Decomposition Of Chloroform Research Articles

Dechlorination of CDCl3 on Fe(111): Implications for disinfection by-product degradation

Disinfection by-products are produced in the water supply by reactions of organic matter with halogenated disinfectants. Remediation of disinfection by-products can be accomplished by decomposition through reductive dehalogenation or corrosion reactions. Iron is ubiquitous in soils and pipeline systems, which comes into contact with municipal water sources. This study investigated the decomposition of chloroform, a model disinfection by-product, with an Fe(111) surface to measure the dechlorination mechanism using surface vibrational spectroscopy at the gas/solid interface. It was found that chloroform physisorbs on Fe(111) at -118°C and undergoes dissociative adsorption above -50°C. Vibrational modes are compared with density functional theory cluster models to identify the molecular orientation and indicate a difference in the C-Cl stretching modes that is coverage dependent. The desorption energy of chloroform from Fe(111) was measured as 67.5 (+/- 0.018) kJ/mol for the monolayer and 52.7 (+/- 2.2) kJ/mol for the multilayer. At 25 °C, d-chloroform is shown to dissociate as observed by Auger electron spectroscopy. The co-adsorption of water vapor, provide OH sites on the iron surface that appears to block a fraction of surface sites, allowing for less adsorption and chlorine deposition on Fe(111). The results show that Fe0 sites catalyze the dechlorination of chloroform, while OH sites oxidize the surface, suggesting that in aqueous solutions, metallic Fe is needed for dehalogenation.

Crystallization control based on A-site cation strategy for blue FAPbBr3 perovskite nanoplatelets with pure emission

Two-dimensional (2D) lead halide perovskite with attractive properties is considered one of the most promising candidates for preparing blue-emitting materials and corresponding optoelectronic devices. For the formamidinium-based (FA) nanoplatelets (NPLs), despite exhibiting better optical performance compared to their counterparts, it is still challenging to precisely control their emission in the blue region during synthesis and the influence of chloroform on the components of FAPbBr3 have not been investigated thoroughly. Herein, it is revealed that the decomposition of chloroform during the synthesis will introduce Cl into the crystal with the assistance of surface ligands, leading to the mixed-halide perovskite. Further, an A-site cation strategy was introduced for tuning the spectra of FAPbBr3 NPLs. The addition of Cs with a small ionic radius can shrink the arrangement of octahedrons and enhance their interactions, which will promote the seeding growth of perovskite and form uniform crystals. With help of surface ligands, these uniform crystals will further grow to form homogeneous perovskite NPLs. The obtained NPLs show the pure emission from sky-blue to deep-blue. To the best of our knowledge, it is the first report about finely tuning the emission of FAPbBr3 in the blue region. This crystallization control strategy by introducing Cs is beneficial for their further applications in the field of photoelectric devices.

Supramolecular porphyrin as an improved photocatalyst for chloroform decomposition.

In this work, the outlying decoration of the free-base meso-(4-tetra) pyridyl porphyrin (H2TPyP) with the RuCl(dppb)(5,5'-Me-bipy) ruthenium complex (here named Supra-H2TPyP) is observed as an improved molecular photocatalyst for dye-mediated chloroform (CHCl3) decomposition via one-photon absorption operating in the visible spectral range (532 nm and 645 nm). Supra-H2TPyP offers a better option for CHCl3 photodecomposition when compared to the same process mediated by pristine H2TPyP, which requires either excited-state- or UV absorption. The chloroform photodecomposition rates for Supra-H2TPyP as well as its excitation mechanisms are explored as a function of distinct laser irradiation conditions.

An Easy and Reliable Method for the Mitigation of Deuterated Chloroform Decomposition to Stabilise Susceptible NMR Samples

Highly reactive decomposition products of deuterated chloroform can deteriorate samples dissolved in this commonly used solvent for nuclear magnetic resonance (NMR) spectroscopy. Samples for metabolomics studies often contain a complex mixture of sensitive substances such as phospholipids, peptides, unsaturated fatty acids or vitamins. If these react with decomposition products (of chloroform), abnormal NMR spectra could result, e.g., signal shifts depending on pH, attenuation of signals over time due to chemical changes of analytes or new signals from reaction products. Such irreproducibly influenced spectra are especially problematic for non-targeted analysis methods using automated chemometrical data evaluation. To prevent these artefacts, chlorine, phosgene and hydrochloric acid need to be eliminated from deuterated chloroform before its use. Since the common stabilisation methods have proven to be insufficient for sensitive NMR samples, another purging method has been tested: Mitigation is easily and reliably achieved by washing the deuterated chloroform with concentrated disodium carbonate solution and subsequent desiccation with oven-dried disodium carbonate.

