纳米赤铁矿电极光电催化特性及苯酚降解活性研究

伴随环境污染问题日益加剧,借助半导体材料实现光能的光电转化在催化及环境领域引起广泛关注。本文借助电化学方法快速高效地合成不同沉积时间纳米赤铁矿薄膜电极。X射线衍射(XRD)、Raman光谱测试表明其成分为赤铁矿物相;原子力显微镜(AFM)观测颗粒尺寸约52.1(±1.48)nm×50.5(±1.49)nm,表面高度起伏分布于70~100 nm,且分布特征符合正态分布规律。紫外可见漫反射吸收谱显示电极可显著吸收350~600 nm波长范围可见光,计算得禁带宽度约2.0~2.1 e V。光电化学实验光电流密度-时间曲线及电流-电压曲线表明电极有良好的可见光光电催化活性,且反应符合Langmuir-Hinshelwood多相反应动力学模型。进一步选取效果较显著的沉积时间10 min电极研究其光电催化降解苯酚活性,0.65 V vs.SCE(饱和甘汞电极)恒电势光照条件下6 h苯酚降解率达62%,拟合一级动力学反应模型可知,反应速率常数k为0.16 h-1(R2=0.996)。综上,本文研究结果显示电化学法简单高效合成的纳米赤铁矿具有良好半导体性能且能够可见光光电催化降解苯酚等有机污染物。     

东海龙井1~#钻井自生菱铁矿的一般特征和成因探讨

矿物分布自430米(M-3号样品)起断续有出现,含量比较高。在全井的颗粒百分数(即在300～400颗碎屑矿物中自生菱铁矿所占百分数)最高达86％,最低1.2％。自生菱铁矿富集在一套灰色～黑灰色泥岩夹粉砂质泥岩的互层中,呈圆球粒状、哑铃状、粒状、棒状,扁形放射状、块粒状等。以块粒状为主,球粒状、哑铃状为次,其它少量。其颜色有灰白色、灰色、灰棕色、淡黄色、淡棕色、棕黑灰色,从上到下由浅变深,球粒状,     

红山古玉孔洞内首次发现球粒状铁质矿物

本文通过对红山古玉孔洞内球粒状磁铁矿、针铁矿、赤铁矿和金属铁等铁质成分的研究,并与宇宙尘和古生代海洋沉积形成的鲕状赤铁矿进行对比,论证了磁铁矿等铁质矿物球粒的成因.运用这一研究成果,可作为识别红山古玉的一种有效的手段.     

凉山瓦西乡南红玉中的赤铁矿包裹体特征与成因

瓦西乡产出的南红玉中的红色点状及火焰纹典型包裹体分别是石英中的红色球粒与红色管状包裹体。鏡下及扫描电镜(SEM)研究,红色球粒分布在"三色"层水晶的菱面体单形晶面的间歇层面中,由红色核、黑色壳和红色表层组成;火焰纹管状包裹体主要出现在条带水晶中,管的方向垂直水晶的菱面体晶面,管的内壁呈黑色,外壳为红色。其球粒表层或管外壳的颜色、厚度及透光性则直接影响南红的颜色质量与润泽性。研究表明,球粒状和火焰状包裹体主要由片状、鳞片状或板片状赤铁矿组成;球粒圈层中的赤铁矿晶体c轴取向呈规律变化,可能与其V2O5含量有关。据水晶晶体中的球粒、管及共生矿物绿帘石、黄铜矿包裹体的红外光谱(IR)及流体包裹体均一法测温与激光拉曼(LRS)分析,球或管的赤铁矿属含有机质的低温热液(约160℃)成因,成矿溶液中的有机质也是促使铁氧化物凝聚形成具不同圈层结构的红色球粒与管的主要原因。有机质可能来自下二叠统茅口组碳酸盐。     

球粒状(綠)帘石的结构特征与成因

球粒状(綠)帘石产出于四川雷波基性火山碎屑岩的晶洞或层间裂隙中,与其共生的有石英、赤铁矿等矿物.镜下研究表明,绿帘石至少有2个世代,第一世代(綠)帘石呈浅(綠)色的针状体,集合体为菊花状;第二世代(綠)帘石呈暗(綠)色的柱状或楔形,集合体为球粒状或椭球状.它们都由球核与球枝两部分组成,两者间有明显的接触界线,表明球核与球枝不是同时结晶的产物,而是有先后形成关系.EPMA分析表明绿帘石成分中普遍含有较高的SrO(0.51%～1.13%),与其共生的水晶晶体的流体包裹体测温及拉曼光谱分析表明,气液包裹体主要由H2O及微量CH4组成,,(綠)帘石属低温(164～177℃)与低盐度(7.31%～7.73%)的热液产物.(綠)帘石的球粒是在低温、过饱和度大、环境条件转变时快速结晶形成的.     

