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11.
Ling Gao Ying Wang Yang Xu Shi Lu Zhou Ting Ting Zhuang Zheng Ying Wu Jian Hua Zhu 《洁净——土壤、空气、水》2008,36(3):270-278
A new effort to control the pollution caused by smoking by use of zeolite sieving the N‐nitrosamines in smoke is depicted and assessed in this paper, which is a first preliminary approach to demonstrate the performance characteristics of zeolite for the reduction of the concentration of N‐nitrosamines in the cigarette smoke. Smoking causes global pollution and is difficult to control because smoke is a complex system containing thousands of components. A new strategy is presented here for the reduction of the harmful effects of smoking through dispersion of zeolite into the tobacco rod of cigarettes to eliminate the N‐nitrosamines once they form in the smoke, and both in vitro and in vivo tests were employed to check the efficiency of this strategy. The impact of zeolite on the combustion of tobacco and the total toxicity of smoke are evaluated for the first time. Lower mutagenic activity and higher CHO cell livability were found for the test cigarette containing zeolite in comparison with the control, and no significant damage was detected in 30‐day animal experiments when exposed to the cigarette smoke. This confirms the feasibility of the new strategy and promotes the potential application of zeolite for protecting public health. 相似文献
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Adsorption of H2O, NH3 and C6H6 on H- and alkali metal-exchanged structures of mordenite and on corresponding cations on the smectite layer is investigated
by ab initio density-functional calculations. Proton or an alkali metal cation compensates one Al/Si framework substitution
and resides in the extra-framework position of zeolite or above flat smectite layer close to the Al/Si substitution. Pronounced
similarities between zeolite and smectite are observed in changes of the adsorption energies and location of the external
cation with changing character of the external cation. Calculated adsorption energies exhibit the following trend: E(NH3) > E(H2O) > E(C6H6). Because of looser contact with the framework, zeolitic cations are stronger adsorption centers and calculated adsorption
energies of zeolites are by ~20–30% larger than cations of smectites. The highest adsorption energy is calculated for H-exchanged
structures and down the group of alkali metal cations a decrease of the adsorption energy is observed. Deviations from the
smooth variation of the adsorption energy are caused by: (1) formation of strong hydrogen bonds in H-exchanged structures,
(2) adsorption induced migration of the external Li+ cation, and (3) steric hindrances of the flat C6H6 molecule adsorbed on the cation in the cage of zeolite. 相似文献
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Soil‐mix technology is effective for the construction of permeable reactive barriers (PRBs) for in situ groundwater treatment. The objective of this study was to perform initial experiments for the design of soil‐mix technology PRBs according to (i) sorption isotherm, (ii) reaction kinetics and (iii) mass balance of the contaminants. The four tested reactive systems were: (i) a granular zeolite (clinoptilolite–GZ), (ii) a granular organoclay (GO), (iii) a 1:1‐mixture GZ and model sandy clayey soil and (iv) a 1:1:1‐mixture of GZ, GO and model soil. The laboratory experiments consisted of batch tests (volume 900 mL and sorbent mass 18 g) with a multimetal solution of Pb, Cu, Zn, Cd and Ni. For the adsorption experiment, the initial concentrations ranged from 0.01 to 0.5 mM (2.5 to 30 mg/L). The maximum metal retention was measured in a batch test (300 mg/L for each metal, volume 900 mL, sorbent mass 90–4.5 g). The reactive material efficiency order was found to be GZ > GZ‐soil mix > GZ‐soil‐GO mix > GO. Langmuir isotherms modelled the adsorption, even in presence of a mixed cations solution. Adsorption was energetically favourable and spontaneous in all cases. Metals were removed according to the second order reaction kinetics; GZ and the 1:1‐mix were very similar. The maximum retention capacity was 0.1–0.2 mmol/g for Pb in the presence of clinoptilolite; for Cu, Zn, Cd and Ni, it was below 0.05 mmol/g for the four reactive systems. Mixing granular zeolite, organoclay and model soil increased the chemisorption. Providing that GZ is reactive enough for the specific conditions, GZ can be mixed to obtain the required sorption. Granular clinoptilolite addition to soil is recommended for PRBs for metal contaminated groundwater. 相似文献
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Based on the connectivity relations among tetrahedron sites and the NMR spectra, we propose an ordered distribution of aluminum
atoms in the framework of analcime with space groups of Pbcb and Pcaa. The symmetries of the ordered distributions are formally
the same as Pcca. These symmetries are much lower than those reported by others such as Ia3d, I41/acd, Ibca, and I2/a. The lowering of symmetry results apparently from the fact that aluminum atoms in the framework of analcime
were strictly discriminated from silicon atoms. Dependence of the populations of Si(nAl)s upon Al content was estimated from 29Si MAS NMR, and can be successfully simulated by the ordered distributions. In the simulation, a small number of defects in
the Al distribution were introduced into the ordered distribution mainly to adjust the deviation of Al content per unit cell
from the typical composition. Analysis of the powder X-ray diffraction patterns of analcime was carried out, which suggests
that the space groups proposed in the present work offer a better fit than the ones reported previously.