The synthesis and identification of previously unreported artefacts formed during phosgene-contaminated chloroform extraction of amphetamine-type substances

Amphetamine-type substances (ATS) are the most common illicit drugs synthesised in domestic clandestine laboratories. Liquid-liquid extraction of exhibits remains a key step in the analysis of exhibits, with chloroform often the solvent of choice in clandestine laboratory analysis. The decomposition of chloroform to phosgene is well known, with artefacts from extraction with phosgene-contaminated chloroform reported in the literature. This laboratory has observed artefacts upon the phosgene-contaminated chloroform extraction of ATS, some of which are in contrast to those reported in the literature by previous authors and which were not identified in the current literature.This paper presents the synthesis and characterisation of the previously unreported artefacts 1-methyl-2-phenethyl isocyanate, N,N'-bis(1-methyl-2-phenethyl) urea, N,N'-bis(1-methyl-2-phenylethyl)-N,N'-dimethylurea, 1-methyl-2-(3,4-methylenedioxy-phenyl)ethyl isocyanate and N,N'-bis(1-methyl-2-(3,4-methylene-dioxyphenyl)ethyl)-N,N'-dimethylurea from amphetamine, methylamphetamine, 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxymethylamphetamine (MDMA), respectively.

Rapid decomposition of chloroform by a liquid phase plasma reaction with titanium dioxide and hydrogen peroxide

• Chloroform in aqueous solution was successfully degraded by liquid phase plasma reaction. • The operation parameters of power supply played an important role in the chloroform degradation reaction. • Degradation rate of chloroform is proportional to an increase in operation parameter. • Addition of titanium dioxide or hydrogen peroxide to liquid phase plasma reaction improved the degradation of chloroform. • When titanium dioxide and hydrogen peroxide used simultaneously, the synergetic effect was observed. The degradation of chloroform in a liquid phase plasma (LPP) reactor was examined according to the operating parameters and other influencing factors. The operating parameters included the applied voltage, frequency, and pulse width. The effects of titanium dioxide, hydrogen peroxide, and their combination on the degradation of chloroform were evaluated in terms of the influencing factors. Increasing the operating parameters up to the maximum allowed in the LPP process made chloroform decompose much faster than that of the minimum. On the other hand, increasing either the titanium dioxide or hydrogen peroxide concentrations in the reactant solution did not always destroy the chloroform efficiently compared to degradation without their loading. Although the impact of titanium dioxide was slightly higher than that of hydrogen peroxide, the synergistic effect between them enhanced the breakdown of chloroform further. Overall, both the operating parameters and influencing factors should be determined carefully to maximize the decomposition efficiency in the given treatment system, particularly for processes involving the LPP reaction.

Process for Chloroform Decomposition: Nonthermal Plasma Polymerization with Methane and Hydrogen

This paper describes an alternative process for chloroform decomposition via nonthermal plasma polymerization at atmospheric pressure and investigates the effect of methane and hydrogen addition on the process. The effect of both additives was assessed separately, where experiments were conducted in a double dielectric barrier discharge reactor under nonoxidative conditions. The most profound impact of the additives was a significant increase in the yield of non-cross-linked polymer produced compared to that in their absence. The addition of methane resulted in a 120% increase in polymer yield, while in hydrogen the increase was 31%. Critical parameters such as effect of the methane and hydrogen concentration on the conversion of chloroform at various applied voltages, the product distribution, mass balance, and polymer characterization are elucidated in this paper. Single pass conversions of 61% and 68% (with corresponding mass balances of 98% and 95%, respectively) were achieved for CHCl3 + CH4 and CHCl3 + H2 feed scenarios, respectively. Furthermore, a polymerization mechanism which explains the formation of major chain structures as well as structural defects in the polymer is expounded upon in the paper.

