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871.
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
872.
The infrared reflectivity spectra of two natural cassiterite single crystals from Portugal and Vietnam have been studied and analysed in the frequency range of 15–4000 cm–1 at room temperature. The optical mode parameters are deduced by simulation of the experimental spectra using the factorised form of the dielectric function. The difference with synthetic SnO2 spectra is a dip near 500 cm–1 understood as the activation of an infrared forbidden E
g
mode due to the amount of Fe3+ and Ti4+ impurities. Another result of this work is the derivation of the correct values of the static dielectric constant of cassiterite. 相似文献
873.
Two chemical processes can remove Mg2+ from suspensions containing amorphous silica (am-SiO2) at low temperatures: adsorption and precipitation of a Mg-hydroxysilicate resembling sepiolite. Mg2+ removal from am-SiO2 suspensions was investigated, and the relative role of the two removal processes evaluated, as a function of: pH, ionic strength, Mg2+ concentration, and temperature.The extent of Mg2+ adsorption onto am-SiO2 decreases with increasing NaCl concentration due to displacement of Mg2+ by Na+. At NaCl concentrations of 0.05 M and above, adsorption occurs only at pH values above 8.5, where rapid dissolution of am-SiO2 gives rise to high concentrations of dissolved silica, resulting in supersaturation with respect to sepiolite. Removal of Mg2+, at concentrations of 40 to 650 μM, from am-SiO2 suspensions in 0.70 M NaCl at 25 °C occurs at pH 9.0 and above. Experiments show that under these conditions adsorption and Mg-hydroxysilicate precipitation remove Mg2+ at similar rates. For 0.05 M Mg2+, at 0.70 M ionic strength and 25 °C, measurable Mg2+ removal occurs down to ca. pH 7.5 but is primarily due to Mg-hydroxysilicate precipitation. For the same solution conditions at 5°C, Mg2+ removal occurs above pH 8.0 and is primarily due to adsorption.Assuming that increasing pressure does not greatly enhance adsorption, Mg2+ adsorption onto am-SiO2 is an insignificant process in sea water. The surface charge of pristine am-SiO2 in sea water is primarily controlled by interactions with Na+. The principal reaction between Mg2+ and am-SiO2 in marine sediments is sepiolite precipitation.The age distribution of sepiolite in siliceous pelagic sediments is influenced by temperatures of bottom waters and by geothermal gradients. 相似文献
874.
Bedard Jean H. J.; Marsh Bruce D.; Hersum Taber G.; Naslund H. Richard; Mukasa Samuel B. 《Journal of Petrology》2007,48(12):2289-2326
The Jurassic Ferrar dolerite sills of the McMurdo Dry Valleys,Antarctica represent the plumbing system for flood basalt eruptionsassociated with the breakup of Gondwana. Among the Ferrar sills,the 350–450 m thick cumulate-textured Basement Sill isdifferentiated into a Lower Marginal Zone (LMZ) gabbronorite,a thick Lower Zone (LZ) orthopyroxene–plagioclase orthocumulatepyroxenite, a strongly layered mela- to leuco-gabbronorite MiddleZone (MZ), a thick Upper Zone (UZ) gabbronorite with ferrogabbroicpods, and an Upper Marginal Zone (UMZ) gabbronorite. Texturesand mineral compositions in the LZ pyroxenite and MZ–UZgabbronorites are nearly identical, the main distinction beingthe greater relative proportion of plagioclase in the MZ–UZgabbronorites, and of pigeonite in the UZ. Most orthopyroxenein the LZ, MZ and UZ occurs as sub-euhedral, normally zonedprimocrysts, commonly with rounded