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1.
The literature on polyethylenes has been reviewed with an emphasis on the identification of gaseous products generated under various thermal decomposition conditions and the toxicity of those products. This review is limited to publications in English through 1984. The analytical chemical studies of the thermal decomposition products generated under vacuum, inert and oxidative experimental conditions are described. In oxidative atmosphere, which most closely simulate real fire conditions, carbon monoxide (CO) was found to be the predominant toxicant. Acrolein was another toxicant often noted in these reviewed studies. More acrolein was generated under non-flaming than under flaming conditions. Results from seven different test procedures were considered in assessing the acute inhalation toxicity of combustion products from various polyethylene formulations. The combustion products generated from the polyethylenes studied in the non-flaming mode appeared to be slightly more toxic than those produced in the flaming mode. In the non-flaming mode the LC50 values ranged from 5 to 75 mg l?1. In the flaming mode the LC50 values ranged from 31 to 51 mg l?1. The toxicity of the degradation products of polyethylenes appears to be similar to that found for other common materials designed for the same end uses. 相似文献
2.
The literature on rigid polyurethane foam has been reviewed with an emphasis on the gaseous products generated under various thermal decomposition conditions and the toxicity of those products. This review is limited to publications in English through 1984. Carbon monoxide (CO) and hydrogen cyanide (HCN) were the predominant toxicants found among more than a hundred other gaseous products. The generation of CO and HCN was found to increase with increasing combustion products from various rigid polyurethane foams. Lethality, incapacitation, physiological and biochemical parameters were employ as biological end points. In general, the combustion products generated from rigid polyurethane foam in the flaming mode appear from to be more toxic than those produced in the non-flaming mode. The LC50 values for 30-min exposures ranged from 10 to 17 mg l?1 in the flaming mode and were greater then 34 mg l?1 in the non-flaming mode. With the exception of one case, in which a reactive type phosphorus containing fire retardant was used, the addition of fire retardants to rigid polyurethane foams does not appear to generate unusual toxic combustion products. 相似文献
3.
David A. Purser 《火与材料》1992,16(2):67-75
Fluropolymers, especially polytetrafluoroethylene (PTFE), have good fire-resistance properties, but their application is limited by concerns over the toxicity of their thermal decomposition products. In experiments using a tube furnace system similar to the DIN 53 436 method, the 30-minute (+ 14 days observation) LC50 in mass loss terms was found to be 2.9 mgI?1 (Standard Error 0.40) under non-flaming conditions, approximately ten times as toxic as wood and most other materials. Toxicity was due to upper respiratory tract and airway irritation, and was consistent with the known effects of carbonyl fluoride and hydrogen fluoride. When decomposed in the NBS cup furnace test under-non-flaming conditions, PTFE evolved extreme-toxicity products with an LC50 of approximately 0.05 mgI?1 (mass loss), approximately 1000 times as toxic as wood and most other materials. Toxicity was due to deep lung irritation and oedema. Investigations of the range of conditions under which the extreme toxicity of PTFE products occurs in both small-scale (200-litre) and intermediate-scale (6 m3) experiments have shown that the highest toxicity occurs when PTFE is decomposed under non-flaming conditions over a temperature range of 400–650°C, and when the primary decomposition products are subjected to continuous secondary heating. At higher or lower temperatures, when the sample is flaming, when decomposition products from wood are also present in the chamber, when secondary heating is curtailed, or when the molecule contains hydrogen as well as fluorine, the toxicity of the products is greatly reduced, tending towards the region of ten times the potency of most other materials. Extreme toxicity is associated with a particulate, but the particulate atmosphere is not always extremely toxic, the potency decreasing as the fumes age. 相似文献
4.