黄羊山石墨矿床地质特征及成岩年代研究

黄羊山矿床是最近在新疆发现的一个超大型晶质石墨矿床,预测晶质石墨矿物量至少为72.64 Mt。该矿床赋存于花岗岩内,90%的石墨呈球粒状构造,球粒直径最高达20 cm,世界罕见。通过钻孔岩芯编录、探槽编录、镜下观察和锆石U-Pb定年,研究了该矿床矿化情况、矿物组合和成岩年代,探讨了矿床成因。研究表明,黄羊山石墨矿床成岩于(306±4)Ma,属晚石炭世。石墨球粒和基质的岩性相同,皆为碱长花岗岩,只是石墨球粒内较为富集黑云母、角闪石和单斜辉石。与石墨伴生的金属矿物主要为磁黄铁矿、黄铜矿、钛铁矿和赤铁矿。由于石墨的强还原性,这些金属矿物多分布于石墨球粒内,形成典型的环带结构。石墨矿化可分为岩浆热液期和热液叠加期2期,前者是主成矿期,形成球粒状和浸染状构造石墨,后者形成脉状构造石墨。石墨晶体呈片状和胶状结构,片状石墨横截面呈针状,定向性明显。石墨矿石的全岩碳同位素呈负低值,表明构成石墨的碳来自地层有机物。岩浆在上侵过程中同化混染了地层有机物,在岩浆演化晚期熔体相与流体相分离时,碳质溶入流体相中,当温度和压力降低时石墨从岩浆热液中沉淀成矿。中粒钠铁闪石花岗岩、细粒黑云母花岗岩和中粒黑云母花岗岩中皆含石墨球粒,黄羊山岩体仍具有巨大找矿潜力。     

球粒状緑帘石的结构特征与成因

球粒状緑帘石产出于四川雷波基性火山碎屑岩的晶洞或层间裂隙中,与其共生的有石英、赤铁矿等矿物。镜下研究表明,緑帘石至少有2个世代,第一世代緑帘石呈浅緑色的针状体,集合体为菊花状;第二世代緑帘石呈暗緑色的柱状或楔形,集合体为球粒状或椭球状。它们都由球核与球枝两部分组成,两者间有明显的接触界线,表明球核与球枝不是同时结晶的产物,而是有先后形成关系。EPMA分析表明緑帘石成分中普遍含有较高的SrO(0.51%~1.13%),与其共生的水晶晶体的流体包裹体测温及拉曼光谱分析表明,气液包裹体主要由H2O及微量CH4组成,,緑帘石属低温(164~177℃)与低盐度(7.31%~7.73%)的热液产物。緑帘石的球粒是在低温、过饱和度大、环境条件转变时快速结晶形成的。     

天然赤铁矿促进红壤微生物胞外电子传递机制研究

为了研究天然赤铁矿对微生物胞外电子传递机制,以长沙和海口红壤为例,构建了双室反应体系对红壤微生物与天然赤铁矿间氧化还原作用及胞外电子传递过程进行表征。研究显示,增加赤铁矿作为电子受体后,长沙与海口红壤体系开路电压由425.28、414.64 m V提升至511.46、532.52 m V,最大输出功率由221.5、171.0 m W/m~3提升至431.4、260.2 m W/m~3。电化学循环伏安测试显示在0.43、0.55 V(相对于饱和甘汞电极;vs.SCE)处出现Fe(Ⅲ)还原峰及Fe(Ⅱ)氧化峰,指证新氧化还原反应的引入。电化学阻抗谱(EIS)拟合结果显示赤铁矿电极极化内阻R_p自44840Ω降至665Ω,从动力学层面表明电极反应导致的电势降低有利于电子转移。实验研究结果表明,红壤环境中以赤铁矿为代表的铁氧化物能够有效参与并促进微生物胞外电子传递。     

