天然勃姆石热相变体γ-Al2O3交换氟离子的研究

天然勃姆石矿在适当焙烧条件下可相变成γ-Al₂O₃,而γ-Al₂O₃,具有吸附水体中F^-的性能。吸附F^-后可用稀NaOH溶液解吸,酸中和再生。解吸后的含氟NaOH废液可用石灰粉回收,既减少了NaOH的消耗,又避免了对环境的污染。     

花岗岩—H2O—HF体系相关系及氟对花岗质熔体结构的影响

通过在0.1GPa压力下钠长花岗岩-H₂O-HF体系相关系实验获得,随体系F含量的增加,石英的温度稳定域上限升高,长石的温度稳定域上限降低;石英、碱性长石的晶-液平衡热力学计算表明,F导致花岗质熔体中组分SiO₂的活度增加,组分NaAlSi₃O₈和KAlSi₃O₈的活度减小,且NaAlSi₃O₈活度较KAlSi₃O₈活度减小幅度大。这些结果显示了F在花岗质熔体中与Si以外的阳离子Al、Na、K等产生了结合,且F与Na结合的优先性大于K,破坏了具有电荷平衡离子Na、K的AlO₂^-四面体,使熔体架状网格中Si/(Si+Al)和K/Na比值增大。通过F与H₂O对花岗岩体系相平衡的影响比较,作者认为F不与Si结合是它与OH^-在干扰熔体结构方面的最大区别。     

AlPO4高温高压相变研究

利用配有电阻炉外加热装置的金刚石对顶砧及紧装式六面顶高压容器,在500—1700℃和常压至17.8GPa温压范围内,对AlPO₄进行了实验研究。常压下,磷铝石(石英型AlPO₄)向鳞石英型AlPO₄转变的温度约为778℃,鳞石英型向方英石型AlPO₄转变的温度约为1100℃,块磷铝石α-β相转变的温度为586℃。在5.4 GPa和1300℃以下,块磷铝石保持稳定,在5GPa和大于1700℃时,发现AlPO₄分解为Al₂O₃,(刚玉)和P₂O₅鳞石英型AlPO₄在6GPa及500℃转变成斜方晶系新相,新相在室温常压下的晶胞参数为:a=4.930Å,b=7.200Å和c=6.165Å,鳞石英型AlPO₄及块磷铝石在11GPa以上均变为NiSO₄型结构。文中讨论了AlPO₄与SiO₂的异同,并给出了一个AlPO₄可能的相图。     

玄武岩的 MnO-TiO2-P2O5判别图的修改与补充

近些年来,人们广泛地利用火山岩的主元素或微量元素的特征对火山岩进行地球化学、成因岩石学和构造岩石学的研究。Mullen(1983)利用玄武岩的 MnO、TiO₂和P₂O₅建立大洋型玄武岩的 MnO×10-TiO₂-P₂O₅×10的构造背景判别图(以下简称MTP图)和圈出了大陆拉斑玄武岩在 MTP 图中的分布范围。他选择了能反映玄武岩形成过程中的重要地球化学特征和成因机制的元素组作为该图的端元组分。     

具有良好热稳定性的勃姆石纳米粉体的制备及表征

以Al(NO3)3·9H2O与氨水作用制备出勃姆石(AlOOH)沉淀,通过超声胶溶将沉淀转化为勃姆石溶胶,向所获溶胶中加入聚乙二醇使之凝胶化,再经冷冻干燥脱水,得疏松勃姆石粉体.对该粉体及其煅烧产物进行SEM,XRD表征,发现400℃/2 h煅烧产物仍然为勃姆石相,表明此方法合成的勃姆石有良好的热稳定性,用Scherrer公式计算的晶粒尺寸为10 nm左右;1 200℃/2 h煅烧产物为结构疏松、粒度微细的θ-Al2O3及α-Al2O3混相产物.     