The current English literature through 1984 on the products of pyrolysis and combustion from polystyrenes and the toxicity of those products is reviewed. Among 57 compounds detected by chemical analyses of the thermal decomposition products produced under various atmospheric conditions (vacuum, inert and oxidative), the main volatile component is the styrene monomer, Evidence is provided that the mass fraction of styrene increases with furnace temperatures at least through 500°C. At 800°C and above, the concentration of styrene decreases. In oxidative atmospheres, carbon monoxide (CO), carbon dioxide (CO2) and oxidative hydrocarbons are formed. The concentrations of CO and CO2 are a function of temperature and combustion conditions, i.e. greater amounts are produced in the flaming than in the non-flaming mode. Eleven different test procedures were used to evaluate the toxicity of the pyrolysis and combustion atmospheres of polystyrenes. The more toxic environments produced under flaming conditions appear to be mainly attributed to CO and CO2 but rather to some other toxicant, probably the styrene monomer. When compared with other common materials used in buildings and residences, polystyrenes, in general, are among the least toxic. 相似文献
5.
James B. Larsen Gordon L. Nelson Brian K. Williams Eric G. Spencer Lisa M. Spencer 《火与材料》1994,18(2):121-130
Experiments were conducted on 34 plastic materials having a variety of metallic coatings to determine the toxicity of their thermal decomposition products. Mice were exposed for 30 min in a dome exposure chamber to the products obtained by ramp-heating the samples from 200°C to 800°C. An LC50 value was obtained for each material. Postmortem examinations were conducted on all dead mice, and on survivors after 14 days, to determine the gross pathological effects of exposure; particular attention was devoted to pulmonary pathology. The exposure protocol chosen has been extensively criticized, but it is very useful to study the effects of stress on mice, which was the most important part of this work. Experiments were made involving unrestrained mice in groups of four, restrained mice in groups of four and unrestrained single mice. The LC50 values for single unrestrained mice were greater, by factors of 2–3, than those for four restrained mice, with the differences being shown to be statistically significant. This suggests that stress on the test animals will tend to reduce the LC50 values in bench-scale smoke toxicity tests. The LC50 values for all of the materials tested were equal to or higher than the value of 8 mg1?1 representative of the contribution of carbon monoxide to post-flashover fires. Moreover, no ‘supertoxicants’ were found in the smoke of any of the materials tested. Finally, the coatings did not adversely affect the smoke toxicity of the substrate materials by a factor higher than 2–3 in any of the cases investigated. Uncoated polyethylene was the most toxic substrate material tested (LC50 = 16 mgl?1) and uncoated NORYL® resin was the least toxic (LC50 = 91mgl?1). Metallic coatings involving Cu, Ni, graphite, and Zn typically had no statistically significant effect on the smoke toxicity of the substrate materials, although Ni coatings increased the smoke toxicity of ABS I and of white polycarbonate structural foam, by factors of 2–3. Overall smoke toxicities were well correlated with production of carbon monoxide (r=0.84) and carbon dioxide (r=0.82); oxygen levels and chamber temperature did not vary beyond acceptable limits. The materials tested generating the more toxic smokes (including polyethlene, polystyrene, and several polycarbonates) produced severe lung damage at low concentrations. The LC50 of these materials was also typically greater than predicted on the basis of CO production. Other materials (including several coating on NORYL® resin and Lexan® polycarbonate) produced pulmonary damage at higher concentrations amd had LC50 values more closely correlated with CO production. None of the polyurethane materials tested produced severe lung damage at the concentrations employed. 相似文献
6.
The literature on polyamides was reviewed to determine the nature and extent of information available on these materials which are commonly used in consumer and industrial applications. This review was limited to aliphatic polyamides normally called nylon and excludes aromatic polyamides such as Nomex and bicomponent polymers consisting of nylon and other polymers. The review was further limited to those publications in English through June 1984. Typical pyrolysis products from a broad range of nylons do not appear to differ greatly. Many of the decomposition products detected in vacuum pyrolysis experiments appear as products of thermal degradation in inert and air atmospheres. In air, a general reduction in the quantities of heavier hydrocarbons is noted along with an increase in the production of CO, CO2, H2O, NH3, HCN and NOx. The toxicity of the thermal degradation products from various types of nylon has been evaluated by nine different protocols. Reported LC50 values range from 10.8 m l?1 to 61.9 mg l?1. Dyes apparently do not affect the materials' combustion products toxicity but an increase in the amount of backcoating on a nylon fabric increases toxicity. Time to death measurements show that volatile products from nylons are less toxic than those from rayons or cotton, while the blending of wool with nylon greatly increases the toxicity of the thermal decomposition products. In general, however, the overall toxicity of the thermal degradation products from nylon do not appear to be greatly different than those from many other polymeric materials. Large-scale test results are ambiguous, and it is difficult to interpret the results in terms of a single component in a multicomponent system. 相似文献
7.
