Number Of Chlorine Atoms Research Articles

Combination of oxidative and reductive effects of phenolic compounds on the degradation of aniline disinfection by-products by free radicals

In this study, we selected 13 phenolic compounds containing -COOH, -CHO, -OH, and -COCH3 functional groups as model compounds for dissolved organic matter (DOM), and explored the redox reactions during the co-degradation of phenolic compounds with aniline disinfection by-products (DBPs) at the molecular level. When phenolic compounds and aniline DBPs were degraded, phenoxy radicals and aniline radicals were the most important intermediates. Phenoxy radicals can degrade aniline DBPs via hydrogen atom abstraction (HAA) reactions, and the reaction rates were related to the reduction potentials of the compounds. Compounds containing electron-withdrawing groups were more likely to oxidize aniline DBPs. Aniline DBPs were more easily degraded by phenoxy radicals when they contained electron-donating groups, and the increase in the number of chlorine atoms inhibited the reaction rates of aniline DBPs degradation by phenoxy radicals. Although phenolic compounds can reduce aniline DBPs, there was no significant correlation between the reaction rates and the reduction potentials of the compounds. Considering the redox effects of phenolic compounds on aniline DBPs, co-degradation simulations showed that phenolics inhibited the degradation efficiency of aniline DBPs. This work provided new insights into the transformation mechanisms and degradation efficiencies of DOM and aniline DBPs when they were co-degraded.

Modeling of experimental excess molar enthalpy with Wilson, UNIQUAC, and NRTL for mixtures of acetophenone with chloro derivatives of ethane and ethene at T = 298.15 K

The excess molar enthalpy HmE, was determined for systems consisting of acetophenone with chloro alkanes and alkenes derivatives. These derivatives include 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, trichloroethene and tetrachloroethene at a temperature of T = 298.15 K. The Redlich-Kister relation fitting was used to analyze the HmE values obtained from this experimental data. Additionally, the excess partial molar enthalpy HiE was derived from the experimental HmE values. The intermolecular interaction function such as ∂HiE∂xi and ∂HjE∂xjwere also calculated. For the system consisting of acetophenone + 1,1,1-trichloroethane or + tetrachloroethene, the HmE values were found to be positive. Conversely, the HmE values for acetophenone + 1,2-dichloroethane or + 1,1,2,2- tetrachloroethane or + trichloroethene were observed to be negative. The magnitude of the HmE values increased in chloroethanes as the number of chlorine atoms increased, and became more negative in chloroethenes. Based on the local composition theory, the Wilson model, the universal quasichemical (UNIQUAC) model, and the non-random two-liquid (NRTL) model were used to correlate these thermodynamic data. The results showed good agreement with the experimental enthalpy data.

Density functional theory study on the enhanced adsorption mechanism of VOCs by Cu4 cluster decorated UiO-66

Volatile organic compounds (VOCs) are a class of air pollutants that greatly harm human health and the ecological environment, convenient and effective treatment of VOCs has become a challenge. This work proposed a transition metal cluster decorated UiO-66 (a typical type of metal-organic framework) as the effective adsorbent for the purification of VOCs with typical functional groups based on density functional theory (DFT) calculations. The results show that the VOCs adsorption energy on the modified UiO-66 increased significantly, especially for Cu4 cluster-modified UiO-66, and the adsorption energy of trichloroethene is greater than that of the other considered VOCs, which may be induced by halogens or carbon-carbon double bond in trichloroethene. We compared chloromethane, chloroethylene, and ethylene and found that VOCs with carbon-carbon double bond have stronger adsorption energy, increasing with the number of chlorine atoms. The density of states (DOS), Hirshfeld charge analysis, and orbital distribution further confirm the charge distribution in UiO-66 after the decoration of the Cu4 cluster. Cu4 cluster can act as a bridge to promote the formation of chemical bonds between UiO-66 and VOCs molecules. Therefore, Cu4 cluster-modified UiO-66 can be a promising VOCs adsorption material, especially for vinyl chloride molecules.

Spinel ferrite nanoparticles as potential materials in chlorophenol removal from wastewater.

