Efficient DDT and trichlorophenol detoxification using NaBH4 and Devarda alloy

DDT—1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane—is a pesticide that has been widely used to control insects in agriculture. TCP—2,4,6-trichlorophenol—has been used in pesticide formulations as a preservative, disinfectant and antiseptic. Detoxification of DDT and TCP is very difficult due to their stable chemical structure. Here, a mixture of NaBH₄ and Devarda alloy was applied for the first time to detoxify DDT and TCP. Results show 94 % dechlorination of DDT at 100 °C and 97 % dechlorination of TCP at 80 °C. The presence of diphenyl ethane suggests the complete dechlorination of DDT. The formation of benzene suggests a strong reduction. The method is efficient, cost-effective and may be applied at the industrial-level.     

High-valent iron-based oxidants to treat perfluorooctanesulfonate and perfluorooctanoic acid in water

Perfluoroalkyl and polyfluoroalkyl substances are occurring in consumer and industrial products. They have been found globally in the aquatic environment including drinking water sources and treated wastewater effluents, which has raised concern of potential human health effects because these substances may be bioaccumulative and extremely persistent. The saturated carbon–fluorine bonds of the substances make them resistant to degradation by physical, chemical, and biological processes. There is therefore a need for advanced remediation methods. Iron-based methods involving high-valent compounds are appealing to degrade these substances due to their high oxidation potentials and capability to generate environmentally friendly by-products. This article presents for the first time the oxidation ability of tetraoxy anions of iron(V) (Fe^VO₄ ^3?, Fe(V)), and iron(IV) (Fe^IVO₄ ^4?, Fe(IV)), commonly called ferrates, in neutral and alkaline solutions. Solid compounds of Fe(V) (K₃FeO₄) and Fe(IV) (Na₄FeO₄) were added directly into buffered solution containing perfluorooctansulfonate and perfluorooctanoic acid at pH 7.0 and 9.0, and mixed solutions were subjected to analysis for remaining fluoro compounds after 5 days. The analysis was performed by liquid chromatography–mass spectrometry/mass spectrometry technique. Fe(IV) showed the highest ability to oxidize the studied contaminants; the maximum removals were 34 % for perfluorooctansulfonate and 23 % for perfluorooctanoic acid. Both Fe(V) and Fe(IV) had slightly higher tendency to oxidize contaminants at alkaline pH than at neutral pH. Results were described by invoking reactions involved in oxidation of perfluorooctansulfonate and perfluorooctanoic acid by ferrates in aqueous solution. The results demonstrated potentials of Fe(V) and Fe(IV) to degrade perfluoroalkyl substances in contaminated water.     

Color removal efficiency of dyes using nanozerovalent iron treatment

In this study, zerovalent iron nanoparticles (Fe⁰) were synthesized by chemical reduction method using ferric chloride hexahydrate (FeCl₃?·?6H₂O) as a starting material. Sodium borohydride (NaBH₄) was used as a reducer. The synthesized nanozerovalent iron (NZVI) was separated using magnets. The X-ray diffraction pattern of iron (Fe) nanoparticles showed that the presence of intensive diffraction peak at 2θ value of 45.33° from the lattice plane of face-centered cubic Fe unequivocally indicates that the particles are made of pure Fe. The size of the synthesized NZVI was found to be 16.64?nm. The scanning electron micrograph revealed that the particles have a hexagonal and spherical shape in nature. EDX showed the surface atomic distribution and chemical composition of NZVI. The decolorization efficiency rose with increasing concentration of nanoparticles as well as with time. Maximal color removal efficiency was 90.72% when using 0.5?g/100?mL Fe nanoparticle for acridine orange. Data revealed that the function of NZVI on color removal efficiency was statistically significant. The correlation coefficient between NZVI concentration and time showed a strong negative correlation for dyes used in the experiment.     

Individual and combined toxicity of some petroleum aromatics to the marine amphipod Elasmopus pectenicrus

Toxicity of 4 components of petroleum oils to the marine amphipod Elasmopus pectenicrus (Bate) has been assessed. Two ephemeral aromatic hydrocarbons, naphthalene (A) and 1, 2, 4-trimethylbenzene (B) were more toxic than two persistent aromatics, o-cresol (C) and o-toluidine (D). The acute toxicity concentrations obtained for individual aromatic compounds were always greater than the actual concentrations found in the water-soluble fractions (WSF) of fuel oils. Results from mixtures of 2 or more components indicated that the LC₅₀ levels were primarily determined by the more toxic substances, A and B. Naphthalene and 1, 2, 4-trimethylbenzene became more toxic to the E. pectenicrus when present in a mixture of more than 2 components, and the toxicity increased with increasing numbers of components present. Synergistic effects, therefore, possibly occur in the whole WSF. No antagonistic effects were observed among the 4 petroleum aromatics.University of Texas, Marine Science Institute Contribution No. 290     