plagioclase inclusions. Plagioclaseis usually sub-euhedral and normally zoned, but can containsodic cores interpreted to be xenocrystic. Orthopyroxene andfeldspar compositions thoughout the sill are generally fairlyuniform, and resemble the compositions of micro-phenocrystsin the chilled margins. We infer that the sill was filled bya c. 1250°C slurry of orthopyroxene + plagioclase phenocrystsor primocrysts that subsequently unmixed in response to buoyancyforces. The LZ websterite contains numerous anorthosite to gabbronoriteschlieren, veins and pipes (< 2 m diameter), which we interpretas fossil segregation channels. Textures and mineral compositionsin these felsic channels are very similar both to UZ and MZgabbronorites, and to the groundmass separating accumulatedorthopyroxene primocrysts in the LZ and MZ. We infer that plagioclase-charged,hydrous pore melt from the pyroxenite may have segregated, pooledand ascended through these conduits to feed growth of the UZgabbronorite. Detailed mapping shows that the pipes are separatedby about 15 m on average. Calculations suggest that this numberdensity of conduits could have drained the LZ cumulates of theirinterstitial melt + plagioclase in about 8 days. Sequences (eachc. 5–10 m thick) of layered leuco-gabbronorite in theMZ could represent intra-cumulate sills that formed from plagioclase-richslurries ascending in segregation channels. Fe–Ti-richpyroxenitic veins and pods (some pegmatitic) and an unusualcoarse-grained plagioclase facies occur at the contacts betweenmassive leuco-gabbronorite layers in the MZ. Discordant ferro-pegmatitepods and dykes occur throughout the UZ. We interpret these Fe-richpegmatoidal rocks as evolved residual melts expelled from thecompacting gabbronoritic cumulates of the MZ and UZ. KEY WORDS: Ferrar; cumulates; differentiation; Antarctica; layering 相似文献
875.
G. T. Skublov Yu. B. Marin S. G. Skublov Yu. N. Tarasenko 《Geology of Ore Deposits》2008,50(7):535-550
Volkhovites—tektite-like glasses—have been detected in the Holocene glacial drift along the right bank of the Volkhov River. A cryptomagmatic model of their formation and pre-Holocene age of volkhovite melts, cinder, and frothed glasses has been suggested (Skublov et al., 2007). Four geochemical types of volkhovites are distinguished: (1) manganous (Mn, Fe, Cr, V, Si, Nb, Pb, H), (2) magnesian (Mg, Al, Ti, F, B), (3) potassic (K, Rb, Cs), and (4) calcic (Ca, REEs, Ba, U, Th, Ta, Hf, Y, Sc, Cl). In light of the geochemical data, volkhovites are regarded as natural silicate glasses of kimberlite-carbonatite composition. Their types are called kimberlitic (Mn type), kimberlitic-carbonatitic (Mg type), lamproitic-carbonatitic (K type), and carbonatitic (Ca type). Volkhovites are suggested to be indicators of undiscovered diamond mineralization of kimberlite or carbonatite (Chagatai) types. 相似文献
876.
V. V. Yarmolyuk V. P. Kovach V. I. Kovalenko E. B. Salnikova A. M. Kozlovskii A. B. Kotov S. Z. Yakovleva A. M. Fedoseenko 《Petrology》2011,19(1):55-78
Data on the composition, inner structure, and age of volcanic and siliceous-terrigenous complexes and granitoids occurring
in association with them in the Caledonian Lake zone in Central Asia are discussed in the context of major relations and trends
in the growth of the Caledonian continental crust in the Central Asian Foldbelt (CAFB). The folded structures of the Lake
zone host basalt, basalt-andesite, and andesite complexes of volcanic rocks that were formed in distinct geodynamic environments.
