Fenton degradation of organic compounds promoted by dyes under visible irradiation

The influence of dyes on the Fenton reaction of organic compounds under visible irradiation (lambda > 450 nm) was examined. It was found that the presence of dyes could accelerate greatly the Fenton reaction of organic compounds such as salicylic acid, sodium benzenesulfonate, benzyltrimethylammonium chloride, and trichloroacetic acid under visible irradiation and that a complete mineralization of those compounds could also be achieved. The dyes such as Alizarin Violet 3B which has an anthraquinone structure unit showed much more significant effect on the reaction than the dyes such as malachite green without the quinone unit. A reaction mechanism of dye AV as a cocatalyst in the photo-Fenton reaction of organic compounds under visible irradiation is proposed based on the cycle of Fe(3+)/Fe(2+) catalyzed by quinone species and an electron transfer from the excited dye molecule to Fe3+.     

多元复合纳米光催化剂的制备及可见光下降解染料废水

以钛酸四丁酯为Ti源,通过溶胶-凝胶法制备TiO2、CdS/TiO2、BiPO4/TiO2、CdS/BiPO4/TiO2(BCT),对制备的材料进行UV-Vis、XRD、SEM、TG-DTG表征,并在可见光下对玫瑰红B模拟染料废水进行光催化,考察pH、煅烧温度、催化剂用量对降解效果的影响,对4种材料的光催化效果进行对比...     

A new route for degradation of volatile organic compounds under visible light: using the bifunctional photocatalyst Pt/TiO2-xNx in H2-O2 atmosphere

The bifunctional photocatalyst Pt/TiO2-xNx has been successfully prepared by wet impregnation. The properties of Pt/ TiO2-xNx have been investigated by diffuse reflectance spectra, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, a photoluminescence technique with terephthalic acid, and electric field induced surface photovoltage spectra. The photocatalytic activity of the sample was evaluated by the decomposition of volatile organic pollutants (VOCs) in a H2-O2 atmosphere under visible light irradiation. The results demonstrated that nitrogen-doped and platinum-modified TiO2 in a H2-O2 atmosphere could enormously increase the quantum efficiency of the photocatalytic system with excellent photocatalytic activity and high catalytic stability. The increased quantum efficiency can be explained by enhanced separation efficiency of photogenerated electron-hole pairs, higher interface electron transfer rate, and an increased number of surface hydroxyl radicals in the photocatalytic process. A mechanism was proposed to elucidate the degradation of VOCs over PtTiO(2-x)Nx in a H2-O2 atmosphere under visible light irradiation.     

Persistent organic pollutants in fish: biomonitoring and cocktail effect with implications for food safety

The impact of anthropogenic wastes of persistent organic pollutants (POPs) on the marine environment has increased in the last decades. POPs include polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCs). To assess the levels of these POPs in the wild fish population, pelagic and benthopelagic predator fish species were selected as biomonitors. For detection and quantification of POPs in muscular tissues, a simple extraction through Accelerated-Solvent-Extraction (ASE) with an ‘in-line’ clean up purification approach was applied, followed by a GC–MS/MS analysis. Concentrations of sum DDT, sum HCH and endrin correlated with all PCB concentrations. Significant differences among fish species were found for all OCs and all PCBs except PCB 31 and 101. Blackspot seabream had the highest PCB concentrations; OCs were highest in tuna. Due to major concerns regarding fish population losses and the possible human chronic exposure to contaminated fish, studies addressing combined effects of multiple POPs (‘cocktail effect’) should be implemented. Our data motivate further experimental and observational studies in fish to define adequate baseline levels for cumulative human exposure and potential role of these contaminants for food safety.     

Photochemical alkylation of inorganic selenium in the presence of low molecular weight organic acids

Using a flow-through photochemical reactor and a low pressure mercury lamp as a UV source, alkyl selenium species are formed from inorganic selenium(IV) in the presence of low molecular weight organic acids (LMW acids). The volatile alkyl Se species were cryogenically trapped and identified by GC-MS and GC-ICP-MS. In the presence of formic, acetic, propionic and malonic acids, inorganic selenium(IV) is converted by UV irradiation to volatile selenium hydride and carbonyl, dimethylselenide and diethylselenide, respectively. Se(IV) was successfully removed from contaminated agricultural drainage waters (California, U.S.A.) using a batch photoreactor system Se. Photochemical alkylation may thus offer a promising means of converting toxic selenium salts, present in contaminated water, to less toxic dimethylselenide. The LMW acids and photochemical alkylation process may also be key to understanding the source of atmospheric selenium and are likely involved in its mobility in the natural anaerobic environment.     

