Measurement of Solute Diffusion Behavior in Fractured Waste Glass Media

Determination of aqueous diffusion coefficients of solutes through fractured media is essential for understanding and modeling contaminant transport at many hazardous waste disposal sites. Development of experimental methods and measurements for the characterization of diffusion in fractured glass media is necessary for the design and performance assessment of glassified radionuclear waste disposal facilities. We report on the use of time-lag diffusion experimental method to assess the diffusion behavior of three different solutes (Cs, Sr, and pentafluoro benzoic acid) in fractured, immobilized low activity waste (ILAW) glass forms. A fractured media time-lag diffusion experimental apparatus, which allows the measurement of diffusion coefficients, has been designed and built for this purpose. Use of time-lag diffusion method, a considerably easier experimental method than the other available methods, was not previously demonstrated for measuring diffusion in fractured waste glass media. Hydraulic conductivity, porosity, and diffusion coefficients of a solute were experimentally measured in fractured glass blocks using this method for the first time. Results agree with the range of properties reported for similar rock media earlier, indicating that the time-lag experimental method can effectively characterize the diffusion coefficients of fractured ILAW glass media. Data presented are rare and useful for the design of vitrified glass disposal facilities.     

Bearing Capacity of Desiccated Tailings

The development of matric suctions in soils contributes to their shear strength, resulting in an enhanced factor of safety against bearing-capacity failure. In this paper, matric suction profiles of desiccated mine tailings are predicted from a steady-state solution for evaporative conditions, and from an isothermal mathematical model that simulates liquid and vapor water flow through soils. The shear-strength envelope with respect to matric suction is established by testing reconstituted tailings samples in a modified triaxial cell, in which matric suction can be controlled. The contribution of matric suction to the shear strength is interpreted as an additional apparent cohesion for use in bearing-capacity calculations. Because of the nonlinearity of the shear-strength profile, a numerical method of analysis is adopted to predict the ultimate bearing capacity of the desiccated tailings. A subsequent decrease in bearing capacity following 2D water infiltration into a partially capped tailings deposit and accompanying suction loss is investigated.     

An analysis of concentration profiles for fluxes,diffusion depths,and zero-flux planes in multicomponent diffusion

Concentration profiles developed during isothermal, multicomponent diffusion for a single-phase, solid-solid diffusion couple are expressed on the basis of a relative concentration variable for each component and analyzed for the determination of interdiffusion fluxes. The individual concentration profiles intersect at a common cross-over composition where the relative concentrations of all components are identical. New relations are developed for describing internal consistency among the concentration profiles of the various components. A link is made between the cross-over composition and the depths of the diffusion zone on either side of the Matano plane for a diffusion couple. The cross-over composition is interpreted as the average relative concentration of each component over the diffusion zone. The identification of a zero-flux plane from concentration profiles is also described. The analysis offers several advantages in presenting as well as checking the self-consistency of results as illustrated with a single phase Cu-Ni-Zn diffusion couple annealed at 775 °C.     

Effect of Moisture on the Adsorption of Volatile Organic Compounds by Zeolite 13×

The adsorption of volatile methanol, acetone, and benzene onto zeolite 13× was studied in the presence of water vapor. Breakthrough curves for these volatile organic compounds (VOCs) were measured by using a gas-phase Fourier transformation infrared (FT-IR) spectrometer instead of a gas chromatograph (GC) because a gas-phase FT-IR spectrometer provides a more rapid response to the change of gas concentration than that of GC. To observe the influences of humidity (i.e., water vapor) on the performance of zeolite 13× during the VOC adsorption, the adsorption experiments were carried out at three different initial concentrations and two humidity conditions for each VOC. The results showed a significant influence of increased humidity on the breakthrough time, the shapes of breakthrough curves, and the uptake of VOCs. For the case of the benzene and water vapor coadsorption system, the presence of the moisture caused a greater decrease in the VOC uptake as well as the breakthrough time than for the other VOC–water coadsorption systems. A modified Freundlich-type isotherm was introduced in this study to describe the decrease in the uptake of VOCs in the presence of the moisture. This modified empirical equation provided a good fit to experimental results, with an average error of 8%.     

