Chlorine Atmosphere Research Articles

Spatial Distributions and Sources of Inorganic Chlorine in PM2.5 across China in Winter

Chlorine is an important atmospheric photochemical oxidant, but few studies have focused on atmospheric chlorine. In this study, PM2.5 samples were collected from urban and rural sites across China in January 2018, and concentrations of Cl− and other water-soluble ions in PM2.5 were analyzed. The size-segregated aerosol Cl− data measured across Chinese cities by other studies were compiled for comparison. The observed data demonstrated that the Cl− concentrations of PM2.5 in northern cities (5.0 ± 3.7 µg/m3) were higher than those in central (1.9 ± 1.2 µg/m3) and southern cities (0.84 ± 0.54 µg/m3), suggesting substantial chlorine emissions in northern cities during winter. The concentrations of Cl− in aerosol were significantly higher in urban regions (0.11–26.7 µg/m3) compared to than in rural regions (0.03–0.61 µg/m3) across China during winter, implying strong anthropogenic chlorine emission in cities. Based on the mole ratios of Cl−/Na+, Cl−/K+ and Cl−/ SO 4 2 − and the PMF model, Cl− in northern and central cities was mainly sourced from the coal combustion and biomass burning, but in southern cities, Cl− in PM2.5 was mainly affected by the equilibrium between gas-phase HCl and particulate Cl−. The size-segregated statistical data demonstrated that particulate Cl− had a bimodal pattern, and more Cl− was distributed in the fine model than that in the coarse mode in winter, with the opposite pattern was observed in summer. This may be attributed to both sources of atmospheric Cl− and Cl− involved in chemical processes. This study reports the concentrations of aerosol Cl− on a national scale, and provides important information for modeling the global atmospheric reactive chlorine distribution and the effects of chlorine on atmospheric photochemistry.

A Large Source of Atomic Chlorine From ClNO2 Photolysis at a U.K. Landfill Site

AbstractNitryl chloride (ClNO2) acts as a source of highly reactive chlorine atoms as well as an important NOx reservoir. Measurements of ClNO2 at an operational U.K. landfill site are reported here for the first time. A peak concentration of 4 ppb of ClNO2 was found with a peak mean nighttime maximum of 0.9 ppb. Using models based upon the photolysis of observed ClNO2 and atmospheric chlorine chemistry, chlorine atom concentrations reaching in excess of 1.20 × 105 molecules/cm3 in the early morning following sunrise are calculated. These concentrations are approximately 10 times higher than previously reported in the United Kingdom, suggesting a significant impact on the oxidizing capacity around such sites. Given the ubiquity of landfill sites regionally and globally, and the large abundances of Cl atoms from the photolysis of ClNO2, chlorine chemistry has a significant impact on ozone formation and volatile organic compounds oxidation as shown by WRF‐Chem modeling.

Difluorochloromethane treated thin CdS buffer layers for improved CdTe solar cells

One of the major improvements for CdTe solar cells is the increase of the current density by enhancing the transparency of the buffer layer. CdS, with its 2.4 eV band gap, results in being opaque at low wavelength regions. For this reason, in order to gain in blue and UV light, extremely thin CdS has to be applied, if the buffer is not substituted with other materials. On the other hand, by thinning the CdS layer we create pinholes also due to the wide intermixing of CdTe and CdS layers and subsequently consumption of CdS.For this reason we have applied and compared different CdS post-deposition treatments in order to stabilize the layer and avoid excess intermixing. Treatments at temperatures above 500 °C in an argon and chlorine atmosphere on 80 nm thick CdS have led to the fabrication of more stable samples compared to untreated CdS, resulting in improved performance with a 10% increase in current density and a 5% increase in open circuit voltage and fill factor. Moreover, light transmission of the CdS treated layers from 300 to 450 nm is increased by about 10%.In this paper, a study of treated thin CdS with recrystallization treatments is presented; the layers have been analysed by means of X-ray photoelectron spectroscopy, X-ray diffraction and atomic force microscopy. Finished CdTe devices made on thin CdS are characterized in terms of current-voltage and quantum efficiency.

