邻菲啰啉与铬的极谱行为的研究及应用     

郝恩坤  冯虎平  董学军 《岩矿测试》1993,(1)

在氨性介质中,邻菲啰啉与Cr(Ⅵ)有一峰电流较大的催化波,Cr(Ⅵ)浓度在0.006～0.16μg/ml范围内与峰电流呈线性关系,检测限为7.7×10~(-8)mol/L,该法可用于矿石和水样中Cr的测定。  相似文献   

微波诱导等离子体原子发射光谱法测定铍铬钼钒锆锗的研究   总被引：1，自引：0，他引：1  

张晓惠  侯明轶 《岩矿测试》1992,11(3):221-224

研究了用微波诱导等离子体原子发射光谱法(MIP-AES)测定Be、Cr、Mo、V、Zr和Ge。确定了最佳实验条件,其检出限分别为:0.038,0.030,0.015,0.030,0.024和0.11μg/ml。对实际样品进行了测定,结果令人满意。  相似文献   

Some aspects of geochemistry of pyrophyllite and diaspore deposits of Bundelkhand complex     

Rajendra P. Sharma 《Journal of Earth System Science》1980,89(1):1-15

Pyrophyllite and diaspore contain significantly enriched amounts of loss mobile elements like Ti and Cr by a factor of about 3 and Zr by a factor of about 2 as compared to Bundelkhand rocks and granites. This pattern suggests a bauxiticlaterite type of origin for pyrophyllite and diaspore occurrences in the Bundelkhand complex. This feature is comparable with the laterites of Kot area in western India. Phase boundaries of kaolinite and diaspore as a function of pH, pSi, and pA1 suggest that these minerals have formed in a very low dissolved Si (1 ppm) environment. Incongruent and congruent dissolution of kaolinite seem to be responsible for depletion of Si and A1 during lateritisation. This fact is supported by the balance calculations carried out with Ti as an index element.  相似文献   

Crystal field and covalency of octahedral chromium in natural ^[8](Mg_1?xCa_x) ₃^[6] (Al_0.67Cr_0.33)₂Si₃O₁₂ garnets from upper mantle rocks     

Alexej N. Platonov  Klaus Langer  Stanislav S. Matsyuk 《Physics and Chemistry of Minerals》2008,35(6):331-337

In the course of a thorough study of the influences of the second coordination sphere on the crystal field parameters of the 3d ^N -ions and the character of 3d ^N –O bonds in oxygen based minerals, 19 natural Cr³⁺-bearing (Mg,Ca)-garnets from upper mantle rocks were analysed and studied by electronic absorption spectroscopy, EAS. The garnets had compositions with populations of the ^[8] X-sites by 0.881 ± 0.053 (Ca + Mg) and changing Ca-fractions in the range 0.020 ≤ w _Ca[8] ≤ 0.745, while the ^[6] Y-site fraction was constant with x _Cr³⁺ _[6] = 0.335 ± 0.023. The garnets had colours from deeply violet-red for low Ca-contents (up to x _Ca = 0.28), grey with 0.28 ≤ x _Ca ≤ 0.4 and green with 0.4 ≤ x _Ca. The crystal field parameter of octahedral Cr³⁺ 10Dq decreases strongly on increasing Ca-fraction from 17,850 cm⁻¹ at x _Ca[8] = 0.020 to 16,580 cm⁻¹ at x _Ca[8] = 0.745. The data could be fit with two model which do statistically not differ: (1) two linear functions with a discontinuity close to x _Ca[8] ≈ 0.3, (2) one continuous second order function, The behaviour of the crystal field parameter 10Dq and band widths on changing Ca-contents favour the first model, which is interpreted tentatively by different influences of Ca in the structure above and below x _Ca[8] ≈ 0.3. The covalency of the Cr–O bond as reflected in the behaviour of the nephelauxetic ratio decreases on increasing Ca-contents.  相似文献   

Adsorption Behavior of Cr(VI) on Al-Fe Cointercalated Bentonite     

Chun-Yan Cao  Yan Yin  Li-Yu Du 《Marine Georesources & Geotechnology》2016,34(8):764-769

