Development of passive samplers for the detection of chlorinated hydrocarbons in sewers

1998 ◽  
Vol 37 (1) ◽  
pp. 311-318 ◽  
Author(s):  
Katrin Vorkamp ◽  
Bettina S. Haas ◽  
Reimer Herrmann
Keyword(s):  
Gas Phase ◽  
Laboratory Experiments ◽  
Chlorinated Hydrocarbons ◽  
Passive Samplers ◽  
Sampling System ◽  
Sampling Device ◽  
Sewer Systems ◽  
Different Temperatures ◽  
Volatile Chlorinated Hydrocarbons ◽  
Kinetics Of

In this work a system of passive samplers was developed to examine volatile chlorinated hydrocarbons in the gas phase of sewer systems. The adsorption kinetics of chloroform, trichloroethylene and perchlor-ethylene on the adsorption materials Tenax TA, Amberlite XAD-2, Activated Charcoal, Carbosieve S-III and Carboxen-553 were surveyed in laboratory experiments. The highest values of recovery were found for Tenax TA. Further experiments were conducted, regarding the influence of different temperatures. The only significant deviation from the reference kinetics was observed at a temperature as low as 4°C. In order to examine sewer gases a stainless steel sampling system was designed which contained six glass cartridges filled with Tenax TA, and which could be fixed to th steps in the manholes. Using this system, samples were taken at seven locations within the sewer network of Bayreuth, a medium-sized town with little industry, in order to optimise the period of sampling. At least one of the three compounds could be detected at six locations within one week of sampling. An amount of perchloroethylene which exceeded all other results by two orders of magnitude indicated the large adsorption capacity of the chosen material Tenax TA. A linear decrease with increasing height above the waste water table was found; furthermore the sampling device was proved suitable for the localisation of sources of discharge.

Analysis of chlorinated hydrocarbons in gas phase using a portable membrane inlet mass spectrometer

2016 ◽  
Vol 8 (36) ◽  
pp. 6607-6615 ◽  
Author(s):  
Stamatios Giannoukos ◽  
Boris Brkić ◽  
Stephen Taylor
Keyword(s):  
Gas Phase ◽  
Mass Spectrometer ◽  
Gaseous Phase ◽  
Chlorinated Hydrocarbons ◽  
Volatile Chlorinated Hydrocarbons ◽  
First Time

A compact portable membrane inlet mass spectrometer (MIMS) has been used for the first time to detect and monitor, both qualitatively and quantitatively, volatile chlorinated hydrocarbons in the gaseous phase.

Growth kinetics of chemically vapor deposited SiO2 films from silane oxidation

1998 ◽  
Vol 13 (8) ◽  
pp. 2308-2314 ◽  
Author(s):  
Fernando Ojeda ◽  
Alejandro Castro-García ◽  
Cristina Gómez-Aleixandre ◽  
José María Albella
Keyword(s):  
Gas Phase ◽  
Deposition Rate ◽  
Growth Kinetics ◽  
Film Growth ◽  
Chemical Vapor ◽  
Intermediate Species ◽  
Pressure Oxygen ◽  
Pressure Chemical ◽  
Different Temperatures ◽  
Kinetics Of

The growth kinetics of SiO2 thin films obtained by low-pressure chemical vapor deposition (CVD) from SiH4/O2/N2 gas mixtures has been determined at different temperatures and flow rates. The results show that the film growth is originated by some intermediate species (e.g., SiOxHy) produced in the gas phase. At low temperatures the deposition rate is limited by some homogeneous reaction with an apparent activation energy of 1.42 eV. Furthermore, the observation of critical limits when total pressure, oxygen/silane flow ratio, and temperature are decreased gives support to a branching-chain mechanism of deposition. Finally, we have observed that the deposition rate shows a hysteresis behavior when varying the temperature within the 300–400 °C range, which has been attributed to the inhibition of silane oxidation by the Si–OH surface groups of the films grown on the reactor walls.

Kinetics of Gas Phase Synthesis of Ethyl-tert-butyl Ether (ETBE) on H3PW12O40/MCM-41 Catalyst

2018 ◽  
Vol 69 (11) ◽  
pp. 3042-3047
Author(s):  
Song Il Kong ◽  
Anca Borcea ◽  
Diana Cursaru ◽  
Dragos Ciuparu
Keyword(s):  
Partial Pressure ◽  
Gas Phase ◽  
Butyl Alcohol ◽  
Butyl Ether ◽  
Phase Synthesis ◽  
Tert Butyl ◽  
Tert Butyl Alcohol ◽  
Different Temperatures ◽  
Kinetics Of ◽  
Mcm 41

The mechanism and kinetics of gas phase synthesis of ethyl-tert-butyl ether (ETBE) in the reaction between tert-butyl alcohol (TBA) and ethanol (EtOH) were investigated performing the reaction in a continuous flow quartz reactor at different temperatures and atmospheric pressure, using a heteropoliacid catalyst with 30wt% loading, dispersed on MCM-41. The Eley-Rideal reaction mechanism was previously proposed based on experimental observations that showed the rate of ETBE increased when partial pressure of tert-butyl alcohol increased, and the partial pressure of ethanol decreased, without significant effects on product selectivity. The kinetic model based on the Eley-Rideal mechanism was proposed and successfully employed to model accurately the experimental data at three different temperatures. The apparent activation energy and the frequency factor of the etherification reaction were 39.42 kJ/mol and 1.69 x 108 mol/kg . h . bar, respectively.

