Long-Term Tritium Transport through Field-Scale Compacted Soil Liner

A 13-year study of tritium transport through a field-scale earthen liner was conducted by the Illinois State Geological Survey to determine the long-term performance of compacted soil liners in limiting chemical transport. Two field-sampling procedures (pressure-vacuum lysimeter and core sampling) were used to determine the vertical tritium concentration profiles at different times and locations within the liner. Profiles determined by the two methods were similar and consistent. Analyses of the concentration profiles showed that the tritium concentration was relatively uniformly distributed horizontally at each sampling depth within the liner and thus there was no apparent preferential transport. A simple one-dimensional analytical solution to the advective–dispersive solute transport equation was used to model tritium transport through the liner. Modeling results showed that diffusion was the dominant contaminant transport mechanism. The measured tritium concentration profiles were accurately modeled with an effective diffusion coefficient of 6×10?4?mm2/s, which is in the middle of the range of values reported in the literature.     

Evaluation of Multidimensional Transport through a Field-Scale Compacted Soil Liner

A field-scale compacted soil liner was constructed at the University of Illinois at Urbana-Champaign by the U.S. Environmental Protection Agency (USEPA) and Illinois State Geological Survey in 1988 to investigate chemical transport rates through low permeability compacted clay liners (CCLs). Four tracers (bromide and three benzoic acid tracers) were each added to one of four large ring infiltrometers (LRIs) while tritium was added to the pond water (excluding the infiltrometers). Results from the long-term transport of Br? from the localized source zone of LRI are presented in this paper. Core samples were taken radially outward from the center of the Br? LRI and concentration depth profiles were obtained. Transport properties were evaluated using an axially symmetric transport model. Results indicate that (1) transport was diffusion controlled; (2) transport due to advection was negligible and well within the regulatory limits of ksat ? 1×10?7?cm/s; (3) diffusion rates in the horizontal and vertical directions were the same; and (4) small positioning errors due to compression during soil sampling did not affect the best fit advection and diffusion values. The best-fit diffusion coefficient for bromide was equal to the molecular diffusion coefficient multiplied by a tortuosity factor of 0.27, which is within 8% of the tortuosity factor (0.25) found in a related study where tritium transport through the same liner was evaluated. This suggests that the governing mechanisms for the transport of tritium and bromide through the CCL were similar. These results are significant because they address transport through a composite liner from a localized source zone which occurs when defects or punctures in the geomembrane of a composite system are present.     

Ceria-Modified Clay Supported Palladium Catalysts for Complete Oxidation of Volatile Organic Compounds

Ceria- and alumina-pillared interlayered clays were synthesized in the presence of PEO surfactant by using laponite clay as raw material.And the synthesized pillared clays were used as supports to load palladium catalysts for complete oxidation of benzene.Nitrogen adsorption/desorption experiments reveal that the pillared clays have higher tests show that ceria pillar exhibited promoting effect on the activity of the palladium catalysts, and ceria-pillared clay supported palladium catalyst catalyzed the complete oxidation of benzene at less than 250 ℃.The calcination temperature affects the activity of the catalysts significantly, and it is found that the optimal calcination temperature are 600 and 400 ℃ for ceria- and alumina-pillared clay supported palladium catalysts, respectively.     

