Hydrometallurgical processing and recovery of molybdenum trioxide from spent catalyst   总被引：5，自引：0，他引：5  

Kyung Ho Park  B. Ramachandra Reddy  D. Mohapatra  Chul-Woo Nam 《International Journal of Mineral Processing》2006,80(2-4):261-265

Hydrometallurgical processing of spent hydrodesulphurisation (HDS) catalyst for the recovery of molybdenum using sodium carbonate and hydrogen peroxide mixtures was investigated. The results indicated that the recovery of molybdenum was largely dependent on the concentrations of Na₂CO₃ and H₂O₂ in the reaction medium, which controls the acidity of the leach liquor and carry over of impurities such as Al, Ni, P, Si and V. Leaching process was exothermic and leaching efficiency of molybdenum decreased with increasing solid to liquid ratio. Large scale leaching of spent catalyst, under optimum conditions: 20% pulp density, 85 g/L Na₂CO₃, 10 vol.% H₂O₂ and 1 h reaction, resulted a leaching efficiency of 84% Mo. The obtained leach liquor contained (g/L): Mo — 22.0, Ni — 0.015 and Al — 0.82, P — 1.1, Si — 0.094 and minor quantities of V — 8 mg/L, As and Co — < 1 mg/L. Recovery of Mo from leach solution as MoO₃ of 97.30% purity was achieved by ammonium molybdate precipitation method.  相似文献   

Classifying coastal waters: Current necessity and historical perspective     

J. C. Kurtz  N. D. Detenbeck  V. D. Engle  K. Ho  L. M. Smith  S. J. Jordan  D. Campbell 《Estuaries and Coasts》2006,29(1):107-123

Coastal ecosystems are ecologically and commercially valuable, productive habitats that are experiencing escalating compromises of their structural and functional integrity. The Clean Water Act (USC 1972) requires identification of impaired water bodies and determination of the causes of impairment. Classification simplifies these determinations, because estuaries within a class are more likely to respond similarly to particular stressors. We reviewed existing classification systems for their applicability to grouping coastal marine and Great Lakes water bodies based on their responses to aquatic stressors, including nutrients, toxic substances, suspended sediments, habitat alteration, and combinations of stressors. Classification research historically addressed terrestrial and freshwater habitats rather than coastal habitats. Few efforts focused on stressor response, although many well-researched classification frameworks provide information pertinent to stressor response. Early coastal classifications relied on physical and hydrological properties, including geomorphology, general circulation patterns, and salinity. More recent classifications sort ecosystems into a few broad types and may integrate physical and biological factors. Among current efforts are those designed for conservation of sensitive habitats based on ecological processes that support patterns of biological diversity. Physical factors, including freshwater inflow, residence time, and flushing rates, affect sensitivity to stressors. Biological factors, such as primary production, grazing rates, and mineral cycling, also need to be considered in classification. We evaluate each existing classification system with respect to objectives, defining factors, extent of spatial and temporal applicability, existing sources of data, and relevance to aquatic stressors. We also consider classification methods in a generic sense and discuss their strengths and weaknesses for our purposes. Although few existing classifications are based on responses to stressors, may well-researched paradigms provide important information for improving our capabilities for classification, as an investigative and predictive management tool.  相似文献   

The Dynamic Fracture Process in Rocks Under High-Voltage Pulse Fragmentation     

Sang Ho Cho  Sang Sun Cheong  Mitsuhiro Yokota  Katsuhiko Kaneko 《Rock Mechanics and Rock Engineering》2016,49(10):3841-3853

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Abrasiveness of Common Rocks in Hong Kong     

Y. K. Ho  S. T. C. So  T. M. F. Lau  R. C. M. Kwok 《Rock Mechanics and Rock Engineering》2016,49(7):2953-2958

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Public health implications of social media use during natural disasters,environmental disasters,and other environmental concerns     

Kathryn C. Finch  Kassandra R. Snook  Carmen H. Duke  King-Wa Fu  Zion Tsz Ho Tse  Atin Adhikari  Isaac Chun-Hai Fung 《Natural Hazards》2016,83(1):729-760

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Near real-time high-resolution airborne camera,AEROCam, for precision agriculture     

Xiaodong Zhang  Ho Jin Kim  Clinton Streeter  David A. Claypool  Ramesh Sivanpillai  Santhosh Seelan 《国际地球制图》2013,28(7):537-551

Precision agriculture often relies on high-resolution imagery to delineate the variability within a field. Airborne Environmental Research Observational Camera (AEROCam) was designed to meet the needs of agriculture producers, ranchers, and researchers, who require high-resolution imagery in a near real-time environment for rapid decision support. AEROCam was developed and operated through a unique collaboration between several departments at the University of North Dakota, including the Upper Midwest Aerospace Consortium (UMAC), the School of Engineering and Mines, and flight operations at the John D. Odegard School of Aerospace Sciences. AEROCam consists of a Redlake MS4100 area-scan multi-spectral digital camera that features a 1920 × 1080 CCD array (7.4-μm detector) with 8-bit quantization. When operated at ～2 km above ground level, multispectral images with four bands in the visible and near infrared have a ground sample distance of 1 m with a horizontal extent of just over 1.6 km. Depending on the applications, flying at different altitudes can adjust the spatial resolution from 0.25 to 2 m. Rigorous spectral and radiometric calibrations allow AEROCam to be used in a variety of applications, qualitative and quantitative. Equipped with an inertial measurement unit (IMU) system, the images acquired can be geo-referenced automatically and delivered to end users near real time through our Digital Northern Great Plains system (DNGP). The images are also available to zone mapping application for precision farming (ZoneMAP), an online decision support tool for creating management zones from remote sensing imagery and data from other sources. Operational since 2004, AEROCam has flown over 250 sorties and delivered over 150,000 images to the users in the Northern Great Plains region, resulting in numerous applications in precision agriculture and resource management.  相似文献   

