掺铁二氧化钛薄膜的自组装制备、表征与光催化性能研究

采用自组装方法于低温液相反应体系中成功制备出大尺寸二维纳米二氧化钛薄膜和掺铁二氧化钛薄膜。样品通过荧光发射光谱、拉曼光谱、高分辨透射电镜等方法进行表征,并研究了紫外光和可见光下Fe3+/TiO2纳米薄膜对甲基橙溶液(MO)的光催化降解过程,探讨了Fe3+对TiO2的光催化活性的影响。结果表明,此方法不需要高温煅烧即可得到高催化活性的金红石和锐钛矿混合型二氧化钛薄膜,以金红石为主。Fe3+掺杂明显提高了TiO2对甲基橙溶液的光催化降解效率:掺杂Fe3+浓度为0.5 mmol/L时光催化效果最优,且更利于较低浓度甲基橙溶液的降解,在紫外光和可见光下对初始浓度5 mg/L甲基橙溶液的降解率分别达到98.62%和89.24%。     

自然光下羟基氧化铁处理水溶液中甲基橙的研究

自然界广泛存在羟基氧化铁,研究其在地质中的光催化作用对环境的污染防治有着重要意义。在自然光照下,用针铁矿和四方纤铁矿处理甲基橙溶液,不同反应时间取样经高速离心后,用紫外/可见分光光度计和傅立叶变换显微红外光谱仪(FTIR)进行分析。结果表明,FeOOH/Visible light体系能使甲基橙溶液脱色率达83%,四方纤铁矿比针铁矿有更好的光催化降解效果;FeOOH/Visible light体系能将甲基橙分子中的偶氮键打开,从而使溶液脱色,FeOOH/Visible lihgt/H2O2则能进一步降解甲基橙,使其分子中的苯环部分打开。     

镍酞菁修饰镍铝水滑石的制备及光催化性能研究

通过共沉淀法将水溶性四羧基镍酞菁(Ni Pc)负载到镍-铝碳酸根水滑石(Ni Al-LDHs)上,制备负载型催化剂(Ni Pc/Ni Al-LDHs)。采用XRD、FT-IR、UV-Vis、TG-DTA和SEM等技术对酞菁衍生物和Ni Pc/Ni Al-LDHs的结构进行表征。结果表明Ni Pc没有改变Ni Al-LDHs的晶型结构和热稳定性能。在10 mg/L、25 m L的甲基橙溶液、p H值为3、H2O2用量50μL的条件下,Ni Pc/Ni Al-LDHs协同H2O2光催化氧化降解甲基橙3 h后,甲基橙剩余率为16.33%。溶液p H值在3~7范围内,Ni Pc/Ni Al-LDHs/H2O2都能有效光催化氧化降解甲基橙,且光催化氧化降解过程涉及到羟基自由基反应。     

TiO2/蛭石复合材料的制备及光催化性能研究

以天然层状蛭石为载体,钛酸四丁酯为钛源,采用溶胶-凝胶法制备了TiO2/蛭石复合光催化材料,利用XRD、SEM、TG-DTA、FTIR和BET等分析技术对催化剂进行了表征,通过对甲基橙溶液的降解实验检测了其光催化活性。探讨了催化剂用量、甲基橙初始浓度、pH值、煅烧温度等对光催化效率的影响规律。结果表明:采用溶胶-凝胶法制备的TiO2/蛭石经过200℃焙烧后,具有较好的光催化效率,利用300 W的高压汞灯紫外光辐照90 min,甲基橙溶液的脱色率达99%,COD去除率达81%。     

H_2O_2增效TiO_2/凹凸棒石光催化体系降解亚甲基蓝

以钛酸四丁酯为前驱体,天然凹凸棒石为载体,采用溶胶凝胶法制备了TiO_2/凹凸棒石复合光催化剂,并用XRD、TEM对其进行表征.以亚甲基蓝染料为模拟污染物,采用300 W汞灯为紫外光源,以光催化实验来评价该催化剂的活性,并研究了H_2O_2的引入对光催化活性的影响.实验结果表明,H_2O_2能显著提高染料的脱色效率:亚甲基蓝的初始浓度为50 mg/L,催化体系为2 mmol/L H_2O_2+0.5 g/L TiO_2/凹凸棒石+UV(紫外线),光催化10 min后其脱色率为95%,相对于单独的0.5 g/L TiO_2/凹凸棒石+UV催化体系,其脱色率提高了约50%.全波段扫描显示,加入H_2O_2后,亚甲基蓝在290 nm对应的苯环吸收蜂急剧下降,665 nm对应的最大吸收峰则近乎消失,且没有新的吸收峰产生.     