An efficient Al-Fe cointercalated bentonite composite material (Al-Fe/Bent) which is capable of removing hexavalent chromium [Cr(VI)] from aqueous solutions was prepared. The batch experiment studies were conducted to evaluate the adsorption performance of Cr(VI) contained in aqueous solution. The XRD results showed the spacing of layers of bentonite was increased due to the aluminum and iron polycation intercalated into the layer of bentonite. The removal rate of Cr(VI) from the aqueous solution could be up 87.4% under the condition of the dosage of Al-Fe/Bent 8 g/L, pH 4, and a contact time of 60 min. The equilibrium data fitted well to the Freundlich model. The adsorption process could be well described by the pseudosecond order kinetic model.  相似文献   

Assessing the effectiveness of nanoscale zero-valent iron particles produced by green tea for Cr(VI)-contaminated groundwater remediation          下载免费PDF全文

Hui Li  Zhan-tao Han  Qiang Deng  Chun-xiao Ma  Xiang-ke Kong 《地下水科学与工程》2023,11(1):55-67

Nanoscale zero-valent iron particles (NZVI) produced by using green tea (GT) extract as a reductant can remove Cr(VI) from water effectively, which can be utilized in groundwater remediation. In order to define the reaction mechanism and removal effect in the aquifer, in this study, GT-NZVI particles were prepared and measured by some characterization methods to define their surface performance, and then batch and one-dimensional experiments were carried out to reveal the reaction properties of GT-NZVI and Cr(VI) in groundwater. The results showed that the prepared GT-NZVI particles were regular spherical with a diameter of 10–20 nm, which could disperse in water stably. The main component of GT-NZVI was α-Fe with superficial polyphenols as a stabilizer. GT-NZVI suspension had good ability to reduce the Cr(VI) to Cr(III) in water. When the concentration of GT-NZVI was 1 g/L, the removal efficiency of Cr(VI) with an initial concentration of 100 mg/L reached 92.8% in 1 h reaction. In column tests, GT-NZVI passed through the natural sand column successfully with an average outflow percentage of 71.2%. The simulated in-situ reaction zone (IRZ) with GT-NZVI was used to remediate Cr(VI) contaminated groundwater. The outflow concentration of Cr(VI) kept in 0.14–0.32 mg/L corresponding to the outflow rate below 0.32% within 15 days, and the removal efficiency of Cr(VI) by IRZ with GT-NZVI decreased with the increase of aquifer medium particle size, groundwater flow rate and ionic strength. Most of Cr(III) as reduzate was adsorbed or immobilized on the surface or in the lattice of GT-NZVI, which indicated effective immobilization for chromium.  相似文献   

The Formation and Evolution of Uvarovite in UHP Serpentinite and Rodingite and its Constraints on Chromium Mobility in the Oceanic Subduction Zone     

ZHANG Cong  SHEN Tingting  ZHANG Lifei  LIN Congcong  ZHANG Zhongwei  Qin Xueqing  HU Han  QIU Tian  XIANG Zhenqun  ZHANG Jianxin 《《地质学报》英文版》2021,95(5):1456-1471

The uvarovite-andradite and uvarovite-andradite-grossular solid-solution series are rare in nature. The discovery of uvarovite-andradite in serpentinite and rodingite from the ultra-high pressure (UHP) metamorphic belt in southwestern Tianshan provided an opportunity to investigate its behavior in the subduction zone. Uvarovite (defined as chromium-garnet) from serpentinite is homogeneous in a single grain, covering compositions in the uvarovite-andradite solid solution series of Adr58–66Uv33–41, with few grossular components. Uvarovite from rodingites contain various Cr2O3 contents (1.7–17.9 wt%) and mineral compositions being in the range of Adr21–31Uv41–50Grs22–37, Adr52–90Uv5–25Grs0–21 and Adr19–67Uv3–63Grs13–42. Discontinuous chemical variation of uvarovite from core to rim indicates that uvarovite formed by consuming andradite and chromite, which could provide Ca, Cr, Al and Fe. Raman signals of water were identified for uvarovite from both serpentinite and rodingite, with high water content in uvarovite from serpentinite. The high pressure mineral assemblage, as well as the association with perovskite, indicated that the studied uvarovite from serpentinite and rodingite was formed through high pressure metamorphism, during the subduction zone serpentinization and rodingitization. High alkaline and highly reduced fluids released from serpentinization or rodingitization in the oceanic subduction zone promote the mobility of chromium and enable its long-distance migration.  相似文献   