Modeling of Moisture Diffusion in FRP Strengthened Concrete Specimens

Modeling the movement and distribution of moisture in the fiber-reinforced polymer (FRP) composites strengthened concrete structure is important because the interfacial adhesion between FRP and concrete is susceptible to moisture attack. Using relative humidity as the global variable, the moisture diffusion governing equation was derived for the multilayered system in this study. The moisture diffusivity (diffusion coefficient) and the isotherm curve, which correlates the moisture content to environmental relative humidity, of each constitutive material (concrete, epoxy, and FRP) were experimentally determined. A multilinear diffusivity model was developed for concrete based on desorption test, and a linear diffusivity model was proposed for epoxy adhesive based on absorption test. A simple method was developed to directly measure the FRP/concrete interface region relative humidity (IRRH). Finite-element analysis was performed to study the moisture diffusion in the FRP-adhesive-concrete system. The IRRH values were obtained for different environmental relative humidity in the numerical study. The error between the experimental and numerical results of IRRH at test locations was less than 5% RH. The good agreement between experimental and numerical results indicates that the approach developed in this study worked well.     

Application of Three-Dimensional Hydrodynamic Model for Lake Okeechobee

A 3D hydrodynamic and heat transport model was developed for Lake Okeechobee. Continuity, momentum, and temperature transport equations were solved. Dynamically coupled transport equations for turbulent kinetic energy and turbulent scale also were solved. The numerical scheme used spatial finite differencing and a three-time-level, external-internal mode splitting procedure. A 28-day calibration was conducted, using measured bathymetry, rainfall, relative humidity, total solar radiation, wind velocity, inflow, and outflow data. During the calibration period, little rainfall occurred, and lake water levels receded. Water surface elevation, horizontal velocities, and temperature were computed. Agreement between observed and simulated values was based on graphical comparisons, minimizing mean absolute and root-mean-square errors, and spectral analysis. Comparisons showed that the model reproduced general observed trends and short-term fluctuations. The model's heat transport and turbulence closure schemes behaved as expected with regard to water column stratification and mixing. Simulation accuracy may potentially be improved by adding wind-wave and vegetation resistance algorithms to the model.     

Self-Aeration and Friction over Rock Chutes in Uniform Flow Conditions

Interaction between the free surface and the bed material in flow over rock chutes under macroroughness conditions leads to a high air entrainment into the flow. The note reports on an experimental study about air diffusion features in the flow over a long rock chute. Air concentration profiles and water depths over a uniform bed material were measured. An empirical equation for the average air concentration in macroroughness condition for steep slopes is proposed. A new Darcy-Weisbach equivalent friction factor for long chutes as a function of the slope and the relative equivalent depth has also been found.     

The role of hydrogen in corrosion fatigue of high purity Al-Zn-Mg exposed to water vapor

Corrosion fatigue tests were performed on samples of a high purity Al-Zn-Mg alloy in humid nitrogen gas after pre-exposure to either vacuum or humid air. The results of these tests were compared to the results of fatigue tests performed in dry nitrogen, used as an inert reference environment, after the same pre-exposure treatments. The pre-exposure times were calculated by assuming that bulk diffusion of hydrogen was the rate limiting process in either hydrogen adsorption or desorption. Water vapor in the testing environment resulted in reduced fatigue lives; however, pre-exposure to humid air was just as detrimental as water vapor in the test environment. The pre-exposure embrittlement effect of humid air was found to be completely reversible when the samples were stored in a vacuum long enough to remove hydrogen, assuming a bulk diffusion coefficient of 1 x 10^-13 m²/sec. These results confirm the hypothesis that the reduced fatigue lives of Al-Zn-Mg alloys in water vapor is due to hydrogen embrittlement.     

Liquid Volume Fluxes in Stratified Multiphase Plumes

This paper presents an optimization scheme to estimate the internal entrained fluid fluxes for multiphase plumes in stratification from indirect experimental measurements and applies the results to field-scale plumes. Experiments were conducted in linear stratification using dispersed phases of air bubbles and glass beads (the latter creating an inverted plume). Comparison of pre- and postexperiment salinity profiles provided direct measurements of the net liquid fluxes in the plume; fluorescence profiles provided direct measurements of the fluxes of passive tracer. To separate the net flux measurements into upward and downward flows this paper applies a constrained Bayesian estimation technique based on a conceptual model of the plume. This method provides estimates of the ambient and counterflowing entrained fluid fluxes, the peeling efficiency (percent of entrained fluid that detrains) and the buoyancy flux continuing above the first peel. These quantities correlate with the non-dimensional slip velocity UN, defined as the ratio of the bubble slip velocity us to a characteristic plume fluid rise velocity (BN)1/4; B is the total kinematic buoyancy flux, and N is the buoyancy frequency. The results show that the peeling efficiency is the dominant quantity that controls the plume behavior, and that it is dependent on several processes occurring within the plume. Applications of the results are presented for accidental oil-well blowouts in the deep ocean.     

