanced oxidation processes, and UV light, as well as disinfectants such as chlorine, chloramines and chlorine dioxide. This summary is followed by an overview of existing RDA approaches and their application for the assessment of aqueous environmental matrices, with an emphasis on drinking water. RDA can be applied beyond drinking water, however, to evaluate source waters and wastewater for human and environmental health risks. Finally, future research demands for the detection and identification of electrophiles in drinking water via RDA are outlined.

Photocatalytic H2 Production from Naphthalene by Various TiO2 Photocatalysts: Impact of Pt Loading and Formation of Intermediates

This work presents a comparative study of the efficiency of two commercial TiO2 photocatalysts, Aeroxide P25 (ATiO2) and Sachtleben Hombikat UV100 (HTiO2), in H2 production from an aqueous solution of naphthalene. The TiO2 photocatalysts were platinized by the photodeposition method varying the platinum content of the suspension to 0.5, 1.0, and 5.0 wt%. A full physicochemical characterization for these materials was performed, showing no structural effects from the deposition method, and confirming a well dispersion of nanosized-Pt0 particles on the surface of both photocatalysts. Pristine ATiO2 shows around 14% higher photocatalytic fractional conversion of naphthalene than pristine HTiO2 after 240 min of irradiation, while both materials exhibit negligible activity for H2 formation. The 0.5 wt% Pt- HTiO2 increases the photocatalytic fractional conversion of naphthalene from 71% to 82% and produces 6 µmol of H2. However, using a higher Pt content than the optimal platinization ratio of 0.5 wt% dramatically inhibits both processes. On the other hand, regardless of the fractional ratio of Pt, the platinization of ATiO2 results in a decrease in the fractional conversion of naphthalene by 4% to 33% of the pristine value. Although the presence of Pt islands on the surface of the ATiO2 is essential for the H2 evolution, no dependency between the Pt ratio and the H2 formation rate was observed since all the platinized materials show a similar H2 formation of around 3 µmol. Based on the EPR results, the higher photocatalytic activity of the Pt-HTiO2 is attributed to the efficient charge carrier separation and its larger surface area. The recyclability test confirms that the inhibition of the photocatalytic process is related to the deactivation of the photocatalyst surface by the adsorption of the photoformed intermediates. A strong relationship between the photocatalytic activity and the kind of the aromatic compounds was observed. The H2 evolution and the photooxidation of the aromatic hydrocarbons exhibit higher photonic efficiencies than that of their corresponding hydroxylated compounds over the Pt-HTiO2.

The Effect of Packing Material Properties on Tars Removal by Plasma Catalysis

Plasma catalysis has been utilized in many environmental applications for removal of various hydrocarbons including tars. The aim of this work was to study the tars removal process by atmospheric pressure DBD non-thermal plasma generated in combination with packing materials of various composition and catalytic activity (TiO2, Pt/γAl2O3, BaTiO3, γAl2O3, ZrO2, glass beads), dielectric constant (5–4000), shape (spherical and cylindrical pellets and beads), size (3–5 mm in diameter, 3–8 mm in length), and specific surface area (37–150 m2/g). Naphthalene was chosen as a model tar compound. The experiments were performed at a temperature of 100 °C and a naphthalene initial concentration of approx. 3000 ppm, i.e., under conditions that are usually less favorable to achieve high removal efficiencies. For a given specific input energy of 320 J/L, naphthalene removal efficiency followed a sequence: TiO2 > Pt/γAl2O3 > ZrO2 > γAl2O3 > glass beads > BaTiO3 > plasma only. The efficiency increased with the increasing specific surface area of a given packing material, while its shape and size were also found to be important. By-products of naphthalene decomposition were analyzed by means of FTIR spectrometry and surface of packing materials by SEM analysis.