莱河矿(Fe0.52+Fe1.03+SiO4)的超结构

莱河矿于1976年在中国辽宁省的磁铁矿床中首次被发现,许多人对它进行过研究。该矿物为黑色、不透明,化学式为Fe_0.58²⁺Fe_1.0³⁺Mg_0.03Si_0.96O₄,虽然它的晶体结构近似于橄榄石,但已确定为单斜晶系,空间群为P2₁/b。本文作者利用X射线、电子探针、高分解能透过电子显微镜对该矿物进行了系统的研究,发现它具有假双晶、超结构和显微条纹结构。     

梅山铁矿富铁熔浆运移的探讨

梅山铁矿床是产于中生代陆相火山岩中的一个大型富铁矿,属矿浆成因。本文通过对矿体中的V₂O₅/TFe比值的变化,V₂O₅/TFe与铁、磷组分的关系,成矿构造,矿体中的晶洞构造,成矿温度,围岩蚀变及硫同位素等方面的研究,认为,形成梅山铁矿富铁矿体的富铁熔浆是在矿床的南端汇集并形成,并向北从相对高处向相对低处侧向流动。形成这样的地质环境条件主要是岩浆侵入作用导致上覆火山岩的褶皱构造、侵入体的岩穹构造及接触破碎带构造等。     

一种斜长石地质温度计的改进

鲍温(N. L. Bowen)在他的关于斜长石熔融特性的经典论述中曾证明,钠长石(NaAlSi₃O₈)和钙长石(CaAl₂Si₂O₈)在高温下形成一个连续的固溶体系列,他按照理想溶液的模式对其试验资料进行了解释。许多年来,岩石、矿物学工作者一直试图以鲍温1913年的斜长石系统的实验研究为基础,找出岩浆岩中斜长石结晶温度与平衡共存的斜长石晶体和液体成分间的关系。库多和韦尔(A.M. Kudo和D.F. Weill)首次获得成功,他们于1970年,主要根据花岗岩和钠长石-钙长石二元系的实验资料,用一种经验的方法建立起一个地质温度计,目前已被通称为Kudo-weill斜长石地质温度计。     

青海湖沉积物中的粘土矿物

本文对青海湖沉积物中的粘土矿物和沉积环境进行了初步研究。沉积物的粒度成分一般以粉砂级为主,湖周沉积物较粗,湖内沉积物较细。湖中粘土矿物以伊利石-绿泥石为主,含少量蒙脱石和高岭石等。沉积物表层未见蒙脱石,粘土中Al₂O₃、K₂O和MgO的相对百分含量的特征与海粘土的化学成分特征相似。     

红枫湖夏季分层期间pCO2分布规律的研究

在夏季分层期间对红枫湖南、北湖湖心的水样进行分层采集,同时测定了分层水样的温度、pH、HCO₃-浓度、溶解氧(DO)、叶绿素a(Chl-a)及铵根离子(NH₄+)、硝酸根离子(NO₃-)、磷酸根离子(PO₄3-)的浓度,水体中CO₂的分压(pCO₂)由化学平衡及亨利定律求得。研究结果表明:光合作用、有机质降解及水体热分层是影响红枫湖夏季pCO₂分布的主要因素。其中,温水层CO₂欠饱和是光合作用吸收CO₂引起的,温跃层中pCO₂的急剧增加是光合产物降解产生CO₂引起的。静水层沉积物附近pCO₂最高并且还有持续增加的趋势,说明沉积物中有机质降解是静水层中CO₂增加的主要原因,夏季湖底水温较高加快了沉积物中有机质的降解。分层现象使pCO₂在水体中的分布差别明显,并且使静水层中CO₂得到积累。此外,夏季红枫湖水体中pCO₂的变化与NH₄+、PO₄3-的变化密不可分,表现为温水层中光合作用消耗NH₄+、PO₄3-,有机质降解过程伴随NH₄+、PO₄3-的释放。     

Volatile organic compounds decomposition using nonthermal plasma coupled with a combination of catalysts