Peer reviewed: tracking the distribution of persistent organic pollutants

Control strategies for these contaminants will require a better understanding of how they move around the globe.     

SPME-GC-MS analysis of volatile organic compounds in honey from Basilicata. Evidence for the presence of pollutants from anthropogenic activities

Solid‐phase microextraction gas chromatography‐mass spectrometry analysis of nineteen samples of honey from Basilicata (southern Italy) showed the presence of some flavour components never described before in honey. Furthermore, some phenyl‐substituted hydrocarbons were detected. These compounds may be derived from the wastewater treatment plant in the area. Furthermore, in honey collected near an oil extraction plant, hydrocarbons were found; these may be derived from such plants present in the area.     

Fenton oxidation products derived from hydroxycinnamic acids increases phenolic‐based compounds and organic acid formation in sugar processing

The hydroxycinnamic acids (HCAs), caffeic acid (CaA), p‐coumaric acid (pCoA) and ferulic acid (FeA) are the main phenolic acid colour precursors present in sugar cane juice. The Fenton oxidative degradation products of these HCAs and mixture using Fe²⁺/H₂O₂ at pH 4.72 at 25 °C were identified using chromatography and mass spectrometry techniques. Oxalic (≤14 wt%), isobutyric (≤13.5 wt%) and formic acids (≤1.3 wt%) were the main organic acids formed. CaA produced the highest proportion of oxalic and isobutyric acids, while FeA produced the highest proportion of formic acid. The presence of increased proportion of oxalic acid in juice will increase the proportion of calcium oxalate scale in sugar mill heat exchangers. The phenolic‐based products identified include protocatechuic aldehyde and 4‐hydroxybenzoic acid and the basic phenols, p‐allyphenol, p‐vinylguaiacol, trans‐isoeugenol, which when present in juice may react with juice constituents to increase juice colour in subsequent processing.     

织物基CNT/BiVO4光催化材料的制备及其在可见光下对染料的降解

利用钒酸铋(BiVO₄)具有无毒、降解效率高等优点,研究采用酸化碳纳米管(α-CNT)对BiVO₄进行改性,制备α-CNT/BiVO₄复合催化剂,采用泡沫法将α-CNT/BiVO₄复合催化剂处理在棉织物上,对亚甲基蓝(MB)溶液进行降解。结果显示:可见光照射90 min的降解效率高达95.8%,更容易降解有机污染物,同时还能解决催化剂颗粒在废水处理中难以回收利用的问题,对处理印染废水具有广阔的应用前景。     

Transformation of carbon tetrachloride by thiol reductants in the presence of quinone compounds

Quinones are present in trace amounts in natural organic matter. The addition of thiol compounds to quinones produces reactive electron-transfer species that may be important for the transformation of chlorinated hydrocarbons under sulfate-reducing conditions. This study systematically investigated the transformation of carbon tetrachloride (CCl4) in homogeneous aqueous solutions containing quinones as electron-transfer mediators and thiol compounds as bulk reductants. The thiol compounds, including sodium hydrosulfide (NaHS) and cysteine, were found to effectively transform CCl4. The transformation of CCl4 followed pseudo-first-order kinetics, and the pseudo-first-order rate constants (kobs) were (3.24 +/- 0.46) x 10(-7) and 1.04 x 10(-7) s(-1), respectively, when solutions contained NaHS and cysteine alone. Addition of quinone compounds, including anthraquinone-2,6-disulfonate (AQDS), benzoquinone (BQ), juglone (JQ), naphthoquinone (NQ), lawsone (LQ), and menadione (MQ), increased the transformation rate and efficiency of CCl4. The kobs values for CCl4 transformation in the presence of quinones were 2.6-71 times higher than those for the thiol compounds alone. The enhancement efficiency followed the order JQ > NQ > BQ > AQDS > LQ > MQ. Spectroscopic studies indicated that the quinone compounds generated various active electron-transfer mediators to transfer electrons from the bulk reductants to CCl4. BQ and NQ produced mercaptoquinones as active redox mediators that significantly enhanced the transformation rate of CCl4 in the presence of NaHS. The addition of thiol reductants produced large amounts of AQDS semiquinone radical as the electron shuttle. In addition, MQ and LQ were reduced by NaHS to give hydroquinone, which slightly enhanced the transformation efficiency of CCl4. These results clearly indicate that the enhanced efficiency of quinones for the transformation of chlorinated hydrocarbons is specifically related to the produced reactive species. Mercaptoquinone is a more active mediator than either semiquinone or hydroquinone for transferring electrons in a reducing environment containing thiol reductants.     

