Concept: Hydrogen chloride
Simultaneous removal of nitrate and pentachlorophenol from simulated groundwater using a biodenitrification reactor packed with corncob
- Environmental science and pollution research international
- Published almost 5 years ago
Both nitrate and pentachlorophenol (PCP) are familiar pollutants in aqueous environment. This research is focused on the simultaneous removal of nitrate and PCP from simulated contaminated groundwater using a laboratory-scale denitrification reactor packed with corncob as both carbon source and biofilm support. The reactor could be started up readily, and the removal efficiencies of nitrate and PCP reached up to approximately 98 % and 40-45 % when their initial concentrations were 50 mg N/L and 5 mg/L, respectively, after 15-day continuous operation at 10 h of hydraulic retention time (HRT) and 25 °C. Approximately 91 % of PCP removal efficiency was achieved, with 2.47 mg/L of chloride ion release at 24 h of HRT. Eighty-two percent of chlorine in PCP removed was ionized. The productions of 3-chlorophenol and phenol and chloride ion release indicate that the reductive dechlorination reaction is a major degradation pathway of PCP under the experimental conditions.
Bioaccessibility of Fukushima-Accident-Derived Cs in Soils and the Contribution of Soil Ingestion to Radiation Doses in Children
- Risk analysis : an official publication of the Society for Risk Analysis
- Published 7 months ago
Ingestion of contaminated soil is one potential internal exposure pathway in areas contaminated by the Fukushima Daiichi Nuclear Power Plant accident. Doses from this pathway can be overestimated if the availability of radioactive nuclides in soils for the gastrointestinal tract is not considered. The concept of bioaccessibility has been adopted to evaluate this availability based on in vitro tests. This study evaluated the bioaccessibility of radioactive cesium from soils via the physiologically-based extraction test (PBET) and the extractability of those via an extraction test with 1 mol/L of hydrochloric acid (HCl). The bioaccessibility obtained in the PBET was 5.3% ± 1%, and the extractability in the tests with HCl was 16% ± 3%. The bioaccessibility was strongly correlated with the extractability. This result indicates the possibility that the extractability in HCl can be used as a good predictor of the bioaccessibility with PBET. In addition, we assessed the doses to children from the ingestion of soil via hand-to-mouth activity based on our PBET results using a probabilistic approach considering the spatial distribution of radioactive cesium in Date City in Fukushima Prefecture and the interindividual differences in the surveyed amounts of soil ingestion in Japan. The results of this assessment indicate that even if children were to routinely ingest a large amount of soil with relatively high contamination, the radiation doses from this pathway are negligible compared with doses from external exposure owing to deposited radionuclides in Fukushima Prefecture.
The pressure-temperature phase diagram of ice displays a perplexing variety of structurally distinct phases. In the century-long history of scientific research on ice, the proton-ordered ice phases numbered XIII through XV were discovered only recently. Despite considerable effort, none of the transitions leading from the low-temperature ordered ices VIII, IX, XI, XIII, XIV and XV to their high-temperature disordered counterparts were experimentally found to display the full Pauling entropy. Here we report calorimetric measurements on suitably high-pressure-treated, hydrogen chloride-doped ice XIV that demonstrate just this at the transition to ice XII. Dielectric spectroscopy on undoped and on variously doped ice XII crystals reveals that addition of hydrogen chloride, the agent triggering complete proton order in ice XIV, enhances the precursor dynamics strongest. These discoveries provide new insights into the puzzling observation that different dopants trigger the formation of different proton-ordered ice phases.
The in situ immobilization of metal-contaminated sediment, using various amendments, has attracted great attention owing to their cost-effectiveness. The present study investigated the effectiveness of Chinese loess on Cu, Zn, Cd and Pb stabilization by decreasing their bioavailability in contaminated sediment. The loess was mixed with the sediment in doses of 0, 0.5, 1, 2, 5, 10 and 20 kg. Approximately 70 d after loess application, the effectiveness was evaluated using the Tessier sequential extraction procedure and single extractants, including ethylenediaminetetraacetic acid disodium salt (EDTA-2Na), diethylenetriaminepentaacetic acid (DTPA), calcium chloride (CaCl2) and hydrochloric acid (HCl). The results indicated that the loess can effectively transform Cu from the carbonate fraction into the residual fraction when the loess dose was ≥5 kg. However, loess had little effect on Zn, Cd and Pb immobilization. Correlation analysis showed that these four extractants can provide a good indication of the toxicity of Cu, Zn, Cd and Pb in the amended sediment. Additionally, the organic matter content in the amended sediment decreased by 1.4% for CK, 1.6% for L0.5, 1.7% for L1, 1.5% for L2, 1.5% for L5, 1.9% for L10 and 1.9% for L20 (CK: untreated sediment; L0.5 to L20 represent loess doses of 0.5, 1, 2, 5, 10 and 20 kg, respectively) compared to the initial organic matter content in the unamended sediment, which may increase the atmospheric carbon dioxide owing to the degradation of organic matter.