Comparative Labelling and Biokinetic Studies of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn)

1977 ◽  
Vol 16 (01) ◽  
pp. 30-35 ◽  
Author(s):  
N. Agha ◽  
R. B. R. Persson
Keyword(s):  
Complex Formation ◽  
Significant Influence ◽  
Room Temperature ◽  
Ph Value ◽  
Maximum Activity ◽  
Reduction Step ◽  
Labelling Yield ◽  
Different Temperatures ◽  
Kinetics Of

SummaryGelchromatography column scanning has been used to study the fractions of 99mTc-pertechnetate, 99mTcchelate and reduced hydrolyzed 99mTc in preparations of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn). The labelling yield of 99mTc-EDTA(Sn) chelate was as high as 90—95% when 100 μmol EDTA · H4 and 0.5 (Amol SnCl2 was incubated with 10 ml 99mTceluate for 30—60 min at room temperature. The study of the influence of the pH-value on the fraction of 99mTc-EDTA shows that pH 2.8—2.9 gave the best labelling yield. In a comparative study of the labelling kinetics of 99mTc-EDTA(Sn) and 99mTc- DTPA(Sn) at different temperatures (7, 22 and 37°C), no significant influence on the reduction step was found. The rate constant for complex formation, however, increased more rapidly with increased temperature for 99mTc-DTPA(Sn). At room temperature only a few minutes was required to achieve a high labelling yield with 99mTc-DTPA(Sn) whereas about 60 min was required for 99mTc-EDTA(Sn). Comparative biokinetic studies in rabbits showed that the maximum activity in kidneys is achieved after 12 min with 99mTc-EDTA(Sn) but already after 6 min with 99mTc-DTPA(Sn). The long-term disappearance of 99mTc-DTPA(Sn) from the kidneys is about five times faster than that for 99mTc-EDTA(Sn).

Kinetics of Methane-Oxidizing Biofilms for Degradation of Toxic Organics

1988 ◽  
Vol 20 (11-12) ◽  
pp. 167-173 ◽  
Author(s):  
S. E. Strand ◽  
R. M. Seamons ◽  
M. D. Bjelland ◽  
H. D. Stensel
Keyword(s):  
Chlorinated Hydrocarbons ◽  
Enzymatic Oxidation ◽  
Diffusion Kinetics ◽  
Toxic Compound ◽  
Biofilm Model ◽  
Uptake Rates ◽  
Substrate Diffusion ◽  
Toxic Organics ◽  
Competitive Substrate ◽  
Kinetics Of

The kinetics of methane-oxidizing bioreactors for the degradation of toxic organics are modeled. Calculations of the fluxes of methane and toxic chlorinated hydrocarbons were made using a biofilm model. The model simulated the effects of competition by toxics and mediane on their enzymatic oxidation by the methane monooxygenase. Dual-competitive-substrate/diffusion kinetics were used to model biofilm co-metabolism, integrating equations of the following form:where S1 and S2 are the local concentrations of methane and toxic compound, respectively, and r and K are the maximum uptake rates and Monod coefficients, and x is the distance into the biofilm.

Diffusion model for deposition of epitaxial GaAs layers prepared by the MOCVD method

1991 ◽  
Vol 56 (10) ◽  
pp. 2020-2029
Author(s):  
Jindřich Leitner ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma ◽  
Rudolf Hladina
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Kinetic Model ◽  
Gas Phase ◽  
Substrate Surface ◽  
Deposition Process ◽  
Hydrogen Atmosphere ◽  
Epitaxial Gaas ◽  
Kinetics Of ◽  
Good Agreement

The authors proposed and treated quantitatively a kinetic model for deposition of epitaxial GaAs layers prepared by reaction of trimethylgallium with arsine in hydrogen atmosphere. The transport of gallium to the surface of the substrate is considered as the controlling process. The influence of the rate of chemical reactions in the gas phase and on the substrate surface on the kinetics of the deposition process is neglected. The calculated dependence of the growth rate of the layers on the conditions of the deposition is in a good agreement with experimental data in the temperature range from 600 to 800°C.

scholarly journals Thermodynamic and detailed kinetic study of the formation of orthophthalaldehyde-agmatine complex by fluorescence intensities

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Khémesse Kital ◽  
Moumouny Traoré ◽  
Diégane Sarr ◽  
Moussa Mbaye ◽  
Mame Diabou Gaye Seye ◽  
...  
Keyword(s):  
Complex Formation ◽  
Thermodynamic Parameters ◽  
Initial Rate ◽  
Reaction Medium ◽  
Standard Entropy ◽  
Step Size ◽  
Formation Reaction ◽  
Different Temperatures ◽  
Kinetics Of ◽  
Complex Formation Process

Abstract The aim of this work is to determine the thermodynamic parameters and the kinetics of complex formation between orthophthalaldehyde (OPA) and agmatine (AGM) in an alkaline medium (pH 13). Firstly, the association constant (Ka) between orthophthalaldehyde and agmatine was determined at different temperatures (between 298 K and 338 K) with a step size of 10 K. Secondly, the thermodynamic parameters such as standard enthalpy (ΔH°), standard entropy (ΔS°),and Gibbs energy (∆G) were calculated, where a positive value of ΔH° (+45.50 kJ/mol) was found, which shows that the reaction is endothermic. In addition, the low value of ΔS°(+0.24 kJ/mol) indicates a slight increase in the disorder in the reaction medium. Furthermore, the negative values of ΔG between −35.62 kJ/mol and −26.02 kJ/mol show that the complex formation process is spontaneous. Finally, the parameters of the kinetics of the reaction between OPA and AGM were determined as follows: when the initial concentration of AGM (5 × 10−6 M) is equal to that of the OPA, the results show that the reaction follows an overall 1.5 order kinetics with an initial rate of 5.1 × 10−7Mmin−1 and a half-life of 8.12 min. The partial order found in relation to the AGM is 0.8. This work shows that the excess of OPA accelerates the formation reaction of the complex.

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