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1.
The sorption of Pu(VI) onto TiO(2) was studied as a function of pH (2-10) and Pu concentration (10(-8)-10(-4) M) under an N(2) atmosphere, in 0.016 and 0.1 M NaClO(4). A batch-wise method was used, in which pH was measured in separate experimental containers after removal of a sample to determine the amount of Pu that had been sorbed. As Pu is radioactive, it was used as a tracer and measured by liquid scintillation counting. No ionic strength dependence was discerned, which was taken as an indication of inner sphere complex formation. In the interval of pH 2-7 the system could be described by the formation of two positively charged surface complexes using a 1-pK Stern model. Sorption of the plutonyl ion (PuO(2)(2+)) and the first hydrolysis species (PuO(2)(OH)(+)) was estimated using FITEQL to logK(1)=6.9 and logK(2)=1.4, respectively. 相似文献
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PAN DuoQiang FAN QiaoHui DING KeFei LI Ping LU Yan YU Tao XU Jiang & WU WangSuo Radiochemistry Laboratory School of Nuclear Science Technology Lanzhou University Lanzhou China 《中国科学B辑(英文版)》2011,(7)
The surface properties of intrinsic and activated attapulgite were studied using potentiometric titration.The sorption mechanisms of Th(IV) on intrinsic and activated attapulgite were investigated by employing surface complexation model and FITEQL 3.2 code.The results indicated that the sorption sites of intrinsic attapulgite involved in the sorption process were main ion exchange site(≡ XNa/K),strong site(≡ SsOH) and weak site(≡ SwOH),while only strong site(≡ SsOH) and weak site(≡ SwOH) were predominant fo... 相似文献
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Dr. Run Long 《Chemphyschem》2013,14(3):579-582
We investigated the interfacial electronic structure and charge transfer properties of graphene quantum dot (GQD) physisorption and chemisorption on the TiO2 (110) surface from density functional theory calculations. The simulations show that a slight charge transfer occurs in physisorption case while a significant charge transfer takes place in chemisorption configuration. We present a detailed comparison of the similarities and differences between the electronic structures. The similarities originate from the positive work function difference in both the physisorption and chemisorption configurations, which is able to drive electron transfer from GQD into TiO2, leading to charge separation across the GQD–TiO2 interface. The differences stem from the interaction between the GQD and TiO2 substrate. For example, GQD bounds to TiO2 surface through van der Waals interactions in the case of physisorption. In the chemisorption configuration, however, there exists strong covalent bonding between them. This leads to much more efficient charge separation for chemisorption than for physisorption. Furthermore, the GQD–TiO2 composites show large band‐gap narrowing that could extend the optical absorption edge into the visible‐light region. This should imply that chemisorbed GQDs produce a composite with better photocatalytic and photovoltaic performance than composites formed through physisorption. 相似文献
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Wen‐Fei Huang Hsin‐Tsung Chen M.C. Lin 《International journal of quantum chemistry》2013,113(12):1696-1708
The adsorption and reactions of the SiHx (x = 0–4) on Titanium dioxide (TiO2) anatase (101) and rutile (110) surfaces have been studied by using periodic density functional theory in conjunction with the projected augmented wave approach. It is found that SiHx (x = 0–4) can form the monodentate, bidentate, or tridentate adsorbates, depending on the value of x. H coadsorption is found to reduce the stability of SiHx adsorption. Hydrogen migration on the TiO2 surfaces is also discussed for elucidation of the SiHx decomposition mechanism. Comparing adsorption energies, energy barriers, and potential energy profiles on the two TiO2 surfaces, the SiHx decomposition can occur more readily on the rutile (110) surface than on the anatase (101) surface. The results may be used for kinetic simulation of Si thin‐film deposition and quantum dot preparation on titania by chemical vapor deposition (CVD), plasma enhanced CVD, or catalytically enhanced CVD. © 2013 Wiley Periodicals, Inc. 相似文献
6.