A series of experiments were performed for toluene decomposition from a gaseous influent at normal temperature and atmospheric pressure by nonthermal plasma coupled with a combination of catalysts technology. Nonthermal plasma was generated by dielectric barrier discharge. γ-Al₂O₃ was used to be a sorbent and a catalyst carrier. Nanocatalysts were MnO₂/γ-Al₂O₃ coupled with modified ferroelectric of nano-Ba_0.8Sr_0.2Zr_0.1Ti_0.9O₃. γ-Al₂O₃ played an important role in prolonging reaction time of nonthermal plasma with volatile organic compounds molecules. MnO₂/γ-Al₂O₃ has an advantage for ozone removal, while nano-Ba_0.8Sr_0.2Zr_0.1Ti_0.9O₃ is a kind of good ferroelectric material for improving energy efficiency. Thus these packed materials were incorporated together to strengthen nonthermal plasma power for volatile organic compounds decomposition. The results showed the synergistic technology resulted in greater enhancement of toluene removal and energy efficiencies and a better inhibition for ozone formation in the gas exhaust. Based on the data analysis of the Fourier transforms infrared spectrum, the reaction process of toluene decomposition and the mechanism of synergistic effect are discussed. The results showed in a complex oxidation mechanism of toluene via several pathways, producing either ringretaining or ringopening products. The final products were carbon dioxide and water.     

松辽盆地油田地下水化学场的垂直分带性与平面分区性

松辽盆地地下水动力场的形成与演化控制了地下水化学场的形成与分布,地下水化学分布特征又反映地下水动力场的演化结果。在地下水化学场的形成过程中,影响沉积盆地地下水化学性质的因素较多,这些因素对地下水化学性质的影响作用在垂向上具有阶段性,在平面上具有选择性。前者导致地下水化学性质的垂直分带性,从浅到深可以划分出:1)大气水下渗淡化带,2)近地表蒸发浓缩带,3)泥岩压实排水淡化带(C₁)—压滤浓缩带(C₂),4)粘土矿物脱水淡化带和5)渗滤浓缩带等5种水化学剖面单元类型。后者决定了地下水化学场的平面分区性:1)盆地边缘为大气水下渗淡化区,2)盆地中央为泥岩压实排水淡化区,3)越流区为过渡区,4)越流-蒸发区为浓缩区。在泥岩压实排水形成的离心流方向上,矿化度、Na⁺浓度、Cl^-浓度和盐化系数升高,(CO₃^2-+HCO₃^-、SO₄^2-浓度、钠氯系数(γNa⁺/γCl^-)和脱硫系数(SO₄^2-/SO₄^2-+Cl^-)降低。在大气水下渗向心流方向上,矿化度、离子浓度和钠氯系数、脱硫系数和盐化系数一致升高。     

Internally-Consistent Thermodynamic Data for Minerals in the System Na2O-K2O-CaO-MgO-FeO-Fe2O3-Al2O3-SiO2-TiO2-H2O-CO2

Internally consistent standard state thermodynamic data arepresented for 67 minerals in the system Na₂O-K₂O-CaO-MgO-FeO-Fe₂O₃-Al₂O₃-SiO₂-TiO₂-H₂O-CO₂.The method of mathematical programming was used to achieve consistencyof derived properties with phase equilibrium, calorimetric,and volumetric data, utilizing equations that account for thethermodynamic consequences of first and second order phase transitions,and temperature-dependent disorder. Tabulated properties arein good agreement with thermophysical data, as well as beingconsistent with the bulk of phase equilibrium data obtainedin solubility studies, weight change experiments, and reversalsinvolving both single and mixed volatile species. The reliabilityof the thermodynamic data set is documented by extensive comparisons(Figs. 4–45) between computed equilibria and phase equilibriumdata. The high degree of consistency obtained with these diverseexperimental data gives confidence that the refined thermodynamicproperties should allow accurate prediction of phase relationshipsamong stoichiometric minerals in complex chemical systems, andprovide a reasonable basis from which activity models for mineralsmay be derived.     