Aktuelle und künftige Emissionen treibhauswirksamer fluorierter Verbindungen in Deutschland

The fluorinated compounds sulphur hexafluoride (SF₆), perfluorocarbons (CF₄, C₂F₆) and hydrofluorocarbons (HFCs) are atmospheric trace gases with extremely high global warming potentials (GWP). The study examines the real emissions of these compounds in Germany between 1990 and 1995, and develops projections for the years up to 2020. These projections indicate that annual perfluorocarbon releases will drop between the years 1990 and 2000 from 335 t/34 t to 100 t/10 t due to automation measures at the main source (aluminium smelting). Sulphur hexafluoride emissions, however, will remain in the range between 200 and 300 t per annum until the year 2020. By far the largest emitters are car tyres and sound-insulation glazing, non-electrical swithgear, the latter being relatively well sealed and linked to management and reprocessing concepts for used gas. As concerns hydrofluorocarbons which have only been used since 1990 with the specific intention of substituting chlorofluorocarbons (CFCs), an increasing degree of CFC substitution in stationary and mobile refrigeration technology, in canned PUR foams and in asthma sprays must be expected to lead to steeply rising emissions to levels exceeding 9,700 t/a from the year 2007 onwards, if halogen-free alternatives are not used more strongly. Assuming these trends, the cumulative emissions of the stated fluorinated compounds will correspond to a global warming impact of 25 million t CO₂ (GWP time horizon: 100 years) by the year 2020.     

A novel procedure for acid-catalysed K2FeO4 oxidation of benzyl alcohol in organic phase

Recent investigations have shown that ferrate(VI) salts oxidize organic compounds in aqueous phases with fast reaction from seconds to minutes and poor selectivity. Few studies have used ferrate(VI) in organic phases. The main issues are the poor solubility of K₂FeO₄ in common organic solvents and the low reaction rate. Therefore the interests to date are focused on finding a more effective catalyst in the organic oxidation. Up to now no work has been reported on acids as catalysis for the oxidative abilities of K₂FeO₄ in organic phases. Here we present a novel procedure for oxidizing benzyl alcohol to benzaldehyde without an overoxidation to benzoic acid by K₂FeO₄ in an organic phase. Using benzyl alcohol as a model, the catalytic activity of various acid solutions was measured. We found that the reactivity of K₂FeO₄ to the oxidation of benzyl alcohol can be highly enhanced by addition of a small amount of acid solution at room temperature. The catalytic ability of acid solutions follows the order acetic acid < oxalic acid < phosphomolybdic acid < phosphotungstic acid. On the basis of a theoretical analysis, a reaction mechanism is proposed. This method provides a new green way for oxidizing organic substances by K₂FeO₄ in nonaqueous media_.     

Electrochemical remediation of phenanthrene from contaminated kaolinite

In this work a two-stage process combining soil electrokinetic remediation and liquid electrochemical oxidation for the remediation of polluted soil with organic compounds has been developed and evaluated using phenanthrene-spiked kaolinite. Application of an unenhanced electrokinetic process resulted in negligible removal of phenanthrene from the kaolinite sample. Addition of co-solvents and electrolyte to the processing fluid used in the electrode chambers enhanced phenanthrene desorption from the kaolinite matrix and favoured electro-osmotic flow. Near-complete removal of phenanthrene was achieved using Na₂SO₄ and ethanol in the processing fluid. Phenanthrene was transported towards the cathode chamber where it was collected. The cathodic solution containing the pollutant was treated by electrochemical oxidation; complete degradation of phenanthrene occurred after 9 h using Na₂SO₄ as electrolyte.     