Enhanced photocatalytic degradation of dye pollutants under visible irradiation on Al(III)-modified TiO2: structure, interaction, and interfacial electron transfer

Aluminum(III)-modified TiO2 was prepared by sol-gel process via a sudden gelating method. The structure of the modified material and the local environment of aluminum were investigated using X-ray diffraction, HRTEM, XPS, 27Al MAS NMR, and xi-potential measurements. The effect of the aluminum modification on interaction between the dye and photocatalyst, the interfacial electron transfer process, and thereby the degradation of dye pollutants under visible irradiation were also examined by FTIR spectra and UV-vis diffuse reflectance spectra. It was found that, rather than incorporating into the crystal lattice of TiO2, the aluminum forms an overlayer of Al2O3 on the surface of TiO2, interfaced with Ti-O-Al bonds. It is interesting that the carboxylate-containing dyes such as Rhodamine B (RhB) adsorb preferentially on the Al2O3, rather than the Ti(IV) sites on the surface of TiO2. The photodegradation rate observed for RhB is nearly 5-fold faster than that obtained in the pristine TiO2 system. The photodegradation of dyes on the aluminum(III)-modified photocatalyst is of great dependence on the structure and anchoring group of the dyes. Structure with carboxylate as anchoring group and amino group as electron donor is favorable for degradation. The mechanistic details are discussed on the basis of experimental results.     

泡豇豆发酵过程中有机酸变化及对亚硝酸盐降解的影响

为了探究泡菜发酵过程中有机酸变化规律,以豇豆为原料自然发酵制作泡菜。采用高效液相色谱法(HPLC)对泡豇豆在发酵过程中蔬菜组织和发酵液中的有机酸种类及含量进行分析测定,并对各有机酸降解亚硝酸盐的能力进行比较。结果表明,蔬菜组织和发酵液中含有8种有机酸,分别为草酸、酒石酸、苹果酸、乳酸、乙酸、柠檬酸、富马酸和琥珀酸;各有机酸变化趋势有所不同,发酵7 d后,蔬菜组织中柠檬酸含量最高,为641. 59 mg/(100 g),发酵液中苹果酸含量最高,为195. 39 mg/(100 g);各有机酸降解亚硝酸盐能力大小顺序依次为草酸、酒石酸、苹果酸、柠檬酸、琥珀酸、乙酸、乳酸、富马酸。此研究为阐明泡菜中亚硝酸盐降解机理提供了理论基础。     

Photoacoustic analysis of some milk products in ultraviolet and visible light

The research reported here demonstrates the possibility of using photoacoustic spectroscopy for milk product analysis. Milk products including yogurt, cheese, and market milk were analyzed in the ultraviolet visible range. A strong absorption peak was present at 280 nm for all the products. Relationship was linear between relative protein concentration of skim milk and the photoacoustic signal at 280 nm (r2 greater than .99). Powdered milks, prepared from skim milk that had been subjected to different heat treatments before drying, were analyzed, and a second absorption peak at 335 nm was noted for milks subjected to high heat treatment prior to the drying process. This second absorption peak appears associated with Maillard reaction products. Analysis of stored UHT heat-treated milk and infant formulas showed a similar peak at 335 nm. The results suggest that the Maillard reaction is initiated during UHT treatment of milk, and associated pigments develop only during storage. The presence of the 335-nm band in the photoacoustic spectra of infant formulas is considered as the result of heat sterilization. It is anticipated that as photoacoustic spectroscopy becomes more common, its usefulness in the milk industry, in particular, and in food science, in general, will increase.     