Removal of a Volatile Organic Compound in a Hybrid Rotating Drum Biofilter

A hybrid bioreactor, combining an activated sludge process (ASP) and a rotating drum biofilter (RDB), was developed and evaluated for the treatment of volatile organic compounds (VOCs) in waste gas streams. The effects of the influent VOC concentration and the organic loading rate on the VOC removal efficiency and on the pattern of biomass accumulation were investigated. Toluene was used as the model VOC, the flow rate of the waste gas stream was 0.59 L/s, and the empty-bed retention time (EBRT) in the ASP portion was 46 s with an actual retention time of about 2 s. The EBRT in the RDB portion was 38 s based on the drum volume. When the VOC feed concentration increased from 221 to 884 mg toluene/m3 (from 57.2 to 229 ppm), correspondingly the organic loading rate of the hybrid bioreactor increased from 1.58 to 6.32 kg chemical oxygen demand/m3/day (from 0.505 to 2.02kg?toluene/m3/day) based on the drum volume, both the ASP and RDB decreased, and the overall toluene removal efficiency declined from 99.8 to 74.1%. Biomass accumulation at different medium depths became more even when the organic loading rate was increased. Part of the applied VOC was biodegraded by the ASP, which suggests that this hybrid bioreactor could achieve longer runs between medium cleanings and higher VOC removal efficiencies than a single RDB bioreactor without an ASP portion at the same organic loading rate.     

Modeling Volatile Organic Compound Sorption in Activated Carbon. II: Multicomponent Equilibrium

A new approach is presented for modeling multicomponent volatile organic compound (VOC) sorption equilibrium in ultra- and supernanoporous activated carbons. The model uses “Dubinin–Astakhov thermal equation of equilibrium adsorption” (DA-TEEA) for single-component adsorption thermodynamics and “ideal/real adsorbed solution theories” (IAST/RAST) for the multicomponent mixing rules. Use of the Henry’s Law adsorption isotherm resolves the singularity of DA-TEEA at zero-coverage conditions. The introduced method predicts multicomponent adsorption equilibria of VOCs based on equilibrium data of only one similar component. Single and binary adsorption equilibria of acetone and benzene vapors in Kynol ACFC-5092-20 activated-carbon-fiber-cloth adsorbents are predicted with the presented models and compared with modeled and measured characterization data available in the literature. The Wilson model for nonideal binary solution mixtures is used to predict the activity coefficients needed in DA-TEEA/RAST. Modeled results are compared against measured characterization data. The selected Henry’s Law upper-bound pressure (HUBP) is found to be an important factor controlling the accuracy of the multicomponent equilibrium models. An optimum HUBP can generate highly accurate results from both DA-TEEA/IAST and DA-TEEA/RAST. The accuracy realized by applying this method to acetone–benzene mixtures is sufficient for engineering design and development purposes.     

Calibration of a Model for Volatile Organic Compound Mass Removal by Multiphase Extraction

A number of remedial technologies are based on multiphase extraction, the simultaneous removal of contaminated liquids and vapors from soil or rock through one or more wells subjected to a high vacuum. This technical note proposes an empirical model for predicting cumulative contaminant-mass removal by multiphase extraction as a function of remedial-system run time. Model calibration employs early-time mass-removal data.     

Modeling Volatile Organic Compound Sorption in Activated Carbon. I: Dynamics and Single-Component Equilibrium

Design and development of new sorption technologies for control of volatile organic compound (VOC) laden air discharges from industrial sources require characterization of proposed novel processes and systems. Extensive capital, labor, and time are needed to obtain multicomponent adsorption characteristic data through laboratory experiments. As a substitute for laboratory characterization experiments, this paper presents steps for computationally predicting VOC sorption equilibrium and nonequilibrium processes in activated carbon. The method of predicting sorption equilibrium has been described in detail, since it is critical for modeling even nonequilibrium sorption dynamic processes that are constructed as successions of equilibria steps. An accurate single-component “thermal equation of equilibrium adsorption” (TEEA) is presented by modifying the Dubinin–Astakhov (DA) adsorption isotherm. DA-TEEA is capable of accurately predicting thermodynamics of single-component vapor adsorption in ultra- and supernanoporous adsorbents. The adsorption affinity factor, determined from dispersion interaction theory, enables the DA-TEEA to predict adsorption equilibrium characteristics of VOCs from adsorption equilibrium data of only one similar reference adsorbate.     

