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Base-catalysed decomposition of polychlorinated biphenyls in transformer oils by mixture of sodium hydroxide, glycerol and iron.

ABSTRACT: In this research, a method based on base-catalysed decomposition (BCD) was developed using sodium hydroxide and glycerol for dechlorination of transformer oils with low levels of polychlorinated biphenyls (PCBs). PCB removal and dechlorination efficiencies were measured by gas chromatography and the silver nitrate titration method, respectively. PCB dechlorination and removal efficiencies after 4?h at 250°C and in the presence of iron were 97.4% and 99.8%, respectively. However, in the absence of iron the same efficiencies were calculated to be 79.4 and 99.7%, respectively. The dielectric loss factor of oil refined at 250°C was 0.0064 and did not meet the required standards to be reused in the transformers. However, that refined at 200°C satisfied the standards with acceptable conversion rates. Use of iron, besides increasing conversion rates, changed the mechanism of the reaction from nucleophilic substitution to a combination of hydrodechlorination and nucleophilic substitution. In the presence of iron, highly chlorinated PCBs were converted to less chlorinated PCBs, and this caused the concentration of less chlorinated PCBs to reach a peak and then decline thereafter. The production of PCB 36 confirmed this. However, in the absence of iron particles, all changes in the PCB concentration curves were downward.

SUBMITTER: Akhondi M

PROVIDER: S-EPMC6030273 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Base-catalysed decomposition of polychlorinated biphenyls in transformer oils by mixture of sodium hydroxide, glycerol and iron.

Akhondi Milad M Akhondi Milad M Dadkhah Ali A AA

Royal Society open science 20180613 6

In this research, a method based on base-catalysed decomposition (BCD) was developed using sodium hydroxide and glycerol for dechlorination of transformer oils with low levels of polychlorinated biphenyls (PCBs). PCB removal and dechlorination efficiencies were measured by gas chromatography and the silver nitrate titration method, respectively. PCB dechlorination and removal efficiencies after 4 h at 250°C and in the presence of iron were 97.4% and 99.8%, respectively. However, in the absence o ...[more]

PMID: 30110405

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Project description:While many neurodevelopmental disorders (NDDs) are thought to result from interactions between environmental and genetic risk factors, the identification of specific gene-environment interactions that influence NDD risk remains a critical data gap. We tested the hypothesis that polychlorinated biphenyls (PCBs) interact with human mutations that alter the fidelity of neuronal Ca2+ signaling to confer NDD risk. To test this, we used three transgenic mouse lines that expressed human mutations known to alter Ca2+ signals in neurons: (1) gain-of-function mutation in ryanodine receptor-1 (T4826I-RYR1); (2) CGG-repeat expansion in the 5' non-coding portion of the fragile X mental retardation gene 1 (FMR1); and (3) a double mutant (DM) that expressed both mutations. Transgenic and wildtype (WT) mice were exposed throughout gestation and lactation to the MARBLES PCB mix at 0.1, 1, or 6 mg/kg in the maternal diet. The MARBLES mix simulates the relative proportions of the twelve most abundant PCB congeners found in serum from pregnant women at increased risk for having a child with an NDD. Using Golgi staining, the effect of developmental PCB exposure on dendritic arborization of pyramidal neurons in the CA1 hippocampus and somatosensory cortex of male and female WT mice was compared to pyramidal neurons from transgenic mice. A multilevel linear mixed-effects model identified a main effect of dose driven by increased dendritic arborization of cortical neurons in the 1 mg/kg PCB dose group. Subsequent analyses with genotypes indicated that the MARBLES PCB mixture had no effect on the dendritic arborization of hippocampal neurons in WT mice of either sex, but significantly increased dendritic arborization of cortical neurons of WT males in the 6 mg/kg PCB dose group. Transgene expression increased sensitivity to the impact of developmental PCB exposure on dendritic arborization in a sex-, and brain region-dependent manner. In conclusion, developmental exposure to PCBs present in the gestational environment of at-risk humans interfered with normal dendritic morphogenesis in the developing mouse brain in a sex-, genotype- and brain region-dependent manner. Overall, these observations provide proof-of-principle evidence that PCBs interact with heritable mutations to modulate a neurodevelopmental outcome of relevance to NDDs.

Project description:BACKGROUND:Xenobiotic metabolism is complex, and accounting for bioactivation and detoxification processes of chemicals remains among the most challenging aspects for decision making with in vitro new approach methods data. OBJECTIVES:Considering the physiological relevance of human organotypic culture models and their utility for high-throughput screening, we hypothesized that multidimensional chemical-biological profiling of chemicals and their major metabolites is a sensible alternative for the toxicological characterization of parent molecules vs. metabolites in vitro. METHODS:In this study, we tested 25 polychlorinated biphenyls (PCBs) [PCB 3, 11, 52, 126, 136, and 153 and their relevant metabolites (hydroxylated, methoxylated, sulfated, and quinone)] in concentration-response (10?nM-100?M) for effects in human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs) and endothelial cells (ECs) (iPSC-derived and HUVECs). Functional phenotypic end points included effects on beating parameters and intracellular Ca2+ flux in CMs and inhibition of tubulogenesis in ECs. High-content imaging was used to evaluate cytotoxicity, mitochondrial integrity, and oxidative stress. RESULTS:Data integration of a total of 19 physicochemical descriptors and 36 in vitro phenotypes revealed that chlorination status and metabolite class are strong predictors of the in vitro cardiovascular effects of PCBs. Oxidation of PCBs, especially to di-hydroxylated and quinone metabolites, was associated with the most pronounced effects, whereas sulfation and methoxylation of PCBs resulted in diminished bioactivity. DISCUSSION:Risk characterization analysis showed that although in vitro derived effective concentrations exceeded the levels measured in the general population, risks cannot be ruled out due to the potential for population variability in susceptibility and the need to fill data gaps using read-across approaches. This study demonstrated a strategy for how in vitro data can be used to characterize human health risks from PCBs and their metabolites. https://doi.org/10.1289/EHP7030.

Dataset Information

Base-catalysed decomposition of polychlorinated biphenyls in transformer oils by mixture of sodium hydroxide, glycerol and iron.

Publications

Base-catalysed decomposition of polychlorinated biphenyls in transformer oils by mixture of sodium hydroxide, glycerol and iron.

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