2-Bromoanthraquinone as a highly efficient photocatalyst for the oxidation of sec-aromatic alcohols: experimental and DFT study

Anthraquinones are recognized as high efficiency photocatalysts which can perform various redox reactions in aqueous or organic phases. We have experimentally proven that 2-BrAQ can undergo hydrogen transfer with an alpha-aromatic alcohol under light conditions, thereby efficiently oxidizing the aromatic alcohol to the corresponding product. The yield of 1-phenethanol to acetophenone can reach more than 96%. In subsequent catalyst screening experiments, it was found that the electronegativity of the substituent at the 2 position of the anthraquinone ring and the acidity of the solvent affect the photocatalytic activity of anthraquinones. After using various aromatic alcohol substrates, 2-BrAQ showed good conversion and selectivity for most aromatic alcohols, but showed C-C bond cleavage and low selectivity with non-α-position aromatic alcohols. In order to explore the mechanism of the redox reaction of 2-BrAQ in acetonitrile solution, the corresponding free radical reaction pathway was proposed and verified by density functional theory (DFT). Focusing on calculations for 2-BrAQ during the reaction and the first-step hydrogen transfer reaction between the 2-BrAQ triplet molecule and the 1-phenylethanol molecule, we recognized the changes that occurred during the reaction and thus have a deeper understanding of the redox reaction of anthraquinone compounds in organic systems.

Synthesis of Biochar-Supported K-doped g-C3N4 Photocatalyst for Enhancing the Polycyclic Aromatic Hydrocarbon Degradation Activity

The development of novel and green photocatalysts have attracted considerable attentions due to their excellent performance for environmental remediation, especially for the degradation of persistent pollutants. In this work, the biochar-supported K-doped g-C₃N₄ composites with the high photocatalytic activity under visible light irradiation was prepared by the calcination-impregnation method. The crystal structure, apparent morphology and functional group composition of the as-prepared photocatalytic materials were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscope (FTIR). Moreover, the characterization of UV-Vis diffuse reflectance spectra (UV-Vis DRS) and photoluminescence technique (PL) verified the good optical properties of resultant samples. Naphthalene was selected as the representative compound to evaluate the photocatalytic performance of the prepared photocatalysts under visible light irradiation. The evaluation results showed that the biochar-supported K-doped g-C₃N₄ composites exhibited excellent photocatalytic activity (82.19%). Moreover, the photocatalytic degradation rate basically remained unchanged after five cycles, indicating the good stability of the prepared photocatalysts. In addition, a possible mechanism for the photodegradation process was proposed on the basis of the main intermediates detected by gas chromatography-mass spectrometer (GC-MS). This study may provide a promising approach for the polycyclic aromatic hydrocarbon degradation by waste utilization of agricultural biomass and increasing the photocatalytic performance of pure g-C₃N₄.

Changes in ecotoxicity of naphthalene and alkylated naphthalenes during photodegradation in water

Crude oil released into the environment contains many polycyclic aromatic hydrocarbons (PAHs). Alkylated PAHs are more abundant than unsubstituted PAHs and their toxicity is also of serious concern. Among the various physical, chemical, and biological weathering processes of crude oils, photodegradation is one of the most important for determining the environmental fate of oil residues. In this study, the photodegradation rate constants of naphthalene and alkylated naphthalenes were determined under simulated laboratory conditions at different temperature. Changes in the luminescence inhibition of Aliivibrio fischeri, as an indicator of the baseline toxicity, were observed in photodegradation mixtures. The major transformation products were also identified by gas chromatography-mass spectrometry. The photodegradation of naphthalene and the eight alkylated naphthalenes was described well by pseudo-first-order kinetics regardless of experimental temperature. The measured toxicity of the reaction mixtures obtained by photodegradative weathering slightly increased initially and then decreased with further weathering. In all cases, the observed toxicity was greater than accounted for by the parent compounds, indicating that the photodegradation products also contributed significantly to the overall toxicity of the mixtures. The identified photodegradation products were mostly oxygenated compounds such as alcohols, aldehydes, ketones, and quinones, which warrant further investigation.