Transport of Colloids and Associated Hydrophobic Organic Chemicals through a Natural Media Filter

In this project, the ability of natural media filtration (NMF) to remove colloidal particles and associated hydrophobic organic compounds from the aqueous phase was evaluated by performing sorption and transport experiments with leaf compost media. Phenanthrene sorption isotherm experiments for compost and model colloidal (latex) particles found that phenanthrene has a greater affinity for the colloidal particles than for the compost materials. In column experiments, the transport of phenanthrene through the NMF in the presence and absence of two colloidal particles with different hydrophobicities [sulfate (more hydrophobic) and carboxylate (less hydrophobic)] showed that the effluent phenanthrene concentration in the presence of colloids, particularly sulfate latex particles, is much higher than that in the absence of colloids. The results from a mathematical model used to evaluate data from the column experiments suggest that enhancement of contaminant transport can be significant under the following conditions: high colloidal concentrations, high partition coefficient between contaminant and colloids, or a slow desorption rate of contaminant from colloids.     

Effects of Clay Content and Temperature on Crude Oil (Nonvolatile Components) Transport in Unsaturated Soils: Centrifuge Study

Surface soil contamination due to oil spill is one of the major environmental concerns. The extent of the contaminated depth governs the design and installation of remediation method and monitoring system. Physical modeling of oil contaminant in unsaturated soils was conducted using a centrifuge. Preliminary results on effects of clay content and temperature on the contaminant profile near the surface are presented. The experimental results indicate that centrifuge modeling may be a viable method to study the problem of immiscible oil movement in partially water-saturated soils.     

Estimation of Mass Transport Parameters of Organic Compounds through High Density Polyethylene Geomembranes Using a Modifield Double-Compartment Apparatus

A modified double-compartment apparatus (MDCA) is used to estimate mass transport parameters of organic compounds through high density polyethylene (HDPE) geomembranes and to investigate the effects of aging and external tension of HDPE geomembranes on the mass transport of organic compounds. A developed one-dimensional partition–diffusion mass transport model successfully explains the mass transport of the organic compounds through the HDPE geomembranes in a dilute aqueous solution–geomembrane system. Similar to batch immersion tests, the HDPE–water partition coefficient (KHDPE–W) values of organic compounds are found to have close relationships with the octanol–water partition coefficient and the aqueous solubility; furthermore, the diffusion coefficient (D) values decrease with the increase of their molecular diameter. For HDPE geomembranes served in the landfill liner for 5 years and stretched by 8% of their initial length, KHDPE–W values for organic compounds increase by 5–58%, D values for organic compounds increase by 10–86%, and breakthrough times are faster, indicating more amounts of organic compounds may break through the HDPE geomembrane in fields than expected. The mass transport parameters from MDCA tests could be used with those from batch immersion tests interchangeably after mass loss and immobilization of organic compounds in MDCA tests are considered.     

Induction of Volatile Organic Compounds in Leaves of Lycopersicon Esculentum by Nd^3＋

The effects of Nd^3＋ on the quality and quantity of volatile organic compounds （VOCs） in the leaves of Lycopersicon esculentum were studied. The results demonstrate that Nd^3＋ can increase the total amount of VOC by 75% after treatment for 120 h, as compared with the control. Phyto-oxylipins, terpenoids and aromatic compounds were increased by 73%, 38% and 21%, respectively. （E）-2-hexenal, the most abundant constituent is increased by 74%, β- phellandrene and α-caryophyllene in terpenoids,     

Modeling the Temperature Dependence of Adsorption Equilibriums of VOC(s) onto Activated Carbons

In order to optimize the efficiency of the removal of volatile organic compounds (VOCs) by adsorption onto activated carbon beds, process simulations taking into account exothermicity effects are helpful. Significant temperature increases may arise in the bed during the VOC adsorption cycle, especially when high concentrations have to be treated. Consequently, reliable and easy-to-handle isotherms remain a key hurdle to build realistic models. In this study, adsorption models were tested to describe a set of experimental data obtained for three VOCs (acetone, ethyl formate, and dichloromethane) adsorbed onto five commercial activated carbons at four different temperatures (20, 40, 60, and 80°C). A new expression of the Freundlich equation [qe = (a1T+a2T2)Ce(1/nf)] was shown to be statistically the most efficient to describe the adsorption isotherms of VOCs, single or in mixtures. A second-order polynomial temperature-dependence was introduced in this expression. The so-adapted Freundlich relationship gave a mean coefficient of determination of 0.97 for single-component adsorption and a correlation coefficient of 0.98 for binary mixtures.     