Ralf Tonner Dr. 《Chemphyschem》2010,11(5):1053-1061
The optimal adsorption modes for the amino acids glycine and proline on the ideal TiO2(110) surface are investigated by using density functional theory (PBE) applying periodic boundary conditions. Binding modes with anionic acid moieties bridging two titanium atoms after transferring a proton to the surface are the most stable configurations for both molecules investigated—similar to previous results for carboxylic acids. In contrast to the latter compounds, amino acids can form hydrogen bonds via the amino group towards the surface‐bound proton; this provides an additional stabilisation of 15–20 kJ mol?1. Zwitterionic binding modes are less stable (by 10–20 kJ mol?1) and are less important for proline. Neutral modes are energetically even less favourable. Calculations of vibrational frequencies and core‐level shifts complement the adsorption study and provide guidance for future experimental investigations. Control of the computational parameters is crucial for the derivation of accurate results. The layout and thickness of the slab model used are also shown to be decisive factors. Calculations with a different GGA‐functional (PW91) provide very similar relative energies, although the absolute energies change by about 20 kJ mol?1. Results derived with the hybrid functional PBE0 show an even greater stabilisation of the anionic binding modes with respect to the zwitterionic modes. A previously observed discrepancy between experimental and theoretical results for glycine could be solved, although the experimentally proposed free rotation of the C? C bond could not be reproduced. 相似文献
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Summary The sorption of Th(IV) onto TiO2 was studied by the batch technique as a function of pH and ionic strength at moderate concentration (10-4-10-5 mol/l) and in the presence and absence of phosphate. It was found that the sorption rate of Th(IV) was relatively slow, the
sorption percent was abruptly increased from pH 2 to 4, and the sorption was decreased with increasing ionic strength as a
whole. In the concentration range of Th(IV) from trace concentration to 1.4 . 10-4 mol/l and in the absence of phosphate, the sorption isotherms were roughly fitted the Freundlich equation at different ionic
strengths and approximately constant pH. These sorption characteristics of Th(IV) onto TiO2 were compared with those of uranyl on the same sorbent. In addition, the positive effect of phosphate on the sorption of
Th(IV) onto TiO2 was demonstrated obviously and can be attributed to strong surface binding of phosphate, and the subsequent formation of
ternary surface complexes of Th(IV). The difference between the sorption characteristics of Th(IV) ions and uranyl ions onto
TiO2 is discussed. 相似文献
8.
The
aim of our research was to prepare yellow pigments based on structure of pseudobrookite
Fe2TiO5. Part of Fe was substituted
with Li and Ti from Fe2TiO5
to Li0.05Fe0.07Ti2.44O5.
Synthesis and pigmentary-application properties in the Li2O–Fe2O3–TiO2 system were studied for 800 and 900°C using classical ceramic
method of preparation. The main attention was aimed to usage of four different
sources of titanium compounds as raw materials. We studied the influence of
different sources of titanium compounds on the structural and the colour properties
of the prepared pigments. The thermal analysis was used for characterization
of titanium compounds and determination of their thermal stability. 相似文献
9.
Ahmed R. Elsalamouny Osman A. Desouky Saad A. Mohamed Ahmed A. Galhoum 《Journal of Dispersion Science and Technology》2017,38(6):860-865
Treatment of aqueous solution contaminated by uranium and thorium using a new Mannich type resin was studied. Different instrumental techniques such as elemental analysis, FTIR, and thermogravimetric analysis were employed for full characterization of the synthetic resin. Adsorption behavior was studied by batch experiments to determine the optimum conditions for U(VI) and Th(IV) ion removal. The adsorption studies showed the best fit with the second order rate equation and Langmuir model. The adsorption process is endothermic, spontaneous, and of increased disorder. The regeneration of sorbent was carried out using diluted HCl and the reuse of sorbent remains appreciable. 相似文献