The volcanic rocks of the basalt complex are noted for high concentrations of TiO2 and alkalis, occur in association with fine-grained siliceous siltstone and siliceous-carbonate rocks, are thus close to
oceanic-island complexes, and were likely formed in relation to a mantle hotspot activity far away from erosion regions supplying
terrigenous material. The rocks of the basalt-andesite and andesite complexes have lower TiO2 concentrations and moderate concentrations of alkalis and contain rock-forming amphibole. These rocks are accompanied by
rudaceous terrigenous sediments, which suggests their origin in island-arc environments, including arcs with a significantly
dissected topography. These complexes are accompanied by siliceous-terrigenous sedimentary sequences whose inner structure
is close to those of sediments in accretionary wedges. The folded Caledonides of the Lake zone passed through the following
evolutionary phases. The island arcs started to develop at 570 Ma, their evolution was associated with the emplacement of
layered gabbroids and tonalitetrondhjemite massifs, and continued until the onset of accretion at 515–480 Ma. The accretion
was accompanied by the emplacement of large massifs of the tonalite-granodiorite-plagiogranite series. The postaccretionary
evolutionary phase at 470–440 Ma of the Caledonides was marked by intrusive subalkaline and alkaline magmatism. The Caledonides
are characterized by within-plate magmatic activity throughout their whole evolutionary history, a fact explained by the accretion
of Vendian-Cambrian oceanic structures (island arcs, oceanic islands, and back-arc basins) above a mantle hotspot. Indicators
of within-plate magmatic activity are subalkaline high-Ti basalts, alkaline-ultrabasic complexes with carbonatites and massifs
of subalkaline and alkaline gabbroids, nepheline syenites, alkaline granites, subalkaline granites, and granosyenites. The
mantle hotspot likely continued to affect the character of the lithospheric magmatism even after the Caledonian folded terrane
was formed. 相似文献
877.
Mobile sediment in an urbanizing karst aquifer: implications for contaminant transport 总被引:1,自引:0,他引:1
Here we investigate geochemical characteristics of sediment in different compartments of a karst aquifer and demonstrate
that mobile sediments in a karst aquifer can exhibit a wide range of properties affecting their contaminant transport potential.
Sediment samples were collected from surface streams, sinkholes, caves, wells, and springs of a karst aquifer (the Barton
Springs portion of the Edwards (Balcones Fault Zone) Aquifer, Central Texas) and their mineralogy, grain-size distribution,
organic carbon content, and specific surface area analyzed. Statistical analysis of the sediments separated the sampling sites
into three distinct groups: (1) streambeds, sinkholes, and small springs; (2) wells; and (3) caves. Sediments from the primary
discharge spring were a mix of these three groups. High organic carbon content and high specific surface area gives some sediments
an increased potential to transport contaminants; the volume of these sediments is likely to increase with continued urbanization
of the watershed.
Received: 13 April 1998 · Accepted: 6 October 1998 相似文献
878.
G. J. Redhammer G. Roth W. Paulus G. André W. Lottermoser G. Amthauer W. Treutmann B. Koppelhuber-Bitschnau 《Physics and Chemistry of Minerals》2001,28(5):337-346
Single crystals of Li-aegirine LiFe3+Si2O6 were synthesized at 1573?K and 3?GPa, and a polycrystalline sample suitable for neutron diffraction was produced by ceramic sintering at 1223?K. LiFe3+Si2O6 is monoclinic, space group C2/c, a=9.6641(2)?Å, b= 8.6612(3)?Å, c=5.2924(2)?Å, β=110.12(1)° at 300?K as refined from powder neutron data. At 229?K Li-aegirine undergoes a phase transition from C2/c to P21 /c. This is indicated by strong discontinuities in the temperature variation of the lattice parameters, especially for the monoclinic angle β and by the appearance of Bragg reflections (hkl) with h+k≠2n. In the low-temperature form two non-equivalent Si-sites with 〈SiA–O〉=1.622?Å and 〈SiB–O〉=1.624?Å at 100?K are present. The bridging angles of the SiO4 tetrahedra O3–O3–O3 are 192.55(8)° and 160.02(9)° at 100?K in the two independent tetrahedral chains in space group P21 /c, whereas it is 180.83(9)° at 300?K in the high-temperature C2/c phase, i.e. the chains are nearly fully expanded. Upon the phase transition the Li-coordination changes from six to five. At 100?K four Li–O bond lengths lie within 2.072(4)–2.172(3)?Å, the fifth Li–O bond length is 2.356(4)?Å, whereas the Li–O3?A bond lengths amount to 2.796(4)?Å. From 57Fe Mössbauer spectroscopic measurements between 80 and 500?K the structural phase transition is characterized by a small discontinuity of the quadrupole splitting. Temperature-dependent neutron powder diffraction experiments show first occurrence of magnetic reflections at 16.5?K in good agreement with the point of inflection in the temperature-dependent magnetization of LiFe3+Si2O6. Distinct preordering phenomena can be observed up to 35?K. At the magnetic phase transition the unit cell parameters exhibit a pronounced magneto-striction of the lattice. Below T N Li-aegirine shows a collinear antiferromagnetic structure. From our neutron powder diffraction experiments we extract a collinear antiferromagnetic spin arrangement within the a–c plane. 相似文献
879.