Platinum Nanosheets between Graphite Layers.

Two-dimensional platinum nanosheets were obtained by the hydrogen reduction of platinum tetrachloride intercalated between graphite layers, the latter was prepared by the treatment of the mixture of platinum tetrachloride and graphite powder under chlorine atmosphere. The size of platinum nanosheets was 1-3 nm in thickness with a width in the range of 5-300 nm. These nanosheets contain a number of hexagonal holes and edges with an angle of 120°. This review discusses the reduction and oxidation behavior of platinum species and structure of platinum nanosheets between graphite layers. The selective hydrogenation catalyzed by these platinum nanosheets entrapped between the graphite layers is also demonstrated.

A study on kinetics of roasting of ore from tomtor field

Research on kinetics of change of phosphorus, niobium, vanadium and titanium content during high-temperature roasting of ore from Tomtor field mixed with active additives: bicarbonate (NaHCO3), sodium carbonate (Na2CO3), alkalis (КОН, NaOH) is conducted. An equation of ore roasting kinetics is proposed and values of constant rate of high-temperature ore roasting for phosphorus, niobium, vanadium and the titanium under various conditions are calculated. Relationships of constant rate of high-temperature ore roasting in the atmosphere of air oxygen, argon and molecular chlorine to the temperature of roasting and content of active additives are obtained. It is established that in the atmosphere of air oxygen, ore roasting is most effective with additions of NaHCO3, Na2CO3, NaOH, taken with the ratio (1:1). It is shown that roasting of ore in admixture with carbonates and alkalis can translate into a solution for subsequent leaching at minimum 95.0% of phosphorus and 44.0% of vanadium contained in the original ore. It is established that the greatest rate of roasting in the atmosphere of oxygen is characterized by ore roasting in a mixture of NaHCO3 and NaOH. The constant rates of that process for phosphorus and vanadium are calculated. It is established that filter cake forming after ore roasting requires further processing because it contains high concentrations of vanadium and other valuable metals.

Secondary organic aerosol from chlorine-initiated oxidation of isoprene

Abstract. Recent studies have found concentrations of reactive chlorine species to be higher than expected, suggesting that atmospheric chlorine chemistry is more extensive than previously thought. Chlorine radicals can interact with hydroperoxy (HOx) radicals and nitrogen oxides (NOx) to alter the oxidative capacity of the atmosphere. They are known to rapidly oxidize a wide range of volatile organic compounds (VOCs) found in the atmosphere, yet little is known about secondary organic aerosol (SOA) formation from chlorine-initiated photooxidation and its atmospheric implications. Environmental chamber experiments were carried out under low-NOx conditions with isoprene and chlorine as primary VOC and oxidant sources. Upon complete isoprene consumption, observed SOA yields ranged from 7 to 36 %, decreasing with extended photooxidation and SOA aging. Formation of particulate organochloride was observed. A high-resolution time-of-flight chemical ionization mass spectrometer was used to determine the molecular composition of gas-phase species using iodide–water and hydronium–water cluster ionization. Multi-generational chemistry was observed, including ions consistent with hydroperoxides, chloroalkyl hydroperoxides, isoprene-derived epoxydiol (IEPOX), and hypochlorous acid (HOCl), evident of secondary OH production and resulting chemistry from Cl-initiated reactions. This is the first reported study of SOA formation from chlorine-initiated oxidation of isoprene. Results suggest that tropospheric chlorine chemistry could contribute significantly to organic aerosol loading.

