Results 1 - 10 of 2343
Results 1 - 10 of 2343. Search took: 0.03 seconds
|Sort by: date | relevance|
[en] This document provides stakeholder evaluations on innovative technologies to be used in the remediation of volatile organic compounds from soils and ground water. The technologies evaluated are; in-well vapor stripping, in-situ bioremediation, and gas membrane separation
[en] In this research, the adsorption equilibria of trichloroethylene (TCE) and benzene vapors onto hypercrosslinked polymeric resin (NDA201) were investigated by the column adsorption method in the temperature range from 303 to 333 K and pressures up to 8 kPa for TCE, 12 kPa for benzene. The Toth and Dubinin-Astakov (D-A) equations were tested to correlate experimental isotherms, and the experimental data were found to fit well by them. The good fits and characteristic curves of D-A equation provided evidence that a pore-filling phenomenon was involved during the adsorption of TCE and benzene onto NDA-201. Moreover, thermodynamic properties such as the Henry's constant and the isosteric enthalpy of adsorption were calculated. The isosteric enthalpy curves varied with the surface loading for each adsorbate, indicating that the hypercrosslinked polymeric resin has an energetically heterogeneous surface. In addition, a simple mathematic model developed by Yoon and Nelson was applied to investigate the breakthrough behavior on a hypercrosslinked polymeric resin column at 303 K and the calculated breakthrough curves were in high agreement with corresponding experimental data.
[en] The electron beam flue gas treatment technology was invented in Japan in 1970's. The paper presents the outlook of the Japanese activities on the development and present state of EBFGT technology. (author)
[en] Complete text of publication follows. Egg is one of the most consumed food in the world. Its importance and consumption are raising due to its nutritional value. Selenium-fortified eggs can easily find in the local markets and the determination of selenium fortification level in egg is important because of its toxicity and essentially. The main aim of this work was to provide a simple, fast and accurate method for selenium determination in both commercially available eggs and selenium-fortified eggs. A number of procedures exist for the determination of selenium. However, as selenium exists in volatile and unstable forms and because of inhomogeneity of many types of materials, the methods of sampling, preparation and storage are equally important as the applied analytical methods. Therefore, great care is necessary to avoid contamination or loss of the analyte. In this study, a very simple and fast alternative dissolution procedure with tetramethyl ammonium hydroxide (THAH) was proposed. The samples simply mixed with a few millilitres of TMAH solution in an open flask. Dissolution was obtained in fifteen minutes with a low temperature heating which is around 60 deg C. Mild heating was found to be necessary not only for to reduce the dissolution time but also reduce the contamination risk. In the presence of modifiers (Pd, Pd+Mg as non permanent and Ru, Rh as permanent) selenium was analysed by using graphite furnace atomic absorption spectrometry (GFAAS) technique. The results were compared with modified AOAC standard spectrophotometric method. In order to test the accuracy of the proposed method, standard reference material, whole egg powder NIST-SRM 8415 was analysed and result was found to be in good agreement with the certified value, according to the t-test for a 95% confidence level. In addition, interference effect of species such as Fe, Zn, Cu, Al, Mg, Mn and Pb were also examined.
[en] Previous research showed a cut-off along homologous volatile organic compounds (VOCs) in their ability to produce acute human mucosal irritation. The present study sought to specify the particular cut-off homolog for sensory eye irritation in an acetate and n-alcohol series. A 1900-ml glass vessel system and a three-alternative forced-choice procedure served to test nonyl, decyl, and dodecyl acetate, and 1-nonanol, 1-decanol, and 1-undecanol. Flowrate to the eye ranged from 2 to 8 L/min and time of exposure from 3 to 24 s. Decyl acetate and 1-undecanol were the shortest homologs that failed to produce eye irritation under all conditions, producing a cut-off effect. Increasing the vapor concentration of decyl acetate and 1-undecanol by 3 and 8 times, respectively, via heating them to 37 deg C made either or both VOCs detectable to only half of the 12 subjects tested, even though the higher vapor concentration was well above a predicted eye irritation threshold. When eye irritation thresholds for homologous acetates and n-alcohols were plotted as a function of the longest unfolded length of the molecule, the values for decyl acetate and 1-undecanol fell within a restricted range of 18 to 19 A. The outcome suggests that the basis for the cut-off is biological, that is, the molecule lacks a key size or structure to trigger transduction, rather than physical, that is, the vapor concentration is too low to precipitate detection
