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排序方式: 共有1147条查询结果,搜索用时 15 毫秒
31.
C.C. Yang 《Cement and Concrete Research》2006,36(7):1304-1311
In this study the electrochemical technique is applied to accelerate chloride ion migration in concrete to determine the chloride ions in anode cell, and the pore characteristic of the same mortars in concrete was obtained from the mercury intrusion porosimetry (MIP). The plain ordinary Portland cement and the constant aggregate with eight w/c ratios ranging from 0.3 to 0.65 were used. A good linear relationship between the steady-state migration coefficient and non-steady-state migration coefficient based on the same experimental setup and specimens was obtained. Both of the steady-state migration coefficient and non-steady-state migration coefficient were linearly related to the capillary pore volume and the critical pore diameter. 相似文献
32.
介绍了一种测定废水中LAS浓度的新方法。克服了常规方法亚甲基蓝比色法要绘制标准曲线,操作过程复杂等局限性。该方法测定过程简单,结果准确,标准偏差为1.4l,变异系数为3.92%。 相似文献
33.
《Journal of Great Lakes research》2022,48(1):24-36
In Ontario, there is limited comprehensive research regarding the contribution of chloride in groundwater to surface water systems. The delivery of chloride via groundwater can contribute to the degradation of the Great Lakes and their tributaries. Thus, this review intends to fill or identify knowledge gaps regarding assessing groundwater as a potential source of road salt, the single largest use of salt in urban cold region environments, contamination to surface water by synthesizing existing groundwater chloride research in the Lake Ontario Basin. Knowledge regarding source characterization, properties, pathways, and impacts of chloride in the environment is essential to evaluate the contribution of chloride via groundwater. Past groundwater chloride research in the basin is primarily concentrated in highly urbanized areas and has identified localized trends of increasing groundwater chloride concentrations in these regions; however, few investigations have been conducted in varying land uses (e.g., rural or less urbanized watersheds) or at sufficient temporal and/or spatial scales. Significant chloride accumulation is occurring in watersheds and aquifers within the basin. Concentrations are expected to increase until equilibrium is obtained, thus resulting in sustained yearlong elevated concentrations in tributaries. Recently, chloride loading to Lake Ontario has increased significantly, with groundwater inputs having the potential to support long-term increases in chloride concentrations in the lake. However, few studies have evaluated the explicit contribution via groundwater to Lake Ontario, and therefore a knowledge gap continues to exist. We provide a synthesis of additional research priorities to better understand the magnitude of groundwater chloride issues in the basin. 相似文献
34.
Chang?Duk?Kang Sang?Jun?SimEmail author Young?Sang?Cho Woo?Sik?Kim 《Korean Journal of Chemical Engineering》2003,20(3):482-486
The removal of copper from wastewater by ferric/limestone coagulation followed by screen filtration was carried out at a laboratory
scale. The optimum coagulant (FeCl3) dose and working pH were 50 mg// of Fe(m) and pH 7.5, respectively, through jar tests. For the efficient removal of copper
from wastewater, we developed a novel process including the co-precipitation of copper with FeCl3, alkalization in a limestone aeration bed, and separation of precipitates in a sedimentation tank coupled with internal stainless
steel screen filter. The performance results showed that removal of copper from the solution was over 99.5%. The pH was effectively
maintained over 7.5 in limestone bed during the whole process. Ferric hydroxide/copper aggregates were removed over 99% by
stainless steel screen filter of 1,450 mesh. Periodic air backwashing alleviated fouling of the filter surface. 相似文献
35.
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37.
The study reported in this article deals with understanding the physical, chemical and microstructural differences in sulfate attack from seawater and groundwater. Portland cement mortars were completely immersed in solutions of seawater and groundwater. Physical properties such as length, mass, and compressive strength were monitored periodically. Thermal analysis was used to study the relative amounts of phases such as ettringite, gypsum, and calcium hydroxide, and microstructural studies were conducted by scanning electron microscopy. Portland cement mortars performed better in seawater solution compared to groundwater solution. The difference in performance could be attributed to the reduction in the quantity of the expansive attack products (gypsum and ettringite). The high Cl concentration of seawater could have played an important role by binding the C3A to form chloroaluminate compounds, such as Friedel's salt (detected in the microstructural studies), and also by lowering the expansive potential of ettringite. Furthermore, the thicker layer of brucite forming on the specimens in seawater could have afforded better protection against ingress of the solution than in groundwater. 相似文献
38.
