排序方式: 共有39条查询结果,搜索用时 15 毫秒
1.
Ayoko Godwin Adefikayo Iyun Johnson Femi El-Idris Ibrahim Faskari 《Transition Metal Chemistry》1992,17(1):46-49
Transition Metal Chemistry - The kinetics of the silver(I) ion catalysed reduction of peroxodisulphate by 12-tungstocobaltate(II) anion in aqueous HC1O4 has been studied. Although the reaction in... 相似文献
2.
G. Adefikayo Ayoko 《Transition Metal Chemistry》1990,15(6):421-424
Summary The kinetics of oxidation of hypophosphorus and arsenious acids by 12-tungstocobaltate(III) anion have been studied in aqueous hydrochloric acid at constant ionic strength (I=2.0 M NaCl). The reactions obey the second-order rate law d[oxidant]/dt=2k [oxidant] [reductant]. Variation of [H+] in the range 0.10–1.50 M has no effect on the rates. Possible mechanistic interpretations of these observations are suggested. 相似文献
3.
4.
Application of organoclays for the adsorption of recalcitrant organic molecules from aqueous media 总被引:2,自引:0,他引:2
Water purification is imperative for the welfare of a healthy population. Water is widely contaminated by recalcitrant organic chemicals such a pesticides, herbicides and hormones. One inexpensive method for purifying water from these types of molecules is through adsorption. One suite of materials for this adsorption is based upon organoclays. This paper reviews the adsorption of organics on organoclays. 相似文献
5.
Sara J. Palmer Ray L. Frost Godwin Ayoko Tai Nguyen 《Journal of Raman spectroscopy : JRS》2008,39(3):395-401
Raman spectroscopy has been used to characterise synthetic mixed carbonate and molybdate hydrotalcites of formula Mg6Al2(OH)16((CO3)2−,(MoO4)2−)·4H2O. The spectra have been used to assess the molecular assembly of the cations and anions in the hydrotalcite structure. The spectra may be conveniently subdivided into spectral features on the basis of the carbonate anion, the molybdate anion, the hydroxyl units and water units. Bands are assigned to the hydroxyl stretching vibrations of water. Three types of carbonate anions are identified: (1) carbonate hydrogen‐bonded to water in the interlayer, (2) carbonate hydrogen‐bonded to the hydrotalcite hydroxyl surface, (3) free carbonate anions. It is proposed that the water is highly structured in the hydrotalcite, as it is hydrogen bonded to both the carbonate and the hydroxyl surface. The spectra have been used to assess the contamination of carbonate in an open reaction vessel in the synthesis of a molybdate hydrotalcite of formula Mg6Al2(OH)16((CO3)2−, (MoO4)2−)·4H2O. Bands are assigned to carbonate and molybdate anions in the Raman spectra. Importantly, the synthesis of hydrotalcites from solutions containing molybdate provides a mechanism for the removal of this oxy‐anion. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
6.
Yuri Park Godwin A. Ayoko Janos Kristof Erzsébet Horváth Ray L. Frost 《Journal of Thermal Analysis and Calorimetry》2012,107(3):1137-1142
High resolution thermogravimetric analysis (TG) has attracted much attention in the synthesis of organoclays and its applications.
In this study, organoclays were synthesised through ion exchange of a single cationic surfactant for sodium ions, and characterised
by methods including X-ray diffraction (XRD) and TG. The changes of surface properties in montmorillonite (MMT) and organoclays
intercalated with surfactant were determined using XRD through the changes in the basal spacing. The TG was applied in this
study to investigate more information of the configuration and structural changes in the organoclays with thermal decomposition.
There are four different decompositions steps in differential thermogravimetric curves. The obtained TG steps are relevant
to the arrangement of the surfactant molecules intercalated in MMT and the thermal analysis indicates the thermal stability
of surfactant modified clays. This investigation provides new insights into the properties of organoclays and is important
in the synthesis and processing of organoclays for environmental applications. 相似文献
7.
The rates and mechanism of the reaction of 12-tungstocobaltate(III) anion with thiocyanate and iodide ions have been examined in aqueous acidic solution and constant ionic strength I = 1.00M (LiClO4). The reactions follow second-order kinetics, i.e. first-order in both the oxidant and the reductant and the rate constants are found to be independent of hydrogen ions in the range [H+] = 0.10–1.00M. Outer-sphere mechanism is postulated for the systems based on the relative inertness of the oxidant and linear free energy relations are employed in demonstrating that in the reaction involving thiocyanate ion, the rate determining step is the diffusion apart of the product while the corresponding step in the iodide reaction is the electron transfer. The latter reaction is also catalysed by both bromide and chloride ions and this is rationalised in terms of possible stabilization of atomic iodine as product by these halide ions. 相似文献
8.
Summary The stoichiometry and kinetics of the oxidation of hydroxylammonium ion by the 12-tungstocobaltate(III) anion has been studied in hydrochloric acid medium. The ratio of mols of oxidant consumed per mol of hydroxylammonium ion is 11 and the evolution of nitrogen is confirmed. In the 0.1–1.0 mol dm–3 [H+] region, the oxidation is acid-independent and obeys the empirical rate law: –d[oxidant]/dt=k[oxidant] [reductant] where k=(3.51±0.18)×10–4 mol–1dm3s–1 at 22.4±0.1C and I=2.0 mol dm–3 (NaCl). Possible reaction steps and mechanism are suggested. 相似文献
9.
Mobolanle Adegboyega Olatunji Godwin A. Ayoko Florence O. Ohiani 《Transition Metal Chemistry》1994,19(2):253-256
Summary The stoichiometries, kinetics and mechanisms of oxidation of (NH2)2CS (1) and (Me2N)2CS (2) to the corresponding disulphides by CoIIIM (M = W12O40
∞-) in aqueous HC1O4 were investigated. The reaction with (1) follows the empirical rate law- d[oxidant] = k[reductant][oxidant] where k = 12.5 ± 0.3 m−1 s−1 at 25° C, while that with (2) follows the equation- d[oxidant] = a + b [reductant] [reductant] [oxidant] where a = 5.4 × 104 M−1s−1 and b = 3.3 × 106M−2 s−1 at 25° C. Free radicals are important in the reactions and possible reaction mechanisms are suggested and discussed. 相似文献
10.
Godwin Adefikayo Ayoko Johnson Femi Iyun Ibrahim Fasakari El-Idris 《Transition Metal Chemistry》1993,18(3):275-278
Summary The very slow reduction of ClO
inf3
su–
by [CoW12O40]6- is markedly catalysed by Ag1 in aqueous HClO4 solution at I = 1.0 M (NaClO4). The reaction obeys the rate law: -d[reductant]/dt where a = (1.28 ± 0.10) × 10-4M-1s-1 and b = (2.22 ± 0.20) × 10-4M-3s-1, at T = 60.1 ± 0.1°C and [H+] = 0.10–1.50 M. Activation parameters have been determined for each pathway and the reaction is discussed in terms of the outer-sphere mechanism.Part III: ref. 1. 相似文献