太阳能电池协同强化水钠锰矿光电催化染料降解研究

电催化、光催化、光电催化等电化学技术以其高效、廉价、环保等特点被认为是一种极具前途的环境污染深度净化技术,在有机废水处理等方面得以广泛应用。本文借助电化学电量控制法制备了水钠锰矿电极,通过X射线衍射(XRD)、扫描电镜(SEM)表征其物相形貌,UV-Vis漫反射吸收谱结果表明水钠锰矿对300~600 nm波长范围可见光表现出良好吸收能力,计算其直接带隙约为2.14 e V,Mott-Schottky曲线计算其平带电位约1.15 V,0.1 mol/L Na2SO4介质中载流子浓度约为3.3×1019cm-3,是良好的可见光激发n型半导体材料。同时,本文以廉价高效的太阳能电池板取代了传统电化学工作站等外加电场设备,成功实现了协同强化水钠锰矿光电催化降解作用。协同作用下甲基橙60 min降解率为90.2%,效率远高于水钠锰矿光催化(2.2%)与电极电催化(33.6%)作用,强化了水钠锰矿光电催化降解反应,节省能耗的同时显著提高了降解效率。批次循环降解实验表明第4轮降解率(86.8%)较之第1轮(90.3%)降低程度5%,表明其具有良好长时间运行稳定性。     

纳米水钠锰矿可见光光电化学响应与甲基橙降解活性

伴随环境污染问题日益加剧,光能的光电转化在催化及环境领域引起广泛关注。水钠锰矿是地表常见锰矿物之一,本文借助电化学电量控制法快速高效制备了纳米水钠锰矿电极。X射线衍射(XRD)、Raman光谱测试表明物相单一为水钠锰矿;原子力显微镜(AFM)观察电极微观形貌可见表面分布有不规则多边形格子状空隙,测定沉积电量为0.5、1.0、1.5 C水钠锰矿厚度分别约为30、200、450 nm。紫外可见漫反射吸收谱显示电极可显著吸收300~600 nm波长可见光,Tauc方程计算电极间接带隙约0.8~1.3 eV,直接带隙约2.0~2.3 eV,Mott-Schottky曲线计算平带电位约1.15 V,三电极载流子浓度分别为3.26×10~(19)、4.63×10~(19)、2.70×1020 cm~(-3)。光电流密度-时间曲线及线性扫描伏安曲线表明电极有良好光电化学响应活性Evs.SCE=1.0 V(饱和甘汞电极)恒电势光照条件下,150 min后0.5、1.0、1.5 C水钠锰矿电极对5 mg/L甲基橙降解率分别为66.3%,70.0%,67.5%,拟合反应速率常数k分别为0.44 h~(-1)、0.48 h~(-1)、0.46 h~(-1)(R20.996)。综上,本文研究表明纳米水钠锰矿电极能有效可见光光电催化降解甲基橙等有机污染物。     

Color centers in topaz: comparison between neutron and gamma irradiation

Neutron- and gamma irradiation-induced paramagnetic centers in natural colorless topaz from four different Brazilian localities were studied by electron paramagnetic resonance (EPR) and optical absorption as a function of irradiation dose and thermal treatment. Gamma irradiation doses were applied up to 1,000 kGy with a dose rate of 15 kGy h⁻¹. For the neutron irradiation experiments, a neutron flux of 4 × 10¹² cm⁻² s⁻¹ was used with an integrated flux of up to 1 × 10¹⁸ cm⁻². From the experiments, it is concluded that brownish colors are induced by gamma-rays and may be associated with a single broad isotropic EPR line with g = 2.015(2). Both the EPR line and the related optical absorption band at 460 nm (2.7 eV) are lost during thermal treatments between 150 and 200°C. Fast neutrons create the paramagnetic peroxyl radicals O₂ ⁻ and the paramagnetic O⁻ hole centers. The O⁻ centers have the same thermal stability as the optical absorption band at 620 nm (2.0 eV). It is confirmed that the absorption due to the O⁻ center is responsible for the blue color in topaz. Both color centers and their absorption bands are discussed in the context of O⁻ bound small polarons.     

Estimation of methane emission from whole waste landfill site using correlation between flux and ground temperature

A methodology to estimate a methane emission in a waste landfill site was developed. The methane flux at a waste landfill site in summer, autumn, and winter was within the following ranges: from −1.3×10⁻² to 16, from −6.4×10⁻² to 7.5, and from −1.6×10⁻³ to 1.5×10⁻² g-CH₄ m⁻² h⁻¹, respectively. In those seasons, the mean methane emission rate and coefficient of variation were 1.1 g-CH₄ m⁻² h⁻¹ ±290%, 0.57 g-CH₄ m⁻² h⁻¹ ±347%, and 5.4×10⁻² g-CH₄ m⁻² h⁻¹ ±370%, respectively. These results simultaneously showed that fluctuations of methane emission from the landfill surface were both of spatial and temporal variability. In each season, an exponential relationship was observed between the methane flux density and the ground temperature. Total methane emissions were estimated to be 5.7×10⁻², 7.1×10⁻³, and 1.7×10⁻³ g-CH₄ m⁻² h⁻¹ in the summer, autumn, and winter surveys, respectively, using a temperature surrogated-kriging method. The results of this study would improve upon the labor-intensive closed-chamber method, and could be a more practical way to estimate methane emissions from waste landfills.     