Altitudinal and seasonal variations of persistent organic pollutants in the Bolivian Andes Mountains

Polyurethane foam disk passive air samplers were deployed over four periods of approximately 3 months along an altitudinal gradient (1820, 2600, 4650, and 5200 masl) on the east side of the Andean mountain range in Bolivia. The purpose of the study was to assess the gas-phase concentration and the altitudinal and seasonal trends of organochlorine pesticides and polychlorinated biphenyls (PCBs). Target compounds that were regularly detected included alpha- and gamma-hexachlorocyclohexane (HCH), endosulfans, and select PCB congeners. Endosulfans and HCH concentrations increased with altitude. Enrichment factors (concentration at the highest altitude divided by concentration at the lowest altitude) ranged from 10 to 20 for HCHs and 3 to 10 for endosulfans. Air parcel back trajectory analysis indicated that, in general, the high-altitude sites were exposed to a larger airshed and hence susceptible to long-range atmospheric transport from more distant regions. Seasonal differences were also observed with SigmaHCH concentrations peaking during periods 2 and 3 (March-September 2005). Airsheds (derived from the analysis of back trajectories) for periods 2 and 3 were less oriented along the Andes range (mountain air) with greater input from coastal regions. Endosulfans peaked during periods 1 and 2 (February-June 2005) and also exhibited the highest air concentrations of the target compounds, reaching approximately 1500 pg/m3 at the two highest elevation sites. PCB air concentrations at all sites were generally typical of global background values (<12 pg/m3) and showed no increase with altitude. This is the first study to measure air concentrations of persistent organic pollutants (POPs) in Bolivia and one of only a few studies to investigate altitudinal gradients of POPs.     

Bioamplification and the selective depletion of persistent organic pollutants in Chinook salmon larvae

The maternal provisioning of yolk to eggs transfers significant quantities of persistent organic pollutants (POPs). As yolk utilization progresses via metabolic activity, there is a potential to realize further increases in POP concentrations if yolk lipids are depleted at a faster rate than POPs, a condition referred to as bioamplification. This study investigated the bioamplification of POPs in Chinook salmon ( Oncorhynchus tshawytscha ) eggs and larvae. Chinook eggs were sampled from the Credit River, ON, Canada, and brought to an aquaculture facility where they were fertilized, incubated, and maintained posthatch until maternally derived lipid reserves became depleted (approximately 168 days). The loss of chemicals having an octanol-water partition coefficient (log K(OW)) greater than 5.8 was slow to negligible from days 0-135. However, during the increase in water temperatures in early spring, K(OW)-dependent elimination of POPs was observed. Bioamplification was maximized for the highest log K(OW) POPs, with an approximate 5-fold increase in lipid equivalents concentrations in 168 day old larvae as compared to newly fertilized eggs. This study demonstrates that later yolk-sac Chinook larvae (before exogenous feeding) are exposed to higher lipid equivalents POP concentrations than predicted by maternal deposition, which could lead to underestimates in the toxicity of critical life stages.     

Food web magnificaton of persistent organic pollutants in poikilotherms and homeotherms

Food web magnification of persistent organic pollutants (POPs) was determined for the Barents Sea food web using 615N as a continuous variable for assessing trophic levels (TL). The food web investigated comprised zooplankton, ice fauna and fish (poikilotherms, TL 1.7-3.3), and seabirds and seals (homeotherms, TL 3.3-4.2), with zooplankton representing the lowest and glaucous gull the highest trophic level. Concentrations of lipophilic and persistent organochlorines were orders of magnitude higher in homeotherms than in poikilotherms. These compounds had significantly higher rates of increase per trophic level in homeotherms relative to poikilotherms, with the highest food web magnification factors (FWMFs) for cischlordane and p,p'-DDE. Some compounds, such as transnonachlor and HCB, had similar rates of increase throughout the food web, whereas compounds that are more readily eliminated (gamma-HCH) showed no relationship with trophic level. It is preferable to calculate FWMFs with regard to thermal groups, because the different energy requirements and biotransformation abilities between poikilotherms and homeotherms may give different rates of contaminant increase with trophic level. When biomagnification is compared between ecosystems, FWMFs are preferable to single predator-prey biomagnification factors. FWMFs represent a trophic level increase of contaminants that is average for the food chain rather than an increase for a specific predator-prey relationship. The Barents Sea FWMFs were generally comparable to those determined for marine food webs with similar food chain lengths in the Canadian Arctic.     