An alternative method for in vitro fire smoke toxicity assessment of polymers and composites using human lung cells has been investigated. A range of building and train interiors including polyethylene (PE), polypropylene (PP), polycarbonate (PC), polymethyl methachrylate (PMMA), polyvinyl chloride (PVC), fiberglass‐reinforced polymer (FRP), and melamine‐faced plywood (MFP) were studied. The exposure of combustion toxicants to human lung cells (A549) at the air/liquid interface was acquired using a Harvard Navicyte Chamber. Cytotoxic effects on human cells were assessed based on cell viability using the MTS assay (Promega). Cytotoxicity results were expressed as no observable adverse effect concentration (NOAEC), 10% inhibitory concentration (IC10), 50% inhibitory concentration (IC50), and total lethal concentration (TLC) values (mg/l). Mass loss data and toxic product yield were also determined. Results suggested that PVC (IC50 1.99 mg/l) was the most toxic materials followed by PP, FRP‐16, PC, PMMA, FRP‐10, PE, and melamine plywood. Some materials revealed to be more toxic under flaming combustion (PP, PC, FRP‐16, and FRP‐10), while others (PVC, PMMA, PE, and melamine plywood) appeared more toxic under non‐flaming combustion. The method developed can be used to screen the toxicity of materials which would be important information in building and mass transport material selection. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
8.
A series of gas chromatographic–mass spectrometric analyses was carried out on polyethylene, polypropylene, polystyrene and polyamide in CAB 4.5 and CAB 650 chambers in the flaming and non-flaming combustion mode. The combustion products formed were identified and used to characterize the combustion process in both chambers; procedures were selected for testing polymeric materials for the dangerous effects of their combustion products. 相似文献
9.
Samir A. M. Abdelgaleil Magdy I. E. Mohamed Mohamed E. I. Badawy Sailan A. A. El-arami 《Journal of chemical ecology》2009,35(5):518-525
A comparative study was conducted to assess the contact and fumigant toxicities of eleven monoterpenes on two important stored
products insects—, Sitophilus oryzae, the rice weevil, and Tribolium castaneum, the rust red flour beetle. The monoterpenes included: camphene, (+)-camphor, (−)-carvone, 1-8-cineole, cuminaldehyde, (l)-fenchone, geraniol, (−)-limonene, (−)-linalool, (−)-menthol, and myrcene. The inhibitory effect of these compounds on acetylcholinesterase
(AChE) activity also was examined to explore their possible mode(s) of toxic action. Although most of the compounds were toxic
to S. oryzae and T. castaneum, their toxicity varied with insect species and with the bioassay test. In contact toxicity assays, (−)-carvone, geraniol,
and cuminaldehyde showed the highest toxicity against S. oryzae with LC50 values of 28.17, 28.76, and 42.08 μg/cm2, respectively. (−)-Carvone (LC50 = 19.80 μg/cm2) was the most effective compound against T. castaneum, followed by cuminaldehyde (LC50 = 32.59 μg/cm2). In contrast, camphene, (+)-camphor, 1-8-cineole, and myrcene had weak activity against both insects (i.e., LC50 values above 500 μg/cm2). In fumigant toxicity assays, 1-8-cineole was the most effective against S. oryzae and T. castaneum (LC50 = 14.19 and 17.16 mg/l, respectively). Structure-toxicity investigations revealed that (−)-carvone—, a ketone—, had the highest
contact toxicity against the both insects. 1-8-Cineole—, an ether—, was the most potent fumigant against both insects. In
vitro inhibition studies of AChE from adults of S. oryzae showed that cuminaldehyde most effectively inhibited enzyme activity at the two tested concentrations (0.01 and 0.05 M) followed
by 1-8-cineole, (−)-limonene, and (l)-fenchone. 1-8-Cineole was the most potent inhibitor of AChE activity from T. castaneum larvae followed by (−)-carvone and (−)-limonene. The results of the present study indicate that (−)-carvone, 1,8-cineole,
cuminaldehyde, (l)-fenchone, and (−)-limonene could be effective biocontrol agents against S. oryzae and T. castaneum. 相似文献
10.