静电自组装制备斜发沸石负载纳米TiO2吸附及光催化降解甲基橙染料研究

为了实现纳米TiO2的固定化负载,提高材料对污染物的光催化效率,采用静电自组装方法制备了天然斜发沸石负载纳米TiO2光催化材料。采用硅烷偶联剂(OCH3)3Si(CH2)3SH干法改性斜发沸石,采用30%H2O2/HOAc氧化剂将偶联剂巯基基团(—SH)氧化为易电离的磺酸基基团(—SO3H),带负电荷的沸石与钛聚合阳离子在静电引力的作用下自发地组装在一起,经一定温度的焙烧得到斜发沸石负载纳米TiO2光催化材料。采用XRD和SEM对材料进行分析和表征,采用甲基橙染料评价材料的吸附和光催化性能,结果表明:沸石负载纳米TiO2对甲基橙染料具有吸附与光催化的协同作用,静电自组装方法制备的材料的光催化性能较传统方法有所提高。     

天然沸石对提高TiO2光催化活性的作用

以天然沸石为载体,研究了其负载TiO2后对甲基橙溶液的光催化降解效果,探讨了TiO2与沸石的结合类型。通过对负载前后反应动力学模式变化的研究,阐释TiO₂/沸石体系的光催化反应进程。从复合前后样品的AFM、IR、发射光谱变化上看,部分TiO₂与沸石载体形成了新的Ti－O－Si或Ti－O－Al的化学键。光催化实验结果和动力学分析显示,在反应的初始阶段,当TiO₂中引入多孔的沸石载体后,催化剂对甲基橙的降解过程由原来纯粹的吸附控制模式向反应控制模式转变,但还没有达到纯粹的反应控制的程度。沸石载体是通过提高吸附过程的速率,来提升初始阶段的光催化反应速率（R₀）的。     

微波处理TiO2柱撑蒙脱石的光催化性能

采用微波处理方法合成了TiO2结晶体柱撑蒙脱石光催化材料,采用XRD、BET吸附和降解甲基橙实验分析了柱撑蒙脱石的结构、锐钛矿金红石晶相比例、比表面积和光催化性能。结果证实,微波功率与辐照时间等条件将影响材料的结构与性能;与传统加热方式比较,微波处理可获得锐钛矿相含量高的混晶TiO2;该TiO2柱撑蒙脱石具备优异的光催化性能。     

铁(氢)氧化物矿物对有机污染物的光催化氧化作用

对水溶液中(氢)氧化铁的光催化氧化反应的发展与机理研究进行了总结,着重对近十年来应用针铁矿／过氧化氢进行光催化氧化环境中有机物的研究进展及其环境矿物学意义作了概述和探讨。采用天然生物矿化的纳米针铁矿／过氧化氢以偶氮染料甲基橙为光解模型物进行了光催化氧化的初步研究,结果表明铁细菌形成的针铁矿具有降解生物难降解的有机污染物的能力。在甲基橙溶液初始浓度为30mg／L,铁细菌矿化的针铁矿用量2．5g／L,反应体系H2O2的初始浓度97mmol／L,pH值为6．92,15W紫外灯照射2h后,甲基橙浓度可降低33％。     

TiO2-蒙脱石光催化降解苯酚的实验研究

本文采用TiCl4在HCl中水解制备二氧化钛柱撑蒙脱石(TiO2-PILM)纳米材料，通过X射线衍射和BET N2比表面积分析对其进行表征，并研究其对苯酚在紫外光下的催化降解曲线，考察了苯酚的初始浓度、TiO2-PILM投放量、苯酚溶液pH值对光催化降解效果的影响。结果表明，制备的结构稳定的TiO2-PILM具有2．26nm大晶面间距和285．7m^2／g大比表面积。TiO2-PILM对苯酚有一定的光催化降解性，其过程是先吸附后降解。随苯酚初始浓度、TiO2-PILM投入量和苯酚溶液pH值的升高，TiO2-PILM对苯酚降解速率增大。在苯酚初始浓度为5mg／L、投样量为1g／L、pH为10时，TiO2-PILM对苯酚有较好的降解效果。     

Correlation of 13C12C and 34S32S secular variations

Statistical evaluation of 3056 δ¹³C measurements in carbonate rocks and fossils shows that they record a 2‰ ¹³C depletion from the late Proterozoic to the early Paleozoic, a 2.5‰ enrichment to the Permian, and a 1.5‰ depletion to the Cenozoic. These variations, not controlled primarily by facies or alteration phenomena, correlate negatively with the δ³⁴S sulfate secular trend, as confirmed by collation of 1083 δ³⁴S measurements. The correlation suggests that the biologically mediated redox fluxes of the C and S cycles have been approximately balanced through this long span of geological time, generally levelling available oxygen. Such a redox system is consistent with the controlling mechanism proposed by Garrels and Perry (1974). Consequently, the sedimentary reservoirs of C_organic as well as S_{bacteriological'}have varied through geological time.     