Photocatalytic Degradation Enhancement in Pickering Emulsions Stabilized by Solid Particles of Bare TiO2

Pickering emulsions provide a new way to enhance the efficiency of photocatalytic degradation of water-insoluble pollutants. Indeed, the semiconductor solid particles dually act as the photocatalyst and stabilizer of the emulsion droplets whose size dramatically affects the photocatalytic reaction. The present work aims at the validation of this concept by using bare TiO₂ without any surface modification. Nanostructured TiO₂ has been prepared by a simple sol-gel process and characterized by X-ray diffraction, specific surface area analysis, scanning electron microscopy, and diffuse reflectance spectroscopy. The emulsions were prepared by using 1-methylnaphthalene (1-MN) as a model organic contaminant scarcely soluble in water and bare TiO₂ as the photocatalyst/stabilizer. The emulsions have been characterized by electrical conductivity, optical microscopy, and light-scattering analyses. The photocatalytic degradation of 1-MN was 50 times faster in stable Pickering emulsions with respect to the case of biphasic liquid systems containing TiO₂. This finding allows us to propose Pickering emulsions stabilized by TiO₂ nanoparticles as an effective and novel way to intensify the photocatalytic degradation of water-insoluble organic pollutants.

Naphthalene remediation form groundwater by calcium peroxide (CaO2) nanoparticles in permeable reactive barrier (PRB)

This study investigated the applicability of synthesized calcium peroxide (CaO₂) nanoparticles for naphthalene bioremediation by permeable reactive barrier (PRB) from groundwater. According to the batch experiments the application of 400 mg/L of CaO₂ nanoparticles was the optimum concentration for naphthalene (20 mg/L) bioremediation. Furthermore, the effect of environmental conditions on the stability of nanoparticles showed the tremendous impacts of the initial pH and temperature on the stability and oxygen releasing potential of CaO₂. Therefore, raising the initial pH from 3 to 12 elevated the dissolved oxygen from 4 to 13.6 mg/L and the stability of nanoparticles was significantly improved around 70 d. Moreover, by increasing the temperature from 4 to 30 °C, the stability of CaO₂ declined from 120 to 30 d. The continuous-flow experiments revealed that the naphthalene-contaminated groundwater was completely bio-remediated in the presence of CaO₂ nanoparticles and microorganisms from the effluent of the column within 50 d. While, the natural remediation of the contaminant resulted in 19.7% removal at the end of the experiments (350 d). Additionally, the attached biofilm on the surface of the PRB zone was studied by scanning electron microscopy (SEM) which showed the higher biofilm formation on the pumice surfaces in the bioremediation column in comparison to the natural remediation column. The physic-chemical characteristics of the effluents from each column was also analyzed and indicated no negative impact of the bioremediation process on the groundwater. Consequently, the present paper provides a comprehensive study on the application of the CaO₂ nanoparticles in PAH-contaminated groundwater treatment.

Solar energy harvesting by magnetic-semiconductor nanoheterostructure in water treatment technology

Photocatalytic degradation of toxic organic pollutants in the wastewater using dispersed semiconductor nanophotocatalysts has a number of advantages such as high activity, cost effectiveness, and utilization of free solar energy. However, it is difficult to recover and recycle nanophotocatalysts since the fine dispersed nanoparticles are easily suspended in waters. Furthermore, a large amount of photocatalysts will lead to color contamination. Thus, it is necessary to prepare photocatalysts with easy separation for the reusable application. To take advantage of high photocatalysis activity and reusability, magnetic photocatalysts with separation function were utilized. In this review, the photocatalytic principle, structure, and application of the magnetic-semiconductor nanoheterostructure photocatalysts under solar light are evaluated. Graphical abstract ᅟ.