Oxidative coupling of methane (OCM) was carried out over Na+-ZrO2-Cl /A1[2O3 catalysts in a temperature range from 1023 to 1123 K. The catalysts were prepared by impregnating the α- or γ-Al2O3 supports with sodium carbonate and/or zirconyl chloride. The OCM activity was examined using the catalysts prepared by three
different preparation procedures. The best catalyst was the one prepared by subsequent impregnation of sodium carbonate-preimpregnated
γ-Al2O3 with a mixed solution of sodium carbonate and zirconyl chloride. It was found that preimpregnated sodium played an important
role in reducing the combustion activity of the γ-Al2O3. The catalyst with an optimal composition showed the highest C2 selectivity and yield of 40.8% and 15.1%, respectively. From the X-ray diffraction analysis it was found that tetragonal
ZrO2 was formed and that NaCl existed in the catalysts with relatively high sodium contents. 相似文献
39.
A.H Moreira A.V BenedettiP.T.A Sumodjo J.A GarridoP.L Cabot 《Electrochimica acta》2002,47(17):2823-2831
The electrochemical corrosion and passivation of Al5Zn1.7Mg0.23Cu0.053Nb alloys, submitted to different heat treatments (cold-rolled, annealed, quenched and aged, and quenched in two steps and aged), in sulphate-containing chloride solutions, has been studied by means of cyclic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). The cyclic polarization curves showed that sulphate addition to the chloride solution produced a poor reproducible shift of the breakdown potential to more positive potentials. The repassivation potentials, much more reproducible, and practically separating the passive from the pitting potential region, were slightly displaced in the negative direction with that addition. When the alloys were potentiodynamically polarized in the passive potential region, sulphate was incorporated in the oxide film, thus precluding chloride ingress. In addition, Zn depletion was favoured, whereas Mg losses were avoided. Different equivalent circuits corresponding to different alloys and potentials in the passive and pitting regions were employed to account for the electrochemical processes taking place in each condition. This work shows that sulphate makes these alloys more sensitive to corrosion, increasing the fracture properties of the surface layer and favouring the pitting attack over greater areas than chloride alone. 相似文献
40.
Delphine Patriarche Emmanuel Ledoux Rgine Simon-Coinon Jean-Luc Michelot Justo Cabrera 《Applied Clay Science》2004,26(1-4):109
Argillites are one of the geological formations studied by IRSN for their confining properties for isolation of radioactive wastes. One of the main objectives is the study of water transport through rocks with very low water content and very low hydraulic conductivity by modeling of natural tracer profiles. This paper presents the protocol developed for and applied to the acquisition of data for chloride content in interstitial water of the Toarcian argillites at the Tournemire site (Southern France). This protocol is based on laboratory diffusion experiments and on modeling. Experimental data obtained during the transient and steady-state parts of diffusion experiments enable, respectively, the assessment of the diffusion coefficient and the determination of Cl concentration in pore water. Using this protocol, profiles with depth for both of these data sets have been acquired along the geological sequence. Taking into account the present knowledge of the geological and hydrogeological history of the Tournemire massif, a conceptual model granting the main role for mass transport to diffusion has been proposed. According to this conceptual model, a one-dimensional numerical model was built for simulating the mass transport of chloride through the sedimentary column, over 53 Ma. The good agreement between experimental data and calculated values for both diffusion coefficients and concentrations of chloride confirms that diffusion is likely the main process for mass transport in the massif. This model was also tested with the deuterium content of interstitial water, applying variable concentrations at the aquifer system boundaries for reflecting the thermal dependency of isotopic composition in precipitation. These simulations also reveal the likely important role of heterogeneities, such as fractures, in the variability of tracer concentrations with regards to a simple diffusion profile. 相似文献