Persistent organic pollutants (POPs) including chlorophenols (CPs) are increasing in water effluents, creating serious problems for both aquatic and terrestrial lives. Several research attempts have considered the removal of CPs by functionalised nanomaterials as adsorbents and catalysts. Besides the unique crystal structure, spinel ferrite nanomaterials (SFNs) own interesting optical and magnetic properties that give them the potential to be utilised in the removal of different types of CPs. In this review, we highlighted the recent research work that focused on the application of SFNs in the removal of different CP substances based on the number of chlorine atom attached to the phenolic compound. We have also discussed the structure and properties of SFN along with their numerous characterisation tools. We demonstrated the importance of identifying the structure, surface area, porosity, optical properties, etc. in the efficiency of the SFN during the CP removal process. The reviewed research efforts applied photocatalysis, wet peroxide oxidation (WPO), persulfate activated oxidation and adsorption. The studies presented different paths of enhancing the SFN ability to remove the CPs including doping (ion substitution), oxide composite structure and polymer composite structure. Experimental parameters such as temperature, dosage of CPs and SFN structure have shown to have a major effect in the CP removal efficiency. More attention is needed to investigate the different properties of SFN that can be tailored through different techniques and expected to have major role in the removal mechanism of CPs.

LDI mass spectrometry and quantum chemical calculations of four, five, and six atomic clusters of tantalum oxochloride anion-radicals

Quantum-chemical calculations of isomers of bulk closed “cage” structures of four, five and six atomic clusters of tantalum oxochloride anion-radicals, identified by LDI mass spectrometry in the gas phase, have been performed. The structure and relative thermodynamic stability of the isomers of clusters [Ta4OxCly]- (x = 6–9; y = 9, 7, 5,3), [Ta5OxCly]- (x = 8–12; y = 8, 6, 4, 2) and [Ta6OxCly]- (x = 12–15; y = 7, 5, 3, 1) of various configurations (tetrahedron, trigonal bipyrmide, tetragonal pyramid, trigonal prism, pentagonal pyramid and octahedron position of tantalum atoms) and different positions of oxygen and chlorine atoms have been studied. Some patterns of relative thermodynamic stability of isomers have been established. In the series of cluster radical anions of the same geometric configuration [TanOxCly]- (n = 4–6), the relative stability of geometric isomers depends on the ratio of the number of oxygen and chlorine atoms. For all anion-radicals [TanOxCly]- (n = 4–6) isomers having an anionic fragment with terminal oxygen and chlorine atoms (≡ТаOCl-) are energetically more favorable, than those with three of thes chlorine atoms (≡ TaCl3-). The average length of the Ta–Ta distances, in a series of cluster anions of tantalum oxochlorides [TanOxCly]- (n = 4–6) of the same geometric configuration, increases with a decrease in the number of oxygen atoms (an increase in the number of chlorine atoms). In the closed “cage” structures of the cluster anion radicals of tantalum oxochlorides, together with the oxygen, the chlorine can also act as a bridging atom, but the total binding energy of such isomer is higher.

β-cyclodextrin-based porous carbon with tunable pore and interface allows efficient removal of chlorophenols from aqueous solution

Chlorophenols (CPs), a kind of important intermediate for fine chemicals, exists widely in the aqueous environment and poses a significant danger to humans. Therefore, developing advanced materials to enable the effective capture of CPs is highly desired. Herein, β-cyclodextrin-based porous carbon (CPAC) with exceptional capacities for CPs has been designed and tested. These porous carbon adsorbents were successfully synthesized via stepwise carbonization, affording abundant N and O functional groups, high surface area (as high as 3982 m2·g−1) and controlled pore size to optimize for rapid CPs uptake. According to the CPs uptake measurements, CPAC exhibited exceptional CPs adsorption performance. CPAC showed high adsorption capacities (1085.08 mg·g−1 for 2,4,6-trichlorophenol) and fast adsorption kinetics for CPs. CPAC can effectively recover multi-component CPs from complex aqueous media, and the special pore structure reduces the competitive adsorption between CPs. And the recyclability studies showed that CPAC maintained its structural integrity and the initial CPs uptake capacity, highlighting its potential for practical application. Besides, DFT calculations indicate that hydrogen bonding and π-π interactions are key factors. Among them, the molecular conformation of CPs and the number of chlorine atoms on phenol play a crucial role in the adsorption behavior and adsorption energy.

