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591.
592.
以热酸活化过的海泡石为吸附剂,研究其对亚甲基蓝、结晶紫和甲基绿3种染料的吸附动力学过程,并分析了浓度、温度等因素对海泡石吸附效果的影响。结果表明,温度的变化对吸附的影响较小,而染料溶液浓度的改变则会对吸附产生很大的影响,由此确定出较适合的反应条件。采用傅立叶红外光谱技术对吸附前后海泡石的结构进行了分析,发现亚甲基蓝由于分子体积较小可以进入海泡石内部通道,而大体积的结晶紫和甲基绿的吸附主要发生在海泡石外表面,且一价有机阳离子会在中性位置发生吸附,形成带电或中性复合物。 相似文献
593.
J. Alonso‐Azcrate M. Rodas L. Fernndez‐Díaz S.H. Bottrell J. R. Mas S. Lpez‐Andrs 《Geological Journal》2001,36(2):159-170
The low‐grade metasediments of the Cameros Basin, northern Spain, host a number of deposits of spectacular quality pyrite mineralization. These formed during regional metamorphism and the pyrite crystals exhibit a wide range of morphologies. On the basis of pyrite crystal habit, the deposits can be classified into two groups: Group I comprises deposits with cubic, elongated or platy crystals; Group II comprises deposits characterized by pyritohedra and cubo‐pyritohedra with striated faces, along with blocky crystals and fine‐grained aggregates. Group I deposits are formed in sequences dominated by meandriform fluviatile sediments, while Group II is hosted by deltaic plain and lacustrine metasediments. Temperature differences between deposits and As content are possible causes of the different pyrite morphologies in the deposits, but no significant variation exists between the two groups for either factor. Comparison with experimentally grown pyrite crystals suggests that Group I deposits have morphologies indicative of lower degrees of pyrite supersaturation than pyrite crystals in Group II deposits. The sedimentary facies hosting Group II deposits provides a greater availability of sedimentary sulphur (pyrite and sulphates). Moreover, reactions involving sulphate during metamorphism may have modified fluid chemistry, which would also act to produce higher degrees of pyrite saturation in fluids derived from the sulphate‐rich deltaic plain and lacustrine metasediments hosting the Group II deposits. This hypothesis is confirmed by sulphur isotope data on the pyrites, which show a larger component of34S‐enriched sulphate‐derived sulphur in these deposits. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
594.
以安徽省含山县天然硬石膏(Ⅱ型无水石膏)为主要原料,研究了5种化学激发剂(K2SO4、FeSO4.7H2O、CaO、Na2C2O4、煅烧明矾)对天然硬石膏水化作用的影响。采用重量法测定了不同掺量时硬石膏的水化率,用X射线粉末衍射和扫描电子显微镜分析了硬石膏水化产物组成及其微观结构,探讨了天然硬石膏水化活性的激发机理。研究结果表明,激发剂可以明显提高硬石膏的水化率,且水化硬化体的微观结构也有显著改善;掺加5.0%的煅烧明矾时,硬石膏的水化效果最好,28d后,水化率可达74.32%。 相似文献
595.
Partial melting has been shown to be an important mechanism for intracrustal differentiation and granite petrogenesis. However, a series of compositional differences between granitic melt from experiments and natural granites indicate that the processes of crustal differentiation are complex. To shed light on factors that control the processes of crustal differentiation, and then the compositions of granitic magma, a combined study of petrology and geochemistry was carried out for granites (in the forms of granitic veins and parautochthonous granite) from a granulite terrane in the Tongbai orogen, China. These granites are characterized by high SiO2 (>72 wt%) and low FeO and MgO (<4 wt%) with low Na2O/K2O ratios (<0.7). Minerals in these granites show variable microstructures and compositions. Phase equilibrium modelling using P–T pseudosections shows that neither anatectic melts nor fractionated melts match the compositions of the target granites, challenging the conventional paradigm that granites are the crystallized product of pure granitic melts. Based on the microstructural features of minerals in the granites, and a comparison of their compositions with crystallized minerals from anatectic melts and minerals in granulites, the minerals in these granitoids are considered to have three origins. The first is entrained garnets, which show comparable compositions with those in host granulites. The second is early crystallized mineral from melts, which include large plagioclase and K-feldspar (with high Ca contents) crystals as well as a part of biotite whose compositions can be reproduced by crystallization of the anatectic melts. The compositions of other minerals such as small grained plagioclase, K-feldspar and anorthoclase in the granites with low Ca contents are not well reconstructed, so they are considered as the third origin of crystallized products of fractionated melts. The results of mass balance calculation show that the compositions of these granites can be produced by mixing between different proportions of crystallized minerals and fractionated melts with variable amounts of entrained minerals. However, the calculated modal proportions of different crystallized minerals (plagioclase, K-feldspar, biotite and quartz) in the granites are significantly different from those predicted by melt crystallization modelling. Specifically, some rocks have lower modes of biotite and plagioclase, whereas others show lower K-feldspar modes than those produced by melt crystallization. This indicates that the crystallized minerals would be differentially separated from the primary magmas to form the evolved magmas that produce these granites. Therefore, the crystal entrainment and differential melt-crystal separation make important contributions to the composition of the target granites. Compared with leucogranites worldwide, the target granites show comparable compositions. As such, the leucogranites may form through the crystal fractionation of primary granitic magmas at different extents in addition to variable degrees of partial melting. 相似文献
596.
597.
根据雷达探测的云回波雷达反射率因子和多普勒速度,利用两种独立的双频反演算法,估算了云微物理参数。利用离散偶极子近似(Discrete Dipole Approximation,DDA)计算了云滴后向散射截面和衰减截面,根据模拟数据实验了三种频段组合的反演结果,探讨算法对滴谱参数、粒子形状的敏感性,比较两种方法反演水云和冰云的优劣。结果表明:双频比(Dual-Frequency Ratio,DFR)和多普勒速度差(Doppler Difference of Velocity,DDV)在水云中都可独立推导中值直径(D_(0)),但在高频波段,基于DFR的算法对雨、云水和水汽的衰减非常敏感,而基于DDV的方法受衰减的影响较小。鉴于高频波段衰减完全订正的困难性,水云的DDV反演方法比DFR更直接准确。对于冰云,DFR的技术相较于DDV的方法具有明显的优势,因为两频段处的DFR在冰云中的动态范围更大,而DDV的动态范围相对于系统和测量误差较小。 相似文献