Tetrahydrofuran Degradation Research Articles

Attributing Effects of Aqueous C 60 Nano-Aggregates to Tetrahydrofuran Decomposition Products in Larval Zebrafish by Assessment of Gene Expression

BackgroundC60 is a highly insoluble nanoparticle that can form colloidal suspended aggregates in water, which may lead to environmental exposure in aquatic organisms. Previous research has indicated toxicity from C60 aggregate; however, effects could be because of tetrahydrofuran (THF) vehicle used to prepare aggregates.ObjectiveOur goal was to investigate changes in survival and gene expression in larval zebrafish Danio rerio after exposure to aggregates of C60 prepared by two methods: a) stirring and sonication of C60 in water (C60–water); and b) suspension of C60 in THF followed by rotovaping, resuspension in water, and sparging with nitrogen gas (THF–C60).ResultsSurvival of larval zebrafish was reduced in THF–C60 and THF–water but not in C60–water. The greatest differences in gene expression were observed in fish exposed to THF–C60 and most (182) of these genes were similarly expressed in fish exposed to THF–water. Significant up-regulation (3- to 7-fold) of genes involved in controlling oxidative damage was observed after exposure to THF–C60 and THF–water. Analyses of THF–C60 and THF–water by gas chromatography–mass spectrometry did not detect THF but found THF oxidation products γ-butyrolactone and tetrahydro-2-furanol. Toxicity of γ-butyrolactone (72-hr lethal concentration predicted to kill 50% was 47 ppm) indicated effects in THF treatments can result from γ-butyrolactone toxicity.ConclusionThis research is the first to link toxic effects directly to a THF degradation product (γ-butyrolactone) rather than to C60 and may explain toxicity attributed to C60 in other investigations. The present work was first presented at the meeting “Overcoming Obstacles to Effective Research Design in Nanotoxicology” held 24–26 April 2006 in Cambridge, Massachusetts, USA.

High efficiency degradation of tetrahydrofuran (THF) using a membrane bioreactor: identification of THF-degrading cultures of Pseudonocardia sp. strain M1 and Rhodococcus ruber isolate M2.

A mixed microbial culture capable of growing aerobically on tetrahydrofuran (THF) as a sole carbon and energy source was used as the inoculum in a 10 l working volume membrane bioreactor. Following start-up, the reactor was operated in batch mode for 24 h and then switched to continuous feed with 100% biomass recycle. On average, greater than 96% of THF fed to the reactor was removed during the 8-month study. THF loading rates ranged from 0.62 to 9.07 g l(-1) day(-1) with a hydraulic retention time of 24 h. THF concentrations as high as 800 mg/l were tolerated by the culture. Biomass production averaged 0.28 kg total suspended solids/kg chemical oxygen demand removed, i.e., comparable to a conventional wastewater treatment process. Periodic batch wasting resulted in a solids retention time of 7-14 days. Reactor biomass typically ranged from 4 to 10 g/l volatile suspended solids and the effluent contained no solids. Pure THF-degrading cultures were isolated from the mixed culture based on morphological characteristics, Gram-staining and THF degradation. Based on 16S rDNA analysis the isolates were identified as Pseudonocardia sp. M1 and Rhodococcus ruber M2.

Physico‐Chemical Properties of Nb/Ti Binary Oxides and their Photo‐Catalytic Activities

AbstractA series of binary Nb/Ti ox ides was prepared by co‐precipitation. Their structure and physico‐chemical properties in term of surface area, surface acidity, bandgap energy and life time of the radiation‐excited electron‐hole pair were examined. These properties were correlated to their catalytic activities in photodegradation of oxygenated organic pollutants in water. The organic pollutants under investigation were phenol, cyclohexanol and tetrahydrofuran (THF). The lab‐made titanium oxide and those doped with a small amount of Nb (molar ratio of Nb/(Nb+Ti) less than 20%) showed higher activities in degradation of the organic pollutants. However, the mineralization efficiencies were different for the three oxygenated organic pollutants. Nearly complete mineralization to form CO2 could be achieved in the degradation of phenol. For cyclohexanol, only ca. 50% selectivity of CO2 was obtained over all the catalysts. Similar low efficiency in complete mineralization was observed in the degradation of THF, but higher selectivity (ca. 65–75%) of CO2 could be obtained on the binary oxide with Nb content less than 4 molar %. In contrast, the binary Nb/Ti oxide with equal Nb and Ti molar content gave the poorest catalytic activity. The photocatalytic activity is generally correlated well to the life time of the radiation‐excited electron‐hole pairs. The contribution of surface acidity to the photocatalytic activity was only demonstrated on the niobia‐dominant oxide catalysts to ward THF. The photocatalytic activity was found to have no correlation with the crystal line structure, the bandgap energy, the surface area or the surface hydroxyl density.