Naphthalene degradation by catalytic ozonation based on nickel oxide: study of the ethanol as cosolvent

Naphthalene (NA) is a polycyclic aromatic hydrocarbon with toxic properties in aquatic systems. Ozonation (O₃) and catalytic ozonation (O₃-cat) processes are attractive alternatives of degradation for this kind of compound. NA (20 mg L^-1) degradation by conventional and catalytic ozonation in the presence of a cosolvent (ethanol) was the aim of this study. This solution was proposed to simulate some aspects of real wastewaters where not only water acts as solvent. Two proportions of the mixture ethanol/water were selected (30:70 and 50:50) with the purpose of studying the cosolvent effect on NA degradation system by ozonation. O₃-cat process used nickel oxide as catalyst (0.1 g L^-1). The degradation analysis of NA by O₃-cat in two different proportions of cosolvent showed that in the case of 30:70 (ethanol/water), a 95 % of NA elimination in 60 min was obtained, while in the case 50:50 (ethanol/water), only 55 % was achieved. The O₃ process showed similar results of degradation to the initial compound in comparison with catalytic system. According to these results, there is an inhibition effect in pollutant removal by ethanol due to the higher ethanol concentration; the lower elimination rate of NA was obtained (by 40 % during the 60 min). The by-products analysis of ozonation process detected oxalic and formic acids. Treatments with NiO presented less production of organic acids in comparison with conventional ozonation process. The high concentration of ethanol has a relevant factor in the elimination of NA and formation of organic acids; samples with 50 % of cosolvent have showed a higher concentration of organic acids. X-ray photoelectron spectroscopy (XPS) study of O₃-cat of diluent (O₃-NiO control) and O₃-NA-NiO showed the presence of -CO₃ absorbed on catalyst due to ethanol decomposition.

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.

Selective Photooxidation Reactions using Water-Soluble Anthraquinone Photocatalysts

The aerobic organocatalytic oxidation of alcohols was achieved by using water‐soluble sodium anthraquinone sulfonate. Under visible‐light activation, this catalyst mediated the aerobic oxidation of alcohols to aldehydes and ketones. The photo‐oxyfunctionalization of alkanes was also possible under these conditions.

Analysis of Photoirradiated Water Accommodated Fractions of Crude Oils Using Tandem TIMS and FT-ICR MS

For the first time, trapped ion mobility spectrometry (TIMS) in tandem with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) is applied to the analysis of the low energy water accommodated fraction (WAF) of a crude oil as a function of the exposure to light. The TIMS-FT-ICR MS analysis provided, in addition to the heteroatom series identification, new insights into the WAF isomeric complexity (e.g., [m/z; chemical formula; collision cross section] data sets) for a better evaluation of the degree of chemical and structural photoinduced transformations. Inspection of the [m/z; chemical formula; collision cross section] data sets shows that the WAF composition changes as a function of the exposure to light in the first 115 h by initial photosolubilization of HC components and their photo-oxidation up to O_4-5 of mainly high double bond equivalence species (DBE > 9). The addition of high resolution TIMS (resolving power of 90-220) to ultrahigh resolution FT-ICR MS (resolving power over 400k) permitted the identification of a larger number of molecular components in a single analysis (e.g., over 47k using TIMS-MS compared to 12k by MS alone), with instances of over 6-fold increase in the number of molecular features per nominal mass due to the WAF isomeric complexity. This work represents a stepping stone toward a better understanding of the WAF components and highlights the need for better experimental and theoretical approaches to characterize the WAF structural diversity.

Nanoparticle Self-Assembled Grain Like Curcumin Conjugated ZnO: Curcumin Conjugation Enhances Removal of Perylene, Fluoranthene, and Chrysene by ZnO