All organic materials burn and give off toxic products. These always include water, carbon dioxide, and the single gas causing the greatest hazard in fires—carbon monoxide (CO). The intrinsic toxicity of the smoke of all combustible materials, including PVC, is very similar in terms of lethality, with very few exceptions. Toxicity of vinyl compounds is due to two major gases: CO and hydrogen chloride (HCI). Since natural combustible materials are not chlorinated, speculation has arisen about the toxicity of HCl and of PVC smoke. Recent studies have shown that it takes similar doses of HCl and CO to kill rats. Furthermore, rats and baboons will tolerate the same levels of HCl. However, mice are much more sensitive than either rats or baboons towards HCl. Baboons are a very good model for humans; therefore, mice will be killed by exposure to much lower HCl levels than those required to kill humans. HCl concentrations in real fires are quite low: HCl decays rapidly by reacting with wall materials such as gypsum, cement, or ceiling tile. It does not, however, react rapidly with plastic or glass walls, which is where toxicity tests are carried out. Therefore PVC smoke is less hazardous in reality than it appears to be from toxicity test results. Since most products have similar intrinsic toxicities, as regards lethality, the real toxicity in a fire is a consequence of the rate of generation of gases. PVC is a difficult polymer to ignite and burns very slowly, so that it will give off less toxic products per unit time than many other common materials and cause lower fire hazard. 相似文献
11.
Sylvia Orbn 《大分子材料与工程》1985,137(1):269-279
Thermal stability of vinyl chloride/carbon monoxide copolymers synthetized in the presence of different proportions of carbon monoxide was studied in nitrogen, oxygen or air stream at 180°C. Dehydrochlorination rate increases proportionally to the incorporated carbonyl content. Effect of air and oxygen on acceleration of the decomposition is higher for PVC samples of regular structure than for the vinyl chloride/carbon monoxide copolymers. In the infra-red spectra recorded after the thermal oxidative decomposition, a broad absorption band appears between 1600 and 1800 cm?1. Two peaks show the most emphasized increase: one at 1720 to 1730 cm?1 assigned to the carbonyl group and another at about 1770 cm?1 of unidentified origin. Additional oxidation products from the polyene yield a “shoulder” in the spectrum between 1600 and 1690 cm?1. 相似文献
12.
G
Ran Dave Hans Blanck Kersti Gustafsson 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1979,29(4):249-257
Aquatic environments are the main recipient for chemicals lost from solvent extraction plants. Therefore, the toxicity of these chemicals to aquatic organisms must be considered. So far the effects of solvent extraction chemicals on aquatic organisms have been underestimated. The toxicity of some commonly employed solvent extraction chemicals to a green alga, Chlorella emersonii, a fish, Salmo gairdneri, and two cellulose-degrading bacteria, Cellulomonas sp. and Sporocytophaga myxococcoides, are reported. For most aliphatic amines studied (Primene JM-T, Amberlite LA-1, Adogen 283, Alamine 336 and Aliquat 336) inhibition of growth (algae and bacteria) and mortality of fish are shown at nominal concentrations below 1 mg dm?3 (EC50s and LC50s). Other chemicals tested (Adogen 383, TBP, HDEHP, NA SUL AS-50, LIX 64N, Versatic 10 and 2-ethylhexanol) are less toxic, having EC50s for inhibition of growth and/or LC50s between 0.3 and 100 mg dm?3. The acute toxicity to fish is shown to be dependent on ambient temperature for all chemicals studied. Solvent extraction chemicals spread into the environment have the potential to produce toxic effects on aquatic organisms. It is therefore recommended that the status of aquatic life in natural waters receiving solvent extraction chemicals is monitored. 相似文献
13.