膨润土负载纳米铁镍同步修复地下水中三氯乙烯和六价铬复合污染     

邓日欣  罗伟嘉  韩奕彤  李志雄  陈家玮 《岩矿测试》2018,37(5):541-548

纳米零价铁原位注射修复地下水污染是近年发展的新技术,以往研究多侧重于单一目标污染物的去除效果及作用机理,但是地下水多种污染物共存问题不容忽视。本文针对典型污染物三氯乙烯TCE和六价铬Cr(Ⅵ),运用合成的活性高、稳定性强的膨润土负载纳米铁镍(B-Fe/Ni)开展修复实验,研究B-Fe/Ni对TCE和Cr(Ⅵ)共存复合污染的修复效果及其作用机制。通过一步法合成B-Fe/Ni,对TCE和不同浓度Cr(Ⅵ)混合污染的去除进行试验研究,对反应前后的样品B-Fe/Ni进行表征,并跟踪反应过程中TCE和Cr(Ⅵ)的浓度变化。结果表明:B-Fe/Ni同步去除水中TCE和Cr(Ⅵ)快速高效,50 mg/L Cr(Ⅵ)在2 h内能被B-Fe/Ni (1 g/L)完全去除而不受共存TCE(0. 1 mmol/L)的影响,然而TCE降解速率会随共存Cr(Ⅵ)的浓度(0、10、30、50 mg/L)增大而降低。经透射电镜-电子能谱及X射线光电子能谱表征验证,这是由于B-Fe/Ni与Cr(Ⅵ)快速反应,生成部分Fe-Cr共沉淀会覆盖B-Fe/Ni表面的活性位点,抑制了TCE的降解,但通过分析TCE降解产物可知,B-Fe/Ni同样能对TCE完全脱氯。因此,B-Fe/Ni适用于地下水复合污染修复,实际应用时需考虑多种污染物共存的相互影响,选择适宜试剂用量和注射方式,这对纳米零价铁修复技术的发展具有重要理论意义和应用参考价值。  相似文献   

地下水中稳定铬同位素的生物地球化学作用   总被引：2，自引：0，他引：2  

徐芬  马腾  Andre Ellis  刘存富  高永娟  李理 《地学前缘》2012,19(4):183-193

铬是地下水中常见的一种变价重金属污染物,在自然界中广泛分布且应用广泛。将Cr(Ⅵ)还原为Cr(Ⅲ)是地下水铬污染防治中的主要策略。在Cr(Ⅵ)的非生物还原过程中存在铬同位素分馏现象,通过地下水中铬同位素组成的变化情况可以定量地指示Cr(Ⅵ)的还原程度和速率。这被认为是一个重要发现,在地下水铬污染防治中有着广阔的应用前景。文中对铬与铬的来源、地下水中铬同位素的测定方法、铬同位素的生物地球化学作用、铬同位素在地下水污染防治中的应用等进行了系统综述。研究认为：微生物广泛参与地下水中铬的氧化与还原作用,并有可能产生显著的铬同位素分馏。地下水中被还原的Cr(Ⅵ)在微生物作用下有可能被活化,用非生物还原条件下的铬同位素分馏规律指示地下水中Cr(Ⅵ)还原程度可能会产生较大的误差。开展地下水中铬同位素的生物地球化学作用研究,特别是生物氧化Cr(Ⅲ)过程中的铬同位素分馏规律研究,对于更全面地认识铬同位素的指示作用具有重要意义。  相似文献   

含铬蒙脱石中铬离子占位位置研究          下载免费PDF全文

努尔太·麦地娜  图尔荪·麦尔旦  蔡元峰  王洪涛  潘宇观 《高校地质学报》2014,20(4):558

采用提纯后的蒙脱石在不同浓度硫酸铬溶液中进行交换吸附制备了含铬蒙脱石,并利用包括粉末X射线衍射术 （XRD）、电子自旋共振谱术（ESR） 和傅里叶变换红外吸收光谱术（FTIR） 等分析测试手段对铬在蒙脱石中的吸附位置进 行了探索研究。研究结果显示铬离子不仅置换了层间域中的Ca2+,K+和Na+等,而且置换了位于八面体位的Mn2+ 和少量 Al3+,并较大量的进入硅氧四面体的六边形孔洞、甚至有可能置换极少量的四面体位的Al3+和Fe3+等。此外,根据X射线衍 射分析可知,在0.2 mol/L硫酸铬溶液中充分交换吸附后的蒙脱石存在两层水型和单层水型两种含铬蒙脱石,其水合阳离子 分别为[Cr(H2O)6]3+和[Cr(H2O)3O3]3+,当吸附量增大至一定程度后水合铬离子借助TOT结构片的硅氧四面体的底氧形成配位多 面体。  相似文献