Liquidus Equilibria in the System K2O-Na2O-Al2O3-SiO2-F2O-1-H2O to 100 MPa: II. Differentiation Paths of Fluorosilicic Magmas in Hydrous Systems

We investigated phase equilibria in the six-component systemNa₂O–K₂O–Al₂O₃–SiO₂–F₂O_–1–H₂Oat 100 MPa to characterize differentiation paths of naturalfluorine-bearing granitic and rhyolitic magmas. Topaz and cryoliteare stable saturating solid phases in calcium-poor systems.At 100 MPa the maximum solidus depression and fluorine solubilityin evolving silicic melts are controlled by the eutectics haplogranite–cryolite–H₂Oat 640°C and 4 wt % F, and haplogranite–topaz–H₂Oat 640°C and 2 wt % F. Topaz and cryolite form a binaryperalkaline eutectic at 660°C, 100 MPa and fluid saturation.The low-temperature nature of this invariant point causes displacementof multiphase eutectics with quartz and alkali feldspar towardsthe topaz–cryolite join and enables the silicate liquidusand cotectic surfaces to extend to very high fluorine concentrations(more than 30 wt % F) for weakly peraluminous and subaluminouscompositions. The differentiation of fluorine-bearing magmasfollows two distinct paths of fluorine behavior, depending onwhether additional minerals buffer the alkali/alumina ratioin the melt. In systems with micas or aluminosilicates thatbuffer the activity of alumina, magmatic crystallization willreach either topaz or cryolite saturation and the system solidifiesat low fluorine concentration. In leucogranitic suites precipitatingquartz and feldspar only, the liquid line of descent will reachtopaz or cryolite but fluorine will continue to increase untilthe quaternary eutectic with two fluorine-bearing solid phasesis reached at 540°C, 100 MPa and aqueous-fluid saturation.The maximum water solubility in the haplogranitic melts increaseswith the fluorine content and reaches 12· 5 ±0· 5 wt % H₂O at the quartz–cryolite–topazeutectic composition. A continuous transition between hydrousfluorosilicate melts and solute-rich aqueous fluids is not documentedby this study. Our experimental results are applicable to leucocraticfluorosilicic magmas. In multicomponent systems, however, thepresence of calcium may severely limit enrichment of fluorineby crystallization of fluorite. KEY WORDS: granite; rhyolite; topaz; cryolite; magmatic differentiation     

Comparison of Mo/MgO and Mo/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts: impact of support on the structure and dibenzothiophene hydrodesulfurization reaction pathways

The MgO and P₂O₅-promoted γ-Al₂O₃ supports with alkaline and acidic natures, respectively, were prepared, impregnated with Mo atoms, and compared for dibenzothiophene (DBT) hydrodesulfurization (HDS) reaction. Ultraviolet spectroscopy and the principal component analysis were used to identify the impact of the supports on the reaction pathways. The catalysts were characterized by BET surface analysis, X-ray diffraction, temperature-programmed reduction, Fourier transform infrared, and X-ray photoelectron spectroscopy. The γ-Al₂O₃-supported catalyst favors the hydrogenation pathway relative to the MgO-supported catalyst, which facilitates the direct desulfurization route. The different performance was attributed to the dissimilar Mo phases that emerged during the activation procedure. The activation under sulfo-reductive condition changed the Mo atoms on γ-Al₂O₃ support into the sulfide phase while extra oxidation took place for the MgO-supported catalyst. The migration and consumption of loosely bonded bulk oxygen atoms with under-coordinated Mo atoms on the MgO support were introduced as a possible reason for such extra oxidation. DFT calculations predicted an interaction between the Mo/MgO catalyst and DBT via the electron donation from the catalyst oxygen atoms to the aromatic rings, resulting in weakening and breaking of the C–S bonds. In spite of the higher resistance of the MgO-supported catalyst toward coking and its superior activity, its lower hydrogenation capability suggested using a dual-function catalyst. Accordingly, two catalysts were mixed and the synergism was observed in the HDS reaction of thiophene.     