High Performance Micro-Supercapacitors Integrated on Both Silicon Chips and Flexible Polyimide Substrate

Modern microelectronic systems, such as electronic papers, smart clothes, sensors or biomedical devices, demand new energy storage devices to achieve their tasks (1, 2). While batteries suffer from limited power capabilities and cyclability, owing to the faradic mechanisms involved during energy delivery and harvesting, electrochemical double layer supercapacitors (or so called EDLCs) can handle fast charge and discharge over 1,000,000 cycles (3). Indeed, EDLCs store energy via reversible adsorption of ions from an electrolyte at the surface of high-surface-area carbons, or by fast redox reactions occurring at the surface of metal oxide or polymer electrodes (4). However, standard electrode preparation, consisting in mixing the active material with a polymer binder, is not compatible with micro-fabrication processes. Therefore, high performance micro-supercapacitors have to be prepared using non wet processing routes. In this work, nanoporous carbide-derived carbon (CDC) films were integrated onto silicon chips by removing under chlorine atmosphere the metallic atoms of a thin film titanium carbide (TiC) precursor sputtered on silicon wafers (5). The TiC precursor could be patterned through reactive ion etching, thus leading to interdigitated on-chip CDC-based micro-supercapacitors after partial chlorination. The as-prepared devices provided capacitance values up to 410 F.cm-3 (205 mF.cm-2) in 1M H2SO4 with more than 50% of the initial capacitance preserved for 0.9 s discharge time (6). Full chlorination could lead, in certain conditions, to self-supported CDC films of several mm², which were transferred on PET. The flexible CDC electrode delivered 240 mF.cm-2 in sulfuric acid (6). A second strategy consisted in the preparation of flexible micro-supercapacitors via laser-writing of commercial RuO2 on polyimide substrate. Indeed, laser-writing provides facile and scalable engineering with low cost (7), as less than 1 mg.cm-2 of active material are needed in micro-electrodes. Thus, RuO2 interdigitated electrodes were obtained from laser-writing of a precursor mixture of commercial RuO2.xH2O powder and HAuCl4.3H2O salt, spin-coated onto KaptonTM. Laser-writing led to current collector-free and mechanically stable flexible interdigitated RuO2 electrodes. Capacitance values of ~ 30 mF.cm-2 were recorded at 20 mV.s-1 in 1M H2SO4 for the flexible device. This work open the way for the design of high performance micro-devices at large scale. 1. S. Zhai, H. E. Karahan, L. Wei, Q. Qian, A. T. Harris, A. I. Minett, S. Ramakrishna, A. K. Ng, and Y. Chen, Textile energy storage: Structural design concepts, material selection and future perspectives. Energy Storage Mater. 3, 123–139 (2016). 2. J. R. Miller, Valuing reversible energy storage. Science. 335, 1312–1313 (2012). 3. P. Simon and Y. Gogotsi, Materials for electrochemical capacitors. Nat. Mater. 7, 845–854 (2008). 4. T. Brousse, D. Belanger, and J. W. Long, To Be or Not To Be Pseudocapacitive? J. Electrochem. Soc. 162, A5185–A5189 (2015). 5. J. Chmiola, C. Largeot, P. L. Taberna, P. Simon, and Y. Gogotsi, Monolithic Carbide-Derived Carbon Films for Micro-Supercapacitors. Science. 328, 480–483 (2010). 6. P. Huang, C. Lethien, S. Pinaud, K. Brousse, R. Laloo, V. Turq, M. Respaud, A. Demortière, B. Daffos, P. L. Taberna, B. Chaudret, Y. Gogotsi, and P. Simon, On-chip and freestanding elastic carbon films for micro-supercapacitors. Science. 351, 691–695 (2016). 7. M. F. El-Kady and R. B. Kaner, Direct laser writing of graphene electronics. ACS Nano. 8, 8725–8729 (2014).

Processing of magnesium bearing materials by dry chlorination - An overview of kinetic aspects

This paper is focused on the reactivity of Cl2 towards MgO in presence of a reducing (CO) and oxidizing (O2) agent at temperatures up to 1025 °C. Kinetics parameters are determined by thermogravimetry under isothermal conditions. The overviewed results showed that the carbochlorination (Cl2+CO) occurred at temperatures lower than oxychlorination (Cl2+O2). The reaction of MgO with Cl2+CO from 425 °C to 600 °C proceeds with an activation energy (Ea) of about 49 kJ/mol, while the reaction rate does not longer depend on the temperature between 600 and 675 °C. The reaction of MgO with Cl2+O2 at 850-1025 °C was characterized by a value of Ea of 214 kJ/mol indicating that the overall rate of the process is controlled by the rate of chemical reaction. Oxychlorination can also be used for removing the impurities contained in the industrial magnesium raw materials. Further, the behavior of the MgO in chlorine atmosphere leads to give an insight about the reaction mechanisms useful for the selective chlorination of complex ores and concentrates containing magnesium oxide.