Kinetics study of photocatalytic process for treatment of phenolic wastewater by TiO2 nano powder immobilized on concrete surfaces

In this study, kinetics of photocatalytic degradation of phenolic wastewater in immobilized photocatalytic reactor was investigated. Immobilization of titanium dioxide (TiO₂) nano powders on concrete surfaces were accomplished with epoxy concrete sealer. Kinetics of photocatalytic reactions has been proposed to follow the Langmuir–Hinshelwood model in different initial phenol concentration, pH, and UV lamp intensity. First-order reaction kinetics with respect to the pollutant concentration was obtained for the reaction. Effect of UV lamp intensity showed that kinetic constants were proportional to the power of 0.73–1 of the photonic flow. In all cases kinetic constant increases as pH of the system reached up to 12 units. Several reaction intermediates were identified using the GC/Mass analysis. Products at the initial stage of the reaction were aromatic compounds, contained hydroquinone, benzoquinone, and catechol. These intermediates underwent further photocatalytic oxidation to aliphatic compounds and finally into CO₂ and H₂O after 4?h. Kinetic constants of intermediate compounds were determined using mathematical–chemical equations and nonlinear regression. Data showed that the differences between the mathematical model and Langmuir–Hinshelwood model for the kinetic constant was less than 5%.     

Role of heavy polar organic compounds for water repellency of sandy soils

Separation and chemical characterisation of specific compounds responsible for soil water repellency has not previously been achieved. Here we describe the extraction, separation and analysis by gas chromatography-mass spectrometry of organic compounds found in wettable and water repellent sandy soils from the Netherlands and United Kingdom. Fatty acids (C₁₆–C₂₄), amides (C₁₄–C₂₄), alkanes (C₂₅–C₃₃), aldehydes/ketones (C₂₃–C₃₁) and complex ring-containing structures were detected in all samples. We found a greater abundance of high molecular mass polar compounds in the water repellent samples.     

The use of metabolic ratios for determining the catabolic substrates of a solitary ascidian

In a previous study, Hatcher (1989: Mar. Biol. 102: 445–452) found that variations in CO₂ and O₂ respiration rates in individual marine invertebrates led to RQ (respiratory quotient) values which were variable and often outside theoretical limits. The present study was designed to examine the variability in several excretionbased metabolic ratios which are often used as alternatives for the RQ in qualitative predictions of catabolic substrates. The experimental organism was a solitary ascidian,Herdmania momus (Savigny), collected near Perth, Western Australia, between January and July 1984. Respiration and excretion rates ofH. momus were examined as a function of a progressive nutritional stress, and covariation was examined. Nutritional stress accounted for more of the variation over time in respiration rates (40 to 50%) than in NH ₄ ⁺ excretion rates (20%). Significant net exchanges of dissolved organic compounds were measured. Qualitative predictions of catabolic substrates were based on a comparison of metabolic ratios with theoretical limits. The O:PO ₄ ^3- ratios were lower than the theoretical limits. The values of the O:NH ₄ ⁺ and NH ₄ ⁺ :PO ₄ ^3- ratios were not influenced by nutritional conditions but changed as a function of reproductive condition of the ascidians. Based on the results of this study, it was concluded that metabolic ratios measured on individual ascidians cannot be reliable predictors of catabolic substrates.     

Metal Interactions in carcinogenesis†

Mixed exposures to a number of metallic compounds may give rise to a carcinogenic response in humans.

An interaction between occupational exposure to arsenic and cigarette smoking has been documented epidemiologically. A multiplicative effect was indicated concerning the occurrence of lung cancer when both of the exposures were present. Several experimental studies have been reported in the literature concerning interactions between benzo(a)pyrene and Fe₂O₃ as well as some other metallic compounds like Ni₃S₂, PbO, MgO and TiO₂ in relation to respiratory carcinogenicity. There is also limited evidence of a positive interaction between arsenic trioxide and benzo(a)pyrene. Particles containing V and Ni were obtained from the flue gases of power plants burning heavy fuel oil. Such particles were not carcinogenic themselves but enhanced the carcinogenicity of benzo(a)pyrene even more efficiently than Fe₂O₃.

Increased dietary selenium intakes can decrease the carcinogenicity of several organic carcinogens in animals and dietary zinc can effectuate both enhancement and inhibition of carcinogenicity depending on dietary concentration.     