Mechanochemical remediation of soil contaminated with heavy metals and persistent organic pollutants by ball milling with nZVI-CaO-Ca3(PO4)2 additives

Mechanochemical method was proposed for the remediation of soil contaminated with heavy metals (HMs, Cu, Pb, and Cd) and persistent organic pollutants (POPs, PBDEs and PCBs) through ball milling with nanoscale Zero-valent Iron (nZVI)-CaO-Ca3(PO4)2 (NCC). The mechanical energy supplied by ball milling and NCC considerably enhanced the stabilization of HMs (Cu 99.22%, Pb 100.00%, and Cd 98.42%) as well as the efficiency of POP degradation (BDE209 99.57%, PCB3 94.55%, PCB4 94.07%, PCB5 86.96%). Upon an increase in the rotation speed from 0 to 650 rpm, the weak acid extractable fraction (F1) of Cu, Pb, and Cd gradually transformed into relatively stable (F2 + F3) and residual forms (F4) and gradually reached a steady state. Moreover, under the influence of SiO2 and excited-state PO43- in the soil, HMs also transformed from their originally mobile form to other stable forms. The C-O and C-Br bonds of BDE209 were cleaved during mechano-chemical reactions, yielding perbromobenzene, 2,3,4,5,6-pentabromophenol, and other low-brominated phenols such as 1,2,3,4,5-pentabromo-6-(2,3-dibromophenoxy)benzene. The C-Cl bonds of PCBs underwent selective cleavage, resulting in the formation of low-chlorinated biphenyls and hydrocarbons. Furthermore, the stability of C-Cl bonds increased with a higher number of chlorine atoms in PCBs, making them more difficult to degrade. This study offers an environmentally friendly and highly effective remediation approach for POPs-HMs contaminated soil.

Thyroid hormone transporters binding affinity of methoxypoly chlorinated biphenyls: Insights from molecular simulations and fluorescence competitive binding experiment

Triiodothyronine (T3) and thyroxine (T4) are essential for regulating cell metabolic rate and promoting the development and differentiation of brain tissue, especially in fetuses and newborns. In particular, it has been proved that MeO-PCBs have high binding to thyroid hormone transporters and can competitively bind to thyroid carrier proteins, thus destroying the transport of the thyroid hormone. Fluorescence competition binding experiments and docking results showed that the binding affinity decreased with the increase in number of chlorine atoms of MeO-PCBs. The interaction mechanism of MeO-PCBs with thyroid transporter (TTR) and thyroid binding globulin (TBG) was compared by computational simulation and the binding free energies were calculated by the molecular mechanics/Poisson-Boltzmann surface area (MM/PBSA) method. Electrostatic potential analysis, Hirshfeld surface analysis and electron density difference maps confirmed the existence of electrostatic interactions. Secondly, noncovalent interaction (NCI) analysis further indicated that the main driving force for the combination of MeO-PCBs to TTR and TBG were electrostatic interaction and van der Waals interaction. The conformational changes of the protein after binding were studied by a molecular dynamic simulation.

Design, Synthesis, and Bioactivity of Novel Quinazolinone Scaffolds Containing Pyrazole Carbamide Derivatives as Antifungal Agents.

In this study, 32 novel quinazolinone-scaffold-containing pyrazole carbamide derivatives were designed and synthesized in a search for a novel fungicide against Rhizoctonia solani. Single-crystal X-ray diffraction of 3-(difluoromethyl)-N-(2-((6,7-difluoro-4-oxoquinazolin-3(4H)-yl)methyl)phenyl)-1-methyl-1H-pyrazole-4-carboxamide (6a11) confirmed the structure of the target compounds. The in vitro antifungal activity of the target compounds against R. solani was evaluated at 100 µg/mL. The structure-activity relationship analysis results revealed that antifungal activity was highest when the substitution activity was at position 6. Moreover, the position and number of chlorine atoms directly affected the antifungal activity. Further in vitro bioassays revealed that 6a16 (EC50 = 9.06 mg/L) had excellent antifungal activity against R. solani that was higher than that of the commercial fungicide fluconazole (EC50 = 12.29 mg/L) but lower than that of bixafen (EC50 = 0.34 mg/L). Scanning electron microscopy), 7.33 (SEM) revealed that N-(2-((6,8-dichloro-4-oxoquinazolin-3(4H)-yl)methyl)phenyl)-3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carboxamide (6a16) also affected the mycelial morphology. The findings revealed that molecular hybridization was an effective tool for designing antifungal candidates. Meanwhile, pyrazolecarbamide derivatives bearing a quinazolinone fragment exhibited potential antifungal activity against R. solani.