Surface study of HF- and HFH2SO4-treated feldspar using Auger electron spectroscopy

Auger electron spectroscopy has been used to study K-feldspar that has been reacted with both aqueous 10% HF and a 50% mixture of a 10% HF/0.1 N H₂SO₄ solution. In the feldspar/HF system, the resulting feldspar surface was shown to have been fluorinated; depth profiling, using argon ion sputtering, showed the fluorination to have occurred substantially into the mineral bulk. In the feldspar/ $\text{HF}\text{H}{}_2\text{SO}{}_4$ system, the resulting surface contained both fluorine and sulfur. The fluorination had again penetrated into the bulk, but the sulfur could be removed with mild argon ion sputtering. The $\text{Al}\text{F}$ signal ratio was much lower on the feldspar surface treated with the 10% HF/0.1 N H₂SO₄ solution than the feldspar surface treated with the weaker 10% HF acid solution.     

18O16O ratios in Luna 16 fines

Partial fluorination experiments developed on a 26 mg sample of Luna 16 fines show a big ¹⁸O enrichment in the first oxygen evolved similar to those observed by Epstein and Taylor on Apollo samples and probably related to the high solar wind content of this sample.     

Organic carbon 13C12C variations in estuarine sediments

The δC¹³ value for sedimentary organic carbon in four estuaries of the Gulf of Mexico increases with radial distance from the river mouth. Mass balance calculations indicate that terrestrial organic carbon is limited to sediments within a relatively short distance from the river mouth. This distance is a function of the discharge rate of the river. For the Mississippi River, terrestrial organic carbon is limited to sediments within 69 km of the mouth of Pass à Loutre and 61 km of South Pass. These data indicate that the low δC¹³ (< ?22%.) values reported for Pleistocene sediments in the Gulf of Mexico may be the result of factors in addition to the postulated large influx of terrestrial organic carbon.     

Further 40Ar39Ar evidence for the multi-collisional heating of the Kirin chondrite

Results of an ${}^{40}\text{Ar}{}^{39}\text{Ar}$Ar age spectrum obtained on a sample of the Kirin chondrite (K-5-13) show a similar character to previous published analyses of Kirin samples K-1 and K-2. The K-5-13 age spectrum shows clear evidence of having been substantially outgassed during a presumed collisional event about 0.5 Ga, ago, in good agreement with the estimate obtained from K-2, The differing amounts of ⁴⁰Ar loss registered by K-2 and K-5-13 during the 0.5 Ga event of about 60 and 50%, respectively, allows calculation of their vertical separation in the parent body at about 10cm.     

An algorithm for finding composition,molar volume and isochors of CO2-CH4 fluid inclusions from Th and Tfm (for Th < Tfm)

A modified Redlich-Kwong equation of state is used to calculate the solubility of CO₂ in methane at various temperatures and pressures. From the solubility of CO₂ in CH₄ at the triple point and at final melting (T_h < T_fm), and the molar volume of solid CO₂, the volume of solid at the triple point, and the molar volume of the inclusion can be calculated using a mass balance. The pressure at the melting point is calculated from the equation of state.The algorithm predicts composition, molar volume, pressure at final melting and the isochor pressure (for a given temperature of trapping) for CO₂-CH₄ fluid inclusions for the case T_h < T_fm, given T_h, T_fm and experimental data on P_h and d_co2 (solid) at T_h.     

Calculated phase equilibria in K2O-FeO-MgO-Al2O3-SiO2-H2O for sapphirine-quartz-bearing mineral assemblages