A novel, high-efficiency and high-selectivity construction of β-trifluoromethyl enol ether via base-induced/promoted C-O coupling of trifluoromethylated vinyl chloride and phenols is presented with a broad substrate scope. The reaction mechanism, especially the significantly high selectivity, was excavated and understood via DFT calculation, and is well supported by the experimental observation.
Fullerene C98 possesses 259 isomers obeying the isolated pentagon rule (IPR), from which two, nos. 116 and 248, have been confirmed earlier as chloro derivatives. High-temperature chlorination of C98-containing mixtures afforded crystals of several chloro derivatives, and their structure elucidation by X-ray crystallography revealed the presence of new isomers, nos. 107, 109, and 120, in the fullerene soot. Evidence for an isomer of no. 111 is also presented. In addition, a new chloride of the known isomer 248 has been isolated and structurally studied. The chlorination patterns of the chlorides are discussed in terms of the formation of isolated C═C bonds and aromatic substructures on the fullerene cages.
Some chemicals were usually utilized in the hydrothermal dechlorination (HTD) of chlorine-containing wastes without revealing their roles. This work intends to investigate the role of chemical additives in the HTD of PVC (polyvinyl chloride). Several chemicals, including Na2CO3, KOH, NaOH, NH3·H2O, CaO and NaHCO3, were added into the PVC HTD process, which was conducted in subcritical Ni(2+)-containing water at 220 °C for 30 min. The results show the alkalinity of additives had notable effects on the dechlorination efficiency (DE) of PVC due to the neutralization between HCl and additives. The most effective additive is Na2CO3, with the maximum DE of 65.12% at a Na2CO3 concentration of 0.025 M in this study. According to SEM, the hydrochar obtained from the HTD with Na2CO3 become more porous and looser than the others did, which contributed to the acceleration of PVC dechlorination. The DE vibration with the concentration of additives was different. For Na2CO3, it was firstly increased and then decreased with Na2CO3 concentration increasing from 0.01 M to 0.04 M. As for KOH and NaOH, it kept reducing with the concentration increasing from 0.02 M to 0.08 M. The drop in DE was ascribed to surface poisoning and a loss in the supported active phase resulting from the metal chloride species formed. FTIR analysis shows that the elimination of hydrogen chloride was the main route for HTD of PVC. All the results provide some fundamental data to find some cheap but efficient chemicals with aim to recycle the chlorinated organic wastes effectively.
A new photoredox-catalyzed chlorotrifluoromethylation reaction of internal arylalkynes under mild conditions using visible light has been developed. The reactions proceed with high levels of regio- and stereoselectivity and utilize commercially available CF3SO2Cl as both the CF3 and Cl source. In the mechanistic pathway for this process, generation of the CF3 radical and chloride ion occurs by Ir(ppy)3-photocatalyzed reductive decomposition of CF3SO2Cl. The synthetically important trifluoromethyl-substituted vinyl chlorides produced in this process can be readily transformed to 1,1-bis-arylalkenes by using Suzuki coupling.
A unique, platinum-catalyzed, direct C-H acylation of 2-(aryloxy)pyridines with acyl chlorides is discovered. The reaction requires neither an oxidant nor other additives. When both ortho positions of the aryl group are accessible, the double acylation occurs readily to produce the diacylated products. Aliphatic, aromatic, and α,β-unsaturated acyl groups can all be introduced. The acylation reaction may proceed through an analogous aromatic electrophilic substitution triggered by the nucleophilic attack of the platinum at the acyl chloride.
Copper contamination of self-assembled organic monolayer modified silicon surfaces following a ‘click’ reaction characterized with LAPS and SPIM
- Langmuir : the ACS journal of surfaces and colloids
- Published about 1 month ago
A copper(I) catalyzed azide alkyne cycloaddition (CuAAC) reaction, combined with microcontact printing was employed successfully to pattern alkyne terminated self-assembled organic monolayer modified silicon surfaces. Despite the absence of a copper peak in X-ray photoelectron spectra (XPS), copper contamination was found and visualized using light-addressable potentiometric sensors (LAPS) and scanning photo-induced impedance microscopy (SPIM) after the ‘click’ modified silicon surfaces were rinsed with hydrochloric acid (HCl) solution, which has been frequently used to remove copper residues in the past. Even cleaning with an ethylenediaminetetraacetic acid (EDTA) solution did not remove the copper residue completely. Different strategies for avoiding copper contamination, including the use of bulky chelators for the copper(I) catalyst and rinsing with different reagents, were tested. Only cleaning of the silicon surfaces with an EDTA solution containing trifluoroacetic acid (TFA) after the ‘click’ modification proved to be an effective method as confirmed by LAPS and SPIM results, which showed the expected potential shift due to the surface charge introduced by functional groups in the monolayer and allowed, for the first time, to image the impedance of an organic monolayer.