Constraints on Arctic Atmospheric Chlorine Production through Measurements and Simulations of Cl2 and ClO

During springtime, unique halogen chemistry involving chlorine and bromine atoms controls the prevalence of volatile organic compounds, ozone, and mercury in the Arctic lower troposphere. In situ measurements of the chlorine monoxide radical, ClO, and its precursor, Cl2, along with BrO and Br2, were conducted using chemical ionization mass spectrometry (CIMS) during the Bromine, Ozone, and Mercury Experiment (BROMEX) near Barrow, Alaska, in March 2012. To our knowledge, these data represent the first ClO measurements made using CIMS. A maximum daytime ClO concentration of 28 ppt was observed following an early morning peak of 75 ppt of Cl2. A zero-dimensional photochemistry model was constrained to Cl2 observations and used to simulate ClO during a 7-day period of the field campaign. The model simulates ClO within the measurement uncertainty, and the model results highlight the importance of chlorine chemistry participation in bromine radical cycling, as well as the dependence of halogen chemistry on NOx levels. The ClO measurements and simulations are consistent with Cl2 being the dominant Cl atom source in the Arctic boundary layer. Simulated Cl atom concentrations, up to ∼1 × 106 molecules cm-3, highlight the importance of chlorine chemistry in the degradation of volatile organic compounds, including the greenhouse gas methane.

Atmospheric changes caused by galactic cosmic rays over the period 1960–2010

Abstract. The Specified Dynamics version of the Whole Atmosphere Community Climate Model (SD-WACCM) and the Goddard Space Flight Center two-dimensional (GSFC 2-D) models are used to investigate the effect of galactic cosmic rays (GCRs) on the atmosphere over the 1960–2010 time period. The Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) computation of the GCR-caused ionization rates are used in these simulations. GCR-caused maximum NOx increases of 4–15 % are computed in the Southern polar troposphere with associated ozone increases of 1–2 %. NOx increases of ∼ 1–6 % are calculated for the lower stratosphere with associated ozone decreases of 0.2–1 %. The primary impact of GCRs on ozone was due to their production of NOx. The impact of GCRs varies with the atmospheric chlorine loading, sulfate aerosol loading, and solar cycle variation. Because of the interference between the NOx and ClOx ozone loss cycles (e.g., the ClO + NO2+ M → ClONO2+ M reaction) and the change in the importance of ClOx in the ozone budget, GCRs cause larger atmospheric impacts with less chlorine loading. GCRs also cause larger atmospheric impacts with less sulfate aerosol loading and for years closer to solar minimum. GCR-caused decreases of annual average global total ozone (AAGTO) were computed to be 0.2 % or less with GCR-caused column ozone increases between 1000 and 100 hPa of 0.08 % or less and GCR-caused column ozone decreases between 100 and 1 hPa of 0.23 % or less. Although these computed ozone impacts are small, GCRs provide a natural influence on ozone and need to be quantified over long time periods. This result serves as a lower limit because of the use of the ionization model NAIRAS/HZETRN which underestimates the ion production by neglecting electromagnetic and muon branches of the cosmic ray induced cascade. This will be corrected in future works.

Toward graphene chloride: chlorination of graphene and graphene oxide

Chlorinated graphene derivates with chlorine concentration exceeding 11 at% were synthesized by high temperature exfoliation in chlorine atmosphere. Halogen graphenes have a great potential for electronic and electrochemical devices.