Temperature dependence of photoluminescence emission characteristics in a natural fluorite

Summary The temperature dependence of photoluminescence emission of a natural fluorite has been studied in the wavelength region of 380–500 nm and in the temperature range of 17.5–300 K. The emission spectra of the sample show a broad emission band between 380 and 500 nm for temperatures above 100 K. At 100 K and below, vibronic lines appear on the emission band at approximately 413.3, 418.1, 419.3, 420.2, 423.9 and 427.1 nm. This broad emission band and the vibronic lines in fluorite are usually associated with phonon-coupled electronic transitions from 4f⁶5d to 4f⁷ in the Eu²⁺ ion. Temperature dependences of the peak energy, intensity and full-width at half-maximum of the broad emission band are discussed, and the behaviour explained in terms of a configurational coordinate model. The excited state vibrational energy was obtained to be 0.023 ± 0.001 eV and this is lower than the LO phonon energy of 0.062 eV in pure fluorite. The activation energy of thermal quenching of the photoluminescence intensity was found to be 0.022 ± 0.002 eV.     

Detection of radio emission from the AXP 4U 0142+61

The detection of pulsed radio emission from the X-ray pulsar AXP 4U 0142+61 with a period of P = 8.68832935(6) s and a period derivative of $ \dot P $ \dot P = 18.713(4) × 10⁻¹³ s/s is reported. The observations were carried out on two high-sensitivity radio telescopes of the Pushchino Radio Astronomy Observatory: the Large Phased Array at 111MHz and the DKR-1000 at 40MHz.Mean pulse profiles are presented; the measured flux density is S ₁₁₁ = 30 ± 20 mJy. The estimated distance derived from the dispersion measure, 27 pc/cm³, is 1.4 kpc, and the integrated radio luminosity is L _R = 1.5 × 10²⁷ erg/cm. Comparison with X-ray data shows an appreciable difference in the pulse duration (the radio pulse is about a factor of 20 more narrow) and strong variations in the flux density.     

Electrical properties of opal-CT

 The electrical properties of opal-CT are validated at temperatures from 600 to 840 °C and frequencies from 5 Hz to 10 MHz. The opals are hydrothermal, containing less than 11270 ppm total of Al, Fe, Ca, Na, and K, and from 1.17 to 17.63 wt% H₂O interstitial and structural. Opal-CT shows fine crystallites, measuring from 19.4 to 22.7 μm, of an ordered tridymite-M stratification with high-cristobalite, embedded in a non-crystalline matrix. When heated to 600 °C, the non-crystalline phase devitrifies to the same stacked high-cristobalite-tridymite-M crystals. Opals containing less than 2070 ppm of cationic impurities are characterized by one single high-frequency complex impedance arc corresponding to the bulk polarization of the crystalline phase, of capacitances between 25 and 30×10⁻¹² F and resistances from 132 to 890 ohm. Opals having over 6300 ppm of cationic impurities show two superimposed high- and low-frequency complex impedance arcs. The high-frequency arc corresponds to the bulk polarization of the crystalline phase, of capacitance between 8 and 15.7×10⁻¹² F and resistance from 14 to 236 ohm, less than the capacitance of 0.25 to 0.53×10⁻⁹ F and resistance from 26 to 360 ohm of the non-crystalline minor intergranular material represented by the low-frequency impedance arc. The electric module shows one single vertex, ascribed to the bulk polarization of the crystalline phase. The conductivities are from 10⁻⁷ to 10⁻⁴ ohm⁻¹cm⁻¹, in the range of poor ionic conductors, essentially constant below 1.8 kHz, rapidly increasing at higher frequencies, due to ionic and electronic charge carriers. The activation energy changes between 0.905 and 1.003 eV for the conduction mechanism in the crystalline phase and from 0.924 to 1.087 eV in the non-crystaline phase. X-ray diffraction and impedance spectroscopy confirm that opal-CT is a crystalline stacked sequence of tridymite-M and cristobalite-high, in a non-crystalline matrix. Received October 20, 1995/Revised, accepted June 15, 1996     

Mapping of accumulated nitrogen in the sediment pore water of a eutrophic lake in Iowa, USA