STRESS-METAMORPHISM AND ISOTOPIC AGE OF SHEAR ZONE GRANITOID TECTONITES OF IRTYSH SHEAR ZONE (ALTAI REGION) 总被引:1,自引:0,他引:1
B.M.Chikov V.A.Ponomachuk S.V.Zinoviev B.N.Lapin A.T.Titov A.V.Travin S.V.Palessky 《大地构造与成矿学(英文版)》2002,26(1):36-51
The Irtysh shear zone (ISZ) of Altai region is the lineament structure of the collision-suture type, where granites of Kalba complex and granodiorites of Zmeinogorsk complex are exposed to regional gneiss-formation and stress-metamorphic alterations. This study is based on detailed structural observations at special grounds using optical and electron microscopy, and on the behavior analysis of isotopic systems from altered granitoids.Within the ISZ area we have established the continuous rows of granitoid stress-metamorphism from initial recrystallization of protolite, its cataclasis and mechanical flaring up to complete recrystallization with alteration of mineral composition and formation of the streaky complexes of granite tectonites of blastomylonite and blastocataclasite types. The directed alteration of rocks has several impulse and is expressed by a change in morphology of mineral grains and their relations, magnification of deformation component in the rock structure, and formation of new mineral phases on the basis of initial ones without surface fluidization. At transformation of isotopic systems from granitoid, their feldspars,biotite and hornblende, we can observe “rejuvenation“ of the rock substrate from 270- 290 Ma for Kalba granitoids to 220-235 Ma for their tectonites, and for Rudny Altai granodiorites, their ages changes from 285-317 Ma to 232-257 Ma for their tectonites. 相似文献
880.
The origin of reaction textures in mantle peridotite xenoliths from Sal Island, Cape Verde: the case for “metasomatism” by the host lava 总被引:1,自引:1,他引:1
Cliff S. J. Shaw Florian Heidelbach Donald B. Dingwell 《Contributions to Mineralogy and Petrology》2006,151(6):681-697
Reaction zones around minerals in mantle xenoliths have been reported from many localities worldwide. Interpretations of the origins of these textures fall into two groups: mantle metasomatic reaction or reaction during transport of the xenoliths to the surface. A suite of harzburgitic mantle xenoliths from Sal, Cape Verde show clear evidence of reaction during transport. The reactions resulted in the formation of olivine–clinopyroxene and Si- and alkali-rich glass reaction zones around orthopyroxene and sieve-textured clinopyroxene and sieve textured spinel, both of which are associated with a Si- and alkali-rich glass similar to that in the orthopyroxene reaction zones. Reaction occurred at pressures less than the mantle equilibration pressure and at temperatures close to the liquidus temperature of the host magma. In addition, there is a clear spatial relation of reaction with the host lava: reaction is most intense near the lava/xenolith contact. The residence time of the xenoliths in the host magma, determined from Fe–Mg interdiffusion profiles in olivine, was approximately 4 years. Our results cannot be reconciled with a recent model for the evolution of the mantle below the Cape Verde Archipelago involving mantle metasomatism by kimberlitic melt. We contend that alkali-rich glasses in the Sal xenoliths are not remnants of a kimberlitic melt, but rather they are the result of reaction between the host lava or a similar magma and xenolith minerals, in particular orthopyroxene. The formation of a Si- and alkali-rich glass by host magma–orthopyroxene reaction appears to be a necessary precursor to formation of sieve textured spinel and clinopyroxene. 相似文献