18OSO4 and 18OH2O as prospective indicators of elevated arsenic in the Goose River ground-watershed, Maine

Anomalous geogenic arsenic occurs in drinking water from the Goose River crystalline ground-watershed in mid-coastal Maine. Isotope investigations were useful in understanding release areas of arsenic into affected water wells. The isotope composition of sulfate associated with probable arsenian pyrite oxidation is described. Correlation of '¹⁸O_SO4 enrichment [+4.57 to +7.46‰ Vienna Standard Mean Ocean Water (VSMOW)] is discussed with specific and recurring areas of elevated arsenic (10-52 µg l^-1). Although arsenic concentrations were highly variable over 2 years per well, '¹⁸O_SO4 values were always consistent and suggested a specific and consistent risk for elevated arsenic occurrences for each well. The '¹⁸O values in the water molecule (-12.07 to -8.81‰ VSMOW) and the '¹⁸O_SO4 values may serve as prospective indicators of prominent zones of aeration at depth in discrete fracture zones. The '¹⁸O values in the water molecule and sulfate ion appear to indicate that more than 60% of O₂ incorporated into the SO₄^2- ion are from dissolved oxygen and belong to distinct fractured areas. These aeration zones or oxidation fronts, as outlined by oxygen isotopes, are sentinels for high arsenic risk in groundwater.     

Adsorption of organic matter at mineral/water interfaces: I. ATR-FTIR spectroscopic and quantum chemical study of oxalate adsorbed at boehmite/water and corundum/water interfaces

The types and structures of adsorption complexes formed by oxalate at boehmite (γ-AlOOH)/water and corundum (α-Al₂O₃)/water interfaces were determined using in situ attenuated total reflectance fourier transform infrared (ATR-FTIR) spectroscopy and quantum chemical simulation methods. At pH 5.1, at least four different oxalate species were found at or near the boehmite/water interface for oxalate surface coverages (Γ_ox) ranging from 0.25 to 16.44 μmol/m². At relatively low coverages (Γ_ox < 2.47), strongly adsorbed inner-sphere oxalate species (IR peaks at 1286, 1418, 1700, and 1720 cm⁻¹) replace weakly adsorbed carbonate species, and a small proportion of oxalate anions are adsorbed in an outer-sphere mode (IR peaks at 1314 and 1591 cm⁻¹). IR peaks indicative of inner-sphere adsorbed oxalate are also observed for oxalate at the corundum/water interface at Γ_ox = 1.4 μmol/m². With increasing oxalate concentration (Γ_ox > 2.47 μmol/m²), the boehmite surface binding sites for inner-sphere adsorbed oxalate become saturated, and excess oxalate ions are present dominantly as aqueous species (IR peaks at 1309 and 1571 cm⁻¹). In addition to these adsorption processes, oxalate-promoted dissolution of boehmite following inner-sphere oxalate adsorption becomes increasingly pronounced with increasing Γ_ox and results in an aqueous Al(III)-oxalate species, as indicated by shifted IR peaks (1286 → 1297 cm⁻¹ and 1418 → 1408 cm⁻¹). At pH 2.5, no outer-sphere adsorbed oxalate or aqueous oxalate species were observed. The similarity of adsorbed oxalate spectral features at pH 2.5 and 5.1 implies that the adsorption mechanism of aqueous HOx⁻ species involves loss of protons from this species during the ligand-exchange reaction. As a consequence, adsorbed inner-sphere oxalate and aqueous Al(III)-oxalate complexes formed at pH 2.5 have coordination geometries very similar to those formed at pH 5.1.The coordination geometry of inner-sphere adsorbed oxalate species was also predicted using quantum chemical geometry optimization and IR vibrational frequency calculations. Geometry-optimized Al₈O₁₂ and Al₁₄O₂₂ clusters with the reactive surface Al site coordinated by three oxygens were used as model substrates for corundum and boehmite surfaces. Among the models considered, calculated IR frequencies based on a bidentate side-on structure with a 5-membered ring agree best with the observed frequencies for boehmite/oxalate/water samples at Γ_ox = 0.25 to 16.44 μmol/m² and pH 2.5 and 5.1, and for a corundum/oxalate/water sample at Γ_ox = 1.4 μmol/m² and pH 5.1. Based on these results, we suggest that oxalate bonding on boehmite and corundum surfaces results in 5-coordinated rather than 4- or 6-coordinated Al surface sites.     