某铜矿尾矿渣微生物柱浸及其动力学

采用两段微生物柱浸对某铜矿尾矿渣中的有价金属进行二次回收研究。考察预处理酸度、接种量、尾矿和废石装矿方式及废石粒度等因素对铜、锌浸出的影响。结果表明,两段微生物柱浸无论改变接种量还是预处理酸度,尾矿最终铜离子浸出率均大于30%,在预处理酸度为5%、接种量10%、-2 mm废石粒级的条件下,铜浸出率可达到38.8%,锌浸出率可达到87.45%。不同的装矿方式浸出差异性不大,分层装尾矿和采场废石并不能有效改善柱子的渗透性。柱浸体系中铜锌浸出动力学模型表明,铜、锌的浸出符合内扩散控制模型。     

工业废水中化学耗氧量（COD）催化快速法测定研究

研究了采用催化快速法测定工业废水中化学耗氧量（COD）的含量。该方法检出限范围为45～1000mg/L,COD含量与吸光度成线性关系,相对标准偏差为2.5%,该方法适用于监测工业外排废水。     

Observations of solution transport,permeability, and leaching reactions in large,controlled, copper-bearing waste bodies

The leaching characteristics (waste-body temperature profiles, total daily oxygen consumption, and copper extraction as well as solution chemistry features) are compared for two vastly different, large (1.7 × 10⁵ kg) low-grade, copper-bearing waste bodies. One column, a Kennecott-Santa Rita waste (0.36% total Cu) was primarily a chalcocite waste with little detectable acid consumption, requiring essentially no neutralization while the other column; a Duval-Sierrita waste (0.34% total Cu) was primarily a chalcopyrite waste with high acid consumers present in the host rock, and requiring a lengthy neutralization period. This latter column which measured 3.1 m in diameter, was appropriately scaled down with two smaller columns measuring 0.38 and 0.10 m in diameter, respectively. The initial permeability and drain-down characteristics are compared along with final permeabilities in the Kennecott-Santa Rita waste body (following the conclusion of leaching experiments). A post-leaching [Cl^?] tracer test conducted on the Kennecott-Santa Rita column suggests that, consistent with indications from permeability data, dead spaces occurred within the waste body and these features seem to have contributed to the leaching performance and characteristics. Scaling experiments were observed to accurately characterize and follow the neutralization of the Duval-Sierrita waste (as determined by monitoring effluent solution pH), but there was little correlation between copper extracted in the large Duval-Sierrita waste column (3.1 m diameter) and the smallest laboratory column (0.1 m diameter).     

Ceramic humidity sensors based on magnesium aluminate spinel. II. Relation between the parameters of water adsorption kinetics and the service characteristics of ceramic humidity sensors in the MgAl2O4 system

he parameters of water vapor adsorption on the surfaces of powders and compacted powders (compacts) are compared with data on the variation of the electrical resistance of the same compacts in media with various water vapor contents. A study of the kinetic features of water vapor adsorption from the air indicated that powders with small specific surfaces adsorb water vapor and are saturated more rapidly than do powders with large specific surfaces, while their absolute moisture content is lower. The amount of water vapor adsorbed on the surface varies in the same way. The data are consistent with the results from porous structure studies. The rate of water vapor adsorption and the amount adsorbed increase for smaller pores, in which the water vapor condenses more quickly. Data on the specific surface of compacted and sintered materials, their porous structure and their adsorptivity of water vapor provide a basis for making a prior choice of technological parameters of the ceramic treatment so as to enhance the quality of humidity meters. Deceased. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos 7–8(402), pp. 46–50, July–August, 1998.     

SVE Design: Mass Transfer Limitation due to Molecular Diffusion

Vaporization and soil adsorption are the two mass transfer mechanisms that control contaminant recovery rates for soil vapor extraction (SVE) systems. At most soil remediation sites, contaminants are distributed among three phases, namely, soil particles, pore water, and soil vapor. Contaminant mass transfer from adsorption sites into a convective vapor stream involves desorption, diffusion through pore water, and vaporization into soil vapor. An SVE design model is proposed to describe this three-phase mass transfer process and assist the design and evaluation of SVE systems. The model contains analytical solutions developed to estimate contaminant concentrations in the vapor phase and predict contaminant removal rates. Monitoring data from two full-scale SVE systems were used for model development and calibration. The results suggest that contaminant diffusion through the pore water is the rate-limiting step and leads to remediation inefficiency of an SVE system. Mass transfer retardation from molecular diffusion in water is likely the major contributing component to the venting efficiency coefficient of Staudinger et al.     