Thermal properties and decomposition mechanism of disubstituted fused 1,2,4-triazoles considered as potential anticancer and antibacterial agents

Thermal resistance is a very important parameter when assessing the therapeutic usefulness of potential pharmaceutics. Therefore, the thermal behaviour and the decomposition mechanism in the atmosphere of helium and synthetic air of disubstituted fused 1,2,4-triazoles—which may be potential anticancer and antibacterial agents—were studied with a use of simultaneous thermal analysis: thermogravimetry/differential scanning calorimetry (TG/DTG/DSC) coupled online with Fourier transform infrared spectroscopy. It was confirmed that the thermal stability of the tested compounds is directly depended on their structure and thus on the number of chlorine atoms as substituents. The pyrolysis process of disubstituted fused 1,2,4-triazoles in inert conditions runs in two main, non-well-separated stages connected with the emission of NH3, HCN, acetonitrile, aromatics with an OH group, aromatics with a NH2 groups, H2O, CO2 and alkene fragments. However, the thermal stability of those compounds in synthetic air atmosphere is comparable or lower than their thermal stability in helium atmosphere. The decomposition of the tested compounds runs through at least three main stages, resulting in the emission of the same type of volatiles as in inert conditions plus the additional emission of CO and some carbonyl fragments for compounds with no or one chlorine atom as a substituent. The results indicate a simultaneous cleavage of C–N, N–N and C–O bonds during heating of the tested disubstituted fused 1,2,4-triazoles in inert conditions and additional combustion process of pre-formed residues in oxidative conditions.

A simple assessment of toxicity towards Chlorella vulgaris of organic aromatic compounds in environmental protection

A new approach is introduced for the assessment of toxicity to living organisms from the deposition of different types of organic aromatic compounds in the aquatic environment. Several simple models are introduced for reliable prediction of pIC50, pIC20, pLOEC, and pNOEC towards Chlorella vulgaris (C. vulgaris) of organic aromatic compounds. They need structural parameters as simple descriptors rather than complex descriptors, which are used in the available quantitative structure-activity/toxicity relationship (QSAR/QSTR) models. The largest available reported data of pIC50 for 145 aromatics are used to obtain suitable simple descriptors. A core correlation is introduced for estimating pIC50, which is based on the number of chlorine atoms and molecular weight as well as the contributions of nitro groups and intramolecular hydrogen bonding in phenol derivatives under certain conditions. Its reliability is improved by considering two isomeric structural parameters. Reliable models for pIC20, pLOEC, and pNOEC are also derived and tested using six descriptors. Since the outputs of available QSAR/QSTR models are restricted to phenol and aniline derivatives, the predicted results of the new models are compared with the reported data of one of the best available complex QSAR/QSTR models. Various statistical parameters confirm that the models for pIC50, pIC20, pLOEC and pNOEC show high reliability as well as accuracy, precision, and suitable goodness-of-fit. For example, the predicted results of root mean squared error (RMSE) of pIC50 for 67 and 13 of training-test and external chemical sets of the new/QSTR models are 0.256/0.285 and 0.215/0.376, respectively.

ClO2 pre-oxidation changes dissolved organic matter at the molecular level and reduces chloro-organic byproducts and toxicity of water treated by the UV/chlorine process

The formation of undesirable chloro-organic byproducts is of great concern in the UV/chlorine process. In this study, chlorine dioxide (ClO2) pre-oxidation was applied to control the formation of chloro-organic byproducts and the toxicity in UV/chlorine-treated water. The molecular-level changes in dissolved organic matter (DOM) were tracked by using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and ClO2 pre-oxidation was found to preferentially react with DOM moieties with high aromaticity level and with a carbon number of > 18, producing compounds with a higher degree of oxidation and lower aromaticity. The ClO2-treated DOM was found to be less susceptible to attack by radicals and free chlorine in the UV/chlorine process compared to the raw DOM. ClO2 pre-oxidation resulted in a significant decrease in the number of unknown chloro-organic byproducts (i.e., –17%) and the total intensity of organic chlorine detected by FT-ICR-MS (i.e., –31%). The molecular characteristics, such as O/C, aromaticity index, and the average number of chlorine atoms, of these unknown chloro-organic byproducts generated in the scenarios with and without ClO2 pre-oxidation were also different. Additionally, ClO2 pre-oxidation reduced the genotoxicity (SOS/umu test) and cytotoxicity (Hep G2 cytotoxicity assay) of UV/chlorine-treated water by 26% and 20%, respectively. The findings in this study highlight the merits of ClO2 pre-oxidation for controlling chloro-organic byproducts and reducing the toxicity of water treated by the UV/chlorine process in actual practice.