Cs(ATZ)化合物的合成及表征

A new compound of Cs (ATZ) was synthesized by reaction of CsOH aqueous solution with 5-aminotetrezole. This compound was identified by C, H and N elemental analysis and quantitative analysis of Cs atom. The molecular formula is Cs (ATZ). The physicochemical properties were characterized by FTIR, Raman spectroscopy and X-ray power diffraction and the peaks of FT-IR were also assigned.     

聚酯纺粘土工布和GCL在垃圾填埋场中的应用

主要介绍了土工布和膨润土防水毯（GCL）在垃圾卫生填埋场应用中的特点和作用，阐述了在卫生填埋场设计中选择土工布和GCL应注意的一些问题。     

聚酯纺粘土工布和GCL在垃圾填埋场中的应用

主要介绍了土工布和膨润土防水毯(GCL)在垃圾卫生填埋场应用中的特点和作用,阐述了在卫生填埋场设计中选择土工布和GCL应注意的一些问题。     

有机污染物(菲)在弱透水层中的越流迁移特征

采用高渗透压渗流试验装置.模拟已被污染的浅层地下水越流通过弱透水层污染深层地下水的过程,研究不同矿化度、不同pH条件下有机污染物(菲)通过饱和黏性土弱透水层时的质量浓度变化特征.结果表明;矿化度的增加有利于弱透水层吸附截留渗滤液中的菲;高矿化度水中的Na+交替土层中的Ca2+、Mg2+,使水中的Ca2+、Mg2+质量浓度增加,与HCO3、菲组合形成络合物;不同pH条件下,Ca2+、Mg2+抖、HCO(-3)-对菲的迁移有阻滞作用,SO(2/4)-参与还原反应并可与菲形成络合物,对菲迁移有促进作用.菲在弱透水层中的迁移能力很弱,衰减率达82%～96%,高渗透压下菲的污染锋面迁移速度为0.714 m/d,pH=8时菲通过弱透水层的迁移质量浓度最小.控制渗滤液的pH、组分可有效阻止菲在弱透水层中的迁移.     

Study of Transport and Separation of Rare Earth Ions through the Emulsion Liquid Membrane of Bis(2,4,4-trimethylpentyl)phosphinic Acid-Span 80-Toluene

It is indicated from a study of transport of rare earth ions through the emulsion liquid mem-brane of bis(2,4,4-trimethylpentyl)phosphinic acid-Span 80-toluene that transporting rare earth ions com-pletely and rapidly was realized under the optimum experimental conditions:1.0×10~(-3)～3.0×10~(-3)mol/Lbis(2,4,4-trimethylpentyl)phosphinic acid and 2%～4%(W/V)Span 80 in toluene solution as membranephase,0.50～2.0 mol/L HCl as inner phase,rare earth ion solutions with pH 3.5～5.0 as outer phase.Ac-cording to the differences of transport behavior for rare earth ions,it is possible to separate rare earth ionsfrom mixed solutions of rare earth ions by this liquid membrane system.     

一步还原法制备(W-Ti-Ta-Nb)C复合碳化物的研究

研究了一步还原法制备(W-Ti-Ta-Nb)C复合碳化物过程中,不同煅烧温度、煅烧时间和混料时间对产品固溶相比例、化合碳含量、游离碳含量的影响.通过正交试验优化得出最佳制备工艺条件为:煅烧温度2 100 ℃,煅烧时间50 min,混料时间3 h.所得复合碳化物粉末为100%的固溶相,其中化合碳的含量为10.67%,游离碳的含量为0.15%.     

Behavior and Mechanisms of Deformation in Intermetallic Compound Al_(66) Mn_9Ti_(25) La

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