Ruptured fission yeast walls. Structural discontinuities related to the cell cycle

Distributions of rupture sites of fission yeast cells ruptured by glass beads have been related to a new morphometric analysis. As shown previously (Johnson et al., Cell Biophysics, 1995), ruptures were not randomly distributed nor was their distribution dictated by geometry, rather, ruptures at the extensile end were related to cell length just as the rate of extension is related to cell length. The extension patterns of early log, mid-log, late log, and stationary phase cells from suspension cultures were found to approximate the linear growth patterns of Kubitschek and Clay (1986). The median length of cells was found to decline through the log phase in an unbalanced manner.     

Experimental Validation and Applications of a Fluid Infiltration Model

Horizontal infiltration experiments were performed to validate a plug flow model that minimizes the number of parameters that must be measured. Water and silicone oil at three different viscosities were infiltrated into glass beads, desert alluvium, and silica powder. Experiments were also performed with negative inlet heads on air-dried silica powder, and with water and oil infiltrating into initially water moist silica powder. Comparisons between the data and model were favorable in most cases, with predictions usually within 40% of the measured data. The model is extended to a line source and small areal source at the ground surface to analytically predict the shape of two-dimensional wetting fronts. Furthermore, a plug flow model for constant flux infiltration agrees well with field data and suggests that the proposed model for a constant-head boundary condition can be effectively used to predict wetting front movement at heterogeneous field sites if averaged parameter values are used.     

Quaternary diffusion in the Cu−Ni−Zn−Mn system at 775°C

Quaternary diffusion was investigated in the α (fcc) region of the Cu−Ni−Zn−Mn system at 775°C with solid-solid diffusion couples assembled with alloys characterized by similar concentrations of one of the components. The concentration profiles of the quaternary couples were examined on the basis of a relative concentration variable for each component; the profiles for any given couple exhibited a common cross-over composition. The interdiffusion fluxes of the components were calculated directly from the concentration profiles. Interdiffusion of each component up its own concentration gradient was observed in several couples, while the zero-flux planes for the individual components were identified in selected couples. The common cross-over composition reflected the relative diffusion depths in the terminal alloys of the single-phase quaternary diffusion couples. The quaternary diffusion paths were presented on the basis of relative concentration variables for the individual components.     

Interdiffusion in the Ni-Cr-Co-Mo system at 1300 °C

Interdiffusion was investigated with solid-solid diffusion couples in theα (fcc) region of the quaternary Ni-Cr-Co-Mo system at 1300 °C for the determination of diffusion paths and diffusional interactions among the components. The concentration profiles for a given couple exhibited a common cross-over composition, Y_c, which reflected the relative depths of diffusion in the terminal alloys. Interdiffusion fluxes were calculated directly from the concentration profiles, and the quaternary interdiffusion coefficients were calculated at selected compositions. Ni and Co exhibited uphill diffusion against their individual concentration gradients in a direction opposite to the interdiffusion of Cr. Quaternary diffusion paths were presented as a set of partial diffusion paths on the basis of relative concentration variables.     

沸石柱吸附钨冶炼废水中氨氮的试验研究

用沸石填料柱建立模拟装置,研究沸石吸附模拟氨氮废水和钨冶炼废水的动态规律、再生性质、穿透曲线、水力负荷曲线,吸附动力学等。试验结果表明,进水速度为2.72 BV时,处理氨氮浓度为50 mg·L-1模拟废水和98 mg·L-1钨冶炼废水,在穿透点分别为C/C0=0.3和0.15时,天然沸石柱可处理水量分别为126 BV、43 BV,改性后沸石柱可处理水量分别为157 BV、46 BV;随水力负荷增大,沸石柱可处理水量减小;吸附饱和沸石用8%NaCl溶液解吸再生效果好,成本低,但再生后的沸石吸附容量会变小;动力学分析发现,沸石柱吸附氨氮速度较快,是处理氨氮废水的优良吸附材料。     

Effect of Humidity on Wear of TiN Coatings: Role of Capillary Condensation

Metallurgical and Materials Transactions A - Coated ball-on-disk wear configuration was used to study the effect of relative humidity, water vapor pressure, and water on wear of TiN coatings in the...