Effect of TiO2/GAC and water vapor on chloroform decomposition in a hybrid plasma-catalytic system

ABSTRACTThis paper presents the combination of TiO2/GAC catalyst and NTP for the decomposition of chloroform using a DBD reactor. The experiments were performed using an AC transformer as the power supply system to determine the optimal conditions of the chloroform conversion in the presence of a hydrogen-rich substance, that is, water vapor. TiO2/GAC enhanced the removal efficiency and also CO2 selectivity significantly, leading to an acceptable conversion rate at SIEs higher than 400 J L−1. The adsorption property of GAC was noticed to be an effective factor for catalytic activity by increasing the residence time, although the higher retention time prevented the accurate determination of chlorine and carbon balance. Selectivity toward HCl was improved considerably from 24.3% to 64.3% over catalyst when water was fed as a hydrogen-rich compound. At the same time, the harmful chlorinated by-products such as TCBA and TCE declined significantly. A noticeable enhancement in the selectivity toward CO2 was observed when both catalyst and water were introduced, regardless of the inlet concentration. Our findings suggest that the hybrid of NTP with TiO2/GAC will highly be effective in the abatement of chloroform, and the addition of H2O will successfully decline harmful chlorinated by-products.

Halogen-bonded network of trinuclear copper(II) 4-iodo-pyrazolate complexes formed by mutual breakdown of chloro-form and nanojars.

Crystals of bis-(tetra-butyl-ammonium) di-μ3-chlorido--tris-(μ2-4-iodo-pyrazolato-κ2N:N')tris-[chlorido-cuprate(II)] 1,4-dioxane hemisolvate, (C16H36N)2[Cu3(C3H2IN2)3Cl5]·0.5C4H8O or (Bu4N)2[CuII3(μ3-Cl)2(μ-4-I-pz)3Cl3]·0.5C4H8O, were obtained by evaporating a solution of (Bu4N)2[{CuII(μ-OH)(μ-4-I-pz)} n CO3] (n = 27-31) nanojars in chloro-form/1,4-dioxane. The decomposition of chloro-form in the presence of oxygen and moisture provides HCl, which leads to the breakdown of nanojars to the title trinuclear copper(II) pyrazolate complex, and possibly CuII ions and free 4-iodo-pyrazole. CuII ions, in turn, act as catalyst for the accelerated decomposition of chloro-form, ultimately leading to the complete breakdown of nanojars. The crystal structure presented here provides the first structural description of a trinuclear copper(II) pyrazolate complex with iodine-substituted pyrazoles. In contrast to related trinuclear complexes based on differently substituted 4-R-pyrazoles (R = H, Cl, Br, Me), the [Cu3(μ-4-I-pz)3Cl3] core in the title complex is nearly planar. This difference is likely a result of the presence of the iodine substituent, which provides a unique, novel feature in copper pyrazolate chemistry. Thus, the iodine atoms form halogen bonds with the terminal chlorido ligands of the surrounding complexes [mean length of I⋯Cl contacts = 3.48 (1) Å], leading to an extended two-dimensional, halogen-bonded network along (-110). The cavities within this framework are filled by centrosymmetric 1,4-dioxane solvent mol-ecules, which create further bridges via C-H⋯Cl hydrogen bonds with terminal chlorido ligands of the trinuclear complex not involved in halogen bonding.

Spectroscopic analysis of porphyrin compounds irradiated with visible light in chloroform with addition of β-myrcene

The behaviour of two porphyrins, 5,10,15,20-tetraphenyl-21H,23H-porphine (H2TPP) and 5,10,15,20-tetra(4-pyridyl)-21H, 23H-porphine (H2TPyP), as well as their Zn(II) complexes (ZnTPP and ZnTPyP), have been studied analysing their absorption and steady-state fluorescence spectra in chloroform with addition of β-myrcene. After irradiation with visible light the free-base porphyrins have been converted to the form of dication on account of hydrochloric acid generated as a result of chloroform decomposition induced by β-myrcene. Whereas in case of their Zn(II) complexes the mechanism of action is more complicated, leading presumably to the formation of the aggregated metalloporphyrin species with chloride ions playing the bridging role. The pseudo-first-order rate constants of the absorption quenching process were calculated for all the systems examined, with respect to the porphyrin concentration. The most effective irradiation was observed in case of H2TPP porphyrin.