Sapphirine, coexisting with quartz, is an indicator mineral for ultrahigh‐temperature metamorphism in aluminous rock compositions. Here a new activity‐composition model for sapphirine is combined with the internally consistent thermodynamic dataset used by THERMOCALC, for calculations primarily in K₂O‐FeO‐MgO‐Al₂O₃‐SiO₂‐H₂O (KFMASH). A discrepancy between published experimentally derived FMAS grids and our calculations is understood with reference to H₂O. Published FMAS grids effectively represent constant a_H2O sections, thereby limiting their detailed use for the interpretation of mineral reaction textures in compositions with differing H₂O. For the calculated KFMASH univariant reaction grid, sapphirine + quartz assemblages occur at P–T in excess of 6–7 kbar and 1005 °C. Sapphirine compositions and composition ranges are consistent with natural examples. However, as many univariant equilibria are typically not ‘seen’ by a specific bulk composition, the univariant reaction grid may reveal little about the detailed topology of multi‐variant equilibria, and therefore is of limited use for interpreting the P–T evolution of mineral assemblages and reaction sequences. Calculated pseudosections, which quantify bulk composition and multi‐variant equilibria, predict experimentally determined KFMASH mineral assemblages with consistent topology, and also indicate that sapphirine stabilizes at increasingly higher pressure and temperature as X_Mg increases. Although coexisting sapphirine and quartz can occur in relatively iron‐rich rocks if the bulk chemistry is sufficiently aluminous, the P–T window of stability shrinks with decreasing X_Mg. An array of mineral assemblages and mineral reaction sequences from natural sapphirine + quartz and other rocks from Enderby Land, Antarctica, are reproducible with calculated pseudosections. That consistent phase diagram calculations involving sapphirine can be performed allows for a more thorough assessment of the metamorphic evolution of high‐temperature granulite facies terranes than was previously possible. The establishment of a a‐x model for sapphirine provides the basis for expansion to larger, more geologically realistic chemical systems (e.g. involving Fe³⁺).     

sol18O16O of Archean clastic metasedimentary rocks: a petrogenetic indicator for Archean gneisses?

The oxygen isotopic compositions of over 100 Archean clastic metasedimentary, felsic metavolcanic and gneissic rocks from selected areas within the Superior Province have been determined. δ¹⁸O values of low grade, immature clastic metasediments range from 8.0 to 13.3%. and hence are somewhat depleted in ¹⁸O relative to other clastic metasediments. The lower ¹⁸O content is attributed to the large proportion of unaltered rock fragments in the Archean metasediments. Felsic metavolcanics have a similar range of δ¹⁸O values (7.3 to 13.0%..δ¹⁸O values for the middle amphibolite facies Pakwash paragneiss (8.8–11.7%.) are higher than those determined for the amphibolite to granulite facies Twilight paragneiss (7.3–9.2%.). Archean orthogneisses such as the Clay Lake gneiss (7.0–9.0%.), the Cedar Lake gneiss (7.4–8.7%.) and the Footprint gneiss (5.9-8.8%.) have δ¹⁸O values similar to those of the Twilight paragneiss. Therefore, at least at metamorphic grades higher than middle amphibolite facies, Archean metasedimentary gneisses may have δ¹⁸O values that are indistinguishable from those of Archean orthogneisses, and hence are no longer isotopically recognizable as metasedimentary rocks.     

Calculated phase equilibria in K2O-FeO-MgO-Al2O3-SiO2-H2O for silica-undersaturated sapphirine-bearing mineral assemblages

Silica‐undersaturated, sapphirine‐bearing granulites occur in a large number of localities worldwide. Such rocks have historically been under‐utilized for estimating P–T evolution histories because of limited experimental work, and a consequent poor understanding of the topology and P–T location of silica‐undersaturated mineral equilibria. Here, a calculated P–T projection for sapphirine‐bearing, silica‐undersaturated metapelitic rock compositions is constructed using THERMOCALC for the FeO‐MgO‐Al₂O₃‐SiO₂ (FMAS) and KFMASH (+K₂O + H₂O) chemical systems, allowing quantitative analysis of silica‐undersaturated mineral assemblages. This study builds on that for KFMASH sapphirine + quartz equilibria [Kelsey et al. (2004) Journal of Metamorphic Geology, vol. 22, pp. 559–578]. FMAS equilibria are significantly displaced in P–T space from silicate melt‐bearing KFMASH equilibria. The large number of univariant silica‐undersaturated KFMASH equilibria result in a P–T projection that is topologically more complex than could be established on the basis of experiments and/or natural assemblages. Coexisting sapphirine and silicate melt (with or without corundum) occur down to c. 900 °C in KFMASH, some 100 °C lower than in silica‐saturated compositions, and from pressures of c.≤1 to ≥12 kbar. Mineral compositions and composition ranges for the calculated phases are consistent with natural examples. Bulk silica has a significant effect on the stability of sapphirine‐bearing assemblages at a given P–T, resulting in a wide variety of possible granulite facies assemblages in silica‐undersaturated metapelites. Calculated pseudosections are able to reproduce many naturally occurring silica‐undersaturated assemblages, either within a single assemblage field or as the product of a P–T trajectory crossing several fields. With an understanding of the importance of bulk composition on sapphirine stability and textural development, silica‐undersaturated assemblages may be utilized in a quantitative manner in the detailed metamorphic investigation of high‐grade terranes.