Photocatalytic degradation of aqueous organic solvents in the presence of hydroxyl radical scavengers

Tetrahydrofuran (THF) and 1,4‐dioxane (DIOX) are two common solvents that are found in contaminated groundwater. Photocatalytic degradation of these two organic solvents in water was studied in the presence of carbonate and bicarbonate, which are hydroxyl radical scavengers. The reactions were performed in an annular slurry photoreactor. It was found that bicarbonate and carbonate ions acted as hydroxyl radical scavengers and slowed down the DIOX degradation rate but did not significantly affect the THF degradation rate. The slight enhancement in the THF degradation rate in the presence of sodium bicarbonate may be due to the increase in pH. In addition, it appears that bicarbonate and carbonate ions were reduced to other organic species during the photocatalytic reaction.

Tetrahydrofuran degradation by a newly isolated culture of Pseudonocardia sp. strain K1

An organism capable to grow aerobically on tetrahydrofuran as sole source of carbon and energy was isolated from a waste water treatment plant. The organism designated as strain K1 was identified as Pseudonocardia sp. by chemotaxonomic and morphological characteristics as well as analysis of the gene encoding the 16S rRNA. The highest binary sequence similarity value of 99.0% was obtained to Pseudonocardia sulfidoxydans and Pseudonocardia hydrocarbonoxydans. Optimal growth with a doubling time of 14 h was observed at a tetrahydrofuran concentration of 20 mM and pH 7.0 at 28°C. Under these conditions the substrate was completely degraded within 72 h. In situ concentrations of up to 60 mM were tolerated by the organism without a significantly increased doubling time. The strain also grew on diethyl ether, polyethylene glycol and on γ-butyrolactone and 4-hydroxybutyrate – two potential intermediates in tetrahydrofuran degradation – as sole carbon and energy source.

Tetrahydrofuran degradation by a newly isolated culture of Pseudonocardia sp. strain K1.

An organism capable to grow aerobically on tetrahydrofuran as sole source of carbon and energy was isolated from a waste water treatment plant. The organism designated as strain K1 was identified as Pseudonocardia sp. by chemotaxonomic and morphological characteristics as well as analysis of the gene encoding the 16S rRNA. The highest binary sequence similarity value of 99.0% was obtained to Pseudonocardia sulfidoxydans and Pseudonocardia hydrocarbonoxydans. Optimal growth with a doubling time of 14 h was observed at a tetrahydrofuran concentration of 20 mM and pH 7.0 at 28 degrees C. Under these conditions the substrate was completely degraded within 72 h. In situ concentrations of up to 60 mM were tolerated by the organism without a significantly increased doubling time. The strain also grew on diethyl ether, polyethylene glycol and on gamma-butyrolactone and 4-hydroxybutyrate - two potential intermediates in tetrahydrofuran degradation - as sole carbon and energy source.

Photocatalytic degradation of aqueous tetrahydrofuran, 1,4‐dioxane, and their mixture with TiO2

Photocatalytic degradation of tetrahydrofuran, 1,4‐dioxane, and their mixture in a slurry photoreactor was studied. Using both GC/MS and ion chromatography (IC) methods, possible intermediates were detected and the reaction mechanism pathways for both compounds were proposed. Kinetic models were developed and the kinetic parameters were estimated using a statistical method of non‐linear parameter estimation in which all experimental data were utilized. It was shown that tetrahydrofuran was disappeared via direct oxidation as well as hydroxyl radical attack. A modified Langmuir‐Hinshelwood described the degradation behavior of tetrahydrofuran and the binary system. 1,4‐Dioxane obeyed a simple Langmuir‐Hinshelwood kinetic form in the single compound system.

Reactions of Tetrahydrofuran and Lithium Hexafluoroarsenate with Lithium

As part of a basic study of the secondary Li electrode, the reactions of tetrahydrofuran (THF) with Li have been evaluated. Tetrahydrofuran is reductively cleaved by Li to lithium n‐butoxide , the enolate anion of acetaldehyde, and ethylene. The anion is reduced by Li to which further reacts with to form a brown film on Li. The brown film appears to be composed of an polymer and . These products were observed to form irrespective of electrolyte purification procedure. In fact, highly purified media reacted most readily with Li presumably due to the absence of protective film‐forming gases such as and . Extended preelectrolysis of electrolytes formed large amounts of basic material, as expected. The same experiment performed on electrolyte revealed essentially no change in the medium's pH. Apparently, the from and the basic material from THF degradation effectively neutralize each other. A mechanism which accounts for Li‐cyclic ether reactivity is proposed.