The stabilities of gibbsite,boehmite, aluminous goethites and aluminous hematites in bauxites,ferricretes and laterites as a function of water activity,temperature and particle size

Stability relationships between Al-goethite, Al-hematite, boehmite and gibbsite are presented in terms of water activity [H₂O], temperature (T), grain size and bulk-composition in the system Fe₂O₃-Al₂O₃-H₂O at a total pressure of 1 bar.Al-goethite and Al-hematite are treated as ideal solid solutions, the former of the end-members FeOOH (goethite) and AlOOH (diaspore) and the latter of the end-members Fe₂O₃ (hematite) and Al₂O₃ (corundum). Using log K_sp provided by the literature for the various phases involved, the common associations observed in laterites, bauxites and ferricretes do not have stability fields over geologically reasonable intervals of [H₂O] and T. Consequently a new internally consistent set of log K_sp values is proposed and used, and allows such associations to have actual stability fields in the appropriate diagrams. The new log K_sp values used in the calculations are such that the solubilities of the end members are greater than those commonly listed. This is in agreement with natural observations which show that such minerals, are generally poorly crystallized and of very small size. The assumption of an ideal solid solution in aluminous goethite and aluminous hematite combined with the new log K_sp values leads to prediction of composition limits for these two minerals which agree well with observed values. The fact that an ideal solid solution must extend continuously from one end-member to the other is masked by the appearance of other stability fields (e.g. gibbsite or boehmite) which cross and overlap a part of the solid solution stability fields of AlOOH-FeOOH and Fe₂O₃-Al₂O₃.     

The combined effects of chlorine and fluorine on the viscosity of aluminosilicate melts

The effect of fluorine and fluorine + chlorine on melt viscosities in the system Na₂O-Fe₂O₃-Al₂O₃-SiO₂ has been investigated. Shear viscosities of melts ranging in composition from peraluminous [(Na₂O + FeO) < (Al₂O₃ + Fe₂O₃)] to peralkaline [(Na₂O + FeO) > (Al₂O₃ + Fe₂O₃)] were determined over a temperature range 560-890 °C at room pressure in a nitrogen atmosphere. Viscosities were determined using the micropenetration technique in the range of 10^8.8 to 10^12.0 Pa s. The compositions are based on addition of FeF₃ and FeCl₃ to aluminosilicate melts with a fixed amount of SiO₂ (67 mol%). Although there was a significant loss of F and Cl during glass syntheses, none occurred during the viscometry experiments. The presence of fluorine causes a decrease in the viscosity of all melts investigated. This is in agreement with the structural model that two fluorines replace one oxygen; resulting in a depolymerisation of the melt and thus a decrease in viscosity. The presence of both chlorine and fluorine results in a slight increase in the viscosity of peraluminous melts and a decrease in viscosity of peralkaline melts. The variation in viscosity produced by the addition of both fluorine and chlorine is the opposite to that observed in the same composition melts, with the addition of chlorine alone (Zimova M. and Webb S.L. (2006) The effect of chlorine on the viscosity of Na₂O-Fe₂O₃-Al₂O₃-SiO₂ melts. Am. Mineral.91, 344-352). This suggests that the structural interaction of chlorine and fluorine is not linear and the rheology of magmas containing both volatiles is more complex than previously assumed.