Effect of carbon nanotube modification on poly (butylene terephthalate)-based composites

AbstractThe influence of the chemical modification of carbon nanotubes on the mechanical, thermal and electrical properties of poly(butylene terephthalate)-based composites was investigated. Polymer composites based on poly(butylene terephthalate) were obtained via in situ polymerisation or extrusion. Commercially available multi-walled carbon nanotubes (Nanocyl NC7000) at different loadings (mass %: 0.05, 0.25, 1, 2) were used as fillers. The functionalisation process took place under a chlorine atmosphere followed by a reaction with sodium hydroxide. The effect of carbon nanotube modification was analysed according to the changes in the polymer thermal and mechanical properties. An addition of modified carbon nanotubes in the amount of 0.05 mass % improved the mechanical properties of the composites in terms of both Young’s modulus and tensile strength by 5–10 % and 17–30 % compared with composites with unmodified carbon nanotubes and neat poly(butylene terephthalate), respectively. The in situ method of composite preparation was a more effective technique for enhancing the matrix–filler interactions, although a significantly lower amount of fillers were used than in the extrusion method.

In Ukrainian

in Ukrainian

The origins of perchlorate in the Martian soil

AbstractPerchlorate (ClO4−) has been detected on Mars, but its production and distribution are unclear. Mechanisms requiring atmospheric chlorine are insufficient for measured concentrations. We conducted studies under Mars conditions using halite (NaCl) alone, soil simulants consisting of silica (SiO2), Fe2O3, Al2O3, and TiO2. After 170 h irradiation, samples analyzed by ion chromatography (IC) showed ClO4− and ClO3− present in all samples. When SiO2 was added, yield increased from 2 to 42 nmol and 0.4 to 2.6 nmol, respectively. We attribute this to SiO2 and metal oxides acting as photocatalysts, generating O2− radicals from O2 which react with chloride. Results show ClO4− and ClO3− can be produced photochemically on Cl minerals without atmospheric chlorine or aqueous conditions, and explain high concentration of ClO4− and ClO4−/Cl− ratios detected by Phoenix. They provide evidence that its distribution on Mars is dictated by distribution of chlorine and provide insight into the oxidizing nature of the soil and its potential effects on organics.

Frequency-energy and amplification characteristics of the CuCl laser with an internal reactor

A new method for the creation of vapor of a working substance in lasers on atomic transitions is presented. The frequency-energy and amplification characteristics of the CuCl laser that is excited by a barrier discharge are studied. Such a method for the excitation allows an increase in the working lifetime of the active element, since the internal electrodes are rapidly destroyed in chlorine atmosphere. The experimental dependences show that such an approach makes it possible to construct lasers with output parameters that are no worse than the parameters of conventional lasers on metal halides and the amplification characteristics are similar to those of the known active elements.

Structure and Bonding in Chlorine-Functionalized Nanodiamond--Nuclear Magnetic Resonance and X-Ray Photoelectron Spectroscopy Study.

We report on investigation of detonation nanodiamond annealed at 800C°in chlorine atmosphere by means of 1H, 13C and 35Cl nuclear magnetic resonance and X-ray photoelectron spectroscopy. The results of these methods are found to be consistent with each other and evidence formation of chlorine-carbon groups and sp2 carbon shell on the nanodiamond surface. The data obtained provide detailed information about the structure and bonding in this diamond nanoparticle. Interaction of nuclear spins with unpaired electron spins of dangling bonds results in fast 13C nuclear spin-lattice relaxation.

Mechanism for formation of atmospheric Cl atom precursors in the reaction of dinitrogen oxides with HCl/Cl−on aqueous films