Curcumin conjugated ZnO, referred as Zn(cur)O, nanostructures have been successfully synthesized, these sub-micro grain-like structures are actually self-assemblies of individual needle-shaped nanoparticles. The nanostructures as synthesized possess the wurtzite hexagonal crystal structure of ZnO and exhibit very good crystalline quality. FT-Raman and TGA analysis establish that Zn(cur)O is different from curcumin anchored ZnO (ZnO@cur), which is prepared by physically adsorbing curcumin on ZnO surfaces. Chemically Zn(cur)O is more stable than ZnO@cur. Diffuse reflectance spectroscopy indicates Zn(cur)O have more impurities compared to ZnO@cur. The solid-state photoluminescence of Zn(cur)O has been investigated, which demonstrates that increase of curcumin concentration in Zn(cur)O suppresses visible emission of ZnO prepared through the same method, this implies filling ZnO defects by curcumin. However, at excitation wavelength 425 nm the emission is dominated by fluorescence from curcumin. The study reveals that Zn(cur)O can remove to a far extent high concentrations of perylene, fluoranthene, and chrysene faster than ZnO. The removal depends on the extent of curcumin conjugation and is found to be faster for PAHs having smaller number of aromatic rings, particularly, it is exceptional for fluoranthene with 93% removal after 10 minutes in the present conditions. The high rate of removal is related to photo-degradation and a mechanism has been proposed.

Preparation and photocatalytic activity of WO3–MWCNT nanocomposite for degradation of naphthalene under visible light irradiation

Preparation and application of the novel and high performance WO₃–MWCNT photocatalyst for photodegradation of naphthalene under visible light irradiation.

Thermal catalytic oxidation of octachloronaphthalene over anatase TiO2 nanomaterial and its hypothesized mechanism

As an environmentally-green technology, thermal catalytic oxidation of octachloronaphthalene (CN-75) over anatase TiO₂ nanomaterials was investigated at 300 °C. A wide range of oxidation intermediates, which were investigated using various techniques, could be of three types: naphthalene-ring, single-benzene-ring, and completely ring-opened products. Reactive oxygen species on anatase TiO₂ surface, such as O₂^−• and O²⁻, contributed to oxidative degradation. Based on these findings, a novel oxidation degradation mechanism was proposed. The reaction at (101) surface of anatase TiO₂ was used as a model. The naphthalene-ring oxidative products with chloronaphthols and hydroxyl-pentachloronaphthalene-dione, could be formed via attacking the carbon of naphthalene ring at one or more positions by nucleophilic O²⁻. Lateral cleavage of the naphthalene ring at different C₁-C₁₀ and C₄-C₉, C₁-C₂ and C₄-C₉, C₁-C₂ or and C₃-C₄ bond positions by electrophilic O₂^−• could occur. This will lead to the formation of tetrachlorophenol, tetrachloro-benzoic acid, tetrachloro-phthalaldehyde, and tetrachloro-acrolein-benzoic acid, partially with further transformation into tetrachlorobenzene-dihydrodiol and tetrachloro-salicylic acid. Unexpectedly, the symmetric half section of CN-75 could be completely remained with generating the intricate oxidative intermediates characteristically containing tetrachlorobenzene structure. Complete cleavage of naphthalene ring could produce the ring-opened products, such as formic and acetic acids.

Investigation of the impacts of ethyl lactate based Fenton treatment on soil quality for polycyclic aromatic hydrocarbons (PAHs)-contaminated soils

This study aims to investigate the impacts of ethyl lactate (EL) based Fenton treatment on soil quality for polycyclic aromatic hydrocarbons (PAHs)-contaminated soils. Accumulation of oxygenated-polycyclic aromatic hydrocarbons (oxy-PAHs) was observed, but quantitative measurement on the most abundant compound 9,10-anthraquinone (ATQ) showed lower accumulation of the compound than that reported for ethanol (ET) based Fenton treatment. In general, as compared to conventional water (CW) based Fenton treatment, the EL based Fenton treatment exerted either a lower or higher negative impact on soil physicochemical properties depending on the property type and shared the main disadvantage of reduced soil pH. For revegetation, EL based Fenton treatment was most appropriately adopted for soil with native pH >/~ 6.2 in order to obtain a final soil pH >/~ 4.9 subject to the soil buffering capacity.