This paper examines the smoke emission and properties of polypropylene and flame retarded polypropylene injection moulded plaques. The prepared samples were irradiated in a Stanton Redcroft NBS type smoke box with an incident radiant energy of 2.5 W/cm2. Nucleating agents were also introduced to increase the particle size of the smoke produced. The conclusions reached from this work on the emission of smoke in a non-flaming mode were that as the flame retardant additive content was increased, the optical density decreased, thus extending the time for escape. The emission of smoke from these polymers subjected to other radiant sources and in a flaming and non-flaming mode is being investigated further. 相似文献
14.
James B. Larsen Katherine T. Fokakis Melissa A. Massett Lisa A Ciccarelli Lisa R. Smith 《火与材料》2000,24(2):77-83
Stress is known to alter physiological homeostasis and distort experimental results. In particular, stress associated with restraint and group‐interaction may modify the lethality of toxic substances. Median lethal concentrations (LC50) for carbon monoxide (CO) were determined using restrained or unrestrained mice exposed for 30 min as groups or individuals. To evaluate stress levels, the serum concentration of corticosterone (COS) was determined for each exposure configuration by radioimmunoassay. Additional LC50 values for CO were determined after treating groups of restrained mice with mifepristone (10 mg/kg), to block the effects of COS, and groups of unrestrained mice with exogenous COS (2 mg/kg), to elevated the serum level. The LC50 value obtained using restrained mice exposed in groups (0.26%) was significantly lower (p<0.05) than the values derived from all other exposure configurations (0.41–0.58%). The higher LC50 values did not differ significantly, although the highest values were obtained from individual exposures. Levels of COS were strongly correlated with CO toxicity (r=0.90). The LC50 obtained from mifepristone‐treated mice (0.41%) was significantly higher (p<0.05) than that obtained from restrained groups of untreated mice (0.26%). However, treatment with COS did not alter the LC50 obtained from unrestrained groups of mice (0.41%). The results suggest that restraint and interaction must be coupled to significantly modify estimates of toxicity, and that effective interaction between restrained mice can occur (probably mediated by olfactory cues). Both factors appear to elevate stress levels in mice, and stress appears to increase the sensitivity of mice to intoxication by CO. However, COS may not be entirely responsible for the effects of stressors on toxicity. Copyright © 2000 John Wiley & Sons Ltd 相似文献
15.
Cu2+‐Organic montmorillonites were prepared by modifying Na+ montmorillonite (Na+‐MMT) with silane coupling agents and cupric sulfate. PVC/organic montmorillonite composites were prepared by the melt intercalation method. Morphological structure of modified MMT and PVC/MMT was obtained by using XRD and SEM. The XRD results showed that silanes and Cu2+ were intercalated among interlayers and that modified MMT may have exfoliated dispersion in PVC. Effects of Cu2+‐organic montmorillonites on decomposition and smoke emission of poly(vinyl chloride) (PVC) in the flaming mode were investigated by using a cone calorimeter at an incident heat flux of 25 kW·m?2. Cone experimental data demonstrated that the Cu2+‐organic montmorillonites prepared were new effective smoke suppressants. They clearly promoted an early HCl elimination, crosslinking reactions, and char residue formation, based upon the decomposition parameters of mass loss, mass loss rate, and time of initial decomposition (tinitial). Cu2+‐Organic montmorillonites decreased peak heat release rate, total heat release, peak smoke production rate, total smoke production, and smoke extinction area during the flaming process. The smoke‐reducing efficiency of Cu2+‐organic montmorillonites (Cu2+‐OMMTs) was the best. However, the content of cupric ion was only 0.6–0.8% in Cu2+‐OMMTs and 0.03–0.04% in PVC composites. They may make the smoke‐reducing efficiency reach 45–50%. This result further demonstrates that Cu2+ ion is a very effective smoke suppressant for PVC. J. VINYL ADDIT. TECHNOL., 13:31–39, 2007. © 2007 Society of Plastics Engineers. 相似文献
16.