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Titanium dioxide (TiO2) thin films have been deposited on silicon and glass substrates by the sol-gel process using titanium iso-propoxide [Ti(O-i-C3H7)4]. The bond configuration of the TiO2 thin films was analyzed by using FTIR in the wavenumber range from 400 to 4000 cm–1. The spectral transmittance of as-deposited TiO2 films deposited on fused silica glass was measured in the wavelength range from 200 to 900 nm. X-ray diffraction measurements were performed to determine the crystallinity of the TiO2 films. As-deposited films were amorphous. As the film was annealed at higher temperature, the structure was transformed from amorphous to the anatase crystalline state. The chemical composition of the deposited film was investigated using X-ray photoelectron spectroscopy (XPS). The films are essentially stoichiometric with carbon as the dominant impurity on the surface. Raman spectra show the characteristic of TiO2 anatase phase. The electrical properties of the TiO2 films were measured using capacitance-voltage (C-V) and current-voltage techniques. From C-V measurements, the dielectric constants were calculated to be approximately 26 for the as-deposited films and 75–82 for films annealed at 700°C in different atmosphere. For the as-deposited samples, the breakdown voltage was 2.7 MV/cm, and for an electric field of 1 MV/cm, the leakage current was 5 × 10–5 A/cm2 and the resistivity was 2.2 × 1010 -cm. 相似文献
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Qingshan Zhang 《Journal of Dispersion Science and Technology》2013,34(10):1358-1361
Titanium dioxide (TiO2) powders were synthesized by the hydrothermal method. The TiO2 powders were composed of nanorods with dimensions of 10–18 nm and 60–180 nm in diameter and length, respectively. The in vitro bioactivity of the TiO2 powders was examined by evaluation of hydroxyapatite (HAp) formation ability in simulated body fluid (SBF). The results showed that TiO2 nanorods induced the formation of nanocrystalline HAp after soaking in SBF after 1 day rapidly. Our study indicates that TiO2 nanorods are bioactive and might be used for preparation of new biomaterials. 相似文献
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K. W. Busch M. A. Busch S. Gopalakrishnan E. Chibowski 《Colloid and polymer science》1995,273(12):1186-1192
Potentiometric titrations of TiO2 (anatase) suspensions in solutions of 10–2, 10–3, and 10–4 M NaCl prior to treatment with a radiofrequency (RF) electric field gave values of pHpzc and pHiep of 5.75±0.1 and 5.85±0.1, respectively, within the range of literature values. Surface charge plots versus pH for untreated samples gave curves with a common intersection point, indicating that NaCl acts as an indifferent electrolyte. Identical suspensions of anatase were then exposed for 30 min to an RF electric field with a peak-to-peak, no-load amplitude of 34V and a frequency of 44 MHz. Portions of the treated suspension were titrated after different time periods following removal of the field (2, 15, 30, and 45 min). At 2 min, the pHpzc had shifted to 6.50±0.1, and at 15, 30 and 45 min, the curves for the three NaCl concentrations were found to lack a common intersection point, an effect which became more pronounced with time. It is proposed that RF treatment results in the formation of a porous gel layer of hydrous titanium dioxide on the surface of the anatase particles that subsequently undergoes a slow ion-exchange reaction involving ions of the supporting electrolyte. 相似文献
16.
用分子轨道理论研究NO气体在TiO2表面吸附 总被引:4,自引:0,他引:4
根据一氧化氮(NO)气体在二氧化钛(TiO)表面吸附和脱附的实验结果,揭示了气体脱附量的变化规律.利用MOPAC和GAUSSIAN分子轨道理论计算了在TiO2(110)表面上吸附NO分子的原子簇模型,电荷分布以及原子簇的能级,推断了NO在TiO(110)表面吸附的稳定性. 相似文献
17.
The energetic and electronic properties of N/V‐doped and N‐V‐codoped anatase TiO2 (101) surfaces are investigated by first‐principles calculations, with the aim to elucidate the relationship between the electronic structure and the photocatalytic performance of N‐V‐codoped TiO2. Several substitutional and interstitial configurations for the N and/or V impurities in the bulk phase and on the surface are studied, and the relative stability of different doping configurations is compared by the impurity formation energy. Systematic calculations reveal that N and V impurities can be encapsulated by TiO2 to form stable structures as a result of strong N‐V interactions both in the bulk and the surface model. Through analyzing and comparing the electronic structures of different doping systems, the synergistic doping effects are discussed in detail. Based on these discussions, we suggest that NOVTi codoping cannot only narrow the band gap of anatase TiO2, but also forms impurity states, which are propitious for the separation of photoexcited electron–hole pairs. In the case of NOVTi‐codoped TiO2 (101) surfaces, this phenomenon is especially prominent. Finally, a feasible synthesis route for NOVTi codoping into anatase TiO2 is proposed. 相似文献
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5,10,15,20-四(2-噻吩基)金属卟啉修饰TiO2光催化剂的制备及光催化性能 总被引:1,自引:0,他引:1
合成了5,10,15,20-四(2-噻吩基)卟啉(H2TTP)及它的钴铜锌三种金属卟啉, 并用上述三种金属卟啉分别敏化锐钛矿型的二氧化钛, 制备了CoTTP-TiO2, ZnTTP-TiO2, CuTTP-TiO2三种光催化剂, 对这三种光催化剂进行了扫描电镜(SEM)、X射线光电子能谱(XPS)、紫外-可见漫反射光谱(UV-vis)、红外光谱(IR)的表征. 在300 W汞灯和400 W金卤灯照射下, 制备的光催化剂对4-硝基苯酚溶液的降解表现出比未修饰二氧化钛高的催化效率, 光催化降解反应符合反应一级动力学方程. 相似文献
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介孔二氧化钛微球的合成与表征 总被引:1,自引:0,他引:1
以非离子型表面活性剂TO8为模板剂,采用溶胶凝胶-表面活性剂法合成了介孔TiO2微球.运用SEM,TG—DTA,XRD,BET,UV等测试手段对其进行表征并探讨了TO8的加入量和不同热处理方式对样品形貌、结构的影响.实验表明TiO2微球呈单分散性,球径约800nm;介孔结构,孔径约3.5nm且分布较窄.TiO2微球为单一锐钛矿相,在190~380nm范围内有强紫外吸收.热处理时采取分步焙烧、控制升温速率和高温焙烧时间,可获得比表面较大的介孔TiO2微球. 相似文献