Tuning the electron transfer rates in near-infrared PbS quantum dots-anthraquinones complex by different chlorine-substituted

The electron transfer (ET) from photoinduced quantum dot (QDs) to electron acceptors through a nanoscale interface plays a crucial part in the functionality and efficiency of QDs-photonic device. The driving force play a crucial part in the ET process of most QD-based system relying on the Marcus ET theory. However, there has rarely reports about tuning the driving force with substituents in acceptor molecules. Here, the ET process between near-infrared (NIR) PbS quantum dot (QDs) and different chlorine-substituted Anthraquinone (AQ) derivatives was studied via the femtosecond transient absorption spectroscopy. The ET process was gradually accelerated by adding chlorine atoms in these AQ molecules. Through the calculation of Marcus ET theory, the driving force of the complexes was gradually increased with the number of chlorine atoms substituted in AQ molecules, thus facilitating ET process. Our findings broaden the application of NIR PbS-organic compounds in photovoltaic devices.

THEORETICAL PROPOSAL OF NEW MOLECULES TO REPLACE CHLORDANE

Chlordane was a most used as insecticide by farmers. Today, it is banned owing to its toxicity, bio-accumulative and persistence properties. Since then ¶tits prohibition has created more unexploited stocks in the environment. ¶In order to still allow the use of these products, we theoretically proposed new molecules derived from it. To meet this objective, we have reduced the number of chlorine atoms in the chlordane molecule to four. Thus, t¶he QSAR and QSPR models already established made it possible to theoretically determine and the of 70 molecules proposed. ¶The analysis of the results allowed to retain two molecules. These are (1S,2S,3R,6R,7R)-3,8,10,10-tetrachlorotricyclo[5,2,1.02,6]dec-8-ene) and (1R,2R,3R,6R,7S)-3,8,7,8-tetrachloro-tricyclo[5.2.1.02,6]dec-8-ene. Both¶bothbbbbbbbggddaaa molecules seem to present the best values of and BCF.¶¶In order to also verify the influence of fluorine on chlordane, we carried out another study. In this part, we have considered the two abovementioned molecules on which a substitution of four hydrogen atoms by four fluorine atoms was made. This gave the following two molecules: (1R,2S,3S,4R,6R,7S)-3,8,10,10-tetrachloro-1,4,7,9-tetrafluorotricyclo[5,2,1,02,6]dec-8-ene and (1S,2S,3R,4S,6S,7S)-1,3,7,8-tetrachloro-4,9,10,10-tetrafluorotricyclo[5,2,1,02,6]dec-8-ene. Both ¶both molecules show higher BCF values ​​than the formers. This would mean that organochlorine compounds which have fluorine atoms are storable. Besides, when we consider the fact that these molecules are more absorbent, (1R,2S,3S,4R,6R,7S)-3,8,10,10-tetrachloro-1,4,7,9-tetrafluorotricyclo[5,2,1,02,6]dec-8-ene and (1S,2S,3R,4S,6S,7S)-1,3,7,8-tetrachloro-4,9,10,10-tetrafluorotricyclo[5,2,1,02,6]dec-8-ene appear to be less accumulable and less toxic than (1S,2S,3R,6R,7R)-3,8,10,10-tetrachlorotricyclo[5,2,1.02,6]dec-8-eneand (1R,2R,3R,6R,7S)-3,8,7,8-tetrachloro-tricyclo[5.2.1.02,6]dec-8-ene.