Decomposition of chloroform and succinic acid by ozonation in a suction-cavitation system: Effects of gas flow

Abstract The conductivity of aqueous solutions containing 1 mM chloroform increases upon the chloroform decomposition that is induced by hydrodynamic cavitation in the suction-cavitation system. However, the rate of increase in conductivity (RIC) drops significantly, from 1.314 μS cm −1 min −1 without gas flow to 0.552 μS cm −1 min −1 with 25 mL min −1 of air flow. The RIC decreases further with increasing air flow, until pseudo-zero growth is reached at 200 mL min −1 air flow. Introducing O 3 at 33 mL min −1 gas flow (effective cavitation) improves RIC, from 0.4193 to 0.5509 μS cm −1 min −1 , but the enhanced rate (31.4%) is lower than at 200 mL min −1 of gas flow (little effective cavitation). The concentrations of dissolved O 2 , O 3 and H 2 O 2 , that is formed on-site, increase with increasing gas flow and orifice plate hole diameter. Succinic acid (0.42 mM) is not oxidized by O 3 or H 2 O 2 alone, but is rapidly degraded by a combination of O 3 /H 2 O 2 in the suction-cavitation system. The degradation rate of zero-order kinetics increases from 2.604 to 4.788 μM min −1 as orifice diameter increases from 5 to 8 mm. Increasing O 3 gas flow and temperature favor SA degradation. Increasing H 2 O 2 concentration is more effective in producing OH radicals and promoting the oxidation of succinic acid than increasing O 3 input amount.

Dechlorination and decomposition of chloroform induced by glow discharge plasma in an aqueous solution

In this study, efficient dechlorination and decomposition of chloroform (CF) induced by glow discharge plasma (GDP) in contact with a sodium sulfate solution was investigated. Intermediate byproducts were determined by ionic chromatography and headspace gas chromatography, respectively. Results showed that CF can be effectively dechlorinated and decomposed under the action of GDP. Both removal and dechlorination of CF increased with increasing pH and with addition of hydroxyl radical scavengers to the solution. Addition of H2O2 to the solution slightly decreased the CF removal. Formic acid, oxalic acid and dichloromethane were determined as the major intermediate byproducts. Final products were carbon dioxide and hydrochloric acid. Hydrated electrons were the most likely active species responsible for initiation of the dechlorination, and hydroxyl radicals may be the ones for the oxidation of the organic intermediate byproducts. Hydrolyses of the chloromethyl radicals contributed much in the mineralization of the organic chlorine. Reaction mechanism was proposed based on the dechlorination kinetics and the distribution of intermediate byproducts.

Decomposition of gas-phase chloroform using nanophotocatalyst downstream the novel non-thermal plasma reactor: by-products elimination

Combination the non-thermal plasma technique by photocatalytic oxidation can enhance volatile organic compounds degradation. In this study, the decomposition of chloroform vapors in a novel non-thermal plasma reactor as well as an integrated system of this reactor in conjunction with the photocatalysis process was investigated. Expanded graphite was used as discharge electrode of dielectric barrier discharge reactor and the support of TiO2 and ZnO catalysts as well. Results showed that chloroform degradation increased in hybrid system. The non-thermal plasma reactor had high content of NO and NO2, whereas the concentration of these two pollutants dropped dramatically in hybrid system; moreover, the generated ozone from the non-thermal plasma process was degraded on the photocatalyst and consequently was not detected in the output gas of the combined system. The generated organic by-products in non-thermal plasma process (phosgene and trichloroacetaldehyde) were reoxidized with un-oxidized chloroform in the second stage of the combined system. This increased the selectivity of CO2 and Cl2.

Photocatalysis of chloroform decomposition by tetrachlorocuprate (II) on Dowex 2-X8.

Heterogenized on a polystyrene anion exchange resin and in the presence of oxygen, CuCl4(2-) catalyzes the photodecomposition of chloroform at wavelengths above 345 nm with greater efficiency than an equivalent amount in homogeneous solution. The reaction is proposed to proceed in two stages, the first stage yielding CCl4 and HO2(-) as products, the second consisting of a chain reaction resulting from the CuCl4(2-)-catalyzed photodissociation of CCl4, yielding phosgene with CCl3 radicals as chain carriers. Photodecomposition is retarded by added Cl(-), CH3CN, C6H12 or C2H5OH, which is ascribed to the displacement of CHCl3 molecules from the vicinity of the copper by attraction to the polystyrene matrix or to the alkylammonium cation sites.