Nitryl chloride (ClNO2) and nitrosyl chloride (ClNO) are potential sources of highly reactive atmospheric chlorine atoms, hence of much interest, but their formation pathways are unknown. This work predicts production of these nitrogen oxychlorides from ab initio molecular dynamics (AIMD) simulations of N2O5 or an NO2 dimer on the surface of a thin film of water which is struck by gaseous HCl. Both of these heterogeneous reactions proceed at the liquid/vapor interface by an SN2 mechanism where the nucleophile is chloride ion formed from the ionization of HCl on the aqueous surface. The film of water enhances the otherwise very slow gas phase reaction to occur by (1) stabilizing and localizing the adsorbed N2O5 or NO2 dimer so it is physically accessible for reaction, (2) ionizing the impinging HCl, and (3) activating the adsorbed oxide for nucleophilic attack by chloride. Though both nitrogen oxychloride products are produced by SN2 reactions, the N2O5 mechanism is unusual in that the electrophilic N atom to be attacked oscillates between the two normally equivalent NO2 groups. Chloride ion is found to react with N2O5 less efficiently than with N2O4. The simulations provide an explanation for this. These substitution/elimination mechanisms are new for NOx/y chemistry on thin water films and cannot be derived from small cluster models.

Recent Northern Hemisphere stratospheric HCl increase due to atmospheric circulation changes.

The abundance of chlorine in the Earth's atmosphere increased considerably during the 1970s to 1990s, following large emissions of anthropogenic long-lived chlorine-containing source gases, notably the chlorofluorocarbons. The chemical inertness of chlorofluorocarbons allows their transport and mixing throughout the troposphere on a global scale, before they reach the stratosphere where they release chlorine atoms that cause ozone depletion. The large ozone loss over Antarctica was the key observation that stimulated the definition and signing in 1987 of the Montreal Protocol, an international treaty establishing a schedule to reduce the production of the major chlorine- and bromine-containing halocarbons. Owing to its implementation, the near-surface total chlorine concentration showed a maximum in 1993, followed by a decrease of half a per cent to one per cent per year, in line with expectations. Remote-sensing data have revealed a peak in stratospheric chlorine after 1996, then a decrease of close to one per cent per year, in agreement with the surface observations of the chlorine source gases and model calculations. Here we present ground-based and satellite data that show a recent and significant increase, at the 2σ level, in hydrogen chloride (HCl), the main stratospheric chlorine reservoir, starting around 2007 in the lower stratosphere of the Northern Hemisphere, in contrast with the ongoing monotonic decrease of near-surface source gases. Using model simulations, we attribute this trend anomaly to a slowdown in the Northern Hemisphere atmospheric circulation, occurring over several consecutive years, transporting more aged air to the lower stratosphere, and characterized by a larger relative conversion of source gases to HCl. This short-term dynamical variability will also affect other stratospheric tracers and needs to be accounted for when studying the evolution of the stratospheric ozone layer.

Synthesis of magnesium aluminate spinel by periclase and alumina chlorination

A pyrometallurgical route for the synthesis of magnesium aluminate spinel by thermal treatment of a mechanical mixture containing 29wt% MgO (periclase) and 71wt% Al2O3 (alumina) in chlorine atmosphere was developed and the results were compared with those obtained by calcining the same mixture of oxides in air atmosphere. Isothermal and non-isothermal assays were performed in an experimental piece of equipment adapted to work in corrosive atmospheres. Both reagents and products were analyzed by differential thermal analysis (DTA), X-ray diffraction (XRD) and X-ray fluorescence (XRF). Thermal treatment in Cl2 atmosphere of the MgO–Al2O3 mixture produces magnesium aluminate spinel at 700°C, while in air, magnesium spinel is generated at 930°C. The synthesis reaction of magnesium aluminate spinel was complete at 800°C.

Synthesis of cordierite by dolomite and kaolinitic clay chlorination. Study of the phase transformations and reaction mechanism

The focus of analysis in this work has been the study of the synthesis of cordierite using a pyrometallurgical route which involved thermal treatment in a chlorine atmosphere of a kaolinitic clay and dolomite mixture as raw material. The reaction mechanism was also investigated. Isothermal and non-isothermal chlorination assays were conducted in experimental equipment adapted for working in corrosive atmospheres. The temperature effect on the reactions yielding cordierite were studied. Both reagents and products were analyzed by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). The experimental results have shown that cordierite starts to be produced at 700°C, and that the elimination of iron, which is present as an impurity, begins at about 700°C. The most favorable chlorination temperature was 900°C, since at this temperature a selective production of cordierite and an efficient elimination of iron were achieved.