Comparison of the smoke toxicity of four vinyl wire and cable compounds using different test methods
Four vinyl wire and cable materials were tested using five smoke toxic potency test methods: the NBS cup furnace test (in its flaming and non-flaming modes), the NIST radiant test, the NIBS IT50 test (also using the radiant apparatus) and the UPITT test. One of the materials is a standard poly(vinyl chloride) (PVC) flexible wire and cable material, used commercially for wire insulation. The three other materials tested represent a new family of vinyl thermoplastic elastomer alloys, which are advanced materials with good fire performance, particularly in terms of heat release and smoke obscuration. It was found that the smokes from all four materials are similar in terms of their toxic potencies, and that they are all within the ‘common’ range of toxic potency found. In particular, the toxic potencies of the smoke from the new vinyl thermoplastic elastomer alloys are not significantly different from those of other traditional vinyl wire and cable compounds. The results of the tests were also interpreted in terms of the toxicities and concentrations of the individual gases emitted. The fractional effective dose of the toxicants analysed was sufficient to account for the toxicity of the smoke for the NBS cup furnace and the NISt radiant test. It was not able to account for the toxicity found in the UPITT test. The adequacy of the test protocols themselves was also investigated. It was found that the UPITT and the NIBS IT50 method are inadequate for measurement of smoke toxicity. It was also found that the NIST radiant test protocol is the one most likely to lead to the smallest amount of future testing. 相似文献
17.
Bernhard Schartel Ralf Kunze Dietmar Neubert Adams Tidjani 《Polymer International》2002,51(3):213-222
The flame retardant effect of zinc sulphide (ZnS) in plasticised poly(vinyl chloride) (PVC‐P) materials was investigated. PVC‐P containing different combinations of additives such as 5% ZnS, 5% of antimony oxide (Sb2O3) and 5% of mixtures based on Sb2O3 and ZnS were compared. The thermal degradation and the combustion behaviour were studied using thermogravimetry (TG), coupled with FTIR (TG–FTIR) or with mass spectroscopy (TG–MS), and a cone calorimeter, respectively. A detailed and unambiguous understanding of the decomposition and release of the pyrolysis products was obtained using both TG–MS and TG–FTIR. The influence of ZnS, Sb2O3 and the corresponding mixtures on the thermal decomposition of PVC‐P was demonstrated. Synergism was observed for the combination of the two additives. The combustion behaviour (time to ignition, heat release, smoke production, mass loss, CO production) was monitored versus external heat fluxes between 30 and 75 kW m?2 with the cone calorimeter. Adding 5% of ZnS has no significant influence on the fire behaviour of PVC‐P materials beyond a dilution effect, whereas Sb2O3 works as an effective fire retardant. Synergism of ZnS and Sb2O3 allows the possibility of replacing half of Sb2O3 by ZnS to reach equivalent fire retardancy. © 2002 Society of Chemical Industry 相似文献
18.