Enhanced performance of non-thermal plasma coupled with TiO2/GAC for decomposition of chlorinated organic compounds: influence of a hydrogen-rich substance

BackgroundNo study was found in the literature on the combination of TiO2/GAC catalyst and non-thermal plasma for chlorinated volatile organic compounds abatement in air. This paper presents this hybrid process for the decomposition of chloroform (as a target compound) using a multi-pin to plate discharge reactor. The experiments were performed using a high frequency pulsed transformer as the power supply system to examine the effect of SIE, frequency, as well as initial concentration on the chloroform removal efficiency (RE). Toluene was added as a hydrogen-rich source to shift the reactions into the formation of environmentally desirable products.ResultsRE of around 60% was observed with the NTP-alone process at the highest possible SIE (3000 J L−1), while it rocketed up to 100% (total oxidation) in the presence of TiO2/GAC at SIE of 1000 J L−1. About 100% O3 destruction over TiO2/GAC and both adsorption and catalytic activities of GAC may be considered as the reasons for better performance of the hybrid process. Toluene feeding diminished the chlorinated by-products such as Cl2 and TCE significantly. The selectivity towards CO2 was noticed to enhance noticeably, when both catalyst and toluene were introduced, regardless of the input concentration.ConclusionsOur findings suggest that the hybrid of NTP with TiO2/GAC will highly be effective in the abatement of chloroform, and the addition of toluene will successfully decline harmful chlorinated by-products.

Photodecomposition of dichloromethane catalyzed by tetrachloroferrate(iii) supported on a Dowex anion exchange resin

The FeCl4(-) ion, heterogenized on a Dowex ion exchange resin, catalyzes the aerobic photodecomposition of neat CH2Cl2. Phosgene production was used to characterize the extent of decomposition, although it appears to be a secondary product from the decomposition of chloroform, which is suggested to arise from the reaction of dichloromethanol with hydrogen chloride. The yield of CHCl3 increases when the production of phosgene is suppressed by water or acetonitrile. CuCl4(2-), likewise heterogenized on Dowex, is photocatalytically inactive.

Catalysis of the Photodecomposition of Chloroform by a Polystyrene Anion Exchange Resin

Irradiation at wavelengths above 360 nm of a suspension of Dowex 2-X8 anion exchange resin (Cl¯ form) in chloroform causes the decomposition of chloroform with formation of COCl2 and HCl. The presence of CCl4 as the most important secondary product, along with the lack of any photodecomposition in CDCl3, the absence of photodecomposition when O2 is excluded, and the lack of any secondary products related to CHCl2 radicals rule out a mechanism based on sensitized C–Cl dissociation, as occurs in the direct UV photolysis of chloroform. A mechanism is proposed in which an initial photoreaction produces COCl2 and HCl at a slow rate, along with CCl4. A second photoreaction causes Cl dissociation from CCl4, greatly increasing the net rate of COCl2 and HCl formation after a sufficient concentration of CCl4 is attained.

Photocatalysis of Chloroform Decomposition by the Hexachlororuthenate(IV) Ion

Dissolved hexachlororuthenate(IV) effectively catalyzes the photodecomposition of chloroform to hydrogen chloride and phosgene under near-UV (λ>345nm) irradiation, whereby RuCl6(2-) is not itself photocatalytically active, but is photochemically transformed into a species that is active, possibly RuCl5 (CHCl3 )(-) . Conversion to a photoactive species during irradiation is consistent with the acceleration of the decomposition rate during the early stages and with the apparent inverse dependence of the decomposition rate on the initial concentration of RuCl6(2-) . The displacement of Cl(-) by CHCl3 in the coordination sphere to create the photoactive species is consistent with the retardation of photodecomposition by both Cl(-) and H2 O. The much smaller photodecomposition rate in CDCl3 suggests that C-H bond dissociation occurs during the primary photochemical event, which is also consistent with the presence of a CHCl3 molecule in the first coordination sphere.

Chlorinated englerins with selective inhibition of renal cancer cell growth.

The chlorinated englerins (3-9) were isolated from Phyllanthus engleri and shown to selectively inhibit the growth of renal cancer cells. The compounds were shown to be extraction artifacts produced by exposure to chloroform decomposition products during their isolation. The most active compound, 3, was synthesized from englerin A (1).

Enhancement of chloroform degradation by the combination of hydrodynamic and acoustic cavitation

The decomposition of chloroform by the combination of hydrodynamic and acoustic cavitation (Hydrodynamic–Acoustic-Cavitation/HAC) has been investigated. The flow rate and the hole diameter of the orifice plate remarkably affect the conversion of chloroform in the combined system. The conversion increases with increasing fluid velocity without any restriction. With a 2.8 mm orifice plate the conversion reaches an optimal value. A synergistic effect has been obtained by the hybrid method of acoustic and hydrodynamic cavitation. The total synergistic effect achieves 17% and 73% per pass, respectively. The analysis of the energy efficiencies shows different results. Due to high optimization potential, this hybrid method can be visualized as a new step for wastewater treatment.