[en] Full text: In situ bioremediation is a well-established remedial technology for source treatment of chlorinated volatile organic compounds (VOCs) in groundwater. The technology can be used singularly, or incorporated as an element of a broader remedial strategy, to shorten the life cycle of a groundwater treatment program. The success of the treatment technology is contingent upon development of a sound site conceptual model, which entails a comprehensive understanding of site geochemistry, geology, hydrogeology, risk management, and regulatory objectives. The design of an effective bioremediation program involves a fundamental understanding of microbial reductive dechlorination processes harmoniously paired to the site hydrodynamic conditions that govern amendment distribution. The goal is to support efficient and complete reductive dehalogenation of chlorinated VOCs by achieving broad distribution of relatively low concentrations of electron donors throughout the treatment area. This presentation focuses on key design considerations related to amendment composition and concentration that influence the ability to achieve optimal concentrations of amendments within a treatment area to support efficient microbial reductive dechlorination processes. (author)
[en] A new technique for direct trace element analysis of solid combustible materials is described. The samples (up to 10 mg) are weighed on a graphite platform wich is then placed in a quartz tube, at the focal point of three infrared lamps. When the lamps are turned on, the sample burns in a stream of air, and the resulting dry aerosol containing volatile elements such as Hg, Cd, Bi, Tl, Zn, Pb and Cu is carried into the mixing chamber and thence into the flame, where the atomic absorption measurement is carried out. This technique overcomes chemical sample preparation steps, avoiding contaminations of losses associated with these steps. A ''furnace in flame'' system where the aerosol is transported to a flame heated T-tube is also described. The influence of flame stoichiometry, observation height, platform material and air flux intensity was studied inorder to determine optimal analytical conditions. (author)
[pt]Durante a combustao de uma amostra ocorre a passagem dos elementos mais volateis para o aerossol entao formado (fumaca). A tecnica consiste em aproveitar este processo como forma de introducao de amostras em absorcao atomica. Amostras de ate 10mg de materiais combustiveis sao pesadas sobre uma plataforma de grafite, que e colocada no interior de um tubo de quartzo, atraves do qual flui uma corrente definida de ar. A queima de amostra e iniciada pelo ''flash'' de tres lampadas infravermelhas nela focadas e os elementos volateis, agora contidos no aerossol, sao carreados para a camara de mistura e dai para a chama, onde se da o processo de atomizacao-absorcao. Desta forma, amostras podem ser analisadas diretamente, com as consequentes vantagens em termos de serem evitadas contaminacoes ou perdas associadas a etapa de abertura. Numa outra montagem, o aerossol e carreado para um tubo T aquecido pela chama. Foi estudada a influencia do fluxo de ar, da massa de amostra, da estequiometria da chama, da altura de observacao na chama e do material da plataforma, entre outros fatores, determinando-se as condicoes otimas de analise. (autor)
[en] Passive sampling is based on free flow of analyte molecules from the sampled medium to a collecting medium due to a difference in chemical potential of the analyte between the two media. It has many advantages compared to active sampling, including simplicity, low cost and no need for trained personnel. A new permeation-type passive sampler has been developed at the University of Waterloo and is available commercially under the name “Waterloo Membrane Sampler” (WMS). It uses mostly off-the-shelf components, which makes it simple and inexpensive. In WMS, a polydimethylsiloxane (PDMS) membrane separates the sampled medium from the sorbent. Analyte uptake rate is determined by the permeability of the membrane to a given analyte. (author)
[en] Complete text of publication follows. Crude oil is a complex blend of hundreds of organic compounds, and it also contains metals, such as Zn, Co, Cr, Cu, Fe, Ni and V, in the form of salt like compounds or organometallic complexes. Metals in fuels can form deposits, promote corrosion of engines, degrade fuels and cause atmospheric pollution upon their release. The determination of trace elements in crude oil is necessary for quality control purposes; however, the analysis of oil samples is a challenge and is usually carried out after digestion, dilution with an organic solvent or emulsification. A simple, fast and sensitive method is proposed for the simultaneous determination of Co and V in crude oil by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) without any sample preparation, except for a 10-minute homogenization in an ultrasonic bath. Aliquots of 0.6-8.0 mg sample were directly weighed onto solid sampling graphite platforms and inserted into the graphite furnace. The use of a linear CCD array detector that covers a spectral range of about 0.5 nm makes possible the simultaneous determination of Co at its main resonance line at 240.725 nm and of V at a secondary line at 240.674 nm. For the determination of total Co and V, Pd and Triton X-100 were added as modifiers, whereas no modifier was used for the determination of the non-volatile fractions of V and Co. A pyrolysis temperature of 1300 deg C has been chosen to avoid losses of Co and an atomization temperature of 2650 deg C to ensure complete atomization of V. Various combinations of pixels were chosen for the determination of Co, depending on its concentration. Two certified reference materials and five crude oil samples have been analyzed. The results were in agreement with the certified or reported values at a 95% confidence level. The limits of detection (3σ, n = 10) were 7 and 8 μg kg-1 for Co and 1.0 and 1.2 mg kg-1 for V without and with modifier, respectively. The precision, expressed as relative standard deviation (RSD), ranged from 2 to 20%.