Received: 5 April 1997 / Revised, accepted: 12 March 1998 相似文献
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太平洋富稀土深海沉积物中稀土元素赋存载体研究 总被引：9，自引：1，他引：8
太平洋深海沉积物中富含稀土(含Y,简称REY),尤其是(含)沸石粘土,其主要由粘土组分、沸石、鱼牙骨、微结核及生物残渣等组成,目前对于该类稀土矿床中REY的赋存载体存在争议。本文在中、西太平洋选取两个富REY的沸石粘土样品利用地球化学和矿物学对稀土赋存状态进行定量研究。矿物微区成分表明,鱼牙骨主要成分为磷灰石,含有最高的REY含量,为2497×10~(- 6)~18623×10~(- 6),微结核和沸石颗粒含有较低的REY含量,分别为246×10~(- 6)~333×10~(- 6)和29.36×10~(- 6)~256×10~(- 6)。通过三种矿物相在沉积物63~250μm粒级组分中各自所占质量比例,计算得出磷灰石对REY的贡献率可达90%以上,说明此粒级中磷灰石为主要REY赋存载体,然而相对全岩总的REY含量,该粒级中磷灰石的贡献仍较小。通过对全岩和粉砂级组分(小于63μm)主微量地球化学分析和XRD矿物相分析表明,2个样品中REY主要存在于粉砂级组分中,其中的磷灰石对全岩REY的贡献最高均可达70%左右。另外通过对粘土组分(2μm)研究发现2个样品粘土组分的REY含量相似,分别为530×10~(- 6)和631×10~(- 6),粘土组分对全岩沉积物的REY贡献意义不大,对整个沉积物REY而言其贡献率仅为2%~5%左右。因此认为磷灰石为整个沸石粘土中REY主要赋存载体。 相似文献
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对改性沸石去除氨氮的条件及机理进行了实验探讨。结果表明 ,沸石经过活化剂处理后具有降低水中氨氮的作用。影响沸石去除氨氮的主要因素包括沸石与含氨氮溶液作用时间、沸石用量、溶液中氨氮浓度、沸石的粒度和溶液的温度等 ,探讨了沸石去除氨氮的机理 ,初步认为主要是由于离子交换作用和吸附作用共同完成的。 相似文献
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N. K. Moroz I. S. Afanassyev E. A. Paukshtis G. P. Valueva 《Physics and Chemistry of Minerals》2003,30(4):243-247
A new 1H NMR approach was applied to study the influence of recurring dehydration on the acidity of a natural Ca-rich zeolite clinoptilolite. It has been found that thermal cycling progressively increases the rate of the proton exchange between water molecules in the rehydrated state. The observed effect is interpreted as a result of the irreversible accumulation of specific structural defects represented by Brønsted acid sites: each dehydration at 720 K adds to the acid sites in an amount of the order of 10?3 per unit cell. The number of these defects, detected by NMR in hydrated mineral, is in reasonable agreement with their amount estimated for the dehydrated state with an IR-spectroscopy CO-probe method. A comparison of the results obtained for two distinct zeolite samples shows that the Ca2+ ions are of first importance in the dehydration-induced formation of the active acid sites. The barrier for the proton-transfer reaction between the acid sites and H2O molecules in hydrated clinoptilolite is found to be 46 kJ mol?1, which is not too different from the value of 54 kJ mol?1 reported recently for natural chabazite. 相似文献