Polyethylene-water partition coefficients for polychlorinated biphenyls: Application of QSPR predictions models with experimental validation

The water environmental recalcitrance and ecotoxicity caused by polychlorinated biphenyls (PCBs) are international issues of common concern. The partition coefficients with PCBs between low-density polyethylene (LDPE) and water (KPE-w) are significant to assess their environmental transport and/or fate in aquatic environment. Even moderately hydrophobic PCBs, however, possess large KPE-w values, which makes directly experimental measurement labored. Here, based on the combination of quantitative structure-property relationships (QSPRs) and machine-learning algorithms, 10 in-silico models are developed to provide a quick estimate of KPE-w. These models exhibit good goodness-of-fit (R2adj: 0.919–0.975), robustness (Q2LOO: 0.870–0.954) and external prediction performances (Q2ext: 0.880–0.971), providing a speedy feasibility to close data gaps for limited or absent experimental information, especially the RF-2 model. Particularly, an additional experimental verification is performed for models by a rapid and accurate three-phase system (aqueous phase, surfactant micelles and LDPE). The results of the experiments for 16 PCBs show the modeling results agree well with experimental values, within or approaching the residuals of ± 0.3 log unit. Mechanism interpretations imply that the number of chlorine atoms and ortho-substituted chlorines are the great effect parameters for KPE-w. This result also heightens interest in measuring and predicting the KPE-w values of chemicals containing halogen atoms in water.

Human hepatic microsomal sulfatase catalyzes the hydrolysis of polychlorinated biphenyl sulfates: A potential mechanism for retention of hydroxylated PCBs

Polychlorinated biphenyls (PCBs) are persistent environmental contaminants that continue to be of concern due to their varied toxicities. Upon human exposure, many PCBs with lower numbers of chlorine atoms are metabolized to hydroxylated derivatives (OH-PCBs), and cytosolic sulfotransferases can subsequently catalyze the formation of PCB sulfates. Recent studies have indicated that PCB sulfates bind reversibly with a high affinity to human serum proteins, and that they are also taken up by cells and tissues. Since PCB sulfates might be hydrolyzed to the more toxic OH-PCBs, we have investigated the ability of human hepatic microsomal sulfatase to catalyze this reaction. Twelve congeners of PCB sulfates were substrates for the microsomal sulfatase with catalytic rates exceeding that of dehydroepiandrosterone sulfate as a comparison substrate for steroid sulfatase (STS). These results are consistent with an intracellular mechanism for sulfation and de-sulfation that may contribute to retention and increased time of exposure to OH-PCBs.

Extraction of Chlorobenzenes and PCBs from Water by ZnO Nanoparticles

Metal oxide nanoparticles have great potential for selective adsorption and catalytic degradation of contaminants from aqueous solutions. In this study, we employ mass spectrometry and molecular dynamics simulations to better understand the chemical and physical mechanisms determining the affinity of chlorobenzenes and polychlorinated biphenyls (PCBs) for zinc oxide nanoparticles (ZnO NPs). The experiments and simulations both demonstrate that the adsorption coefficients for chlorobenzenes increase steadily with the number of chlorine atoms, while, for PCBs, the relation is more complex. The simulations link this complexity to chlorine atoms at ortho positions hindering coplanar conformations. For a given number of chlorine atoms, the simulations predict decreasing adsorption affinity with increasing numbers of ortho substitutions. Consequently, the simulations predict that some of the highest adsorption affinities for ZnO NPs are exhibited by dioxin-like PCBs, suggesting the possibility of selective sequestration of these most acutely toxic PCBs. Remarkably, the experiments show that the PCB adsorption coefficients of ZnO NPs with diameters ≤ 80 nm exceed those of a soil sample by 5–7 orders of magnitude, meaning that a single gram of ZnO NPs could sequester low levels of PCB contamination from as much as a ton of soil.