Ecofriendly in-line process monitoring: a case study. Anthracene photodegradation in the presence of refuse-derived soluble bio-organics

Photodegradation of anthracene has been studied in aqueous solutions containing soluble bio-organic substances isolated from urban refuse. To perform a preliminary rapid feasibility study of this process while reducing the amount of analytical effort and reagents, an experimental set-up was developed comprising a Teflon coil surrounding a UV-lamp and coupled with an in-line spectrofluorimeter. In this fashion only few millilitres of solution are needed to study the degradation process. Furthermore, the in-line spectroscopic approach enables monitoring of the process without consumption of reagents. Additional studies by liquid chromatography and use of toxicity tests clearly indicated that the apparent inhibition effect of bio-organic compounds on anthracene degradation is not relevant. The results imply that urban refuse may be used as an auxiliary in the recovery of polycyclic aromatic hydrocarbons from contaminated soil by washing, without deleterious effects on the photodegradation of anthracene and other aromatic pollutants.

Feasibility of Raman microspectroscopic identification of biomarkers through gypsum crystals

The miniaturized Raman spectrometer is considered to be a candidate instrument for the Pasteur payload (the ExoMars mission scheduled for 2018). This mission will, for the first time, combine mobility and access to subsurface locations where organic molecules might be well preserved. Evaporitic crystals are among the potential protected habitats that have been postulated. Various concentrations of biomarkers (beta-carotene, glycine and phthalic acid) dispersed in a gypsum matrix were analyzed through transparent mineral (gypsum) plates of different thicknesses. By doing so, conditions were simulated in which biomarkers were trapped within evaporitic crystals. Using a long-working distance objective, all studied concentrations of biomarkers mixed in gypsum powder were detected. The characteristic Raman bands were easily observable for a 10% mixture of all chosen biomarkers not only through a 3.3 mm plate and but even through a 5.2 mm plate. It was possible to detect key Raman bands of 1% phthalic acid/gypsum mixture and 1% beta-carotene/gypsum mixture even through a 5.2 mm gypsum plate. The 1% beta-carotene/gypsum mixture was still clearly distinguishable through an 8.5mm gypsum crystal due to the known resonance Raman effect of the molecule.

Raman spectroscopic identification of phthalic and mellitic acids in mineral matrices

Raman spectroscopy has many advantages for planetary exploration, and the Raman technique is currently being developed for future space missions. The Raman microspectroscopic study of organic acids (phthalic and mellitic acids) in experimentally prepared mixtures with halite and gypsum was performed using near infrared 785 nm and visible 514 nm excitation wavelengths. Gypsum and halite matrices were chosen as analogues of Martian minerals. Carboxylic acids mixed with mineral powders were also investigated through a UV-transparent crystal of gypsum and halite (approximately 2 mm, resp. 5 mm thick), thereby creating a type of artificial inclusion that could potentially be present in Martian minerals. The detection limit of phthalic acid mixed in mineral matrices and analyzed through crystals was 1 wt% using both excitation wavelengths. A Raman mellitic acid signal was obtained at a concentration as low as 1 wt% in halite matrix, and at a concentration of 5 wt% when analyzed through halite crystal. In the case of mellitic acid mixed with gypsum and for analyses through a gypsum crystal, the detection limit is 5 wt% using both excitation wavelengths.

Photocatalytic and combined anaerobic-photocatalytic treatment of textile dyes

A photocatalytic process based on immobilized titanium dioxide was used to treat crude solutions of azo, anthraquinone and phthalocyanine textile dyes. In addition, the process was applied to the treat autoxidized chemically reduced azo dyes, i.e. representatives of recalcitrant dye residues after biological sequential anaerobic-aerobic treatment. Photocatalysis was able to remove more than 90% color from crude as well as autoxidized chemically reduced dye solutions. UV-absorbance and COD were also removed but to a lower extent (50% in average). The end products of photocatalytic treatment were not toxic toward methanogenic bacteria. The results demonstrate that photocatalysis can be used as a pre- or post-treatment method to biological anaerobic treatment of dye-containing textile wastewater.