Solubility of hydrophobic organic pollutants in binary and multicomponent aqueous solvents

The present paper deals with the application of fluctuation theory of solutions to the solubility of poorly soluble substances of environmental significance in aqueous mixed solvents. The fluctuation theory of ternary solutions was first used to derive an expression for the activity coefficient of a solute at infinite dilution in a binary mixed solvent. This equation contains the activity coefficients of the constituents of the solute-free mixed solvent and the molar volume of the solute-free mixed solvent. Further, the derived expression for the activity coefficient of a solute at infinite dilution was used to generate a number of expressions for the solubility of solids in aqueous mixed solvents. Several expressions for the activity coefficients of the components were considered: first, the mixed solvent was considered an ideal mixture; second, the activity coefficients of the constituents of the binary solvent were expressed using the two-suffix Margules equations; third, the activity coefficients of the constituents of the binary solvent were expressed using the Wilson equations. The obtained expressions were applied to 25 experimental data sets pertaining to the solubilities of hydrophobic organic pollutants (HOP) in aqueous mixed solvents. It was found that the suggested equations can be used for an accurate and reliable correlation of the solubilities in aqueous mixed binary solvents. The best results were obtained by combining our expression for the activity coefficient of a solute at infinite dilution in a mixed solvent with the Wilson equations for the activity coefficients of the constituents of a solute-free mixed solvent. The derived equations can also be used for predicting the solubilities of poorly soluble environmentally important compounds in aqueous mixed solvents using for the Wilson parameters those obtained from vapor-liquid equilibrium data. A similar methodology was applied to the solubility of poorly soluble substances of environmental significance in multicomponent (ternary and higher) aqueous mixed solvents. The expression for the activity coefficient of a solute in an ideal multicomponent mixed solvent was used to derive an equation for the solubility of a poorly soluble solute in an ideal multicomponent mixed solvent in terms of its solubilities in two subsystems of the multicomponent solvent and their molar volumes. Ultimately the solubility could be expressed in terms of those in binary or even in the individual constituents of the solvent and their molar volumes. The computational method was applied to predict the solubilities of naphthalene and anthracene in ternary, quaternary and quinary aqueous mixed solvents. The results were compared with experiment and good agreement was obtained.     

Persistent organic pollutants in British Columbia grizzly bears: consequence of divergent diets

Nitrogen and carbon stable isotope signatures in growing hair reveal that while some British Columbia grizzly bears (Ursus arctos horribilis) rely entirely on terrestrial foods, others switch in late summer to returning Pacific salmon (Oncorynchus spp.). Implications for persistent organic pollutant (POP) concentrations and patterns measured in the two feeding groups of grizzly bears were profound. While the bears consuming a higher proportion of terrestrial vegetation ("interior" grizzlies) exhibited POP patterns dominated bythe more volatile organochlorine (OC) pesticides and the heavier polybrominated diphenyl ethers (PBDEs: e.g., BDE-209), the bears consuming salmon were dominated by the more bioaccumulative POPs (e.g., DDT, chlordanes, and BDE-47). The ocean-salmon-bear pathway appeared to preferentially select for those contaminants with intermediate partitioning strength from water into lipid (log Kow approximately 6.5). This pattern reflects an optimum contaminant log Kow range for atmospheric transport, deposition into the marine environment, uptake into marine biota, accumulation through the food web, and retention in the bear tissues. We estimate that salmon deliver 70% of all OC pesticides, up to 85% of the lower brominated PBDE congeners, and 90% of PCBs found in salmon-eating grizzly bears, thereby inextricably linking these terrestrial predators to contaminants from the North Pacific Ocean.     

Protein haze formation in wines revisited. The stabilising effect of organic acids

The effect on the wine protein haze potential of five organic acids commonly encountered in wines (l(+)-tartaric, l(−)-malic, citric, succinic and gluconic acids) was assessed. All five acids, tested at 20 mM, reduced dramatically the haze potential of proteins, either in wine or dissolved in water, throughout the range of pH values typical of wines (i.e., from 2.8 through 3.8). Subtle differences among the acid effects did not correlate with the number of their carboxyl groups, but were attributed to electrostatic interactions that depend upon the acid pK_a values, the protein pI values and the medium pH. These results invalidate or question the validity of all experiments on wine proteins involving wine model solutions containing organic acids. Overall, the results obtained in the present work clearly indicate that organic acids with a common occurrence in wines exhibit a stabilising effect upon the haze potential of the wine proteins.