Effect of chlorine atoms in choline chloride-monocarboxylic acid for the pretreatment of oil palm fronds and enzymatic hydrolysis

Choline chloride (ChCl) and various monocarboxylic acids (monochloroacetic acid, MCA; dichloroacetic acid, DCA; trichloroacetic acid, TCA) with increasing numbers of substituted chlorine atoms were utilized for the pretreatment of oil palm fronds (OPFs). To the best of our knowledge, this study was the first attempt to utilize these three novel solvents in biomass pretreatment. The result of ChCl:TCA was excluded due to instability in conducting the pretreatment. Under the recommended conditions of 120 °C and 60 min, similar delignification percentages of 75.96% and 74.89% were obtained for ChCl:MCA and ChCl:DCA, respectively. Enzymatic hydrolysis of the pretreated OPFs was demonstrated after pretreatment. By using ChCl:DCA, a shorter duration of enzymatic hydrolysis (24 h) enabled glucan conversion of pretreated OPFs up to 89%. Although a longer duration of 72 h was imposed, glucan conversion of only 82% could be obtained by using ChCl:MCA. Thus, a solvent with a higher number of chlorine atoms (ChCl:DCA) could lead to more effective enzymatic hydrolysis. The results were compared to the literature findings, and ChCl:DCA was determined to be one of the most effective solvents for biomass pretreatment under relatively mild conditions.

Partitioning and potential sources of polychlorinated naphthalenes in water-sediment system from the Yangtze River Delta, China

Spatial trends, partitioning behavior, and potential sources of polychlorinated naphthalenes (PCNs) in water-sediment system from the Yangtze River Delta (YRD) were investigated in this study. The total concentrations of 75 PCNs in water and sediment samples were 0.022–0.310 ng/L and 0.01–1.59 ng/g dry weight, respectively. The homolog patterns in the sediment and water samples were somewhat different. Di-to tetra-CNs made larger contributions in the sediment, while the mono-to tri-CNs were dominant homologs in the water. Overall, the low-chlorinated naphthalenes (mono-to tetra-CNs) were found to be the dominant homologs in the YRD water and sediment samples, and the homolog group contributions to the total PCNs concentrations decreased as the number of chlorine atoms increased. CN-5/7 and CN-24/14 were found at high concentrations in both the water and sediment. Partitioning and transfer of PCNs between water and sediment were assessed by calculating the partition coefficients and fugacity fractions. The partition coefficients showed that PCNs were not in equilibrium status in the water–sediment system, and hydrophobicity played an important role in PCNs partitioning. The fugacity fractions indicated that mono- to tri-CNs had stronger tendencies to escape from the sediment into the water, while the high-chlorinated naphthalenes close to equilibrium. Principal component analysis and correlation analysis indicated that industrial thermal processes and the use and disposal of products containing PCNs industrial products are sources of PCNs in the YRD water-sediment system.

Chloride-attachment atmospheric pressure photoionisation for the determination of short-chain chlorinated paraffins by gas chromatography-high-resolution mass spectrometry

In this work, a new gas chromatography-high-resolution mass spectrometry (GC-HRMS) method based on atmospheric pressure photoionisation (APPI) has been developed for the accurate determination of short-chain chlorinated paraffins (SCCPs) as a reliable alternative to the established methods. To the best of our knowledge, this is the first time these compounds has been analysed by GC-MS using atmospheric pressure photoionisation (APPI). Efficient ionisation of SCCPs was achieved using the new GC-APPI source by the formation of [M+Cl]– adduct ions in negative ion mode using dopant-assisted APPI with a mixture of acetone/CCl4 (3:1, v/v). Operating at a resolution of 70,000 FWHM (full width at half maximum) and monitoring the [M+Cl]– adduct ions for each congener group, a selective determination of the SCCPs was achieved, avoiding isobaric interferences between homologue groups with different carbon chain length and chlorination degree. Moreover, the GC-APPI-HRMS response of each congener group was mainly influenced by its concentration and did not depend on the number of chlorine atoms in the molecule as occurs with the GC-MS methods based on the electron-capture negative ionisation (ECNI). Thus, the contribution of the different carbon and chlorine homologue groups in the SCCP mixtures was determined by the internal normalization method, and the quantification was performed independently of the chlorine content of the SCCP standard mixture employed. The developed GC-APPI-HRMS method offers some interesting advantages over the existing methods, particularly the possibility to quantify individual SCCP congener groups, the use of a simple calibration method for quantification, and an important time-saving in the data processing, especially over ECNI-based traditional methods. The GC-APPI-HRMS method allowed the determination of SCCPs at low concentration levels in fish samples with low method limits of detection (17–34 pg g−1 wet weight for total SCCPs), good precision (RSD < 7%) and trueness (relative error < 8%) and can be proposed as a reliable alternative of the established methods for the determination of these pollutants in environmental samples.