Photocatalytic degradation of chlorophenols using Ru(bpy) 3 2+ /S2O 8 2−

Advanced oxidation processes, such as photocatalysed oxidation, provide an important route for degradation of wastes. In this study, the lowest excited state (³MLCT) of Ru(bpy)₃²⁺ is used to break down chlorophenol pollutant molecules to harmless products. This has the advantage of using visible light and a short-lived catalytically active species. Photolysis of deaerated aqueous solutions of a variety of mono- and poly-substituted chlorophenols has been followed in the presence of Ru(bpy)₃²⁺/S₂O₈²⁻ with near visible light (λ > 350 nm) by UV/visible absorption spectroscopy, luminescence, potentiometry, NMR and HPLC techniques. Upon irradiation, a decrease is observed in the chlorophenol concentration, accompanied by the formation of Cl⁻, H⁺ and SO₄²⁻ ions as the main inorganic products. Benzoquinone, phenol, dihydroxybenzenes and chlorinated compounds were the dominant organic products. As the ruthenium(II) complex is regenerated in the reaction, the scheme corresponds to an overall catalytic process. The kinetics of the rapid chlorophenol photodechlorination has been studied, and are described quite well by pseudo-first order behaviour. Further studies on this were made by following Cl⁻ release with respect to the initial Ru(bpy)₃²⁺ and S₂O₈²⁻ concentrations. A comparison is presented of the photodechlorination reactivity of the mono and polychlorophenols studied at acidic and alkaline pH.     

Supramolecular complex formation,a possible antigenotoxic mechanism of glucomannan against aflatoxin B1

Abstract

Glucomannan is a highly branched polysaccharide with glycosidic linkages, constituted of mannoses and glucoses. In recent years, its usefulness due to its immunological, antioxidant and antimutagenic activity has been recognized. The aim of the study was to determine the antigenotoxic ability of glucomannan extracted from Candida utilis orally administered (100–700?mg/kg) to mice, which subsequently received 1?mg/kg aflatoxin B₁. Hepatocytes obtained from these animals 4–16?h post administration were examined by means of the comet assay. The antigenotoxic effect was found to be higher than that observed in previous studies with α-mannan and β-D-glucan isolated from Saccharomyces cerevisiae., In order to explore the possibility of formation of a supramolecular complex between glucomannan and aflatoxin B₁, both compounds were co-crystallized, their melting points determined, and the complex analyzed through ultraviolet spectroscopy. The spectroscopy data suggest that the protective effect of glucomannan is related to the formation of a supramolecular complex between the two compounds.     

Catalytic decomposition of polychlorinated biphenyls (PCBs)

In this study, polychlorinated biphenyls (PCBs) were decomposed by low‐temperature heat treatment with metallic catalyst, and with metallic catalyst and a hydrogen source. Of the catalysts used, iron (Fe) was the most active catalyst for the decomposition of PCBs, and the decomposition was due to dechlorination. The addition of hydrogen sources accelerated the decomposition of PCBs in the presence of catalyst. Surface analysis of the catalyst using X‐ray photoelectron spectroscopy (XPS) suggested that the emitted chlorine was presumed to form metal chloride. The reactions of each homolog can be expressed by a successive first‐order reaction model. This means that a substituted chlorine is successively detached during this reaction. The overall decomposition rate in this reaction system was controlled by that of the lower chlorinated homologs. The decomposition rates with Fe and NaBH₄ for the lower chlorinated homologs were about 10 times as fast as the rates with only Fe.     

Troposphärisches Ozon: Entstehung, Konzentrationsvariabilität und Wirkung unter dem Gesichtspunkt der Ozonminderung

This paper is an attempt to summarise and critically assess our knowledge on the formation, variation in concentrations and impact of ozone under the aspect of abatement strategies. The present ozone budget is determined to about 50% through human activities where methane and carbon monoxide contribute more than 80% to ozone formation. This “residual” or “background” ozone determines the annual mean ozone concentration. Due to the long time period (months and years) required for CH₄ and CO oxidation, both compounds do not contribute to the excessive ozone concentrations often found in the summer. Moreover, the increase in tropospheric ozone is becoming a global problem. Because emissions of CH₄ and CO are increasing globally, the “background” ozone will also increase in the future. Non-methanehydrocarbons (NMHC) may produce O₃ within a few days because of their high reactivity concerning oxidants. For photochemical O₃ formation, the source-sink budget has to be taken into account for making an estimation of the net ozone formation. Ozone accumulation only occurs when the removal potential (especially heterogeneous processes within clouds, but also a reduction in the net photochemical formation) of the air mass is small. This “excess” ozone has been reduced successfully within the last decade, most likely as a result of automobile catalyst use. An impact of O₃ on humans has been found only for concentrations >100 ppb. Thus, O₃ should not be a problem for people. Although vegetation is much more sensitive (esp. conifers), it is not possible to present reliable thresholds at present. There is evidence that the dose (accumulation exposure) is an important criterion. Therefore, a mean annual concentration which may possibly be increasing further should be the target of air pollution controls. Former measures and ideas of ozone controlling have no usefulness in this sense.     