Formation and Movement of the ESIW as Modeled by MICOM     

Kuk Jin Kim  Young Ho Seung 《Journal of Oceanography》1999,55(2):369-382

The presence of the minimum salinity and oxygen-rich East Sea Intermediate Water (ESIW) off Korean coast has raised many questions about its origin and movement. This study attempts to answer these questions in the context of numerical model. For this, the Miami Isopycnic Coordinate Ocean Model is used with surface and inflow boundary conditions based on available data. Model results show that the ESIW forms most distinctly off Vladivostok, where the center of doming structure is observed, and moves southward along Korean coast forming a large cyclonic gyre around the doming. The renewed ESIW has the character of minimum potential vorticity common to usual mode waters. These results are compatible with various indications made in previous observational and theoretical studies. However, it is not known whether the doming structure is a result of convection or the latter is favored by the former. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Indian summer monsoon onset vortex formation during recent decades     

R. Deepa  Jai Ho Oh 《Theoretical and Applied Climatology》2014,118(1-2):237-249

This study investigates the decrease in the frequency of onset vortex of summer monsoon during recent decades using the National Center for Environmental Prediction–National Center for Atmospheric Research reanalysis (1982–2011) data. Onset vortices are known to occur over the Arabian Sea mini warm pool where the sea surface temperature peaks just before the onset of monsoon. Even though the Arabian Sea mini warm pool intensifies during the recent decades, they are not seen as a regular feature. It is found from the analysis of irrotational and non-divergent wind component at 850 and 200 hPa that during the recent decades, convergent winds dominate at upper levels and divergent winds at lower levels which inhibits convection. Moreover, the cyclonic shear vorticity shows a decrease in the recent decades which tend to reduce the boundary layer moisture convergence and lower tropospheric humidity which is an important component for the initiation of a cyclonic system. The recent decades are characterized by weak convection due to the presence of strong northerlies and descending motion at lower levels in the southeast Arabian Sea. The response of atmospheric circulation to the interdecadal variations in the warm pool and the corresponding decrease in the frequency of onset vortex formation is analyzed in detail.  相似文献   

Graded-Density Reservoirs for Accessing High Stress Low Temperature Material States   总被引：1，自引：0，他引：1  

Raymond F. Smith  K. Thomas Lorenz  Darwin Ho  Bruce A. Remington  Alex Hamza  John Rogers  Stephen Pollaine  Seokwoo Jeon  Yun-Suk Nam  J. Kilkenny 《Astrophysics and Space Science》2007,307(1-3):269-272

In recently developed laser-driven shockless compression experiments an ablatively driven shock in a primary target is transformed into a ramp compression wave in a secondary target via unloading followed by stagnation across an intermediate vacuum gap. Current limitations on the achievable peak longitudinal stresses are limited by the ability of shaping the temporal profile of the ramp compression pulse. We report on new techniques using graded density reservoirs for shaping the loading profile and extending these techniques to high peak pressures.  相似文献   

Sequential extraction and leaching characteristics of heavy metals in abandoned tungsten mine tailings sediments   总被引：1，自引：0，他引：1  

Pyeong-Koo Lee  Min-Ju Kang  Ho Young Jo  Sang-Hoon Choi 《Environmental Earth Sciences》2012,66(7):1909-1923

The chemical speciation of potentially toxic elements (As, Cd, Cu, Pb, and Zn) in the contaminated soils and sulfides-rich tailings sediments of an abandoned tungsten mine in Korea was evaluated by conducting modified BCR sequential extraction tests. Kinetic and static batch leaching tests were also conducted to evaluate the potential release of As and other heavy metals by acidic rain water and the leaching behaviors of these heavy metals. The major sources of the elements were As-, Zn- and Pb-bearing sulfides, Pb carbonates (i.e., cerussite), and Pb sulfates (i.e., anglesite). The biggest pollutant fraction in these soil and tailing samples consists of metals bound to the oxidizable host phase, which can be released into the environment if conditions become oxidative, and/or to residual fractions. No significant difference in total element concentrations was observed between the tailings sediments and contaminated soils. For both sample types, almost no changes occurred in the mobility of As and the other heavy metals at 7 days, but the mobility increased afterwards until the end of the tests at 30 days, regardless of the initial pH. However, the mobility was approximately 5–10 times higher at initial pH 1.0 than at initial pHs of 3.0 and 5.0. The leached amounts of all the heavy metal contents were higher from tailings sediments than from contaminated soils at pH > 3.0, but were lower at pH < 3.0 except for As. Results of this study suggest that further dissolution of heavy metals from soil and tailing samples may occur during extended rainfall, resulting in a serious threat to surface and groundwater in the mine area.  相似文献