A large pool of nitrogen in the sediment pore fluid of a eutrophic lake in Iowa, USA, was mapped in this study. Previously, the lake had supported fishing and boating, but today it no longer supports its designated uses as a recreational water body. In the top 5 cm of the lake bottom, the pore water nitrogen ranges between 3.1 and 1,250 μg/cm³ of sediments, with an average of 160.3 μg/cm³. Vertically, nitrate concentrations were measured as 153 μg/cm³ at 0–10 cm, 162 μg/cm³ at 10–20 cm, and 32 μg/cm³ at 20–30 cm. Nitrate mass distribution was quantified as 3.67 × 10³ kg (65%) in the bottom sediments, 172 kg (3%) in suspended particulates, and 1.83 × 10³ kg (32%) in the dissolved phase. Soil runoff nutrients arrive at the lake from the heavily fertilized lands in the watershed. Upon sedimentation, a large mass of nitrogen desorbs from mineral particles to the relatively immobile pore fluid. Under favorable conditions, this nitrogen diffuses back into the water column, thereby dramatically limiting the lake’s capability to process incoming nutrients from farmlands. Consequently, a condition of oxygen deficiency disrupts the post-season biological activities in the lake.     

锆石Ge含量和年龄对云南临沧锗矿床物质来源的约束

云南临沧锗矿床产在以临沧花岗岩为基底的中新世断陷盆地中。已有研究表明,成矿元素Ge来自基底花岗岩,但临沧花岗岩是复式岩基,具有多期次的岩浆活动,而Ge来自哪期岩浆活动并不清楚。文章对采自晓街、临沧、勐库和勐海的7个花岗岩样品(纵贯临沧岩基)进行了LA-ICP-MS锆石原位Ge元素含量分析和U-Pb年代学研究。研究结果表明,岩基主体岩浆活动时代与前人研究成果一致,为(215.6±2.7)Ma~(236.9±3.7)Ma,同时也有少量继承锆石(303~2533 Ma);w(Ge)在主岩浆期的锆石中为0.23×10-6~4.21×10-6,平均0.53×10-6,在继承锆石中为0.34×10-6~3.43×10-6,平均1.18×10-6;而在本次研究中新发现的年龄为106.5 Ma和87.7 Ma的年轻锆石中w(Ge)高达102×10-6。因此,推测临沧锗矿床中Ge来源于晚期岩浆或热液作用。这个结果为成矿理论的深入研究提供了新依据。     

金红石微量元素电子探针分析

金红石电子探针微量元素分析一般以人工合成的氧化物来作为监测标样,尚较缺乏对金红石标样进行系统地测试分析。本文运用CAMECA SXFive电子探针对金红石标样R10进行微量元素分析,根据金红石中主要微量元素在地质学中的应用,本次共分析了Al、Si、Ti、Fe、Cr、Zr、V、Nb、Ta等9个元素,Ti、Si元素作为本次分析的监测元素。本文通过调整加速电压和电流、背景和峰值测试时长以及干扰谱峰处理等来提高微量元素分析精度和准确度。分析结果显示,其中,Zr(780±29×10~(-6))(1SD,n=25)、Nb(2799±66×10~(-6))、V(1276±33×10~(-6))、Fe(4309±34×10~(-6))、Cr(718±31×10~(-6))的分析结果与二次离子质谱(SIMS)和激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)的推荐值在误差范围内一致。大部分元素数据波动范围在10%以内,V、Fe元素的数据波动范围仅在5%以内。V、Nb和Fe测试精度比前人电子探针分析结果有较大提高。金红石Zr测试误差传递给金红石Zr温度计给出的温度误差一般22℃。本文还对金红石Zr温度计应用、提高Ta元素分析精度和准确度、金红石Fe~(3+)分析等问题进行了探讨。     

Water and the density of silicate glasses

A review of published and newly measured densities for 40 hydrous silicate glasses indicates that the room-temperature partial molar volume of water is 12.0 ± 0.5 cm³/mol. This value holds for simple or mineral compositions as well as for complex natural glasses, from rhyolite to tephrite compositions, prepared up to 10–20 kbar pressures and containing up to 7 wt% H₂O. This volume does not vary either with the molar volume of the water-free silicate phase, with its degree of polymerization or with water speciation. Over a wide range of compositions, this constant value implies that the volume change for the reaction between hydroxyl ions and molecular water is zero and that, at least in glasses, speciation does not depend on pressure. Consistent with data from Ochs and Lange (1997, 1999), systematics in volume expansion for SiO₂–M₂O systems (M=H, Li, Na, K) suggests that the partial molar thermal expansion coefficient of H₂O is about 4 × 10⁻⁵ K⁻¹ in silicate glasses. Received: 30 June 1999 / Accepted: 5 November 1999