In vivo effects of acute administration of potassium tetranitrodiammine cobaltate(III) on rat erythrocytes

Potassium tetranitrodiammine cobaltate(III) K[Co(NH₃)₂(NO₂)₄] is a coordination complex having Co(III) as the central atom. Cobalt(III) compounds are being advocated for their anticarcinogenic potential. In the present study, we have for the first time evaluated this compound for its toxicity to rat RBC. The parameters studied include the effects of potassium tetranitrodiammine cobaltate(III) on GSH, GST, catalase, G6PD, acid phosphatase, GOT, and GPT. Scanning electron microscopy of RBCs of potassium tetranitrodiammine cobaltate(III) treated rats has also been carried out for evaluating its influence on the red cell morphology. The data showed that potassium tetranitrodiammine cobaltate(III) treatment causes marked biochemical changes in the rat RBCs along with changes in their shapes characterized by the formation of acanthocytes. The results thus suggest that acute administration of potassium tetranitrodiammine cobaltate(III) is potentially toxic to rat RBCs.     

Cytotoxic activity of spark‐decomposed sulfur hexafluoride and analysis of cytotoxic contributions of individual spark decomposition products†

Sulfur hexafluoride decomposed by electrical sparks has been found to by cytotoxic to hamster cells when tested in an in vitro cell survival assay, while SF₆ shows no cytotoxic activity. Chemical analysis of spark‐decomposed SF₆ has identified and quantified the following compounds: SOF₂, SO₂F₂, SF₄, SOF₄, SiF₄, SO₂ and HF. Each of these gases, at concentration ranges expected in spark‐decomposed SF₆, were tested for cytotoxic activity toward hamster cells. Of the gases showing cytotoxic activity, SO₂F₂ and SOF₄ were similar in activity, as were SOF₂ and SF₄, while the behavior of SiF₄ was different from the rest. None of these individual gases, at concentrations expected in spark‐decomposed SF₆, has sufficient cytotoxic activity to account for the cytotoxic effect of spark‐decomposed SF₆ observed in our assay system. A four‐component mixture of some of the gases enumerated above (at concentrations overestimating their abundance in spark‐decomposed SF₆) was much less cytotoxic than the spark‐decomposed SF₆ gas. A mathematical simulation of the cytotoxic activity of a mixture of gases at concentrations found in spark‐decomposed SF₆ was made, assuming independent cytotoxic effects from each component. The simulated cytotoxic effect thus computed was less than that seen in spark‐decomposed SF₆. Since individual components or mixtures of the major decomposition products do not account for the observed biological activity of spark‐decomposed SF₆, this suggests there may be one or more components, present in the spark‐decomposed gas at very low concentrations, which may have a very strong cytotoxic activity.     

High reduction of 4-nitrophenol using reduced graphene oxide/Ag synthesized with tyrosine

There is a demand for the development of environmental friendly methods for the synthesis of graphene composites. Reduced graphene oxide/silver (RGO/Ag) nanocomposites are very good catalysts. Here, we propose a simple, green method for the synthesis of RGO/Ag nanocomposite using the amino acid tyrosine as bioreductant and stabilizing agent. RGO/Ag nanocomposite was characterized by using various analytical techniques and studied for its catalytic degradation of 4-nitrophenol. Results of attenuated total reflectance Fourier transform infrared spectroscopy and Zeta potential at ?55 mV reveal the surface capping of tyrosine onto the reduced graphene oxide nanosheets. RGO/Ag nanocomposites show excellent catalytic reduction of 4-nitrophenol with NaBH₄, when compared to actual individual silver nanoparticles.     

Low level inhalation experiments with four different cadmium compounds in rats†

This long‐term inhalation study was designed to describe the toxicity and the carcinogenic risk from Cd compounds because it had been shown from former long‐term inhalation studies that cadmium choloride induced primary lung tumors in Wistar rats. It was therefore logical to examine whether other cadmium compounds to which human beings are more frequently exposed have also carcinogenic potency. In a long‐term inhalation study cadmium aerosols consisting of cadmium chloride (CdCl₂), cadmium oxide (CdO) as dusts and fumes, cadmium sulfate (CdSO₄), cadmium sulfide (CdS) and a combination of cadmium oxide/zinc oxide were used. Wistar rats were continuously exposed in inhalation chambers for 18 months 22 hrs a day or for 40 hrs a week. The studies will be terminated at the mean survival life time of the species. The aerosols were generated by several different systems. The particles of the cadmium aerosols have the average mass medium diameters in the range from 0.2 to 0.5 μm.