Four wire coating materials (two of them based on PVC and the two others based on XLPE) were assessed for the irritancy of their smoke, under non-flaming conditions, by using the respiratory depression method, expressed as the RD50. The DIN 53 436 combustion tube was used as the fire model, at a temperature of 550°C (smouldering mode), and the animal model was the mouse. Animals were exposed for 10 min, at concentrations too low to cause lethality. It was found that there was relatively little difference between the irritancy of all four smokes. This was an unexpected result, since it had been predicted that PVC smoke would be much more irritating than XLPE smoke. In fact, the smoke from the PVC compounds had an RD50 roughly in the range of 100–1000 ppm, while the smoke from the XLPE compounds had an RD50 roughly in the range of 10–100 ppm. This means that PVC smoke is somewhat less irritating than XLPE smoke. The components in the smoke of all materials were determined by a combination of continuous gas analysis, ion chromatography and gas chromatography/mass spectrometry, with the objective of understanding the factors causing the irritancy. Hydrogen chloride, one of the major decomposition products of PVC, is also the most important smoke constituent causing irritancy of the smoke. Its irritancy, however, was insufficient, by a considerable margin, to explain the full degree of irritancy found. The RD50 of HCl is, like that of PVC smoke, in the range of 100–1000 ppm. On the other hand, the only compound found in the smoke of XLPE compounds with an RD50 in the same 10–100 ppm range as he overall smoke is methyl vinyl ketone. Unfortunately, the concentration of methyl vinyl ketone was much too low to account for the irritancy levels encountered. Literature data indicate that polyethylene smoke is rich in long-lived free radicals and that PVC smoke does not contain them. Moreover, such free radicals are associated with various illnesses, particularly with respiratory symptoms. Thus, it is speculated that such free radicals could be the cause of the high irritancy of the smoke from the XLPE wire coating materials. 相似文献
19.
Celalettin Özdemir Muhammed K Öden Serkan Şahinkaya Dünyamin Güçlü 《Coloration Technology》2011,127(4):268-273
In the present study, Fenton and sono‐Fenton processes were applied to the oxidative decolorisation of synthetic textile wastewater including CI Reactive Orange 127 and polyvinyl alcohol. Process optimisation [pH, ferrous ion (Fe2+) and hydrogen peroxide (H2O2)], kinetic studies and their comparison were carried out for both of the processes. The sono‐Fenton process was performed by indirect sonication in an ultrasonic water bath, which was operated at a fixed 35‐kHz frequency and 80 W power. The optimum conditions were determined as [Fe2+] = 20 mg l?1, [H2O2] = 15 mg l?1 and pH = 3 for the Fenton process and [Fe2+] = 25 mg l?1, [H2O2] = 5 mg l?1 and pH = 3 for the sono‐Fenton process. The colour removals were 89.9% and 91.8% by the Fenton and sono‐Fenton processes, respectively. The highest decolorisation was achieved by the sono‐Fenton process because of the production of some oxidising agents as a result of sonication. Consequently, ultrasonic irradiation in the sono‐Fenton process slightly increased the colour removal to 91.8%, while decreasing the hydrogen peroxide dosage to one‐third of that of the Fenton process. 相似文献
20.
Chiranjivi Bhattarai Vera Samburova Deep Sengupta Michealene Iaukea-Lum Adam C. Watts Hans Moosmüller 《Aerosol science and technology》2013,47(11):1266-1282
Biomass burning (BB) emissions and their atmospheric oxidation products can contribute significantly to direct aerosol radiative forcing of climate. Limited knowledge of BB organic aerosol chemical and optical properties leads to large uncertainties in climate models. In this article, we describe the experimental setup and the main findings of a laboratory BB study aimed at comprehensive optical, physical, and chemical characterization of fresh and aged BB emissions. An oxidation flow reactor (OFR) was used to mimic atmospheric oxidation processes. The OFR was characterized in terms of OH? production rate, particle transmission efficiency, and characteristic lifetimes of condensible compounds. Emission factors (EFs) of main air pollutants (particulate matter, organic carbon [OC], elemental carbon [EC], carbon monoxide [CO], and nitrogen oxides [NOx]) were determined for five globally and regionally important biomass fuels: Siberian (Russia), Florida (USA), and Malaysian peats; mixed conifer and aspen fuel from Fishlake National Forest, Utah, USA; and mixed grass and brush fuel representative of the Great Basin, Nevada, USA. Measured fuel-based EFs for OC ranged from 0.85?±?0.24 to 6.56?±?1.40?mg g?1. Measured EFs for EC ranged from 0.02?±?0.01 to 0.16?±?0.01?mg g?1. The ratio of organic mass to total carbon mass for fresh emissions from these fuels ranged from 1.04?±?0.04 to 1.34?±?0.24. The effect of OFR aging on aerosol optical properties, size distribution, and concentration is also discussed.Copyright © 2018 American Association for Aerosol Research 相似文献