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渗透系数是可渗透反应墙(PRB)正常运行的关键参数之一,与PRB活性填充材料的选择密切相关。本试验采用常水头渗透系数测试法,首先选用斜发沸石、红辉沸石为作为PRB的活性介质材料,考察了沸石矿物的类型和粒径对PRB渗透系数的影响,试验结果显示,同一粒径的斜发沸石PRB和红辉沸石PRB渗透系数相差一个数量级;处于同一数量级渗透系数沸石PRB,斜发沸石的粒径大于红辉沸石的粒径。在此基础上,以膨润土作为掺和活性介质材料,讨论了渗透系数处于同一数量级沸石PRB,掺和比例对渗透系数的影响,结果表明,膨润土的掺和能导致沸石PRB渗透系数量级上的差异,与斜发沸石相比,红辉沸石更有利于实现沸石PRB系统渗透系数的可调性。 相似文献
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根据宣城沸石化学成分、可交换阳离子组成和热处理晶体结构演化,判断宣城沸石为富钙斜发沸石,具有低热稳定性的特点。通过正交实验研究了沸石CEC测定的最佳条件,并在此条件下对不同温度焙烧后沸石CEC进行了测定。结果表明,焙烧温度小于400℃时,沸石CEC变化很小;250℃时CEC稍微升高,达到最大值,这是由于焙烧导致体积密度降低、计算基准差异造成的;在250~400℃之间,焙烧样品CEC缓慢降低;焙烧温度大于400℃,沸石CEC迅速降低。热分析和X射线衍射分析结果证实,沸石晶体结构发生变化的起点在250℃,结构发生突变的温度为400℃。在高温焙烧中沸石CEC迅速降低是沸石晶体结构破坏所致。富钙沸石作为离子交换剂使用时,热加工温度不能超过400℃。 相似文献
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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。 相似文献
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The hydration state of Na- and K-exchanged clinoptilolite from Castle Creek (Idaho, U.S.A.) has been measured by a pressure
titration method to 300 °C and P
H2O<30 bars. The water content of clinoptilolite can be predicted as a function of water activity and temperature with the equation:
a
H2O = [exp[[−ΔH
h
∘/nRT] + [ΔS
h
∘/nR] − 1/nRT· [W1
X
h + W2
X
h
2]− ln(X
a/X
h)]]−1 where T is degrees in Kelvin, ΔH
h
∘ is the standard molal enthalpy of hydration, ΔS
h
∘ is the entropy of hydration, X
h and X
a are, respectively, the mole fractions of the hydrous and anhydrous components of the solid solution, W
1 and W
2 are interaction parameters, n is the maximum number of moles of H2O per formula unit (based on 12 oxygens), and R is the gas constant. This equation can be used to locate clinoptilolite-H2O isohydrons in a
H2O-T space below the liquid-vapor equilibrium curve of water. The standard molal Gibbs free energy of hydration is −47.62 ± 5.52 kJ/mol
H2O and −5.40 ± 2.71 kJ/mol H2O for the Na- and K-clinoptilolite, respectively. These standard-state thermodynamic properties of clinoptilolite hydration
are in good agreement with previous data at low H2O pressures. The experiments indicate that clinoptilolite progressively dehydrates with increasing temperature at pressures
along the liquid-vapor equilibrium curve. Kinetic data above 150 °C show that clinoptilolite dehydration and hydration reactions
are fast and reversible and that steady-state hydration states are attained in minutes.
Received: 19 June 1998 / Revision, accepted 14 December 1998 相似文献
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Steve J. Chipera Fraser Goff Cathy J. Goff Melissa Fittipaldo 《Journal of Volcanology and Geothermal Research》2008
Quantitative X-ray diffraction analysis of about 80 rhyolite and associated lacustrine rocks has characterized previously unrecognized zeolitic alteration throughout the Valles caldera resurgent dome. The alteration assemblage consists primarily of smectite–clinoptilolite–mordenite–silica, which replaces groundmass and fills voids, especially in the tuffs and lacustrine rocks. Original rock textures are routinely preserved. Mineralization typically extends to depths of only a few tens of meters and resembles shallow “caldera-type zeolitization” as defined by Utada et al. [Utada, M., Shimizu, M., Ito, T., Inoue, A., 1999. Alteration of caldera-forming rocks related to the Sanzugawa volcanotectonic depression, northeast Honshu, Japan — with special reference to “caldera-type zeolitization.” Resource Geol. Spec. Issue No. 20, 129–140]. Geology and 40Ar/39Ar dates limit the period of extensive zeolite growth to roughly the first 30 kyr after the current caldera formed (ca. 1.25 to 1.22 Ma). Zeolitic alteration was promoted by saturation of shallow rocks with alkaline lake water (a mixture of meteoric waters and degassed hydrothermal fluids) and by high thermal gradients caused by cooling of the underlying magma body and earliest post-caldera rhyolite eruptions. Zeolitic alteration of this type is not found in the later volcanic and lacustrine rocks of the caldera moat (≤ 0.8 Ma) suggesting that later lake waters were cooler and less alkaline. The shallow zeolitic alteration does not have characteristics resembling classic, alkaline lake zeolite deposits (no analcime, erionite, or chabazite) nor does it contain zeolites common in high-temperature hydrothermal systems (laumontite or wairakite). Although aerially extensive, the early zeolitic alteration does not form laterally continuous beds and are consequently, not of economic significance. 相似文献
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内蒙古多伦县沸石岩特征研究 总被引:6,自引:1,他引:5
本文首次报道内蒙古多伦县的白石头沟口和二等泉两个矿区的沸石岩特征。研究区沸石岩的矿物组合为斜发沸石、蒙脱石、长石、鳞石英、石英和少量的丝光沸石。沸石岩化学成分比较稳定,两个矿区沸石岩的SiO2/Al2O3比值均在5.6左右,属高硅型沸石岩;白石头沟口沸石岩w(K2O)>w(CaO)>w(Na2O);二等泉沸石岩w(CaO)>w(K2O)>w(Na2O),属钙-钾型或钾-钙型沸石岩。沸石岩平均吸铵量约为94×10-2mmol/g,阳离子选择交换性能表现为K+>Na+,Ca2+>Mg2+。多数沸石岩的热稳定性可稳定至700℃不破坏结构。酸碱度平均值为7.34~7.75。 相似文献